Microbes, Foodborne
Illness, and Food
Preservation
How do Microbes
Affect Us?
•Food Spoilage
•Foodborne Illness
What is Food Spoilage?
• Microbes in food can cause the
food to spoil (rot)
• Microbes cause millions of
dollars of food to spoil each
year
What is Foodborne Illness?
What is it?
• A disease caused by consuming contaminated
foods or beverages
• Contamination caused by bacteria or virus
– Pathogen• harmful bacteria that can cause disease
What’s the Problem?
Some microbes make us sick when
we eat them. You can’t see these
microbes!!!!!!
The greatest dangers
are microbes that
produce toxins and
causes human illness!
Is Foodborne Illness a Big Problem?
• Over 76 million
Americans get sick from
foodborne microbes each
year!
• About 5,000 Americans
die from foodborne illness
each year.
What Happens?
• Microbes pass from stomach to intestines
– Microbes attach to intestine wall and prevent
water from being absorbed, or nutrients from
being absorbed
– Certain microbes release a toxin that will enter the
bloodstream and travel through the entire body
• Up to 5000 people die every year
Symptoms
• Range from mild stomach &
intestine problems to DEATH,
including
• Upset Stomach
• Abdominal Cramps
• Nausea and vomiting
• Diarrhea
• Fever
• Dehydration
How Does Food get Contaminated?
• Food is exposed to pathogens
-When grown or raised
1. animals have pathogens
in intestines already
2. vegetables grown in dirty
soil, or watered with contaminated water
-In factory or Slaughter House
1. meat exposed to pathogens from other
meats
Example of Bacteria in Food
Bacteria naturally living in
milk will spoil milk in two
or three hours if left at
room temperature.
Putting milk in the refrigerator doesn’t
kill bacteria already there, but it slows
down the bacteria enough that the milk
will stay fresh for a week or two.
How does Food get Contaminated?
By humans in their own kitchen
1. Poor hygiene
2. Using used dirty utensils
3. Using an old cutting board
4. Not washing your counters
5. Leaving food out of refrigerator
6. Not washing food
How can we Prevent Foodborne
Illnesses?
1. Proper Hygiene and Handling of Food to
keep pathogens away
2. Food Preservation Methods to keep
food from spoiling
Why Does Preserving Food Help?
The basic idea - food preservation either:
– Slows down the activity of diseasecausing bacteria
– Kills the bacteria altogether
Is Food Preservation New?
• Food preservation is one of the oldest
technologies used by human beings.
• Some food preservation methods have
been around for thousands of years (e.g.
pickling and sun-drying), while others are
more modern (e.g. pasteurization and
irradiation).
What is “sterile”?
• A food that is sterile contains no bacteria.
• Unless sterilized and sealed, all food
contains bacteria.
How Does This Work?
• We preserve food by changing the
environment that the food is in (e.g.
changing the temperature, oxygen, pH or
by removing water).
Can you think of the
different ways that food is
preserved?
Common Food Preservation Methods
Include:
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Refrigeration and freezing
Canning
Dehydration (Drying Food)
Freeze-Drying
Salting
Pickling
Pasteurization
Fermentation
Chemical Preservation
Irradiation
Food Preservation Methods: The
Details
Food Preservation
• Physical Methods
Refrigeration and Freezing
• Refrigeration and freezing
are the most popular forms
of food preservation in use
today.
• Refrigeration = 32 ° F to 40 ° F
• Freezing = below 32° F
Refrigeration and Freezing
a. Refrigeration slows the
growth of bacteria
1. bacteria is less active,
but they are not killed
2. Food will still eventually
spoil in time
b. Freezing kills bacteria or
cause it to become
completely inactive
Canning Food
-Used since 1825
=Food can be stored for long periods of time
b. Process
1. Food is heated to a temperature that
kills all bacteria
2. Container is sealed to prevent new bacteria
from getting to food
c. Can be in any sealable container
1. Milk cartons, fruits in jars, vegetables in cans
Canning
• Once you open the
can, bacteria enter
and begin
attacking the food,
so you have to
"refrigerate the
contents after
opening"
Drying
• Evidence shows that Middle East and
oriental cultures actively dried foods in the
hot sun as early as 12,000 B.C..
• Drying removes water from the food.
Since most bacteria die or become
inactive when dried, dried foods kept in
air-tight containers can last quite a long
time.
Drying (Dehydration)
a. Food can be stored for long periods of time
b. Drying removes water from food
1. Bacteria grown in moist environments
c. Process uses fans and high temperatures to
dry the food
d. Examples
1. beef jerky, powdered milk, pasta, instant
rice, fruit chips
Sun-Dried Raisins
Salting
a. salt causes the
moisture to come
out of the food
b. Eliminates water so
bacteria can’t liv
b. one of oldest
preservation method
Pasteurization
a. Food is heated to high
temperature for a short
time at 145-165°F to kill
all microbes
b. Used on milk and juices
c. Food must be refrigerated
after pasteurization
Food Irradiation
a. Food is sterilized by using energy in the form
of radiation
1. Does NOT make food radioactive
b. Microbes are killed by radiation
c. Used on fruit and vegetables
1. Kills insects, fungi, and
bacteria
2. Delays ripening so food can be shipped
Irradiation
• Irradiation DOES NOT make food
radioactive. The food never touches a
radioactive substance. Irradiation
destroys insects, fungi, and bacteria.
Vacuum Packing
a. Air is removed from package before it is sealed
b. Without oxygen, bacteria and mold can not grow
Food Preservation
Chemical Methods
Pickling
a. Acidic environments
prevent the growth of
bacteria.
b. Usually uses vinegar,
salt water, or an alcohol
to preserve food
c. Will drastically change
the flavor of food so is
not good for all types of
food
Pickling or Fermentation
• These leave food
with a higher level
of acid, making it
an inhospitable
environment for
spoilage bacteria.
2. Fermentation
a. encourages growth of
“good” bacteria and
prevent growth of
“bad” bacteria
b. Examples of fermented
food:
1. bread, yogurt, wine,
cheese, soy sauce
c. Foods must be
refrigerated
Fermentation
• Fermentation refers to the activity of
bacteria and fungi.
• These microbes break food molecules into
simple substances.
Smoked Foods
• Smoking adds
chemicals from
smoke to food
that help destroy
potential spoilage
organisms.
3. Smoking
a. Used to preserve meats
1. Heat Kills bacteria
2. chemicals from
smoke kill microbes
3. Outer surface of
meat is dried removing
moisture
Food Preservatives
• If you look at the ingredient labels of
different foods, you will see different types
of chemicals used.
• All of these chemicals either prevent the
activity of bacteria or kill the bacteria.
• Pancake syrup can sit out because of
the ingredients it contains.
Chemical Preservation
• There are three classes of chemical
preservatives commonly used in foods:
– Benzoates (such as sodium benzoate)
– Nitrites (such as sodium nitrite)
– Sulphites (such as sulphur dioxide)
The End