INFLUENCE OF POSTHARVEST TEMPERATURES AND THE RATE OF FRUIT RIPENING ON INTERNAL POSTHARVEST ROTS AND DISORDERS OF NEW-ZEALAND HASS AVOCADO FRUIT

Postharvest rots and internal disorders of 'Hass' avocado (Persea americana) fruit develop during the latter stages of fruit ripening, with symptoms first appearing when fruit are minimally ripe but often becoming quite severe before the fruit are oversoft. Fruit ripened at 20 degrees C and assessed at the same stage of ripeness, just before the flesh becomes oversoft, had fewerpostharvest rots if they had been previously stored at 4 or 6 degrees C, than if they had been stored at either lower or higher temperatures. Postharvest disorders increased with increased length of storage. Fruit failed to ripen properly at 30 degrees C. Even at 25 degrees C (a temperature typically experienced by fruit exported from New Zealand), the level of postharvest disorders was greater than in fruit ripened at 20 degrees C. Best final quality was obtained with fruit coolstored at 6 degrees C and then ripened at 15 degrees C. However, if fruit are to be ripened at c. 25 degrees C, then final quality was better if the fruit were not coolstored but held at a temperature closer to the final ripening temperature. Fruit from a single orchard block, harvested, coolstored, and ripened together, individually reached minimum eating ripeness over an 8-day period. Fruit which ripened earliest had the fewest disorders, with later ripening fruit typically having high levels of postharvest rots and internal browning.