The Science of Cooking Every Question Answered to Perfect Your Cooking

How Can I Tell If an Egg Is Fresh?

How can I tell if an

EGG IS FRESH?

Gases pass into and out of an eggshell’s microscopic pores, affecting how long the egg will last.

As soon as an egg is laid, moisture starts to egg should be discarded. The water test, below, can

evaporate from the white through the pores of also help you assess the freshness of an egg

the shell. The shrinking interior of the egg MEASURING UP before using it.
pulls in 4ml of air each day, forming a slowly Once it’s cracked, check the white and yolk.

expanding air bubble called the “air cell.” EGG INSPECTORS Egg whites have two layers: a thick, gloopy

How to gauge freshness MEASURE THE HEIGHT OF layer surrounded by a thin, watery layer. In an
THE EGG WHITE, SCORED old egg, the thin white loses its stickiness and
The expanding air bubble serves as a guide AS “HAUGH UNITS,” TO forms a pool, the thick white reduces, and the
yolk gets weaker. The yolk soaks up moisture
to the age of an egg. If you hold an egg close ASSESS FRESHNESS.

to your ear and shake it, a sloshing noise from the egg white as it ages, stretching it and

suggests that the air bubble has grown sufficiently making it waterlogged. The yolk looks flabbier, is

for the egg contents to splash around inside it and the more likely to break, and will have a diluted flavor.

TYPE OF TEST FRESH 1 2 3 5+
EGG WEEK OLD WEEKS OLD WEEKS OLD WEEKS OLD

The water test A small air bubble As the egg loses The growing air An egg that stands
means this fresh moisture, it bubble means the upright is past its
Carefully place an egg in a bowl of egg is dense becomes less egg gradually loses peak of freshness.
water. If the egg floats, as shown far enough to sink. dense and starts density and is
right, so much moisture has evaporated to tilt. almost upright.
from the egg and the air bubble has Air bubble less
grown to such an extent that it is no than 1/8in (3mm) Extensive moisture
longer dense enough to sink and loss causes old
should be thrown away. Eggs that eggs to float.
sink to the bottom but tilt or stand
upward are past their best, but
usually perfectly safe to eat. Eggs
that lie flat at the bottom of the
bowl are the freshest.

The cracking test A fresh egg has Egg white Egg whites spread Over time, the yolk Watery white
a high yolk and thins more on older eggs. flattens out and the spreads out
When cracked, a fresh egg has a thick white. more.
thick, slightly cloudy white and a White holds shape white loses color.
high, round yolk. As eggs age, the
white becomes thinner and more
transparent and the yolk flatter.

Using eggs as they age Fresh eggs with At around one Older egg whites Keep older eggs in Once an egg has
firm whites are week, eggs are can be easier to the fridge and use reached this stage,
The freshest eggs are the best. ideal for most still relatively fresh, whip into peaks for making cookies it should be
However, although the success of some uses, especially although not ideal for meringues. or boiling and discarded.
cooking methods depends on freshness, poaching and for poaching. pickling as they’re
older eggs can still produce good results boiling (see p100). easier to peel.
for certain uses.

100 // 101 The Science of Eggs and Dairy

Is it true that only

FRESH EGGS POACH WELL?

Poaching an egg so that it is a tidy, compact sphere with a runny center takes some care.

It is easy to make a mess of a poached egg, but fresh eggs white becomes as it is progressively diluted by water
give the best results because they have a strong membrane spreading from the thick egg white. And while older eggs
surrounding the yolk. Once outside of its shell and plunged can make a well-shaped poached egg, the lack of a strong
in hot water, the membrane holds together remarkably well. membrane and a spreading white makes it harder to achieve.

In addition, fresh eggs have more of the thick egg white and Apart from the appearance of the egg, another reason
less of the thinner, watery egg white (see p99) that causes to use the freshest eggs for poaching is that they have a
the straggly white mess that disfigures so many poached better taste, with no off flavors. The step by step below
egg attempts. The older an egg is, the runnier the thin guides you through the best practice for poaching.

IN PRACTICE MAKING THE PERFECT POACHED EGG

Along with freshness, there are several methods that will help you keep the
white together in the pan, such as adding salt and vinegar to the cooking
water. The steps below will help you perfect your egg-poaching technique.

#1 #2 #3

REMOVE THE THIN EGG WHITE AID EGG-WHITE COAGULATION TURN UP THE HEAT
Crack the egg and put it into a sieve Half-fill a saucepan with water, taking Heat the water to just below a light
or slotted spoon to get rid of any thin note of the amount of water that has simmer—about 180–190ºF (82–88ºC).
egg white. Removing the thin white been used. For around each liter of You could use a digital thermometer to
at this stage will prevent it from water, add 1/4oz (8g) of vinegar and 1/2oz measure the temperature of the water.
separating during cooking and reduce (15g) of salt. These two substances Avoid using rapidly boiling water,
the amount of straggly, detached disturb the proteins in the egg when because the turbulence will break the
strands of egg white appearing in the it is added, helping the white solidify egg white apart. The bubbles will also
cooking water. If poaching multiple more quickly. This reduces the amount disturb the water’s surface, making it
eggs, place each strained egg into an of time it has to spread out while still more difficult to see whether the egg
individual ramekin. in its runny, uncooked form. is cooked, and the higher temperature
will make it easier to overcook.

POACH IN ADVANCE

POACHED EGGS KEEP IN
THE REFRIGERATOR FOR UP
TO TWO DAYS. REHEATED

IN WATER, THEY TASTE
FRESHLY COOKED.

#4 #5 #6

SWIRL THE WATER LOWER THE EGG WATCH IT RISE
If poaching only one or two eggs, Gently drop the egg into the water Cook the egg for 3—4 minutes.
create a mini-whirlpool in the center from as close as possible using the Vinegar reacts with the egg white to
of the heated cooking water by ramekin or a slotted spoon. It should release carbon dioxide during cooking.
swirling it in the pan. The circular sink to the bottom of the pot. At this As the proteins coagulate, tiny gas
motion will keep the egg together stage, you can continue to stir the bubbles are caught in the solidifying
when it first enters the water. water gently around the egg to keep white, reducing its density. Conversely,
it intact. If you are poaching multiple the salt increases the density of the
eggs at the same time, gently stir the water slightly, so that, when cooked,
individual eggs around so that they the egg rises to the surface. Remove
remain separate. it with a slotted spoon and blot with
a paper towel.

102 // 103 The Science of Eggs and Dairy

How can I cook soft-boiled eggs with THIN WHITE
158°F 70°C
RUNNY YOLKS? THICK WHITE
140°F 60°C
A flowing, golden yolk in a solid white can be tricky to achieve.
YOLK
Part of the trick to cooking an egg as you The thick egg white cooks first, followed by 155°F 68°C
want it is to understand that it has three layers the yolk, and lastly the thin, watery egg white—
(not two): the thin egg white, thick egg white, this contains the least protein. In truth, there Setting times
and egg yolk. Each layer has different types is no perfect formula for runny yolks because
and amounts of protein, which cook at different every egg is a little different. The methods As shown above, the yolk sets
temperatures (see right) and at different rates. below assume a large egg at room temperature. after the thick egg white, but

before the thin egg white.

COOKING COOKING HOW IT WORKS HOW EFFECTIVE WHAT TO LOOK OUT FOR
METHOD TEMPERATURE IS IT?
BOILING Chilled eggs cook better at the longer end
STEAMING 212°F The egg is plunged A high temperature of the time range, while old and medium-sized
SOUS VIDE 100°C into boiling water and and short cooking time eggs cook slightly quicker. Water temperature
cooked for 3–5 minutes. make the margin of error drops with each egg added, so allow longer
for under- or overcooking for multiple eggs.
196°F The egg is placed in a the yolk small. Increase cooking time by 40 seconds
91°C lidded pan with a thin Cooked at a lower for chilled eggs; reduce by 30 seconds for
145°F layer of boiling water temperature, this gives medium-sized eggs. Minimize carryover
63°C and steamed for 5 more control; both the cooking by dousing eggs in cold water for
minutes 50 seconds. thick and thin egg white 20–30 seconds after cooking.
The egg is placed in will cook. Very effective. Crack the cooked egg instead of peeling
a hot water bath and A low temperature it, because the thin white will be runny.
cooked for 45 minutes. gives more control but Use instead of poached eggs.
the thin egg white
remains watery.

What’s the best method for

PEELING HARD-BOILED EGGS?

You can sidestep the problem of the egg white crumbling as you peel the shell.

Two thin membranes separate the egg white from the another when they cool, effectively gluing the shell to the
shell—an inner membrane encloses the egg white, and an egg white. “Shocking” the egg in ice-cold water (cool water
outer membrane coats the inside of the shell. Between is not cold enough) immediately after cooking for a couple
the two membranes is an air-filled bubble (which causes of minutes firms up the membrane proteins and causes the
an old egg to float in water; see p99). The proteins within egg white to shrink back from the shell—the shell and outer
the membranes unravel during cooking, then stick to one membrane then peel away easily.

“ A boiled egg will cook more
slowly at altitude because it is
cooking at a lower temperature—
the low atmospheric pressure
”at high altitudes makes water
boil at a lower temperature.

104 // 105 The Science of Eggs and Dairy

How do I make the perfect

SCRAMBLED EGGS?

One of the simplest dishes any cook can attempt, perfect scrambled
eggs are easy to achieve with a little understanding of chemistry.

When a beaten egg is cooked, it miraculously thickens into a custard-like
mass as the proteins change shape and interlink (see below). Eggs
contain dozens of different protein types, each with a different unraveling,
or “denaturing,” temperature, so they gradually form clumps and solidify,
making scambled eggs a forgiving dish to cook. These proteins provide the
cooked egg with texture, but can also cause sticking by chemically fusing to
the metal of the pan. Continuous stirring and scraping is essential, and
adding a teaspoon of oil or butter helps prevent sticking.

#1 Coiled protein Proteins in IN PRACTICE
#2 Unraveled protein raw egg
#3 #1
Meshed proteins Long, tightly coiled protein
molecules float freely in the INFUSE MILK WITH FLAVOR
watery egg yolk and white, Pour 1 pint (600ml) whole milk into
resembling nests of uncooked a heavy-bottomed pan. Add the seeds
noodles. Beat the egg with a of 1 vanilla bean to the pan, along with
fork or whisk until yolk and the empty bean. Place the pan over
white are combined—this medium heat and bring to just below
disperses protein and fat. boiling point. Heating helps to infuse
the milk with the vanilla’s flavor
Proteins in molecules. As soon as the milk bubbles,
partially cooked egg remove it from the heat. Leave for 15
minutes to infuse flavor further.
Heat gives protein molecules
energy, making them vibrate
and move quickly and strike
one another. The proteins
unravel and start to stick to
one another, so stir the
mixture constantly to prevent
large protein clumps forming.

Proteins in
scrambled egg

Around 140°F (60°C), the
molecules begin to mat,
forming a messy tangle.
These quickly create solid
masses. Keep stirring until
the egg reaches your desired
texture, add pepper, then
serve immediately.

What Is the Secret of Creamy, Smooth Custard?

What is the secret of

CREAMY, SMOOTH CUSTARD?

Custard forms the basis of many luscious desserts, and making it is simple to master.

A custard is a sweetened milk or cream sauce into tough lumps, “curdling” the custard.

thickened with egg. Understanding a few Continuously stirring the mixture forces the

key principles will help you combine proteins to stretch out into a loose, three-

these ingredients into a silky-smooth USES FOR CUSTARD dimensional mesh, and helps prevent lumps.

custard (see below). Eggs thicken milks AS WELL AS BEING A SAUCE Molecules in milk and cream, as well as
and creams into custard because of their FOR DESSERTS, CUSTARD IS sugar, obstruct the proteins, increasing their
special blend of proteins. Rather than USED TO MAKE ICE CREAM, fusing temperature from 140°F (60°C) to
clumping into scrambled egg, they can be 174–81°F (79–83°C). Heating gradually over
CRÈME CARAMEL, AND

coaxed into a threadlike mesh or scaffolding CRÈME BRÛLÉE. a gentle heat is essential so that you can stop

throughout the liquid. Left to their own devices when the mixture thickens (at 173°F/78°C), but

in a heated pan, egg proteins huddle together and set before clumping.

