Enzyme treatments of the dissolved and colloidal substances present in mill white water and the effects on the resulting paper properties

The composition of the dissolved and colloidal fractions of a "model" white water prepared from a spruce-pine-fir/hemlock thermomechanical pulp was de termined. The impact of these fractions on paper properties was assessed an d the ability of enzymes to degrade the different components was investigat ed. The colloidal particles in the white water had an average size of 0.5 m u m and a size range from 0.1 mu m to 2 mu m Lignins, resin and fatty acids , and esterified extractives, such as sterol esters and triglycerides, were the main constituents of the colloidal particles, while the lignans and ne utral polysaccharides were predominantly dissolved in the white water. Redu ctions in paper strength were mainly caused by the dissolved substances, wh ereas the colloidal substances were primarily responsible for the reduction in paper porosity and optical properties. Added laccases were able to degr ade most of the extractives while lipases specifically hydrolyzed esterifie d extractives present in the colloidal fraction.