ORN ANONG CHAIYACHET*, NIPHATTHA THIAPKHUN AND OOM KINGRUNGRUEANG
Division of Biotechnology, Faculty of Science and Technology, Rajabhat Maha Sarakham University, Talat, Mueang, Maha Sarakham, P.O. Box 44000, Thailand
*(e-mail: ornanong.ch@rmu.ac.th; Mobile: 66-89276 7907)
(Received: February 25, 2025; Accepted: March 24, 2025)
ABSTRACT
The purpose of this study was to investigate the effects of various factors on vinegar production from the gac fruit [Momordica cochinchinensis (Lour.) Spreng.] using Acetobacter aceti (TISTR 354) and to evaluate the physico-chemical properties and antioxidant activity of gac fruit vinegar. Gac fruit vinegar was produced through a two-stage fermentation process involving alcoholic fermentation by Saccharomyces cerevisiae and ethanol oxidation by acetic acid bacteria. The fermentation parameters included initial alcohol concentrations of 5, 7 and 9% (v/v), 10% (v/v) inoculum, pH 4.88, and 7 °Brix of total soluble solid (TSS) incubated statistically at room temperature for 15 days. At the end of the fermentation, gac fruit vinegar at different initial alcohol concentrations had acetic acid content ranging from 4.60-5.05%, pH values within 4.41-4.56, TSS content of 8.50-9.13 °Brix, and alcohol content of 3.97-5.70%. The L*, a* and b* values showed lightness (L*) shifting toward white, a* values shifting negatively (–a*) toward green, and b* values shifting positively (+b*) toward yellow. The antioxidant activity, calculated as a percentage of the radical scavenging activities, was 19.44-40.97%. Gac fruit vinegar fermented with 9% initial alcohol showed the highest acetic acid content and antioxidant activity among the vinegars included in this study. The findings of the study can be used to improve the production of fermented vinegar and promote the use of gac fruit as a functional food.
Key words: Acetic acid, Acetobacter aceti, antioxidant activity, gac fruit, vinegar