Relationships between antioxidant activity and quality indices of soy sauce: an application of multivariate analysis

Summary Antioxidant activities (AA) and quality indices including the contents of total nitrogen, amino nitrogen, total acidity, sodium chloride, total solids (TS), non‐salt soluble solids and Browning Index (BI) were determined in forty‐one commercial soy sauces. The relationships between quality indices and AA were elucidated by multivariate analysis techniques. Results showed that production location, fermentation process and styles had significant (P < 0.05) impacts on the characteristics of soy sauces. Satisfactory discrimination between dark and light soy sauces was achieved by principal component analysis. Using cluster analysis, the group of dark soy sauce with strong AA was obtained. Results from partial least squares regression (PLS) showed that TS and BI were two major indices contributing to the AA of soy sauce. Moreover, a PLS model was constructed to effectively predict AA of soy sauces based upon quality indices.