Long-term potato storage
Keeping potatoes is as important as producing them. Potato tuber contains about 75% water, due to this it gets very easily sick during storage from so-called storage diseases: wet rot, dry rot, rot due to potato blight, etc.
But the potato has built up, over time, and some positive traits, which ensure some resistance to preservation. Let’s see what these are.
Maturity: for long-term storage, potatoes must be picked at full maturity. Harvesting them must be done on time.
– new potatoes: they are harvested for fresh sale . They are not harvested for storage, especially long-term storage. At the time of harvest they are considered a delicacy / truffle.
– mature potatoes: most potato crops are prone to medium and long term storage. Storage conditions differ depending on the variety and final use of stored potatoes: sale as such or potato processing industry.
Temperature: the storage temperature of the potatoes is determined by the final use of the stored potatoes.
Humidity: relative humidity should be maintained between 90 – 95%. If the relative humidity drops below the level of 90% the potatoes will dry out and show wrinkles on the surface.
Lighting: potatoes must be stored in total and constant darkness.
Ventilation: it must be ensured at a minimum level, to avoid dehydration, but sufficient to eliminate the surplus of CO2 generated by potatoes during storage.
During the storage of potatoes must be observed the 5 steps as follows:
– Stage 1 (blowing): it is a very important and delicate process at the same time. It has the role of removing excessive moisture from the tubers without dehydrating them and preventing the spread of infections in the potato mass.
Process: including mechanical ventilation with fresh air at a temperature of 2..3°C lower than the temperature of potatoes.
Duration: between 3 – 5 days.
– Stage 2 (wound healing): it is a process in which potatoes are kept for a long period of time, the period in which potatoes have the opportunity to heal surface injuries sustained during harvesting, transportation and storage. This healing is done to prepare potatoes for storage. The decrease in the number of” open wounds ” leads to a decrease in the chances of infection during storage. Of major importance is the system of maintaining the necessary humidity.
Attention: if during this period the development of “potato blight” is observed, the affected potatoes should be removed.
Process: mechanical ventilation with cold intake at a temperature 15-16°C / humidity 95%.
Duration: 15-25 days.
– stage 3 cooling : after blowing and wound healing the cooling process is very important. Cooling should be done in such a way that the potatoes do not lose weight and pre-prevent the formation of sugar in the potato. It is very important that during the cooling period the heating of potatoes is not carried out – this accidental heating can cause the beginning of the germination period which is fatal for the stored potato.
Process: mechanical ventilation (10-12 times / day), gradual cooling with 0.3-0.5°C / day with an air temperature not lower than 2°C compared to the temperature of potatoes.
Duration: 30-60 days.
– Step 4 storage: starts when the potatoes have reached the final storage temperature. Temperature / humidity conditions may vary depending on the final destination of the potatoes, namely: potatoes for chips will store at +..+ 12°C / 90% rH , potatoes for frying will store at + 5… + 6°C / 90% rH , potatoes for consumption will store at +4++7°C / 90% rH, potatoes for seed will store at+3.5…+5°C / 90% rH, potatoes for starch will store at+4. + 5°C / 90% rH.
Process: mechanical ventilation with cooled air, maintaining constant temperature + humidity.
Duration: 90-180 days.
– stage 5 heating: this stage begins about 10 – 15 days before the delivery of potatoes and represents the reverse process of cooling potatoes.
This heating stage is performed with two purposes: time is given to the reducing sugars produced during cooling to turn into starch( avoid the Maillard reaction), condensation is avoided on the surface of the potatoes at the time of delivery.
Process: increase the storage temperature to a level of + 8..+ 10°C.
Duration: 10-15 days.
For storing potatoes you can choose one of the following systems:
– simple wooden boxes with the possibility of good ventilation (ventilation) stored in mechanically ventilated spaces and equipped with refrigeration / humidification systems.
– wooden boxes provided with a suction side and a pressure side stored in ventilated / refrigerated spaces provided with a logical process unit.
– bulk storage in warehouses provided with ventilation through the floor / ventilation channels and equipment for temperature / humidity control.