Pectin

D-Galacturonic acid is the principal constituent of pectin, but some neutral sugars are also commonly present in pectin. The D-galacturonic acid units are linked together by α(1-4) glycosidic linkages. The polygalacturonic acid is partly esterified with methyl groups and the free acid groups may be partly or fully neutralized with sodium, potassium or ammonium ions. The ratio of esterified galacturonic acid groups to total galacturonic acid groups – termed the degree of esterification (DE) – has vital influence on the properties of pectin, especially the solubility and the gel-forming characteristics.