From Fresh Leaves to Tea Infusion: Investigating the Origins, Key Variables, and Sensory Impact of 3-Alkyl-2-Methoxypyrazines in Green Tea.

This study investigated methoxypyrazines (MPs) in green tea infusions using solid-phase microextraction (SPME) and stable isotope dilution assay (SIDA) to extract and quantitate. Quantitative results showed that MPs (IPMP, SBMP, and IBMP) originated from fresh leaves and decreased gradually during processing. Stems of new shoots had the highest MPs levels, which declined from the first to fourth leaf, and shading increased MPs in older leaves. Quantification of relevant amino acids showed that MPs were strongly correlated with glycine, valine, and isoleucine. In 21 green tea infusions, IBMP appeared in 20 samples (average 2.38 ng/L, max 6.35 ng/L), while IPMP and SBMP were rarer. Addition tests confirmed that IBMP above 10 ng/L caused a strong green pepper off-flavor, but at lower levels (2 and 5 ng/L), it enhanced the green tea's top note and green aroma. Overall, the study demonstrates that parts per trillion level MPs significantly affected green tea aroma, providing insights for processing and quality control.