Roasting
is pivotal for enhancing the flavor of Wuyi rock tea (WRT).
A study investigated a novel compound that enhances the umami taste
of WRT. Metabolomics of Shuixian tea (SXT) and Rougui tea (RGT) under
light roasting (LR), medium roasting (MR), and heavy roasting (HR)
revealed significant differences in nonvolatiles compounds. Compared
LR reducing sugars and amino acids notably decreased in MR and HR,
with l-alanine declining by 69%. Taste-guided fractionation
identified fraction II–B as having high umami and sweet intensities.
A surprising taste enhancer, N-(1-carboxyethyl)-6-(hydroxymethyl)
pyridinium-3-ol (alapyridaine), was discovered and identified. It
formed via the Maillard reaction, positively correlated with roasting
in SXT and RGT. Alapyridaine levels were highest in SXT among the
five oolong teas. Roasting tea with glucose increased alapyridaine
levels, while EGCG inhibited its formation. HR-WRT exhibited enhanced
umami and sweet taste, highlighting alapyridaine’s impact on
WRT’s flavor profile. The formation of alapyridaine during
the roasting process provides new insights into the umami and sweet
perception of oolong tea.