How Jam Is Made
Jam and Jelly are sweet spreads made from boiled fruit or fruit juice to which sugar has been added. The major difference between jam and jelly is that jelly is made only from fruit juice while jam is made from fruit pulp that has been crushed, mashed, ground, or chopped into pieces. A type of jam containing whole fruits is known as preserve, while a jam containing fruit peel as well as pulp is called a marmalade. Another major difference between jam and jelly concerns their consistency. Jam is a thicker mass that spreads out slightly when unmolded. Jelly retains its shape when turned out of its container and quivers slightly when touched.
The consistency of jam or jelly depends on the proportions and handling of the fruit or juice and the content of acid, sugar, and pectin. All fruits contain some natural pectin and mild acid. Some, such as apples and grapes, contain enough of both to make a good jam or jelly. Others, however, such as elderberries, ,will not make good jam or jelly unless additional acid and 'pectin are included. Acid may be added as one tablespoon of lemon juice or % teaspoon of crystalline citric acid for each cup of fruit or juice. Commercial pectin is available in both liquid and powdered forms, and both are highly satisfactory with any fruit. In using commercial pectin, it is important to follow the directions on the package since the two forms are not interchangeable and each is used differently.
The sugar content of jam or jelly also helps produce the desired consistency. In addition, it serves as a preservative, contributes to the flavor, and has a firming effect on the fruit pulp in jam. Light corn syrup or honey can be used to replace some, but not all, of the sugar called for in jam and jelly recipes.
Once it is made, the jam or jelly should be stored in a cool dry place to retard the growth of mold and prevent the loss of moisture and color. Once the container has been opened, it is best to store it in the refrigerator.
The making of jam and jelly probably began centuries ago in the Middle Eastern countries where cane sugar grew naturally and where fruits were abundant. It is believed that the Crusaders first introduced the sweets to Europe when they returned from the Middle East, and by the late Middle Ages, jams, jellies, and fruit conserves were popular in Europe. By the end of the 17th century, books on jam-making were published.
In the United States, early settlers in New England preserved fruits with honey, molasses, or maple sugar. Pectin extracted from apple parings was used to thicken jellies.