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

Abstract

Omega-3 (-3) polyunsaturated fatty acids are highly susceptible to oxidation, have an intense odour and poor water solubility, which makes its direct application in foods extremely difficult. In order to reduce its oxidation process and improve the stability in an aqueous medium, protein-based nanoemulsions were produced and characterized. Lactoferrin (Lf) was used as a 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 -3 encapsulated. Nanoemulsions were characterized by physical and chemical stability at 4 and 25 °C. Results obtained revealed that Lf concentration influence the nanoemulsion size in which higher Lf concentrations decrease nanoemulsion size. It was also observed that nanoemulsions are physically stable when stored at 4 °C for 69 days while at 25 °C showed instability. The radical scavenging capacity of the nanoemulsions did not show significative changes over storage at 4 and 25 °C while a significative increase in oxidation was registered. Release profile at 37 °C showed that -3 had a slow release 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 g/mL of -3 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. FTIR-ATR, Raman spectroscopy and Circular Dichroism (CD) showed Lf structural changes after drying processes. This work provides important information regarding nanoemulsions design and drying technologies aiming the encapsulation of lipophilic compounds for pharmaceutical and food applications.