jam a mixture of fruit and sugar boiled together, poured into jars, and sealed to give a long-keeping preserve with a wet semi-solid consistency, known to a food scientist as a gel. There are distinctions to be observed beween jam, where the fruit is almost formless and the texture is thick yet almost flowing; jelly, where the fruit is strained for its juice then cooked with sugar and gelled (and which in the USA is a frequent colloquial usage for jam); marmalade, which in England means citrus jam with peel, but in France may mean a fruit paste or cheese; and conserve or preserve, where the fruit is in almost its original form, cooked in a very thick syrup. Such things are based on widespread and ancient methods of preserving fruit. Similar confections are made throughout Europe and the Middle East. Although the ancient world knew about preserving fruit in honey—the ancestor of quince cheese, melomeli, mentioned by Columella is an instance—jams and jellies needed cane sugar to become a kitchen staple.
