Fresh purple onions were used as material, ultrasound-assisted complex enzymatic method was used to extract total flavonoids from it. Then, the crude extracts were used as fermentation materials to fermente for flavonoid-rich onion wine. The growth rate of flavonoids and alcoholic content were used as indicators to evaluate the quality of onion wine. This experiment explored the impact of following factors on quality of onion wine, which includes the amount of onion powder, fermentation time, sugar content, fluid loading volume, pH of broth, inoculum volume, etc. Plackett-Burman design was used to choose the important factors of influencing onion wine fermentation. Response surface methodology(RSM) was employed to maximize the growth rate of flavonoids (Y1)and alcoholic content(Y2) on a central composite design in involving 3 factors(fermentation time, sugar content, fluid loading volume) at 3 levels. The optimal technological conditions could be concluded as follows: sugar was 19 °Brix, fermentation time was 7 d, loaded liquid was 80%. Eventually, the optimum fermentation conditions was: adding 5 g onion powder in flavonoid-rich broth, adjusted pH to 4.0, sugar was 19 °Brix, the solution volumn with onion powder was 20 mL, fermentation time was 7 d, loaded liquid was 80%. In the validation test of the response surface method, the growth rate of flavonoids reached to 48.76%, flavonoids content achieved to (1.24±0.06) g/100 mL in onion wine. The alcoholic content can be achieved at 11.1%(V/V)，which can meet the requirements of the plant liqueur.
Caixia, SUN; Chengrong, WANG; Hao, WU; and Shaolan, YANG
"Researches on fermentation conditions of flavonoid-rich wine of onions,"
Food and Machinery: Vol. 32:
2, Article 40.
Available at: https://www.ifoodmm.cn/journal/vol32/iss2/40
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