5-1

The Flow of Food: An Introduction

5-2

Apply Your Knowledge: Test Your Food Safety Knowledge 1. True or False: Chicken held at an internal temperature of

125°F (52°C) has been temperature abused

2. True or False: Infrared thermometers are best for measuring the internal temperature of food

3. True or False: When checking the temperature of a roast using a bimetallic stemmed thermometer, only the tip of the thermometer stem should be inserted into the product

4. True or False: A thermometer calibrated by the boiling-point method must be set to 135°F (57°C), after being placed into the boiling water

5. True or False: Washing and rinsing a cutting board will prevent it from cross-contaminating the next product placed on it

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The Flow of Food

To keep food safe: Prevent cross-contamination Prevent time-temperature

abuse

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Preventing Cross-Contamination

Create physical barriers between food products: Assign specific equipment to each type

of food Clean and sanitize work surfaces,

equipment, and utensils after each task

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Preventing Cross-Contamination

Create procedural barriers between food products: Prepare raw meat, fish, and poultry and

ready-to-eat food at different times (when using the same prep table)

Purchase ingredients that require minimal preparation

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Preventing Time-Temperature Abuse

This includes: Minimizing the time food spends in

the temperature danger zone Determining the best way to monitor

time and temperature Making thermometers available Regularly recording temperatures and

the times they are taken

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The TemperatureDanger Zone

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Temperature-Measuring Devices

Bimetallic Stemmed Thermometer

Indicator Head

Calibration Nut

Holding Clip

Stem

Sensing Area

Dimple

5-8

Temperature-Measuring Devices

Photos courtesy of Cooper-Atkins Corporation

Immersion Probe Surface Probe Penetration Probe

Thermocouples and Thermistors Measure temperature through a metal

probe or sensing area Display results on a digital readout Often come with interchangeable probes

5-9

Temperature-Measuring Devices

Infrared Thermometers Used to measure the surface

temperature of food and equipment Must be held as close to the product as

possible Remove barriers between thermometer

and product Follow manufacturers’ guidelines

Photos courtesy of Cooper-Atkins Corporation

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Apply Your Knowledge: Pick the Right Thermometer

Which temperature-measuring device should be used to check the following?

C. Bimetallic stemmed thermometerB. ThermocoupleA. Infrared thermometer

1. Internal temperature of a hamburger patty2. Surface temperature of a steak3. Internal temperature of a roast4. Internal temperature of a large stockpot of soup

1

2

3

4

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5-11

Calibrating Thermometers

Calibration Adjusting a thermometer in order

to get an accurate reading

Two methods Boiling-point method Ice-point method

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Calibrating Thermometers

Boiling-Point Method1. Bring clean tap water to a boil

2. Submerge the sensing area of the thermometer stem or probe in the water for thirty seconds

3. Hold the calibration nut and rotate the thermometer head until it reads 212°F (100°C)

Note: The boiling point of water varies depending upon your elevation

1

2

3

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Calibrating Thermometers

Ice-Point Method

1. Fill a large container with crushed ice and water

2. Submerge the thermometer stem or probe in the water for thirty seconds

3. Hold the calibration

nut and rotate the thermometer head until it reads 32˚F (0˚C)

5-14

General Thermometer Guidelines

When using thermometers: Keep thermometers and their

storage cases clean Calibrate them regularly to

ensure accuracy Never use glass thermometers

to monitor food temperature Insert the thermometer stem or

probe into thickest part of product (usually the center)

Wait for the thermometer reading to steady before recording the temperature of a food item

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Apply Your Knowledge: Calibrate the Thermometer

Put the steps for calibrating a thermometer in the proper order:

A. Rotate the head of the thermometer until it reads 32F (0C)

B. Submerge the sensing area of the thermometer stem or probe, and wait for the reading to steady

C. Fill a container with crushed ice and clean tap water

D. Hold the adjusting nut with a wrench or other tool

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A

B

C

D