Abstract: A process for the preparation of stabilized glycoproteins without the introduction of foreign molecules. Susceptible monosaccharides covalently attached to the protein part of the molecule undergo periodate oxidation and, after elimination of the remaining periodate, the oxidized glycoprotein is incubated in a buffer under conditions favorable for the reaction between the aldehyde groups generated in the sugar part and the amino acid residues from the protein part. The oxidized carbohydrate chains act as a polyaldehyde crosslinker, with the cross-linking reaction producing intramolecularly and intermolecularly linked derivatives. The amount and size of the intermolecularly linked derivatives are controlled by degree of oxidation and protein concentration. The thermal stability, depends on the degree of oxidation and under optimal conditions is about 10 times better than the stability of native invertase.