Ascorbic acid alleviates the autolysis of the sea cucumber Apostichopus japonicus via the activation of antioxidant enzymes to remove reactive oxygen species during live storage

The autolysis during live sea cucumber transportation is the main concern for the industry. This study aims to determine the effectiveness of ascorbic acid (AA) in reducing autolysis during the storage of live sea cucumbers. The live sea cucumbers were exposed for 5 days to seawater containing different concentrations of AA: 0, 5, 10, 15, 20, 25, 30, and 35 mg/L. Stored sea cucumber evaluation factors, including individual appearance, sensory score, histologic section, seawater ammonia nitrogen content, and free protein content, were tested. The reactive oxygen species (ROS) and malondialdehyde (MDA) accumulation, activity change of catalase (CAT), glutathione peroxidase (GSH-PX), and superoxide dismutase (SOD), and genes expression level change of succinate dehydrogenase (SDH), lactate dehydrogenase (LDH), SOD, and GSH-PX were compared after storage. The results showed that the AA addition of 25 mg/mL led to a good live sea cucumber condition. The sensory score for AA treatment reached 79.8% of the fresh group, and its stored seawater contained the lowest levels of ammonia nitrogen and soluble protein among all treatment groups. Although the villi in the 25 mg/L treatment group showed slight breakage, they maintained a relatively intact structure with clear cytoplasm and nuclei. The lowest ROS and MDA levels were observed in the intestine and respiratory tree of the 25 mg/L treatment group. The addition of 25 mg/L of AA maximized the activities of CAT, GSH-PX, and SOD. Moreover, the expression of SDH, LDH, SOD, and GSH-PX genes was upregulated 8.8-fold, 5.8-fold, 5.1-fold, and 16-fold compared with the fresh group, respectively. Live sea cucumbers can be transported with 25 mg/L AA treatment, which prevents autolysis-induced deterioration.