1. The Flow of Food: an Introduction
Chapter Number 5
The Flow of Food: an Introduction
Class Name
Instructor Name
Date, Semester
Book Title
Book Author

2. Learning Objectives After this presentation, you should be able to complete the following Learning Outcomes
5.0
5.1
Ways of preventing cross-contamination
5.2
Ways of preventing time-temperature abuse
Different types of temperature-measuring devices and their uses
5.3
At the end of this lecture each student should have a general understanding of the chapter contents and a firm ability to accomplish the learning outcomes on this slide.
How to calibrate and maintain different temperature-measuring devices
5.4
5.5
General guidelines for thermometer use

3. 5.0 KEY TERMS • Flow of food: Path food takes
through an operation, from
purchasing and receiving through
storing, preparing, cooking, holding,
cooling, reheating, and serving.
• Bimetallic stemmed thermometer:
The most common and versatile
type of thermometer, measuring
temperature through a metal probe
with a sensor in the end. Most can
measure temperatures from 0°
to 220°F (–18° to 104°C) and are
accurate to within ±2°F or ±1°C.
They are easily calibrated.
• Thermocouples: Thermometers that
check food temperature through a
sensor on the tip of a metal probe.
• Thermistors: Thermometers that
check food temperature through a
sensor on the tip of a metal probe.
• Time-temperature indicator (TTI):
Time and temperature monitoring
device attached to a food shipment
to determine if the product’s
temperature has exceeded
safe limits during shipment or
subsequent storage.
• Calibration: Process of ensuring
that a thermometer gives accurate
readings by adjusting it to a known
standard, such as the freezing point
or boiling point of water.

4. • Ice-point method: Method of Boiling-point method: Method of
5.0
KEY TERMS
• Ice-point method: Method of
calibrating thermometers based on
the freezing point of water.
Boiling-point method: Method of
calibrating a thermometer based on
the boiling point of water.

5. Ways of Preventing Cross-Contamination
5.1
Ways of Preventing Cross-Contamination
CROSS-CONTAMINATION
Many things can happen to food as it moves from purchasing and receiving through storing, prepping, cooking, holding, cooling, reheating, and serving.
This path is known as the flow of food.

6. Ways of Preventing Cross-Contamination
5.1
Ways of Preventing Cross-Contamination
CROSS-CONTAMINATION
Cross-contamination is a major hazard in the flow of food.
Pathogens can be spread from food or unwashed hands to prep tables, utensils, equipment, or other food.
Cross-contamination can occur at almost any point within the flow of food.
When you know how and where it can happen, it is fairly easy to prevent.

7. Ways of Preventing Cross-Contamination
5.1
Ways of Preventing Cross-Contamination
GUIDELINES FOR PREVENTING CROSS-CONTAMINATION
Using separate equipment
Use separate equipment when preparing each type of food.
Colored cutting boards and utensil handles can help you keep equipment separate.
Cleaning and sanitizing
Clean and sanitize all work surfaces, equipment, and utensils after each task.
Pathogens, such as Salmonella spp., can contaminate food through cross-contamination.

8. Ways of Preventing Cross-Contamination
5.1
Ways of Preventing Cross-Contamination
GUIDELINES FOR PREVENTING CROSS-CONTAMINATION (cont.)
Prepping food at different times
When using the same table to prep different types of food, prep raw meat, fish, and poultry at different times from ready-to-eat food so that the chance for cross-contamination can be minimized.
Buying prepared food
Buy food items that do not require much prepping or handling.

9. Ways of Preventing Time-Temperature Abuse
5.2
Ways of Preventing Time-Temperature Abuse
TIME-TEMPERATURE CONTROL
Time-temperature abuse is another major hazard in the flow of food.
TCS food has been time-temperature abused any time it remains between 41° and 135°F (5° and 57°C).
This is called the temperature danger zone because pathogens grow in this range. They grow especially fast between 70°F and 125°F (21° and 52°C).

10. Ways of Preventing Time-Temperature Abuse
5.2
Ways of Preventing Time-Temperature Abuse
TIME-TEMPERATURE CONTROL
TCS food is being time-temperature abused whenever it is handled in the following ways:
Cooked to the wrong minimum internal temperature
Held at the wrong temperature
Cooled or reheated incorrectly 
Time also plays a critical role. The longer food stays in the temperature danger zone, the more time pathogens have to grow.
To keep food safe, you must reduce the time food spends in this temperature range.
TCS food must be thrown out if it stays in the temperature danger zone for four hours or more.

11. Ways of Preventing Time-Temperature Abuse
5.2
Ways of Preventing Time-Temperature Abuse
AVOIDING TIME-TEMPERATURE ABUSE
Food handlers should avoid time-temperature abuse by following good policies and procedures.
The ones you establish should cover the following areas:
Monitoring
Learn which food items should be checked, how often, and by whom.
Assign duties to food handlers in each area.
Make sure they understand what to do, how to do it, and why it is important.

12. Ways of Preventing Time-Temperature Abuse
5.2
Ways of Preventing Time-Temperature Abuse
AVOIDING TIME-TEMPERATURE ABUSE
Tools
Make sure the correct kinds of thermometers are available.
Give food handlers their own thermometers.
Have them use timers in prep areas to check how long food is in the temperature danger zone.
Recording
Have food handlers record temperatures regularly.
Make sure they write down when the temperatures were taken.
Provide sample forms for recording this information next to cooking and holding equipment.

