Presentation on theme: "Preserving the Harvest: Canning Basics. Canning Basics How does canning (processing) preserve food? 1.Creates an airtight seal of the lids 2.The heat."— Presentation transcript:
Preserving the Harvest: Canning Basics
Canning Basics How does canning (processing) preserve food? 1.Creates an airtight seal of the lids 2.The heat kills any bacteria that could cause illness or spoilage. Photo courtesy of the National Center for Home Food Preservation.
Two Methods of Canning Boiling water bath Pressure Method depends on the acidity of the food. – High acid foods ( < pH of 4.6) water bath canner – Low acid foods (> pH 4.6) pressure canner Photo courtesy of National Center for Home Food Preservation
The pH of food decides which canning method to use pH = < 4.6 High Acid Foods PicklesApricots Apples Raspberries Apricots Strawberries Oranges Blueberries GrapefruitBlackberries PeachesPineapple GrapefruitKraut PlumsPears Figs pH >4.6 Low Acid Foods Okra Beans Hominy Squash Potatoes Olives Pumpkins Spinach Shrimp Carrots Peas Clams Turnips Corn Meat Cabbage Poultry Asparagus Onions WATER BATH CANNER PRESSURE CANNER Source: So Easy to Preserve, 5 th edition, University of Georgia, 4
Use the right processing method to prevent botulism. Clostridium botulinum Often found in the soil; found in 2 forms Vegetative cells (active cells – produce a deadly toxin) – Anaerobic (can live without oxygen) – Killed by boiling in water (212 degrees) Spores (often in the soil; inactive; in hibernation) – Spores can only be killed if they are boiled at 240 degrees (must be done with a pressure canner) – Loves a low-acid environment 5
How botulism can be a problem Fresh green beans with inactive spores. Green beans canned in a water bath canner instead of pressure canner. The lids sealed, creating an anaerobic environment. The spores wake up and become active. They divide, become overpopulated and start to die off. When this happens, they produce the botulism toxin. The green beans are now contaminated with the botulism toxin. You cant see the toxin! 6
Pressure Canner – A special type of canner that has a lid which is able to be tightly closed so steam cannot escape. – The pressure generated in this type of canner allows the food to be heated at temperatures higher than 212 degrees (boiling temperature). – The recommended method of canning for low acid foods like vegetables, meat, & poultry.
Unsafe Methods of Canning Open kettle Steam canning Microwave oven canning Oven canning Dishwasher canning
Recipes Use only uses recipes that have been tested using research-based methods. Recipes from cookbooks, family/friends, and some internet sites may not be suitable for use. We do not encourage people to alter or make up their own recipes – it is not safe!
Where to get tested Recipes YES! Current Extension publications USDA Makers of home canning equipment & ingredients NO! Personal internet sites Cookbooks Back to nature publications Out-of-date Extension publications 10
Equipment for Canning Lid lifter Jar lifter Funnel Jar wrench – NOT RECOMMENDED 11 Jars
Prepare jars before use! Check for cracks and chips. Wash in hot, soapy water and rinse. Keep them hot until they are ready to be filled. If jars are processed in a pressure canner (no matter how long) or if they are processed in a boiling water bath canner for 10 minutes or longer, they do not have to be sterilized.
Lids 2-piece lid is recommended – Self-sealing lid + a screw band (ring) Buy the amount of lids that will be used in a year; old lids may not seal well Bands can be reused; Lids are used only once. Photo courtesy of National Center for Home Food Preservation
Headspace The space in the jar between the underside of the lid and the top of the food or its liquid. Amount of headspace needed depends on the type of food and the method of canning. – This will be stated in the recipe. Too little headspace food may boil over onto the rim of the jar and prevent it from sealing. Too much headspace the processing time may not be enough to get all the air out of the jar, resulting in a poor seal. May also result in discolored food.
