Chemical and Biochemical Factors That Influence the Gelation of Soybean Protein and the Yield of Tofu

Soybeans contain around 40% of high quality protein and 20 % of oil. Soy protein has long been used as ingredients for its emulsification and texturizing properties in a variety of foods, soymilk and tofu being the most popular. Soymilk is essentially a water extract of soybeans and there are many variations on the basic soymilk processing steps. Tofu, or bean curd, is made by coagulating soy milk, and then pressing the resulting curds into blocks. This thesis was mainly devoted to thermal denaturation and coagulation of soy proteins and targeted several selected important factors as they relate to the functional properties. The effects of different chemical coagulants as well as proteases on yield and quality of tofu from soybeans were studied. Eight tested chemical coagulants were able to coagulate the soymilk and the results showed that the concentration of soymilk and type of coagulant had a great influence on the properties of the tofu gel. The results also confirmed that the use of a suitable concentration of the quick-acting coagulants is more critical than that of the slow-acting coagulants in tofu making. In general, the extent of soymilk gelation is not determined by a single characteristic but rather results from a combination of factors. The gelation ability of various most common commercially available proteases to coagulate non-defatted soymilk was surveyed and the thermal stabilities of selected protease systems were compared. The difference in the temperature where the enzyme shows its highest activity seemed to be the most significant indicator when choosing a suitable enzyme for a certain industrial application. The three most effective and versatile