Wednesday, August 13, 2014

The Science of Canning: Part II

OK, now that we've got the science of canning down pat (and I gave you the weekend to either ponder tonicity or conclude that I'm nuts), it's time to put it into practice.

(Note, and I am not kidding about this:  This blog is not the substitute for following good canning practices.  I am not responsible for canning errors, failures, or food spoilage.  You are responsible for your own food safety.  The system I'm about to share does not replace the need to follow a proven canning recipe and the practices set forth by the USDA.)

OK, legal disclaimer out of the way, let's play a game! Your challenge is to can some food, and get the highest score possible:

Canning/Preserving Method

  • Pressure canning:  The most secure of all canning methods, this does a complete job of killing all bacteria in the food and on the inside of the jar with both pressure and heat.  5 points
  • Water bath canning:  For most high-acid foods, this is the right choice, doing a nearly complete job on the bacteria with heat.  4 points
  • Freezing:  Good for short term storage of less than a year, this doesn't kill bacteria but slows them way down.  3 points
  • Open kettle canning:  This traditional method of canning relies on having hot jars and hot food to sterilize the jar and headspace and seal the jar.  It is no longer considered safe by the USDA, although there are some home canners that still use it.  2 points
The Canning Environment

  • Acidity:  Boosting the acid, often through the addition of cider vinegar, is a time honored way of preserving food.  In fact, acid plus salt is the reason that you can leave a pickle crock standing out in a general store with no problem to the pickles.  The value of acidity depends on how much is in the food itself and how much you add.  2-3 points
  • Salt/Sugar:  By playing with the tonicity in the canning environment, you can kill the little bacteria that threaten your food.  Like acidity, the effectiveness depends on how much you add.  2-3 points
  • Spices:  Herbs and spices often have their own food preservation qualities, which is why they have traditionally been used in preservation.  We no longer routinely rely on spices to preserve our food, but they help.  1 point

  • Give yourself 1 point for setting up your kitchen like an operating theater, complete with a clean apron for you, sterilized jars, and clean utensils.
  • Give yourself 1 point for following a modern canning recipe to the letter, not deviating on amount of acid, salt, or sugar, and for processing the items for the full time specified.

If you are playing along, look at your canning processes and try to get a score of at least 6 on every project. Examples:
  • Canned stew beef:  Proper recipe and procedure (1 point) + pressure canning (5 points) = 6 points
  • Pickles:  Acid (2 points) + Salt (2 points) + Water bath canning (4 points) = 8 points
  • Freezer jam:  Sugar (2 points) + Freezer (3 points) + Clean environment (1 point) = 6 points

Again, this is not a substitute for following proper instructions, but it should be a way for you to think about your food preservation in a scientific way and assess whether your recipes and process are up to snuff!  And, for you preppers out there, this is a good way to start thinking about food preservation in a grid-down situation when you may not have all the resources you would ideally want on hand.
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