Pressure Canning


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

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Pressure Canning

  1. 1. Simple, Safe, Easy to Learn Pressure Canning
  2. 2. Today’s Topics <ul><li>How to use a pressure canner </li></ul><ul><li>Learn to save the bounty of fresh produce all year long </li></ul><ul><li>Learn what spoils food </li></ul><ul><li>Use the principles of safe food preservation when using a pressure bath canner </li></ul>
  3. 3. Basics for Handling Food Safely <ul><li>Prevent bacteria from spreading through your kitchen </li></ul><ul><ul><li>Wash hands! </li></ul></ul><ul><ul><ul><li>20 seconds before and after handling food </li></ul></ul></ul><ul><ul><li>Sanitize! </li></ul></ul><ul><ul><ul><li>Cutting boards, utensils, and countertops </li></ul></ul></ul><ul><ul><ul><li>Solution of 1 tablespoon of unscented, </li></ul></ul></ul><ul><ul><ul><li>liquid chlorine bleach in 1 gallon of water </li></ul></ul></ul>
  4. 4. <ul><li>Before preserving any food </li></ul><ul><li>consider the types of foods your family enjoys and the usefulness of the preserved product in your lifestyle. </li></ul>
  5. 5. <ul><li>Methods of Food </li></ul><ul><li>Preservation </li></ul><ul><li>Canning </li></ul><ul><li>Freezing </li></ul><ul><li>Drying </li></ul><ul><li>Fermentation </li></ul><ul><li>Advantages of Food Preservation </li></ul><ul><li>Year round availability of foods </li></ul><ul><li>Less spoilage </li></ul><ul><li>Eliminate or reduce microbial hazards </li></ul><ul><li>Increased convenience </li></ul>
  6. 6. Basics of Home Canning <ul><li>Food is placed in a jar and is heated to a temperature that destroys microorganisms </li></ul><ul><li>The heat also inactivates enzymes that lead to food spoilage </li></ul><ul><li>As air is driven from the jar during heating, it creates a vacuum seal as it cools </li></ul>
  7. 7. UNsafe Methods of Canning <ul><li>Open kettle </li></ul><ul><li>Oven </li></ul><ul><li>Microwave </li></ul><ul><li>Dishwasher </li></ul><ul><li>Steam </li></ul><ul><li>Canning powders </li></ul><ul><li>Jars with wire bales and glass lids </li></ul><ul><li>Zinc lids </li></ul>
  8. 8. Equipment Needed for Canning <ul><li>Jars & Lids </li></ul><ul><li>Water bath canner </li></ul><ul><li>Pressure canner (dial or weighted gauge) </li></ul><ul><li>Canning rack </li></ul><ul><li>Jar lifter </li></ul><ul><li>Current safe canning </li></ul><ul><li>recommendations </li></ul>
  9. 9. Jars and Lids <ul><li>Wash canning jars; don’t use if nicked or scratched – keep hot until used </li></ul><ul><li>Prepare 2-piece canning lids and ring bands by package instructions </li></ul><ul><li>Remove air bubbles (plastic knife) </li></ul><ul><li>Wipe jar rims with wet, clean cloth </li></ul><ul><li>Adjust two-piece lids; tighten fingertip-tight </li></ul>
  10. 10. Canning Jars <ul><li>Glass, Mason-type intended for canning </li></ul><ul><li>Available in regular or wide mouth </li></ul><ul><li>Two-piece self sealing lids </li></ul><ul><li>Range from 4 ounces (½ pint) to ½ gallon </li></ul>
  11. 11. Canning Method <ul><li>The canning method that is approved for a food depends on the type of food </li></ul><ul><li>Foods are divided into two main categories: </li></ul><ul><ul><li>“ Acid” foods: those that contain acid </li></ul></ul><ul><ul><li>“ Low acid” foods: those that have very little or no acid </li></ul></ul>
  12. 12. “ Acid” Foods <ul><li>pH less than 4.6 </li></ul><ul><ul><li>Generally all fruits </li></ul></ul><ul><ul><li>Tomatoes, with added acid </li></ul></ul><ul><ul><li>Sauerkraut and fermented pickles </li></ul></ul><ul><ul><li>Foods to which large amounts of acid are added </li></ul></ul>
