Abstract: The effect of aspartic acid as a catalyst on the transformation of protopanaxadiol-type ginsenosides (PDG) and Maillard reaction in high temperature steam was investigated. The antioxidant activity of the reaction products in vitro was also determined. The results showed that PDG was transformed into 20S-Rg3, 20R-Rg3, Rk1 and Rg5; the transformation pathway was as follows: PDG → 20S-Rg3/20R-Rg3 → Rk1/Rg5. The contents of 20R-Rg3 and Rg5 showed a gradual increase with increasing heating temperature, while the contents of 20S-Rg3 and Rk1 decreased. The 1,1-diphenyl-2- picrylhydrazyl radical scavenging capacity of the reaction products increased with increasing heating temperature, which was mainly attributed to the Maillard reaction products from aspartic acid and saccharides produced from PDG hydrolysis. This study can provide a basis for the development of green and environmental-friendly rare ginsenosides into health foods.

Key words: aspartic acid, protopanaxadiol-type ginsenosides, rare ginsenoside, antioxidant activity, Maillard reaction