Ultrasound-assisted chitosan-based emulsification: Nanoencapsulation of bioactive compounds from Nannochloropsis...

This study evaluated the influence of chitosan protonation state and concentration on the physicochemical, rheological, thermal, and antioxidant properties of chitosan-based emulsions (conventional or Pickering) containing carotenoids from microalgae. The chitosan used had a deacetylation degree of 84.7 ± 2.4 % and molecular weight of 650 ± 28 kDa, favoring electrostatic and hydrophobic interactions. All emulsions formed nanocapsules ranging from 265 to 470 nm. Pickering emulsions showed greater aggregation and lower zeta potential values, leading to reduced colloidal stability compared to conventional systems. Higher chitosan concentrations increased apparent viscosity, especially in Pickering emulsions, which exhibited pseudoplastic behavior. Thermodynamic analysis indicated that flow resistance was associated with strong interfacial interactions. Conventional emulsions exhibited higher enthalpy and glass transition temperatures, suggesting denser polymer networks. Antioxidant activity, assessed by ABTS inhibition, was enhanced in emulsions with higher chitosan content, which showed a delayed release of bioactives compounds over 30 days. This effect could attributed to stronger electrostatic and hydrophobic interactions between chitosan and the carotenoid-rich extract, promoting improved interfacial stabilization and protection of bioactives.