Analysis of non-volatile and volatile metabolites reveals the influence of second-drying heat transfer methods on green tea quality

Second-drying is a key process of green tea manufacturing, however, hitherto the effect of second-drying methods on green tea quality has not been assessed. In this study, we compared the effect of three heat transfer drying methods (heat radiation, heat convection, and heat conduction) on green tea quality. Gas chromatography-tandem dual mass spectrometry was used to detect volatile compounds, while absolute quantitative methods were used to detect the non-volatile ones. We identified 45 non-volatile metabolites, 101 volatile metabolites, and 15 objective flavor indicators. Seventeen differential non-volatiles and 8 differential volatiles were screened. Microwave second-drying in heat radiation was the optimal method for green tea flavor, as it can promote the retention of chlorophyll, the degradation of flavonoid glycosides, and the enrichment of amino acids, soluble sugars, nonanal, trans-??-ionone, linalool, and jasmone. The results provide a theoretical basis and technical guidance for the precise and directional processing of high-quality green tea.

Automated summary

This study compared the effects of three heat transfer drying methods on green tea quality. The results showed that microwave second-drying in heat radiation was the optimal method, as it improved the flavor of green tea, retained chlorophyll, degraded flavonoid glycosides, and enriched amino acids, soluble sugars, and aromatic compounds.