MAKING CUSTARD use 10fl oz (300ml) heavy cream and 10fl oz (300ml) whole
milk. You can also add one or more extra egg yolks, but be
This method produces a pouring custard, also known as a careful not to add too many, as this can create an eggy flavor.
crème anglaise, ideal for drizzling over desserts or as a base
for making ice cream (see pp116–117). For a thicker custard,

#2 #3 #4

COMBINE EGG PROTEINS AND SUGAR ADD HOT INGREDIENTS TO COLD HEAT TO FORM A PROTEIN MESH
Place 4 large egg yolks and 1¾oz (50g) Transfer the milk into a heatproof cup, Pour the mixture back into the pan. Place
fine sugar in a large, heatproof bowl. remove the vanilla bean, and rinse the over medium heat and stir constantly.
The egg proteins and fat in the yolk will pan to remove any residue. Gradually pour Check the texture regularly—at around
thicken the custard, as well as add a rich the still-warm milk mixture onto the egg 172°F (78°C), egg proteins start to form a
flavor. Whisk together until smooth and mixture in a thin stream, whisking all the mesh that thickens the mixture so that it
pale in color to ensure that the sugar is time. Adding the warm milk slowly, while coats the back of a wooden spoon, which
fully dissolved. The sugar will increase whisking, ensures that the temperature is the correct texture. As soon as this
the temperature that the egg proteins will of the egg mixture rises gradually. This happens, remove the pan from the heat.
denature at (see opposite), making it hard prevents the egg proteins from getting Use immediately, or allow to cool before
for them to bind into uneven lumps. too hot and clumping together. storing in the refrigerator.

106 // 107 The Science of Eggs and Dairy

Does it matter if yolk gets into my

WHIPPED EGG WHITES?

Whipped correctly, egg whites will inflate eight-fold into a snow-like foam.

Egg whites are mostly water and protein—and no fat. will displace proteins as they try to mesh around pockets
Whipping unravels the tightly wound proteins into strands of air (see below). Egg yolk is particularly potent: just
that trap air bubbles puff it up into a pillowy foam (see one drop in two egg whites will make it impossible to
below). Some recipes add acids, such as cream of tartar, form an egg white foam, but you may be able to rescue
lemon juice, or vinegar, to help unravel the proteins; it if there is only a trace of yolk (see What you can do,
copper atoms have a similar effect, which is why copper below). Sugar interferes with foam creation too, but it
bowls are traditionally used for whisking. Fat and grease helps stiffen the egg whites later; so add it in the middle
spell disaster for an egg white foam because oil molecules stage of whipping.

Droplet
of yolk

ALL IMAGES TO BE SHOT

Proteins Air bubbles Proteins Air bubble
pushed away. bursts.
Proteins in Proteins and air in Proteins and air in
raw egg white whipped egg whites completed foam Yolk is present

Tightly wound proteins must The friction of whipping tears Protein strands cluster around Egg yolk “pops” air
be unraveled, or denatured, to and denatures the proteins, the bubbles, trapping air. bubbles by pulling the egg
create foam. Whip egg whites the proteins, and also introduces Further whipping meshes the white proteins away from
in a clean, grease-free bowl to air bubbles. Keep whipping proteins together, creating a the walls of the air bubbles.
eliminate fat. the egg whites vigorously. firmer texture. This makes it hard, or
impossible, to whip
egg whites into a foam.

What you can do

If there is only a trace of yolk,
you may just need to whip a
little more. If that fails, add cream
of tartar (which as an acid speeds
protein unraveling) and whip
again—this may rescue the
foam, but there is
no guarantee.

How Can I Prevent Broken Mayonnaise?

How can I prevent

BROKEN MAYONNAISE?

Blending egg yolk with oil and flavorings creates a creamy sauce.

Mayonnaise is actually a gel of microscopic oil droplets Add the oil slowly, a little at a time, and blend
suspended in a watery liquid. This combination is thoroughly, as shown below. The concentrated lecithin
possible because egg yolk contains an emulsifier—a in the thick yolk will coat each microscopic oil droplet.
substance that binds oil and water—called lecithin. To make Use ingredients at room temperature—lecithin takes
mayonnaise you must blend approximately four parts oil longer to emulsify water with oil when chilled.
into one part water—each teaspoon of oil must be broken Adding the oil too quickly may cause breaking,
up into 10 billion droplets to mix properly. Start with but your mayonnaise can be rescued (see What you
minimal liquid—just egg yolk (which is 50 percent water). can do, below).

Merged oil

ALL IMAGES TO BE SHOT

Egg-yolk Egg-yolk Merging oil
water water droplets

Lecithin Oil Mayonnaise
molecules droplets has broken

Oil droplets in Oil droplets in Oil droplets in Breaking occurs when
raw egg yolk thickened mixture finished mayonnaise large oil droplets merge
instead of staying separate.
Oil will naturally aggregate The mixture thickens as the Individual microscopic oil drops This happens when oil is
into large drops. Beat the yolk oil breaks into smaller drops. float in the base liquid, held in added too quickly, before
well, and then add oil little by Drizzle in the remaining oil place by lecithin. Once all the they have been whisked
little, blending fully before very slowly, whisking oil is incorporated, add other into small enough
adding more oil. vigorously the entire time. watery ingredients and seasoning. particles.

What you can do

Add 1–2 tsp water and whisk
again. If that fails, slowly re-add
the separated mix into a fresh
egg yolk.

In focus 108 // 109 The Science of Eggs and Dairy

MILK

A nutrient-dense beverage in itself, milk transforms into a host of key KNOW YOUR MILK
ingredients including butter, cream, yogurt, cheese in all its varieties,
crème fraîche, and more. Different types of milk have varying levels
of fat and sugar, which can affect how they
The cornerstone to dairy milk’s versatility is back in the correct ratio. Today, nearly all are used. Sugar levels vary only a little in
the role of its proteins and fats. Fats in milk commercially produced dairy milk is dairy milks, although non-dairy milks
are wrapped into microscopic globules with a homogenized to stop further separation: it is tend to contain less sugar. Milk is also
water-soluble skin. Less dense than water, these sprayed through nozzles at high pressure to break a high-quality source of protein.
float to the surface and knit together to form a large fat globules into smaller fragments that find
thick, fatty layer. In the processing of most milks, it hard to bind together and cannot float to the DAIRY
fat is separated to produce cream and skim milk. top, giving a smooth mouthfeel. Non-dairy milks
For 1%, 2%, and whole milk, fat is then added (see right) offer a nutritious alternative. Whole cow’s milk
Rich in natural fats,
SCIENCE COOKING FAT: whole milk is the milk of
3.25 PERCENT choice for baking, helping
CURD PROTEINS CLUMP CURDS ARE REMOVED AND SUGAR: HIGH to keep baked goods moist,
WHEN THEY COME INTO USED TO MAKE CHEESE, with a good “crumb” for a
CONTACT WITH ACIDS, AND light, moist texture.
WHEY PROTEINS TANGLE WHILE THE DELICATE WHEY
MESH HELPS TO FORM A FAT: 2% cow’s milk
INTO A MESH WITH 2 PERCENT Lower in fat, this has slightly
H E AT. FROTH ON MILK. SUGAR: HIGH more protein than whole
milk. It tastes less rich, but
still works well for both
drinking and cooking.

PROTEIN FAT: LESS THAN Skim cow’s milk
0.5 PERCENT This low-fat milk is is perfect
SUGAR: HIGH for frothing coffee drinks as
there are fewer fat globules
to prevent the whey proteins
from thickening and foaming.

When curdled by an FAT: Goat’s milk
acid, curd proteins in 4 PERCENT This strong-flavored milk
milk clump together, SUGAR: HIGH is good for making cheese,
forming the basis butter, and ice cream. Small
of cheese. fat globules and little protein
mean it is slow to separate.

Pasteurization FAT: Sheep’s milk
Milk is heated to 7 PERCENT This is creamier than cow’s
a high temperature SUGAR: HIGH milk and has nearly twice
to kill off bacteria the amount of protein,
before drinking. making it ideal for cheese
making and yogurt.

NON-DAIRY

Naturally sweet Soy milk
Milk contains up to This high-protein milk
5 percent of the milk sugar is produced by pressing
lactose, giving it a subtle, ground soybeans. The
slightly sweet flavor. plant-based protein
source has far less fat
SCIENCE FAT: 1.8 PERCENT than cow’s milk. Use
SUGAR: LOW soy milk in baking and
MILK CONTAINS THE cooking where milk is a
SUGAR LACTOSE, WHICH FAT: 1.1 PERCENT minor ingredient.
REACTS WITH PROTEINS SUGAR: LOW
TO BROWN SURFACES AND Almond milk
FAT: Made from ground
UNLOCK FLAVORS. 1.5 PERCENT almonds and water, this
SUGAR: MEDIUM is low in protein, fats,
SUGARS COOKING MYTH BUSTER and sugars. If used in
FAT: place of dairy milk in
AT HIGH TEMPERATURES, Myth 1.8 PERCENT baking, add extra fat. In Focus: Milk
LACTOSE AND PROTEINS EVAPORATED AND CONDENSED MILK SUGAR: LOW
INTERACT TO PRODUCE Oat milk
ARE INTERCHANGEABLE This is made from
RICH BUTTERSCOTCH soaked oat groats,
FLAVORS Truth which are then blended
and strained. A creamy,
Brushing pastry with Evaporated milk is milk boiled under low full texture makes this
milk before baking pressure until its volume has halved. It is used a good substitute for
provides the ingredients dairy milk in baking.
for Maillard browning, to thicken sauces, soups, and smoothies.
(see p16) creating a Condensed milk is sweetened evaporated Coconut milk
rich-tasting crust. This distinctive milk
milk that is 55 percent sugar, and this comes from the grated
is used in candy and desserts. flesh of coconuts, which
is soaked and strained.
When left to stand, a
thicker “cream” rises
to the surface, which
can be used in sauces
and sweet desserts.

110 // 111 The Science of Eggs and Dairy

Why do we

PASTEURIZE MILK?

Every cook wants to use the best ingredients, but while raw milk tastes better, it’s not without its risks.

Like any raw animal product, milk is prone to unpasteurized “raw” milk tends to come from small farms
contamination—a cow’s udders don’t swing far from its with high levels of hygiene where infections are uncommon.
rear. Industrialization multiplied this risk—with large However, raw milk still carries risk, with 60 percent of food
quantities of milk collected in huge vats, one bad batch poisoning outbreaks in the US arising from unpasteurized
could contaminate an entire load. Pasteurization, heating milk. Raw milk cheese is generally safe, as harmful microbes
milk to high temperatures, is a method of killing these are killed by the salt and acidity. Nearly every major health
microbes, making milk safe for the masses. Today, body advises us to avoid drinking unpasteurized milk.

COMPARING TYPE OF MILK THE PROCESS
MILKS
RAW unheated
Three levels of processing Exactly as you’d
are used with dairy milks: expect, raw milk is Raw milk is not heat-treated,
raw, pasteurized, and not heated in any way so is taken straight from the cow
ultra-heat treatment. Each for safety. It is bottled and refrigerated until it is sold.
has its own advantages as it comes out of the
and disadvantages udder, full of flavorful
for the cook. creaminess.

PASTEURIZED 162°F 72°C + 15 seconds
Milk is passed through Pasteurized milk is heated
a pipe and heated to high Heating milk to 161°F for just long enough to kill
temperatures for a short (72°C) destroys the majority harmful microbes, in order
period of time. This makes of harmful microbes that to preserve as much flavor
it safer, without sacrificing could be present in raw milk. as possible.
too much flavor. Its
nutritional benefits are
identical to raw milk.

UHT (LONGLIFE) +284°F 140°C 4 seconds
UHT (“ultra-heat” Milk that is intended to have Because UHT milk is
treatment) uses a long shelf life is ultra- heated to such a high
high temperatures heated to 284°F (140°C) in temperature, it doesn’t need
to kill harmful pressurized tubes to eradicate to be heated for quite as
microbes. This has virtually all of the microbes. long as pasteurized milk.
a negative effect
on milk’s flavor.

Can I Cook Successfully with Low-Fat Dairy Products?

