Jelly, jam and preserves are all made from fruit mixed with sugar and pectin. Pectin is an indigestible carbohydrate (fiber). It is found in the cell walls of most fruit. When heated with sugar in water, pectin gels, giving jam, jelly and preserves their thickness.
The difference between the three spreads comes in the form that the fruit takes.
- In jelly, the fruit comes in the form of fruit juice. Jelly has the smoothest consistency and is usually clear.
- In jam, the fruit comes in the form of fruit pulp or crushed fruit. This makes jam less stiff than jelly.
- In preserves, the fruit comes in the form of chunks in a gel or syrup. Preserves will have more fruit in them than jam will. Marmalade is a type of preserve with citrus fruits in it.
Jell-O is entirely different. It is made from gelatin, which is a protein made from animal skins and bones. Jell-O will have artificial colorings and flavorings but no fruit, unless you add it yourself when you make it.
Which spread should you use? That depends on what you're trying to do. For sandwiches, jelly or jam is preferred as they spread easier. For recipes, preserves would deliver more fruit flavor, though jam could also be used.