4.2 Monitoring Time and Temperature

Monitoring time and temperature is the cornerstone of food safety. You cannot manage what you cannot measure—and in food service, that means using the right thermometers correctly and knowing when to check temperatures.

Why Thermometers Matter

You cannot:

• See bacteria
• Smell most pathogens
• Taste contamination
• Judge doneness by appearance alone

You CAN:

• Measure exact internal temperatures
• Verify food reached safe cooking temps
• Confirm proper holding temperatures
• Document compliance for health inspectors

Critical Fact: Guessing temperatures is not acceptable. ServSafe and health codes require actual temperature measurements with calibrated thermometers.

Types of Food Thermometers

ServSafe recognizes several types of thermometers, each with specific uses and advantages.

1. Bimetallic Stemmed Thermometer

Description:

• Traditional dial thermometer with a metal stem
• Temperature sensing area is from tip to the dimple (usually 2-3 inches)
• Displays temperature on a dial face
• Can measure temperatures from 0°F to 220°F

Best Uses:

• Checking temperatures of thick foods like roasts and large cuts of meat
• Checking final cooking temperatures
• General-purpose temperature checking

Limitations:

• Must be inserted deep (up to the dimple) to get accurate reading
• Not suitable for thin foods like hamburger patties or fish fillets
• Slower response time than digital thermometers

Accuracy: ±2°F when properly calibrated

2. Thermocouple Thermometer

Description:

• Digital thermometer with interchangeable metal probe
• Temperature sensor located in the tip (only ⅛ inch)
• Displays temperature on digital screen
• Very fast response time (2-5 seconds)
• Measures temperatures from -40°F to 450°F

Best Uses:

• Checking thin foods like burgers, chicken breasts, and fish fillets
• Taking multiple quick temperature readings
• When speed and accuracy are critical

Advantages:

• Doesn't need to be inserted as deep as bimetallic stemmed thermometers
• Extremely fast readings
• Highly accurate
• Can have interchangeable probes for different tasks

Accuracy: ±1°F or better

3. Thermistor (Digital Thermometer)

Description:

• Digital thermometer similar to thermocouple
• Uses a resistor (thermistor) to measure temperature
• Temperature sensor in the tip
• Digital display with fast response time

Best Uses:

• All-purpose temperature checking
• Both thick and thin foods
• General temperature monitoring

Advantages:

• Fast and accurate
• Easy to read digital display
• Suitable for most food service applications

Accuracy: ±1°F or better

4. Infrared (Laser) Thermometer

Description:

• Non-contact thermometer that measures surface temperature
• Uses laser pointer to aim
• Instant temperature reading
• Cannot measure internal temperature

Best Uses:

• Measuring surface temperatures of equipment (griddles, ovens, refrigerators)
• Checking temperatures of food surfaces during receiving
• Monitoring hot holding equipment surfaces

Critical Limitations:

• CANNOT measure internal temperature of food
• CANNOT measure air temperature
• CANNOT be used through glass or metal
• Not suitable for verifying cooking temperatures

How to Use:

• Hold as close to the food/equipment as possible without touching
• Remove anything between the thermometer and the surface
• Point laser at the center of what you're measuring

Accuracy: Generally ±2°F, but only for surface measurements

For the Exam: Infrared thermometers CANNOT measure internal food temperatures. They are for surfaces only. Use them for equipment checks, not for verifying that chicken reached 165°F internally.

Thermometer Calibration Methods

Thermometers must be accurate to be useful. Regular calibration ensures your thermometer gives correct readings. Calibrate thermometers:

• Daily or before each shift
• After dropping or bumping the thermometer
• After extreme temperature changes (going from freezer to hot oven)
• Any time accuracy is in question

Method 1: Ice-Point Method (32°F / 0°C)

The ice-point method is the easiest, fastest, and most accurate method for most operations.

Steps:

1. Fill a large container with ice (use crushed ice if possible)
2. Add clean tap water until the container is full
3. Stir the mixture and let it sit for 30 seconds
4. Insert the thermometer probe into the ice water
   • For bimetallic: Insert stem to the dimple
   • For thermocouple/thermistor: Insert at least ½ inch deep
5. Wait 30 seconds or until the reading is steady
6. Reading should be 32°F (0°C)
7. If not at 32°F, adjust the thermometer:
   • Bimetallic: Turn the calibration nut with pliers or wrench until it reads 32°F
   • Digital: Press the reset or calibrate button (check manufacturer instructions)

Why 32°F? This is the freezing point of water at sea level—a scientifically reliable reference point.

