Figure 4.

Aroma compound concentrations in phenylalanine degradation pathway Phe, phenylalanine; PAld, phenylacetaldehyde; 2PE, 2-phenylethanol; PAR, phenylacetaldehyde reductase. (A) Aroma compound concentrations in phenylalanine degradation pathway during the enzymatic reaction of black tea; (B) The known pathway of L-phenylalanine degradation; (C) Identification the transformation of L-phenylalanine to aroma compound with [²H₈] L-phenylalanine. Data shown as the mean ± SD (n = 3). ** p < 0.01 vs. CK. Bars indicate the means ± S.D. (n = 3) of three biological replicates, and bars with different letters are significantly different at p ≤ 0.05 according to Duncan’s multiple range test.