Abstract: Different techniques for extracting kiwifruit seed oil from kiwifruit seeds were discussed, and the oil components were analyzed. Kiwifruit seed oil was extracted by solvent extraction and supercritical CO2 fluid extraction. The experimental results show that the extraction of kiwifruit seed oil from kiwifruit seeds, using super, critical C02 extraction method has obvious advantages compared with other extraction methods. It is a safe and reliable method with broad application prospects. According to gas chromatography analysis, kiwi seed oil contained 69.5% linolenic acid.
Key words: kiwi seed oil; supercritical CO 2; extraction; linolenic acid In recent years, supercritical fluid extraction has been rapidly developed as a new separation technique. CO2 is chemically stable, non-toxic, non-corrosive, non-flammable, non-explosive, and can be easily reached at critical temperatures (Tc=304.13K) and critical pressure (Pc=7.375MPa). It does not destroy molecular structure when operated at mild temperatures. The unparalleled advantages of organic solvents have broad application prospects in the fields of food, medicine, bioengineering, chemical industry and environmental protection. Kiwifruit is a kind of vine, also known as vine pear and carambola. It is one of the special fruits in China. In recent years, it has developed rapidly in production and processing. It has successively developed a series of foods such as kiwi fruit juice, jam, preserved fruit, dried fruit and fruit wine, which are welcomed by consumers. However, the development and utilization of its by-product kiwifruit seeds has not been paid enough attention. Kiwifruit seeds are small, shaped like sesame, non-toxic. The oil content (mass fraction) of the grain was determined to be 22% to 24%, and the main components of kiwifruit seed oil were analyzed by gas chromatography to be unsaturated fatty acids such as linolenic acid and linoleic acid. Linoleic acid and linolenic acid are essential for the synthesis of human biofilms and hormones, and the body cannot synthesize itself. Must be provided by meal. Therefore, the extraction of oil from kiwifruit seeds has a high use value.
Currently, oil extraction from kiwi seed oil is by pressing or organic solvent extraction. The yield of the pressing method is low. In the organic solvent extraction, there is solvent residue, which requires subsequent processing, and the obtained kiwi seed oil is dark in color and somewhat odorous. In this study, supercritical CO 2 was used as a solvent to extract high quality kiwi seed oil from kiwifruit seeds and compared with the solvent method.
1 Materials and methods
1.1 Materials and equipment Kiwi seed, Shaanxi Zhouzhi Zhonghua kiwi seed; petroleum ether: analytical grade, boiling range 60 ~ 90 ° C; n-hexane: analytical purity; CO2 (99.99%), Shaanxi Xinghua Co., Ltd.; 0.01g balance; GC -5A gas chromatograph; HA120-40-01 supercritical extraction device, Jiangsu Nantong Huaan Supercritical Extraction Co., Ltd.
1.2 Experimental methods
1.2.1 Solvent extraction The kiwifruit seeds are pulverized, put into a container, refluxed with an organic solvent, filtered, evaporated, concentrated, etc., and then subjected to a purification step to obtain a pale yellow kiwi seed oil.
1.2.2 Supercritical CO2 extraction A certain amount of crushed kiwi seeds are placed in the extraction column, and the CO2 cylinder is opened. After passing through the filter, the CO2 is pressurized by the membrane press to the required pressure, and the buffer tube is heated by the water jacket. The extraction is carried out from the bottom into the extraction column, and then the CO in which the solute is dissolved is separated into the separation column through the middle portion. The separated product is discharged from the shut-off valve at the bottom of the separation column, and the remaining part enters the collecting column to further separate the remaining solute. The gaseous CO2 is vented after being measured by the rotor flow meter, and is sampled from the separation column at regular timing for weighing analysis.
2 Results and discussion
2.1 Solvent method
2.1.1 Solvent Selection The extraction of oils and fats can be carried out with non-polar solvents and polar solvents. In this experiment, petroleum ether and n-hexane were selected as solvents. With intermittent reflux extraction, the reflux time, the number of extractions, and the solid-liquid ratio of the extract (solvent volume: mass of the raw materials) remained unchanged, and the extraction temperature was slightly lower than the boiling point of the solvent. Extraction results.