Milk consistency Unhomogenized Can I cook successfully with
fat globules
In times gone by, the cream in LOW-FAT DAIRY
milk used to rise to the top of Nozzle Forcer PRODUCTS?
the bottle. Nowadays, this
doesn’t happen in industrially Homogenized Low-fat foods just need a little more care when cooking.
produced milk—including UHT fat globules
and most pasteurized milk (see Fat is vital for flavor perception, mouthfeel, and texture.
below)—because of a process Cooking with lower quantities of it can be a challenge. Fat
called homogenization. In order globules capture flavor-containing molecules and spread
to prevent separation and them through a cooked dish; fats then coat the tongue so
improve the creaminess, milk flavors linger for longer on the palate. Low-fat sauces curdle
is forced through nozzles at high when heated, and, in desserts, cheesecakes are more difficult
pressure. This breaks fat globules to set with low-fat cream cheese. In savory dishes, extra
into smaller pieces that cannot spices and seasoning can help make a delicious dish when
reconnect to one another and so using low-fat dairy. Add extra garlic, onions, herbs, or spices
are unable to float to the top. to the dish, and aim to stimulate as many taste sensations as
possible by using salty, bitter, sour, and sweet ingredients.
THE RESULT

HOW TO USE LONGEVITY SAFETY 70% WATER 83% WATER Fat comparison
Undeniably richer Raw milk begins Because raw 30% FAT 15% FAT
and more creamy, to lose its flavor milk contains With 30 percent
raw milk retains after only a day. lots of microbes, FULL-FAT LOW-FAT fat, full-fat crème
all of its flavor It starts to go bad drinking it has CRÈME FRAÎCHE CRÈME FRAÎCHE frâiche can be
molecules and 7–10 days after its risks. Health heated without
protein, so it is ideal production. bodies advise curdling. Low-fat
for making cheeses. against doing so. crème frâiche is
likely to curdle
HOW TO USE LONGEVITY SAFETY if added to hot
Ideal for drinking and Pasteurized milk Consuming dishes, so is best
for use in sauces stays flavorful pasteurized used for desserts.
and custards, for several days milk in any form
pasteurized milk before it starts is low-risk, as 1% STABILIZER
retains flavor to lose its flavor. long as it is used 1% THICKENER
molecules while It lasts up to before its given
homogenization 2 weeks after expiration date. KNOW THE DIFFERENCE
(see box, above) pasteurization.
adds creaminess. Full-fat dairy products Low-fat dairy products
Although full-fat products are They contain fewer calories
HOW TO USE LONGEVITY SAFETY rich and flavorful, they can be per gram than their full-fat
Ultra-heat treatment Because almost Even safer than very high in fat and calories. counterparts, but at what cost?
destroys proteins all microbes are pasteurized; there
and sugar, reducing destroyed and are almost no Flavor Flavor
creaminess and UHT is sealed in risks associated Dairy fats amplify other Pair with high-quality
giving a “burnt” sterile packaging, with consuming flavors, so adding cream or ingredients and plenty of
taste. Best used it can last for as UHT milk, as long butter to a dish usually seasonings to help boost
only if access to a long as 6 months as it’s within its improves its flavor. flavor with less fat.
fridge is limited. after it is treated. “use by” date.
Nutrients Nutrients
Full-fat butter and cream Low-fat foods contain similar
contain protein and calcium, amounts of nutrients to
but are high in saturated fat, full-fat ones, but look out for
so consume in moderation. added salt and sugar.

112 // 113 The Science of Eggs and Dairy

Which type of TYPES OF CREAM PROCESS
How cream is made Spinning and
CREAM diluting
SHOULD I USE? Large processing plants separate
fat globules from milk in high-speed Milk has around 3.7–6
For such a straightforward product, shopping for centrifuges, creating “0 percent fat” percent fat when it
cream can be surprisingly confusing. skim milk and thick, or heavy, cream leaves the udder,
that is about 50:50 fat to liquid. depending on the breed
Cream is the cornerstone on which much classical French of cow. When processed
RAW MILK in a spinning centrifuge,
and European cooking has been built. Cream is made up of the fat-free skim milk is
thrown off, leaving a
the microscopic spheres of “milk fat,” or “butterfat,” high-fat cream. The
faster the spinning, the
separated from milk (see right), which glide over the tongue more liquid is flung out
and the denser the cream
and give a silky mouthfeel unlike any other oil or fat. Added will be. A centrifuge spun
at 150 revolutions a
to other foods, cream carries flavor molecules and amplifies second collects cream
that has 45–50 percent
flavor in sweet and savory dishes, while also carrying its own fat and skim milk that is
almost devoid of fat.
buttery notes. Although delicate in consistency, cream is Light cream, whipping
cream, and heavy cream
more robust than milk, and heavy creams can easily bubble are then made by adding
some separated cream
on high heat without curdling. back into the skim milk.

The large selection of creams to choose from can be Heating

bewildering, but the key difference in most creams is Cream was traditionally
heated to make a denser,
simply the amount of milk fat they richer product, and this
technique is still used
contain. The chart opposite shows today for clotted cream.

the quantity of fat in the HOW MUCH FAT? 0% FAT 45–50% Fermenting
different types of cream and FAT
SKIM Before centrifuges were
how this affects how each THE TERMS “BUTTERFAT” MILK THICK CREAM used, it would take hours
type of cream can be used. AND “MILK FAT” CAN for thick cream to
separate from milk. It
USUALLY BE USED would often ferment due
to microbes in the milk.
I N T E R C H A N G E A B LY — B O T H Cream is diluted with After cream has been
different amounts of skim diluted (see above), this
REFER TO THE FATS IN milk to create the various method is used today
in carefully controlled
DAIRY PRODUCTS. cream types. conditions to make
sour cream and
Fat globules Less dense than crème frâiche.
in milk water, fat globules
rise to the surface.
Fat globules in milk are less dense than
the liquid in which they float. Protein Fat globules
molecules attach to fat globules, causing cluster,
them to latch onto each other when close creating a
together, and then rise. Being buoyant, fat dense fluid.
globules were traditionally skimmed off the
surface for cream. Today, cream is extracted in a Fat globules
centrifuge and homogenized before being sold (see p110). have a water-
soluble skin.

Which Type of Cream Should I Use?

PRODUCT FAT CONTENT HEAT WHIP POUR BEST USED FOR
LIGHT CREAM IT? IT? IT?

18% FAT X X Light cream isn’t suitable for cooking because its lower fat
content means it is likely to curdle when heated, especially
if is mixed with an acid. Use light cream for pouring over
fruit, drizzling onto soups before serving, or adding to
desserts for a finishing flourish and creamy flavor contrast.

35% FAT Cream with over 35 percent fat can be

X whisked into a sturdy, pillowy foam. The whisk
smashes fat globules apart, which then
coagulate around air bubbles.

WHIPPING CREAM

48% FAT All creams with over 25 percent fat are safe for cooking

X on high heat as they do not curdle. The large number of
fat globules in the cream means that the curdling casein
proteins floating in the liquid are unable to join together
to form lumps.

HEAVY CREAM

55% FAT XX The heating process that makes clotted cream

CLOTTED CREAM X produces complex burned and buttery notes as the
sugars and proteins react and interact with the fats.
This dense, rich cream is traditionally eaten in the UK
as an accompaniment to scones and desserts or
made into ice cream.

This fermented cream has a fresh tang, adding richness
and tartness to both savory and sweet dishes. However,
X X X20% FAT the fat content is not high enough to stop casein proteins
from clumping together and separating a sauce with acid
ingredients. It’s used in goulash, soups, and spicy
SOUR CREAM South American dishes.
CRÈME FRÂICHE
30% FAT This is fermented in the same way as sour cream, but a

X X higher fat content makes this thicker cream suitable for
cooking because it won’t curdle when heated with acid
ingredients such as tomatoes. Use crème frâiche to
enrich a pasta dish, or add to soups and other sauces.

114 // 115 The Science of Eggs and Dairy

How can I heat milk

WITHOUT A SKIN FORMING?

Though often discarded, the skin that can form on heated milk is actually full of highly nutritious whey proteins.

Milk is a versatile ingredient, providing delicate to unravel at around 158ºF (70ºC). If milk is heated

flavors while able to withstand prolonged for long enough, sticky, cooked whey proteins

heating. Unlike the proteins in other foods, FULL OF GOODNESS will float to the surface and settle as a tacky
milk curd proteins do not unravel when layer. With time and continued cooking, this

heated to a boil, and can survive at SKIN THAT FORMS ON SOY layer will thicken and dry out, eventually

temperatures of up to 338ºF (170ºC). It MILK CAN BE DRIED AND forming a “skin” on the surface. If the skin
can be simmered happily for a long time, COOKED AS “YUBA,” A is left in place and the milk is unstirred, the
gradually developing hints of vanilla, almond, temperature of the milk beneath the skin
and butter as new flavor molecules evolve. HIGHLY NUTRITIOUS MEAT will soar—as it would if it was in a sealed
A LT E R N AT I V E .

As the milk boils, the milk sugars (lactose) and pan—and will boil over the side of the pan in

proteins are brought together, triggering the Maillard an explosive fashion. Once a skin has thickened and

reaction (see pp16–17), to create intense butterscotch congealed, stirring won’t break it up and it will need to be

flavors. However, the less abundant whey proteins in milk picked off. To avoid burned milk and a skin from forming

(see p108) aren’t completely heat-resistant, and these start in the first place, try one or more of the suggestions below.

Seal in steam with a lid Seal in steam with parchment

Once the milk has been heated As an alternative to a lid, place a
and is cooling, placing a lid on the sheet of parchment paper—known
as a “cartouche”—directly on top
pan will keep the steam trapped of the milk to stop steam from
inside, making it harder for a skin escaping. A cartouche can also be
used if heating milk in a microwave.
to dry out and set firmly.

Break up HOW TO PREVENT A SKIN FORMING Add sugar granules
whey proteins
For sweet custards and
Regular stirring stops whey proteins sauces, sprinkle sugar on
from clumping. Whisking the the surface as it is cooling.
surface during heating also makes The jagged granules will
it hard for whey to form a skin. As prevent the whey proteins
the milk cools and settles, whey from easily forming a skin.
will readily rise, so continue to stir. Unraveled, whey proteins
coagulate together and rise
When the temperature to the surface of the milk to
reaches 158ºF (70ºC), form a solid skin.
coiled-up whey proteins

start to unravel and
stick to one another.

“ In East-Asian cuisine,
the milk skin is considered
the essential element in a
“double skin milk pudding,”
”a panna cotta–type dessert
that has been heated and
cooled twice.

116 // 117 The Science of Eggs and Dairy

Can I make ice cream at home without an

ICE-CREAM MAKER?

Without an ice-cream maker, time needs to be given to stirring and churning.

An ice-cream maker is convenient, but it’s perfectly around air bubbles, strengthening their structure. It

possible to make ice cream without one (see step is these suspended air bubbles that help give a

by step below). Coaxing a sugar-cream mix into SMOOTH ICE CREAM light, soft mouthfeel. Ice crystals are the enemy
the silky-smooth dessert we all know and love of smooth ice cream, and so sugar, along with

needs time and care, and it’s helpful to have an COMMERCIAL ICE CREAM a little salt, should be added to disrupt the
appreciation of the molecular structure of your IS PUMPED THROUGH formation of ice crystals. Even the tiniest of
ingredients. Milk fat globules that capture the ice crystals feel unpleasant,y gritty on your
churned air have water-soluble coats (see PIPES COOLED TO AROUND tongue, so it’s vital to keep them as small
pp108–9) that need to be stripped away to –40˚F (–40˚C) TO as possible. When freezing, speed is of
make ice cream. When combined with an REDUCE CRYSTAL the essence—the faster the ice cream is
FORMATION.

emulsifier, such as lecithin from egg yolks, this coat is frozen, the smaller the ice crystals will be.

peeled off, allowing fat molecules to coalesce into larger, Bearing these principles in mind, it’s possible to

creamy blobs. Whisking the mixture causes these fats to gather make delicious ice cream at home.

