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Supercritical CO2 fluid extraction makes grape seed oil more pure

Foreword:

A large number of studies have confirmed that grapeseeds contain 14% to 17% oil, of which 92% of unsaturated fatty acids,especially linoleic acid content of up to 76%; also contains vitamins A, D, E,K, P and so on. Grape seed oil has the functions of clearing blood vesselcholesterol, preventing arteriosclerosis, anti-oxidation, nourishing braincells, regulating autonomic nerves, etc. It has a wide application prospect inthe food, medicine, chemical, cosmetics and other industries. Supercriticalfluid extraction (supercritical fluid) Extracti on, SFE) technology usessupercritical fluid as solvent, using its good solubility and permeability, andby adjusting the temperature and pressure parameters of the system, thesolubility of the fluid in the supercritical state to the specific component issharply increased. , thereby achieving a process of separating the mixture. Thecarbon dioxide critical temperature (31.06 ° C) and the critical pressure (7.38MP) are lower, and the extraction operation can be performed near roomtemperature, which reduces the thermal decomposition of the heat sensitivesubstance during the extraction process while reducing the requirements on theequipment and energy consumption. At the same time, carbon dioxide isnon-flammable, non-toxic, environmentally friendly, inexpensive and easy toobtain, and is the most commonly used supercritical extraction solvent.Supercritical fluid extraction technology combines the advantages and functionsof liquid-liquid extraction and distillation, and overcomes the problem ofresidual organic solvents in traditional extraction methods. Therefore, it hasbeen widely used in food, spice, chemical, pharmaceutical, biological and otherindustries.

Grape is an important fruit crop. In China, viticultureis developing very fast. It grows from the south of Heilongjiang to Guangxi.Grape seed generally accounts for 3% to 7% of the total weight of the grape. Asa complex of wine, it is a high-quality edible oil resource. The price andnutritional value of grape seed oil are much higher than ordinary edible oilsand therefore have great development value. Supercritical CO2 fluid extractionnot only has its own technical advantages, but also can complete the degummingprocess, and partially play the role of deacidification, deodorization anddecolorization, greatly simplifying the subsequent process, but it is necessaryto pay attention to the influencing factors in the extraction.


1. Physiological function and application of grape seedoil

Grape seed is a by-product of winemaking. If it is notused, it will not only pollute the environment, but also be a waste ofresources, because grape seed also contains 13% to 15% of oil and fat, andunsaturated fatty acid content in grape seed oil. Up to 90%, of which linoleicacid content is as high as 80%, comparable to safflower seed oil. Linoleic acidis an important raw material for the synthesis of peanut dilute acid. Not onlyarachidonic acid is the main substance for the synthesis of prostaglandins, butalso has the functions of preventing thrombosis and expanding blood vessels.

In addition, grape seed oil also contains a richphysiological oily ingredients, making it have some physiological functionsdifferent from ordinary edible oils [12-15]. Such as lowering blood pressure,clearing cholesterol, and nourishing brain cells. Now, it is used as a specificnutrient health oil for infants, the elderly, high-altitude workers, andhypertensive patients. In addition, well-processed grape seed oil can also beused as a base for cosmetics and pharmaceuticals.

2. Characteristics of supercritical CO2 fluid extraction

Supercritical CO2 fluid extraction technology is simplein process and convenient in operation; it overcomes the need of distillationheating in the separation process of solvent extraction, and the oil is easilyoxidized and rancid; it also overcomes the characteristics of low efficiency ofthe pressing method, cumbersome refining process and unsatisfactory oil color.

The supercritical CO2 fluid extraction technology usesnon-toxic, non-residual CO2 instead of water or organic solvent as theextraction medium, and is extracted under conditions close to room temperature,without solvent residual pollution and no pollution to the environment. Thetechnology reduces the disadvantages of natural materials to heat or chemicalinstability during processing, and preserves the original flavor and nutrientsof natural products.


3. Test content

3.1 Main instruments and materials

Spe-ed supercritical extraction device, wherein theextraction kettle is 20mL; high purity CO2, purity 99.9%; SDC-6 type lowtemperature thermostat; TYW-2 air compressor; grape seed (commerciallyavailable), crushed by universal crusher After that, the particle sizedistribution is shown in Table 1.

