Microencapsulation of astaxanthin by ionic gelation: effect of different gelling polymers on the carotenoid load, stability and bioaccessibility

Astaxanthin (ASX) is a carotenoid characterised by numerous health-promoting properties but biased by scarce chemical stability. Our aim was to microencapsulate ASX through ionic gelation to improve its stability and bioaccessibility, evaluating the performance of low-methoxyl pectin (LMP) and chitosan, besides the most common alginate. Three formulations were tested: 3% pectin (Pec), 3% pectin + chitosan shell (PecChi), and 1.5% alginate - 1.5% LMP + chitosan shell. The results showed that chitosan deposited onto PecAlChi and PecChi beads improved particle sphericity and limited oil oxidation during processing. PecAlChi provided the highest encapsulation efficiency (87%) and bioaccessibility (58%). The stability test at 65 °C x 24 days showed different polymer-dependent degradation kinetics, with PecChi providing the highest stability (48%). In conclusion, encapsulation performance strongly depended on the chitosan shell and the gelling polymers. This suggests that tuning the alginate/pectin ratio may lead to the best compromise between stability and bioaccessibility