Modernist Cuisine - Volume 2

7

truth is a bit more complicated. Some smokers and Ultimately, of course, your main concern is not Although it's common practice, we
some styles ofsmoking do not produce enough the humidity per se but how fast and far the don 't recommend wetting wood
carbon monoxide and nitrous oxide to make a smoked food has dried. The best gauge of that is chips to increase hum idity. Wetting
visible ring, yet they can still produce very good the pellicle, the coating that forms from vapors, chips lowers the temperature of the
smoked flavor. Also, smoke rings won't form in oils, and tars in smoke as they react with proteins, smoldering wood so much that the
foods that don't contain myoglobin-that is, in any sugars, and starches on the food surface. Phenols smoke can turn acrid.
foods that aren't muscle tissue. and carbonyls that adhere to the surface react to
become glossy resins that impart a shiny finish. In The tanning properties ofsmoke
Thus, the smoke ring is a sufficient indicator of high-protein foods, formaldehyde and creosote can be prob lematic fo r poultry,
technique, but not a necessary one. Let taste, also firm the surface in a process similar to making the sk in too to ugh and
rather than the presence of a flavorless smoke ring, tanning. leathery.
be your guide to the quality ofsmoked food .
A skilled craftsman can watch the development
Wet Food, Dry Food of the pellicle and know whether or not the drying
is going right or horribly wrong. A dry, tacky
Meeting the second challenge ofsmoking- pellicle with uniform coloration is a sure sign of
ensuring your food stays moist enough to capture quality smoking. Such a pellicle contributes
flavorful vapors but is not so wet that it drips- directly to the flavor and texture; it also confirms
usually means, in practice, adding humidity to the that conditions were optimal for the adsorption
air in the smoker. Smoldering wood produces a and diffusion of flavorful compounds.
dense smoke that is far drier than the relative
humidity of70%-80% that is usually ideal. A hardened pellicle, on the other hand, signals
Advanced smoking equipment controls humidity overdrying, and a pale, wet, or streaky one means
directly by adding the right amount ofwater vapor that the food was too wet. Iftoo much water
to maintain a desired relative humidity. In more accumulates on the surface, Maillard-like reactions
traditional equipment, you can counter the between carbonyls and the food can't happen, and
parching effect of smoke by placing broad, shallow proper color and flavor won't develop. Texture can
trays ofwater in the bottom of the smoker or by suffer as well. Hot-smoking fish at a relative
frequently misting warm water into the chamber.
humidity above 60% at so oc I 122 op (or lower
Complicating matters is the fact that the humid-
ity in smokers varies constantly and evades direct humidities at higher temperatures) quickly gelati-
measurement. Relative-humidity meters are of nizes collagen fibers. The weakened flesh tears
limited use in smoking chambers because they under its own weight, often right off the hook.
quickly become coated with particles ofsoot and
droplets oftar that compromise their accuracy. Cold-Smoking
Sophisticated smokers use wet- and dry-bulb
thermometers to calculate relative humidity instead. Traditionally, smoking was a way to preserve food
in the absence of refrigeration. The volatile acids in
smoke kill bacteria on the surface offood, and

TRADI TI ONAL COOK I NG Wood pellets (left) and chips (right) are
both perfectly acceptable fuels for
smoking. Pellets work best in smokers that
have a hopper or an augur system;chips
are fine for hand feeding.

14 1



7

thorough drying discourages microbial activity texture of food cold-smoked over days and weeks, Cold-smoked food is low in
throughout the food interior. there are no shortcuts. The extended drying po lycyclic aromat ic hydrocarbons,
cannot be fully replicated in any other way. carcinogenic compounds that
But cold-smoking, as the name suggests, condense out of smoke vapo r at
The challenge, then, is to keep the temperature low temperatures. Early evidence
typically takes place at 20-30 oc I 68-85 °F or and humidity of the smoke just right for such long for the presence of these toxins in
periods. If the smoke is too warm, too dry, or both, wood smoke came from the high
lower, temperatures that are too cool to pasteurize then evaporation at the surface of the food out rate of cancer in chimney swee ps.
food. Moreover, the drying stage often involved in paces the migration ofwater from the interior, and
cold-smoking can take days or even weeks to a crust forms that seals moisture in the food. This The epitome of traditional cold-
complete-days and weeks in which the smoking unfortunate condition is known as case harden- smoking for preservation is
food is vulnerable to the growth of microbial ing, and it tastes as bad as it sounds. katsuobushi, an essentialJapanese
contaminants. As a result, many traditional preparation of skipjack tuna in
cold-smoked foods are first treated with curing Many cooks try to meet the challenge simply by which the fish is briefly boiled,
salts, particularly nitrate and nitrite salts. The wetting their smoldering wood, hoping that this fe rmented wi th a mo ld, cold-
cures prevent the growth ofanaerobic bacteria will raise the humidity and lower the temperature smoked, then fu lly dried.
and, in combination with smoke, inhibit the of the smoke. It will-but it will also make the
production of the spores that cause botulism. food acrid because the wood will smolder at a Smoke has natural antioxida nts that
much lower temperature than is ideal. A better offset the tendency of salt to
These days, cold-smoked food is preserved strategy is simply to move the fire box further accelerate oxidation and rancidity
mostly in refrigerators, and we prize it less for its away so that the smoke cools more before reaching in cured foods.
shelflife than for its unique flavors-in particular, the smoking chamber, where you raise the humid-
the warm and peaty notes ofcreosols and malti- ity with trays ofwarm water. Smoking in desert climes, such as
tols, which stay in the gaseous phase even at the American Southwest, is often
relatively cool temperatures. Contemporary Some high-tech smokers have refrigeration coils best done in the even ing or at night.
practitioners don't use nearly as much salt as was in the chamber that make it easy to control the The ai r is so dry during the heat of
the historical norm, and some no longer cure the smoke temperature accurately. These devices the day that it makes it extremely
food at all. Thanks to refrigeration, the long drying usually also offer a way to inject low-temperature difficu lt to raise the humidity in the
stage isn't strictly necessary, either. steam into the chamber to control the humidity smoker enough. At night, the
directly. This sophisticated smoking equipment humid ity natura lly rises as the
Ifyou abandon the curing and drying steps, comes at a cost, but ifsmoking is a centerpiece of desert cools, making it easier to
however, be aware that you do invite some haz- your cooking, the extra control and flexibility are smoke at high humidity.
ards. The cold-smoking chamber can be a breed- probably worth the investment.
ing ground for anaerobic bacteria, so it's unwise to
cold-smoke at room temperature for more than Hot Barbecue
four hours. Consider decontaminating the food
surface by either blanching or parcooking before At the high temperatures at which you hot-smoke
smoking. And ifyou're cold-smoking sausages or
other forcemeats, you must add curing salts (in food-at least 52 oc I 125 oF, but more often
many places, this is more than just sound advice; 70-80 oc I 160-175 °F-the potent clove and
it's also a legal requirement). You can safely
cold-smoke for longer times without taking these vanilla flavors of the heavier volatile compounds
precautions only ifyour smoker operates at dominate. Smoking times tend to be much shorter
than those for cold-smoking because in contempo-
refrigeration temperatures (10 oc I 50 oF). rary hot-smoking the goal is to cook the food and
pasteurize it rather than to dry it out to preserve it.
Even if you don't have to add curing salts for The higher heat hastens the formation of a colorful,
safety, you may want to do so for practical reasons. glossy pellicle, and the shorter cooking time means
In cold-smoked meats and seafoods, the salts that humidity control is less of a problem, too.
accelerate the formation of a pellicle, which
otherwise appears only slowly as drying limps One notable exception to this generalization is
along. Curing salts draw proteins, sugars, and American-style barbecue. In barbecue, smoking
other small molecules to the food surface, where times commonly reach eight hours and beyond.
they concentrate. The effect, which occurs with The slow, humid cooking tenderizes the meat as it
even a very briefsalt packing, creates a good base smokes by dissolving collagen.
for faster reactions with the vapors in the smoke.
In one style ofAmerican barbecue, whole hogs
But ifyou want to re-create the traditional dry

TRADITI ONAL COOKI NG 143



CONTROVERSIES Myth: Membranes on food block flavor penetration .
No, they don't. Biological membranes can block some
Myths and Lore of Smoking liquids, but vapors pass right through them and dissolve
into the moist flesh beneath. There seem to be two schools
Of all traditional cooking techniques, smoking has perhaps of thought on whether to remove the membrane from pork
the most ardent practitioners, who profess the most ribs: some swear it is essential to take it off, even as others
elaborate belief systems. Maybe that's because the process are equally adamant about leaving it on . The reality is that
of smoking is somehow inherently mysterious and this is a simple matter of personal preference. The
ritualistic. Or maybe it's because most cooks don't membrane will not stop smoke or flavor from penetrating.
understand the scientific facts behind smoking. We don't
want to appear irreverent, but we feel compelled to point Myth: On ly raw food abso rbs flavor.
out some cherished precepts of smoking that simply aren't As long as the surface ofthe food stays moist, aromatic
true or are widely misunderstood. vapors will continue to adsorb there and diffuse into the
food.ln fact, we've had great success cooking food sous vide
Myth: The smoke ri ng adds flavor. before smoking it. This misconception probably arose
The smoke ring results from reactions between a protein because of case hardening, an unfortunate consequence of
molecule in red meat called myoglobin and the gases poor technique in which smoking food develops a dry,
nitrous oxide and carbon monoxide in smoke. The product hardened pellicle that does block flavor penetration.
ofthose reactions can be seen but not tasted. The
reactions do, however, prevent rancid flavors from Myt h: Tars and oil droplets in the smoke create
developing, and they also stabilize the color ofthe the pe llicle and color t he food .
myoglobin to an attractive pink hue that persists during Actually, like flavor, the color of smoked food comes from
and after cooking. reactions with the invisible components of smoke-the
gaseous volatiles-rather than the smoke you can see, which
Myt h: Soaki ng wood in flavo rful liquids contributes is a combination of liquid droplets and sooty solids. The
to the taste of the food. gloss and shine of a great pellicle comes from a
Most ofthese liquids react when heated to form vapors combination of resins that form when carbonyls and
with an entirely different composition than the liquid. By phenols in the vapor interact with proteins, sugars, and
dousing your wood with them, all you're really doing is starches on the food surface.
lowering the smoldering temperature of the wood- and
likely damaging the quality of the smoke. Myth: Fat is essential for good smoked flavor.
There is some truth to this assertion . The fat content of meats
Myth: O nly so lid chunks of wood generate qua lity smoke; and seafood dramatically impacts how well food absorbs
sawdust or pellets won't work. flavor from smoke vapors. Flavorful phenols in the smoke
Pellets and sawdust are perfectly respectable materials for vapor adhere most readily to fatty tissue, and, as a result, the
smoking, but the people who use them often close the flue fat in food accumulates aromas that would otherwise be
too much, thus starving their smolders of oxygen-a greatly diminished in or even missing from the food . But too
practice that will, indeed, create poor-quality smoke. much fat covering the surface of meat actually prevents
these flavors from diffusing into the flesh itself.

These pork spare ribs are in the early stage of
hot-smoking, when neither the pellicle nor the
smoke flavor has had time to develop fully.
Hot-smoking works well for meat because the
high temperatures and elevated humidity
tenderize tough cuts by melting and dissolving
collagen fibers.