IN PRACTICE MAKING ICE CREAM creamy texture. The cooked egg and milk proteins help
stabilize the mixture. You can use ready-made, high-fat fresh
When making ice cream at home, it’s best to start with custard, or make your own using the method on pp104–05.
a custard as your base, as it contains a natural emulsifier in
the form of egg yolks and sufficient sugar and fat to create a

#1 #2 #3

PREPARE AND COOL THE CUSTARD MINIMIZE ICE-CRYSTAL FORMATION WHISK REGULARLY
Place a shallow, freezerproof metal Pour the cooled custard into the Continue to check the mixture every
or plastic container in the freezer. pre-chilled container. Shallow 30 minutes, whisking vigorously each
Keeping equipment cold speeds containers are best because they have time. Whisking not only breaks up ice
freezing, which helps achieve a a larger surface area, which speeds crystals, but also incorporates air,
silky-smooth ice cream. Prepare a freezing to give a smoother finished improving the texture. Make sure that
double quantity of custard (see texture. Place the container in the you close the freezer door quickly after
pp104–105) and pour it into a heatproof freezer. After 45 minutes, remove the opening, to help maintain sub-freezing
bowl. Place the bowl of custard inside mixture from the freezer and whisk it temperatures. Continue for about
a larger bowl filled with ice cubes, then vigorously to break up the ice crystals. 3 hours, until the ice cream has
leave to cool, stirring occasionally. Return it to the freezer. begun to set and solidify.

Do Ice-Cream Makers Make Creamier Ice Cream Than Whisking by Hand?

Do ice-cream makers make creamier

ICE CREAM THAN
WHISKING BY HAND?

For ice-cream enthusiasts, a maker is a worthwhile investment.

In the same way that bread makers have taken all the wrist work out
of making a fresh loaf of bread, so ice-cream makers have done away with
the tiresome churning needed to make ice cream. It is possible to make
delicious ice cream without an ice-cream maker (see facing page), but
if you’re serious about ice-cream making, it’s a good idea to invest.
Continuous churning smashes large ice
crystals before they have a chance to
gain a foothold, making light, fluffy
ice cream that would be difficult
to make by hand. Churning also
gradually adds air bubbles to
the mix, turning milky-sweet
slush into a frozen
aerated foam.

Microscopic
ice crystals
Tiny air cavities

Sugar solution

Fat globules clump together
around air bubbles.

#4 STRAWBERRY Molecular anatomy
ICE CREAM of ice cream
FINAL FREEZE TO SOLIDIFY
Once the ice cream is well set and you The smooth surface of ice
can no longer whisk it, return to the cream is in fact a landscape of
freezer and chill for a final hour. This microscopic airy caves. Each
final freeze solidifies the ice cream hollow is contained by a mushy
completely before serving. As it’s only wall made of fat and supported
possible to beat a certain amount of air by ice crystals. Continuous
into the mixture by hand (see right), churning with an ice-cream
this ice cream can deteriorate if left in maker and rapid freezing shrink
the freezer, so serve within 2–3 days. the gritty-textured ice crystals.

118 // 119 The Science of Eggs and Dairy

Is it worth

MAKING MY OWN YOGURT?

Preparing yogurt at home is relatively simple and can produce interesting flavor variations.

Yogurt was first discovered five millennia ago when The two bacteria we use today, Streptococcus

our ancestors realized that letting whole milk thermophilus and Lactobacillus delbrueckii, work

“go bad” produced a long-lasting sour, together as a pair, feeding on each other.

thickened milk. Traditionally, various ORIGINS OF YOGURT Bacteria for yogurt making can be bought

bacteria species and types would “chew” THE WORD YOGURT DERIVED as a dried culture, although it is easier to use
milk sugars, gradually producing acid, which FROM THE TURKS, WHO a spoonful of an existing yogurt as a “starter”
slowly destabilized casein proteins, causing NAMED THE DENSE MILK for new yogurt, as shown below, since most
them to mat into a gel-forming lattice, rather “YOGURMAK,” MEANING yogurts contain live bacteria. Yogurt starters

than into clumps. Today, yogurt bacteria have “TO THICKEN.” can be propagated for years and handed down,

been sanitized and standardized, and, apart potentially nurturing rare, alternative flavor-

from probiotic yogurts, only two yogurt bacteria are generating bacteria. However, research shows that

commonly used. As with cheese, what we have gained in many heirloom cultures actually originated from a yogurt

reliability and safety, we have lost in diversity and variety. that contained the two most common commercial strains.

IN PRACTICE MAKING YOUR OWN YOGURT you can start a new batch using a few spoonfuls of the
yogurt you have made, within seven days, while the
The yogurt-making step-by-step process shown here uses acid-making microbe numbers are still high.
existing live yogurt to create a new batch of homemade
yogurt. Once you have completed your batch of yogurt,

#1 #2 #3

UNWIND CURD PROTEINS ADD THE CULTURE DEVELOP LACTIC ACID
Heat 3½ pints (2 liters) whole milk Transfer the cooled milk to two Screw or clip the lids tightly onto
over low heat until it reaches 185ºF 1¾-pint (1-liter) sterilized preserving the jars and wrap the jars in clean tea
(85ºC), stirring occasionally. Heating jars (or a thermos), leaving a little towels, leave in a warm place for 6–8
removes unwanted bacteria, unsettles space at the top of each jar. Add hours to ferment. This gives time for
the curd proteins so they will unwind 1–2 tablespoons of live yogurt to the bacteria to create lactic acid, which
more easily, and cooks some whey each jar and stir well to combine. destabilizes the proteins and creates a
proteins to help thicken the yogurt. lattice-like gel.
Remove the pan from the heat and
allow the milk to cool to 104–113ºF
(40–45ºC), a temperature ideal for
bacterial growth.

Is It Worth Taking Probiotic Yogurt?

Why does yogurt separate

IN SPICY DISHES?

Yogurt is a key ingredient in many Indian and Pakistani dishes.

The trick to using yogurt while retaining a glossy curry sauce is knowing
when to add it. Yogurt contains the same milk proteins that can curdle milk
and light cream, and, having a similar fat content to milk, it will separate into
curds and whey when cooked at high heat alongside acids. It isn’t the spices
that make yogurt separate, but acidic ingredients such as tomatoes, vinegar,
lemon juice, or fruits. The higher the temperature, the faster the curdling, so
to avoid yogurt separating, add it toward the end of cooking, when a dish is
cooling, not simmering. Alternatively, use crème frâiche, which has a similar
refreshing fermented flavor, but a fat content of 30 percent, so it can be
simmered without separating.

+ + = CURDLES
E A S I LY
Acid
Simmering food Acid and heat
+
+ = LESS The combination of
Acid LIKELY TO heat and acid, shown
Little CURDLE left, causes yogurt to
heat curdle. Although acidic
Full-fat yogurt is less likely to itself, yogurt’s curd
curdle as fat globules prevent protein lattice is flimsy
casein proteins linking together. and crumples into
lumps if overstressed
by heat and strong acid.

Is it worth taking

PROBIOTIC YOGURT?

#4 Bugs in our intestines boost our immunity and provide nutrients.

ENJOY OR REFRIGERATE Each person’s mix of intestinal microbes is unique and affected by overall
Once fermented, the yogurt is ready health, stress levels, and, most critically, diet. Science shows us that an
to eat, or can be stored in the fridge unbalanced population of gut microbes (the “intestinal flora”) is linked to
for up to two weeks, where bacteria many medical maladies. Probiotic yogurts contain large amounts of “good
growth will slow. For thicker, bacteria,” which can help push out bugs that can take a toll on our health,
Greek-style yogurt, strain the yogurt helping restore digestive health and well-being. Often, though, claims are
at this point through a very fine overhyped. We do know that probiotics are good for preventing diarrhea
cheesecloth or coffee-filter paper when traveling, and for treating antibiotic-related diarrhea by nurturing
for several hours until thickened. good gut bacteria eradicated by antibiotics. However, products vary and those
prescribed by doctors can contain more bacteria.

In focus 120 // 121 The Science of Eggs and Dairy

CHEESE

There are over 1,700 types of cheese in the world, and this huge variety KNOW YOUR CHEESE
stems from simply fermenting the curds found in animal milks.
The many processing decisions made by
On its most basic level, cheese is a congealed cheeses, and tiny grains for hard cheeses. The the cheese maker—including which milk
lump of curdled milk that has been fermented curds are drained of excess whey and scooped to use, how small to cut the curds, and how
into molds. Fresh, soft cheeses may be left for long to age the cheese—impact the flavor
(partially digested) by microbes. Cheese- and properties of the finished cheese.
making starts with a choice of milk, which can a few hours or days to solidify, but aged cheeses
will undergo a series of further processes before
be from a cow, buffalo, goat, sheep, and even SOFT CHEESE
being ready to eat. Some cheeses are weighted
camel milk. Many cheese makers choose to
or pressed to remove moisture and create a
use raw, rather than pasteurized, milk (see
harder-textured cheese, and some are “washed”
p110–111), as this retains the subtle flavor Paneer
molecules that are lost in high heats. “Starter” in brine, wine, or cider to create a soft rind A young cheese,
bacteria are added, and the milk is then heated patinated with flavorful molds. Cheeses are paneer is acid-set, so
to the ideal temperature for the new microbes left to mature in temperature- and humidity- remains solid when
controlled rooms for months at a time, to allow FAT CONTENT: 26–28% cooked. Fry and add
to flourish. Then, acid or rennet (see p125) is AGED FOR: 1 DAY+ to vegetable curries.
microbes to develop complex flavors. FLAVOR: MILD
added to the milk, which causes proteins in Mozzarella
FAT CONTENT: 21–23% Set using rennet,
the milk to clump together, ensnaring milk’s AGED FOR: 1 DAY+ mozzarella curds
FLAVOR: MILD are kneaded to form
creamy fat globules, and float to the surface. layers, so it can be
FAT CONTENT: 20–23% used melted or cold.
These clumps of fat and protein are AGED FOR: 2 MONTHS+
Feta
“curds,” and the remaining liquid is SCIENCE COOKING FLAVOR: MEDIUM Traditionally kept
“whey.” Buoyant curds are cut into in olive oil or brine,
FAT CONTENT: 24% feta adds salty flavor
pieces—walnut-sized pieces for soft BACTERIA, FUNGI, AND USE STRONG-FLAVORED AGED FOR: 3–5 WEEKS and crumbly texture
to salads, pastries,
YEASTS FERMENT MILK CHEESES SPARINGLY. PAIR FLAVOR: MEDIUM and pies.

CURDS, ADDING COMPLEX CHEESES WITH INGREDIENTS Camembert
Fungi from the
Molds spread on the surface FLAVORS TO DIFFERENT THAT COMPLEMENT THEIR penicillin family
of aged cheese grow into a TYPES OF CHEESE. FLAVOR PROFILE. give Camembert its
living rind that stops the mushroomy aroma.
cheese from drying out. Serve as it is, or bake
until oozing.
COLOR

Blue molds from the
penicillin family grow
inside blue cheeses.

FAT CONTENT: 43–44% Bavaria Blu
AGED FOR: 4–6 WEEKS Made from a mixture
of milk and cream,
FLAVOR: MILD Bavaria Blu is a mild
blue cheese with high
fat content. Its rich
flavor complements
rye and nut breads.

HARD CHEESE

FAT CONTENT: 28–30% Monterey Jack
AGED FOR: Based on a Spanish-
Mexican cheese,
1–12 MONTHS Monterey Jack is
FLAVOR: MEDIUM sweet and tart in
flavor. Grill it or grate
it atop beans or chili.

FAT CONTENT: 28–32% Emmentaler
AGED FOR: This herbaceous,
fragrant cheese is made
4–18 MONTHS with milk from cows
FLAVOR: MILD that graze in Alpine
meadows. Grate into
fondues, grill on bread,
or eat cold.

CAMEMBERT The type of milk helps to Manchego
determine the color of the cheese. Dry in texture with
a nutty flavor that
Very ripe soft cheeses Surface microbes FAT CONTENT: 39–40% matures to peppery
often have a soft, release protein-digesting AGED FOR: when aged, Manchego
is best served raw.
collapsing interior. enzymes, which create 6–18 MONTHS Slice it finely, or cut
an oozy texture. FLAVOR: MEDIUM it into thin wedges.

