Abstract
Six kinds of soybean milk were prepared by extraction of soybean immersed in water for thirty minutes at 50, 60, 70, 85, 100 or 120°C, respectively. Control soybean milk was prepared without heating and the effect of heating on the physicochemical properties of protein in soybean milk was studied, comparing the results with those obtained by heating of skimmilk.
1. It was observed by use of electron microscope that protein particles of soybean milk tended to aggregate at lower heating temperature forming giant particles above 100°C, than those of skimmilk.
2. On higher heating temperature the increase of acid-soluble nitrogen compounds was observed both with soybean milk and skimmilk.
3. From the study on the effect of heating on centrifugal sedimentation (6, 590 X g) of nitrogen Compounds, it became clear that on heating between 50-100°C, 20-50% of total nitrogen of soybean milk was present in the sediment. Heating to 120°C caused a remarkable increased in the rate of total nitrogen sedimentation. Similar tendency was observed with skimmilk.
4. The rate of trichloroacetic acid-soluble nitrogen in acid-soluble nitrogen compounds was larger with soybean milk than with skimmilk.
5. The soluble and insoluble fractions in saturated magnesium sulfate solution were found to decrease in both soybean milk and skimmilk with higher heating temperature. With heating above 100°C, these fractions disappeared wholly.
