Effects of extrusion process variables on extractable ginsenosides in wheat-ginseng extrudates

To evaluate effects of extrusion process variables on ginsenosides in wheat-ginseng extrudates, a wheat flour-ginseng powder blend (10% ginseng powder, w/w) was extruded in a twin-screw extruder with full factorial combinations of feed moisture (25, 30, and 35%), screw speed (200 and 300 rpm), and zone 5 barrel temperature (110, 120, 130, and 140 degrees C). The quantities of ginsenosides (Rb1, Rc, and Rd) extracted from the wheat-ginseng extrudates extruded at a zone 5 barrel temperature of >or=120 degrees C were significantly higher than those extracted from the nonextruded blend. New ginsenosides (Rg2 and Rg3), which were not present in the nonextruded blend, were found in certain wheat-ginseng extrudates, indicating that high temperature extrusion processing could lead to degradation of acidic malonyl ginsenosides (Rb1, Rc, and Rd) into neutral ginsenosides (Rb1, Rc, and Rd, respectively) as well as modification of protopanaxadiol-type and protopanaxatriol-type ginsenosides into Rg3 and Rg2, respectively.