Preservative — By binding water, sugar acts as a very effective, natural preservative. For example, the high sugar levels in jams, jellies and sauces make them more immune to the microorganism development common in thinner, high-moisture products like commercial applesauce. Sugar is the preferred sweetener in cereal coatings because of its ability to crystallize into a frosty surface forming a hard, continuous glaze. This protects the product from air and moisture, extending its shelf life.
Reducing the amount of free water in food.