How to make blackberry jam

Why apple, and why jelly

Blackberry pectin is decent in early-season fruit picked at the tip of the cluster and falls off sharply in the wet, late fruit picked in September. Acid falls with it. A late-season blackberry jam made with nothing added is very likely to be runny.

A cooking apple, grated or chopped and cooked with the fruit, supplies both pectin and acid, adds bulk and costs almost nothing. Around a quarter apple to three-quarters blackberry by weight is the traditional proportion and it does not dilute the flavour noticeably.

The pips are the other issue. Blackberry seeds are hard and numerous, and many people find them unpleasant in a jam. Straining the cooked fruit gives bramble jelly — clear, deep purple and pip-free — at the cost of about a third of the yield.

Bramble jelly

The classic. FoodHQ does not publish keeping times, jar-processing schedules or the acidity figures that decide whether a sealed preserve is safe on a shelf. Those are safety numbers set by a food safety authority rather than by a cookery writer. In the UK the Food Standards Agency is the authority — follow its guidance on sterilising, sealing and storing, and treat this page as the explanation of what is happening in the pan.

1. Put the blackberries in a pan with chopped cooking apples, skins, cores and all, and just enough water to stop them catching.
2. Simmer until everything has collapsed — twenty to thirty minutes — crushing the fruit against the side of the pan as it softens.
3. Scald a jelly bag or a large square of muslin, set it over a bowl, and tip the pulp in.
4. Leave it to drip. Overnight is usual. Do not squeeze the bag — squeezing forces fine solids through and gives a cloudy jelly.
5. Measure the juice. Add sugar in proportion — commonly an equal weight — and put two plates in the freezer.
6. Dissolve the sugar over a low heat, then boil hard and test on a cold plate from about eight minutes.
7. Skim carefully. Jelly shows every speck, so this matters more than it does for jam.

Jam rather than jelly

Quicker, higher yield, and pips.

• Same fruit and apple mixture, simmered until soft, with no straining.
• Sieve half of it if you want fewer pips without losing the yield entirely.
• Add the sugar once the fruit has broken down, then boil hard to setting point.
• Lemon juice — one per kilo — if the fruit is late-season and soft.
• A crab apple or two if you have them, which are even higher in pectin than cooking apples.
• Blackberry and elderberry together is traditional in some places, though elderberries must be cooked and are not eaten raw.

Picking for jam rather than for eating

Early is better

August fruit has more pectin and more acid than September fruit. It also has fewer grubs and less mould.

Include some firm ones

Slightly under-ripe berries raise the pectin and improve the set. They are no use raw and useful here.

Wash and float

A short soak in lightly salted water brings out any small grubs. Rinse afterwards.

Freeze first if you like

It makes no difference to the finished jam and lets you accumulate enough fruit over several outings.

Quantity

A kilo of blackberries with three hundred grams of apple makes roughly four or five jars of jam, or three of jelly.

Common questions