How to make strawberry jam

Why it is difficult

A set needs pectin held together by acid in a low-water environment. Strawberries supply very little pectin, not much acid, and around ninety per cent water. Boiling long enough to drive off that water destroys the fresh flavour that made you pick strawberries in the first place.

So a good strawberry jam is always a compromise, and the three standard solutions all shorten the boil rather than lengthening it.

The other decision is texture. Cut strawberries collapse completely; small whole ones can be kept intact, which makes a far more attractive preserve.

The three ways round it

• Jam sugar. Sugar with added pectin and citric acid. The simplest answer, and the one that works first time. The boil is short and the flavour stays fresh.
• Lemon juice plus a high-pectin partner. A proportion of redcurrant juice, gooseberries or a grated cooking apple, plus the juice of a lemon or two per kilo of fruit.
• Macerate overnight. Layer the fruit with the sugar and leave it. The sugar draws out juice, which can then be boiled down separately to a syrup before the fruit goes back in for a few minutes only. More work, best flavour, and the fruit stays whole.
• Commercial liquid pectin, added at the end according to the packet, which is reliable and slightly less good in flavour.
• Not: boiling it for forty minutes. That gives a dark, caramelised, stiff jam that no longer tastes of strawberries.

Whole-fruit strawberry jam by maceration

Ratios here are for texture 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.

1. Choose small, firm, slightly under-ripe berries. Large soft ones collapse whatever you do.
2. Hull them and leave them whole. Weigh them.
3. Layer them in a bowl with an equal weight of sugar and the juice of a lemon per kilo. Cover and leave overnight in a cool place.
4. Next day, tip everything into a preserving pan. Lift the fruit out with a slotted spoon and set it aside.
5. Boil the syrup hard on its own for ten minutes or so, until it has thickened noticeably. Put two plates in the freezer.
6. Return the fruit, bring back to a rolling boil, and cook for five to eight minutes more. Test on a cold plate.
7. Let it stand ten minutes before potting so the berries distribute rather than floating.

What changes the result

Fruit ripeness

Slightly under-ripe berries carry more pectin and hold their shape. A punnet of very ripe fruit makes better eating and worse jam.

Pan width

Wide and shallow evaporates fast. A deep saucepan is the commonest reason a jam needs an extra twenty minutes.

Lemon quantity

The juice of one to two lemons per kilo of fruit. It affects the set far more than the taste.

Butter

A small knob added at the end disperses the scum, which saves skimming. Traditional and effective.

Vanilla or black pepper

A split pod, or a few grinds of pepper, both work well with strawberry and are worth trying once.

Common questions