Before starting this Plum Jam recipe, make sure you have organised all the necessary ingredients.
Cut the plums in half and remove the pits.
Add 550 grams of granulated sugar...
... and combine with a spatula. Store in the fridge for about one hour.
In a saucepan, pour the plums macerated in sugar.
Cook over medium heat until the sugar has melted and turns into a syrup. If the heat is too high, the sugar will turn into a caramel. Bring to a gentle boil...
... then continue cooking over medium heat until you get the right consistency.
This should take 45 minutes to 1 hour. Stir frequently.
... add the pectin, combined with the remaining 50 grams of sugar beforehand. It is essential to combine the pectin and castor sugar together beforehand to avoid lumps. Cook for a further 5 minutes to allow the pectin to dissolve.
Blend the tartaric acid in the lemon juice, then add to the jam. Tartaric acid will add some tang to the jam, but also enhances the gelling properties of pectin.
When the jam is cooked, skim the foam on the surface...
... then pour the boiling jam into glass jars which have been washed with soapy water and air dried beforehand.
Close each jar with a lid...
... and flip. Leave the jars upside down to cool. This will ensure a natural sterilization process. These plum jam jars will store perfectly for several months.
To assess whether the jam has the right consistency, pour a spoonful of boiling jam in a cold plate, then tilt the plate.
The jam should run down slowly and not be too liquid.