42-2 |
The effect of heat processing and total solids on the viscosity of soymilk |
J. KAWADA1, T. Tanaka1, M. Suzuki2, H. Shidara1, and M. Kikuchi1. (1) Morinaga Milk Industry Co.,Ltd., Engineering Research Center, 4-515, Tateno, Higashiyamato-city,Tokyo, 207-0021, Japan, (2) Morinaga Milk Industry Co.,Ltd., Food Research and Development Laboratory, 5-1-83,Higashihara, Zama-city,Kanagawa, 228-8583, Japan With the growing interest in health food, there is increasing opportunity for developing production equipment and processes specifically for soybean food. To design equipment to exacting specifications it is particularly important to understand the viscosity of soymilk. Compared with cow's milk, the viscosity of soymilk increases significantly as total solids increase. Even when total solids remain constant, viscosity varies greatly depending on the production process and operating conditions. The objective of the research was to examine the effect of various factors on the viscosity of soymilk. Uncooked (unheated) soymilk, cooked (heated) soymilk and sterilized soymilk were prepared and observed by a scanning electron microscope. Viscosity and the degree of denaturation of soybean protein in the soymilk were measured and particle distribution was analyzed. The apparent viscosity at 20 of each soymilk at the sharing rate of 100[1/s] was evaluated. In the SEM photomicrograph, the difference between uncooked soymilk and cooked soymilk was clearly observed. Then, it was found that the relationship between the volume fraction of total solids and relative viscosity could be expressed by transforming Brinkman's equation hr=(1-fv)-2.5. For example, sterilized soymilk was expressed by hr=(1-fv)-23. In this equation, the exponent was divided into kE and kp, where kE is a constant descriptive of permanent aggregation and kp is that of dynamic aggregation. The equations to understand the viscosity of each soymilk at varying total solids were acquired. Then, it was proved that the exponent in each equation was correlated with the degree of denaturation of soybean proteins. As a result, it became possible to design production equipment to more precise specifications.
Session 42, Food Engineering: Rheology and texture
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