AVOCADO (PERSEA-AMERICANA MILL) QUALITY CHANGES IN RESPONSE TO LOW-TEMPERATURE STORAGE

Avocado (Persea americana Mill. cv. Hass) fruit were stored at 2, 5, and 8 degrees C for four weeks to determine maximum cold-storage life. Skin colour, fruit firmness, mesocarp appearance, pectinmethylesterase (PME), polygalacturonase (PG), and cellulase (CX) activity were determined weekly during cold storage, and three times a week during subsequent transfer to 22 degrees C. Fruit held at 2 degrees C remained hard green during four weeks, and ripened normally upon removal to 22 degrees C. At the two higher temperatures fruit ripening started during storage. At 5 degrees C, ripening commenced during the fourth week of storage, and minor mesocarp discolouration was observed at full ripeness at 22 degrees C. Fruit held at 8 degrees C ripened after two weeks in storage, resulting in more intense mesocarp discolouration and vascular browning at full ripeness, upon transfer to 22 degrees C. For current Australian commercial storage of avocados cv. Hass, 7 degrees C is too warm, and may be reduced to 2 degrees C for preclimacteric fruit. Results indicate that fruit held at 2 degrees C can be stored for at least four weeks, and possibly five weeks without injury.