Investigation of protein structure and quality of Acipenser sinensis frozen by liquid nitrogen

Background: The quality of Acipenser sinensis deteriorates significantly during frozen storage due to its high water, protein, and unsaturated fatty acid content. Conventional freezing methods are insufficient to preserve it effectively. This study investigated the effects of liquid nitrogen freezing (LNF) on the quality and myofibrillar protein (MP) characteristics of A. sinensis during frozen storage. Results: Freezing A. sinensis with LNF resulted in faster freezing, lower free water content, smaller ice crystals, and less structural damage to MPs than refrigerator freezing (RF). It also resulted in higher shear force, Ca²⁺-ATPase activity, and total sulfhydryl content, as well as lower total volatile basic nitrogen (TVBN) values, thawing loss rate, and disulfide bond content, demonstrating that LNF can inhibit protein denaturation and delay the deterioration in the quality of A. sinensis during frozen storage. There were no significant differences between LNF-80 and LNF-110 in quality and myofibrillar protein characteristics of A. sinensis. Conclusions: Liquid nitrogen freezing can maintain the quality of A. sinensis and reduce the degree of MP denaturation and oxidation during frozen storage. Freezing with LNF at −80 °C might be more appropriate for A. sinensis. The study has important implications for the application of cryogenic storage technology to aquatic products.