Marmalade is a citrus preserve — most classically bitter Seville orange — made by boiling the fruit's juice, pulp and, crucially, its shredded peel with sugar until it sets into a glowing amber, softly gelled spread threaded with strips of rind. It is the quintessential British breakfast preserve, spread thin on buttered toast, and it stands apart from ordinary jam by its use of the whole citrus fruit, peel and all, which gives it a distinctive bittersweet, aromatic edge. Nutritionally it is, like jam, almost pure sugar, with only a trace of the fibre and vitamin C surviving the boil.