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Carrot, Daucus carota / Umbelliferae (Apiaceae)
Postharvest Atmosphere Management
The best conditions for long term conservation, up to several months, are temperatures at 0 to 1ºC and 95 to 98% relative humidity, in order to reduce weight loss and to maintain the original quality of the root. The soluble sugar content increases under these conditions, there is an increase of reducing sugars whereas the sucrose remains stable. The amount of carotenes is not affected by these conditions, since it remains constant through all the period. The same happens with the fiber content.

The product’s quality preservation is based on a fast decrease in temperature, that must drop to 5-8ºC. This also prevents damages by hits during the harvesting. The water pre-cooling is the most suitable method used for carrots.

The carrots allow a relatively long storage, although the exact duration and the type of conservation used depends on the type of produce. The carrots with foliage behave in similar way to the leaf vegetables and they can only be kept for few days.

The produce harvested before its maturity (tender carrots) has a higher tendency to perish than the ripe produce; due to its high water content, it also tends to lose turgidity. Ripe carrots, sometimes stored up to 6 months, are usually marketed, like carrots with foliage, in few days. The unripe carrots are kept up to 2 months.

The carrot may acquire a bitter taste when ethylene is in the environment, so it is not advisable to store or transport carrots with other products that give off ethylene, such as tomatoes, melons or apples.
Distribution
During transport and distribution the ethylene concentration must be avoided, since this species is very sensitive to it. The satisfactory conditions vary depending on the type of transport, whether it is by sea or road. The distribution of carrots must be carried out at 5-10ºC and average moisture.

The road transport must be at temperature above 20ºC, depending on the duration. The sea transport must be carried out at 0ºC, and 95-100% relative humidity.

Concerning distribution, temperatures between 5 and 10ºC and average humidity and ventilation are recommended. Direct light must be avoided.
Postharvest Problems
Carrots may show several problems of conservation, caused by unsuitable conditions in the storage rooms, low relative humidity, or by certain fungi that cause rottings in the roots.

Carrots may show different physiological alterations or diseases during their conservation:

Blightness and loss of weight: They are due to the loss of water, and they are prevented in humidity saturated atmospheres.

Sprouting and roots: during the storage, carrots tend to sprout and to give off roots. This process is favoured by high temperatures.

Erwinia is a bacterium that causes humid rotting. This organism infects the vegetable through damages and leaves. The affected area becomes soft and humid and it darkens. The rotting spreads very fast towards the heart of the vegetable.

Watery soft rot: It is caused by the Sclerotinia fungus. The first symptoms are soft and watery injuries, with a white and cottony down that may cover all the vegetable. There appear great, black and irregular matters.

Gray rot: It is caused by the fungus Botrytis, and it develops through the damages caused by harvesting or handling. Gray short hair covers the carrots.

Bitter rot: It is caused by the Geotrichum fungus, that attacks through any area of weak tissues. The infected area decolours and becomes watery. The carrots give off a vinegar smell, and a white down develops on the carrot.

Black rot: Caused by the Stemphylium fungus, it covers the affected areas with a black down.
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