Temperature is the most effective weapon against bacteria. Cold slows or stops their multiplication. Heat kills most of them. Between the two lies the danger zone, 5 °C to 63 °C, where they grow quickly. The values in this lesson come from the Código de Boas Práticas para a Restauração (AIHSA), a sector good practice guide, and not from the law. Annex II, Chapter IX, of Regulation (EC) No 852/2004 requires that foods which allow micro-organisms to multiply are not kept at temperatures that put health at risk, and that the cold chain is not broken.
Cold
- Refrigeration: 0 to 5 °C.
- Freezing: below -18 °C. Freezing is done in quick-freezing equipment, so that the food freezes in the shortest possible time.
- Take out of the cold only what you are going to use. Short periods outside the cold are allowed during preparation, but without risk to health.
- Check and record the temperatures of the equipment.
Defrosting
- The best way is to defrost in the fridge. Once defrosted, the food must be cooked within 24 hours.
- Alternatives: in the microwave, at the right power, or in a sealed bag under cold running water.
- The food is placed in a container with a rack, so that it does not sit in the liquid that drains off, and with a label.
- Never at room temperature, on the worktop.
- Some small foods, such as rissoles or frozen chips, can be cooked while still frozen.
Cooking
- In the centre of the food, the temperature must be above 75 °C. If it is not reached, cooking is continued.
- It is measured with a probe thermometer, at the thickest point. The probe is cleaned and disinfected between measurements.
- Lightly cooked foods, such as a rare burger or a soft egg, carry more risk.
- In dishes that end up lightly cooked, such as bacalhau à Brás (a Portuguese salt cod and egg dish), the Code suggests using pasteurised egg.
Cooling
When they are meant to be served or stored cold, cooked dishes must cool as quickly as possible (Annex II, Chapter IX). Divide into small portions and use shallow containers, an ice bath or a blast chiller. Then it goes into the fridge. It is not left to cool slowly on the worktop.
Hot holding, reheating and buffets
- Keep hot food always above 63 °C.
- Reheat to above 75 °C at the core.
- Cold dishes on display: below 7 °C.
- In self-service and buffets, the display time of food must be 2 hours at most, and the temperature of the bain-marie is checked regularly (every 2 hours, for example).
Frying
- Do not exceed 180 °C; lower to about 100 °C when you are not frying.
- Drain food well before putting it in the oil and do not overload the fryer.
- Check the quality of the oil with polar compounds tests and by observation: burnt smell, dark and cloudy colour, smoke at 170 °C and foam with bubbles. When the oil breaks down, change it.
- Clean the fryer every time you change the oil.
Key points
- Cold: 0 to 5 °C; frozen: below -18 °C.
- Cooking: above 75 °C in the centre.
- Hot: above 63 °C; cold on display: below 7 °C.
- Defrost in the fridge and use within 24 hours.