Blueberry Jam

This is a traditional Scottish-style blueberry jam (the recipe text uses “blaeberries", the Scots word for the wild bilberries that grow on highland moors). Rhubarb does the pectin work that store-bought powders normally handle, which keeps the ingredient list to three things and the flavor honest.

Cooking the rhubarb gently first releases its pectin and breaks the stalks down before sugar enters the picture. Sugar locks vegetables and fruit at whatever firmness they are when it dissolves, so getting the rhubarb to soft pulp before sweetening matters.

Adding blueberries at the very end keeps them mostly intact in the finished jam. They release juice during the rapid boil, deepening the color to almost-purple, but enough whole berries survive to give texture in the spread.

The wrinkle test on a chilled plate is the most foolproof setting point check. Skip the thermometer if you do not have one. A wrinkled surface when you push the cooled jam with a fingertip means you are done.

Jam Tips

• Use older, more pectin-rich rhubarb. Early-season stalks have less pectin than late-season ones.
• Skim the foam off the surface just before potting. Trapped foam looks ugly in a clear jar.
• Sterilize jars in a hot oven at 250°F (120°C) for fifteen minutes, or run them through a dishwasher hot cycle.
• Pour while the jam is still warm, around 180°F (80°C). Cold jam in cold jars is a sealing risk.

Variations

• Add a strip of lemon zest during the boil for citrus brightness, removing it before potting.
• Stir in two tablespoons of cassis or blueberry liqueur off the heat for adult depth.
• Use bilberries or wild blueberries if you can forage them. The flavor is more intense than cultivated.