Deciphering the thermal regulation of myofibrillar protein-capsaicin hydrogels: From temperature-dependent gelation behavior to potential CAP-protein interactions.

Ramped heating from 50 °C to 90 °C was applied to elucidate how temperature regulates the gelation behavior and hydrogel properties of myofibrillar proteins-capsaicin (MPs-CAP) blends. The hydrogels were characterized in terms of macroscopic properties, water status, microstructure, intermolecular forces, and rheological behavior. The results showed non-monotonic trends in whiteness, hardness, springiness, and water-holding capacity, with an initial increase followed by a decrease as temperature rose, and optimal performance was observed at 70 °C. At 50-70 °C, heating unfolded MPs and facilitated the integration of CAP through hydrophobic interactions, which likely reinforced the network structure. CAP appeared to participate in network formation; this association, in combination with hydrogen bonding, created a dense and uniform three-dimensional network. This network converted free water into immobilized water via capillary effects, endowing the hydrogels with favorable water-holding capacity and thermal stability (Tp = 138.33 °C). Above 70 °C, excessive and disordered aggregation of MPs, along with increased release of CAP, was accompanied by pore enlargement, implying possible dissociation of CAP from the network. These results reveal the non-monotonic temperature-dependent behavior of MPs-CAP gelation, providing a theoretical basis for precise thermal processing of protein gels containing hydrophobic bioactive ingredients.