Pectins

Pectins are complex polysaccharides particularly prevalent in fruits such as apple pulp (10-15%) an orange and lemon rinds (20-30%).

When fruit becomes overripe, the ripe is broken down into its constituent monosaccharide sugars.

It is the major constituent of the primary cell walls of plant tissues and also the middle lamella. The middle lamella is the material which lies outside the cell walls between cells and provides the packing material which helps to bind the cells together.

Pectins are heteroglycans and have complex structures that are based on polygalacturonan backbone of alpha(1-4) linked D-galacturonic acid residues, some of which are methylated.

Pectins are highly hydrophilic and are best known for their ability to form gels. Pectins are mainly used in food as gelling agents, especially in jams and preserves.

Gels consist of a three dimensional polymeric network of chains that entrap water. The water that is introduced into the walls by pectins imparts plastic properties into the wall and modulates the ability of the wall to be stretched.

Pectin gels are stabilized by junction zones, which are crystalline regions where smooth regions align themselves.

The gel formation or thickening properties of pectins depends on the ration of methyl ester, carboxyl and amide groups.

The physicochemical properties of the pectins, either within the cell wall matrix or after extraction, are important from both functional and nutrition.

They have a physiological role as dietary fiber along the human digestive tract and in food, also exhibit a variety of functional properties, mainly related to texture.
Pectins