Canning is a great way to take control of the foods we eat. When you process fruits and vegetables yourself, you knowwhere they come from, and what has been added to them. You can avoid excess sugar and unwanted preservatives, and still enjoy safe and tasty home-cooked products. In the winter time it’s satisfying and comforting to go your own kitchen cabinet for beautifully preserved, locally grown, summer foods. The process of canning is also interesting and fun to do with a partner or friend.
Canning is a process of preserving food by heating it to destroy unwanted micro-organisms and sealing it into a jar, to keep oxygen out. Some organisms can survive heating to boiling temperature, and an oxygen free environment. However, these organisms cannot survive in a high acid environment. So, to safely can foods using boiling water, you need to create a high acid environment inside the jar. To can products that are not high in acid, you need to heat the contents beyond boiling temperature, using a pressure canner.
Boiling water canning is only safe for preserving high-acid foods, such as most fruits, tomatoes (with added lemon juice or citric acid) or foods with added acid such as pickles, catsup, salsa and chutney. Any time a low acid food is added to the product to be canned (such as onions, garlic, cucumbers or peppers) lemon juice or vinegar must be added (and a trusted canning recipe followed) in order to safely can with the boiling water method. Otherwise, you need to use a pressure canner (see pressure canner instructions in this packet)
It is easy to get started canning. You need a few special items, but most of them are inexpensive or easy to find second-hand.
You will need:
• ball jars, designed for canning, these can be used over and over
• a canning bath (large enamel pot with a rack inside to hold the jars) or a large stock pot with some sort of rack
• flat lids designed for canning jars (these MUST be new. Do not reuse these)
• screw-on metal bands to go over the lids (these can be reused, and should be removed once the sealed jar has cooled)
• a jar lifter
• a canning funnel
• a clean small cloth
• ladle, spoon, knife and other basic utensils for prepping the food
Always be sure to follow trusted canning recipes closely. This is not the place to experiment, especially when it comes to the amount of vinegar or lemon juice required in a recipe. Tweaking spices to your own tastes is fine, just be sure keep the ratio of added acid to product consistent with a recipe designed for boiling water bath canning. Get your hands on a good canning book such as the Ball Blue Book of Preserving, or Putting Food By, and use that as your reference guide. County Extension websites (such as Purdue’s) are also great sources for trustworthy, detailed information on canning all sorts of foods.
• Tomatoes - about 23-25 lbs to make 7 quarts of
tomatoes (of course, you can reduce the size of
• lemon juice - bottled, about 1/2 cup (or citric acid--use 1/2 teaspsoon in each quart jar)
• 1 Water bath Canner
• 1 large pot (to scald or blanche the tomatoes)
• 1 large pot (to heat the peeled tomatoes)
• 1 small pot or kettle -for water to sanitize the
• Paring knife, for coring tomatoes
• Pint or quart canning jars
• Lids - thin, flat, round metal lids with a gum
binder that seals them against the top of the
jar. They may only be used once.
• Rings - metal bands that secure the lids to the
jars. They may be reused many times.
• Jar grabber (to pick up the hot jars)
• Lid lifter (optional) –it has a magnet to pick the
lids out of the boiling water where you sanitize
• Jar funnel
• Large spoons and ladles
Get the jars and lids sanitizing. The dishwasher is fine for the jars; especially if it has a "sanitize" cycle. I start that while I'm preparing everything else, so it's done by the time I'm ready to fill the jars. If you don't have a dishwasher, submerge the jars in a large pot (the canner itself) of water and bring it to a boil. If using a dish washer, be sure to let it go through the rinse cycle to get rid of any soap!
Get the canner heating up. Fill the canner about 1/2 full of water and start it heating (with the lid on).
Get a large pot of water heating for blanching the tomatoes for peeling.
Start the water for the lids. When it boils, pour it over the lids and rings. Cover and let sit until you are ready to seal the jars.
Remove the tomato skins. Put the tomatoes, a few at a time, in a large pot of boiling water for no more than 1 minute (30 - 45 seconds is usually enough) Then plunge them into a waiting bowl of ice water. This makes the skins slide right off of the tomatoes! Then you can cut the tomatoes in quarters and remove the tough part around the stem and any bruised or soft parts. Why remove the skins? They become tough when you cook them!
Heat the quartered tomatoes just to boiling, stirring to prevent burning. Before you fill each jar with tomatoes, add 1 Tablespoon of lemon juice to the bottom of each pint jar (2T for a quart. jar). The additional acid makes all types of tomatoes safe for boiling water bath canning, and retains color and flavor.
Fill the jars with heated tomatoes. Leave 1/2 inch head-space at the top. Wipe off the rim of the jar with a clean damp cloth, then put the flat part of the lid on, and the ring. Just screw them on snugly, not too tight. Be sure the contact surfaces (top of the jar and underside of the ring) are clean to get a good seal!
Carefully lower the jars into the canner and make sure they are covered with at least 1 inch of water. Bring the water back to boiling. Process the jars in a boiling-water bath for 35 minutes for pints and 40 minutes for quarts. After the processing time has passed, lift the jars out of the water and let them cool without touching or bumping them in a draft-free place (best to leave them overnight). Once the jars are cool, check that they are sealed, verifying that the lid has been sucked down. Just press in the center, gently, with your finger. If it springs up and down (often making a popping sound), it is not sealed. If you put the jar in the refrigerator right away, you can still use it. Some people replace the lid and reprocess the jar, but it is best to heat the contents back up, re-jar them (with a new lid) and process for the full time in the canner. With all the extra heating, and processing, you may loose some quality, but it will be safe to consume.
This document was adapted from the "Complete Guide to Home Canning," Agriculture Information Bulletin No. 539, USDA, revised 1994.