  13. 13. “ Low Acid” Foods <ul><li>pH greater than 4.6 </li></ul><ul><ul><li>Generally all vegetables </li></ul></ul><ul><ul><li>Meats </li></ul></ul><ul><ul><li>Poultry </li></ul></ul><ul><ul><li>Seafood </li></ul></ul><ul><ul><li>Soups </li></ul></ul><ul><ul><li>Mixed canned foods </li></ul></ul>
  14. 14. Two Methods of Canning <ul><li>Boiling Water Canning </li></ul><ul><ul><li>Used for “acid” foods, pH below 4.6 </li></ul></ul><ul><li>Pressure Canning </li></ul><ul><ul><li>Used for “low acid” foods, pH above 4.6 </li></ul></ul>
  15. 15. Methods of Packing <ul><li>Raw Packing </li></ul><ul><ul><li>Raw food placed directly into jar; boiling hot liquid added to cover the food </li></ul></ul><ul><ul><li>Carefully add jars to canner to avoid breakage from heat shock </li></ul></ul><ul><li>Hot Packing </li></ul><ul><ul><li>Food is cooked in liquid before packing; cooking liquid poured over food </li></ul></ul><ul><ul><li>Less floating of foods in the jar </li></ul></ul><ul><ul><li>Easier to pack, foods more pliable </li></ul></ul><ul><ul><li>Fewer jars needed </li></ul></ul>
  16. 16. Canning Fruit <ul><li>Preventing Darkening </li></ul><ul><li>1 teaspoon (3000mg) ascorbic acid to one gallon of water </li></ul><ul><li>Commercial ascorbic acid mixture </li></ul><ul><li>Heating the fruit </li></ul><ul><li>Canning Liquids </li></ul><ul><li>Sweet syrup </li></ul><ul><ul><li>Helps retain shape, color and flavor of fruit </li></ul></ul><ul><ul><li>Not necessary for safety </li></ul></ul><ul><li>Juice </li></ul><ul><ul><li>Commercial unsweetened apple, pineapple or white grape juice </li></ul></ul><ul><li>Water </li></ul><ul><ul><li>Can add non-nutritive sweeteners (Splenda®) </li></ul></ul><ul><ul><li>Missing preservative aspects of sugar </li></ul></ul>
  17. 17. Acidifying Tomatoes <ul><li>Tomatoes have pH between 4 and 4.6 (borderline for BWC) </li></ul><ul><li>For pints: </li></ul><ul><ul><li>¼ teaspoon citric acid </li></ul></ul><ul><ul><li>OR </li></ul></ul><ul><ul><li>1 tablespoon bottled lemon juice </li></ul></ul><ul><li>For quarts: </li></ul><ul><ul><li>½ teaspoon citric acid </li></ul></ul><ul><ul><li>OR </li></ul></ul><ul><ul><li>2 tablespoons bottled lemon juice </li></ul></ul><ul><li>Least taste change with citric acid </li></ul><ul><li>Can add sugar to offset acid from lemon juice </li></ul>
  18. 18. Headspace <ul><li>The space in the top of the jar between the inside of the lid and the top of the food or liquid </li></ul><ul><li>Check directions for correct headspace for each food </li></ul><ul><li>1 inch to 1 ¼ inch for “low acid” foods </li></ul>
  19. 19. Process Times Affected by: <ul><li>Acidity of food </li></ul><ul><li>Preparation style of food </li></ul><ul><li>Composition of the food </li></ul><ul><ul><li>Viscosity, tightness, heat transfer, starches/fats/bones </li></ul></ul><ul><li>Temperature of food when jarred </li></ul><ul><li>Temperature of processing </li></ul><ul><li>Size & shape of jar </li></ul>
  20. 20. Why Do Low Acid Foods Have to be Pressure Canned to be Safe? <ul><li>Clostridium botulinum ! </li></ul><ul><ul><li>C. botulinum forms protective, heat-resistant spores </li></ul></ul><ul><ul><li>Spores require higher temperatures for destruction in a reasonable period of time (usually 240 o F or above at sea level) </li></ul></ul>
  21. 21. What Does This Mean? <ul><li>Follow directions exactly! </li></ul><ul><li>How to slow heat penetration: </li></ul><ul><ul><li>Adding extra sugar or fat </li></ul></ul><ul><ul><li>Having food pieces larger than called for in directions </li></ul></ul><ul><ul><li>Adding thickeners </li></ul></ul><ul><li>Note: Heat-up and cool-down in pressure canners is counted toward heat penetration so don’t quick-cool the canner! </li></ul>
