Enhanced antioxidant capacity of brown rice vinegar supplemented with soy residue

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AbstractBackground and ObjectivesThis study aimed to prepare and use soy residue as a supplement to enhance the antioxidant activities of grain vinegar, which has relatively lower antioxidant activities than fruit vinegar. Brown rice vinegar (BRV) was supplemented with 30% (BROV3) and 50% (BROV5) soy residue, respectively.FindingsAfter 3 days of alcohol fermentation, the BROVs had lower sugar content (6.43–9.4 °Brix [Bx]), alcohol content (4.47%–7.5%), and pH (3.65–3.66) but higher acidity (0.75%) than BRV (12.47 °Bx, alcohol content 11%, pH 3.72, acidity 0.66%). During 10 days of acetic fermentation, the BROVs showed higher pH (3.23–3.38) and lower acidity (4.05%–4.35%) than BRV (pH 2.88, acidity 4.86%). As the soy residue was increased, the contents of essential amino acids increased from 22.03 mg/L (BRV) to 515.27 mg/L (BROV5), but those of desirable volatile compounds decreased, and those of undesirable compounds increased. The polyphenolics, flavonoids, and isoflavone contents and 2,2‵‐diphenyl‐1‐picrylhydrazyl (DPPH) and 2, 2‐azino‐bis‐3‐ethylbenzothiazoline‐6‐sulfonic acid (ABTS)+ radical‐scavenging activities of the BROVs increased while increasing soy residue.ConclusionsAlthough soy residue addition decreased certain desirable volatile compounds and increased certain undesirable ones, overall, it improved the antioxidant activity and quality of brown rice vinegar.Significance and NoveltyThe potential of soy residue for enhancing vinegar functionality was confirmed.