Abstract: To study the effect of Lactobacillus kefir on the fermentation of quinoa thick pulp and the antioxidant properties of quinoa fermented drink, the acidity and the total viable counts were used as evaluation indicators, and the fermentation was optimized by response surface method. Quinoa fermented milk was mixed with fruit and vegetable juice, freeze-dried and then used to simulate in vitro gastrointestinal digestion. The content of flavonoids and polyphenols and the dynamic changes of DPPH free radical, ·OH, ·O-2 scavenging rate, and iron reducing power in the quinoa thick pulp unfermented group, quinoa drink fermented by kefir group, and fruit and vegetable juice mixed with quinoa fermented by kefir group were compared. The results showed that the optimal conditions for quinoa thick pulp fermentation were: inoculation amount 5.2%, fermented at 37.4℃ for 12.4 h. After digestion, the content of flavonoids and polyphenols for these three groups increased significantly. The DPPH free radical, ·OH, ·O-2 free radical scavenging rate and iron reducing power of the fruit and vegetable juice mixed with quinoa fermented by kefir group were 10.9%, 7.6%, 11.8%, 0.190 higher than those of the quinoa thick pulp unfermented group, respectively, and 4.8%, 1.9%, 4.1%, 0.022 higher than those of the quinoa drink fermented by kefir group, respectively.
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