Effect of Processing on Reduction of Pesticides Residues in Long Grain Rice

Pesticides play a key role in preventing and controlling pests and illnesses, allowing to enhance the quality of agricultural products during cultivation and storage. Good practices in pesticides management are crucial because these compounds are associated with adverse health side effects mainly due to chronic toxicity. Rice is a primary staple food for a significant portion of the global human population. For this reason, there is an increasing interest in the development of methodologies to detect pesticides residues in rice-based food and feed samples with low detection limits.In the present study, different processing methods were tested in order to evaluate the effects of washing, washing with vinegar, cooking (traditional method) and steam cooking on reduction of 121 pesticides residues in long grain rice. The traditional cooking method consists of placing the rice submerged in water, where the water is twice the amount of rice. QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) was chosen as the pesticide extraction method and the extract was analyzed by high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). A rice sample (200 g) was contaminated at a level of 50 µg/kg and afterwards sub-samples were subjected to different processing methods.The washing method with vinegar presented the greatest efficacy, with a reduction of pesticides residues in the range of 26.8-80.3%. The rice samples submitted to both processing methods (wash with vinegar and cooking) presented higher reduction factors, where more than half of the pesticides are below their LOQ, in a total of 62 pesticides. In this line, it is recommended to use, at domestic and industrial levels, both methods in order to better guarantee food safety. The removal of pesticide residues due to processing is affected by the degree of adsorption of pesticides by the cereals’ grains, pesticide residues’ solubility in water and heat-induced breakdown.