Why it works first time
Raspberries are naturally acidic, which is exactly the condition pectin needs, and they carry a moderate but sufficient amount of it — more in slightly under-ripe fruit.
They also have almost no structure. Heat a pan of raspberries and they break down within two minutes, releasing their juice and their pectin immediately. There is no simmering stage needed to soften skins as there is with currants.
The consequence is a very short boil, which is why raspberry jam tastes so much more of fresh fruit than most preserves.
The method
Ratios are for set and flavour. 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.
- Weigh the raspberries. Include a handful of slightly under-ripe ones if you have them, for the extra pectin.
- Put two small plates in the freezer.
- Warm the fruit gently in a wide preserving pan for two or three minutes until the juice runs. No water is needed at all.
- Add an equal weight of sugar and stir over a low heat until every grain has dissolved. Do not let it boil before then.
- Bring to a full rolling boil and time it. Start testing at five minutes.
- Test on a frozen plate: a teaspoonful, a minute's wait, push with a fingertip. A wrinkled surface means set.
- Skim, stand for a few minutes, and pot.
Controlling the seeds
Raspberry seeds are numerous and hard, and how many you leave in is entirely a preference.
- All in — the traditional jam. Full flavour and full texture.
- Half sieved. Press half the cooked fruit through a sieve and return it to the pan with the rest. A good compromise and the most popular.
- Fully sieved gives raspberry jelly rather than jam. Expect roughly a third less yield, and a softer set since some pectin stays behind in the pulp.
- Sieve before the sugar, always. Sieving a finished jam is unpleasant and much less effective.
- Keep the sieved seeds and pulp, which still hold flavour. Steep them in vinegar for raspberry vinegar, or in gin.
Variations worth making
- Raspberry and redcurrant
- A quarter redcurrant by weight. Firmer set, sharper flavour, and a classic combination.
- Raspberry and rose
- A teaspoon of rose water stirred in off the heat. The two share aromatic compounds and it is a genuine pairing rather than a novelty.
- Frozen fruit
- Works perfectly, and often better — freezing ruptures the cells so the juice runs immediately. Do not thaw first.
- Less sugar
- Three-quarters sugar to fruit gives a fresher, looser preserve. It will need jam sugar or a shorter shelf life.
- Yellow raspberries
- Lower in acid, so add the juice of a lemon per kilo.
Common questions
Do I need to add pectin?
No. Raspberries have enough, especially with some under-ripe fruit in the mix.
Do I need to add water?
No. They release plenty of their own within two minutes of heating.
How do I make it seedless?
Sieve the cooked fruit before adding the sugar. Expect less yield and a slightly softer set.
Can I use frozen raspberries?
Yes, straight from frozen. They are often better than fresh for jam.
Why is my raspberry jam dark?
Boiled too long. It needs only five to ten minutes at a rolling boil — start testing early.
Try this next
- Raspberry the fruit itself
- How to make jam the general principles
- How to make strawberry jam the difficult contrast
- Redcurrant the classic partner