Biomedical Engineering Reference
In-Depth Information
Chapter 20
Pectic Polysaccharides of Fruits: Characterization,
Fractional Changes and industrial application
Kausik Majumder
iNtroduCtioN
Cell wall is a unique feature in a plant cell. This extra-protoplasmic entity is a funda-
mental distinguishing feature that makes a mark on a plant cell from the correspond-
ing unitary biological material of the animal kingdom. The somatic cells of plants are
characterized by three peripheral layers and this come to the vision of the scientist long
before the underlying material that is the protoplasm was discovered. This structural
barrier of a plant cell, which is looked upon as a secretory product of protoplasm is
however, destined with a number of important functions to perform. In addition to pro-
viding the skeletal support, cell walls are known to participate in a number of physi-
ological functions and have an important role in the carbon economy of the biosphere
(Goodwin and Mercer, 1988).
Structurally, the cell wall is equipped with several complex organic compounds,
chemically recognized as cellulose, hemicellulose, lignin, and the pectic substances.
Among these polymers, pectic substances find their location in the middle lamella and
also the primary wall of the cell wall. The proportion of the pectic material in the cell
wall however, depends much on the type of layers present in it. For it is known that
the amount of this component extracted from meristemetic or parenchymatous tissues
may comprise of 15-30% of the wall material in contrast to 0.5-1.5%, that is extract-
able from tissues, which are highly lignified (Tarchevsky and Marchenko, 1991). This
review aims to give insight into how the various structural changes that occur in the
pectic polymers during fruit development and ripening. To the end, a brief note on
industrial significance and application of this natural polymer are discussed.
struCture, ClassiFiCatioN aNd NomeNClature oF PeCtiC
suBstaNCes
Pectic polysaccharides or substances are polygalacturonate molecule in which 1→4,
α-D-galacturonic acid chains are linked with branches of L-rhamnopyranosyl resi-
dues with neutral side chains of L-arabinose, D-galactose, and D-xylose (Saulnier and
Brillouet, 1998). The carboxyl groups of galacturonic acid are partially esterified by
methyl groups and partially or completely neutralized by sodium, potassium or am-
monium ions (Kashyap et al., 2001). Some of the hydroxyl groups on C
2
and C
3
may
be acetylated and the monomer is thought to have the C
1
confirmation (Pilnik and
Voragen, 1970). The primary chain consists of α-D-galacturonic units linked α-(1→4),
with 2-4% of L-rhamnose units linked β-(1→2) and β-(1→4) to the galacturonic units
Search WWH ::
Custom Search