TRADITIONAL COOKING 1 45

SMOKING EQUIPMENT

Contemporary smoking equipment comes in a wide range
of styles and prices. Although many designs use traditional
methods of smoking food, at least one-the Handheld
Smoker-was inspired by an entirely different kind of smok-
ing. Not all systems are capable of true smoking or of the long
smoking times at low temperatures that barbecue demands.
A Traeger pellet smoker or a Bradley makes a great entry-level
appliance for the barbecuer.

Stove-top smokers work fine for lightly seasoning pork chops
or fish . And handheld smokers cater to the trend among cooks
to capture smoke in a bell ja r, then place it over the food during
service, as a garnish. But if you're planning to make smoked
food the centerpiece of a restaurant menu, you might want to
invest in a commercial smoker such as the Enviro-Pak.

Custom-built smoker (right)

Price: vari es wid ely
Pros: sizes range fro m bac kya rd units fo r the ho me enthu sias t to caterin g
un it s for big part ies; ve ry goo d fo r traditi o nal cl osed- pit sm o king
Cons: afford s onl y limited co ntrol of th e smold erin g temp erature and
humidity; requires con sid erabl e skill and practi ce to o perate

Handheld smoker

Price: in ex pensive
Pros: suppli es smo ke fo r a visual and arom atic ga rni sh; sui ta bl e fo r ve ry
lightl y smo kin g foo ds
Cons: not ca pabl e of tru e smokin g

Stove-top smoker

Price: inex pensive
Pros: conveni ent and easy to use; suitabl e for light smokin g
Cons: ca nnot eas il y generate high-qu ality smo ke; not suitabl e for co ld-
smoking or lengthy hot-s moking

14 6 VO LU M E 2 · TE CHNI QUE S AND EQUI PM ENT

7

Pellet smoker Bradley smoker

Pri ce : varies by model Pri ce: moderate ly expensive
Pros: pellet-fueled; suitable for co ld- and hot- Pros: provides reasonable temperature control in the smoking chamber;
smoking; digital control available good for cold- and hot-smoking
Con s: affords only limited control of the smoldering Con s: provides only modest control of the smoldering temperature;
temperature and hum idity; most models cannot cannot perform cold-smoking below ambient temperature
perform cold-smok ing below ambient temperature

Enviro-Pak smoker 147

Price: very expensive
Pros: a computer controls the smoldering temperatu re, as well as the
te m perature, vo lume and humidity of the smoke entering the chamber
with high accuracy; allows sophisticated programming
Cons: large and expensive; requires complex installation

TRADITIONAL COOKING

Un like the smoke from smoldering may cook and smoke for up to 24 hours, with the advocates of this method recommend smoking in
wood, smoke from burning wood is smoke fed from open fires that burn logs ofwood. 20-minute rounds, separated by five-minute
naturally humid because water The smoke from open flames is humid, which pauses, for as many rounds as are needed.
vapor is the main product of helps to keep the surface of the meat from drying
combust ion. too much. Premier Texas barbecue joints such as Finally, the smoking stops, and the food cooks
Kreuz Market and Smitty's Market shunt the in hot, dry air just long enough for the color and
The bursts ofsmoke used in humid smoke from the open fire into a smoking surface texture to finish developing. Although any
progressive smoking aid the chamber. smoker can accomplish the smoking steps easily
penetration of flavorfu l compounds enough, the cooking and drying steps work best in
better than continuo us smoking Other American barbecuers hot-smoke with a combi oven or a water-vapor oven, which both
does. Continuous smoking can smoldering wood. Although humidity is ample at offer greater humidity control.
create an excessively thick surface first as steam wafts from the food, long smoking
fi lm that prevents adhe red mol- sessions require supplemental moisture from The advantage of progressive smoking is that it
ecu les from diffusing into the food water-filled pans or spritzes from water bottles- separates the drying and smoking stages, which
interior. or from basting with wet mops, glazes, or sauces. maximizes the retention of juices and oils. The
food stays moister and thus absorbs flavorful
For more on cooking with combi ovens and Smoking Progress vapors better. Controlled studies have shown that
water-vapor ovens, see chapter 8 on Cooking in progressive smoking produces better appearance,
Modern Ovens, page 150. For more on cooking German sausage makers have a more high-tech aroma, and bacteriological control.
sous vide, see chapter 9, page 192. approach to humidity control during hot-smoking.
Called progressive smoking, the process was If this technique seems unorthodox to you, we
created to make it easier to strip the casings from have an even more heretical suggestion. We
smoked sausages, but it has impressive advantages advocate smoking food cooked sous vide-that
for all other kinds ofhot-smoked foods. is, with the food vacuum-sealed in a plastic bag,
then cooked in a water bath. Cook the food sous
As the name implies, progressive smoking is vide as long as you like, remove it from the bag,
performed in stages. First you cook the food at and dry the surface in a standard oven at a low
high humidity to the desired core temperature. temperature until it is just tacky. Then smoke it in
Then a briefperiod at low humidity dries the a humid environment (ideally around 80%
surface, which initiates the formation of the relative humidity) until the smoked appearance
pellicle. Next the food is smoked in humid air for 20 and flavor develop fully. Depending on the
minutes to several hours, depending on the size of desired degree of smokiness and color, this stage
the food. To get a strong but balanced smoke flavor, can be as brief as 30 minutes or as long as a
couple of hours.

148 VOLUM E 2 · TECHNIQUES AND EQUIPM ENT









COOKING IN MODERN OVENS

Culinary tools and implements have come surface texture-the crispy crust or lack thereof.
The ability to manipulate moisture, both
a long way from ancient days when an open fire pit
was the only place to cook. Ovens were among the outside the food as well as inside it, is the defining
first advances wrought by civilization; by difference that set modern oven technology apart
3200 B.C., every house in the settlements of the from earlier methods. Water-vapor ovens and
Indus Valley Civilization had its own clay oven. combi ovens control the water content of the
Early ovens were designed to trap the heat of a fire heated air, so they can preserve the moisture
in the walls of the oven and divert the smoke away content offood; microwave ovens exploit the
from the users, tasks that they performed well. By moisture content of food to heat it. Although the
the early 20th century, inventors had developed technologies are unrelated, they are both exam-
gas and electric ovens that allow far greater ples of modern approaches to one ofhistory's most
control ofheat and had done away with smoke ancient cooking tools.
entirely.
Some traditional cooks worry that these newer
Yet for all the advanced features on today's devices might somehow devalue their hard-won
ovens-broilers, forced convection, self-cleaning skills or could even do away with the need for
cycles, and so on-they still operate on the those skills entirely. Water-vapor ovens, combi
principle that controlling heat is the most impor- ovens, and microwave ovens do circumvent, or
tant aspect of cooking. It turns out, however, that even render obsolete, certain standard cooking
heat is just one of two critical factors that deter- techniques. But like most tools, a modern oven
mine how food cooks. The other is humidity: the performs only as well as its operator understands
water content ofthe air surrounding the food. it. The devices cannot exceed or replace the skills
Humidity governs the temperature at which food of the practiced cook; they can only help to better
actually cooks. It is also crucial for the food achieve the results the cook intends.

Racks of vacuum-packed carrots steaming
in acombi oven (left) and roasting hams
(right) highlight the versatility and large
capacity of modern ovens. Roast chicken
(opening photo) is one of the iconic foods
prepared best by combi ovens. The ovens
can produce acrispy, golden-brown skin on
many birds simultaneously. To see how the
ham turned out in the end, see page 101.

COOKING IN MODERN OVENS 1 53

COOIZING WITH MOIST AIR

For more on the basic physics of heat Cooks have long understood the importance of Along with greater control over the cooking
conduction, see Heat in Motion, page 1-277. For keeping food humidified while it is heating. environment and expanded cooking envelope
more on relative humidity, the heat released by Moisture control is the reason they wrap baked come higher costs, particularly for the fully
condensation, and evaporative cooling, see potatoes in foil, cover casserole dishes, roast in featured models. CVaps are less complex and
Vaporization and Condensation, page 1-314. bags, and braise and baste. Trapping the water priced more modestly. But like combi ovens,
vapor from cooking food is a crucial element of water-vapor ovens demand considerable time and
Steam burns hurt so badly precisely cooking sous vide as well (see chapter 9, page 192). effort to master-it takes a practiced operator to
because the condensing steam make the most ofthem.
passes so much heat into the skin. In Ofcourse, the reason that cooks have had to
that case, your skin is below the dew devise all manner of techniques to counteract the Whether high-tech ovens are worth the expense
point temperature of the steam. drying effects of hot air is that, until recently, they and effort depends primarily on how well you
could not rely on existing equipment to do it for learn to use them. It is helpful to first review the
them. That situation changed a few decades ago, underlying physics ofhow heat interacts with
when engineers set out to develop improved moisture in the air, because that is fundamental to
food-holding cabinets and ovens for catering, how these appliances work.
institutional service, and fast-food vending. These
innovators introduced two separate but related Air gains and loses heat much more readily than
technologies to control, more precisely, the water (especially liquid water) does. A small
moisture content of the hot air and, consequently, alteration in the power output ofa heating element
that of the cooking food. in an oven therefore causes a much greater tem-
perature change than does the same power rise in
One ofthese groundbreaking technologies was the heating element ofa water bath. Although air
developed by Winston Shelton, a former General temperature responds rapidly to the application of
Electric engineer who, in the early 1970s, worked heat, it conducts heat poorly.
with "Colonel" Harland Sanders to design and
manufacture the Collectramatic pressure fryer Heat transfer from air to food is much more
that became the standard cooker for the Kentucky efficient when water vapor is condensing onto
Fried Chicken chain of restaurants (see page 120). cooler food than it is when hot air is simply
convecting around the food (see It Matters How
In the early 1980s, Shelton's Winston Industries You Heat, page 1·283). The net result of all these
introduced the CVap brand water-vapor oven, factors is that an oven filled with dry air heats food
which cooks with heated water vapor as well as hot quite slowly compared to an oven containing
air (CVap is short for "controlled vapor"). A few humid air. Moist air also smooths out temperature
years before that, in 1976, German engineers at swings in the food and helps minimize hot and
the company that would later become Rational cold spots.
AG invented an appliance known as the combi
oven-so named because it can cook with ambi- There is, however, a limit to how much water
ent air as an ordinary convection oven does, cook vapor air can hold before the water condenses into
with injected steam, or do both in combination. fog or dew. All else being equal, the hotter the air,
the more water it can hold. The weather-report
These advanced ovens, and the many variations metric known as relative humidity describes how
that other manufacturers have created since, have close the air is to its maximum water-carrying
their strengths and weaknesses, but overall, they capacity at any given temperature.
have proved to be extremely useful kitchen tools.
You can use these modern ovens quite successfully Virtually all air contains water, and the relative
for proofing, thawing, holding, roasting, baking, humidity of air striking a cool object can soar to
steaming, poaching, and-in the case ofthe combi 100%. This is the process that makes a chilled
oven-"oven frying." Their exceptional versatility bottle ofwine "sweat" on a humid summer day and
means that these devices can provide most of the that deposits drops of dew on grass on a cold night.
functions of convection ovens, steamers, holding Indeed, the temperature at which the water vapor
cabinets, and grills-all in a single unit. in a given volume ofair starts to condense to liquid
droplets is called the dew point.

