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.
