Lactoferrin-based nanoemulsions to improve the physical and chemical stability of omega-3 fatty acids

Abstract

Omega-3 (ω-3) polyunsaturated fatty acids are highly susceptible to oxidation and have an intense odour and poor water solubility, which make their direct applications in foods extremely difficult. In order to reduce their oxidation process and improve their stability in aqueous medium, protein-based nanoemulsions were produced and characterized. Lactoferrin (Lf) was used as an emulsifier at different concentrations (0.2% to 4% w/w). High energy methods (Ultra-Turrax and high-pressure homogenizer) were applied to produce Lf-based nanoemulsions with ω-3 PUFAs encapsulated. The nanoemulsions were characterized in terms of physical and chemical stability at 4 and 25 °C. The results obtained revealed that the Lf concentration influences the nanoemulsion size in a manner that higher Lf concentrations decrease the nanoemulsion size. It was also observed that the nanoemulsions are physically stable when stored at 4 °C for 69 days while at 25 °C they showed instability. The radical scavenging capacity of the nanoemulsions did not show significant changes over storage at 4 and 25 °C while a significant increase in oxidation was observed. The release profile at 37 °C showed that ω-3 PUFAs were slowly released at pH 2 but was rapidly released at pH 7.4 from Lf nanoemulsions. Moreover, MTT assay revealed that 2% (w/w) Lf nanoemulsions with 12.5 μg mL⁻¹ ω-3 PUFAs were not cytotoxic to Caco-2 cells. Nanoemulsions with high physical and chemical stability were selected and dried by two different methodologies: freeze-drying and nano spray-drying. ATR-FTIR spectroscopy, Raman spectroscopy and Circular Dichroism (CD) showed Lf structural changes after the drying processes. This work provides important information regarding nanoemulsions’ design and drying technologies aiming at the encapsulation of lipophilic compounds for pharmaceutical and food applications.