Headspace 1-inch headspace (just below the finish) 1-1/4 inch headspace (midway on shoulder) 1-1/2 inch headspace (just below the shoulder) 1/2 inch headspace (just below the middle glass lug) 1/4 inch headspace (just below the first glass thread)
Packing Methods Raw pack – Place raw, unheated foods in the jar – Pour boiling water, juice or syrup over the food until proper headspace is reached Hot pack – Food is heated/boiled for recommended amount of time then packed in jars – Boiling liquid is added until proper headspace is reached
Packing Methods Foods often have a preferred method for packing (follow recipe instructions). If you have the choice between raw and hot pack, hot pack has some advantages: – Food is easier to pack (compared to raw) – Less floating of the food – Color and flavor is better Raw packed tomatoes that have been canned. Photo courtesy of National Center for Home Food Preservation
Filling and Sealing jars Once jars are filled, release air bubbles – Place a flat plastic spatula between the food and the jar. Adjust the headspace. Wipe the jar rim with a damp paper towel. Place lid on the jar; add screw band and slightly tighten (not too loose or too tight) Wiping the rims of jars. Photo courtesy of National Center for Home Food Preservation
A metal knife can scratch the inside of the jar, causing it to become weak and breaking later during processing. The wrong way The right way Using a bubble freer, plastic or rubber knife or spatula will get the air out without causing damage to the jars.
Processing Times The amount of time jars spend in the canner so foods are properly heated and the lids seal. Kills bacteria in the food so spoilage or foodborne illness doesnt happen. This is a critical step in food preservation! Processing times depend on: – Food (type, thickness, how it is packed) – Size of jar – Type of canner
Processing Times Processing times are based on RESEARCH and should not be adjusted. – Exception: locations with high altitude Under processing can lead to food that is spoiled or unsafe Over processing can lead to overcooked food
Why adjust processing times at high altitude? At high altitudes, water boils at a lower temperature and is not hot enough to kill bacteria. Solution? – Boiling water bath canner - boil longer – Pressure canner - raise the pressure Use tested recipes and guidelines for canning at higher altitudes. 23
What happens during processing? Heat kills bacteria that can cause illness or spoilage. Air is pushed out of the jar during the heating process; as the jar cools afterwards a vacuum seal is formed. The vacuum seal keeps air and bacteria from getting back into the food.
My jars are done – now what? Pressure canner: Wait 10 minutes after canner has depressurized before removing jars. Remove jars with a jar lifter. Do not tilt the jars. Place hot jars on dry towels or cake cooling rack to keep jars from touching a cold surface. Do not disturb while the jars cool (12-24 hours). Photo courtesy of National Center for Home Food Preservation
Make sure your jars are sealed Press the middle of the lid with your finger. If the lid springs up when you lift your finger, the seal is not good. While cooling, you may hear a pop noise coming from the jars. This is a sign that the lids have sealed but it is a good idea to check them again 12 to 24 hours later.
Storing Canned Foods Remove screw bands; wipe jars to remove any food residues. Label and date the jars. Store in clean, cool, dark, dry place = date jars were processed B-2 = second batch of jars processed Label with the food processed (Pears)
When to Discard Home-Canned Foods Jars not processed right and the mistake is noticed more than 24 hours later. Unexplained cloudy canning liquid Strange odor Mold growth Jar that did not seal and it has been longer than 24 hours. Bulging lid
GREEN BEAN RECIPE Select tender, crisp pods. Remove and discard diseased and rusty pods. Wash beans and trim ends. Break or cut into 1 inch pieces or leave whole. Pack beans tightly into hot jars, leaving 1 inch headspace. Add ¼ teaspoon salt to pints; 1 teaspoon to quarts, if desired. Fill jar to 1 inch from top with boiling water. Remove air bubbles. Wipe jar rims. Adjust lids and process. Process in a Dial Gauge Pressure Canner at 11 pounds pressure OR in a Weighted Gauge Pressure Canner at 10 pounds pressure: Pints – 20 minutes Quarts – 25 minutes
County Extension Agent Jana Osbourn, Bandera County Website:
Acknowledgements National Center for Home Food Preservation. Georgia Cooperative Extension, So Easy to Preserve, 5 th edition. Food Safety Advisor Volunteer Handbook, Washington State University & University of Idaho