Underlying the mechanisms of incorporation of κ-carrageenan on the formation of low-salt myofibrillar protein gels during heating process: Perspective on the dynamic changes of protein structures and molecular interactions

This study aimed to systematacially investigate the effects of kappa-carrageenan (KC) concentration on the formation of myofibrillar protein (MP) gels under low-salt condition based on the dynamic changes of protein structures and molecular interactions during heating process. The results indicated that incorporating KC markedly improved the water holding capacity (WHC) and gel strength of MP gels (P < 0.05). Those properties were most improved by adding 0.4% KC with WHC of 71.44% and gel strength of 1.62 N. During the heating process, when the temperature was above 50 degrees C, KC addition significantly increased the turbidity and particle size and decreased solubility of MP in a concentration-dependent manner, as well as exhibiting higher surface hydrophobicity at 0.2% KC concentration (P < 0.05), indicating that KC accelerated the rate of aggregation of MP during heating process. The dynamic rheological behaviors indicated that the addition of KC promoted the early unfolding and aggregation of MP at a relatively lower temperature, which was verified by the fluorescence denaturation mechanism results. Moreover, the addition of KC significantly promoted the heat-induced conformational transition of MP from alpha-helix companied with beta-sheet and beta-turn, which was due to the interaction between MP and KC accelerating the formation of MP gels during the heating process. Intermolecular forces results revealed that the aggregation of myosin head and cross-linking of myosin tail of MP added KC was enhanced by ionic bonds, hydrophobic interactions, and disulfide bonds, which facilitated the better gel performance. Our present results provided a comprehensive understanding of gelation mechanism of MP-KC mixed gels under low-salt condition, with implications for the practical application of KC in meat processing.