Functional constituents of fruit juices after acetic acid fermentation

Vinegar is essentially an aqueous solution of acetic acid; traditionally used as a food flavoring preservative, and as a therapeutic agent. Fruit vinegar has a growing demand in the food sector worldwide. However, the use of vinegar as a beverage is a noteless concept in the Sri Lankan context. The present study focuses on developing fruit-based vinegar using locally available fruits (mango and jackfruit) in Sri Lanka, and evaluating the effectiveness of fermentation performance at different temperatures. Alcoholic juices fermented by employing Saccharomyces cerevisiae were subjected to acetification by pre-cultured Acetobacter pasteurianus PP21. Samples were fermented at both 30 °C and 36 °C temperatures. Brix value, titratable acidity, and alcohol content of each sample were measured over the fermentation period until the expected acidity level (4% v/v) of vinegar is achieved. Compared to the acetic acid production at 36 °C, both mango and jackfruit vinegar showed their peak acetic acid production of 4.5 ± 0.015% (w/v) and 4.2 ± 0.04% (w/v) respectively, at 30 °C. The final Brix value of mango and jackfruit vinegar produced at 30 °C and 36 °C was found to be constant at 3.6, 5.7 and 3.1, 5.7 °Bx respectively. Furthermore, the final alcohol level of all the vinegar samples was found to be less than 0.5% (v/v). Moreover, the antioxidant activity, phenolic content and flavonoid contents of both mango and jackfruit vinegar were significantly higher (p<0.05) at 36 °C compared to vinegar produced at 30 °C. As per the results, both mango and jackfruit can be used successfully in fruit vinegar production and both 30 °C and 36 °C.