Degradation of glyphosate along coffee roasting: Do residue levels in green beans mirror exposure derived from coffee consumption?

Robusta and Arabica green beans were supplemented with carbon 14-glyphosate labelled on each carbon position alternatively prior to roasting, up to 220 °C for Robusta and 200 °C for Arabica (2, 5 and 10 min). The results of the study point a significant decomposition of glyphosate that happens during roasting, from at least 42 % to > 74 % depending on roasting conditions (time, temperature) and coffee variety. The data obtained with C-labelled glyphosate materials suggest that the carboxymethyl branch of the compound degrades more effectively than the phosphonomethyl moiety. The degradation of glyphosate does not lead to the formation of aminomethylphosphonic acid (AMPA). The results of the study indicate that carbon dioxide, methylamine and dimethylamine are major degradation products of glyphosate formed along coffee roasting, likely released with the roasting gas. Ultimately, the results of the study show that levels of glyphosate in green beans do not mirror those in coffee beverages.