EFFECT OF FERMENTATION PROCESSES ON PHENOLIC CONTENT AND ANTIOXIDANT ACTIVITY DURING PRODUCTION OF BLACK CARROT VINEGAR

Black carrots and black carrot-derived products have gained great popularity in recent years due to their significant content of health-promoting bioactive compounds. Therefore, this study focuses on the production of vinegar from black carrot juice (BCJ) derived from black carrot juice concentrate (BCJC), to attain a food product with nutritional added value. In this study, the effect of alcoholic fermentation by Saccharomyces cerevisiae and acetic acid fermentation by four different vinegar starters (grape, apple, alcohol vinegar, and the mixture of grape and apple vinegar) on some physicochemical properties (pH, total acidity, total dry matter, reducing sugar, total phenolics, and antioxidant activity) of BCJ was investigated. The results obtained indicated that processing the BCJ into black carrot wine (BCW) led to an overall reduction of only 4% in total phenolic contents, and a further decrease of 21-32% in total phenolic content was observed in black carrot vinegars (BCVs) due to the acetification process, on a weight-to-volume basis (mg/L). A similar decreasing trend was also determined for the antioxidant activity throughout the vinegar production process. Total phenolic content was not affected by inoculation with any of the seed vinegars since the difference between the total phenolic contents with respect to the four different vinegar starters was statistically insignificant (P > 0.05). In general, the BCW and BCVs (regardless of the type of inoculum) produced in this study exhibited better bioactive properties compared to their commercial counterparts (C-BCW and C-BCV). In conclusion, vinegar was successfully produced from black carrot by retaining a considerable amount of its nutraceutical components