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Fruit and vegetable storage - conditions
Potato storage
Potatoes can be stored both in mechanically-ventilated warehouses, as well as in refrigerated warehouses. Specific potato-storage requirements must be met for them to be kept in the best state for a long time.
Thus, in mechanically-ventilated warehouses, potatoes are stored in piles with a height of 4 m. There are 5 storage stages, and ventilation differs depending on the stage.
The first stage, the drying starts with the introduction of potatoes into the warehouse; its goal is to dry wet tubers, in order toprevent the spreading of infections. It takes 3-5 days, during which potatoes are ventilated with fresh air at a temperature 2°C lower than that of the potatoes and a humidity of 75-85 %.
The second stage, wound-healing, takes between 2 and 4 weeks. This period is necessary as, during this stage, wounds are healed by the formation of the wound periderm.
The third stage is cooling and consists of decreasing the potatoes' temperature down to the storage value. Cooling must be gradual, by 0.3-1°C per day, in order toprevent sugar formation in the tubers. This aspect is particularlyimportantfor chips potatoes, in which case highsugar content causes the chips to go black when fried.This stage takes 30-60 days;the ventilation time is 8-12 hour per day in several series.
The cooling stage finishes when potatoes have reached the best storage temperature. This may vary between 3.5 and 5°C for seed potatoes, 5 and 7°C for consumption potatoes and between 8° and 12°C for chips potatoes.
The fourth stage, storage, follows and it takes between 3 and 6 months. The goal of this stage is o maintain a constant temperature.Cooled ventilation air is used; its temperature should be 1-2°C lower than that of the potatoes.
The fifth stage, preheating, occurs two weeks before taking the potatoes out of the bays. At this stage, the potatoes' temperature is increased to 7-10°C.
Potatoes' storage in refrigerated warehouses is slightly different. Potatoes are stored in crates which are piled on 6-8 levels, and cooled air circulates in the spaces between the crates.
Potatoes can be stored in piles, as well, but solely in refrigerated bays with in-floor ventilation, the pile height ranges between 4 and 5.5 meters.
In refrigerated warehouses, potatoes can be stored longer, 7-8 months; the best storage temperature is 3-5°C and a relative humidity of 80-85%.
Onion storage
Onion can also be stored in mechanically-ventilated, as well as refrigerated warehouses.
In mechanically-ventilated warehouses, onion is stored in piles with a height ranging from 3 to 3.5 m. In this case, too, specific storage stages are observed, and the ventilation period depends on the stage.
Thus, the first stage is hat of drying, which lasts between 8 and 10 days, the ventilation time is 18-20 hours per day. Dry air is blown from outside at a temperature 6°C higher than that of the onion and a relative humidity of 60-70%.
The cooling stage starts when the bay is filled and finishes when the onion reaches the storage temperature.Ventilation is done at night, for 8-12 hours per day.
The storage stage takes between 3 and 6 months and the storage temperature is maintained around 0°C and relative humidity around 75%.
Onion can be stored in refrigerated warehouses in piles (in warehouses with in-floor ventilation) or in crates. The same technological stages of ventilation are observed as in the case of mechanically-ventilated storage.
Carrot and root vegetable-storage
Root vegetables (carrots, parsley, parsnip, celery, red beet, radishes) are stored in refrigerated warehouses. Within maximum two days after being harvested, they must be stored.
Before storage, root vegetables with go through the conditioning stage, which represents the quality sorting and removing leaves.
Root vegetables are stored in wood or plastic crates. They must not be washed and must be stored in warehouses with no source of light. The best storage temperature is around 0°C and relative humidity of 90-95%. The storage period ranges between 5 and 6 months.
Apple storage
Apples are stored in refrigerated warehouses with normal or controlled atmosphere, as well as in warehouses with natural ventilation.
Apples must be stored immediately after being harvested and be stored in lots of the same cultivar.
Apples are stored in crates piled on 8-9 levels, with a height of 5-7 m, the distance between the highest crate and the ceiling must be 80 cm. A gap of approximately 20-30 cm must be left between the walls and the plies so that air can circulate.
The filling of a bay should not take longer 2 weeks; during this period ventilation must be provided.
The storage temperature depends on the apple cultivar. Thus, Golden and Red delicious apples are stored at a temperature varying between 0 and +1°C. Ionathan and Ioared apples, more sensitive to cold, are stored at temperatures between +3 and +4°C. The air relative humidity is 90-95%.
In refrigerated warehouses with controlled atmosphere (2-3% O2 and 1-3% CO2), the storage temperature will be 0.5-1°C higher, depending on the cultivar.
The storage length differs depending on the cultivar, Golden and Red delicious apples can be stored for 5-6 months in refrigerated warehouses with normal atmosphere and 7-8 months in controlled atmosphere warehouses.
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