ABSTRACT
Pectins are natural hydrocolloids found in higher plants, widely used as gelling agents, stabilizers, and emulsi‚ers in the food industry (May, 1990). This heteropolysaccharide consists of homogalacturonan (“smooth” regions), composed of an α-(1 → 4)D-GalAp chain, and rhamnogalacturonan (“hairy” regions) showing the repeating disaccharide GalAp-α-(1 → 2)-Rhap-α-(1 → 4)-GalA pα-(1 → 2)-Rhap. In addition, arabinose and galactose side chains can also be attached creating heteropolysaccharide complexes of rhamnogalacturonan with arabinans, galactans, and arabinogalactans (Willats et al., 2006). Pectin forms gels under certain circumstances but the gelling mechanism is highly dependent on the degree of methoxylation (DM). In this regard, the presence of methoxylated carbonyl groups gives raise to a classi‚cation of this polysaccharides into high methoxy (HM) pectin with DM > 50% and low methoxy (LM) pectin with DM < 50%. HM pectin forms gels in the presence of high sugar concentration, usually sucrose or fructose and low pH; whereas LM pectin does, in the presence of divalent ions (e.g., calcium) (Ström et al., 2007). Pectin is widely used in jams and jellies, fruit preparations, fruit drink concentrates, fruit juice, desserts, and fermented dairy products (May, 1990). Although most plant tissues contain pectin, commercial production around the world is based almost entirely on citrus and apple peel (Rascón-Chu et al., 2009).
