JAMS and JELLIES are conserves of the pulp and juice of succulent and juicy fruits prepared by boiling with sugar. They differ from each other only in the fact that jam is a thick pulpy opaque preparation, sometimes of the entire fruit—rind, pulp, and kernel—and sometimes of fruits only partly broken, as in the case of black currant jam, while jellies are pure transparent gelatinous preparations of juices alone. The preparation of these preserves was formerly a purely domestic art; but of recent years manufactures of very large dimensions have sprung up for the preservation of many of the commoner fruits, as an example of which the marmalade trade may be cited, marmalade being simply a form of jam. The principal fruits commonly used for jam-making are varieties of plums, apricots, cherries, black currants, gooseberries, strawberries, raspberries, mulberries, cranberries, oranges, and quinces; rhubarb stalks are also employed. Jellies have a wider signification than is comprehended in the above definition, which embraces fruit jellies alone, as many jellies have for their basis isinglass and other gelatinyielding bodies of animal origin, and starches also form with boiling water a kind of jelly. Fruit jellies owe their property of gelatinizing to the presence or development of a gummy principle in their composition, called pectin. Except in its gelatinizing effect pectin is in no way related to gelatin, being indeed a non-nitrogenous body closely allied to cellulose. Pectin is only found in very ripe fruits, but an allied body, pectose, which is abundant in growing and partially ripened fruits, is easily transformed into pectin by the action of heat, and such a transformation takes place in the boiling of the juices of acid unripe fruits. In the preparation of ...