2.2.2 Effect of raw material particle size on extraction yield Extracting oil from kiwifruit seeds must first be broken in order to allow the solvent to enter the interior quickly. Three samples obtained by crushing 3 parts of the material were extracted with petroleum ether. The No. 1 sample was pulverized by a large hole mesh sieve, the No. 2 sample was pulverized by a small hole mesh sieve, and the No. 3 sample was pulverized by a small hole mesh sieve for 2 times.
It can be seen that when the particle size is too large, the extraction yield is low, the process time is prolonged, and the cost is increased; when the particle size is too small, the pulverization process is easy to adhere to the wall due to the high oil content of the seed, and the extraction yield is also lowered.
2.2 Supercritical Co2 extraction
2.2.1 Effect of pressure on extraction results Extraction pressure is the main parameter affecting the solubility of the extract in supercritical fluids. The solvency of supercritical CO2 increases with increasing pressure, because increasing pressure not only increases the density of CO2, but also reduces the mass transfer resistance between molecules, increases the mass transfer efficiency between solute and solvent, and facilitates the extraction of target components. .
The variation of kiwifruit seed oil extraction with pressure was observed under the conditions of the same feed amount of 300g, temperature of 45 °C and constant flow rate of 4.1 L/min. It can be seen from the figure that as the extraction pressure increases, the amount of extraction increases. Considering that the investment and operating costs of equipment under high pressure will be greatly increased, we have chosen an extraction pressure of about 30 MPa.
2.2.2 Effect of extraction temperature on the extraction results The effect of temperature is more complicated and related to pressure. Generally, increasing the extraction temperature can increase the volatility of the extract, thereby increasing the yield, but the temperature increases, the density of the supercritical fluid decreases, the solubility decreases, and the oil yield decreases.
The effect of temperature on the solubility of kiwifruit seed oil in CO2 under different pressures is indicated. When the pressure is 35MPa, the temperature rise accelerates the diffusion rate of the solute, the solubility of the oil in CO2 also increases, and the extraction increases with the increase of temperature, which is similar to the solubility characteristic of the liquid; when the pressure is At 25 MPa, the temperature rises and the solubility decreases. This is because at low pressure, the density of supercritical CO2 is inherently small, and its solubility is also small. At this time, the increase in temperature causes the volatility of the oil to increase and the diffusion coefficient to increase, so that the solubility becomes larger. The decrease in solubility caused by the decrease in CO2 density, so the amount of extraction decreases with increasing temperature. However, too high a temperature will increase the operating energy consumption and increase the cost.
2.2.3 The effect of CO2 flow on the extraction results is the relationship between CO2 flow and extraction. It can be seen from the figure that as the flow rate of CO2 increases, the amount of extraction gradually increases until the extraction is substantially completed. The flow rate is large, although it is favorable for extraction, but the flow rate is too large, and the contact between CO2 and materials is insufficient. Therefore, the increase of extraction amount tends to be moderated, and the increase of flow rate will increase the operation cost; when the flow rate is too low, the yield in the same time Also lower. So you must choose the right traffic.
2.2.4 The effect of extraction time on the extraction results can be seen. At the beginning of the extraction, the extraction amount increases linearly with time. With the extension of time, the oil content in the material gradually decreases. After 2.5 hours, the extraction is almost complete and then extended. Time, the amount of extraction is not much improved, and there will be other impurities other than oil extraction. From the extraction efficiency, the suitable extraction time is 2.5h.
2.3 Results of supercritical extraction After optimization of the conditions of supercritical CO 2 extraction, the suitable process conditions were obtained: extraction pressure 30 MPa, extraction temperature 45 ° C, CO 2 flow rate 5 L / min, extraction time 2.5 h. The result of the extraction under this condition.
It can be seen that the supercritical extraction has a higher oil extraction rate and an average oil extraction rate of 23.02%. According to the literature, the kiwifruit seed oil generally has a oil content of 23.5%. The oil extraction rate can be selected by the method of supercritical CO 2 extraction. Up to 97.9%.
