- 10 cups fresh blueberries
- 1 cup white sugar
- 1/2 a lemon
Yield: Two 500 ml jars of jam.
Use your largest pot when making jam. It needs to be big enough so that the fruit goes no more than 1-2 inches up the sides of the pot. If you want to double the batch, use two pots – one pot for each batch of jam. Otherwise, your jam might not thicken up.
Put the blueberries in the pot on low, then heat the fruit slowly until a gentle boil is reached.
Add the sugar and lemon juice, then cook over medium heat, stirring frequently, until a teaspoon of hot jam sets on a cold plate (see below), about 20-25 minutes.
Just make sure you keep stirring the jam as it cooks or it will burn, especially in the last stages of cooking.
Cold Plate Test for Jam
Put 3-4 small plates into the freezer when you start cooking the jam.
When you think the jam is almost ready, take one of the plates from the freezer and spoon some hot jam on the cold plate. Tip the plate to one side. If mixture is thin and pours off the plate, it’s not ready yet. The jam should be thick and run slowly along the plate.
Preparing Jars and Lids
While the jam is cooking, prepare your jars and lids. To do so, fill a large pot or canning kettle with enough water to fully immerse your jars in 1 inch of water.
Bring jars to a boil, then reduce to medium, keeping everything at a nice gentle boil while you wait for the jam to finish cooking. Pre-heating the lids and rings is not necessary.
When the jam is ready, remove the jars from the hot water by inserting a wooden spoon or tongs into the jars then tipping the water out as you lift the jars out of the pot.
Place an open-mouthed jar funnel into the top of the jar, then pour the jam into the jar through the funnel, leaving a ¼’ of space at the top of each jar for expansion. If you spill jam on the rim of the jar, wipe it clean with a damp paper towel – not a kitchen cloth as it may not be sterile.
Put a lid on the jar and tighten it (not too tight), then put the jar back into the hot water using the jar lifters.
Continue with the rest of the jars until all the jam is done, then boil the jars for 5 minutes. Make sure the water covers the jars by 1 to 2 inches during processing.
Remove jars from hot water with the jar lifters and set on a tea towel to cool. You will hear cheerful popping sounds as the jars cool down- this is normal and means that the jars are properly sealed.
Enjoy your beautiful jam on freshly baked bread, baguette or croissants – or simply on a spoon, straight out of the jar.