Irradiação com UV-C para controle de Sitophilus sp e aflatoxina em grãos de milho armazenados

Abstract

Corn (Zea mays) is one of the main grains used in human diet and animal feed production due to its protein and carbohydrate content. Controlling pests and pathogens that attack stored grains, such as weevils and fungi, aims to minimize post-harvest losses, often leading to the use of traditional chemical control agents, which are frequently applied indiscriminately, resulting in environmental and human health damage. An alternative potential method for pest control in silos is ultraviolet light irradiation, in the wavelength range of 100 to 280 nm, known as UV-C, which possesses high disinfecting and germicidal properties. However, studies on its use for pest control in stored grains are still limited. Thus, the present study aimed to evaluate the effectiveness of UV-C radiation in controlling weevils and fungi in corn grains, as well as optimize the exposure time and radiation intensity, without compromising food quality. In the first stage of this research, the UV-C light irradiation (254 nm) was evaluated in a single exposure stage for durations of 0, 1, 2, 3, 4, 5, and 6 hours, with live and dead insect counts conducted every 14 days over a total period of 126 days. Each sample unit initially contained 20 weevils placed in 200 grams of corn grains. In the second stage, a similar methodology was employed, but with intermittent exposure periods of 0, 15, and 30 minutes of irradiation every 15 days over a total period of 120 days, followed by an investigation of aflatoxin concentration and physical characteristics of the grains. The results from the first stage indicated that a single exposure to radiation was not effective in controlling the insects. However, in the second stage, with intermittent irradiation, a significant reduction (up to 50%) in the number of live weevils was observed at the end of the study period, when compared to samples that did not undergo irradiation. The reduction showed no statistical difference between 15 and 30-minute exposure periods. The determination of aflatoxin concentration showed significant positive effects on grain quality, as the contaminant was reduced to undetectable levels in most assays, with the depth of the grain layer notably influencing this reduction. Finally, the ideal location for applying radiation in a grain receiving and storage facility was indicated, considering the results obtained in this study and the characteristics of the structures comprising the unit. The application of UV-C light showed promising results in the control of insects and fungal contaminants, with short intermittent applications being sufficient to reduce the initial population of weevils and aflatoxin concentration. The results justify the importance of continuing the work, including the implementation of a prototype in the indicated location and evaluations of the method on a larger scale.