Total amino acid analysis
Each fresh mushroom sample (0.2–1 g) was hydrolysed
under nitrogen gas with 15 ml of 6 N HCl in an
autoclave at 110 °C for 24 h and neutralized to pH 7.00
by 4 N NaOH. Alkaline hydrolysis for tryptophan
determination was done according to the method of
Wu and Tanoue13. Briefly, the fresh mushroom
sample (1–3 g) was hydrolysed under nitrogen gas
with 10 ml of 4 N NaOH and 200 μg of ascorbic
acid as antioxidant in an autoclave at 110 °C for 16 h
and adjusted to pH 9.00. The hydrolysate was filtered
through a 0.45 μm cellulose acetate membrane filter
before injection into the HPLC.