High internal phase Pickering emulsion stabilized by thermally treated quinoa protein isolate: Improved stability and bioaccessibility of curcumin and astaxanthin

High internal phase Pickering emulsions (HIPPEs) were stabilized by thermally treated quinoa protein isolate (QPI), including atmospheric pressure boiling (AB), high pressure boiling (HPB), and baking (B), respectively, for the encapsulation of curcumin (CUR) and astaxanthin (AST) to retard its degradation during storage and improve their bioaccessibility. The QPI dispersion was sonicated to generate nanoparticles for the production of HIPPEs. Thermal treatments caused the reduction in the particle size and increased water contact angle compared to the control QPI nanoparticles, and further improving the emulsion properties of QPI. The microstructure results further supported the nature of oil-in-water of HIPPEs stabilized by QPI nanoparticles by showing that the nanoparticles formed a tight interfacial film and closely coated the surface of oil droplets. Thermal treatment reduced the droplet size by approximately 11%, 15%, and 3% for HIPPEs stabilized by AB-QPI, HPB-QPI, and B-QPI, respectively, compared to those of control QPI, which effectively improved the emulsion's viscoelasticity and storage stability. Retention rate and bioaccessibility of CUR and AST in HIPPEs were improved compared to the encapsulation by corn oil, showing HPB-QPI > AB-QPI > B-QPI > control QPI. HIPPEs stabilized by thermally treated QPI-protected lipophilic bioactive compounds and were beneficial for the advancement of functional foods based on QPI.

Practical Application

The emulsifying properties of QPI nanoparticles were significantly improved after thermal treatment. High internal phase Pickering emulsion stabilized by thermally treated QPI nanoparticles significantly improved the stability and bioaccessibility of curcumin and astaxanthin. It provides a theoretical basis for utilizing thermally treated QPI nanoparticles as emulsifiers in delivery systems, broadening the development of curcumin and astaxanthin in the food and pharmaceutical fields.