Six Hours From Pot to Plate: A School Kitchen Outbreak
A boarding school in Enugu with 180 students runs a kitchen staffed by two cooks and four student helpers. On Monday, jollof rice is cooked at 11:00 in two large pots, left covered on the floor of the store and served at 17:00; the pot is still warm to the touch at service. The walk-in refrigerator reads 9°C and the freezer reads −3°C with meltwater on the floor. A single hand basin at the door has no soap and one roller towel used by everyone. Raw chicken is cut on the same wooden board used for vegetables after a quick rinse. Borehole water is stored in an open drum and drawn with a bucket. The refuse bin has no lid. Two food handlers have no current medical certificates. On Wednesday, 14 students report vomiting and diarrhoea, and the school nurse asks the kitchen for an explanation.
1. Identify the four highest-risk failures and rank them by severity multiplied by likelihood. Justify each ranking using control-point reasoning rather than general advice.
Read the worked answer
Rank 1 is the rice held from 11:00 to 17:00 in a warm pot. Cooked rice is a classic Bacillus cereus risk: spores survive boiling, germinate as the rice cools slowly, and produce a toxin that is not destroyed by reheating. Six hours in the warm zone, with the pot still warm, gives near-certain amplification, and the vomiting pattern matches a short incubation toxin. Rank 2 is the refrigerator at 9°C. Above 5°C, Salmonella, Listeria and Staphylococcus can multiply; with the freezer at −3°C, frozen food is also partly thawing and may be refrozen, adding another hazard. Rank 3 is the wooden board used for raw chicken and then vegetables. Raw poultry juice carrying Salmonella or Campylobacter reaches ready-to-eat food with no further cooking step; a rinse does not sanitise wood. Rank 4 is handwashing with no soap and a shared towel, combined with open drum water and an unlidded bin, which spreads faecal organisms to food and surfaces.
The ranking reflects severity × likelihood. Rice and the fridge have high severity and high likelihood; cross-contamination is high severity but slightly lower likelihood because vegetables may be cooked; hand hygiene is high likelihood but often lower dose. The missing medical certificates and the bin are contributory and should be corrected, but they are not the immediate cause.
2. State exactly what should have happened to the rice if service was at 17:00, and what must now be done with Monday's rice and the refrigerator contents.
Read the worked answer
If service is at 17:00, the rice must either be held hot at 63°C or above from the end of cooking until service, checked with a probe thermometer every hour and logged, or cooled rapidly and reheated once. Rapid cooling means reducing from 63°C to 21°C within two hours and then to 5°C within a further four hours, in shallow trays in the refrigerator, not in a deep pot. Reheating must bring the whole mass to at least 74°C, stirred and probed in the centre, and reheated rice must not be cooled and reheated again.
Monday's rice must be discarded. It has spent six hours in the danger zone, and reheating will not destroy the Bacillus cereus toxin; serving it would continue the outbreak. It should be placed in a closed waste bin away from the kitchen. The refrigerator contents must be assessed item by item: any high-risk food such as cooked meat, milk or stew that has been above 5°C for an unknown period should be discarded; raw items that are still cold may be moved to a working unit. The refrigerator should be defrosted, cleaned and sanitised, and not reloaded until it holds 5°C or below. The nurse should be given the menu, the service times and a food sample if one was kept.
3. Design a one-page monitoring sheet the school can actually use. Name three checks, their frequency, target, the corrective action and who signs.
Read the worked answer
The sheet should have one row per check and columns for date, time, reading, initials, corrective action and verifier signature. Check 1 - cold storage: twice daily at 07:00 and 16:00. Target: refrigerator 5°C or below, freezer −18°C or below. Corrective action: move food to a working unit, call the technician, discard high-risk food above 5°C for more than two hours, record the discard. Signed by the cook on duty, verified weekly by the matron.
Check 2 - hot holding: every hour from the start of cooking until service ends. Target: 63°C or above in the centre of each pot. Corrective action: reheat to 74°C within 30 minutes if below 63°C, or discard if it has been below 63°C for more than two hours. Signed by the server, verified by the kitchen supervisor.
Check 3 - handwashing station: at the start of each shift and again after every break. Target: soap present, running water, disposable towels, bin emptied. Corrective action: restock before any food handling continues; if water is unavailable, stop service and use boiled or chlorinated water. Signed by the helper on duty, verified by the nurse or matron. Add a delivery check when meat arrives: target 5°C or below, corrective action reject. The sheet must be simple enough to complete during service, not a file that is filled in afterwards.