Micro-encapsulation

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Microencapsulation is a process in which tiny particles or droplets are surrounded by a coating to give small capsules, with useful properties.^[1][2] In general, it is used to incorporate food ingredients,^[3] enzymes, cells or other materials on a micro metric scale. Microencapsulation can also be used to enclose solids, liquids, or gases inside a micrometric wall made of hard or soft soluble film, in order to reduce dosing frequency and prevent the degradation of pharmaceuticals.^[4]

In its simplest form, a microcapsule is a small sphere comprising a near-uniform wall enclosing some material. The enclosed material in the microcapsule is referred to as the core, internal phase, or fill, whereas the wall is sometimes called a shell, coating, or membrane. Some materials like lipids and polymers, such as alginate, may be used as a mixture to trap the material of interest inside. Most microcapsules have pores with diameters between a few nanometers and a few micrometers. Materials generally used for coating are:

• Ethyl cellulose
• Polyvinyl alcohol
• Gelatin
• Sodium alginate

The definition has been expanded, and includes most foods, where the encapsulation of flavors is the most common.^[5] The technique of microencapsulation depends on the physical and chemical properties of the material to be encapsulated.^[6]

Many microcapsules however bear little resemblance to these simple spheres. The core may be a crystal, a jagged adsorbent particle, an emulsion, a Pickering emulsion, a suspension of solids, or a suspension of smaller microcapsules. The microcapsule even may have multiple walls.