Postharvest disinfestation heat treatments: response of fruit and fruit fly larvae to different heating media.
Shellie K. C., Mangan R. L.
Author Affiliation: United States Department of Agriculture, Agricultural Research Service, Crop Quality and Fruit Insect Research Unit, 2301 S. International Boulevard, Weslaco, TX 78596, USA.
Postharvest Biology and Technology 21 : 51-60
Abstract : The surface heat transfer efficiency of 2 heating media (water, and forced air with and without a water vapour-pressure deficit) was compared using 4 commodities: mangoes, pawpaws, grapefruits and oranges. Forced vapour-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 pawpaws and mangoes. Differences in the O2 and CO2 concentration inside grapefruits were apparent among those exposed to an identical heat dose in HW, forced water vapour-pressure deficit air (MFA), or a forced, vapour-pressure deficit atmosphere of 1 kPa O2 with 20 kPa CO2 (MFCA). The altered atmosphere that developed inside fruits during heating in HW or MFCA was shown to enhance efficacy of heat as a disinfestation treatment for Anastrepha ludens larvae. 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 vapour pressure of the atmosphere used to heat a commodity influences the thermal stress delivered to that commodity during heating. Forced, water vapour-pressure-deficit atmospheres with altered levels of O2 and or CO2 have commercial potential for providing quicker, less severe heat disinfestation treatments.