Comparison of physicochemical properties and antioxidant activities of fermented soybean-based red pepper paste, Gochujang, prepared with five different red pepper (Capsicum annuum L.) varieties

The purposes of this study were to identify physicochemical properties and evaluate bioactive compound levels and antioxidant characteristics at 30 day intervals during the 90 days of fermentation of gochujang fortified with five different varieties of red pepper: Juktoma pepper (RP1), facing heaven pepper (RP2), Thai chili pepper (RP3), bird's eye pepper (RP4), and red bell pepper (RP5). Physicochemicals properties, including reducing sugar, capsaicin, pH, beta-carotene, and color parameters, of gochujang were evaluated. Antioxidant compounds of total polyphenols and total flavonoids were analyzed with antioxidant activities of DPPH and FRAP assays. The results showed that gochujangs (GRP1, GRP5) fortified with RP1, and RP5, had consistently higher values of reducing sugars, total polyphenols, and total flavonoids with antioxidant activities, but lower values of capsaicin, pH, beta-carotene, and color parameters as compared to GRP2, GRP3, GRP4 during 90 days of fermentation. GRP5 especially had the highest reducing sugar, amino acid contents, total polyphenols, and total flavonoids with antioxidant activities and the lowest value of capsaicin during the 90 days of fermentation.