Skip to main content
Cooking tips and recipes, plus food news and views.
The Washington PostDemocracy Dies in Darkness

This small-batch blueberry jam recipe has a surprising secret ingredient

(Scott Suchman for The Washington Post/food styling by Lisa Cherkasky for The Washington Post)
Blueberry Jam
Total time:1 hour, 15 mins, plus 24 hours resting time
Total time:1 hour, 15 mins, plus 24 hours resting time
Placeholder while article actions load

Cookbook author Camilla Wynne calls her blueberry jam Bleu Matin (or Blue Morning). “Blue” refers to the macerated and slow cooked blueberries, and “morning” to the fact that coffee beans are steeped into those berries while they bubble away.

I found an old-school technique to conquer my jam fears. Then I tried to figure out if it’s safe.

The coffee brings out the tart, fruity notes of the blueberries and tempers the sweetness of the jam. In her book “Jam Bake,” Wynne focuses on small-batch preserving and skips the water-bath canning approach (in which your filled jams are immersed in boiling water) for a riff on the old-fashioned open-kettle method, which relies on the heat of the jam itself to secure an airtight seal on your jars.

Wynne preheats her jars in the oven to sterilize them and ensure enough heat for proper sealing. (There is no need to sterilize the jar lids with this method because the jars are turned upside down during the canning process.) Whether this approach is as safe as the water-bath method endorsed by the USDA remains a concern for many.

This jam can be finished in a water bath, if you prefer. Click here for step-by-step instructions to water bath canning.

Related recipe: Coffee-Dusted Blueberry Meringues

This is a small-batch jam recipe. If you decide to make a larger batch, you will need a large pot and, likely, longer cooking time for the berries.

Equipment: You’ll need a 6-quart or larger heavy pot, such as an enamel-coated cast iron Dutch oven (not aluminum), a candy thermometer, as well as canning jars, lids and rings (we used eight 4-ounce jars). Also helpful: a canning funnel.

Storage: Without any processing, the jam can be refrigerated for up to 10 days or frozen for up to 3 months. Or it can be processed into the oven-sterilized jars or in a water-bath canner for 10 minutes, after which it should be shelf-stable for up to 18 months.

How to preserve summer tomatoes so you can enjoy them all year long

Make ahead: The blueberries can be macerated for up to 1 week before making the jam.

Want to save this recipe? Click the bookmark icon below the serving size at the top of this page, then go to My Reading List in your user profile.

Scale and get a printer-friendly, desktop version of the recipe here.


  • 3 1/3 pounds (1500 grams/5 to 6 pints) washed and stemmed blueberries
  • 3 1/2 cups (700 grams) granulated sugar
  • 5 tablespoons fresh lemon juice (from about 2 large lemons)
  • 1 1/2 tablespoons whole coffee beans

Step 1

Prepare the berries: In a large bowl, combine the blueberries, sugar and lemon juice and let macerate until the berries start to release a bit of juice, at least 15 minutes at room temperature, or cover and refrigerate for up to 1 week.

Place 3 soup spoons or small plates in the freezer. You will use these to test your jam’s consistency.

Step 2

Sterilize the jars: Position a rack in the lower third of the oven, place an oven thermometer in the oven, making sure it is the correct temperature, and preheat to 250 degrees. Wash the jars with soap and water. Place them upside down on a large, rimmed baking sheet and transfer the sheet to the oven for at least 20 minutes before you need them. (The jars can remain in the oven until the jam is ready.)

Step 3

Make the jam: Put the coffee beans in a large tea ball or tie them up in a piece of cheesecloth. Transfer the macerated mixture to a heavy-bottomed 6-quart pot or preserving pan set over medium-high heat. Add the coffee beans and cook, stirring often, until the blueberries begin to give up some juice and the sugar starts to dissolve, about 10 minutes.

Step 4

Ladle out about a third of the mixture into a blender and puree. Use caution: The berries will be hot. Return the puree to the pot, increase the heat to high, if needed, and bring to a hard, vigorous boil, stirring frequently to prevent scorching. The mixture may start to sputter, so be careful to avoid getting burned.

Step 5

The jam must be at least 194 degrees to be safely preserved, but it will likely be much hotter and remain above that temperature throughout the canning process. (If it falls below that temperature, stop and reheat it over low heat, and have a candy thermometer handy to check the temperature again.)

As your jam gets closer to being ready, 25 to 30 minutes, the bubbles will shift from frothy and disorderly to blinking, bulging spheres, and the surface will start to look glossy. A spatula pulled through it should be met with resistance.

Step 6

To test if the jam is ready, drizzle a scant teaspoon of the mixture onto a frozen spoon or plate. It should firm up as the jam cools. Wait a few seconds, then touch the jam with your finger. If it meets your standards of jam-like consistency, it’s done. If it’s runnier or looser than you’d like, cook it a few minutes, and then test it again.

When the desired consistency is reached, remove the jam from the heat and discard the coffee beans.

Step 7

Working quickly, remove the baking sheet with the jars from the oven and place on a heatproof surface. Using an oven mitt or tea towel, hold the jar steady. Using a ladle and canning funnel, if you have one, transfer the jam to jars, leaving a 1/4-inch headspace at the rim -- this is the space between the jam and the lid of the jar. (You can use a ruler or the measuring notches on the end of an air bubble remover to check this if you like.). If the jars are underfilled, they may not seal and may have an increased risk of contamination. Repeat with the remaining jars and jam.

Step 8

Dampen a paper towel or clean tea towel and wipe the outer jar edges and threads of the jar, if necessary. Place the flat lids, gasket side down, on top. Add the outer ring and tighten until you feel resistance, then turn about a quarter turn more. Invert the jars for 2 minutes. Flip the jars right side up and let the jam sit, undisturbed, for 24 hours.

Step 9

Keep the jars on the baking sheet throughout the process for easy cleanup, and so the filled jars can be moved more easily without disturbing them as they rest for 24 hours.

To check to see the jars have sealed properly, when cooled, remove the ring on each jar and lift it by the flat lid. If the lid releases, the seal is unsuccessful. Jars that do not seal can be refrigerated for up to 10 days or the jam can be frozen for up to 3 months.

Label and date each jar, and store in a dark, cool and dry space such as a cupboard, pantry or cellar for up to 1 year.

Nutrition Information

Per serving (2 tablespoons)

Calories: 113; Total Fat: 0 g; Saturated Fat: 0 g; Cholesterol: 0 mg; Sodium: 1 mg; Carbohydrates: 29 g; Dietary Fiber: 1 g; Sugar: 27 g; Protein: 0 g

This analysis is an estimate based on available ingredients and this preparation. It should not substitute for a dietitian’s or nutritionist’s advice.

Adapted from “Jam Bake: Inspired Recipes for Creating and Baking with Preserves” by Camilla Wynne (Appetite by Random House, 2021).

Tested by Ann Maloney; email questions to

Scale and get a printer-friendly, desktop version of the recipe here.

Browse our Recipe Finder for more than 9,500 Post-tested recipes.

Did you make this recipe? Take a photo and tag us on Instagram with #eatvoraciously.

More blueberry recipes from Voraciously:

3-ingredient blueberry muffins from TikTok’s favorite grandma are a true delight

8 delicious recipes to showcase summer’s blueberry bounty

The smartest no-cook dessert you can make is a fool