Home Food Preservation: What’s
New and What’s Old—and Unsafe!
Joye M. Bond, PhD, RD
Department of Family Consumer Science
Minnesota State University, Mankato
Food Preservation Methods
Canning
 Freezing
 Drying
 Pickling
 Sugar concentrates
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◦ Jams, jellies, butters, preserves, etc.
History of USDA Publications
1909—Canning Vegetables in the Home
 WWI—Can the Kaiser
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WWII—Victory Gardens
Early 1950s—USDA research switched to
freezing
 Complete Guide to Home Freezing was
drafted in 1980s, but never published
 Majority of today’s processes are based
on USDA research from 1944-46
 Some limited research by various
universities after USDA stopped
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1980s—USDA/Penn State Center of
Excellence
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Conducted extensive literature review
Evaluated tomato processes
Fruit pie fillings
National training for Extension faculty
Published Complete Guide to Home Canning in
1988 (revised in 1989, 1994, 2009)
National Center for Home Food
Processing and Preservation
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University of Georgia—lead institution
◦ Literature review
◦ Updating of USDA/Extension publications
◦ New website: National Center for Home
Food Preservation
◦ Instructional video series
◦ Web-based curriculum on home food
preservation
◦ Original applied research
Applied Research
Microbial issues of herbs and spices used
in home food preparation of flavored
vinegars, salsas, & oils
 Canning fruit with Splenda®
 Development of “specialty” foods—salsas,
sugar concentrates, relishes, sauces, and
marinades
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Why Preserve at Home?
Save food from a “time of plenty” to a
“time of need”
 Prevent spoilage until food can be eaten
 Know what is in the food
 Personal satisfaction
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How Methods Preserve Food
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Refrigeration
◦ Extends shelf-life by slowing growth of
microorganisms and action of enzymes
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Freezing
◦ Lowered temperature lowers the available
water (Aw)
How Methods Preserve Food
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Canning fruits and tomatoes
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Removal of O2
Sealed jar
Heat (boiling water processed)
Acidity (natural or added)
Canning vegetables and meats
◦ Removal of O2
◦ Sealed jar
◦ Heat (pressure processed)
How Methods Preserve Food
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Sweetening & Acidifying (jams, jellies,
spreads)
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Lower (Aw)
Removal of O2
Sealed jar
Heat (boiling water processed)
Acidity of the fruit
How Methods Preserve Food
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Pickling & Fermenting
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Increased acidity—added or created
Heat (boiling water processed)
Removal of O2
Sealed jar
How Methods Preserve Food
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Drying
◦ Lower (Aw)
Home canning is back!
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And botulism still does occur…
◦ July 2012—Oregon, home-canned foods
served at a barbecue
◦ 2008, 2009—Ohio and Washington, green
beans
Basics of Home Canning
Food in a jar is heated to a temperature
that kills microorganisms
 Heat also inactivates enzymes that cause
food spoilage
 With jars, air is driven from the jars with
heating; as jar cools, a vacuum seal is
created
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Vacuum Seal
Holds lid on jar
 Prevents recontamination of food
 Prevents air from drying out food
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Two Methods of Canning
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Boiling Water Canning
◦ Used for acid foods
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Pressure Canning
◦ Used for low acid foods (and some acid
foods)
Acid Foods
pH≤4.6
 Most fruits (some exceptions, e.g.,
melons)
 Tomatoes are borderline—specific
amounts of citric acid or lemon juice
must be added before canning to acidify)
 Sauerkraut
pH of Some Common Foods
Acidified Foods
pH≤4.6
 Mixtures of acid and low acid foods with
an equilibrium pH≤4.6
Low Acid Foods
pH>4.6
 Most vegetables
 Meats, poultry, seafood
 Soups
 Mixtures of acid and low acid foods
(e.g., spaghetti sauce—meat, vegetables,
tomatoes; salsa—tomatoes, onions,
peppers)
Why Two Methods?
