Whey proteins are used in a wide range of food products because of their high nutritional value and the ability to contribute to the unique functional properties of the final products. The functional properties of whey proteins are affected not only by the whey origin, season dependent variations of protein and non-protein components amount, but also by the conditions of processes involved in their isolation, purification and modification (temperature, pH, pressure, chemicals). In this research, tribomechanical micronization (TM) was used as a technique that could be useful in modification of some functional properties of whey proteins. Therefore, two different commercial powdered whey protein isolates (WPI) were used for analysis. Surface hydrophobicity and emulsifying properties (emulsifying activity and emulsion stability) were determined before and after TM treatment. The results obtained showed increases in surface hydrophobicity of WPI after TM treatment indicating that TM could induce changes of protein conformation and increase exposure of the previously buried hydrophobic regions. Emulsions prepared with tribomechanically treated WPI showed higher emulsion activity and better emulsion stability. The results obtained suggest that TM can be useful and fast process technique for improvement of functional properties of WPI.Proteini sirutke upotrebljavaju se u velikom broju prehrambenih proizvoda zbog njihove visoke nutritivne vrijednosti i jedinstvenih funkcionalnih svojstava. Funkcionalna svojstva proteina sirutke ovise ne samo o podrijetlu sirutke, sezonski ovisnih količina proteinskih i neproteinskih komponenti, već i o uvjetima procesa koji su uključeni u njihovu izolaciju, pročišćavanje i modifikaciju (temperatura, pH, tlak, kemijski dodaci). U ovom radu, tribomehanička mikronizacija (TM) je korištena kao potencijalna tehnika za unapređenje pojedinih funkcionalnih svojstava proteina sirutke. Analizirana su dva različita komercijalna izolata proteina sirutke u prahu (WPI). Površinska hidrofobnost i emulgirajuća svojstva (sposobnost stvaranja emulzija i stabilnost emulzije) određena su prije i poslije TM obrade. Dobiveni rezultati su pokazali povećanje površinske hidrofobnosti WPI nakon TM obrade što ukazuje na činjenicu da TM može izazvati konformacijske promjene proteina i povećati izloženost prethodno skrivenih hidrofobnih područja. Emulzije pripremljene s tribomehanički obrađenim WPI pokazale su veću aktivnost i bolju stabilnost emulzija. Dobiveni rezultati ukazuju da TM može biti učinkovita tehnika za poboljšanje funkcionalnih svojstava WPI
