I’ve crafted this blueberry rosemary jam recipe to make sure that delicate fresh blueberry flavour doesn’t get lost along the way. And to do that, I rely on two simple methods.
First, most so-called easy blueberry jam recipes lean heavily on sugar—not just for sweetness, but also for setting and preservation. They use high methoxyl (HM) pectin, also known as high methyl ester pectin—the same kind you’ll find in supermarket “jam sugar.” But without a high proportion of sugar, HM pectin won’t set properly.
The traditional 1:1 ratio of fruit to sugar has the unfortunate effect of smothering the blueberry flavour. To preserve as much of that delicate flavour as possible, you need low methoxyl pectin (LM)—or low methyl ester pectin. LM pectin sets through a reaction with calcium and acid (typically lemon juice) rather than relying on sugar.
And for the record, all pectins—HM or LM—are naturally plant-derived and vegan.
The second trick to keeping that low sugar blueberry jam flavour clean and bright lies in two small but powerful additions. The lemon juice helps the LM pectin set and sharpens the blueberry’s freshness, while the rosemary adds a savoury, herbal depth that makes the flavour linger.
Let me step this easy blueberry jam recipe out for you.
Blueberry rosemary jam ingredients
- 500g frozen blueberries
- 1 large granny smith apple
- 125ml water
- 200g raw sugar
- 1-2 sprigs fresh rosemary
- ½ teaspoon lemon zest
- ¼ teaspoon table salt
- 1 teaspoon low methoxyl pectin
- 1 teaspoon calcium water
- 1 tablespoon + 2 teaspoons lemon juice
Frozen blueberries are best for this recipe
Yes, in this case fresh is not best—and what a relief considering how expensive fresh blueberries can be. Those supermarket punnets have been hand selected for their perfection, so why would you want to mash them into a jam? You want the berries that didn’t make the cut and ended up frozen in your jam.
And there’s a solid reason for using frozen berries in your blueberry rosemary jam. The freezing causes the cells of the berries to rupture, allowing the juice to be released and softening the fruit. This means it will take less cooking time to break down the blueberries, helping preserve their fresh, natural flavour in the final jam.
Low methoxyl pectin with calcium
My low sugar blueberry jam recipe does have one specialty product that you’re not going to find on supermarket shelves—the low methoxyl (LM) pectin.
The best known brand is Pomona’s Universal Pectin, which comes from the USA and is available on Amazon in Australia.
But we also have a local supplier here in Queensland—Green Living. They import LM pectin from Europe and create their own low methoxyl pectin with calcium. It’s available in a variety of sizes and has an impressively long shelf life (which I generally ignore). They’re a great option if you’re planning to explore more home preserving.
Exactly how low sugar can I go?
The LM pectin method of making low sugar blueberry jam leaves it up to you to decide how much sugar to add.
The recipe does need some sugar (or a granulated substitute like xylitol) to help the pectin distribute evenly through the fruit and avoid clumping. And I use raw sugar to help ramp up depth of flavour in the final jam.
Traditional jams use a 1:1 ratio of fruit to sugar. In this recipe, I’ve adopted a 1:0.4 ratio of fruit to sugar (500g blueberries and 200g sugar). This balance keeps the blueberry flavour bright and natural without leaning too sweet.
You can use sugar substitutes—but I would not recommend them with this jam as they have a lingering aftertaste that would overwhelm the delicate blueberry flavour. I was not happy with the result when I tried the recipe with xylitol.
You can experiment with other sweeteners like coconut sugar, honey, or maple syrup – though you’ll need to adjust the volumes to suit your preferred sweetness and palate.
Why use fresh rosemary?
If you’re wondering whether dried rosemary will do—don’t. Use fresh rosemary sprigs. The essential oils in the leaves are what carry its aromatic character, and those oils are the key to how the savoury herbal note weaves through the jam. Dried rosemary has lost those volatile oils and leaves behind a dull, woody flavour instead of the fresh perfume that gives this easy blueberry jam recipe its depth.
Get organised!
If you’ve never made jam before, this blueberry rosemary jam is the perfect place to start. It’s small-batch, simple, and forgiving—especially if you get yourself organised before you turn on the stove. A little prep up front makes the process calm, clean, and quick.
What equipment do I need?
This low sugar blueberry jam recipe makes about 750ml of jam (roughly 1½ cups) using my 1:0.4 fruit-to-sugar ratio.
