Food Thermometers: Safe Cooking Temperatures

Kitchen Thermometers

• Using a food thermometer is essential when cooking meat, poultry, and egg products
• It helps prevent undercooking and foodborne illnesses

Why Use a Food Thermometer?

• The only reliable way to ensure food safety and determine "doneness"
• Ensures food is cooked to a safe minimum internal temperature
• This process destroys harmful microorganisms

“Doneness”

• Refers to the desired state of cooked food
• Indicates sensory aspects like texture, appearance, and juiciness
• Differs from safety temperatures in that it is subjective

Color Isn't Reliable

• Color changes are unreliable for determining if pathogens are killed
• Ground beef may brown before reaching a safe temperature
• Using color alone risks pathogen survival
• Hamburgers should be cooked to 160 °F, checked with a thermometer, regardless of color

Saftey vs Doneness

• The temperatures to destroy different microorganisms vary, as well as the "doneness"
• Visual signs of "doneness" can lead to overcooking and dryness
• Using a food thermometer ensures safety without overcooking
• Cook raw beef, pork, lamb, and veal steaks, chops, and roasts to 145°F, measure with a thermometer, and let rest for at least three minutes before carving
• Consumers may choose to cook meat to higher temperatures for personal preference
• Poultry should be cooked to 165°F (thermometer)
• Food thermometers should be used to ensure safe holding temperatures: ≤40°F for cold food, ≥140°F for hot food

Types of Thermometers

• Food thermometers vary in type, style, technology, and price

Digital Food Thermometers

Thermocouple

• Displays temperature rapidly (2-5 seconds) on a digital display
• Measures temperature at the junction of two fine wires in the probe tip
• Some have thin probes (like hypodermic needles) and can be used in scientific laboratories
• Others may have a thickness of 1/16 of an inch

Thermistors

• Use a resistor to measure temperature
• Probe thickness is approximately 1/8 inch
• Register temperature of digital display in approximately 10 seconds
• Can measure temperature in thin and thick foods
• The center of food is cooler than the outer surface, place the tip in the center of the thickest part of the food

Oven Cord Thermometers

• Allows temperature checking without opening the oven
• A base unit with a digital screen is attached to a thermistor-type food thermometer proof by a long metal cord
• The probe is inserted into the food, and the cord extends from the oven to the base unit; the base can be placed on the counter or attached to the stovetop or oven door by a magnet
• It is programmed for the desired temperature and beeps when it is reached
• Designed for ovens, can be used for foods on the stove, but cannot be calibrated

Thermometer Fork Combination

• Combines a cooking fork with a food thermometer
• Temperature indicated on a digital display or indicator lights (2-10 secs)
• Thermometer accurate to measure the internal temperature of even the thinnest food, useful for grilling using the thermometer fork
• Should be used towards the end of cooking time and cannot be calibrated

Dial Food Thermometers

Bimetallic-coil Thermometers

• Coils containing two bonded metals with different expansion rates
• Connected to a temperature indicator, expands when heated
• Senses temperature from its tip and up the stem for 2 to 2 1/2 inches
• Thermometer has a dial display and available as oven-safe and instant-read

"Oven-safe" Bimetallic-coil Thermometers

• Designed to remain in food while cooking, generally for large items like roasts or turkey
• If not left in food, takes 1 to 2 minutes to register the correct temperature

“Instant Read” Bimetallic-coil Thermometers

• Accurately measures temperature of relatively thick foods (beef roasts) or deep foods (stockpot)
• The temperature-sensing coil on the stem is between 2 to 2 1/2 inches long and it is relatively thick
• It is not appropriate to measure the temperature of any food less than 3 inches thick.

Concerns About "Instant Read" Bimetallic-coil Thermometers

• 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
• 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, and to equilibrate (come to temperature) at least 1 minute before reading the temperature

“Instant Read” Bimetallic-coil Thermometers

• It quickly measures temperature of food in approximately 15 to 20 seconds
• Should be near the end of estimated cooking time
• For accurate temperature measure, the probe needs to be inserted full length of sensing area (2 to 3 inches)
• For thin foods, probe needs to be placed sideways

Single-Use Temperature Indicators

• Emergence of disposable temperature indicators have been developed
• Read package directions to ensure reach is consistent
• Made from temperature-sensitive materials, inserted into food
• Sensors change color when food reaches safe temp, can't be left in food while cooking

Pop-Up Timers

• Commonly used since 1965
• Constructed of food grade nylon
• Contains a stainless steel spring and organic firing material; once material dissolves, the stainless steel spring releases the stem to "pop up"
• Proper placement important and checking with a conventional food thermometer, recommended

