NUTRITIVE VALUE OF MEAT, POULTRY,
EGG AND FISH
Meat :
Meat refers to the flesh of warm
blooded, four legged animals chiefly cattle, sheep and pigs. Meat of sheep
which is under 12 months age is sold as lamb. After the age of 12months, it is
called mutton.
Pork is the meat of swine (pig)
slaughtered between the age 5 and 12 months. Veal is the meat of cattle that is
slaughtered 3 to 14 weeks after birth.
If slaughtered between 14 to 52 weeks the meat is called
calf. Meat obtained from cattle slaughtered one year after birth is called
beef.
Meat is a very good source of
protein. The average protein content of meat varies from 16 - 25 percent. The
amino acid pattern of meat protein is of outstanding nutritive value. The fat
content of meat varies from 5 - 40 percent.
Depending on the type, breed and age
of the animal, fat is distributed throughout meat in small particles of large
masses. Fat deposited uniformly in small sheets in the connective tissue within
the muscle is called 'marbling'. This contributes tenderness and flavour to the
meat.
Meat fats are rich in saturated fatty acids. The cholesterol
content of meat is 75 mg / 100 gm. Carbohydrate is found in small quantities
and present in the form of glycogen and glucose.
Meat
is a good source of iron, zinc and phosphorpus. It also contains sodium and
potassium. It is an excellent source of B-complex vitamin particularly B12
which is absent in plant foods. Liver is an excellent source of iron and
vitamin-A.
Changes in Meat :
After slaughtering, the lean tissues undergo a series of
complex physical and chemical changes. As a result muscles loose their soft
pliable nature and become rigid, stiff and inflexible. This is termed as 'rigor
mortis'.
Stiff muscle starts to soften and
becomes tender when it is held in a cold room temperature between 0 o C to 20 o C for 1 - 4 weeks. This is known as
'ripening' or 'ageing'.
During ageing the humidity of the
room is to be controlled. Tenderness of meat can also be obtained by the use of
mechanical methods such as pounding, cutting and grinding which break muscle
fibre. Addition of salt, vinegar, lime juice and enzymes viz., papain, bromelin
and ficin also help in tenderising meat.
Changes that occur during cooking:
·
On heating, the red pigment turns
brown due to the denaturation of protein pigment.
·
Heat treatment also brings about
inactivation of enzymes and denaturation of proteins, which makes meat tougher.
Hence, adopting correct cooking methods, time and temperature will result in a
well-cooked product.
·
Heating results in release of
volatile compounds from both fat and lean meat which contributes to the flavour
and taste of cooked meat.
·
Heating melts meat fat which
increases palatability of meat when eaten warm.
·
There is loss of water on heating
which does not change the nutritive value but may affect juiciness and bring
about shrinkage in volume and weight.
Minerals
like calcium may be lost in meat dripping due to the dissolution of calcium
from bones. There is loss of B-vitamins also.
Poultry:
The term poultry refers to domestic
fowls reared for their flesh and egg. It includes chicken, duck, geese, turkey,
pigeon etc.
Poultry meat has a high protein
content varying from 18 to 25 percent. It contains all the essential amino
acids required for body building.
Fat content of poultry is influenced
by age and species of the bird. Young birds have little fat content. Chicken
fat is unsaturated and is therefore better than the fat of red meat. Poultry
flesh is a good source of B-vitamin and minerals.
Egg :
The term egg mainly refers to the
egg of hen and duck. An average egg weighs 50 gms. approximately and is
composed of the shell, egg white and yolk. The weight is distributed in the
different parts as follows.
Percentage composition of egg
Part Weight%
Shell 8
- 11
White 55
- 61
Yolk 27
- 32
Egg is a rich source of protein and
lipids. Egg protein is of high quality as compared to any dietary protein and
therefore is used as a standard for evaluating the protein quality of other
foods. The nutrient composition of egg white and yolk differ considerably and
is represented in the following table.
Percentage
nutrient composition of egg white and yolk
Nutrient Egg white Egg
yolk
Water 88.0
% 48.0 %
Protein 11.0
% 17.5 %
Fat 0.2
% 22.5 %
Mineral 0.8
% 2.0 %
Vitamin and minerals in Egg:
Egg yolk is rich in vitamin-A. Thiamin and riboflavin are
present in appreciable amounts. Calcium is present in the yolk in small
amounts.
Phosphorus is abundant in the yolk. Eggs are an important
source of bioavailable iron and a fair source of sodium, magnesium chlorine,
potassium and sulphur.
Fish:
Fishes are classified as shell fish
and fin fish. The nutrient composition of fish of a given species varies
depending on the season of year and maturity. However most fish contain 15 - 24
percent protein, 0.1 - 22 percent fat and 0.8 - 2 percent minerals.
Fish proteins are easily digestable and are of high
biological value. The fat content is influenced by the species, feeding habits
and maturity of fish. Glycogen is present in fish but is in lesser quantities
than meat.
Fish oils are an excellent source of vitamin A and D. They
are a good source of thiamin, riboflavin and niacin. Small fishes that can be
eaten with bones contribute a significant amount of calcium.
Ocean fish are a rich source of iodine. Oysters are an excellent
source of copper. Fishes contain omega - 3 polyunsaturated fatty acids. These
acids are found to prevent the degeneration diseases of the heart.
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