Blog de SVPlants
7 Sep 2014
Advice for the harvest and post-harvest handling of leeks.

The post-harvest period runs from when the leeks leave the field to the time they are consumed. The crop and all its inherent quality attributes may be lost if it is not carefully and appropriately handled before, during and after harvesting. Apart from this obvious observation, it is worth mentioning a number of recommendations to guarantee that our leeks reach our customers and consumers in the best conditions, ensuring optimum freshness, texture and taste.

  • Before harvesting:

Keep your leek plants clean and free from fungi and bacteria.

  • During harvesting:

Harvest early in the morning or in the afternoon, avoiding midday. You want your leek plants to be refrigerated at the lowest temperature possible.

Place your leek plants in boxes or containers that allow free circulation of air inside.

Do not overload the boxes or containers of leeks as you want them to be cooled quickly and uniformly.

  • Post-harvesting and storage:

Precooling is an essential step immediately after harvesting; hydrocooling and vacuum cooling are both recommended methods, as is contact icing, a common practice in North America. This involves bringing the crop to 0ºC as soon as possible and keeping it at this temperature and at a relative humidity as close to 100% as possible. Under these conditions the plants can be stored for between 2 to 3 months.

A low temperature delays leaf sheath elongation and its curvature, both being factors that affect quality. It also causes a loss in the intensity of the green colour, another sign of freshness. Leek plants do not produce ethylene but are moderately sensitive to this gas, which can hasten softening and the appearance of diseases. Leeks are not sensitive to cold injury; they show moderate wilting with a weight loss starting at 15%. Another serious problem that leek plants can have during storage is rot caused by fungi and bacteria. The most common is grey mould, caused by the fungus Botrytis porri. Other plant diseases caused by Phytophthora porri are downy mildew and Alternariaporri. A bacterium that affects leeks during storage is Erwinia carotovora, which results in a wet rot.

The use of modified atmospheres allows leek plants to be stored for up to 5 months. However, these practices are not normally used on leeks given that they keep well on their own for several months. That said, the optimum conditions for this vegetable type are 1-6% oxygen and 5-10% carbon dioxide, at a temperature of 0ºC. 

In some countries they have managed to extend the freezing period up to 5 months at temperatures close to –3ºC. The leeks are covered in plastic to avoid them drying out. At the end of storage they need to be slowly defrosted at 0.5ºC for a period of 48 hours. If the leek plants are cleaned and vacuum packaged in bags, this will result in fewer losses.

  • Distribution:

Leek plants should be transported at temperatures close to 0ºC. However, they are regularly distributed at 5-10ºC; under these temperature conditions there can be high weight loss, meaning that measures must be taken to prevent the product from dehydrating. Moisture levels should be high and direct sunlight and stacking should be avoided.

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