ORANBO

Rapid (pre-)cooling is often neglected in many citrus packinghouses, but should be seriously considered

as a means of improving fruit quality at destination markets. Cooling reduces respiration, slows

pathogen growth, reduces water loss and increases shelf-life. Common cooling methods for oranges

include room-cooling and forced-air cooling. For room-cooling and forced-air cooling,

maintaining good airflow through cartons is important to rapidly remove heat from

the product. To facilitate this, carton design should include at

least 5% side venting, designed to line up with adjacent carton vents and allow

airflow through the

entire load.

Under normal weather conditions, fruit store better on the tree than in

cold storage.

Cold storage should not be attempted if the fruit storage potential has been

expended

by prolonged tree storage. Once harvested, fruit quality will not improve.

Before placing into

storage, fruit should be pre-cooled to slow respiration and treated with an approved fungicide

to reduce decay. Oranges can be stored for up to 12 weeks under optimum storage conditions.

Ultimate storage-life depends on cultivar, maturity, pre-harvest conditions, and postharvest

handling. Oranges begin to freeze in storage at about -1 °C. During storage, fruit should be

inspected often for signs of decay or disorders. Such problems will advance rapidly once the fruit

are removed from cold storage. Recommended storage conditions are 0°C to 8°C

and 85% - 95% RH, variety/type/origin dependent.

Excessively rapid warming of refrigerated fruit results in condensation and spoilage. Levels of

respiratory gases which promote ripening, such as ethylene as well as carbon dioxide, should

be kept as low as possible. If ventilation is inadequate, storage damage, such as a bitter flavour

and peel scab, may occur. The supply of fresh air must thus be constant in order to dissipate

these gases.

Symptoms of chilling injury include pitting, brown staining, increased decay, internal discoloration,

off-flavors, and watery breakdown that may take 60 days to develop at 5 °C or become evident 1

to 2 days after moving to room temperature. After removing fruit from chilling temperatures,

respiration and ethylene production both increase. The development and severity of chilling

injury in citrus is influenced by both pre-harvest and postharvest factors. Pre-harvest factors

include cultivar, weather conditions, and even location of fruit on the tree (sun-exposed fruit

are more susceptible to chilling injury). Postharvest, development of chilling injury symptoms

can be reduced through temperature conditioning before storage, use of high CO2

atmospheres (eg., in CA or through the use of wax coatings or plastic film wraps),

intermittent

warming, and use of benzimidazole fungicides (eg., thiabendazole and benomyl).

The best means of preventing chilling injury is by storing fruit at non-chilling temperatures.

Fungicides are diphenyl, orthophenylphenol (OPP) and thiabendazole (TBZ). Diphenyl can

be recognised from its naphthalene-like odour. The fungicides primarily prevent blue and

green moulds, but they do impair flavour and indication of their use is mandatory.

Seawater, rain and condensation water promote (green and blue) mould growth.