Canners: pH testing?


Typical recipe collections for canning include a warning, often in bold, all-caps print, along the lines of, "Follow these recipes exactly exactly exactly or you will die of botulism." Now, clearly, what they mean is, "don't adjust recipes in ways that push the pH high enough that botulism can grow," but they don't want the liability of telling people how to make up recipes.

So, can one simply pick up some pH test strips at the friendly local hardware store and use those to make sure that recipes come out to an appropriate acidity? It seems the magic number for botulism is 4.6. Is "pH lower than 4.6" prior to processing sufficient, or is there some buffer needed to account for changes during processing? (Me = not a chemist.)

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I'm not chemist either, but...

We have never tested the pH of our canned goods. And we have reduced the vinegar content in some brines, where the recommended amount gave us cherry tomatoes that tasted like cider vinegar, carrots that tasted like cider vinegar and so on.

For what it's worth, the only problem I can see with pH-testing your brine is that any liquid left in the veggies will mix with the brine over time, so the pH result at canning is probably too low--but I have no idea by how much. (This mixing is one of the reasons why you salt many vegetables before canning, to draw out excess water.)

I suppose my recommendation is to follow the recipe. If it yields tongue-burningly astringent pickles, then you'll probably be safe reducing the vinegar content somewhat.

And of course dial "91" and keep your finger poised over the "1" when you have the first tasting!


Whenever I open a jar - particularly the first jar I open of any given batch - there's a long routine of peering, sniffing, holding up to the light, sniffing some more, asking Cara if she thinks it looks or smells strange, and finally tasting a minuscule portion, making sure that somebody's in sight in case I keel over. Ah, paranoia!

(Hmmm...Wikipedia says typical onset time of symptoms is 12-36 hours, or up to 10 days. Crap - now I have to be paranoid for a whole week and a half?!)

pickling versus canning

One question I have is how often botulism has been a problem with pickled or brined foods. Most of the home-canned foods that get mentioned in the wikipedia piece--carrot juice, canned green beans--have no acid added to them. Also, of course, the whole point of proper heat processing and sterilization is to ensure that you don't have to count on the pH as your sole line of defense.

Another thing to check for is any release of gas when you open the jar.

Sounds like a question for The Splendid Table

This sounds like the perfect question for the lady that hosts "The Splendid Table" on NPR. I'm fairly certain WUOM carries the broadcast. There's never a question that can't stump this foodie lady.