In vitro digestibility and IgE reactivity of enzymatically cross-linked heterologous protein polymers

Homologous and heterologous cross-linked polymers of whey protein isolate (WPI), soy protein isolate (SPI) and casein (CN) and their binary mixtures, viz., WPI+SPI, WPI+CN and SPI+CN, were produced using transglutaminase, and their in vitro IgE reactivity and digestibility under simulated gastro-intestinal conditions were studied. The results showed that the IgE reactivity of protein components in heterologous polymers was significantly lower than that in homologous polymers, suggesting that each protein component masked the IgE-reactive epitopes in the other protein component more effectively in heterologous polymers than in homologous polymers. In vitro digestion under simulated gastro-intestinal conditions revealed that both homologous and heterologous polymers were less digestible than untreated proteins, but the peptides released during the time course of digestion were less IgE-reactive. The results of this study indicate that hypoallergenic protein products could be produced by transglutaminase-mediated heterologous polymerization of protein mixtures.