(105b) Fluid-Filled Microcapsules for the Food Industry

Fluid-filled microcapsules for the food industry

In the past years micro encapsulation is increasingly used. The objective is thereby not only the protection of the products ? microcapsules open new possibilities for the controlling of the release of active substances. In the food industry the control of release characteristics in the range between 10 °C (50 °F) to 100 °C (212 °F) is of special interest and represents a special challenge for process engineering. This challenge can be fulfilled using a high pressure technology called PGSS (Particles from Gas Saturated Solutions).

The possibilities of the high pressure spray process PGSS for the production of fluid-filled particles for the food industry will be shown in the presentation. The PGSS process permits a careful processing in an inert gas atmosphere at low temperatures, moderate pressures and is suitable to produce powders and composites of solids, very viscous melts and even liquid substances. With this technique powders with different particle morphology and ?size distribution are obtained. At the same time compressed CO₂ has a strongly germ-killing effect.

For the generation of fluid-filled food particles a shell material (e.g. chocolate, palm- or castor-fat) is provided in a melted condition. The core material (e.g. liquid extracts or flavors) and a supercritical fluid (mostly CO₂) are admixed into a mixing system. Inside the mixing system the core material is dispersed in the continuous liquefied shell material. This dispersion is expanded through a nozzle into a spray tower to ambient pressure, forming fine droplets. Simultaneously, the Joule-Thomson phenomenon of the expanding gas causes the solidification of the droplets. Finally fine powders are obtained, which consist of a dispersed liquid phase encapsulated by the shell material.

No organic solvents, emulsifying agents or other additives are necessary for the production of these microcapsules. Thus the PGSS process offers a special preservation of the products and is environmentally friendly. The production of composites has been demonstrated in the last years with many different systems. As an example three SEM pictures of fluid-filled food particles are shown in Figure 1.

Figure 1: Microcapsules of different shell and core materials

Dry and free flowing powders with a dispersed content of up to 60 wt.-% liquid (e.g. rum, honey and soy sauce) were achieved. In the presentation not only the encapsulation technique will be shown, but also the influence of different quantities of liquid on the powder parameters like the morphology, the bulk density and the particle size distribution.