Keeping Hot Food Hot: Food Thermometer Use and Calibration for Food Safety

The favorite saying of dads everywhere is “hot food hot and cold food cold.”  It’s also inadvertently a great reminder to put one of the most important tools in your kitchen arsenal to work on a regular basis: the Food Thermometer.

Food thermometers come in a variety of different types–from meat thermometers to freezer thermometers–and they’re critical for ensuring that foods are stored and served at safe temperatures. This quick but thorough guide will cover the importance of thermometer calibration, break down the different types, best practices around their care and use, and more. Here's what we'll cover:

Importance of thermometer calibration

Different types of thermometers in the kitchen

Using a food thermometer

Let’s dive in. 

Importance of thermometer calibration 

We’ve already briefly touched on the importance of thermometer use in basic food safety practices, but it’s important to highlight just how vital it is. You can’t tell if food has reached a safe internal temperature just by looking at it or even by measuring a single section of it.

Serving unsafe food comes with many risks: foodborne illness, investigation into kitchen safety practices, potential fines, and even impacting restaurant staff and overall business. 

Food safety risks

As we’ve noted, you never want the kitchen to serve unsafe food to customers, including undercooked food. Unfortunately, food that is cooked properly can also run the risk of harboring dangerous bacteria if it spends too long in a “temperature danger zone.” According to the Food and Drug Administration (FDA), that’s between 41 degrees and 135°F (or 5 and 57.22°C).1

This is the temperature zone where bacteria grow the most rapidly, doubling in number in as little as 20 minutes. Food should never be left out of the refrigerator for more than two hours (or one hour if it’s above 90°F). 

Just remember the favorite saying of dads and keep: 

• Hot food hot, at or above 135 °F (57.22°C) 

• Cold food cold, at or below 41 °F (5°C) 

Quality of food 

The quality of the food that leaves your kitchen is critical to the reputation of your establishment and can also have an impact on business. Thermometer use here is important to ensure that you’re serving the best food possible; overcooked food might be safe, but it is not often delicious (unless directly ordered that way by the customer).

High-quality food leads to higher levels of customer satisfaction, which makes those customers more likely to leave a good review and recommend your establishment by word of mouth to friends, family, coworkers, and even strangers on the Internet. That, in turn, increases your overall reputation and works to bring in more business.

Now that we’ve covered why using a thermometer is so important, we’ll get into the how–including taking the time to calibrate it regularly. 

How to calibrate your thermometer 

Before attempting to calibrate a thermometer, be sure that it’s one that can be calibrated. Digital thermometers will have instructions on the package, as will dial thermometers. Most of these will have a nut under the dial that can be adjusted.

There are two main methods available: 

• Freezing method 0°C (32°F)

• Boiling method 100°C (212°F)

For the freezing method, use a glass of ice water. Be sure to immerse the thermometer’s stem a minimum of two inches into the liquid, keeping it away from the sides and bottom of the glass (touching those can result in an inaccurate reading). Wait at least 30 seconds before making any adjustments.

For the boiling method, bring a clean pot of water to a full, rolling boil. Be sure to immerse the thermometer in a minimum of two inches of liquid–once again avoiding the sides and bottom–and wait at least 30 seconds before making any adjustments.

For true accuracy, you also have to be mindful of the type of water you use– distilled results in the most accurate reading–and the atmospheric pressure. Meaning if you’re at altitude, adjust accordingly.

For more thorough instructions, see the the U.S. Department of Agriculture (USDA) guidelines for calibration of kitchen  thermometers.2

How often to calibrate 

Recommendations vary, but food thermometers should be calibrated at least daily to ensure food-safe temperatures in all food going out of the kitchen.

Other times to check your thermometers: 

• Before their very first use

• After being dropped (oops!) 

• When moved from one temperature range to another

• After a long time in storage (that candy thermometer) 

• After a power outage (for appliance thermometers) 

Different types of thermometers in the kitchen 

There are a wide range of kitchen thermometers out there. Some are absolutely necessary to ensure food safety–like those for appliances–and some you won’t need in every kitchen if they’re specialized around something you don’t serve.

Below is a quick guide; for a more in-depth breakdown, see the USDA’s guide.3

Digital food thermometers 

Digital thermometers can give the fastest available readings but vary in price and how they are meant to be used. Be sure to read any manufacturer’s instructions for proper calibration and storage.

Types of digital food thermometers: 

• Thermocouples 

• Thermistors

• Oven cord

• Thermometer + fork combo

Dial food thermometers 

These food thermometers give readings that are just as accurate but take a little bit longer than their digital cousins. Be sure to read any manufacturer’s instructions for proper calibration and storage for these as well. 

Types of dial food thermometers: 

• Bimetallic-coil thermometers 

• “Oven-safe” bimetallic-coil thermometers 

• “Instant read” bimetallic-coil thermometers 

• Single-use temp indicators 

• Pop-up timers 

Other types of food thermometers

More specialty types of thermometers exist, either to ensure food safety for very specific types of cooking or to ensure that a recipe turns out correctly. For example, candy/jelly/deep-fry thermometers measure the highest temperature range and are meant to help with those specific cooking styles.

The most old-fashioned kitchens might still use a traditional liquid-filled thermometer. Care must be taken not to break it, and proper placement is especially important to get an accurate reading with these types of thermometers. 

Appliance thermometers

These thermometers are critical to ensure that food is stored at and cooked to the proper temperature. Every kitchen should have them, especially in the event of a power outage. 

Types of appliance thermometers: 

• Refrigerator/freezer

• Oven 

Using a food thermometer 

Just as temperature is taken differently for dogs and humans, different thermometer placement is necessary to ensure a specific food has reached the correct internal temperature. 

Proper placement 

For meat, place the thermometer midway into the cut and be sure to avoid the bone if one is present. For foods like hamburgers or chicken fried steak, be sure to insert the thermometer into the thickest part and keep it away from any bone, fat, or gristle to ensure an accurate reading. For irregularly shaped foods, measure in several different areas.

For poultry, the thermometer goes in the innermost part of the thigh and wing and the thickest part of the breast. For pieces of poultry, again measure the thickest area, avoiding any bones. As always, measure irregularly shaped foods in several different areas. 

For thin foods, it’s best to remove the food from the heat source and insert the thermometer sideways if necessary (don’t burn your fingers!). Digital thermometers can work better for these types of foods. 

Finally, for combination dishes like soups or stews, measure into the thickest part of the food and measure in several different areas if necessary. 

Best practices

You’ll want to keep thermometers clean and sanitized between uses to help ensure you’re getting the right reading on the next use and that you’re not cross-contaminating foods. That means using hot, soapy water and taking care not to submerge any parts of the thermometer that need to stay dry. 

Be sure to store thermometers properly; put them somewhere they’re not likely to break but are still as convenient as possible to use regularly. 

Final Thoughts 

Hot food hot and cold food cold: remember that, and you’ll keep customers (not just dads) happy and safe. 

One final important note: always check your local food code to ensure you’re following their food safety guidelines for professional kitchens! USDA guides are just a starting point. 

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