Cereal_grains_for_the_food_and_beverage_industries_2075944_z_lib

Table 2.4 Taxonomic details of maize grain Maize 73

Systematic name Chromosomes Common name

Zea mays L. 2n = 20 Maize, corn
Zea mays convar amylacea 2n = 20 Soft maize, flour maize
Zea mays convar ceratina 2n = 20 Waxy maize
Zea mays convar averta 2n = 20 Popcorn
Zea mays convar indentata 2n = 20 Dent corn
Zea mays convar indurata 2n = 20 Flint maize
Zea mays convar saccharata 2n = 20 Sweet corn, sugar maize
Zea mays convar tunica 2n = 20 Pod maize

(2n = 20,) and two perennials; Z. perennis (2n = 40) and Z. diploperennis
(2n = 20). The true ancestor of maize is unknown, but it shares a common
ancestor with the weedy species teosinte (Z. mexicana) (Wayne, 1995).
Although hundreds of maize cultivars exist, varieties that are commercially
grown specifically for human consumption include Z. mays var. indentata
Sturt (dent), indurate Sturt (flint), amylacea Sturt (flour), saccharata Sturt
(sweet), everta Sturt (popcorn), as well as waxy, high-amylose and high-
lysine specialty corn varieties (Pomeranz, 1987; Nuss and Tanumihardjo,
2010) (Table 2.4).

Maize share many characteristics with other grasses, such as: conspicuous
nodes in the stem, a single leaf at each node, the leaves in two opposite
ranks. Corn is normally a monoecious plant; the male and female flowers
are separated but on the same plant. On the branches, only the female
organs (called the ear) develop in the florets while the male part of the
flower – the tassel – produces pollen and is at the top of the plant. Maize
develops from a small seed to a plant, which is generally 2.0–3.5 m tall, in
a few weeks. Plant size, length of growth period and yield potential vary
greatly depending on the production location, the environment, fertiliza-
tion, irrigation and agricultural practices. Maize plants can develop 20–21
leaves and produce silk (the tuft of long fine styles on an ear of maize) in
about 65 days and reach physiological maturity in 125 days; however,
the number of leaves and time between the growth phases vary with
hybrid maturity, location, planting date, etc. (Ritchie, 1993). Maize is typi-
cally planted 4–5 cm deep in rows which are 50–100 cm apart. Where cul-
tivation and harvesting are mechanized, row spacing of approximately
76 cm appears to be the standard. The root system achieves its greatest
depth in the middle of the reproductive stage. In deep soils the roots may
reach a depth of 2.0 m; the highly branched root system is located in the
upper (0.8–1.0 m) section of the soil with about 80 % of the soil water
uptake occurring from this depth (Farnham et al., 2003; FAO, 2012).

Temperature, moisture and solar radiation are key factors which deter-
mine whether or not maize is adapted to a particular area. Temperatures

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74 Cereal grains for the food and beverage industries
between 21 and 32 °C ensure the fastest rate of development (Brown, 1977);
however, lack of water during this time often represents the greatest limit-
ing factor to a higher yield. In particular, the most critical period of maize
growth, during which water stress affects yield, is between two weeks before
and two to three weeks after silking (Singh and Singh, 1995) Thus, an opti-
mized irrigation schedule is necessary to allow moderate plant stress at
vegetative and maturity stages (Otegui et al., 1995). Moreover, profitability
is also influenced by N fertilization, which is one of the main production
costs (Berenguer et al., 2009).

2.1.3 Structure of the maize kernel
The maize kernel is the largest of the cereal grains (≈ 10 times larger than
small-grain cereals) with an average weight of 300 mg. It can differ signifi-
cantly in colour from white to yellow, orange, red, purple or brown. The
colour difference may be due to the genetic difference in pericarp, aleurone,
endosperm and germ. However, only the yellow or white dent maize (Z.
mays var. indentata) are grown commercially (Fig. 2.2). In poultry feed, the
yellow maize contributes to the yellow colour of egg yolks, as well as the
skin and fat of meat poultry, and also represents an important nutritional
source of carotenoids. Some white dent maize is produced for breakfast
cereal (e.g., corn flakes) production (Corke, 2004). Differences in the shape
and size of the maize kernels are dependent on different genetic pools and

Fig. 2.2 Maize kernels.

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Maize 75

Soft/floury endosperm
Hard/horny endosperm

Crown

Germ Tip cap Pericarp
Tip cap
Aleurone layer
Scutellum
Embrio

Fig. 2.3 A maize kernel in longitudinal cross-section, showing its component parts.

the position they assume on the cob. Those located at the shank end are
larger and rounded, while those located in the middle show flattened sides
due to pressure from the tight packing in rows on the cob. After removal
of the husk, the maize grain is easily separated from the cob.

The maize fruit is a caryopsis (a dry, indehiscent, single-seed fruit) in
which the mature ovary wall (pericarp) does not separate naturally from
the seed. The caryopsis is attached to the cob by the pedicel that ensures
transfer of the photosynthesis products into the developing kernel. When
the caryopsis is removed from the cob, the pedicel is broken and the conical
structure that remains attached to the caryopsis is called the tip cap (Figs.
2.3 and 2.4). The cob or ear, which normally contains 800 seeds attached in
rows, is wrapped by modified leaf sheaths forming husks which, along with
the silks, emerge from the distal open end of the protective husk (Kent and
Evers, 1994a).

The outermost structure of the kernel is termed the seed coat or pericarp
(Figs. 2.3 and 2.4) and this contributes the colour to the maize kernel (Corke,
2004). The thickness of the pericarp, which is genotype-dependent, ranges
from 25 to 140 µm and accounts for about 5–6 % of the dry weight of the
whole kernel. All parts of the pericarp are composed of dead cells that are
cellulosic tubes (Darrah et al., 1994). The aleurone layer is the outer layer
which covers the entire endosperm and the germ and acts as a semi-permeable
membrane by restricting the flow of large molecules in and out of the
endosperm (Li and Vasal, 2004). It consists of large dense cells (see Plate II
in the colour section between pages 230 and 231) which are rich in minerals
and proteins of high quality. These proteins are unavailable to digestive
enzymes unless the cells are opened by grinding (Saunders et al., 1969).

The endosperm comprises 82–84 % of the dry weight of the whole kernel
and represents a source of starch (86–89 % dry bases) and most of the avail-
able protein (7–10 % dry bases). The maize endosperm is comprised of

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76 Cereal grains for the food and beverage industries

Starchy endosperm
Corneous endosperm

Embryo
Pericarp

Tip cap

5 kV ×18 1 mm AMRF, UCC

Fig. 2.4 Scanning electron microscope (SEM) micrographs representative of the
maize kernel in longitudinal cross-section.

elongated cells packed with starch granules of 5–30 µm in diameter encased
in a protein matrix (see Plate III). The narrow region between the starch
granules is filled with protein bodies embedded in matrix protein. The
protein bodies are 2–3 µm in diameter and contain almost entirely zein, a
protein fraction which is extremely low in lysine (Watson, 2003).

Maize types are classified by endosperm hardness. Flint maize, which is
particularly popular in Argentina and in some parts of Italy and Africa,
has a rounded (not indented) crown (top kernel) and the hardest kernels.
This is due to the high concentration of corneous endosperm. It is physi-
cally very hard, even after the resulting corn meal prepared from it is
cooked (Watson, 2003; Corke, 2004). Popcorn is a special type of small flint
maize that was selected by Indians in early Western civilizations (Watson,
2003). Flour maize also has a rounded or flat crown and contains virtually
all soft endosperm that can be easily crushed to a friable powder. It is
physically susceptible to storage pests (mainly insect) and fungal attack. It
is grown for direct consumption as a food by certain indigenous popula-
tions of Latin America (Corke, 2004). Dent maize has a high proportion
of floury endosperm, with some corneous or hard endosperm, and is the
most widely produced commercial maize. As the name implies, dent maize
has an indentation (depressed crown) at the top of the grain that forms

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Maize 77

during maturity as the kernel dehydrates due to the floury endosperm
component.

The embryo, which constitutes the living part of the maize kernel, is
completely enclosed in shield-shaped scutellum that acts as its nutritive
organ. Walls of the scutellum cells are thick and contain numerous pits and
intercellular spaces that facilitate the movement of material among the cells
(Watson, 2003). The embryo makes up 11 % of the kernel dry weight and
is responsible for a much higher proportion of the grain than in other
cereals. It contains 83 % of the total kernel lipids, 70 % of the kernel sugars,
78 % of kernel minerals and 26 % of the kernel proteins (in particular the
non-storage protein, e.g. hormones that are mobilized during germination)
and vitamins (Watson, 2003; Eckhoff, 2004b).

2.2 Maize carbohydrate composition and properties

Polysaccharides, proteins and lipids represent the three major constituents
of the maize kernel. A typical maize kernel is composed of 70–75 % starch,
8–10 % protein, 4–5 % lipid, 1–3 % sugar, and 1–4 % ash (Table 2.5), sup-
plying approximately 365 kcal/100 g of energy (USDA/ARS, 2012). Maize
has a low protein content, generally averaging 8–10 %, and is especially
deficient in lysine (0.25 %) when compared to oats or barley (0.4 %) and
wheat (0.6 %). Starch is the major constituent of the maize kernel. The
embryo is particularly rich in lipids, minerals and sugars. Vitamins are gen-
erally concentrated in the embryo, especially the fat-soluble vitamins A and
E. Maize contains a proportion of all of the important vitamins with the
exception of vitamin B12 (Log and Wright, 2003).

The main chemical constituents of the maize caryopsis are carbo-
hydrates. They are present in different tissues of the maize kernel. Among

Table 2.5 Proximate composition of maize grain

Constituent Range (per 100 g)

Moisture (g) 7–23
Starch (g) 61–78
Protein (g) 6–12
Lipid (g) 3.1–5.7
Ash (g) 1.1–3.9
Fibre (g) 8.3–11.9
Pentosans (g) 5.8–6.6
Cellulose plus lignin (g) 3.3–4.3
Sugar (g) 1.0–3.0
Total carotenoids (mg) 0.5–4.0

Source: Adapted from White and Johnson (2003).

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78 Cereal grains for the food and beverage industries

Table 2.6 Proportion of free sugars in the anatomical
fraction of the maize kernel

Kernel fraction % of dry matter

Endosperm 0.5–0.8
Embryo 10.0–12.5
Pericarp
Tip cap 0.2–0.4
Whole grain 1.6
1.1–2.2

Source: Watson (2003).

the carbohydrates present, starch is the major component (72 % of
the kernel dry weight) and is mainly concentrated in the endosperm
(Watson, 2003). Conversely, sugars are mainly concentrated in the embryo
(Table 2.6).

2.2.1 Starch
Starch is composed of two glucan polymers, amylose and amylopectin,
which are structurally arranged in insoluble polygonal/round granules
(Fig. 2.5) and of different sizes that can reach up to 25 µm in diameter. In
the maize endosperm, starch granules are stored in a cellular organelle
called the amyloplast, which accounts for approximately 87.6 % of the total
endosperm dry weight. As observed in other cereal grains, starch granules
are mainly composed of a branched fraction, amylopectin, and a linear frac-
tion, amylose. Amylose, which makes up 25–30 % of maize starch, is essen-
tially a linear polymer of α-(1→4)-linked d-glucopyranosyl units (Watson,
2003). Amylopectin, which makes up 70–75 % of the maize starch, consists
of α-(1→4) linked d-glucosyl chains and is highly branched through
α-(1→6)-bonds. The α-(1→4)-linked unit chains can be of two lengths;
either 12–20 or 40–60 glucose units (Marshall and Whelan, 1974).

In addition to amylose and amylopectin, starch granules contain small
quantities of other minor components, such as proteins, lipids and minerals
(phosphorus), which are either on the surface of or within the granules
(Morrison, 1978). Generally in maize, the starch, lipid, protein and mineral
contents decrease relative to granule size (Dhital et al., 2011). The lipid
content ranges from 0.6 to 1.1 % on a dry weight basis (Morrison et al.,
1984) in non-waxy (amylose-containing) maize starches, while its content is
negligible in waxy maize starches (Morrison and Milligan, 1982). Moreover,
starch lipids are mainly characterized by free fatty acids (FFA) (51–62 %)
and low levels of lysophospholipids (24–46 %) (Morrison and Milligan,
1982). South et al. (1991) and Morrison et al. (1984) demonstrate a signifi-
cant positive correlation between amylose and lipid contents in maize

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Maize 79

5 kV ×1, 000 10 μm AMRF, UCC

Fig. 2.5 SEM micrographs of fractured endosperm showing round and polygonal
shape starch granules.

starches, although they provide no evidence of the possible biochemical role
of lipids.

Starch granules also contain proteins at levels ranging from 0.3 to 1.0 %
(Johnson and May, 2003). Starch granule-associated proteins are defined
as those which are distinctly different from storage proteins and are bound
to the granule surface or are integral components within the starch granule
(Baldwin, 2001). Mu-Forster et al. (1996) showed that the internalized
granule-associated polypeptides include starch-biosynthetic enzymes, such
as waxy protein, and starch branching enzymes that are intrinsically associ-
ated with the starch granule matrix. The surface-localized polypeptides
are virtually all zeins (class of prolamine) and constitute approximately
50 % of total granule-associated proteins/polypeptides (Mu-Forster and
Wasserman, 1998).

In addition to lipids and proteins, phosphorus is an important non-
carbohydrate component of maize starch. Maize starch granules have
numerous pores distributed randomly on the surface. Phosphorus, which is
primarily present as phospholipids phosphorus (69 % of the total phospho-
rus in normal maize starch) (Lim et al., 1994; Kasemsuwan and Jane, 1996),
is mainly localized in the channels under these pores (Naguleswaran et al.,
2011).

Maize starch physical properties are strongly influenced by the structure
of the polysaccharides and the percentage distribution of amylose and
amylopectin. High-amylose starch, which is gelatinized at higher tempera-
tures, can be used to form gels and films. In contrast, waxy-starch granules
have a lower gelatinization temperature and are more rapidly digested by
animal amylase (Boyer and Shannon, 2003).The average gelatinization

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80 Cereal grains for the food and beverage industries

temperatures of maize starch usually range between 67 and 68 °C (Méndez-
Montealvo et al., 2006), but higher gelatinization temperature values (71.9–
78.8 °C) have also been reported (Dong et al., 2008). Yuan et al. (1993)
suggested that the high gelatinization temperature of maize starch might
be due to the greater proportion of longer chains in the amylopectin mol-
ecule. These chains could form long double helices (not necessarily entirely
in crystallites) that would require a higher temperature to dissociate com-
pletely than that required for shorter double helices. Generally, maize with
a high gelatinization temperature is used in the production of maize flour
since high temperature is necessary during processing, while the maize with
low gelatinization temperatures may be used for tortilla production with
the traditional nixtamalization process (Méndez-Montealvo, 2005). (Nixta-
malization is an ancient process widely utilized in the production of tortillas
and other related maize-based food products which involves an alkali steep-
ing and cooking of grains (i.e., cooking in lime), followed by grinding of the
resulting nixtamal (the alkaline-cooked maize grains) (Robles et al., 1988;
Noda et al., 1998). These treatments give rise to diverse changes in the maize
components. The alkali-thermal treatment partially gelatinizes the starch,
resulting in partial saponification of the lipids and also solubilizing a portion
of the proteins surrounding the starch granules.

Maize also contains a starch fraction which is called resistant starch (RS)
and is classified as dietary fibre because it escapes digestion in the small
intestine. In maize, the content of RS is approximately 2 % on dry matter
basis (Rendon-Villalobos et al., 2002). RS is fermented by bacteria when it
reaches the large intestine (Bello-Perez and Paredes-Lopez, 2009; Brites
et al., 2011), which increases the production of short-chain fatty acids
(SCFA), increases faecal volume and reduces faecal pH (Phillips et al., 1995;
Jenkins et al., 1998), causing reduced blood glucose levels (Hoebler et al.,
1999) and intestinal transit times (Kim et al., 2003). Additionally, RS from
maize has been shown to reduce serum cholesterol in rats (de Deckere
et al., 1992). Due to these health benefits, different bakery products, such as
breads, muffins and breakfast cereals, can be prepared by using RS as a
source of fibre. RS have been incorporated into a variety of baked goods,
many of which are batter-based systems, such as cakes, cake-like muffins or
brownies (Sajilata et al., 2006; Romo et al., 2008). In general, application
tests showed that RS acts as texture modifier by imparting a favourable
tenderness to the crumb (Sajilata et al., 2006).

