Stability of Whey Protein Nanoparticles at Various Protein Concentrations

Background: Different pH, temperature, protein concentration and presence of ions such as calcium and sodium can easily affect functional properties and size of protein nanoparticles. This study determined the stability of whey protein nanoparticles at various protein concentrations. Methods: Whey protein isolate (WPI) nanoparticles with controlled size were produced by pH cycling and different concentration of CaCl2. After preparation, the samples were diluted 1 to 1 and 1 to 3 with water and stored at 4° C for 1, 15 and 28 days. The particle size, optical density of nanoparticle dispersions were investigated after one day. Stability of nanoparticles also had been evaluated during 28 days at 4° C. Results: The size of nanoparticles can be controlled by adding different amount of CaCl2 , and adjusting pH or aging time of WPI solution before ultrasonication. There was no significant difference between nanoparticles at protein concentrations of 0.5 and 1%, but at 2% protein concentration, the nanoparticles were larger. Conclusion: Size of all of WPI nanoparticles was reduced one day after preparation; but, there was no noticeable change during 28 days.