Wash water disinfection of a full-scale leafy vegetables washing process with hydrogen peroxide and the use of a commercial metal ion mixture to improve disinfection efficiency

Hydrogen peroxide (H2O2) was used to maintain the microbial wash water quality of a full-scale leafy vegetables (radicchio, sugar loaf, curled endive, lollo, lollo rosso) wash water process. Despite addition of 300 L/h of 1.8% H2O2 to a 450 L washing bath (333 ± 50 kg/h fresh-cut produce introduction speed), the H2O2 quickly decreased and a lower wash water contamination of aerobic psychrotrophic plate count (APC) and enterococci than without addition of H2O2 could not be maintained. There was no significant difference between the APC on fresh-cut leafy vegetables washed with H2O2 and those washed with water. In a second part, lab-scale experiments were performed to assess the impact of a commercial metal ion formulation (Bacsan®, containing a. o. Cu2+, Zn2+, Ag+) on the stability of H2O2 in artificial wash water, made from iceberg lettuce and tap water. Bacsan improved the stability of H2O2 in artificial lettuce wash water and fresh-cut leafy vegetables wash water from a processing company and synergistically increased the disinfection efficiency of APC and Escherichia coli (E. coli) compared to H2O2 or Bacsan. Increasing chemical oxygen demand (COD) had detrimental effect on the H2O2 stability and disinfection efficiency. Addition of Ag+ to Bacsan further synergistically enhanced the H2O2 stability. H2O2 is not suited as an in situ wash water disinfectant to avoid cross-contamination in fresh-cut leafy vegetables washing processes due to the slow water disinfection kinetics and the rapid H2O2 consumption. However, H2O2/Bacsan shows potential for use in off-line processes. •H2O2 was used in washing process to lower microbial load on lettuce and in water.•No increased microbial removal with 1.8% H2O2 than with water wash.•Rapid decomposition of H2O2, microbial wash water quality was not maintained.•Stability of H2O2 in wash water was improved with use of metal ions (Bacsan®).•Combination of H2O2 and metal ions resulted in synergistic water disinfection.