Thés biologiques

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Re: Thés biologiques

Message par matière grisonnante » 15 Septembre 2020, 13:42

A propos de pesticides, Sciences Thé mentionne l'article Rinsing Tea before Brewing Decreases Pesticide Residues in Tea Infusion, dont voici le résumé :
Rinsing dried tea leaves before brewing is a traditional way of preparing rolled oolong tea in China. This study analyzes how rinsing green, black, and oolong tea before brewing affects the levels of pesticide residues in the tea infusion. Eight representative insecticides of different polarities were tracked, namely, three neonicotinoids (acetamiprid, imidacloprid, and thiamethoxam), two organophosphates (dimethoate and malathion), and three pyrethroids (bifenthrin, β-cypermethrin, and fenvalerate). The results showed that the eight pesticides transferred into the rinse water at rates between 0.2 and 24% after 5, 10, 20, or 30 s. Rinsing tea before brewing reduced the pesticide risk levels by 5−59% in the tea infusion. Five functional components, such as epigallocatechin gallate and caffeine, were reduced by 0−11% in the tea infusion. The results can be used to develop an effective method of rinsing tea before brewing that reduces pesticide exposure risks.

La figure 2 montre que rincer pendant 5 secondes (après avoir mélangé eau et feuilles pendant 5 s, donc 10 s de contact feuilles-eau en tout) enlève une partie des pesticides, et que rincer pendant 30 secondes n'est pas beaucoup plus efficace que pendant 5 s.