It is difficult to preserve the aroma of sesame oil using traditional extraction methods. However, the use of supercritical fluid technology can make sesame oil more fragrant and fresh. Let’s take a look at how this innovative extraction method changes the quality of sesame oil.
If you have ever visited a traditional market, you may have stopped to smell the delicious scent of sesame oil wafting from the interior of a mill or rice cake shop. The aroma of freshly pressed sesame oil, which is made by roasting sesame seeds and pressing them in a press, is so delicious that it can make you dizzy. However, the fragrant aroma that actually wafted from the mill was actually the aroma components that were “discarded” because they could not be dissolved in sesame oil and flew into the air. The loss of flavor was unavoidable during the mechanical pressing and squeezing of sesame seeds.
This problem of losing the aroma of sesame oil can be related to an everyday episode experienced by many people. When we cook at home with sesame oil, we often expect that savory aroma, but the sesame oil used in the food often does not have the flavor we expect. This is because most of the flavor disappears during the mechanical pressing process, and this problem has been a major concern for cooks who use sesame oil primarily.
So, is there a way to squeeze sesame oil without losing its flavor? The answer lies in “supercritical fluid”. When the temperature of water drops below zero, it freezes into ice, and when it boils, it turns into steam and disappears. In this way, matter can exist as a solid, liquid, or gas. Supercritical fluid is a state that is none of these. Imagine heating a liquid, collecting the resulting vapor in a closed container, and then continuing to increase the temperature and pressure. As the pressure increases, the distance between the gas molecules becomes as close as that of a liquid, but the temperature is so high that it does not become a liquid. When the temperature and pressure exceed a certain “critical point,” the substance becomes neither a liquid nor a gas, but an intermediate state called a supercritical fluid.
Supercritical fluids have the properties of both liquids and gases. First, because the pressure is very high, they have a density close to that of a liquid. In general, when the density increases, another solid or liquid can be well dissolved, but supercritical fluids have good solubility. However, they have diffusion properties comparable to those of gases, allowing them to quickly penetrate into any corner of a confined space.
These properties of supercritical fluids offer many potential applications in the fields of chemistry and biology. For example, in the medical industry, supercritical fluids play an important role in the extraction and purification of certain drugs. Supercritical fluids are also widely used in environmental science for the removal of pollutants and in environmentally friendly extraction processes. The versatile properties of supercritical fluids can provide an innovative method for extracting sesame oil.
So how is sesame oil extracted with supercritical fluid? Supercritical fluid is used in various fields due to its unique properties mentioned above, and one of them is supercritical fluid extraction technology. When a chemical substance called cosolvent is added to supercritical fluid, only the desired target substance can be selectively dissolved depending on the type and amount. It is possible to selectively dissolve it with high diffusivity, permeability and solubility, so it is possible to extract only the specific substances we want from natural products. And after extraction, it is easy to separate the extract by simply returning the supercritical fluid to a gaseous state by controlling the temperature and pressure. This is economical and environmentally friendly because the solvent that has been converted into a gas can be used in the extraction process by applying the appropriate temperature and pressure to create a supercritical state. The most commonly used solvent for supercritical fluid extraction is carbon dioxide, which is also used in the sesame oil extraction process. Carbon dioxide has a relatively low critical temperature of 31°C, so it is safe because it does not damage natural products and is non-toxic. It is also easy to obtain and inexpensive because it is a by-product of various chemical processes.
Now let’s go inside the factory that produces sesame oil using supercritical extraction technology. First, roasted sesame seeds are put into an extractor to extract sesame oil. Then carbon dioxide, which has reached a supercritical state through a pre-treatment process, is put into the extractor, which is completely sealed. The supercritical carbon dioxide enters and exits the very fine pores on the surface of the sesame seeds to extract the oil components. The supercritical carbon dioxide containing sesame oil passes through the separator, turns into a gas, and is separated from the sesame oil as it loses its solubility in the sesame oil. The extracted sesame oil is aged and packaged, and the separated carbon dioxide is returned to the pre-treatment process and becomes supercritical, recirculating the entire process.
Sesame oil extracted by supercritical carbon dioxide has many advantages over sesame oil extracted by conventional mechanical pressing. Due to the nature of the supercritical fluid, which requires maintaining the temperature and pressure above the critical point, the entire process is carried out in a closed state, resulting in superior preservation of the flavor and aroma of sesame oil compared to the open-type pressing extraction process. In addition, the press extraction process roasts sesame seeds at high temperatures to produce a strong aroma to compensate for the loss of this aroma. During this process, some of the sesame seeds burn, producing carbonized substances that are mixed into the sesame oil and cause a bitter aftertaste. On the other hand, the supercritical extraction process does not result in any loss of flavor or aroma, so the sesame seeds are not roasted at high temperatures, which eliminates the risk of carbonization and minimizes the degradation of sesame seed nutrients. Other advantages of the process over the conventional method include the fact that sesame hulls are not mixed into the sesame oil and that most of the nutrients, such as tocopherol, can be extracted other than the oil components.
Supercritical extraction is also used in a wide range of applications, from food and luxury goods that we encounter in our daily lives, such as the extraction of caffeine from decaffeinated coffee, the extraction of essences from hops, which are the raw ingredients of beer, and the separation of nicotine from tobacco, to high value-added industries such as natural medicinal ingredients, cosmetic ingredients, and fragrances. Compared to existing extraction processes, which use organic solvents that cause environmental problems or are harmful to the body, supercritical extraction is safe, clean and reusable, making it economical. Supercritical extraction is expected to be widely used in the food and pharmaceutical industries.
The possibilities for its use in the food industry are endless. Supercritical fluid extraction technology can make a significant contribution to improving the quality of health supplements, natural spices and various food ingredients. In particular, as consumers increasingly pursue healthier diets and the importance of natural ingredients grows, supercritical extraction is attracting attention as an environmentally friendly and effective method. We are excited to see what innovations this technology will bring and how it will change the way we eat.
