Relationship between the whiteness of scoured wool and the level of residual nitrogen-containing contaminants [Protein contaminant layer, Merino fleece]

Samples of Merino fleece wool that had been scoured either in the laboratory or in commercial plants were analyzed for whiteness, residual solvent extractables, ash content, and residual nitrogen-containing contaminants. A statistically significant linear correlation existed between whiteness and residual nitrogen containing contaminants for laboratory scoured wool, provided that the wool had not been excessively yellowed as a result of highly alkaline (i.e., pH ≥ 11) treatments. For wools from a commercial plant using immersion bowls, whiteness and residual nitrogen-containing contaminants were linearly correlated. Whiteness at each stage of scouring (bowl 4— dryer) deteriorated as the time of scouring increased. Whiteness and residual con taminants were also linearly correlated for wool scoured by a Lo-flo system. The whiteness of the product deteriorated slightly as the time of scouring increased; however, the decrease in whiteness could not be attributed to inefficient removal of contaminants as with the commercially scoured samples. The decrease was possibly due to staining of the wool by either the Lo-flo liquor or the alkaline rinse bowl. When the level of residual solvent extractables and ash content was high, a statistically significant correlation existed between both of these contaminants and the whiteness of scoured wool.