Abstract:Total phenol, total flavonoid, dark color substance, amino acid nitrogen, salt-free solid, reducing sugar, total sugar, total acid, and free amino acid contents in a black soybean sauce and four other kinds of soy sauces were compared. In addition, DPPH and ABTS radical scavenging activity, reducing power, and metal ion-chelating activity of the selected soy sauces were comparatively analyzed. Correlation, cluster, and principal component analyses were performed to elucidate the internal relationship between antioxidant substances and antioxidant activity in the five soy sauces. The contents of six active ingredients, except for amino acid nitrogen, salt-free solid, and free amino acids, were significantly higher in the black soybean sauce than in the other four kinds of soy sauce (p<0.05). Furthermore, except for metal ion chelation, the antioxidant activity was significantly higher in the black soybean sauce than in the other four soy sauces (p<0.05). Correlation analysis showed that total phenols, total flavonoids, and dark color substances were the main components responsible for the significant difference in antioxidant activity among the five soy sauces. Cluster and principal component analyses indicated that the comprehensive quality of the black soybean sauce was significantly higher than that of the other four kinds of soy sauce. The findings provide supportive data and a scientific basis for further research on the antioxidant activity of black soybean sauce and will help consumers select an appropriate soy sauce.
