Chemical composition of grain products
Protein. The fullest are proteins of germ in which irreplaceable amino acids are favorably balanced. A little smaller value proteins endosperm have. Comparative data on the content of irreplaceable amino acids in proteins of germ and endosperm are provided in the table.
Protein of germ approaches on the amino-acid structure squirrels of animal origin.
The general for all grain products is the low maintenance of lysine. The best amino-acid structure characterizes proteins bean in which the quantity of lysine, threonine, valine exceeds by 2-3 times contents them in proteins of grain cereals.
The protein of soy containing in comparison with protein of grain cereals in 4-5 times more of lysine, threonine, isoleucine and valine 2-3 times more leucine, tryptophane and other amino acids is especially valuable on the amino-acid structure. On the content of methionine, this major lipotropic factor, protein of soy is equivalent to cottage cheese casein.
|Amino acid||Contents in %|
|in whole grain||in germ||in endosperm|
Fat. Grain products (except soy and oil-bearing crops) differ in the low content of fat and cannot be its source. The amount of fat in the majority of grain products does not exceed 2%. The main amount of fat in grain products is in germ and covers of grain. Endosperms it is extremely poor in fat in this connection products of processing of grain in which covers and germinal part of grain are removed for example high-grade flour, as a rule, contain not enough fat.
Fats of grain products belong to biologically valuable fats. They include the high-valuable nonlimiting fatty acids (linoleic, linolenic) which are not synthesized in human body and also phosphatides including lecithin. Fat of germinal part of grains contains vitamin E (tokoferola) in significant amounts.
High content of nonlimiting fatty acids in fat of grain products has also the negative side as unsaturated fatty acids are unstable, easily are oxidized and promote damage of grain products at their storage.
Carbohydrates. The main value of the majority of grain products, especially grain cereals, consists in the high content in them of carbohydrates which amount in grain cereals reaches more than 65%, and in bean more than 50%. Carbohydrates are mainly presented in the form of the starch concentrated in endosperm.
Mineral substances. The main amount of mineral substances of grain products is concentrated in germinal part and covers. In this regard removal of germ and covers by production of high-grade flour and grain leads to depletion of their mineral composition. The general content of mineral substances in grain products fluctuates from 1,5 to 4%.
Grain products in significant amount contain potassium, phosphorus, magnesium and in smaller quantity calcium. At the usual mixed food only at the expense of grain products about 1600 mg of phosphorus, 2000 mg of potassium, 250 mg of calcium, 900 mg of magnesium which could satisfy in large part need of the person for these substances are delivered to organism within a day. However it is necessary to consider that phytin connections in which there are in grain calcium and phosphorus differ in bad comprehensibility in this connection, despite their rather high content in grain products, they are badly used by organism.
The researches in public conducted by V. P. Bogoroditska have shown what at inclusion in the usual mixed diet of the haricot rich with phytin connections, use of calcium and phosphorus at all observed persons went down, and the balance from positive became negative.
The sodium phytin entered into usual diet also lowered use of calcium and phosphorus at all persons which were under supervision. Iron which contains in grain products on average in number of 2-3 mg of % is slightly better acquired.
Vitamins. In grain products almost all vitamins of group B are well provided. Grain products contain 0,4-0,7 mg of % of thiamin, about 0,2 mg of % of Riboflavinum and 2-5 mg of % of nikotinamid. Besides, the pyridoxine (0,5 mg of %), pantothenic and paraaminobenzoic acids, inositol and biotin, and also tokoferola are provided to them.
Vitamins of grain products are concentrated most in germ and covers of grain. During removal of the last the received products (flour, grain) contain few vitamins. In this regard on the content of vitamins (and mineral substances) the products received from whole grain that is with use for the food purposes of germinal part and covers of grain are the most valuable.
Enzymes. In grain products in significant amount many enzymes which activity can lead to essential changes of organic substances of grain products and to their damage are provided. The strengthened enzymatic activity is noted at increase of humidity of grain and high temperature of storage.