Since ancient times, lavender essential oil has been extracted using steam distillation. (Well, I’m talking about the French method. 🙂 ) When we used the essential oil CO2 extraction equipment to extract lavender (supercritical CO2 extraction method), the situation changed; an incredible change.
This is a test in a Chinese university laboratory. The test results have been written into a paper and have been published in Chinese scientific journals. We can even find this paper on the Internet.
Laboratory used BIT2L’s supercritical CO2 extraction machine to carry out the experiment of extracting lavender essential oil.
Taking the extraction rate of lavender essential oil as an index, selecting extraction pressure, extraction temperature, CO2 flow rate and extraction time as influencing factors, the optimal extraction process conditions for supercritical extraction of lavender essential oil were determined by orthogonal test method.
The best process is that the CO2 flow rate is 25L/h, the extraction temperature is 45℃, the extraction pressure is 22MPa, the extraction time is 1h, and the extraction rate of essential oil is 4.497%. The extraction rate of essential oil was 1.32% by steam distillation for 4 hours.
The supercritical extraction of lavender essential oil has a high yield and a short extraction time.
Lavender essential oil
Essential oil extracted from lavender contains a variety of aromatic compounds and is an important natural fragrance, which is widely used in daily necessities, cosmetics, medicine and other industries.
Unique fragrance of lavender essential oil and its products has many functions such as repelling insects, deodorizing, antibacterial, calming and hypnotic, and relieving mental stress.
How to extract lavender essential oil?
Lavender has a relatively high content of essential oils. Because of its aromatic smell, it is often used as a fragrance, insect repellent and raw material for the preparation of fragrances. The extraction of lavender essential oil usually adopts steam distillation method, it can also be made into extract by solvent method, and supercritical fluid extraction method.
The yield of the steam distillation method is relatively low. The solvent method not only needs to remove the leaching solvent, but also leaves the solvent and chemical substances contained in the product.
Supercritical CO2 extraction method
Supercritical CO2 fluid has high density, low viscosity, and high diffusion coefficient. It can quickly extract the essential oils in lavender at near normal temperature. The process is easy to operate, high in yield, and no harmful chemical residues.
At present, the extraction of lavender essential oil mainly uses steam distillation, which has high extraction temperature, long time and low yield.
Supercritical CO2 (SFE) method is a new method for extracting essential oils efficiently, with simple process operation, high yield and high efficiency.
Laboratory used the orthogonal test method to study the extraction process conditions of supercritical CO2 extraction of lavender essential oil, and obtained the best extraction conditions of lavender essential oil, and compared it with steam distillation.
Weigh 100g of dried lavender, put it into the essential oil extraction device, extract 4h by steam distillation, collect the upper oily matter, saturate it with anhydrous sodium chloride, separate most of the water, add anhydrous sodium sulfate to dry, get shallow 1.32ml of yellow transparent liquid, with a light aromatic smell, the extraction rate is 1.32%.
Supercritical CO2 extraction method
Set the pressure of the separation vessel I to be 70-80bar and the temperature to be 40°C. The pressure of the separation kettle II is 50-60bar, and the temperature is 35°C. Weigh 100g of lavender, put it into a 2L extraction tank, extract according to the following process, collect the extracts of separation kettle I and separation kettle II, and calculate the extraction rate (volume of essential oil/quality of raw material). CO2 cylinder→cooling system→high pressure pump→extraction kettle→separation kettle I→separation kettle II (circulation).
Influence of CO2 flow rate on extraction rate
When supercritical CO2 is used to extract lavender essential oil, the CO2 flow rate is the most important factor affecting the extraction rate.
CO2 flow rate is low, the time it takes for the extraction to be increased, and the utilization rate of the equipment decreases, that is, the cost of consumption increases;
The supercritical fluid flow rate is high, the extraction time is shortened, and the purity of CO2 is high.
Increase in CO2 flow will have beneficial and unfavorable effects on the extraction rate:
A: With the increase of CO2 flow rate, the number of times the solvent extracts the raw materials will increase, and the extracted raw materials can also be better turned, so that the raw materials at all points in the extractor are uniformly extracted, which is beneficial to extraction.
B: When the flow of CO2 increases, the flow rate of CO2 increases, but its contact time with the extracted substance decreases, so that the CO2 fluid does not reach the extraction equilibrium, increasing the amount of CO2, which is not conducive to the improvement of extraction efficiency.
