Slow Cooker Blackberry Jam

Jar of blackberry jam, red checked dish towel and blackberries to the sides.

5 from 1 vote

Slow Cooker Blackberry Jam

You'll only need three recipes to make this tasty jam and your slow cooker does most of the work. Perfect to use your foraged blackberries this autumn.

Course Jam and Curd

Cuisine American, British

Prep Time 5

Cook Time 4

Total Time 4 5

Servings

Calories 67kcal

Author Lucy Allen | BakingQueen74

Equipment

Ingredients

650 g blackberries
450 g jam sugar
3 tbsp lemon juice (from 1 and a half lemons)

UK Measurements - US Measurements

Instructions

Wash the blackberries and remove any stalks or leaves.
650 g blackberries
Put the blackberries, jam sugar and lemon juice in the slow cooker. Cook on low for 1 hour.
After 1 hour, stir to mix the fruit and sugar together, replace the lid and cook for a further 1 hour on low. Here your aim is to ensure the sugar dissolves fully.
450 g jam sugar, 3 tbsp lemon juice
After the two hours, mash the fruit gently using the back of a fork then switch to high. Cook for 2-3 hours.
You’ll find the jam thickens as it cooks.
You should find it is possible for the jam to reach the jam setting temperature of 105°C (220°F) even in the slow cooker! I check this after 2 hours of cooking (i.e. after 4 total hours).
To check if the jam has reached setting point, you can either use a food thermometer as I have done here or you can use the wrinkle test.
For the wrinkle test you will drop a small spoon of the hot jam onto a chilled saucer or small plate (put one into the freezer at the start). Let it cool for a minute, then push with your finger. If it wrinkles on the plate it has reached setting point. If not, leave it on high for another hour.
When you are sure it has reached setting point, pour the jam into sterilised jam jars and seal.

Notes

Recipe tips

To increase the pectin levels in your jam, include some underripe blackberries if you can. They naturally have more pectin than ripe blackberries! Blackberries are a fruit which is naturally quite low in pectin. This will be easier to achieve if you pick the blackberries yourself of course, as you won't find underripe fruit in stores.
Slow cooker jam doesn't come to a rolling boil like jam made the traditional way in a jam pan.
Due to this, slow cooker jam doesn't reduce in the same way which means it naturally contains more water than traditional jam.
This is why we use jam sugar which contains pectin (instead of just normal sugar) in this recipe to help compensate for that higher proportion of water. The pectin helps to achieve that thicker jam consistency. You will most likely still notice that this jam has a slightly looser set than standard jam.
Caramelisation - when jam is cooked for a long period of time, such as in a slow cooker, you might find that the sugars in the jam start to caramelise. This can usually be seen from the colour of the jam changing, and becoming more of a brown colour. To avoid this, stop cooking as soon as your jam has reached the setting point and don't leave it to cook too long.

Sterilising jars

Putting the jars and metal lids in a hot wash in your dishwasher will sterilise them fully.

Otherwise you can wash them by hand in hot soapy water, leave wet and pop them in the oven (upside down on a clean baking tray) set to 120°C (250°F) for 10-20 minutes until dry.

Nutrition