Preparation of microwave-phosphorylated soy protein isolates through a Box–Behnken model optimization

Abstract

Microwave phosphorylation was applied to modify soy protein isolates (SPI) to improve their emulsifying properties. A Box–Behnken model was obtained to optimize preparation conditions by response surface methodology. The four factors investigated were SPI content, sodium tripolyphosphate (STP) addition, microwave power, and reaction time with the emulsifying activity index (EAI) of the modified product as evaluation index. The optimized conditions were found to be SPI content of 71 g/L, STP addition of 115 g/kg, microwave power of 480 W, and reaction time of 3 min. Under these conditions, the EAI and emulsifying stability index (ESI) of the modified SPI were 0.878 and 33.9 min, respectively. Compared to the original SPI, the EAI and ESI of the modified SPI increased about 113.1% and 26.6%, respectively. Modification of SPI with STP under microwave irradiation might be a potential way to increase the emulsifying properties of SPI.