**9.3 Chemical composition**

*Essential Oils - Oils of Nature*

**8.2 Distillation with water vapor**

**9. Classification of essential oils**

and chemical nature of the major components.

of rosemary, mint, sage, lemon, basil).

**8.3 Hydrodistillation**

**9.1 Consistency**

storax, etc.).

oleoresins.

**9.2 Origin**

synthetic.

This process is carried out with an overheated dry steam, usually generated by a boiler or boiler, which penetrates the plant material under pressure higher than atmospheric, the vapor stream breaks the oil cells or channels in the plant and entrains the volatile mixture, which condenses after passing through a refrigerant. Generally the oils are lighter than the water and very little soluble in it; therefore, can be separated by decantation. The exception is nail oil, which is heavier than water and is collected underneath it. The steam entrainment method is used to extract rhizome oils, roots, seeds (vetiver, valerian, ginger, anise, cardamom, etc.)

In this system of extraction uses a humid steam, coming from the water in boiling, that transpasses the vegetal material suspended above and supported on a

Hydrodistillation is a process when the plant material is submerged directly into

We can classify essential oils based on the following criteria: consistency, origin,

For its consistency the essences are divided into: fluid essences, balms and

a.The fluid essences, they are very volatile liquids at room temperature (essences

b.The balms, they are thicker, less volatile, contain mainly sesquiterpenoids and are prone to polymerize (balms of Copaiba, balsam of Peru, balsam of Tolu,

c.The oleoresins, they have the aroma of the plants in a concentrated form, they are typically very viscous liquids or semi-solid substances (rubber, guttapercha, chewing gum, oleoresins) of paprica, of black pepper, of clavero, etc.)

Regarding the origin, essential oils are classified as: natural, artificial and

The natural EOs are obtained directly from the plant and are not subsequently subjected to any physicochemical or chemical modification, they are expensive and

the water, which is heated to boil. This method is used for the distillation of the

plant material delicate, for example, flowers (e.g., ylang-ylang, roses).

and dried or fermented leaves of some plants (e.g., patchouli).

mesh. Most herbaceous plants are distilled by this method.

**8.1 Drag with steam**

**74**

Essential oils differ in composition and properties of fatty acids or fixed oils, which are composed of glycerides; and of mineral oils that are composed of hydrocarbons.

Because essential oils are a part of the metabolism of plants, their chemical composition varies permanently, modifying the proportions of their constituents or transforming one another, according to the part of the plant the moment of its development or the time of day when collect the plant.

The proportion of the components of the mixture varies from one oil to another, that is, each essential oil has its own characteristic mixture of compounds with defined qualitative and quantitative variations. Some may be so simple as cinnamon oil formed in 85% of cinnamaldehyde only, or as complex as jasmine, or chamomile oil with about 130 compounds. A discrimination is made between the compounds contained in an essence, and then we speak of major compounds when the compounds are present in the essence in a proportion >1 or 0.5%.

An essence is in permanent change, not only while it is part of the metabolism of the plant, also after it is extracted; this speaks of a reduced stability and a process of continuous transformation, which generates three stages in the life of an essence: that of maturation or aging, that of stability or useful life and that of decomposition or rancidity, each essence has different times for each stage, including depending on the case, the intermediate stage, where it is considered that the changes do not significantly change the quality of the same, may have a positive or negative trend.

It must be taken into account that given its complex composition, essences have a high probability of undergoing physicochemical modifications by reactions between its own constituents or between these and the medium that includes factors such as: light, temperature, presence of enzymes, the components of the part of the plant where the essence is stored, etc.