SCIENCE COOKING FAT CONTENT: 28% Parmigiano- In Focus: Cheese
AGED FOR:
TEXTURE DEPENDS ON HOW A MOIST, WELL-AGED Reggiano
MUCH WHEY IS LEFT IN THE CHEESE BLENDS BEST IN 18–36 MONTHS Aged for years at
FLAVOR: STRONG a time, Parmigiano
CURDS, WHICH BACTERIA A SAUCE. MILD, SOFT Reggiano, or Parmesan,
ARE USED, AND HOW LONG CHEESES ADD TEXTURE AND is packed with flavor. It
adds umami notes to
THE CHEESE IS LEFT FRESH FLAVORS. pastas, sauces, soups,
TO RIPEN. and salads.

TEXTURE

122 // 123 The Science of Eggs and Dairy

If the veins in blue cheese are mold, Why are some cheeses

WHY IS IT EDIBLE? SO STRONG
AND SMELLY?
We have evolved to live in harmony with bacteria.
With more than 17,000 varieties of cheese worldwide,
The reputation of bacteria as being harmful is undeserved; there is an incredible diversity of taste and aroma.
in fact, many are beneficial. Traditionally, microbes that gave
cheese its character reflected the microbiology of the area. Today, Creamy brie, buttery Gouda, crumbly Parmesan, brothy
cheese is made with pasteurized milk, eradicating naturally Cheddar, and mild-tasting paneer are just some of the
occurring microbes. Of the molds that have survived, Penicillium numerous varieties of cheese. Within this family of cheeses
fungi are most widely used; they cause the blue veins in are the super-smelly ones, such as Muenster, Limburger,
strong-tasting cheeses and are quite safe. One of the oldest Roquefort, and Stilton. The universe of cheese is testimony
blue cheeses, Roquefort, owes its greenish-blue veins to to the creativity of cheese makers throughout the ages, but
Penicillium roqueforti, the same mold used in Stilton and it is the microbes, or bacteria, that are the real stars of the
Danish blue. Gorgonzola and some other French cheeses rely show. The several-hundred-strong ensemble cast of bacteria,
on Penicillium glaucum, which gives a slightly different flavor. fungi, and yeasts brings life to a bland, salty lump of white
curd. By digesting (fermenting), fat, proteins, and milk
“Roquefort owes its greenish-blue sugar, they excrete a complex selection of flavorful
veins to Penicillium roqueforti.” (and sometimes very smelly) molecules, as shown in the
flowchart, opposite. Certain bacteria have especially strong
smells. For example, Muenster and Limburger owe their
“old socks” smell to Brevibacterium, which also flourishes
in the moisture between toes!

Holes are Stand-out smelly cheeses
pierced into
the cheese to The smelliest cheeses tend to be those that
spread mold have “smear cultures” of bacteria or white
throughout. molds deliberately spread over their
surface as they ripen.

Starter CAMEMBERT
bacteria
Proteins ROQUEFORT PONT L’EVEQUE

Fats Microbes MUENSTER
in cheese
EPOISSES BRIE DE MEAUX
As the blue-pigmented
molds feed on milk
fat, they produce
characteristic flavor
compounds. Starter
bacteria (see opposite)
similarly feed on the
fats, sugars, and proteins
to produce flavor.
Mold grows along air holes,
chewing through fat and protein.

Why Are Some Cheeses So Strong and Smelly?

THE CHEESE-MAKING FLAVOR JOURNEY

MILK + STARTER CURDS
BACTERIA
The type of milk that cheese comes from Lactic acid from the starter bacteria
affects its flavor. Cow’s milk can have an These bacteria are introduced at the start curdles the milk: most milk proteins are
earthy taste, goat’s milk has a distinct tang, of the process to feed on milk sugar sensitive to acid, which causes them to
and sheep’s milk carries creamy flavors. lose their shape and stick to each other,
(lactose), digesting it into lactic acid. The
acids kill off harmful microbes and give forming curds. Milk-digesting rennet
ripened cheese its tang. Starter bacteria enzymes are added to further unravel
persist within the cheese, contributing proteins and speed curdling. Tangled
with the milkfat, the curd proteins float to
to its flavor. the surface, where they are drained and
pressed. The amount of moisture in the
curds can lead to hard or soft cheeses,

each with their own flavors.

AMINO PROTEIN RIPENING
ACIDS AND AMINES BACTERIA
Ripening microbes chew off portions
Different amino acids have distinct of proteins, breaking them into small Flavor-generating ripening microbes,
flavors and aromas. For example: pieces, then into amino acids, then added just after curdling or later on,
· Tryptophan has a bitter taste. finally into chemicals called amines, mature cheese over weeks and months,
· Alanine has a sweet taste. creating potent flavors and aromas. The
· Glutamate has a brothy flavor that aldehydes, alcohols, and some types and amounts of microbes affect
stimulates umami taste receptors. acids. Many of the substances carry flavor. Temperature and humidity during
Some bacteria break down amino acids ripening affect the rate of growth and in
into very strong-smelling amines, many their own flavor.
of which smell familiar; for example, turn the taste of the cheese.

putrescene is the smell of
putrid meat.

ALDEHYDES CHEESE

Over many months, smelly amine The character of the final cheese—
fragments can break down in different its distinctive flavor and
ways to produce more pleasant flavor aroma—reflects the type
molecules called aldehydes and alcohols, of bacteria introduced
which range from nutty, woody, spicy, and any variables
in the process.
and grassy to burnt oats. Bacteria
also produce acid, adding
tartness.

STINKING BISHOP

124 // 125

Why does some cheese

GET STRINGY?

Fats bridge Not all cheese forms warm strands between pizza slices.
the protein
strands when Stilton and Cheddar offer a flavor punch, but separate into
they melt. greasy lumps if heated. In hard or mature cheeses, the casein
(curd) proteins are bound so tightly that they don’t soften until
Casein proteins in they are at about 180°F (80°C)—long after the fats have
young cheese liquefied and drained away at 86–104°F (30–40°C). But some
soft cheeses, such as ricotta, don’t melt because they’re made
In cheeses such as by curdling milk with acid, rather than rennet (see opposite);
mozzarella, protein the acid causes curd proteins to knot irreversibly.
networks bind together,
but not tightly enough to How stringy cheeses are formed
clump, and are separated
sufficiently by fat What makes cheese such as mozzarella so stringy is how the
molecules, which allows milk was curdled, how long it ripened, and the balance of fat
them to bridge one another and moisture, which makes casein proteins bind loosely (see
in long, stretchy strands. left). Mozzarella is made by adding bacteria to milk before
rennet, heating, then kneading curds like bread (a technique
Aligned loosely in one direction, these called “pasta filata”) to encourage the protein to align into fibers.
proteins turn stringy as fats melt.

Should I avoid KNOW THE DIFFERENCE

PROCESSED Processed cheese Unprocessed cheese
CHEESE? Processed cheese is usually Natural cheese is sold in a variety
pressed and shaped into slices of shapes and sizes and can then
Processed cheese is made from similar raw materials as before packaging in plastic. It can be grated, sliced, or cut up and
unprocessed, but is far removed from the original food. also be sold in a block or can. used as required.

In the mid-1800s, the first American cheese factory was This is made from To make unprocessed
founded in New York, producing large volumes of fairly a variety of cheeses cheese, the whey is
bland Cheddar. In 1916, entrepreneur James L. Kraft went and contains whey drained off and the
on to pioneer processed cheese from shredded offcuts. The proteins and salt, with cheese is made from
offcuts had been pasteurized, melted, and mixed with citric artificial colorings and the milk curds, rennet
acid and substances called phosphates, which tear calcium preservatives added to enzymes or acid, and
away from the casein (curd) proteins, allowing the curds to give uniformity of taste salt, then ripened
mold together evenly. and appearance and over a period of time.
prolong shelf life.
Today’s processed cheese is an amalgam of different With fewer additives,
cheeses, milk whey proteins, salt, and flavorings, bound with Processed cheeses have this may contain colorings
emulsifiers (substances that allow fats and water to mix). If less calcium (to weaken and enzymes to speed
you prefer “natural” foods you may want to avoid processed the proteins and make ripening. Cheese that
cheese, but it’s nearly impossible to get a glossy magma-like the cheese moldable), isn’t processed develops its
cheese topping on a burger with non-factory-made cheese. and contain thickeners and flavors from the milk and
emulsifiers, which hold fats rennet during ripening.
and water together when
they are heated.

Can I Make Perfect Soft Cheese at Home?

Can I make perfect

SOFT CHEESE AT HOME?

Like brewing beer at home, cheese making can be a simple or involved process.

Cheese-making kits are available, which include together. Acids can also be added directly without the

recipes and “cultures” (pre-prepared and carefully help of bugs. This is done with mascarpone and

measured packets of microbe spores). paneer, when vinegar or lemon juice is added

Unfermented cheese, however, can be made FOR VEGETARIANS to warm milk. Curdling milk is made easier by
at home without any special equipment, adding the protein-breaking enzyme rennet,

culture samples, or even rennet, the enzyme VEGETARIAN RENNET IS found in calf’s offal. This curdles milk rapidly,

commonly used in cheese making (see right). MADE BY GROWING MOLDS causing casein proteins to clump in a structured
The first stage in making cheese is to curdle THAT PRODUCE ENZYMES way. Ripening bacteria, fungi, and yeasts can
then be added to develop flavors. Harder cheese
milk. Microbes in milk, specifically bacteria SIMILAR TO THOSE IN is pressed and left to ripen for weeks or months.
called lactobacilli, digest milk to create lactic acid, CALF RENNET.

which achieve this. Most milk proteins, casein The step by step below is a simple recipe for making

proteins, are sensitive to acid; they lose their shape and stick soft cheese using an acid to help the curdling process.

MAKING SOFT CHEESE airtight container if refrigerated), if at all, and ideally
should be eaten at their ripening temperature because flavor
This quick recipe for ricotta-style soft cheese produces a molecules in chilled cheese are not released as readily.
cheese that is far fresher than its store-bought equivalent.
Cheeses are best stored loosely wrapped (and in an

IN PRACTICE

#1 #2 #3

CURDLE AND SEPARATE THE CURDS DRAIN OUT THE REMAINING WHEY SERVE IMMEDIATELY OR CHILL
Pour 1¾ pints (1 liter) whole milk into Remove the more solid curds from Unwrap the bag to reveal the set
a saucepan over low heat. Heat gently the liquid whey using a slotted spoon. curds, and then serve the soft cheese
to 165–194ºF (74–90ºC). Remove from Place the curds in a muslin bag. Tie right away, or place in an airtight
the heat. Add 1½ tsp salt and 2 tbsp white the bag with string and hang the curds container and store in the fridge for
wine vinegar or the juice of 1 lemon to over a bowl or sink to allow the excess up to three days.
unravel the proteins. Stir and allow to cool whey to drip out. For very soft ricotta,
for 10–15 minutes until the mix has drain for 20–30 minutes, or leave
curdled and the curds have separated. overnight for a crumbly, dry texture.



RICE, GRAINS&PASTA

In focus 128 // 129 The Science of Rice, Grains, and Pasta

RICE

It may be small, but rice is a dense, nutritional storehouse. No KNOW YOUR RICE
wonder it is the staple food of nearly half of the world’s population.
Rice varieties vary in their ratio of amylose
As a seed, rice is designed to nourish the the endosperm are chalky and barely edible to amylopectin starch, but as a general rule
next generation of rice plant—much like an uncooked. Cooking in water at least 150°F (65°C) the longer the grain, the more amylose it
egg nourishes a developing chick. Removing breaks open the hard starch and binds it with contains. Small amylose starch crystals are
each grain’s shell-like, inedible husk reveals an water in a softening process called gelatinization. tightly packed, hence long-grain rices need
edible kernel coated in a nutritious, colored Rice contains two types of starch: amylopectin more time to cook than other types.
bran—this is “brown” rice. The delicate oils in and amylose. Knowing how these starches
the bran oxidize and turn rancid in months, so respond to heat and water helps you pick the SHORT-GRAIN
rice is “polished,” or milled, to improve its most suitable rice variety (see below and panel).
shelf life. This abrasion leaves behind only the
starch-filled core, or endosperm—this is “white” Sticky rice
rice. The densely packed starch crystals in Sometimes called waxy
rice, glutinous rice, or
SCIENCE COOKING AMYLOSE: < 5% sweet rice (although
AMYLOPECTIN: > 95% it neither is sweet nor
STICKY RICE IS HIGH IN AMYLOPECTIN STARCH contains gluten), this
SOFT, LOOSELY PACKED SEEPS READILY FROM RICE white rice becomes
AMYLOPECTIN STARCH GRAINS INTO THE COOKING a sticky mass when
WATER, COATING THEM IN cooked. Thai sticky
AND LOW IN HARD rice is also glutinous
AMYLOSE STARCH. A STICKY GEL. (very low in amylose)
but has longer grains.