2.2.2 Dietary fibre
Dietary fibre is a collective name for the non-starch polysaccharides that
are resistant to digestion and absorption in the human small intestine but
undergo complete or partial fermentation in the large intestine. It can be
classified into soluble components, such as pectins, gums and β-glucans, and
insoluble components, which include cellulose, lignin and hemicelluloses

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Maize 81

(Happi Emaga et al., 2008). Studies on the comparative chemical composi-
tion of several cereal grains have shown that maize has a higher fibre
content (2 %) than rice (0.8 %), wheat (1 %) and millet (1.5 %), but lower
levels than those typical in rye (2.2 %), barley (3.7 %), sorghum (4.1 %), or
oats (5.6 %) (Champagne et al., 2004).

The most important sources of dietary fibre in maize are the bran and
the tip tap (Boyer and Shannon, 2003). Maize bran primary constituents
are 70 % hemicellulose, 23 % cellulose and 0.1 % lignin on a dry-weight
basis (Sandstead et al., 1978). Similar percentages were also reported by
Sugawara et al. (1994). Levels of total fibre, cellulose and hemicellulose, are
higher in maize bran than in wheat or rice brans; however, the lignin content
is much lower (Wang and Liu, 2000). Despite this, maize bran is considered
an optimal source of dietary fibre (Hu et al., 2008). Singh et al. (2012) incor-
porated mechanically processed maize bran into batter in order to eveluate
the resulting cakes. Flour replaced (20 %) by maize bran resulted in cakes
with satisfactory sensory scores based on texture, taste and overall accept-
ability. Additionally, maize bran provides important functional properties
in reduced calorie products (Burge and Duensing, 1989), as it exhibits a
high water-holding capacity. Thus it has an ability to absorb faecal mutagens
in human digestive tracts, thereby protecting the body from their potential
ill effects (Singh et al., 2012).

2.3 Other constituents of the maize kernel

2.3.1 Protein
After starch, (storage) protein is quantitatively the major (and hence the
most important) maize constituent. In addition, maize also contains a whole
array of minor constituents. Some of these, such as vitamins, minerals and
phytochemicals, have a great impact on the functional properties of maize-
based product. Protein is the second most abundant component in maize,
following starch. It ranges between 6 and 12 % with a mean of 9.5 %
(Watson, 2003). Maize protein is primarily found in the germ and endo-
sperm parts of the maize grain, but the protein characteristics differ signifi-
cantly in these two storage parts. Generally, the germ contains 35 % protein,
and is of a high quality, whereas the endosperm has only 9 % protein, which
is of a poor quality, mainly due to its deficiency in the essential amino acids
lysine and tryptophan (Khoi et al., 1987; Zarkadas et al., 1995; FAO/WHO,
2002; Li and Vasal, 2004; Milán-Carrillo et al., 2004) (Tables 2.7 and 2.8).
However, 80 % of total protein content in the kernel is located in the endo-
sperm since it accounts for 80–85 % of the total kernel dry weight, while
the germ constitutes the remaining weight.

In the maize endosperm, proteins occur both as distinct protein bodies
and as a protein matrix (see Section 2.1.3). Traditionally, cereal proteins are
classified into albumin, globulin, prolamin and glutelin according to their

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82 Cereal grains for the food and beverage industries

Table 2.7 Essential amino acid content of dent and flint maize cultivars as compared
with the FAO/WHO Human Nutritional Requirementsa

Maize cultivar EAA daily childhood
requirementsa
Amino acid (g/kg of protein)

Dent Flint

Lysine 20 18 45
Threonine 31 29 23
Valine 50 46 39
Cysteine plus methionine 50 50 22
Isoleucine 38 38 30
Phenylalanine plus tyrosine 98 100 38
Tryptophan 13
67

a FAO/WHO (2002).
Source: Adapted from Zarkadas et al. (1995).

Table 2.8 Min, max and range of amino acid composition of maize grain samples

Amino acids Minimun Maximum Average
(g/100 g dry matter)

Lysine 0.23 0.34 0.29
Threonine 0.27 0.37 0.32
Methionine 0.14 0.23 0.19
Valine 0.33 0.45 0.39
TSAA 0.35 0.50 0.42
Isoleucine 0.25 0.36 0.31
Arginine 0.36 0.54 0.45
Tryptophan 0.05 0.08 0.07

TSAA = total sulphur amino acids.
Source: Adapted from Sriperm et al. (2010).

solubility, as described by Osborne (1924). The protein bodies are mainly
composed of prolamins, referred to as zeins, and are the major protein frac-
tion in the endosperm (52 % of the kernel nitrogen) followed by glutelins
(25 % of the kernel nitrogen) albumins (7 % of the kernel nitrogen) and
globulins (5 % of the kernel nitrogen) (Li and Vasal, 2004; Delcour and
Hoseney, 2010).

Sriperm et al. (2010) investigated the relationships between crude protein
and amino acid composition in more than 290 maize grain samples. Their
results indicated that methionine and arginine were not normally distrib-
uted in maize grain. There were linear relationships between crude protein
and most of the amino acids in maize grain, except for the relationship
between crude protein and threonine or isoleucine.

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Maize 83

Particular efforts for the improvement of the protein quality in maize
began in the mid-1960s with the development of nutritionally improved
hard-endosperm lines, called quality protein maize (QPM) by the Interna-
tional Centre for Wheat and Maize Improvements (CIMMYT) in Mexico.
These lines have good agronomics (interchangeable with normal maize in
cultivation and kernel phenotype) (Prasanna et al., 2001) and processing
properties as well as improved lysine and tryptophan contents, the two
limiting amino acids in endosperm protein (Mertz et al., 1964) essential for
protein synthesis in humans. QPM genotypes contain 22 % more lysine and
27 % more tryptophan, with respect to the normal maize (Li and Vasal,
2004), thus enhancing its nutritive value and reducing the protein deficien-
cies, particularly in young children where maize dominates the diet (Vasal,
2000). Additionally, milling performance (wet and dry milling) and the
physico-chemical properties of starch and oil from QPM did not differ
significantly from those of normal maize (Li and Vasal, 2004).

Generally, the technological process involved in the production of cereal-
based food products, such as cooking, influence the protein digestibility of
the final product. Hamaker et al. (1986) studied the effect of cooking on the
protein profiles and in vitro digestibility of sorghum and maize. They found
that cooking maize had no effect on pepsin digestibility and actually
increased pepsin–trypsin–chymotrypsin digestibility, while sorghum protein
digestibility was significantly decreased. Cooking appears to lead to forma-
tion of disulphide-bonded oligomer-proteins, a phenomenon that occurs to
a greater extent in sorghum than maize (Duodu et al., 2002). This may
explain the poorer protein digestibility of cooked sorghum.

2.3.2 Lipids
Although maize is not considered an oilseed, in 2010, the USA produced
11.2 million tonnes of maize oil followed by China with 2.3 million tonnes.
Commercial maize hybrids contain high levels of lipids (approximately
4.4 % of total grain weight) when compared to other cereals such as brown
rice (2.3 %), wheat (1.9 %), barley (2.1 %) and sorghum (3.4 %). Only pearl
millet and oat groats showed higher lipid contents of 5.4 % and 7 % of total
grain weight, respectively (White, 2003).

Environmental factors and agronomic practices, such as planting dates,
location, years, temperature, rainfall, or fertilization and herbicide use rate,
do not influence the oil content in the maize kernel which instead seens
influenced/controlled by genetic factors (Jellum et al., 1973; Wilkinson and
Hardcastle, 1973, 1974; Earle, 1977); in contrast, maize fertilization with
potassium tends to reduce the linoleic acid percentage (White, 2003).
However, the position of the maize kernel in the cob influences its oil
content. Generally, the kernels located in the middle of the cob are charac-
terized by the highest percentage of oil (White, 2003). Within the maize
caryopsis, lipids are almost exclusively concentrated in the cells of the

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84 Cereal grains for the food and beverage industries

scutellum portion of the germ (76–83 %), followed by pericarp (1–2 %), tip
cap (1 %), starch (1–11 %) and aleurone (13–15 %) (Tan and Morrison,
1979). In the germ, maize oil is arranged into microscopic droplets (1.31 µm
of diameter) known as oil bodies (Watson, 2003). The germ contains
39–47 % lipids, which are mostly triglycerides, with some steryl esters and
diglycerides, as well as small amounts of glycolipids and phospholipids.
Aleurone lipids are mainly triglycerides with some free fatty acids (FFA)
and steryl esters (Tan and Morrison, 1979). Maize oil is an excellent source
of polyunsaturated fatty acids (PUFAs), and is highly stable due to the
elevated levels of natural antioxidants and a low percentage of linoleic acid
(C18 :3, <1 %). Maize oil is also characterized by a low levels of palmitic
acid (C16 :0, 13 %) when compared to pearl millet (20 %), rice (22 %), oats
(20 %), rye (18 %), barley (22 %) and wheat (21 %) (Delcour and Hoseney,
2010). Tocopherols and tocotrienols, collectively called tocols or the vitamin
E complex, are an important group of nutrients associated with maize lipids
due to their non-polar solubility, which will be discussed further in the fol-
lowing section.

2.3.3 Vitamins
Vitamins are nutritional components produced by plants. Cereal grains are
well known to be good sources of some of the B-complex vitamins. The
maize kernel contains two fat-soluble vitamins, A (β-carotene) and E,
and most of the water-soluble vitamins such as thiamine (vitamin B1) and
pyriodixine (vitamin B6), but it is deficient in ascorbic acid (vitamin C)
and cobalamin (vitamin B12) (Nuss and Tanumihardjo, 2010). Niacin (B3)
is present in elevated levels in bound form and, unless properly processed,
is biologically unavailable to humans. In fact, long-term consumption
of improperly prepared maize can lead to pellagra (Watson et al., 2003;
Kies et al., 1984), a vitamin deficiency skin disease. Technological
processing of maize, such as through the use of heat and/or pressure,
can hydrolyze niacin, thus improving its bioavailability and preventing
pellagra.

Carotenoids are mainly found in yellow maize, in amounts ranging
between 0.09 and 72 µg/g (White, 2003), a factor which may be genetically
controlled, while white maize has little or no carotenoid content, owing to
its pale colour. Unfortunately, many populations chronically suffer from
vitamin A deficiency (VAD) but still maintain cultural preferences for
consumption of white maize varieties (FAO, 1997).

In this regard, breeding strategies aiming to generate micronutrient-
enhanced maize have been developed (Ortiz-Monasterio et al., 2007). All
yellow genotypes of maize contain carotenoids, although the fraction of
carotenoids with pro-vitamin A activity is typically small. β-carotene and
β-cryptoxanthin are the most abundant pro-vitamins A in maize, while
α-carotene is present in much smaller amounts (Ortiz-Monasterio et al.,

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Maize 85

2007). The CIMMYT Mexico observed a considerable variation in total
pro-vitamin A (about 0–9 mg/g) among different genotypes of maize, thus
concluding that there is considerable scope for breeding maize with
enhanced pro-vitamin A concentrations and an improved nutritional value
(Ortiz-Monasterio et al., 2007). In the maize kernel, most of the caratenoids
are concentrated in the hard endosperm of the kernel and only small
amounts are in the germ. Besides the genetic predisposition of maize grain
to produce carotenoids, storage conditions seem to dramatically influence
the loss of carotenoids content. Vitamin contents of the maize caryopsis
can be affected by cultural practices and/or grain processing. Specifically,
maize herbicides, mainly mesotrione and atrazine, work synergistically
to up-regulate carotenoid biosynthetic pathways. If applied early post-
emergence, they can increase lutein and zeaxanthin levels by up to 15.6 %
in some sweet corn cultivars (Kopsell et al., 2009).

The other fat-soluble vitamin, vitamin E, which is subject to some genetic
control, is found almost exclusively in the maize germ. Vitamin E, as toco-
pherols, is the predominant fat-soluble vitamin found in maize kernels and
its concentration range is from 0.3 to 0.7 mg/100 g for most varieties (White,
2003). α- and γ-tocopherols are the only vitamin E constituents found in
significant amounts (0.05 and 0.009 % of the total oil, respectively) (Reiners
and Gooding, 1970).

Water-soluble vitamins are mainly located in the endosperm and germ,
and in particular in the aleurone layer. The kernel endosperm contains 80 %
of the vitamin B3, followed by 4 % in the seed coat and 2 % in the germ.
Levels of vitamins B1, B2 and B3 are variable between cultivars. Compared
with wheat grains, maize contains slightly less B1, and about half as much
vitamin B5 (pantothenic acid), B9 (folic acid) and choline (Loy and Wright,
2003).

2.3.4 Minerals
Maize mineral contents range from 1.0 to 1.3 %. The germ alone provides
nearly 80 % of the kernel’s minerals, compared to less than 1 % from the
the endosperm (Earle et al., 1946). Phosphorus (in the form of phytate)
(0.29 % dry basis), K (0.37 % dry basis) and Mg (0.14 % dry basis) are the
most prevalent minerals found in maize, providing nearly 85 % of kernel
mineral content (Watson, 2003). As with most cereal grains, maize is low in
Ca (0.03 % dry basis) and Fe (30 µg/g) (their bioavailability is also retarded
by the phytate concentrated in the maize germ) (Bohn et al., 2008), as well
as in trace minerals such as Mu, Cu, Se, and I (Mertz, 1970).

Genetic and environmental factors (soil quality, growing altitudes) have
substantial impacts on kernel Fe and Zn contents. In this regard, Oikeh
et al. (2003) evaluated the concentrations of these minerals in the grains of
elite late-maturing maize varieties grown in diverse environments and
examined their bioavailability using an in vitro digestion/Caco-2 cell model.

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86 Cereal grains for the food and beverage industries

They found that environment did not have a significant effect on kernel Fe
and Zn levels provided the minimum growth requirements are met; however,
the genotypic variation between cultivars had a highly significant impact.
These authors also highlighted how the genetic differences in the kernel
also influence Fe bioavailability.

Although phytic acid is an essential element during kernel germination,
where it serves as phosphate storage, it negatively affects the bioavailability
of minerals essential for human health (Raboy, 2003) by chelating
multivalent-cation minerals, such as Ca, Fe and Zn. Different food process-
ing methods, including milling, soaking or heating, can degrade or remove
phytic acid to different extents (Hurrell, 2004). Fermentation does not
improve Ca or Zn absorption in children (Thacher et al., 2009); however,
adding exogenous phytase enzymes derived from microbes, plants or fungi
to maize leads to an improved mineral bioavailability (Hurrell et al., 2003;
Revy et al., 2006). In addition to phytic acid chelation, dietary fibre also
contributes to low Fe bioavailability in maize. However, the combination
of organic acids, such as ascorbic and citric acids, with high-fibre whole-grain
maize meal showed an increased Fe bioavailability in humans by limiting
the binding affinity of Fe for intrinsic kernel fibres (Reinhold et al., 1981).

2.3.5 Phytochemicals
Phytochemicals are non-nutritive components present in plants that exert
protective or disease-preventing effects in the diet. Several studies have
reported the antioxidant and anticarcinogenic effects of white corn poly-
phenols such as ferulic and p-coumaric acid along with their respective
derivatives (Andreasen et al., 2001; Anselmi et al., 2004; Trombino et al.,
2004). Many of the polyphenol compounds in maize are covalently bound
to cell wall polysaccharides and function in the kernel as cross-linkers to
strengthen the grain cell wall (Bily et al., 2004). Blue, purple and red pig-
mented corn kernels are also rich in anthocyanins (mainly associated with
the aleurone layer of the endosperm) which have well-established antioxi-
dant and bioactive properties (Fimognari et al., 2004; Matsumoto et al.,
2004).

