Kinetic study of the thermal conversion of ginsenosides using lumped groups in steaming, hydrothermal reactions, and CO2-assisted hydrothermal reactions

Compositional changes and physiological activities of fresh ginseng extracts prepared at various temperatures in subcritical water

Background

Subcritical water (SW) is regarded as an effective conversion technology for lignocellulosic biomass. The effect of SW on ginseng are limited to evaluate the ginsenoside composition of red ginseng, and there is little information on the effects of SW on fresh ginseng.

Methods

The general characteristics of ginseng extracts (GE) prepared with SW were evaluated in terms of brix, reducing sugar and residual solid content, and compositions of GE was estimated using chromatography. For utilization of GE as a bioactive food, the ginsenoside composition, antioxidative activity, angiotensin-converting enzyme (ACE) inhibitory activity, prebiotic potential and taste attributes were measured.

Results

Increasing SW temperature decreased residual solid content of ginseng and the soluble compounds of GE were yielded by SW at 250 °C. Despite that ginsenoside content decreased with SW temperature, a steep increase in Rg5 was observed at 200 °C. The SW at 200-250 °C manifested the highest antioxidant activities and ACE inhibitory activity of GE. However, the GE prepared at greater than 250 °C completely lost prebiotic potentials. Based on electronic-tongue, umami taste was enhanced by SW at 200 °C, but sweetness and bitterness were dominated at 250-300 °C.

Conclusion

The results demonstrated that SW has a potential application to convert lignocellulosic wastes generated from ginseng roots into bioactive food resource, and SW at ∼200 °C can be potentially used to enhance the physiological activities of GE.