Microemulsions as nanoreactors to produce whey protein nanoparticles with enhanced heat stability by thermal pretreatment

Native whey proteins (NWPs) may form gels or aggregates after thermal processing. The goal of this work was to improve heat stability of NWPs by incorporating protein solutions in nanoscalar micelles of water/oil microemulsions to form whey protein nanoparticles (WPNs) by thermal pretreatment at 90 degrees C for 20 min. The produced WPNs smaller than 100 nm corresponded to a transparent dispersion. The WPNs produced at NWP solution pH of 6.8 had a better heat stability than those produced at pH 3.5. The salt concentration (0-400 mM NaCl) in NWP solutions did not significantly change the size of corresponding WPNs. Compared to NWPs, the 5% (w/v) dispersion of WPNs at pH 6.8, 100 mM NaCl did not form a gel after heating at 80 degrees C for 20 min. The improved heat stability and reduced turbidity of WPNs may enable novel applications of whey proteins in beverages. (C) 2009 Elsevier Ltd. All rights reserved.