Effect of Two-step Heat Treatment Processes on the Formation of Protein Particles and Oil Droplets in Soymilk.

Unheated soymilk (raw soymilk), which was prepared in the laboratory, was heated sequentially at two different temperatures. The proportion of protein particles in the soymilk sample subjected to a low-tohigh two-step heating procedure (heating at 70 or 80 °C, then at 100 °C) was almost twice that of a high-tolow two-step heating procedure (heating at 100 °C, then at 70 or 80 °C). The size distribution of oil droplets in the soymilk for two-step heat treatment exhibited a polymodal distribution irrespective of the temperature combinations. However, the low-to-high two-step procedure resulted in an increase in the ratio of aggregated or coalesced oil droplets, in contrast to that for the high-to-low two-step procedure. When using the 7S (ß-conglycinin) and 11S (glycinin) fractions separately, each fraction showed increased aggregation after twostep heat treatment, but a 1:1 mixture of the two fractions did not. [ABSTRACT FROM AUTHOR]