Deacidification and Deodorization of Tea Oil with Countercurrent Supercritical CO2 Extraction
The effects of extraction pressure on the effect of deacidification were investigated under the conditions that the temperature of the four stages of the extraction column were 35 ° C, 50 ° C, 65 ° C and 80 ° C, the separation kettle pressure was 5 MPa and the separation kettle temperature was 40 ° C. It can be seen from Table 5 that under various pressures, the odor of the extracted tea oil is less than 1/4 of the original odor. The odorous substances are concentrated in the extract and have a significant deodorizing effect.
Based on the apparent difference in the solubility of free fatty acids, odorous substances and triglycerides in tea oil in supercritical carbon dioxide fluid. We use supercritical carbon dioxide fluid extraction technology to deacidify and deodorize the tea oil crude oil produced by mechanical pressing or solvent extraction. Compared with supercritical extraction for tea oil extraction, supercritical CO2 extraction is used for tea oil refining. It treats tea oil crude oil instead of tea seeds. It has a large processing capacity and can achieve continuous production. Much smaller. The new process overcomes the shortcomings of the traditional tea oil refining process, and has the advantages of simple process, no organic solvent residue, avoiding damage and loss of effective ingredients, and ensuring the natural quality of tea oil.
Supercritical CO2 countercurrent extraction tea oil device extraction column inner diameter 34 mm, total height 278cm, composed of 4 sections, each section is 67 cm high, and the upper and lower heads are 5 cm high.
Each section is controlled separately. When working, first heat the extraction column and separation kettle separately, and start the refrigerator to cool.
When the temperature of the extraction column, separation kettle and chiller storage tank all reached the experimental requirements, the CO2 coming out of the CO2 gas cylinder was condensed by the cooler, and then input the extraction column and separation kettle from the bottom of the extraction column through a high-pressure pump.
When the pressures of the extraction column and the separation kettle reach the experimentally set value, the tea oil crude oil is input into the extraction column from the middle of the extraction column through the entrainer pump, and the circulation extraction starts. The raffinate oil and extract are discharged from the bottom of the extraction column and separation kettle every 15 minutes.
When the countercurrent extraction pressure is 14 MPa, the temperature of the fourth stage of the extraction column is 35 ℃, 50 ℃, 65 ℃, and 80 ℃, the separation kettle pressure is 5 MPa, the separation kettle temperature is 40 ℃, and the CO2 flow rate is 15 L / h, respectively, at the bottom of section IV Feed at the bottom of section III. The deacidification effect of the bottom feed of section Ⅳ is better than that of bottom feed of section Ⅲ. The reason may be that after the feed, the flow of tea oil in countercurrent contact with supercritical CO2 is greater, and the separation of free fatty acids and triglycerides is more complete.
As the pressure of the extraction column increases, the mass of the raffinate gradually decreases, the mass of the extract gradually increases, and the acid value of the raffinate gradually decreases, and the acid value of the extract gradually decreases. It can be seen that within an appropriate range, the pressure increases and the deacidification effect is enhanced. The reason is that the pressure increases, the density of supercritical CO2 increases, and the ability to dissolve free fatty acids increases. However, when the pressure is too high, the difference in solubility of each component in supercritical CO2 is reduced, which reduces the separation effect, and too much tea oil is lost during extraction. Considering that the extraction pressure is 18.5MPa, the acid value of the tea oil is reduced from 3.66 to 2.60, which is a decrease of 28.96%.
At the experimental pressure, the light components (free fatty acids) in the tea oil were dissolved in supercritical CO2 after feeding, and the supercritical CO2 fluid went up, while the heavy components (triglycerides) mainly went down. At the same time, the light components entrained by the heavy components gradually dissolved in the supercritical CO2 fluid and turned upward. As the temperature gradient of the extraction column increases step by step, the heavy components entrained by the light components gradually precipitate out and form a reflux. It can be seen from Table 3 that the deacidification effect under temperature gradient conditions is better than isothermal conditions. It shows that the temperature gradient that increases step by step is conducive to generating stable reflux and improving separation efficiency.
Under the conditions of countercurrent extraction pressure of 14 MPa, temperature of the four stages of extraction column of 35 ℃, 50 ℃, 65 ℃ and 80 ℃, separation tank pressure of 5 MPa and separation tank temperature of 40 ℃, the effect of CO2 flow rate on deacidification effect was investigated.
When the flow rate of CO2 is 15L / h, the effect of deacidification is the best. The result of experiment 11 shows that the flow rate is too large. Although the diffusion rate of the solute in the fluid is accelerated, the heat and mass transfer is not sufficient, causing back mixing and reducing the separation effect. If the flow rate of CO2 is too high, a flooding phenomenon will occur , that is, the falling tea oil is carried by the rising CO2 due to the increased resistance and flows directly from the top of the extraction column, which destroys the countercurrent extraction.
The effects of extraction pressure on the effect of deacidification were investigated under the conditions that the temperature of the four stages of the extraction column were 35 ° C, 50 ° C, 65 ° C, and 80 ° C, the separation kettle pressure was 5 MPa, and the separation kettle temperature was 40 ° C. It can be seen from Table 5 that under various pressures, the odor of the extracted tea oil is less than 1/4 of the original odor. The odorous substances are concentrated in the extract and have a significant deodorizing effect.
The traditional method of deodorizing tea oil is to heat the tea oil in a deodorizing pot to 240 ° C for several hours. During this process, some of the tea oil's functional ingredients will be destroyed. In contrast, supercritical CO2 countercurrent extraction deacidification is carried out in a low-temperature inert environment, and the functional components in the tea oil will not be destroyed.