Low temperature conditioning treatments reduce external chilling injury of 'Hass' avocados

Storage of avocado fruit is limited by the development of skin damage (external chilling injury) when fruit are stored at temperatures of less than about 3 degreesC. The potential for low temperature conditioning to reduce external damage of 'Hass' avocados was examined. Avocados harvested in early summer were conditioned at temperatures of 4, 6, 8, 10, 12 and 15 degreesC for a period of 0, 1, 2, 3, 4 or 5 days before 3 weeks storage at 0 degreesC. Three days after removal from coolstore, external damage was rated, and internal quality assessed after ripening at 15 degreesC. The experiment was repeated in late summer, but fruit were stored for 4 weeks at 0 degreesC, and only external damage was measured. Control fruit stored at 0 degreesC for either 3 or 4 weeks exhibited severe external damage, manifested as blackening and pitting over almost the whole fruit surface. Conditioning temperatures of 4-10 degreesC reduced skin damage. The optimum temperature/time combinations were 6 or 8 degreesC for 3-5 days prior to 0 degreesC storage. Ripe-fruit quality was also highest in these treatments. Weight loss, ethylene and CO2 production were not associated with the reduction in external damage, and the response observed is therefore likely to be due to a low temperature, rather than a ripening response. (C) 2002 Elsevier Science B.V. All rights reserved.