Fate of imidacloprid and acetamiprid residues during black tea manufacture and transfer into tea infusion

Abstract

The objective of this paper is to investigate the loss/stability of neonicotinoids (imidacloprid and acetamiprid) residues during the manufacture of black tea and to study the transfer of these pesticides from made tea to its infusion. For orthodox black tea, the manufacturing process involves leaf harvesting (plucking two leaves and a bud), withering, rolling, fermentation (oxidation), and drying. Initial withering and final drying resulted in the loss of pesticide residues, but no significant reduction in residue levels resulted from the rolling and fermentation steps. The drying process resulted in a residue transfer of 64–70% and 69–74% of the initial level, whereas the brewing process resulted in a residue transfer of 37–39% and 45–49% of imidacloprid and acetamiprid, respectively, from dried tea into the infusion. The decrease in acetamiprid levels during drying was also significant (8–13%), whereas the total loss during the manufacturing process ranged from 26 to 31%. Further, brewing for longer periods (an extended brewing time) resulted in higher transfer (up to 44% for imidacloprid and 53% for acetamiprid) of pesticides to tea infusion. Further, the extent of pesticide leaching depends on its water solubility, partition coefficient, and the brewing time.

Keywords:

• imidacloprid
• acetamiprid
• residues
• green tea shoots
• made tea
• infusion

Acknowledgements

The authors are especially grateful to the Director of IHBT for providing the facilities necessary for this study and to the National Tea Research Foundation for financial assistance.