Preparation of zein—soy protein isolate composites by pH cycling and their nutritional and digestion properties

Composite proteins with designable nutritional and functional properties are attracting great attention in the food industry. In this study, novel protein composites were fabricated by co-dissolving zein and soy protein isolate (SPI) at pH 12. Different ratios of soy protein isolate vs. zein (S/Z) were showed different characteristics. The supernatant with composite protein S/Z = 1 was indicated a better solubility, a balanced amino acid ratio, and a better digestibility (98.74%); the composite protein S/Z = 0.01 was exhibited higher free radical scavenging ability (>90%,5 mg/mL) and lower trypsin inhibitory activity after gastrointestinal (GI) digestion. This study raise the level of Lys which was limited in the zein. Moreover the level of those that were limited in the SPI such as Met and Cys. In summary, our results demonstrated that the techniques of processing protein ingredients were advanced toward on-demand nutritional properties.