3 Kiwifruit seed oil composition analysis
3.1 Physical and chemical analysis of physicochemical analysis results of kiwi seed oil.
3.2 Chromatographic analysis Take 0.2g of supercritical fluid extracted with human saponification solution (0.5mol / L KOH-methanol) 2mL, mix, saponify in a water bath at 60 ° C until the oil beads disappear, after cooling, add methanol esterification solution ( 2mL of 14% boron trifluoride-methanol) was methylated in a water bath at 60 ° C for 30 min. After cooling, 1 mL of n-hexane and 1 mL of saturated sodium chloride were added. After centrifugation, the supernatant was taken, and the oil composition was analyzed by gas chromatography. Column: 2m × 3mm 3% OV-225/WHP (60/80 mesh) glass column; carrier gas: N2; column flow: 4mL / min; column temperature: 200 ° C; vaporization chamber temperature: 250 ° C; detector temperature : 250 ° C. The content is calculated by the peak area normalization method. Chromatogram of kiwi seed oil.
As can be seen from the table, kiwi seed oil contains 69.5% linolenic acid, and the total amount of unsaturated fatty acids is 96.9%. Unsaturated fatty acids such as linolenic acid have the effects of lowering blood fat, lowering cholesterol, promoting fat metabolism, and regenerating liver cells. Linolenic acid also has high use value by immunizing and anti-allergic reactions, improving and protecting brain neuromembrane function, delaying aging, preventing dry skin and promoting hair growth.
4 Conclusion According to the determination of the oil content of kiwifruit seeds is 23%, kiwi seed oil contains 69.5% linolenic acid, the total amount of unsaturated fatty acids is 96.9%, can be developed as a health oil resource. Extracting high-quality edible health oil from kiwifruit seeds and further developing them into various functional foods, medicines and cosmetics, which can solve the problem of waste disposal of kiwifruit processing enterprises such as kiwi winery and juice beverage factory, and greatly broaden the kiwifruit. In the field of deep processing, turning waste into treasure will bring better economic benefits to the production enterprises. The traditional pressing process has a low oil yield, while the solvent extraction method has residual organic solvents and is harmful to the human body. Compared with supercritical cO2 fluid extraction, there is no solvent residue, no pollution to food, no pollution to the environment, high extraction rate and safe production, and it has a good application prospect.
references:
[1] Chen Kaixun, Ge Hongguang, Yao Ruiqing. Supercritical C02 extraction of tea seed oil [J]. China Oils and Fats, 1996, 21 (5): 3O-34.
[2] Chen Yuan, Yang Foundation. Supercritical CO 2 extraction of linseed oil [J]. Natural Product Research and Development, 2001, 13(3): 14-19.
Key words: kiwi seed oil; supercritical CO 2; extraction; linolenic acid In recent years, supercritical fluid extraction has been rapidly developed as a new separation technique. CO2 is chemically stable, non-toxic, non-corrosive, non-flammable, non-explosive, and can be easily reached at critical temperatures (Tc=304.13K) and critical pressure (Pc=7.375MPa). It does not destroy molecular structure when operated at mild temperatures. The unparalleled advantages of organic solvents have broad application prospects in the fields of food, medicine, bioengineering, chemical industry and environmental protection. Kiwifruit is a kind of vine, also known as vine pear and carambola. It is one of the special fruits in China. In recent years, it has developed rapidly in production and processing. It has successively developed a series of foods such as kiwi fruit juice, jam, preserved fruit, dried fruit and fruit wine, which are welcomed by consumers. However, the development and utilization of its by-product kiwifruit seeds has not been paid enough attention. Kiwifruit seeds are small, shaped like sesame, non-toxic. The oil content (mass fraction) of the grain was determined to be 22% to 24%, and the main components of kiwifruit seed oil were analyzed by gas chromatography to be unsaturated fatty acids such as linolenic acid and linoleic acid. Linoleic acid and linolenic acid are essential for the synthesis of human biofilms and hormones, and the body cannot synthesize itself. Must be provided by meal. Therefore, the extraction of oil from kiwifruit seeds has a high use value.
Currently, oil extraction from kiwi seed oil is by pressing or organic solvent extraction. The yield of the pressing method is low. In the organic solvent extraction, there is solvent residue, which requires subsequent processing, and the obtained kiwi seed oil is dark in color and somewhat odorous. In this study, supercritical CO 2 was used as a solvent to extract high quality kiwi seed oil from kiwifruit seeds and compared with the solvent method.
