FOR MEASURING FOOD TEMPERATURES
by O. Peter Snyder, Jr., Ph.D.
Hospitality Institute of Technology
670 Transfer Road, Suite 21A
St. Paul, MN 55114
1. The coil extends in the stem from about 1/4 inch to about 3 inches
up the stem. This coil measures the average temperature of the food surrounding
the coil. In a pan of hot food, this can be +/-50F, and the coil only gives
the average temperature. For example, the food might be 100F at the top
of the pan and 200F at the bottom of the pan, and the coil reads 150F.
2. The specification that the thermometer is accurate to +/-2F is only
true under perfect laboratory conditions. The thermometer must be perfectly
calibrated in slush ice, not cube ice, and the pointer must be precisely
on 32F. The companies that make these thermometers provide no guarantee
of accuracy at 150F or higher, because the coil, after perhaps as little
as a week of use, can corrode in the stem, causing it to malfunction.
3. For many mechanical reasons, the stem can get filled with liquid from
food or wash water that seeps in around the gasket at the nut. This device
is not designed to be immersed. The Oregon Department of Agriculture has
reported that when inspectors check thermometers in operation, they are
often off by more than 10F.
In summary, because of the problems with construction and calibration,
this device cannot be trusted to give an accurate reading. The thermistor
or thermocouple should be used.
The bimetallic coil thermometer is not a satisfactory device for measuring
food temperatures for the following reasons as shown in the photographs.