Putting up food for winter: Canning

Invented in the 1800’s, most people think immediately of canning in mason jars when they think of home preservation.  Done correctly, home canning is very safe, requires no electricity to store, and food is typically preserved for up to 3 years.

Problem is, canning is time consuming, hot and uses a lot of energy up front.  You also have to buy the canner(s), jars, lids, and so forth.  Finally, one big drawback to canning is that there is a significant loss of nutritional quality in the process: up to 60%.

The drawbacks don’t stop millions from making tasty hoe jams, jellies, tomato salsaa and pickles for their own families and as gifts in cheap and widely available vessels called boiling water bath canners.  Other than jellies, which require a bit of a knack to get to gel up properly every time, these are very easy to make and get a high quality product if you can follow instructions.  And who wouldn’t love a gift of homemade fig preserves tied with a ribbon?  How it works: The sustained high temperature in the jars submerged in boiling water kills most decay causing organisms and forces air out of the jars.  The lid seal prevents new contamination.  The acidic environment inside the jar prevents the growth of botulism.

But for comprehensive food preservation from your garden, you need a pressure canner.  The canner is more expensive, but the jars and such are the same.  There are a few more steps and you need to be more careful to follow them closely, but pressure canning opens up a world of possibilities for canning vegetables and fruit similar to what you might buy in a metal can in the store.  How it works: just the same as boiling water bath, but since the food is not acidic, the entire interior of the jar needs to be brought up to 240F to kill botulism spores, and you can only do that under pressure.

What’s the deal with botulism anyway?  Botulism as a disease causing agent wasn’t discovered until 1897.  Clostridium botulinum, Clostridium butyricum and Clostridium baratiiI are bacteria which create a nerve toxin as part of its life cycle.  Spores are everywhere, but spores are dormant and not dangerous.  However, spores revive and begin their life cycle in anaerobic (oxygen free), warm, wet environments… like the inside of a canning jar.  Botulism illness is fairly rare, but is an often fatal paralytic illness.  See also:

Curiously enough, even fatal paralytic toxins has their uses in small doses: botulism toxin is used in Botox cosmetic treatments for wrinkles.

If you want to learn about canning, the Ball Blue Book is a great place to start.  For more recipes, the Ball Complete Book of Home Preserving includes everything in the Blue Book and more.  There are other books available from major publishers with safe and tested recipes.  These recipes tend to be more exotic or are designed for smaller batches.  For free information, the National Center For Home Food Preservation has everything you need to know online plus recipes. Your local Agricultural Extension office will also have information sources, and your library probably has a copy of the Ball Blue Book.  Be sure to get and use the latest edition.

Beware random canning recipes on the internet — just because you can put something in a jar and seal it doesn’t mean it’s safe.  Just because grandma did it that way doesn’t mean it’s safe either.  Botulism wasn’t even known as an organism until 1897 and the solution, home pressure canning, wasn’t widely available to homemakers until 1938.  (Although it was invented sooner.)  And Listeria didn’t enter the human food chain until about 30 years ago.  Your grandmother used the best knowledge and technology available to her to feed her family.  Do what grandma did and use the safest methods at your disposal.

(By Nicole Castle)


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