Radio frequency irradiation treatment of dates in a single layer to control Carpophilus hemipterus

Stored dates require postharvest disinfestation treatment to prevent damage caused by insects feeding on these fruits. Fruit disinfestation can be achieved with different methods, at present fumigation, heating and refrigeration being the most common pest control methods, though there are drawbacks related to product quality, process efficiency and environmental impact. The aim of this study was to define a procedure for disinfesting dates using Radio Frequency (RF) heating. RF treatments were carried out on dates of the semi-dry Siwi variety, artificially infested with the larvae, pupae and adults of the dried fruit beetle, Carpophilus hemipterus. A pilot-scale radio frequency instrument with 3.5 kW nominal maximum power and a frequency of 27.12 MHz was used to perform the experiments. The internal temperature of the dates was measured during irradiation. An insect mortality assessment was carried out both at the end of RF treatment and on the following days. The effects of a 4-, 5- and 6-minute RF treatment on different stages of C. hemipterus were evaluated, finding that a 6-minute exposure ensured mortality of the larvae, pupae and adults of the pest. No significant alterations in moisture content or colour of the treated dates were evident. RF treatment appeared to be a viable technique for the disinfestation of dates, due to the short treatment time together with the possibility of continuous processing.