Making jelly 101 — a recipeless how-to

I’ve had some quince cores and peels stashed in my freezer since a friend helped me out immensely by preparing the fruit to be candied while I was occupied with brewing-related things. The time has come to turn them into something useful: jelly!

Jelly, at least what North Americans call jelly, consists of pectin-rich fruit juice and sugar boiled until it reaches a point where it sets into a firm mass. Pectin is a soluble fibre found mostly in the cores, seeds, and peels of fruits, especially citrus and orchard fruits like apples. If you’re trying to make a jelly from a low-pectin fruit (the Kilner Jar company has a nice reference here), then you’ll need to add more. You can buy commercial pectin, which comes in standard, low-sugar, and no-sugar varieties, or you can make your own (I’ll get into that later).

To test whether your juice contains enough pectin to make into jelly, just splash a bit into a cup with a small amount of drug-store isopropanol (or methylated spirit, if you have access to it) and swirl the cup gently. If the juice sets into a firm mass that you can lift out with a fork, you’re good to go; otherwise, it needs additional pectin. Throw this mixture out when you’re done, since neither the isopropanol nor the methylated spirit are safe to consume.

To make jelly:

  1. Chop up your fruit and put it into a large pot with just enough water to cover it
  2. Bring it to a boil, then turn off the heat and cover the pot
  3. Let the fruit soften and steep until it is cool
  4. Strain the fruity liquid through a cheesecloth or muslin into a large container
    • If you want a clear jelly, don’t squeeze the cloth since this forces fruit fibres through the weave. If you can’t help doing that, then you can refrigerate the liquid for a while and let the sediment settle, then pour it carefully into your pot to leave the sediment undisturbed. This doesn’t guarantee a clear jelly in the end, but it helps.
  5. Measure the liquid and pour it into a large saucepan
  6. Measure 80% of the liquid’s volume in granulated sugar and add to the saucepan (it must be no more than 1/3 full at this point)
  7. Prepare your boiling water or pressure canner and jars (here‘s a good explanation from Food in Jars)
  8. Boil, stirring to dissolve the sugar, until the mixture starts to rise up and foam, around 195 degrees F or 90 degrees C, then decrease heat to medium while stirring rapidly to break the foam’s surface tension
    • This is the reason why you shouldn’t overfill your pot; I’ve been doing this for over a decade and I still get surprised by how much the mixture foams up, which usually results in an unscheduled cleaning of my range top
    • When you notice that the foam’s texture has become coarser, i.e. with larger bubbles instead of smaller foamy ones, that’s a good indication that your jelly is done or almost done
  9. Pour into hot Mason jars and close with fresh snap lids and rings (refer to the link in step 6 for a detailed how-to)
  10. Process in a boiling water canner for the appropriate amount of time for the size of the jars (here‘s a pretty detailed  PDF chart from the University of Minnesota)

All done!

If you want to make your own pectin, follow steps 1 through 4 above using underripe apples as your base fruit.

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