유산균 접종 및 추가 발효에 따른 숙성연령별 된장의 항산화 활성 및 라디칼 소거 반응 특성

초록

Purpose: This study examined the effects of lactic acid bacteria inoculation and additional fermentation on the antioxidant properties of soybean paste with different aging periods. The objective was to elucidate how the initial aging state of soybean paste influences the antioxidant activity and radical-scavenging reaction kinetics during subsequent fermentation. Methods: Soybean paste aged for 0.3, 2.3, and 8.3 years was inoculated with Lactobacillus plantarum and further fermented at 25°C and 4°C for six months. During fermentation, the titratable acidity was monitored to confirm the microbial metabolic activity. The antioxidant activity was assessed using the Folin-Ciocalteu reagent method and DPPH radical scavenging kinetics, including the initial scavenging rate, time required to reach 50% radical scavenging, and maximum scavenging activity. Results: The titratable acidity increased significantly for up to three months in all treatments, indicating active growth and metabolic activity of the inoculated lactic acid bacteria in the soybean paste matrix. At the initial stage, soybean paste with longer aging periods showed higher reducing capacity and faster initial radical scavenging rates. However, during subsequent fermentation, the long-aged soybean paste showed more pronounced deterioration in the radical scavenging kinetics, which was characterized by decreased initial scavenging rates, prolonged time to reach 50% radical scavenging, and reduced maximum scavenging activity. Kinetic analysis of the DPPH scavenging curves revealed mixed fast and slow kinetic behavior in the younger soybean pastes, whereas the long-aged soybean paste predominantly showed slow kinetic behavior characterized by a downward shift of the reaction curves. Conclusion: These results show that the antioxidant characteristics of soybean paste are determined by the concentration of reducing compounds and by the radical-scavenging reaction kinetics. These properties are largely determined by the initial aging stage of the soybean paste.

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