Optimization of fermentation process of passion fruit-roselle complex fruit wine with immobilized yeast

In order to improve the comprehensive utilization rate of passion fruit and roselle, increase the variety diversity of fruit wine, using Yunnan purple skin passion fruit as raw material with addition of aqueous roselle extracts, the passion fruit-roselle complex fruit wine was prepared by immobilized Saccharomyces cerevisiae. The sensory, physicochemical, microbial quality indexes and antioxidant activity were evaluated. The fermentation process of the passion fruit-roselle complex fruit wine was optimized by single factor tests and response surface tests using sensory score and alcohol content as evaluation indexes. The results showed that the optimal fermentation conditions for passion fruit-roselle complex fruit wine were initial sugar 20 °Bx, yeast inoculum 0.6%, fermentation temperature 28 ℃ and roselle aqueous extract addition 10%. Under these optimal conditions, the complex fruit wine exhibited a clear color, rich fruit aroma, and unique fermented flavor, with a sensory score of 87.8 points and alcohol content of 10.0%vol, and all quality indicators met the relevant regulations specified in NY/T 1508—2017 "Green Food-Fruit Wine." The scavenging rates of the complex fruit wine on 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH), 2,2'-biazobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), hydroxyl and superoxide anion radicals were 73.7%, 100%, 89.2%, and 58.4%, respectively. The results showed that passion fruit-roselle complex fruit wine had better antioxidant activities.