|Budget Amount *help
¥3,800,000 (Direct Cost: ¥3,800,000)
Fiscal Year 2004: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2003: ¥3,000,000 (Direct Cost: ¥3,000,000)
Raw soymilk prepared was subjected to heat treatment. Precipitation of the heated soymilk was measured. Soymilk, which was heated at 70, 80℃, showed more precipitation than the raw soymilk. However the soymilk, which was heated at higher than 90℃ showed less precipitation. From SDS-PAGE patterns, heating of soymilk at higher than 90℃ formed some soluble aggregate from soybean protein constituents, and it is considered that the formation of this aggregate lead to high stability of soymilk. Further, for 2 step heating of soymilk, combination of low temperature and successive higher temperature heating resulted in lower precipitation but higher temperature (115 ℃) and successive lower temperature (70, 80℃) resulted in higher precipitation. From these data, it was considered that lower temperature at second heating allowed the soymilk protein, which was thermally denatured, to be refolded partially, and that these refolding accelerated the formation of precipitation.
Next, to evaluate these phenomenon for other proteins, we chose β-lactoglobulin (β-Lg) in bovine milk whey. β-Lg solution was heated and cooled in ice bath or at room temperature. β-Lg cooled in an ice bath showed higher surface SH content than that cooled at room temperature, resulting in maintenance of high reactivity of protein surface. So in order to estimate the effect of cooling methods (rapid or slow cooling) on physical properties of protein solution, a cold set gel from β-Lg was prepared. As the result, β-Lg cold set gel have larger breaking strain by cooling in ice bath than at room temperature. These data may show that cooling procedure of protein solution after heating is important for control of physical properties of food materials containing mainly proteins.