Sprout suppression is no longer a secondary consideration in processing potato storage. Since the withdrawal of chlorpropham (CIPC), storage strategy has become a determinant of processing performance, regulatory compliance, and available capacity. 

Choices related to sprout inhibitors, temperature regimes, ventilation discipline, and atmospheric control now directly influence fry color stability, intake flexibility, and the economic viability of long-term storage.

For processors operating year-round supply models, storage is a controlled system with limited tolerance for error. Variability introduced during storage is carried forward to the processing line, where it manifests as inconsistent fry color, restricted blending options, higher rejection rates, and reduced throughput. At the same time, storage operators are navigating tighter residue monitoring, higher energy costs, and infrastructure constraints inherited from the CIPC era. The result is a storage environment where sprout control is no longer about suppressing growth alone, but about managing risk across the entire processing chain.

Ventilation And CO₂ Management As Operational Constraints

Regardless of the sprout suppression method used, ventilation has become a critical operational requirement in processing potato storage. Respiration-driven CO₂ accumulation occurs in all stores, but the use of gas-based sprout suppression systems and gas-tight infrastructure increases the need for disciplined degassing before intake.

Elevated CO₂ concentrations affect tuber condition and can interfere with sugar management, increasing the likelihood of fry color deviation. From an operational standpoint, CO₂ levels must also be reduced to ensure safe working conditions during loading and inspection. For processors working to tight delivery windows, the need to ventilate stores prior to dispatch introduces a non-negotiable conditioning phase that must be planned into supply schedules.

This requirement has practical implications. Stores designed for ethylene or other atmospheric treatments cannot be switched rapidly from storage to intake without sufficient purge time. In peak processing periods, inadequate ventilation capacity can become a bottleneck, limiting the speed at which stored volumes can be released to the factory.

Temperature Strategy And Its Impact On Processing Quality

Temperature remains one of the most influential variables in sprout control, but also one of the most sensitive from a processing perspective. Lower storage temperatures reduce sprout pressure and can extend storage duration, but they increase the risk of cold-induced sweetening. For processors, the accumulation of reducing sugars during storage translates directly into darker fry color and greater difficulty meeting customer specifications.

As a result, most processing potatoes in Europe are stored at temperatures that deliberately trade some sprout pressure for sugar stability. This approach reduces the severity of reconditioning requirements later in the season but increases reliance on sprout suppressants to maintain control over longer storage periods.

Where refrigeration is used aggressively as a primary sprout control tool, energy consumption rises sharply and the need for temperature reconditioning becomes more pronounced. Rewarming phases introduce additional handling complexity and reduce operational flexibility. In practice, refrigeration alone rarely provides a viable long-term solution for processing potatoes without supplementary sprout inhibition.

CIPC As A Legacy Constraint On Storage Capacity

Although CIPC no longer plays an active role in sprout suppression, its regulatory and infrastructural legacy continues to shape storage strategy across Europe and the UK. Persistent residues in stores with a history of CIPC use have required regulators to introduce temporary Maximum Residue Levels (tMRLs) to prevent large-scale loss of storage capacity.

In the UK, the CIPC Residues Monitoring Group has repeatedly highlighted the importance of continued residue monitoring. Data submitted to the Health and Safety Executive’s Chemical Regulation Division shows that while detectable residues are declining, they have not yet disappeared entirely from all historically treated stores.

Adrian Cunnington, Chair of the CIPC Residues Monitoring Group, has warned of the consequences of losing regulatory flexibility:

“It is hard to overstate the challenge if we lost our storage capacity; it would be devastating for the industry.”

His statement reflects a broader concern shared across the sector. Without sufficient data to justify temporary thresholds, regulators could revert to default detection limits that would render many stores unusable, regardless of current sprout control practices.

Belgian monitoring data points in the same direction. According to Belgapom, 92% of warehouse samples taken during the 2023–2024 storage season contained no measurable trace of CIPC, with remaining residues below the applicable tMRL. While this confirms a downward trend, it also explains why regulators continue to rely on structured monitoring programmes rather than declaring the issue resolved.

Read the rest of this feature in the free e-copy of the January / February Issue of Potato Processing International, which can be accessed by clicking here.