The Impact of High-Temperature and High-Pressure Steaming Treatment on Bioactive Compounds and Antioxidant Activity in American Ginseng

Thermal processing facilitates the transformation of major ginsenosides into rare ginsenosides, thereby enhancing the bioactive molecular profile of American ginseng. This study examined the impact of 1–4 cycles of high-temperature and high-pressure steaming (HTHPS) on ginsenoside composition, total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity in American ginseng. HTHPS significantly decreased major ginsenoside levels while increasing the content of rare ginsenosides. Following three cycles (HTHPS-3), the concentrations of Rg3, Rk1, Rg5, Rh1, F4, and Rg6 reached 8.68, 6.02, 20.07, 1.92, 3.72, and 2.57 mg/g, respectively, in contrast to their absence in the untreated control. TPC exhibited a 6.74-fold increase after HTHPS-2, whereas TFC showed a 4.27-fold increase following HTHPS-3. Pearson correlation analysis revealed strong positive correlations between rare ginsenosides, TPC, TFC, and antioxidant activity. In summary, HTHPS treatment significantly altered the bioactive profile of American ginseng. HTHPS-2 was more suitable for maximizing TPC and DPPH/ABTS+ radical-scavenging activities, whereas HTHPS-3 favored rare ginsenoside accumulation, particularly Rg3, Rk1, and Rg5, and exhibited a stronger ·OH radical-scavenging capacity. These findings indicate that the preferred number of HTHPS cycles depends on the target bioactive components and functional properties.