Lipid nanoparticles as vitamin matrix carriers in liquid food systems: On the role of high-pressure homogenisation, droplet size and adsorbed materials

Twelve oil-in-water nano-emulsions were prepared using a melt high-pressure homogenisation process (HPH) at 300, 800 or 1200 bar. The resulting emulsions containing 20 wt% palm oil in the absence or presence of α-tocopherol were stabilised by whey proteins alone or in mixture with lecithin. Lipid nanoparticles in these emulsions were characterized for their particle size, surface charge and protein surface concentration (PSC) in relation to their stability against aggregation and coalescence, and to their ability for encapsulation and protection of α-tocopherol against chemical degradation. Increasing HPH values were accompanied by the formation of lipid nanoparticles with decreasing size and PSC, but increasing long-term stability against aggregation and coalescence in parallel with an increase in α-tocopherol degradation (up to 15 wt% for 1200 bar). Presence of α-tocopherol, led to increasing (or decreasing) PSC values with increasing (or decreasing) HPH values for lipid nanoparticles stabilised by proteins alone (or in mixture with lecithins). In addition to these structural properties, the ability for α-tocopherol long-term stability of nanoparticles in emulsions was shown to differ more depending on their adsorbed materials (protein alone, or in mixture with lecithin) than on their particle size values. After 2 months storage, α-tocopherol in emulsions prepared at 300, 800 or 1200 bar was protected against chemical degradation at 79, 77, 67 wt%, respectively, when whey proteins were used alone, instead of 66, 63, 48 wt% when proteins were used in mixture with lecithins. These results indicated the dominant role of adsorbed proteins on the protection of vitamin models by nanoemulsions. They are of a great technological importance for production of lipid nanoparticles presenting a high volume-to-diameter ratio values and consequently high exchange surfaces between the matrix carrier and water and oxygen environmental factors.