Extraction of Oleuropein from Olea europaea Leaves by Supercritical CO2 Extraction Technology
Process parameters of supercritical co2 extraction of oleuropein
Pulverization degree:80 mesh
Extraction pressure: 25 MPa
Extraction temperature: 45°C
Separation pressure I: 12 MPa
Separation I temperature: 45°C
Extraction time: 240 min
Olea belongs to the Oleaceae family and is one of the important fruit trees in the countries along the Mediterranean Sea. Researches on olive oil and polyphenols in olive fruits have been reported, but research reports on olive leaves are rarely seen. In the early 20th century, a polyphenol compound was isolated from olive leaves. It has the structure of a schicyclic alkene station and is called oleuropein. Research at home and abroad shows that oleuropein has antioxidant, anti-tumor and antibacterial properties, Lower blood sugar and other effects. Because of its obvious pharmacological properties, oleuropein is considered to be the most important compound in the olive plant.
The extraction methods of oleuropein usually include alcohol-water extraction, Soxhlet extraction, microwave-assisted extraction, etc. However, there are few reports on the extraction of oleuropein by supercritical CO2 extraction. In view of the fact that the supercritical CO2 extraction technology is non-toxic, cheap and easy to obtain, and the product has no solvent residues, it ensures the pure natural characteristics and natural flavor of the extract.In this study, single factor and orthogonal experiments were used to optimize the technological conditions for supercritical CO2 extraction of oleuropein from olea leaves.
Materials and reagents
Olea leaves were collected in Wudu County, Gansu. The standard oleuropein was purchased from Chengdu Munster Biotechnology Co., Ltd.
HA120-50-01 supercritical co2 extraction equipment, Nantong Huaan Supercritical Extraction Co., Ltd.;
The moisture content of the olea leave sample is measured in two weighing bottles with constant mass. Weigh 3g of the naturally dried and crushed sample, accurate to 0.0001g, and place it in a (105±2)i oven. After drying for 2 h Take it out, put it in a desiccator to cool for 0.5 h, take it out and weigh it; then put it in an oven again for 1 h, take it out, and cool it in a desiccator for 0.5 h, weigh it. If the difference between the two masses does not exceed 0.0002 g, it means that the sample has been dried to an absolute dry state, and the moisture content is calculated. After two parallel tests, the average water content of olive leaves was 8.66%.
For the extraction of oleuropeinness in the sample, the olive leaves were naturally dried and crushed. Accurately weigh 60.0g of olea leave powder, use absolute ethanol as a co-solvent, and perform supercritical CO2 extraction under certain pressure, temperature and CO2 flow conditions.
Effect of extraction pressure
Under the conditions of extraction temperature of 45℃, separation temperature of 45℃, CO2 flow rate of 30kg/h, extraction time of 2 h, and entrainer 300mL of absolute ethanol, the extraction pressure was changed. In the range of 8~15MPa, the product yield increases rapidly, when the pressure exceeds 15 MPa, the product yield increases little. In addition, high pressure has higher requirements for equipment and operation. Therefore, it is more appropriate to select a pressure of about 15 MPa.
Influence of extraction temperature
Select extraction pressure 15 MPa,Changing the extraction temperature, in the range of 35~45℃, as the extraction temperature increases, the yield of oleuropein sweetness increases rapidly; when the temperature is higher than 45℃, the yield of oleuropein sweetness begins to decrease significantly. This is because temperature has two effects on the solubility of CO2 in the supercritical state: On the one hand, under a certain pressure, increasing the temperature will increase the molecular spacing of CO2 as an extractant, and the intermolecular force will decrease accordingly. The density decreases, and the solubility decreases; on the other hand, under a certain pressure, increasing the temperature will accelerate the thermal movement of the molecules of the extract, increase the chance of intermolecular association, and increase the solubility.
Therefore, the influence of temperature on the yield of supercritical extraction should be considered in a comprehensive manner. In addition, as the temperature increases, it is possible to destroy the structure of the extract and reduce the yield of the extract. Therefore, the extraction temperature is about 45°C.
Effect of separation temperature
Select the extraction pressure of 15 MPa and change the separation temperature. The yield at the separation temperature of 45°C is significantly higher than that at 40°C, and the yield decreases significantly after 45°C.
The impact of CO2 flow
Select the extraction pressure of 15 MPa, change the CO2 flow rate, and the CO2 flow rate has little effect on the yield of olives. Increasing the CO2 flow rate can increase the contact area between CO2 and olea leave powder and increase the extraction rate, especially when the raw material is viscous. The CO2 flow rate is not as large as possible. After increasing to a certain extent, the yield of oleuropeinness will gradually decrease. Therefore, about 30 kg/h is a suitable flow.
Effect of extraction time
Select the extraction pressure of 15MPa and change the extraction time.When the extraction time increases, the yield of the extract increases, but when it increases to a certain level, the increase is slow. Considering the cost, the time is better to 3-4H.
The influencing factors on the yield of oleuropeinness were extraction pressure>extraction time>extraction temperature>separation temperature. The main factor should be at the best level, while the secondary factor can be selected according to the overall consideration of cost, time, profit and other aspects.
The optimal extraction process conditions were obtained as follows: extraction pressure 25 MPa, extraction time 4 h, extraction temperature 45 °C, separation temperature 45 °C.
According to the above-mentioned optimal process conditions, 3 repeated experiments were carried out, and the yields of oleuropeinness were 0.444%, 0.435% and 0.427%. It can be seen that the reproducibility is good, and the average value of 3 times is 0.435%.
The optimal process conditions are: extraction pressure 25 MPa, extraction temperature 45 °C, separation temperature 45 °C, extraction time 4 h, CO2 flow rate 30 kg/h. Under the above-mentioned optimal process conditions, the yield of oleuropeinness is 0.435%.