The organisms
- Listeria monocytogenes — soft cheese and ready-to-eat dairy
- Salmonella and E. coli — raw milk and environmental routes
- Psychrotrophic spoilage organisms — shelf life and quality
- Biofilm in lines, valves and dead legs
Why HOCl works against them
Hypochlorous acid does not have a single molecular target. It oxidises membrane lipids, structural and enzymatic proteins, sulfhydryl groups and nucleic acids more or less simultaneously. That breadth is why resistance has not developed to it in the way it has to some quaternary ammonium compounds, and why the same solution handles bacteria, viruses and fungi.
The rate-limiting factors are the same everywhere: concentration at the surface, contact time, and whether organic soil consumed the oxidiser before it arrived.
Contact times to design around
| Target | Concentration | Contact time | Note |
|---|---|---|---|
| Vegetative bacteria | 50–200 ppm | <60 seconds | Clean surface |
| Enveloped viruses | 50–200 ppm | <60 seconds | Readily inactivated |
| Non-enveloped viruses | 100–200 ppm | 1–5 minutes | Norovirus class |
| Yeasts and moulds | 100–200 ppm | <60 seconds | |
| Established biofilm | 200–500 ppm | 5–15 minutes | Combine with mechanical action |
| Bacterial spores | 200–500 ppm | 5–10 minutes | The hard case |
Verifying control
Environmental swabbing before and after implementation is what converts a claim into evidence. Trend the results rather than treating each swab as pass/fail — the shape of the trend is what tells you whether a harbourage site is being controlled or merely disturbed.