Optimization of processing parameters of emerald tea and analysis of the formation mechanism of sweet and astringent balance characteristics

To address the low utilization and economic value of summer-autumn tea, the processing optimization and flavor formation of Emerald tea using sensory evaluation, <i>E</i>-senses, and metabolomics. Optimized parameters included withering (6-8 h, 73-74% moisture), fixation (250-310 °C, 2-4 min), rolling (33-35 rpm, 10-15 min), and drying (80 → 60 °C). This process elevated theanine content, reduced polyphenols, and enhanced the sensory quality of summer-autumn tea to match that of spring tea. Furthermore, the results showed that targeted sugar accumulation and selective degradation of polyphenols govern the sweetness-astringency balance. Ten key flavor compounds were identified, among which soluble sugars contributed significantly to sweetness (Pearson correlation coefficient > 0.85), while flavonoid glycosylation enhanced astringency (such as Eriodictyol (0.6416 mg/g), Chlorogenic acid (14.4636 mg/g), Rutin (159.8994 mg/g)). Emerald tea higher sweetness than traditional green and black tea, confirming rolling as the dominant factor. The present study established a multi-platform data association analysis framework for flavor-targeted improvement of Emerald tea.