Acetic acid bacteria strains were isolated from a variety of fermented foods and fallen fruits. Among them, the strain MAK88, whose acetic acid fermentation ability, acid-tolerance, and alcohol-tolerance were high, was selected and identified as Acetobacter orientalis. A seed culture of A. orientalis MAK88 was inoculated into onion juice, and the optimum conditions of acetic acid fermentation was investigated. The optimum initial concentration of ethanol in onion juice was 5% (v/v) and in that condition, acidity was 4.31% at 144 h of fermentation. The optimum initial concentration of acetic acid was 1% and the final acidity was 5.32%. The optimum fermentation temperature was determined to be 28oC. The most appropriate preparation method of onion juice was to heat the onion at 121oC for 15 min and produce juice with pressure followed by filtering, and then sterilization at 121oC for 15 min. Prepared onion juice was used for fermentation without dilution.

• 이진아(가천대학교 식품생물공학과, Department of Food Science and Biotechnology, Gachon University) | Jin-A Lee
• 이설희(가천대학교 식품생물공학과, Department of Food Science and Biotechnology, Gachon University) | Sulhee Lee
• 박영서(가천대학교 식품생물공학과, Department of Food Science and Biotechnology, Gachon University) | Young-Seo Park Corresponding author