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Broccoli, Brassica oleracea var. italica / Brassicaceae
Postharvest Atmosphere Management
Broccoli
The broccoli has a bad conservation, reason why it is not usually stored. If we want to preserve it, the suitable conditions are 0ºC and high relative humidity, which allows it to be stored for 2 weeks. This period may extend with modified atmospheres, that are spontaneously generated in packages closed with plastics, in which the oxygen is reduced and the carbon dioxide increases as a result of the transpiration of the product.

The broccoli is a highly perishable product, for which it is recommended to be precooled as soon as possible after its harvesting. In this way, the rancidness and yellowness are delayed.

The most recommended methods are water pre-cooling or humid air cooling. The latter, which takes place before the packaging, dampens the broccolis, without contributing to water accumulation. This reduces the risk of bacterial rots, since the growth of these organisms is favoured if there is water in the environment and the temperature is not low enough. Another method used in the United States is precooling with a mixture of water and ice.

The broccoli is stored in counted occasions, and only if the market requires it, since it is very perishable. The optimal conditions at 0ºC and 90-95% humidity allows it to be conserved for 2 weeks. It must be separated from products that produce ethylene, since this species is very sensitive to this gas. It accelerates its aging and therefore shortens the period of conservation.

Modified atmospheres can be used, prolonging the conservation at 0ºC or conserving in higher temperatures. The recommendation is to use a level of 1-2% oxygen and 5-10% carbon dioxide. However, this system is not used commercially. On the contrary, the effect of spontaneous modification that takes place inside the covered plastic packages is often used; with the transpiration of the product there is a reduction of oxygen and an increase of carbon dioxide. In order to obtain these modified atmospheres it is recommended to use materials with suitable permeabilities, that do not confer strange flavours or scents to the heads.
Distribution
As much for the transport as for the distribution of the broccoli, it is recommended to keep humidity as high as possible and temperatures the nearest to 0ºC as possible, given that it is a high perishable vegetable.

The conditions adapted for the transport of broccoli are temperatures of 0 to 5ºC and 90 to 95% of relative humidity. In the United States they sometimes use crushed ice.

Concerning distribution, relative humidity must be always high to avoid the drying of the product; temperatures must be as low as possible.
Postharvest Problems
There are several problems that damage the broccolis during their storage. They may have different physiological alterations such as the browning of the stem’s cut zone or hollow stem, along with diseases caused by certain fungi and bacteria.

During the conservation of the broccoli several pathogens may attack causing rots and therefore diminishing the product quality or making them unsuitable for sale.

Botrytis cinerea: it is a fungus that produces rots with a gray or pale brown coloured down.

Erwinia carotovora: it is a bacterium that attacks mainly in conditions of excessive humidity and high temperatures. It produces a brown and watery spot that extends from the flower buds towards the inside.

Alternaria tenuis: this fungus produces small dark spots on the flower buds. A dark grey or black down appears on them, along with a soft rot.

Other parasites that affect in this stage are the Sclerotinia sclerotiorum fungus and the Pseudomonas maculicola bacterium.

There can also be physiological alterations, such as the development of a hollow stem, characterized by a cavity in the central part of the stem of the inflorescence base. This physiological alteration begins with the browning of the stem’s tissues, with a subsequent disintegration of the pith.

We can also see the browning of the surface of cut in the peduncle. This phenomenon is solved by cutting the brown area, or maintaining the oxygen below 1%.
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