Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev

8 MICRODISTILLATION,THERMOMICRODISTILLATION AND MOLECULAR DISTILLATION TECHNIQUES
8.5.4 Parameters that Affect the MD Process
The amount of low-boiling volatiles as well as dissolved air,
moisture, or other gasses in the feed material has a deleterious effect on
the effi ciency of MD. This is due to the fact that the non-condensable components
cover the condensing surface.
Higher temperature difference between the condensing and
evaporating surfaces yields higher effi ciency. High viscosity liquids (without
mechanical agitation) yield high liquid fi lm thicknesses and hence lower effi -
ciency. As a rule, the relative volatility of organics increases with decreasing
pressure, particularly in the very low pressure range common to MD. Therefore,
low operating pressure generally yields higher effi ciency.
8.5.5 Typical Applications of MD
1. Concretes obtained by solid-liquid extraction are conventionally
converted to the absolutes by dissolving in aqueous alcohol
solvents and then precipitating the waxes by chilling to
sub-zero temperatures. This process is highly energy intensive
due to the electrical energy required for refrigeration.
2. Red palm oil (high vitamin E content).
3. Separation of tocopherols from vegetable oil deodorization
residues.
4. Natural vitamins A, E, K-1 and K-2 (replacing synthetics in
the pharmaceutical industry).
5. Purifi cation and separation of natural extracts into crude
fractions.
6. Recovery of lanolin from wool grease, the soft wax from hair
of sheep (cosmetic industry).
7. Fragrances derived from fatty acids.
8.6 Recovery of Dissolved Essential Oils from
Steam Distillation Condensates
The major prerequisite of the process used for production of
essential oils is that the product obtained must resemble the natural aroma
and fl avor of the original source, which is a combination of different compounds
of varying organoleptic characteristics. Oxygenated organic compounds
like aldehydes, ketones, alcohols and esters are the dominant contributors
to the overall aroma and fl avor. The essential oil produced should
ideally have all these components in the same proportions as in the original
natural product in order to match the natural aroma and fl avor. For example,
steam-distilled rose oil contains less than 1 wt% phenyl ethyl alcohol (PEA)
whereas the solvent-extracted rose oil contains greater than 60 wt% PEA.
It is a common experience that the steam distillation condensate has an
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