Comparative assessment of wall material combinations on the encapsulation of astaxanthin-rich weakened Haematococcus pluvialis

The encapsulation of the Haematococcus pluvialis ( Hp ), a primary natural source of astaxanthin (ASX), is a promising strategy to reduce degradation and enhance bioaccessibility. This study evaluated the effects of alginate (ALG) combined with one of five wall materials: gum arabic (GA), lecithin (LEC), maltodextrin (MD), pectin (PEC), and whey protein concentrate (WPC) on the properties of hydrogels containing weakened Hp ( Hp w) via ionic gelation. Encapsulation efficiency (97.05 - 98.52%) and loading capacity (32.46 - 32.95%) were highest in ALG-WPC- Hp w. Colorimetric analysis revealed significantly more intense coloration in ALG-WPC- Hp w. Confocal microscopy showed homogenous Hp w distribution, rough textures, variable porosity and crack-free surfaces while FTIR spectroscopy and DSC confirmed successful encapsulation of Hp w. While all the wall material combinations enhanced thermal stability of Hp w by shifting the endothermic peak to higher temperatures, the impact of ALG-WPC was particularly intense. Although antioxidant activity slightly declined post-encapsulation, DPPH scavenging remained concentration dependent. ALG-LEC- Hp w exhibited the highest ASX bioaccessibility. All hydrogels retained ≥96% ASX at 4°C and ≥93% at 25°C during 28 days of storage, with ALG-WPC- Hp w demonstrating the highest retention. These findings highlight the influence of carrier combinations for efficient ASX delivery in food, nutraceutical, and feed applications. • Hydrogels had high encapsulation efficiency, with ALG-WPC- Hp w being the highest • Hp w hydrogels retained high antioxidant activity • ALG-WPC- Hp w showed the highest ASX retention during storage • Encapsulation improved ASX bioaccessibility, with ALG-LEC- Hp w showing the highest • Hydrogels displayed rough, fissure-free surfaces with varying porosity