•Chapter Number 5
•The Flow of Food:
an Introduction
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1
5.0
Learning Objectives
After this presentation, you should be able to complete the following
Learning Outcomes
5.1
Ways of preventing cross-contamination
5.2
Ways of preventing time-temperature abuse
5.3
Different types of temperature-measuring
devices and their uses
5.4
How to calibrate and maintain different
temperature-measuring devices
5.5
General guidelines for thermometer use
2
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.
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.
5.1 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.
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.
5.1 Ways of Preventing Cross-Contamination
GUIDELINES FOR PREVENTING CROSSCONTAMINATION
• 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.
5.1 Ways of Preventing Cross-Contamination
GUIDELINES FOR PREVENTING CROSSCONTAMINATION (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.
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).
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.
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.
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.
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.
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
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
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
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.
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.
5.4
Calibrate and maintain different temperaturemeasuring 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
5.4
Calibrate and maintain different temperaturemeasuring 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.
5.4
Calibrate and maintain different temperaturemeasuring devices
HOW TO CALIBRATE THERMOMETERS
• Ice-Point Method
– Thermometers are
often calibrated using
the ice-point method.
Follow these steps to
use this method.
5.5 General guidelines for thermometer use
GENERAL THERMOMETER GUIDELINES
• Cleaning and sanitizing
– Thermometers must be washed, rinsed, sanitized and airdried 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.
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.