A brief study on the degradation kinetics of seven organophosphorus pesticides in skimmed milk cultured with Lactobacillus spp. at 42 °C

Seven organophosphorus pesticides (OPPs) including dimethoate, fenthion, malathion, methyl parathion, monocrotophos, phorate and trichlorphon were added to skimmed milk. The milk was inoculated with one strain of Lactobacillus spp. including L bulgaricus, L paracasei and L plantarum, and cultured at 42 degrees C for 24 h to investigate their impacts on degradation kinetics of the OPPs. The residual OPPs in the milk were extracted by an extraction solvent and quantified in a gas chromatography after purification. Degradation rate constant and half live periods of the OPPs were calculated from a first-order reaction kinetics model. The result shows that the selected Lactobacillus spp. exhibited some acceleration on OPPs degradation totally. Dimethoate and methyl parathion were more stable but malathion was the most labile. Both L bulgaricus and L plantarum had stronger acceleration on the degradation of the OPPs studied. (C) 2011 Elsevier Ltd. All rights reserved.