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Blackcurrant

The blackcurrant is the northern preserving fruit: high in acid, high in pectin, and one of the richest common sources of vitamin C there is — USDA FoodData Central lists raw black currants at about 181 mg per 100 g, several times what an orange carries. It sets into jam with nothing but sugar, and its leaves go into the cucumber crock for their tannin.

The season

July into the first days of August. The bush ripens over a couple of weeks and the berries hold on the stem better than most.

Acidity decides the method

Blackcurrants are strongly acid, around pH 3, which together with their pectin is why they set so readily.

This is a reference guide, not a recipe authority and not medical advice. The one organism the safety rules here are written against is Clostridium botulinum, and the one way to be protected against it is a tested recipe followed exactly — substitutions of the acid, the sugar or the salt are not cosmetic. Where the national food authority publishes advice for a specific food (Baltic fish, wild mushrooms), that advice outranks this page.

Method by method

The classic preparation: Blackcurrant jam that sets itself, and cordial

For jam: put the berries in the pan with a little water and cook until the skins are completely soft — this step is not optional, because blackcurrant skins meeting sugar too early stay leathery in the finished jar. Then add sugar, traditionally around a kilo per kilo of fruit, dissolve it, boil hard and test at 104–105 °C. It will set. No commercial pectin, no lemon, nothing else. For cordial: simmer the fruit with water, strain through a cloth, sweeten to taste, bring back to the boil and either bottle hot and process, or freeze in portions. Heat costs the vitamin C, which is the argument for keeping some of the crop frozen raw.

Preparation that matters

Strigging — pulling the berries off their stems — is the tedious part, and it is easier if you freeze the whole strigs first and rub them between your hands while frozen, when the berries come off cleanly. For jam, a proportion of just-under-ripe fruit adds pectin you do not need and acid you can use. Keep some leaves at picking time: blackcurrant leaves are the traditional tannin source in a cucumber ferment, and they are what keeps those pickles crisp.

What the preserve is worth

Blackcurrants are exceptional for vitamin C — about 181 mg per 100 g in the USDA reference figure — and they are also very high in anthocyanins, which is what makes the juice almost black. The catch is that vitamin C is precisely the nutrient that boiling with sugar destroys, so a jar of blackcurrant jam is not a vitamin C food and a bag of frozen blackcurrants very much is. If you want the nutrition, freeze the crop; if you want the jam, make the jam and enjoy it as jam.

The ways this goes wrong

• Adding sugar before the skins have softened, which is the single reason most home blackcurrant jam is chewy.
• Adding pectin to a fruit that has plenty, giving a rubbery set.
• Assuming the cooked products carry the vitamin C. They largely do not.
• Straining the cordial by squeezing the cloth, which clouds it.

Safety rules, temperatures, blanching times, headspace and the pH 4.6 line: USDA Complete Guide to Home Canning and the National Center for Home Food Preservation guidance (US Government / land-grant publications, public domain). Acidity classes: the FDA's published approximate-pH tables. Jam composition: Directive 2001/113/EC. Fish freezing before raw or lightly cured use: Regulation (EC) No 853/2004, Annex III. Checked 2026-09-06.

Sources for this food

• USDA FoodData Central
• USDA Complete Guide to Home Canning (public domain)

Frequently asked questions

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