STORING AND COOKING
How food cooks
Proteins change
Water begins to escape from
unraveling protein chains in steak and
collects within cells. Under gentle heat,
muscle fibers within a steak begin to
relax and unfold, while the meat’s own
enzymes actively break them down.
Juices leak out
Collagen sheaths around muscle
fibers contract, squeezing cells so that
the water they have accumulated
oozes out. Fiber-weakening enzymes
reach high levels of activity but then
change shape and stop working.
Oxygen leaves
Myoglobin, which gives raw
and rare meat its red color (see
pp.68–69), changes shape. This means
the meat loses its color as myoglobin
can no longer hold on to oxygen,
fading from red to pink to gray-brown.
1 2 3
How food cooks
At the molecular level, cooking involves a complex series of interactions
between heat, water, and individual food components, and
between the components themselves. When cooking,
the perfect balance between temperature, time, and
the desired change in chemistry must be achieved.
What happens when food cooks?
Food, especially meat, is composed of molecules similar to ours—
proteins and fats. Plants mostly comprise of carbohydrates. Heating
these molecules changes their nature, causing some to combine into
new molecules, others to break down into smaller ones, and some to
degrade. When heated, large molecules in food, such as enzymes,
change shape and stop working. Water is a crucial factor: dry cooking
causes water to evaporate; wet cooking can have the opposite effect,
causing food to absorb water, as with rice or pasta.
104ºF (40ºC) 122–140ºF (55–60ºC) 149–167ºF (65–75ºC)
Juices may be reddish
in color but it is not
blood—it is some of
the red pigment
(myoglobin) leaking out
Oxygen leaves meat
Protein
chains
begin to
unravel
DO FOODS LOSE
NUTRIENTS WHEN
COOKED?
Some foods lose a portion
of vitamins when cooked. In
others, the chemical reactions
and release of nutrients while
cooking can improve
their nutritional
value.
PROTEIN
Meat turns gray-brown
as myoglobin changes shape
RAW STEAK
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62 63
STORING AND COOKING
How food cooks
Water boils off
Collagen begins to break down
and liquefy. In a pan-fried steak, water
evaporates, and it becomes dense and
dry. In wet-cooked meat (such as in a
stew) the collagen melts, so the meat
remains succulent and juicy.
Maillard reaction
At the meat’s surface nearest
the heat source, where water has
boiled away, Maillard reactions take
place—combining amino acids and
sugars that turn the meat brown and
provide it with aromas and flavor.
Surface chars
If meat is exposed to high
temperatures, such as those from coals
or flames on a barbeque, or left to cook
for too long, combustion reactions will
take place that produce carcinogenic
compounds (see pp.68–69).
4 5 6
Sugar
combines
with
protein
Meat shrinks; becomes
tough and fibrous from
loss of juices and fluids
Water evaporates
as steam
Cooking vegetables
Vegetables are composed
mainly of carbohydrates, which
are generally much tougher and
more heat resistant than
proteins. The cell walls of plants
in particular are hard to break
down, although heat will
weaken them, allowing water
from inside the cells to leak out.
Vegetables turn tender when
boiled because pectin (a type of
carbohydrate), which sticks cells
together like bricks with mortar,
dissolves at boiling point.
Blending cooked vegetables
will eventually break down cell
walls altogether—this is how
vegetable puree is made.
1
Pectin molecule
2
Sugars break apart
when heated
Pectin
Long chains of
linked sugars (carbohydrates)
hold vegetables such as
carrots together—making
them tough and fibrous.
Bonds broken
When heat is
applied to pectin chains,
they dissolve at boiling
point, making carrots tender.
COOKING WITH A
PRESSURE COOKER
IS EQUIVALENT TO
COOKING WITH AN
OPEN PAN 3.6 MILES
(5.8 KM) BELOW
SEA LEVEL
The story of steak
Many changes happen at the molecular
level to steak meat as its temperature
rises and cooking progresses from one
extreme to the other.
167–194ºF (70–90ºC) 230–239ºF (110–115ºC) 266–284ºF (130–140ºC)
Carcinogenic
compound
PROTEIN
Amino acids
recombine
to create
new protein
chain
COOKED STEAK BURNED STEAK
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62 63
STORING AND COOKING
How food cooks
Water boils off
Collagen begins to break down
and liquefy. In a pan-fried steak, water
evaporates, and it becomes dense and
dry. In wet-cooked meat (such as in a
stew) the collagen melts, so the meat
remains succulent and juicy.
Maillard reaction
At the meat’s surface nearest
the heat source, where water has
boiled away, Maillard reactions take
place—combining amino acids and
sugars that turn the meat brown and
provide it with aromas and flavor.
Surface chars
If meat is exposed to high
temperatures, such as those from coals
or flames on a barbeque, or left to cook
for too long, combustion reactions will
take place that produce carcinogenic
compounds (see pp.68–69).
4 5 6
Sugar
combines
with
protein
Meat shrinks; becomes
tough and fibrous from
loss of juices and fluids
Water evaporates
as steam
Cooking vegetables
Vegetables are composed
mainly of carbohydrates, which
are generally much tougher and
more heat resistant than
proteins. The cell walls of plants
in particular are hard to break
down, although heat will
weaken them, allowing water
from inside the cells to leak out.
Vegetables turn tender when
boiled because pectin (a type of
carbohydrate), which sticks cells
together like bricks with mortar,
dissolves at boiling point.
Blending cooked vegetables
will eventually break down cell
walls altogether—this is how
vegetable puree is made.
1
Pectin molecule
2
Sugars break apart
when heated
Pectin
Long chains of
linked sugars (carbohydrates)
hold vegetables such as
carrots together—making
them tough and fibrous.
Bonds broken
When heat is
applied to pectin chains,
they dissolve at boiling
point, making carrots tender.
COOKING WITH A
PRESSURE COOKER
IS EQUIVALENT TO
COOKING WITH AN
OPEN PAN 3.6 MILES
(5.8 KM) BELOW
SEA LEVEL
The story of steak
Many changes happen at the molecular
level to steak meat as its temperature
rises and cooking progresses from one
extreme to the other.
167–194ºF (70–90ºC) 230–239ºF (110–115ºC) 266–284ºF (130–140ºC)
Carcinogenic
compound
PROTEIN
Amino acids
recombine
to create
new protein
chain
COOKED STEAK BURNED STEAK
US_062-063_How_Food_Cooks.indd 63 18/01/2017 09:42
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