If you’re planning to use the jam straight away – like in my Blueberry Coconut Mini Trifles – there’s no need to haul out preserving jars. A clean glass jar or airtight container from the cupboard will do the job nicely.
The same goes if you’re freezing the jam. Freezer-safe containers or ziplock freezer bags are fine, as long as they’ve just come out of a hot dishwasher cycle.
If you want to process the jam for longer storage, you’ll need three 250ml preserving jars with lids.
A 4–5 litre heavy-based stainless-steel pot is ideal for this recipe. Avoid aluminium—it reacts with acid and can leave a metallic taste. A wide-bottomed pan is best; it helps the jam cook evenly and finish faster, locking in that fresh blueberry flavour.
A ladle is handy if you’re jarring the jam, and a wide-mouth funnel will save you a few burns and sticky benches. If you don’t have one, pour the jam into a large heatproof jug in batches, then pour into jars from there.
Pick your ‘shelf life’
If you’d like your jam to last longer, you’ll need to process it in a boiling water bath after filling. The step-by-step process for that is included in the recipe notes, along with a list of the required equipment.
I’ve put ‘shelf life’ in quotes because I never store my preserves in a cupboard. Queensland homes are not exactly known for their cool cellars. I err on the side of caution and keep everything refrigerated. Processed and stored this way, this low methoxyl pectin jam will easily last a year—but in my house, it rarely makes it that far.
If you plan to process the jam, have your boiling water bath and jars prepped before you start cooking. It makes the final step seamless.
Do I need to sterilise everything?
You don’t need to sterilise your pot or utensils during cooking, but they must be very clean—especially your ladle, funnel, and jug. If they’re glass or stainless steel and you have the means, sterilising them is a smart move.
Whether you need to sterilise your jars depends on how you plan to store the jam. If it’s going straight into the fridge for use within two weeks, or into the freezer, a thorough clean and hot rinse is plenty.
If you’re storing it longer, sterilise your jars and process the filled jars in a boiling water bath (see notes).
Steaming method
You can sterilise jars using the steaming, boiling water, or oven methods. Have them ready before you start cooking—jam moves fast once it reaches gel stage.
Steaming method
If you have a steam oven, this is the easiest option. Steam the clean jars, lids, and sealing rings (if using) at 100°C for 5–10 minutes. Remove carefully (don’t touch the rims or inside) and cool on a clean tea towel.
Boiling water method
Fill clean jars with boiling water, then leave to cool on a clean tea towel. Place metal lids in a heatproof bowl, pour boiling water over them, and let them cool in the water.
Oven method
Preheat your oven to 135°C. Place clean jars and lids on a baking tray and heat for 20 minutes. Turn off the oven and leave them to cool inside. Don’t put rubber sealing rings in the oven—use the boiling water method for those.
Prep the blueberry rosemary jam ingredients
I usually take the frozen blueberries out of the freezer the night before I make my jam and let them defrost in the fridge. Otherwise, take them out when you’re assembling everything you need.
Low methoxyl (LM) pectin is sold with a small packet of calcium powder. There are instructions on the package about how to prepare the calcium water, but here’s my version. I use boiled and cooled water in a clean, sealed plastic container or glass jar with a lid. Measure 125ml of water into the container and add ½ teaspoon of calcium powder. Shake well. And don’t forget to shake the container again just before adding the calcium water to the jam—otherwise the calcium settles at the bottom.
Zest and juice the lemon and set aside 1 tablespoon plus 2 teaspoons of juice and ½ teaspoon of lemon zest (packed).
Peel the apple and grate on a coarse grater, discarding the core. Drizzle the peeled apple with a little leftover lemon juice and toss some juice through the grated apple.
In a small bowl, stir 1 teaspoon of LM pectin into 100g of the sugar (sugar No1) and mix well to distribute the pectin evenly through the sugar. This prevents clumping when added to the hot fruit mixture later.
Now you’re ready to make blueberry rosemary jam!
Cooking low methoxyl pectin jam
I don’t recommend adding the rosemary sprigs directly to the pot. Instead, wrap the sprigs in three layers of cheesecloth and tie the bundle with kitchen string. This keeps the rosemary out of the final product and makes it easy to remove at the right moment.
