Enhancing the gel properties of whey protein isolate via konjac mannan-crosslinking and their application in non-fat yogurt

The effect of different concentrations of konjac mannan (KGM) on the gel properties and structure of whey protein isolated (WPI) was investigated, and the application of KGM-crosslinked WPI in non-fat yoghurt. Among these concentrations, KGM concentrations lower than 0.2% changed the tertiary structure of WPI, exposed hydrophobic groups, improved the thermal aggregation behavior and gel properties. Meanwhile, it significantly increased the gel strength, texture properties and water holding capacity of heat-induced WPI gels. SEM results showed that KGM-crosslinking promoted the formation of a dense and cohesive three-dimensional gel network for WPI. During thermally induced gelation, KGM improves the gelation properties of WPI by swelling through water absorption and filling in between the WPI gel network. At KGM concentrations of 2.5 and 3 mg/mL could lead to higher viscosity, hindered interactions between hydrophobic groups during heating process, impeded aggregation of WPI, thus damaging the structural integrity of the gel network. In addition, the water holding capacity, rheological properties and sensory evaluation of non-fat yoghurt supplemented with KGM-crosslinked WPI were superior to those of pure non-fat yoghurt and pure full-fat yoghurt. This result can provide a guideline for the application of KGM-crosslinked WPI as a gelling agent in non-fat yoghurt products. • Addition of konjac mannan changed the tertiary structure of whey protein isolate. • 0.2% konjac mannan improved whey protein isolate gel properties. • Modified whey protein isolate improved texture and mouthfeel of non-fat yoghurt.