2. Forms of Contamination

Terms to understand

The transfer of pathogens from one food or surface to another
The transfer of allergens from one food or surface to another
Small, living organism that can be seen only with a microscope
A harmful microorganism that makes people sick when eaten or produces a toxin that causes illness
A poison
Common symptoms of foodborne illness
Diarrhea, vomiting, fever, nausea, abdominal cramps, jaundice (yellowing of the skin and eyes)
Onset times
Depend on the type of foodborne illness can range from 30 minutes to 6 weeks


Three Types of Contamination

  • 1. Biological

  • 2. Chemical

  • 3. Physical

3 Major Food Contaminates

1. Biological Contaminants

Biological Contaminants can be divided into four categories:

bacteria image
Virus image
fungi image


Naturally occur in certain plants, mushrooms, and seafood

Seafood toxins
Produced by pathogens found on certain fish: tuna, bonito, mahi-mahi. A histamine (toxin) is produced when fish is time-temperature abused. Also occurs in certain fish that have consumed the toxin Barracuda, snapper, grouper
Symptoms and onset times will vary.

Ciguatera Toxin and Scrombroid Poisoning are examples of seafood toxins

General symptoms

  • Diarrhea or vomiting
  • Tingling of the extremeties
  • Reversal of hot and cold sensations
  • Flushing of the face and/or hives
  • Difficulty breathing
  • Heart palpatations

2.Chemical Contaminants

  • Cleaners
  • Sanitizers
  • Polishes
  • Machine lubricants
  • Pesticides
  • Deodorizers
  • First-aid products
  • Health & beauty products
  • Allergens

Chemical contaminants are also found in certain types of kitchenware and equipment such as:

Toxic Metals

Toxic metals can also be in a foodservice environment and can be found in the following:

Source Pewter Pitcher Copper saucepan image Galvanized Pail
Item Pewter Pitcher Copper Saucepan Galvanized Pail
Toxic Metal Lead Copper Zinc

Adding an acidic food to any of the above items will cause a chemical reaction and the toxic metal will leach into the food.


Any product received in a foodservice operation should come with a Manufacturer’s Safety Data Sheet and provides:

  • A list of all chemicals in the product
  • Directions for proper use
  • First aid instructions
  • Personal protective equipment (safety glasses, protective gloves)

The Occupational Safety and Health Association (OSHA) requires all Safety Data Sheets (SDS) be current and easily accessible

3. Physical Contaminants

  • Metal shavings
  • Wood
  • Glass
  • Bandages
  • Dirt
  • Fly or caterpillar
  • Bones
  • Pits or seeds
  • Symptoms of physical contamination
  • Cuts, dental damage, choking, bleeding & pain
  • Prevention
  • Purchase from approved, reputable suppliers
  • Closely inspect food received
  • Practice good personal hygiene

The Deliberate Contamination of Food

  • Terrorists or activists
  • Disgruntled current or former staff
  • Vendors
  • Competitors

The Food & Drug Administration (FDA) has developed a tool to guard against the deliberate contamination of food


Make sure products received are from safe sources
Monitor the security of products in your facility
Know who is in your facility
Keep information related to food defense accessible
Develop a plan for responding to suspicious activity or a threat to the operation

Responding to a Foodborne Illness Outbreak in your Operation

  1. 1. Gather information
  2. 2. Notify authorities
  3. 3. Segregate product
  4. 4. Document information
  1. 5. Identify staff
  2. 6. Cooperate with authorities
  3. 7. Review procedures

Food Allergens

A food allergen is a protein or ingredient some people are sensitive to which causes a person’s immune system to overreact.

Allergy Symptoms

  • Nausea
  • Wheezing or shortness of breath
  • Hives or itchy rashes
  • Swelling of various parts of the body
  • Vomiting and/or diarrhea
  • Abdominal pain

Symptoms can be serious. A severe reaction is anaphylaxis or anaphylactic shock. An allergic reaction can be life-threatening; whereas, a food intolerance only affects the gastro-intestinal tract and is not life-threatening.

Common Food Allergens

  • Milk
  • Eggs
  • Fish
  • Shellfish
  • Wheat
  • Soy
  • Peanuts
  • Tree nuts

Preventing Allergic Reactions

Purchasing and Receiving
By law, all allergens are listed on a product label. Read product labels so you know what you are working with.
Service Staff
There should be one person on duty who can list all the ingredients on each of your menu items and if staff takes an order that needs to be prepared for a person with allergies, however you communicate the order to the kitchen staff ensure the order is clearly marked.
Kitchen Staff
Before a special order can be prepared, your kitchen staff must wash, rinse, and sanitize all equipment and utensils before preparing the order. They must also wash hands and change gloves before preparing the order.


bacteria image

Bacteria are single-cell microorganisms that are almost everywhere, in air, water, soil, and in and on humans, animals, and plants. They can also survive the harshest of environments from very cold to very hot. Some are beneficial to us and some make us sick or are fatal. They can be seen only by a microscope and can not be seen,tasted or smelled They are of the greatest concern to food service professionals so all the time necessary should be spent to combat them by understanding what conditions favor the growth of pathogenic bacteria and what conditions eliminate or reduce them to a safe level. The right condition for the growth of bacteria and other foodborne microorganisms is remembered by using the acronym