Considering that the flow rate of supercritical fluid cannot be increased indefinitely, and it is restricted by various factors such as the technical parameters of the equipment, production safety, and the pressure of the CO2 storage tank, we designed to choose 15L/h, 20L/h, and 25L/h, three kinds of CO2 flow values are in line with the allowable CO2 flow value of the supercritical CO2 extraction machine. The results show that when the flow rate is 25L/h, the extraction effect is better.
Effect of extraction temperature
Extraction temperature is an important parameter in supercritical fluid extraction, and the influence of temperature on the solubility of supercritical CO2 is more complicated.
We selected three gradients of 35°C, 45°C and 55°C for extraction.
The results show that the optimal extraction temperature is 45℃.
At a temperature of 45℃, the diffusion rate of lavender essential oil is the highest, and the amount of lavender oil precipitation is the highest.
Analyze the reason, under a certain pressure, increasing the temperature is conducive to the increase of solute volatility and the increase of diffusion speed, which is conducive to the extraction of lavender essential oil.
On the other hand, if the temperature is too high, the CO2 density decreases, which leads to a decrease in the solubility of the fluid, which is unfavorable for extraction, and increases the cost, thereby reducing extraction efficiency.
The effect of temperature on the extraction effect should be the result of the combined effect of these two factors.
Influence of extraction pressure
The extraction pressure is another important parameter in supercritical extraction.
Three gradients of supercritical fluid pressure of 160 bar, 220 bar and 280 bar are selected.
The results show that when the pressure is 220bar, the extraction effect is better.
When the pressure is 220bar, the extraction is more complete and more essential oils are obtained.
Analyze the reason, when the temperature is constant, the higher the extraction pressure, the greater the density of the CO2 fluid, the stronger the solubility of the solute, the shorter the extraction time, and the more complete the extraction.
On the other hand, when the temperature is constant, the extraction pressure increases and the fluid flow rate increases, which reduces the mass transfer time of the supercritical fluid in the material, and the extraction rate decreases. Because lavender essential oil contains a variety of effective ingredients, too much pressure will change the effective ingredients. Therefore, in the supercritical CO2 extraction of lavender essential oil, it is not appropriate to choose a higher pressure.
Effect of extraction time on extraction rate
The length of the extraction time depends on the CO2 flow rate to a certain extent. Increasing the CO2 flow rate can increase the mass transfer rate and concentration difference of the material to speed up the extraction, and shorten the extraction time accordingly.
The effect of supercritical CO2 extraction of lavender essential oil on the extraction time is relatively insignificant after one hour.
When CO2 is extracted for one hour, the extraction effect is better.
Effect of different extraction methods on extraction rate
It can be seen from the table below that the supercritical CO2 extraction of lavender essential oil is superior to the traditional steam distillation method in terms of extraction rate and extraction time.
|Test method||Color||Odor||Extraction time/H||Essential oil yield/%|
|Steam distillation method||Light yellow||Light taste||4||1.32|
|Supercritical CO2 fluid extraction||Yellow||Strong, soft, pure||1||4.497|
Verification of optimal extraction conditions
In order to investigate the extraction effect of the above-mentioned optimal extraction conditions, the optimal technological conditions of supercritical CO2 extraction of lavender essential oil were repeated three times.
100g of lavender was extracted with the above optimal conditions for 1h, and the essential oils were 4.39mL, 4.63mL, 4.47mL, and the yields were 4.39%, 4.63%, 4.47%, and the average value was 4.497%, which was the highest yield in the orthogonal experiment. 4.50% is equivalent.
The orthogonal test results of supercritical CO2 extraction are reliable. In the experiment, at 45°C, the conditions required for the highest extraction rate are 220bar and 25L/h, which indicates that during extraction, the extraction temperature and pressure CO2 flow are closely related and affect the extraction efficiency together. Only when the three are coordinated can the optimal Extraction process.
In the orthogonal experiment of supercritical CO2 extraction of lavender essential oil, the CO2 flow rate is the most important factor affecting the extraction rate, followed by the extraction temperature and the extraction pressure. The extraction time within the selected range (1 ~ 3h) has the least effect on the extraction rate. .
In our supercritical CO2 extraction experiment of lavender essential oil, under the optimal extraction conditions (extraction temperature 45℃, extraction pressure 220bar, CO2 flow 25L/h, extraction time 1h), the extraction rate of lavender essential oil is the highest. The supercritical CO2 extraction of lavender essential oil has simple steps, no solvent residues, short extraction time, pure color and taste, and is used in pharmaceuticals, food or cosmetics. It is in full compliance with the current development trend of environmental protection, and has important industrial significance and broad application prospects.