Table 1. Table of particle size distribution aftercrushing of grape seed oil

Particle size/mesh

⩽20

30

40

⩾50

% of quality

19.7

25.5

38.4

16.4


3.2 Steps of supercritical CO2 extraction of grape seedoil

1) Accurately weigh the pulverized, certain-grainedgrape seeds in an extraction vessel at a volume of approximately 60% of thevolume of the kettle, then fix the extraction vessel in a heating furnace andclose the safety door. Ensure that the safety door does not open at will untilthe end of the extraction process. Check that each valve on the extractor isoff.

2) Connect the main power supply, constant temperaturecirculation system power supply and air compressor power supply separately tocheck whether the equipment is working properly.

3) Open the intake valve to allow liquid carbon dioxideto enter the extraction system through the siphon

4) Open the temperature control furnace and exhaustvalve temperature control switch respectively, and set the extractiontemperature and exhaust valve temperature on the temperature control panel.

5) After the kettle temperature reaches the set valueand stabilizes, adjust the system pressure to the set value. Keep the exhaustvalve closed and start the static extraction process.

6) After the static extraction is completed, the ventingvalve is opened to start the dynamic extraction process. Adjust the opening andclosing of the exhaust valve to control the air release rate of carbon dioxide.The supercritical fluid carrying the product expands throttling through thepressure reducing valve, releases the grape seed oil and becomes normalpressure CO2 gas, and the venting flow rate is measured by the float flowmeter.

After the end of the extraction, the extract weight wasaccurately weighed, and the oil content of the grape seed powder was measuredby a Soxhlet extractor, and then the extraction rate of the grape seed oil wascalculated.

Extraction rate = G2/G1X1 × 100%

Among them: G1 - grape seed powder quality (g); X1 -grape seed powder oil content (%); G2 - extracted oil quality (g)


4. Factors affecting the extraction of grape seed oil bysupercritical CO2 fluid

4.1 Effect of pulverization degree on grape seed oilextraction

The particle size of the material has a dual effect onthe extraction. On the one hand, the finer the material, the mass transfer areais increased, and the mass transfer distance and mass transfer resistance arereduced, which is beneficial to the extraction; on the other hand, if thematerial is too fine, it is easily compacted under high pressure, increasingthe mass transfer resistance without Conducive to extraction. Due to the highcontent of grape seed oil, it is generally easy to use about 40 mesh.

4.2 Effect of extraction intensity on grape seed oilextraction

Supercritical CO2 fluids have good mass transfercharacteristics. Increasing the pressure will not only increase the density ofCO2, but also reduce the distance between molecules. At lower temperatures, theextraction rate of grape seed oil gradually increases with increasing pressure,but when the pressure is too high, the extraction rate increases slowly.Because of the high density of CO2 under high pressure, the compressibility issmall, and the increase of pressure has little effect on the solubility of thesubstance. At the same time, high pressure will increase the investment andoperating costs of the equipment. Therefore, it is more appropriate to select28Mpa for extraction from all aspects.

4.3 Effect of extraction temperature on grape seed oilextraction

On the one hand, the elevated temperature increases thediffusion coefficient of the substance, so that the solubility increases, whichis beneficial to the extraction; on the other hand, since the extractiontemperature is an important factor affecting the density of the supercriticalCO2 fluid, when the temperature rises, the CO2 is lowered. The density of thematerial reduces the solubility of the material, which is not conducive toextraction; in addition, the temperature rise will also reduce the quality ofthe product. Therefore, the extraction temperature should not be too high.

At 28Mpa, the extraction rate of grape seed oildecreased with the increase of temperature, but the extraction rate increasedslowly at the specified temperature of 35 °C; when the pressure was less thanor equal to 28Mpa, the temperature was below 35 °C, and the extraction rateincreased with temperature. And rise. For the effect of combined pressure andtemperature, the optimum temperature for extraction should be 35 °C.

4.4 Effect of extraction time on grape seed oilextraction

The supercritical CO2 fluid extraction process isdivided into three stages: the initial stage of extraction, the stage ofconversion, and the final stage of extraction. In the initial stage of extraction,the contact time of the substance with CO2 is small, and the amount of materialper unit time is less; as the extraction time is extended, the extraction stageis gradually increased; the final stage of extraction is due to the low contentof the extracted material in the material. In addition, the amount ofextraction per unit time is reduced. The results show that at 28 °C at 35 °C,the extraction rate is gradually increased below 80 minutes; the extractionrate below 80 minutes is close to the level and no longer increases. Therefore,the time for extracting grape seed oil from supercritical CO2 fluid should be80 minutes.

