Cooling 15 kg of rice overnight in Mosta
An outside caterer in Mosta is preparing a wedding for 180 guests. At 18:00, 15 kg of long-grain rice is cooked and drained. At 20:00 the rice is still in four deep 20-litre pots, covered, at 38 °C in the kitchen (ambient 24 °C). The plan is to leave it overnight, then at 07:00 mix it with chopped ham, hard-boiled eggs, tuna and mayonnaise to make rice salad for the 13:00 buffet. The kitchen has a walk-in chiller at 4 °C with limited space (two shelves free) and a blast chiller that is not working. The catering manager says the rice will 'cool down by itself' and that the mayonnaise is acidic so 'it will be fine'. There is no cooling record. A food handler has been told to stir the pots at 23:00 to help cooling and then go home. You are the food safety supervisor and must decide by 21:00 whether the rice can be used.
1. Assess the microbiological risk in the plan, naming the likely hazard and why cooked rice is particularly associated with it.
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The likely hazard is Bacillus cereus. Its spores survive cooking, and if cooked rice is left warm - roughly between 8 °C and 63 °C - the spores germinate and the bacteria multiply. Some strains produce a heat-stable emetic toxin in the food, so later reheating does not make the rice safe. The plan is high risk: 15 kg in deep pots at 38 °C two hours after cooking, then left overnight in a kitchen at 24 °C. The centre of a deep pot will cool very slowly, so the rice may stay in the danger zone for many hours. Stirring once at 23:00 is not a controlled cooling method and will not protect the centre. Adding ham, eggs, tuna and mayonnaise at 07:00 would not fix the problem; the mayonnaise's acidity is irrelevant if the rice already contains toxin. This is a classic rice-salad outbreak scenario.
2. What should you do with the 15 kg of rice at 21:00? Give a decision and the reasoning, including what you would need to know to make a different decision.
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At 21:00 the rice has been warm for about three hours and there is no rapid-cooling record. It cannot be shown to be safe and should be discarded. Do not serve it, do not chill it for later use, and do not mix it with the other ingredients. The decision would be different only if there were a reliable record showing the rice had been cooled from 63 °C to 8 °C within 90 minutes (or by a validated two-stage cooling), then held at 5 °C or below, and the cold chain had been maintained. That evidence does not exist here, and the blast chiller is broken. Record the discard, the reason, the time and the amount, and inform the catering manager. Arrange an alternative rice dish or buy in a verified chilled product. The wedding can still be catered for, but not with this rice.
3. Set out a cooling and cold-holding procedure that would allow rice salad to be made safely in this kitchen, given the equipment constraints.
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Given the equipment, cook smaller batches. Divide the rice into shallow trays no more than about 5 cm deep, or use several gastronorm pans, and cool rapidly: use the working walk-in chiller with space around each tray, or an ice bath with clean ice and water, stirring with a clean sanitised probe or paddle. Target 63 °C to 8 °C within 90 minutes; if using two-stage cooling, 63 °C to 21 °C within 2 hours and 21 °C to 5 °C within a further 4 hours. Once cold, hold at 5 °C or below, label with the time and date, and use within 24 hours. Keep the rice salad cold at 5 °C until service, and do not mix warm rice with mayonnaise or other cold ingredients. Record the cooling times and temperatures, calibrate the probe, and train staff. If a batch misses the target, discard it.