Michigan State University Extension
Preserving Food Safely - 01600540
Sugar helps in gel formation, serves as a preserving agent and contributes to flavor.
It helps in gel formation by "binding" water. As a result of the binding, pectin precipitates out of solution to form a gel upon cooling.
In addition, sugar acts as a preservative by "tying up" water so most microorganisms cannot grow.
Beet and cane sugar can be used with equal success. Although they come from different sources, they have the same composition.
In recipes with no added pectin, light corn syrup can replace 1/4 of the sugar. Corn syrup can replace 1/2 the sugar in powdered pectin recipes. Where liquid pectin is used, corn syrup can replace 2 cups of the sugar.
Honey can also replace sugar in jams and jellies. Light honey can replace 1/2 the sugar in recipes without added pectin. When pectin is added, 2 cups of honey can replace two cups of sugar in most recipes; 3/4 to 1 cup of sugar can be replaced by honey in small recipes (5-6 half-pint jars).