STICKY AMYLOSE: 10% Risotto rice
RICE AMYLOPECTIN: 90% Only 1–2 times as long
These rice grains as it is wide, this rice is
stick together due soft and creamy when
to a high ratio of cooked. Its high
amylopectin starch. amylopectin content
thickens the sauce as it
cooks. Available brown
(unmilled) or white
(milled), the brown
type has more flavor,
but takes 2–3 times
longer than white
rice to cook.

Bran coating MEDIUM-GRAIN
The bran coating
imbues cooked AMYLOSE: 15–17% Paella rice
brown rice with AMYLOPECTIN: About 2–3 times as
a nutty taste and 83–85% long as it is wide, this
chewy texture. white rice is moist and
Nutrient-dense slightly sticky when
Brown rice contains cooked, but retains
the living “germ” some “bite.” Varieties
of the seed as well include calrose,
as fiber- and protein- valencia, and bomba.
rich bran. Some risotto rice is also
Cooking time medium-grain.
Brown rice takes two
to three times longer LONG-GRAIN
than white rice to cook
because hot water White rice
needs to penetrate Mild-flavored and
the tough bran layer. versatile, long-grain
white rice is one of the
These rice grains most commonly used
stay separate, rice varieties. It’s about
firm, and springy 4 times as long as it is
due to a higher wide, and cooks to a
ratio of amylose fluffy texture due to
starch. higher amylose levels.
Basmati is a popular
SCIENCE COOKING AMYLOSE: 22% long-grain rice from In Focus: Rice
AMYLOPECTIN: 78% South Asia that is firm,
FLUFFY RICE CONTAINS A AMYLOSE STARCH IS aromatic, and nutty.
HIGHER PROPORTION OF DIFFICULT TO SOFTEN, AMYLOSE: 2%
HARD, TIGHTLY PACKED WHICH HELPS RICE GRAINS AMYLOPECTIN: 98% Wild rice
AMYLOSE STARCH THAN HOLD THEIR SHAPE WHEN Although it is called
“rice,” this comes
STICKY RICE. COOKED. from a different
plant. The bran is left
intact, giving it a firm,
chewy consistency. It
requires a lot longer
to cook (up to an
hour) than other
“true” rice varieties.

BROWN LONG- FLUFFY RICE
GRAIN RICE

130 // 131 The Science of Rice, Grains, and Pasta IN PRACTICE

How much water

SHOULD I ADD
TO MY RICE?

Package instructions shouldn’t be taken as gospel.

Each type of rice, whether short-grain, basmati, brown, or wild, absorbs
almost the same amount of water. The real reason we use more water
for long-grain, brown, and wild rices is that these grains take longer to
cook, so more of the cooking water evaporates away during this
time. However, although most rice varieties can absorb as much as three
times their weight in water, too much fluid makes the cooked grains
mushy and slimy. To cook any variety of rice to perfection (slightly
firm and not too sticky), use equal amounts of water and rice—a ratio
of 1:1 water:rice—plus extra water for evaporation. For a reasonable
approximation of the “evaporation water” for white rice fill the pan with
water to about 1in (2.5cm) above the level of the rice. But be aware that
water evaporates faster from wide pans, so these may need extra water.

EVAPORATION

THE SHAPE AND SIZE OF
YOUR PAN, NOT RICE
QUANTI TY, DETERMINE
HOW MUCH WATER
EVAPORATES.

The extra #1
evaporation water
should be above the REMOVE EXCESS STARCH
level of the rice. Rinse the rice before cooking to
Judging water quantity wash off surface starch and reduce
Use equal amounts of water to stickiness. Place 1lb (450g) long-grain
rice and then add 1in (2.5cm) rice in a sieve, and rinse under cold
extra water for evaporation. water until the water runs clear.
Pans with a large diameter Washing also removes dust and
may need a little more water microscopic debris, but avoid repeated
due to greater evaporation. drenching, because this may also wash
off aromatic flavor molecules.

How Can I Cook Fluffy Rice Every Time?

How can I cook

FLUFFY RICE EVERY TIME?

Avoid mushy rice by following some simple principles.

PROTECTIVE BRAN Rice must be heated in water at 150°F on the cooked rice, it dries to a sticky layer.
(65°C) before water can force its way into the To cook rice that is fluffy, rinse off excess
WHITE RICE LEACHES dense, inedible starch granules inside each starch before you heat the rice, and don’t
MORE STICKY STARCH grain, transforming them into a soft, edible soak all-purpose long-grain rice overnight
gel, a process called gelatinization. However, because this will cause the water-engorged
THAN BROWN RICE in the process, white rice can leach a lot of grains to turn mushy and clump together
BECAUSE ITS BRAN HAS starch into the cooking water, turning the during cooking. Also make sure you are
water cloudy. As the starch-filled liquid cools using the right quantity of water (see left).
BEEN REMOVED.

COOKING RICE steamed so that all the remaining cooking water is absorbed,
leaving no starch-filled water behind to form a sticky coating
All you need to cook tender, fluffy, nonsticky long-grain on the rice.
rice is a pan with a tight-fitting lid. The rice is first boiled at
high heat to allow the starches to start gelatinizing, and then

#2 #3 #4

GELATINIZE THE STARCH ABSORB MOISTURE SEPARATE THE GRAINS
Put the rinsed rice in a pan with water. Once the pan has nearly boiled dry When the rice has absorbed the
The water should reach approximately and the grains softened, allow the rice cooking water, remove the pan from
1in (2.5cm) above the level of the rice to absorb the cooking water by lightly the heat to prevent the rice from
in the pan to allow for evaporation steaming it. Cover with a tight-fitting overcooking. With the lid still on, leave
(see left). Bring to a rolling boil with lid, reduce the heat to very low, to stand for 10 minutes or more. As the
the pan uncovered. When rice and simmer gently for a further rice slowly cools, the softened starch
reaches 150°F (65°C), the starches 15 minutes, until the water is crystals will firm up (a process called
begin to swell with water and absorbed. Do not lift the lid and retrogradation), causing the grains to
soften, or gelatinize. let the steam escape or stir the separate. Use a fork to gently fluff up
rice while cooking. the rice just before serving.

132 // 133 The Science of Rice, Grains, and Pasta COOKED-RICE TIMELINE

Is it okay to TIME WHAT WHAT
HAPPENS TO DO
REHEAT COOKED WITHIN
RICE? 10–60 Cooked spores may · Serve as soon
MINS have hatched into as possible.
Reheating rice requires extra care. living bacteria. They
multiply on cooked rice · Cool leftovers—
An unpleasant soil bacteria called Bacillus cereus lives on at room temperature transfer to shallow
the surface of moist rice. Cooking kills the original bacteria, and release toxins. dishes, or rinse and
but not all their hardy spores—these chrysalis-like seeds drain in cold water,
may sprout into life on cooked rice and release toxins that and then refrigerate.
can cause abdominal pain, vomiting, and diarrhea if eaten.
DAY 1 Bacteria grows slowly in · Use today if you
Danger of cooling slowly DAY 2 the refrigerator. Levels want to reheat.
DAY 3 may be low enough for
Bacillus cereus starts to multiply and release its toxins on reheating if cooked rice · Make sure rice
cooked rice between 39–131°F (4–55°C). Cooked rice was cooled within an is piping hot.
becomes unsafe once the bacteria and toxins reach a hour the previous day.
critical level, but the smell and appearance of the rice is · Do not reheat
unchanged. Always cool promptly and store cooked rice more than once.
at less than 41°F (5°C) to slow growth—the quicker you
do this, the safer leftover rice will be to use. Bacteria level is · Use for cold
dangerous for dishes only.
reheating, which
will trigger a surge · Do not reheat.
in toxin production
(see below).

Bacteria level is · Use for cold
dangerous for dishes only.
reheating, which will
accelerate growth and · Do not reheat.
produce more toxins. · Discard if not used.

Bacteria spores
in cooked rice

On cooked rice, heat-resistant Bacillus
cereus spores reawaken into active
bacteria. They can multiply quickly at
room temperature and early in cooking to
release toxins that cause food poisoning.
Reheating cooked rice may kill the new
bacteria, but will not destroy the toxins.

Spores develop into bacteria.

Bacteria release toxins.

Diarrheal toxins Emetic toxins (causing vomiting)
produced at produced at 53–99°F (12–37°C).
50–109°F (10–43°C).

“ You don’t need to cool food
completely before putting it in the
refrigerator—modern appliances
readjust quickly after an influx of
”heat. There is greater risk from
leaving food out at room
temperature.

134 // 135 The Science of Rice, Grains, and Pasta

DATA The Process of RELEASE PRESSURE
Once the food is
How it works PRESSURE cooked through, follow
Food sits in or is suspended COOKING the manufacturer’s
just above a moderate quantity instructions to release
of water or stock. It is cooked Trapped inside a tightly sealed pan, superheated pressure. Drain off
in pressurized steam at above steam inside the pressure cooker cooks food rapidly. excess liquid and serve
normal boiling temperature. the food immediately.
Pressure cookers often languish at the back of the cabinet, unused,
Best for but they are an incredible tool for time-pressed cooks. An extremely #6
Grains, legumes, stocks, stews, tight-fitting lid stops steam from escaping so the air pressure in the
soups, and large cuts of meat. pan rises. This in turn raises the boiling point of water, creating a
very hot, steamy cooking environment. As a result, the cooking
What to consider times for stews, soups, stocks, and grains are cut drastically.
Many pressure cookers have a
steamer basket or trivet, which Water molecules
penetrate grains.
allows food to sit above the
level of the water. This makes Individual grains TURN ON THE HEAT #4
swell sideways as After securing the
it possible to cook several water bonds with lid, place the pan
different foods at the same time. starch to form a on the stovetop over
medium-high heat.
33% soft gel.

Pressure cooking takes Superheated
about a third of the water cooks
time of cooking in grains rapidly.
an open pan.
See inside
UNDER PRESSURE
Because the chamber inside the cooker is under
STEAM IS UNDER HIGH high pressure—around 15psi (pounds per square
PRESSURE, SO IT COOKS inch)—water molecules need more energy to
FOOD QUICKLY AT HOTTER emerge as steam, meaning that water reaches the
boiling point at 248˚F (120˚C), rather than 212˚F
TEMPERATURES THAN (100˚C). These superheated water molecules cook
ARE USUALLY food much faster than boiling or steaming.
POSSIBLE.
Key
CLEAR STOCKS Movement of water molecules
Heat traveling from water
PRESSURE COOKING IS
IDEAL FOR MAKING STOCK.

AT A STEADY PRESSURE,
LIQUID DOESN’T BOIL,
SO IT REMAINS
CLEAR.

The Process of Pressure Cooking

Highly energized #5 VENT STEAM The handle has CLOSE AND LOCK THE LID
water molecules Once the cooker reaches pressure, steam two parts that lock Lock the lid and pan
is emitted from a vent in the lid. At this together to seal in together using the handle.
fill the pan at point, reduce the heat to medium-low, steam—it may This ensures that no steam
twice the density to prevent further pressure increase and also have a can escape, so increases air
of a normal pan, loss of water. Continue to cook for the pressure gauge. pressure inside the cooker.
cooking the food specified cooking time.
from all angles. #3

An airtight sealing ring
helps retain pressure
inside the cooker.

Steam circulates inside
the pressure cooker.

#2 PLACE FOOD IN THE COOKER
Foods such as chicken can be cooked in
a steam basket or trivet above the water. Softer,
faster-cooking foods, including vegetables, are
best cooked in a steamer basket.

#1 ADD LIQUID
The quantity of water, broth, or stock you need
to use depends on the model of pressure cooker
you have, so always check the manufacturer’s
instructions. For grains and vegetables, use around
1 cup of water for every 15 minutes of cooking time.
For soups and stews, liquid should reach between
half and two-thirds of the way up the pan.

Stovetop pressure cookers often
have a thick base made of three
layers of metal, in order to
spread heat evenly.

