Physicochemical properties of β-carotene emulsions stabilized by chitosan–chlorogenic acid complexes

• Chitosan formed covalent complex with chlorogenic acid (CA) successfully.
• The emulsion stabilized by chitosan–CA covalent complex had the smallest droplet size.
• The emulsion prepared by chitosan–CA covalent complex exhibited higher interfacial accumulation of CA.
• β-Carotene emulsion stabilized by chitosan–CA covalent complex exhibited the best physical stability.
• The degradation of β-carotene in emulsions was effectively inhibited by chitosan–CA covalent complex.

The objectives of the present study were to first synthesize chitosan–chlorogenic acid (CA) covalent complex and finally evaluate the ability of chitosan–CA covalent complex and physical complex in stabilizing a model β-carotene emulsion. Chitosan–CA covalent complex was synthesized according to carbodiimide-mediated coupling method. Data of proton nuclear magnetic resonance (1H NMR) indicated that chitosan formed covalent complex with CA successfully. Afterward, the research was focused on testing chitosan–CA complexes in stabilizing β-carotene emulsions. Mean droplet size of emulsion coated by chitosan–CA covalent complex was 364.3 ± 0.8 nm, which was the smallest among all investigated emulsions. In comparison with emulsions stabilized by control chitosan and chitosan–CA physical complex, the emulsion coated by chitosan–CA covalent complex had higher viscosity. Besides, interfacial concentration fraction of CA in the emulsion coated by chitosan–CA covalent complex and the emulsion stabilized by chitosan–CA physical complex was (73.7 ± 4.3)% and (44.9 ± 2.4)%, respectively. The physicochemical stabilities of the emulsion stabilized by chitosan–CA covalent complex were the best among all emulsions.