Abstract:Functional flavonoids were extracted from fresh purple onion by an ultrasonic assisted enzymatic method，and this flavonoid-rich extract was added to wort for beer fermentation.To optimize the fermentation process of flavonoid-rich beer，single factor experiments were carried out on pH value，amount of added flavonoid-rich extract，and yeast inoculation amount.Taking wine precision and flavone growth rate as response values，the Box-Behnken response surface method was used to define an optimal fermentation process for flavonoid-rich beer.The optimal amount of added flavonoid-rich extract was 1.3 mL，optimal pH was 5.1，and optimal yeast inoculum volume was 143 μL per 100 mL of wort.The flavonoid content of the obtained onion beer was high，and the growth rate was 41.9%.The wine precision of the final product was 4.30% vol.The wine was clear and transparent，with a red color and mellow taste.