Abstract: This study was done with the objective to analyze the surface hydrophobicity, amino acid composition, zeta potential and particle size distribution of soybean protein isolates (SPIs) prepared from different soybean varieties and to explore the relationship between surface hydrophobicity and zeta potential as well as particle size distribution of SPI. The surface hydrophobicity of SPIs from different varieties was in the decreasing order: Dongnong 46 > Wandou 24 > Heinong 46 > Wuxing 4 > Zhonghuang 13 > Ji NF 58. The different varieties had a significant effect on the zeta potential and particle size distribution of SPI. Correlation analysis indicated no significant correlation between surface hydrophobicity and amino acid composition. Surface hydrophobicity was positively correlated with absolute value of zeta potential and negatively correlated with particle size. With increasing absolute value of zeta potential, the aggregation of protein molecules was decreased due to repulsive interaction of more like electric charges on their surface, making the protein solution more stable and at the same time reducing the size of the protein particles. As a result, more hydrophobic groups were exposed on the surface of the proteins due to decreased involution degree of hydrophobic groups, thereby leading to an increase in surface hydrophobicity.

Key words: soybean protein isolate, zeta potential, particle size distribution, surface hydrophobicity