This blueberry jam recipe comes together with only five simple ingredients. And while canning may sound like a lot of work, it's actually pretty simple, resulting in a small batch of jam to be enjoyed later!
Before beginning, make sure to have all of the water bath equipment ready, as well as the sterilized jars, lids, and rings.
In a large, heavy-bottomed kettle or Dutch oven, combine the blueberries, sugar, lemon zest, lemon juice, and vinegar.
Bring to a boil over medium-high heat. Once boiling, continue to boil until a rolling boil is achieved, 8-12 minutes. A rolling boil means that as the mixture is stirred, it continues to boil.
Remove the mixture from the heat and pour it into a sieve fitted over a bowl. Drain the blueberries from the juice and set the blueberries aside. Pour the juice back into the kettle, place it back on the stove, and bring it back to a boil.
Continue to boil until the mixture reaches 221°F. This can take more time than one would think as the mixture must cook off excess water in order for the temperature to increase. Once the mixture reaches the correct temperature, add the blueberries back in. Bring to a boil and cook for an additional 2 minutes.
Remove the jam from the heat and pour into prepared jars, leaving ¼-inch of headspace. Wipe off the jar rims with a clean cloth and fit with lids and rings tightened to fingertip strength. Boil in a water bath for 10 minutes. Remove from the water bath and cool on a rack for 12-24 hours before removing rings and storing.