Comparison of Quality Characteristics and Electronic Nose and Electronic Tongue Analysis of Traditional Doenjang with Different Aging Periods

This study examined the changes in the quality characteristics of traditionally fermented soybean paste (doenjang) with aging by comparing three samples aged for different durations .The moisture content, color parameters (L, a, b), pH, salinity, soluble solids (°Brix), reducing sugar, and free amino acid profiles were analyzed.The antioxidant properties were evaluated based on the total polyphenol and flavonoid contents, as well as the DPPH and ABTS radical-scavenging activities.In addition, electronic nose analysis combined with principal component analysis (PCA) was applied to characterize the volatile aroma patterns, and electronic tongue analysis was performed to assess the taste attributes.The moisture content decreased significantly with aging, while the L and a values decreased and the b values increased, indicating intensified browning during long-term aging.pH decreased, whereas salinity, °Brix, and reducing sugar increased with aging, reflecting organic acid accumulation and concentration of soluble components.Long-aged doenjang (Dj-20) exhibited markedly increased levels of free amino acids, particularly glutamic acid and γ-aminobutyric acid, suggesting an enhanced umami and functional value.The total polyphenol/ flavonoid contents and antioxidant activities also increased with aging.The PCA of electronic nose data clearly discriminated the samples according to the aging period, and the electronic tongue results revealed a shift from salty to sweeter/sour and finally umami-dominant taste profiles.Overall, long-term aging improved the sensory and antioxidant properties of traditional doenjang.