FOOD CONSTITUENTS
FOOD
CONSTITUENTS
Food is composed
of the following five constituents:
Carbohydrates
Fats
Proteins
Minerals
Vitamins
Carbohydrates:
Carbohydrates
used in cooking include simple sugars such as glucose (from table sugar) and
fructose (from fruit) and starches from sources such as cereal flour, rice,
arrowroot
and potato.
Fats:
Fats and oils
come from both animal and plant sources. In cooking, fats provide tastes and
textures. When used as the principal cooking medium (rather than water), they
also allow
the cook access
to a wide range of cooking temperatures. Common oil-cooking techniques include
sauteing, stir-frying, and deep-frying. Commonly used fats and oils include
butter,
olive oil,
sunflower oil, lard, beef fat (both dripping and tallow), rapeseed oil or
canola, and peanut oil. The inclusion of fats tends to add flavor to cooked
food.
Proteins:
Edible animal
material, including muscle, offal, milk and egg white, contains substantial
amounts of protein. Almost all vegetable matter (in particular legumes and
seeds) also
includes
proteins, although generally in smaller amounts. These may also be a source of
essential amino acids.
Minerals:
Minerals are the
chemical elements required by living organisms, other than the four elements
carbon, hydrogen, nitrogen, and oxygen which are present in common organic
molecules.
Sometimes these "minerals" come from natural sources such as ground
oyster shells. Sometimes minerals are added to the diet separately from food,
such as mineral
supplements, the
most famous being iodine in "iodized salt." Other minerals are
calcium, chloride, magnesium, phosphorus, potassium, sodium and sulphur. These
minerals are obtained from milk, other dairy products, cereals, legumes, bone
meal, meat, fish, all fruits, vegetables, table & sea salt etc.
Vitamins:
Vitamins are essential
for the normal growth and development. It is a key nutrient that the body needs
in small amounts to grow and stay strong. Examples are vitamins A, C, and E.
Vitamins are found in many fruits and vegetables; especially green peppers,
citrus, strawberries, tomatoes, broccoli, leafy greens, potatoes, animal foods;
such as liver, whole eggs and milk.
EFFECTS OF COOKING
The effect of
cooking upon the food constituents are discussed
below:-
Action of Heat on Carbohydrates
The interaction of heat and carbohydrate is complex. Longchain sugars such
as starch tend to break down into more simple sugars when cooked, while simple
sugars can form syrups. If sugars are heated so that all water of crystallisation
is driven off, then caramelisation starts, with the sugar undergoing thermal decomposition
with the formation of carbon and other breakdown products producing caramel. An
emulsion of starch with fat or water can, when gently heated, provide
thickening to the dish being cooked. In European cooking, a mixture of butter
and flour called a roux is used to thicken liquids to make stews or sauces. In
Asian cooking, a similar effect is obtained from a mixture of rice or corn
starch and water. These
techniques rely on the properties of starches to create simpler mucilaginous
saccharides during cooking, which causes the familiar thickening of sauces.
This thickening will break down, however, under additional heat.
Action of Heat on Proteins
When proteins are heated they become de-natured and change texture. In many
cases, this causes the structure of the material to become softer or more
friable - meat becomes cooked.
Cooking at ordinary temperatures renders protein foods more digestible. At
high temperatures the protein itself gets denatured thus making it of nutritive
value. In some cases, proteins can form more rigid structures, such as the
coagulation of albumen in egg whites.
Action of Heat on Fats
Fat melts when it comes in contact with heat. If heated to a very high
degree for a long time, fats undergo partial decomposition and fatty acids and
glycerol are produced. Glycerol further decomposes into caroling which is an
irritating compound to the digestive system. When fat heated for long time at
too slow temperature it thickens, becoming gummy. This condition is known as
polymerization, and fat that has reached this stage is no longer fit for use.
Action of Heat on Minerals
There is no appreciable loss of minerals due to cooking. Some minerals are
made more readily available by cooking.
Action of Heat on Vitamins
There is some unavoidable loss of vitamins during cooking. The loss is
considerable in respect of thiamine and vitamin C. Vitamin A and D are not
destroyed by the ordinary methods of cooking. Vitamin B may be destroyed during
cooking if cooked at high temperature. The use of baking soda in cooking causes
further destruction of vitamins.
Comments
Post a Comment