01 October 2012

Home canning: vegetarian soup stock

Last week I canned two quarts of vegetarian soup broth. Usually I'm happy to use store-bought soup concentrates, but it's good to have on hand something that doesn't require added water to use, and in a real pinch doesn't even need to be heated up. Just a bottle opener and we're ready to go. To begin:

Math and more photos after the jump . . .

First the math. The "recipe" -- really, just what I rummaged around in the fridge for and found: Carrot tops from a couple of pounds of farmers market carrots; two leeks, including the greens; one medium potato; half a small onion; and salt. No other seasoning, no herbs, because I do not intend this to be a particularly authentic or full-flavored soup base. I simply want a couple of jars of broth in the pantry, put up as cheaply as possible, for a quick dinner (heat up a small amount of raw vegetables or leftovers in the broth, add pasta, bring to a boil, and serve when pasta is done) or for cooking up a rice pilaf. As for cheap, the carrots were priced by the bunch, not by the pound, so the tops were free; the leeks cost $2.00; the potato was about $0.30; the onion was about $0.25; and I used about $0.15 worth of salt and olive oil. I'll add $0.50 for water and cooking gas, for a total of $3.20, or $1.60/qt.

Amazon lists quart boxes of vegetable broth at $39.48/doz., or $3.29/qt. While the commercial broth probably has more flavor to it, I'm happy to pay half the price for just a little less flavor, which I can always tweak and customize later on. And the packaged broth come in those yucky, hard-to-recycle, bad karma aseptic boxes.

On to the canning process. As always, if you are not familiar with home canning, please see the National Center for Home Food Preservation. This blog entry does not substitute for a complete set of instructionson safe home canning practices. A full guide for canning is especially important where, as here, we're talking pressure canning. This food item CANNOT be safely canned in a boiling water bath canner.

First I sauteed the diced onion in a little bit of olive oil. Not a whole lot, because grease is tricky to work with in home canning; you have to get the jar rims very, very clean or the sealing compound on the lidswill fail. I added the coarsely chopped carrot tops and vegetables, plus about a half gallon of water, and simmered it all for about half an hour. While it cooked, I heated up some quart jars in the pressure canner:

Unlike boiling water bath canning, you need only a few
inches of water in the pressure canner. Water in the jars is
there to help them warm up and not break from thermal shock
when the hot broth is added
As the vegetables softened, I pressed them with a potato masher. Then I poured it through a colander into a large mixing bowl and pressed as much of the broth back into the stock pot as I could:

Clockwise from left: mixing bowl with strained broth; canning funnel
and screw bands for jars; vegetables being pressed over the stock pot;
and lids heating in a small saucepan

At this point I think you're supposed to give the vegetables to the pigs. Here at Rowhouse Livin' we compost a very little bit, but sadly most of our food waste goes down our sink disposal. (Why we don't have a garden is a whole other post, but in short it's for architectural reasons.) Continuing:

Internal temperature is 240 degrees F, or 10 pounds of pressure
at sea level, where we are. OK, strictly speaking we're at
39 ft (12 m); but no altitude adjustment is necessary here.
Canner brand name clumsily edited out because no paid endorsement
Love it! Last time I pressure-canned something, I had a steam leak on one side and couldn't bring the temperature up all the way to 240 degrees F. Since it was tomatoes, which most likely didn't really need to be pressure-canned anyway, I put them in the fridge (and we're still leisurely working through the jars). If the canner hadn't gotten up to temperature here, we would have been eating a lot of soup over the weekend!

Since I was working from no recipe, I checked a few modern references for processing times. The Ball Blue Book suggested 35 minutes for its strained vegetable stock. I added five minutes just to be sure. So, 40 minutes later:

Precipitate on the outside is likely potato starch plus
hard-water deposits; precipitate inside is likely
mmm, mmm, good

Each of these quart jars is good for about two meals for Rowhouse Livin's household, because it takes two cups of stock to make a side dish of flavored rice or to start a quick soup. Now they're identified and dated and sitting on my pantry shelf. What will you be eating during a snowstorm this winter?

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