How to Use a Food Thermometer Accurately
At ETI we manufacture a range of different food thermometers, many of which use penetration probes to measure the internal temperatures of liquid and solid foods. There are several different types of food thermometer probes that we make: thermocouple, thermistor and PT100. Each type varies slightly in speed of response, size and accuracy, but each works by inserting the probe into the food being measured, and sending signals to the thermometer unit to produce a reading.
Taking accurate measurements using a probe thermometer might sound simple, but it can be surprisingly easy to do incorrectly. Ensuring that readings are taken properly is essential for the safety and quality of your food.
The type of application will help to determine what level of accuracy is required. Cooking a rare steak will require a high level of accuracy in order to ensure it is spot on, whereas soups or reheated foods require less accuracy because they only need to be 74°C or higher. Read on to learn how to take the temperatures of different types of food.
How to measure solid foods
Whether heating or cooling solid food, the centre of the thickest portion will be the slowest to change in temperature. Therefore, this is the area you will need to measure to ensure it has fully cooked or cooled. To locate the centre of a food such as meat, slowly insert your thermometer into the meat and watch how the temperature drops as you approach the centre, before rising again as you move past it. By doing this you can locate the lowest temperature of the meat, ensuring that this reaches your safe or desired temperature.
For whole birds, the thickest part is usually between the breast and the thigh. Meat like this will usually vary in temperature considerably throughout, providing very different readings in the legs to the breast. It’s a good idea to spot check large pieces of meat to ensure they have come to temperature all over, while also being mindful to avoid bones or gristle as this can provide an inaccurate reading.
For smaller, thinner pieces of meat such as burgers, steaks and chicken breasts or wings, it’s important to make sure that the probe does not go all the way through the meat and onto the surface beneath. Holding the meat between a pair of tongs and taking the temperature from the side instead of above can help to prevent this. Our Thermapen thermometers feature a type K thermocouple probe that only needs to be inserted 3 mm into foods to get an accurate reading, making them ideal for smaller cuts of meat.
How to measure liquid foods
Taking an accurate temperature reading of liquid foods is slightly different to solids because they heat and cool by convection rather than conduction. Therefore, it’s not simply a matter of taking a reading from the centre, but by checking the liquid as a whole. The best way to do this is by stirring the liquid first, and then stirring the thermometer probe through the liquid, watching the temperature change as it moves through the food.
Speed of response
The temperature on some thermometers will take longer to stabilise than others, this is down to the sensor type. For thermometers with slower response times, it’s important to give them time to provide an accurate reading. For thermometers with fast response times, such as our Thermapen One which reads the temperature in one second, it’s good to remember that often the food itself is changing in temperature as the thermometer is reading it, therefore a change in readings is simply a reflection of the food continuing to cook even if it’s off the heat.
What about the thermometer accuracy?
There are a number of factors that give thermometers a guarantee of accuracy, including the competence of the laboratories in which they are calibrated and the documentation for each step of the process. The best way for users to determine the accuracy of their thermometer is through its measurement certainty. The measurement certainty is how much the instrument reading can vary from the true temperature of the thing that is being measured, this is represented by the symbol ±. For example, if measuring the temperature of 100° C boiling water, a thermometer with an accuracy of ± 0.5° C may display a reading from 99.5°C to 100.5°C.
To learn more about accuracy and to learn how to validate the readings on your thermometer using an ice bath, try reading our What Is Thermometer Accuracy blog post.
Top 3 penetration probe thermometers
The latest model of our flagship product, the Thermapen One reads temperatures in just one second. Combining speed, accuracy and ease of use, the One is the perfect thermometer for quickly carrying out a range of HACCP checks.
The Food Check is a great economic choice for food and catering professionals. Featuring a type K thermocouple probe, it has an accuracy of ±0.4 °C and a resolution of 0.1 °C. With a battery life that lasts a minimum of 5 years, the Food Check is perfect for monitoring cooked and chilled temperatures as part of HACCP and health and safety procedures.
The Therma 20 is a thermistor thermometer with a high system accuracy of ±0.4 °C (-24.9 to 109.9 °C). It is compatible with a wide range of probes and has assured accuracy for the life of the thermometer, making it a reliable choice for daily checks.
Here is a chart of chef recommended temperatures to use as a cooking guide.
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