The Effect of Mercaptoethanol on the Interface Properties of Heat-Induced Aggregation of Soy Protein Isolate

In order to investigate the effect of β-mercaptoethanol on the interface properties of soy protein isolate(SPI), the samples (10 mg/mL) were prepared by heating with or without β-mercaptoethanol (2 mmol/L) at pH7.0 and 90 ℃ for 0 and 10 h. The micromorphology and free sulfhydryl group of the samples were observed. Meanwhile, the foaming ability, foam stability, emulsifying activity, emulsifying stability, surface hydrophobicity and turbidity were evaluated. The results showed that irregular aggregations were formed from SPI and SPI with β-mercaptoethanol. The regular spherical particles were formed from SPI by heating, while both regular spherical particles and irregular aggregations were formed from SPI with β-mercaptoethanol by heating. The interface properties of SPI were improved by adding β-mercaptoethanol. Compared with those of SPI, the foaming abilities of SPI with β-mercaptoethanol and the aggregations formed from SPI with β-mercaptoethanol increased by 64.56% and 95.77%, respectively. Moreover, their emulsifying activities increased by 12.94% and 14.61%, respectively. Good emulsifying stability and foam stability of SPI with β-mercaptoethanol and the aggregations formed from SPI with β-mercaptoethanol were found during long time storage. The reason for the good interfacial property was that the higher free sulfhydryl content and surface hydrophobicity of SPI and its aggregations were obtained by the addition of β-mercaptoethanol. The empirical models of Rational function and Linear function of foam stability and emulsion stability for the 4 samples with time were established, which laid a theoretical foundation for the practical application of SPI.