Characterization of Soymilk Prepared by Ohmic Heating and the Effects of Voltage Applied

Abstract

Soymilk was prepared by ohmic heating. Heating time decreased as the applied voltage was increased. Precipitation, viscosity and surface hydrophobicity of protein in the soymilk were increased with the decrease in voltage applied. Voltages of 50 and 100 V resulted in a higher heating rate and consequent formation of a larger amount of protein particles (soluble aggregates), ranging from 40 to 120 nm in size, than the other conditions. Furthermore, soymilk prepared by ohmic heating at 50 or 100 V was converted into firmer tofu curd than that at 30 V. Ohmic heating at 30 V was thought to form larger protein particles than that at 50 and 100 V, and the resultant larger sized aggregates are considered to result in inferior tofu curd texture.