Alum, if used in excess, can cause digestive upsets, and lime decreases the acidity of pickled products. Brined pickles can be fermented in stone crocks, glass jars and bowls, and food-grade plastic containers. Garbage bags or trash liners should never be used. Products should not be fermented in aluminum, copper, brass, galvanized or iron containers. A proper ratio of fruit, pectin, acid, and sugar is needed to make jams and jellies.
Sugar prevents the growth of microorganisms and enables gel formation.
The amount of sugar called for in a recipe should never be decreased, and artificial sweeteners cannot be substituted for sugar in a recipe. However, recipes developed for reduced-sugar fruit spreads can be used. Even though sugar helps preserve jams and jellies, molds can grow on the surface of these products. These molds are not always harmless. Because of possible mold growth, paraffin or wax seals should not be used when making jams and jellies.