Abstract:In this study, the effect of freeze-processing on the microscopic structure and physicochemical properties of soybean oil was evaluated. This study provided a reference for the application of soybean oil as raw material for functional food. Morphological changes in soybean oil particles within cotyledons of soybeans before and after freeze-processing were examined using a transmission electron microscope. Large-diameter oil body was found to be aggregated during freezing. Oil was extracted from soymilk by performing ultra-high-speed centrifugation. Oil body dispersion was visualized by light microscopy and measured by particle size distribution and SDS-PAGE. The results suggested that the smallest diameter of oil body was that of unprocessed oil (0.54 μm), most diameters of freeze-processed oil ranged from 2 to 4 μm, while the number of oil body with a diameter >4 μm increased with increasing freeze duration. Electrophoretic results showed that the amount of oleosin, with a molecular weight of 24 kDa, decreased after freeze-processing. The Zeta-potential and hydrophobicity of oil body at different pH values (pH 2~8) and NaCl concentrations (0~250 mM) were measured. The results indicated that freeze-processing could slightly decrease the isoelectric point (pI) and increase the hydrophobicity at the surface of the oil body.