Various studies have previously investigated the phytochemical and anti-
oxidant capacity of maize during food processing (nixtamalization). For
example, de la Parra et al. (2007) investigated the phytochemical profiles
(total phenolics, anthocyanins, ferulic acid, carotenoids) and antioxidant
activities of five types of corn which were processed into masa, tortillas and
tortilla chips. They found that lime-cooking significantly reduced the phy-
tochemical content of nixtamalized products with the concurrent release of
phenolics and ferulic acid. Del Pozo-Insfran et al. (2006) found that a post-
nixtamalization acidification treatment could reduce polyphenolic and anti-
oxidant losses in a process which contrasts the negative effects of
nixtamalization. This acidification treatment could be incorporated into

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Maize 87

tortilla processing as a means to increase the retention of antioxidant poly-
phenols in processed maize products.

2.4 Maize processing

The different ways of processing maize, such as wet milling, dry milling, the
masa-type process, cooking and extrusion, are able to improve the final
quality of food products. Maize in the form of flour is typically used to make
various products, such as breads, muffins, doughnuts, infant foods, biscuits,
wafers and breakfast cereals, as well as functioning as a filler, binder and
carrier in cereal and meat products (Kent and Evers, 1994b). In view of its
importance as flour, the milling characteristics of maize are significant. Both
dry and wet milling processes are commonly used to make maize flour, and
each has its own characteristics. Maize wet milling is an industrial process
that separates the corn kernel into its starch, protein, germ and fibre frac-
tions. In general, it includes the following steps: steeping to temper the
kernel, milling to free and separate the germ, fibre recovery, milling to free
starch and separation of starch from gluten (Dowd, 2003). On the other
hand, dry milling is a process that is able to separate grain components by
grinding maize into various particle sizes through the use of roller mills
(Vanara et al., 2009). Dry milling yields both flour and semolina, the latter
of which is used for making breakfast cereals, puffed snacks, pasta products
and staple food items like chapati or roti in combination with wheat flour.

The process characteristics of maize dry and wet milling will be detailed
in the next section.

2.4.1 Full-fat dry milling
The full-fat milling process, also known as whole kernel dry milling, is the
oldest maize milling process.The full-fat milling process yields products that
contain most of the maize oil which is naturally found in the grain germ, as
it grinds the maize kernel into uniform particles (flour of meal) as opposed
to fractionation. This product has a relatively short shelf-life because of the
high fat content and endogenous enzymatic activities that can potentially
cause rancidity and off-flavours (Eckhoff, 2004a; Hammond and Jez, 2011).

2.4.2 Maize wet milling
Maize wet milling can be divided into five steps: steeping, germ recovery,
fibre recovery, protein recovery and starch washing. Maize, which has previ-
ously been mechanically cleaned to remove broken pieces of maize, weed
seed, other grains and any other adulterant, is steeped. This step represents
the core of the maize wet milling process in which chemical and physical
reactions promote the diffusion of water through the tip cap of the kernel

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88 Cereal grains for the food and beverage industries

into the cellular components of the embryo and the endosperm,
thus facilitating their further separation (Johnson and May, 2003; Eckhoff,
2004b).

Steeping is accomplished by dropping maize into tanks equipped with a
water-transfer or recirculation pump, with the former used to increase tem-
perature homogeny in interconnected tanks. The amount of water available
for steeping is generally approximately 1.2–1.4 m3/tonnes of which, 0.5 m3/
tonnes is absorbed by the maize kernel to increase the moisture from 16 %
to 45 %, while the remaining 0.7–0.8 m3/ tones is later withdrawn from the
steeping system (Johnson and May, 2003). The steep-water is heated to
52 °C (optimal temperature for lactic acid production carried out by lactic
acid bacteria–LAB) and held for 20–48 h. In such processes, LAB inhibit
pathogenic and spoilage organisms by several mechanisms, such as the
production of organic acids, hydrogen peroxide and antimicrobial sub-
stances, as well as by lowering pH and oxidation reduction potential
(Mbugua and Njenga, 1992).

The steep-water should neither drop below ≈ 47 °C (to avoid yeast prop-
agation with consequent alcohol production) or exceed ≈ 56 ° C (to avoid
the acetic acid bacteria propagation) (Eckhoff, 2004b). Steeping water
is treated with SO2 to a concentration of 3000 ppm. This helps water
diffusion through the maize kernel and has the dual effect of facilitating
protein–starch matrix breakdown as well as controlling microbial propaga-
tion. SO2 is specifically added to the longest steeped maize exposed to the
newest steep-water. Since the steep-water goes from the oldest maize
to the newest maize during the process, the SO2 concentration decrease
significantly to less than 300 ppm allowing the LAB action to increase.
This results in the fermentation of glucose to lactic acid at levels ranging
from 1 to 3 %, with consequent changes in pH. After excess water is
removed, the remaining maize is transferred to the first grind mill or
de-germinating mill. The sluice water is recovered by screening and is then
recirculated.

The first intent after steeping is to recover the swollen germ from the
hydrated maize kernel as quickly as possible to minimize germ damage and
maximize oil recovery. The hydrated maize kernel is transferred into coarse
grinding mills which have one stationary and one rotating disk with spe-
cially designed intermeshing teeth. By adjusting the clearance between the
disks and applying a proper sheer, maize germ can be separated from the
other components with little damage to the germ itself. The maize slurry
from the mill is pumped to flotation tanks or hydroclones where the oil-
containing germ is floated off the top.

After germ separation, de-germed maize slurry is screened using a fibre
– this is a washing system which separates water, loose starch and gluten
(mill starch) from the fibre, bound starch and gluten. The mill starch con-
tinues along the process to separate gluten and starch while the fibre, bound
starch and gluten are finely ground to complete starch dispersion. The

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Maize 89

ground slurry is then pumped under pressure onto a six-stage fibre-washing
system and separated in a series of tanks and fibre wash screens. The sepa-
rated fibre is then dewatered using either a screening centrifuge, screw press
or both in series. The final product is known as ‘gluten feed’ and has a
protein content of approximately 20 % on a dry weight basis (Ramirez
et al., 2008). This name, gluten feed, is inappropriate as corn doesn’t actually
contain gluten but rather is rich in zein. As such, the name for this gluten-
free maize product is scientifically incorrect and simply represents a nominal
aberration.

To make gluten feed, the protein component is separated from the starch
using a disc-nozzle centrifuge, working on density differences of the two
components which allows good separation. This is a continuous centrifuge,
which is in an upward pointing conical shape with an arched base, all con-
tained inside its outer cylindrical casing. Using a continuous drive shaft, the
corn mixture is pumped downwards towards the bottom of the cone’s
central core which is fringed by a stack of discs on each side. When the
mixture reaches the base of the cone, which is under the stacked discs, it is
forced upwards from its confined space through the disc stack. Then the
lighter protein fraction escapes easily through pores in the discs to an over-
flow pipe. However, the heavier starch fraction cannot go through
the size-restricted disc pores and is forced outwards through a nozzle
on the outer sides of the disc stack into the underflow pipe. The protein
(inaccurately referred to as gluten) is sold, usually for animal feed, as maize
gluten meal. The final maize gluten meal generally has a protein content of
approximately 60 % on a dry weight basis and contains xanthophylls that
give it a yellow colour (Ramirez et al., 2008).

Starch recovery is the last step of the maize wet milling process and is
performed in a series of small hydrocyclones, grouped in stages, in a counter-
current fashion. The wash water used in this step is generally deionized
fresh water (Johnson and May, 2003; Eckhoff, 2004b). The purified slurry
starch, with less than 1 % of impurities, contains 60 % moisture and is then
dried further.

Starch is the major product of the wet milling process (Blanchard, 1992)
and is used for the production of ethanol (economically more important)
and in the food industry as an additive or adhesive. The germ is used for
maize oil production (by expulsion or more often by solvent extraction)
and the resultant meal is used as animal feed or added back to the corn
gluten feed. Typical germ contains 48 % oil, 13 % protein, 12 % starch, 2 %
ash and 3 % moisture (Ramirez et al., 2008).

Maize gluten feed is rich in fibre and low protein and is used for beef
cattle. This co-product typically contains 60 % fibre and 20 % protein
(White and Johnson, 2003). Corn gluten meal is the high-protein, low-fibre
fraction and it is used as an energy, protein, vitamin and mineral supply for
poultry and swine. The final corn gluten meal typically has 60 % protein and
10 % moisture (Blanchard, 1992).

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90 Cereal grains for the food and beverage industries

2.4.3 Maize dry milling
After the cleaning step, which includes passage under a magnet to remove
metal, aspiration to remove fine pieces of cob, and screening to separate
the broken kernel from the whole kernel, maize is tempered to about 20 %
moisture and placed in a tempering bin. Tempering is mainly to generate
differential swelling resulting from the germ and pericarp absorbing mois-
ture and swelling faster than the endosperm. These different swelling prop-
erties between the pericarp and the aleuerone layer of the endosperm, and
between the germ and the endosperm, facilitate the further separation of
different maize components. The tempered maize kernels are then pro-
cessed in the de-germinator which, through abrasive action, removes the
germ and the bran from the endosperm, leaving the latter intact. Different
categories of de-germinators are available nowadays, such as Beall type,
impact type, multiple impact/share or compression and roller milling, each
one with its own particular characteristics and performances (Eckhoff,
2004a).

The products obtained from the tempering–de-germing process are
maize grits, maize meal, and maize flour which are obtained as a result of
particle size reduction on the roller mills; however, most of the products
can be classified, according to their size as flaking grits (typically between
5660 and 3360 µm), large grist (typically between 2000 and 1410 µm),
brewer’s grist (typically between 1680 and 590 µm), regular grist (typically
between 1410 and 638 µm), coarse meal (typically between, 638 and 297
µm), dusted meal (typically between 297 and 194 µm), cones (typically
between 297 and 177 µm) and maize flour (typically between 194 and
45 µm) (Johnson, 2000; Duensing et al., 2003). De-germed maize endosperm
products are processed directly into a variety of breakfast cereals and snack
products or used as a carbohydrate source for microorganisms in brewing
and other fermentation industries.

2.4.4 Nixtamalization
The nixtamalization process is commonly utilized in the production of
tortillas and other related maize-based food products. The maize kernels
are cooked with alkali (i.e. lime) and steeped in the cooking water with
subsequent washing, at least twice, ensuring the removal of any remaining
organic components and excess alkali. Nixtamal is the product obtained
after this process, and it is subsequently ground to produce soft dough
named masa. This is the base ingredient for the production of tortillas
(Paredes-Lòpez and Saharopulos-Paredes, 1983). Remarkable physico-
chemical changes occur in the maize during nixtamalization (resulting from
heat treatment, lime addition and the steeping and grinding processes)
which remarkably improve the nutritional quality of the maize. In particu-
lar, partial starch gelatinization, partial lipid saponification, solubilization
of some proteins surrounding the starch granules and the conversion of the

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Maize 91

cell wall hemicellulose components into soluble gums all strongly influence
the rheological and textural properties of the final products (Arámbula
et al., 1999).

2.5 Applications of maize in foods

The popularity of maize as a crop is largely due to its diverse functionality
as a food source for both humans and animals. Maize can be consumed off
the cob, parched, boiled, fried, roasted, ground and fermented for the pro-
duction of many traditional foods, such as breads, tortillas, porridges,
polenta, gruel, cakes, snacks, breakfast foods and alcoholic beverages (Table
2.9) (Vivas et al., 1987; Weber et al., 1993; Nago et al., 1997; Zulu et al., 1997;
Gadaga et al., 1999; Diaz-Ruiz et al., 2003; Onyango et al., 2004; Serna-
Saldivar, 2004; Glover et al., 2005; Amoa-Awua et al., 2007; Singh et al., 2011;
Rocha and Malcata, 2012). Maize kernels can be further processed for use
as food thickeners, sweeteners, cooking oil and non-consumables (Gardner
and Inglett, 1971; Duensing et al., 2003).

Additionally, the use of fresh or immature maize on the cob is practised
worldwide. Maize cobs with or without husks are boiled in water or cooked
over a fire and then flavoured with salt, cream, butter, margarine and other
sauces (Serna-Saldivar, 2004) before eating.

Consumption of maize has risks associated with it due to Fusarium fugal
contamination and this applies to both food and beverages (see Section
2.6). These fungi are the sources of mycotoxins that have been shown to be
carcinogenic toxins as exemplified by fumonisin B1 (Musser and Plattner,
1997). Effective strategies aiming to reduce dietary mycotoxin exposure in
the population, should be focussed on maize consumption by educating
strong maize product consumer communities about the health implications
and risks of mycotoxin ingestion.

2.5.1 Bakery products from maize
Tortillas
Maize tortillas and derived products are still the staple foods of Mexico and
Central America which, along with corn chips and tortilla chips, have widely
penetrated the market of the USA and some countries in Asia and Europe
(Cortés-Gómez et al., 2005). The traditional method to make tortillas from
maize goes back to early Mesoamerican civilizations. Tortilla production is
one of the industrial sectors of highest socioeconomic impact in Mexico,
creating micro industries and is responsible for 225 000 jobs either directly
or indirectly (Gargallo, 2000).

In the traditional process, maize is lime-cooked and steeped in its cooking
water for 8–16 h, followed by washing, at least twice, to remove the cooking
liquor, called nejayote, which is rich in organic components and alkali. The

© Woodhead Publishing Limited, 2013

Table 2.9 Major types of traditional foods from maize

Food Description Country Reference

Whole grain Maize is lime-cooked (25–40 min) until the pericarp is freed USA Rooney and Serna-Saldivar,
Hominy from the endosperm. The cooked maize is washed to 2003
remove all trace of the alkali and pericarp. Then the
© Woodhead Publishing Limited, 2013 Pozole hominy is salted and canned. Mexico Perales R et al., 2003

Nixtamal Made from wide maize kernels that are boiled to bursting Central America Diaz-Ruiz et al., 2003
Porridge point. It is not a common dish, but there is a national
Thin, unfermented market for large, floury maize kernels for its preparation.
Atole
Heat- and alkali-treated maize kernel.
Pinole
Chicha morada Prepared from wet-milled pastes, dry-milled flours, or Mexico, Central Vivas et al., 1987; Rooney
de-germed flours after various treatments, such as cooking, America and Serna-Saldivar, 2003
Mingua roasting, nixtamalization and steeping processes. In Central
America atoles are traditionally served for breakfast or to Mexico Vivas et al., 1987
Canjica lactating mothers and young children. Brazil
Pamonha Betran et al., 2000; Serna-
Prepared from well dry-milled, roasted maize which is then Brazil Saldivar, 2004
mixed with sugar and boiled for 2 min. Brazil
Brazil Rooney and Serna-Saldivar,
Made from blue maize that is cooked in water with sugar for 2003; Serna-Saldivar, 2004
several hours. The mixture is filtered and the purple liquor
is blended with fruit juice (e.g. pineapple) and consumed as Rooney and Serna-Saldivar,
a beverage. 2003; Serna-Saldivar, 2004

Maize grits or immature kernels are mashed or immature Rooney and Serna-Saldivar,
kernels are cooked in water to produce porridges similar to 2003
atole.

De-germed maize kernels are cooked with sugar and milk
and generally consumed as a dessert or breakfast cereal.

Immature maize that is steam cooked in a sack of maize
husks.