1 Materials and methods
1.1 Materials and equipment Kiwi seed, Shaanxi Zhouzhi Zhonghua kiwi seed; petroleum ether: analytical grade, boiling range 60 ~ 90 ° C; n-hexane: analytical purity; CO2 (99.99%), Shaanxi Xinghua Co., Ltd.; 0.01g balance; GC -5A gas chromatograph; HA120-40-01 supercritical extraction device, Jiangsu Nantong Huaan Supercritical Extraction Co., Ltd.
1.2 Experimental methods
1.2.1 Solvent extraction The kiwifruit seeds are pulverized, put into a container, refluxed with an organic solvent, filtered, evaporated, concentrated, etc., and then subjected to a purification step to obtain a pale yellow kiwi seed oil.
1.2.2 Supercritical CO2 extraction A certain amount of crushed kiwi seeds are placed in the extraction column, and the CO2 cylinder is opened. After passing through the filter, the CO2 is pressurized by the membrane press to the required pressure, and the buffer tube is heated by the water jacket. The extraction is carried out from the bottom into the extraction column, and then the CO in which the solute is dissolved is separated into the separation column through the middle portion. The separated product is discharged from the shut-off valve at the bottom of the separation column, and the remaining part enters the collecting column to further separate the remaining solute. The gaseous CO2 is vented after being measured by the rotor flow meter, and is sampled from the separation column at regular timing for weighing analysis.
2 Results and discussion
2.1 Solvent method
2.1.1 Solvent Selection The extraction of oils and fats can be carried out with non-polar solvents and polar solvents. In this experiment, petroleum ether and n-hexane were selected as solvents. With intermittent reflux extraction, the reflux time, the number of extractions, and the solid-liquid ratio of the extract (solvent volume: mass of the raw materials) remained unchanged, and the extraction temperature was slightly lower than the boiling point of the solvent. Extraction results.
2.2.2 Effect of raw material particle size on extraction yield Extracting oil from kiwifruit seeds must first be broken in order to allow the solvent to enter the interior quickly. Three samples obtained by crushing 3 parts of the material were extracted with petroleum ether. The No. 1 sample was pulverized by a large hole mesh sieve, the No. 2 sample was pulverized by a small hole mesh sieve, and the No. 3 sample was pulverized by a small hole mesh sieve for 2 times.
It can be seen that when the particle size is too large, the extraction yield is low, the process time is prolonged, and the cost is increased; when the particle size is too small, the pulverization process is easy to adhere to the wall due to the high oil content of the seed, and the extraction yield is also lowered.
2.2 Supercritical Co2 extraction
2.2.1 Effect of pressure on extraction results Extraction pressure is the main parameter affecting the solubility of the extract in supercritical fluids. The solvency of supercritical CO2 increases with increasing pressure, because increasing pressure not only increases the density of CO2, but also reduces the mass transfer resistance between molecules, increases the mass transfer efficiency between solute and solvent, and facilitates the extraction of target components. .
The variation of kiwifruit seed oil extraction with pressure was observed under the conditions of the same feed amount of 300g, temperature of 45 °C and constant flow rate of 4.1 L/min. It can be seen from the figure that as the extraction pressure increases, the amount of extraction increases. Considering that the investment and operating costs of equipment under high pressure will be greatly increased, we have chosen an extraction pressure of about 30 MPa.
2.2.2 Effect of extraction temperature on the extraction results The effect of temperature is more complicated and related to pressure. Generally, increasing the extraction temperature can increase the volatility of the extract, thereby increasing the yield, but the temperature increases, the density of the supercritical fluid decreases, the solubility decreases, and the oil yield decreases.
The effect of temperature on the solubility of kiwifruit seed oil in CO2 under different pressures is indicated. When the pressure is 35MPa, the temperature rise accelerates the diffusion rate of the solute, the solubility of the oil in CO2 also increases, and the extraction increases with the increase of temperature, which is similar to the solubility characteristic of the liquid; when the pressure is At 25 MPa, the temperature rises and the solubility decreases. This is because at low pressure, the density of supercritical CO2 is inherently small, and its solubility is also small. At this time, the increase in temperature causes the volatility of the oil to increase and the diffusion coefficient to increase, so that the solubility becomes larger. The decrease in solubility caused by the decrease in CO2 density, so the amount of extraction decreases with increasing temperature. However, too high a temperature will increase the operating energy consumption and increase the cost.
