If this is your first time making jam, you may be wondering how you know the jam is done. There’s a whole thing online about the frozen plate method (basically, you put jam on a cold plate, touch it, and see if it wrinkles). But that just makes this easy recipe more complicated than it needs to be.

So, you just have to watch it. You’ll see it changing. It starts as three separate ingredients. Then, the sugar starts to melt down and the mixture becomes foamy and bubbly. The foam then dissipates and the mixture gets darker. And then, finally, the mixture gets really thick and resembles the texture of store-bought jam. That’s when it’s done.

You want to make sure you remove it when it’s done. You can leave it an extra minute just to make sure, but that’s it. If you overcook your jam, it’ll become really solid when it cools completely and it won’t be spreadable at all.

If it’s not blueberry season and you can’t get fresh fruit (or because they’re just overpriced outside of the season), you can use store-bough frozen berries. You just want to make sure that the frozen berries are thawed before using them. Using frozen berries that come from your store’s freezer section can retain water and throw off your jam’s consistency and taste.

If you pick fresh blueberries from your own bush, like us, but don’t have a cup yet, you can put those in a glass container and flash freeze them (just put that in the freezer). When you have enough berries for jam, take those out and gently roll them in your hands to warm them before using them. You don’t need those to thaw completely.

Nope. Store-bought, packaged lemon juice works perfectly in this recipe. However, if you did purchase lemons to use the juice, you could also grate some lemon zest the pan to give it more of a lemon taste.

This recipe uses 1/3 of a cup of sugar, which is really the bare minimum you can go before you change the texture of the jam. See, the sugar also helps to solidify the jam, just like the pectin does. If you reduce the sugar, you risk not having enough to make a solid jelly.

The sugar also helps to preserve the fruit. So, if you don’t use any (or enough), you run the risk of the fruit growing mold in the jar and/or just reducing the shelf life of the jam.

Also, keep in mind that you want to use regular sugar in this recipe. You can’t substitute a sugar substitute for sugar in a no pectin jam. If you can’t have sugar, you’ll want to look for a no sugar needed pectin for your jam. Find out more about that here. 

We personally haven’t tried freezing this jam. However, from everything I’ve read, you can definitely freeze jars of jam (as long as you seal the jars with a proper canning technique, like a hot water bath).
The jam may expand upon freezing, so you want to make sure you leave room at the top of the jar to compensate for that.

You’ll want to thaw the frozen jam in the refrigerator overnight before serving.

Small batch jams are the best because you don’t lose any of the sweet fruit flavor. So the smaller the batch, the sweeter the end result (in my experience, anyway).

You can multiply this recipe by four (so four cups of blueberries, 1 1/3 cup sugar, and 8 teaspoons of lemon juice), if you wanted to make a really large batch of jam. But, keep in mind that you will need to adjust the cooking time to compensate for more blueberries needing to break down. So, instead of only 15 minutes of simmering, you’ll probably need closer to 25 minutes.

If you need to make more than quadruple this recipe, I suggest breaking it into two batches. It’ll take longer that way, but you’ll get the best jam if you do that.