A new peer-reviewed study published in the Journal of Food Science provides some of the clearest comparative evidence to date on the performance of peroxyacetic acid (PAA) versus aqueous chlorine dioxide (ClO₂) in potato wash water systems. The research, titled “Cross-Contamination With Escherichia coli, Listeria monocytogenes, and Murine Norovirus During Potato Washing and Their Inactivation Using Peroxyacetic Acid and Aqueous Chlorine Dioxide,” was conducted by H. Kwon and colleagues and is directly relevant to industrial potato washing and water-reuse environments.

The authors state that the goal of the study was to “evaluate the inactivation of pathogens on potato surfaces by peroxyacetic acid and aqueous chlorine dioxide, and examine the effect of wash water reuse on pathogen cross-contamination between potatoes.” To do this, the researchers inoculated potatoes with Escherichia coli, Listeria monocytogenes, and murine norovirus, then subjected them to wash conditions intended to simulate commercial processing, including scenarios in which contaminated and uncontaminated potatoes shared the same water.

The results show a clear performance difference between the two disinfectants. The study reports that PAA achieved “1.86 to 2.51 log CFU/potato reduction of E. coli at 40 ppm” and that “L. monocytogenes was reduced by 2.01 and 2.59 log CFU/potato at 120 ppm for 30 s and 1 min, respectively.” Chlorine dioxide required substantially higher concentrations and longer exposure times to achieve similar reductions, with the authors noting that “treatments with 80 ppm aqueous ClO₂ for 1–5 min resulted in 1.72–2.57 log CFU/potato reduction of E. coli.”

The gap in performance widened considerably when viral control was tested. According to the study, PAA at concentrations of 40 ppm or higher “significantly reduced murine norovirus by 1.88–2.28 log PFU/potato,” while chlorine dioxide “did not significantly reduce MNV under the same conditions.” For potato processors, the inclusion of murine norovirus is notable because it offers a validated surrogate for human norovirus, one of the most persistent foodborne viruses.

The researchers also examined cross-contamination risks, which remain a significant operational concern for frozen and fresh-cut potato processors. In wash scenarios using untreated tap water, the study found that “cross-contamination resulted in 3.01 and 3.22 log CFU/potato for E. coli and L. monocytogenes, respectively.” PAA eliminated detectable transfer of E. coli, with the authors stating that E. coli was reduced “to below detection limit” under PAA treatment. Chlorine dioxide allowed partial transfer, with reductions ranging between 0.83 and 1.30 log CFU/potato depending on concentration and time.

However, neither PAA nor chlorine dioxide fully prevented cross-contamination of Listeria monocytogenes, especially when wash water was reused. The study reports that under reuse conditions “E. coli was completely inactivated, but L. monocytogenes remained at 2.74–3.46 log CFU/potato,” highlighting the pathogen’s resilience even in the presence of disinfectants. The authors note that this persistence reflects the organism’s long-acknowledged resistance to sanitizers and its ability to survive in low-nutrient, cold-chain environments common in potato processing.

The authors conclude that both PAA and aqueous chlorine dioxide “can reduce microbial load on potato surfaces and mitigate cross-contamination,” but that PAA provides broader efficacy, including against viruses. They emphasise that no single sanitizer can fully eliminate the risk posed by L. monocytogenes during water reuse, stating that “additional hurdles must be considered when wash water is reused.”

For the potato processing industry, the findings reinforce the need for a multi-hurdle sanitation strategy combining chemical disinfection with tight control over water quality, organic load, contact time, and environmental monitoring. The study’s authors indicate that while chemical agents remain essential, their effectiveness is inherently limited when wash water is recycled, making process design and water-quality management equally critical.