Dielectric heating as a potential post-harvest treatment of disinfesting mangoes, Part II: Development of RF-based protocols and quality evaluation of treated fruits

With knowledge of frequency and storage dependent dielectric properties of mangoes, we studied a possible treatment that used radio frequency (RF) heating to reduce thermal treatment times in post-harvest pest control of immature mangoes. In this study, surface heating by hot water (HW) was combined with RF core heating of fruit against Mexican fruit fly (Anastrepha ludens) in mangoes (Mangifera indica cv. Tommy Atkins). Mangoes were first heated in water at 45 °C for 50 min followed by RF heating in a 27.12 MHz, 12 kW RF system for 1 min to reach 48 °C over the whole volume of the fruit. Fruit was then held in water at 48 °C for 4, 6 or 8 min, which corresponded to one level at, one above and another below the time needed to achieve 100% killing of third-instar larvae of Anastrepha ludens at this temperature. The controls were treated in HW at 46.1 °C for 90 min, which is a commercial disinfestation treatment approved by the U.S. Department of Agriculture's Animal and Plant Health Inspection Service (USDA-APHIS) for mangoes before shipping to the USA. After 12 days of storage at 21 °C and 90% relative humidity, RF-treated mangoes were firmer than those treated at 46.1 °C in HW (p < 0.05). Thus, the RF treatment improved the texture of the fruits compared with the currently used commercial HW treatment. RF treatments that brought fruit temperature to 48 °C followed by 6 or 8 min holding at this temperature should achieve the required disinfestation of mangoes without causing quality losses.