Food Preservation for Food
Processors Part I
An interactive module about acidic foods
Module designed by Julie Garden-Robinson, Ph.D., L.R.D., Food and Nutrition Specialist, 2014
The following tips will help you
navigate through each module.
Click
to go back and
to move
forward in the module.
 Before you begin, you’ll take a pretest.




The pretest will open in a new window.
When you are finished with the pretest, close
the window to return to the module.
A
symbolizes a question slide. You’ll
need to click forward to see the answer.
Click this button
to return to your
position in the module after reading the
definition slide.
 When you are finished with the module,
you will take a post-test.



The post-test will open in a new window.
When you are finished with the post-test, close
the window to return to the module.
Pretest
Before
we begin, let’s take a
pretest to see how much you
already know. Click here for
the pretest.
Have a bright idea?
Everyone loves my salsa and always
asks me to bring it to potlucks.
Maybe I should start selling it. I bet I
could make a fortune. Maybe I can
retire and buy a house in Arizona –
no, Florida. Heck, maybe both!
Oh, no! There are regulations?
Hey, wait. Don’t give up.
Go through this interactive module.
It tells you what you need to know
about processing acidified foods.
Salsa is an acidified food.
Before we discuss the acidification
process and regulations, let’s go over some
basics about types of preservation and also
what preserving means.
Food Preservation
Definition:
The process of treating and handling food in
such a way that it stop or greatly slows
spoilage to prevent foodborne illness while
maintaining nutritional value, density,
texture and flavor.
Factors that affect food spoilage
Water availability (moisture)
 Oxygen
 pH
 Temperature

True or false: Oxygen is a factor
affecting food spoilage.
a.
b.
True
False
Click the forward button to see
the answer.
True or false: Oxygen is a factor
affecting food spoilage.
a.
b.
True
False
Oxygen is a factor affecting
food spoilage.
Water Availability
“Water availability” refers to the amount
of water available for microbial growth. It
is shown on a scale from 0 to 1.
 Bacteria grow in moist environments, so
the higher the water availability, the
greater the risk for microbial growth.
 A solute such as salt or sugar added to
water “soaks” up the water, making it
unavailable for bacterial growth.

Water Availability Scale
0aW
Bone
dry
0.8aW
0.2aW
Very dry
(instant
coffee, milk
powder, etc.)
0.6aW
Dried
fruit
1aW
0.99aW
Pure
Moist water
fresh food
(meat/fish)
Water Availability

Bacteria, mold and yeast need a certain
amount of water available to grow. As the
water availability decreases, bacteria,
mold and then yeast cease to grow.



Bacteria stop growing below 0.85aW
Molds stop growing below 0.75aW
Yeast stops growing below 0.6aW
Water availability of some common
foods
Food Example
Water
Availability
Cheese spread
0.95
Soy sauce
0.80
Fudge sauce
0.83
Soft, moist pet food
0.83
Peanut butter
0.70
Dry milk
0.70
Liverwurst
0.96
Salami
0.82
*Water availabilities greater than 0.85
support bacterial growth.
True or false: High water availability
supports bacterial growth.
a.
b.
True
False
Click forward to see the
answer.
True or false: High water availability
supports bacterial growth.
a.
b.
True
False
Most bacteria grow best in
products with high water
availabilities.
Oxygen

Aerobic reactions need oxygen.


The browning of fruit is one example.
Anaerobic reactions do not require
oxygen.

Clostridium botulinum is a type of bacteria that
does not need oxygen to survive.
Fill in the blank: Bacteria that need
oxygen to survive are ______.
a.
b.
Aerobic
Anaerobic
Click forward to see the answer.
Fill in the blank: Bacteria that need
oxygen to survive are ______.
a.
b.
Aerobic
Anaerobic
Aerobic bacteria need oxygen to
survive and grow.
pH
Foods have different pH values.
 Chemical reactions are decreased at very
high and very low pH.
 A pH meter is used to determine the pH
level of foods.

Temperature
Warm temperatures increase chemical
reactions.
 High temperatures can kill harmful
microorganisms.


