Pickering emulsions stabilized by whey protein nanoparticles prepared by thermal cross-linking

• Published in: Colloids and surfaces, B, Biointerfaces Vol. 127; pp. 96 - 104
• Main Authors: Wu, Jiande, Shi, Mengxuan, Li, Wei, Zhao, Luhai, Wang, Ze, Yan, Xinzhong, Norde, Willem, Li, Yuan
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.03.2015
• Subjects: Cross-Linking Reagents - chemistry; Emulsions - chemistry; Heat-resistant protein particles; Hydrogen-Ion Concentration; Microscopy, Confocal; Nanoparticles - chemistry; Oils - chemistry; Osmolar Concentration; Pickering emulsions; Static Electricity; Temperature; Thermal cross-linking; Water - chemistry; Wettability; Whey protein nanoparticle; Whey Proteins - chemistry; Heat-resistant protein particles; Thermal cross-linking; Pickering emulsions; Whey protein nanoparticle
• ISSN: 0927-7765; 1873-4367
• DOI: 10.1016/j.colsurfb.2015.01.029

•It is the first study of thermal cross-linked WPI NPs in Pickering emulsions.•Heat-resistant WPI NPs allow their use in applications requiring heat treatment.•WPI NPs have good partial wetting properties for stabilizing o/w emulsions.•WPI NPs can produce stable o/w emulsions at pH above and below the WPI NP's pI. A Pickering (o/w) emulsion was formed and stabilized by whey protein isolate nanoparticles (WPI NPs). Those WPI NPs were prepared by thermal cross-linking of denatured WPI proteins within w/o emulsion droplets at 80°C for 15min. During heating of w/o emulsions containing 10% (w/v) WPI proteins in the water phase, the emulsions displayed turbid–transparent–turbid phase transitions, which is ascribed to the change in the size of the protein-containing water droplets caused by thermal cross-linking between denatured protein molecules. The transparent stage indicated the formation of WPI NPs. WPI NPs of different sizes were obtained by varying the mixing speed. WPI NPs of 200–500nm were selected to prepare o/w Pickering emulsions because of their good stability against coalescence. By Confocal Laser Scanning Microscopy, it was observed that WPI NPs were closely packed and distributed at the surface of the emulsion droplets. By measuring water contact angles of WPI NPs films, it was found that under most conditions WPI NPs present good partial wetting properties, but that at the isoelectric point (pI) and high ionic strength the particles become more hydrophobic, resulting in less stable Pickering emulsion. Thus, at pH above and below the pI of WPI NPs and low to moderate ionic strengths (1–10mM), and with a WPI NPs concentration of 2% (w/v), a stable Pickering emulsion can be obtained. The results may provide useful information for applications of WPI NPs in environmentally friendly and food grade applications, notably in food, pharmaceutical and cosmetic products.