Jam is a product obtained by cooking fruits, whole or cut into pieces, with sugar, until they reach a certain consistency. Almost all fruits can be used in the preparation of jam, in particular those rich in pectin, a substance that facilitates the thickening of the mixture. When fruits are low in pectin (such as red fruits) are used, it is advisable to add at least one that is rich in pectin (for example apples). To prepare the jam just follow some rules: the fruit must be healthy and ripe at the right point; it should be washed, pitted (not necessarily peeled) and cut into pieces before cooking. The amount of sugar varies depending on whether it is a very or low-sugar fruit (the indicative dose is 750 g of sugar per kilo of fruit).
The cooking must be done initially over high heat, to allow a rapid evaporation of the water contained in the fruit, then with more attenuated heat and stirring without interruption. To check if the jam is ready, trickle a drop on an inclined saucer: if it flows very slowly, it means that the cooking is complete. The jam is then transferred into sterilized airtight jars and stored for at least a month before consuming it.