Uncovering The Steam Vent
I've always heard that when the pressure canner has done its work, you should let it cool down completely without doing anything to hurry it along, like taking the weight off the steam vent, for example.
I admit that I have done that a few times, and I noticed that when I did, the bubbling sound inside the canner got noticably louder. I have also noticed that some broth from inside the jars has been pulled out into the canner.
My questions are:
1. Why does it matter if I take the weight off the steam vent to hurry cooling?
2. Why do I get broth from inside the jars pooling in the canner even though I left plenty of head space?
3. Are these two things related?
Yes the two things are related. If the jars cool too quickly they will expand and push liquid out. Not sure of the science behind it but I do know it happens.
I've also read that jars can break if cooled to quickly.
The other reason it is important to let the canner cool by itself is timing. When the USDA tests to see how long foods need to be pressure canned they include the cool down time in the total cooking time. So if you cool the canner artificially you are also shortening the total cooking time.
You should be letting the canner cool all by itself. When the pressure is back to zero, open the vents and wait two minutes. Then you can remove the lid. It will still be hot! Be sure it is tilted away so the steam doesn't hit you in the face.
Sometimes I notice my jars are really bubbling hard still after I've opened the canner. I'll often leave my jars in the canner for 2 or 3 minutes more when that happens. This allows them to cool more, before removing them from the heat.
pressure canning instructions