In this study, the dissipation of pirimiphos-methyl during wheat fermentation by Lactobacillus plantarum was investigated. Sample preparation for GC/MS detection of pirimiphos-methyl residues from fermented wheat substrate was carried out by two steps: extraction with 25 mL of methanol : acetone = 1 : 1 solvent mix for 30 min, followed by clean-up procedure through a glass column with florisil coupled with elution by 25 mL of ethyl acetate : acetone = 4 : 1. To obtain the highest pesticide degradation level, the fermentation conditions were optimized according to response surface methodology. Our results showed that L. plantarum was able to reduce the level of pirimiphos-methyl in wheat. Although pirimiphos-methyl was partially labile during sterilization prior inoculation (~37–50%), and there was also spontaneous chemical degradation of pesticide (~6–11%), overall L. plantarum enhanced degradation from 15 to 34%, that is, to nearly 81%. Additionally, the effect of pirimiphos-methyl on the lactobacilli growth, and efficiency of fermentation, was studied where pirimiphos-methyl inhibit the growth of bacteria in concentrations higher than 5 mg kg−1, while the presence of pirimiphos-methyl did not overall affect the lactic acid fermentation.
Significance and Impact of the Study
Pesticide residues are an unavoidable part of the environment due to their extensive applications in agriculture. As wheat is a major cultivated cereal, the presence of pesticide residues in wheat is a real concern to human health. Reduction in pesticide residues during fermentation has been studied, but there is a lack of data regarding pesticide residues dissipation during cereal fermentation. Present work investigates the dissipation of pirimiphos-methyl during wheat fermentation by L. plantarum. Results are confirmation that food-processing techniques can significantly reduce the pesticide residues in food, offering a suitable means to tackle the current scenario of unsafe food.