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A Dissipation Pattern of Gibberellic Acid and Its Metabolite, Isogibberellic Acid, during Tea Planting, Manufacturing, and Brewing.

As a widely used plant growth regulator, the gibberellic acid (GA3) residue in tea has potential risk for human health. Herein, the degradation of GA3 and its conversion into main metabolites were investigated during tea planting, manufacturing, and brewing using ultrahigh-performance liquid chromatography tandem mass spectrometry. The metabolite iso-GA3 was first discovered during the tea production chain and identified using Q-Exactive Orbitrap mass spectrometry. GA3 dissipated following first-order kinetics in tea shoots with half-lives ranging from 2.46 to 2.74 days. It was degraded into iso-GA3 in tea shoots, which had a longer residual period than GA3. Meanwhile, external application of GA3 could increase the proportion of growth-promoting endogenous phytohormones and lead to rapid growth of tea plants. During tea manufacturing, iso-GA3 was quickly and massively converted from GA3. Fixing (heat at 220-230 °C) played an important role in the dissipation of GA3 and iso-GA3 during green tea manufacturing, but there were high residues of iso-GA3 in black tea. High transfer rates (77.3 to 94.5%) of GA3 and iso-GA3 were observed during tea brewing. These results could provide a practical reference for food safety in tea and other agricultural products and the guidance for scientific application of GA3 in tea planting.