Food-grade Pickering emulsion as a novel astaxanthin encapsulation system for making powder-based products: Evaluation of astaxanthin stability during processing, storage, and its bioaccessibility

The use of astaxanthin as a food ingredient is limited due to its poor water solubility in aqueous matrices and highly susceptibility to oxidation; hence microencapsulation of this carotenoid is an appropriate technique to increase its stability and functionally. In this study, astaxanthin oleoresin was encapsulated using a food-grade Pickering emulsion to enhance its stability during spray-drying and storage and its bioaccessibility. The oil-in-water (O/W) emulsions were stabilized by protein-based aggregates obtained from a lupin protein-rich cultivar (AluProt-CGNA). The emulsions containing the astaxanthin microencapsulated in its oil phase (core material) were submitted to a spray-drying process at 160 °C and 140 °C. For this, blends of these protein-based aggregates (LP-APs) and maltodextrin (at different ratios) were used as wall material. The emulsion stability, microstructure, powder characteristics, oxidative stability and concentration of astaxanthin, encapsulation efficiency and bioaccessibility after spray-drying were investigated. The results showed that LP-APs exhibit a great potential to perform as stabilizers for Pickering emulsions. The formed O/W emulsions were highly stable against creaming at high concentrations of LP-APs. The results also indicated that spray-drying can be applied to prepare stable astaxanthin emulsions into powders with good oxidative stability. The astaxanthin content in dry emulsions under storage conditions (25 and 45 °C for 4 weeks) was higher in powders containing a higher LP-APs concentration. The encapsulation efficiency was higher than 90% with the emulsion stabilized with 6% of LP-APs. The bioaccessebility of reconstituted astaxanthin powder (with 6% LP-APs) was around 80%.