Boysenberries are large, purple berries that look very similar to blackberries and raspberries. They've become popular for use in jams, jellies, preserves and other desserts such as pies and ice cream. Making boysenberry jam requires only a few simple ingredients, and the gelling point is reached in only a few minutes. However, you will need to allow the boysenberry jam at least half a day to cool in the jars before using.
Use 4 cups of fresh, ripe boysenberries and 4 cups of granulated sugar to make the boysenberry jam. The berries don't require any additional pectin, as they are naturally high in the substance. Use a large, non-reactive saucepan, large stockpot with lid, metal tongs and three ½-pint glass jars with clean lids to prepare the jam. Do not use larger jars, as this can result in a weaker gel due to excess heat during the cooling process. Sterilize the jars in boiling water for 10 to 15 minutes before using, and make sure they are still hot when pouring the jam.
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Clean the boysenberries thoroughly in cool water and then crush them slightly. Put them through a food mill or place them in a fine mesh sieve and crush them gently with your hands by pressing against the bottom. Do not puree the berries, as this can cause a change in acidity, resulting in a weak jam. Place the crushed berries into a large saucepan and turn the heat to medium-high. Bring to a boil and then reduce the heat to medium-low. Add the granulated sugar to the berries, stirring constantly until it is completely dissolved. Increase the heat to medium-high and boil for another five minutes, stirring often, or until the gelling point is reached.
Check for the gelling point by removing the saucepan from the heat. Dip out a small amount of the boiling liquid and place it on a small saucer. Place the saucer in the freezer and wait two to three minutes. Remove the saucer and check the liquid for gelling. If it has gelled, the jam is ready, but if it is still liquid, more cooking time is needed. Try boiling for another five minutes, then check it again.
Processing and Storage
Once the gelling point is achieved, skim off any foam on the surface of the boysenberry jam liquid. Pour immediately into the hot, sterilized jars, leaving about ¼ inch of space at the top of each. Secure the lids in place tightly and prepare a hot water bath for processing. Bring enough water to a boil in a large stockpot to cover at least 1 inch over the top of the jars. Lower the jars into the boiling water with metal tongs, then cover the pot. Boil the jam jars gently for about five minutes.
Use the metal tongs to remove the jars from the boiling water, and place them on clean towels to cool. Allow them to sit undisturbed for at least 12 hours. Disturbing them before this time period can result in a weak jam by breaking the gel. As the boysenberry jam cools, the jar lids will begin to pop. This indicates that the jar has sealed properly. If a jar fails to seal, it should be stored in the refrigerator for no longer than 90 days.
Label each jar with the contents and date. Store sealed jars in a cool, dry place until ready for consumption. Sealed jars of boysenberry jam will keep for up to one year, although it is better to consume the jam within a few months. As a general rule, the shorter the storage time, the more flavor the jam will have.