How to determine canning processing times


I know safety is paramount with canning, and best answer is always to find a trusted recipe. But that's obviously not possible for every conceivable food one might want to can. Besides, trusted recipes came from somewhere (and work even though for example exact pH of fruit varies), and there are plenty of companies out there canning all kinds of things. So:

  • Given pH, jar/bottle size, and hot vs cold pack, can I determine whether boiling water or pressure canning is safe and what processing time is necessary? What if I err on the side of safety and assume pressure canning is required – then can I determine a time?

  • Is there some sufficiently long processing time of pressure canning that will make anything safe, or at least anything meeting some broad criteria? (The idea being not to have to measure pH.)

Best Answer

In answer to your second part, no. If something is not acidic enough for water canning it seems it doesn't matter how long you process it, it isn't safe. This is the reasoning all the cookbooks I've read provide for adding a teaspoon of lemon juice to each pint of tomatoes.

I would therefore use this strategy:

  • get things to the right pH for water or pressure canning as a separate first step. (Fruit will generally be ok, tomatoes need lemon juice, pickles will be ok, etc)
  • check the processing time for pints and quarts of various things (jams, fruit, pickles etc) and look for the pattern: is it consistently 25% more time, or 5 extra minutes? Work out the pattern.
  • repeat for hot vs cold pack: do you halve the time, or subtract 10 minutes, or what?

Now armed with a hot-pack pints recipe, you can adjust it for cold-pack quarts or vice versa. You should also, in poring through these recipes and charts, have come to understand various categories (fruit, jam, pickles, nonpickled vegetables etc) and be familiar with what times they need. Then faced with a chutney, conserve, or pickle that isn't on anybody's list, you should be able to choose what category it most likely belongs to, and safely pick a time for it.