The right temperature for potato storage
Find out which storage temperature suits table, seed and French-fry potatoes and how to avoid rot and sugar defects with the 5-phase plan.
The right temperature for potato storage
Unfortunately, the most common question before storage has no single correct answer. “How cold should the potatoes be?” depends on what they will be used for and what stage of storage you are in. A table potato that is supposed to still look flawless in spring needs something different from a potato that will be processed into fries in February. And the temperature you start with in September is not the temperature you will be storing at in December.
This article provides specific guideline values by intended use, explains the roadmap from harvest to long-term storage, and shows the mistakes that cost substance and money every year.
Why temperature determines success or loss
A harvested potato is not dead. It continues to breathe, breaks down starch and converts it into sugar. It is precisely this metabolism that we want to slow down as much as possible in storage without damaging the tuber.
How strongly temperature drives metabolism in plants is described by the so-called temperature coefficient. For potatoes it is around 1.2 to 1.3. This means: for every 10 °C increase, respiration and sugar breakdown increase by a factor of about 1.3. Cool temperatures therefore slow things down, which is why most potatoes are stored cold.
It would be that simple if it weren't for the crucial catch: at low temperatures the tuber converts more starch into sugar. This is the cold-induced sweetening effect, and it is the reason why there is no single perfect temperature. Every value is a compromise between respiration, sugar formation, sprouting, wound healing and cooling costs.
Storage temperature by intended use
In practice, table potatoes often end up at around 4 °C. This is cold enough to slow sprouting and respiration, yet warm enough to prevent the tuber from noticeably accumulating sugar.
Seed potatoes follow a different logic. Sprouting is desirable later in the field, but not in storage. That is why they are kept cooler and the higher sugar content is accepted, because it is irrelevant for propagation.
Why processing potatoes are kept warmer
Anyone producing for the fries or crisps industry cannot simply cool down to 3 °C. In the cold, reducing sugars accumulate. When fried, these sugars react with the amino acid asparagine to form acrylamide, a substance suspected of increasing the risk of cancer. This is visible in fries and crisps that are too dark and bitter.
This is not just a matter of quality, it is now also regulated. The EU Acrylamide Regulation (EU) 2017/2158 requires storage above 6 °C for processing and a low sugar content in the raw material. Processors pass this requirement on to growers via supply contracts. Anyone supplying processing potatoes therefore deliberately stores warmer than the neighbouring table-potato farm, even if this means more sprout suppression and cooling outside the harvest season. For more on what other rules apply here, see our overview of applicable standards in potato production.
Storing is a schedule, not a setting
The most common misconception: aiming for the target temperature on day one. Freshly harvested potatoes that are blasted directly to 4 °C will not heal their wounds, will condensate in cold spots and, in the worst case, start to rot. Temperature is guided over weeks, not set. A typical cycle for table potatoes has five phases.
1. Drying
Immediately after harvest, soil with residual moisture clings to the tubers, plus dampness from the ground or rain. Moisture on the skin is the ideal breeding ground for fungi and bacteria. That is why the process starts with rapid, vigorous drying with plenty of air. Warm air absorbs more water and dries faster, cold air more slowly. Regardless of temperature, nothing works here without ventilation. Many farms put the crates under powerful fans for a night before they go into the actual store.
2. Wound healing
During harvesting, loading and decanting, tubers fall from a height of over a metre, sustaining cuts and abrasions. These wounds are entry points for diseases and accelerate water loss. The tuber can seal them itself by forming new cell layers over the wound, but only with sufficient warmth.
How much warmth helps here is shown by a simple comparison: at 5 °C practically no protective cell layers form over a wound, at 10 °C there are two, at 20 °C four. That is why, after drying, potatoes are kept for one to two weeks at 12 to 15 °C, with high humidity and enough oxygen. This costs some weight through respiration, but later saves much more by preventing rot.
3. Cooling
Only after wound healing does the temperature slowly move down towards the storage temperature. The keyword is “slowly”: a maximum of 0.2 to 0.3 °C per day, spread over one to two months. Cooling down too quickly creates condensation and stress in the tuber.
The biggest lever here is outside air. In autumn, night temperatures often drop so far that a farm can cool simply by ventilating cleverly with cold outside air and hardly needs active refrigeration. If, on the other hand, outside temperatures rise, or the target temperature is undershot in winter, there is no way around an air-conditioning system. Those who systematically use outside temperatures save the most energy.
