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Grower himself determines the return of storage

24 November 2021

Drying and wound healing at the right temperature

The harvesting conditions and the possible presence of hollow or rotten tubers determine the intensity of drying during the first few weeks after harvesting. This phase of storage has a major impact on the final storage result. The aim should be to prevent fungi and bacteria from affecting healthy potatoes. At the same time, the wound healing must take place. If wound healing is good, loss of moisture during storage will be lower. The loss of moisture due to skin damage is up to 300 times higher than with a well-peeled (or injured healed) skin!
Wound healing is faster at a higher temperature and r.h. (>80%) and a low CO2 content. So when product comes in cold (<12 °C), it is recommended to heat the product with a heater to ± 15°C. Another advantage of this is that, at higher outside temperatures, it is also possible to ventilate with outside air in order to dry out a little more, if desired.


Short but powerful cooling (not too cold)

Short-term cooling with outside air with a larger temperature difference (up to 3°C for potatoes) ensures that ventilation with outside air takes place for a shorter period of time and cooling takes place more quiincrease the rate of cooling. This prevents unnecessary weight loss through external ventilation.

Temperature and r.h. Moisture content g/m3 Energy content (enthalpy) kJ/kg Cooling capacity kJ/kg
Ait for potatoes 13°C, 95 % 10,7 35,3
Outside air 12°C, 80 % 8,6 29,5 5,8
Outside air 10°C, 90 % 8,5 27,2 8,1


The above example shows that the outside air of 12°C and 10°C has approximately the same moisture difference with the potatoes. But the cooling capacity of the colder air is 8.1 – 5.8 = 2.3 kJ/kg = 40% greater! So with 40% less ventilation and drying out, the desired temperature is reached.

However, this does not apply to batches with rot, as it would be better to work with a smaller temperature difference. Cooling will take longer, which will also allow more drying time, so that the moisture from leaking tubers is better drained.


Storage temperature

Rapid cooling to the optimal storage temperature, ensures a lower respiratory rate. Less starch is then converted into sugars, which are used for maintenance respiration of the tubers. This also contributes to limiting weight loss. However, this contribution to the total is less than due to moisture loss due to incorrect ventilation. What is especially important is that the storage temperature is constant and adapted to the variety. The more constant the storage temperature, the less germicidal the potatoes are. Because temperature changes and condensation moisture stimulate germination.

This also means that in changing outside temperatures, close attention is paid to settings that determine when the storage starts with external ventilation (outside temperature versus product temperature). By reducing thit setting, cooling starts just a little earlier, reducing the temperature fluctuations in the product. The Vision Control can also do this automatically with the Weather in Control module.


Mechanical cooling

With a mechanical cooling, keeping the storage temperature constant is no problem. It often results in a high energy bill. Ventilating and cooling with outside air always costs less energy than when the compressor has to be started. The advantage of mechanical cooling is a lower weight loss. In long storage until summer, this can be up to 3% less weight loss. In net terms, therefore, there remains more marketable product.

To limit the energy consumption of the cooling, set the climate computer to not allow it to cool too much at the product temperature during the day. The installation can then cool more efficiently during the night. That saves energy. If energy is generated by solar panels on the farm, the situation can also be reversed, so cooling during the day does save money.


Germ inhibition

The new sprout inhibitors for ware potatoes are a considerable cost item in long-term storage.
The effect of administration must therefore be as high as possible. The application of the new generation of sprouting inhibitors requires that the product, room and cooling system must be dry (no condensation water) and the correct air circulation (reduced speed) is applied. The substance is then distributed in a good way. Keep the room closed for 1 to 2 days after treatment and occasionally ventilate briefly internally. Switch off the cooling for a while to prevent condensation from forming, which can cause the agent to precipitate and possibly damage applied materials in the storage.

Pay close attention to the progress of the germination. That is what determines the moment of the next treatment. A tight and flat storage temperature without condensation is the basis. Sufficient (and not too much) CO2 refreshment based on readings from the CO2 sensor ensures that the baking quality is maintained and extends the time-span of the germination inhibitor. A successful application of germination inhibitors is more than ever the basis for a high retention rate this year.


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