Main article: Food safety
When heat is used in
the preparation of food, it can kill or inactivate
potentially harmful organisms including bacteria and
effect will depend on temperature, cooking time, and
technique used. The temperature range from 41 °F to
135 °F (5 °C to 57 °C) is the "food danger zone."
Between these temperatures bacteria can grow rapidly.
Under optimal conditions, E. coli, for example, can
double in number every twenty minutes.
The food may
not appear any different or spoiled but can be harmful
to anyone who eats it. Meat, poultry, dairy products,
and other prepared food must be kept outside of the
"food danger zone" to remain safe to eat.
Refrigeration and freezing do not kill bacteria, but
only slow their growth.
When cooling hot food, it should not be left
standing or in a blast chiller for more than 90
minutes. Cutting boards are a potential breeding
ground for bacteria, and can be quite hazardous unless
safety precautions are taken. Plastic cutting boards
are less porous than wood and have conventionally been
assumed to be far less likely to harbor bacteria. This
has been debated, and some research has shown wooden
boards are far better. Washing and sanitizing cutting
boards is highly recommended, especially after use
with raw meat, poultry, or seafood.
Hot water and soap followed by a rinse with an
antibacterial cleaner (dilute bleach is common in a
mixture of 1 tablespoon per gallon of water, as at
that dilution it is considered food safe, though some
professionals choose not to use this method because
they believe it could taint some foods), or a trip
through a dishwasher with a "sanitize" cycle, are
effective methods for reducing the risk of illness due
to contaminated cooking implements.
Effects on nutritional content of food
Proponents of Raw foodism argue that cooking food
increases the risk of some of the detrimental effects
on food or health. They point out that the cooking of
vegetables and fruit containing vitamin C both elutes
the vitamin into the cooking water and degrades the
vitamin through oxidation.
Peeling vegetables can also
substantially reduce the vitamin C content, especially
in the case of potatoes where most vitamin C is in the
skin. However, research has also suggested that a
greater proportion of nutrients present in food is
absorbed from cooked foods than from uncooked foods.
Baking, grilling or broiling food, especially
starchy foods, until a toasted crust is formed
generates significant concentrations of acrylamide, a
Cooking dairy products may reduce a protective
effect against colon cancer. Researchers at the
University of Toronto suggest that ingesting uncooked
or unpasteurized dairy products (see also Raw milk)
may reduce the risk of colorectal cancer. Mice and
rats fed uncooked sucrose, casein, and beef tallow had
one-third to one-fifth the incidence of microadenomas
as the mice and rats fed the same ingredients cooked.
This claim, however, is contentious. According to the
Food and Drug Administration of the United States,
health benefits claimed by raw milk advocates do not
exist. "The small quantities of antibodies in milk are
not absorbed in the human intestinal tract," says
Barbara Ingham, Ph.D., associate professor and
extension food scientist at the University of
Wisconsin-Madison. "There is no scientific evidence
that raw milk contains an anti-arthritis factor or
that it enhances resistance to other diseases."
Several studies published since 1990 indicate that
cooking muscle meat creates heterocyclic amines
(HCAs), which are thought to increase cancer risk in
humans. Researchers at the National Cancer Institute
found that human subjects who ate beef rare or
medium-rare had less than one third the risk of
stomach cancer than those who ate beef medium-well or
well-done. While eating meat raw may be the only way
to avoid HCAs fully, the National Cancer Institute
states that cooking meat below 212 °F (100 °C) creates
"negligible amounts" of HCAs. Also, microwaving meat
before cooking may reduce HCAs by 90%.
Nitrosamines, present in processed and cooked foods,
have also been noted as being carcinogenic, being
linked to colon cancer.
Research has shown that grilling or barbecuing meat
and fish increases levels of carcinogenic Polycyclic
aromatic hydrocarbons (PAH). However, meat and fish
only contribute a small proportion of dietary PAH
intake - most intake comes from cereals, oils and
fats. German research in 2003 showed significant
benefits in reducing breast cancer risk when large
amounts of raw vegetable matter are included in the
diet. The authors attribute some of this effect to
Heating sugars with proteins or fats can produce
Advanced glycation end products ("glycotoxins").
These have been linked to ageing and health conditions
such as diabetes.