Effect of fruit coating and packaging on external and internal quality

In order to reach the major markets for South African avocados, it is necessary to hold fruit at low temperature for up to 30 days. The lower the temperature used the less likely the incidence of internal disorders, provided the temperature is not below the threshold for inducing chilling injury. However, the temperature used is often one of compromise, as external chilling injury often occurs at the temperature required to ensure internal quality. This is particularly notable for the green skin cultivars such as ‘Pinkerton’. Previous work on cultivar Fuerte showed an interaction between water loss and chilling injury at low temperature, which could be modified by postharvest treatments. The objective of the study was to investigate options for decreasing external injury but at the same time maintaining high internal quality. Both ‘Pinkerton’ and ‘Hass’ were used in the study. Two wax formulations were applied to fruit, and two types of poly-bag packaging were used. In the latter case fruit were not waxed. One bag was microperforated and the other contained an ethylene scrubber. Fruit were stored for 30 days at 2 0 C, 5.5 0 C and 8 0 C. After removal from storage, ripening was at 20 0 C. After each week of storage samples were removed from the cold store to evaluate fruit condition before and after ripening. In addition, respiration rate of each fruit was determined as was time to ripening and thus shelf life. From the results it is intended to develop an appropriate protocol for quality maintenance.