Aiming at the problems of great difficulty in live preservation, low survival rate and easy quality deterioration during the live transportation of Litopenaeus vannamei, we constructed an eco-critical temperature waterless live-preservation technology system based on precise oxygen regulation. We systematically investigated the regulatory mechanism of oxygenation coupled with low-temperature stress on shrimp survival and quality variation. Through single-factor experiments, we determined the optimal live-preservation parameters as follows: temperature 8 ℃, oxygen concentration 60%, and cooling rate 4 ℃·h⁻¹. Under these conditions, the 10 h survival rate of L. vannamei reached (90.2±5.0)%. We found that this technology can effectively activate the antioxidant enzyme systems (Such as POD and GSH-Px) in shrimp muscle, maintain stable activity of total superoxide dismutase (SOD), and significantly inhibit the accumulation of lipid oxidation products at the early stage of preservation. Flavor analysis reveals that the relative content of aldehyde fishy substances decreased from 22.66% to 14.82%, while the proportion of ketone compounds increased, thus optimizing the flavor profile. The technology significantly improved the texture properties of shrimp muscle; the tissue structure remained basically intact with only slight subcellular damage observed. Multidimensional correlation analysis demonstrates that texture stability was significantly positively correlated with antioxidant capacity, and negatively correlated with oxidation products and volatile aldehydes. This study clarifies the key role of oxygenation during waterless live preservation of shrimp, provides technical support for commercial live transportation and storage, and deepens the understanding of low-temperature stress mechanisms in crustaceans.

The study investigated the semi-hibernation and critical temperature of grass carp based on gradient cooling, and explore the effects of temperature (12-24 ℃) on the survival of grass carp and the concentration of ammonia nitrogen in the water. The temperature was reduced from room temperature (23-25 ℃) to the semi-dormant temperature (16 ℃) at cooling rate of 1, 3, or 5 ℃/h. The control group was reared at room temperature, and sampling was conducted after 0, 12, 24, 36, and 48 h. Serum biochemical and antioxidant parameters were measured to obtain the maximum cooling rate for grass crap. The results showed that the semi-dormant temperature of grass carp was 16 ℃, the critical temperature was 6-8 ℃, and the optimal cooling rate was 3 ℃/h. At 16 ℃, grass carp exhibited delayed stress response and decreased metabolism, and lower concentrations of ammonia nitrogen in the water. Except for aspartate aminotransferase level, the maximum values of other serum biochemical indexes at the cooling rate of 3 ℃/h, were significantly lower than those at 1 and 5 ℃/h (P < 0.05). The activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) exhibited a trend of initially increasing and then decreasing with survival time, whereas the content of malondialdehyde (MDA) showed an opposite trend, reaching a minimum value of 5.27 mmol/mg after 36 h. Compared to the control group, the contents of all biochemical and antioxidant indexes in the three cooling groups showed significant changes with survival time. Therefore, cooling grass carp at a rate of 3 ℃/h could reduce the stress response and allowed it to enter a semi-hibernation state at a more suitable time. The results from this study provide key parameters for the temporary cultivation and transport of grass carp, as well as useful guidelines for reducing the transport mortality.