Postharvest disinfestation heat treatments: response of fruit and fruit fly larvae to different heating media

The surface heat transfer efficiency of three heating media (water, and forced air with and without a water vapor-pressure deficit) was compared using four commodities: mango, papaya, grapefruit, and orange. Forced vapor-saturated-air (VFA), and water (HW) transferred heat most efficiently to the fruit surface. Thermal stress to the fruit was greatest during heating in VFA. Thermal diffusivity of fruit corresponded to fruit density, and was highest for papaya and mango. Differences in the oxygen (O 2) and carbon dioxide (CO 2) concentration inside grapefruit were apparent among those exposed to an identical heat dose in HW, forced water vapor-pressure deficit air (MFA), or a forced, vapor-pressure deficit atmosphere of 1 kPa O 2 with 20 kPa CO 2 (MFCA). The altered atmosphere that developed inside fruit during heating in HW or MFCA was shown to enhance efficacy of heat as a disinfestation treatment. Results from this research suggest that heating in an atmosphere that inhibits fruit respiration does not in itself predispose a fruit to injury. The water vapor pressure of the atmosphere used to heat a commodity influences the thermal stress delivered to that commodity during heating. Forced, water vapor-pressure-deficit atmospheres with altered levels of O 2 and or CO 2 have commercial potential for providing quicker, less severe heat disinfestation treatments.