Q: I tried canning chicken stock, and followed the directions on your blog, but the lids made the “pop” sound as soon as I poured the liquid in and seemed to seal (I hadn’t heated them up yet). Then I processed them. Is this OK? Are the jars safe to eat?
(from Christina, Philadelphia)
Yes! If you had hot liquid, and cold (or even room temperature) jars, it’s possible that you could create a vacuum just by putting on the lids. As the liquid cools, the volume of the air inside decreases, and you get a good, clean seal. This is the same thing that normally happens after you process the jars—it just happened early. When you put the jars into the pressure cooker and crank up the heat, the contents will expand once again, so you’ll still need to check that the jars have sealed once your done.
Just to clarify: you do need to process the jars, even if they’ve sealed, because you need to kill the bacteria with high heat.
One more side note: I’ve seen Christina’s pressure cooker, and while it’s certainly safe to use, it’s a little scary to can with. This is because there is no visual indicator that tells you whether the canner is at pressure once you’ve turned off the heat. It does have a lock, so there’s no chance that you can accidentally open it, but there’s also no way to tell when it’s safe to go in. When you can liquids in a pressure cooker, the general recommendation is that you wait at least 10 minutes after the pressure has dissapated before opening the lid, as the contents of the jars may still be bubbling when the indicator falls. If you have a pressure cooker like this, the answer is simply to wait. There’s no harm in letting them sit there all afternoon, if necessary. Better safe than sorry!