Effect of rotating peanuts on aflatoxin detoxification by ultraviolet C light and irradiation uniformity evaluated by AgCl-based dosimeter

Ultraviolet irradiation (UV) has been used as a non-thermal processing method for food disinfection. In disinfecting solid foods such as peanuts, UV irradiation could be shaded or attenuated with increased distance, resulting in non-uniform dosage distribution. An affordable, rapid, and feasible method for measuring and improving irradiance distribution, however, is unavailable for detoxifying peanuts. In this study, a method was developed for rapidly quantifying UV dosage distribution on peanuts in a UV disinfection process. The darkening of the UV indicator, AgCl, was linearly proportional to the UV dosage from 0 to 120 mJ/cm2 delivered on peanuts. The uniformity of UV dosage distribution was described by measuring the color change of UV indicator at four points on two orthogonal axes of each peanut kernel. The UV indicator coated peanuts were then rotated in a customized cylindrical chamber at different speeds. A rotation speed with more uniform UV dosage distribution was determined and applied to an aflatoxin detoxification process. The results demonstrate that the UV uniformity was significantly improved when peanuts were rotated at 11 rpm in the cylindrical chamber. Furthermore, after irradiating with 2.3 mW/cm2 UV-C for 2 h, the aflatoxin B1 degradation rate increased from 60.8 ± 15.3 pmol g−1h−1 to 75.0 ± 10.9 pmol g−1h−1 in the peanuts rotated at 11 rpm, compared to those that were not rotated.