Food Description Country Reference
Thin, fermented Nago et al., 1998; Serna-
© Woodhead Publishing Limited, 2013 Ogi The general procedure for making ogi includes six main Nigeria
steps: grain steeping in water, wet-milling, wet-sieving, Africa Saldivar, 2004
Uji decanting and fermentation of the slurry for 1–3 days. The South Africa
Mahewu fermented sediment is separated and boiled in water to Rooney and Serna-Saldivar,
yield ogi porridge that is consumed warm or cooled to Mexico 2003; Onyango et al., 2004
Pozol form a gel or pudding.
Gadaga et al., 1999
Maize–finger millet blend diluted with water to give a
30–40 g/100 ml slurry which is then spontaneously or Steinkraus, 1996; Diaz-Ruiz
backslop fermented for 24 h at 25–35 °C. The fermented et al., 2003
slurry is further diluted to 10 g/100 ml, cooked for 30 min,
flavoured with sugar and served warm. (Continued)

Fermented beverage which is prepared from either thin or
thick maize porridge. It is commonly used to wean children
and is introduced to infants between 4 and 18 months. The
maize porridge is mixed with water and sorghum or millet
malt or wheat flour is then added to the mixture and left to
ferment. The fermentation is a spontaneous process carried
out at ambient temperature. This drink is consumed after
standing for about 24 h.

Acid beverage obtained from the natural fermentation of
nixtamal (heat- and alkali-treated maize) dough. In pozol
production, lactic acid bacteria and at least one type of
nitrogen-fixing bacteria is involved, resulting in elevated
nitrogen/protein content of the resulting fermented maize
food.

Table 2.9 Continued

Food Description Country Reference

© Woodhead Publishing Limited, 2013 Thick, fermented Corn grits are cooked in water with sugar or fruit for 1 h. South America Rooney and Serna-Saldivar,
Hanchi Lemon juice is added while cooling. South America 2003
Mazamorra Mexico
Maizena Sweet porridge made from soaked maize cooked in water South America Delgado, 1991; Rooney and
Humita (medium heat) or milk for 15 min to 2 h. Serna-Saldivar, 2003
Tuwo Africa
Porridge consumed exclusively by infants, the elderly and the Brandes, 1992
Polenta infirm who have to rely on mainly liquid diets. Italy and South Rooney and Serna-Saldivar,
America
Steamed foods Green corn is mixed into dough and subsequently mixed with 2003
Couscous meats or cheese and spread on corn husks followed by Vivas et al., 1987; Rooney
cooking in a steamer for 20–40 min.
Tamales and Serna-Saldivar, 2003
Dried maize kernels are ground to obtain a smooth, whitish
paste which is then boiled with water to make a thick Serna-Saldivar, 2004
porridge. The porridge is allowed to cool. Tuwo is taken
with bean soup or with vegetable soups like sesame. Nago et al., 1997; Serna-
Saldivar, 2004
De-germinated corn grits are cooked in water until
gelatinized, then mixed with tomato sauce, cheese, meat, Weber et al., 1993; Rooney
etc. and baked. and Serna-Saldivar, 2003

Granulated corn product which is steam-cooked from the Africa, Brazil
dough (fermented, derivated from dehulled and wet-milled Latin America
grains) or hydrated flour (unfermented dry-milled from
whole grain). The cooked product is consumed with a
sauce. In Africa, ground baobab leaves, peanut butter, okra,
etc. are mixed with the couscous during the final stage of
steaming when it is to be dried and used as a convenient
food.

Lime-cooked maize (masa) mixed with other foods and
wrapped in a corn husk and steamed for 60–90 min.

© Woodhead Publishing Limited, 2013 Food Description Country Reference
Bread Rooney and Serna-Saldivar,
Unfermented Maize is lime-cooked for 15–60 min at near boiling Central and
Tortillas, tacos, temperature and steeped overnight. The dewatered dough North 2003; Serna-Saldivar, 2004
masa is rubbed between the hands to remove the bran, and America Singh et al., 2011
enchiladas, sopes, then baked on a hot grill.
joroch, gorditas, India Alvarez, 1982
papusas etc. Maize meal is kneaded into soft workable dough with warm Rooney and Serna-Saldivar,
Roti, chapati water. After mixing, dough is divided into small balls which Venezuela
are rounded, flattened and sheeted into circular discs that 2003
Arepas are roasted until crisp. After roasting, the roti is coated Worldwide Rocha and Malcata, 2012
with butter oil or butter. Portugal
Corn bread (Continued)
Arepas are produced by adding salt and water to white grits
Fermented or meal flour, followed by mixing and shaping the dough,
Broa by hand, into flat discs (3–4 in. in diameter) and either
baked or fried until golden brown.

Corn flour is mixed with water and/or milk into a dough and
baked at 218 °C for 22–25 min.

Broa is home-baked maize sourdough bread frequently
consumed in Portugal. Sieved maize and rye flours are
mixed (between ca. 15 and 50 %) with water and salt and
the resulting leavened dough from the latest broa is kept as
a starter. The dough is manually kneaded usually for 30
min, after which it is allowed to stand for fermentation to
occur for 1 to 2 h, at room temperature. After proofing the
dough is baked.

Table 2.9 Continued

Food Description Country Reference

© Woodhead Publishing Limited, 2013 Dough Making kenkey involves the production of fermented maize Ghana, West Rooney and Serna-Saldivar,
Fermented meal and further processing into the cooked stiff porridge. Africa 2003; Amoa-Awua et al.,
Kenkey Maize is soaked in water for 12–48 h, ground into dough 2007
and fermented for 2–3 days. A portion of the fermented
Alcoholic corn is half-cooked, blended with the remaining uncooked Serna-Saldivar, 2004;
beverages portion and then moulded into balls and boiled until fully Glover et al., 2005
cooked.
Pito Rooney and Serna-Saldivar,
Maize is soaked in water, drained and held in a moist Nigeria 2003; Serna-Saldivar, 2004
Talla chamber for 5 days of germination. The corn malt is Ethiopia
mashed for 6–10 h, cooled and sieved. Then it is
concentrated and inoculated with starter from a previous
batch and allowed to ferment for 12–36 h by a spontaneous
mixed fermentation involving lactic acid bacteria and
yeasts. Pito is golden-yellow to dark-brown in colour with
taste varying from slightly sweet to very sour and contains
lactic acid, unfermented sugars, amino acids and 2–3 %
alcohol (v/v), as well as vitamins and proteins.

Slurry of toasted, ground and cooked maize is mixed with
flavourings, pieces of freshly baked flat bread/malt,
fermented for several days (5–7) and filtered. Talla has a
smoky flavour and a tan to dark brown colour.

© Woodhead Publishing Limited, 2013 Food Description Country Reference
Munkoyo Zambia Zulu et al., 1997; Rooney
Traditional cereal-based fermented beverage, prepared in
Busas Zambia and the Shaba area in Zaire. Maize kernels Kenya and Serna-Saldivar, 2003
Opaque beer are cooked into porridge and then fermented. The Zambia
Tesguino fermentation is primarily due to lactic acid bacteria and Mexico Rooney and Serna-Saldivar,
yeasts, and occurs at ambient temperatures (25–30 °C) over 2003
24–48 h. The fermented beverage is sweet–sour (pH 3.5),
with less than 5 g ethanol/kg, but becomes more alcoholic Rooney and Serna-Saldivar,
(14–26 g/kg) if it is fermented for a longer period of time. 2003
The beverage is consumed daily by all family members, but
particularly by women and children. Munkoyo beverage Rooney and Serna-Saldivar,
has similarities to mahewu, except that in the preparation 2003
of munkoyo, roots of Eminia, Rhynchosia and Vigna
species are used as the source of amylase instead of wheat
flour and/or sorghum malt which are used as a source of
amylolytic enzymes for the production of mahewu.

Corn flour mixed with water to form dough, held for 4 days,
toasted and fermented for 3–4 days before drinking.

Corn is germinated for 3 days, then the sprouts are dried and
mashed. Corn meal cooked into porridge, mixed with malt,
fermented for 1 or 2 days and consumed while actively
fermenting.

Maize is soaked for 2–3 days, germinated, ground, steeped in
water and fermented until the beverage reaches an alcohol
content of 3–4 %.

98 Cereal grains for the food and beverage industries

alkaline-cooked maize grain, called nixtamal, is then hand-washed and
ground with a stone grinder into a soft dough known as masa. This is then
hand-moulded or pressed into discs which are baked on a griddle. A table
tortilla, made from maize, is thin and puffs out during baking so can be used
as bread. The traditional process for producing nixtamalized flour is a
double-edged sword with the disadvantages of producing contaminating
wastes, having a long processing time, using a lot of water (1.2 m3/tonne of
processed maize) and incurring high energy costs due to the low efficiency
of heat transfer during tortilla baking (Sahai et al., 2001). Different alterna-
tives to traditional nixtamalization processes have been studied (Bazua
et al., 1979; Johnson et al., 1980; Mensah-Agyapong and Horner, 1992;
Martínez-Bustos et al., 2000). Martínez-Montes et al. (2001) and San Martin-
Martinez et al. (2003) efficiently produced tortillas with little water use and
no environmentally deleterious effluents using a selective nixtamalization
process with fractions of the maize grain. Tortilla chips were originally
produced from leftover tortillas that were cut into pieces and fried. Tacos
are soft tortillas wrapped around meat, sauces, beans and other fruits or
vegetables in Mexico. The tacos in the USA, however, are bent into a
U-shape during frying and are filled inside with cheese, refried beans, meat,
sauces, lettuce, tomatoes, peppers, etc. Other masa-based products include
tostados (chalupas), nachos, tamales, atoles (gruel) and pozol, which is a
fermented masa (Duensing et al., 2003; Serna-Saldivar, 2004).

Maize breads
Most maize breads contain wheat flour because maize does not contain the
functional gluten, which gives wheat dough more elasticity and produces a
more aerated and lighter product (Serna-Saldivar, 2004). Broa is a tradi-
tional home-baked maize sourdough bread which is commonly consumed,
especially in the north and central zones of Portugal (Lino et al., 2007;
Rocha and Malcata, 2012). The frequency of domestic bread production
varies, usually every other week during winter, and weekly during summer.
Broa is a bread with a circular to ellipsoidal format, a round top and a flat
base, with a crust of ca 1–2 cm in thickness. The traditional processing
method consists of mixing sieved maize and rye flours (between ca 15 and
50 %) with water, salt and leavened dough from the latest broa batch (which
is kept and passed from batch to batch) serving as a reservoir of adventi-
tious microorganisms with a starter role for fermentation. The dough is
manually kneaded, usually for 30 min, after which it is allowed to stand for
fermentation to occur for 1–2 h, at room temperature. After proofing, the
dough is baked at ca 250 °C for 30 min–3 h (depending on the size of the
dough) (Rocha and Malcata, 2012) and eaten.

Roti
About 35 % of the harvested maize in India is consumed directly as food,
usually in the form of unleavened bread chapatti (roti) that represents a

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Maize 99

staple food for the majority of people living in north Indian states (Sandhu
et al., 2007; Singh et al., 2011). To make roti, cornmeal is kneaded into soft
workable dough with warm water, helping the aggregation of particles due
to partial gelatinization of starch. After mixing, dough is divided into small
balls, which are rounded, flattened and sheeted into circular discs that are
roasted until crisp. After roasting, the roti is coated with butter oil or butter.
In Punjab states of India and Pakistan, roti is traditionally served hot with
Sarson ka saag (mustard leaf gravy) and salad consisting of onion, radish
and lemon (Singh et al., 2011).

Arepas
Arepas (the national maize bread of Venezuela and Colombia) are pre-
pared and consumed by a large proportion of the Venezuelan and Latin
American population, with their popularity increasing in numerous ethnic
restaurants (Alvarez, 1982). Arepas are conventionally produced by adding
salt and water to white corn grits or meal flour, which is mixed into dough
and shaped by hand into flat discs (7–10 cm in diameter) and either baked
or fried until golden brown (Alvarez, 1982). Arepas are stuffed with meat,
cheese, butter and other fillings. Stuffed arepas are also fried to produce
hallaquitas, empanadas and other foods (Serna-Saldivar, 2004).

2.5.2 Corn flakes
Corn flakes are one of the most popular ready-to-eat breakfast cereals in
the world (Fast, 1990). Their production process has remained relatively
unchanged over the past several decades. Corn flakes are produced by two
methods: traditional and extrusion-cooking (indirect method) (Miller, 1988;
Caldwell et al., 1990). In the traditional method, a mixture of de-germed
yellow maize grits, water and flavourings, such as syrup, sugar, malt and salt,
are pressured-cooked. The cooking is completed when the colour of the
grits has changed from chalky-white to light golden brown, the grits have
become soft and translucent and no raw starch remains. The cooked grits
are then dried at 66 °C, tempered to a firm but slightly plastic state, flaked
by passing between rollers and toasted or dried to a final specified moisture
content (Rooney and Serna-Saldivar, 2003; Caldwell and Kadan, 2004).
Before tempering, the cereal is generally treated to restore vitamins lost
through cooking and is often coated with sweet flavourings to make it more
attractive (Sumithra and Bhattacharya, 2008).

Currently, most new breakfast cereals are prepared by continuous extru-
sion. Maize flour or meal is tempered and subsequently combined with
starches, flavourings and colouring agents. These are mixed together by
rotating the extruder screw and are then passed through the heated barrel
to cook. The material is then extruded or forced through the die (mould)
and cut to size. Optionally, a coating is applied using a spray coating drum
to provide the product with a better look and taste or to fortify it with

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100 Cereal grains for the food and beverage industries

vitamins (Caldwell et al., 1990; Fast, 1990). The pellets are dried, tempered,
flaked and toasted as described before. Flakes can easily absorb humidity
which, after having been packed, may result in lower quality or may pose
a health threat through microbial spoilage.

2.5.3 Popcorn
Popcorn is a whole-grain food and represents one of the most popular snack
foods for consumers in a large part of the world (Soylu and Tekkanat, 2007).
Popcorn is a special kind of flint maize that was selected by Indians in early
Western civilizations. The popped grain is used as an ingredient for infant
and other foods (Rooney and Serna-Saldivar, 2003). Expansion volume and
the number of unpopped kernels are the most critical factors determining
the popcorn quality (Song et al., 1991). The expansion volume is a very
important quality criterion commercially, because commercial popcorn
buyers buy by weight and sell the popped corn by volume (Ceylan and
Karababa, 2002). Popping expansion is also a critical parameter to obtain
a good-quality commercial popcorn. Popcorn texture (palatability and ten-
derness and crispness) is positively associated with popping volume (Dofing
et al., 1990). Popcorn’s ability to pop lies in the fact that the kernels contain
a small amount of water stored in a circle of soft starch inside the hard
outer casing. When heated, the water expands, creating pressure (about
8 atm at 177 °C) within the kernel, until eventually the casing gives way, and
the kernels explode and pop, allowing the water to escape as steam, literally
turning the kernels inside out (Hoseney et al., 1983; Goshima et al., 1988).

Low-fat popcorn is a whole-grain food supplying insoluble fibre and less
fat than several commonly consumed grain- or potato-based snack foods.
Nguyen et al. (2011) reported that popcorn can be successfully incorporated
into the diet as a daily snack and is associated with significant improvements
in cardiovascular risk profile. Moreover, Grandjean et al. (2008) suggest that
popcorn may offer a healthful alternative to energy-dense, nutrient-light
snacks, potentially improving the nutrient intake. However, further research
is necessary to confirm beneficial associations between nutrient intakes and
popcorn consumption as well as how its consumption might be used to
achieve recommended nutrient intakes.

2.5.4 Corn oil
Corn oil is characterized by its high levels of vitamin E (tocopherols) and
carotenoids such as lutein and zeaxanthin, which currently receive consider-
able attention as compounds which may play a role in reducing macular
degeneration, an eye disorder (Godber, 2004). Corn oil has been tradition-
ally promoted as an ideal salad and cooking oil, particularly for frying food
due to its palatable flavour stability and a high smoke point. Recent research

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Maize 101

has shown that the oil obtained from maize bran generated during wet
milling contains high levels of plant sterols/stanols and their conjugates, in
particular phytosterol fatty acyl esters, triacylglycerols, tocopherols, free
sterols and ferulate phytosterol esters (Ramjiganesh et al., 2000; Wilson
et al., 2000). The latter fraction includes compounds similar in structure to
those in the ‘oryzanol’ fraction, a generic term given to a group of ferulic
acid esters representing the rice bran oil component that imparts hypocho-
lesterolaemic activity (Kahlon et al., 1992; Rong et al., 1997; Ramjiganesh
et al., 2000; Wilson et al., 2000; Moreau et al., 2002).

