Ingredients
- Blackberries: 4 cups (about 2 lbs or 900g) Fresh Blackberries, ripe but still firm, washed and picked over for any stems or unripe/damaged berries. (Frozen berries can be used, see FAQ).
- Sugar: 3.5 cups (about 700g) Granulated White Sugar. Note: The traditional ratio is often 1:1 fruit to sugar by weight, but blackberries have decent pectin, so you can sometimes slightly reduce sugar. Do not reduce drastically, as sugar is crucial for setting and preservation.
- Lemon Juice: 1/4 cup (about 60ml) Freshly Squeezed Lemon Juice (from approximately 1 large lemon). Do not use bottled lemon juice, as its acidity level can be inconsistent and it lacks the fresh flavour and natural pectin boost.
Instructions
- Prepare the Berries: Gently wash the blackberries under cool running water and spread them on a towel to drain briefly. Carefully pick through them, removing any stems, leaves, unripe (red or green), or moldy berries. Discard any damaged fruit.
- Combine Ingredients: Place the cleaned blackberries in your large, wide, heavy-bottomed pot. Use a potato masher or the back of a fork to gently crush about half to three-quarters of the berries. This helps release their natural juices and pectin. You want a mix of crushed and whole berries for texture.
- Add Sugar and Lemon Juice: Pour the granulated sugar and freshly squeezed lemon juice over the crushed berries in the pot. Stir gently but thoroughly to combine everything.
- Macerate (Optional but Recommended): Cover the pot and let the berry mixture sit at room temperature for 30 minutes to an hour (or even covered in the fridge for a few hours or overnight). This process, called maceration, allows the sugar to draw out more juice from the berries, helps dissolve the sugar crystals before heating, and can improve the final texture and flavour.
- Prepare for Testing: Place 2-3 small ceramic or glass plates in the freezer. You will use these later to test if the jam has reached its setting point (gel stage).
- Cook the Jam: Place the pot over medium-high heat. Stir constantly as the mixture heats up, ensuring all the sugar dissolves completely before it comes to a boil. Once the sugar is dissolved, bring the mixture to a rolling boil – one that cannot be stirred down.
- Boil Vigorously: Reduce the heat slightly to maintain a strong, steady boil, but not so high that it boils over or scorches aggressively. The mixture will foam up significantly at first. Skim off any excessive foam or scum using a metal spoon if desired – this is mostly trapped air and impurities and skimming results in a clearer jam (though it’s not strictly necessary for taste or safety). Stir frequently to prevent the jam from sticking to the bottom of the pot and scorching. This is crucial, as burnt sugar will ruin the flavour. Use a heatproof spatula to scrape the bottom and sides regularly.
- Monitor for Setting Point (This is Key!): This is the most critical phase and requires patience. No-pectin jams take longer to set than those with added pectin. Cooking time can vary significantly (from 15 to 40+ minutes of boiling) depending on the berries’ natural pectin and water content, the size/shape of your pot (wider evaporates faster), and even humidity. Start testing for set after about 15 minutes of vigorous boiling. There are three main ways to test:
- Temperature Test: Use an accurate candy or digital instant-read thermometer. The target temperature for jam setting at sea level is 220°F (105°C). Clip the thermometer to the side of the pot, ensuring the tip is submerged in the jam but not touching the bottom. Note: This temperature can vary slightly based on altitude (decrease by 1°F for every 500 feet above sea level) and sugar concentration, so it’s best used in conjunction with another method.
- Sheet Test (Spoon Test): Dip a cool metal spoon into the boiling jam and lift it horizontally above the pot, turning it so the jam runs off the side. In the early stages, it will drip off in thin streams. As it gets closer to setting, the drops will become heavier and slower. When ready, the jam will momentarily hang on the edge of the spoon, and then two large drops will merge and fall off together as one “sheet.” This takes practice to judge correctly.
- Wrinkle Test (Cold Plate Test – Most Reliable): Remove the pot from the heat while you test to prevent overcooking. Take one of the cold plates from the freezer. Drop a small spoonful (about a teaspoon) of jam onto the freezing cold plate. Return the plate to the freezer for 1-2 minutes. Remove the plate and gently push the edge of the jam puddle with your fingertip. If the surface wrinkles and holds its shape, the jam is set. If it’s still runny and flows back together easily, it needs more cooking time. Return the pot to the heat, boil for another 3-5 minutes, and test again with a fresh cold plate. Continue this process until it passes the wrinkle test.
- Jar the Jam: Once the jam has reached the setting point, remove the pot from the heat immediately. Let it sit for a minute or two, giving it a final stir to distribute the fruit pieces evenly. Carefully ladle the hot jam into your prepared sterilized jars using a canning funnel, leaving about 1/4 inch (0.5 cm) of headspace (the space between the top of the jam and the rim of the jar).
- Seal the Jars: Wipe the rims of the jars clean with a damp paper towel to ensure a good seal. Any stray jam can interfere with sealing. Place the new, flat lids on the jars, ensuring the sealing compound touches the clean rim. Screw on the bands fingertip-tight – just until you feel resistance. Do not overtighten, as air needs to escape during processing.
- Process for Shelf Stability (Optional but Recommended):
- Water Bath Canning: Place the filled jars onto a rack in a large pot filled with hot (not boiling) water. The water should cover the jars by at least 1-2 inches. Bring the water to a full rolling boil. Once boiling, start the timer. Process the half-pint jars for 10 minutes (adjust time for altitude if necessary – add 1 minute for every 1,000 ft above sea level).
- After Processing: Turn off the heat, remove the pot lid, and let the jars sit in the hot water for 5 more minutes. Carefully remove the jars using a jar lifter and place them upright on a towel-lined surface, leaving space between them. Do not tighten bands further. Let them cool completely undisturbed for 12-24 hours. You should hear popping sounds as the jars seal. Check the seals by pressing the center of the lid – it should be concave and not flex up or down.
- Refrigerator/Freezer Jam: If you skip the water bath processing, the jam must be stored in the refrigerator (lasts several weeks) or freezer (lasts up to a year). Ensure jars are freezer-safe if choosing this option.
- Label and Store: Once cool, remove the bands (they can trap moisture and cause rust), wipe the jars clean, label them with the contents and date, and store properly sealed jars in a cool, dark place. Store unsealed or opened jars in the refrigerator.
Nutrition
- Serving Size: one normal portion
- Calories: 45-60