Stability of protein-stabilised β-carotene nanodispersions against heating, salts and pH

BACKGROUND: Milk proteins are used in a wide range of formulated food emulsions. The stability of food emulsions depends on their ingredients and processing conditions. In this work, beta-carotene nanodispersions were prepared with selected milk-protein products using solvent-displacement method. The objective of this work was to evaluate the stability of these nanodispersions against heating, salts and pH. RESULTS: Sodium caseinate (SC)-stabilised nanodispersions possessed the smallest mean particle size of 17 nm, while those prepared with whey-protein products resulted in larger mean particle sizes (45-127 nm). Formation of large particles (mean particle size of 300 nm) started after 1 h of heating at 60 degrees C in nanodispersions prepared with SC. More drastic particle size changes were observed in nanodispersions prepared with whey protein concentrate and whey protein isolate. The SC-stabilised nanodispersions were fairly stable against Na+ ions at concentrations below 100 mmol L-1, but drastic aggregation occurred in >= 50 mmol L-1 CaCl2 solutions. Aggregation was also observed in whey protein-stabilised nanodispersions after the addition of NaCl and CaCl2 solutions. All sample exhibited the smallest mean particle size at neutral pH, but large aggregates were formed at both ends of extreme pH and at pH around the isoelectric point of the proteins. CONCLUSION: The nanodispersions prepared with SC were generally more stable against thermal processing, ionic strength and pH, compared to those prepared with whey proteins. The stable beta-carotene nanodispersions showed a good potential for industrial applications. (C) 2008 Society of Chemical Industry.