1 54 VO LU M E 2 · TE CHNI QUE S AND EQUIP M ENT

Iffood is placed in moist air, and if the tempera- further evaporation stops. The same thing hap- For more on wet-bulb and dry-bulb tempera-
ture of the food is below the dew point of that air, pens in any covered container, such as a pot or a tures and their significance to cooking,see The
droplets ofwater will form on the food. This canning jar. Real Baking Temperature,page 103.
condensation releases a remarkable amount of
heat energy, which tends to heat the food rapidly Low-temperature steam mode can be used to Although it is something of a
up to the dew point temperature. achieve the same effect without having a sealed misnomer to ca ll water vapor that
container. In that case, the moisture to maintain has a temperature below water's
Conversely, evaporating water absorbs a great the humidity comes from the oven, rather than just boiling point "steam," the term
deal of heat and hence cools food. In dry air, from the food. This approach shines when cooks "low-temperature steam" is so
therefore, the heating offood will be offset by the want to achieve effects similar to sous vide with commonly used by oven makers
cooling caused by water evaporating from the food molded foods, such as flan or creme brulee, whose that it has become standard
surface. Because ofevaporative cooling, the shape would be destroyed by vacuum packing. It is termino logy.
temperature that food encounters in an oven is also useful for slow-cooking large roasts or turkeys
rarely as high as that of the surrounding hot air. that are too big to fit inside a sous vide bag. Fog pours from the open door of acombi
Instead, food cooks for most of the time at what oven that has raised the humidity of the
scientists call the wet-bulb temperature, the Another advantage of using low-temperature cooking environment by injecting steam.
temperature measured by a wet thermometer. steam mode is that it effectively increases the Humidity control is a defining feature of
cooking capacity, as reflected by the amount of modern ovens.
The more common temperature measurement heating power available. Water baths are typically
is the dry-bulb temperature, which is the temper- limited to 1.8 kW, so they can't heat large amounts
ature that you measure with an ordinary ther- of food quickly. But even the smallest combi oven
mometer that you keep shielded from direct draws 10 kW of power, and CVap ovens draw a
sunlight and contact with moisture. The dry-bulb minimum of 5 kW.
temperature is the one that you use when you set
the temperature of an ordinary oven. The main disadvantage of using low-
temperature steam mode as an alternative to
Unless the relative humidity is 100%, the cooking in a water bath is that the temperature
wet-bulb temperature is always lower than the control may not be as accurate, particularly for
dry-bulb temperature. Food contains so much
water that most foods spend the majority of their temperatures below 60 •c I 140 •F.
time with their surface at the wet-bulb
temperature. In steam mode, the relative humidity is also
100%, but the temperature is held exactly at the

Cooking aIa Mode

Engineers designed water-vapor ovens and combi
ovens to give cooks better control over the all-
important wet-bulb temperature. These ovens
operate in several modes that are distinguished by
the amount of humidity they employ. To use them
effectively, you need to understand the differences
among the various modes.

The low-temperature steam mode cooks food
with air that has been saturated to 100% relative
humidity, which means that the wet-bulb and
dry-bulb temperatures are the same. "Low"
temperature means heat levels below the boiling

point of water, or 100 ·c I 212 •p (at sea level).

Low-temperature steam mode is the same
cooking environment as that found inside a sous
vide bag or a covered pot. As water evaporates
from the food, it is trapped by the sous vide bag, so
the relative humidity quickly becomes 100% and

COOK I NG I N MO DE RN OV EN S 155

Man ufacturers have chosen to boiling point ofwater (typically near 100 ·c I units' steam mode will reach temperatures as high
sidestep the key concepts of
wet-bul b and dry-bu lb te mpera- 212 •F). Only combi ovens support this mode, as 130 ·c I 266 •p, which falls within the range
tures, pe rh aps in th e be li efthatthe which is no different, in principle, than steaming
prospect of cook ing at two differ- in a pot; it's just much more convenient and can attained by pressure cookers. Although the
ent temperatures simu ltaneous ly handle larger quantities offood. dry-bulb temperature of the oven will indeed
wou ld flummox many cooks.
Instead, the ir owner manua ls ta lk Some manufacturers use the term convection reach 130 ·c I 266 •p, the all-important wet-bulb
vaguely abo ut "doneness," "brown- steaming for the steam mode, because their
ing," and "hum idity," terms that ovens use fan-assisted convection to circulate the temperature cannot exceed 100 •c I 212 •p
only obscure the re leva nt pa rame- air and water vapor over the surface ofthe food, a
te rs. The tab le of cooking strategies feature that hastens heating. Steam mode is useful without applying pressure. The only way to
on page 170 shows the settings on for vegetables and other plant-based foods, which steam food at higher temperatures is with a
two popu lar modern oven mode ls. need the high heat of steaming. Most meat will pressure cooker.
Note that actual res ul ts vary with overcook at steam temperatures ifused for
the bra nd. equilibrium cooking, which we describe below, CVap and combi ovens also have a mode in
but there are some cases in which it is useful. which the wet-bulb and dry-bulb temperatures
can be different, which is called humidity-
Combi oven makers often advertise that their controlled mode, combination mode, or combi
mode. This approach to cooking can do things
that no other kitchen appliance function can.
Humidity-controlled mode lets you specify the

THE TESTING OF

Heat and Humidity Control in Modern Ovens

Combi ovens offer far greater control of temperature than (although, in each case, it need only warm by 10 oc I 18 °F). A
conventional ovens do, and they allow you to control the
humidity, too-but, unfortunately, not as well as we'd like. cold oven would take longerto attain a set point. The oven
Our experiments show that the dry-bulb and wet-bulb also works well for true steaming, in which wet-bulb tempera-
temperatures in these ovens tend to fluctuate by several tures are close to the boiling point of water. Note that the
degrees around the set point. actual wet-bulb temperature is just below the boiling point,
which is typical of "steamers."
These graphs show the actual wet-bulb (blue) and dry-bulb
(red) temperatures for an empty Rational SelfCooking Center Above 100 oc I 212 °F(bottom right graph), the dry-bulb
combi oven in steam mode, right after it was temperature-
calibrated by a factory-authorized technician. The top left temperature continues to rise, butthe wet-bulb temperature
graph shows how a cold oven heats to reach its set point does not. As long as the outside of the food has moisture
rapidly evaporating away, the cooking temperature will
(30 oc I 86° F, in this case). Each subsequent graph, when read remain at this lower wet-bulb temperature, unless the air
pressure is increased .
in rows from left to right, shows how the oven heated from
the ending temperature in the previous graph to a new set We performed our tests with electric ovens. In our experi-
point, indicated by the gray line. ence, gas-fired combi ovens have even larger variations in
temperature because the gas flame produces large pulses of
Below 60 °C I 140 °F, both temperatures depart widely from heat as it turns on and off. We hope that manufacturers will
design and build ovens that incorporate more accurate and
the set point. This is why we hesitate to recommend combi precise temperature and humidity controls. A direct way to
ovens for cooking fish, rare meat, or other foods where you set wetobulb temperature is also a needed feature (see Ways
might need temperature accuracy. A water bath is much to Make Modern Ovens Better, page 167).
better at controlling heat. The manufacturer of the Rational
combi oven reminded us that it is hard to do accurate temper- In combi and convection mode, the dry-bulb temperature
ature control in an empty oven and suggested that the perfor- results are similar to what is shown at right for steam mode: a
mance would be better with an oven full of cold food. That cold oven takes about 10 min to come up to tempera-
might be true, but it still points to a weakness in ture-S min or less ifthe oven is already hot. The wet-bulb
temperature-control performance. Also note that it takes temperature is much more variable than in steam mode; the
more than 10 min for the wet-bulb temperature to stabilize in humidity-control mechanisms have limitations at these
the oven-even at the lowest set point (top left graph). temperatures. These modes are still valuable features, but fine
control of humidity does not seem to be possible with the
For set points from 60-90 °C I 140-194 °F, the accuracy of combi ovens that we have tested.

the oven is quite good, and it gets up to temperature quickly

1 56 VO LU M E 2 · TE CHNI QU ES AN D EQU IP M ENT

temperature at which the food cooks by setting the set at halfspeed, low enough to cook some delicate Low-temperature steam mode on a
wet-bulb temperature directly. At the same time, foods. Alternatively, you can put delicate foods combi oven or water-vapor oven
you can increase the dry-bulb temperature enough inside a very deep hotel pan or a stockpot to shield can be used to cook food so us vide.
to dry and brown the food-a process that occurs them from the full force of the convection fan. Cooking foods in pans or on trays
only when the dry-bulb temperature substantially placed in such ovens yields results
exceeds the wet-bulb temperature. In a conven- The convection oven mode also offers humidity very similar to those of water baths,
tional oven, only the dry-bulb temperature is control but in one direction only: you can set the without the need for bags and
under your control. maximum humidity that the oven will allow. It vacuum-sealing.
will not add moisture to reach that level, but it will
Combi ovens offer a convection oven mode; vent moist air from the oven in an attempt to The popularity of water-vapor
CVaps do not. In this mode, the combi oven prevent the humidity from exceeding that value. ovens and combi ovens as tools for
performs like an ordinary convection oven, low-temperature steaming (without
To get the most out of these devices, you must the need for vacuum-packing food)
reaching temperatures up to 300 oc I sn °F. experiment to understand the nature of the soared in New York City after the
cooking processes they offer as well as your city health department cracked
Although a combi oven can often stand in for a machine's specific options and limitations. Only down on so us vide preparation (see
conventional oven, light baking or delicate dishes with experience will you learn to best exploit their page 1-188).
are out because the force of the oven fan can blow capabilities to prepare your favorite dishes.
a custard clear out of its ramekin. The fan can be

56 122
52
Set point = 50 °C I 172 °F 11 2
44
5 10 15 0 10 15 20

82 ...... 180
172
rr152 78 v

144 74 164

Set point =70 °CI 158 °F 70 f~ Set point =80 °CI 176 °F
LL..-~--~-~---"'136 156
0
10 15 20 10 15 20

130 f==================~ 260
r--,r---~~~. 1

120
240

110

196 220
Setpoint =100 °CI 212 °F 100 ~

5 10 15 20 0 5 10 15 20

These graphs show the dry-bulb (red) and wet-bulb (blue) temperatures in aRational SelfCooking
Center combi oven that is in steam mode (see text at left). Our experiments were performed
immediately after the oven was calibrated by afactory-authorized technician.

COOKING IN MODERN OVENS 157

Dedicated steamers and convec- Water-Vapor Ovens ture stability than any ordinary oven or holding
tion steamers also exist and can cabinet does.
take the role of steam mode, but The basic concept of the water-vapor oven is
they generally have no temperature simple: heat a pan ofwater in the bottom of an Another vapor oven, the Steam' N 'Hold unit
control and only operate at the oven enclosure to cause it to evaporate enough to from Indiana-based company AccuTemp Prod-
boiling point of water. raise the humidity of the air inside, thereby ucts, works by creating a partial vacuum that
keeping more moisture in the cooking food. CVap reduces the air pressure until the boiling point of
AccuTemp also makes the Accu- inventor Winston Shelton figured out how to use water equals the temperature that the cook selects
Steam Griddle, an advanced design this principle to hold prepared dishes for hours for steaming. Consequently, the Steam'N 'Hold
that uses steam to heat the cooking without drying them out. Previous holding can function only in steam mode or low-
surface. For more on using the equipment had improvised on this theme, using a temperature steam mode. The CVap oven is more
Accu-Steam, see page 37. supplementary water vessel to help retain the versatile, so we will discuss that brand in detail.
moisture in food (as steam tables do) or sealing
Achicken bakes in a CVap oven. where it the holding cabinet to prevent the escape of The CVap oven contains both a resistance
both cooks in moist heat and browns moisture (as the cook-and-hold equipment m ade heating element in a pan ofwater at the bottom
slowly in asingle step. by Alto-Shaam and others does). and other heating elements on the sides (see Not
Just Hot Air, page 160). It has two kinds of
But those designs allow cooks to control controls, typically labeled "Doneness" and
temperature and humidity only crudely. Shelton's "Browning" ("Food Temperature" and "Food
oven, while not perfect, enables operators to Texture" on older models), which control the two
manage the humidity much more definitively, respective sets of wet and dry heating elements
partly because the CVap provides better tempera- and thus the oven's wet-bulb and dry-bulb
cooking temperatures.

