Homemade jelly is made by mixing and cooking fruit, sugar, acid and pectin. According to the U.S. Department of Agriculture, the appearance, texture and taste of homemade jelly are dependent upon precise canning techniques. Furthermore, the ingredients must be mixed properly to achieve the most appetizing jelly.
Cutting the cooking time short can cause visible sugar crystals in the jelly. In "The Art of Home Canning," Angelo Sorzio says to cook the jelly longer to avoid the formation of sugar crystals. The Oregon State University Extension Service directs cooks to boil the jelly rapidly and remove it from the heat as soon as it is done.
Type of Fruit
Crystals form in grape jelly because it naturally contains tartaric acid. Cooks can reprocess grape jelly for the same amount of time as originally processed to get rid of the crystals, Sorzio says.
Too much sugar will leave glass-like particles throughout the jelly, Sorzio claims. Choose modern recipes for jelly and follow the instructions exactly to prevent sugar crystals from forming. The U.S. Department of Agriculture cautions that sugar should not be replaced with a substitute unless the recipe includes the correct amounts to use as a substitute.
Sorzio also suggests using a ladle to spoon any type of jelly into clean jars instead of pouring it in from the pan. This technique keeps sugar that does not dissolve from sweeping from the sides of the pan into the jelly. The jars should be hot when the jelly is added.