Pectin is a heterogeneous complex polysaccharide derived from citrus peel or apple pomace. They are produced by extraction under slightly acidic conditions and followed by precipitation by alcohol or di or tri valent ions.

Pectin contains linear segments of (1→4) linked α-D-galactopyranosyluronic acid units with some of the carboxyl groups esterified with methanol. In some pectins, the hydroxyl groups of the galacturonosyl are esterfied with acetic acid.

Pectins can gel by two different mechanisms:

High Methoxy Pectins (HM) require a high concentration of soluble solids and a low pH to form gels.

Low Methoxy Pectins (LM) require the presence of divalent cations for gelling. Most commercial LM pectins are amidated. AMidation causes the pectin to gel at higher temperatures compared to non amidated pectins (under the same conditions) and lesser amount of cations (mainly Calcium) are required for gelation.