This study investigated the effect of a vacuum-gas substitution hot water extraction (HWE) process on Korean red ginseng (KRG) using a specially designed device. The yield, browning, antioxidant activity, and ginsenoside content of KRG extracted under oxygen-free conditions (OFC, dissolved oxygen: 0.47 mg/L) were compared with those extracted under oxygen conditions (OC, dissolved oxygen: 6.46 mg/L). No significant difference was observed in extraction yield between OFC and OC. OFC maintained higher color stability, while OC resulted in higher a* and b* values and an elevated browning index during extraction. Antioxidant activities (DPPH, ABTS, and FRAP) increased up to 60 min and remained high and stable until 180 min under OFC, whereas they significantly decreased under OC. Major ginsenosides (Rb1, Rb2, Rc, and Rg1) were more stable under OFC than under OC. To evaluate the effectiveness of the vacuum-gas substitution HWE process, the optimally extracted samples (90°C for 1 h) were further evaluated for up to 72 h at 25°C and 90°C under both conditions. Under OFC, antioxidant activities remained stable for 72 h at both 25°C and 90°C, whereas storage at 90°C under OC resulted in a progressive decline. Individual ginsenosides exhibited higher stability under OFC than under OC, particularly during storage at 90°C, where severe degradation occurred under OC but was prevented under OFC. Consequently, these results demonstrate that the vacuum-gas substitution HWE process is effective in suppressing oxidative degradation, thereby preserving antioxidant activity and ginsenoside stability during HWE.
Lee et al. (2026) studied this question.