Soy protein
The soybean, Glycine max, is a leguminous crop grown in many parts of the world. Soybeans are of great economic importance as a source of edible oil, high-protein foods, food ingredients, and stockfeed, as well as many industrial products. A soybean contains a large amount of high-quality proteins and has been utilized as an excellent protein source from old times. In particular, soy protein isolate is useful as a food material by virtue of its high protein content and various functional characteristics such as emulsification properties, gelation properties, water holding properties etc. Phytochemicals include isoflavones which occur in a variety of leguminous plants. Soybeans are the most significant dietary sources of isoflavones. Isoflavones have been detected and identified in biological fluids of humans consuming the plant material. Isoflavone is a flavonoid and includes saponins, lignans, alkaloids, catechins, and phenolic acids and also includes malonyl, acetyl, glucoside, and aglycone forms of the isoflavones. Isoflavones have a limited distribution in the plant kingdom and may be physically described as colorless, crystalline ketones. The most common and important dietary source of these isoflavones are soybeans which contain the following isoflavone isomers: genistein, genistin, daidzein, daidzin, glycitein, glycitin, and etc. Isoflavones isolated from soy have become the focus of much research in the areas of heart disease, cancer, osteoporosis and kidney diseases. Soy protein isolate (SPI), soy protein concentrate (SPC), and soy flour (SF) are major sources of soy protein. Soy flours and grits are the least refined forms of soy protein products used for human consumption and may vary in fat content, particle size, and degree of heat treatment. Soy protein concentrates have much of the indigestible oligosaccharides removed such that the raffinose content is less than about 0.5% and the stachyose content is less than about three (3)%. Soy protein concentrates are derived from defatted soybean flakes, grits, or flour. Most of the soy carbohydrate remains in the concentrate. Typically, soy protein concentrate contains about 65% protein, about 25% carbohydrates and the balance is oil, ash and fiber. Soy protein isolates are the most highly refined soy protein products. Isolates are 90% protein on a moisture-free basis. They contain no dietary fiber and are sometimes high in sodium, properties that can limit their application. Their major applications have been in dairy substitution, as in infant formulas and milk replacers. Soy protein concentrates and soy protein isolates are the most highly refined commercially available soy protein-containing products. Both soy protein concentrates and isolates are processed to increase soy protein content. Soybean proteins are a combination of 18 amino acids of wide chemical diversity such as amines, carboxylic acids, hydroxyls, and mercaptan functionalities. Soy protein in the diet actually reduces serum cholesterol levels in people who are at risk. The higher the cholesterol, the more effective soy proteins are in lowering that level.
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