engleski

Encapsulation of thyme (Thymus serpyllum L.) aqueous extract in Ca-alginate beads

Encapsulation of Thymus serpyllum L. aqueous extract within Ca-alginate beads was studied in order to produce dosage formulations containing polyphenolic compounds. Electrostatic extrusion was applied for encapsulation of thyme aqueous extract in alginate gel beads. In addition to hydrogel beads, heat-dried and freeze-dried forms of beads were examined. Encapsulation systems were examined and compared in order to choose the optimal one with respect to entrapment efficiency, preservation of antioxidant activity and thermal behavior under heating conditions simulating the usual food processing. The obtained beads with approximately 2 mg g-1 of gallic acid equivalents encapsulated in 0.015 g mL-1 of alginate were uniformly sized spheres of about 730 μm. Encapsulation efficiency varied in the range 50-80 % depending on the encapsulation method. Besides, the analysis reveals that the encapsulation process and the material used did not degrade the bioactive compounds, as the total antioxidant content remained unchanged. This was verified by the FTIR analysis proving the absence of chemical interactions between extract compounds and alginate. Addition of a filler substance such as sucrose and inulin in the dried product reduced its collapse and roundness distortion during drying process. This study demonstrates the potential of using hydrogel material for encapsulation of plant poplyphenols to improve their functionality and stability in food products.

microencapsulation; Ca-alginate microbeads; polyphenols; electrostatic extrusion

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