Product Knowledge Guide: Thermometers

Thermometers play an integral role in commercial kitchens’ food safety plans. These instruments help monitor temperatures in ovens, grills, fryers, refrigerators, freezers, beverages, milk frothing and food as well as air temperature.

iStock 000019535730 FullThermometers typically feature stainless steel construction with various temperature dial or display sizes. This tool is categorized by type, including thermocouple, thermistor, bimetal, infrared and digital probe, as well as use, such as oven and grill, refrigerator/freezer/air, beverage and frothing, candy and deep fry.

Foodservice operators can choose from a number of thermometer types. Bimetal or dial types are designed to leave in the oven, while others are not. Bimetal thermometer sensors feature two different metals bonded together. When heated, the combination will bend because one metal expands faster than the other. A bimetal strip can be wound in the shape of a one- to two-inch coil, which winds or unwinds as the temperature changes. A pointer attaches to the free end, and the temperature registers on the dial beneath the pointer. These thermometers are durable, inexpensive and recalibratable but take longer to record temperatures since they have to be inserted past the top of the bimetal coil for accurate measurement.

Glass column thermometers contain a food-safe fluid sealed in a glass or plastic tube. A bulb at the column base contains fluid and expands or contracts as the temperature changes. Operators can read the temperature from a scale printed on or near the column. While these thermometers are economical and easy to use, the glass can break, and the use of induction cooktops can interfere with accuracy.

The most popular style of digital thermometer includes a thermistor, which is a tiny, thermally sensitive object located in the thermometer’s tip. A change in electrical resistance takes place with temperature variances, and the passing of a direct current and production of a voltage drop measures resistance. Although less expensive than digital thermocouple thermometers, the speed of response is comparable.

Thermocouple digital thermometers provide the quickest results, showing temperature readings in about two seconds. This type has a thin probe and is most often used to check final cooking temperatures in meat. The thermometer has two different metal wires joined together at one end and connects to a voltage measuring device at the other. When the thermometer is heated or cooled, a voltage is created that can be correlated to temperature. A variety of metal combinations or calibrations are available.

Infrared thermometers quickly measure surface temperatures without touching the item being measured by using infrared light rays. Not only do the thermometers provide temperature readings for hot, small or distant objects or food, but they also eliminate the possibility of cross contamination with temperature monitoring since they don’t come in contact with the food.

Technologically advanced wireless monitoring systems protect inventory and help ensure equipment is working correctly by automatically measuring critical metrics, such as temperature and humidity. Equipment including walk-ins, freezers, dish machines, hot holding boxes and dry storage rooms can be monitored to ensure food quality and safety. If readings fall outside of preset limits, notifications can be sent to the appropriate people.

Portable handheld devices combine sophisticated software with a traditional thermocouple instrument to collect, track and store food temperature data. Some models also allow users to walk through procedural checklists. These portable handheld devices can make adhering to HACCP guidelines less cumbersome. When temperature or a checklist item is out of the designated range, many of today’s models will prompt operators to take corrective action. 

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