How to preserve onion

La conservación de las cebollas en cámaras refrigeradas


Onion, Allium cepa, is a vegetable with beneficial properties for health and one of the essential foods in our cooking.


Like garlic, it is original from Central Asia and Mediterranean Sea regions, but it actually can be found everywhere because it is one of the most cultivated vegetables in the world.


Varieties and planting date are important factors to guarantee the success of its growth, where the variety determines the ideal season for cultivation. In order to preserve all the qualities of onions it is essential to make a good preservation in specialized cooling rooms for onions.


Onion requires several operations before storage, one of the main is drying, which favours its conservation.


The objective of drying is to remove all the superficial humidity from the external layers, sealing the onion and stem. With this process is not intended to dry inside bulbs but only the external layers.


A correct cooling preservation gives us a longer life for onions.

Onion storage
will be made in wooden palots, previously dried. Its location inside the room should be made in order to allow a right air circulation as well for the evaporators as for supported fans, not overloading the storage maximum capacity. Storage should be made in constant humidity and temperature, avoiding fluctuations, and totally darkness, because bulb is still alive.

For this we need a specialized cooling room for onions.


Onion temperature changes should be made slowly, trying to keep the same temperature inside the bulb and in the external layers, because with abrupt changes in temperature bulb cells can be destroyed. It is recommended to cool or heat as maximum 2ºC per day, depending on different factors (temperature, humidity, etc…).


Onion must follow some rules to be storage:


  • It must be a valid variety to be storage.
  • Bulb must be firm and compact.
  • Bulb must have a low content of superficial water (drying).
  • Must be correctly cultivated under good agricultural practice.


Other important factor to bear in mind is shipping, un-storage must be planned during hot and humid conditions.


Temperature: it must be the right one to avoid the onion become rotted, going up to -0,8ºC

Humidity: it must be between 65 and 75%.

Air: for a more homogeneous temperature is important a right air split inside the room.