2.6 Applications of maize in beverages

Maize can be used to make mahewu in Zimbabwe and to make a variety
of maize beers.

2.6.1 Mahewu
Mahewu (amahewu) is a Zimbabwean beverage (Table 2.9), which is pre-
pared from either thin or thick maize porridge (sadza) (Okagbue, 1995) and
is commonly used to wean children (Simango, 1997). Mahewu is made by
mixing maize meal and water in a ratio of approximately 450 g maize to
3.8 L water, followed by boiling for approximately 1.5 h, cooling, and adding
a small quantity of sorghum, millet malt or wheat flour (about 5 % of the
weight of maize meal). The latter cereal additions serve as source of inocu-
lum and source of growth factors for the spontaneous fermentation that
subsequently takes place at ambient temperature for an extended period
of time (about 36 h). The low initial number of desirable LAB allows the
proliferation of certain undesirable microorganisms which convert lactic
acid to unwanted end-products which adversely affect the taste and texture
of mahewu (Holzapfel, 1991; Steinkraus, 1996). At the end of the fermenta-
tion process, a pH of about 3.5 and titratable acidity of 0.4–0.5 % is normally
recorded.

2.6.2 Alcoholic beverages
Maize beer
In many African countries, maize is traditionally used for making maize
beer. In the process of traditional beer-making, the maize is fermented,
cooked and fermented again. After the second fermentation, the product is
sieved to produce a thick opaque liquid containing solid suspensions. In
South Africa, mainly those with low socioeconomic standards consume this
type of beer because it is readily available and cost-effective (Dlamini
et al., 2009).

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102 Cereal grains for the food and beverage industries

Chicha
Chicha is produced in the Andes regions and sometimes in the lower alti-
tude regions of Ecuador, Brazil, Peru, Bolivia, Colombia and Argentina
(Nicholson, 1960). Chicha is a clear, yellowish, sparkling, alcoholic maize
beverage with a flavour similar to cider, which has been consumed by the
Andes Indians for centuries. Chicha is a unique fermentation in which,
traditionally, saliva serves as the source of amylase for conversion of starch
to fermentation sugars. However, malting of maize kernels to produce the
amylases needed for starch conversion is an alternative procedure that is
widely used today. The principal substrate is maize, particularly sweet corn.
To facilitate introduction of saliva into the maize, the kernel is first dry-
ground. The maize flour is then slightly moistened with water, rolled into a
ball of appropriate size which is popped into the mouth and thoroughly
mixed with saliva, through chewing, for the production of gobs. Alterna-
tively, the maize is germinated. In this process, the kernels are soaked
overnight, then drained and kept moist for about three days. The germi-
nated kernels are then sun-dried. Following drying, gobs, or the germinated
grains, are finely ground and mixed with water and boiled several times with
cooling steps in the middle used to facilitate hulls and starch separation.
The resulting strained liquid is then fermented for one day. The chicha is
ready to drink when the sweetness disappears and the flavour turns semi-
sharp. Brown sugar or molasses may be added at the time of the second
boiling to increase the alcoholic content of the chicha (Nicholson, 1960).

Tesguino
Tesguino is a slurry-like, alcoholic beverage, mainly consumed by the indig-
enous Indian peoples of northern and north-western Mexico, prepared by
fermentation of germinated maize or maize stalk juice. Tesguino, when
diluted with water, is commonly drunk by babies and infants, and is also
drunk at meals during family reunions. For the preparation of tesguino, dry
maize kernels are soaked in water for several days, then drained, and ger-
minated. The germinated kernels are ground and subsequently boiled for
8 h in water until the mixture turns yellow. Catalysts such as bark (batari)
or kakwara (Randia echinocarpa, R. watsoni and R. laevigata) and kaya
(Coutarea pterosperma), which are chopped, ground, and boiled many hours
in advance, may then be added to the tesguino. The mixture has to ferment
in a dark place for two to three days to allow development of a pleasant
appearance and flavour (Taboada and Herrera, 1977).

Talla
Talla is an Ethiopian alcoholic beverage generally served on holidays and
at wedding ceremonies. Maize or mixes of grains are used as raw materials
while barley or wheat malt is used for the conversion of the starch to fer-
mentable sugars. Hops (Rhamunus prionoides) called geisho are added as
a flavouring agent. The smoky flavour originates from the toasted grain. In

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Maize 103

addition, pieces of burned flat bread are also added to the brew (Vogel and
Gobezie, 1977). The severe toasting (burning) incorporated into the talla
production process leads to substantial destruction of protein quality of the
raw materials, thus reducing the nutritional value of the final product.

Busaa
Busaa is an indigenous fermented food which is popular in western Kenya
and is consumed as a refreshing drink. Traditionally, maize flour is mixed
with water to form a stiff dough, which is then incubated for three or four
days at room temperature. The fermented dough is pulverized and toasted.
Roasted maize flour is mixed with water to produce a slurry, then placed in
an earthenware pot. Germinated finger millet flour is added to the slurry
and mixed, and the slurry is then fermented at room temperature for two
or three days.The fermented slurry is filtered and the filtrate, which contains
fine flour particles, is called busaa. The final pH of the busaa is approxi-
mately 3.5. Busaa is characterized by an acidic, alcoholic and roasted flavour,
with a smooth texture (Steinkraus, 1996).

2.7 Conclusions

Maize is one of the three most important crops in the world and is a widely
consumed as a multipurpose crop. Maize production and yield have
dramatically increased in the last decade, mainly due to the genetic improve-
ment of the cereal as well as its adaptation to several different environments
and management systems. Maize kernels contains high levels of starch,
protein, oil and other nutritionally valuable substances, such as vitamins E
and A. Nutrient quantities and bioavailability of maize nutrients are influ-
enced by genetics,growing conditions,antinutrient levels,processing/cooking
procedures and storage environments. Additionally, the ease of processing
of maize allows development of a multitude of foods, with each one being
characterized by its own technological characteristics and qualities.

2.8 Future trends

The global human population is expected to grow from ca. 6 billion people
in the year 2000 to 9 billion by the year 2050 (United Nations Population
Division, 2000). While global production of cereals (the most important
food crops) has increased greatly since the 1960s, the per-capita production
has declined unsteadily since 1984 (FAO/UN, 2012). From 1961 to 2010,
global maize production increased more than three times, from 250 million
tonnes to almost 850 million tonnes (FAO/UN, 2012). The vast majority of
this growth was a result of yield growth which represents the most realistic
option for increasing production in the future. The high productivity of the

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104 Cereal grains for the food and beverage industries

maize crop, the appreciable flavour and taste, and the ease of processing
maize in different foods will ensure that more maize will be used in the
future directly for feed and food consumption. Maize could potentially
meet the required quotient of cereals needed in the near future. However,
potential future adaptations to climate change for maize yields would
require either an increased tolerance of maximum temperatures in existing
maize varieties or a change in the maize varieties grown.

2.9 References

alvarez, r. j. (1982). Microbiological safety of baked and fried arepas. Ecology of
Food and Nutrition, 11, 207–210.

amoa-awua, w. k., ngunjiri, p., anlobe, j., kpodo, k., halm, m., hayford, a. e. and
jakobsen, m. (2007). The effect of applying GMP and HACCP to traditional food
processing at a semi-commercial kenkey production plant in Ghana. Food Control,
18, 1449–1457.

andreasen, m. f., kroon, p. a., williamson, g. and garcia-conesa, m. t. (2001). Ester-
ase activity able to hydrolyze dietary antioxidant hydroxycinnamates is distrib-
uted along the intestine of mammals. Journal of Agricultural and Food Chemistry,
49, 5679–5684.

anselmi, c., centini, m., granata, p., sega, a., buonocore, a., bernini, a. and facino,
r. m. (2004). Antioxidant activity of ferulic acid alkyl esters in a heterophasic
system: A mechanistic insight. Journal of Agricultural and Food Chemistry, 52,
6425–6432.

arámbula, v. g., mauricio, s. r. a., figueroa, c. j. d., gonzález-hernández, j. and
ordorica, f. c. a. (1999). Corn masa and tortillas from extruded instant corn flour
containing hydrocolloids and lime. Journal of Food Science, 64, 120–124.

baldwin, p. m. (2001). Starch granule-associated proteins and polypeptides: a review.
Starch, 53, 475–503.

bazua, c. d., guerra, r. and sterner, h. (1979). Extruded corn flour as an alternative
to lime-heated corn flour for tortilla preparation. Journal of Food Science, 44,
940–941.

bello-perez, l. a. and paredes-lopez, o. (2009). Starches of some food crops, changes
during processing and their nutraceutical potential. Food Engineering Reviews, 1,
50–65.

berenguer, p., santiveri, f., boixadera, j. and lloveras, j. (2009). Nitrogen fertilisa-
tion of irrigated maize under Mediterranean conditions. European Journal of
Agronomy, 30, 163–171.

betran, j., bockholt, a. j. and rooney, l. w. (2000). Blue corn. In: hallauer, a. r.
(ed.) Specialty Corns. Boca Raton, FL: CRC Press.

bily, a. c., burt, a. j., ramputh, a. i., livesey, j., regnault-roger, c., philogène, b. r.
and arnason, j. t. (2004). HPLC-PAD-APCI assay of phenylpropanoids in cereals.
Phytochemical Analysis, 15, 9–15.

blanchard, p. h. (1992). Technology of Corn Wet Milling and Associated Process.
Amsterdam: Elsevier.

bohn, l., meyer, a. and rasmussen, s. (2008). Phytate: impact on environment and
human nutrition. A challenge for molecular breeding. Journal of Zhejiang Uni-
versity – Science B, 9, 165–191.

boyer, c. d. and shannon, c. j. (2003). Carbohydrates of the kernel. In: white, p. j.
and johnson, l. a. (eds.) Corn: Chemistry and Technology (2nd edn). St Paul, MN:
AACC International, Inc.

© Woodhead Publishing Limited, 2013

Maize 105

brites, c. m., trigo, m. j., carrapiço, b., alviña, m. and bessa, r. j. (2011). Maize and
resistant starch enriched breads reduce postprandial glycemic responses in rats.
Nutrition Research, 31, 302–308.

brown, m. d. (1977). Response of maize to environmental temperatures – A review.
Agrometereology of the Maize (Corn) Crop. Geneva: World Metereological
Organization.

burge, r. m. and duensing, w.j. (1989). Processing and dietary fiber ingredient appli-
cation of cereal bran. Cereal Foods World, 34, 537–538.

caldwell, e. f. and kadan, r. s. (2004). CEREALS | Breakfast Cereals. In: wrigley,
c., corke, h. and walker, c. (eds) Encyclopedia of Grain Science. Oxford: Elsevier.

caldwell, e. f., dahl, m. and fast, r. b. (1990). Hot cereals. In: fast, r. b. and
caldwell, e .f. (eds) Breakfast Cereals and How They Are Made. St Paul, MN:
AACC International, Inc.

ceylan, m. and karababa, e. (2002). Comparison of sensory properties of popcorn
from various types and sizes of kernel. Journal of the Science of Food and Agri-
culture, 82, 127–133.

champagne, e. t., wood, d. f., juliano, b. o. and bechtel, d. b. (2004). The rice grain
and its gross composition. In: champagne, e. t. (ed.) Rice: Chemistry and Technol-
ogy (3rd edn). St Paul, MN: AACC International, Inc., 77–107.

corke, h. (2004). Grain, morphology of internal structure. In: wrigley, c., corke, h.
and walker, c. (eds) Encyclopedia of Grain Science. Oxford: Elsevier.

cortés-gómez, a., martín-martínez, e. s., martínez-bustos, f. and vázquez-
carrillo, g. m. (2005). Tortillas of blue maize (Zea mays L.) prepared by a frac-
tionated process of nixtamalization: analysis using response surface methodology.
Journal of Food Engineering, 66, 273–281.

darrah, l. l., macmullen, m. d. and zuber, m. s. (2003). Breeding, genetics, and seed
corn production. In: white, p. j. and johnson, l. a. (eds) Corn: Chemistry and
Technology (2nd edn). St Paul, MN: AACC International, Inc.

de deckere, e. a., kloots, w. j. and van amelsvoort, j. m. (1992). Effects of a diet
with resistant starch in the rat. European Journal of Clinical Nutrition, 46 Suppl
2, S121–122.

de la parra, c., serna saldivar, s. o. and liu, r. h. (2007). Effect of processing on
the phytochemical profiles and antioxidant activity of corn for production of
masa, tortillas, and tortilla chips. Journal of Agricultural and Food Chemistry, 55,
4177–4183.

del pozo-insfran, d., brenes, c. h., serna saldivar, s. o. and talcott, s. t. (2006).
Polyphenolic and antioxidant content of white and blue corn (Zea mays L.) prod-
ucts. Food Research International, 39, 696–703.

delcour, j. a. and hoseney, r. c. (2010). Minor constituents. In: delcour, j. a. and
hoseney, r. c. (eds) Principles of Cereal Science and Technology (3rd edn). St Paul,
MN: AACC International, Inc., 71–85.

delgado, l. (1991). Food aid in Peru: Refusal and acceptance in a peasant com-
munity of the central Andes. Food and Foodways, 5, 57–77.

dhital, s., shrestha, a. k., hasjim, j. and gidley, m. j. (2011). Physicochemical and
structural properties of maize and potato starches as a function of granule size.
Journal of Agricultural and Food Chemistry, 59, 10151–10161.

diaz-ruiz, g., guyot, j. p., ruiz-teran, f., morlon-guyot, j. and wacher, c. (2003).
Microbial and physiological characterization of weakly amylolytic but fast-
growing lactic acid bacteria: A functional role in supporting microbial diversity
in pozol, a Mexican fermented maize beverage. Applied and Environmental
Microbiology, 69, 4367–4374.

dlamini, z., mbita, z. and skhosana, l. (2009). Maize beer carcinogenesis: molecular
implications of fumonisins, aflatoxins and prostaglandins. In: preedy, v. r. (ed.)
Beer in Health and Disease Prevention. San Diego, CA: Academic Press.

