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All About Cooking Thermometers

One of the critical factors in fighting food-borne illness is temperature. Bacteria grow slowly at low temperatures and multiply rapidly at mid-range temperatures. To be safe, a product must be cooked to an internal temperature high enough to destroy harmful bacteria.

Using a meat thermometer is a reliable way to ensure that food has reached the proper temperature. However, to be effective, thermometers must be used properly and calibrated correctly. If the thermometer is inserted incorrectly, or placed in the wrong area, the reading may not accurately reflect the internal temperature of the product. In general, the thermometer should be placed in the thickest part of the food, away from bone, fat or gristle. Read the manufacturer's instructions on how to calibrate (check the accuracy of) the thermometer.

According to the U.S. Department of Agriculture, temperature is the only way to gauge whether food is sufficiently cooked. USDA research reveals that the "color test" can give consumers misleading information about the safety of the foods they are preparing, since cooked color varies considerably. For example, freezing and thawing may influence a meat's tendency to brown prematurely.

The chart below provides information on different types of kitchen thermometers available, and tips to consider during their use. A graphic version of the chart suitable for printing is available in PDF format (13K).

Liquid-Filled Thermometer

Speed: 1-2 minutes
Placement: 2 inches deep in thickest part of food
Suggested Use: roasts, casseroles, soups
Considerations:

can be placed in food while cooking
cannot measure thin foods
calibration cannot be adjusted
possible breakage while in food
heat conduction of metal shield can cause false high reading

Bimetal (oven-safe) Thermometer

Speed: 1-2 minutes
Placement: 2 to 2-1/2 inches deep in thickest part of food
Suggested Use: roasts, casseroles, soups
Considerations:

can be placed in food while cooking
not appropriate for thin foods
heat conduction of metal stem can cause false high reading

Bimetal (instant-read) Thermometer

Speed: 15-20 seconds
Placement: 2 to 2-1/2 inches deep in thickest part of food
Suggested Use: roasts, casseroles, soups
Considerations:

checks internal temperature of food at end of cooking time
can be calibrated
cannot measure thin foods unless inserted sideways
cannot be used in oven while cooking food
temperature averaged along 2-3 inches of probe

Thermistor Thermometer

Speed: 10 seconds
Placement: 1/2 inch deep
Suggested Use: hamburger patty, pork chops
Considerations:

digital
measures temperature in thin foods
cannot be used in oven while cooking

Thermocouple Thermometer

Speed: 5 seconds
Placement: 1/4 inch deep or deeper
Suggested Use: hamburger patty, pork chops
Considerations:

digital
quickly measures thinnest foods
can be calibrated

(Source: U.S. Department of Agriculture)

FDA Consumer magazine (September-October 1998)

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