Multi-physical pretreatments combined with hot-air drying affect pesticide residues and quality of jasmine tea

Conventional hot-air drying (HDT) can hardly degrade pesticide residues in jasmine tea effectively, and chemical methods tend to cause secondary pollution, which seriously endangers human health and restricts the sustainable development of the tea industry. To address this issue, this study systematically investigated the effects of four green physical pretreatments (ultrasonic, microwave, high-energy electron beam, and ultraviolet irradiation) combined with HDT on pesticide residues, color parameters, main chemical components, and volatile flavor compounds of jasmine tea. The results showed that all pretreatments altered the color of both dry tea leaves and tea infusions and significantly reduced pesticide residues. Among them, microwave pretreatment (MDT) exhibited the optimal degradation performance, with a total degradation rate of 68.99% for six pesticides, and significantly increased the contents of chemical components such as free amino acids and tea polysaccharides. GC-MS analysis revealed that different pretreatments exerted significant impacts on the aroma profile of jasmine tea. Among the key aroma components, the relative content of trans-linalool oxide (furanoid) increased significantly following MDT and HEDT treatments, and all four pretreatments produced significant effects on the levels of methyl salicylate. This study demonstrates that physical pretreatments can achieve both pesticide residue reduction and flavor quality improvement of jasmine tea, providing a practical technical reference for the industrial processing and quality control of jasmine tea.