Effect of ultrasounds and ball milling on the bioaccessibility of carotenoids from the microalga Chlorella sorokiniana

The bioaccessibility of Chlorella sorokiniana carotenoids is typically low due to the rigidity of its cell wall. This study evaluated the effect of ultrasound and ball milling (BM) on carotenoid bioaccessibility in wild-type and phytoene-enriched C. sorokiniana in three types of matrices: fresh, freeze-dried, and alginate-encapsulated. The in vitro digestion methodology followed the standardized INFOGEST protocol. Ball milling at 30 Hz significantly improved bioaccessibility in wild-type matrices, whereas milder conditions (BM-5 Hz or USD-30%) were more effective in phytoene-enriched and encapsulated samples. Freeze-drying and encapsulation also improved carotenoid bioaccessibility compared to fresh biomass. The addition of yogurt (10% fat) increased the incorporation of carotenoids into micelles, particularly the highly hydrophobic ones α- and β-carotene. Furthermore, the cis isomers showed greater bioaccessibility than their trans counterparts. These results highlight the importance of applying disruption treatments, encapsulation, or fat-addition to improve the bioaccessibility and bioavailable content of microalgal carotenoids.