Extraction Techniques

This article briefly summarizes the main extraction techniques and the relative methods to obtain odors from plants. From the ancient techniques to the most advanced ones of our days.

COLD EXTRACTION

Reserved to citrus fruit peels, it makes use of mechanical actions such as scraping, pressure, centrifugation. The principle consists in pressing the peels to empty the pockets of essential oils. Essential oils or essences are obtained.

ENFLEURAGE 

Cold or hot technique based on the capacity of fat to absorb perfumes. The petals are placed on a sheet of glass called a frame, covered with fat that absorbs the scent. The operation is repeated about 30 times in order to obtain pomade or absolute de pomade. This technique is applied to plants and flowers that have a functional activity even after having been harvested (For example tuberose) 

Used in Persia in the ninth century (enfleurage of the rose on sesame seeds that absorbed all the moisture and the sweet smell of flowers), will arrive in France in the seventeenth century, then in the nineteenth century in Grace when, with the development of washing in alcohol, will reach its maximum level. In general, it takes from 30-50 g to 100 g of flowers per frame on the fat layer. The operation should be repeated at 30 or 40 times until the fat is not saturated of odor. Then the fat is passed into alcohol to extract the olfactory principle: the pomade or pomade absolute.

WATER DISTILLATION

The plant raw materials to be distilled are immersed in boiling water, so as to cause the evaporation of their essential oil, which separates due to the difference in density. The essential oil separates from the water and remains in the superficial layer, the decanted water remains fragrant and can be used in that form.

STEAM DISTILLATION 

The plant raw materials to be distilled are placed on a grid, and not in direct boiling water, so that it is only the steam water ho, and not the boiling of the raw material that causes the evaporation of the essential oil. Essential oils, essences or fractions thereof are obtained. 

MOLECULAR DISTILLATION

Organic solvents under vacuum at low temperature are used to rectify, remove color or fractionate essential oils or absolutes or molecules. More transparent essences or fractions of essences are obtained. Often, the manufacturer will mark the extract with the abbreviation "MD".

EXTRACTION WITH VOLATILE SOLVENTS

Modern technique, it is used both with fresh and dried materials, in which the capacity of some organic volatile solvents to extract the olfactory principles are used to obtain oleoresins, absolutes, concrete or resinoids.

Following repeated washings of the natural matter, the concentrate, perfumed and colored, and the concrete are collected, in the case of flowers and vegetables or fresh matter, and the resinoid, in case the raw material is a balsam, a gum, a resin or in general in the case of vegetables or dry matter.

The concrete and resinoid by extraction with alcohol will become absolute.

EXTRACTION BY CO2 OR SUPERCRITICAL EXTRACTION 

Modern technique in which gases - usually CO2 / carbon dioxide, instead of volatile solvents - are used at low temperature and high pressure to extract the olfactory principles and obtain CO2 absolutes or abstracts.

Carbon dioxide passes from the gaseous state at low density to the liquid state at higher density, called supercritical at a temperature of 32° and a pressure of 73 bar. After extraction the pressure is lowered so that the carbon dioxide returns to its gaseous state releasing the solute substances and in the pure state is concentrated: CO2 absolutes or extracts or SFE (supercritical fluid extraction). 

This method allows the extraction of raw and more volatile materials, usually dry, such as spices, and to obtain very pure odors, as they are not contaminated by heat and solvents. It is one of the most advanced extraction methods from the point of view of technology, environmental sustainability and safety at work.

INFUSION

Appropriate processing for raw and slowly maturing materials of plant and animal origin. The substances are macerated in ethanol at varying concentrations and then filtered. If the operation is done hot it is called infusion, if it is done cold it is called tincture. It is used for vegetable raw matters such as Tonk a bean, vanilla pods, iris rhizomes, and animal raw matters such as castoreum, civet, musk, ambergris.

Sources:

La grammatica dei profumi
Fulvio Ciccolo, 2020