Preserve

preserve a word applied to foods treated by some means to achieve their preservation. Thus foods which have been chilled, frozen, pickled or treated with sugar are all preserved foods.

The words ‘preserve’ and ‘conserve’ are also used more specifically to indicate an (often expensive or unusual) jam. Although this is generally regarded as pretentious today, both words were used this way at least a century before the word ‘jam’ became common.