Place the defrosted blueberries, grated apple, lemon zest, and the rosemary bundle in a 4–5 litre heavy-based stainless-steel pot over medium-high heat. As the berries come to a boil, crush some of them gently with a potato masher. You don’t want to crush them all—this jam benefits from visible whole blueberries throughout. Crush the rosemary bundle occasionally to help release the essential oils and deepen the flavour.
Once the jam is boiling and the blueberry juice has started to release, remove the rosemary bundle and increase the heat to high. Gradually add Sugar No.1 (the 100g mixed with low methoxyl pectin) while stirring well with a wooden spoon or silicone spatula to distribute the pectin evenly. Set a timer for 90 seconds.
Next, add 1 teaspoon of calcium water and 1 tablespoon plus 2 teaspoons of lemon juice, stirring to combine. Continue stirring as you add the remaining Sugar No.2 (100g). Bring the blueberry rosemary jam to a rolling boil—the point when the jam continues to boil even while stirring.
Unlike high methoxyl (HM) pectin, low methoxyl (LM) pectin doesn’t need a high heat to set. Its setting point varies between 50°C and 70°C, and it thickens through the addition of calcium rather than temperature. So you only need to boil the jam long enough for the berries to soften, the sugar to dissolve, and the mixture to thicken slightly.
Start the timer and keep stirring so the low sugar blueberry jam doesn’t catch. The jam will turn glossy and deep purple as it thickens. There should be no visible sugar granules. Remove the pot from the heat after 90 seconds of a full rolling boil. This short boil keeps the flavour bright and fresh.
A foam will form on the surface—skim it off with a spoon before ladling into jars. Alternatively, you can stir in 1 teaspoon of butter to disperse the foam (though this will make the jam non-vegan).
Ladle the hot jam into the sterilised jars or containers, leaving 5–10mm of headspace. Wipe the rims clean with a damp cloth and seal the lids firmly until just tight. If you plan to eat the jam within two weeks, let the jars cool on a tea towel and store them in the fridge.
Freezer blueberry rosemary jam
If you plan to freeze your low sugar blueberry jam, use sealed plastic containers or freezer bags. Let the jam cool until just warm. To fill freezer bags neatly, place the bag inside a large drinking cup and drape the edge over the rim, then spoon in the jam. Carefully seal, pressing out as much air as possible. Lay the bags flat on a rimmed baking tray to freeze, then stack them once solid.
This is not just jam on toast
This low sugar blueberry jam should probably come with a warning. If you try it on a toasted slice of the best sourdough, spread thickly with cream cheese, there’s no going back. You’ll find yourself committing to a four-slice minimum before you can pull yourself away from the breakfast table.
And while this blueberry rosemary jam is breakfast perfection, it’s also the star of my Blueberry Coconut Mini Trifles—a super simple, gluten-free and vegan dessert you can assemble just before serving. The jam adds richness, colour, and that lovely hint of rosemary that stops it from being overly sweet.
Blueberry Rosemary Jam
Equipment
- 4–5 litre heavy-based stainless-steel pot
- Ladle
- Wide-mouth jam funnel
- potato masher
- Cheesecloth
- Kitchen string
- Digital scales
- 3 x 250ml preserving jars with lids
Ingredients
- 500 g frozen blueberries
- 1 large granny smith apple
- 125 ml water
- 200 g raw sugar
- 1-2 sprigs fresh rosemary
- ½ teaspoon lemon zest
- ¼ teaspoon table salt
- 1 teaspoon low methoxyl pectin
- 1 teaspoon calcium water
- 1 tablespoon + 2 teaspoons lemon juice
Instructions
Prep the blueberry rosemary jam ingredients:
- Defrosts 500g frozen blueberries.
- Prepare calcium water by measuring 125ml water that has been boiled and cooled into a clean container with a lid. Add ½ teaspoon calcium powder. Shake well. And don’t forget to shake the container again just before adding the calcium water to the jam—otherwise the calcium settles at the bottom.
- Zest and juice the lemon and set aside 1 tablespoon plus 2 teaspoons lemon juice and ½ teaspoon packed lemon zest.
- Peel the apple and grate on a coarse grater, discarding the core. Drizzle the peeled apple with a little leftover lemon juice and toss some juice through the grated apple.
- In a small bowl, stir 1 teaspoon LM pectin into 100g of the 200g raw sugar and mix well to distribute the pectin evenly through the sugar. This prevents clumping when added to the hot fruit mixture later. Set aside the remaining 100g of sugar.
