Diffusion of polyphenols from alginate, alginate/chitosan, and alginate/inulin particles

Thymus serpyllum L (thyme) aqueous extract was encapsulated within three different types of particles. Thus, electrostatic extrusion was applied to obtain alginate, alginate/chitosan, and alginate/inulin particles with encapsulated extract which is known as a rich source of polyphenolic compounds. The effect of admixed chitosan and inulin was evaluated from the point of polyphenols release by using Franz diffusion cell. The alginate/chitosan particles exhibited the effective diffusion coefficient of 1.94·10⁻⁹ ·m² s⁻¹ which was about 2.7 times lower in comparison to that of alginate/inulin particles and about 6.3 times lower than the effective diffusion coefficient of plain alginate particles. Swelling studies also confirmed decreased permeability of composite particles compared to plain alginate particles. In addition, according to the Korsmeyer–Peppas model, the composite particles exhibited anomalous diffusion of polyphenols controlled by molecular diffusion and polymer relaxation. PRACTICAL APPLICATIONS: The calcium alginate particles are meant for delivery of biologically active compounds in foods with added value. Coating of alginate particles using chitosan has been investigated to control release of encapsulated biologically active compounds, but also as an improver of the particles structure.