Pine nut oil is taken from the natural red pine seed. It is a natural and environmentally-friendly green woody vegetable oil. It is a natural bulk product in nature and is inexhaustible for people to develop and utilize. It not only can increase the variety of edible oils, regulate the nutritional structure of people's food, but also improve economic benefits. Therefore, the development of pine nut oil has broad prospects. Pine nut kernel is rich in unsaturated fatty acids, especially linolenic acid. Lnolenic acid (LNA) has a molecular formula of C18H30O2, which is an essential unsaturated fatty acid with important health care effects. The traditional scouring process extracts linolenic acid oil from pine nuts, which destroys more biologically active components due to high temperature. The supercritical CO2 extraction process utilizes the relationship between the solubility of the supercritical CO2 fluid and its density, that is, the effect of pressure and temperature on the solubility of the supercritical fluid. In the supercritical state, the solubility of CO2 to different solutes varies greatly, so it can be effectively extracted and separated. Supercritical extraction has the characteristics of low operating temperature, good selectivity, complete extraction from extraction to separation, and no residual residue, so it can preserve bioactive components well.
1. Experimental materials and equipment
Pine nuts: Jilin Changbai Mountain. Analytical supercritical fluid extractor: supercritical extraction, HP6890/HP5973 GC/MS: HP Instruments, USA.
2, experimental methods and steps
2.1, experimental methods
Based on several supercritical CO2 experiments, preliminary data of extraction tank pressure and temperature, rectification column temperature and extraction time of linolenic acid extracted from pine nuts were obtained. On this basis, extraction pressure, extraction temperature, extraction time, Four factors of column temperature were determined, and three levels of each factor were determined. The orthogonal experimental design was carried out by using L9 (34), and the experiment was carried out by using 2L extraction kettle. The extraction and separation process was: extraction kettle - rectification column - separation I - Separation II.
2.2, SFE experiment flow chart
3, experimental record data and processing analysis
3.1, SFE condition optimization
3.1.1. Effect of temperature When the temperature is increased, on the one hand, the mass transfer rate of the fluid increases, and the solute cohesive energy is lowered to facilitate the desorption of the extract from the substrate; however, the density of the fluid increases correspondingly. Causes a decrease in solvency. Experiments have shown that the optimum extraction temperature is 40 °C.
3.1.2. Influence of pressure With the increase of pressure, the yield of linolenic acid in pine nuts increases, because the density of fluid increases with the increase of pressure, and the solvency of linolenic acid in pine nuts increases. . The optimum pressure is 35 MPa.
3.1.3. Effect of extraction time With the increase of extraction time, the yield of linolenic acid in pine nuts increased, but the increase over 1.5h was not very significant.
3.1.4. Effect of column temperature Experiments showed that the increase of linolenic acid in pine nuts increased with the increase of column temperature, but the extraction rate of linolenic acid in pine nuts decreased after the column temperature increased to 34 °C.
3.2, experimental raw data record
On the basis of single factor experiment, the linolenic acid in pine nuts was extracted under the different conditions of the four factors and three levels of orthogonal design. The extraction rate was determined. The results are shown in Table 2, and the analysis results of the test data are shown in Table 3.
The test uses a visual analysis method to analyze the magnitudes of the K, k and R (very poor) values of each factor. According to the analysis of the orthogonal test results, the following results can be obtained:
(1) The order of the range R from large to small is D>B>A>C, the larger the difference is, the greater the influence of this factor on the index value, which indicates that the linolenic acid extraction in pine nut kernel is affected during the extraction process. The main factor is the column temperature, followed by the extraction pressure, the extraction temperature, and finally the extraction time.
(2) From the results of variance analysis, the column temperature has a significant effect on the extraction rate of linolenic acid in pine nuts. The extraction pressure, extraction temperature and extraction time have significant effects on the extraction rate of linolenic acid in pine nuts. A2B2C1D2 was chosen as the best solution. The optimal extraction conditions for extracting linolenic acid from pine nuts by supercritical CO2 were: extraction temperature 40 °C, extraction pressure 35 MPa, extraction time 90 min, column temperature 34 °C.
3.3 Comparison with the refined method
The fine pressing method means that the oil material is first ground and crushed, and then the oil is squeezed out, and finally a series of refining and purification are carried out. At present, linolenic acid oil is prepared from pine nuts in China, and this production process is generally adopted. The yield of the extractive extraction method is generally around 21.4%.
The experimental results show that the supercritical CO2 extract has no solvent residue and good color, and the yield of the extract is 34.6%, which is 13.2% higher than the yield of the refined extraction method of 21.4%.
4, extract analysis
HP6890/HP5973 GC/MS, HP-ultra á capillary column: 30:1 split injection, injection volume lìL, inlet temperature 240 °C, electron energy 70eV, ion source temperature 230 °C, quadrupole temperature 150 °C, multiplier voltage 1635V, carrier gas (He) 28.8mL / min.
The results showed that the content of unsaturated fatty acids in the extract was as high as 84.8%, and the content of linolenic acid was particularly rich, reaching 34.6%.
Supercritical CO2 extraction method was used to extract the linolenic acid oil from pine nuts of Changbai Mountain, Jilin Province, and the extraction yield was higher than that of the refined method. Moreover, the supercritical CO2 fluid extraction operation temperature was low, and the natural active ingredients of heat instability and easy oxide were saved in large amount; The supercritical CO2 fluid extraction method uses CO2 as the extraction medium. The system is closed, safe, non-toxic, and there is no solvent residue problem. The extraction and separation are completed once and the quality of the extracted linolenic acid oil can be guaranteed. It is a good new extraction process. .
6.1 Extraction of linolenic acid oil from pine nuts by supercritical CO2 The extraction conditions are: extraction temperature 40 ° C, extraction pressure 35 MPa, extraction time 90 min, column temperature 34 ° C.
6.2 Supercritical CO2 extract has no solvent residue and good color, and its extract yield is 34.6%, which is 13.2% higher than the yield of the refined extraction method.
6.3 The analysis results of HP6890/HP5973 GC/MS showed that the content of unsaturated fatty acids in the extract was as high as 84.8%, and the content of linolenic acid was especially rich, reaching 34.6%. Pine nut oil can be used as a health care oil with extremely high nutritional value.