Measuring the antioxidant capacity of Chinese aged vinegar
One of the most famous Chinese vinegars—Shanxi aged vinegar (SAV)—is produced with solid-state fermentation technology, which can improve the antioxidant activity of the vinegar. In a study published in the Journal of Food Science, researchers set out to investigate correlations between total antioxidant activity (TAC) and total polyphenol (TP) and total flavonoid (TF) contents of SAV, especially during the brewing process.
Vinegars are popular acid condiments providing foods with sour flavor. One of the most famous Chinese vinegars—Shanxi aged vinegar (SAV)—is produced with solid-state fermentation technology, which can improve the antioxidant activity of the vinegar. In a study published in the Journal of Food Science, researchers set out to investigate correlations between total antioxidant activity (TAC) and total polyphenol (TP) and total flavonoid (TF) contents of SAV, especially during the brewing process.
The researchers obtained 45 SAV samples from local supermarkets. The samples ranged in aging time from less than one year to 10 years. They performed analyses to determine values and changing trends of TP, TF, and TAC with aging time of SAV. The TAC of each sample was measured by ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic) acid) and FRAP (ferric reducing/antioxidant power) assays.
The researchers found that TAC, TP, and TF all increased with aging time. In the smoking pei stage, which is a special technique for SAV that differs from other Chinese cereal vinegars, the 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, the researchers analyzed the variation during the brewing process of eight main polyphenol compounds that were responsible for the TAC of SAV. In addition to catechins and chlorogenic acid, gallic acid serves as one of the principal antioxidant ingredients in SAV.
The researchers concluded that the TAC of Shanxi aged vinegar, 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 eight years. During the brewing process, smoking pei technique is important for enhancing the TAC of SAV, suggesting that critical control and thorough study of smoking pei stage are needed to improve the quality of SAV.