Effects of Combined Treatments of Bacteria and Enzyme on the Degradation and Flavor Components of Body Wall of Sea Cucumber

Objective: To investigate the effects of different combined treatments of bacteria and enzyme on the degradation and flavor components of body wall of sea cucumber. Methods: Different treatment methods: Single bacteria (J), single enzyme (M), bacteria before enzyme (JM), bacteria after enzyme (MJ), and bacteria with enzyme (T) (The bacterium was Bacillus amyloliticus and the enzyme was compound protease) were used to degrade the body wall of sea cucumber. Physical and chemical indexes such as amino acid composition and relative molecular mass distribution of polypeptides in the degradation solution were determined. Gas chromatography-ion mobility spectrometry (GC-IMS) and electronic tongue were used to determine the volatile and non-volatile flavor components of the degradation products of body wall of sea cucumber under different treatments. Results: After combined treatments of bacteria and enzyme (JM, MJ, T), compared with single action, the content of relative molecular mass of peptides larger than 1000 Da was decreased by 60.29%, while those smaller than 500 Da was increased by 33.36%. The content of total free amino acid and nucleotide of combined treatments were increased by 1.3 and 4.1 times, respectively, compared with that of bacterial enzyme alone. The volatile compounds in the degradation solution increased from 43 without treatment to 67 after combined treatments, indicating that the flavor components of body wall of sea cucumber became more complex after combined treatment. Combined treatment could reduce the content of small molecular aldehydes, unsaturated aldehydes and other fishy ingredients, increase the content of esters and other pleasant ingredients. Among them, the treatment group with the highest polypeptide content was M (34.770 mg/g), followed by JM (30.733 mg/g), and the sensory score was highest in JM (66.67), followed by J (63.75). In the proportion of the sum of umami and sweet amino acids to the total amino acids, J was the highest, followed by JM and M, and T was the lowest. In the combined treatments of bacterial and enzyme, the relative contents of propionic acid with sour odor and 2-methylpropionic aldehyde with pungent odor were lower, and the relative contents of 2-pentanone with ketone flavor and laurene with aromatic flavor were higher in the JM treatment group. According to the results of each index, the flavor of JM degradation solution was better. Conclusion: The combined treatments of bacteria and enzyme (JM, MJ, T) can remove the fishy taste of the degradation products of sea cucumber, and improve the aromatic flavor at the same time. JM has the highest evaluation of degradation. As a technology to degrade the body wall of sea cucumber, polypeptide degradation products with good flavor can be obtained.