45G-12 |
Influence of soybean storage on the processing of filled tofu |
Z. S. LIU, Department of Cereal and Food Sciences, North Dakota State University, IACC 322, Fargo, ND 58105 and S. K. C. Chang, Dept. of Cereal Science, North Dakota State Univ., IACC 322, Fargo, 58105-5728. Soybeans are subject to storage and transportation after harvest before processing into various soy products. Tofu is an important soy food widely consumed in the Orient and is becoming popular in the United States. The quality of soybean during storage is affected by the original water activity (Aw) of the soybeans, storage environment relatively humidity and temperature. Our objective was to investigate the effect of water activity of soybean and time of storage at 30oC on the tofu-making quality of soybeans. Soybeans with different Aw (0.60, 0.63, 0.66, 0.69, 0.71, 0.74, 0.76, 0.78, 0.80, and 0.81) were sealed separately in cans and stored at 30oC for up to three months. At one-month intervals, soybeans were retrieved from the storage and processed into soymilk. After soymilk concentration was adjusted to 10.5 Brix, the optimal concentration of coagulant for making tofu was measured using a rapid method developed in our lab. Filled tofu was made with the optimal concentration of CaCl2 measured. Our results showed that the color of soybean, soymilk and tofu changed with increasing either water activity or storage time. With increasing either Aw or storage time, soymilk titratable acidity increased and pH decreased. The optimal concentration of coagulant decreased with an increase in either Aw or storage time. The optimal concentration of the coagulant for the soybeans with 0.81 Aw stored for 3 months decreased by approximately 38% of that for the initial soybeans. The breaking strength of tofu made from the soymilk with the same solid content decreased slightly but smoothness did not change as Aw increased or storage time increased. It is concluded that adverse storage of soybeans significantly reduced the optimal concentration of coagulant. This is very important since tofu makers may adjust the coagulant concentration to produce good quality tofu from stored soybeans.
Session 45G, Fruit & Vegetable Products: Vegetables (Fresh)
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