Friday, May 22, 2015

Home Canning FAQs

For the past 20 years I've traveled around the state judging home canning competitions. It's a great opportunity to visit with home canners, learn what's happening in their kitchens, and discuss canning techniques. I've noticed that many canners rely on friends and family for information. While I like the idea of sharing traditions, too often outdated preservation methods are passed along.

Canning standards are updated every few years. Recipes or methods that your grandmother used may be antiquated as produce varieties have evolved with different acid levels, new strains of bacteria exist, and we know a lot more about preservation and safe food handling.

On the heels of a recent botulism outbreak in Ohio which killed one and sickened dozens, I thought I'd revisit questions I'm often asked. This is not a complete list. If you have other questions, leave a note in the comment section below, contact your local extension office, or browse these resources:

Are water bath and pressure canners interchangeable?
A pressure canner is used for low acid foods like green beans, carrots, potatoes, meat, etc. The temperature inside a pressure canner reaches 240 degrees, which is required to kill botulism spores. Water bath canners, used for high acid foods like fruits, bread spreads and pickles reach 212 degrees. Regardless of how long the jars are processed in a water bath canner, the internal temperature will never reach 240 degrees. The canners are not interchangeble.

A water bath canner, left, is used for high acid foods.
A pressure canner, right, is used for low acid foods. 

My jars seal without processing. Do I need the extra step of processing?
The USDA recommends all jars need to be processed in a water bath or pressure canner to be shelf stable. A sealed jar means a vacuum was created and air/bacteria will not get in the jar. It doesn't mean the contents of the jar are sterile. Processing in a canner will sterilize the contents.

Why do I need to use updated recipes?
Home spun family recipes, or any recipe older than 20 years old should be replaced with a more recent, tested recipe. Canning standards are routinely updated. Seek recipes from a reliable source: USDA, local extension, Ball or National Center for Home Food Preservation (see links above).

The Ball Blue Book is great resource with tested, vetted recipes. This is the 2015 edition.

How do I can my spaghetti sauce (or other family favorite)?
Unless you're using a tested canning recipe from a reliable source your recipes cannot be canned. However, many homemade foods can be safely frozen, including spaghetti sauce, chili, salsa and more. Your recipe may differ in acid, viscosity, etc. so applying a processing time from a canning recipe can yield an unsafe product.

What are the signs of spoilage?
Mold, "off" odor, leaking jars and bulging lids are all signs of spoilage. Do not consume. However, botulism is odorless and tasteless, often showing no visible signs of spoilage. As a result, the USDA recommends boiling low acid, pressure canned food for 10-15 minutes before consuming.

Can I reuse the lids?
Two piece lids include a threaded ring and flat lid with a gum adhesive. Rings can be reused as long as they tightly hold the lid agains the jar. Lids can only be used once. New lids promising multiple use are available on the market, but they are not recommended by the USDA.

Two piece lids come with a flat rid and threaded ring. Only the ring can be reused.

Can I alter a canning recipe?
You can safely remove salt, although flavor will be impacted. Adding or removing other ingredients can alter the acidity. It's always best to stick to the recipe.

Why do I need to acidify tomatoes?
Tomatoes come in lots of varieties, some less acidic than others. To make sure tomatoes are properly acidified, add 2 Tbsp lemon juice or 1/2 tsp citric acid to each quart of tomatoes.

Can I use my oven to can food?
During "oven canning" filled jars are placed in a hot oven until the lid gum softens and seals. The contents of the jar aren't processed. It's not canning, and it's not safe.

How long will home canned food last?
Home canned food should be consumed within one year. While it may be safe beyond a year, flavor and nutrition decline.

Want more info on the science of canning? In addition to the sources listed above, I encourage you to read one of my favorite preservation posts, written by a microbiologist.

Have food preservation questions? Leave me a comment below.

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