Fact Sheet 6a:Using a Probe Thermometer
Before taking temperatures:
- Check where your thermometer measures the temperature. Some measure at the tip of the probe and others may need to be inserted 2cm to 3cm into the food.
- Clean the probe. This can be done using sterile wipes or very hot water (above 82°C). Then let the probe air-dry.
- Insert the probe and let the temperature settle and then note the temperature.
- Remember that the temperature at the centre of food may be different from the surface temperature.
- When checking that meat is thoroughly cooked, it is important that the centre of the meat reaches 75°C+ for two to three minutes.
- When measuring liquids or thicker products like custard and gravy, the whole product should be at 75°C.
- If in doubt, measure the food at its coolest place. If the temperature is correct here, the food will be safe.
Calibration is the process of making sure your thermometer is reading correctly.
Thermometer Calibration (cold temperature test)
- Pour a mixture of 50% crushed ice and 50% water (ice slurry) into a suitable container.
- Let the mixture stand for five minutes to allow the temperature of the mixture to evenly distribute.
- Place the probe of the thermometer into the mixture. Make sure your probe is suspended and not sitting on the bottom of the container.
- Wait for approximately two minutes. Write down the reading of the thermometer. It should read 0°C (-1ºC to +1ºC is acceptable).
- If the thermometer reads more than +1°C difference it will need to be re-calibrated or replaced.
Thermometer Calibration (hot temperature test)
- - Boil tap water and place the temperature probe into the boiling water. Wait for a few minutes to allow the temperature to stabilise.
- - Write down the temperature of the thermometer. It should read 100°C (99ºC to 101ºC is acceptable).
- - If the thermometer differs more than ±1°C it will need to be recalibrated and serviced.
Note: Calibration temperatures vary with atmospheric pressure. If you are on a mountain remember that the boiling and freezing points of water will differ from the temperatures we have listed. Use clean water as bore water with mineral salts can give inaccurate readings.