Quality characteristics and antioxidant activity of plum vinegar

This study evaluated the quality characteristics and antioxidant activity of vinegar prepared with the addition of plum (Prunus salicina L.) using a two-step fermentation process. Plum juice underwent alcoholic fermentation for 6 days, followed by acetic acid fermentation with Acetobacter pasteurianus for 20 days. To confirm the physicochemical qualities, pH, sugar and alcohol contents, free sugar, organic acid, free amino acid, and volatile compounds were measured. To examine the antioxidant activity, contents of total polyphenols and flavonoids, and radical-scavenging activities were analyzed. After fermentation, the major free sugars were maltose, fructose, and glucose. The organic acids of plum vinegar were acetic acid, oxalic acid, and succinic acid. Free amino acids were increased by fermentation, in particular, alanine, aspartic acid, GABA, lysine, ammonia, arginine were enriched. Volatile compounds shifted toward fermentation-derived aromas, particularly phenylethyl alcohol and 1-butanol. Although total polyphenols and flavonoids were decreased, they remained higher than in commercial apple vinegar. In addition, plum vinegar significantly enhanced 1,1’-diphenyl-2-picrylhydrazyl radical scavenging activity compared to pre-fermentation juice, and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid scavenging activity was also higher than that of both plum juice and apple vinegar. Therefore, plum vinegar produced by two-step fermentation demonstrated improved physicochemical properties and higher antioxidant activity relative to commercial apple vinegar. These results indicate indicating its potential as a value-added functional vinegar.