The very first jams were made with pectin. (Like the prodigal son it has returned. Anyone stepping in a boiling pot of jam, would indeed get burned.) Pectin was isolated and named in 1825, and was studied with extreme prejudice through the 1950’s. Most plants have pectin, but for the purposes of culinary exhibitionism, apples and citrus peels.
Originally pectins were harvested naturally as by-products, but this wasn’t convenient for the jamming industry. So they figured out a way to dry apple residue and create an extract, which laid the foundations for a long and distinguished history of industrial jam production.
Yet again, the limitation of the process of extract transport (extracts were by definition only a few percent concentrate) allowed for, or even engineered, an innovation: the pectin precipitate. Interestingly, beet and sunflower are rockin’ pectin sources, but haven’t as yet displaced the old dogs of the jam wars.
Pectin is soluble in cold water, but has to be carefully dispersed, or like ida’s turkey curry gravy, it gets lumpy. If you are not in the presence of a high shear mixer, mix it with a little sugar. In fact, pectins disperse easier into a high sugar syrup, to which water can then be added for its dissolution.
Almost Burroughs-esque in nature, pectin is stable under acid conditions, and only loses it under less acidic conditions, or as I refer to it, the morning after. Due to the vagaries of Ester, only pectins of low degree of esterification can survive neutrality.
Pectin freshly extracted has a high degree of esterification (code name methylation), which works for quick set jams. The degree of esterification can be reduced through hydrolysis. The first reduction produces a slow set pectin that can set more slowly or at a lower temperature. Further reduction (ie, below 50% DM/degree of methylation), generates a pectin known as low methoxy, which gels with less solids, as long as you have calcium.
High methoxy pectin is a great gelling agent, provided the correct amount of sugar and acid are respected. Pastry chefs have worked on these principles for years, turning grandma’s jam into pate de fruits. Generally a ph of 3.4 to 3.8 with a minimum sugar concentration of 50-55%. You may adjust the “starchy” feel of the gel by tinkering with the nature of the sugar. For example, high concentrations of glucose tend to make a gel seem a bit pasty, as if it might do with a spot of sun in Seminyak, for example.