The Doneness setting allows cooks to manipu-
late the wet-bulb temperature by setting the
temperature of the water at the bottom of the
machine. As the water warms, it vaporizes into
the oven air. When the preheating process is
complete, both the water vapor and the air will be
at the same temperature as the water in the
pan-the wet-bulb temperature.

Using this setting is much like controlling the
temperature of a water bath, and, like a water
bath, the CVap takes a long time to heat up. In
our experience, you should set aside about 45
minutes to allow the oven to reach the proper
wet-bulb temperature, assuming it starts at room
temperature.

Because water can absorb considerable heat,
any temperature change in a CVap or a water bath
takes time, too. The upside to this delay is that,
once the target temperature is reached, it fluctu-
ates less and hews closer to its set point than a

combi oven does: typically staying within 1-5 oc

/ 2-9 oF. That is still not as precise as a water bath
but is sufficient for most culinary applications.

Unlike the Doneness setting, which is scaled
according to temperature, the Browning control
is demarcated by numbers that run from 0-10
and represent power levels. We feel that this
arbitrary 0-10 scale hinders rather than helps.
Knowledgeable users would strongly prefer to set

1 58 VO LU M E 2 ·TEC HNI QUES AND EQU IP M ENT

the dry-bulb temperature directly, but that option skin or crunchy crust, but a high dry-bulb setting Browning Level and
is not yet available. compensates. You can hold eggs sunny-side up Dry-bulb Temperature
this way without ruining their delicate
Ifyou dial the Browning meter to zero, the consistency. Browning Dry-bulb minus
heating elements on the sides of the oven do not level wet-bulb
energize, and the temperature of the oven air will At Browning settings S-10, you can cook food temperature
be the wet-bulb temperature. Running the CVap and brown it at the same time. To bake chicken,
with Browning at zero is the closest equivalent for example, you can set the Doneness dial to (•c) (• F)
that the CVap has to low-temperature steam
mode. The relative humidity of the air in the oven 60 ·c I 140 •p and the Browning control to eight 0 00
will be at or close to 100%, so the food surface will 1 2.8 5
not dry out, nor will browning occur. Use this or nine. At these higher settings ofthe Browning
setting either to cook sous vide in a CVap or to get control, the CVap oven operates in what amounts 2 5.6 10
sous vide-like results in an open pan. to combi mode, where the wet-bulb temperature is 3 11.1 20
controlled by the Doneness dial, and the dry-bulb 4 16.7 30
CVap users also value the low-temperature temperature is set by the Browning control (albeit
steam mode for holding fully cooked food rela- with no indication ofthe dry-bulb temperature). 5 22.2 40
tively intact, thus keeping dishes warm for hours
without drying them out, which was one ofthe Unfortunately, the wet-bulb and dry-bulb 6 27.8 50
target applications that drove the invention of the temperature settings in the CVap are not com-
technology in the first place. Caterers know, pletely independent. The higher Browning settings 7 41.7 75
however, that holding browned food items often inevitably cause the wet-bulb temperature to creep 8 55.6 100
causes streaking to occur. Moisture inevitably up as the warm oven air starts to heat the water in
condenses on the surface of the food because it is the pan. The oven could be designed to combat 9 69.4 125
cooler than the surrounding air, and the resulting this effect, but that awaits future work. Conse-
droplets run. quently, at high Browning settings, the air inside 10* see note below
the oven eventually gets too humid to dry the food
You can prevent streaking by holding browned surface, and the effective cooking temperature For browning levels 0-9, the dry-bulb
food at settings ranging from 1-4, which engages (the wet-bulb temperature) rises too high to get temperature =the wet-bulb temperature
the side-mounted heating elements. This warming the best results with some foods. (Doneness level) + the temperature
raises the dry-bulb temperature above the wet- difference given in the table above.
bulb temperature, reducing condensation. At In addition, the CVap approach to humidity
these low-to-moderate Browning levels, you need control leads to a relatively narrow range of •At Browning level10, the dry-bulb
not worry about drying the food out completely. temperatures in which it can control the wet-bulb
and dry-bulb temperatures independently. Even temperature is set to 180 ·c I 356 ·r
Surprisingly, these settings permit you to hold with Browning set to 10, the temperature will
crispy food such as fried chicken for long periods. regardless of the wet-bulb temperature.
Without the browning setting, the humid environ- reach a maximum of only 180 •c I 356 •p, a rather
ment of the CVap would inevitably soften a crispy Each Browning level has successively
modest oven temperature for browning. This larger temperature differences to
limitation derives in part from the CVap's heritage approximate a logarithmic scale.
as a holding-cabinet design.
We would prefer setting the dry-bulb
temperature directly, but by using the
table above, one can set it indirectly. You
can calculate the dry-bulb temperature
from the Browning level and wet-bulb
(Doneness) temperature level.

CONTROVERSIES Shelton says that any kind of convection is unlikely to
hasten heating substantially in a water-vapor oven because
Forced Convection rn CVap Ovens the amount of thermal energy that is transferred to the food
by the phase change when water vapor condenses far
Winston Shelton, the inventor of the popular CVap oven exceeds any extra heat transfer caused by circulating air.
and the Collectramatic pressure fryer, the classic cooker of
KFC franchise fame, has strong opinions aboutforced Convection-oven advocates are "word spinners," Shelton
convection in ovens, and none of them are positive. charges: "ma rketers who need to 'featurize' their product to
Shelton says that he put a fan in his CVap water-vapor oven make more money on it." The truth, according to Shelton?
only at the urging of marketing advisors, who maintained "'Co nvection oven-ing' is hogwash ."
that customers would expect the oven to have a fan,
whether or not it speeds heating or helps to deliver heat to
food more evenly. If you ask him, it does neither.

COOKING IN MODERN OVENS 159





For the price of one co mb i oven, As a result, the CVap browns food rather slowly reservoir to generate humidity, combi ovens supply
you could purchase a couple of and achieves only modest levels ofbrowning. moisture directly, by injecting steam into the
water baths, plus a convection oven Although it is quite possible to achieve good results, semisealed oven chamber. The combi oven's ability
and a broiler. Or you cou ld get a such proficiency requires trial and error, and the to use both steam and circulating hot and dry air,
water-vapor ove n and a conven- oven simply may not be suitable for certain tasks. either alone or in combination, can reproduce, in a
tional convection oven. If you have single appliance, many cooking techniques:
the space, installing multip le tools Some chefs have developed recipes using the steaming, proofing, incubating, dehydrating,
yields the same functionality, but Doneness (wet-bulb) and Browning levels on a baking, grilling, frying, and more. Cooks can
with the added benefit that you can CVap to cook and brown certain foods perfectly in program combi ovens to automate routine tasks,
use them simu ltaneous ly. a single step. Developing such a recipe requires and the machines are self-cleaning.
diligence and experimentation. Even then, their
The Rational combi oven was the first formulas work only within a certain range of On the downside, a combi oven is not cheap: as
of its kind and is still a market leader. foods, temperatures, and food sizes. of2010, it costs roughly $12,000 for the half-sheet-
We base our discussion on this particular pan-size programmable ovens we use-and several
brand, but its features are similar to Although it's possible to cook and brown in a times that amount for larger configurations.
those of many other combi ovens. single step with the CVap, we would rather cook Miniature combi ovens designed for commercial
using a multistage process that first employs the kitchens have recently come on the market for as
oven's high heat source for searing and browning, little as $2,000, but these are limited to using much
then uses the CVap in low-temperature steam mode smaller pans. Manufacturers ofkitchen equipment
to finish the cooking. You could also do the reverse: for the home have also started to show interest in
low-temperature steam first, then sear. The multi- combi ovens, so in the future, there will likely be
stage approach gives the cook greater control and many more options.
works with a broad spectrum offoods. In essence, it
is cooking sous vide without the vacuum packing. Combi ovens are also rather expensive to
operate because they consume a lot of energy, at
Combi Ovens least when using those modes that employ high
heat. And while their flexibility is unmatched, the
Many veteran chefs rate the combi oven as the fact remains that a single combi oven can do only
most versatile kitchen tool ever made. Unlike the one cooking task at a time. Ifyou really want to
CVap, which relies on evaporation from a water fully exploit the versatility ofthese machines (and
if you have the necessary budget and space),
buying several small units rather than a single large
one makes sense.

Seasoned cooks especially appreciate the combi
oven's unprecedented ability to get consistent
results in operating conditions that would
otherwise cause fluctuations in the wet-bulb
temperature-deviations that would ordinarily
produce undesirable outcomes. Differing results
can arise, for instance, from the change in cooking
performance when an oven is full or only partially
filled, or from the seasonal change in humidity
between a dry winter morning and a muggy
summer afternoon. Combi oven settings enforce,
more or less, a steady regime of temperature and
humidity that smooths out most variations.

Note that we say "more or less." Our experimen-
tal results (pictured in the graphs on page 157)
reveal that temperatures in combi ovens do tend to
wander a bit more than is ideal. That failing stems in
part from their design. The ovens were developed in
a context that did not put a premium on tempera-

16 2 VO LU ME 2 ·TE CH NI QU ES AND EQU I PM ENT

8

ture accuracy, so this aspect of performance may The "exact percentage" that Rational refers to is Halibut fillets cook in acombi oven.
not have been a high priority for the designers. in fact something more arcane, though in some
ways more absolute. It measures the fraction of the Comb i ovens need to be ca librated
For example, we've seen temperatures fluctuate total mass of air and water in the chamber that is regularly. Their temperature
in our combi ovens because the fans reverse water vapor. If a volume of air has no water in it, controls can be off even when
direction every four minutes. The reversal helps then the so-called Rational humidity is 0%. they're brand-new, so have yours
distribute heat more evenly, but it also causes checked upon in stallation and
momentary, local temperature blips in the oven. In Note that this 0% is purely a theoretical mini- check it again yourself at least once
our experience, the oven temperature tends to mum that is impossible to achieve in practice a year thereafter. Use a digital
drift over time, and you need to calibrate combi because doing so would require perfectly dry air, thermometer positioned in several
ovens frequently ifyou want them to be accurate. which simply does not exist in Earth's atmosphere. places in the oven, and if you find
The minimum humidity that the oven can pro- the readings don't match one
Out of the three Rational combi ovens that we duce depends on how much water is in the air of another or the mach in e's
have, one of them-admittedly, the oldest unit- the kitchen-which can be quite a bit. In a work- temperature setting, have a
has consistently had poor temperature perfor- ing kitchen on an extremely muggy, blisteringly techn ician adjust the unit.
mance despite repeated service calls. The humidi- hot summer day, for example, relative humidity in
ty control on these machines is also rather wobbly, the ambient air could be near 100%. The oven can
again as a result of their design and of intrinsic add water (as steam), but it cannot remove water.
physical limitations. His quite possible that the
increasing focus on Modernist cooking and the On the other hand, if the chamber contains
accuracy it requires will drive manufacturers to only pure water vapor (steam) in the chamber,
improve temperature performance. with no air at all in the oven, then the Rational
humidity is 100%-another condition that could
The other problem with combi ovens concerns never occur in practice.
their humidity settings, which are quite obscure-
to the point where even experienced combi oven Regrettably, this explanation does not appear in
users and company personnel often have the the owner's manual for the unit; we had to extract
wrong idea of what the settings mean. To explain it during detailed correspondence with the compa-
the problem, we'll consider the Rational combi ny's engineers (who were very helpful). Their
oven in detail. It was the first combi oven and reasoning makes sense: by inventing the concept of
remains a leading brand. Other combi ovens have Rational humidity, the engineers created a scale
similar issues, however. that works at all temperatures, whereas relative
humidity becomes completely unhelpful at tem-
Rational Humidity peratures above the boiling point ofwater.

