United States
Hong KongSanitizer concentrations: three chemicals, three ranges
Chlorine at 50 to 100 ppm with 7 seconds contact at 100 ppm and 24°C (75°F). Quaternary ammonium at 200 to 400 ppm per the label, 30 seconds. Iodine at 12.5 to 25 ppm, pH 5.0 or below, 30 seconds. Test strips are required.
Three chemicals, three ranges, and they are worth knowing exactly. Questions in this area give you a number and ask whether it is in range, which means an approximate memory is no memory at all.
| Sanitizer | Range | Contact time | Notes |
|---|---|---|---|
| Chlorine | 50 to 100 ppm | 7 seconds at 100 ppm, 24°C (75°F) | Cheap, fast, corrodes metal, evaporates when hot |
| Quaternary ammonium | 200 to 400 ppm | 30 seconds | Stable and non-corrosive; hard water interferes |
| Iodine | 12.5 to 25 ppm | 30 seconds | Needs pH 5.0 or below and 20°C (68°F) or above; stains |
Stronger is not better
This is counter-intuitive and it is examinable.
Chlorine above 100 ppm on food-contact surfaces is a chemical hazard. It leaves residue, corrodes equipment, and the Code treats residue as contamination. A manager who doubles the dose because the kitchen looks dirty has created a violation, not solved one.
The five factors
- Concentration - inside the range, verified with strips.
- Contact time - the surface stays wet for the full period.
- Temperature - too cold and it under-performs, too hot and chlorine gasses off.
- pH - iodine needs acidity; chlorine loses effectiveness as pH rises.
- Water hardness - minerals interfere with quats particularly.
Questions rarely ask you to list them. They describe a kitchen where one has gone wrong - a cold sink, hard water, a surface wiped dry after two seconds - and ask why the sanitizer is not working.
Chlorine test strips do not read quaternary ammonium and vice versa. A manager with the wrong strips has no measurement at all, which is functionally the same as having none.
Wiping cloths
Cloths used on food-contact surfaces are stored in sanitizer solution between uses, at the correct concentration, in a labeled container.
Not on the counter, not over a shoulder, not in a pocket. And the solution is changed when it becomes soiled or drops out of range, which in a busy kitchen is more often than once a shift.
The order that always applies
Clean first, then sanitize. Sanitizer on a soiled surface is largely wasted, because organic matter binds the active chemical before it reaches anything living.
Which is also why a spray bottle of sanitizer used as a general cleaner is the wrong tool: it is not cleaning, and it is not sanitizing either.
Common questions
What is the correct chlorine sanitizer concentration?
50 to 100 ppm, with 7 seconds of contact at 100 ppm and 24°C (75°F). Above the range it becomes a chemical hazard and leaves residue, which the Code treats as contamination.
What concentration for quaternary ammonium?
200 to 400 ppm, following the manufacturer label, with 30 seconds of contact. Hard water interferes with quats more than with the other sanitizers.
Why is stronger sanitizer not better?
It leaves residue on food-contact surfaces, corrodes equipment, and creates a chemical hazard. Doubling the dose because a kitchen looks dirty produces a violation rather than a solution.
What five factors affect sanitizer effectiveness?
Concentration, contact time, temperature, pH and water hardness. Exam questions usually describe a kitchen where one has gone wrong rather than asking you to list them.
Where should wiping cloths be kept?
In sanitizer solution at the correct concentration, in a labeled container, changed when soiled or out of range. Not on the counter, over a shoulder or in a pocket.