DIAL FOOD THERMOMETERS
Types of dial thermometers & their culinary uses
category of thermometers are also known as bimetallic-coil thermometers.
generally use either bi-therm metals or a spring. Bi-therm stem thermometers
comprise two or more metals that expand at different rates with temperature changes,
causing the dial to turn when expansion and contraction occur. Spring thermometers
have an actual spring, which similarly expands and contracts, causing the dial to
turn. Of the two, bi-therm thermometers are more reliable, and can usually be
re-calibrated. These food thermometers have a dial display and are available as "oven-safe"
This food thermometer is designed to remain in the food while it is cooking in the oven,
and is generally used for large items such as a roast or turkey. This food thermometer
is convenient because it constantly shows the temperature of the food while it is
cooking. However, if not left in the food while cooking, they can take as long as 1 to 2
minutes to register the correct temperature.
The bimetal food thermometer can accurately measure the temperature of relatively thick
foods (such as beef roasts) or deep foods (foods in a stockpot). Because the
temperature-sensing coil on the stem is between 2 to 2 1/ 2 inches long and the stem is
relatively thick, it is not appropriate to measure the temperature of any food less than
3 inches thick. There is concern that because heat conducts along the stem's metal surface faster than
through the food, the area of the food in contact with the thermometer tip will be
hotter than the area a short distance to the side (the "potato nail effect"). To remedy
this, the temperature should be taken in a second, and even third area, to verify the
temperature of the food. Each time the thermometer is inserted into the food, let the
thermometer equilibrate (come to temperature) at least 1 minute before reading the
Some models can be calibrated. Check the manufacturer's instructions.
This food thermometer quickly measures the
temperature of a food in about 15 to 20 seconds. It is not designed to remain in the
food while it is cooking in the oven, but should be used near the end of the estimated
cooking time to check for final cooking temperatures. To prevent overcooking, check the
temperature before the food is expected to finish cooking. For accurate temperature
measurement, the probe of the bimetallic-coil thermometer must be inserted the full
length of the sensing area (usually 2 to 3 inches). If measuring the temperature of a
thin food, such as a hamburger patty or boneless chicken breast, the probe should be
inserted through the side of the food so that the entire sensing area is positioned
through the center of the food. Some models can be calibrated. Check the manufacturer's
Other Types of Thermometers
One of the most recent developments in the
retail food market is the emergence of disposable temperature indicators. Several brands are
available, and all make quick work of determining if a food has reached its final
temperature. These temperature sensors are designed for specific temperature ranges, for
example, 160 -170 °F. It is important that the sensors be used only with foods for which
they are intended. Read the package directions to ensure that the temperature the sensor
will reach is consistent with the safe temperatures listed in this publication. The sensors
are made from special temperature-sensitive materials. The sensor is inserted into a food.
When the food reaches the proper temperature, the sensor changes color. They are designed to
be used only once. However, if the desired temperature has not been reached, they can be
reinserted until the temperature is reached. These sensors cannot be left in a food while it
cooking. They should be used near the end of the estimated cooking time. To prevent
overcooking, check the temperature before the food is expected to finish cooking. Disposable
temperature indicators are made from materials approved by the FDA for contact with food
Commonly used in turkeys and roasting chickens since 1965, the "pop-up" temperature
device is constructed from a food-approved nylon. The inside contains a stainless steel
spring and firing material. The firing material is made of an organic salt compound or an
alloy of metals commonly used in other thermo-sensing devices. The tip of the stem is
imbedded in the firing material until it melts, releasing the stem, which is then "popped
up" by means of the spring. This indicates that the food has reached the final temperature
for safety and doneness. Pop-up timers are reliable within 1 to 2 °F if accurately placed in
a food; however, checking the temperature of other parts of the food with a conventional
food thermometer is recommended.
Also called "spirit-filled" or "liquid in glass" thermometers, these thermometers are the
oldest kind of food thermometer used in home kitchens. They have either metal or glass
stems. As the internal temperature of the food increases, the colored liquid inside the stem
expands and rises to indicate the temperature on a scale. Heat conduction in the metal stems
can cause false high readings. They are designed to remain in the food while it is cooking.
They should be inserted at least 2 inches deep in the thickest part of the food, and are,
therefore, not appropriate for thin foods. Some liquid-filled thermometers can be calibrated
by carefully moving the glass stem within the holder.
/ jelly deep-fry thermometers..
These thermometers will measure temperatures ranging from 100 to 400 °F. They are used to
measure the extra-high temperatures required of candy and jelly making, as well as frying
with hot oil.
For safety, it is important to verify the temperature of refrigerators and freezers.
Refrigerators should maintain a temperature no higher than 40 °F. Frozen food will hold its
top quality for the longest possible time when the freezer maintains 0 °F. An appliance
thermometer can be kept in the refrigerator and freezer to monitor the temperature. This can
be critical in the event of a power outage. When the power goes back on, if the refrigerator
is 40 °F or colder, and the freezer is still colder than 40 °F, the food is safe. These
bimetallic-coil thermometers are specially designed to provide accuracy at cold
Asian Melting Pot
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