About persimmon leaves
Persimmon leaves were used for medicinal purposes during the Ming Dynasty in China, and it is also recorded in Ye Gui’s “Materia Medica Zaixin” in the Ming Dynasty.
Modern research shows that the main chemical components of persimmon leaves are flavonoids, such as astragalin, isoquercetin, rutin, rutin, kaempferol-3-O-β-D-glucoside and so on.
Studies have found that the content of flavonoid glycosides in persimmon leaves is not lower than ginkgo biloba leaves, generally 121.34 mg flavonoid glycosides per 100 g persimmon leaves.
Chinese patent medicine made from persimmon leaves can be used to treat coronary heart disease, angina pectoris, high blood pressure, and has certain anti-cancer effects.
In addition, per 100 g of dried persimmon leaves contain 12.67 g crude protein, 6.84 g crude fat, 54.83 g carbohydrates, 1 543 mg polyphenols, mineral elements, amino acids and vitamins B1, B2, C, and E. Among them, the vitamin C content is the largest among all plant leaves. At the highest level, per 100 g persimmon leaves can contain 2 135 mg. It can be seen that persimmon leaves have high nutritional value and are often used to make health teas.
Weigh 100 g of the processed persimmon leaf powder, and test the effects of extraction pressure, extraction temperature, extraction time, and CO2 flow rate on the yield of persimmon leaf essential oil.
Influence of extraction pressure
When the temperature is constant at 50 ℃, the time is 2.5 h, and the CO2 flow rate is 20 kg/h, the pressure is increased, and the density of supercritical CO2 increases, thereby increasing the dissolution capacity, but the relationship between the two is non-linear; when the pressure When it increases to a certain extent, the increase of dissolving power becomes slow.
From an economic point of view, continuing to increase pressure will increase equipment investment and operating costs, so the pressure should be selected appropriately.
When the extraction pressure is less than 14.0 MPa, the yield of persimmon leaf essential oil is low, and the pressure is between 14.0 and 16.0 MPa, and the extraction rate is greatly increased. When the pressure continues to increase to 20.0 MPa, the extraction rate increases Very small, only 0.3%.
Therefore, considering the practicality of production, the extraction pressure should be around 18.0 MPa.
Effect of extraction temperature
Under different extraction pressures, temperature has different effects on solubility.
When the pressure is high, the density of supercritical CO2 is high, and the compressibility is small. When the temperature is raised, the density of supercritical CO2 decreases less, but the vapor pressure and diffusion coefficient of the components to be separated are greatly increased, thereby improving the solubility;
On the contrary, near the critical point, when the pressure is low, the compressibility of supercritical CO2 is large, and the density of supercritical CO2 drops sharply when the temperature is raised. At this time, although the volatility and diffusion coefficient of the separated components can be improved, it is not enough. Compensate for the decrease in dissolving power caused by density changes.
In the experiment, we used a pressure of 14. 0～18.0 MPa to study the influence of different temperatures on the extraction rate of persimmon leaf essential oil. Under other conditions, the yield of persimmon leaf essential oil first increased with the increase of temperature. , And then began to decrease with the increase of temperature.
The test results show that when the extraction pressure is 18.0 MPa and the extraction temperature is 50 ℃, the extraction rate of persimmon leaf essential oil is the highest.
Influence of CO2 flow
The flow rate of supercritical CO2 mainly affects the extraction time. Generally speaking, the larger the flow, the faster the extraction rate, and the smaller the flow, the slower the extraction rate.
The CO2 flow rate increased from 10 kg/h to 15 kg/h, and the extraction rate increased more.
After the CO2 flow rate is increased to 20 kg/h, although the yield is still increasing, the increase has slowed down.
Considering that the increase in flow rate is not conducive to the separation of the extract and CO2 in the separator, it is better to use 20 kg/h for the flow rate of CO2.
Effect of extraction time
Under normal circumstances, the flow rate is constant, and the longer the extraction time, the higher the yield. At the beginning of the extraction, because the supercritical CO2 did not reach a good contact with the solute, the extraction volume was less.As the extraction time extended, the mass transfer reached a good state, and the extraction volume per unit time increased until it reached the maximum. The reduction in the content of the components to be separated in the object reduces the extraction volume.
With the extension of the extraction time, the yield of persimmon leaf essential oil gradually increases
When it reaches a larger value at 2.5 h, continue to extend the extraction time, the yield will not increase much, or even drop slightly, so it is better to use 2.5 h in production.
The supercritical CO2 extraction method can effectively extract the essential oil of persimmon leaves, and the extract is high in purity and has a positive fragrance.
The order of influence on the extraction rate of persimmon leaf essential oil is: extraction pressure> extraction temperature> CO2 flow rate> extraction time.
The process conditions that can be used in the production are: extraction pressure 18.0 MPa, extraction temperature 50 ℃, CO2 flow rate 20 kg/h, extraction time 2.5 h, and the extraction rate of persimmon leaf essential oil reaches 3.1%, which is higher than steam distillation 1. 38% of the law increased by 55%.
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