Dissipation dynamics of methomyl, phoxim, and pymetrozine during mulberry (Morus alba L.) leaves harvest, tea processing and brewing

Abstract

Mulberry leaf tea is known for its health benefits; however, concerns remain about pesticide residues during harvest, processing, and brewing. The dissipation dynamics of methomyl, phoxim, and pymetrozine were systematically investigated in this study. In fresh leaves, their half-lives ranged from 1.1 to 2.3 days, with dissipation rates of 64.6–87.8 % within three days. During tea processing, dissipation rates in black and green tea ranged from 46.3 % to 78.9 %, influenced by the initial pesticide levels and processing conditions. The dissipation of pesticides was significantly influenced by drying and spreading/withering. During brewing, pesticide leaching was closely related to water solubility, with 33.8–76.9 % of methomyl and pymetrozine transferring to the infusion, compared to just 0.32–3.2 % for the less water-soluble phoxim. Overall, at least 85 % of the pesticides dissipated across harvest, processing, and brewing, suggesting negligible health risks based on risk quotient assessment.