Onions can be stored in one of the following ways:
🔰 in bulk
🔰 in very large boxes (crate)
🔰 in packages placed on pallets
🔰 in packaging bags like Rachel bag
🔰 in small containers
🔰 optimal storage conditions
Long-term storage of onions can be done at different temperatures as follows, depending on the storage system and the type of onion's resistance to cold:
⚫️ The temperature and relative humidity of the warehouse must remain constant during storage. Acceptable change of temperature and also relative humidity is from +1 to -1 degrees Celsius and +5% and -5% relative humidity respectively. ⚫️Relative humidity of the warehouse is very important for onion storage. Usually, the relative humidity of 5-65% is known as the standard condition for onion storage.
⚫️ Natural or artificial ventilation should be used for storage at ambient temperature in warehouses that do not have artificial cold.
⚫️ Whenever the temperature outside If the warehouse is lower than the temperature inside it, the outside air can be allowed into the warehouse.
⚫️In order to avoid the risk of cold damage to onions, you should not let air whose temperature is less than 3 degrees Celsius into the warehouse. In terms of quality, during the storage period of onions in cold storage, stems and roots are not produced during the first two months. But after this period, more care is needed in keeping onions in the warehouse. Root growth is the result of high humidity and stem growth is due to the high temperature of the warehouse. ⚫️ Temperature of 10 to 20 degrees Celsius is the worst temperature for onion storage and reduces its quality. But at a temperature of 2 to 4 degrees Celsius, onions can be stored for up to 5 months, but with an increase in the duration of storage at a high temperature, germination becomes faster.
⚫️Onion spiciness index, pyruvic acid, is directly related to the storage temperature and the amount of water in the onion tissue.
⚫️In general, sorting and especially the grading of onions of different cultivars in terms of size has a positive effect on the quality of stored onions. .
⚫️The harvest of the onion crop should be done with full care and its injury should be avoided as much as possible. Let it dry. Nitrogen fertilizers, when used excessively, shorten the shelf life of onions. When transferring onions to the warehouse, mud, soil, and field pollution should be removed. ⚫️Onions that have not obtained the desired dryness in the field should be dried by air circulation.
⚫️The environment of the cold room should be dark.
⚫️Whenever the temperature difference with the environment outside the warehouse is more than 10 degrees Celsius when the onion leaves the cold storage, the temperature of the onion should be gradually brought closer to the air temperature with special equipment to prevent the accumulation of water droplets. and bubbles should be prevented.
⚫️ Modern onion warehouses should be designed in such a way that ventilation is possible from all sides. The ground level is spaced and the roof of the warehouse should be about 60 cm higher than the stored onions.