Structure, rheology and functionality of whey protein emulsion gels: Effects of double cross-linking with transglutaminase and calcium ions

This article focused on the formation, physicochemical properties, and functionality of whey protein isolate (WPI) emulsion gels induced by crosslinking with transglutaminase and/or Ca2+ ions. The emulsion gels were fabricated using the combination of high-energy homogenization and cold-gelation. The microstructure, rheology and processing characteristics of the emulsion gels were then evaluated. Cross-linking with transglutaminase led to the formation of emulsion gels containing small particle aggregates, whereas cross-linking with Ca2+ led to the formation of larger particle aggregates. As expected, the apparent viscosity, strength, water holding capacity and hardness of the emulsion gels increased after crosslinking, especially when transglutaminase and Ca2+ ions were added together. Moreover, WPI hydrogels had higher gel strength in the presence of oil droplets than in their absence, suggesting that the droplets reinforced the gel structure. FTIR confirmed that the crosslinking agents promoted the aggregation of the proteins, thus forming an emulsion gel network. The results of this study may facilitate the design of new food materials with novel or improved textural and sensory characteristics.