Estabilização de emulsões de óleo de chia em água utilizando nanopartículas de concentrado proteico de soro do leite

Abstract

Emulsions are thermodynamically unstable or metastable multiphase systems that require agents to promote their stabilization. Nanoparticles (NPs) can be used to stabilize emulsions, as is the case with Pickering emulsions. In these emulsions, stabilization occurs through solid particles rather than surfactants, as in a conventional emulsified system. The formulation of food products containing oils stabilized by solid nanoparticles aligns with the demand for healthier, additive-minimized foods. A promising option for producing solid particles for this purpose is whey protein concentrate (WPC). However, studies aimed at evaluating the potential for stabilizing food oil emulsions require further investigation. This study aimed to obtain WPC NPs with and without the addition of cross-linking agents (citric acid and tannic acid) and study the application of these NPs in Pickering emulsion stabilization. It was found that tannic acid was the cross-linking agent that promoted the highest degree of cross-linking (96.9±2.96%), which may be associated with a higher number of hydroxyl groups present in it. As for the characterization of NPs, they exhibited spherical shapes with similar sizes among the sample groups. Ultrasonication for 1 minute did not influence their characteristics. Unlike pH (in the range of 2-9), which affected diameter, polydispersity index (PDI), and zeta potential of the samples, larger sizes were observed across the entire pH range in samples cross-linked with tannic acid. An increase in alkalinity resulted in more negative surface charges for all samples. The addition of NaCl (0.1-0.6 mol/L) also led to changes in the nanoparticles, with a higher salt concentration reducing the magnitude of the zeta potential, indicating lower stability. Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed bands indicating cross-linking of the samples. Subsequently, Pickering emulsions were prepared with different NP concentrations (0.1, 0.5, 1, and 2%) and oil ratios (80:20, 50:50, and 20:80 water-to-oil), with microscopy and rheology assessed immediately after formulation. The macroscopic stability was evaluated over 9 days. Rheological analyses indicated that the samples exhibited nonNewtonian pseudoplastic behavior, as viscosity decreased with increasing shear rate. Emulsions with the addition of nanoparticles showed higher viscosity compared to samples without nanoparticles. It was observed that tannic acid-cross-linked nanoparticles provided good storage stability for emulsions with an 80:20 (water-to-oil) fraction and at concentrations of 2% and 1%, as there was no macroscopic separation during the 9-day evaluation period. The results indicated that the produced nanoparticles have emulsifying capacity, encouraging further research on their use in the production of food emulsions.