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• Waxing of apples may increase the residual risk of pesticides. • The molecular model of a waxy apple coating was established. • Ozone could be used as a rapid method to remove pesticide residues from fruits. Dissipation of an organophosphorus pesticide, trichlorfon, in natural and waxed apples during storage was studied. The results showed that the trichlorfon content in natural and waxed apples decreased by 85% and 64%, respectively, during storage. The morphology of the surface film was dense and regular, which resulted in a higher water vapor resistance and a lower respiration rate in the waxed apples. This indicates that waxing affected the dissipation of pesticide residues in the apple storage environment, increasing food safety risk. Ozone was used to remove the residual pesticides on the apple surface. The trichlorfon degradation rate reached 73%. The ozone treatment had no effect on the surface color of the apple, which means that the fruit can be pre-treated with ozone prior to waxing or storage. [ABSTRACT FROM AUTHOR]

• Lactobacillus plantarum can degrade 81.28% of dimethoate in milk rapidly. • Enzyme is the main mechanism for Lactobacillus plantarum to degrade dimethoate. • Five degradation products of dimethoate were identified by UPLC-QTOF/MS. Bioremediation of pesticides in contaminated foodstuffs using probiotics has attracted great attention in recent years, but some intermediate products may have profound effects on the toxicity of treated food. Therefore, this work studied the degradation mechanism of dimethoate in milk by L. plantarum, and analyzed the toxicity of degradation products. The results showed that under the optimal conditions, L. plantarum can degrade 81.28% of dimethoate. Dimethoate had high binding affinities to phosphatase with the free energy of –16.67 kcal/mol, and amino acid residues, Gln375 and SER415 played important roles in the catalysis process. Five degradation products were identified using UPLC-QTOF/MS, and their toxicity was estimated using quantitative structure–activity relationship models. Some intermediate products were predicted to be toxic, which should not be ignored, but the overall toxicity of milk decreased after fermentation. Furthermore, the pH and titratable acidity of the fermented milk were 4.25 and 85 ◦T, respectively. [ABSTRACT FROM AUTHOR]

• The degradation rate of different OPPs by L. plantarum is different. • Phosphatase from L. plantarum has no selectivity for OPPs degradation. • The selective uptake determines the degradation difference of OPPs in L. plantarum. • The selective uptake of pesticides by L. plantarum was discussed for the first time. Organophosphorus pesticides (OPPs) are widely used worldwide, leading to varying degrees of residues in food. Lactic acid bacteria (LAB) can degrade OPPs by producing phosphatase. This study explored the reasons for the variation in the degradation of different OPPs by Lactobacillus plantarum. The results showed that the degradation effects of OPPs by L. plantarum (intact cells) varied greatly, the degradation rate constant of phoxim was 1.65-fold higher than that of dichlorvos. However, the phosphatase extracted from L. plantarum had no degradation selectivity for OPPs in vitro. It was speculated that the selective uptake of cells determines this degradation selectivity. The results of molecular docking supported this hypothesis because there was no difference in the binding energies between phosphatase and OPPs, while the binding energies between phosphate-binding protein and pesticides were different, and they were negatively correlated with the degradation rate constants of the eight OPPs by L. plantarum. [ABSTRACT FROM AUTHOR]

• The effect of enzymolysis on trichlorfon was analyzed. • The properties of trichlorfon molecules were analyzed. • The transformation pathway of trichlorfon was proposed. • The toxicity of the trichlorfon and transformation products were evaluated. Trichlorfon is one of the most widely used organophosphorus pesticides in agriculture. In this study, the extent of transformation of trichlorfon to dichlorvos (DDVP), during the polygalacturonase (PG) treatment of apple pulp was monitored. A transformation pathway is proposed for trichlorfon molecules, based on density functional theory (DFT) calculations. The transformation of trichlorfon involves hydroxyl substitution and cleavage, which was confirmed by molecular electrostatic potential (MEP) and frontier molecular orbital (FMO) theory. In addition, the toxicity of trichlorfon and its transformed products was analyzed using Ecological Structure Activity Relationships (ECOSAR) software. The binding sites of the two pesticides are located in the hydrophobic grooves of the acetylcholinesterase (AChE) active site region and both pesticides form hydrophobic interactions and hydrogen bonds with a large number of surrounding amino acid residues. DDVP binds more strongly with AChE, so it is a better AChE inhibitor and more toxic than trichlorfon. [ABSTRACT FROM AUTHOR]