© Woodhead Publishing Limited, 2013

106 Cereal grains for the food and beverage industries

dofing, s. m., thomas-compton, m. a. and buck, j. s. (1990). Genotype × popping
method interaction for expansion volume in popcorn. Crop Science, 30, 62–65.

dong, h. z., hou, h. x., liu, c. f. and zhang, h. (2008). Relationships between some
physicochemical properties of starches from maize cultivars grown in East China.
Starch, 60, 305–314.

dowd, m. k. (2003). Improvements to laboratory-scale maize wet-milling procedures.
Industrial Crops and Products, 18, 67–76.

duodu, k. g., nunes, a., delgadillo, i., parker, m. l., mills, e. n. c., belton, p. s. and
taylor, j. r. n. (2002). Effect of grain structure and cooking on sorghum and maize
in vitro protein digestibility. Journal of Cereal Science, 35, 161–174.

duensing, w. j., roskens, a. b. and alexander, r. j. (2003). Corn dry milling: pro-
cesses, products, and applications. In: white, p. j. and johnson, l. a. (eds) Corn:
Chemistry and Technology (2nd edn). St Paul, MN: AACC International, Inc.,
407–447.

earle, f. r. (1977). Protein and oil in corn – variation by crop years from 1907 to
1972. Cereal Chemistry, 54, 70–79.

earle, f., curtis j. j. and hubbard j. e. (1946). Composition of the component parts
of the corn kernel. Cereal Chemistry, 23, 504–511.

eckhoff, s. r. (2004a). MAIZE | Dry Milling. In: wrigley, c., corke, h. and walker,
c. (eds) Encyclopedia of Grain Science. Oxford: Elsevier.

eckhoff, s. r. (2004b). MAIZE | Wet milling. In: Wrigley, c., corke, h. and walker,
c. (eds) Encyclopedia of Grain Science. Oxford: Elsevier.

fao (1992). Food Balance Sheets. Rome: FAO.
fao (1997). White Maize: a Traditional Food Grain in Developing Countries. Rome:

Food and Agriculture Organization of the United Nations; Metico: International
Maize and Wheat Improvement Center. Available at: http://www.fao.org/docrep/
W2698E/W2698E00.htm [accessed November 2012].
fao (2012). Crop Water Information: Maize. Rome: FAO. Available at: http://
www.fao.org/nr/water/cropinfo_maize.html [accessed November 2012].
fao/un (2012). FAOSTAT database: http://faostat3.fao.org/home/index.html.
fao/who (2002). Protein and Amino Acid Requirements in Human Nutrition. WHO
Technical Report Series No.935. Geneva: Joint FAO/WHO/UNU Expert
Consultation.
farnham, d. e., benson, g. o. and pearce, r.b. (2003). Corn perspective and culture.
In: white, p. j. and johnson, c. a. (eds.) Corn: Chemistry and Technology (2nd eds).
St Paul, MN: AACC International, Inc.
fast, r. b. (1990). Manufacturing technology of ready-to-eat cereals. In: fast, r.b. and
caldwell, e. f. (eds.) Breakfast Cereals and How They Are Made. St Paul, MN:
AACC International, Inc.
fimognari, c., berti, f., nüsse, m., cantelli-forti, g. and hrelia, p. (2004). Induction
of apoptosis in two human leukemia cell lines as well as differentiation in human
promyelocytic cells by cyanidin-3-O-β-glucopyranoside. Biochemical Pharmacol-
ogy, 67, 2047–2056.
gadaga, t. h., mutukumira, a. n., narvhus, j. a. and feresu, s. b. (1999). A review of
traditional fermented foods and beverages of Zimbabwe. International Journal of
Food Microbiology, 53, 1–11.
gardner, h. w. and inglett, g. e. (1971). Food products from corn germ: enzyme
activity and oil stability. Journal of Food Science, 36, 645–648.
gargallo, c. j. (2000). La industria de la tortilla en México. Memorias de la 2a. expo-
tortilla México. Retos y avances de la industria frente al nuevo milenio. México:
Asociación de Industriales de la Tortilla.
glover, r. l. k., abaidoo, r. c., jakobsen, m. and jespersen, l. (2005). Biodiversity of
Saccharomyces cerevisiae isolated from a survey of pito production sites in
various parts of Ghana. Systematic and Applied Microbiology, 28, 755–761.

© Woodhead Publishing Limited, 2013

Maize 107

godber, j. s. (2004). Oil from rice and maize. In: wrigley, c., corke, h. and walker,
c. (eds) Encyclopedia of Grain Science. Oxford: Elsevier.

goshima, g., aoyama, h., nishizawa, k. and tsuge, h. (1988). Popping mechanism of
popcorn grain. Journal of the Japanese Society for Food Science and Technology–
Nippon Shokuhin Kagaku Kogaku Kaishi, 35, 147–153.

grandjean, a. c., fulgoni iii, v. l., reimers, k. j. and agarwal, s. (2008). Popcorn
consumption and dietary and physiological parameters of us children and adults:
analysis of the National Health and Nutrition Examination Survey (NHANES)
1999–2002 Dietary Survey Data. Journal of the American Dietetic Association, 108,
853–856.

hamaker, b. r., kirleis, a. w., mertz, e. t. and axtell, j. d. (1986). Effect of cooking
on the protein profiles and in vitro digestibility of sorghum and maize. Journal of
Agricultural and Food Chemistry, 34, 647–649.

hammond, b. g. and jez, j. m. (2011). Impact of food processing on the safety assess-
ment for proteins introduced into biotechnology-derived soybean and corn crops.
Food and Chemical Toxicology, 49, 711–721.

happi emaga, t., robert, c., ronkart, s. n., wathelet, b. and paquot, m. (2008). Dietary
fibre components and pectin chemical features of peels during ripening in banana
and plantain varieties. Bioresource Technology, 99, 4346–4354.

hoebler, c., karinthi, a., chiron, h., champ, m. and barry, j. l. (1999). Bioavailability
of starch in bread rich in amylose: Metabolic responses in healthy subjects and
starch structure. European Journal of Clinical Nutrition, 53, 360–366.

holzapfel, w. h. (1991). Industrialisation of mageu (mahewu) and sorghum beer
fermentation. In: westby, a. and reilly, p. j. a. (eds). Traditional African Foods –
Quality and Nutrition. Proceedings of a Regional Workshop Held at Tanzania.
Stockholm: International Foundation for Science.

hoseney, r. c., zeleznak, k. and abdelrahman, a. (1983). Mechanism of popcorn
popping. Journal of Cereal Science, 1, 43–52.

hu, y.-b., wang, z. and xu, s.-y. (2008). Treatment of corn bran dietary fiber with xyla-
nase increases its ability to bind bile salts, in vitro. Food Chemistry, 106, 113–121.

hurrell, r. f. (2004). Phytic acid degradation as a means of improving iron absorp-
tion. Internation Journal for Vitamin Nutrition and Reseach, 74, 445–452.

hurrell, r. f., reddy, m. b., juillerat, m.-a. and cook, j. d. (2003). Degradation of
phytic acid in cereal porridges improves iron absorption by human subjects. The
American Journal of Clinical Nutrition, 77, 1213–1219.

janick, j. and caneva, g. (2005). The first images of maize in Europe. Maydica, 50,
71–80.

jellum, m. d., boswell, f. c. and young, c. t. (1973). Nitrogen and boron effects on
protein and oil of corn grain. Agronomy Journal, 65, 330–331.

jenkins, d. j. a., vuksan, v., kendall, c. w. c., würsch, p., jeffcoat, r., waring, s.,
mehling, c. c., vidgen, e., augustin, l. s. a. and wong, e. (1998). Physiological
effects of resistant starches on fecal bulk, short chain fatty acids, blood lipids and
glycemic index. Journal of the American College of Nutrition, 17, 609–616.

johnson, l. a. and may, j. b. (2003). Wet milling: the basis for corn biorefineries. In:
white, p. j. and johnson, l. a. (eds) Corn: Chemistry and Technology. St Paul, MN:
AACC Internation, Inc.

johnson, g. j. (2000). Corn: the major cereal of the Americas. In: kucd, k. and ponte,
j. g. (eds.) Handbook of Cereal Science and Technology (2nd edn). New York:
Marcel Dekker.

johnson, b. a., rooney, l. w. and khan, m. n. (1980). Tortilla-making characteristics
of micronized sorghum and corn flours. Journal of Food Science, 45, 671–674.

kahlon, t. s., chow, f. i., sayre, r. n. and betschart, a. a. (1992). Cholesterol-lowering
in hamsters fed rice bran at various levels, defatted rice bran and rice bran oil.
Journal of Nutrition, 122, 513–519.

© Woodhead Publishing Limited, 2013

108 Cereal grains for the food and beverage industries

kasemsuwan, t. and jane, j. l. (1996). Quantitative method for the survey of starch
phosphate derivatives and starch phospholipids by P-31 nuclear magnetic reso-
nance spectroscopy. Cereal Chemistry, 73, 702–707.

kent, n. l. and evers, a. d. (1994a). Botanical aspects of cereals. In: kent, n. l. and
evers, a. d. (eds) Kent’s Technology of Cereals (4th edn). Oxford: Pergamon.

kent, n. l. and evers, a. d. (1994b). Kent’s Technology of Cereals (4th edn). Oxford:
Pergamon.

khoi, b. h., dien, l. d., lásztity, r. and salgó, a. (1987). The protein and the amino
acid composition of some rice and maize varieties grown in North Vietnam.
Journal of the Science of Food and Agriculture, 39, 137–143.

kies, c., kan, s., fox, h.m. (1984). Vitamin B-6 availability from wheat, rice, and corn
brans for humans. Nutrition Reports International, 30, 483–491.

kim, w. k., chung, m. i. k., kang, n. e., kim, m. h. and park, o. j. (2003). Effect of resistant
starch from corn or rice on glucose control, colonic events, and blood lipid con-
centrations in streptozotocin-induced diabetic rats. The Journal of Nutritional
Biochemistry, 14, 166–172.

kopsell, d. a., armel, g. r., mueller, t. c., sams, c. e., deyton, d. e., mcelroy, j. s. and
kopsell, d. e. (2009). Increase in nutritionally important sweet corn kernel carot-
enoids following mesotrione and atrazine applications. Journal of Agricultural and
Food Chemistry, 57, 6362–6368.

lee, e. a. (2004). MAIZE | Genetics. In: wrigley, c., corke, h. and walker, c. (eds)
Encyclopedia of Grain Science. Oxford: Elsevier.

li, j. s. and vasal, s. k. (2004). MAIZE | Quality protein maize. In: wrigley, c., corke,
h. and walker, c. (eds) Encyclopedia of Grain Science. Oxford: Elsevier.

lim, s. t., kasemsuwan, t. and jane, j. l. (1994). Characterization of phosphorus in
starch by P-31-nuclear magnetic-resonance spectroscopy. Cereal Chemistry, 71,
488–493.

lino, c. m., silva, l. j. g., pena, a., fernández, m. and mañes, j. (2007). Occurrence of
fumonisins B1 and B2 in broa, typical Portuguese maize bread. International
Journal of Food Microbiology, 118, 79–82.

loy, d. d. and wright, k. (2003). Nutritional properties and feeding value of corn and
its by-products. In: white, p. j. and johnson, l. a. (eds) Corn: Chemistry and Tech-
nology. St Paul, MN: AACC International, Inc.

marshall, j. j. and whelan, w. j. (1974). Multiple branching in glycogen and amylo-
pectin. Archives of Biochemistry and Biophysics, 161, 234–238.

martínez-bustos, f., garcía, m. n., chang, y. k., sánchez-sinencio, f. and figueroa,
c. j. d. (2000). Characteristics of nixtamalised maize flours produced with the use
of microwave heating during alkaline cooking. Journal of the Science of Food and
Agriculture, 80, 651–656.

martínez-montes, j. d. l., sánchez-sinencio, f., ruiz, m. t. and martínez-bustos,
f. (2001). Selective nixtamalization process for the production of fresh whole corn
dough, nixtamalized corn flour and derived products. US Patent 6,265,013.

matsumoto, m., hara, h., chiji, h. and kasai, t. (2004). Gastroprotective effect of red
pigments in black chokeberry fruit (Aronia melanocarpa Elliot) on acute gastric
hemorrhagic lesions in rats. Journal of Agricultural and Food Chemistry, 52,
2226–2229.

matthiole, p. a. (1579). Commentaires sur les six livres de Dioscoride. Lyon:
G, Rouille.

mbugua, s. k. and njenga, j. (1992). The antimicrobial activity of fermented uji.
Ecology of Food and Nutrition, 28, 191–198.

méndez-montealvo, g, solorza-feria, j., velázquez del valle m., gomez-montiel,
n., parede-lopez, o., bello-perez, c. a. (2005). Chemical composition and calori-
metric characterization of hybrids and varieties of maize cultivated in Mexico
Agrociencia, 39, 267–274

© Woodhead Publishing Limited, 2013

Maize 109

méndez-montealvo, g., sanchez-rivera, m. m., paredes-lopez, o. and bello-perez,
l. a. (2006). Thermal and rheological properties of nixtamalized maize starch.
International Journal of Biological Macromolecules, 40, 59–63.

mensah-agyapong, j. and horner, w. f. a. (1992). Nixtamalisation of maize (Zea mays
L) using a single screw cook-extrusion process on lime-treated grits. Journal of
the Science of Food and Agriculture, 60, 509–514.

mertz, e. (1970). Nutritive value of corn and its products. In: inglett, g. (ed.) Corn:
Culture, Processing, Products. Westport, CT: AVI.

mertz, e. t., nelson, o. e. and bates, l. s. (1964). Mutant gene that changes protein
composition + increases lysine content of maize endosperm. Science, 145,
279–280.

milán-carrillo, j., gutiérrez-dorado, r., cuevas-rodríguez, e. o., garzón-tiznado,
j. a. and reyes-moreno, c. (2004). Nixtamalized flour from quality protein maize
(Zea mays L). optimization of alkaline processing. Plant Foods for Human Nutri-
tion (formerly Qualitas Plantarum), 59, 35–44.

miller, r. c. (1988). Continuous cooking of breakfast cereals. Cereal Foods World,
33, 284.

moreau, r. a., whitaker, b. d. and hicks, k. b. (2002). Phytosterols, phytostanols, and
their conjugates in foods: structural diversity, quantitative analysis, and health-
promoting uses. Progress in Lipid Research, 41, 457–500.

morrison, w. r. (1978). Wheat lipid-composition. Cereal Chemistry, 55, 548–558.
morrison, w. r. and milligan, t. p. (1982). Lipids in maize starch. In: inglett, g. e.

(ed.) Recent Progress in Chemistry and Technology. New York: Academic
Press.
morrison, w. r., milligan, t. p. and azudin, m. n. (1984). A relationship between the
amylose and lipid contents of starches from diploid cereals. Journal of Cereal
Science, 2, 257–271.
mu-forster, c. and wasserman, b. p. (1998). Surface localization of zein storage
proteins in starch granules from maize endosperm. Proteolytic removal by ther-
molysin and in vitro cross-linking of granule-associated polypeptides. Plant Physi-
ology, 116, 1563–1571.
mu-forster, c., huang, r., powers, j. r., harriman, r. w., knight, m., singletary, g. w.,
keeling, p. l. and wasserman, b. p. (1996). Physical association of starch biosyn-
thetic enzymes with starch granules of maize endosperm. Granule-associated
forms of starch synthase I and starch branching enzyme II. Plant Physiology, 111,
821–829.
musser, s. m. and plattner, r. d. (1997). Fumonisin composition in cultures of
Fusarium moniliforme, Fusarium proliferatum, and Fusarium nygami. Journal of
Agricultural and Food Chemistry, 45, 1169–1173.
nago, m., akissoe, n., matencio, f. and mestres, c. (1997). End use quality of some
African corn kernels .1. Physicochemical characteristics of kernels and their rela-
tionship with the quality of “Lifin’’, a traditional whole dry-milled maize flour
from Benin. Journal of Agricultural and Food Chemistry, 45, 555–564.
nago, m. c., hounhouigan, j. d., akissoe, n., zanou, e. and mestres, c. (1998). Char-
acterization of the Beninese traditional ogi, a fermented maize slurry: physico-
chemical and microbiological aspects. International Journal of Food Science and
Technology, 33, 307–315.
naguleswaran, s. l., j., vasanthan, t. and bressler, d. (2011). Distribution of granule
channels, protein, and phospholipid in triticale and corn starches as revealed by
confocal laser scanning microscopy. Cereal Chemistry, 88, 87–94.
nguyen, v., kawiecki, d., pardo, s., papadopoulos, t., cooper, l., lowther, b.,
lowndes, j., angelopoulos, t. and rippe, j. (2011). A daily popcorn snack improves
cardiovascular disease risk profile. Journal of the American Dietetic Association,
111, A95.

