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The need to ventilate and cool in potato storages

December 20, 2022

Plants grow because they capture carbon dioxide with the aid of energy from solar radiation. Photosynthesis generates sugars that upon respiration produce the energy needed for the biochemical processes associated with growth.

These processes include the production of proteins and starch. Where photosynthesis incorporates carbon dioxide, respiration releases it. Photosynthesis is a reduction process that requires energy, respiration is an oxidizing process where energy is released as heat. As a result, potatoes after harvest no longer accumulate sugars that are transformed into starch, as they did before harvest when still growing. After harvest, they only respire sugars producing carbon dioxide and heat (C6H12O6 + 6O2 -> 6CO2 + 6 H2O + energy).

Unfavorable conditions

With tubers piled in bulk in a heap, in bags or boxes they accumulate carbon dioxide and heat, two conditions that disfavor their storability. The respiration rate of all living organisms including potato tubers rises with temperature and the temperature of the potato tubers increases with respiration. These two selfreinforcing activities are stopped or reversed when the tubers are ventilated to cool down and remove carbon dioxide. There are other sources of heat that need to be removed from the store: the additional heat introduced by the tubers when harvested at high temperature, leakage of heat from outside notwithstanding insulation and heat leaks through doors and shutters. Besides, machines such as fans also produce heat that needs to be removed from the store.

Potato tubers stored at a higher temperature respire at a higher rate. The rate increases about two-fold with each 10 °C temperature increase, the Q10 temperature coefficient. Respiration, beside carbon dioxide, also produces heat. Freshly harvested tubers have a high respiration rate because of the processes involved in skin hardening but once cured the rate and heat production drops to half the initial rate. At the end of the storage period sprouting causes another increase in the respiration rate and heat production. Ventilation with air cooler than the surrounding tubers cools them down and lowers the respiration rate and heat production.


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