Study on the Biological Characteristics and the Activities of Main Efficacy Enzymes in the Fermentation Process of Loquat Ferments

In order to explore the biological characteristics and the change rule of the activities of main efficacy enzymes in the fermentation process of loquat ferments, loquat was used as the raw material, and the changes of the metabolites such as the number of effective viable bacteria, total acid, pH value, organic acid, total phenol, amino acid and the main efficacy enzymes during the fermentation process were analyzed. The results showed that: in the fermentation process, the number of effective viable bacteria increased rapidly within 1-5 days, reaching the level of 10⁹, and remained above 10⁸ orders of magnitude within 20-140 days, effectively maintaining a stable microbial ecological environment. The pH value decreased first and then remained stable at about 3.5, while the total acid content increased to 6.26 g·L^-1 and then tended to be stable. The total phenol content showed an increasing trend from 1 to 65 days and decreased slowly from 65 to 140 days. The loquat ferments contained 17 kinds of amino acids, and the amino acids with higher content were mainly the aspartic acid, glutamic acid, alanine, cystine, methionine and isoleucine. With the increase of fermentation time, the content of each amino acid fluctuated at different stages, and the content of total amino acid and essential amino acid increased gradually. The change rule of the activities of different efficacy enzymes in the ferments was more complex. The protease activity showed a gradual increasing trend from 1 to 35 days, with the highest enzyme activity of 15.14 U·mL^-1. It showed a slow decreasing trend from 35 to 65 days after the fermentation, and the acid protease activity tended to be stable from 65 to 140 days. The activity of SOD enzyme showed an increasing trend in the stage of 1 to 65 days, with the highest enzyme activity of 42.0 U·mL^-1, and showed a slow decreasing trend from 65 to 140 days after the fermentation. The β-glucanase activity showed an increasing trend from 1 to 20 days, with the highest enzyme activity of 4.52 U·mL^-1, and it tended to be stable from 20 to 140 days after the fermentation. The lipase activity was low, and showed an increasing trend from 1 to 5 days, and reached the maximum value of 0.12 U·mL^-1 on the 5th day. The lipase activity gradually decreased with the prolongation of fermentation time. The above research results could provide certain basis for the medium-test preparation and quality optimization of loquat ferments, as well as the construction of their comprehensive evaluation system.