No, not when the boiling-water-bath or pressure-canner method is used, because the containers and lids are sterilized during processing. But be sure jars and lids are clean.
Why is no liquid added when tomatoes are canned?
Because tomatoes provide their own juice if pressed gently when packed raw, or when heated before packing hot into jars.
Is it safe to add celery, green pepper, and onion to tomatoes when canning them?
No. Adding other vegetables lowers the acidity of tomatoes. Acidity helps protect against the growth of botulinum bacteria, which can produce a fatal toxin in canned foods. Specific recipes, times, and temperatures determined scientifically for vegetable mixtures need to be used for their safe canning.
Why is headspace important in canning?
Headspace—the distance between the surface of food and the underside of the lid—allows for expansion of solids or bubbling up of liquid during processing. If headspace is not adequate, some food in the container will be forced out, leaving food particles or sirup on the sealing surface and preventing a seal.
When too much headspace is allowed, some air may remain in the jar after processing, causing food at the top of the jar to darken.
What causes jars to break in a canner?
Breakage can occur for several reasons: (1) Using commercial food jars rather than jars manufactured for home canning, (2) Using jars that have hairline cracks, (3) Putting jars directly on bottom of canner instead of on a rack, (4) Putting hot food in cold jars, or (5) Putting jars of raw or unheated food directly into boiling water in the canner, rather than into hot water (sudden change in temperature—too wide a margin between temperature of filled jars and water in canner before processing).