An effective scalable method to prepare whey protein isolate-galactooligosaccharide conjugates and application in...

Whey protein isolate (WPI) glycation via Maillard reaction has gained increasing interest as the conjugation can significantly improve WPI characteristics such as heat, pH and ionic strength stability. In this study, a novel method was developed via wet heating combined with molecular crowding effect and water activity adjustment, to provide a potential approach to produce whey protein isolate-galactooligosaccharide (WPI-GOS) conjugates with high grafting degree (DG, 67.11%) and low browning at industrial scale. Effects of parameters including temperature, pH, heating time, protein and carbohydrate concentrations, and water activity were investigated to determine the optimal reaction conditions. The obtained WPI-GOS conjugates exhibited good stability at wide ranges of pH (2-7), temperature (up to 88 °C), and ionic strength (0-200 mM NaCl). It also showed excellent encapsulation efficiency (EE, 88.84%), loading capacity (LC, 25.38%), and in vitro protection effect of epigallocatechin-3-gallate (EGCG). This novel development opens up promising opportunities to produce other protein-carbohydrate conjugates via wet heating, and provides a new approach for industry to fabricate delivery systems for bioactive compounds.