Average Size of Formulation Units in nm Sizes below 150 nm may be Invisible to the Naked

Solutions 0.1

Micellar solutions 0.5

Macromolecular solutions 0.5

Microemulsions Liposomes SUV Nanospheres Nanocapsules Liposomes LUV Liposomes MLV Microcapsules Simple emulsions Multiple emulsions

5-20 20-150 100-500 100-500 200-500 200-1000 5000-30,000 500-5000 10,000-100,000

Abbreviations: SUV is small unilamellar vesicles, LUV is large unilamellar vesicles, and MUV is multilamellar vesicles.

Since the introduction of the encapsulation of volatiles (essential oils/lower terpenes), the number of applications has multiplied. Encapsulation of volatiles gives us a more predictable and long-lasting effect of the products. The areas of applications are large and the industry of essential oils and terpenes foresee many prospects for microencapsulated products. Application markets of encapsulated essential oils and terpenes are:

Medicine

Food, household items, and personal care

Biotechnology

Pharmaceuticals

Electronics

Photography

Chemical industry

Textile industry

Cosmetics.

It is therefore easy to understand that the encapsulation procedures will open up a much larger market for essential oil/terpene products. Experience from all the areas mentioned above can be applied to the study of volatile compounds in products.

In the area of essential oils and lower terpenes, simple encapsulation procedures from the area of drug delivery are applied. The essential oils or single active constituents are mixed with a hydro-philic polymer and spray-dried using a commercial spray-drier. Depending on whether we have an emulsion or a solution of the volatile fraction in the polymer, we obtain monolithic particles or a normal microcapsule.

The most usual polymers used for encapsulation are:

Oligosaccharides from a-amylase

Modified starches from maize, cassava, rice, and potato

Acacia gum

Gum arabic

Alginate

Chitosan.

Many different emulsifiers are used to solubilize the essential oils totally or partly, prior to the encapsulation procedure. This can result in a monolithic particle or a usual capsule, where the essential oil is surrounded by a hydrophilic coating. When the mixture of an essential oil and a hydrophilic polymer is achieved, the application of a spray-drying procedure of the resulting mixture will result in the formation of microcapsules. The techniques for achieving an encapsulated product in high efficiency will depend on many technical parameters and can be found in the patent literature. Normally a mixture of essential oil:hydrophilic polymer (4:1) can be used, but this will also depend on the type of equipment used. The reader is advised to refer to the parameters given for the polymer used in the experiment. To achieve the encapsulated product, a mixture of low pressure and temperature is used in the spray-drying equipment and a loss of essential oil/volatiles is inevitable. However, a recovery of more than 70% can be achieved by carefully monitoring the production conditions.

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