Effect of layer (calcium phosphate–chitosan)-by-layer (mesquite gum) matrix on carotenoids-in-water-emulsion properties

Layer-by-layer calcium phosphate (CP)–chitosan (Ch)/mesquite gum (MG) matrixes were designed for protecting and stabilizing red chili oleoresin-in-water emulsions. Potentiometric titration, turbidity and ζ-potential measurements were used for establishing the interaction windows for obtaining CP–Ch complexes. The CP–Ch mass ratio of 1.24 showed the maximum soluble complex formation and a positive charge (∼18.5 mV) for allow the interaction with MG. Then, red chili oleoresin-in-water emulsions were formed by a layer-by-layer deposition of MG/CP–Ch complexes (C/WRMG/CP–Ch). The results show that high mass ratio of MG was required to form a dense interfacial layer to improve the stability of the system. The droplet size distribution remained unchanged up to 720 h. Rheological measurements of C/WRMG/CP–Ch indicate that both, the storage (G′) and loss (G″) moduli showed increasing values with frequency (∼0.4–11.0 Hz) independently of shear strain applied (1, 5, 10%), attributed to the formation of MG/CP–Ch interlinked network in the continuous phase. The emulsion providing best stability and protection against carotenoid degradation was that made with CP–Ch mass ratio of 1.24 and MG/CP–Ch mass ratio of 10. The mean half-time life of the C/W10 was 502 days compared to 0.24 days for the free unprotected carotenoids.