Complex Coacervation (Gelatin) Microencapsulation
The complex coacervation encapsulation technique uses coating materials derived from natural plant and animal sources. Gelatin is derived from either pork or bovine sources, and although it surprises some people, Kosher gelatin is available. The other component of complex coacervation microencapsulation is often acacia, also known as gum acacia or gum arabic, which is made from the bark of several species of acacia trees. Microencapsulation via gelatin and/or gelatin-acacia is an emulsion technique, where the material to be encapsulated is emulsified in a water solution. Hence the fill material must be insoluble in and non-reactive with water. The technique is often used to encapsulate oils and other hydrophobic liquids for use in food and pharmaceuticals.
Typical Core Materials
Any liquid with negligible miscibility in water, reasonable viscosity, and pH between 4 and 8 can in principle be used as a core with this method. Hydrophobic liquids, such as edible oils and flavorings, are frequently used. Also, solid particles and powders can be encapsulated in gelatin-acacia capsules.
Wall Material
A co-polymer of the natural polymers gelatin and acacia. Gelatin alone has also been used. Walls are insoluble in water, and can be made thicker or thinner to control the core release rate. If the walls are cross linked, they become much tougher and less leaky.
Release Mechanism
Gelatin-acacia capsules are broken by pressure or mechanical forces, such as chewing, and by digestion.
Capsules
Gelatin-acacia capsules are a true core-shell type microcapsule. For liquids, the fill or payload, can reach up to 90% or more, depending on the material. Capsule size can presently be varied between 25 and 300 microns; larger sizes may be accommodated for some materials.
Present Production Capacity
Gelatin-acacia encapsulation is a batch process, with present batch capacity at about 4 kg of capsules. The process is being scaled up to attain about 50 kg per batch.
The gelatin-acacia technique is a well established technique and produces food grade capsules with stable, digestible or chewable walls. It is ideal for applications calling for hydrophobic liquids (i.e., oils), small capsules (below 20 microns), and edible materials.