2.2.3 The effect of CO2 flow on the extraction results is the relationship between CO2 flow and extraction. It can be seen from the figure that as the flow rate of CO2 increases, the amount of extraction gradually increases until the extraction is substantially completed. The flow rate is large, although it is favorable for extraction, but the flow rate is too large, and the contact between CO2 and materials is insufficient. Therefore, the increase of extraction amount tends to be moderated, and the increase of flow rate will increase the operation cost; when the flow rate is too low, the yield in the same time Also lower. So you must choose the right traffic.
2.2.4 The effect of extraction time on the extraction results can be seen. At the beginning of the extraction, the extraction amount increases linearly with time. With the extension of time, the oil content in the material gradually decreases. After 2.5 hours, the extraction is almost complete and then extended. Time, the amount of extraction is not much improved, and there will be other impurities other than oil extraction. From the extraction efficiency, the suitable extraction time is 2.5h.
2.3 Results of supercritical extraction After optimization of the conditions of supercritical CO 2 extraction, the suitable process conditions were obtained: extraction pressure 30 MPa, extraction temperature 45 ° C, CO 2 flow rate 5 L / min, extraction time 2.5 h. The result of the extraction under this condition.
It can be seen that the supercritical extraction has a higher oil extraction rate and an average oil extraction rate of 23.02%. According to the literature, the kiwifruit seed oil generally has a oil content of 23.5%. The oil extraction rate can be selected by the method of supercritical CO 2 extraction. Up to 97.9%.
3 Kiwifruit seed oil composition analysis
3.1 Physical and chemical analysis of physicochemical analysis results of kiwi seed oil.
3.2 Chromatographic analysis Take 0.2g of supercritical fluid extracted with human saponification solution (0.5mol / L KOH-methanol) 2mL, mix, saponify in a water bath at 60 ° C until the oil beads disappear, after cooling, add methanol esterification solution ( 2mL of 14% boron trifluoride-methanol) was methylated in a water bath at 60 ° C for 30 min. After cooling, 1 mL of n-hexane and 1 mL of saturated sodium chloride were added. After centrifugation, the supernatant was taken, and the oil composition was analyzed by gas chromatography. Column: 2m × 3mm 3% OV-225/WHP (60/80 mesh) glass column; carrier gas: N2; column flow: 4mL / min; column temperature: 200 ° C; vaporization chamber temperature: 250 ° C; detector temperature : 250 ° C. The content is calculated by the peak area normalization method. Chromatogram of kiwi seed oil.
As can be seen from the table, kiwi seed oil contains 69.5% linolenic acid, and the total amount of unsaturated fatty acids is 96.9%. Unsaturated fatty acids such as linolenic acid have the effects of lowering blood fat, lowering cholesterol, promoting fat metabolism, and regenerating liver cells. Linolenic acid also has high use value by immunizing and anti-allergic reactions, improving and protecting brain neuromembrane function, delaying aging, preventing dry skin and promoting hair growth.
4 Conclusion According to the determination of the oil content of kiwifruit seeds is 23%, kiwi seed oil contains 69.5% linolenic acid, the total amount of unsaturated fatty acids is 96.9%, can be developed as a health oil resource. Extracting high-quality edible health oil from kiwifruit seeds and further developing them into various functional foods, medicines and cosmetics, which can solve the problem of waste disposal of kiwifruit processing enterprises such as kiwi winery and juice beverage factory, and greatly broaden the kiwifruit. In the field of deep processing, turning waste into treasure will bring better economic benefits to the production enterprises. The traditional pressing process has a low oil yield, while the solvent extraction method has residual organic solvents and is harmful to the human body. Compared with supercritical cO2 fluid extraction, there is no solvent residue, no pollution to food, no pollution to the environment, high extraction rate and safe production, and it has a good application prospect.
references:
[1] Chen Kaixun, Ge Hongguang, Yao Ruiqing. Supercritical C02 extraction of tea seed oil [J]. China Oils and Fats, 1996, 21 (5): 3O-34.
[2] Chen Yuan, Yang Foundation. Supercritical CO 2 extraction of linseed oil [J]. Natural Product Research and Development, 2001, 13(3): 14-19.
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