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Physicochemical properties of Fujian Yongchun aged vinegar (FYAV) and Shanxi mature vinegar (SMV) were compared in terms of the fermentation methods applied and aging periods (3, 5, 8, and 10 years), and combined E-nose/E-tongue analyses were performed to assess their flavors. Compared with submerged fermentation-derived FYAV, solid-state fermentation-derived SMV showed higher values of pH, brix, soluble solids, total phenolic content, and antioxidant activity, but not total acidity or total organic acids. Aging period resulted in an increase in pH, total phenolic content, and antioxidant activity. Principal component analysis based on E-tongue/E-nose analyses was performed to distinguish between the vinegars produced by different fermentation methods and under aging periods. Solid-state fermentation and an aging process were considered good techniques for vinegar brewing, considering the various organic acids and high levels of total phenolics and antioxidant activity.

Rice vinegar (RV) is primarily made from fermented rice or rice wine in Korea, China, and Japan. Ten commercially available naturally-fermented rice vinegars produced in Korea (KRV1∼4), China (CRV1∼2), and Japan (JRV1∼4) were comparatively investigated for their physicochemical properties and antioxidant activities. KRV showed a significantly higher total acidity range (5.07∼6.27) than both CRV (4.67∼4.84) and JRV (4.64∼4.84). These acidity ranges corresponded with respective standards of each country: Korea (Food Code), China (GB), and Japan (JAS). Six different organic acids were detected in RVs; acetic acid and succinic acid were the most prominent. Thirty different amino acids were detected in RVs, and main identified amino acids were alanine (KRV), phenylalanine and aspartic acid (CRV), and leucine and alanine (JRV). γ-Aminobutyric acid was detected at high concentration in KRV1. KRV1 showed maximum total phenolic content, and DPPH and ABTS radical scavenging activities of samples were also determined with significantly increasing tendency. KRV1 (produced from brown rice with aging period of >1 year) exhibited the highest free amino acid content and antioxidant activity as compared to CRV and JRV.