Chitosan oligosaccharides exerted a concentration-dependent effect for inhibiting transglutaminase-induced cross-linking of whey protein isolate and enhancing its interfacial properties and bioactivities.

In-depth research has been conducted on the modification of proteins using COS with TG as a catalyst. However, the effect of different COS concentrations on TG-catalyzed COS-WPI has not been elucidated. This study investigated the effects of varying COS concentrations (0-50 mg/mL) on the reaction properties, interfacial characteristics, and biological activities of TG-catalyzed WPI. SDS-PAGE analysis revealed that increasing COS concentration remarkably inhibited formation of the macromolecular aggregates at 180 kDa in the TG-catalyzed WPI. Compared with WPI, as the COS concentration increased from 0 to 50 mg/mL, the α-glucosidase inhibitory activity, xanthine oxidase inhibitory activity, DPPH free radical scavenging capacity of TG-catalyzed COS-WPI were gradually enhanced (P < 0.05). Principal component analysis and heat maps showed that at 50 mg/mL COS, the TG-catalyzed WPI exhibited the optimal biological activities, at 30 mg/mL COS exhibited the optimal interfacial properties. This work first discovered that COS concentration was negatively related with TG-crosslinked WPI aggregates. Additionally, combination of COS and TG would be effective approach to provide protein-based ingredients with high bioactivity and interfacial properties for the food industry.