Mechanisms and effects of different crosslinking degrees on gelling properties and in vitro digestibility of heat-induced microbial transglutaminase-mediated myofibrillar protein gels with or without κ-carrageenan

This study investigated the effects of different levels (0, 0.1, 0.3, and 0.5 %, w/w) of microbial transglutaminase (TG) on the gelling properties and in vitro digestibility of heat-induced myofibrillar protein (MP) gels with or without κ-carrageenan (KC, 0.2 %, w/w). The results indicate that the crosslinking degree of MP gels was gradually enhanced with increasing levels of TG alone (P < 0.05). However, regardless of TG level, KC incorporation effectively inhibited TG-induced crosslinking through the steric effect and subsequently promoted the water-holding capacity, gelling properties and rheological characteristics of the MP gels (P < 0.05), as well as led to the development of a more uniform and denser gel network structure. Moreover, compared with the MP gels with TG alone, KC addition increased the presence of hydrogen bonds, hydrophobic interactions, and disulphide bonds among the gels (P < 0.05). Additionally, the existence of KC significantly decreased the in vitro digestibility of TG-mediated MP gels mainly because TG-induced crosslinking promoted physical interaction between KC and MP. Therefore, the present study provides essential information regarding the influence of KC on the gelling properties and in vitro digestibility of heat-induced TG-mediated MP gels.