Metabolic syndrome (MetS) is a global health problem, and EPA/DHA-enriched phospholipids (EPA/DHA-PLs) have been found to have positive effects on MetS improvement. Currently, research on EPA/DHA-PL mainly focuses on special and rare seafood, such as phospholipids derived from krill, sea cucumber, squid, and fish roe. However, it has been recently demonstrated that abundant EPA/DHA-PL can also be found in bulk fish and its by-products. Nonetheless, there is still limited research on the biological activities of EPA/DHA-PL derived from these sources. The aim of this study was to investigate the effect of phospholipid extracts from the heads of salmon and silver carp (S-PLE and SC-PLE) on the high-fat-diet-induced MetS in C57/BL mice. After an 8-week intervention, both SC-PLE and S-PLE had a significant ameliorating effect on MetS. Moreover, SC-PLE was more effective than S-PLE in reducing liver inflammation and fasting glucose. Both of the PL extracts were able to regulate the expression of key genes in lipid synthesis, fatty acid β-oxidation, and insulin signaling pathways. Compared with S-PLE, dietary SC-PLE had a greater influence on liver metabolomics. Pathway enrichment analysis showed that the differential metabolites of SC-PLE were mainly involved in arachidonic acid metabolism and glutathione metabolism. The results indicated that the different metabolic regulation methods of S-PLE and SC-PLE could be related to their variant molecular composition in EPA/DHA-PL.

Freezing has been widely used to preserve the freshness and quality of crayfish (Procambarus clarkii). However, temperature fluctuations during transportation and storage inevitably affect the quality attributes of crayfish. In this study, the effect of liquid nitrogen freezing (LNF) on crayfish myofibrillar protein (MP) was investigated under freeze–thaw (FT) cycles. The small ice crystals formed by LNF could reduce the conversion of sulfhydryl groups to disulfide bonds, preventing the exposure of hydrophobic groups, thereby maintaining the functional properties of MP. LNF could prevent the degradation and oxidation of MP and maintain its compact and smooth microstructure. Compared to refrigerator freezing (RF), LNF showed a stronger protective effect on the secondary and tertiary structures of MP, alleviating their conformational changes. Therefore, LNF could be an alternative freezing method to preserve crayfish quality against FT cycles during transportation and storage.

Cryoprotectants are widely used to protect muscle tissue from ice crystal damage during the aquatic products freezing process, but traditional phosphate cryoprotectants may cause an imbalance in the calcium-to-phosphorus ratio for the human body. This study evaluated the effects of carrageenan oligosaccharides (CRGO) on quality deterioration and protein hydrolysis of crayfish (Procambarus clarkii) during superchilling. The physical-chemical analyses showed that CRGO treatments could significantly (p < 0.05) inhibit the increase of pH values, TVB-N, total viable counts, and thawing loss, and improve the water holding capacity and the proportion of immobilized water, which indicated that CRGO treatment effectively delayed the quality deterioration of crayfish. The myofibrillar protein structural results demonstrated that the increase of the disulfide bond, carbonyl content, S₀-ANS, and the decrease of total sulfhydryl content were suppressed significantly (p < 0.05) in CRGO treatment groups. Furthermore, SDS-PAGE results showed that the band intensity of myosin heavy chain and actin in CRGO treatment groups were stronger than in the control. Overall, the application of CRGO to crayfish might maintain better quality and stable protein structure during the superchilling process, and CRGO has the potential to replace phosphate as a novel cryoprotectant for aquatic products.

The traditional pulverizing technologies face limitations such as nutrient loss, risk of dust explosions and poor properties of powder. Liquid nitrogen freezing and pulverizing (LNFP) is an innovative technology combining low-temperature freezing and pulverizing, which can maintain high nutritional value and performance of food powders. This paper primarily reviews the basic principles of LNFP, the advantages compared to traditional pulverizing technologies (e.g., high-speed airflow pulverizing and ball pulverizing), relevant equipment, applications in animal-derived products, the improvement and innovation direction, and the combination with other food processing techniques. Although LNFP has potential in food processing, it still faces challenges such as food form, thawing loss and enzyme changes. In addition, the cost is also an issue. In the future, combining auxiliary methods with LNFP technology may improve product quality and processing outcomes of animal-derived products.