Gamma irradiation (60 Co) in postharvest of common beans (Phaseolus vulgaris L.), has already proven beneficial, regarding the prolongation of shelf life and physical, chemical, and organoleptic aspects of grains. However, few prior studies have investigated the effect of gamma irradiation on the dissipation of pesticides in foods, especially insecticides in beans. This study aimed to evaluate the waste dissipation of two insecticides, imidacloprid and thiamethoxam, used in the cultivation of common bean, a variety of Carioca, using gamma irradiation. Ground bean samples were spiked each insecticide in the laboratory at 3, 4, and 5 mg/kg, and were then irradiated at 0, 1, and 2 kGy per irradiator with a 60 Co source. Liquid chromatography-tandem mass spectrometry was used to quantify the insecticides. The irradiation promoted dissipation of thiamethoxam at 1 and 2 kGy doses, with the highest dissipation verified at 2 kGy. In general, at this higher dose of irradiation the reduction dissipation of thiamethoxam was 66% of the mean value found in the treatment without irradiation and ∼44% relative to the 1 kGy dose. Conversely, imidacloprid showed no effect of irradiation on waste dissipation, except in the treatment of 5 mg/kg at 2 kGy dose. From the results, it was concluded that the gamma irradiation might have applicability in dissipating thiamethoxam in real bean samples.
Practical application: Pesticide residues remaining from bean cultivation, sensitive to optimal doses of gamma irradiation, can be transformed into other less harmful or nonharmful substances, increasing the quality of the beans before the food arrives at the consumer's table. Irradiation of the grains after harvest also eliminates the need for application of other pesticides to preserve the grains during storage, as the technique is capable of eradicating deteriorating agents, such as microorganisms and insects.
Keywords: chromatographic analysis; common bean; food safety; insecticide degradation; quality control.
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