Rice before milling has
adequate nutritional value. This tend to reduced during milling for example/ milling
removes about 80 percent of vitamins from brown rice and thus causing
beriberi and other nutritional deficiencies however, most rice consumers still prefer well
milled rice since brown rice has an unfavorable chewier texture and flavour. Although the nutritional value
of rice varies with different varieties soil fertility fertilizer applied and other environmental conditions the following trends still
exist by comparison with other cereals low fat content after removal of the bran, low protein content
(7-10 percent) and high
digestibility of protein (USA Rice Federation, 2002).
In addition to varietal difference, protein content is affected
by environmental conditions such as oil
and nitrogen fertilizer application. Protein is mainly distributed the bran and peripheral of
the endosperm. The
central part of the rice grain only contains has small portion of the proteins.
Rice protein has all essential amino acids, in rather a well-balanced proportion for human body
(USA Rice Federation 2002). The protein content of whole rice kernel is variable, ranging between 7-9 percent. It has high levels of aspartic
acid, glutamic acid but low levels of essential amino acid. Lysine and other amino acids such as isoleusin threonie, tryptophan, methionine and cystin (Enwere
1998).
Rice is unique in richness of -alkali- soluble protein or glutelin about
70%) where as the Other cereals are rich in
alcohol-soluble protein or prolamin (rice has about 3 percent prolamin in its
gross protein content). The other components of rice protein include 4-9
percent water soluble proteins or albumins and about 10 percent salt soluble
protein globulin. Rice protein are rich in
argrinine and contain trytophan and histidin but are poor in lysined and threomine (USAj Rice Federation 2002). Carbohydrates
More
than 90 percent
of the energy
in rice comes
from carbohydrates. Rice contains both simple and
complex carbohydrates. Simple carbohydrate or sugar includes glucose,
frugse, lacose and suerose. Complex carbohydrate in rice are
starch and fibres. About 85 percent of the rice
grain weight is starch. Amylose is the linear fraction of the starch and is negatively co-related with
cohesiveness, tenderness, colour and gloss
of cooked rice (USA Rice Federation 2002). Normal rice starch contain about 21-33% amylase and 64-79 percent
amylopectin while some waxy varieties contain 0.2
percent amylase (Enwere 1998).
Milled rice contains
from 10-22 percent the rice lipids have high content of linoleum and lioleic
acids but low levels of myristic plamitic, palmitoleic
and stannic acids. Rice is a health, food because it does not contain any cholesterol/ but does contain
linoleic acid accounting for 30 percent of the total rice fats that cannot be
converted from carbohydrate protein
or other fats (Enwere 1998).
Vitamins
Rice contains several
kinds of vitamin. Thiamine (Vitamin B 1,) has positive Wealth effect for bsan and heart, but
unfortunately, it cannot be stored in human
body and must be supplied in daily diet. Riboflavin, (vitamin B2) is important for energy production
and health of the skin and eyes. Rice have very small amount of
riboflavin, Niacin (vitamin B 3) is
essential for health skin, digestive and nervous systems. Pyridoxine (vitamin B6) indirectly helps to control amino acid
in the body. A shortage of pyridoxine has a negative effect on the central
nervous system. The foliate or folic
acid is important for the manufacture of DNA and haemoglobin. Rice also traces of
vitamin E that protects vitamin A and essential fatty acids from oxidation (ya et al, 2000).
Minerals
Iron is important in human foe- oxidation and other
enzymatic reaction. Phosphorus is critical for healthy
bones and teeth and other metabolisms. Phosphorus
in rice can be absorbed when supplemented with
milk or vegetables. Rice also has traces of calcium, potassium and sodium (USA Rice Federation, 2002). 2.7