The control panels of Rational combi ovens Unfortunately, most ofthe Rational humidity
feature two buttons that operators find fairly scale is useless because it represents values of heat
straightforward to use: a blue one for moist heat and humidity that the oven cannot attain, even in
(steam) and a red one for dry heat. When you hit
either of the keys, a pane below the buttons principle. At 30 ·c I 86 •p (the lowest temperature
illuminates with either blue or red bars that can be
set from zero to 100. setting on a Rational combi oven\ the only valid
Rational humidity settings are between 0% and
Rational's user manual describes this action as 2.6%. Any setting above 2.6% is impossible to
setting "the exact percentage ofhumidity." That
description might, however, lead operators to achieve.At 60 •c I 140 •p, a common cooking
suppose that the scale corresponds to relative
humidity, or the amount ofwater vapor in air temperature, the valid range is 0%-13%. Even at
expressed as a percentage of the air's total carrying
capacity at that temperature. Indeed, some 90 •c I 194 •p, the valid range runs only from
Rational employees told us just that. The trouble is
that this interpretation cannot be accurate be- 0 %- 5 8 %.
cause relative humidity loses any useful meaning at Imagine cooking on the humid summer day
temperatures above the boiling point ofwater.
described earlier, with outside temperatures

around 40 ·c I 104 •p and relative humidity near

100%. The minimum possible Rational humidity
would be 4.6% (at any temperature). Setting the
oven to 0% will not help.

On a very cold winter day, in contrast, you could
get closer to the mark. If the outside temperature

COOKING IN MOD ER N OV ENS 1 63

For the best results, control both is below 0 ' C I 32 ' F, and you bring the external air One could argue that the S% setting results in
temperature and humidity in your greater repeatability because at that setting, the
kitchen. This will improve the into the kitchen unchanged (without further Rational humidity will be the same whether it is a
reliability of your combi oven but humidification), you could get the oven to operate dry or moist day. This is true, but the oven's
also has many other advantages under conditions that correspond to 1% on the humidity controls do not seem to be accurate
because humidity affects almost Rational humidity scale-but still not all the way enough for that subtle point to matter.
every aspect of cooking. toO%.
The situation is a bit different when the oven
A further limitation on the Rational humidity gets to temperatures above the boiling point of
system is the fact that the food itself gives offwater
vapor as it heats, and that causes the humidity in water (100 ' C I 212 ' Fat sea level, lower at higher
the oven to rise. The oven can compensate for this
effect somewhat by venting the humid air, then elevations). At the high end of the scale, 100%
refilling with new kitchen air heated to the right Rational humidity then means that there is no air
level. But the compensating effect is limited by the left in the oven at all; it is filled with pure steam. If
electrical power available. The oven must recircu- the oven vented the combination ofsteam and
late at least some of the air; it does not have condensed fog as fast as it could and replaced that
enough power to heat kitchen air all the way up to combination with pure steam, it could make the
most oven temperatures, then dump it, the way a Rational humidity very high. The oven is limited,
hair dryer does. The amount ofair that the oven however, by the heat capacity of its boiler (or, for
must recirculate depends on the temperature some ovens, the capacity of the steam generator).
setting and the oven's power rating. It can only vent gases as fast as the steam generator
can replace the steam-air mix with steam, and that
The practical consequences of these deficiencies rate is limited by the electrical power. So the oven
will never replace all the air with steam.
is that, below 100 ' C I 212 ' F, you have only very
In practice, a different limitation makes this
crude control over humidity-not the sophisticat- insufficiency moot. The only practical reason to raise
ed command suggested by the control panel. the humidity ofan oven is to make the wet-bulb
Realistically, you have only two settings to consid- temperature approach the boiling point ofwater
er: 0% and 100%. Use 0% to dehydrate the food.
Use 100% ifyou are performing low-temperature (100 ' C I 212 ' Fat sea level). The wet-bulb temper-
steaming, a process in which you want the dry-
bulb and wet-bulb temperatures to be the same. ature can never exceed the boiling point, even with
100% Rational humidity. And as the humidity
Oven temperature (' F) rises, incremental increases in humidity make less
and less ofa difference to the wet-bulb temperature.
100 120 140 160 180
Even at a dry-bulb temperature of300 ' C I
bcO
S72 ' F, theory tells us that the wet-bulb tempera-
"E
ture for 30% Rational humidity will be 81 ' C I
:;: 178 ' F. At SO%, it will be 89 ' C I 192 ' F, only a

Theoretically possible small improvement. Note that dry-bulb tempera-

Oven temperature (' C) ture is not much of a factor: at 100 ' C I 212 ' F, the

The Rational humidity setting spans 0%-100%, but most of that range is impossible to achieve at temperatures wet-bulb temperature at 30% Rational humidity is
below the boiling point of water. The red zone indicates settings that can be achieved-but only when the kitchen-
air is dry enough.The green zone denotes those settings that are practical for cooking under most circumstances. 77 ' C I 171 ' F, and at SO%, it is 87 ' C I 189 ' F
The blue range shows settings that the oven can achieve in theory but that are difficult to attain in practice and that
would not significantly change cooking conditions in any case. All Rational humidity settings higher than those in the (again, this is from theoretical calculations). The
green range produce the same effect. Note that we assume sea level elevation, where boiling point is 100 'C I 212 'F; wet-bulb temperature only changes by a few
the curve would shift to the right at higher elevations, where the boiling point is lower.
degrees as the dry bulb increases by 200 ' C I 360 ' F

and also by only a few degrees as the humidity
changes from 30% Rational humidity to SO%
Rational humidity.

Meanwhile, our experimental data show that
the wet-bulb temperature in a Rational fluctuates

by 10 ' C I 18 ' F over the course of 10-20 minutes

in even the best and most stable cases. So the
reality is that, once the dry-bulb temperature is

164 VO LU ME 2 · TEC HNI QUES AND EQUI PMEN T

above the boiling point, Rational humidity all dry-bulb temperatures produce the same It is much harder to set the wet-
settings above, say, 40% do not differ from one bulb temperature in a comb i oven
another in any meaningful way. wet-bulb temperature of about 67 ·c I 153 ·F, than in a CVap oven. At tempera-
tures below the boiling point of
At the low end of the humidity scale, another set which varies from 64-72 •c I 147-162 •F. water, the wet-bu lb and dry-bulb
of restrictions apply. The only way the oven can temperatures are the same insid e
minimize humidity is by venting moist air from the At Rational humidity of 30% or greater, the the oven. Above the boiling point,
oven and replacing it with kitchen air, which must results at dry-bulb temperatures below the boiling the wet-bulb temperature is, in
first be heated to the proper temperature. The point are basically the same as for 0% Rational principle, a comp li cated math-
available power limits the rate at which the oven humidity. That's because the range ofpossible ematica l funct ion of the humidity,
can generate this hot, dry air. The extent to which Rational humidity is restricted-and because the dry-bulb temperature, and fan
this becomes a limitation also depends on tempera- controls are just not that accurate. Again, the speed. But we found that, in
practice, the empirical oven results
ture. Heating ambient air to 60 ·c I 140 ·F takes wet-bulb temperature is about 45 •c I 113 ·F, with do not match the results of the
calcu lations very well.
less energy than heating it to 300 •c I 572 •F. Using a similar range. Dry-bulb temperatures above the
boiling point produce a wet-bulb temperature of
a very low humidity setting (0%-10%) with high
oven temperature is likely not to achieve what it about 84 •c I 183 •F, which varies from 80-86 •c I
ought to, but the oven will try its best to get there.
176-187 °F.
In our experience, in either convection mode or Note, however, that these results are all approx-
combi mode, you again basically have two choices:
0% and 100% Rational humidity. For dry-bulb imate: your oven's performance may vary. Note
temperatures below the boiling point, all dry-bulb also that these results are from sea leveli you can
temperatures produce the same wet-bulb tempera- expect somewhat different results from combi
ovens located at higher elevations.
ture, which is about 45 •c I 113 •F but varies from
All this criticism may leave the impression that
42-48 ·c I 108-118 •F. Above the boiling point, the humidity control on the Rational combi oven
is a bad thing. Quite the contrary: humidity
control on combi ovens is a great feature that you

Effective Cooking Temperatures in a Rational Combi Oven

In the four cooking modes offered by a Rational cooking oven, the effective cooking temperature (the wet-bulb temperature)
depends on both the dry-bulb temperature that has been set as well as the Rational humidity setting. The table below shows
the ranges of wet-bulb temperature that are accessible in each mode.

Mode Dry-bulb Rational Wet-bulb temperature Note
temperature setting humidity actually achieved

(•c) ("F) (•c) (•F)

low-temperature 30-60 86-140 100% same as dry bulb poor temperature control
steam 60-90 140-194 good temperature control

steam 100-129 212-264 100% 98 (96-99) 208 (205-210) good temperature control

convection 30-100 86-212 0% 45 (42-48) 113 (108-118) useful primarily for dehydration
orfor dehydration and cooking combined

~ limit 42-88 108-190 poor control of wet-bulb temperature, which
varies with oven load and moistness offood

100-300 212-572 0 % 80-88 176- 190 oven keeps humidity as low as it can; best
regime for browning

~30 % poor control of wet-bulb temperature, which
varies with oven load and moistness of food

combi 30-100 86- 212 0% 45 (42-48) 113 (108-118) functions just like convection mode

30-60 86-140 ?.maximum * same as dry bulb poor temperature control

60-90 140-194 good temperature control

100-300 212-572 ~30 % 84 (80-88) 183 (176-190) more reliable than convection mode because
moisture is added

*Maximum Rational humidity in combi mode depends on the dry-bulb temperature setting. It is 2.6% at 30 •c I 86 •Fand 58% at 90 •c I 194 "F.
Note that Rational humidity settings above 50% are difficult for the oven to achieve in practice.

COOKIN G IN MO DE RN OV ENS 16 5

A PANOPLY OF PANS

Combi ovens call for a range of accessories to
accommodate their many uses. The various
pans used in combi ovens testify to just how
versatile these appliances can be. Some of
these pieces, such as the hotel pans, are
standard-issue essentials; other pans are
more specialized.

