The Dish Machine Reading 25 ppm
At 2 p.m. the dish room is backed up. The single-tank, low-temperature conveyor machine runs a 60-second cycle with a chlorine sanitizing rinse. The CFPM dips a test strip in the rinse water and matches it to 25 ppm; the machine's gauge reads 118 °F. A dish employee has been stacking racks so the plates overlap at the edges, and he is drying them with a cloth bar towel so they can be re-stacked faster. On the prep counter, three wiping cloths sit in a bucket of cloudy water labeled 'quat, 200 ppm' - no test strip has been used since yesterday. A stack of 'clean' plates from this machine is already out on the line.
1. Is this machine sanitizing? State the required standards and what must happen to the plates already on the line.
Read the worked answer
No, it is not sanitizing. Two independent failures:
| Parameter | Required | Actual | Result |
|---|---|---|---|
| Chlorine concentration | 50–100 ppm (minimum 50 ppm) | 25 ppm | Fail - half the minimum, not sanitizing |
| Rinse water temperature (low-temp chlorine machine) | 120 °F minimum | 118 °F | Fail - below the minimum |
At 25 ppm the solution is a weak rinse, not a sanitizer. Biofilm and pathogens survive, and the plates look clean because they are wet and hot - the appearance is the trap.
The plates on the line are not clean. They must be pulled:
- Remove from service immediately; do not let the line use them.
- Re-wash, rinse, and sanitize - either after the machine is repaired and verified, or by the manual method.
- Manual method: 3-compartment sink - wash in detergent at the required temperature, rinse in clean water, then immerse in 50–100 ppm chlorine (or 200–400 ppm quat) for at least 30 seconds of contact time, then air-dry on a rack.
- Verify with the correct test strip before the first rack goes through.
Also: the machine must be taken out of service until it holds 50 ppm chlorine at 120 °F on every cycle. If the chemical pump has failed, repair it or run manual until it is fixed. There is no acceptable 'run it twice' workaround.
2. Identify the operational errors on the dish line and the corrections.
Read the worked answer
1. Overlapping/overloaded racks.
- The spray and rinse cannot reach the food-contact surface of an overlapping plate, and the sanitizer cannot contact what it cannot wet.
- Correct: racks loaded so water flows freely, plates not nested, cups and bowls inverted, utensils separated. One layer where the rack calls for it.
- Correct: check that the conveyor speed and the rack pattern match the machine's data plate.
2. Towel-drying.
- A bar towel is a recontamination device: it moves soil and microorganisms from the towel onto a just-sanitized surface, and the towel itself is damp and stored in a warm dish room.
- Correct: air-dry on a clean, self-draining rack. Never towel-dry dishes, utensils, or glassware.
3. No verification.
- Nobody tested the sanitizer concentration until the CFPM did. Test strips must be used at the start of each shift and periodically during operation, with the strip matched to the sanitizer chemistry (chlorine strips for chlorine, quat strips for quat - do not mix).
- The temperature gauge must be monitored each shift; irreversible registering thermometers or plate-level checks must be used where required.
4. Traffic pattern.
- Soiled and clean dish traffic should not cross. Clean items should be stored covered or inverted, protected from splash and from the employee's hands on food-contact surfaces.
3. Evaluate the wiping-cloth bucket and specify the correct procedure for wiping cloths.
Read the worked answer
What is wrong:
- The bucket is cloudy - a dirty solution is a microbial bath. Once the cloth has picked up food soil, the sanitizer is depleted and the cloth now redistributes contamination across every surface it touches.
- No test strips used since yesterday. A label saying 200 ppm quat is a claim, not a measurement. Quat also has a narrower effective pH range and is easily exhausted by soil and by mixing with detergent residue.
- Concentration for quaternary ammonium on food-contact surfaces: 200–400 ppm per the label; for chlorine, 50–100 ppm. Verify with the matching test strip, at the correct temperature and contact time.
Correct procedure:
- Store wet wiping cloths between uses in a sanitizing solution at the proper concentration - never on a counter, never in a pocket, never dry on the cutting board.
- Test the solution with the correct strip when it is made and periodically thereafter. Record it.
- Change the solution when it is visibly soiled, cloudy, or greasy, and at a defined interval - typically every few hours - not 'when it looks bad.'
- Keep separate buckets for food-contact surfaces and for non-food-contact areas; never use a cloth that wiped a floor or a raw-meat station on a prep table.
- Use the two-cloth or clean-cloth approach: wipe with a clean cloth, then sanitize the surface, allowing the full label contact time before air-drying.
- Launder cloths after use; do not reuse a soiled cloth by dunking it back in the bucket all shift.
The broader point: sanitizer concentration, water temperature, contact time, and cleanliness of the solution are one system. Knowing the number on the label without testing is the same failure mode as the dish machine - assuming instead of verifying.