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Table 2 Determination of free D -amino acids in grain vinegar samples

From: Distribution of D-amino acids in vinegars and involvement of lactic acid bacteria in the production of D-amino acids

Amino acid Rice vinegar Nonglutinous brown rice vinegar Nonglutinous brown rice black vinegar High-brix nonglutinous brown rice black vinegar High-brix nonglutinous brown rice black vinegar matured in barrel
μMa % D b μM % D μM % D μM % D μM % D
D-Asp 7.2 2.7 62.3 3.2 48 2.5 97.3 3.4 631.3 20.5
D-Ser c 30.6 1.6 18.9 1.0 64.5 2.1 431.4 16.1
D-Gln
D-His
D-Thr
D-Arg N. D. d N. D. N. D. N. D. 15.7 0.6 93.2 5.4
D-Ala 15.0 2.3 118.9 3.7 85.1 2.5 203.8 4.2 534.4 9.2
D-Tyr 148.3 8.7
D-Val N. D. N. D. 6.3 0.2
D-Met
D-Trp
D-Phe 8.2 0.6 9.3 0.6 29.5 1.2 214.9 11.4
D-allo-Ile
D-Leu N. D. N. D. N. D. N. D. 12.6 0.3 224.7 6.7
D-Glu N. D. N. D. 40.3 1.9 31.7 1.4 62.0 2.3 241.6 16.6
D-Asn 17.7 1.7 10.2 0.9 52.0 2.8 188.9 17.1
  1. aConcentrations cited are smaller one among the amino acid concentrations determined using NAC and NBC as chiral regents.
  2. bRelative percentages of D-amino acids were calculated as 100 × [D-amino acid]/[D-amino acid + L-amino acid].
  3. c−, not detected.
  4. dN. D., not determined. The D-amino acid peak was confirmed, but the concentration of the D-amino acid was too low to be determined.