Decay incidence and quality of different citrus varieties after postharvest heat treatment at laboratory and industrial scale

• The extent of fungal growth in citrus was inversely related to temperature.
• Industrial scale application succeeded in reducing the natural decay incidence.
• Heat treatments at 45 and 53 °C were not detrimental to citrus quality.
• The most suitable heat treatment was 3 min at 53 °C.

Mandarins (Fortune, Ortanique, Ellendale, Clemenules and Hernandina) and oranges (Navelate, Navelina, Lanelate, Salustiana and Valencia) were inoculated with the fungi Penicillium digitatum and Penicillium italicum and then subjected to postharvest heat treatment at laboratory scale by dipping in water at various temperatures for different treatment times before storage. 53 °C (45 °C for varieties showing mottled fruits after heat treatment at 53 °C) and 3 min were found to be the most suitable conditions regarding decay incidence reduction, which were selected for the assays at industrial scale by using a heat water showers system in a commercial orchard. Heat treatment significantly reduced firmness and decay incidence in fruits after 5-day storage at 5 °C and 7 days of shelf life at 20 °C, and induced a delay in the evolution of skin colour. Other main quality parameters, such as juice content, soluble solids, pH, titratable acidity and sensory quality were unaffected. It was demonstrated that hot water postharvest treatments may be implemented in the citrus industry to extend shelf-life of fruits.