4. Holding
During long-term storage, it is all about maintaining the condition achieved: cool target temperature, high humidity, enough oxygen, no condensation. This is achieved through regular, controlled air exchange. Especially with processing potatoes stored at warmer temperatures, sprouting can occur during this phase and require the use of a sprout suppressant.
5. Rewarming
Shortly before removal from storage or processing, table and seed potatoes are rewarmed to up to 10 °C. At these temperatures the tuber is less susceptible to bruising, and minor damage from sorting and packing heals better. Depending on the technology, rewarming takes a few days in a lightly cooled store or just a few hours in a heated environment.
Temperature and humidity cannot be separated
Talking about temperature without considering humidity is misleading. Water makes up around 70% of the potato's mass, and potatoes are sold by weight. Every gram of evaporated water is lost money. An equilibrium where water loss is practically zero is reached at around 4 °C and about 98% relative humidity.
But high humidity has a downside. If the air temperature drops to the dew point, or humid air hits cold surfaces, water condenses as droplets. It is precisely this condensation on the tubers that triggers mould and rot. The trick is to keep humidity high while still avoiding any condensation. Anyone who lowers the temperature too quickly or ventilates unevenly creates these damp pockets in the pile. How different storage types affect ventilation is covered in our comparison of crate types for storage.
The most common temperature mistakes
- Too cold too soon. Cooling to storage temperature immediately after harvest, without wound healing. Result: unhealed wounds, more rot.
- Cooling too quickly. More than 0.3 °C per day creates condensation and stress. The tubers start to “sweat”.
- Too cold for the intended use. Storing processing potatoes below 6 °C and then wondering why the fries are too dark. The cold-induced sweetening effect is difficult to reverse after delivery.
- Measuring in only one place. A sensor in the middle of the store says nothing about the warm core of a pile or the cold corner by the door. Temperature differences in the store are the rule, not the exception.
- Monitoring only during the harvest period. Most people monitor closely immediately after harvest. Afterwards, a check every one to two weeks is considered enough – until a damp lot quietly deteriorates unnoticed.
Quick checklist for practical use
- Crop wet at harvest? Dry quickly and vigorously first, before even thinking about cooling.
- Allow one to two weeks for wound healing at 12–15 °C and high humidity.
- Then lower slowly, by a maximum of 0.2–0.3 °C per day.
- Choose target temperature according to use: seed 3–4 °C, table 3–6 °C, crisps 6–8 °C, fries 7–10 °C.
- Keep humidity high (aim for 90–95%), but avoid condensation on cold surfaces.
- Use outside air consistently for cooling as long as it is cold enough.
- Rewarm to up to 10 °C before processing or loading.
- Measure at several points and document the values, don't just keep them in your head.
From gut feeling to verifiable curve
Many farms run their stores based on experience, and often it works well. The store manager in charge “has it in his head”, knows where the critical spots are and checks them more often. The only problem is: this knowledge is locked in one person, is difficult to pass on and provides no evidence in case of a dispute.
The point at which temperature management goes from experience to verifiable data is continuous recording. Several sensors per store, a continuous curve instead of individual readings, and documentation showing that a lot has actually gone through the wound-healing phase and was then cooled down along the intended curve. This is exactly where digital storage documentation comes in: it records the temperature and humidity curve for each store or lot, makes deviations visible early and also provides the evidence that buyers and certifiers require. The real benefit is not the neat curve, but the early warning before a damp corner turns into a pocket of rot.
Frequently asked questions
What is the best temperature for storing table potatoes? For fresh consumption, 3 to 6 °C is usual, in practice often around 4 °C. More important than the exact value is that wound healing takes place at 12–15 °C first and is followed by slow cooling.
Why are potatoes for fries and crisps stored warmer? Because cold increases the sugar content. Reducing sugars lead to darker colour, bitter taste and more acrylamide when fried. That is why processing potatoes are kept above 6 °C, crisps at 6–8 °C, fries at 7–10 °C.
How quickly may potatoes be cooled? A maximum of 0.2 to 0.3 °C per day, spread over one to two months. Faster cooling creates condensation and damages the tubers.
Why are my potatoes sprouting despite cooling? Sprouting can be slowed below around 3 °C, but then the sugar content rises sharply. Anyone who has to store at warmer temperatures, for example with processing potatoes, generally needs an approved sprout suppressant. You can find which ones these are in our standards overview.
Can I cool with outside air alone? Often yes in autumn, because night temperatures support the target curve. In mild weather or if the target temperature is undershot in winter, active cooling or heating control is needed.
