Soybean is mainly used for the preparation of many food products, of which soy milk and tofu are the most popular. Soy milk is an aqueous product of soybean which is prepared by several methods, differing in processing parameters. Tofu is the coagulated product of soy protein, soy lipid and other components trapped in its network. The biochemical composition of tofu has important parameters, which determine its nutritional and nutraceutical quality. The degree of soy milk coagulation is influenced by soybean varieties, nature of coagulants, coagulating conditions and protein-lipid interaction. The gelation of soy milk protein is a complex phenomenon, which is determined by several factors. The gel properties of soy protein are affected by protein concentration, heating temperature, ionic strength and pH. The commonly used coagulants in tofu preparation are salt of calcium, magnesium, citric acid, acetic acid and Glucono-Delta-Lactone (GDL). The type of tofu is determined by the concentration and nature of coagulants. Each coagulant has a different Optimum Coagulant Concentration (OCC) to produce different types of tofu. This review focuses on the mechanism and factors influencing the process of coagulation and quality of tofu.

The major source of protein of animal origin is meat and poultry, whereas cereals are the major source of vegetable protein. The steadily increasing cost of animal protein and increasing population have compelled the food industry to focus attention on the low cost of vegetable source of protein, principally oil seeds. The least expensive source of high quality food grade protein is soybean that contains more than 40% protein. Soybean (Glycine max), a native of China, is used as an important source of dietary protein and oil. The protein produced by soybeans per unit area of land is higher than that of any other crop, however, it contains some Anti Nutritional Factors (ANF). During the past decades, suitable processing methods have been found for minimizing some undesirable components mainly ANFs and converting the protein to a more readily utilizable form. The whole soybean, containing about 40% protein and almost 20% oil on a dry weight basis provides an excellent source of quality protein and edible oil (Table 1). There exists great variation in chemical composition of soybean among different varieties. The chemical composition of soybean is more important than any other parameters because it plays a major role in different attributes of soy-based food products. Several important compositional factors affecting the quality of soy-based food products include protein content, protein solubility, 7S/11S storage protein ratio and phytate content.

Tofu (soy paneer) is a curd-like product prepared by gelation of soy protein. It is very difficult to make tofu with a consistent quality (nutritional and nutraceutical) and yield because it depends upon several factors. In tofu preparation, high protein recovery and high solid yield are always preferred by tofu industries. The chemical composition of tofu is an important parameter, because it determines the quality as well as quantity. The composition of tofu depends mainly on soybean varieties and method of tofu preparation. Several studies indicate that mainly soy milk quality and its subsequent coagulation process influence the quality and yield of tofu.

Chemistry Journal, Biochemical Mechanisms, Soy Protein Gelation, Anti Nutritional Factors, Chemical Compositions, Coagulation Process, Glycinin, Polypeptide Chains, Trimeric Glycoprotein, Physicochemical Properties, Denaturation Process, Hydrogen Bonding, Gel Formation Process, Gelation Mechanism, Soy Milk, Biochemical Investigations, Soy Phytoestrogens, Steroid Hormones.