. . . .. ........... .... -... -.. ... .. -.... ... .... ... ..... ... .. .-~.·........ .-. ... ... ... -. ... ..

.

Perforated hotel pan, or "steamer pan" Hotel pan Combi grill
Depth s range fro m 1-2 0 em I Y2-8 in
Ava il abl e w ith o r w ith o ut Te fl on coatin g M ark s foo d, ju st as a co nve nti o nal grill does
and in o ne-h alf and o ne-third sizes

Perforated baking sheet Enameled pan Poached-egg pan

Ho les in th e non sti ck sheet help th e bottom Coating w ith stand s high heat Ind ented and coate d w ith Tefl o n
of bread to bake rather than stea m and ca n pro du ce sea rin g effects fo r easy remova l

Wire basket Chicken rack Pizza stone

Allows full access to hot air Ho ld s bird s up right fo r optimum cri sping; A custo m-m ad e sheet of thi ck met al fo r
for simul ated frying a du ck rac k is also ava ilabl e bakin g p izza pi es

1 66 VO LU M E 2 · TE CHNI QUE S AND EQUI PM ENT

can use to make terrific food. There is just plenty in bulk, and they also take advantage of the speed Large roasts can be successfully
ofroom to improve the current technology with a of the deviceSj combi ovens come up to tempera- cooked to rare temperatures in a
different interface and approach. ture within 5-10 minutes and cook far faster than combi oven. Even though the
either a water bath or a CVap does. temperature is not perfectly
Cooking in a Combi accurate, the fluctuations tend to
In our experience, however, combi ovens are not average out when a large piece of
Fortunately, a cook need not know the precise particularly adept at holding temperatures below meat is cooked over a long period
wet-bulb temperature in a combi oven to get of time. Small er food pieces with
fantastic results (see the table of cooking strategies 60 ·c I 140 •F. We've used them to cook fish, which shorter cooking times are more
on page 170). We have favorite applications for these we most often prefer steamed at 45 •c I 113 •p, and problematic. The shorter the
ovens when they operate in several different modes. cook ing time, the more important
to prepare steaks, which we like rare to medium rare the fluctuations become.
Low-temperature steaming, for instance, works
very well in combi ovens, especially at tempera- (50-55 •c I 122-131 •F). The equilibrium cook-

tures of 60 ·c I 140 •p and higher. Set the unit to ing approach, similar to that used for sous vide (see

steam mode with humidity at 100% and the page 243), is to set the oven to a temperature 1 •c I

temperature anywhere between 30-100 ·c I 2 •p above the desired core temperature. Unfortu-
nately, the temperature in a combi oven varies so
86-212 •p, This mode excels for poultry, meats, much at temperatures this low that a water bath is
and all manner of plant foods . Conventional a much better place to cook fish and red meat.

steaming at 100 •c I 212 •p works well, too. To circumvent this shortcoming, you can adopt
a "hotter-than-core" cooking approach (see page
The advantage ofthe combi oven, when used
this way, is its capacity: how else can you steam 245) with the combi oven set at 60 ·c I 140 •p, the

4.5 kg I 10 lb of broccoli or prepare a hotel pan of lowest temperature at which it seems to provide
reasonably accurate and precise performance. The
rice? Caterers often rely on combi ovens to steam risk with this approach is overcooking the food.
Even when the core is cooked perfectly, some

INNOVATIONS

Ways to Make Modern Ovens Better

Modern humidity-controlled ovens such as CVaps and This deficiency results largely from their heritage. The
combi ovens share a common flaw: they don't let you set CVap started out as a holding oven, and the combi oven was
the wet-bulb and dry-bulb temperatures directly (although meant to be a catchall appliance for commercial kitchens,
the CVap does let you set it indirectly). Why the designers a culinary utility fielder. Neither was originally envisioned as
chose to make them that way is difficult to comprehend . a precision tool for high-end cooking. Design engineers have
These two temperatures are the primary parameters that made clear improvements in each of these oven types. But
control cooking, and they are based on concepts that are they have not yet captured theirfull potential.
reasonably easy to grasp. Substituting the arbitrary scales
of "Browning" and "Humidity" may seem simpler in theory, Accurate and stable control of wet-bulb and dry-bulb
but in practice, it means that users need lots of trial and temperatures is critical to successful high-end cooking using
error to find the settings that work best. these techniques. To brown food perfectly without over-
cooking its interior, for instance, an oven must be able to
So we appeal to the oven makers of the world, especially maintain low wet-bulb temperatures and high dry-bulb
the many innovative engineers and designers who work in temperatures simultaneously. The ideal wet-bulb tempera-
the industry: please give us ovens that let us select separate
wet-bulb and dry-bulb temperatures! And while you're at it, ture is 45 oc I 113 °Ffor cooking fish, 50-55 oc I 122-131 °Ffor
clever engineers, perhaps you could solve a related prob- rare to medium-rare meat, and 60 - 70 oc I 140-158 °Ffor
lem: the inadequate precision of the humidity- and temper-
ature-control systems in these ovens. Both temperature braised dishes. You want to hold those wet-bulb tempera-
and humidity levels stray from the set points more than tures steady while maintaining dry-bulb temperatures in the
they should.
range ofl00- 300 oc I 212- 572 °F. These conditions are

physically possible, but they would require upgraded
heating- and humidity-control systems in modern ovens.

COOK I NG IN MO DE RN OV ENS 167

Rational ovens feature a probe that outer portions will be overcooked because hotter- As mentioned earlier, the oven will never actually
you insert into the center of the than-core cooking always creates a gradient of achieve 90% Rational humidity, but there is little
food to track the core temperature. temperatures in the food. To compensate some- reason to change the setting.
The probe has five separate sensors what, use the oven's temperature probe to measure
to give you a more accurate core temperature. You may need to set the probe Program Cooking
reading; the machine's digital for less than the target temperature to compensate
control chooses the lowest. That for overshoot. Busy cooks can easily become enamored of the
way, you don 't need to hit dead combi oven's unique ability to do program
center of the food with the tip of We have had success cooking large pieces of cooking and to carry out programmed recipes
the probe. food, such as roasts, in this fashion. Built-in automatically. This convenient feature is made
programs such as "overnight roasting" effectively possible by the unit's built-in computer controls
For large cuts of meat, overnight mimic the results ofcooking sous vide. But you and the temperature sensors on a probe that you
roasting is effective even with will probably get more desirable outcomes ifyou insert into the food. The combi oven is perhaps
core temperatures in the range cook thinner cuts of red meat or fish sous vide in a the most digitally enabled kitchen equipment
water bath or CVap oven, both ofwhich perform available today.
of 50-60 oc / 122-140 °F. The size of better at low temperatures.
Once the cook enters the sequence ofdesired
the meat compensates for tempera- Convection mode is quite handy in a combi cooking steps, the program takes the oven
ture fluctuations, which average out oven for dehydration and browning. Dehydrating through that sequence-different modes at
during the long cooking time. food by setting the Rational humidity to 0% and various temperature and humidity settings for
specified time periods. You can create your own
For more on how dehydration works, the temperature below 30-90 oc I 85- 195 op is a custom programs for common cooking tasks, or
see Drying,page 428. you can use the factory-installed programs.
common choice that quickly dries foods without
Cauliflower steaming in bulk quantities cooking them. Remember that drying is a diffu- The idea is to make it simple for kitchens that are
highlights the large capacity acombi oven sion process, so you can shorten the drying time staffed by mostly unskilled workers to consistently
possesses. by slicing the food as thinly as possible. produce decent-quality food.Just place food in the
oven and press graphical icons on a touch screen;
To brown or sear food using convection mode, the combi oven does the rest. The programs may, in
set the Rational humidity to 0% and the tempera- some cases, prompt you to insert a temperature
probe, but that's the most you' ll be asked to do,
ture to 175-300 oc I 347-572 °F. The higher the beyond perhaps removing the cooked food.

temperature, the faster the surface of the food will Cooks can customize their own programs,
desiccate and brown. which can use any or all ofthe oven's modes. A
program can h<~ve many steps-hundreds in
The combi mode works fine for everyday baking principle, but we've never seen more than a
as well. The default setting for combi mode on the handful. Each step can include any combination
Rational oven selects 90% humidity, which is a of changes to the temperature, humidity, and
reasonable choice for many general baking tasks. mode. The oven monitors the temperature probe
to determine when the food is done; it can even
prompt the operator to load or unload the oven.

These programs work very well in certain
settings. The executive chef of a chain restaurant
could, for example, supervise the creation of a
program for a new dish, then distribute it to each
kitchen. Home cooks can automate simple tasks
that they find themselves doing repeatedly, or that
they tend to botch regularly. We are quite pleased
with several programs that we created (for an
example, see page 176).

Program cooking bothers some chefs, who
complain that it can never produce the same

1 68 VOLUM E 2 · TE CHN IQUES A ND EQU I PM ENT

8

results that they could do manually. In some by the manufacturer's concern for food safety), Each brand of combi oven has its
cases, there may be an additional motivation for but for a conventional and fast technique, it does own set of features. This discussion
these complaints: the worry that automation will a great job. We developed a chicken program that, focuses on the Rationa lSelfCook-
make their jobs obsolete. But professionai chefs to our taste, does even better (see How to Roast a ing Center, the company's most
have little real cause for concern. Using a combi Chicken in a Combi Oven, page 178), but it takes advanced model.
oven in program mode is definitely a labor saver, several times longer to cook.
but it's unlikely to replace a chef's skills in any
meaningful way. Perhaps the most appreciated built-in feature
is the self-cleaning program. Combi ovens get
That said, several of the factory-installed very messy, because the high-velocity air tends to
programs do an excellent job and may even be splatter juices and drippings all over the inside of
useful in preparing high-end food. The overnight the oven. Thankfully, the self-cleaning program
roasting program is a case in point: it sears a roast handles the dirty work. Just put cleaning com-
or other large cut of meat (including poultry), then pound (which comes in large tablets) into the
cooks it for many hours via low-temperature oven, and start the program. Even the dirtiest
steam, and holds it until serving time. The process oven comes out sparkling-clean afterward.
generally takes four to eight hours, but you can
extend it to 24 hours if desired. The result easily Other programs are less successful. The
matches the quality oflong-term cooking sous combi-fry program cooks frozen french -fried
vide, but with the advantage that many roasts can potatoes so that they can almost pass as deep-
cook simultaneously in a combi oven. fried . This program works well enough for
service in a school cafeteria and other institu-
The built-in roast chicken program also per- tional settings or for vanquishing late-night
forms quite well. It directs one of the machine's munchies. But few gourmands would consider
most complex cooking procedures, which takes these combi fries a real substitute for true deep-
trussed chickens through multiple steps to produce fried potatoes.
roasts that have extremely crispy skin and succu-
lent interiors. The engineers at Rational developed As smart devices get ever more capable (and
the program to allow the combi oven to match the presumably less costly), there's no reason that the
qualities found in rotisserie-cooked chicken for combi oven won't eventually be able to carry out
restaurants and take-out sections in grocery stores. programmed, or even interactive, cooking tasks
that better emulate the skills of a practiced cook.
The result tends to be a bit overcooked, in part Even so, it will at most merely free up cooks to
due to excessive temperatures (perhaps dictated pursue new ways to create terrific dishes.

