The content of unsaturated fatty acids in blackberry seed oil is relatively high. Its main fatty acid composition and content are: linoleic acid 61.22%, linolenic acid 17.60%, oleic acid 14.72%, palmitic acid 3.71%, and stearic acid 2.18%.
Blackberry seeds, which are the by-products of processing blackberry concentrated juice (pulp), fruit juice and fruit wine, are used as raw materials, washed and separated, and then integrated. The blackberry seed oil is extracted by freeze-drying dehydration, freeze crushing, and supercritical CO2 fluid to improve The utilization rate of BlackBerry increases its added value.
Instruments and equipment
Supercritical CO2 fluid extraction process of blackberry seed oil: blackberry seed→cleaning and impurity removal→freezing crushing→sieving→freeze drying→weighing→charging→supercritical CO2 extraction→separation→blackberry seed oil
The physical properties of blackberry seeds for supercritical extraction determine the extraction conditions as follows: the feed amount is 100 g, the extraction pressure is 30 MPa, the extraction temperature is 45 ℃, the CO2 flow rate is 25 L/h, the extraction time is 60 min, the separation pressure is 7 MPa, and the separation temperature is 35 ℃, respectively. The effects of crushing degree of blackberry seeds (20, 40, 60 mesh) and water content (1.17%, 3.43%, 5.35%, 8.54%) on oil yield were investigated to determine the suitable physical conditions for supercritical extraction of blackberry seeds.
The effect of pulverization on the yield of blackberry seed oil
As the degree of pulverization increases, the oil yield of blackberry seeds gradually increases. When the particle size of the raw material decreases, the contact area between the supercritical fluid and the supercritical fluid increases, and the internal mass transfer resistance decreases, which significantly increases the extraction speed. However, if the particle size of the raw material is too small, the bulk density of the raw material may increase, which may cause the raw material to rapidly clump under pressure and affect the extraction effect.
And in the experiment, it is found that if the degree of pulverization is greater than 60 mesh, the material that is too fine will enter the pipeline with the CO2 fluid through the filter screen, causing pipe blockage, which is not conducive to the use and maintenance of the instrument. Comprehensive consideration, the blackberry seed grind degree is 60 meshes.
The influence of water content on oil yield
When the water content of blackberry seeds is in the range of 1.17% to 8.54 %, the oil yield of blackberry seed oil first increases and then decreases. When the water content is between 3.43% and 5.35%, the oil yield is significantly higher than other water contents.
The water content of the material is an important factor that affects the extraction efficiency. The appropriate amount of water in the blackberry seeds can act as an entrainer and help increase the oil yield.
However, the higher the water content of blackberry seeds, the more advantageous it is. When the water content is too high, a water film is easily formed on the surface of the material, which is not conducive to dissolving the target components.
In addition, it was found in this experiment that when the moisture content of blackberry seeds is too high, the phenomenon of “ice blocking” is likely to occur, and the extracted oil is turbid and the color darkens. Some studies believe that this phenomenon is caused by excessive extraction pressure.
However, further research in this experiment believes that the reason may be that the high water content in the blackberry seeds leads to the extraction of water-soluble pigments such as chlorophyll in the blackberry seeds.
Therefore, the water content of blackberry seeds should be between 3.43% and 5.35%.
The influence of CO2 flow rate on the extraction effect
CO2 flow rate is an important economic factor in the extraction process.
With the increase of CO2 flow rate, the oil yield of blackberry seed oil increases, and the oil yield rate at 25 L/h is significantly higher than other CO2 flow rates (P＜0.05). After that, the CO2 flow rate increases, and the oil yield rate of blackberry seed oil shows a decreasing trend. .
On the one hand, the increase in CO2 flow rate can increase the mass transfer driving force of the extraction process, speed up the mass transfer rate, and reach equilibrium solubility faster, thereby improving the extraction efficiency and shortening the extraction time; on the other hand, excessive CO2 flow will cause The residence time of CO2 in the extractor is shortened, so that the contact time of CO2 with the extract is reduced, and the production cost is increased.
Effect of extraction pressure on the yield of blackberry seed oil
The extraction pressure has a significant effect on the oil yield of blackberry seed oil.
At the beginning of extraction, the oil yield of blackberry seed oil increased rapidly, but when the extraction was carried out to 45 minutes, the oil yield increased more slowly, and the oil yield increased very little after 60 minutes.
And as the extraction pressure gradually increases, the oil yield of blackberry seed oil also increases, but when the pressure increases to 30 MPa, the oil yield increases slowly. Moreover, the increase in extraction pressure will increase the energy consumption and equipment investment, as well as the increase of impurities in the extracted target components.
Therefore, the extraction pressure is proposed to be around 30 MPa.
The effect of extraction temperature on extraction effect
Under the extraction pressure of 30 MPa, the effect of extraction temperature on the oil yield of blackberry seed oil showed a trend of increasing first and then decreasing. The oil yield was the highest at 45 ℃, which was 18.6%.
And during the extraction process, as the temperature rises, the solubility of impurities in the material increases, and the probability of being extracted also gradually increases, which will reduce the purity of the target component, and high temperature can also cause some thermal stability. Poor decomposition of matter.
Therefore, the extraction temperature should be carefully selected to 45 ℃.
The effect of extraction time on extraction effect
The longer the extraction time, the higher the yield of blackberry seed oil.
In the initial stage of extraction, the oil yield of blackberry seed oil increased significantly with the extension of the extraction time; but after 60 minutes of extraction, the oil yield increased slowly.
Therefore, in order to reduce energy consumption and improve extraction efficiency, the extraction time is determined to be 60 min.
The effect of separation temperature on the extraction effect
The separation temperature has no significant effect on the oil yield of blackberry seed oil.
Generally, a lower separation temperature is conducive to the stability of the active ingredients in the extract. However, it was found in experiments that when the separation temperature was 30 ℃, more white solid CO2 particles were sprayed out of the separation kettle along with the blackberry seed oil.
It shows that at this temperature, CO2 cannot be completely gasified, that is, it cannot achieve good separation from blackberry seed oil. When the separation temperature is 35 ℃, almost no solid CO2 particles are found in the material taken.
The separation temperature was determined to be 35°C.
The effect of separation pressure on the yield of blackberry seed oil
The oil yield of blackberry seed oil reached the highest value at 7 MPa, and then showed a decreasing trend with the increase of separation pressure.
The higher separation pressure not only is not conducive to the complete separation of the CO2 fluid and the blackberry seed oil, but also causes unnecessary energy waste. Therefore, the separation pressure in this experiment is determined to be 7 MPa.
Best process parameters for supercritical CO2 extraction of blackberry seed oil
The degree of pulverization is 60 mesh, the water content is 3.43% ~ 5.35%, the extraction pressure is 30 MPa, the extraction temperature is 40 ℃, the CO2 flow rate is 25 L/h, the extraction time is 60 min, the separation pressure is 7 MPa, and the separation temperature is 35 ℃. Under these conditions, the oil output rate is 18.6%
The physicochemical index of blackberry seed oil extracted by supercritical CO2 after freezing powder and freeze-drying is significantly better than that of Soxhlet method and supercritical CO2 extraction by blackberry seed oil after high-speed crushing and hot air drying. Because the temperature can always be maintained at a low level throughout the processing process, no organic solvents are used, and there is no solvent residue. Therefore, the functional components in the oil are better protected, and the obtained blackberry seed oil has good quality and is green and environmentally friendly.
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