Amino Acids in White Peony Teas of Different Grades

  Objective  The amino acids in white peony teas of various quality grades were compared.

  Method  Free amino acid compositions of 9 white peony tea specimens were determined using AQC pre-column derivatization combined with the ultra-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The analytical results on 35 amino acids were compared for the study by the partial least squares discrimination analysis (PLS-DA) and cluster analysis.

  Result  Aside from β-aminobutyric acid, homocysteine, cysteine, cystine, and tyrosine, the remaining 30 amino acids in the tea samples showed higher contents than the limit of quantitation. The correlation analysis on the data indicated a significant correlation between the amino acid composition and the quality of the teas. For instance, γ-aminobutyric acid, serine, proline, tryptophan, and glycine significantly affected the taste, while γ-aminobutyric acid was crucial on the astringency, of the brewed tea as shown in a taste test. The other amino acids appeared to interactively contribute to the sensory quality.

  Conclusion  Either individually or interactively, free amino acids had a significant effect on the taste, therefore, the grading of the white peony teas.