Jiwang Chen

Crayfish processing by-products are rich in astaxanthin, exhibiting considerable potential for value-added utilization. This study evaluated the efficiency of different solvents in extracting astaxanthin from crayfish cephalothorax using high-performance liquid chromatography (HPLC) based on geometric isomer composition. The Folch extraction system, with lower polarity, extracted astaxanthin more effectively than the Bligh-Dyer method. Freeze-drying significantly improved the recovery of total lipids and astaxanthin, whereas oven-drying led to partial degradation. Among single organic solvents, acetone achieved the highest extraction efficiency for freeze-dried samples, yielding 337.55 μg/g (dry basis), with isomer distribution of 57.52% all-trans, 8.83% 9-cis, and 33.65% 13-cis. The distribution of astaxanthin varied notably with solvent polarity, predominantly appearing in the neutral elution fraction in esterified and all-trans forms. These results highlight the critical influence of solvent choice and drying method on astaxanthin recovery and provide readily scalable process parameters for the industrial extraction and isomer-specific quality control of this bioactive compound from crayfish processing by-products.

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.

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.

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. © 2025 Society of Chemical Industry.

The quality of frozen crayfish (Procambarus clarkii) is challenged by freeze–thaw (FT) cycles during storage. The effect of freezing methods on the quality of crayfish during FT cycles was investigated by comparing physicochemical properties, microstructure, and myofibrillar protein (MPs) properties. Three methods were used for crayfish freezing, including air convective freezing (AF) at −20 °C and −50 °C, as well as liquid nitrogen freezing (LNF) at −80 °C. The frozen crayfish were thawed at 4 °C after 45 d of frozen storage as 1 FT cycle. After 5 FT cycles, the water holding capacity of LNF crayfish (70.8%) was significantly (p < 0.05) higher than that of −20 °C AF crayfish (60.6%) and −50 °C AF crayfish (63.5%). The drip loss of LNF crayfish (7.83%) was significantly lower than that of AF crayfish. Moreover, LNF maintained the gel strength and the thermal stability of MPs from crayfish with higher gel storage modulus and enthalpy. These results demonstrated that LNF minimized the formation of large ice crystals, preserving the structural integrity of muscle and the properties of MPs, thereby maintaining crayfish quality. This study investigated the effect of LNF in preserving crayfish quality during FT cycles, providing valuable insights for reducing the quality degradation of aquatic products during storage and transportation.