Submitted to: Textile Research Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 3, 2002
Publication Date: February 1, 2003
Citation: Textile Research Journal 73(2):157-160 (2003) Interpretive Summary: Separation of cotton fiber from the seed requires optimal moisture levels, and this is achieved at the cotton gin by the application of heat to the seed cotton. This heating has been shown by several physical tests to have a potential detrimental effect upon cotton quality. Changes to the chemical structure of cotton fiber components are the basis for this decrease in quality, but little research has been performed to ascertain the chemical changes which are responsible. In this study, the pectin component of cotton fiber is characterized and measured as a function of applied temperature and heating time. Results indicate that even at normal gin operating temperatures, significant degradation of cotton fiber pectin may occur. Though pectin makes up only 1% by weight of the cotton fiber, it is located on the surface of the fiber, and any change in its composition may have marked effects upon the efficiency with which the fibers are spun into yarn, due to changes in the surface propertiess of th fiber.
Technical Abstract: Polygalacturonic acid, calcium polygalacturonate, and samples of two cotton varieties were subjected to elevated temperatures for varying increments of time. The galacturonic acid residues of the heat-treated samples were quantified by digestion with pectinase along with EDTA, and the resultant solutions analyzed by high performance anion exchange chromotagraphy. Results indicate that galacturonic acid content decreases exponentially as a functon of heating time, and that the rate constant for the degradation is temperature dependent. The energy of activation for the degradation of polygalacturonic acid is substantially lower than that of calcium polygalacturonate, and that of the cotton samples is essentially identical with that of calcium polygalacturonate. This phenomenon along with supporting data indicates that cotton fiber pectin is primarily non- esterified polygalacturonic acid with a large percentage of the galacturonic acid residues cross-linked by calcium ions. The energy of activation for the degradation of cotton fiber pectin is substantially lower than that of cellulose, suggesting that heating of cotton at normal ginning temperatures may lead to a degradation of the pectin component. This change in pectin composition may in turn affect fiber spinning performance due to changes in the surface properties of the fiber.