Impact of heat sanitation of fresh whole cantaloupe on fruit quality and volatile metabolism.

Harmful microorganisms can contaminate fresh fruits and vegetables and with this cause outbreaks of foodborne illness. Therefore, mitigation strategies are needed to eliminate or restrict the multiplication of potential pathogens while maintaining fresh produce quality. This study assessed a vapour heat treatment on the control of Listeria on whole fresh cantaloupes (Cucumis melo) and its impact on quality, composition and fruit physiology. Fruit inoculated with Listeria innocua, a non-pathogenic surrogate of Listeria monocytogenes, were treated with 84°C vapour heat for 240 s, followed by storage at 4, 7 or 10°C for 0, 7, 10 or 14 days. At these times, fruit were analyzed for visual appearance, firmness, soluble solids, titratable acidity, flesh colour, respiration rate, and volatile production. On average, the heat treatment achieved 4-log reductions in surrogate pathogen densities. However, the heat treatment caused discoloration of the rind affecting the visual quality of whole fruit. No discoloration or deterioration of flesh tissue, change in flesh firmness, soluble solids or titratable acids was associated with the heat treatment. Fruit respiration measured after warming fruit to 20°C was reduced in heat-treated fruit throughout storage, averaging a CO2 production rate of 16.2 compared to 38.2 mg/kg h for non-heated fruit. This suggested permanent physiological damage occurred to the rind tissue. Heat treatments reduced acetaldehyde, had no effect on ethanol and increased ethyl acetate emissions. Storage at 10°C stimulated the emission of all three volatiles. The heat treatment stimulated the production of methyl, ethyl and acetate esters, but inhibited ester production during storage at temperatures that induced ripening. The vapour heat treatment was an effective sanitation treatment, but caused injury to the melon rind. Therefore, this treatment has potential to ensure safety of fresh-cut melon products.