Oh, how I love blueberries.
I saw a recipe for Blueberry Lime jam in the book put out by Ball, the company who makes most of the canning jars and equipment you see out there. But there was SO much sugar in the recipe – 5 cups of sugar to 4 1/2 cups of berries. So I checked in with Christopher Kimball (okay, not really HIM, but his Yellow Farmhouse Cookbook that I've been looking at a lot lately), and I used the proportions in his "Master Recipe for Simple Fruit Jam" instructions. He comes up with a cup and three quarters of sugar to 4 cups of fruit for long-term storage (in other words, for canning rather than keeping in the fridge), so I went with that, pretty much. I also increased the quantities because of all the berries I had, and I left out the pectin. Blueberries have pretty high amounts of natural pectin, so I didn't think the jam required it.
So my version is as follows:
8 cups of prepared blueberris (stems and leaves removed, berries rinsed and crushed)
5 cups of sugar
the juice of 2 and a half limes (that's what we had)
the zest of 1 lime (next time I'd increase this, but only one lime had zest-worthy skin)
Combine everything in a big bowl, stir to combine and let sit for 2 hours (per Mr. Kimball). I actually ended up leaving all this in the bowl for more like 4 hours because I also had dinner to make and needed some of the same pans as I'd use in the jam-making process. I don't think any harm was done.
Put the mixture in a large, heavy saucepan or pot and bring to a boil over medium heat, stirring occasionally, until the sugar is dissolved.
Crank up the heat to medium-high. The mixture will become foamy, and you can skim off some of the foam if there's too much of it. Keep cooking, and stirring, until the mixture thickens and the liquid becomes syrupy.
Keep stirring, but don't overcook. Per Mr. Kimball, "the mixture will become substantially thicker and a wooden spoon will leave a trail on the surface of the skillet." You can use the metal bowl test to check for doneness as well – put a little metal bowl in the fridge or over an ice bath, drizzle some of the jam onto it and wait a minute or so, then run your finger through the jam. If the trail left by your finger remains, the jam is good to go. If the jam seeps back into that empty space, you need to keep cooking it.
While your jam has been cooking, hopefully you were getting all your canning equipment ready.
Assuming you were doing that, here we go – ladle the jam into your prepared jars, leaving a quarter inch of space at the top of the jar. Seal them and process in the hot water bath for 12 minutes. Shut off the heat, let sit in the water another five minutes before removing the jars and placing them on a towel for 24-48 hours.
Check the lids (when you press on them, they should not bounce up and down) to make sure the seal is good and then slap some labels on the jars and place them in your pantry, or wherever you keep jams.
(There's a boy who loves his jam.)
Of course, it may be necessary to taste the jam.
You know, to make sure it came out right.
It's your responsibility, after all.