Encapsulation and release profiles of caffeine from microparticles

The purpose of this study was to encapsulate caffeine in alginate-chitosan cross-linked microparticles enriched with ascorbic acid by applying electrostatic extrusion technique. Three different forms of caffeine were encapsulated: liquid extract of caffeine from the plant guarana (Paullinia cupana), food-grade solid caffeine and analytical-grade caffeine. High performance liquid chromatography (HPLC-PDA) was used to evaluate the release kinetics of caffeine from microbeads in water, while the corresponding antioxidant capacity was evaluated by applying the ABTS radical scavenging assay. Scanning electron microscopy and laser diffraction particle size determination were used to provide information about the physical properties of microparticles. The microbeads encapsulating caffeine were uniformly sized spheres of about 600-800 μm. The encapsulation efficiency of all microparticles ranged between 70-80%. Caffeine was mainly released within 10-15 min, depending on the used caffeine form, while the ascorbic acid was relatively rapidly released from microbeads according to antioxidant capacity exhibited in water. The obtained results suggest that electrostatic extrusion can be applied for the entrapment of caffeine in alginate-chitosan microbeads, while the addition of ascorbic acid further enhances the antioxidant activity of such obtained microcapsules

Chitosan microbeads for encapsulation of thyme (Thymus serpyllum L.) polyphenols

In this work chitosan microbeads were prepared by emulsion technique and loaded with thyme polyphenols by diffusion from an external aqueous solution of Thymus serpyllum L. The effects of concentrations of chitosan (1.5-3% (w/v)) and GA (glutaraldehyde) (0.1-0.4% (v/v)), as a crosslinking agent on the main properties of microbeads were assessed. The obtained microgel beads from similar to 220 to similar to 790 mu m in diameter were exposed to controlled drying process at air (at 37 degrees C) after which they contracted to irregular shapes (similar to 70-230 mu m). The loading of dried microbeads with polyphenols was achieved by swelling in the acidic medium. The swelling rate of microbeads decreased with the increase in GA concentration. Upon this rehydration, thyme polypheriols were effectively encapsulated (active load of 66-114mg GAEg(beads)(-1)) and the microbeads recovered a spherical shape. Both, the increase in the amount of the crosslinking agent and the presence of polyphenols, contributed to a more pronounced surface roughness of microbeads. The release of encapsulated polyphenols in simulated gastrointestinal fluids was prolonged to 3 h

Effects of different carrier materials on physicochemical properties of microencapsulated grape skin extract

The goal of this study was to investigate the characteristics of grape skin extract (GSE) spray dried with different carriers: maltodextrin (MD), gum Arabic (GA) and skim milk powder (SMP). The grape skin extract was obtained from winery by-product of red grape variety Prokupac (Vitis vinifera L.). The morphology of the powders, their thermal, chemical and physical properties (water activity, bulk and tapped densities, solubility), as well as release studies in different pH conditions were analyzed. Total anthocyanin content and total phenolic content were determined by spectrophotometric methods. MD and GA-based microparticles were non-porous and spherical, while SMP-based ones were irregularly shaped. The process of spray drying Prokupac GSE using these three carriers produced powders with low water activity (0.24-0.28), good powder characteristics, high yields, and solubility higher than 90%. The obtained dissolution/release profiles indicated prolonged release of anthocyanins and phenolic compounds in different mediums, especially from GSE/GA microparticles. These results have shown that grape skin as the main by-product of wine production could be used as a source of natural colorants and bioactive compounds, and microencapsulation as a promising technique for the protection of these compounds, their stabilization in longer periods and prolonged release