Determination of quality and antioxidant activity of traditional homemade fruit vinegars produced with double spontaneous fermentation

The quality and antioxidant potential of six traditional homemade vinegars produced using traditional methods was object of this study. The physicochemical characterization of vinegars produced from apple (Malus domestica), raspberry (Rubus idaeus), blueberry (Vaccinium myrtillus), blackberry (Rubus fruticosus), rose hip (Rosa canina) and persimmon (Diospyros kaki), was performed by measuring the ethanol content, total acidity, pH and dry matter in different vinegar production steps throughout a double spontaneous fermentation process, i.e., without any addition of yeasts or acetic acid bacteria. А spontaneous fermentation of fruits for vinegar production encompasses initially an alcoholic fermentation for 24 days, where fructose, glucose and sucrose, as most abundant sugars, are broken down into carbon dioxide (CO2) and ethanol as main metabolic compounds, as well as other metabolic by‐products and volatile com‐ pounds in trace amounts. The highest total phenolic compounds were measured by vinegar produced from rose hip (20.2 mg of gallic acid/mL) while the lowest concentration was determined for apple vinegar (0.29 mg of gallic acid/mL). The results from total phenolic com‐ pounds were in strong correlation with the antioxidant capacity. In this way, the use of traditional processes for the production of fruit vinegars proved to be very promising in terms of producing differentiated vinegars and, concomitantly, reaching high levels of health‐promoting antioxidant capacities