Pro Tip: The ice-point method works at any altitude. The boiling-point method requires altitude adjustments.

Method 2: Boiling-Point Method (212°F / 100°C)

The boiling-point method is less commonly used but still acceptable.

Steps:

1. Bring clean tap water to a rolling boil
2. Insert the thermometer probe into the boiling water
   • Do not let the probe touch the bottom or sides of the container
   • Insert to the dimple (bimetallic) or at least ½ inch (digital)
3. Wait 30 seconds or until the reading is steady
4. Reading should be 212°F (100°C) at sea level
5. If not at 212°F, adjust the thermometer using calibration nut or reset button

Important Altitude Adjustments: Water boils at lower temperatures at higher altitudes. Adjust your target calibration temperature:

For the Exam: Know both calibration methods. Ice-point method is 32°F/0°C; boiling-point method is 212°F/100°C at sea level.

Proper Temperature-Taking Technique

Knowing how to use a thermometer correctly is just as important as having one.

The Six Rules of Temperature Taking:

1. Insert in the Thickest Part

• This is where food takes the longest to cook
• It's the area most likely to harbor bacteria if undercooked
• Example: Insert into the center of a thick chicken breast

2. Avoid Bone, Fat, and Gristle

• Bones conduct heat differently and give false readings (usually higher)
• Fat doesn't reach the same temperature as muscle meat
• Always measure the meat portion, not touching bones

3. Take Multiple Readings for Large Items

• Check several spots on large roasts or turkeys
• Measure at least two locations for accuracy
• Use the lowest reading as your guide

4. Clean and Sanitize Between Uses

• Wipe probe with clean cloth
• Wash probe with hot soapy water
• Sanitize with sanitizing solution
• Air-dry or wipe with clean cloth
• Prevents cross-contamination

5. Wait for the Reading to Stabilize

• Bimetallic: 15-30 seconds
• Thermocouple: 2-5 seconds
• Thermistor: 10 seconds
• Wait until numbers stop moving

6. Don't Let Probe Touch the Pan

• Pan surface is much hotter than food
• Touching pan gives falsely high reading
• Hold thermometer probe in center of food, away from edges

Common Mistake: Taking temperature too close to the edge of food or touching the pan. Always measure the center of the thickest part.

When to Check Temperatures

Temperature checks are required at specific points throughout the flow of food. Missing these checks can lead to foodborne illness outbreaks and health code violations.

Temperature Checkpoints in the Flow of Food:

For the Exam: You must check temperatures at receiving, during cooking, during cooling, when reheating, and during hot/cold holding. Document all temperature readings.

Why Every 4 Hours for Holding?

The FDA recommends checking holding temperatures at least every 4 hours because:

1. Bacteria can reach dangerous levels in 4 hours if food enters the danger zone
2. Gives you time to take corrective action before food becomes unsafe
3. Catches equipment failures early before large amounts of food are lost
4. Meets regulatory requirements for active managerial control

Best Practice: Check holding temperatures every 2 hours instead of every 4 hours. This provides an earlier warning if something goes wrong.

Temperature Monitoring Best Practices

Create a Temperature Log:

• Record all temperatures with date and time
• Include food item, temperature, and employee initials
• Note any corrective actions taken
• Keep logs for health department inspection (usually 6 months to 1 year)

Train All Staff:

• Every employee should know how to take temperatures correctly
• Demonstrate proper thermometer use and calibration
• Quiz staff regularly on temperature requirements

Post Temperature Guidelines:

• Display minimum internal cooking temperatures in kitchen
• Post hot and cold holding temperature requirements
• Keep calibration instructions near thermometers

Maintain Your Thermometers:

• Store in protective case when not in use
• Replace batteries in digital thermometers regularly
• Have backup thermometers available
• Replace thermometers that cannot be calibrated

Remember: Temperature monitoring is not optional—it's required by law and critical for preventing foodborne illness. Make it a routine part of every shift.