Production of vinegar from waste fruits using <i>Acetobacter</i> species

Abstract

Vinegar is an organic substance that contains about 5% acetic acid and is made from the oxidative fermentation of alcohol by acetic acid  bacteria. The aim of this study was to produce vinegar from the juices of waste fruits. Proximate and physicochemical analysis was  carried out on the juices of orange, sugarcane, tomato, and pineapple using standard techniques. Twenty-one (21) species of acetic acid  bacteria were isolated and identified using glucose-yeast-Calciumcarbonate (GYC) agar. The juices were fermented for 7 days using  Saccharomyces cerevisiae, and subsequently, for 28 days, four alcohol-tolerant Acetobacterspecies were selected and inoculated into the  fermenting media. The produced vinegar was sensory evaluated, following a nine-point hedonic scale. The antibacterial and antifungal  effects of the vinegar were tested on fresh cabbage at various contact times (0, 5, and 10 min) and concentrations (5, 10, and 15 % v/v).  The physicochemical parameters analyzed in fermentation using S. cerevisiae showed a decrease in pH, specific gravity, and brix, while  the percentage of alcohol content increased. As the fermentation using Acetobacter species progressed, pH further decreased, titratable  acidity increased in a range of 6.6-7.7%, and specific gravity also decreased while specific gravity increased in Acetic acid fermentation.  Sensory evaluation showed a score range of 5.7–6.8 for pungency, 6.8–7.4 for appearance, 6.4–7.9 for aroma, 5.8–7.4 for taste, and 6.9–7.9  for acceptability. The best results for bacterial and fungal loads 5 on cabbage were at a concentration of 15% at 10 min. Drastic reduction  of bacterial load was from 2.07×10 to 4 4 3 2.7×10 CFU/g, while fungal load reduced from 4.9×10 to 6.7× 10 CFU/g. To evaluate  significance, an ANOVA was performed (p<0.05) and Duncan's test was used for multiple comparisons. Vinegar was successfully tested to  be effective as an antimicrobial agent. Future research should look into process optimization, strain improvement, and the adoption of  agro-allied wastes for biotechnology.