Essential Oil Extraction Processes: Expression
It’s true that essential oils are an essential part of aromatherapy. But contrary to what some people think, the term ‘essential’ doesn’t mean essential as in ‘being a necessary part of’. Instead, essential oils are the oils extracted from the ‘essence’ of a plant – those parts that contain the plant’s aroma molecules.
Using different methods of extraction guarantees that the highest concentrations of oils can be extracted. Essential oils are gathered from many different types of plants and many different parts of those plants. Flowers, fruits, herbs, stems, roots, leaves, buds, blossoms, seeds, nuts and even tree bark produce some of the most aromatic and therapeutic essential oils. Essential oil extraction methods fall under three main categories: expression, solvent extraction and distillation. The following is an overview of these extraction processes and methods.
The expression form of essential oil extraction does not involve the use of a heat source. This is the method commonly used to extract oils from the rinds of citrus. In earlier times, rinds were squeezed by hand and a sponge was used to collect the essential oils. The fruit would be removed and then the rinds along with the pith would be soaked in water to make them easier to work with. They’d then be turned upside-down. Turning them upside-down caused the cells containing the oils to break apart. Once broken, the oils would drip out and soak into a nearby sponge. When the sponge became saturated, the oils were squeezed into a container so they could be decanted.
Ecuelle a Picuer
Another expression method involved sticking pins into the skins of fruit for the purpose of damaging the cells that contain the essential oils. The apparatus used had a built-in container for collecting the oils and the other parts of the fruit that ended up in the collection area. The final steps involved separating the essential oils and decanting them. This is called the ecuelle a picuer method.
Those were quite laborious processes, and thankfully, technological advances led to the invention of machines to do this type of tedious work. Nowadays, oils from rinds are extracted using centrifugal force. This rapid process is called Machine Abrasion.
This form of expression extraction is also used to extract essential oils from nuts and seeds and from the rinds of citrus. Mechanical pressure is used to force the oils out. The oils extracted contain water, but this water will, in time, evaporate, leaving just the essential oils. The downside of using this extraction method is that the cold pressed oils spoil more quickly than those extracted using other methods. That’s why, to eliminate waste, it’s important to purchase these essential oils in small quantities.