Heating pattern in dates subjected to postharvest radio frequency treatment

Radio Frequency (RF) electromagnetic fields are used for heating up different materials, including dry fruit, with the purpose of drying and/or disinfesting from insect pests. This kind of heating appears to be an interesting alternative to traditional disinfestation methods for these fruits, though sometimes heating inhomogeneity can be observed in the treated materials. In order to better understand this effect on dates, in a disinfestation protocol definition perspective, a specific study has been carried out, based on the results of the authors’ previous experiments. The heating pattern of various samples of fresh dates has been evaluated in order to better understand the diffusion of radiation during continuous treatment, as for industrial disinfestation process, and define means for mitigating possible heating inhomogeneity, besides the ones suggested by relevant literature (moving and heating). Dates of two different varieties, spread in single layer on a conveyor belt mover, have been treated for 4, 5 and 6 minutes with 27.12 MHz RF radiation and for each batch the internal single temperatures of a sample of 5 dates, positioned in different areas of a tray, have been recorded during the treatment and for 3 min after the end. The results show that the heating rate and the temperatures vary with the position of the dates in the tray, but the differences are limited within non-significant values for each treated batch. This makes further improvements in irradiation procedure unnecessary and confirms the efficacy of a 6 min disinfestation treatment for this kind of product, though the most appropriate treatment time must be determined for different varieties and conditions