Thyme, also known as thyme, is a perennial deciduous subshrub in the Lamiaceae family.
Originally produced in southern Europe, it is mainly used for health care vegetables, tea making, making sachets, pillows, condiments, refining natural flavors, and raw materials for food industry.
It is also a natural spice for bartending, and it can also be used as a seasoning for soups. The aromatic smell released can prevent colds and have certain effects on skin tinea, coughs and other diseases.
In China, it is widely distributed in low hills and shady slopes in Liaoning, Shandong, Hebei, Shanxi, Shaanxi and other provinces.
Thyme essential oil
Usually thyme essential oil is obtained by steam distillation and processing through oil-water separation.
The yield of thyme essential oil obtained by steam distillation is too low and the cost is too high, thus restricting its production and use.
This article uses Gansu thyme as raw material, and uses supercritical CO2 extraction (SFE-CO2) to extract thyme essential oil.
The extraction process conditions were studied, and the best experimental conditions were screened to obtain essential oils with higher yields.
Accurately weigh 300g of the crushed (20 mesh) thyme raw material, put it into the extraction tank, use 95% ethanol as a co-solvent, and add 3% of the volume of the extraction tank (ethanol is an extremely strong nucleophilic addition property. Sexual substances can increase the polarity of the solvent CO2, and at the same time increase the polarity of the oil to be extracted, resulting in an increase in the separation factor of the entire system, thereby increasing the extraction rate).
Then the CO2 in the supercritical state was introduced, and the flow rate was 25L/min. At different temperatures, the extraction pressure and extraction time were changed, and the thyme was continuously extracted, and the extracts entered the separation tank for separation.
The pressure of the first separation and fractionation column is set to 9MPa, and the separation temperature is set to 50 ℃;
The separation pressure of the second separation and desorption tank is set to 4.5～5MPa, and the separation temperature is set to 50°C.
The liquid collected from the two separation kettles is then refined to obtain a pure reddish essential oil.
The CO2 is recycled after gasification, and the extract is released from the bottom of the separation tank. Weigh and calculate the yield.
Effect of extraction pressure on the yield of thyme extract
As the extraction pressure increases, the CO2 density increases, and the solubility of the solute increases, which is conducive to extraction. On the other hand, the diffusion coefficient of the solute will decrease, which is not conducive to extraction. Usually, the former plays a leading role.
The extraction time is 4h, the extraction temperature is 40 ℃, and the CO2 flow rate is 25L/min. At different temperatures, as the extraction pressure increases, the extraction yield will increase, but after the pressure rises to a certain level, the extraction yields The increasing trend of the rate began to slow down, when it reached 25MPa, the yield basically no longer increased, at this time the extraction yield was 4.22%.
Considering comprehensively, it is more appropriate to select the extraction pressure of 25 MPa.
Effect of Temperature on the Yield of Thyme Extract
Under the same extraction pressure, the temperature is high, and the basic yield is also high. When the temperature is 40 ℃, the extraction yield is the highest.
If the temperature is too high, the yield will decrease instead.
This is because the temperature rise increases the diffusion coefficient of the substance, and the mass transfer rate of the fluid is accelerated, which is conducive to extraction; on the other hand, the temperature rise will cause the density of the fluid to decrease, thereby reducing the ability to dissolve organic matter, and the aromatic components are cooled by the separation kettle. If the effect is not sufficient, it will cause volatilization loss and oxidation, and increase the decomposition loss, which is not conducive to extraction.
Considering comprehensively, it is more appropriate to select the extraction temperature of 40 ℃.
Effect of extraction time on the extraction effect of thyme
When the extraction pressure is 25MPa, the extraction temperature is 40 ℃, and the CO2 flow rate is 25L/min, when the extraction starts, with the extension of the extraction time, the extraction yield shows a rapid increase trend. After 3h, the increase in yield tends to be small, and after 4h, the extraction yield is basically not Furthermore, from the perspective of energy saving (water and electricity), the relatively moderate extraction time is: 3～4h.
100g of thyme crushed sample, cold immersed in 25% NaCl solution for 24 h, and then distilled in a vacuum distiller for 3 to 4 h. Collect the distillate. After the salt is saturated, it is extracted 3 times with ether. The extract is concentrated and then used with anhydrous Na2 SO4 was dried to obtain 1.5903g of light red, transparent, aromatic essential oil, with a yield of 1.59%.
From the above results, the yield of thyme essential oil extracted by supercritical CO2 fluid can be as high as 4.22%, which is far greater than the yield of steam extraction.
Process parameters: CO2 extraction pressure: 25MPa; temperature: 40 ℃; time: 4h; flow rate: 25L/min. The oil yield of essential oil extracted by supercritical CO2 is as high as 4.22%.