Page 154 - Advances in Textile Biotechnology

Enzymatic versus chemical processing of cotton 135

referring to whether or not they are a fat or oil (solid or liquid triglyceride)
that can be hydrolyzed into the salt of a fatty acid and an alcohol.

Of the non-saponifiable compounds, the high-molecular-weight alcohols
and esters and fatty acids are more diffi cult to remove unless the materials
they are attached to in the cuticle structure are excised. A comprehensive
listing of these compounds is reproduced in Table 6.1 (Agrawal, 2005). Most
of these compounds have melting points below the boiling point of water
(100 °C) and high-temperature treatments can be effective in removal, or

at least in redistribution on the cotton fiber surface. Removal or redistribu-
tion of the wax materials can be of great importance in allowing access to
the primary wall non-cellulosic compounds.

6.3 Cotton seed coat fragments
Greige (undyed) cotton fabric coming off the loom contains, in addition to
the starch size, a certain amount of cellulosic matter from plant fragments
created during harvesting. These are more prevalent in mechanically har-
vested cotton than in that picked by hand. Opening, blending and subse-
quent operations in the yarn-spinning process remove most of this plant
structure matter. More problematic are seed coat fragments that are not
removed during the yarn spinning processes because the fi bers attached to
these become part of the yarn structure. These seed coat fragments are
visible as small dark dots in the fabric. Figure 6.4 shows seed coat fragments
in the fabric, and under magnifi cation.
Seed coat fragments are created during the ginning process when the
cotton seeds are removed from the harvested cotton mass by the saw teeth
on the rollers in the gin. The fragments result when various forces applied

to separate fibers from the seed coat pull off pieces of the coat and cause

(a) (b)
6.4 Seed coat fragments in fabric: (a) unmagnifi ed, (b) ×100.

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