Polymerization and gelation of thiolated β-lactoglobulin using potassium iodate as oxidizing agent were investigated. At least 8 sulphydryl groups per dimer of thiolated β-lactoglobulin were required using a 5% protein solution to obtain primarily polymers with MW of >600 000. Thiolated β-lactoglobulin with >18 sulphydryl groups per dimer (80% thiolation) formed strong gels instead of soluble polymers at a concn. of 5% with potassium iodate at room temp. The gelation time was <30 s and the gel formation was independent of pH over a range of 6.0 to 10. The gel was transparent and not dispersed when heated at 100°C for >30 min.