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Fruits & Others

Postharvest Handling of Avocados

€ West Indian

€ Guatemalan

€ Mexican

€ Under the minimum size requirement

€ Broken or absent pedicel

€ Unhealed wounds or any fresh mechanical damage

€ Excessive healed scars or blemishes

€ Soft or loose stone

Temperature	Ripening Time
(Y´C)<	(Days)
9	32
12	24
15	16
18	12
21-30	9
*Values are for mid-season California avocados.

Avocados can be shipped by air or sea if high-quality fruits are used and if careful grading and handling are employed. Air-freighted fruits can be harvested one or two days prior to shipment and precooled to 12oC. For sea shipment, fruits should be harvested on the day prior to departure and should be precooled using hydrocooling or forced air. Hydrocooling normally takes 15 to 30 minutes, depending on fruit size and the cooling system used. Forced air cooling takes three to six hours to bring the fruit to the desired temperature if the carton design, palletization, and air movements are compatible.

Shipment of the West Indian varieties Pollock and Lula should be made at 12oC with 95 percent relative humidity and in refrigerated holds or reefer containers. These two varieties are particularly susceptible to chilling injury at low temperatures. Other varieties such as Fuerte and Hass can be shipped at lower storage temperatures (5oC to 7oC) for as long as three to four weeks.

Avocados normally benefit from storage in a controlled atmosphere, with optimum storage conditions being 8 to 10 percent carbon dioxide, 2 to 3 percent oxygen, and 8oC to 10oC.

Avocados do not ripen on the tree; optimum temperatures for ripening are 16-24oC; at higher temperatures the fruits may develop off flavors.

Potential Postharvest Losses

Avocados are vulnerable to a number of factors and diseases that affect fruit quality:

Mechanical damage: In all varieties, bruising and puncturing result in localized softening and the presence of secondary microbial infection. In ³loose stone² varieties, the stone may move about inside the fruit if poor handling occurs during shipment. Internal bruising then occurs but is invisible until the fruit is cut.

Low temperature: Avocados, like many other tropical and subtropical fruits, are prone to chilling injury when kept at temperatures below 10oC for extended periods. Chilling injury in avocados is characterized by surface and internal discoloration, a failure to fully ripen, and the development of off flavors. In green-skinned avocados, surface discoloration is easily seen. In dark-skinned fruit, which turns black on ripening‹for example the Hass variety‹surface discoloration is not easily visible. Internally, however, the vascular system darkens and the pulp turns gray to brown. Most California avocados can withstand three to four weeks of storage at temperatures between 1oC and 5oC; fruits held at 9oC and 10oC ripen normally without chilling injury symptoms. The Pollock and Lula varieties are susceptible to chilling injury below 12oC. Normally fruits are susceptible to chilling injury only before softening occurs. The correct storage conditions differ among varieties and must be employed to ensure maximum quality maintenance.

Pathological Factors: All avocados are susceptible to anthracnose (Colletotrichum gloeosporoides) and Dothiorella fruit rot (Dothiorella gregaria Sacc.). Anthracnose infections occur through lesions caused by other organisms (such as scab and Cercospora spots [Cercospora purpurea]) or by mechanical damage. Fungus does not develop until the fruit begins to ripen. The lesions start as brown or black spots that enlarge, become sunken, and crack. Diplodia stem end rot (Botryodiplodia theobromae) begins at the stem end of the fruit and develops as the fruit softens. This disease can be prevented by harvesting only mature fruit.