Effective UV wavelength range for increasing aflatoxins reduction and decreasing oil deterioration in contaminated peanuts

Many studies have demonstrated that UV radiation can degrade aflatoxins (AF) in contaminated foods. However, the effective wavelength ranges for AF decomposition and their impacts on the quality of foods have not been elucidated. This study investigated the AF reduction and oil quality change in peanuts subjected to three types of 17 W low-pressure (LP) UV lamps covering UV-A (Max. emission: 365 nm), UV-B (Max. emission: 310 nm), and UV-C (Max. emission: 254 nm) ranges and a 2000 W medium-pressure UV lamp covering from UV-A to UV-C. We used peeled-kernels for this study since the peanut skin represented an ability to protect AF from being degraded by UV. LP UV-A lamp treatment has shown the highest AF reduction in artificially spiked peeled-kernels and no detectable oil deterioration. With the same delivered UV dosage as LP lamp, MP lamp has shown the same level of AF reduction as LP UV-A lamp did, indicating such treatment was energy inefficient. Treating Aspergillus nomius inobulated peeled-kernels by two LP UV-A lamps (2.76 mW/cm2) for 1.0 h reduced 40% of AF if the kernels were milled into 1 mm-diameter particle, implying that exposing the interior part of kernels to UV radiation is necessary for an AF decontamination process. In the oil deterioration test, we found that UV-C strongly induced the oil oxidation of peanuts. Accordingly, we concluded that UV-A is the effective wavelength range to degrade AF as well as maintain the oil quality in foods allowing UV radiation to well penetrate the sample, such as liquid foods with low turbidity or solid foods in the particle form. These results also justify the use of solar radiation as an AF decontamination method, rendering this method to be employed in in areas that lack infrastructure.