Comparing Cooking Modes

CVap water-vapor ovens and Rational combi ovens have different strengths and weaknesses.

Mode CVap Rational Operating co nditio ns Note
low-temperature steam very good good for combi ovens, temperature
dry-bulb and wet-bulb temperatures are control is typically poor below
steam n/ a very good identical and less than 100 ' C/ 212 ' F; 60 ' C/ 140 ' F
combi (humidity-controlled) good fair to good relative humidity is 100% CVaps generate too small a volume
convection fair very good of steam to perform true steaming
dry-bulb and wet-bulb temperatures are
program n/ a very good 100 ' C / 212 ' F; relative humidity is 100% CVaps cannot attain temperatures
high enough or humidities low
dry-bulb and wet-bulb temperatures enough to do conventional baking
diverge; oven directly controls humidity applies to combi ovens only;
CVaps can only store single settings
same as convection baking in a conven-
tional oven; no moisture is added
by the oven

control of oven temperature and
humidity is automated

COOKING IN MO DE RN OV EN S 16 9

STRATEGIES FOR COOKING IN CVAP OVENS AND COMBI OVENS

Combi oven settings

Temp erature Humidity
------------------

Method Cooking mode (%) Note

incubation, fermentation, low-temperature steam 30-50 85-120 100
or proofing

dehydration co nve ct ion 30-90 85-195 0

low-temperature or low-temperature steam 30-60 86-140 100 limited, due to temperature in accuracy
sous vide cooking 140-212 100 good temperature accuracy
60-100 212
steaming more consistent than co nvection
steam 100 mod e
baking
combi mode 60-300 140-450 90

convection 60-300 140-450 0 promotes drying and browning more
than combi mode

frying or grilling convection 180-300 355-450 0

programmed cooking all mod es full range full range built-in coo king programs available;
custom programming possible

Frying potatoes with herbs Baking hamburger buns

170 VOLUME 2 ·TECHNIQUES AND EQUIPMENT

8

CVap settings Examp le use
Done ness yogurt, sausage fermentation

(°F) Browning Note

30-50 85-120 0

30-60 85-140 1-6 set browning hig her for faster drying fruit leather, vegetable chips,
35-93 95-200 0 bacon and ham chips

fish, shellfish, poultry, red meats

not recommended vegetables, grains, braised meat
60-100 140-210 1-10
low maximum temperature and difficulty achieving low baguettes, brioches, rustic loaves
humidity limit its suitability for many baking applications

not applicable choux pastries, pizzas, gratin

not applicable CVaps are not designed to reach the high dry-bulb fried chicken, onion rings,
not applicable temperatures necessary for frying and grilling grilled fish and steak, ham

no programmability features are available in CVaps, but fried rice, rib roasts, omelets
com mon settings can be stored as presets

Steaming sausages Making yogurt

COOKING IN MODERN OVENS 171









EXAMP L E REC IP E

CANTONESE FRIED RICE Yields 1.2 kg
PROCEDURE
INGREDIENT QUANTITY SCALING
56 g 7% CD Preheat oven to 245 •c / 475 •F.
Chi cken fat, rendered, 10% 0 Add fat to nonstick roast ing pan, and let heat.
see page 3·116 BOg 10%
100% ® Add mushrooms, followed by sausage, and oven-fry until mu shrooms softe n and
Shiitake mushroom, thinly BOg sausages blister, about 5 min .
sli ced BOO g 10%
Chinese sausage, thinly sliced 5% 0 Add, stir to eve nl y distribute other ingredi ents into ri ce.
0.25%
jasmine rice, cooked 10% ® Oven-fry for 3 min .
and cooled ® Add, stir to distribute eve nly, and oven-fry for abo ut 30 s.
20 %
Garlic chives, cut into BO g 0 Fold into ri ce and oven-fry for about 2 min.
5 em / 2 in lengths 40g 4%
Scallions, white only, fine 2g ® Remove ri ce mi xture from oven, leav ing heat on .
julienne BOg 3% ® Make a well in th e middle of the fried ri ce.
1.5%
Red Thai chili, seeded and 0.4% @ Return ri ce mixture to 245 •c / 475 •Foven to heat.
cut in fine julienne @ Add egg, and allow to cook until just coagulated, abo ut 1'/2 min.

English peas, shu cked and @ Remove fried rice from oven.
blan ched (frozen peas work) @ Combine liqu ids an d stir into fried ri ce evenly to season.
@ Check seasoni ng and serve.
Duck egg, beaten 160g
(four eggs)

White soy sauce 32g

Dark soy sa uce 24g
Mushroom soy sauce 12 g
Toasted sesame oil 1.5g
(2008)

4 6a 6b

176 VOLUME 2 · TECHNIQUE S AND EQUIPMENT

lla llb 8

This recipe uses a combi oven as a substitute
for a wok to fry the ingredients. A combi oven has
a big advantage over a wok if you want to cook in
quantity. In the example photos, we made one
half-sheet pan of rice, but we could have made
five pans' worth simultaneously.

13

A variety of vegetables will work, such as mush-
rooms or scallions (photo below). It's entirely up
to the cook what to include.

COOKING IN MODERN OVENS 177





EXAMPLE RECIPE-----------------------------------------------------------------------------------

COMBI OVEN RIB EYE Yields 900 g

INGREDIENT QUANTITY SCALING PROCEDURE
Beef rib eye, bone in 900g 100%
Unsalted butter, melted as needed <D Brush rib eye with butter.
Salt to taste This cooking program uses 25 min
0 Place meat on perforated rack, of drying to prepare the surface for
searing. During the drying steps, the
and begin program. temperature is increased, but the
humidity is decreased so that the
® After stage 5, brush with more butter. wet-bulb temperature does not exceed
the cooking temperature. The tempera-
(2010) ture is increased in stages to give the
oven time to get rid of the extra humid-
PROGRAM ity. The temperatures at left are for what
we judge to be a medium-rare steak.
STAGE TEMP HUMIDITY COMMAND The temperatures can be adjusted for
1 55 "CI 131 "F other levels of doneness by using the
2 55 "CI 131 "F 100% 0 Preheat the oven to 54 "CI 131 "Fin steam mode table below.
3 55 "CI 131 "F
4 58 "CI 136 "F 100% ® Steam until core temperature reaches 54 "CI 129 "F, aboutl h.
5 61 "Ci l42 "F
6 0% @ Dry for 5 min.
7 300 "CI 575 "F
0% 0 Dry for 5 min.

0% ® Dryforl5 min.

® Remove steak from oven.

0% @) Preheat oven until it reaches temperature, about 10 min.

8 300 "CI 575 "F 0% @ Searfor2 min.

@ Turn and sear another 2 min.

STAGE RARE MEDIUM RARE MEDIUM
51 "C1 124 "Fwith 100% humidity
to core of 50 "Ci l22 "F 55 "CI 131 "Fwith 100% humidity 60 "CI 140 "Fwith 100% humidity
to core of 54 "CI 129 "F
2 51 "C1 124 "Fwith 0% humidity for 5 min 55 "CI 131 "Fwith 0% humidity for 5 min to core of 58 "CI 136 "F
58 "CI 136 "Fwith 0% humidity fo r 5 min
3 53 "CI 127 "Fwith 0% humidity for 5 min 60 "CI 140 "Fwith 0% humidity for 5 min
61 "CI 142 "Fwith 0 % humidity forl5 min 63 "CI 145 "Fwith 0% humidity for 5 min
4 56 "CI 133 "Fwith 0% humidity forl5 min
66 "CI 151 "Fwith 0% humidityforl5 min

A CVap oven will not get
hot enough for the brown-
ing stage, but you can do
stage 1 in CVap with
Doneness at the same
temperature as the combi
oven examples and with
Browning at zero. Sear with
a torch, plancha or other
means (see page 267). The
drying stage can be done
by then increasing the
Texture setting to 4.

180 VOLUME 2 · TECHNIQUE S AND EQUIPMENT

EXAMPLE REC I PE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

COMBI OVEN-STEAMED BROCCOLI Yi elds1.5 kg

INGREDIENT QUANTITY SCALING PROCEDURE
Rice vinegar lOOg 10%
Sherry vinegar 100g 10% CD Whisk together to make pickling brine.
Water 64g 6.4%
Sugar 28 g 2.8% 0 Bring to simmer.
Salt 3g 0.3%
Broccoli stems, peeled 40g 4% ® Rese rve.
and thinly sliced
Shallots, thinly sli ced 28g 2.8% @ Combine.
Currants 18g 1.8% ® Pour warm brine over broccoli-stem mixture to pickle.
100% ® Cool completely.
Broccoli florets 1 kg
20% 0 Reserve.
Broccoli, sma ll florets 200g 5%
Frying oil 50g ® Arrange florets in one layer in combi oven steam basket.
5% ® Steam at 90 "C/ 195 "F and 100% humidity for 8 min, or until des ired texture is achieved .
Salt to taste 3% @ Toss sma ll florets in oil, and place on baking sheet.
to taste
Pickling brine, ® Oven fry in combi oven at 270 "CI 520 "Fand 0% humidity for 4 min.
from above 50g
30 g @ Drain.
Toasted pumpkin seeds @ Season steamed and fried broccoli.
100g @ Strain reserved pickled mixture, reserving brine.
Chili oil @ Toss steamed and fried broccoli with pickles, brine, pumpkin seeds, and chili oil.
see page330
Salted lardo, frozen and 10% @ Drape over warm broccoli mix, and serve.
very thinly sliced

(2 010)

COOKING IN MODERN OVENS 181

COOKING WITH MICROWAVES

For moreonradiative heat transfer, Numerous misconceptions surround the micro- microwaves are tuned to a particular frequency
see Heat in Motion, page 1·277. wave oven, despite the fact that nearly every home that excites vibrations in water molecules-vibra-
in the developed world now seems to contain one. tions that generate heat.
Microwaves do n't normally heat The common notion that microwaves cook food
dishes or co ntain ers. Ifyo u put a from the inside out is incorrect, for example; they Water molecules can receive this kind of
ce rami c dish co nta ining metal in a penetrate only a centimeter or two (perhaps V2- transmission because they are polar (see Why
mi crowave oven, howeve r, it will l in) beyond the food surface. And although the Water Is Weird, page 1·298). This means that they
heat up -pe rh aps enough to break. phrase "nuking" food in the microwave has have a weak positive charge at one end and a slight
So me special brow ning dishes are entered the lexicon, microwave radiation has negative charge at the other. When polar mole-
designed to heat safely in a mi cro- nothing to do with nuclear radiation. cules are subjected to an electric field, they rotate
to align themselves with the field lines-an
wave oven. Microwaves are simply light waves, just like electric version of the way a magnetic compass
those that comprise visible light. And just like needle spins to face north and south.
visible light, infrared light, and radio signals,
microwaves are a specific class of invisible light In the rapidly alternating electric field of a
waves. In the case of microwaves, their wave- microwave oven, the molecules ofwater and other
length-the distance between neighboring polar substances spin back and forth repeatedly,
sinusoidal crests that distinguishes light waves- transforming electromagnetic radiation into heat.
ranges from about one millimeter to one meter Fats and oils are not polar molecules, but they can
(0.04-39 in). They feature much shorter wave- also be vibrated in other ways using microwaves,
lengths and higher frequencies-measured in so they also become a source of heat generation.
hertz (cycles per second)-than do radio waves. Their vibrations set neighboring molecules in
On the other hand, microwaves have longer motion, which conducts the heat further afield and
wavelengths and lower frequencies than the eventually heats the entire food by conduction.
infrared light waves that we recognize as radiant
heat. Microwaves themselves carry little power; Microwave ovens do not heat air, dishes, or the
most hair dryers pull more wattage than micro- walls of the oven. They heat only water and oil. Dry
wave ovens do. substances will not heat up at all in a microwave
oven. That explains why you can microwave water
Like grills and broilers, microwave ovens deposit in a paper cup and still remove the cup with your
energy and thus heat into food by radiative transfer, bare hands: the water heats up; the paper doesn't.
but the radiative heating of a microwave works
very differently than these other methods do. The A fatty food was key to the discovery ofthe
cooking potential ofmicrowaves. A Raytheon
scientist named Percy Spencer was touring the

