Study Finds No Difference In Fry Color Between DMN And Restrain’s InhibitR™ Technology
New independent research has found no statistical difference in fry colour between potatoes stored under conventional DMN treatment and those managed with Restrain’s InhibitR™ technology, according to a study commissioned by Restrain and conducted by the Chambre d’Agriculture du Nord–Pas-de-Calais. The full extract of the research is presented in the company’s Fry Colour Performance Analysis report.
Fry colour remains one of the most sensitive quality markers for processors, directly linked to reducing sugars formed during storage. Variations in temperature, CO₂ levels, sprout-control performance, and general store management can all influence the Maillard reaction during frying, often creating costly inconsistencies for processors. As the sector continues to use a mix of sprout inhibitors—oils, DMN, ethylene—consistent storage behaviour remains a priority across Europe.
The study compared two widely used processing varieties, Fontane and Markies, across four commercial stores in northern France. Each store applied either DMN or InhibitR™ following standard protocols. According to the report (pp. 4–6), fry colour was evaluated three times during the season—February, April, and May—using the USDA Fry Colour Chart (000–4 scale), with each assessment based on 20 fries per sample fried at 180°C for three minutes in sunflower oil.
Across both the 2023–2024 and 2024–2025 storage seasons, the results showed no measurable difference between the two treatments. The fry colour indices for both varieties remained within customer specifications, with most stores presenting near-identical average values between 2.1 and 2.2. Even when some stores saw slightly elevated sugar levels in April during the 2024–2025 season, all sites returned to target fry colour by May—a pattern consistent across both DMN and InhibitR™ applications.
The Chambre d’Agriculture concluded that InhibitR™ performs equivalently to DMN in maintaining fry colour and long-term storage quality (p. 6). According to the report, this reinforces Restrain’s objective of generating transparent, third-party-validated data to support growers and processors. The company notes that it has now expanded its research programme to 20 additional monitoring sites across Europe, tracking fry-colour evolution every two weeks throughout the season (p. 7).
As the industry continues to balance sustainability pressures, regulatory compliance, and the need for high-quality output, independent analyses such as this provide critical evidence on the performance of alternative sprout-control technologies. Restrain states that further results will be published as the monitoring programme continues into 2026.
“This article is based on research conducted by the Chambre d’Agriculture du Nord–Pas-de-Calais and commissioned by Restrain. All findings and conclusions reflect the data presented in the study.”