  22. 22. Pressure Canners <ul><li>Flat rack in bottom </li></ul><ul><li>Pressure regulator or indicator </li></ul><ul><ul><li>Dial gauge or weighted gauge </li></ul></ul><ul><li>Vent pipe for pressurizing </li></ul><ul><li>Safety valves or overpressure plugs </li></ul><ul><li>Safety locks when pressurized </li></ul><ul><li>Flexible gasket in lid or metal-to-metal seal </li></ul>
  23. 23. Using PC the First Time <ul><li>Some parts may need assembling; see manufacturer’s directions </li></ul><ul><li>Become familiar with parts and their functions </li></ul><ul><li>Usually need to clean to remove manufacturing oils </li></ul><ul><ul><li>(cover, body & gasket) </li></ul></ul><ul><li>Parts are usually pre-lubricated </li></ul><ul><ul><li>Before EACH use: be sure vent pipes are clear and open </li></ul></ul>
  24. 24. Venting the Canner <ul><li>As the water boils in the canner, the “empty” space becomes a mixture of steam and air </li></ul><ul><li>The temperature of a steam/air mixture is lower than the temperature of pure steam </li></ul><ul><li>Venting eliminates (“exhausts”) the air so processing takes place in a pure steam environment </li></ul><ul><ul><li>Process times are intended only for a pure steam environment </li></ul></ul>
  25. 25. Venting the Canner <ul><li>USDA instructs to vent ALL pressure canners </li></ul><ul><ul><li>The one difference in “following manufacturer’s directions” if not included there </li></ul></ul><ul><li>Without proper venting, up to 30% of the sterilizing value of a 20-minute process may be lost </li></ul>
  26. 26. Venting the Canner Directions <ul><li>Steam must flow freely from the open vent-port in the lid for 10 minutes prior to pressurizing </li></ul><ul><li>After putting filled jars in the pressure canner, fasten the lid in place </li></ul><ul><li>Leave the vent-port open </li></ul><ul><li>Turn the heat on high </li></ul><ul><li>When water boils, steam will start to come out of open vent </li></ul><ul><li>Wait until there is a constant, strong funnel of steam, then start timing 10 minutes </li></ul><ul><li>At the end of the 10 minutes, place weight in place to start pressurizing the canner </li></ul>
  27. 27. Altitude Adjustments <ul><li>As altitude increases, temperatures decrease at a given pressure </li></ul><ul><li>As altitude increases, increase pressure </li></ul><ul><li>Dial Gauge: </li></ul><ul><ul><li>1001-2000 ft: +1 psig </li></ul></ul><ul><ul><li>2001-4000 ft: +2 psig </li></ul></ul><ul><li>Weighted Gauge: </li></ul><ul><ul><li>1001 ft and above: +5 psig </li></ul></ul>
  28. 28. Pressure Canner Processing <ul><li>Have 2 -3” of water in the canner </li></ul><ul><ul><li>(140 °F for raw pack, 180°F for hot-pack) </li></ul></ul><ul><li>Place jars on rack in canner </li></ul><ul><li>Put lid on canner with weight off or petcock open </li></ul><ul><li>Heat on high until steam flows from the petcock or vent port </li></ul>
  29. 29. Pressure Canner Processing <ul><li>Exhaust canner 10 minutes </li></ul><ul><ul><li>All pressure canners, according to USDA </li></ul></ul><ul><li>Close vent or petcock </li></ul><ul><li>Start process time when correct pressure is reached </li></ul><ul><li>Regulate heat to maintain a steady pressure at or slightly above the correct pressure </li></ul>
  30. 30. Pressure Canner Processing <ul><li>9. Adjust pressure for altitude, if needed </li></ul><ul><li>Turn off heat at end of processing </li></ul><ul><li>Let pressure drop to 0 psig naturally </li></ul><ul><li>Wait about 1-2 minutes after pressure drops to 0 psig to make sure all pressure is gone </li></ul><ul><ul><li>(For some canners, check that locks in handles are released) </li></ul></ul>
