Global: Reconditioning Cuts Glucose in Cold-Stored Potatoes by About 50%
Studies from Kenya and Switzerland and Canadian storage guidance show how warm reconditioning at 13–22°C reverses part of cold-induced sweetening and improves chip and fry colour.
Cold storage keeps potatoes from sprouting, but it has a cost. Below about 7°C, tubers turn part of their starch into reducing sugars, glucose and fructose. In the fryer these sugars give dark chips and fries and more acrylamide. Reconditioning, a period of warmer storage before processing, is the standard way to reverse part of this sweetening.
The New Brunswick Department of Agriculture in Canada says reducing sugars accumulate below 7.2°C and that below 3°C the build-up also harms flavour and cooking quality. It recommends reconditioning at 13.0–15.5°C for 4 to 6 weeks before shipping. With a typical 1.5°C difference between the bottom and top of a pile, a set point of 14°C keeps the top below 15.5°C.
Recent studies measure the effect. In Foods (2024), Gikundi, Buzera, Orina and Sila stored three Kenyan varieties at 4°C for 30 days and then reconditioned them at about 22°C for 9 days. Glucose fell by 49.5% to 54.1% and fructose by 38.2% to 57.5%, depending on variety. Glucose content explained 80.5–97.6% of the variation in fry lightness and 88.4–94.2% for chips. The authors give target glucose levels of 12–22 mg per 100 g for fries and 8–14 mg per 100 g for chips.
A study by Agroscope in Switzerland and partners, published in 2024, compared six varieties. Storage at 4°C prevented sprouting for up to 4.5 months. Verdi, Lady Claire and Kiebitz showed only small glucose increases after up to four months at 4°C. Pirol, Agria and Markies sweetened strongly. For Markies, slowly raising the temperature to 15°C significantly reduced glucose and acrylamide.
Reconditioning has limits. New Brunswick notes that it works only to some degree, depending on variety. It does not fix senescent sweetening, which appears when tubers age, often in years of short dormancy. That colour loss is irreversible. According to the same guidance, long storage above 10°C causes this second type of sugar build-up.
Why it matters
With chlorpropham (CIPC) banned in the EU, cold storage is one of the main non-chemical ways to control sprouting. It works for processing only if varieties resist cold sweetening or can be reconditioned. Store managers need a reconditioning plan, with weeks, temperatures and sugar tests, before they lower the temperature, not after dark fry colour appears.
Photo: Potatoes transported to a cold store in India (illustrative). Suyash Dwivedi / Wikimedia Commons, CC BY-SA 4.0
