Jam Making

For preserves to gel and reach the desired consistency, the sugar must be added because it attracts and holds water. This process leaves less water available to which pectin can form bonds. Pectin, a natural gelling component of many fruits (citrus, apples, and some berries are particularly rich sources of it), will gel only in the presence of sugar and acid (usually lemon, another citrus juice, or citric acid) in certain proportions. Optimum acidity is a pH (the measure of acidity or alkalinity) between 3.0 and 3.5. The pectin molecules link to each other, forming a network to trap the fruit pulp and sugar. The acid advances the process by reducing the small electrical charge carried by pectin molecules in water, which tends to make the molecules repel each other. Once released, the chainlike pectin molecules can bind the sugar solution and fruit pulp together.