Anna Louise Blackberry jam is the preserve I associate most specifically with the end of British summer — the hedgerow blackberries ripening in late August and September, the afternoons of picking them with stained fingers and a container that fills more slowly than expected.
The kitchen filled with the deep, slightly winy fragrance of blackberries cooking with sugar into something jewel-dark and intensely flavoured.
I make this jam every year from fresh hedgerow blackberries when they are available, and from frozen blackberries throughout the rest of the year.
Frozen blackberries give a completely excellent jam — vivid, well-set, deeply flavoured — and are available year-round, which means this recipe is not limited to the six weeks of British blackberry season.
The challenge with blackberry jam — and the reason some home-made versions disappoint — is the pips. Blackberry seeds are small, hard, and numerous, and a blackberry jam made without straining has a slightly gritty, slightly uncomfortable texture.
I always strain half the cooked blackberry pulp through a fine sieve before the sugar goes in, giving a jam that has some whole blackberry pieces and some completely smooth, pip-free jelly.
Ingredients for Mary Berry Blackberry Jam
For the Blackberry Jam (Makes approximately 5 x 450g jars)
- 1.2kg fresh or frozen blackberries — if frozen, do not defrost
- Juice of 2 large unwaxed lemons — essential for the set, as blackberries are low in pectin
- 900g granulated sugar — warmed in a low oven for fifteen minutes before adding
How to Make Mary Berry Blackberry Jam
Step 1 — Cook the Blackberries
Place the blackberries and lemon juice in a large preserving pan or heavy-based saucepan. If using frozen blackberries, place them in the pan straight from frozen — they do not need defrosting.
Heat over a medium heat, stirring occasionally, for fifteen to twenty minutes until the blackberries have completely broken down and released all their juice. The contents of the pan should look like a thick, deeply coloured, slightly seedy purée.
Step 2 — Strain Half the Pulp
This is the step that gives the jam its best texture. Place a fine sieve over a large bowl. Ladle half the blackberry pulp into the sieve. Press firmly with the back of a spoon to push the juice and soft pulp through — leaving the seeds behind. Discard the seeds.
Return the strained juice to the pan with the remaining unstrained blackberry pulp. Stir to combine. The pan now contains a mixture of whole softened berry pieces and completely smooth, seed-free juice — giving the ideal texture in the finished jam.
Step 3 — Add the Warm Sugar
Add the warm granulated sugar to the blackberry mixture. Stir continuously over a medium heat until every grain has completely dissolved — test by running a spoon along the base of the pan. The liquid should feel completely smooth with no graininess.
Step 4 — Boil to Setting Point
Increase the heat to high. Bring to a vigorous rolling boil. Boil for 8 to 15 minutes — begin testing for setting point at 8 minutes.
Wrinkle test: Place a teaspoon of jam on a cold plate from the freezer. Leave one minute. Push with your finger — if the surface wrinkles and does not flood back, setting point is reached. If it floods back immediately, boil for another three minutes and test again.
Sugar thermometer: Setting point is 104–105°C.
Blackberry jam reaches setting point quickly because of the lemon juice — check early and often to avoid over-boiling, which gives a very firm, slightly caramelised jam.
Step 5 — Pot and Seal
Remove from the heat when setting point is reached. Skim any foam from the surface.
Leave to stand for five minutes — this allows the berry pieces to distribute evenly through the jars rather than all floating to the top.
Stir gently. Ladle into warm sterilised jars. Seal immediately. Label and store in a cool, dark place.
My Top Tips For Perfect Mary Berry Blackberry Jam
Strain half the pulp for the best texture. All jam — no straining at all — gives a dense, slightly gritty jam with seeds throughout. All strained — completely smooth jelly — loses the whole berry pieces that are one of the pleasures of blackberry jam. Half and half gives the ideal result: clear, jewel-dark jelly with suspended whole softened berry pieces and no unpleasant grittiness.
Lemon juice is essential — blackberries are low in pectin. Blackberries contain some pectin but not enough for a reliable set without help. The juice of two lemons provides both additional pectin and acidity. Without it the jam may not set at all, or will set very loosely.
Warm the sugar before adding. Cold sugar drops the temperature of the pan significantly and slows the dissolving and subsequent boiling process. Fifteen minutes in a low oven gives sugar that dissolves quickly and gets the jam to its rolling boil much faster.
Blackberry jam sets quickly — start testing early. The combination of blackberry’s moderate pectin, the lemon juice, and the vigorous boiling gives setting point rapidly. I start testing at eight minutes — some batches set in ten, some in fifteen. Testing early prevents over-boiling, which gives a very firm, slightly caramelised result.
Make it in late August or September from hedgerow fruit if you can. Wild hedgerow blackberries have a specific, deeply complex flavour that cultivated blackberries and frozen blackberries replicate less completely. If you have access to wild blackberries, make this jam in season — it is the finest version.
Serving Suggestions
Spread on warm toast — the most natural application. As a filling in a Victoria sponge alongside whipped cream. On warm scones with clotted cream. Stirred into natural yoghurt. As a filling in a Swiss roll — see the Swiss roll recipe on this site. As a gift — blackberry jam in a labelled jar with a ribbon is one of the most appreciated homemade gifts I know.
How to Store Mary Berry Blackberry Jam
Sealed, unopened jars: Store in a cool, dark place for up to 12 months.
Opened jar: Refrigerate and use within 6 weeks.
Mary Berry Blackberry Jam Recipe
Ingredients
Method
- Place blackberries (straight from frozen if using frozen) and lemon juice in a large preserving pan. Heat over medium heat 15–20 minutes until completely broken down into a thick, seedy purée.
- Strain half the pulp through a fine sieve — press firmly to extract juice and soft pulp, discarding seeds. Return strained juice to pan with remaining unstrained pulp. Stir.
- Add warm sugar — stir continuously over medium heat until every grain has dissolved.
- Increase heat — bring to a vigorous rolling boil. Boil 8–15 minutes. Test for set at 8 minutes using wrinkle test or thermometer (104–105°C). Boil and test until setting point reached.
- Remove from heat. Skim foam. Stand 5 minutes — stir gently. Ladle into warm sterilised jars. Seal immediately. Label and store.
Notes
Frequently Asked Questions
Can I use all frozen blackberries?
Yes — frozen blackberries give a completely excellent jam. They release their juice quickly when heated and give a vivid, well-flavoured result. Use them straight from frozen without defrosting.
Can I add apple to help the set?
Yes — one Bramley apple, peeled, cored, and roughly chopped, cooked with the blackberries gives additional natural pectin and a slight apple flavour that suits blackberry very well. Traditional recipes often include apple for this reason.
My jam has not set — what should I do?
Return to the pan, add the juice of one more lemon, and boil hard for five to eight minutes. Test again. The additional lemon juice provides extra pectin and acidity that often rescues a loose set.
Can I use jam sugar instead of granulated?
Yes — jam sugar with added pectin gives a very reliable, firm set with blackberries. Reduce the boiling time to five to eight minutes and test carefully — jam sugar can give an overly firm result if boiled too long.
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