Take 10 g of the sample, grind it into a slurry with a mortar, add 10 mL of distilled water, 1 mL of 0.01 mol/L sodium hydroxide solution, and cool in a boiling water bath for 30 minutes. Draw 2 mL of the clear sample solution, put them in 25 mL volumetric flasks, add water to make up to 4.0 mL, and then add ninhydrin solution (20 g/L) and phosphate buffer solution (pH 8.04). 1mL, mix well, heat for 15min on a boiling water bath, take out and quickly cool to room temperature, add water to the mark, and shake well. After standing for 15 min, the absorbance A value was measured at a wavelength of 570 nm. The instrument used was U-1800 ultraviolet-visible spectrophotometer (Hitachi). Use the measured A value to find the corresponding amino acid micrograms on the standard curve. The standard curve is developed with reference to the color reaction of ninhydrin solution.

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