Oranges

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Infobox on Oranges
Example of Oranges
Oranges.jpg
Freshness facts
Optimum carrying temperature 2°C to 7°C (dependent upon cultivar/origin)
Some examples:
Navel:
Moroccan, Spanish, 2°C to 3°C
Salustiana:
Spanish, 2°C
Valencia Late:
Moroccan, Cyprus, 2°C to 3°C
Spanish, 2°C
South African, 4,5°C
USA (California), 2°C to 7°C
Highest freezing point -0,8°C
Acceptable product temp. at loading into containers Max. 5°C above carrying temperature
Optimum humidity 90%
Ventilation setting for containers 25 m³/hr
Storage life 2-3 months
Climacteric / non-climacteric Non-climacteric
Ethylene production Very Low
Ethylene sensitivity Moderate
Modified / controlled atmosphere 0%-5% CO2; 5%-10% O2
Potential benefits Low O2 delays senescence
Elevated CO2 may reduce chilling injury symptoms in some cases
Availability
Morocco
Spain
South Africa
South America
November - June
October - July
May - September
June - November

Harvesting and handling

The orange shape varies from spherical to oblong and ranges from seedless (0 to 6 seeds) to seeded (> 6 seeds). Peel color at maturity ranges from light to deep orange but may remain green under warm conditions.
Late season ‘Valencia’ oranges may turn from orange to green (re-green) under warm conditions.

Sweet oranges are generally classified into one of four groups: 1) round oranges like ‘Valencia,’ ‘Hamlin,’ ‘Pineapple’ and ‘Shamouti’; 2) navel oranges like ‘Washington Navel’; 3) blood or pigmented oranges like ‘Moro’ and ‘Tarocco’; and 4) acidless oranges like ‘Succari.’ The fruit can also be divided into early, middle and late ripening varieties.

Like all other citrus fruits, oranges are non-climacteric with no postharvest ripening phase.

A high quality orange is mature, with good color intensity that is uniformly distributed over the surface. Fruit must be firm with a fairly smooth texture and shape that is characteristic of the variety. Grade standards for sweet oranges are based on maturity, color intensity and uniformity, firmness, shape, size, smoothness, freedom from decay, as well as freedom from defects (bruises and abrasions), insects, fungal attack (eg., cake melanose), growth cracks, chemical burns, and physiological disorders.

Cooling and storage

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.

Mixed loads

Oranges should not be shipped with ethylene-emitting products which might promote decay.

Cautions

Low O2 delays senescence. Elevated CO2 may reduce chilling injury symptoms in some cases.

Storage disorders

Alternaria rot, Anthracnose, Aspergillus rot, Black mould rot, Black pit, Black spot, Blue mould, Brown rot, Canker, Chilling injury, Degreening failure, Fusarium, Green mould rot, Grey mould rot, Insect damage, Melanose, Rind discolouration, Scab, Scald, Senescent breakdown, Sooty blotch, Sooty mould.