The three key environmental factors that require monitoring and control during potato storage to maintain quality and reduce stress are temperature, humidity, and CO2. When these environmental factors are outside of desired ranges, the potatoes are subject to stress.

In-store, potato tubers continue to respire, consuming O2 and internal sugars (converted from stored starches) and producing CO2, water, and heat.

Even though the respiration rate of well-stored, dormant spuds is rather low, experts say that several factors (e.g. warm temperatures, stress, injury, physiological age, ethylene) can cause the respiration rate to increase. Respired CO2 in a bin of stored tubers will accumulate quickly if not removed by ventilation. CO2 concentrations, which greatly exceed ambient levels, can easily occur in cultivar storage bins, accompanied by depletion of O2.

Several studies have shown that tuber respiration rate is highly dependent on ambient temperature. Also, elevated CO2 (5, 10, and 15%) reduces suberization. Lofty CO2 either increases or inhibits sprouting, depending on the maturity of the tubers. Raised CO2 in combination with rather low O2 concentrations, i.e. classical controlled atmosphere conditions, inhibits sprouting, while exposure to CO2 concentrations above 10% can cause tissue necrosis.

Despite these conflicting findings, or possibly due to them, many storage operators now monitor the CO2 concentration in the atmosphere of their potato rooms to protect processing color. Automated equipment engages the ventilation system when the CO2 concentration passes a selected threshold, usually 0.5 to 1%, v/v.

From farmer to fryer, the cultivars (especially the ones grown to make potato chips) are sensitive to environmental conditions that affect their fry quality (appearance, taste, and appeal when processed). One of the most unpopular chip defects – dark brown spots on the chips – is a result of exposure to elevated levels of carbon dioxide (CO2) during storage.

You can read the rest of this article in your complimentary e-copy of Issue 2 of Potato Business Digital 2022 magazine, which you can access by clicking here.