Thermometers

Kitchen thermometers. © CooksInfo / 2013

Kitchen and food-use thermometers are used for several purposes. One key purpose is food-safety, by ensuring that food is either stored at or cooked to a safe temperature range. Another purpose is to gauge what state of physical transformation a food being cooked is at.

Thermometer choices

Thermometers come in many different varieties and scales. The choice isn’t just between Fahrenheit or Celsius: some of the simpler ones are not really thermometers at all. They just show ranges — rare, medium, burnt-offering, etc. Some have mercury in them, but most are pure metal these days because it is safer (and cheaper.) Some are so high-tech they’re even fun (toys for boys.)

Digital ones require batteries. Dial ones are also called “analog.”

Digital ones are better for checking thinner foods — they are the ones that food safety experts recommend for checking hamburgers. Large-dial ones are better for large pieces of meat.

When using a mercury thermometer, keep it upright while cooking and while it is hot. If you lay it down, the heated mercury may separate into small beads and render the thermometer useless in the future. Always let glass thermometers cool completely before cleaning or they may shatter.

What all thermometers have had in common is that they had to touch the food to work. This leads to the possibility of cross-contamination. We need a thermometer that you can just point at something on the grill, click a button to shoot and presto, there’s your temperature, with no surface contact needed. There are now (since about 1998) infra-red thermometers that do something like this, except they have one show-stopping limitation: they can only measure the surface temperature of food, and, given the nature of how infra-red rays work, it’s not likely that this limitation can be overcome with this technology.

Cooking Tips

From time to time, check the accuracy of your food thermometers. Bring some water to a rolling boil, put the thermometer skewer 5 cm (two inches) in, not allowing it to touch the bottom, and hold it there. If there’s a lot of steam, mind the steam: you may even want to put an oven glove on. Hold it there: after 30 seconds, an Instant Read Meat Thermometer should be reading 100 C (212 F). An Oven Safe Meat Thermometer may take up to two minutes to show the correct temperature. If your dial-type thermometer is off and has a nut underneath the dial part, then you can “calibrate” it by adjusting the nut. If your thermometer is designed so that you can’t calibrate it in this way, then you need to plan in the future to take into account how much it is off by, or pitch it and buy a new one.

Literature and Lore

“In the days of wood-fired stoves about all a good cook could guess were the differences between slow, moderate, fairly hot, hot, and very hot. Next came gas oven with marks on the gas tap called ‘Regulo’; these were an improvement but still not ideal. Then came the oven-door thermometers with a precision of plus or minus about twelve degrees – if they were carefully and regularly calibrated. Needless to say this was rarely done, so cooks knew that they had to ‘learn the oven’ whenever they needed to cook in a strange place – really not much better than the old wood stove days.

Through all of this, cooks also had to contend with words such as ‘Cool oven’ to ‘Very hot oven’, the Regulo marks, Fahrenheit, centigrade, and finally Celsius temperatures… When we are cooking on an old Fahrenheit stove we simply halve the Fahrenheit temperature to give us a guide to the correct temperature in degrees Celsius.” ^[1]Pomroy, Wendy and Pat Naughton. Metric cooking with confidence. Metricationmatters.com 2008. Page 4.

Sources

Blewitt, Tom. Infrared thermometers help food safety professionals prevent foodborne illness. Melville, NY: Engineering Services, Underwriters Laboratories Inc., 1999.

Health Canada. “Food Safety Tips for Using Food Thermometers”. Publication P0285E-03. March 2003.

USDA Food Safety and Inspection Service. The Thermy™ Campaign. May 2002.

Types of cooking thermometers

Bimetallic-Coil Thermometers

Bimetallic-coil thermometers have in them a coil made of two different metals, which expand at different rates. This causes the coil also to expand, thus moving a dial. These type of thermometers must be inserted into meat a minimum depth for accurate...

Candy Thermometer

A candy thermometer (aka deep fry thermometer) can be used to test the temperature of mixtures for candy, jam or jellies or of oil being heated for deep-frying.

Cheese Thermometer

A cheese thermometer is used to gauge the temperature of milk when making dairy products such as cheese or yoghurt.

Chocolate Thermometer

A chocolate thermometer is used when tempering chocolate. Tempering is a delicate operation and requires a thermometer to precisely measure stages of physical transformation of the chocolate.

Meat Thermometers

A meat thermometer is used to gauge the temperature of meat being cooked, to see if it is fully and safely cooked. There are many different types.

Disposable Meat Thermometers

Disposable meat thermometers are single-use temperature indicators that give you an idea of the temperature range a piece of meat being cooked is at.

Fork Thermometers

A fork thermometer is a digital thermometer built into a large fork. These are designed for people who are grilling (barbequing.)

Instant Read Meat Thermometers

Instant read meat thermometers are thermometers that give you nearly instantly the internal temperature of meat that is being cooked.

Oven Cord Meat Thermometers

Oven cord meat thermometers are thermometers that let you check the temperature of something cooking in the oven without opening the oven door.

Oven Safe Thermometers

Oven safe meat thermometers are meant to be inserted into meat before the meat is placed in an oven to cook.

Pop-Up Timers

Pop-up timers are devices designed to let you see visually when a piece of meat has reached a certain state of doneness during cooking. There's a spring inside them, which is held in place by a substance which melts at the right temperature, releasing...

Oven Thermometers

Oven thermometers help you to verify that your oven is actually operating at the temperatures you expect it to be.

Refrigerator Thermometers

Refrigerator thermometers are used to measure the running temperature of refrigerators and freezers in order to ensure that they are operating in a safe range to prevent food spoilage.