Oranges

Infobox on Oranges
Example of Oranges
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

Oranges

Harvesting and handling

Oranges, as is usual for citrus fruit, are most significantly classed by seasonal availability:

• winter oranges from the countries of the Mediterranean from November to June
• summer oranges from overseas countries from June to November
  
  

Oranges are also divided into early, middle and late ripening varieties. The varieties also sometimes share a typical fruit colour, a distinction being drawn between blond, blood and late oranges. Navel oranges are the most important variety of blond oranges. Blood oranges are subdivided into deep blood oranges (peel and pulp red) and light blood oranges (peel with or without slight red coloration, pulp red). The degree of ripeness of citrus fruit is determined on the basis of three criteria:

• by the ripeness index: this is determined by the Brix value, which is a measure of the sugar/acid ratio of the fruit.
• by cutting at purchase:freshness is determined by cutting the fruit in half from the stem-end to the opposite end. If the fruit is withered at the stem-end, it must not be shipped;
• by peel colour: the colour of the peel is not necessarily a reliable indicator of ripeness, but its surface gloss is.
  
  

Waxing to prevent loss of aroma and weight is required because the washing process removes the natural wax layer. The film of wax sprayed onto the peel only partially seals the pores so that the fruits are still able to respire. A high quality orange is mature, with good colour 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. Fruit should be free from decay, defects, and blemishes.

Cooling and storage

Prompt cooling soon after harvest should be applied and optimum pulp temperatures should be reached within a few days from harvest. The addition of fresh air is extremely important as citrus fruit can start to ferment within a few hours due to anaerobic respiration. If ventilation is inadequate, storage damage may occur, taking the form of a bitter flavour and peel scab. Depending upon the species and variety, all citrus fruits are highly cold-sensitive. Grapefruit, lemons and limes are more susceptible to chilling damage than are oranges and mandarins, and late-ripening varieties are more temperature-sensitive than early varieties.

Chilling damage is manifested in citrus fruits in particular by spots on the peel (brown dots on the peel), accompanied by a bitter taste and unpleasant odour, rot and cell wall collapse. The glossiness of the peel is lost and the albedo layer (inner layer of the peel), which is normally white, turns a dark colour. When the fruit is divided up, the segments, which have a low juice content, break up and the whole fruit is glassy and soft. The severity of the chilling damage is determined not only by the extent to which the temperature has fallen beneath the limit, but also by the length of exposure to this temperature. Moreover chilling severity depends upon cultivar, production area, harvest time and maturity-ripeness stage at harvest. Moderate to severe chilling injury is usually followed by decay.

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.

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.