Pressure Canning

Susan Shockey, PhD, of the OSU Extension-Franklin County, discusses the basics of pressure canning various fruits and vegetables.

1. Simple, Safe, Easy to
Learn
Pressure Canning

2. Today’s Topics
•How to use a pressure canner
•Learn to save the bounty of fresh produce
all year long
•Learn what spoils food
•Use the principles of safe food
preservation when using a pressure bath
canner

3. Basics for Handling Food Safely
•Prevent bacteria from spreading through
your kitchen
–Wash hands!
20 seconds before and after handling food
–Sanitize!
Cutting boards, utensils, and countertops
Solution of 1 tablespoon of unscented,

liquid chlorine bleach in 1 gallon of water

4. Before preserving any food
consider the types of foods
your family enjoys and the
usefulness of the preserved
product in your lifestyle.

5. Methods of
Food
Preservation
•Canning
•Freezing
•Drying
•Fermentation
Advantages of
Food
Preservation
•Year round
availability of
foods
•Less spoilage
•Eliminate or
reduce microbial
hazards
•Increased
convenience

6. Basics of Home Canning
•Food is placed in a jar and is heated to a
temperature that destroys microorganisms
•The heat also inactivates enzymes that
lead to food spoilage
•As air is driven from the jar during heating,
it creates a vacuum seal as it cools

7. UNsafe Methods of Canning
•Open kettle
•Oven
•Microwave
•Dishwasher
•Steam
•Canning powders
•Jars with wire bales and glass lids
•Zinc lids

8. Equipment Needed for Canning
•Jars & Lids
•Water bath canner
•Pressure canner (dial or weighted gauge)
•Canning rack
•Jar lifter
•Current safe canning
recommendations

9. Jars and Lids
•Wash canning jars; don’t use if nicked or
scratched – keep hot until used
•Prepare 2-piece canning lids and ring bands by
package instructions
•Remove air bubbles (plastic knife)
•Wipe jar rims with wet, clean cloth
•Adjust two-piece lids; tighten fingertip-tight

10. Canning Jars
•Glass, Mason-type intended for canning
•Available in regular or wide mouth
•Two-piece self sealing lids
•Range from 4 ounces (½ pint) to ½ gallon

11. Canning Method
•The canning method that is approved
for a food depends on the type of food
•Foods are divided into two main
categories:
–“Acid” foods: those that contain acid
–“Low acid” foods: those that have very little
or no acid

12. “Acid” Foods
•pH less than 4.6
–Generally all fruits
–Tomatoes, with added acid
–Sauerkraut and fermented pickles
–Foods to which large amounts of acid are
added

13. “Low Acid” Foods
•pH greater than 4.6
–Generally all vegetables
–Meats
–Poultry
–Seafood
–Soups
–Mixed canned foods

14. Two Methods of Canning
•Boiling Water Canning
–Used for “acid” foods, pH below 4.6
•Pressure Canning
–Used for “low acid” foods, pH above 4.6

15. Methods of Packing
•Raw Packing
–Raw food placed directly into jar; boiling hot
liquid added to cover the food
–Carefully add jars to canner to avoid breakage
from heat shock
•Hot Packing
–Food is cooked in liquid before packing;
cooking liquid poured over food
–Less floating of foods in the jar
–Easier to pack, foods more pliable
–Fewer jars needed

16. Canning Fruit
Preventing Darkening
•1 teaspoon (3000mg)
ascorbic acid to one
gallon of water
•Commercial ascorbic acid
mixture
•Heating the fruit
Canning Liquids
•Sweet syrup
–Helps retain shape, color
and flavor of fruit
–Not necessary for safety
•Juice
–Commercial unsweetened
apple, pineapple or white
grape juice
•Water
–Can add non-nutritive
sweeteners (Splenda®)
–Missing preservative
aspects of sugar

17. Acidifying Tomatoes
•Tomatoes have pH between 4 and 4.6
(borderline for BWC)
•For pints:
–¼ teaspoon citric acid
OR
–1 tablespoon bottled lemon juice
•For quarts:
–½ teaspoon citric acid
OR
–2 tablespoons bottled lemon juice
•Least taste change with citric acid
•Can add sugar to offset acid from lemon juice

18. Headspace
•The space in the top of the jar between
the inside of the lid and the top of the food
or liquid
•Check directions for correct headspace for
each food
•1 inch to 1 ¼ inch for “low acid” foods

19. Process Times Affected by:
•Acidity of food
•Preparation style of food
•Composition of the food
–Viscosity, tightness, heat transfer,
starches/fats/bones
•Temperature of food when jarred
•Temperature of processing
•Size & shape of jar

20. Why Do Low Acid Foods Have
to be Pressure Canned to be
Safe?
•Clostridium botulinum!
–C. botulinum forms protective, heat-resistant
spores
–Spores require higher temperatures for
destruction in a reasonable period of time
(usually 240
o
F or above at sea level)

21. What Does This Mean?
•Follow directions exactly!
•How to slow heat penetration:
–Adding extra sugar or fat
–Having food pieces larger than called for in
directions
–Adding thickeners
•Note: Heat-up and cool-down in pressure
canners is counted toward heat
penetration so don’t quick-cool the canner!

