Soymilk preparation

Table II gives the results of residual trypsin inhibitor levels for the various soymilk preparations. The 90 and 120 sec microwave treatments were the most effective in inactivating the trypsin inhibitor complex while hot water treated and unheated samples showed the highest levels. It is not surprising to find that microwave processing is more efficient than hot water in suppressing trypsin inhibitor considering the rapid penetration of food material by microwaves and the susceptibility of protein action to small heat induced changes in tertiary structure. Hence, Collins and McCarty (12) found microwaves produced a more rapid destruction of endogenous potato enzymes (polyphenol oxidase and peroxidase) than hot water heating.

Tezuka, M. H. Taira Y. Igarashi K. Yagasaki T. Ono. Properties of tofus and soymilks prepared from soybeans having different subunits of glycinin. J. Agric. Food Chem. 2000, 48, 111 1—1117. 

In 1991, a processing plant was constructed in Jefferson, Iowa (MicroSoy Corp.), to make easily-extractable full-fat flakes from white hilum soybeans for export to make soy milk and tofu. Using these flakes eliminates the need for soaking the beans prior to wet grinding reducing soymilk preparation time. 

Tofu. Tofu is prepared by adding a coagulant such as calcium sulfate to soymilk to precipitate the protein and oil into a gelatinous curd. The curd is then separated from the soluble portion (whey), pressed, and washed to yield a market-ready product. Tofu, a traditional food in Japan (90), was populari2ed in the United States in the late 1970s and is available in many U.S. supermarkets. 

Figure 1, a modification of the method used by Puski and Melnychyn (JO, shows the preparative procedure used to isolate an acid-precipitated fraction of soymilk protein (RDP). 

The major reason for this difficulty arises from the fact that there are complex interactions of many factors that are involved in the making of tofu (Saio, 1979 Skurray et al., 1980 deMan et ah, 1986 Beddows Wong, 1987a, 1987b Ohara et ah, 1992 Shi Ren, 1993 Shih et ah, 1997 Liu, 1999 Kim Wicker, 2005 Mine et al., 2005 Poysa et al., 2006 Yoon Kim, 2007). These factors (or variants) mostly center around three key areas (i.) the way soymilk is prepared, (ii.) the way soy protein is coagulated, and (iii.) the way tofu is pressed and packaged. 

Chen, S. Preparation of Fluid Soymilk. In Proceedings of the World Congress on Vegetable Protein Utilization in Human Foods and Animal Feedstuffs. Applewhite, T.H. Ed. AOCS Press Champaign,... 

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