Clostridium botulinum
 Yeast, molds, and most bacteria killed
fairly easily at boiling temperatures
(212˚F at sea level)
 C. botulinum forms spores that require a
higher temperature for destruction in a
reasonable amount of time (usually 240˚F
at sea level)
Preventing Botulism
Spores won’t germinate in acid foods
 Spores killed when heated long enough at
a specific temperature
 USDA usually recommends 240˚F at sea
level
 Pressure canner must be used for all low
acid foods
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Preventing Botulism
Proper preparation and process time
 Canner must be accurate and operated
correctly
 Altitude adjustments need to made as
needed
 Use directions from a reputable source
National Center for Home Food
Preservation
 Beware of “granny’s method”
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Methods of Pack
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Raw pack
◦ Boiling liquid is poured over the food
Methods of Pack
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Hot Pack
◦ Cooked in liquid before packing; cooking
liquid poured over food in jar
◦ Heat in preparation kills some microbes
◦ Cooking before packing changes the way food
will heat while in the canner, so time might be
different than raw pack
Headspace
¼ -inch: jellied fruit products
 ½ -inch: fruits, tomatoes, pickles
 1-1¼ -inch: low acid foods
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Boiling Water Canning
Water temperature is no higher than
212˚F
 Process times increased for altitudes over
1000 ft
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Boiling Water Canning
Water is high enough to cover filled jars
by 1-2 inches over top of jars
 Filled and closed jars are placed on rack
in canner to prevent breakage
 Jars are processed for specific time after
water comes to a boil
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Boiling Water Canning
At end of process time, turn off heat and
remove lid
 Wait 5 minutes
 Remove jars to a protected surface to
cool
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Pressure Canner Processing
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Go to:
http://nchfp.uga.edu/multimedia/slide_sho
ws/CanLowAcid_web08.ppt
Jars and Lids
USDA recommendations based on 2piece metal lid system
 Wash canning jars; don’t use if nicked or
scratched—keep hot until used
 Prepare 2-piece canning lids and rings
using manufacturer’s instructions
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Filling and Closing Jars
Fill according to recipe recommendations
 Remove air bubbles
 Re-adjust headspace if necessary
 Wipe jar rims with clean, dampened cloth
 Adjust lids fingertight
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National Surveys of Home Food
Preservation
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Source of canning instructions
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Family or friends—51%
General cookbook—17%
Ball Blue Book—7.5%
Pressure canner manufacturer—12.6%
Internet—3%
Magazines, newspapers—4%
State Extension Service—3%
Other—13%
Surveys
Many people not using pressure canning
for low acid foods
 Large percentage still using “open kettle”
or “oven” methods of canning
 Large percentage change
recommendations to fit their needs
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Recommended Resources
National Center for Home Food
Preservation | Publications Home
 National Center for Home Food
Preservation
 So Easy to Preserve
 Any Land-grant University Extension
Service
 Reputable manufacturer books, pectin
packages, etc.
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Salsa!
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http://nchfp.uga.edu/publications/uga/Toma
toSalsa_web.ppt
Salsa!
Mixture of low acid and acid foods
(tomatoes, onions, peppers)
 Hot pack
 Use a tested recipe
 Needs to be acidified to be safe
 Don’t increase the amount of onions or
peppers (both low acid)
 Can alter amounts of dried spices
 If you aren’t sure, freeze or refrigerate the
salsa—don’t can it
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Resources
◦ Adapted from Current Science and Practice in
Home Food Preservation webinar, Elizabeth
L. Andress, PhD, Project Director, National
Center for Home Food Processing and
Preservation, The University of Georgia.
August 2012.
◦ Salsa information reprinted with permission
of the University of Georgia. National Center
for Home Food Preservation and Simmons, H.
2008. Step-By-Step Canning of Tomato Salsa
Using Slicing Tomatoes. Athens, GA: The
University of Georgia, Cooperative Extension.