Safflower oil is a vegetable oil extracted from the seeds of the genus Carthamus tinctorius L., and its linoleic acid content is the highest among all vegetable oils, while linoleic acid is a human body but not in the body. Self-synthesized fatty acids can significantly reduce the amount of cholesterol in human plasma, prevent heart and cerebrovascular diseases, and safflower seed oil is considered to be one of the best edible oils in the world. At present, the method of extracting safflower seed oil is mainly a pressing method or an extraction method. The yield of the pressing method is low, and the purity of the safflower seed oil obtained by the extraction method is not high, and there is solvent residue, and the effects are not satisfactory. Supercritical CO2 has good solubility in fat-soluble substances. As an extraction medium, the extraction amount can be increased, and the product can be separated by itself without any residue. The authors examined the effects of supercritical CO2 extraction process parameters on safflower seed oil extraction to clarify the process control factors and obtain high quality safflower seed oil.
1.1 Raw materials and reagents
Safflower seeds (water content 5.6%, oil content 26.7%), produced in Xinjiang Jimsar. Carbon dioxide (purity 99.5%), Taiyuan Fertilizer Plant.
The experiment used a self-made semi-continuous supercritical extraction device. The volume of the extractor and separator are 0.5L and 0.2L, respectively. The extraction temperature can be adjusted from room temperature to 353K, the maximum extraction pressure is 32 MPa, and the flow rate is adjustable from 0 to 4.5 L·h-1.
The CO2 is filtered from the cylinder into the condenser and turned into a liquid. The plunger pump is metered into the extractor to extract the smashed safflower seeds. The throttle valve controls the step-down pressure and will carry the safflower seed oil CO2. The fluid is sent to separators I and II in turn, the density of supercritical CO2 is reduced, and safflower seed oil is separated from CO2 by itself. The safflower seed oil was detected and analyzed by GC7890 gas chromatograph (Tianmei).
2 Results and discussion
2.1 Effect of extraction pressure on the extraction of safflower seed oil
The loading amount is 50g, the extraction temperature is 323K, the CO2 flow rate is 4.5L·h-1, and the two-stage separation (the same below) is carried out under the conditions of 12MPa/313K, (5-6) MPa/313K, and the extraction pressure is investigated (20). The effect of ~28MPa) on the extraction amount of safflower seed oil, the results are shown in Figure 1.
It can be seen from Fig. 1 that, in the case where the extraction temperature is constant, the time for the extraction to reach equilibrium is shortened as the extraction pressure is increased, and the extraction amount of safflower seed oil is significantly increased. When the extraction time is 120min and the extraction pressure is increased from 20MPa to 28MPa, the extraction amount of safflower seed oil is increased from 5.73g to 11.95g, which is about 1 times, indicating that higher extraction pressure is beneficial to the extraction of safflower seed oil. This is similar to the supercritical CO2 extraction of other seed oils. This is because the increase in pressure causes the density of supercritical CO2 to increase, so that the solubility of the oil increases and the time for the extraction to reach equilibrium is relatively shortened.
2.2 Effect of extraction temperature on the extraction of safflower seed oil
The extraction pressure was 28 MPa, and other conditions were the same as 2.1. The effect of extraction temperature (308-323 K) on the extraction amount of safflower seed oil was investigated. The results are shown in Fig. 2.
It can be seen from Fig. 2 that between 308 and 318 K, the extraction amount increases as the extraction temperature increases; when the extraction temperature increases from 318 K to 323 K, the extraction amount decreases slightly. This is similar to the supercritical CO2 extraction of other seed oils. Temperature has two effects on the dissolution of fats and oils in CO2 fluids. On the one hand, increasing the temperature leads to an increase in the diffusion coefficient of the oil molecules, the viscosity of the CO2 fluid decreases, the mass transfer coefficient increases, and the solubility of the oil increases therein; on the other hand, the density of the supercritical CO2 fluid increases with temperature. The decrease leads to a decrease in the solvation effect of the CO2 fluid and a decrease in the solubility of the oil in the CO2. The overall impact depends on the combined effects of the two above. The extraction temperature is between 308 and 318K. The former is the dominant factor, which leads to an increase in the extraction amount. Between 318 and 323K, the latter has a significant influence, resulting in a slight decrease in the extraction amount.
2.3 Effect of extraction time on the extraction of safflower seed oil
The extraction pressure was 28 MPa, the extraction temperature was 318 K, and other conditions were the same as 2.1. The effect of extraction time on the extraction amount of safflower seed oil was investigated. The results are shown in Fig. 3.
It can be seen from Fig. 3 that the extraction amount increased linearly in the first 1 h of extraction, and the increase was decreased between 1 and 2 h after extraction. When the extraction time was 2 h, the total amount of the product reached 12.32 g, and the extraction was nearly complete; the product increased slowly after 2 h of extraction. Therefore, the optimum extraction time was determined to be 2 h.
2.4 Effects of other factors on the extraction of safflower seed oil
The CO2 flow rate, the moisture and particle size of the raw materials are also important factors affecting the supercritical CO2 extraction process. Under the maximum flow rate of CO2 (4.5L·h-1), the extraction pressure and extraction temperature were set to 28MPa and 318K, respectively. The effect of the charge on the extraction amount was investigated. The results are shown in Fig. 4.
It can be seen from Fig. 4 that the absolute amount of safflower seed oil extracted per unit time does not differ greatly with the change of the charge amount, but the more the charge amount, the lower the oil yield per unit mass of raw material. This is because the maximum extraction capacity of a certain amount of CO2 is constant, resulting in a decrease in the relative extraction amount with an increase in the amount of charge.
Because water has a certain solubility in high pressure CO2, if the moisture content of the raw material is high, the water will act as an entrainer. The effect of the water content of the raw material on the extraction amount is shown in Fig. 5.
It can be seen from Fig. 5 that the drying of the raw material has little effect on the extraction of the total amount of the product, but the yield of the oil after drying is relatively high, and the oil-water separation process of product collection can be omitted. The moisture content of the raw materials used in this experiment was only 5.6%. In addition, in order to improve the extraction efficiency, the raw materials generally need to be broken. However, the particles need not be too small to avoid clogging the sieve holes or being taken out of the extractor, and the safflower seeds have a high oil content and the particle size is too small to stick together. The average particle size of the raw materials used in this experiment was 1.26 mm.
2.5 Analysis of the composition of safflower seed oil
By controlling the separation conditions of supercritical extraction, the safflower seed oil collected from the separator I accounts for about 85% of the total amount of the product, and is a light yellow transparent liquid at room temperature, and the physical quality is obviously superior to the safflower produced by the solvent extraction method. Seed oil. The oil was hydrolyzed and then methyl esterified. The fatty acid was analyzed by gas chromatography. The external components were determined to obtain four main components. The relative content was calculated by area normalization method. The results are shown in Table 1.
It can be seen from Table 1 that the main components of the safflower seed oil in the separator I are effectively enriched, and the contents of linoleic acid and unsaturated fatty acid are as high as 79.16% and 91.37%, respectively, and the impurity content is reduced as compared with the solvent extraction method.
(1) Extraction of safflower seed oil by supercritical CO2 fluid, the extraction amount increases with the increase of extraction pressure; compared with the extraction pressure, the influence of extraction temperature is small, and the extraction amount increases with the increase of extraction temperature. value.
(2) Supercritical CO 2 fluid extracts safflower seed oil, and its main components can be effectively enriched by controlling the separation conditions. The obtained safflower seed oil has a significantly improved content of linoleic acid and unsaturated fatty acid, and is an ideal health-care edible oil.