Enzymatic Modification of Starch for Surface Sizing

The oldest use of enzymes in the pulp and paper industry is in the modification of starches for surface sizing and coating. This practice dates back to the early 1970s and is now carried out more frequently within the paper mills. Starch imparts many beneficial properties to paper, including strength, stiffness, and erasability. Properly controlled enzymatic modification of starch provides the papermaker ample opportunities to get uniform quality of starch paste, to produce starch paste as per requirement, and to produce quality surface sized papers with the minimum cost of the starch component. Starch modified with alpha-amylase enzyme meets almost all the properties required for surface sizing of writing and printing grades of paper. It does not require much capital investment to switch over from oxidized starch to in situ modification of native starch with enzyme. The process of enzyme modification is applicable to different types of starches although the operating conditions in terms of enzyme dose and reaction time may vary. Enzyme-modified starch is available from starch producers or can be produced on-site at the paper mill using a batch or continuous process.