Modifications of Soy Protein Isolates Using Ultrasound Treatment for Improved Emulsifying Properties

Soy protein isolates (SPI) were modified by ultrasound treatment (200W, 400W, 600W), and the emulsifying properties of USPI (ultrasound treated SPI) were investigated. Analysis of mean droplet sizes and creaming indices of emulsions (20% v/v oil, 1.6% w/v emulsifier) formed by control SPI and USPI-200−600W showed that ultrasound treatment could improve the emulsifying capability and emulsion stabilizing ability (against creaming) of SPI. And the improvements were significantly influenced by the power level of ultrasound. Some USPI (e.g., 400W) was capable of producing stable fine emulsions. A variety of physicochemical and interfacial properties of USPI in relation to emulsifying properties have been investigated. The results showed that compared with control SPI, USPI-400W had a higher protein adsorption fraction (F ads ) and a lower saturation surface load (Г sat ), which was mainly due to its higher PS and surface hydrophobicity (H 0 ), and may explain its markedly improved emulsifying capability. This study showed that ultrasound treatment could be an effective way for the functionality modification of globular proteins.