Wedding catering: slow cooling, a warm holding cabinet and 42 cases of diarrhoea
A catering company prepares chicken rendang and steamed rice for a 200-guest wedding at a community hall. The rendang is cooked at 6 pm on Friday, left in two large pots on the kitchen counter until 11 pm to cool, then placed in a chest freezer that is already packed with raw chicken; the freezer thermometer reads -8°C. On Saturday morning the pots are moved to the hall, where the rendang is reheated in one pot until steam is visible and then held in a warmer set at 48°C from 11 am to 4 pm. The rice is cooked at 9 am, kept in rice cookers on 'warm' and served at 2 pm. Guests eat between 1 pm and 3 pm. From 11 pm Saturday to 3 am Sunday, 42 guests report abdominal cramps and watery diarrhoea; most recover within 24 hours. Two guests are hospitalised for dehydration. No vomiting and no fever are reported.
1. Which foodborne hazard and organism best fit the incubation period and symptoms? Justify your answer by linking the evidence to the organism's behaviour.
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Most likely Clostridium perfringens. The incubation period (about 8-14 hours), watery diarrhoea and abdominal cramps without vomiting or fever, and the meat-stew vehicle fit C. perfringens. Cooking kills vegetative cells but not heat-resistant spores. The rendang then cooled on the counter for five hours, passed slowly through the danger zone, and was held at 48°C, a temperature that allows spores to germinate and cells to multiply rapidly. Reheating until 'steam is visible' is not a validated core temperature. The toxin is formed in the intestine after ingestion of large numbers of cells, so reheating does not necessarily protect if multiplication has already occurred.
Alternatives to keep in mind: Bacillus cereus (diarrhoeal type) from rice held warm has a similar 8-16 hour incubation; Salmonella from raw chicken cross-contamination would usually produce fever and a longer incubation (12-72 hours); Staphylococcus aureus would produce vomiting within 2-6 hours. Without stool and food cultures the diagnosis is epidemiological, so samples of leftover rendang and rice should be collected. The overall pattern points to temperature abuse of a meat dish, not to a single 'bad ingredient'.
2. Map the failures to HACCP steps or critical control points and explain which control would have prevented the outbreak.
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The failures map onto several CCPs in a cook-chill catering process:
- Cooling CCP: cooked rendang should go from 60°C to 21°C within 2 hours and from 21°C to 5°C within a further 4 hours. Here it sat at ambient for five hours, so spore germination and multiplication were likely.
- Cold storage CCP: the freezer read -8°C and was overloaded with raw chicken. Frozen storage should be -18°C or colder, and cooked food must be above raw food or in a separate unit to prevent drip cross-contamination.
- Reheating CCP: reheating must reach a validated core temperature, typically at least 75°C, measured with a probe. 'Steam visible' is not a measurement.
- Hot holding CCP: potentially hazardous food should be held at 60°C or above. A warmer at 48°C is inside the danger zone and allows multiplication during five hours of service.
- Cross-contamination: raw chicken stored with cooked rendang creates a separate biological hazard, even if the main outbreak is temperature-related.
The single control that would most likely have prevented this outbreak is rapid cooling followed by cold storage at 5°C or below, with reheating to 75°C and hot holding at 60°C or above as backstops. Each step needs a probe thermometer, a time/temperature log, a named person responsible and a corrective action such as discarding food that exceeded the limit.
3. Draft the corrective action and verification plan the caterer must implement before the next event, including records and staff roles.
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Corrective action plan:
- Stop using the current cooling method. Purchase or hire a blast chiller, or use shallow pans and an ice bath with stirring; record start and end temperatures and times.
- Separate raw and cooked storage. Use a dedicated cooked-food freezer or shelf; raw food goes below cooked food; do not overload; monitor the freezer at least twice daily.
- Validate reheating and hot holding. Provide probe thermometers; reheat to at least 75°C core; hold at 60°C or above; discard food held below 60°C beyond the safe limit.
- Write and train. Convert these rules into a one-page HACCP-style SOP with CCP limits, monitoring frequency, corrective action and verification. Train all chefs and service staff and keep attendance records.
- Records: receiving temperatures, cooking, cooling, reheating, hot/cold holding, cleaning, thermometer calibration, staff health and training. Add a pre-event checklist signed by the chef-in-charge.
- Incident response: notify the district health office, cooperate with the investigation, retain leftover food and packaging, and review the event with staff.
Verification: the manager should audit one full event against the logs, check probe calibration in ice water, observe cooling and reheating directly, and review any customer complaints. The plan is not verified until the records show that the limits were actually met, not simply that a form was signed.