Using Food Thermometers - Dial Versus Digital

By Megan Lane, Penn State Food Science Undergraduate Student

In a recent study published in the July/August 2014 edition of Food Protection Trends, Instant-read Food Thermometer Accuracy in Measuring End-point Temperature in Ground Beef Patties Prepared by Three Methods, researchers evaluated the dial and digital food thermometers for measuring cooking temperature in ground beef patties. While both types of thermometers demonstrated to be useful in determining the temperature of foods, the digital food thermometer proved to be the better choice for multiple reasons.

First is the sensor area. Dial food thermometers have a sensor spanning from the tip of the probe, two to three inches up the stem of the probe. Digital food thermometers have a sensor located in the tip of the probe, measuring to be about one centimeter in length. Because the length of the sensor is much shorter in digital thermometers, it’s useful when measuring thin pieces of meat or foods like hamburgers.

Second is the accuracy. Dial thermometers are a lower grade of technology, so they need to be calibrated upon their initial use and then on a regular basis after that. If it’s not calibrated, dial thermometers will not be as accurate as they could be. Digital thermometers, on the other hand, do not need to be calibrated, making them more accurate to begin with and easier to use. In this study, investigators found that dial thermometers were ± 2°C to 6°C (without calibration), while digital thermometers were ± 1°C compared to the standard.

Third is the time it takes to get the reading. Even though both types of thermometers are advertised to be “instant-read food thermometers,” these readings are not instant. It is important to note that both types need time for readings to stabilize in order to provide accurate results. In this study, it was found that a dial thermometers response time ranged from 18 – 55 seconds, whereas a digital thermometers response time ranged from only 16 – 40 seconds.

Lastly is the price. Dial food thermometers are cheaper than digital food thermometers, but the increased price of digital thermometers provides more benefits (faster stabilization time, no need for calibration, the ability to be used in thinner products, and finally, more accurate readings).

This study also evaluated the process of measuring temperature in ground beef patties. A key point of the study showed that as the meat cooks, a temperature gradient exists at different points within the meat patty and decreases the accuracy of thermometer readings. The accuracy of the readings was also varied by the frequency of patty flips and whether or not the patties had toppings on them. Researchers suggested that in order to reduce variation, burgers be flipped frequently and that they be plain. The problem with this recommendation is that constant flipping dries burgers out and people do like to add toppings during cooking. Therefore, consumers should take this into account to ensure burgers reach the proper temperature.