Introduction

What is Microencapsulation ?

Application of Microencapsulation

Hot melt coating

Cyclodextrins

Extrusion

Emulsion Stabilisation

Jet break-up Processes

Super Critical Fluid technology

Complex Coacervation

Introduction

Extrusion technology was initially applied in the plastics processing area and after years of development and application, it has become a well-elaborated tool with technical solutions available for other fields like the pharmaceutical industry (for the production of controlled release formulations). The basic idea behind encapsulation using extrusion is to create a molten mass in which the active agents (either liquids or solids), are dispersed or dissolved. Upon cooling, this mass will solidify, thereby entrapping the active components.

Technology

Schematic representation of an extruder for encapsulation

Extruders are thermo-mechanical mixers that consist of one or more screws in a barrel. Transport of material within the extruder takes place by the rotational, and sometimes also oscillating, movement of the screw(s). The extruder barrel may be heated, or sometimes cooled. In the context of encapsulation, extrusion can be defined as a processing technique in which melting of the matrix polymers, mixing of components, and shaping of these mixtures are combined to yield a product. Generally, extruders consist of at least one rotating screw inside a barrel. The barrel is often divided into sections to allow for the section-controlled variation in temperature. Connected to the end of the barrel is a “pre die” and the “die head” which latter determines the shape of the final product. Most commercial extruders have a modular design with the option to use a range of screw elements. This allows the process conditions to meet particular requirements in terms of amount and type of shear.

Application

The efficiency and cost effective encapsulation of a wide range of components by extrusion technology were clearly in favor of the development of such flexible and continuous process. As both hydrophilic and hydrophobic components can be encapsulated either in hydrophilic or hydrophobic matrix materials, melt-extrusion is able to encapsulate :
  flavors
  fragrances
  essential oils
  agrochemicals
  nutraceuticals
  pharmaceutically active compounds (e.g. for oral dosage forms, implants, topical films)
  living cells