Reducing a canning recipe

Small Batchin’: Tomato Vanilla JamDisclaimer: For those of who own and operate math skills in an expert fashion: Don’t read this. You might very well be insulted. For the rest of us who need a refresher on 8th grade algebra (or the art of ratios), please do read on.

Early on in my canning career, I realized small-batch (and sometimes super-small-batch) is my preferred jar style. Hence, I needed to get tight with numbers since winging it and approximating can get you killed in canning-land.

You don’t have to be able to do mental math (though it can be helpful), all you really need is a calculator. Knowing equivalents or having easy access to a chart with info like how many teaspoons are in a Tablespoon, etc. is extremely helpful, too. I’m going to demo recipe reduction with Christine Ferber’s Ripe Tomato with Vanilla recipe (from Mes Confitures).

As written:

  • 4 lbs tomatoes (3.5 net, which means seeded and cored)
  • 4.25 cups granulated sugar
  • Juice of 1 small lemon
  • 7 oz Green Apple Jelly (another recipe in her book, which I, of course, don’t have on hand)
  • 2 vanilla beans

The essential factor in recipe reducing is to figure out how much of the featured produce you actually have. I realized (after 6 months of using recipe receipts, the produce scale at my co-op, and other drastic measures) that I needed to own a kitchen scale if I was truly to become Small Batch Kickass (thanks Julia). I bought one, and now I weigh the hell out of all fruit and veg I encounter.

Back to the recipe…

I had 1lb 12oz whole tomatoes at the start, which reduced to a measly 1/2-lb after the seeding and coring process. I based my reduction on the net value (1/2-lb), regardless of Ferber’s dreamland wherein you only lose a tiny portion of the volume after draining the juicy suckers.

1-2-3 Reduce!Here’s where you pull out your calculator:

Divide .5 by 3.5, the answer is: 0.1428…

This is your core ratio; you (we) are making 15% of the original recipe. You now go through each ingredient listed and multiply by .15 (I rounded up to make things neat). [If you’re nervous about making such calls, then by all means just multiply each ingredient by the exact number you see on your screen, 0.1428…]

  • Sugar: 4.5 x .15=0.675 cups sugar [that’s a half cup and about 1 Tbs]
  • Lemon: 15% of one whole lemon juiced is about 1 tsp. [A whole lemon produces about 2 Tbs of juice, halved is 1 Tbs (in which there are about 3 tsp) so 15% of the whole (2 Tbs) is roughly a tsp)
  • Jelly: 7 x .15=1.05 oz jelly [luckily I had a jar of Julia’s jelly on hand, this recipe isn’t it exactly, b/c my jar didn’t have star anise, but you get the point] I know from the equivalents chart that my half-pint jar is 8oz (or 1 cup), and if I need 1 oz, that’s and 1/8th cup, which is 2 Tbs.
  • Vanilla beans: 2 x .15=0.3 of a bean. I sliced my vanilla bean in three and threw 1/3 in the pot.

If you get confused during the multiplication process, remember to check in with and assess the measurement (italicized for emphasis above) for perspective and try to reason through it (like with the jelly portion). Spices get a little crazy in the reducing process, i.e. reducing a Tbs of something. Usually ‘a pinch’ suffices (and let’s face it, you’re not going to hurt yourself or others with dried spices, so pinch away)!

Gooo small batch; now you’re cooking!