Physical and oxidative stability of high fat omega-3 PUFA delivery oil-in-water emulsions stabilized with modified phosphatidylcholine and oil-water interface characteristics of a model emulsion system using small angle X-ray and neutron scattering techniques
We have investigated the effects of modified phosphatidylcholine (PC) with different alkyl chain lengths (PC_C14 and PC_C16) and covalently attached caffeic acid on the physical and oxidative stability of 70% fish oil-in-water emulsions. Modified PCs were used in combination with sodium caseinate (CAS) and soy-PC. Physical stability of the emulsions improved with increasing concentrations of modified PCs, due to their high surface activity. PC_C14 led to smaller droplets and higher viscosity, whereas PC_C16 had higher protein surface load, which indicated a thicker interfacial layer. Due to the attachment of caffeic acid, which brings the antioxidant near the interface, modified PCs enhanced the oxidative stability of the emulsions compared to emulsions with PC and free caffeic acid. PC C16 led to higher oxidative stability compared to PC C14, mainly explained by provision of a thicker interfacial layer. Additionally, interfacial structure of 70% fish oil-in-water emulsions stabilized with combinations of CAS and soy-PC was investigated using small angle X-ray and neutron scattering techniques. In water, CAS formed aggregates with the hard sphere diameter of 20.4 nm, whereas PC appeared as multilayers whose coherence length spanned from 40 to 100 nm. In emulsion, PC monolayer separated oil and water phases and 80% CAS particles were loosely bound to the interface forming a laterally heterogeneous interface. The distance between aggregated CAS particles in emulsion increased compared to CAS in water. PC multilayers became larger in the presence of oil-water interface compared to PC in water and the bilayers became larger with increasing PC concentration.