Effects of different times of low temperature anhydrous preservation on survival, nutritional composition, enzyme activities and antioxidant indexes of Cipangopaludina chinensis

Cipangopaludina chinensis is an economically important aquatic snail with high medicinal value in China. To improve the technology of preserving C. chinensis and to promote the sustainable development of the snails rice noodle industry, in this study, 1,500 healthy C. chinensis with an initial body mass of (21.71±2.70) g were used to investigate the effects of survival, morphological indices, nutritional composition, fatty acids, digestive enzyme activity and antioxidant indices of storing snails for 0, 14, 28, 42 and 56 d under 4 °C anhydrous conditions. The results showed that the survival rate of snails stored at 4 °C for a short period of time (14-28 d) exceeded 93%, but after 42 days, the value fell below 78%. The liver weight and liver/body ratio of 28 and 42 d of hypothermia were significantly higher than those of the control . Compared with the control, body mass decreased by 7.6% at 56 d of hypothermia, while liver weight was markedly increased. The results of nutritional composition examination showed no difference in crude protein, crude ash and moisture of muscle between the groups, and the crude fat content showed an increasing trend, with 28, 42 and 56 d being considerably higher than the control. The glycogen content showed an overall upward trend, among which the difference between 14 and 56 d was significant. Fatty acid detection revealed that the contents of SFA and MUFA showed an overall downward trend, with 28-56 d dramatically lower than those of the control and 14 d. The PUFA contents at 28 and 42 d were notably higher than the other treatments. All digestive and antioxidant enzyme activities in this study showed an overall decreasing trend. The amylase activity of the control was significantly lower than that in 14 d, but remarkably higher than that in 42 d. Then, except for the 42 d trypsin, the lipase and trypsin content of the other treatments was substantially less than that of the control. The glutathione catalase of the 42 d group was significantly lower than that of the other groups, and the activities of superoxide dismutase, catalase and malondialdehyde at 42 d were dramatically lower than those of the control. In summary, it is shown that anhydrous preservation for more than 42 days at 4 °C will lead to a higher mortality rate of C. chinensis. After 42 d, the digestive enzyme and antioxidant enzyme activities in the body are reduced, and the internal environmental balance is disrupted, which in turn led to high mortality. During the stress period, C. chinensis mainly use protein as an energy source, and then a large amount of saturated fatty acids and monounsaturated fatty acids are consumed as energy materials, while polyunsaturated fatty acids are better retained. This study provides a scientific basis for understanding the physiological and biochemical adaptation countermeasures of snails under different times of low-temperature anhydrous preservation and improving their storage and transportation management.