Heat-induced gelation of SAM myofibrillar proteins as affected by ionic strength, heating time and temperature: With emphasis on protein denaturation and conformational changes

There is a growing consumption of scallop adductor muscle (SAM) based food due to its great nutritional value and high digestibility. SAM gelation has a key effect on final products, however, the gelling properties of SAM, particularly the denaturation and conformational changes of proteins, are far less known. Thus, the present study aimed to improve our understanding on the gelation of SAM as affected by different heating temperatures, time, and ionic strength at low salt concentration ranges. Protein denaturation is the primary reason for the physicochemical changes of minced SAM during thermal gelling. Both gel strength and storage modulus showed positive correlations with heating temperature and time. However, the water holding capacity decreased gradually from 60 to 90 °C due to the shrinkage of myofibril proteins induced by protein denaturation, resulting in the transformation of immobilized water into free water, as proved by LF-NMR results. DSC and FTIR results indicated that heating at 90 °C led to complete degeneration of myosin and actin, and partial conversion of α-helices to β-sheets and random coil, resulting in a more rigid gel. It was further discovered that rapid heating (90 °C-10min) of low salt SAM at 1.5% NaCl concentration during gelation contributed to a superior gel strength and the reinforcement of fine-stranded three-dimension gel matrix as revealed by SEM. The investigation of heat-induced SAM provides a practical value for the processing of low-salt minced SAM products for the food industry.