A joint Serbo-Croat study found that the nature of the herbal extract affected its encapsulation potential by the alginate-chitosan microbeads, with the highest polyphenol content observed for the raspberry leaf extract, and the lowest for the olive leaf extract.
“In order to utilize plants in the production of various food matrices, it is mostly important to precisely determine their composition, as to enable the preservation of these compounds during handling and processing of final plant containing product, which are often affected by the aggressive manufacturing conditions in food production,” explained the researchers in Food Research International.
“Since this new alternative of micro-encapsulated plant polyphenols could be used for different applications in food and pharmaceutical industries, further studies are necessary to evaluate ascorbic acid stability and release kinetics,” they added.
Encapsulation tests
Led by Drazenka Komes from the Faculty of Food Technology and Biotechnology at the University of Zagreb in Croatia, the researchers investigated the antioxidant activity of a variety of herbal extracts in alginate-chitosan microbeads.
The researchers chose to use sodium alginate (FMC Biopolymer) and chitosan (Acros Organics) because of its extensive study as a drug deliver system and for the “excellent biocompatibility” between alginate and chitosan.
“In order to maximize the encapsulation efficiency of polyphenolic compounds, and minimize loss of their biological activity, avoiding exposure to high temperatures and organic solvents a mild encapsulation method should be adopted with the use of food grade materials,” they explained.
Spray drying, a common technique, is not ideal, they added, since the high temperatures employed may degrade the polyphenols in the herbal extracts. They therefore applied the electrostatic extrusion technique, which provides a means “to produce particles of micro size which is a desired feature from the aspect of textural and sensorial properties of food products enriched with those encapsulates”.
The herbal extracts tested included hawthorn (Crategus laevigata), raspberry leaf (Rubus idaeus L.), olive leaf (Olea europea L.), ground ivy (Glechoma hederacea L.), yarrow (Achillea millefolium L.), and nettle (Urtica dioica L.).
Results showed that the raspberry leaf encapsulating microbeads displayed the highest polyphenol content, followed by hawthorn and yarrow. The olive leaf microbeads had the lowest polyphenol content, added the researchers.
The largest particle size was observed for the nettle extract-containing microbeads, and this was related to the high content of micronutrients, including copper, zinc and strontium.
“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,” they concluded.
Source: Food Research International
May 2011, Volume 44, Issue 4, Pages 1094-1101
“Encapsulation of polyphenolic antioxidants from medicinal plant extracts in alginate–chitosan system enhanced with ascorbic acid by electrostatic extrusion”
Authors: A. Belscak-Cvitanovic, R. Stojanovic, V. Manojlovic, et al.