What is essential oil?
Essential oils (also known as volatile oils, ethereal oils or aetheroleum) are natural products extracted from various parts of plants (flower, leaf, stem, fruit, seed, twig, bark or root). They are concentrated hydrophobic herbal liquids that are composed of highly powerful and volatile chemical compounds (mostly terpenoid substances). Essential oils have complex structures and may consist of hundreds of different molecules. They are extracted from the plants through different methods such as steam distillation, water distillation, cold pressing (for citrus peel oils) and supercritical fluid extraction. Steam distillation is the oldest and the most common method of obtaining essential oils.
Essential oils have been used for thousands of years. They exhibit different kinds of biological activities such as antibacterial, antioxidant, antiviral, insecticidal, etc. Thanks to modern extraction methods and their therapeutic and preventive properties, today essentials oils found their place in various applications including cosmetics, pharmaceuticals, perfumery, aromatherapy, agriculture, cleaning products and food industry.
What is fixed oil?
Fixed oils (often called fatty oils or carrier oils in aromatherapy) are non-volatile oils composed of fatty acids such as oleic acid, palmitic acid and stearic acid. They are obtained by pressing the plant material. Fixed oils are rich in calories and they exist mostly in the seeds of plant source, as reserve substances.
Fixed oils are important not only from the nutritional viewpoint, but also in terms of their medicinal and pharmacological properties. Olive, coconut and sesame oils are among the most popular fixed oils.
What is hydrosol?
Hydrosols (also known as hydrolats, floral waters or distillates) are natural liquids which are by-products of the steam distillation process of plant materials. When steam passes through various parts of the plant, it forces pockets (glands) that consist volatile compounds to open and they evaporate into the steam. The steam then condensed to liquid by cooling. Due to the difference in specific gravity of essential oil and liquid, the essential oil floats to the surface and the remaining liquid is called hydrosol.
Hydrosols consist of approximately 0.02-0.5% essential oils. Because of liquid soluble components in the plant material, hydrosols have similar scent to the essential oil but with a fresher note. Hydrosol, which is obtained during the first half of the steam distillation process, is regarded to be of high quality. Like essential oils, hydrosols have been used in conventional medicine for thousands of years and today they are widely used in cosmetics and aromatherapy.
What is steam distillation?
Steam distillation is the oldest and most common method for obtaining essential oils. In this process, steam is directed through plant material (either flower, leaf, stem, fruit, seed, twig, bark or root) where it forces pockets (glands) that consist volatile compounds to open. Hereby these compounds evaporate into steam. At this point the steam temperature is of utmost importance. The temperature of steam needs to be sufficiently hot so as to allow volatile compounds to part from the plant. However, if the steam is too hot, the plant material is damaged and subsequently undesired chemicals also evaporate that impairs the quality of essential oil. The literature indicates that the ideal steam temperature is between 98 - 100°C, which can only be obtained under atmospheric pressure.
The steam with volatile compounds passes through a cooling system where it condenses into a liquid consisting of essential oil and water. In the final phase, the liquid comes into a separation apparatus (often called Florentine flask) where the essential oil floats to the top as it is lighter than water and the remaining water (hydrosol, hydrolat or floral water) remains at the bottom.
In steam distillation process, aside from the plant itself, the most important parameters that affect the quality of essential oil are time, temperature, pressure and the quality of the distillation equipment.
What is cold pressing?
Cold pressing is the method of fixed oil extraction from oilseeds (such as sesame, flax, black cumin, grape seed, pomegranate seed, etc.) without actually using heat. Basically, it is a mechanical process in which the oil is extracted from the seeds via mechanical pressure and intense friction, at a temperature that does not exceed 40°C. Although cold pressing is slower and less efficient than industrial methods, it is an environmentally friendly method and does not require heat or chemical solvents which degrade the oil's flavour and nutritional quality. As the final product is unrefined and unprocessed, cold pressed oils are rich in oleic acid and Vitamin E and retain healthy antioxidants.