Effects of microbial transglutaminase on the gelling property and in vitro digestibility of fish scale gelatin from grass carp

Fish scales are good sources of gelatin, but the wide application of fish scale gelatin (FSG) is highly restricted due to its poor gelling property. In this study, microbial transglutaminase (MTG) was utilized to improve the gelling property of FSG from grass carp. The effects of MTG on the gel strength, textural property, rheological property, triple-helix structure, chemical structure, thermal property, and microstructure of FSG were investigated. Then, the in vitro gastric and simulated intestinal digestibility of the cross-linked FSG were further studied. The cross-linking of FSG by MTG at all concentrations increased the gel strength, hardness, chewiness, peak temperature, and sol-gel transition temperatures. The MTG at a low concentration promoted the formation of an ordered triple-helix structure and a compact network in FSG, while the high-concentration MTG had an opposite effect. Besides, the cross-linking of FSG by MTG generally increased the digestion time of FSG and allowed the release of more unique peptides during gastric and intestinal digestion. Peptides with various bioactivities were released after the simulated intestinal digestion of the native and modified FSGs. This study may provide some guidance for the deep utilization of FSG in the food industry and further promote the exploitation of fish scales.