Blackberries are one of the truly simple pleasures of summer, and it only takes a few handfuls to make a flavorful homemade blackberry jam.
Blackberries are naturally high in pectin, so it’s easy to make a simple blackberry jam with no added pectin. All you need is blackberries and a hint of sugar for blackberry jam, but a little splash of lemon juice will help bring out the berry flavor.
Sugar in blackberry jam is a matter of personal preference, and I make just about all my jams from low sugar recipes. A standard full sugar blackberry jam uses equal parts blackberries and sugar. The resulting jam is very sweet, and a bit cloying in my opinion.
The main benefit of using more sugar is yield. Since there’s so much sugar, the blackberry jam reaches gel stage very quickly and hardly cooks down at all. The texture in a full sugar jam is also a bit less chunky, with fewer seeds per spoonful. It only takes a few minutes of stirring and the jam thickens right up, which means less time and more jam for your blackberry harvest.
To make a standard blackberry jam without pectin, simply weight your fruit and add an equal weight of sugar. Then follow all the steps in the “low sugar” recipe below.
That said, all that extra yield comes at the expense of flavor in my opinion. Full sugar jams taste more like candy than fruit. Low sugar blackberry jam is simple to make, still without any pectin, and the blackberry flavor is out of this world.
My low sugar blackberry jam recipe is about as fruit forward as it gets. I use 1 part sugar to 5 parts blackberries, and the sugar is barely noticeable. Most low sugar blackberry jam recipes are a bit more conservative and opt for a higher 1:3 or 1:4 sugar to fruit ratio. So in truth, this is a VERY low sugar blackberry jam recipe.
Feel free to adjust to your own tastes, and know that there’s no wrong way to make a blackberry jam. The fruit contains plenty of acid and sugar on its own, and it’s completely safe for home canning even with no sugar at all.
Yes, it is possible to make a completely sugar free blackberry jam that is safe for canning. The lemon juice is optional too.
Start by cooking the blackberries with sugar, however much you’ve decided to use. Honey or maple also work well in this recipe too, but they’re slightly sweeter than table sugar, so only use about 2/3rds sweetener with those. If you’ve opted for a no sugar added blackberry jam, that’s fine too. Just place the blackberries in a pot and mash them slightly to release some of their juices.
If you’re using lemon juice, add it now because a little bit of liquid will help with the initial cooking. After a minute or two on the heat, the blackberries will have let out plenty of juice and the mixture will quickly come to a boil.
Be aware that blackberry jam foams heavily during cooking. You need to watch the jam pot continuously and stir down the foam as it rises.
Some people add 1/4 teaspoon of butter at this stage to help control the foaming. While the safe canning police will tell you never to can butter or dairy products, there’s a big difference between canning jam with a tiny bit of butter and actually canning up a jar of butter.
The national center for food preservation actually suggests adding a small amount of butter to jams as they cook to cut down on foaming because a hot scalding pot of boiling jam can be dangerous, and a tiny bit of butter in jam is nothing to get your panties in a bunch about.
Still, even though adding a small amount of butter to jam is safe, I still don’t do it. Why? I like standing by the stove stirring the jam pot, and staying present while the jam is cooking ensures it doesn’t burn. Beyond that, the National Center for Food Preservation notes, “Adding 1/2 teaspoon of butter or margarine with the juice and pectin will reduce foaming. However, these may cause off-flavor in long-term storage of jellies and jams.”
Butter or not, the foam will subside as the blackberry jam approaches gel stage. The consistency of the jam will noticeably change, and it’ll take on a thicker, glossier look. You can test for gel stage on a plate kept in the freezer. Once the blackberry jam reaches the gel stage, pour it into prepared canning jars, leaving 1/4 inch headspace.
Process both pint and half pint jars for 5 minutes in a boiling water bath canner.
Blackberry Jam Won’t Gel?
This is important…If your blackberry jam doesn’t gel, then you didn’t cook it long enough. Simply put, it will gel once it’s cooked down far enough. Be patient, keep cooking it, with the flame on low as it gets closer to finished to prevent scorching.
If you want the highest yield possible, with the least amount of time spent cooking, add equal parts sugar and fruit (by weight). That will gel quickly, but is a very sweet jam. Adjust the sugar level to your own tastes (and patience for standing tending the jam pot).
- 5 cups blackberries
- 1 to 2 cups sugar (see note)
- 1 to 2 tbsp lemon juice (optional)
- Add blackberries, sugar and lemon juice to a saucepan. Be sure there are several inches of headspace to allow for foaming.
- Turn the heat to medium-low and simmer the jam until it reaches gel stage, stirring to keep the bubbles down. In this low sugar batch, it should take 20-30 minutes for a low sugar jam. (increasing the sugar will cause the jam to gel faster and result in a higher yield)
- Test for gel stage on a plate in the freezer.
- Pour jam into prepared canning jars, leaving 1/4 inch headspace. Store in the refrigerator, or process in a water bath canner for 5 minutes.
This low sugar recipe yields roughly two half pint jars. This recipe can be multiplied up to 4x, making a batch that starts with up to 20 cups of blackberries for a larger batch. Do not increase the batch size beyond 4 times, extra large jam batches often have trouble reaching gel stage properly.
To make a conventional blackberry jam without pectin, add equal parts sugar and fruit by weight and follow the same instructions. The yield will be much higher.
Neither the sugar nor the lemon juice are necessary for safe canning, and both can be increased, decreased or eliminated without affecting the safety of this canning recipe.
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