136 // 137 The Science of Rice, Grains, and Pasta

Why is Do I really need to

WHOLE GRAIN SOAK PULSES
BETTER THAN BEFORE I
PROCESSED?
COOK THEM?

Whole grains contain bran—rich in key nutrients. Soaking reduces cooking time, but at a cost.

Whole-grain foods, also called whole wheat or whole meal, Beans and lentils, known as “pulses” when dried, are rich
are made from grains and cereals that contain all of the bran in protein, carbohydrates, fiber, and many nutrients, such as
and germ (see below). Flours labeled “brown” contain the essential B vitamins. Many recipes say that pulses need to
less bran, while the labels “multigrain,” “stone-ground,” be soaked before cooking, but this is not quite the case.
or “100 percent wheat” indicate that they contain the
nutrient-dense germ, but not all of the bran. For pulses to be edible, the moisture lost in the drying
process must be restored. This can be done by simply
Bran carries both nutty flavor notes and many nutrients. cooking them for a long time (up to 2 hours for large
The fiber of bran is not digested, but bulks up food, beans). Soaking restores some water into the dried beans
triggering feelings of fullness. A fifth of the fiber is before cooking, reducing cooking time, but usually affects
“soluble,” which turns into a gloopy gel in the gut, texture, turning beans mushy and making them blander.
helping to slow sugar and cholesterol absorption from food. Use the chart, opposite, as a guide on whether or not to soak.

WHOLE GRAINS Brush “Many recipes say that pulses
This is part of the need to be soaked before cooking,
GRAINS THAT ARE ALMOST grain’s inedible husk,
ALWAYS “WHOLE” INCLUDE which is removed but this is only a half-truth.”
CORN, RICE, OATS, WHEAT from all grains.
Should I salt the water? Soaking in salty
BERRIES, TEFF, Bran water increases
AND QUINOA. Made of tough The notion that it is bad to add salt size by 80%
fiber, this is rich to beans before or during cooking CANNELLINI BEAN
Endosperm in B vitamins, is wrong. Adding salt to the water
This starchy minerals, and (about 3 tsp/15g per quart/liter)
core contains disease-fighting enhances flavor and stops pulses
a small antioxidants. from becoming too waterlogged
amount of and mushy because salt
protein, fiber, Multi-layered, “pulls” a little of the water
and iron. edible bran. away from the less-salty
bean, slowing the speed at
Germ Anatomy which water penetrates the
This sprouting of a grain skin. Salt will eventually
part of the seed penetrate the bean, where
The grain it destabilizes the tough
has omega-3 shown is a pectin glue that holds the
fats, vitamins, wheat kernel. cells together, ultimately
and minerals. Of the weight, cooking them quicker and
83 percent is more evenly.
the endosperm,
14 percent is the Soaking in plain water
bran, and 3 percent increases size by 120%
is the germ.

Do I Really Need to Soak Pulses Before I Cook Them?

TYPE OF PULSE THE EFFECTS OF SOAKING

The size of the pulse you are using affects how Overnight soak Rehydration boost Integrated quick soak
much cooking time it needs and how much it
benefits from soaking. Leave pulses in cold Soak for 30–60 minutes Boil pulses 1–2 minutes,
water overnight (or for a in cold water just before remove from heat, cover,
period of around 8 hours cooking to kick-start and soak in the hot water
before cooking). rehydration. for 30 minutes; then cook.

Split peas and beans Unless very old, a long Split pulses rehydrate The shorter cooking time
soak isn’t needed as the quickly when cooked, so for split pulses means an
These small pulses have exposed core means there’s little to gain from integrated soak is
been cracked down the they hydrate rapidly. a short presoak. unnecessary.
middle after harvesting, so Short soakings speed Saves just 5 minutes
they have an exposed core. cooking slightly without overall cooking time,
causing loss of texture. but allows more
SPLIT PEAS Gives just a small flavor-generating
reduction in cooking reactions.
Small pulses Small pulses can time, but preserves Large pulses rehydrate
become waterlogged flavor and texture. and preserve flavor.
Includes pinto beans, from a long soak and Shaves off around 30
adzuki beans, and any lose bite and subtle flavor. minutes cooking time.
pulse the size of a black
bean and smaller.

BLACK BEANS

Large beans Soaking overnight can
and chickpeas reduce cooking time
by up to 40 percent,
Includes beans that but can affect flavor.
are cannellini size
and larger. Dried KIDNEY BEAN CHICKPEA
chickpeas are dense
so slow to rehydrate.

BEAN SIZE COMPARISON OLD AND DRY

Use this chart to figure out whether (or how) REGARDLESS OF SIZE, THE
to soak each type of pulse. OLDER A PULSE IS, THE

SPLIT PULSE SMALL PULSES CHICKPEA AND MORE IT WILL HAVE DRIED
LARGE PULSES OUT, SO SOAKING IS
BENEFICIAL.

SPLIT PEA PUY SOYBEAN BLACK PINTO CHICKPEA CANNELLINI KIDNEY BUTTER
LENTIL BEAN BEAN BEAN BEAN BEAN

“ The word “quinoa” is a
Spanish version of the Quechua
word “kinua” or “kinÚwa.” “Qui”
is pronounced “kee” rather than
“kwi.” Quechuan people are likely
to pronounce it phonetically
”as “kee-NOO-ah.”

Why Exactly Is Quinoa So Special?

Why exactly is

QUINOA SO SPECIAL?

The Incas cultivated and ate quinoa as a staple food and gave it a sacred status, calling it the “mother grain.”

Marketed as a “whole food,” quinoa is increasingly While nutritionally quinoa is considered a

popular, with all the hallmarks of a “superfood”: whole grain, it isn’t a true grain because it is

it is gluten-free, is nutritious, and, originating not the seed of a grass plant; rather, quinoa

from South America, has a long, fascinating NUTRIENT FEAST is related to beets and spinach, so

history. Sidelined by wheat and other crops, HIGH IN PROTEIN, QUINOA it is called a “pseudograin.” Quinoa also
quinoa is, however, a “superfood” that might BOASTS ALL NINE looks different from other grains, sporting
live up to the hype, being extremely high in wormlike strings when cooked (see below).
protein and full of nutrients (see box, right). ESSENTIAL AMINO ACIDS,
OMEGA FATS, B VITAMINS,

About the same size as mustard seeds, the AND MINERALS.

most popular variety, “white” quinoa, looks “Similar in appearance
like couscous and can be cooked in the same way as to couscous, quinoa is cooked
rice (see pp130–131), producing a fluffy grain. It can also
be popped like popcorn if you dry roast it, turning it into a in the same way as rice.”
crunchy topping for soups and breakfast cereals.

UNCOOKED COOKED
Other grains
The germ, The germ may A BITTER BITE
In most grains, such as the part that split open after
pearl barley and millet, sprouts into a new cooking but the QUINOA IS RINSED OF
the germ, which contains plant, is housed germ remains ITS NATURAL COAT OF
many of the nutrients, is inside the grain. inside. PARASITE-REPELLING
buried inside the starchy
core. Whole-grain foods BITTER SAPONINS.
preserve the germ, but
in refined grains this is
often removed through
milling (see p136).

Quinoa The quinoa When cooked, the A QUICK DISH
germ is on germ separates,
This differs in appearance the edge of indicating that QUINOA IS A FAST-
from other grains because the grain. the grain is COOKING STAPLE TO
the protein- and cooked through. R U S T L E U P, CO O KI N G I N
mineral- rich embryo JUST 15–20 MINUTES.
part of the seed (the
germ) is coiled
around the outside
rather than buried
in the core.

140 // 141 The Science of Rice, Grains, and Pasta

How can I keep beans from The pressure that
builds to a bang
GIVING ME GAS?
Cooking popcorn causes its core to heat up, turning the water
Don’t be put off by beans—in fact, eat more. inside to steam. Entombed within the popcorn’s tough hull, the
steam cannot escape, so as the kernel gets hotter, the pressure
Rich in fiber, protein, and essential nutrients, beans are rises. At 356°F (180°C), the pressure inside has soared to nine
thoroughly good for health. However, for people who do times normal air pressure, and the hull explodes with a bang.
not normally eat this high-fiber food, a meal of beans gives
the gas-producing bacteria in the gut a sudden excess of Starch erupts Steam pressure breaks
fuel to feast on, thus proliferating. These bacteria digest from the kernel. the kernel open.
the food that we can’t, namely fiber, and produce gas as a
by-product. Soaking dried beans and peas before cooking
and draining away the water is thought to help remove
some soluble fibers, such as the oligosaccharides, which
are usually the culprit for producing gas. Soaking cannot
remove insoluble fiber, however, so this is often ineffective.
A better strategy is to eat beans and other pulses regularly
in small quantities, so that gas-producing bacteria do not
suddenly overrun their non-gas-producing counterparts.

Is it true that uncooked Germ
Starch molecules
KIDNEY BEANS ARE
POISONOUS? cook in the
heated core.
Like many plants, kidney beans contain toxic substances.
#1 #2 #3
Kidney bean plants are poisonous, producing a toxic
substance to keep animals from eating them. In kidney RAW KERNEL STEAM BUILDS HULL “POPS”
beans the poison is called phytohemagglutinin, which, The unpopped Cooking turns Pressure builds:
if swallowed, damages the gut lining, leading to severe kernel consists the water inside at 356°F (180°C),
vomiting and diarrhea. As few as four raw kidney beans of a starchy core the kernel to nine times normal
are enough to send the intestines into a painful rage. steam at 212°F air pressure, the
Phytohemagglutinin is destroyed only at high temperatures; and water (100°C), but it hull ruptures with
it actually becomes more potent when warmed, so droplets encased cannot escape the a “pop,” the sound
undercooked beans are even nastier than raw ones and dense, tough hull. of escaping gas.
have been known to cause outbreaks of poisoning after in a tough,
being stewed at a low temperature for many hours. When dense hull.
fully softened, kidney beans must be boiled hard for at
least 10 minutes to destroy the phytohemagglutinin and
make them safe; this can be done toward the beginning or
at the end of cooking. Canned beans are already cooked
so they are always safe. Cannellini beans and broad beans
contain phytohemagglutinin in smaller amounts, so while
less dangerous, these also should be cooked well.

Why Does Popcorn Pop?

Why does

POPCORN POP?

Cooking triggers an incredible explosion that turns hard-shelled seeds into fluffy white popcorn.

Popcorn is special among corn varieties. The kernels core, and this water will turn to steam when heated and cause
of all types of dried corn will pop, but most do it with a a violent eruption. For this reason, popcorn should be stored
whimper—popcorn seeds have a remarkably dense and in an airtight container to preserve the residues of moisture that
tough outer hull formed from very tightly knit cellulose power its explosion when cooked. Old, very dry popcorn will
fibers, which gives them their explosive popping potential. not pop, and will instead be left as burned, acrid-tasting
unpopped kernels at the bottom of the pan, called “old maids.”
The popcorn plant looks almost identical to a regular corn
plant, except that the tassels on the stalks droop on As a whole grain, popcorn is high in fiber and low in
popcorn plants rather than stand upright as they do on sweet calories, especially when air-popped (blasted with hot air)
corn. The kernels, which are mostly starch and water, are rather than cooked in oil. Weight for weight, popcorn contains
left to dry on the cob until they can easily be rubbed off. more antioxidants per serving than most fruit
At harvest, they contain about 14 percent moisture in the and vegetables and more iron than beef.

Starch spurts from the core The whole bloom takes only
in all directions due to the spinning one-fifteenth of a second to
motion, cooling rapidly as it expands. form after the hull cracks.
The dense hull is
finally overcome
by steam pressure.

#4 #5 #6

PROPULSION STARCH BLOOMS FLUFFY CORN
Heat has cooked The force of the In milliseconds,
the starchy core, steam causes the the innards cool
and as it emerges cooked starchy and set into a
from the cracked innards to gush bloom of crisp,
hull, it sends the from the kernel white starch that is
kernel spinning. up to 40–50 times
as it spins in its original size.
the air.

142 // 143 The Science of Rice, Grains, and Pasta

How can I make my own

FRESH PASTA?

Making your own pasta is surprisingly simple, but the type of flour you use can make all the difference.

