Optimization of fermentation process and determination of antioxidant activity in vivo of kiwifruit Jiaosu

In order to further prolong the processing industry of kiwifruit, taking kiwifruit as raw material, the fermentation conditions of kiwifruit Jiaosu were optimized by single factor tests, Plackett-Burman tests and response surface tests, and the removal effect of kiwifruit Jiaosu on 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS⁺), 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl free radical and Fe³⁺ relative reducing capacity were analyzed. The results showed that the optimal fermentation process of kiwifruit Jiaosu was as follows: solid to liquid ratio 38:100 (g:ml), bacteria (Saccharomyces cerevicae:Lactobacillus plantarum:Lactobacillus bulgaricus=3:1:1) inoculum 0.24%, sugar addition 12%, fermentation time 144 h, temperature 26.4 ℃. The superoxide dismutase (SOD) activity of the kiwifruit Jiaosu under the optimal conditions could reach 1893.30 U/ml. The results of antioxidant tests showed that the clearance rates of DPPH·, ABTS⁺·, ·OH and Fe³⁺ relative reducing capacity were 37.2%, 80.13%, 79.01% and 24.65%, respectively, which improved 7.98%, 2.50%, 2.41% and 3.58% respectively compared with that of before optimization. In conclusion, the SOD activity of the kiwifruit Jiaosu and the antioxidant activity were improved after fermentation process optimization.