Date of Award


Degree Name

Bachelor of Science


Pulp and Paper Technology


The objective of this study was to explore the use of enzyme conversion as a method of reducing the viscosity of casein without substantially affecting its adhesive strength. By doing so casein could be made applicable for use in high-solids coatings, where both low coating viscosity and high adhesive strength as desirable.

With this objective in mind casein samples were hydrolized to different degrees using enzymes, and the strength and viscosity properties of the adhesive were studied. Coatings were prepared at various solids contents using the converted casein as the coating adhesive. The viscosities of the coatings were measured, and the coating strengths were predicted on the basis of previous results.

It was found that the adhesive strength of the casein decreases in proportion to the amount of enzyme used to hydrolyze the sample. On the other hand, the strength of the casein decreases at an increasing rate with respect to viscosity, as the extent of hydrolysis is increased. In both instances, relationships are apparent over a small conversion range.

When hydrolyzed casein is incorporated in coatings of various solids contents, the reductions in coating viscosity with increased casein hydrolysis are even less apparent, while the coating strength decreases rapidly. Suitable coatings can be prepared at from 45% to 48% solids. Hence, it appears that enzyme hydrolysis is not a practical method of rendering casein adhesives suitable for use in high-solids paper coatings, where good strength is important.