5. Summary

In the technique of extracting grape seed oil bysupercritical CO2 fluid, the pulverization degree extraction time temperatureis an important factor affecting the efficiency of extracting grape seed oil.

Grape seed oil contains a large amount of unsaturatedfatty acids necessary for the human body. Long-term consumption has the effectsof reducing blood pressure, lowering blood fat, softening blood vessels,lowering cholesterol, and preventing cardiovascular and cerebrovasculardiseases. Therefore, grape seed oil has a good health care function.

The raw material used for grape seed oil is theeasy-to-plant waste of the wine, which will become waste if not used, and willpollute the environment. The use of new technologies for comprehensiveutilization can greatly increase the value of the grapes. Therefore, it hasgreat development prospects.


6. SFE technology prospects

6.1 At present, the research and application of SFEtechnology in the world is in the ascendant. Germany, Japan and the UnitedStates are in a leading position. Research results in medicine, chemicalindustry, food, light industry and environmental protection are constantlycoming. The industrialized large-scale SFE equipment has 5000L~10000L. On thescale, Japan has successfully developed a supercritical chromatographicanalyzer. At present, the research focus of supercritical fluid extraction inthe world has been transferred. In order to obtain high value-added productswith higher purity, more and more research on countercurrent extraction andfractionation extraction of supercritical fluids is carried out; the reactionunder supercritical conditions is studied. It has become more important tofocus on various types of reactions, especially in the case of supercriticalwater and supercritical carbon dioxide; the field of supercritical fluidtechnology is more widely used. In addition to the extraction of naturalproducts, organic synthesis, environmental protection, material processing,paint printing, biotechnology and medicine; basic theoretical research onsupercritical fluid technology has been strengthened. These trends in the worlddeserve our attention.

6.2 China has carried out research on supercriticalfluid technology since the late 1970s and early 1980s, and the state has givengreater support to the research of this technology. According to preliminarystatistics, by 1999, the National Natural Science Foundation of China hadfunded more than 20 basic research projects with a funding amount of more than1 million yuan. During the "Eighth Five-Year Plan" period, thenational science and technology research project also specifically supportedthe application and engineering research of supercritical fluid extraction. Thetotal funding reached several million yuan, plus the matching funds of variousministries and commissions, provinces and cities, estimated to reach tens ofmillions of yuan. According to incomplete statistics, more than 10 sets ofsupercritical extraction devices of more than 100L have been built in China,and the largest scale has reached 1000L. The products produced include seabuckthorn oil, wheat germ oil, lecithin, capsanthin, artemisinin, etc. . Thereare about 120 sets of small and medium-sized devices below 25L, almost everyprovince, city and city. Undoubtedly, China has achieved encouraging results inthe basic and applied research of SFE technology. However, compared with the world'sadvanced level, the number of research and the number of equipment are notsmall, but the quality of equipment is not high, the measurement methods arerelatively backward, and the depth and breadth of research are quite different.The low level of repetition is more serious. Sustainable development is a newmodel for the development of human society and one of the basic nationalpolicies of all countries in the world. In order to achieve sustainabledevelopment of the society, it does not pollute the environment and does notcause harm to future generations. In the 21st century, the chemical industryand the pharmaceutical industry must research and develop new technologies forclean production and green industry by adjusting their industrial structure andproduct structure. new technology. SFE technology is such a new technology thathas developed rapidly in the past 30 years. From this strategic height, weshould understand the importance of SFE technology research and promotion andapplication, formulate research plans, increase investment, strengthen thebasic and applied research of the technology, and make it truly used forindustrial production, benefiting human beings and benefiting society.

6.3 SFE technology is essential for the modernization oftraditional Chinese medicine. It is necessary to shift from simple intermediateraw material extraction to taking into account the development and utilizationof new Chinese medicines for compound Chinese medicine, or to improve orsecondary development of currently produced famous Chinese patent medicines; tostrengthen the application of analytical supercritical fluid extraction orsupercritical chromatography in traditional Chinese medicine analysis,Continuous reform of traditional analytical methods; supercritical fluidcrystallization technology and preparation of ultrafine particles can be usedin the development of new dosage forms of traditional Chinese medicine, andshould be strengthened in the application of traditional Chinese medicine preparationsto promote the modernization of traditional Chinese medicine preparations.