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Temperature Control

Temperature control at different stages

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  • Cooking

    Q. What temperature should food I cook food to?

    Food should be cooked thoroughly to kill food poisoning bacteria. The core temperature should reach 75° C instantaneously or equivalent, e.g., 70° C for two minutes. The core is taken as the centre or thickest part of the food.

    There are equivalent time/temperature combinations which can be used to achieve a reduction in Listeria monocytogenes, which are outlined below:

    For more information on equivalent time/temperature combinations refer to Guidance Note 20.

  • Hot Holding

    Q. What temperature should I hot hold cooked food at?

    Keep hot food above 63° C (for example in a bain marie). This is outside the danger zone (5° C - 63° C). Bacteria grow best in warm temperatures, approximately 25° C – 40° C. Lukewarm food is dangerous as it is a perfect environment for bacteria to thrive. If cooked food is not stored above 63° C, it should be used up within two hours of cooking. Ensure the first batch of cooked food being hot held is served first. Where possible, do not mix batches. It is recommended that the first batch is used before adding a different batch.

  • Reheating

    Q. What is the correct temperature that food should be reheated to?

    Food must only be reheated once following cooking or hot holding. The food should be reheated to piping hot, greater than or equal to 70° C at the core of the food.

  • Refrigeration

    Q. What is the correct temperature for my fridge?

    The thermostat of all fridges and chill storage cabinets should be set at a temperature that will ensure that the temperature of the food is between 0° C and 5° C. This is to keep the food outside the danger zone (5° C – 63° C) so bacteria will not multiply (or will multiply very slowly). In general, fridges set at 3° C or 4° C will ensure that the food is between 0° C and 5° C.

  • Cooling

    Q. How long can cooked food be kept at room temperature before refrigerating?

    Following cooking, food which will not be consumed immediately should be cooled as quickly as possible and put in the fridge within two hours. Do not overload the fridge with warm food as this will raise the overall temperature of the fridge which increases the possibility of bacteria growing in the food.

    Q. How can I cool down cooked food safely within 2 hours?

    To speed up the cooling process for large quantities of hot food, you can use one or more of the following options:

    • Use a blast chiller to chill down food especially if you chill lots of food in your business. A blast chiller is specially designed to chill hot foods quickly and safely.
    • Divide food into smaller portions. Smaller amounts of food cool down more quickly.
    • Pour hot liquids or sauces into larger containers. The surface area will be increased and therefore the liquids will cool down more quickly.
    • Place containers of hot food in cold water/ice bath. The cold water/ice bath makes the contents of the containers cool more quickly.
    • While food is cooling down, stir regularly with a clean utensil. Stirring helps food cool more evenly.
    • Move hot food to a colder area (e.g., a larder). Food will cool more quickly in a colder place.
    • Some ovens have a ‘cool’ setting, which can help to cool down food by increasing the airflow around it (the oven should be cool first).
  • Freezing

    Q. What is the correct temperature for my freezer?

    Freezers should be maintained at -18° C or colder in food businesses. Ice cream can be stored at -12° C in food service areas. The temperature in domestic ice boxes can vary from -6° C to -18° C, depending on the star rating. But remember, the warmer the temperature, the shorter the shelf life of the frozen food. If a freezer is located in a warm area of a premises, the temperature should be lower, as required.

    Q. Can I refreeze food that has been already thawed?

    No, only freeze food once. When food is defrosted, bacteria can multiply. If this is frozen again the amount of bacteria could be at a dangerous level.

    However, you can defrost food, cook it and freeze it again. For example, frozen minced can be defrosted, used to make a lasagne, and frozen for use later.

  • Defrosting

    Q. How should I defrost food?

    The best place to defrost food is in the fridge. This ensures that the temperature of the surface of the food will not exceed 5° C. Do not rinse frozen food under the cold tap in a sink to defrost.

    A fast way to defrost food is in the microwave on the ‘defrost’ setting. This method is not recommended for foods which will not be cooked immediately, as the temperature of the outside of the food is likely to rise above 5° C, allowing food poisoning bacteria to grow.

    Q. How long can I keep defrosted food in the fridge before cooking it?

    Once the food is fully defrosted it is best to cook it straight away. Once cooked it can be stored in the fridge again (for 2-3 days) or frozen.

  • Checking temperature

    Q. How do I check that the temperature of food is correct?

    You should use a calibrated probe thermometer to check and monitor the temperature of food, as part of your food safety management system (i.e., HACCP plan). You should record the temperature measured. You should sanitise the probe thermometer using antibacterial/sterile wipes before and after use, to prevent cross contamination. Make sure wipes do not dry out because if they do they will be ineffective.

    You should take the temperature of the food at the core of the food. If this is not possible, (e.g., vacuum packed and frozen foods) you should measure the temperature between packs. Your temperature probe should have an accuracy of at least ±0.5° C. Do not use mercury thermometers as it would present a contamination risk if it breaks.

  • Thermometer calibration

    Q. How do I know that my probe thermometer is accurate?

    You should check your thermometer at least twice a year to ensure that it is accurate. This is called calibration. To check your thermometer is accurate for:

    • Low temperatures: Place tip of thermometer probe into crushed ice and a little cold water - wait for the display to stabilise then measure reading (it should be between -0.5° C and +0.5° C)
    • High temperatures: Immerse the tip of thermometer probe in boiling water, wait for the display to stabilise and record reading (it should be between 99.5° C and 100.5° C)

    If you find that your thermometer is faulty, either replace it or return it to the manufacturer/supplier for external calibration. In this event a spare thermometer is required.