SELECTION OF A SURFACE COATING AND OPTIMIZATION OF ITS CONCENTRATION FOR USE ON HASS AVOCADO (PERSEA-AMERICANA MILL.) FRUIT

Effects of surface coatings on gas exchange characteristics of 'Hass' avocados (Persea americana Mill.) were used to select a suitable coati ng and to optimise its concentration for use on avocado fruit at 20 de grees C, 60% relative humidity. Of six different surface coatings used , ''Avocado wax'' provided the greatest level of benefit (reduction in mass loss and enhanced sheen) for a given level of risk (modification of internal oxygen and carbon dioxide partial pressures). At the othe r extreme, 2% carboxymethylcellulose provided no benefit but substanti ally increased risk of fermentation. ''Apple clear'' treated fruit had lowest rates of mass loss, but had poor visual quality. Of the Avocad o wax concentrations assessed, 11% was the optimum. Concentrations gre ater than this provided marginal further gains in the reduction of mas s loss, but imposed unacceptable levels of risk of anaerobiosis in the fruit. A packhouse trial confirmed this concentration as optimum, but achieved somewhat lower levels of benefit.