Microencapsulation at AVEKA

AVEKA has a number of microencapsulation techniques and technologies that can be applied to a range of materials.  Our broad scientific and engineering expertise gives us the ability to investigate and tailor the microencapsulation approaches to meet your needs.

The choice of microencapsulation approach is determined by several key factors, including:

  1. The material to be encapsulated: is it solid or liquid, water soluble or hydrophobic?
  2. How is the encapsulated material to be released from the microcapsules when needed--by dissolution of the capsule walls, mechanical breakage, melting, or digestion processes?
  3. What kind of controlled release is desired--gradual, sudden, or tied to a pH, temperature, or other physical/chemical change?
  4. What is the desired size range of the particles?
  5. What is the desired capsule loading (i.e., the ratio of fill or core material to shell)?
  6. Is the microencapsulated product intended for human consumption (foods, flavors, nutritional supplements, or pharmaceuticals) or for use in animal feeds?
  7. What are the quantities and price targets for the material?

AVEKA's microencapsulation technologies include alginate beads, PMU beads, water beads and complex coacervation as well as the use of spray drying and prilling to encapsulate materials. These techniques are described below with details located on other pages.

Starch Beads FragrantAlginate Beads
This encapsulation technique makes relatively large (up to 3 mm diameter), soft crushable spheres of alginate, a natural polymer extracted from seaweed.  Pigments, sun screen materials such as TiO2, and oils of all kinds can be incorporated into these soft beads.  Since alginate is approved for food, cosmetic, and pharmaceutical uses, it is well suited for a broad range of applications. The beads are matrix-type capsules, that is, they hold any fill throughout the bead, rather than having a distinct shell as in a core-shell type capsule. In addition, when the beads are made with an additive such as starch, then may be carefully dried to become hard beads that may be used for releasing fragrances or to carry other solid materials in water.

PMU Beads
These are made by in-situ polymerization that deposits a polymeric shell on a non-aqueous liquid droplet or on a solid particle. The wall material is polyoxymethylene urea (PMU), also known as urea formaldehyde. This technique produces a capsule that is durable and fairly tight against fill leakage, yet can be broken by moderate pressure between thumb and fingertip, making it well suited to personal care, cosmetic, and fragrance applications. It is most well-known in scratch and sniff applications.

Water Beads
Using an innovative AVEKA patented process, hydrophobic fumed silica forms a shell around droplets of water. The resultant powder is free-flowing and dry, but easily rubs out leaving a moist, cooling sensation. Water beads have uses in the personal care industry.

Coacervation
This method is well suited to encapsulating oils and other hydrophobic compounds in capsules ranging from 25 to about 300 microns. Coacervation allows a wide range of wall materials, enabling the optimum choice for your application. In simple coacervation, a single wall component is used. Gelatin, polyvinyl alcohol, methyl cellulose, polyvinyl pyrrolidone, and many other polymers or hydrocolloids can be used in simple coacervation. AVEKA has developed a new patent pending process for the formation of these core/shell capsules using a food grade hydrocolloid system. These new capsules can be made in sizes ranging from 100 microns to 3000 microns with an active load up to 80 wt %. To form more rugged capsules, complex coacervation may be used. The most studied complex coacervation system uses a gelatin-acacia co-polymer as a wall material. Gelatin-acacia microcapsules can be broken by pressure, digestion, or chewing. A well established technique, gelatin-acacia encapsulation has been widely used for food and flavoring applications.

Spray Drying
Spray drying is a relatively cost effective way of converting a liquid solution or suspension into dry powder form.  At AVEKA, spray drying can be used to encapsulate oils with a water soluble shell material, usually a sugar or starch. This technique produces a capsule in the size range 5 to 30 microns, with moderate fill loading (30-50%). It can also be used to create clusters of solid particles for slow dissolution. For more information, please refer to the page on Spray Drying under Process Technologies.

Prilling
Prilling (also referred to as spray chilling, spray congealing, and melt spraying) can be used to produce hard or soft capsules from 20 microns to 2 mm in size.  In prilling, the material to be encapsulated is introduced into a melted wax or other polymer, then the wax mixture is sprayed into droplets and cooled to a solid. The capsules act as a matrix for the fill material, rather like a sponge. Prilled microcapsules release the fill material via melting, pressure, dissolving, or digestion. If heat release is desired, the polymer matrix can be selected to melt in the desired temperature range. The matrix capsule morphology can also provide a continuous release of the fill compound. For more information, please refer to the page on Prilling under Process Technologies.

Biaxial Prilling
This is a method for forming a core shell type of structure by atomizing a core liquid in the presence of a polymer or hydrocolloid material. In many cases, the polymer or hydrocolloid material forms a shell around the core droplet resulting in a microencapsulated active ingredient. Typically, the shell is a meltable polymer with a low viscosity such as a wax or low molecular weight polymer, and the core is an aqueous solution. In most cases practical throughputs limit the size of microcapsule from 300 to 2000 microns. While there are many ways to bring together the shell and core materials, AVEKA has focused on atomization of the core liquid coaxially with the wall material in a simultaneous process.