Effects of sequential enzymatic hydrolysis and transglutaminase crosslinking on functional, rheological, and structural properties of whey protein isolate

Abstract

This work investigated the effect of transglutaminase (TGase) crosslinking condition on the functional, rheological, and structural properties of hydrolyzed whey protein isolate (WPI) at three hydrolysis degrees (DHs) (7.61%, 9.22%, 18.55%). Between three DHs crosslinking, it was found that low DH coexistent with higher fluorescence intensity, sulfhydryl content and emulsifying activity, and moderate DH had higher thermal stability and viscosity. In crosslinking process, increasing the temperature had significant effect on solubility, emulsification, and viscosity of TGase-induced hydrolysate with moderate DH (p < 0.05), while the sulfhydryl contents decreased to various degrees. And the best reaction temperatures of hydrolysate with moderate DH were identified for thermal stability (50 °C/30 °C), solubility (30 °C), emulsifying activity/emulsifying stability (EAI/ESI) (50 °C/40 °C) and viscosity (40 °C), respectively. With increasing TGase concentrations, hydrolysate with moderate DH had best thermal stability at 30 U/g, while the highest EAI and the lowest ESI was at 40 U/g. The process conditions adopted enzymatic hydrolysis coupled with TGase-induced crosslinking could significantly influence the protein conformation, consequently determining their specific functional properties. The understanding of hydrolysis and crosslinking effects on properties could assist in selecting the appropriate method to optimize the utilization of WPI in the food industry.