  31. 31. Pressure Canner Processing <ul><li>13. Remove weight or open petcock- wait 10 min </li></ul><ul><li>14. Open canner (Be careful of steam!) </li></ul><ul><li>15. Remove jars to padded surface or rack </li></ul><ul><li>16. Cool jars 12 to 24 hours, undisturbed </li></ul><ul><li>17. Check that jars have sealed </li></ul>
  32. 32. Opening the Canner <ul><li>In pressure canning, turn heat off at end of process and let jars cool in canner until pressure is gone </li></ul><ul><li>When the canner lid is opened, tilt it so the steam is pushed away from your face </li></ul><ul><li>The steam, water and jars in the canner will still be very hot, even bubbling or boiling </li></ul>
  33. 33. Opening the Canner <ul><li>Dial Gauge </li></ul><ul><ul><li>After it reads 0 psig, carefully remove the weight </li></ul></ul><ul><ul><ul><li>If there are piston locks in the lid or handle, make sure they have also opened </li></ul></ul></ul><ul><ul><li>Wait 10 minutes, then open lid </li></ul></ul><ul><ul><li>Remove jars from canner </li></ul></ul>
  34. 34. Opening the Canner <ul><li>Weighted Gauge </li></ul><ul><ul><li>Time the cooling process </li></ul></ul><ul><ul><ul><li>Heavy-walled older canners: 30 min full of pint jars, 45 min full of quarts </li></ul></ul></ul><ul><ul><ul><li>Thinner wall newer canners: 20 to 30 minutes </li></ul></ul></ul><ul><ul><li>If there are piston locks in the lid or handle, see that they have also opened </li></ul></ul><ul><ul><li>Carefully remove the gauge </li></ul></ul><ul><ul><li>Wait 10 minutes, then open lid </li></ul></ul><ul><ul><li>Remove jars from canner </li></ul></ul>
  35. 35. Cooling Jars <ul><li>Remove jars from canner using a jar lifter </li></ul><ul><li>Do not retighten lids, as this may cut through the gasket and cause seal failures </li></ul><ul><li>Cool on towels or racks at room temperature for 12 – 24 hours </li></ul>
  36. 36. Storing Home Canned Food <ul><li>Label and date all jars </li></ul><ul><li>Store in a cool, dry, dark place </li></ul><ul><li>Avoid temperature extremes </li></ul><ul><li>Use within 1 year for best quality </li></ul>
  37. 37. Storing Canner <ul><li>Thoroughly dry canner, lid and gasket- do not put lid in water </li></ul><ul><ul><li>Older canners : Take off removable petcocks or safety valves. Wash and dry. Reassemble carefully. </li></ul></ul><ul><li>Clean openings by running clean pipe cleaner or thin strip of cloth through them </li></ul><ul><li>Store canner with crumpled clean paper or paper towels in it; do not fasten the cover </li></ul><ul><li>Wrap cover in paper and turn upside down on the canner bottom </li></ul>
  38. 38. Summary <ul><li>Canning food is an excellent way to preserve the harvest of summer for months to come. </li></ul><ul><li>Determine if the food is “acid” or “low acid” </li></ul><ul><li>Pressure canning is required for “low acid” foods. </li></ul><ul><li>Vent or exhaust the pressure canner before starting processing time. </li></ul>
  39. 39. Questions? <ul><li>“ This material has not been peer-reviewed for statewide distribution --blind peer review pending.” </li></ul>
  40. 40. References: <ul><li>United States Department of Agriculture (2009).  Complete Guide to Home Canning.  Agriculture Information Bulletin No. 539. </li></ul><ul><li>National Center for Home Food Preservation. </li></ul><ul><li>Ohio State University Extension, Canning Basics , </li></ul><ul><li>Ohio State University Extension, Basics for Canning Vegetables , </li></ul>