Comparing the standard chromatographic peaks of 17 free amino
acids at known concentrations (Fig. 2A1)with the peaks from our experimental
samples (Fig. 2A [0 d]; 2B [initial fermentation]; 2C [mid fermentation];
2D [end-fermentation]) we could quantify their relative
concentrations at each stage of fermentation. The standard curve of the
concentration y (mg/L) for the peak area x is shown in Table 1-1, and
the measured results of free amino acids in suan-cai during natural
fermentation are shown in Table 1-2.