Extraction of Tannin from Lonicera edulis and Its Effect on Yeast Fermentation Performance

In order to study the optimum tannin content in Lonicera edulis juice fermented by yeast, the processing of tannins extracted from Lonicera edulis by ultrasonic-assisted was optimized by single factors and orthogonal test. The purified and concentrated tannin extract was added to the simulated Lonicera edulis juice to study the effect of different concentrations of tannins on the yeast. In addition, the optimal tannin concentration was verified for yeast fermentation of Lonicera edulis juice. Results showed that, the optimal conditions for extracting tannins from Lonicera edulis were as follows: Ethanol volume fraction 50%, liquid to solid ratio 1:60 (g/mL), ultrasonic temperature 50 ℃, ultrasound time 40 min, under which, the tannin extraction rate reached 14.68%. Yeast grew well and had the highest activity during the stable period when the tannic acid concentration of the simulated juice was 400 mg/L. Compared with the original fermented juice, the alcohol and total acid content of the fermented fruit juice with the optimum tannin content hydrolyzed by tannins increased by 84.21% and 14.58%, and the residual sugar content and astringency were reduced by 57.91% and 86.32%, respectively. Total ester content increased by 38.45%. The optimum tannin content had a significant promoting effect on the fermentation ability of yeast, the fruit juice reduced astringency and had the moderate sour and sweetness with a strong fruity and fermented aroma.