Encapsulation of bixin in sodium caseinate to deliver the colorant in transparent dispersions

Bixin, the major colorant component of annatto, is water insoluble and sensitive to degradation by temperature, pH, and light stresses. In this work, we studied an encapsulation process by spray drying warm 40% v/v aqueous ethanol solution with dissociated sodium caseinate (NaCas) and dissolved bixin. Upon hydration of spray-dried powder, transparent dispersions were observed at a wide pH range away from the isoelectric point (pI) of NaCas. The stability of bixin was much improved and the consistent yellow color was obtained. The volume–length mean particle diameters of capsules were around 250 nm in dispersions, slightly bigger than that of NaCas, based on dynamic light scattering, but the difference was not observed based on atomic force microscopy. Capsules and the mixture of NaCas and bixin showed different fluorescence and FTIR spectra. At pH near the pI of casein, soluble soybean polysaccharides adsorbed strongly onto capsules and stabilized them from aggregation. The simple encapsulation approach studied in the present work showed a promising process to enhance the stability and dispersibility of carotenoids using NaCas as a carrier, especially in transparent dispersions.

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► Powdered bixin was prepared by spray drying warm aqueous ethanol solution with caseinate.
► Dispersions with hydrated bixin-loaded capsules were transparent at a wide range pH.
► Encapsulated bixin had improved stability against degradation.
► SSPS prevented the precipitation of bixin-loaded casein particles at acidity near pI of casein.
► AFM and light scattering results suggested strong adsorption of SSPS on casein particles.