The Thermapen® has a micro-thermocouple located at the very tip of its probe shaft. A thermocouple is a set of two heat-sensitive wires that produce a voltage related to temperature difference. This technology is typically found only in professional-grade thermometers and is what sets your Thermapen apart from other digital instant-read thermometers.
Because the micro-thermocouple is so small, your Thermapen need only be inserted at least 3 mm to get an accurate reading. Other cooking thermometers may need 12 mm or more of immersion.
To take a temperature reading with the Thermapen, penetrate the food with the probe and place the very tip of the probe in the area where a temperature measurement is needed. When testing doneness in most foods, the coldest part will be the very center of the thickest portion. With larger foods, take quick readings with your Thermapen in several locations to verify that the entire portion is done. If chilling food, the center of the thickest part will be the last to cool.
Different parts of a piece of meat will be at different temperatures during the cooking process. It is not unusual for the internal temperature of a large roast or turkey to vary by as much as 10 to 15°C throughout the meat or bird. Even a steak or a boneless chicken breast will show differences of many degrees as the tip of the Thermapen probe moves from the surface toward the center of the piece, or from end to end.
To get a proper reading with the Thermapen, insert the probe tip into the thickest part of the meat from the top*. Make an effort to avoid any obvious bone or gristle. Note the temperature.
Slowly push past the center and watch the temperature rise in real-time at every depth in the piece of meat. Slowly withdraw the probe and watch the temperature change in the opposite direction. If the meat has already been cooked on both sides the very center of the thickest part should have the lowest reading. That is the best place to gauge doneness.
Experiment with your Thermapen and gain confidence. Learn to quickly check a piece of meat, a roast, or a whole bird in several places and depths to gauge overall progress during cooking. Lesser quality thermometers such as dial types or slower digitals may not show as much temperature difference. Only a very fast and sensitive thermometer like the Thermapen can show the exact temperature at its tip.
* Many experts recommend inserting your thermometer probe from the side of a steak or pattie to ensure that you get the probe tip right in the center, where the temperature will be lowest. You can use a pair of tongs to gently lift the piece of meat off the heat with one hand while you take a Thermapen reading from the side with your other hand.
A Thermapen is ideal when baking bread. First, you can use it to check the temperature of the liquid, which is crucial in many recipes. And you can use it to be sure your bread is done. Rustic breads are generally done at 93 to 98°C, while rich, buttery yeast breads are done when they reach 88 to 94°C.
For free form loaves, insert the probe through the side or bottom of the loaf, making sure the probe reaches the center. For loaves baked in a pan, to avoid creating a hole in the top crust, insert the thermometer from the side, just above the edge of the pan, directing it downward toward the center of the loaf.