Antioxidant Activity of Chinese Shanxi Aged Vinegar and Its Correlation with Polyphenols and Flavonoids During the Brewing Process.

One of the most famous Chinese vinegars, Shanxi aged vinegar (SAV), is produced with solid-state fermentation technology. Total antioxidant activity (TAC) is a special property for SAV. In this study, we investigate correlations between total antioxidant activity (TAC) and total polyphenol (TP) and total flavonoid (TF) contents of SAV, especially during the brewing process. For SAV, TAC, TP, and TF increased with the increase of aging time. The correlation coefficients between TAC and TP were 0.869 and 0.934, respectively, when analyzed with the method of ABTS and FRAP. They were 0.828 (ABTS) and 0.877 (FRAP) between the TAC and TF. In smoking pei stage that is a special technique for SAV different from other Chinese cereal vinegars, TAC increased by 120% (ABTS) and 111% (FRAP) mainly due to the increase of TP (89%) and TF (75%), which was more obvious than that during alcohol fermentation and acetic acid fermentation stages. Moreover, variation during brewing process of 8 main polyphenol compounds that were proved responsible for the TAC of SAV was analyzed. In addition to catechins and chlorogenic acid, gallic acid serves as one of the principal antioxidant ingredients in SAV. PRACTICAL APPLICATION: Total antioxidant activity (TAC) of Shanxi aged vinegar (SAV), which is highly correlated with total polyphenol and total flavonoid, increased with aging time, however, there is a little loss of total antioxidant after more than 8 y. During the brewing process smoking pei technique is important for enhancing the TAC of SAV suggesting critical controlled and thoroughly study of smoking pei stage are needed to improve the quality of SAV.