In case any of you missed my first experience bottling butter, check it out here before reading the rest of this post. I'll wait . . .
Okay, back now? So the two main problems with bottling butter were 1-not high enough temperature to kill botulism spores, and 2-jar lids did not seal completely even though they "popped" down.
Chef Tess commented that she pressure cans her butter, and in my half scientific opinion, that would theoretically solve both problems. It would definitely get the butter hotter (hot enough for any other food to be past the fear of botulism growing), and the lids would seal securely since it was heated so long in the canner. You can your butter using the same canning time and pressure as if you were canning meat (check your canner's instructions--I can my meat 55 mins at 12 lbs). Then proceed with the shake shake shake as it cools to avoid separation.
So I called my local extension agent who told me in effect that there is no research to show that pressure canning butter works. (Which also means there is no research to show it doesn't work.) She sent me to the FAQ section of the National Center for Home Food Preservation, but it only discusses the problems with the non-pressure-canned method. The major concern is the possible extent to which the fat in the butter could protect those nasty dangerous little botulism spores which may or may not be present to begin with from cooking to death during the canning process. She told me if I want to bottle butter in the pressure canner to do it at my own risk, but she wouldn't do it and for sure wouldn't do it using the non-pressure-canning method.
So there you have it. I'm not in any real hurry to bottle more butter (I usually just keep a bunch in the freezer), but if I wanted to, I would feel pretty safe using the pressure canning method. But just in case you die from botulism tainted bottled butter, I didn't recommend it. ;)
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