Cell walls pectic substances

IS A GENERAL MODEL FOR PLANT CELL WALL PECTIC SUBSTANCES FEASIBLE ... 

Effect of a new canning process on cell wall pectic substances, calcium retention and texture of canned carrots... 

Roeck, A.D., Sila, D.N., Duvetter, T., Loey, A.V., and Hendrickx, M. 2008. Effect of high pressure/high temperature processing on cell wall pectic substances in relation to firmness of carrot tissue. Food Chemistry 107 1225-1235. 

The common hemiceUulose components of arborescent plants are listed in Table 3. Xylans, arabinogalactans, and pectic substances are common to all while only traces (if at all) of glucomaimans are found in the cell walls of bamboo. Other polysaccharides are found in trace amounts in wood as well as in bark, growing tissues, and other specialized parts of trees. 

The plant cell wall is a polymeric mesh consisting of cellulose, hemicellulose, pectin and protein. Cellulose and hemicellulose are integral components of the cell wall, but pectic substances are located mainly in the outer wall regions within the middle lamella (McNeil et ai, 1984). Pectic substances are more susceptible to enzymatic degradation, because they are more exposed than other cell wall components. Therefore, pectin-degrading enzymes may play a central role in the penetration of plant tissue by bacteria. 

To date, the structural features of pectic polysaccharides and plant cell walls have been studied extensively using chemical analysis and enzymatic degradation. In addition, research on isolation and physicochemical characterisation of pectin from citrus peels, apple peels, sunflower head residues and sugar beet pulp has been reported (2). However, the pectic polysaccharides extracted from wheat straw have only previously been reported by Przeszlakowska (3). The author extracted 0.44% pectic substances from Author to whom correspondence should be addressed. 

The components of the plant cell wall (8-21) are the middle lamella (intercellular substance), the primary wall, and the secondary wall. The middle lamella is the pectic layer between cells and holds adjoining cells together as do membrane carbohydrates. The primary wall is thin (1-3 pm) and flexible containing cellulose, hemicelluloses, pectins, and glycoproteins. This wall provides mechanical strength, maintains cell shape,... 

Comparison of the Overall Composition of Cell Wall Preparations. As can be seen from Table I, cell wall preparations showed a significant difference in their polymer composition. The endosperm cell walls resembled primary walls, since they were virtually free of lignin but rich in pectic substances. On the other hand, the cell wall preparations obtained from the caryopsis coat and the aleuron tissue were highly lignified, and their pectic content was very low. The germ cell wall showed a somewhat intermediate composition between these two types, probably reflecting the fact that it consists of several different tissues. 

Desired organoleptic properties, particularly textural ones, are a direct consequence of these microstructural changes. A chip must be firm and snap easily when deformed, emitting a crunchy sound (Krokida et al., 2001a), whereas in thick products the better the contrast between a rich and soft inner structure and a crispy outside, the better the product (Moreira, 2006). Firmness is often related to starch swelling and gelatinization, as well as to the stability of pectic substances of the cell wall and middle lamellae. 

I Vegetative cells always with cell wall composed of pectic substances and silicon, cell wall invariably bivalved, but never a complexly... 

Pectinases These enzymes carry out the hydrolytic degradation of the D-glycosidic linkage in pectins. The latter substances, also known as pectic substances, are polymeric components of plant cell walls and. like starch, are composed of sugar residues linked by glycosidic bonds. The chemistry is the same as that shown for the amylases previously described. The main application of pectinases is in the production of fruit juices, wines, and certain other food products. 

Most of the cells of wood are long, narrow hollow fibers and tubular-shaped cells arranged with their long axes parallel to the axis of the tree trunk. Certain food storage cells lie in radial bands, termed wood rays, which are perpendicular to the tree axis. The walls of this complex system of plant cells form the basic framework and material of all wood substance, All wood substance is composed of two basic chemical materials, lignin, and a polysaccharidic system, which is termed holoceliulose. The latter embraces cellulose and the hemicelluloses, a mixture of pentosans, hexosans and polyuronides, and in some instances small amounts of pectic materials. Wood cell wall tissue also always retains small amounts of mineral matter (ash). 

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