COATING TO ENHANCE FRUIT LIFE

Surface coatings can reduce weight loss and retard ripening and could therefore be valuable in developing more distant export markets for the New Zealand avocado industry. This programme is evaluating benefits and risks of waxing avocados. Waxing reduced weight loss by up to 50%, depending upon coating type and concentration. Waxing depressed fruit internal oxygen and increased internal carbon dioxide, modestly with dilute coatings at 15°C but more dramatically with higher wax concentrations and storage temperatures. Coating could cause fermentation if transit, ripening or shelf-life temperatures were too high. At 20°C, a good balance between reduced weight loss (benefit) and reduced internal O2 (risk) was achieved by coating with 11% 'Avocado wax', relative to other concentrations investigated. At 10%, it slightly extended marketable life, an effect linked to lower incidence of anthracnose. However, even with this substantially diluted wax, there was an increased incidence of incomplete ripening (hard, unripe tissue within the flesh of the ripened fruit), particularly in fruit ripening at higher temperatures. Severity was linked to excessive internal atmosphere modification in coated fruit at high temperatures. Overall, it appears that commercial wax formulations must be diluted substantially to avoid risks of excessive internal atmosphere modification in the coated fruit. Nevertheless, we believe that this simple technology could enhance market returns provided that its application and subsequent handling of the fruit are appropriately managed. Further characterisation of the interaction of initial fruit attributes, coating treatment and ripening environment should be used to optimise waxing for the New Zealand industry.