FAT TOM image

Please Note: The six conditions of FAT TOM apply to bacteria. They do not apply to viruses



Bacteria, just like humans and animals require nourishment. In particular they require proteins and carbohydrates.As can be observed, TCS foods generally are high in proteins and carbohydrates
ACIDITY Bacteria grow well in an environment that is slightly or non-acidic, when the Ph value is between 4.6 and 7.5. (see below for an explanation of Ph values)
TEMPERATURE Bacteria grow well in the Temperature Danger Zone (between 41°F and 135°F) They grow even faster in a segment of the Temperature Danger Zone that we will describe as the critical Temperature Danger Zone: between 70°F and 125°F. You will see the critical temperature danger zone come into play in certain processes in a later lesson.
TIME When food is in the Temperature Danger Zone bacteria, on average, will double every twenty minutes. Starting with one bacteria, they will rise to a level of over 1 billion in 10 hours. You can allow TCS foods in the Temperature Danger Zone up to four hours. If it has been in the temperature danger Zone for 4 hours or longer, it must be thrown out. Bacteria have multiplied to harmful levels. The time TCS food spends in the Temperature Danger Zone is also cumulative. Each amount of time it spends in the Temperature Danger Zone cannot add up to 4 hours or more.
Oxygen Most, but not all, bacteria require oxygen for growth. Aerobic bacteria grow in the prescence of oxygen while anaerobic bacteria will grow without oxygen
MOISTURE Bacteria require a high level of moisture to grow and multiply. Moisture levels are measured using the Water Activity ( Aw ) Scale. We can generally define Water Activity (Aw) as an indication of the amount of Free Water in a food. The scale runs between 0 and 1 with pure distilled water having a Aw value of 1 which means it is 100% water. Bacteria grow well in a food with a water activity value of .85 or higher. So what does free water in a food mean? If you add salt to a glass of water that has a water activity of 1 it will lower the water activity level. Some water molecules in the water will bind to the salt molecules thus reducing the water activity level. Those water molecules that bind to the salt molecules are no longer available for bacteria (no longer “free”) Adding enough salt will lower the water activity to below .85 thus restricting/eliminating bacterial growth. As known, man has been using salt as a means of preserving food for thousands of years.


The Ph Scale

The amount of acid in a food is measured using the Ph Scale. The scale runs from 0 to 14 with pure distilled water having a Ph value of 7 indicating that it is neither acidic or alkaline. It is totally neutral. As the scale progresses toward 0 the acid level increases. For example, a Ph value of 6.5 means the food is ever so slightly acidic; whereas, a food with a Ph value of zero indictes it is 100% acid. Bacteria grow well in a food that is slightly or non-acidic. With a Ph value between 4.6 and 7.5 as shown in the diagram below.

Ph Scale image

As outlined in the following chart, the amount of acid in a product increases tenfold for each Ph value. A change in Ph value from 7 to 6 shows a tenfold increase in the amount of acid in a product. A change in Ph value from 6 to 5 also shows a tenfold increase in the amount of acid in a product and so forth. As you can observe, changes between the lower Ph values show a dramatic change in the amount of acid.

Ph value of certain foods chart

Time and Temperature

Bacteria grow best in the Temperature Danger Zone. At those temperatures some bacteria can double their population every 20 minutes. With each 10°F temperature drop below the Temperature Danger Zone, the bacterial growth slows down, taking twice the time to double the population. As the temperature rises above the Temperature Danger Zone bacteria stop growing and start dying. Foods cooked to the required minimum internal temperature will kill bacteria.

TCS foods grow bacteria if the temperature is in the Temperature Danger Zone). Foods on a warming table kept above 135°F stays safe and foods kept at refrigerator temperatures (41°F) or below also stay safe, at least for a few days.

Time goes with temperature as it takes time for bacteria to reproduce. The food safety rules allow up to 4 hours for TCS foods to be in the 41°F – 135°F temperature range. This 4 hours includes all the times the food is brought into the Temperature Danger Zone, like each time you reheat leftovers.

Some especially vulnerable foods for the time rule are leftovers and partially cooked foods—they need to be cooled quickly. Leftovers from a buffet or picnic, or a large pot of beans that is allowed to sit, are prime candidates for foodborne illness.

In summation, the way to control bacteria growth in a foodservice establishment is to control Time and Temperature. Time and Temperature are the two conditions that can be controlled in a foodservice establishment. The other four conditions are too complex to control.

