LIGNIN

Lignin is a macromolecule characterised by monolignols, the starting material being phenylalinine. It is common in trees and herbaceous plants, where is part of the cell walls, including the xylem fibres. After cellulose it is the most abundant organic compound, accounting for up to 33% of the dry mass of wood. It fills space between cellulose and pectin, giving rigidity, conducting water and providing defence against pathogens.

Lignin has both a negative and a positive side; it must be removed from plants when processed for paper and textiles, but is in fact on its own a very commercial compound. Studies of its uses began in 1927, when the Marathon Corp. in Rothschild, Wisconsin took an interest in it; since then this firm has been renamed LignoTech USA, and is owned by a Norwegian company, Borregaard.

The commercial uses of lignin and its derivatives include raw materials for use in vanillin, ethanol, humic acid, environmentally friendly dust suppression agents, dispersants in high performance cement applications, textile dyes and agricultural chemicals.

When burned, methoxy phenols are formed, of which guaicol and syringol are responsible for the flavour of smoked foods.

(for related post, see note below on pectin)

PECTIN

Pectin is a heterosaccharide, found in the cell wall of plants. The term 'pectin' includes a number of compounds which vary in the order of the monosaccharides. Under acidic conditions, it forms a gel, most well known from its use in marmalade and other jams. In fruit it is a welcome ingredient, which breaks down during maturation to pectinic and pectic acids in the presence of the enzyme pectinose. In general, hard fruits contain more pectin than soft fruits.

In fibre plants, pectin is removed out of necessity so as to isolate the cellulose, which is the main compound in paper and textiles. Hot water is one way of removing pectin, which is why hot-water retting and boiling have been methods of the hemp farmer.

Today hot-water retting is being explored along with enzyme retting. The goal of researchers is the removal of pectin from the stem so as to produce a pure cellulose fibre, free from pectin and other substances, such as lignin.