Mary Berry Blackberry Jam Recipe

This Mary Berry-inspired blackberry jam is everything I want from a homemade preserve: glossy, jewel-dark, and bursting with a proper blackberry tang. The texture is softly set and spoonable, with a clean fruit flavour that tastes wonderful on toast and scones. It’s an easy, beginner-friendly recipe as long as you follow a few simple jam-making rules. Total time is about 45 minutes, plus cooling.

Ingredients

For the blackberry jam

1kg blackberries (fresh or frozen)
1kg granulated sugar
2 tbsp lemon juice (or juice of 1 large lemon)
25g butter (optional, helps reduce foaming)

For sterilising and potting

3 clean jam jars with lids (about 3 x 340g jars)
Small tray (for warming jars in the oven)
2 small plates (for the set test)

How to Make Mary Berry Blackberry Jam Recipe

Prepare the oven: Preheat the oven to 140°C or 120°C fan. Wash your jars and lids in hot soapy water, rinse well, then place the jars (not the rubber seals, if you have them) on a tray in the oven for 15 minutes to sterilise and dry. Put 2 small plates in the freezer for your set test.
Mix and soften the fruit: Tip the blackberries and lemon juice into a large, wide pan (a preserving pan is ideal). Warm gently for 5 to 8 minutes, stirring often, until the berries soften and release plenty of juice.
Dissolve the sugar fully: Add the sugar (and the butter, if using). Keep the heat low and stir patiently until the sugar has completely dissolved. This matters: if you boil before the sugar dissolves, you risk a grainy, crystallised jam.
“Bake” the jam (boil to setting point): Turn the heat up and bring the jam to a full rolling boil. Boil hard for 8 to 12 minutes, stirring occasionally so the base doesn’t catch. The jam will look glossy and slightly thicker as it nears setting point.
Test the set: Spoon a little jam onto one of the chilled plates. Leave it for 30 seconds, then push the edge with your finger. If the surface wrinkles, it’s ready. If it stays runny, boil for 2 more minutes and test again with the second plate.
Cool and remove foam: Take the pan off the heat. Skim away any foam with a spoon, then leave the jam to sit for 10 minutes. This short rest helps the fruit distribute evenly, so it doesn’t all float to the top of the jars.
Assemble (pot and seal): Carefully pour or ladle the hot jam into hot sterilised jars (a jug and funnel helps). Wipe rims clean, seal with lids, and leave to cool completely. Label once cold.

Tips

Why didn’t my blackberry jam set?

Usually it just needs a little longer at a rolling boil. Return it to the pan, boil for 2 minutes, then test again on a chilled plate. Also make sure you used the full amount of sugar, as reducing it affects the set.

How do I stop jam from crystallising?

Dissolve the sugar completely before you increase the heat. Stir over low heat until you can no longer feel any grit at the bottom of the pan, then bring it to the boil.

How do I reduce foam on top of jam?

A small knob of butter helps, and skimming at the end is easiest after the jam has rested for a few minutes. Foam is harmless, but removing it gives you a clearer, prettier finish in the jar.

Can I use frozen blackberries?

Yes. Tip them straight into the pan and soften gently until fully thawed and juicy before adding the sugar. Frozen fruit can take an extra minute or two to reach setting point.

Serving Suggestions

Spread thickly on hot buttered toast or crumpets
Spoon into yoghurt or porridge
Serve with scones, clotted cream, and a pot of tea
Use as a filling for Victoria sponge, jam tarts, or thumbprint biscuits

Storage

Room temperature

Store sealed, unopened jars in a cool, dark cupboard for up to 12 months. Once opened, refrigerate.

Refrigerator

After opening, keep the jar in the fridge and use within 4 to 6 weeks. Always use a clean spoon to avoid introducing crumbs that can shorten the shelf life.

Freezing

Jam freezes well for up to 6 months. Freeze in freezer-safe containers with a little headspace, then thaw overnight in the fridge. Give it a good stir before using.

Nutrition

Calories: 52 kcal
Carbohydrates: 13 g
Protein: 0.1 g
Fat: 0 g
Saturated fat: 0 g
Sodium: 1 mg

Nutrition values are estimates and will vary depending on brands, fruit sweetness, and portion size.

FAQs

How long does homemade blackberry jam take to set?

Most blackberry jam sets as it cools, so it may still look a little loose when it first goes into the jar. You’ll get the best read once it’s completely cold, usually after several hours or overnight.

Do I need pectin for blackberry jam?

No. Blackberries and lemon juice usually provide enough natural pectin for a good set when cooked properly. If you prefer a firmer set, you can use jam sugar, but it isn’t essential for this recipe.

What is the best sugar to use for blackberry jam?

Granulated sugar is the classic choice and gives a clean flavour. Caster sugar also works, but avoid brown sugar here if you want a bright, fresh blackberry taste.

Can I reduce the sugar in blackberry jam?

It’s not recommended for a traditional preserve. Sugar is key for both the set and the keeping quality. If you want a lower-sugar version, use a tested low-sugar pectin recipe designed for that purpose and follow safe preserving guidance.

Why is my jam runny even after boiling?

Either it didn’t boil hard enough, long enough, or the set test was skipped too early. Pop a plate in the freezer, reboil the jam for 2 minutes, then retest. Repeat as needed until the jam wrinkles on the chilled plate.