In this article we show how various degrees of glycosylation can be used to control the thermal stability of proteins. The primary amines of beta-lactoglobulin were glycosylated with glucose or fructose within a range of non-denaturing reaction parameters. The modified fractions were characterized and analyzed for structural stability and hydrophobic exposure. The modification procedure gave rise to the production of glycoproteins with a well-defined Gaussian distribution, where glucose appeared more reactive than fructose. The integrity of the secondary, tertiary, and quaternary structures remained unaffected by the modification procedure. However, upon heating the stability of the modified fractions increased up to 6 K. Here we demonstrate the effects on the thermodynamic properties of proteins by glycosylation; this work serves as a first step in understanding and controlling the process underlying aggregation of glycosylated proteins. (C) 2004 Wiley Periodicals, Inc.