Forms of Contamination that Cause
Foodborne Illness
Unit 3: Food Safety
 Infection or intoxication caused by
the transfer of microbial or chemical
contaminants from food or water
to humans.
Biological
• Most foodborne illnesses are caused by pathogens,
a form of biological contaminant.
Chemical
• Foodborne illness is also contributed to consuming
beverages or food contaminated with foodservice
chemicals.
Physical
• Food can also be contaminated when objects get
into the food. Even when natural objects are left in
food like bones.
Microorganisms are small living organisms like
bacteria that can only be seen through a
microscope. Harmful microorganisms are called
pathogens. Some pathogens make you sick when
you eat them, others produce poisons or toxin
within your body.
The four types of pathogens:
• Bacteria
• Viruses
• Parasites
• Fungi
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Bacteria can be found anywhere and they
live in our bodies. Some types of bacteria
keep us healthy and other make us sick.
Bacteria cannot be seen, smelt or tasted.
If conditions are correct, bacteria will grown
in rapid numbers.
The most important way to prevent bacteria
from causing a foodborne illness is to control
time and temperature.
Bacteria need six conditions to grow that we refer to as FAT
TOM.
F—Food
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The nutrients in food promoted the growth of microorganisms. Foods that contain moisture and are
protein-rich are most susceptible. For example: meat, milk, eggs and fish.
A—Acidity
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Bacteria grow in foods that have little to no acid.
pH is used to test the acidity of foods. The pH scale ranges from 0 – 14.0. A value of 0 is highly acidic,
while a value of 14 is highly alkaline or basic. A pH of 7 is neutral.
Bacteria grows best in food that is neutral or slightly basic.
T—Temperature
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Bacteria can grow rapidly between 41°F and 135°F (5°C to 57°C).
This is referred to as the temperature danger zone (TDZ).
Bacteria grow even more rapidly from 70°F to 125°F (21°C to 52°C).
Bacteria growth is limited when food is held above or below the temperature danger zone.
T—Time
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Bacteria need time to grow. The more time spend in the temperature danger zone [41°F and 135°F
(5°C to 57°C)], the more opportunity bacteria have to grow to unsafe levels.
O—Oxygen
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Number of Cells
Time in TDZ
1 cell
0 min.
2 cells
20 min.
4 cells
40 min.
8 cells
1 hr.
16 cells
1 hr. 20 min.
> 1 billion cells
10 hrs.
Some bacteria need oxygen to grow, others grow when there is no oxygen.
M—Moisture
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Bacteria grow well in foods with high levels of moisture.
The amount of moisture in a food is known as the water activity (aw). The aw scale ranges from 0.0 to
1.0. The higher the value, the more available moisture in the food. For example, water has a water
activity of 1.0.
Viruses are carried by humans and animals. They require
a living host to grow.
• Viruses do not grow in food but they can still be
transferred through food and infectious to the food.
• People can get viruses from food, water, or any
contaminated surface. Foodborne illness from viruses
usually occur through fecal-oral routes. Norovirus is one
of the leading causes of foodborne illness and is often
transmitted through airborne vomit particles.
• Viruses are not destroyed through normal cooking. This
is why personal hygiene is so important when handling
food and food-contact surfaces.
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Parasites require a host to live and reproduce.
Parasites are commonly found in seafood,
wild game, and food processed in
contaminated water, such as produce.
One way to prevent foodborne illnesses from
parasites is to purchase food from reputable
suppliers.
Cooking food to the required minimum
internal temperatures is also important.
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Fungi includes yeasts, molds, and
mushrooms.
Some molds and mushrooms produce toxins
that cause foodborne illness.
Throw out all moldy food, unless mold is a
natural part of the food.
Harmful mushrooms are difficult to recognize,
purchase all mushrooms from approved,
reputable suppliers.
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Chemicals (cleaners, polishes, machine
lubricants, sanitizers, and/or pesticides) can
contaminate food if they are used or stored
the wrong way.
The best way to prevent chemical
contamination is to store chemicals away
from prep areas, food-storage areas, and
service areas.
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Some common objects that can get in food
are shavings from metal cans, wood,
fingernails, staples, bandages, glass, jewelry
and dirt.
Mild to fatal injuries are possible.
Purchase food from approved, reputable
suppliers to prevent physical contamination.