22. Pressure Canners
•Flat rack in bottom
•Pressure regulator or indicator
–Dial gauge or weighted gauge
•Vent pipe for pressurizing
•Safety valves or overpressure plugs
•Safety locks when pressurized
•Flexible gasket in lid or metal-to-metal
seal

23. Using PC the First Time
•Some parts may need assembling; see
manufacturer’s directions
•Become familiar with parts and their
functions
•Usually need to clean to remove
manufacturing oils
–(cover, body & gasket)
•Parts are usually pre-lubricated
–Before EACH use: be sure vent pipes are
clear and open

24. Venting the Canner
•As the water boils in the canner, the
“empty” space becomes a mixture of
steam and air
•The temperature of a steam/air mixture is
lower than the temperature of pure steam
•Venting eliminates (“exhausts”) the air so
processing takes place in a pure steam
environment
–Process times are intended only for a pure
steam environment

25. Venting the Canner
•USDA instructs to vent ALL pressure
canners
–The one difference in “following
manufacturer’s directions” if not included
there
•Without proper venting, up to 30% of the
sterilizing value of a 20-minute process
may be lost

26. Venting the Canner Directions
•Steam must flow freely from the open vent-port in the lid
for 10 minutes prior to pressurizing
•After putting filled jars in the pressure canner, fasten the
lid in place
•Leave the vent-port open
•Turn the heat on high
•When water boils, steam will start to come out of open
vent
•Wait until there is a constant, strong funnel of steam,
then start timing 10 minutes
•At the end of the 10 minutes, place weight in place to
start pressurizing the canner

27. Altitude Adjustments
•As altitude increases, temperatures decrease at
a given pressure
•As altitude increases, increase pressure
•Dial Gauge:
·1001-2000 ft: +1 psig
·2001-4000 ft: +2 psig
•Weighted Gauge:
·1001 ft and above: +5 psig

28. Pressure Canner Processing
1.Have 2 -3” of water in the canner
a.(140°F for raw pack, 180°F for hot-pack)
2.Place jars on rack in canner
3.Put lid on canner with weight off or petcock
open
4.Heat on high until steam flows from the
petcock or vent port

29. Pressure Canner Processing
1.Exhaust canner 10 minutes
a.All pressure canners, according to USDA
2.Close vent or petcock
3.Start process time when correct pressure is
reached
4.Regulate heat to maintain a steady pressure at
or slightly above the correct pressure

30. Pressure Canner Processing
9.Adjust pressure for altitude, if needed
2.Turn off heat at end of processing
3.Let pressure drop to 0 psig naturally
4.Wait about 1-2 minutes after pressure drops
to 0 psig to make sure all pressure is gone
a.(For some canners, check that locks in handles
are released)

31. Pressure Canner Processing
13.Remove weight or open petcock- wait 10 min
14.Open canner (Be careful of steam!)
15.Remove jars to padded surface or rack
16.Cool jars 12 to 24 hours, undisturbed
17.Check that jars have sealed

32. Opening the Canner
•In pressure canning, turn heat off at end of
process and let jars cool in canner until
pressure is gone
•When the canner lid is opened, tilt it so the
steam is pushed away from your face
•The steam, water and jars in the canner
will still be very hot, even bubbling or
boiling

33. Opening the Canner
•Dial Gauge
–After it reads 0 psig, carefully remove the
weight
•If there are piston locks in the lid or handle, make
sure they have also opened
–Wait 10 minutes, then open lid
–Remove jars from canner

34. Opening the Canner
•Weighted Gauge
–Time the cooling process
•Heavy-walled older canners: 30 min full of pint jars,
45 min full of quarts
•Thinner wall newer canners: 20 to 30 minutes
–If there are piston locks in the lid or handle,
see that they have also opened
–Carefully remove the gauge
–Wait 10 minutes, then open lid
–Remove jars from canner

35. Cooling Jars
•Remove jars from canner using a jar lifter
•Do not retighten lids, as this may cut
through the gasket and cause seal failures
•Cool on towels or racks at room
temperature for 12 – 24 hours

36. Storing Home Canned Food
•Label and date all jars
•Store in a cool, dry, dark place
•Avoid temperature extremes
•Use within 1 year for best quality

37. Storing Canner
•Thoroughly dry canner, lid and gasket-
do not put lid in water
–Older canners: Take off removable petcocks or
safety valves. Wash and dry. Reassemble carefully.
•Clean openings by running clean pipe
cleaner or thin strip of cloth through
them
•Store canner with crumpled clean paper
or paper towels in it; do not fasten the
cover
•Wrap cover in paper and turn upside
down on the canner bottom

38. Summary
•Canning food is an excellent way to
preserve the harvest of summer for
months to come.
•Determine if the food is “acid” or “low acid”
•Pressure canning is required for “low acid”
foods.
•Vent or exhaust the pressure canner
before starting processing time.

39. Questions?
“This material has not been peer-reviewed
for statewide distribution --blind peer
review pending.”

40. References:
United States Department of Agriculture (2009). Complete Guide to Home
Canning. Agriculture Information Bulletin No. 539.
National Center for Home Food Preservation. www.uga.edu/nchfp
Ohio State University Extension, Canning Basics ,
http://ohioline.osu.edu/hyg-fact/5000/pdf/5338.pdf
Ohio State University Extension, Basics for Canning Vegetables,
http://ohioline.osu.edu/hyg-fact/5000/pdf/5344.pdf