Supercritical fluid extraction technology is an innovative way to preserve the aroma and taste of sesame oil and minimize the loss of natural ingredients. It can be applied to a variety of industries, including food, medicine, and cosmetics, and is environmentally friendly and economical compared to traditional mechanical extraction methods.
Anyone who has ever been to a traditional market can recall passing by a mill or rice cake shop and being stopped in their tracks by the aromatic smell of sesame oil wafting from inside. The aroma of freshly pressed sesame oil, which is made by roasting sesame seeds and pressing them in an expeller, is intoxicating. But in fact, the fragrant aromas that emanate from the mill are actually “discarded” aromatic components that have not yet been incorporated into the sesame oil and have been blown into the air. The mechanical pressing and squeezing of the sesame seeds inevitably resulted in the loss of flavor.
This problem of sesame oil losing its flavor can be linked to an everyday episode that many people experience. When we use sesame oil to cook food at home, we often look forward to the aromatic flavor, but when it arrives at the table, it often doesn’t have the flavor we expect. This is because most of the aroma is already lost during the mechanical milking process, which has been a major problem for many chefs who use sesame oil.
So, is there a way to press sesame oil without this loss of flavor? The answer lies in “supercritical fluids”. Water turns into ice when the temperature drops below freezing, and vapor when boiled. Similarly, matter can exist as a solid, liquid, or gas. A supercritical fluid is another state that is none of these. Imagine heating a liquid and evaporating the gas in a sealed container, then continuing to increase the temperature and pressure. As the pressure increases, the distance between the gas molecules becomes as close as a liquid, but because the temperature is higher, it doesn’t become a liquid. When the temperature and pressure exceed a certain “critical point,” the substance is neither liquid nor gas, but somewhere in between, and is called a supercritical fluid.
Supercritical fluids have the properties of both liquids and gases. First, they have a density that is almost liquid because the pressure is so high. Generally speaking, higher densities make it easier to dissolve other solids or liquids, and supercritical fluids have good solubility. However, they also have a diffusivity comparable to that of a gas, which allows them to quickly penetrate into the nooks and crannies of small spaces.
These properties of supercritical fluids offer many possible applications in the chemical and biological fields. For example, in the medical industry, supercritical fluids play an important role in the extraction and purification of certain drugs. In environmental science, supercritical fluids are also widely used in pollutant removal and environmentally friendly extraction processes. These versatile properties of supercritical fluids can also provide an innovative way to extract sesame oil.
So how do we use supercritical fluids to extract sesame oil? Supercritical fluids have many applications due to their unique properties, one of which is extraction. The addition of a chemical called a cosolvent to supercritical fluids allows them to selectively dissolve only the target substance of interest, depending on the type and amount of the cosolvent. Their high diffusivity, permeability, and solubility allow them to selectively dissolve the specific substances we want to extract from natural products. After extraction, the supercritical fluid can be easily separated from the extract by simply adjusting the temperature and pressure to return it to a gaseous state. This is economical and eco-friendly because the solvent that has turned into a gas can be used in the extraction process by applying the right temperature and pressure to make it supercritical again. The most common solvent used in supercritical fluid extraction is carbon dioxide, and supercritical carbon dioxide is also used in the process of extracting sesame oil. Carbon dioxide has a relatively low critical temperature of about 31℃, so it is safe and non-toxic without damaging natural products. It is also a byproduct of many chemical processes, so it is easy to obtain and inexpensive.
Now, let’s take a look inside a factory that produces sesame oil using supercritical extraction technology. To extract sesame oil, roasted sesame seeds are placed in an extractor, which is completely enclosed, and then carbon dioxide, which has reached a supercritical state through a pretreatment process, is introduced into the extractor. The supercritical carbon dioxide enters and exits the tiny pores on the surface of the sesame seeds and extracts the oil. The oil-containing supercritical carbon dioxide then passes through a separator, where it turns into a gas and separates from the sesame oil as it loses its solubility in the oil. The extracted sesame oil is aged and packaged, and the separated carbon dioxide goes back into the pretreatment process to become supercritical and recirculate through the entire process.
Sesame oil extracted with supercritical CO2 has many advantages over sesame oil extracted with conventional mechanical pressing. Due to the nature of the supercritical fluid, which must be maintained at temperatures and pressures above the critical point, the entire process takes place in a sealed environment, which preserves the flavor and aroma of the oil better than the open pressing process. In addition, to compensate for this loss of flavor, the pressing process roasts the sesame seeds at high temperatures to produce a rich aroma, which burns some of the sesame seeds and produces hydrocarbons, which are incorporated into the oil and cause a bitter aftertaste. The supercritical extraction process, on the other hand, eliminates the need to roast the sesame seeds at high temperatures to create carbons and minimize nutrient degradation because there is no loss of flavor and aroma. Other advantages of supercritical extraction over conventional processes include the fact that sesame seed residue is not mixed into the sesame oil, and that most of the nutrients such as tocopherols can be extracted in addition to the oil.
Supercritical extraction has a wide range of other applications, from everyday food and beverages such as caffeine extraction in the production of decaffeinated coffee, extraction of sap from hops, the raw material for beer, and separation of nicotine from cigarettes, to high-value-added industries such as natural medicinal ingredients, cosmetic ingredients, and flavors. Compared to conventional extraction processes that utilize organic solvents that cause environmental problems or are harmful to the body, supercritical extraction is safe, clean, reusable, and economical. Supercritical extraction is expected to find many applications in the food and pharmaceutical sectors in the future.
The possibilities in the food industry are endless. Supercritical fluid extraction technology can make a significant contribution to improving the quality of dietary supplements, natural spices, and various food ingredients. Especially now that natural ingredients are becoming increasingly important as consumers seek to eat healthier, supercritical extraction is gaining traction as an environmentally friendly and effective method. We look forward to seeing what innovations this technology will bring to the table and how it will change the way we eat.
