Pectin is an indigestible soluble fiber which when combined with water forms a colloidal system and gels upon cooling. It has a wide range of uses. It can be found as a gelling, thickening or stabilizing additive in food, an ingredient in laxatives, a demulcent in throat lozenges, and a vegetable glue for cigars. Pectin used for cooking is divided into two categories, high methoxyl (HM) and low methoxyl (LM).
HM pectins are most commonly used to create jams and jellies. HM pectins require the presence of sugar and specific levels of acidity. The amount of acid in your base solution will directly affect the setting time of the pectin. HM pectins are further broken down into the categories of rapid set and slow set. Each subset is categorized by setting time and/or temperature. Rapid set HM pectins are often used for jellies that have ingredients suspended inside the gel structure, such as chunky marmalades or hot pepper jelly, while slow set HM pectins are often used for clear jellies like apricot or grape.
LM pectins simply require the presence of calcium to activate the gelling process. They are often used to produce low or no sugar jellies. Unlike HM pectins, LM pectins form thermally irreversible gels. Amidated LM pectins are treated with ammonia so that they require less calcium than conventional LM pectins to gel. They have a complementary relationship with dairy and are able to utilize their whey proteins as a source of calcium while also enhancing their innate capabilities for gelation, emulsification and the ability to produce stable foams.
Pectins are most commonly extracted from fruit, usually from apple pomace or citrus peel. These two sources are readily available for commercial production as by-products of the juice industry. Proprietary formulations vary from company to company, so when you purchase commercially produced pectin be sure to follow the guidelines provided by the manufacturer.