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Cherry, Prunus avium / Rosaceae
Postharvest Atmosphere Management
After the harvesting it is recommended to transport the cherries in freezer lorries. If this is not possible, we must take into account that they must be put in cold rooms within the 4 hours that follow the harvesting, considering that they must not be subject to high temperatures during the transport. The processes causing quality loss are three times faster at 20ºC than at 10ºC. At any rate, it is necessary to reduce as much as possible the time between the harvesting and the arrival at the cold storage room.

During the transport and storage takes place the ‘respiration’ of the fruit. It is very important to keep them at low temperatures so that the rate of respiration of the fruit and the subsequent heat emission is the minimum. When emitting heat, the temperature increases, so the foodstuffs decompose rapidly.

The temperature at which the cherries must be put under depends on their immediate use; if the fruit is intended for immediate consumption, it will not require the same treatment for keeping quality. If the cherries are sold the day after their harvest, they should be stored in cold rooms at 8-12ºC. However, if they have to be kept for more than 8 days after their harvesting, they must be stored in cold storage rooms at 0ºC to assure their arriving to the consumer in perfect condition.
Days from harvesting to marketing::Optimal temperature (ºC)
1-2::8-12
4-6::4-8
6-8::0-4
8+::0


Source: Cherries: WEBSTER A.D. & N.E. LOONEY (1996). Crop Physiology Production and Uses.

When the cherries arrive from the field they are usually cooled with different methods before they start preparing them, this is what we call precooling. For this purpose they use water or air at low temperatures.

Relative humidity, the water content in the air, is due to be taken into account for preserving the cherries. Cherries have high quantities of water; if the environment is extremely dry the fruit has a tendency to loose water and to dry, and that is why this parameter should be controlled. Therefore, we must keep relative humidity as high as possible, so the cherry looses the lesser quantity of water possible.

Once we have removed the leaves and the cherries that satisfy the minimum requirements, they are subject to a second precooling before they are packaged. Immediately afterwards they are taken to the cold rooms where they will be kept until they are sold.

Inside these rooms there is a modified atmosphere that diminishes the deterioration of the fruit. The temperature is usually around 0ºC. The fruit is put in polyethylene bags, a kind of plastic where the oxygen levels are between 3-10% and carbon dioxide at 10-15%. All these procedures allow to keep the harvest without losing its properties from 6 to 10 weeks. It is possible to maintain the cherries in perfect condition for a time, but, with no doubt, cherries are not adapted to be stored for long periods of time.
Postharvest Problems
If the keeping quality processes are not carried out properly or if the produce is not packaged correctly, there may appear some diseases that could spoil the fruit in short time.

Cherries may show various physiological alterations or diseases during their storage and conservation.

- Brown rot: Caused by a pair of fungi called Monila fructicola and Monila laxa3; the symptoms are brown or black spots that spread rapidly all over the fruit. On the damaged tissue there grows some short hairs.

- Gray mould (Botrytis cinerea): It is possibly the worse disease of the harvested cherries. The infection takes place in the field and later on it is developed in the storage rooms. At the beginning it is a brown spot, afterwards the fruit meat turns watery and the spot acquires a darker colouring.

- Blue rot: Caused by the fungus Penicillium expansum, it normally gets in the fruit through a damaged part of the skin. The first symptom is a light brown spot, then the damaged tissue seems to be soft and watery, later on the skin tears off and there appear white spots of mould.

- Ryzopus spp. rotting: The infection takes place in the same way as the blue rot; this fungus does not develop below 8ºC. It shows white fibers that will develop spore heads.

- Alternaria (Alternaria spp): It has the form of a spot in the skin with olive coloured spores and white fibers. The damaged tissue is later on teared off from the meat that surrounds it.

- Fungus Cladosporium herbarium: When the tissue deteriorates it turns dry and hard and the colour changes from gray to black. Usually, this fungus infects the fruit through the injuries of the skin.
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