Pectin is a naturally-occurring thickening agent that is most often used by adding it to jams, jellies and similar products to help them gel and thicken. Pectin creates a thick, clear set when it gels. It is a carbohydrate (a polysaccharide) found in and around the cell walls of plants, and helps to bind those cells together. All fruit has pectin in it, but the amount varies widely. Apples and oranges contain the most pectin, and the pectin from both fruits is used commercially to thicken many different types of products. Pectin generally needs a high sugar content and some acid, such as citric acid, to activate, and some commercially available pectins include citric acid as an ingredient to help ensure that consumers get their desired result when working with their products. Pectin can be bought at the grocery store in both powder and liquid forms, and it can also be introduced to a recipe by adding fruit that has a high natural pectin content, such as apples or plums.
Gelatin and pectin both produce clear gels with a high sheen, but the products are not the same. Pectin is a water-soluble fiber, while gelatin is a protein derived from animals. Pectin is used almost exclusively in high-sugar products, like jams. Gelatin, on the other hand, is used in a much wider variety of foods, including mousses, marshmallows and frostings because gelatin sets in a cool environment and does not require that specific ingredients be included to activate it.