Pectin is the gelling gum behind jam. It is a natural polysaccharide from the cell walls of fruit — extracted commercially from citrus peel and apple pomace left over from juicing — that sets a sweet, acidic liquid into a spreadable gel. There are two working types: high- methoxyl (HM) pectin, which needs plenty of sugar and acid to set, and low-methoxyl (LM) pectin, which sets with calcium and far less sugar.
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