Rheological and microstructural properties of cold-set emulsion gels fabricated from mixed proteins: Whey protein and lactoferrin.

Cold-set emulsion gels were fabricated from oil droplets coated by mixed proteins: whey protein and lactoferrin. The impact of protein composition, droplet concentration, pH, and ionic strength on the microstructure, texture, and stability of the cold-set emulsion gels was determined. Protein composition had a major influence on gel strength, with the strongest emulsion gels being formed at an optimized protein composition (0.5 wt% whey protein and 1.5 wt% lactoferrin). The storage modulus of the emulsion gels increased from 149 to 1590 Pa as the droplet concentration increased from 10 to 40 wt%. The gel strength could also be modulated by adjusting pH, with the strongest gels being formed at pH = 6.5, where the net charge on the droplets was neutral. Increasing the ionic strength weakened the electrostatic interactions, which inhibited droplet aggregation and led to a decrease in gel strength. These results may be useful for designing cold-set emulsion gels with rheological properties that can be tailored for specific commercial products.

Enhancement of the solubility, stability and bioaccessibility of quercetin using protein-based excipient emulsions.

Emulsion-based excipient foods were developed to improve the bioaccessibility of an important hydrophobic nutraceutical: quercetin. Protein-stabilized oil-in-water excipient emulsions were prepared using sodium caseinate, whey protein isolate, or soy protein isolate as an emulsifier. These emulsions were then mixed with powdered quercetin and heated to simulate a cooking process. The excipient emulsions had relatively small droplet sizes (d < 270 nm) and remained stable against coalescence after exposure to boiling (100 °C for 60 min). In particular, casein was shown to be better at adsorbing to oil-water interface and contributed to a more stable interfacial layer than the other two proteins. Quercetin was solubilized in the emulsions during heating, which may be attributed to dissolution in the oil phase and complexation with proteins. There were appreciable differences in quercetin bioaccessibility in excipient emulsions stabilized by different emulsifiers (≈74% for casein, 54% for whey protein, 22% for soy protein, and 58% for Tween). This study suggests that milk proteins may be natural alternatives to synthetic surfactants for forming stable excipient emulsions capable of enhancing nutraceutical bioaccessibility.