Quality characteristics and antioxidant activity of traditional Korean soy sauce based on the proportion of onion juice

Abstract

The aim of this study was to improve the quality and functionality of Korean soy sauce made with onion juice. At the end of fermentation, the titratable acidity of the soy sauce containing 100% onion juice was the highest at 2.90%. The salt (NaCl) content was highest and lowest in the samples without and with onion juice supplementation, respectively. The protein content ranged from 11.09-12.50%. The sensory evaluation revealed that the soy sauce sample containing 70% onion juice had the highest scove at 5.0-5.8 levels in terms of sweetness, salty taste, delicate flavor, and overall preference. Quercetin content was 1.73 mg/100 g and 1.68 mg/100 g in soy sauce containing 70% and 100% onion juice, respectively. However, quercetin was not detected in the soy sauce without onion juice supplementation. Total polyphenol and flavonoid contents, as well as antioxidant activity, increased proportionally to the amount of onion juice added. Overall, it was confirmed that the addition of onion juice improved the quality and functionality of Korean soy sauce.