ABSTRACT
China is the birthplace of soybeans. In Oriental countries such as China, Korea and Japan, soy foods have been consumed for thousands of years. In the1800s, soybeans were introduced to America, but large-scale production of
soybean began only after World War II. In the first part of the 20th century, soybeans were known to the Westerners as an oilseed and feed-stuff only. Aside from the image problem, the major obstacles in the utilization of whole soybean for foods in the Western society include the beany flavor and the flatulence factor. Substantial use of soybeans for
I. Introduction ....................................................................................................................................................171-1 II. Tofu Processing Methods ..............................................................................................................................171-2
A. Soaking ....................................................................................................................................................171-3 B. Grinding ..................................................................................................................................................171-3 C. Heating ....................................................................................................................................................171-4 D. Separation of Soymilk ............................................................................................................................171-5 E. Coagulation of Soymilk ..........................................................................................................................171-5
1. Type of Coagulants ..........................................................................................................................171-5 2. Soymilk Concentration ....................................................................................................................171-6 3. Coagulant Concentration ..................................................................................................................171-6 4. Coagulation Temperature ..................................................................................................................171-6 5. Coagulation Methods ......................................................................................................................171-6
F. Pressing of Curd ......................................................................................................................................171-7 III. Roles of Soy Proteins in Tofu Making ............................................................................................................171-8
A. Storage Proteins of Soybeans ..................................................................................................................171-8 B. β-conglycinin (7S Protein) ......................................................................................................................171-8 C. Glycinin (11S Protein) ............................................................................................................................171-8 D. Gelation of Purified Soy Proteins ..........................................................................................................171-9 E. Soy Proteins in Tofu Making ................................................................................................................171-10
IV. Molecular Models for Tofu Curd Formation ................................................................................................171-11 A. Role of Protein Charges ........................................................................................................................171-11 B. Role of Lipids in Curd Formation ........................................................................................................171-11 C. Role of Phospholipids in Curd Formation ............................................................................................171-11 D. Hypothesized Molecular Model of Tofu Curd Formation ....................................................................171-11
V. Role of Phytic Acid in Tofu Making ............................................................................................................171-12 VI. Roles of Isoflavone and Saponins in Tofu Making ......................................................................................171-13
VII. Effect of Lipoxygenase on Tofu Making ....................................................................................................171-14 VIII. Effect of Soybean Storage on Tofu Making ..................................................................................................171-15
IX. Evaluation of Soybean Cultivars for Tofu Making ......................................................................................171-16 Acknowledgment ......................................................................................................................................................171-19 References ................................................................................................................................................................171-20
part of defatted soy meal was used or processed further for human foods. However, since 1980s, soybeans have been used for making a variety of soy foods in America. Hence, some soybeans are known as vegetable legumes and soy foods are popular vegetable foods. In very recent years, because several soybean components have been discovered to possess health benefits, hence, soy foods have become health foods. Consumption of soy foods in America has increased dramatically in the last few years. Soy foods are finding their ways in the main stream supermarkets. The total retail value of soy foods has exceeded 4 billion US dollars. The United States of America produces one half of the world soybeans, which are estimated to be approximately 159 million metric tons (1). Only approximately 5% of the US soybeans are used for making foods. However in the last three years, it was estimated that the annual soy food market had increased by 25% per year. Soymilk, tofu and meat analogs are the three major soy food types in the USA. The increases in soymilk and tofu retail values in the USA are about 40-50% and 15-20%, respectively, each year since 1997 (P. Golbitz, personal communication, 2000), while the overall growth of the US food industry has been only 3% per year. It has been predicted by the United Soybean Board that by the year of 2010, soyfoods’ retail value will reach 100 billion dollars in the United States.
