It is pumpkin season, and of course, there’s countless blog posts and YouTube videos out there telling you, in an expert tone, how to can pumpkin for pie, pumpkin puree, and more.
These posts are all wrong, because the latest recommendations by the USDA are that you CANNOT can pumpkin puree.
I could not, in good conscience, suggest to any reader, that they can pumpkin puree based on that science.
Pumpkin is a low acid vegetable. It is also very dense. Even in a pressure canner, which gets over 220 degrees, it is too dense for the heat to reliably penetrate the puree to kill any potential botulism spores.
Don’t worry, new canners; there are VERY FEW items that you cannot preserve in a home canning setup and this is one of them. Truly, very few. And, just like when you bake bread, you don’t have to understand why or how the bread rises. You DO have to follow the directions in order for it to work. Canning is the same. You just have to follow the directions.
All foods have an acid value, lemons have an acid level of a 2 (high acid!) and tangerines are significantly, and somewhat surprisingly less acid 4. It will list all the low acid veggies, like pumpkin too. You may, according to the USDA, can in a pressure canner cubed pumpkin, but I would consider this to be an intermediate canning activity.
Furthermore, the USDA goes on to say how the final product of pressure canned cubed pumpkin isn’t as good as frozen.
I can’t see how anyone, when fully informed, would decide to can pumpkin, cubed or pureed, if the best product is preserved frozen. I’d recommend wide mouth pint jars for freezing. Those jars have a freezer safe line right on them, are easy to clean by hand or in the dishwasher, and are my favorite for canning.
Cubed pumpkin (rather than a puree) is required because a trusted recipe source (the USDA for example) TESTED the size of the cubes (1 inch by 1 inch) and measured the heat inside those little cubes to be sure that it was hot enough inside to kill the spoilers that would make you sick.
It is for this reason that you cannot ever can spaghetti squash at all—it won’t hold a cube shape and becomes a mushy mass that the heat, again, can’t reliably penetrate.
You can read the aforementioned page on the USDA site for more detailed, and tested by science specifics on exactly what you can and cannot do with pumpkin.
To be clear, “puree” also refers to pumpkin butter, pumpkin pie filling, mash, mush, or anything that’s not a 1x1 inch chunk. No pumpkin baby food, no smooth pumpkin of any kind.
Canning pumpkin simply isn’t safe. Enjoy it in muffins, lattes, frozen if you must, but don’t can it.
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