Analysis of the Adsorption and Release Processes of Bioactives from Lamiaceae Plant Extracts on Alginate Microbeads

Abstract

Microencapsulation is a frequently used method for protection of functional properties of bioactives. In this study, alginate was used for microencapsulation of the bioactives from five Lamiaceae family plants: lavender, lemon balm, peppermint, sage, and thyme. Analysis of the adsorption and release processes of Lamiaceae bioactives on alginate microbeads was also performed. Based on the analysis of the extract used for the adsorption process, it was concluded that the highest amount of polyphenols (30% of the polyphenols contained in the extract) was transferred to the microbeads from the thyme extract. Also, a period of bead shrinkage during the adsorption process was detected which lasted until 30 min for thyme, 50 min for lavender, lemon balm, and peppermint, while the shrinkage for the sage extract lasted for 60 min. During the release process, a simultaneous rise of conductivity, total dissolved solids (TDS), polyphenolic (TPC), and antioxidant capacity values in the release media was detected at regular time intervals. The best suited model for the description of the release kinetics was the Korsmeyer-Peppas model, based on which it was concluded that the lemon balm polyphenols entrapped in the alginate matrix were released the fastest (k\u2009=\u20090.326\u2009±\u20090.048 min−1) and that the release was governed by a pseudo-Fickian diffusion mechanism, since the calculated release exponent values (n) were lower than 0.5.