Establishment of fermentation kinetic model and antioxidant activity of kiwifruit wine fermented by black tea fungus liquid

In this study, black tea fungus liquid kiwifruit wine was prepared by fermentation with kiwifruit with skin and black tea fungus liquid as raw materials. By exploring microbial growth, the consumption of matrix (reducing sugar) and the production trend of product (ethanol) in the fermentation process, the relevant kinetic equations were established, and its active ingredient and antioxidant activity were determined. The results showed that the correlation coefficients R² of Boltzmann model reflecting the changes of yeast growth and ethanol production and Logistic model reflecting reducing sugar consumption, were all more than 0.98, which could effectively reflect the dynamic characteristics of kiwifruit wine fermented with black tea fungus liquid. With the prolongation of fermentation time, the contents of total phenols and total flavonoids in kiwifruit wine fermented by black tea fungus liquid increased first and then decreased, and reached the highest values of 1 101.69 mg/ml and 735.35 mg/ml at 192 h of fermentation. The free radical scavenging rates of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) increased first and then decreased, reaching the highest of 93.6% and 91.5% at 192 h of fermentation. The scavenging rate of hydroxyl radical (·OH) showed an increasing trend, and reached the highest at 336 h of fermentation, which was 54.48%. The results revealed the changes of metabolites and antioxidant activity during the fermentation of black tea fungus liquid kiwifruit wine, which provided a theoretical basis for its industrial production.