13. Ways of Preventing Time-Temperature Abuse
5.2
Ways of Preventing Time-Temperature Abuse
AVOIDING TIME-TEMPERATURE ABUSE (cont.)
Time and temperature control
Have procedures that limit the time food spends in the temperature danger zone.
Corrective actions
Make sure food handlers know what to do when time and temperature standards are not met.

14. Different types of temperature-measuring devices and their uses
5.3
Different types of temperature-measuring devices and their uses
CHOOSING THE CORRECT THERMOMETER
The most important tool you have is the thermometer. There are many types of thermometers. Three types are commonly used in operations:
Bimetallic stemmed thermometers
Thermocouples
Thermistors

15. Different types of temperature-measuring devices and their uses
5.3
Different types of temperature-measuring devices and their uses
BIMETALLIC STEMMED THERMOMETERS
Checks temperatures from 0° to 220°F (–18° to 104°C)
Use it to check food temperatures both during receiving and in a hot- or cold-holding unit.
When checking temperatures, insert the stem into the food up to the dimple for proper reading.
Useful for checking the temperature of large or thick food.
Not practical for thin food, such as hamburger patties.
If you buy bimetallic stemmed thermometers for your operation, make sure they have the following features.
Calibration nut
Easy-to-read markings
Dimple

16. Different types of temperature-measuring devices and their uses
5.3
Different types of temperature-measuring devices and their uses
THERMOCOUPLES AND THERMISTORS
Thermocouples/ thermistors
Check temperatures through a metal probe and display digitally
Sensing area on the tip of their probe.
Not necessary to insert them into the food as far as bimetallic stemmed thermometers
Good for checking the temperature of both thick and thin food

17. Different types of temperature-measuring devices and their uses
5.3
Different types of temperature-measuring devices and their uses
INFRARED THERMOMETERS
Infrared (Laser) Thermometers
Measures the temperatures of food and equipment surfaces
Quick and easy to use as they do not need to touch a surface to check its temperature
Less chance for cross-contamination and damage to food
Cannot measure air temperature or the internal temperature of food
Follow these guidelines for using infrared thermometers.
Distance
Hold the thermometer as close to the food or equipment as you can without touching it.
Barriers
Remove anything between the thermometer and the food, food package, or equipment.
Avoid taking readings through metal, such as stainless steel or aluminum.
Do not take readings through glass.
Manufacturer’s directions
Always follow the manufacturer’s guidelines for most accurate readings.

18. Different types of temperature-measuring devices and their uses
5.3
Different types of temperature-measuring devices and their uses
TIME-TEMPERATURE INDICATOR (TTI)
Time-temperature indicator
Attached to packaging by the supplier
A color change appears in the TTI window if the food has been time-temperature abused during shipment or storage.
This color change is not reversible, so you know if the item has been abused.
Some suppliers place temperature-recording devices inside their delivery trucks.

19. Calibrate and maintain different temperature-measuring devices
5.4
Calibrate and maintain different temperature-measuring devices
HOW TO CALIBRATE THERMOMETERS
Thermometers can lose their accuracy when they are bumped, dropped, or experience severe temperature change.
There are two ways to calibrate a thermometer:
ice-point method
boiling-point method

20. Calibrate and maintain different temperature-measuring devices
5.4
Calibrate and maintain different temperature-measuring devices
HOW TO CALIBRATE THERMOMETERS
Boiling-Point Method
To calibrate a thermometer using the boiling-point method, follow these steps:
Bring clean tap water to a boil in a deep pan.
Put the thermometer stem or probe into the boiling water. Make sure the sensing area is submerged. Wait 30 seconds or until the indicator stops moving. Do not let the stem or probe touch the container.
Adjust the thermometer so it reads 212°F (100°C). This temperature will vary depending on the boiling point for your elevation. Water’s boiling point is about 1°F (about 0.5°C) lower for every 550 feet (168 meters) above sea level.

21. Calibrate and maintain different temperature-measuring devices
5.4
Calibrate and maintain different temperature-measuring devices
HOW TO CALIBRATE THERMOMETERS
Ice-Point Method
Thermometers are often calibrated using the ice-point method. Follow these steps to use this method.

22. General guidelines for thermometer use
5.5
General guidelines for thermometer use
GENERAL THERMOMETER GUIDELINES
Cleaning and sanitizing
Thermometers must be washed, rinsed, sanitized and air-dried before and after use.
Keep storage cases clean as well.
Calibration
Calibrate thermometers before each shift and before the first delivery arrives.
Accuracy
Food thermometers need to be accurate to +/- 2°F or +/- 1°C.
Air temperature/food storage equipment need to be accurate to +/- 3°F or +/- 1.5°C.

23. General guidelines for thermometer use
5.5
General guidelines for thermometer use
GENERAL THERMOMETER GUIDELINES (cont.)
Glass thermometers
Glass thermometers, such as candy thermometers, can be a physical contaminant if they break.
They can only be used when enclosed in a shatterproof casing.
Checking temperatures
When checking the temperature of food, insert the thermometer stem or probe into the thickest part of the food.
Take another reading in a different spot. The temperature may vary in different areas.
When using a bimetallic stemmed thermometer, insert the stem all the way into the food from the tip to the end of the sensing area.
When checking the internal temperature of thin food, such as meat or fish patties, use a small diameter probe.
Before recording a temperature, wait for the thermometer reading to steady.