- Wrap 1–2 sprigs of fresh rosemary in three layers of cheesecloth and tie securely with kitchen string. This makes it easy to remove later while still allowing the rosemary oils to infuse into the jam.
Combine the fruit and aromatics:
- Add 500g frozen blueberries (defrosted), grated apple, ½ teaspoon packed lemon zest, and the prepared rosemary bundle to a 4–5 litre heavy-based stainless-steel pot.
- Pour in 125ml water, then place the pot over medium-high heat.
- As the berries begin to release their juices and come to a simmer, use a potato masher to crush some of the blueberries—just enough to release juice and texture. Leave a few whole berries so the jam has visible pieces of fruit.
- Occasionally press the rosemary bundle with the masher to release more flavour.
Bring to a boil and add pectin mixture:
- Once the blueberries are simmering, remove the rosemary bundle.
- Increase the heat to high and gradually add Sugar No.1 (100g raw sugar mixed with 1 teaspoon low methoxyl pectin), stirring constantly with a wooden spoon or silicone spatula to distribute the pectin evenly. Stir for about 90 seconds.
- Add 1 teaspoon calcium water and 1 tablespoon plus 2 teaspoons lemon juice to the pot, stirring well to combine.
- Next add Sugar No.2 (the remaining 100g raw sugar).
- Continue stirring and bring the jam to a rolling boil—meaning the mixture continues to boil even while being stirred. Keep it at this stage for 90 seconds to two minutes.
- Boil just long enough for the jam to turn glossy and deep purple.
- Remove from heat. A light foam may form on top—skim it off with a spoon or stir in 1 teaspoon butter if you don’t need the jam to stay vegan.
Jar and store:
- Ladle the hot jam into sterilised jars or containers using a wide-mouth funnel, leaving 5–10mm of headspace at the top.
- Wipe the rims clean with a damp cloth and secure the lids until just tight.
- If consuming within two weeks, let the jars cool on a tea towel and refrigerate. For longer storage, process the jars in a boiling water bath as outlined in the notes.
Freezing option:
- For freezer jam, let the mixture cool until just warm.
- Spoon the jam into freezer-safe containers or bags, removing as much air as possible.
- Lay flat on a tray to freeze, then stack once solid.
Just before you cook with abandon…
Boiling water bath processing method
Assemble the equipment
Bring water to boil in large, deep pot with a lid. The pot needs to be large enough to hold the jars and enough boiling water to cover the jars by at least 3cm once they’re submerged. Find a rack for the bottom of the pot (or a folded tea towel) to prevent the jars from rattling and bumping each other. You can use a cake rack. I use a stainless-steel steamer insert from a rice cooker.
Fill the pot with enough water to cover the jars by at least 2.5 cm (1 inch) once they’re submerged. Cover and bring the water to a boil before you start your jam, keep it simmering. Bring it to a full rolling boil as you finish the jam.
Have a clean tea towel on the kitchen bench ready for the finished jars.
Keep the kettle boiled in case you need to top up the pot of boiling water.
Process the jars
Lower the jars filled with blueberry rosemary jam into the simmering water, using a jar lifter or jar tongs. Make sure they are fully submerged and that the water is back to a rolling boil once all jars are in. Process for 5 minutes for 250ml jars and 10 minutes for 500ml jars.
The processing time may need to be adjusted for altitude as the temperature at which water boils changes with altitude. I live at sea level and I am not a scientist! May I suggest Googling this question if needed?
Cool jars and check seals
Use the jar tongs to lift the jars out and carefully set them upright on the clean tea towel. Leave them undisturbed for 12–24 hours. As they cool, you should hear the lids ‘pop,’ indicating the lid has sealed. After cooling, check the seals by pressing the centre of each lid—it should not flex up and down. Any jars that haven’t sealed properly should be refrigerated and eaten first.
Label and store
Once sealed, label and the date jars of low sugar raspberry jam. Store them in a cool, dark place.
Freezer friendly
If you want a longer shelf life and don’t want the trouble of the water bath processing, this jam freezes beautifully. Once completely cool, spoon into freezer-safe containers or ziplock bags and freeze flat for easy stacking. Defrost overnight in the fridge before use.
Vegan and plant-based
All pectins—HM or LM—are naturally plant-derived and vegan. And this easy blueberry jam recipe is vegan and gluten free.
