Residue changes and processing factors of thirteen pesticides during different tomato pickle processes

Abstract

Tomatoes grown in an experimental greenhouse were sprayed with 13 selected pesticides at the recommended field doses, and used for pickle processing. Three different pickle processing techniques (natural fermentation, starter added fermentation and canning) were applied during the trials. Two strains of Lactobacillus plantarum were used as starter cultures in starter added fermentation trials. Changes in pesticide residues, pH levels and microbiological populations were periodically analysed and processing factors (PFs) were calculated at the end of the processing period. Yeasts-moulds and enterobacteria were not detected in any of the trials. Mesophilic aerobic bacteria were detected during both fermentation treatments (natural and starter added), whereas lactic acid bacteria were only observed in starter added trials. The initial pH levels of brines in all treatments were measured as 2.7 at the beginning of the processes and changed depending on the type of treatment. Lower pH values were detected in starter added treatments. Following the harvest day, significant reductions were observed in pesticide concentrations during both types of fermentation (natural and starter added) trials (p < .01) with the exception of bifenazate and abamectin. But on the contrary, residue changes were not significant (p > .05) throughout the canning process. Since bifenazate and abamectin are more stable at lower pH, their residue levels were not affected by the methods applied during fermentation processes. Only PF of canning process for bifenazate was higher than 1 and calculated as 1.17. All other PF values were lower than 1, indicating that the treatments caused degradation of the active compounds. Processing methods affected the pesticide residue levels in different ways, as a result of various degradation mechanisms.