Monday, June 25, 2012
We've made carrot cake, carrot cake jam and dehydrated carrots. I decided we needed something a little different for the last of the carrots that came out of the garden. We have pressure canned low acid vegetables before, but never carrots. Last weekend seemed like an ideal time to give it a try. Pressure canning is a little more complicated than boiling water bath canning. It's not more difficult, but there is more of a danger factor. You need to know what you're doing to avoid a catastrophic canner failure (big boom in your kitchen...not advised) or giving yourself botulism (also not advised). So if you're new to canning, maybe try a few boiling water bath recipes first to get comfortable with the rules of preparing jars and then read the instruction book for your pressure canner cover to cover.
Back to our carrots. First, all the carrots needed to be trimmed, washed and peeled
After carefully opening the lid, I used a jar lifter to pick up the jars and this happened:
The other likely culprit would be if I put the bands on too tight. This would account for the sealing failure too. Bands should be put on fingertip tight and I did have a moment of "hmm....maybe that was too much" when I put the bands on the last two jars, but I went ahead and put them in the canner anyway. When jars are processed, air inside the jar needs to be pushed out. This is how you get the seal: air heats up and expands, and some leaves the jar, when the jars cool down, the remaining air contracts. At this point, you might say the lid gets sucked down. Which would be scientifically inaccurate. In reality, you just have a pressure differential. There is more pressure pushing down on the jar from the outside than there is on the inside (since you removed some of the air). The higher pressure outside pushes the lid down. The rubbery material on the lid is pushed down on the rim of the jar and the center of the lid is pushed down so it no longer flexes when you push on it. So if you put your bands on too tight, no air can escape. That means a jar either won't seal, or it will break to make an exit for the air. And that's today's little "physics as it applies to canning" lesson.
The broken jar was a lost cause. Jars that don't seal properly can be reprocessed, but food quality is often not as good. Pressure canning is also a bit time consuming and we weren't going to be pressure canning anything else. The alternative to reprocessing is to just store the food a different way, such as putting it in the refrigerator and using it soon.
All in all, I'd say we were pretty successful though. Canning carrots was much less time intensive than the sweet potatoes we can every year. Just gotta be more careful with those bands next time!