Mizuhopecten yessoensis is a nutritious, low-fat, high-value shellfish that contains a lot of protein, mainly myofibrillar protein (MP). Alginate oligosaccharides are low-molecular-mas, highly water-soluble marine oligosaccharides, which have immunoregulatory, antioxidant, hypoglycemic and lipid-lowering properties. This study aimed to investigate the effects of an enzymatic hydrolysate of alginate oligosaccharides at a concentration of 0.45 g/100 mL on the in vitro digestion characteristics, structure and physicochemical properties (intrinsic fluorescence spectrum, UV absorption spectrum, reactive sulfhydryl content, and surface hydrophobicity) of scallop myofibrillar protein. The results showed that the hydrolysate significantly affected the digestion characteristics of MP. During gastric digestion, the addition of the hydrolysate delayed the exposure of hydrogen bonds in MP, enhanced the surface hydrophobicity and maintained the structure of the protein. With increasing digestion time, the fluorescence intensity and reactive sulfhydryl content of MP gradually decrease.

In this study, myofibrillar proteins (MP) from silver carp (Hypophthalmichthys molitrix) were modified by addition of 0, 2, 4 g/100 mL of Patinopecten yessoensis mantle polypeptides (PMP). By measuring the sulfhydryl contents, carbonyl contents, Fourier transform infrared (FTIR) spectra, ultraviolet (UV) absorption spectra and endogenous fluorescence spectra of MP and PMP-MP, we evaluated the effect of PMP on the structure of MP. The results showed that the total sulfhydryl, active sulfhydryl and carbonyl contents of MP decreased with increasing PMP concentration; there was no significant difference in the α-helix content of MP after modification, but the β-sheet content decreased and the β-turn content increased with increasing PMP concentration. The addition of PMP was beneficial to maintain the stability of MP structure. PMP also effectively delayed the carbonylation of MP. PMP can be considered as a potential natural antioxidant, cryoprotective agent and gel texture enhancer.

In this study, 2 mT low magnetic field (LMF), 0 mT magnetic field (NMF), and conventional freezing (CF) were used to conduct a 28-day freezing experiment on myofibrillar proteins of silver carp muscle. Changes in the structure and functional properties of the proteins were investigated by measuring surface hydrophobicity, sulfhydryl content, solubility, turbidity, thermal stability, Fourier transform infrared (FTIR) spectra, endogenous fluorescence spectra, and ultraviolet (UV) absorption spectra. The results showed that the application of LMF freezing could inhibit protein aggregation, exposure of interior hydrophobic groups, and α-helix unfolding, weaken α-helix to β-sheet transition and maintain good secondary and tertiary structure stability. There was no significant difference in total sulfhydryl content, solubility, or turbidity between the CF and NMF groups. As it provided lower freezing temperatures, CF inhibited the aggregation of proteins and the exposure of interior hydrophobic groups, but simultaneously made the protein structure sparse and unstable. Compared with CF, LMF freezing could better protect and improve protein structure and function. Overall, LMF freezing can inhibit protein denaturation and maintain good protein structure and function. Compared with CF (-30 ℃), LMF freezing (-20 ℃, 2 mT) has the potential for energy saving.