© Woodhead Publishing Limited, 2013

110 Cereal grains for the food and beverage industries

nicholson, g. e. (1960). Chicha maize types and chicha manufacture in Peru. Eco-
nomic. Botany, 14, 290–299.

noda, t., takahata, y., sato, t., suda, i., morishita, t., ishiguro, k. and yamakawa, o.
(1998). Relationships between chain length distribution of amylopectin and gela-
tinization properties within the same botanical origin for sweet potato and buck-
wheat. Carbohydrate Polymers, 37, 153–158.

nuss, e. t. and tanumihardjo, s. a. (2010). Maize: a paramount staple crop in the
context of global nutrition. Comprehensive Reviews in Food Science and Food
Safety, 9, 417–436.

oikeh, s. o., menkir, a., maziya-dixon, b., welch, r. and glahn, r. p. (2003). Genotypic
differences in concentration and bioavailability of kernel-iron in tropical maize
varieties grown under field conditions. Journal of Plant Nutrition, 26, 2307–2319.

okagbue, r. n. (1995). Microbial biotechnology in Zimbabwe: current status and
proposals for research and development. Journal of Applied Science in Southern
Africa, 1, 148–158.

onyango, c., henle, t., hofmann, t. and bley, t. (2004). Production of high energy
density fermented uji using a commercial alpha-amylase or by single-screw extru-
sion. Lebensmittel Wissenschaft Und Technologie, 37, 401–407.

ortiz-monasterio, j. i., palacios-rojas, n., meng, e., pixley, k., trethowan, r. and
peña, r. j. (2007). Enhancing the mineral and vitamin content of wheat and maize
through plant breeding. Journal of Cereal Science, 46, 293–307.

osborne, t. b. (1924). The Vegetable Proteins. New York: Longmans Green and Co.
otegui, m. e., andrade, f. h. and suero, e. e. (1995). Growth, water use, and kernel

abortion of maize subjected to drought at silking. Field Crops Research, 40,
87–94.
paredes-lòpez, o. and saharopulos-paredes, m. (1983). A review of tortilla produc-
tion technology. Bakers Digest, 13, 16–25.
perales r, h., brush, s. and qualset, c. (2003). Dynamic management of maize
landraces in central Mexico. Economic Botany, 57, 21–34.
phillips, j., muir, j. g., birkett, a., lu, z. x., jones, g. p., o’dea, k. and young, g. p.
(1995). Effect of resistant starch on fecal bulk and fermentation-dependent events
in humans. American Journal of Clinical Nutrition, 62, 121–130.
piperno, d. r., ranere, a. j., holst, i., iriarte, j. and dickau, r. (2009). Starch grain
and phytolith evidence for early ninth millennium B.P. maize from the Central
Balsas River Valley, Mexico. Proceedings of the National Academy of Sciences,
106, 5019–5024.
pomeranz, y. (1987). Modern Cereal Science and Technology. Weinheim: VCH.
prasanna, b. m., vasal, s. k., kassahun, b. and singh, n. n. (2001). Quality protein
maize. Current Science, 81, 1308–1319.
raboy, v. (2003). myo-Inositol-1,2,3,4,5,6-hexakisphosphate. Phytochemistry, 64,
1033–1043.
ramirez, e. c., johnston, d. b., mcaloon, a. j., yee, w. and singh, v. (2008). Engineering
process and cost model for a conventional corn wet milling facility. Industrial
Crops and Products, 27, 91–97.
ramjiganesh, t., roy, s., nicolosi, r. j., young, t. l., mcintyre, j. c. and fernandez, m.
l. (2000). Corn husk oil lowers plasma LDL cholesterol concentrations by
decreasing cholesterol absorption and altering hepatic cholesterol metabolism in
guinea pigs. Journal of Nutritional Biochemistry, 11, 358–366.
ranere, a. j., piperno, d. r., holst, i., dickau, r. and iriarte, j. (2009). The cultural
and chronological context of early Holocene maize and squash domestication in
the Central Balsas River Valley, Mexico. Proceedings of the National Academy of
Sciences, 106, 5014–5018.
reiners, r. a. and gooding, c. m. (1970). Corn oil. In: inglett, g. (ed.) Corn: Culture,
Processing, Products. Westport, CT: AVI.

© Woodhead Publishing Limited, 2013

Maize 111

reinhold, j. g., garcia, j. s. and garzon, p. (1981). Binding of iron by fiber of wheat
and maize. American Journal of Clinical Nutrition, 34, 1384–1391.

rendon-villalobos, r., bello-perez, l. a., osorio-diaz, p., tovar, j. and paredes-
lopez, o. (2002). Effect of storage time on in vitro digestibility and resistant starch
content of nixtamal, masa, and tortilla. Cereal Chemistry, 79, 340–344.

revilla, p., soengas, p., cartea, m. e., malvar, r. a. and ordas, a. (2003). Isozyme
variability among European maize populations and the introduction of maize in
Europe. Maydica, 48, 141–152.

revy, p. s., jondreville, c., dourmad, j. y. and nys, y. (2006). Assessment of dietary
zinc requirement of weaned piglets fed diets with or without microbial phytase.
Journal of Animal Physiology and Animal Nutrition, 90, 50–59.

ritchie, s. w. (1993). How a Corn Plant Develops. Ames, IA: Iowa State University
of Science and Technology Cooperative Extension Service.

robles, r. r., murray, e. d. and paredeslopez, o. (1988). Physicochemical changes of
maize starch during the lime-heat treatment for tortilla making. International
Journal of Food Science and Technology, 23, 91–98.

rocha, j. m. and malcata, f. x. (2012). Microbiological profile of maize and rye flours,
and sourdough used for the manufacture of traditional Portuguese bread. Food
Microbiology, 31, 72–88.

romo, m., mize, c. and warfel, k. (2008). Addition of Hi-maize, natural dietary
fiber, to a commercial cake mix. Journal of the American Dietetic Association,
108, A76.

rong, n., ausman, l. m. and nicolosi, r. j. (1997). Oryzanol decreases cholesterol
absorption and aortic fatty streaks in hamsters. Lipids, 32, 303–309.

rooney, l. w. and serna-saldivar, s. o. (2003). Food use of whole corn and dry-milled
fractions. In: white, p. j. and johnson, l. a. (eds.) Corn: Chemistry and Technology
(2nd edn). St Paul, MN: AACC, Inc.

sahai, d., mua, j. p., surjewan, i., buendia, m. o., rowe, m. and jackson, d. s. (2001).
Alkaline processing (nixtamalization) of white Mexican corn hybrids for tortilla
production: significance of corn physicochemical characteristics and process con-
ditions. Cereal Chemistry Journal, 78, 116–120.

sajilata, m. g., singhal, r. s. and kulkarni, p. r. (2006). Resistant starch–a review.
Comprehensive Reviews in Food Science and Food Safety, 5, 1–17.

san martín-martínez, e., jaime-fonseca, m. r., martínez-bustos, f. and martínez-
montes, j. l. (2003). Selective nixtamalization of fractions of maize grain (Zea
mays L.) and their use in the preparation of instant tortilla flours analyzed using
response surface methodology. Cereal Chemistry, 80, 13–19.

sandhu, k. s., singh, n. and malhi, n. s. (2007). Some properties of corn grains and
their flours I: Physicochemical, functional and chapati-making properties of flours.
Food Chemistry, 101, 938–946.

sandstead, h. h., munoz, j. m., jacob, r. a., klevay, l. m., reck, s. j., logan, g. m.,
dintzis, f. r., inglett, g. e. and shuey, w. c. (1978). Influence of dietary fiber
on trace-element balance. American Journal of Clinical Nutrition, 31, S180–
S184.

saunders, r. m., walker, h. g. and kohler, g. o. (1969). Aleurone cells and the digest-
ibility of wheat mill feeds. Poultry Science, 48, 1497–1503.

serna-saldivar, s. o. (2004). MAIZE | Foods from maize. In: wrigley, c., corke, h.
and walker, c. (eds) Encyclopedia of Grain Science. Oxford: Elsevier.

simango, c. (1997). Potential use of traditional fermented foods for weaning in
Zimbabwe. Social Science Medicine, 44, 1065–1068.

singh, b. r. and singh, d. p. (1995). Agronomic and physiological responses of
sorghum, maize and pearl millet to irrigation. Field Crops Research, 42, 57–67.

singh, n., singh, s. and shevkani, k. (2011). Maize: composition, bioactive constitu-
ents, and unleavened bread. In: perry, v., watson, r. s. and patel, v. b. (eds) Flour

© Woodhead Publishing Limited, 2013

112 Cereal grains for the food and beverage industries

and Breads and their Fortification in Health and Disease Prevention. San Diego,
CA: Academic Press.
singh, m., liu, s. x. and vaughn, s. f. (2012). Effect of corn bran as dietary fiber addi-
tion on baking and sensory quality. Biocatalysis and Agricultural Biotechnology,
1, 348–352.
song, a., eckhoff, s. r., paulsen, m. and litchfield, j. b. (1991). Effects of kernel size
and genotype on popcorn popping volume and number of unpopped kernels.
Cereal Chemistry, 68, 464–467.
south, j. b., morrison, w. r. and nelson, o. e. (1991). A relationship between the
amylose and lipid contents of starches from various mutants for amylose content
in maize. Journal of Cereal Science, 14, 267–278.
soylu, s. and tekkanat, a. (2007). Interactions amongst kernel properties and expan-
sion volume in various popcorn genotypes. Journal of Food Engineering, 80,
336–341.
sriperm, n., pesti, g. m. and tillman, p. b. (2010). The distribution of crude protein
and amino acid content in maize grain and soybean meal. Animal Feed Science
and Technology, 159, 131–137.
steinkraus, k. h. (1996). Handbook of Indigenous Fermented Foods (2nd edn). New
York: Marcel Dekker.
sugawara, m., suzuki, t., totsuka, a., takeuchi, m. and ueki, k. (1994). Composition
of corn hull dietary fiber – Zusammensetzung der Rohfaser von Maisschalen.
Starch, 46, 335–337.
sumithra, b. and bhattacharya, s. (2008). Toasting of corn flakes: Product charac-
teristics as a function of processing conditions. Journal of Food Engineering, 88,
419–428.
taboada, j. m. u. and herrera, t. (1977). Microbiological studies on tesguino, a fer-
mented maize beverage consumed in Northern and Central Mexico. In: Sympo-
sium on Indigenous Fermented Foods, 21–27 November Bangkok.
tan, s. and morrison, w. (1979). The distribution of lipids in the germ, endosperm,
pericarp and tip cap of amylomaize, LG-11 hybrid maize and waxy maize. Journal
of the American Oil Chemists’ Society, 56, 531–535.
tenaillon, m. i. and charcosset, a. (2011). A European perspective on maize history.
Comptes Rendus Biologies, 334, 221–228.
thacher, t. d., aliu, o., griffin, i. j., pam, s. d., o’brien, k. o., imade, g. e. and abrams,
s. a. (2009). Meals and dephytinization affect calcium and zinc absorption in
Nigerian children with rickets. The Journal of Nutrition, 139, 926–932.
trombino, s., serini, s., di nicuolo, f., celleno, l., andò, s., picci, n., calviello, g. and
palozza, p. (2004). Antioxidant effect of ferulic acid in isolated membranes and
intact cells: Synergistic Interactions with α-Tocopherol, β-Carotene, and Ascorbic
Acid. Journal of Agricultural and Food Chemistry, 52, 2411–2420.
united nations population division. (2000). World Population Prospects the 2000
Revision Highlights. New York: Population Division, Department of Economic
and Social Affairs, United Nations.
usda/ars (2012). USDA National Nutrient Database for Standard Reference, Release
25. Nutrient Data Laboratory Home Page, http://www.ars.usda.gov/ba/bhnrc/ndl
[accessed December 2012].
vanara, f., reyneri, a. and blandino, m. (2009). Fate of fumonisin B1 in the process-
ing of whole maize kernels during dry-milling. Food Control, 20, 235–238.
vasal, s. (2000).Quality protein maize story. Food and Nutrition. Bulletin, 21,
445–450.
vivas, n. e., waniska, r. d. and rooney, l. w. (1987). Thin porridges (atole) prepared
from maize and sorghum. Cereal Chemistry, 64, 390–394.
vogel, s. and gobezie, a. 1977. Ethiopian tej. In: Symposium on Indigenous
Fermented Foods, 21–27 November, Bangkok.

© Woodhead Publishing Limited, 2013

Maize 113

wang, s. and liu, f. (2000). The preparation, property and application of a highly
active corn dietary fiber. Food Science, 21, 22–24.

watson, s. a. (2003). Description, development, structure, and composition of the
corn kernel. In: white, p. j. and johnson, l. a. (eds) Corn: Chemistry and Technol-
ogy (2nd edn). St Paul, MN: AACC International, Inc.

wayne, s. c. (1995). Corn, cultivar developed in the United States. In: wayne, s. c.
(ed.) Crop Production, Evolution, History and Technology. Hoboken, NJ: Wiley.

weber, c. w., kohlhepp, e. a., idouraine, a. and ochoa, l. j. (1993). Nutritional com-
position of tamales and corn and wheat tortillas. Journal of Food Composition
and Analysis, 6, 324–335.

white, p. j. (2003). Lipids of the kernel. In: white, p. j. and johnson, l. a. (eds) Corn:
Chemistry and Technology (2nd edn). St Paul, MN: AACC International, Inc.

white, p. j. and johnson, l. a. (2003). Corn: Chemistry and Technology. (2nd edn). St
Paul, MN: AACC International, Inc.

wilkinson, r. and hardcastle, w. (1973). Commercial herbicide influence on corn-
oil composition. Weed Science, 21, 433–436.

wilkinson, r. and hardcastle, w. (1974). Influence of herbicide mixtures on corn-oil
quantity and composition. Canadian Journal of Plant Science, 54, 471–473.

wilson, t. a., desimone, a. p., romano, c. a. and nicolosi, r. j. (2000). Corn fiber oil
lowers plasma cholesterol levels and increases cholesterol excretion greater than
corn oil and similar to diets containing soy sterols and soy stanols in hamsters.
The Journal of Nutritional Biochemistry, 11, 443–449.

yuan, r. c., thompson, d. b. and boyer, c. d. (1993). Fine-structure of amylopectin in
relation to gelatinization and retrogradation behavior of maize starches from 3
Wx-containing genotypes in 2 inbred lines. Cereal Chemistry, 70, 81–89.

zannini, e., jones, j. m., renzetti, s. and arendt, e. k. (2012). Functional replacements
for gluten. Annual Review of Food Science and Technology, 3, 227–245.

zarkadas, c. g., yu, z. r., hamilton, r. i., pattison, p. l. and rose, n. g. w. (1995).
Comparison between the protein-quality of northern adapted cultivars of common
maize and quality protein maize. Journal of Agricultural and Food Chemistry, 43,
84–93.

zulu, r. m., dillon, v. m. and owens, j. d. (1997). Munkoyo beverage, a traditional
Zambian fermented maize gruel using Rhynchosia root as amylase source. Inter-
national Journal of Food Microbiology, 34, 249–258.

© Woodhead Publishing Limited, 2013

Pericarp

Aleurone layer

Proteins

Starch granules

Plate I Confocal laser scanning microscope (CLSM) micrograph of the aleurone
layer and endosperm of wheat kernel, stained with three fluorescence dyes: red:

proteins, yellow: cell walls, green: starch granules; magnification = 40×.

50.0 µm
Plate II Confocal laser scanning microscope (CLSM) micrograph section of the
maize kernel showing starch storage granules stained with fluorescein isothiocya-

nate (FITC) for starch (green) and rhodamin B for protein (red).

© Woodhead Publishing Limited, 2013

A
P

FE
CE

200.0 µm
Plate III Confocal laser scanning microscope (CLSM) micrograph endosperm
section showing the corneous endosperm (CE), the floury endosperm (FE), peri-
carp (P) and aleurone layer (A) of the kernel. Starch storage granules stained
with fluorescein isothiocyanate (FITC) for starch (green) and rhodamin B for

protein (red).

