The thick and mellow flavor of green tea serves as a core sensory indicator for assessing its quality grade and market value. This characteristic fundamentally represents the dynamic equilibrium of multiple flavor-contributing substances within the tea leaves, coupled with the synergistic effects of multi-sensory perception. Currently, the characteristics, chemical composition, and interactions underlying the thick and mellow flavor of green tea are the subject of intense research, yet no consensus has been reached within the academic community. This review systematically details the research progress on the chemical and quality characteristics and interactive effects of green tea’s thick flavor. First, the physiological basis for perceiving this thick and mellow flavor—the multisensory integration mechanism involving taste, smell, and oral tactile sensations—is explored. Second, evaluation methods for the thick and mellow flavor of green tea, including sensory analysis, instrumental analysis, and the integrated application of artificial intelligence technologies, are outlined. Third, the chemical basis of the thick and mellow flavor of green tea and the mechanisms of its interactions are systematically summarized. This review aims to systematically analyze the formation mechanisms and regulatory characteristics of the thick and mellow flavor of green tea, providing valuable reference for standardizing green tea flavor quality control.

Single-source Jinxuan (Camellia sinensis) tea leaves were processed into teas with varying fermentation degrees to minimize genetic and environmental interference. Non-volatile component differences between fermented and non-fermented teas were identified, with fermented teas showing reduced tea polyphenols and soluble sugars but elevated theaflavins and theasinensin A(TSA). Fermented teas exhibited stronger in vitro digestive enzyme inhibition, particularly α-glucosidase (α-Glu), with TSA (R = 0.97) and theaflavin-3-gallate (R = 0.93) showing the strongest correlations (p < 0.001). In vivo, TSA's hypoglycemic effect in diabetic mice was mediated by enhanced insulin secretion, linked to lipid, amino acid, and fatty acid metabolism. These findings elucidate fermented tea's superior digestive enzyme inhibition and provide a foundation for optimizing hypoglycemic effects through processing.