ProteinsProteins are essential constituents of plants and animals cells. In animals the muscular tissue of the body is composed of protein. In plants the proteins is enclosed in the cellulose (the fibrous framework of plants). There are therefore two source of proteins: animal proteins and vegetable proteins. 1. Animal proteins is obtained from meat, poult, fish, egg, milk, and cheese. 2. Vegetable protein is obtained from pules foods (eEtty.g we have things like beans, peas), nut, and unpolished cereals. The chief funtion of this nutrients is the building up, replacing and repairing of the body tissue. When there is an excess of it, it is of particular importance to go growing children.
THE COMPOSITION OF PROTEINproteins are composed of amino acid units of different kinds of different arrangements. Some of them can be converted by the body into the ones in needs (the body does not need all of them), but there are ten amino acids which the body cannot make and which must therefore be surplied in the diet. These are called essential amino acids, In the most cases animal proteins contains these in the correct proportion for human needs, while vegetable proteins may lack one or other of them. Therefore animal proteins are often termed first-class proteins, if vegetable proteins are mixed with animal proteins the correct essential amino acids can be obtained. The need for protein depends upon a person's sex, size and age. It is most important for growing children, while adults needs rest of it. Woman, however, requires a greater amount of protein; infants, adolescents, pregnant and nursing woman should normally get about 14 pre cent of their total calories from protein, while other need about 11 per cent of their calories in the form.
Properties of proteins
1. Some proteins dissolves in water, eg. albumen. This coagulates on heating.
2. Most do not dissolve in water, but many are soluble in salt and water mixtures of various strengths.
3. When protein are heated violently their essential qualities are changed. this is usually accompanied by hardening.
Gelatine is an animal protein derived from meat, calves, hoofs,etc. it is completely deficient in at least one of the essential amino acids,and is therefore of little food value unless supplemented by other proteins. Soya beans are a valuable source of high quality vegetable protein; the proteins of soya beans contain all the essential amino acids.
Soya bean flour and soya bean paste are being introduced into the diets of many countries; because of its high protein value - which is comparable to meat it is used as a meat substitute in the diet. Soya beans are now being grown in the United States. They are grown mainly as a source of vegetable oil as soya beans need heat treatment to make them palatable, but new methods of processing them are now being developed.
Also i will still post more about the properties of Protein and there classifications.