Recently published research on the effectiveness of different sanitizers in iceberg lettuce wash water reinforced previous findings that such sanitizers are not designed to reduce pathogens on finished product.

Gordon Davidson, a post-doctoral researcher at the University of California-Davis, led a team that compared five different sanitizer options and plain tap water. They published their results in the Journal of Food Protection and are preparing to publish results from the next phase of research in the coming weeks.

“One of the major misconceptions is that the purpose of sanitizers in wash water is to reduce pathogens on the food,” Davidson said Nov. 25. “With this work we showed again that is not what they are designed to do.”

However, Davidson said sanitizers are absolutely crucial for food safety because they are effective in reducing pathogens in the wash water itself, which reduces opportunities for cross-contamination. Another key finding revealed that spent centrifuge water can provide processors with a good checkpoint for the safety of fresh-cut leafy greens.

Davidson said by testing spent centrifuge water producers can get a big picture look at how well their processes are working. That information can give insight into what the pathogen level will be on finished product.

The research team specifically checked the effectiveness of the sanitizers on reducing the amount of E. coli 0157:H7 on iceberg lettuce, wash water and equipment surfaces. None of the sanitizers were more effective than tap water on reducing the E. coli on the iceberg lettuce.

However, the researchers found chlorine-based treatments were “significantly more effective than water alone” at reducing the E. coli in the wash water.

The five commercial produce sanitizer treatments assessed at strengths of 30 parts per million were:

  •  peroxyacetic acid — Tsunami 100 from Ecolab;
  •  mixed peracid — Tsunami 200 from Ecolab;
  •  available chlorine — XY-12 from Ecolab at pH 7.85;
  •  available chlorine — XY-12 acidified to pH 6.50 with citric acid from Sigma-Aldrich; and
  •  available chlorine — XY-12 acidified to pH 6.50 with T-128 from SmartWash Solutions.