The effect of coatings and packaging on fruit quality in avocado cv Hass stored at low temperature for phytosanitary purposes

Avocado fruit are usually considered to be chilling sensitive. However, for export to certain markets, a low temperature shipping protocol will be necessary to satisfy phytosanitary regulations. Previous work has shown that shipping at 2oC results in good internal quality, but that external damage may be problematical unless some form of acclimation or modifi cation to the fruit environment is imposed. Packaging to decrease water loss, appeared to help. However, most of the work has been done on green skins, and little is known about the reaction of ‘Hass’ fruit, particularly from different areas. Fruit were sourced from Limpopo Province (warm with early maturing fruit) and KwaZulu-Natal (KZN) (cool with late maturing fruit). Limpopo fruit were transported to Pietermaritzburg, with a variable temperature regime, while KZN fruit were immediately subjected to low temperature storage at 2oC, as well as an acclimation regime of 10oC for 2 days before storage. Fruit mass loss was noted in relation to fruit left unwaxed, waxed and packed in polypropylene bags. Final chilling injury after 30 days at 2oC was noted. Results indicated that controlling water loss could substantially reduce risk of external chilling injury. Further, critical mass loss (assumed to be mainly water) appears to be between 5% and 6% of fresh mass, after which chilling injury rapidly increases with further mass loss. Considerable mass loss occurs early in the fruit cooling cycle. The acclimation process used did not appear to enhance quality signifi cantly. It is concluded that provided that fruit mass loss postharvest can be controlled, preferably to less than 6% of fresh mass, ‘Hass’ fruit can successfully be shipped under phytosanitary protocols. Nevertheless, it is suggested that further work is necessary in relation to fruit maturity and precooling systems.