Pectin is a complex polysaccharide formed by dimethyl polygalacturonic acid chains of 300–1000 galacturonic acid units connected by C1– C4 α-glycosidic linkages.
Three major pectic polysaccharides (homogalacturonan, rhamnogalacturonan-I and rhamnogalacturonan-II) are thought to occur in all primary cell walls.
In a plant, pectin is present in the middle lamella, primary cell and secondary walls and is deposited in the early stages of growth during cell expansion. Its functionality to a plant is quite divers.
Pectin biosynthesis, function, modification, and degradation are involved in several key processes during plant development, including cell wall expansion, cell adhesion, organ formation, cell separation, and phyllotactic patterning.
Pectin plays an important role in the formation of higher plant cell walls, which lend strength and support to a plant and yet are very dynamic structures.
In the fruits of plants, pectin helps keep the walls of adjacent cells joined together. As a fruit becomes overripe, the pectin in it is broken down to simple sugars that are completely water-soluble. As a result, the overripe fruit becomes soft and begins to lose its shape.
Pectin influences various cell wall properties such as porosity, surface charge, pH, and ion balance and therefore is of importance to the ion transport in the cell wall.
Because of its ability to form a thick gel-like solution, pectin is used commercially in the preparation of jams, jellies, frozen foods, and more recently in low-calorie foods as a fat and/or sugar replacer.
Pectin is commonly extracted from raw materials by aqueous extraction; the most common methods include direct boiling, microwave heating, ultrasonic, autoclave and electromagnetic induction. The yield of pectin varies with respect to the extraction conditions such as temperature, extraction time, pH and the raw material.
Although present in the cell walls of most plants apple pomace and orange peel are the two major sources of commercial pectin due to the poor gelling behavior of pectin from other sources.
Pectin in plant cell wall
