Protein-stabilized nanoemulsions and emulsions: comparison of physicochemical stability, lipid oxidation, and lipase digestibility.
The properties of whey protein isolate (WPI) stabilized oil-in-water (O/W) nanoemulsions (d(43) ≈ 66 nm; 0.5% oil, 0.9% WPI) and emulsions (d(43) ≈ 325 nm; 0.5% oil, 0.045% WPI) were compared. Emulsions were prepared by high-pressure homogenization, while nanoemulsions were prepared by high-pressure homogenization and solvent (ethyl acetate) evaporation. The effects of pH, ionic strength (0-500 mM NaCl), thermal treatment (30-90 °C), and freezing/thawing on the stability and properties of the nanoemulsions and emulsions were compared. In general, nanoemulsions had better stability to droplet aggregation and creaming than emulsions. The nanoemulsions were unstable to droplet flocculation near the isoelectric point of WPI but remained stable at higher or lower pH values. In addition, the nanoemulsions were stable to salt addition, thermal treatment, and freezing/thawing (pH 7). Lipid oxidation was faster in nanoemulsions than emulsions, which was attributed to the increased surface area. Lipase digestibility of lipids was slower in nanoemulsions than emulsions, which was attributed to changes in interfacial structure and protein content. These results have important consequences for the design and utilization of food-grade nanoemulsions.
Institute of Food, Nutrition and Human Health, Massey University, Auckland, New Zealand.
Sung Je
SJ
Lee
Seung Jun
SJ
Choi
Yan
Y
Li
Eric Andrew
EA
Decker
David Julian
DJ
McClements
D000818:Animals; D055598:Chemical Phenomena; D004655:Emulsions / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008049:Lipase / Q000737:chemistry*; D008055:Lipids / Q000737:chemistry*; D008894:Milk Proteins / Q000737:chemistry*; D009994:Osmolar Concentration; D010084:Oxidation-Reduction; D055550:Protein Stability; D013552:Swine; D013696:Temperature; D000067816:Whey Proteins
D004655:Emulsions; D008055:Lipids; D008894:Milk Proteins; D000067816:Whey Proteins; D008049:Lipase