100.0 µm
Plate IV Confocal laser scanning microscope (CLSM) micrograph section of the
barley endosperm with starch storage granules stained with fluorescein isothiocya-

nate (FITC) for starch (green) and with rhodamin B for protein (red).
© Woodhead Publishing Limited, 2013

3

Rice

DOI: 10.1533/9780857098924.114

Abstract: Rice (Oriza sativa L.) is the staple food for nearly two-thirds of the
world’s population. In 2010, China, India, Indonesia, Bangladesh, Vietnam and
Myanmar alone provided more than 75 % of the world’s total rice production.
Rice has the lowest protein content of all the cereals; however, rice protein is
highly nutritious and has one of the highest lysine contents among the cereals.
Rice is rich in starch, low in fibre and has no detectable levels of vitamins A, C or
D. Rice is consumed in the form of noodles, puffed rice, fermented sweet rice and
snack foods produced by extrusion cooking. It is used for making bakery
products, sauces, infant foods, breakfast cereals, alcoholic beverages and vinegar.
Continuing population growth and consequent rice consumption increases will
mean that the global demand for rice will expand significantly in the near future.
An integrated approach that involves more efficient and environmentally
sustainable agricultural practices, pest management and the development of new
rice varieties adapted to country-specific farming conditions suitable for a
changing climate should be vigorously pursued.

Key words: rice, chemical composition, rice utilization in food and beverages.

3.1 Introduction

Rice (Oriza sativa L.) is the leading food crop in the developing world in
terms of total world production (672 × 106 tonnes) (FAO/UN, 2012). It
represents the staple food for almost two-thirds of the world’s population
(Roy et al., 2011).

Rice provides 21 % of global human per capita energy and 15 % of per
capita protein (Maclean et al., 2002; Guimarães, 2009). However, the world’s
stocks of stored rice grain have been falling in negative correlation to each
year’s consumption levels which now exceeds actual annual production
(Shiina and Global, 2010). Rice is generally considered a semi-aquatic
annual grass plant, which can be grown under a broad range of climatic
conditions (Yoshida, 1981). Cultivated rice belongs to the species O. sativa
and O. glaberrima. While O. sativa is the predominant species, O. galber-
rima is cultivated on a limited scale and only in Africa. The major rice

© Woodhead Publishing Limited, 2013

Rice 115

producers in 2010 were China, India, Indonesia, Bangladesh, Vietnam and
Myanmar producing alone more than 75 % (506 × 106 tonnes) of the world
production. Rice grain (rough rice or paddy) comprises the edible rice
caryopsis of fruit (brown, dehulled or dehusked rice) enclosed in a protec-
tive covering, the hull (husk). During the milling process, rough rice is
milled to produce polished edible grain by first subjecting to dehusking and
then to the removal of brownish outer bran layer known as whitening.
Finally, polishing is carried out to remove the bran particles and provides
surface gloss to the edible white portion.

The way rice is generally consumed differs from its major food-crop rela-
tives. Wheat and barley are mostly consumed after the grain is ground to
flour. Rice is primarily consumed as polished grain; however, a small amount
of the rice crop is used to make ingredients for processed foods and as
animal feed. Rice flour possesses unique attributes, such as a bland taste,
white colour, ease of digestion and hypoallergenic properties (Kadan et al.,
2001). Rice is consumed in the form of noodles, puffed rice, fermented sweet
rice and snack foods made by extrusion cooking (Mercier et al., 1989). It is
used for producing bread, cakes, cookies (alone or blended with wheat) and
canned foods, and for the production of alcoholic beverages or as an adjunct
in their production, for example beer. Furthermore, the low levels of sodium,
absence of gliadin and presence of easily digested carbohydrates have made
rice one of the most suitable cereal grain flours for the preparation of foods
for coeliac patients (Zannini et al., 2012).

3.1.1 History, production, price, yield and area
The genus Oryza, named by Linnaeus in 1753, originated in the Gondwa-
naland continent and, following the fracture of the supercontinent, became
widely distributed in the humid tropics of Africa, South America, South and
Southeast Asia and Oceania (Chang, 1976). The date and the geographical
location of rice domestication have long been a subject of debate. Indeed,
it is also widely recognized that domestication is not a single ‘event’, but
rather a dynamic evolutionary process that occurs over time and, in some
species, continues to this day (Gepts, 2010). The most ancient archaeological
finds, in the Yangzi delta in China, date back to 5000 BC (Latham, 1998).
Historical records suggest multiple domestications for rice (O. sativa)
(Kovach et al., 2007) between 2000 and 1500 BC in areas including central
India, northern Burma, northern Thailand, Laos, Vietnam and into south-
east China (Chang, 1976). In India, the earliest known remains of rice are
dated around 1500 BC. In Japan, rice seems to have been introduced from
the Yangzi region around 400 BC (Latham, 1998). From this broad area, the
cultivation of rice extended to Indonesia, the Philippines and northern
Australia. Subsequently, traders spread the grain throughout Asia, the
Middle East and Europe (Marshall et al., 1994). In North and South America,
rice was introduced relatively recently with the first official documentation

© Woodhead Publishing Limited, 2013

116 Cereal grains for the food and beverage industries

Table 3.1 Rice and total cereal grain production and producer price in the world
from 2000–2010

Year Total rice Total cereal Rice as Area rice Rice Producer price
production % of total harvested yield (US $/tonnes)
(Mt) production grains (Mha) (t/ha)
(Mt)a

2000 599.3 2044 29.3 154.0 3.9 298.99
2001 599.8 2093
2002 571.3 2077 28.7 151.9 3.9 294.28
2003 587.0 2260
2004 607.9 2247 27.5 147.6 3.9 285.51
2005 634.3 2219
2006 641.2 2335 26.0 148.5 4.0 314.85
2007 657.1 2503
2008 689.0 2470 27.1 150.5 4.0 342.73
2009 684.7 2472
2010 672.0 2412 28.6 154.9 4.1 367.91
Average 631.2 2285
27.5 155.2 4.1 394.70

26.3 154.9 4.2 431.74

27.9 157.6 4.4 513.30

27.7 158.3 4.3 494.54

27.9 153.6 4.4 –

27.6 153.4 4.1 373.85

aTotal cereal production includes corn, rice, wheat, barley, sorghum, millet, oats, rye, mixed
grain.
Source: Data from FAO/UN (2012).

of rice as a commercial crop dated 1686 (Dethloff, 1982). Nowadays, rice is
grown in every continent (except Antarctica), in over 100 countries from
53° north to 40° south, and from sea level to an altitude of 3000 m (Childs,
2004).

In 2010, the production of rice approached that of wheat (Table 3.1) with
672.0 × 106 tonnes (FAO/UN, 2012) produced worldwide. Rice and wheat
represent the two most important food grains, since corn is mainly used as
feed grain, except in South America and parts of Asia. Depending on the
climate, soil condition, variety, agricultural practices and other conditions,
rice yields can range from 0.7 to 10.8 tonnes/ha (FAO/UN, 2012). Nowa-
days, rice yields worldwide tend to be higher than 4 tonnes/ha on average
(FAO/UN, 2012) (Table 3.1). Rice is cultivated in 114 countries and China
is currently, and has historically been, the world’s leading rice-producer.
Table 3.2 lists the top 10 rice-producing countries, over the five-year period
2006–2010.

Among the top 10 rice-producing countries, China contributed, during
the period 2006–2010, 28.6 % of the world’s rice production from 18.9 % of
the world’s rice-growing area, while India contributed 20.5 % of the produc-
tion from 27 % of the area. China produces a larger amount of rice than
India (191.5 compared to 37.3 million tonnes per year, 2006–2010) but from
almost 30 % less rice cultivation area (29.5 comparing to 42.0 million ha per
year, 2006–2010). This is mainly due to the high rice yield registered in

© Woodhead Publishing Limited, 2013

Rice 117

Table 3.2 Rice production estimates in the 10 leading-producing countries; five-
year average 2006–2010

Rank Country Production Area harvested Rice yield World

(Mt) (Mha) (t/ha) production (%)

1 China 191.5 29.5 6.5 28.6
2 India 137.3 42.0 3.3 20.5
3 Indonesia 60.5 12.4 4.9 9.0
4 Bangladesh 11.1 4.1
5 Viet Nam 45.5 7.3 5.2 6.8
6 Myanmar 37.8 8.00 4.0 5.7
7 Thailand 32.1 10.7 2.9 4.8
8 Philippines 31.4 3.7 4.7
9 Brazil 16.0 4.3 4.2 2.4
10 Japan 11.7 2.8 6.7 1.7
Total 10.7 1.6 4.5a 1.6
574.5 129.7 85.8

aAverage of rice yield among the 10 leading producing countries.
Source: Data from FAO/UN (2012).

China (6.5 tonnes/ha), second only to Japan with 6.7 tonnes/ha (FAO/UN,
2012) (Table 3.2). Throughout the last 10 years, rice production has gradu-
ally increased by approximately 10 %, growing from 599.3 × 106 to 672.0 ×
106 tonnes, mainly due to an improved yield that has been increased by
≈ 11 % (Table 3.1).

As reported in Table 3.3, there are broad variations in rice prices among
the top 10 producer countries with Bangladesh and Japan having the lowest
and highest rice prices, respectively. Japan’s rice price is almost five times
higher than the average world rice price for 2009, at levels of 2348.9
US $/tonne and 94.54 US $/tonne, respectively (FAO/UN, 2012). Moreover,
during the last number of decades world average rice prices increased from
286.23 US $/tonnes in 2000 to 494.54 US $/tonnes in 2009 which represents
an increase of more than 40 % (FAO/UN, 2012).

3.1.2 Phytology, classification and cultivation
Cultivated rice (O. sativa L.) is a cereal grain grass belonging to the tribe
Oryzeae (Tzvelev, 1989), under the sub-family Pooideae, in the grass family
Poaceae (also known as Gramineae) (Tzvelev, 1989). Vaughan (1994) indi-
cated that the genus Oriza has 22 species. However, only O. sativa and O.
glaberrima are cultivated. The number of chromosomes of cultivated rice
and its related species varies from 24 to 48, with the ‘n’ number equal to
12. O. sativa is a diploid species with 2n = 24 chromosomes. Generally, the
rice plant is characterized by round, hollow, jointed culms, with rather flat,
sessile leaf blades and a terminal panicle. Although the rice plant is an

© Woodhead Publishing Limited, 2013

Table 3.3 Rice prices (US $/tonne) in producer countries from 2000–2009

© Woodhead Publishing Limited, 2013 Rank Country Crop years
2004 2005
2000 2001 2002 2003 2006 2007 2008 2009

1 China 205.4 151.7 140.9 207.8 314.1 321 331.1 227 278 284

2 India 132.6 124.6 124.1 134.2 207.7 203.7 259 154.1 385.7 376.3

3 Indonesia 127.1 112.3 133.9 140.5 176.1 210.3 231.7 277.5 280 209

4 Bangladesh 118.5 108.1 114 103.2 142.8 143.9 139 153 174 187.5

5 Viet Nam n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a.

6 Myanmar n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a.

7 Thailand 108.5 108.6 117.6 134.2 165.5 172.2 180.5 326.7 290.8 291

8 Philippines 190.5 160.2 170.9 163.1 168.6 189.4 203.9 243.6 318.8 306.9

9 Brazil 136.1 124.7 133.5 190.1 217.2 203.5 208.8 256.4 356.8 339.2

10 Japan 2231.7 1970.7 1888.8 2399.4 2292 2016.7 1864.9 1811.9 2046.3 2348.9

Average 406.3 357.6125 352.9625 434.0625 460.5 432.5875 427.3625 431.275 516.3 542.85

n.a. = not available.
Source: Data from FAO/UN (2012).

Rice 119

annual species, under favourable environmental conditions, O. sativa may
grow more than once per year. Similarly to other taxa belonging to the tribe
Oryzeae, rice may be classified as semi-aquatic plants, although extreme
variants are grown not only in deep water (up to 5 m) but also on dry land
(Chang, 1985). In Africa, the rice cultivated belongs to the species O. glaber-
rima Steud. that differs from O. sativa mainly in its lack of secondary
branching on the primary branches of the panicle. It is also a strictly annual
plant (Chang, 1965).

The majority of commercial rice varieties range from 1 to 2 m in
height; however, the rice plant varies in size from dwarf mutants (only
0.3–0.4 m tall) to floating varieties (more than 7 m tall). The vegetative
structures consist of fibrous roots, culms (made up of series of nodes and
internodes) and leaves that consist of a leaf sheath and leaf blade (lamina).
The leaf sheath is continuous with the blade. It envelops the culm
above the node in varying length, form and tightness (Chang, 1965). It
supports the plant during the vegetative growth, being photosynthetically
active and acting as a storage site for starch and sugar before heading
(Chang, 1964). The panicle is composed of a panicle neck node (base),
rachis (axis), primary and secondary branches, pedicles, rudimentary
glumes and spikelets (or flower). Panicle shapes range from compact to
intermediate to open. Compact shape is preferred in the modern cultiva-
tion because this type has generally been associated with higher yields
(IBPGR-IRRI, 1980).

The duration of growth for cultivated rice varies from 80 to 280 days and
can be generally divided into early (80–130 days), intermediate (130–160
days) and late (160+ days) maturing cultivars (Yoshida, 1981). In the rice
plant, three growth phases can be distinguished: the vegetative phase –
when the plant begins to partition assimilation to the developing panicle;
the reproductive phases with panicle (flowering) development; and the
ripening or grain-filling phase which begins after anthesis and ends at matu-
ration (Tanaka, 1965).

Different environmental factors influence the development of the rice
plant, such as temperature, day length, nutrition, planting density and
humidity (Nemoto et al., 1995). Although normally a cereal of the wetland,
rice can be grown either on dry land or under water. The common practice
of flooding the paddy fields has been adopted as a means of irrigation and
also to control weeds (Kent and Evers, 1994). The Malayan word padi
means ‘of rice straw’, but the anglicized form of the word, paddy, is used to
refer both to the water-covered fields in which rice is grown and also to the
harvested rice, with attached husk or hull. Rice can be cultivated in temper-
ate and tropical areas, and in cool and warm regions. It is grown, for
example, in hot, wet climates, as well as in the foothills of the Alps, up to
1220 m in the Andes of Peru, 1830 m in the Philippines and 3050 m in India.
This wide adaptability of the rice plant partially explains its importance as
a food crop worldwide (Kent and Evers, 1994).

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120 Cereal grains for the food and beverage industries

3.1.3 Structure of the rice kernel
The rice grain (rough rice or paddy) consists of an outer protective covering,
the hull (husk), and the edible rice caryopsis or kernel (brown, cargo,
dehulled or dehusked rice). The main parts of the rice grain are the hull
(20 %), pericarp (2 %), tegmen (seed coat), aleurone layer (5 %), endosperm
(89–94 %) and embryo (2–3 %) (Delcour and Hoseney, 2010).

The hull consists of lemma, palea, rachilla, and sterile lemmas (Fig. 3.1).
The dehulled rice grain (caryopsis) is called brown rice because of the
pericarp colouring. A rice caryopsis has the same gross structure as that of
other cereals (Fig. 3.2). It varies from 5 to 8 mm in length and weighs about
25 mg.At the mature stage, the rice caryopsis is enclosed in a tough siliceous
hull (husk) (Fig. 3.2) that represents approximately 18–20 % by weight of
the rice grain (Champagne et al., 2004). The rice hull is composed of two
modified leaves, namely lemma and palea, which are joined together longi-
tudinally (Fig. 3.2). This outer layer provides protection for the rice cary-
opsis from insect infestations and fungal damage and against large humidity
fluctuations in the external environment (Marshall et al., 1994).

Inside the hull, three distinct layers, the pericarp, seed coat and nucellus,
surround the starchy endosperm. These layers comprise the bran fraction
of the rice grain representing about 5–8 % of the brown rice weight (Cham-
pagne et al., 2004).

The pericarp is fibrous and varies in thickness. Next to the pericarp there
are two layers of crushed cells representing the remains of the inner integu-
ments – the tegmen or seed coat. In coloured rice, the pigments are located
in the seed coat or in the pericarp.

The aleurone layer (Fig. 3.2) completely surrounds the endosperm and
the outer side of the embryo. The cells surrounding the starchy endosperm
are cuboidal, containing mainly protein bodies (aleurone grains) and lipid

Lemma

Palea Kernel (brown rice)
Lemma Palea
Embryo
Sterile lemmas
Rachilla Sterile lemmas
Pedicel

Pedicel

Fig. 3.1 Structure of the rice grain.

© Woodhead Publishing Limited, 2013