DEVELOPMENT OF HIGH INTERNAL PHASE EMULSION STABILIZED BY SODIUM CASEINATE-QUERCETIN COMPLEXES

The replacement of saturated and trans fats is a current trend in the food industry, since the high consumption of these fats has been related to the emergence of inflammatory and cardiovascular diseases. In this sense, new strategies have been studied to maintain the technological properties provided by these fats, such as the high internal phase emulsions (HIPEs). HIPEs show a dispersion phase above 74 % w/w, which provides interesting characteristics, such as viscosity and texture similar to that provided by saturated fats. In this context, this research aimed to evaluate the production and characterization of oil-in-water HIPEs stabilized with a covalent complex formed by sodium caseinate (SC) and quercetin (Q). The complex between the protein and the phenolic compound, ratio 1:1 (SC:Q), was produced in an alkaline solution (pH 9) and in the presence of oxygen for 24 hours. After this time, the solution containing the complexes was dialyzed and then freeze-dried. The control (SC) was also carried out by the same process; however, without the presence of Q. For the production of HIPEs, aqueous solutions of SC and SC:Q (1.5 and 2.0%w/v) in phosphate buffer (pH7, 10mM) were prepared. Then, this aqueous phase (20%w/w) was homogenized with the dispersed fraction (sunflower oil) using a stator rotor (10,000 rpm) for 3 minutes. The complexes were evaluated by interfacial tension, and the HIPEs characterized by droplet size distribution, microscopy, oxidative and kinetic (Turbiscan-TSI) stability for 45 days at 25 °C. The initial interfacial tension between water and sunflower oil was about 25 mN/m, which reduced to approximately 15 and 14 mN/m with the addition of SC or SC:Q (2% w/v), respectively. Interestingly, it was impossible to incorporate all the oil in the emulsion produced at the lowest concentration of SC, indicating that the SC:Q complex can facilitate the formation of HIPEs. The emulsions showed a bimodal droplet size distribution, with D[4.3] between 13 and 15 µm. However, the peak mode showed no significant difference. The microscopic images of the HIPEs allowed the visualization of the formation of the oil-in-water emulsion and confirmed the presence of droplets of different diameters. During storage, no significant difference was observed in relation to TSI of the HIPEs, indicating a high kinetic stability. In addition, HIPEs produced with a high concentration of complexes showed a slight reduction in the hydroperoxides index after 45 days at 25 °C. That is, depending on the concentration used, it is possible that the complex causes a protective effect against the oxidation of the lipid phase of the emulsion. These results show that the modification of SC with Q can contribute positively to the development of HIPEs, bringing benefits concerning the reduction of lipid oxidation. Furthermore, the kinetic stability of HIPEs makes them quite promising to produce foods with reduced saturated fat content and trans-fat replacement.