The Wedding Buffet That Struck Overnight
A 220-guest wedding buffet at a Dubai hotel runs from 20:00 to 23:30. Chicken shawarma sliders, a cream-filled 'kunafa' dessert, and a rice dish sit on unrefrigerated chafing dishes. The hotel's log shows the shawarma was cooked to 74°C at 18:00, then held in a hot box; the probe reading at 21:00 was 48°C. The kunafa was prepared at 15:00 and left on the buffet at ambient (24°C) from 20:00. Rice was cooked at 17:00 and reheated at 19:30 to 70°C but held at 52°C. From 02:00 to 09:00 the next morning, 31 guests report vomiting with a mean onset of 4 hours; 12 report watery diarrhoea with onset 14–20 hours. No fever is reported. The hotel has no record of buffet temperature checks after 21:00.
1. Which food vehicle and hazard best explain the 4-hour vomiting cluster, and which explains the 14–20-hour diarrhoea cluster? Justify using incubation and symptom pattern.
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4-hour vomiting cluster: The kunafa fits best. Staphylococcus aureus intoxication has an incubation of roughly 1–6 hours and causes violent vomiting with little or no fever. The kunafa was made at 15:00 and held at 24°C for 5 hours before service - ample time for staph to multiply and produce heat-stable toxin. Cooking would not destroy the toxin, so the food is the vehicle regardless of later handling.
14–20-hour diarrhoea cluster: The rice held at 52°C is the strongest candidate. Bacillus cereus (diarrhoeal type) has an incubation of 8–16 hours and causes watery diarrhoea. Rice cooked at 17:00 and held warm is a classic vehicle. The shawarma held at 48°C is also a risk for Clostridium perfringens (8–16 hours, diarrhoea), but the 48°C reading is below the 63°C hot-hold minimum and would support growth.
Key reasoning: Two distinct incubation windows and symptom sets point to two separate hazards, not one. The absence of fever argues against invasive infection (e.g. Salmonella) and toward toxin-mediated or toxico-infection illness.
2. The hotel claims the shawarma was 'safe because it was cooked to 74°C.' Evaluate this claim against the 48°C holding reading.
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Cooking to 74°C achieves a 6-log reduction at the moment of cooking, but it does not sterilise the food. Spores of B. cereus and C. perfringens survive 74°C, and any recontamination from hands, utensils or the hot box reintroduces vegetative cells.
The critical failure is the holding temperature. Hot holding must be ≥63°C. A reading of 48°C sits squarely in the temperature danger zone (5°C–63°C), where bacteria multiply rapidly. From 18:00 to 21:00 is 3 hours, and the buffet continued to 23:30 - potentially 5.5 hours in the danger zone. C. perfringens can double every 7–10 minutes at favourable temperatures, so a small surviving population can reach infectious dose.
The claim is therefore false: cooking is a kill step, not a preservation step. The failure is holding, and the absence of post-21:00 checks compounds it.
3. List the corrective actions and record-keeping changes the hotel must make to prevent recurrence, framed around HACCP monitoring and verification.
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Corrective actions:
- Discard all buffet food held below 63°C for more than 2 hours; document disposal.
- Reheat rice and shawarma to ≥74°C before returning to hot hold.
- Move the kunafa to a refrigerated display (≤5°C) or hold under time-as-a-control (max 4 hours, labelled with discard time).
Monitoring:
- Probe every hot-held item at least every 2 hours and record; set a critical limit of ≥63°C.
- Calibrate probes daily and record.
- Assign a named person per service to sign the temperature log.
Verification:
- Weekly review of logs by the food safety officer.
- Quarterly internal audit and trend analysis of deviations.
- Retain logs for the period required by Dubai Municipality (typically 12 months) and make them available on inspection.
Root cause: No monitoring after 21:00 and no time-based backup control. Add a documented time-as-a-control procedure for high-risk items.