How is sesame oil made?

The solvent extraction method involves separating the majority of the oil from the seeds by applying mechanical pressure before extracting the additional oil from the solid fraction using a solvent. The primary solvent used during the extraction of the sesame oil is hexane. This allows the oil contained in the seeds to be dissolved before being evaporated using a rotary evaporator. The oil is then refined to remove impurities.

Solvent extraction offers a very high yield of oil recovery. In fact, it is the most commonly used extraction method worldwide today for obtaining sesame oil. However, this technique has some drawbacks, starting with the relatively significant amount of time it requires. On the other hand, the use of a chemical solvent such as hexane is not environmentally friendly and can significantly impact the quality of the oil.

When CO2 is in what is known as a "supercritical" state, it has a significant transport and extraction capacity and can be used to extract vegetable oils such as sesame oil. To do this, sesame seeds are placed in an extractor. A flow of CO2 in a supercritical state is then sent through the extractor, it absorbs the sesame oil, and then transitions into a gaseous phase which allows for the separation of the CO2 and the oil. The latter is then collected in a separator.

Unlike solvent extraction, supercritical CO2 extraction is environmentally friendly. Indeed, CO2 is a natural, non-toxic compound that is readily available. Moreover, this method does not alter the quality of the oil and does not produce any toxic by-products. However, the equipment required for supercritical CO2 extraction can be quite expensive.

The cold-press method is a traditional technique for producing vegetable oils used by the earliest farmers. The appeal of this technique lies in the fact that it allows the extraction of oil from seeds while preserving all the nutrients, minerals, and enzymes of the raw material. Cold pressing also helps to protect the oil from rancidity and eliminates potential interactions with potentially toxic chemicals.

The high quality of the oil obtained through this process is due to the minimal heat generated by the pressure. Thus, compounds sensitive to high temperatures are preserved. Vegetable oils obtained by cold pressing are generally derived from organic farming and can then be used in the food or cosmetic industry. The different stages of the oil extraction process are:

1. The harvesting of seeds:

   The extraction of sesame oil begins with the harvesting of the seeds. It is crucial that these seeds have reached maturity to ensure a high oil content. Mature seeds are easy to identify as their husk is cracked and they display a more pronounced brown colour.

2. The cleansing:

   Once the harvest is complete, the seeds undergo cleaning. This stage serves to eliminate any impurities that may have found their way onto the seeds. These could be remnants of husks, small leaves, insects, or even dust particles.

3. The drying process:

   The cleaned seeds are then dried. This crucial step allows for the removal of any trace of moisture in the seeds, which could compromise the quality of the oil. The drying of sesame seeds can be done in open air or in a specialised dryer. In both cases, it lasts between two to three days, depending on the size and quantity of the seeds.

4. The press:

   The sesame seeds are then placed into a press. Within this press, the seeds are mechanically compressed and pressed at room temperature. The oil is thus mechanically extracted due to the gentle pressure exerted on the cells of the seeds, which release the oil they contain.

5. The filtration:

   Immediately after cold pressing, sesame oil is raw and not yet ready for sale. It must first be filtered to remove any potential solid residues and hydrophilic compounds through centrifugation. Impurities such as colloidal materials, phospholipids, and excess free fatty acids (FFAs) are thus eliminated, leaving only the oil.

6. The refinement:

   Refining is a process that involves treating the oil in various ways, often through successive distillations. Among other things, it helps to enhance the stability of the oil and extend its shelf life.

7. The packaging:

   Packaging is the final step before the product is put on sale. The sesame oil, used in food or cosmetics, indeed needs to be packaged in suitable containers, made of relatively thick and opaque glass. This helps to protect it against the negative effects of light rays, which can oxidise it and degrade its quality

The vegetable oil of sesame used to formulate Typology products has been extracted from the seeds through cold pressing, using plants sourced from organic farming.

• ÇALIMLI A. & et al. Extraction of sesame seed oil using supercritical CO2 and mathematical modelling. Journal of Food Engineering (2010).

• WARRA A. & al. Methods of extraction for Sesame (Sesamum Indicum L.) seed oil and its potential in the cosmetic industry: a review. Bayero Journal of Pure and Applied Sciences. (2011).

• SOUSA E. & al. Extraction, fatty acid profile and antioxidant activity of sesame extract (Sesamum Indicum L.). Brazilian Journal of Chemical Engineering (2012).