High temperatures are critical for certain
preservation methods:



Pressure canning
Boiling-water canning
Low temperatures can slow and
eventually stop chemical reactions.
Preserve foods by:

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Adding an acid
Adding salt
Drying to remove moisture
Adding sugar
Adding chemical preservatives
Heating
Vinegar
+
(Acid)
Now that we know what to control to
prevent food from spoiling, let’s review
some methods of preservation.
Types of preservation:
Drying
Curing and smoking
Freezing and refrigeration
Fermentation
Pressure canning
Making jam and jelly
Pickling/acidification
Which of the following is a preservation
method?
a.
b.
c.
d.
Drying
Freezing
Smoking
All of the above
Click the forward button
to see the answer.
Which of the following is a preservation
method?
a.
b.
c.
d.
Drying
Freezing
Smoking
All of the above
“D” is the correct
answer.
Drying
One of the oldest methods of preservation
 Removes moisture to delay and prevent
bacterial growth
 Safe and easy-to-learn method of
preservation
 A food dehydrator
often is used
 Meats and fruits, such
as jerky, apples, bananas,
mangos and tomatoes, are
popular items to dry

Fill in the blank: Drying preserves food
by ______.
a.
b.
c.
adding an acid
lowering the temperature
reducing the moisture content
Click the forward button
to see the answer.
Fill in the blank: Drying preserves food
by ______.
a.
b.
c.
adding an acid
lowering the temperature
reducing the moisture content
“C” is the correct answer. A
food dehydrator or oven on a
low temperature is used to dry
foods for preservation.
Curing and Smoking
Meats must be cured before they are
smoked.
 Curing uses salt to reduce the moisture
available to microorganisms.
 Nitrates and nitrites are added to inhibit
the growth of Clostridium botulinum.
 Curing can take several hours to several
weeks.

Fill in the blank: Curing preserves food
by ______.
a.
b.
c.
adding an acid
lowering the temperature
reducing the moisture content
Click the forward button
to see the answer.
Fill in the blank: Curing preserves food
by ______.
a.
b.
c.
adding an acid
lowering the temperature
reducing the moisture content
"C” is the correct answer.
Salt is added to products
being cured to reduce the
moisture content.
Smoking
After a product is cured, it can be smoked.
 Smoking usually is done in a smokehouse.
 The combination of heat and smoke dries
and preserves the food.
 Smoking adds flavor to the product.
 Meat, poultry, game and fish all can be
smoked.

Freezing and Refrigeration
Are commonly used processes for
preserving
 Stops the growth of bacteria (freezing) or
slows the growth of bacteria
(refrigeration)
 Slows most chemical reactions

Does freezing food kill bacteria?
a.
b.
Yes
No
Click the forward button
to see the answer.
Does freezing food kill bacteria?
a.
b.
Yes
No
“B” is the correct answer.
Bacteria is not killed by
freezing foods, but the lower
temperature slows the growth
of bacteria.
Fermentation

A microorganism such as yeast is added to
a product to convert carbohydrates into an
acid or an alcohol.


These microorganisms consume the food and
produce byproducts.
Yogurt is one example.

Bacteria is added to milk. The bacteria eat the
sugar and produce lactic acid.

Lactic acid reduces the pH of yogurt, which inhibits
bacteria growth.
Which preservation method involves
bacteria or yeast?
a.
b.
c.
d.
Drying
Fermenting
Pickling
Freezing
Click the forward button to
see the correct answer.
Which preservation method involves
bacteria or yeast?
a.
b.
c.
d.
Drying
Fermenting
Pickling
Freezing
“B” is the correct answer. Yogurt
is an example of fermentation.
Pressure Canning

Kills bacteria with high temperatures.


A temperature greater than 240 F must be
reached.
Pressure canning is used when the
product has a pH above 4.6.
Jams and Jellies
Sugar reduces the amount of available
water.
 Jams and jellies normally have a pH lower
than 4.6.
 Jams and jellies cook during processing.

Post-test
Now you have some basic knowledge
about why we preserve food and the
methods of food preservation.
 Before you move on to the next module,
let’s take a post-test to see what you’ve
already learned.

Click here to take the post-test
Learn more about food preservation
with the following online resources

National Center for Home Food
Preservation


FDA - Acidified and Low Acid Canned
Foods

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www.uga.edu/nchfp/
www.fda.gov/food/guidanceregulation/guidanc
edocumentsregulatoryinformation/acidifiedlacf/
default.htm
NDSU Extension Service Food Preservation
and Storage

www.ag.ndsu.edu/food