Sugar and Pectin

Sugar not only sweetens jam but it also works with pectin as a setting agent, and inhibits the growth of microorganisms. Jams must contain over 55 per cent sugar to inhibit the growth of microorganisms, so the amount of sugar needed to preserve the fruit will depend on its natural sweetness. Follow the recipe carefully as using too much sugar will cause the jam to crystallise; too little sugar and the jam won’t set.

Pectin is found in the skin, flesh and seeds of most fruits in varying degrees. It is particularly high in citrus pith and apple skin.