Both Jam and Jelly are forms of fruit products widely eaten as a food accompaniment. They differ in the ingredients, fruit's physical form and also the way they're made. Jelly refers to a type of clear fruit spread consisting of firmed fruit (or vegetable) juice made with pectin. Jam refers to a product made with whole fruit, cut into pieces or crushed. While jams contain fruit pulp, jellies have the juice form of fruit.
edit Production of Jam and Jelly
In general jam is produced by taking mashed or chopped fruit or vegetable pulp and boiling it with sugar and water. The proportion of sugar and fruit varies according to the type of fruit and its ripeness, but a rough starting point is equal weights of each. When the mixture reaches a temperature of 104 °C (219 °F), the acid and the pectin in the fruit react with the sugar and the jam will set on cooling. Jelly is generally made by cooking fruit juice and sugar with pectin as a jelling agent and lemon juice as an acid to maintain a consistent texture.
edit History of Jam and Jelly
The making of jam and jelly began centuries ago in the Middle Eastern countries, where cane sugar grew naturally. It is believed that returning Crusaders first introduced jam and jelly to Europe; by the late Middle Ages, jams and jelly were popular there. The use of cane sugar to make jam and jelly can be traced back to the 16th century when the Spanish came to the West Indies where they preserved fruit. Marmalade, a kind of fruit preserve, is thought to have been created in 1561 by the physician to Mary, Queen of Scots, when he mixed orange and crushed sugar to keep her seasickness at bay. In the United States, early New England settlers preserved fruits with honey, molasses or maple sugar. Pectin extracted from apple parings was used to thicken jellies. The Food and Drug Administration established Standards of Identity for what constitutes jam and jellies and fruit butters in 1940.
edit Differences in Physical Form
Jelly is firm and will hold its shape. Jam doesn't hold its place and is more of a soft pulp. While good Jelly is always clear and sparkling when properly set, jam cannot be sparkling as it holds the dark shade of its retaining fruit pulp.
edit Differences in Ingredients
Generally, jelly contains no pieces of fruit, although specialty jellies, like pepper jelly, may include pieces of jalapeño or other pepper. Jam may contain crushed fruits or vegetable pulp. While in Jelly, the fruit portion comes as a juice, in Jam it comes as a pulp.
Most commonly available Jelly flavors are Strawberry, Cherry and grape while the most common Jam flavors are Orange, Mango, Mixed fruit and Strawberry.