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Chinese cabbage, Brassica rapa / Cruciferae (Brassicaceae)
Postharvest Atmosphere Management
It is always recommended to precool Chinese cabbages, specially when the environmental temperature at the moment of harvesting is high.

Cabbages must be cleared from damaged external leaves before they are stored. If they are maintained between 0 and 1ºC with a humidity near 100%, they last 1 or 2 months. The temperature varies according to the variety, since some varieties are more sensitive to cold than others.

As other cabbages, this species is sensitive to ethylene, that produces the decolouring and abscission of the leaves; thus, there must be an adequate ventilation in the storage room.

Modified atmosphere is not very usual for Chinese cabbages, since the suitable conditions are still not very clear and they lack commercial interest. However, and as general standard, it is recommended 1 to 2% of oxygen content and 0 to 5% of dioxide carbon, at a temperature of 0ºC.
Distribution
Chinese cabbages must be distributed at low temperatures and high relative humidity in order to avoid water loss, specially when the pieces are not prepackaged in plastic. Besides, high ethylene concentrations must be avoided.

Given the sensitivity of Chinese cabbages to ethylene, it is important that they do not travel together with species that produce this gas. They must also have a suitable ventilation.
Postharvest Problems
During conservation, Chinese cabbages can be attacked by diseases such as gray rot or alternaria rot. There are also physiological alterations that diminish their quality, like yellowness and browning of the main nerves.

Among the pathogenic diseases are the following:

Alternaria brassicae produces alternaria rot. This disease consists of spreading round spots of necrotic tissue.

Erwinia carotovora is a bacterium that causes a soft rot, mainly in cases of scarce ventilation. It is characterized by humid and soft areas, that give off a bitter and unpleasant scent.

Gray rot: it is caused by the Botrytis cinerea fungus, and it is characterized by gray down in the rotten area.

Other fungi that affect Chinese cabbages are Mycosphaerella brassicicola and Rhizoctonia solani. The former produces dark brown or black annular spots, where the tissue dries.

The most important physiological alteration of the Chinese cabbages when storaged is the yellowness and bnrowning of the main nerves. It develops in the most external leaves, beginning in the base and spreading upwards and towards the interior. This alteration is considered to be due to cold in long storage. The varieties have a different sensitivity to this problem.

" Tip burn": this alteration is characterized by the death of the internal tissue, on which later on appear rots caused by fungi or bacteria. It is thought that the death of these tissues is influenced by problems of calcium transport in the plant.

Another alteration affecting Chinese cabbages is the appearance of small black spots.
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