The effect of milling and pressing soybeans at high temperatures (50–90C) was examined for laboratory‐scale soymilk preparation. Soymilk that was milled and pressed at high temperatures showed more precipitate and a slightly lower protein content. The surface sulfhydryl content and surface hydrophobicity of the soymilk protein increased with milling temperature, which indicates some acceleration of the thermal denaturation of proteins. Ultracentrifugation and laser diffraction particle size analysis of the soymilk showed that milling at 90C resulted in highly dispersed protein aggregates and emulsions.
Practical Applications
Processing method for soymilk was improved to decrease beany flavor derived from lipoxygenase. Now soybean is milled at high temperatures to inactivate lipoxygenase activity, but there are no useful data on the quality of the resulting soymilk. In this study, milling at 90C showed more disperse soymilk than at 80C by considering droplet size distribution and protein denaturation behavior. These data are useful for estimation of the quality of soymilk beverage and for improvement of soymilk processing for more palatable beverages.
Soymilk-like white opaque liquid was prepared from whole soybean seeds without imbibition by the nama-shibori method. The solid content of the resulting liquid (non-imbibed soymilk) increased with an increase in blender revolutions and milling time, becoming almost equivalent to that of standard soymilk (imbibed soymilk) after milling at 12,000 rpm or more for 8 min. The precipitate obtained from the nonimbibed soymilk was lower than that from imbibed soymilk after milling for 4 min; however, it was higher after milling for 8 min. The non-imbibed soymilk showed bimodal particle size distribution, differing from imbibed soymilk prepared by milling at 12,000 rpm or less, which showed a unimodal distribution. The findings suggest that non-imbibed soymilk is of slightly lower quality than imbibed soymilk prepared from imbibed soybean seeds, but overall the differences were considered minimal.
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