Title:Encapsulation of Liquids Via Extrusion - A Review
Volume: 21
Issue: 40
Author(s): Markus W. Tackenberg and Peter Kleinebudde
Affiliation:
Keywords:
Encapsulation, extrusion, microcapsule, active ingredients, flavours, plasticization, melting, emulsifier.
Abstract: Various encapsulation techniques are known for pharmaceutical applications. Extrusion is of minor importance.
However, extrusion is used to obtain granules with encapsulate liquid active ingredients (AI) like essential
oils and flavours for food applications since decades. Many of these AIs can be used for agrochemical, home
care, and pharmaceutical products, too. Thus, the focus of this review is on the interdisciplinary presentation and
evaluation of the available knowledge about the encapsulation process via extrusion. The desired microcapsule
structure is discussed at the outset. The microcapsule is compared to the alternative glassy solid solution system,
before an overview of suitable excipients is given. In the next section the development of the extrusion technique,
used for encapsulation processes, is presented. Thereby, the focus is on encapsulation using twin-screw extruders.
Additionally, the influence of the downstream processes on the products is discussed, too. The understanding of the
physical processes during extrusion is essential for specifically adjustment of the desired product properties and
thus, highlighted in this paper. Unfortunately not all processes, especially the mixing process, are well studied. Suggestions for further
studies, to improve process understanding and product quality, are given, too. The last part of this review focuses on the characterization
of the obtained granules, especially AI content, encapsulation efficiency, and storage stability. In conclusion, extrusion is a standard
technique for flavour encapsulation, but future studies, may lead to more (pharmaceutical) applications and new products.
