Blueberry Jam from Frozen Blueberries - Rise and Bake with Julie

Prep Time:1

Cook Time:4

Canning Time:5

Total Time:1 9

Servings: 1/2 pints

5 c. frozen blueberries, thawed & juice reserved (*see instructions for beginning weight) 600-650g
1 tbsp. lemon juice, bottled
5 ½ c. granulated sugar 1,100g
¾ c. liquid (reserved blueberry juice & water) 180g
1 tsp. butter, optional (to reduce foaming) optional
1 (1.75 oz) box powdered pectin

Weigh 800–900 grams of frozen blueberries and thaw completely in a large bowl (refrigerate overnight or use a microwave on low defrost setting).
Drain thoroughly through a fine-mesh strainer, reserving the juice. Weigh 600–650 grams (about 5 cups) of drained blueberries. If short, thaw and drain additional berries to reach the target weight.
Measure exactly ¾ cup (180 g) of liquid using reserved juice, adding water only if needed. Do not exceed ¾ cup to ensure proper gelling.

Use an immersion blender or potato masher to crush the drained berries to your preferred consistency (smooth or chunky).

In a large, heavy-bottomed pot, combine the crushed berries, ¾ cup liquid, 1 tbsp lemon juice, and powdered pectin. Stir well to dissolve pectin.
Bring to a full rolling boil (a boil that doesn’t stop when stirred) over high heat, stirring constantly to prevent scorching.
Add 5½ cups (1,100 grams) sugar, optional butter, and optional flavorings (½ tsp nutmeg/cinnamon or 1 tsp vanilla). Stir to dissolve sugar.
Return to a full rolling boil and boil for exactly 1 minute, stirring constantly.

To ensure proper set, place a small plate in the freezer for 10 minutes. Spoon a small amount of hot jam onto the chilled plate, return to the freezer for 1 minute, then push the jam with your finger. If it wrinkles and holds its shape, it’s ready. If too runny, boil for an additional 30–60 seconds and retest.
Remove from heat and skim any foam with a spoon.

Refrigerator/Freezer Storage: Pour jam into clean containers, cool, and refrigerate for up to 3 weeks or freeze for up to 6 months.
To Water Bath Can: Sterilize 6–7 half-pint jars by boiling for 10 minutes (or use a dishwasher’s sterilize cycle). Keep jars hot.
Pour hot jam into hot jars, leaving ¼ inch headspace (use a headspace tool or ruler for accuracy). Wipe rims with a clean, damp cloth.
Place prepared flat lids on jars and screw bands to fingertip tight (tighten until resistance is met, then a slight turn more).
Place jars in a water bath canner with water covering jars by at least 1 inch. Bring to a boil and process for 5 minutes at sea level (adjust for altitude: 7 minutes for 1,001–3,000 feet, 10 minutes for 3,001–6,000 feet, 15 minutes for above 6,000 feet).
Turn off heat, let jars sit in the canner for 5 minutes, then remove with a jar grabber. Place on a towel-lined surface and cool undisturbed for 12–24 hours.
Check seals: Press the center of each lid; it should not flex. Alternatively, tap with a spoon for a clear, ringing sound. Refrigerate or freeze any unsealed jars.
Remove screw bands, wipe jars clean with soapy water, and store in a cool, dark place for up to 1 year.

Liquid Control: Use exactly ¾ cup (180 g) liquid (juice + water) to avoid a runny jam. Excess liquid from undrained berries can prevent proper gelling.
Blueberry Measurement: Start with 800–900 grams frozen blueberries to ensure 600–650 grams of drained berries after thawing. Weighing after draining ensures the correct fruit solids for a proper set.
Troubleshooting Runny Jam:
- Ensure a full rolling boil for 1 minute after adding sugar to activate pectin.
- Use the gel test to confirm set before jarring.
- If jam remains runny after cooling, reprocess with additional pectin (follow package instructions) or store in the refrigerator/freezer.
Pectin: Use standard powdered pectin (e.g., Sure-Jell regular). Low-sugar pectin with 3–4 cups (600–800 grams) sugar can be used for a firmer, less sweet jam, following package instructions. Altitude: Adjust water bath processing time based on your altitude to ensure safe canning.
Flavor Tip: To enhance blueberry flavor without excess liquid, simmer reserved juice to reduce slightly (e.g., reduce 1 cup to ¾ cup) before measuring.