Emulsification properties of fruit juice-hydrolyzed soy protein

Abstract

Previous research has demonstrated the effect of enzymatic hydrolysis on the emulsifying properties of soy protein isolate (SPI). The present authors previously reported on the preparation of stable emulsions by the addition of oil and vinegar to a commercial SPI hydrolysate. In this paper, emulsions prepared by the direct introduction of fruit juices from several tropical fruits to SPI were examined. The purpose of this research was to elucidate whether the production of stable emulsions such as those made with the proteolytic enzyme papain was possible by this method. Stable emulsions were obtained from papain and pineapple, kiwi, melon, fig, and unripe papaya fruit juices. The appearance of the emulsions, the SDS-PAGE patterns of hydrolyzed SPI, and the pseudo-plastic behavior of the emulsions varied depending on the type of fruit, fruit production area, fruit ripeness, the reactive conditions of the fruit juices, and SPI. A relationship between the decrease in 11S acid subunits and emulsion stability was suggested.