Description
A rich, old-fashioned blackberry jam made with fresh blackberries and sugar, without boxed pectin. Slow cooking concentrates the berry flavor and creates a thick, spreadable preserve.
Ingredients
6 cups mashed blackberries
4 cups granulated sugar
2 tablespoons lemon juice, optional
Instructions
- Wash and sort the blackberries, removing stems, leaves, and damaged fruit. Crush the berries until you have 6 cups of mashed fruit.
- Transfer the mashed blackberries to a large, deep pot. Add the granulated sugar and optional lemon juice, and stir thoroughly.
- Place the pot over medium-high heat and cook, stirring frequently, until the mixture reaches a full boil.
- Continue boiling for about 20–30 minutes, stirring constantly as the mixture thickens to prevent scorching and control foam.
- Cook until the jam reaches the gel stage, around 220°F (104°C) near sea level. Alternatively, use the freezer plate test: spoon a small amount onto a chilled plate, chill briefly, then push it with a finger. The jam should wrinkle slightly and not immediately run back together.
- Remove the finished jam from the heat and skim away excess foam if necessary.
- Ladle the hot jam into properly prepared, sterilized canning jars, leaving about ¼ inch of headspace.
- Wipe the jar rims and apply lids and bands according to the manufacturer’s directions. Process using a tested boiling-water canning method with the processing time adjusted as required for jar size and altitude.
- Remove the processed jars and allow them to cool completely without disturbing them. Check the seals before labeling and storing.
Notes
Lemon juice is optional and adds brightness that helps balance the sweetness of ripe blackberries.
For a smoother, less seedy jam, press some or all of the crushed berries through a fine-mesh sieve before cooking.
For variations, add a small amount of cinnamon or vanilla, or replace some of the blackberries with raspberries while keeping the total quantity of mashed fruit the same.
Cooking time can vary depending on the width of the pot, moisture content of the berries, and intensity of the heat.
Do not casually reduce the sugar when preparing jam for shelf-stable canning. Use a specifically tested low-sugar canning recipe when significantly reducing sugar.
Frozen blackberries can be used. Thaw them first and include their released juices when measuring the fruit.
Only store jars at room temperature when they have been processed using a tested water-bath canning method appropriate for the jar size and altitude and have sealed correctly. Refrigerate after opening.
Discard any jar showing signs of spoilage, leakage, mold, unusual odor, or a failed seal without tasting the contents.
- Prep Time: 5 minutes
- Cook Time: 25 minutes
- Category: Condiments and Preserves
- Method: Stovetop
- Cuisine: American
Nutrition
- Serving Size: 1 serving
- Calories: 72 kcal
- Sugar: 17 g
- Sodium: 1 mg
- Fat: 0.2 g
- Saturated Fat: 0 g
- Unsaturated Fat: 0.2 g
- Trans Fat: 0 g
- Carbohydrates: 18 g
- Fiber: 1 g
- Protein: 0.4 g
- Cholesterol: 0 mg
