Encapsulation of polyphenolic antioxidants from medicinal plant extracts in alginate-chitosan system enhanced with ascorbic acid by electrostatic extrusion

In this study the encapsulation of raspberry leaf, hawthorn, ground ivy, yarrow, nettle and olive leaf extracts was performed by electrostatic extrusion in alginate-chitosan microbeads, with ascorbic acid being used for the dissolution of chitosan. The original and encapsulated plant extracts were characterized for their polyphenol content and composition, mineral content and antioxidant capacity. Raspberry leaf encapsulating microbeads exhibited the highest total phenol content and antioxidant capacity, followed by hawthorn, while olive leaf microbeads contained the lowest total phenol content. High encapsulation efficiency was obtained for all extract encapsulating microbeads (80-89%). Nettle extract-containing microparticles were characterized with the largest particle size and irregular shape, due to a high content of microelements (copper, strontium, and zinc), which affected the geling process of alginate. Although the antioxidant stability of hydrogel microcapsules was deteriorated during refrigerated storage, which might be attributed to the instability of ascorbic acid, the obtained microbeads deliver significant biological activity and antioxidant potential which may increase the daily intake of antioxidants when implemented in a food product. (C) 2011 Elsevier Ltd. All rights reserved.