Liquid-filled Thermometers

• Spirit filled or liquid in glass
• Oldest kind of food thermometer, metal or glass stems
• As temperature increases, liquid rises to indicate temperature on scale
• Should be inserted at least 2 inches deep, not appropriate for thin foods

Candy/Jelly/Deep Fry Thermometers

• Measures temperatures 100 to 400 °F
• Extra-high temperatures can be required for candy and jelly making, as well as frying with hot oil

Appliance Thermometers

Refrigerator/Freezer Thermometers

• Verify temperatures of refrigerators and freezers
• Refrigerators should maintain temps of 40 °F or below
• Freezers max quality hold at 0 °F or below

Oven Thermometers

• Verify that the oven is heating to desired temps
• Measure temperatures from 100 to 600° F

Food Thermometers Quick Guide

Thermocouple

• Speed: 2-5 seconds
• Placement: 1/4" or deeper
• Measures temps of thick/thin foods
• Not designed to remain in food while cooking
• Check temperature near end
• Can be calibrated
• Expensive

Thermistor

• Speed: 10 seconds
• Placement: At least 1/2" deep
• Measures thick/thin foods
• Check temperature near end
• Can be calibrated

Oven Cord Thermometer

• Speed: 10 seconds
• Placement: At least 1/2" deep
• Can be used in most foods
• Can be used outside oven/covered pot
• Cannot be calibrated

Thermometer Fork Combination

• Speed: 2-10 seconds
• Placement: At least 1/4" in thickest part of food
• Can be used in most foods
• Check temperature near end
• Cannot be calibrated
• Convenient for grilling

Ovensafe, Bimetal

• Speed: 1-2 minutes
• Placement: 2-2 1/2" deep
• For roasts/casseroles/soups
• Can remain in food while cooling
• Some can be calibrated

Instant-Read, Bimetal

• Speed: 15-20 seconds
• Placement: 2-2 1/2" deep
• For roasts/casseroles/soups
• To check at end of cooking
• Some can be calibrated

Single Use Temperature Indicators

• Speed: 5-10 seconds
• Placement: Approx. 1/2" deep
• Designed to be used only once
• Temperature-sensitive material changes

Liquid-Filled

• Speed: 1-2 minutes
• Placement: At least 2" deep
• Used in roasts/casseroles/soups
• Can remain in food while cooking
• Some can be calibrated

Safety and Doneness

• Most pathogens destroyed at 140-165 degrees F
• Higher temperatures may be needed for consumer palatability

Recommended Internal Temperatures

Ground Meat and Meat Mixtures

• Beef, Pork, Veal, Lamb: 160 degrees F
• Turkey, Chicken: 165 degrees F

Fresh Beef, Pork, Lamb and Veal

• Steaks, Roasts and Chops: 145 degrees F

Ham

• Fresh: 145 degrees F
• Precooked: 140 degrees F

Poultry

• Chicken, Turkey, Duck, Goose: 165 degrees F
• Poultry Breast, Roast: 165 degrees F
• Stuffing: 165 degrees F

Eggs/Egg Dishes

• Eggs: Cook until yolk is white and firm
• Egg Dishes: 160 degrees F

Leftovers/Casseroles

• Reheat to 165 degrees F

Using a Food Thermometer

• Most give accurate reading within 2-4 degrees F
• Must be placed in proper location in the food
• Placed in the thickest part of the food, away from bone, fat, or gristle

Check Manufactures Instructions

• Read and follow
• Indicates how far the thermometer needs to inserted in a food to give accurate reading
• Dial thermometers much penetrate 2-3 inches into the food
• Digital thermometers read in small area of the tip

Poultry

• Recommend poultry to 165 degrees F
• Check temperature in thigh or wing
• Poultry parts, insert food thermometer into the thickest area avoiding the bone

Thin Foods

• Thermistor is recommended
• Insert into the side of the food

Combination Dishes

• Place food thermometer into thickest portion of food
• Check for containing ground meat and poultry separately

Thermometer Care

• Should be washed with hot soapy water
• Most thermometers should not be immersed in water
• Hand wash carefully

Calibrating a Thermometer

• Follow direction on package
• Method 1 Uses ice water
• Method 2 Uses boiling water

Ice Water

• Tap water and Finely crushed ice
• Minimum of 2 inches of mixture

Boiling Water

• Clean tap water
• Minimum of 2 inches to wait at least 30 seconds