Simple, Small Batch Black & Blueberry Jam

Name: Simple, Small Batch Black & Blueberry Jam
Prep time: 5 min
Cook time: 10 min
Total time: 75 min
Ingredients: 1 cup mixed blueberries & blackberries; 1¼ cup granulated sugar; 1 tbsp. lemon juice; 2 tsp. cornstarch

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This tasty black and blueberry jam is so nice to serve with homemade pastries or even to give as a thoughtful present! If you have a cup of berries, you probably have everything you need to make it in your kitchen, already!

A jar of jam tied with a string with a sprig of lavender tucked into the string with a lace table cloth in the background.

This recipe is made without pectin and with a small amount of cornstarch instead to help “gel” the jam. We’re also making a small batch, and not canning for long-term storage.

This jam will stay fresh for at least a month, but it probably won’t last that long. It has such a sweet, summer berry taste that you’ll love to cover fresh pastries with it in the morning.

I highly suggest serving it with these delicious lavender lemon scones!

A scone with jam on a decorative plate next to a spoon with jam, a few berries and a few dry roses.

How to Make Black & Blueberry Jam – Step by Step

1. Juice 1 tbsp. fresh lemon juice.

2. Add lemon juice and 1 cup mixed blue and blackberries to an enamel or stainless steel sauce pan and cook them over a medium flame.

3. Just as you begin cooking, mash the berries with a potato masher, making sure to leave some berries chunkily mashed. Allow to cook for about 3 minutes until bubbling.

4. Add 1¼ cup sugar, stir and increase to a high flame. Bring to a bubbling boil. Once the berries are boiling, reduce to a medium simmer for about 5 minutes. Continue to stir.

A collage of 4 numbered images showing how to make black and blueberry jam.

5. If the jam still appears to be very liquidy after that 5 minutes of simmering and stirring, add 2 tsp. cornstarch. If you’ve added cornstarch, give it a nice stir and let it cook for another two minutes on a simmer. Once the consistency is a syrupy thickness, it’s done.

NOTE: The sourness of your berries will be a factor in the consistency of your jam. If they’re sour, it may not require cornstarch, if they’re sweet, they may require up to 1 tbsp.

6. If you’ve cooked it properly and it’s still runny, simply strain a bit of the liquid. Keep in mind you probably won’t have to strain too much if this happens, as your jam gels as it cools, so it might seem more runny than it actually will become. Add to a jar and refrigerate.

2 numbered images showing how to finish making black and blueberry jam.

A Few Common Questions

1. Can I Use Frozen Berries Instead of Fresh?

You can, but make sure to thaw the berries completely first. However, I’ve never had frozen blueberries that tasted as good as fresh ones, and that makes a bit of a difference with this jam. It loses a bit of its pizzaz with frozen blueberries.

But if it’s all you have, and you’ve allowed your berries to thaw to room temperate, go ahead and use them, making sure to also use any juices that may have seeped out while thawing.

2. Can I use less sugar?

Don’t use less sugar. You may have the inclination to reduce the sugar in your recipe. Don’t do it. The sugar is the main gelling component of the jam and helps to keep it from going bad too soon.

3. How long will the jam last?

Since we’re not canning this jam, it won’t stay good forever. It will last nicely for about 3 weeks or so when sealed in a container and refrigerated.

A Few Tips

1. Berries that are more sour tend to work better for jams because they have more natural pectin which helps them gel, but store-bought berries tend to be riper and sweeter.

If you can’t find sour berries, no worries, the cornstarch in the recipe should do the trick, and even if it doesn’t and your jam comes out a little runny, there’s still a fool-proof way to make sure your jam is a nice consistency that you’ll find below 😉

2. Don’t overcook your jam. If you’ve added your cornstarch and your jam is simply not gelling, make sure not to overcook it in hopes of reducing it. If it’s overcooked, it will taste like molasses or burnt caramel and will need to be thrown away.

3. Don’t purée your berries before your cook, otherwise you’ll just end up wit a berry soup that’s not very appetizing. Use a potato masher to break the berries up as they cook, leaving some berries a bit chunky.

4. You can make your jam last longer by adding a drop or two of rum or vodka to the lid of your jar. It will help to prevent the spread of mold.

Blueberry jam in a glass jar on top of a marble table with a lace runner. There are 3 berries beside the jar.

Help Yourself To a Few More of My Sweet Treats:

Beautiful Lemon and Raspberry Cheesecake Bars
Sunshine Lavender Lemon Bars
Creamy, No-Bake Lemon Cheesecake Mousse with Strawberries
Panna Cotta with Strawberry Rhubarb Compote

For more inspiration, follow me on INSTAGRAM, on PINTEREST, TIKTOK and FACEBOOK! And if you ever make any of my tasty drinks or treats, take a picture and tag me. I want to see!