Major Bacteria that Cause Foodborne Illness

The FDA has identificed seven types of bacteria that cause severe illness and are highly contagious



Virus image

Living beings made of cells, consume energy and reproduce. Viruses are not made of cells, do not need energy to exist and only can reproduce using other living cells like human cells. So for them to make a copy of themselves they must use living cells like human or animal cells. They can not grow and divide on food, but they can be transferred to a human body by food or water or contaminated surfaces. People can also transmit them to food and to other people, in addition to food-contact surfaces. They are able to survive cooking and freezing temperatures. It can be transmitted through vomit particles. Foodborne illnesses most often occur through the fecal-oral route. A person using the restroom does not wash their hands and contaminates whatever they touch with a virus. Practicing good personal hygiene especially proper hand care by food handlers, washing, cleaning and sanitizing food-contact surfaces and a quick vomit cleanup and removal from the site are important measures for stopping the spread of viruses.
The FDA has particularly identified two highly contagious viruses that can cause severe illnesses. The staff who have been diagnosed with these viruses must be excluded from the operation. Eating a small amount of these viruses can make a person sick.

Viruses are not controlled by Time and Temperature. The best way to prevent illnesses from viruses is to practice good personal hygiene, particularly proper hand care.


Major Viruses that Cause Foodborne Illnesses

Virus Source Linked Foods Prevention Methods
Hepatitis A Human Feces
  • Ready to eat food
  • Shellfish
  • Exclude staff with Hepatitis A
  • Exclude staff who have jaundice for 7 days or less
  • Wash hands
  • Purchase shellfish from approved reputable suppliers
Norovirus Human Feces
  • Ready to eat food
  • Shellfish
  • Exclude staff with Norovirus
  • Exclude staff vomiting or diarrhea
  • Wash hands
  • Purchase shellfish from approved reputable suppliers



Mold imageMolds are microscopic fungi that live on plant or animal matter. No one knows how many species of fungi exist, but estimates range from tens of thousands to perhaps 300,000 or more. Most are filamentous (threadlike) organisms and the production of spores is characteristic of fungi in general. These spores can be transported by air, water, or insects.

Unlike bacteria that are one-celled, molds are made of many cells and can sometimes be seen with the naked eye. Under a microscope, they look like skinny mushrooms. In many molds, the body consists of:

  • Root threads that invade the food it lives on
  • A stalk rising above the food, and
  • Spores that form at the ends of the stalks.

The spores give mold the color you see. When airborne, the spores spread the mold from place to place like dandelion seeds blowing across a meadow. Molds have branches and roots that are like very thin threads. The roots may be difficult to see when the mold is growing on food and may be very deep in the food. Foods that are moldy may also have invisible bacteria growing along with the mold. Some molds cause allergic reactions and respiratory problems. And a few molds, in the right conditions, produce “mycotoxins,” poisonous substances that can make you sick.

You only see part of the mold on the surface of food — gray fur on forgotten bologna, fuzzy green dots on bread, white dust on Cheddar, coin-size velvety circles on fruits, and furry growth on the surface of jellies. When a food
shows heavy mold growth, “root” threads have invaded it deeply. In dangerous molds, poisonous substances are often contained in and around these threads. In some cases, toxins may have spread throughout the food.

  • May produce a toxin
  • Grows well in acidic food with little moisture
  • Slowed but not destroyed at low temperatures
  • Food with mold should be thrown out unless it is a natural part of the food such as certain cheeses


Yeast on strawberriesYeasts are usually egg-shaped, and tend to be smaller than molds. Like molds, yeasts can be spread via air currents. They reproduce by a process known as budding. Visible colonies of yeast are generally slimy in appearance and creamy white.Yeasts are able to grow in foods with a low pH (5.0 or lower) and in the presence of sugars, acids, and other easily metabolized carbon sources. During their growth, yeasts metabolize some food components and produce metabolic end products. This causes the physical and chemical properties of a food to change, and the food is spoiled. The growth of yeast within food products is often seen on their surfaces, as in cheeses or meats, or by the fermentation of sugars in beverages, such as juices, and semiliquid products, such as syrups and jams.

  • May produce a smell or taste of alcohol as it spoils food
  • My produce a white or pink discoloration or slime and may even bubble
  • Grows well in acidic food with little moisture
  • Food containing yeast must be thrown out


parasites imageParasites may be present in food or in water and can be identified as causes of foodborne or waterborne illness in the United States. They range in size, from tiny single-celled organisms to worms visible to the naked eye. Their lifecycle may also vary. While some parasites use a permanent host, others go through a series of developmental phases using different animal or human hosts. The illnesses they can cause range from mild discomfort to debilitating illness and possibly death.

Parasites are organisms that derive nourishment and protection from other living organisms known as hosts. They may be transmitted from animals to humans, from humans to humans, or from humans to animals. Several parasites have emerged as significant causes of foodborne and waterborne illness. These organisms live and reproduce within the tissues and organs of infected human and animal hosts, and are often excreted in feces.

Parasites require a living host to survive and reproduce. Can range from single cells to worms up to 2 meters long that can be visible with the naked eye. Parasites can be transferred from host to host by eating anything that has touched the feces of an infected person or animal. Parasites are primarily found in seafood. Some exmples of parasites are:

  • Anisakis – found in fish/seafood and causes tickling sensation in the throat
  • Trichinella – found in pork and wild game
  • Giardia – found in contaminated water and causes diarrhea and abdominal cramps.

To prevent foodborne illnesses caused by parasites is to purchase food from approved, reputable suppliers and making sure fish that will be served raw or undercooked have been properly frozen by the supplier.