The Washington Post

Blueberry Jam

Blueberry Jam 32.000

Scott Suchman for the Washington Post; food styling by Lisa Cherkasky for The Washington Post

Aug 23, 2021

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. 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.

Equipment: You'll need a 6-quart or larger heavy pot, such as an enamel-coated cast-iron Dutch oven (not aluminum) and a candy thermometer. Also helpful: a canning funnel.

Active time: 1 hour 15 mins, plus 24 hours' resting time

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

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

Storage Notes: 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.


When you scale a recipe, keep in mind that cooking times and temperatures, pan sizes and seasonings may be affected, so adjust accordingly. Also, amounts listed in the directions will not reflect the changes made to ingredient amounts.

Tested size: 32 servings; makes eight 4-ounce jars

  • 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

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Prepare the berries: In a large bowl, combine the blueberries, sugar and lemon juice and let macerate until 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.

Sterilize the jars: Position a rack in the lower third of the oven, place an oven thermometer in the oven to make sure it is the correct temperature, and preheat to 250 degrees. Wash the jars and lids with soap and water. Place the jars 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.)

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.

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.

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

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.

To test if the jam is ready, drizzle a scant teaspoon of the mixture onto a frozen spoon or plate. Wait a few seconds, then touch the jam with your finger. It should firm up as the jam cools. 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 more minutes and test it again.

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

Working quickly, remove the baking sheet with the jars from the oven and place them 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.

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.

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 that 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.

NOTE: This is a small-batch jam recipe. If you decide to make a larger batch, you will need a larger pot and, the berries will likely need to cook longer.

The jar lids should be washed and dried, but do not have to go in the oven.

Recipe Source

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

Tested by Ann Maloney.

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Nutritional Facts

Calories per serving (2 tablespoons): 113

% Daily Values*

Total Fat: 0g 0%

Saturated Fat: 0g 0%

Cholesterol: 0mg 0%

Sodium: 1mg 0%

Total Carbohydrates: 29g 10%

Dietary Fiber: 1g 4%

Sugar: 27g

Protein: 0g

*Percent Daily Value based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.

Total Fat: Less than 65g

Saturated Fat: Less than 20g

Cholesterol: Less than 300mg

Sodium: Less than 2,400mg

Total Carbohydrates: 300g

Dietary Fiber: 25g

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