Amino acid determination
The amino acid composition of the samples was analyzed by using an A300
automatic amino acid analyzer (Membra Pure GmbH, Germany). Hydrochloric
acid was employed to hydrolysis ginseng extract at 110 °C for 24 h. The
hydrolyzed extract was filtered into a 25 mL volumetric flask. Then, 1
mL sample was absorbed and deacidified at 60 °C in a vacuum until a
small amount of stain was left at the bottom. The tested buffer was
added and mixed with the stain, and the resulting solution was filtered
through a 0.45 μm filter for analysis.