Microwaves are aform of electromagnetic Microwave oven (2.4 GHz) Air-traffic control (2-4 GHz)
radiation with frequencies between 300 Cordless phone (2.4 GHz)
megahertz (MHz) and 300 gigahertz Police radar (7-40 GHz)
(GHz). Microwave ovens, cordless phones, Wi-Fi (2.4 GHz) Cosmic microwave
and wireless Internet connections all Bluetooth (2.4-2.5 GHz) background radiation (160 GHz)
operate at frequencies near 2.4 GHz,
which cannot be used for long-distance Automatic garage door opener Infrared
signals, because water molecules in the
atmosphere interfere with their transmis- Radio
sion-the same phenomenon that makes
these wavelengths perfect for cooking. 300 MHz 300 GHz

Global Positioning System,GPS
(1.2 GHz and 1.6 GHz)

Microwaves: 300 MHz- 300 GHz

182 VOLUM E 2 ·TEC HNIQUE S AND EQUIPMENT

company's radar lab in 1945, when he found that a tremendous impact on the way that they cook Popcorn was one of the first foods cooked
piece ofequipment had melted a chocolate bar food. In a microwave, small things take longer to in amicrowave oven and remains one of
that he was carrying in his pocket (see page 1·22). cook than larger ones-just the opposite ofwhat the most popular.
The device responsible was a magnetron, a micro- happens in conventional ovens (see Why Micro-
wave transmitter that served as the heart of the waves Heat Small Foods Slowly, page 188).
powerful but compact and therefore mobile Popcorn pops well in a microwave because all of
microwave radar set that British engineers perfect- the kernels are crowded together to form one
ed during the Second World War to detect Ger- target mass that "sees" and absorbs the micro-
man airplanes and ships. British innovations to waves. Put a whole bag ofpopcorn in the micro-
the magnetron boosted its power by a factor of 100 wave, and the first kernels pop in less than a
over competing designs. minute. An isolated, individual kernel, in contrast,
can take minutes to pop. That is why, at the end of
Despite the name, the microwaves that these the cooking cycle, a few recalcitrant kernels pop
ovens emit are in fact macroscopic: their wave- with long periods ofsilence in between-it takes
the microwaves longer to heat the smaller, individ-
length is 122 mm I 4.8 in long, corresponding to a ual kernels.

frequency of2.45 GHz. The reason that it is safe to Despite their macroscopic wavelength, micro-
put screened windows on microwave ovens is that waves do not pass through large objects the way
light waves of such a long wavelength cannot that radio waves (whose wavelength is much
escape through the fine holes of the window mesh; longer) do. Because microwaves penetrate only a
they merely reflect back inside. couple ofcentimeters into food, whole chickens,
roasts, and other very thick items do not cook
Microwaves are, in fact, so long from peak to
peak that they often "miss" smaller food items that
people place in the ovens, and that property has a

COOKING IN MODERN OVENS 183

FROM WARTIME TO SUPPERTIME

The microwave oven is an offshoot of military radar technology
developed by British engineers to detect enemy planes and
ships during the Second World War. One key advantage of
the new device was its size: it was compact and portable.
That same feature allowed a new generation of users to tuck a
microwave cooking appliance into the slot above a stove. Its
sophisticated electronics fit into a small space outside the oven
chamber.

This motor runs the fan that············: The waveguide carries the
distributes microwaves microwaves from the magnetron
evenly in the oven. to the food

: · · · · ·The magnetron generates
the microwaves.

· · · · · · · · · · · Afan coo ls the
magnetron and
its power supply.

The glass door has ·
a perforated metal
shield that allows
you to see inside,
but preve nts
microwaves from
leaving the oven.

Controls allow • · • · • • · · · · • · · · · · · · · • •
the user to set
cooking times
and power leve ls.

: .............. A power supply converts line
power to forms suitable for
the inte rnal electronics

18 4 VOLUM E 2 ·TECHNIQUES AND EQUIPMENT









quickly in a microwave oven. For the heat to reach fundamental cooking process. Microwaves heat Tilapiacooks beautifu lly in a microwave;
the center of the food, it must move by the slow food by exciting water molecules in the food to see our recipe on page 3-115.
process of thermal conduction, just as if that food vibrate, but food cannot brown until the applied
were cooking in a conventional oven or on a stove heat drives off all of the water at the surface. The
basic physics indicates that, at just the moment
top. A one-gallon I 3.8-liter jug ofwater, for exam- when the last bit ofwater vaporizes from the food
surface and the oven is primed to start browning,
ple, will take about the same time to come to a boil microwaves become essentially ineffective, for
in a microwave as it would on a hot plate or stove there is too little water left in the food for them to
top. The best approach to microwave cooking is thus vibrate and heat the dish!
to choose food that is not too small and not too big.
Another problem for browning is that micro-
Engineers have fitted microwave ovens with waves penetrate food, whereas browning is a
metal fans to "stir" the incoming microwaves by surface phenomenon. In a hot oven-or under a
reflecting them every which way, much as a mirror broiler-you create a browned layer less than
ball distributes a reflected spotlight around a
dance floor. Sending the microwaves in all direc- 1 mm I 1/32 in thick. In a microwave, you can't heat
tions helps to distribute their heating effect
throughout the food. Without this diversion, the just the top millimeter; you must heat a layer
waves would travel as a single beam from the 10-20 times that thickness.
magnetron duct, blazing a hot trail straight
through any food in their way, while leaving You can exploit the limitation on browning in
surrounding food raw. This tendency also explains drier foods by using microwave ovens to fully
why many microwave units feature rotating desiccate them without ever burning them: items
turntables. such as herbs (see page 3-312) and meat jerky (see
page 3-184), for example, in which browning is not
Even ifyou size the food to match the beam important or desirable. Microwave ovens also
pattern, however, microwave ovens can be tricky allow you to crisp food with little fear ofburning it.
to operate because they do not have standard Dry foods that are naturally high in fat will brown
power settings. You have to get used to your own because fat will not evaporate the way water does,
machine's idiosyncrasies, and that generally so it keeps on heating the food after the water is
involves determining the most favorable cooking gone. In some cases, you can brown food in a
times for various dishes by crude trial and error. microwave by first rubbing oil on its surface.

What's more, many cheaper microwave ovens Engineers have developed various hybrid
have only the most basic of controls. In these schemes to compensate for the microwave's
models, the microwaves are either on or off; the browning problem. Some of these hybrid devices
only variables you set are the total cooking time are microwaves that incorporate a broiler element
and the power level, which is accomplished by for browning. Others, such as the TurboChef
cycling the magnetron on and off. Power level is brand high-power microwave oven, include a
usually measured by a numerical scale that convection oven as well. The TurboChef oven uses
corresponds to the ratio of the time power is on microwaves for rapid heat transfer while also using
versus the total cooking time. Full power means
that the magnetron is on all the time, 50% power hot air (up to 260 ·c I 500 •p) for browning.
means that it is on half the time, and so forth.

Newer, more costly microwave ovens incorpo-
rate inverter technology, which directly controls
the strength of the microwaves so that the magne-
tron can stay on throughout the cooking process.
Although that feature ought to be an improve-
ment, in practice the results are pretty similar to
on- off power control for most cooking situations.

One of the main shortcomings of microwaves is
that they will not normally brown food. This is
unavoidable; it results from the technology's

COOKING IN MOD ERN OVENS 18 9

HOW NOT TO Do Irresponsible Things with a Microwave

We certainly do not recommend using kitchen equipment 1 Plasma grapes: cut a grape in half down th e center, leaving a seam of skin connecting
irresponsibly-but the reality is tha t peop le have been the two halves. Microwave on high . Hovering blobs of plasma emerge from the grape.
sticking odd things in microwaves for years, as hundreds of
rather amazingYouTube.com videos show. These ques- 2 Toothpick inferno: stick a toothpick into a piece of cork, light the other end on fire,
tionable escapades may damage your microwave and and putthe burning toothpick into the microwave (cork base down) under a clear
could even be d a nge rous, so again, for the record, we glass. Balls of fire will unfurl from the burning toothpick.
suggest you not perform these actions, interesting though
they may seem! 3 Sparks from aluminum foil: crinkled foil and foil edges cause arcing.

4 Incandescent light show: fill one glass with water and put a light bulb in another
glass. Put both glasses in the microwave turntable and turn it on for three seconds
(use the low-power setting if it has one). Don't leave it for too long and be careful
when you remove the glasses: the light bulb gets hot.

5 Soap monster: microwaves heat the fats in soap, causing rapid and uneven foamy

expansion. Put a bar of soap in a big bowl - the soap expands a lot. This trick also

works with marshmallows.

6 Dancing plasma: put a short candle in the microwave, with an inverted glass jar
over it, propped up so air can get in. Light the candle and start the microwave. The
microwaves excite the hot gases, turning them into a plasma.

7 CD light show: a microwaved music CD or CD-ROM (left) generates a spectacular
light show as electrical currents short out the thin layer of metal on the otherwise
plastic disc. Don't let the CD cook for more than five seconds or it will start to smoke,
releasing hazardous gases.

THE PHYSICS OF despite the fact that the term "nuke" has entered common
parlance.
Microwave Myths and Reality
Myth: Microwaves cook from the inside out.
Microwaves are perhaps the most misunderstood Fact: It may seem that way, because the interior of food
appliance in the kitchen . Here we explode several heats so much faster in a microwave than in a convention-
common myths. al oven and because you don't typically put very large
foods into microwave ovens. But microwaves actually
Myth: You can't put metal in a microwave. penetrate only a couple centimeters into food; the rest of
Fact: Microwaves already have plenty of metal in them: the the food heats by conduction, just as it does in conven-
walls of the oven, the fan, and so on, are all metal! What tional ovens.
you need to be careful of is m etal that has sharp points or
edges. Those features concentrate the electrical field in the Myth: Microwaves are always faster than conventional
oven and cause arcing. Arcing in and of itself isn't too ovens.
dangerous, but it can ignite dry flammables in the oven. Fact: There's an optimum size offood that microwaves will
The reason not to use metal cookware is that microwaves indeed heat very fast. But very large foods, such as roasts,
cannot penetrate metal, so your food will not cook. and very small foods, such as individual kernels of pop-
corn, will heat much more slowly than they do in conven-
Myth: Microwave ovens use nuclear radiation. tional ovens, and very dry foods may not heat at all.
Fact: Microwaves are electromagnetic radiation that
occurs at frequencies between 300 MHz and 300 GHz.
They are made of the same stuff as visible light and have
nothing to do with radioactivity or nuclear reactors,

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