Effect of fermentation temperature on the activity of key enzymes for pectin degradation in apricot wine

The high pectin content in the raw materials of Saimaiti apricot wine can easily lead to excessive methanol, which restricts the safety of the product. The study regulated the fermentation temperature and measured the activities of the key pectin-degrading enzymes, including pectin methyle- sterase (PME), polygalacturonase (PG), and pectin lyase (PL), as well as the methanol production every other day, the effect of temperature on enzyme activity and the correlation between enzyme activity and methanol production were analyzed. The results showed that temperature had a significant positive regulatory effect on the activities of the three enzymes. As the fermentation temperature increased, the enzyme activities also increased. As the fermentation time prolonged, the pectinase activity gradually declined, and the methanol content gradually decreased. The activities of PME and PG were significantly positively correlated with the methanol content (P<0.05). After 11 d of fermentation at 18 ℃, the final enzyme activities of PME, PG, and PL in the apricot wine were 120 U/g, 350.59 U/g, and 42.94 U/g, respectively, and the methanol production was only 191.83 mg/L, significantly lower than that of other groups (P<0.05). The alcohol content was 7.88%vol, and the CO₂ release was 1.90 g/100 ml, second only to the 30 ℃ treatment group. The physicochemical indicators of the apricot wines in all groups met the national standards for wine. Among them, the Saimaiti apricot wine fermented at 18 ℃ had a relatively high malic acid content (4.26 mg/ml), the lowest lactic acid content (0.81 mg/ml), and a soluble solid content of 5.7 °Bx. Therefore, fermentation temperature of 18 ℃ for apricot wine was beneficial for reducing the formation of methanol during the fermentation process and improving the quality of the fruit wine.