Pasta-making recipes often suggest using “00” flour, rubbery pasta. Durum wheat flour, used in pasta, has a

which is the Italian grade for the most finely milled, high protein (gluten) content, so it isn’t suitable

powdery flour. These tiny particles mix easily for fresh pasta recipes that contain eggs.

and help make a silky-smooth pasta; however, A STRONG DOUGH The step by step below shows you how to
00 flour is not essential. White all-purpose or make pasta dough by hand. A food processor

cake flours also give excellent results and IF YOUR FLOUR DOESN’T is useful for making pasta in larger batches,

have an equivalent protein content—00 flour CONTAIN HARD LUMPS, but care is needed to avoid overmixing, which
is typically low in protein at 7–9 percent. A THERE'S NO NEED TO SIFT can cause too much gluten to form and make
low-protein flour is important when making a stiff dough. Pulse for 30–60 seconds, stopping
fresh egg pasta because the eggs provide the AS YOU WANT TO AVOID when the mix has a coarse, couscous-like
AN AIRY MIX.

protein needed to bind the pasta together, so texture that presses together into a dough; then

using a high-protein flour would result in a dense, turn out and knead the dough on the work surface.

IN PRACTICE MAKING FRESH PASTA piece individually until around 2mm thick. The flour used
in this recipe is 00 flour, but an all-purpose flour, or a cake
Using a pasta machine, as shown here, is by far the easiest flour/all-purpose flour mix (2:1), can be used instead.
way to roll out and thin pasta dough. If you are using a
rolling pin, divide the dough into pieces and roll out each

#1 #2 #3

COMBINE THE EGGS AND FLOUR KNEAD AND REST DOUGH ROLL AND FLATTEN DOUGH
Pour 6oz (165g) 00 flour onto a clean, Push the remaining flour into the Unwrap the dough. On a floured
dry work surface and make a well in center. Knead the dough firmly by surface, roll the dough out into a
the center so liquid doesn’t escape. hand for 10 minutes to build gluten circle and then pass it through a pasta
Crack 2 eggs into the well and add networks and create a strong, elastic machine three times on the thickest
½ tsp salt. Drizzle with olive oil for a dough. If too dry, add a little water setting to further develop the gluten.
smooth, easy-to-handle dough. Beat or olive oil for moisture; add flour to Fold the dough into thirds, flatten it,
the eggs in the well lightly with a fork, absorb moisture if too wet. Wrap in and pass through the machine again.
and then gradually draw flour into the plastic wrap to keep it moist, and rest Repeat six times.
center and bind with the eggs. it in the refrigerator for an hour for
the starch granules to absorb moisture
and the gluten fibers to spring back.

“A low-protein
flour is needed

in egg pasta
to keep the
pasta from
becoming too

dense and
rubber y.”

#4 #5 Pairing pasta and sauces

ROLL TO FINAL THICKNESS CUT TO SIZE Pasta comes in a multitude of shapes and
Continue to roll the dough through the Fold the dough into thirds with the sizes, many devised for a specific type of
machine on decreasing settings until folds at the top and bottom, and then dish. Pasta geometry should be paired with
you reach one notch before the finest cut it into strips: ½in (1cm) wide is the the thickness and viscosity (or stickiness)
setting—this is the ideal thickness for standard size for pappardelle, ¼in (6mm) of the sauce.
cut pastas. Dough intended for stuffed for tagliatelle. Cook until al dente in
pastas should be rolled all the way to boiling water (see pp144–145). · Traditional spaghetti noodles tangle
the finest setting. easily, so they naturally entwine with and
hold sauces containing coarsely cut
vegetables, seafood, or meat pieces.

· Flat strips, such as tagliatelle, capture
thick sauces, such as bolognese or ragù,
well, but the long, flat surface sticks and
clumps together with sticky cheese sauces.

· Tube-shaped pasta noodles, such as
penne, with a smaller surface area, slide
past each other in gloppy sauces, so they
work well with thick, oily, and thin sauces.

· Ridged pasta Thin, oily, or tomato-based
sauces pair with ridged, spiraled, or
textured shapes, such as penne rigate,
because the contours and bumps help the
low-surface-tension sauce cling to the pasta.

· Shell-shaped pasta is ideally
proportioned to capture a medium-
thickness sauce.

· Round gnocchi potato dumplings
are well suited for thick cheese sauces
because these larger dumplings are less
likely to gravitate toward each other and
clump together.

144 // 145 The Science of Cooking Rice, Grains, and Pasta

Is fresh pasta better KNOW THE DIFFERENCE

THAN DRIED? Dried pasta Fresh pasta Stir pasta
Available in a range of shapes This has a relatively short in the early
Many of us think of dry pasta and varieties, dried pasta is a shelf life and needs to be kept
as a cheap alternative to fresh, convenient pantry basic. refrigerated before use. stages of
but in Italy these are treated cooking to
Dried pasta is made with Fresh pasta substitutes prevent it
as separate ingredients. strong durum wheat flour water for either whole
and water. The kneaded eggs or egg yolks. The sticking
Dry pasta is usually cheaper than fresh, but dough is rested so the fat lends tenderness while together.
not necessarily inferior; indeed its production gluten networks strengthen. the egg protein substitutes
in Italy is highly regulated. Conversely, It is then rolled repeatedly for the gluten in durum
mass-produced fresh pasta can have a gluey before being cut into flour, strengthening the
texture that is a poor imitation of truly shapes. The high gluten pasta so it can withstand
freshly made pasta. levels give the pasta enough boiling water. The durum
strength to withstand being wheat flour is thus not
Dried and fresh pasta have different cooked in boiling water. needed.
uses in Italy. Fresh pasta, made with
eggs, has a tender consistency and more Dried pasta takes longer to Fully hydrated, it cooks in
luxurious buttery flavor than dried and pairs cook (9–11 minutes) boiling water very quickly
well with creamy or cheese-based sauces. because the starch granules (in 2–3 minutes).
Dried pasta has a firmer bite so is easier to need to rehydrate fully first.
cook al dente, and is robust, so best paired
with oily, meaty sauces (the exception being
bolognese, traditionally served with fresh
tagliatelle). Choosing which pasta to use
really comes down to ingredients rather
than pasta type.

How does adding salt

TO MY PASTA WATER HELP?

The traditional way to cook pasta is to throw the pasta into a large pot of water
and add a sprinkle of salt, but the benefit of the salt is often misunderstood.

Adding salt to pasta water improves the rather than raise the temperature. Salted water

taste of pasta, makes it easier to cook it al does boil slightly faster, but the difference

dente, and removes some of the sticky is negligible. More notable is the effect

starch. Some also believe that adding A PINCH OF SALT of salt on how the starch cooks. The

salt speeds cooking, but in fact the IT WOULD TAKE 4 TBSP OF mesh of wheat protein strands (gluten)
opposite is true. SALT TO RAISE THE from the flour encases the starch
BOILING POINT OF 1 granules. We cook pasta to crack open
The speed of boiling starch particles so they absorb water
QUART OF WATER BY JUST

Adding salt to almost simmering water HALF A DEGREE. and coalesce into a gel. Wheat starch

makes the water bubble up to give the gels at 131ºF (55ºC), but salt interferes

illusion that the salt is bringing on a boil, but with this process, nudging this temperature

the particles of salt simply stimulate bubbles, up, so the pasta actually cooks a little more slowly.

Does Adding Oil to Cooking Water Keep Pasta from Sticking?

Does adding oil to cooking water

KEEP PASTA FROM STICKING?

Dribbling a dash of olive oil into the cooking water is common practice,
believed to give pasta a smooth coating and to keep it separated.

Clumps of bland, sticky pasta aren’t early stages of cooking, when starch

appetizing. Advice on how to on the pasta surface turns into a

stop pasta sticking ranges from sticky gel. As pasta firms, the

adding olive oil to stirring SAUCE THAT STICKS pieces will separate and you

the water. Knowing how and KEEP SOME OF THE can stop stirring.
when to apply the advice STARCHY PASTA WATER
will help you perfect your TO USE AS A THICKENING When to add oil
pasta cooking.
AND BINDING AGENT The next sticking point is at

Adding a dash IN YOUR SAUCE. the end of cooking, as pasta
of lubricating
oil before The role of stirring cools and starch from the water
serving helps
pasta to Observant cooks will be skeptical of becomes gluey. Unless using a sauce, a
separate.
the merits of adding oil to the cooking water drizzle of olive oil now coats the pasta to stop

as oil simply blobs on the surface, away from it sticking. Rinsing cooked pasta in fresh hot

the pasta. It is more effective to stir pasta in the water also removes this starchy glue.

How starch acts on pasta Starch seeps from the pasta
surface into the cooking water.
Dried pasta takes about 8 minutes to cook.
Knowing the right moment to stir or add oil
will ensure it doesn’t stick.

BEFORE COOKING 1–2 MINUTES 3–6 MINUTES 7–8 MINUTES AFTER COOKING
Dry pasta contains Pasta swells as it Starch continues Once outer starch Add a drizzle of
starch granules takes in water, and to soften on the layers have olive oil (if not
that are held in gets sticky as starch surface of the firmed, they stop using a sauce) or
place by a protein turns gel-like. Stir pasta. Stir sticking together rinse the pasta in
mesh. Cooking continuously occasionally to and you can stop just-boiled water
breaks open the now to help keep the pasta stirring the pasta. to stop it sticking.
granules. stop sticking. separated.



VEGETABLES, FRUITS,
NUTS & SEEDS

148 // 149 The Science of Vegetables, Fruits, Nuts, and Seeds

Are organic fruits and vegetables

BETTER THAN NON-ORGANIC?

Many believe that organic produce, grown without artificial pesticides or fertilizers, has better flavor and more nutrients.

Taste isn’t just about a food’s aroma and flavor molecules. KNOW THE DIFFERENCE

Research shows that our beliefs about the food we eat

tangibly affect its flavor, and that the moral satisfaction we Small-scale production Large-scale production
Produce from small farms can Mass-producing fruits and
get when we eat ethically produced organic produce enhances have the edge in terms of flavor. vegetables can impact flavor.

our enjoyment of the food. The nutritional and flavor claims Harvest from small farms Intensively produced
distributed locally has less fruits and vegetables are
made by organic food producers, however, are not always borne time to degrade and is less more likely to be damaged
likely to be bruised, which if harvested by machine,
out by science. Testing shows mixed results helps preserve flavor. impacting flavor and
nutrients (see opposite).
for nutrient levels, the consensus being Small farms are more
likely to grow intense- Mass-produced varieties
that organic has only a slight tasting heirloom varieties can taste bland, but some
(see below) and sweet- have been bred to be
SOIL DEEP edge. The flavor molecules tasting vine-grown produce sweeter and more palatable
in organic and nonorganic than industrial-scale farms. than bitter heirloom
varieties (see below).
MORE NUTRITIONALLY produce are similar and trained

IMPORTANT THAN ORGANIC tasters rarely spot differences.
STATUS IS THE QUALITY Farming methods can impact
OF THE SOIL AND quality (see right). Organic
THE MINERALS IT produce is most likely to
PROVIDES.

come from small, local farms.

HEIRLOOM FRUITS AND VEGETABLES Are heirloom varieties

Dozens of traditional fruit and vegetable varieties exist, TASTIER?
compared to the handful of highly productive commercial
varieties we are used to buying. Keeping rare varieties of fruits and vegetables alive
helps us to continue diversity in the plant kingdom.
HEIRLOOMS 93%
CAN HAVE of vegetable Heirloom breeds are traditional varieties that have
INTENSE crop varieties are not been cross-pollinated in the past 50 years for
FLAVOR. estimated to have intensive farming. They promise us a flavor of the
become extinct in past, with a stronger tasting, more nutritious product.
the past century. Heirloom varieties can offer more vitamins and
antioxidants, although the total mineral content is
THE BITTER-TASTING MANY dictated by soil quality, rather than the actual breed.
CRAB APPLE HAS VARIETIES
15 TIMES MORE CAN HAVE A It is no secret that many fruit and vegetable breeds
SOUR TASTE. of old were smaller, tougher, and more bitter tasting
ANTIOXIDANTS THAN than the produce of today, which has been specifically
THE SWEET, MORE bred to be larger, softer, and generally sweeter. Whether
WATERY GOLDEN heirlooms are tastier really comes down to personal
DELICIOUS. preference, but for the cook in search of an intensity
of flavor that modern vegetables don’t deliver, an
heirloom variety can be a worthwhile investment.