Method 1. Use cod liver or minced fish as raw material
Preparation of crude fish oil Take the fresh cod liver that has been removed from the gallbladder, washed and chopped, put it in a pot, add water, pass steam to 80°C, flow out the oil, filter, cool the filtrate to 0°C, precipitate solid fat, and filter under pressure , the filtrate is crude fish oil.
Fish oil [water]→[80°C] oil quality [filter]→crude fish oil or minced fish as raw material, minced, mixed with starch at 7-10°C, extracted with hexane for 15 minutes, filtered to obtain filtrate. The filtrate was washed with sodium chloride solution, then dehydrated with anhydrous sodium sulfate, and the hexane was recovered to obtain crude fish oil.
Minced fish [starch, hexane] → [7-10°C, 15min] filtrate [NaCl] → [anhydrous sodium sulfate] crude fish oil
Preparation of refined fish oil Take crude fish oil, add sodium hydroxide ethanol solution to saponify, filter, add acid to the filtrate, add water-insoluble organic solvent to extract, wash the extract with water, remove the organic layer, the water layer is light red or reddish brown The clear liquid was placed at 10°C for 30 minutes without solid precipitation to obtain refined fish oil.
Crude fish oil [alkaline ethanol solution] → filtrate [organic solvent] → [HCl] extract [washed] → refined fish oil
Pre-concentration and alcoholysis ethyl esterification of refined fish oil, use urea inclusion crystallization method to remove less saturated fatty acid in fish oil to obtain fatty acid ethyl ester of fish oil.
Refined fish oil [ethanol, urea inclusion crystal] → fish oil fatty acid ethyl ester
Preparation of DHA Put the fish oil fatty acid ethyl ester into the extraction tank, open the steel cylinder, after the CO2 is condensed, pressurize it to the set pressure by the high-pressure metering pump, and then preheat it to the working temperature, then enter the extraction tank. SC-CO2 carries fish oil fatty acid ethyl ester into the rectification column, and the components come out from the top of the column according to their solubility, and enter the separator for reception after decompression. Experimental conditions: extraction pressure is 11-15MPa, extraction temperature is 35°C; rectification pressure is 11-15MPa, rectification temperature is 40-85°C. Collect the EPA-rich fraction at 12-13.5MPa and the DHA-rich fraction at 14-15MPa, and measure with gas chromatography, EPA and DHA are purified to 90%. The EPA-rich fraction and the DHA-rich fraction are subjected to secondary extraction at 11.5-13MPa and 13.5-15MPa respectively, and the EPA is purified to 67%, and the DHA is purified to more than 90%.
Fish oil fatty acid ethyl ester [supercritical CO2 extraction] → [separation] DHA
Method 2: Use herring scraps as raw materials
Extraction of fish oil Mince herring scraps, add half the amount of water, adjust the pH to 8.5-9.0, keep warm for 45 minutes, add 5% salt, stir to dissolve, continue to keep warm for 15 minutes, filter, squeeze the filter residue, combine the filtrate and squeezed liquid , centrifuged while hot to make herring oil. The total content of EPA and DHA in herring oil is 8.9%.
Herring leftovers [H2O, 5%NaCl]→[pH8.5-9][filtered, centrifuged]→herring oil
Preparation of Polyunsaturated Fatty Acid (PUFA) Take herring oil, add sodium hydroxide ethanol (95%) solution, fill with nitrogen and reflux for saponification, cool the saponified solution to 15-20°C, a large amount of sodium salt of fatty acid is precipitated, squeeze and filter, and cool the filtrate To -20 ℃, and then press filter. Add an equal volume of water to the filtrate, adjust the pH to 3-4, and centrifuge for 10 minutes to obtain PUFA-I. Dissolve PUFA-I in sodium hydroxide ethanol solution, cool at -20°C, press filter, add a small amount of water to the filtrate, cool at -10°C, and remove cholesterol crystals by suction filtration. Add a small amount of water to the filtrate, cool at -20°C, centrifuge for 5 minutes, pour off the upper layer, and centrifuge for 10 minutes after the lower jelly (PUFA sodium salt) is acidified to obtain PUFA-II. The total content of EPA and DHA in PUFA-II is 64.8%.
Herring oil [NaOH ethanol] → [nitrogen] saponified liquid [cooling] filtrate [pH3-4] → [centrifugation] PUFA-I [NaOH ethanol] → PUFA-II
Method 3: Using arachidonic acid as raw material
Arachidonic acid is used as raw material to obtain EPA through desaturation. EPA grows through the C2 chain to obtain docosapentaenoic acid. Docosapentaenoic acid is desaturated to obtain DHA.
Arachidonic acid [desaturation] → EPAEPA
[C2 chain growth] → docosapentaenoic acid [desaturation] → DHA
Method 4. Supercritical multi-component fluid precision distillation technology
At present, the high vacuum distillation method, molecular distillation method, silver nitrate complex method, simple supercritical CO2 extraction and industrial chromatography preparation technology commonly used at home and abroad have many disadvantages and shortcomings, and are not suitable for high-purity EPA and DHA. Industrialization development. Using supercritical multi-fluid precision distillation technology to directly separate high-purity EPA and DHA, it is operated under normal temperature conditions, and the products are not easy to be oxidized and degraded. chemical production.
Method 5. Extraction of fish oil by light alkali hydrolysis
This process is to use light lye to decompose cod liver protein tissue and destroy the binding relationship between protein and liver oil, so as to more fully separate fish oil. This method of liver oil has good quality and low price, and most fish oil factories in my country use this method to produce fish oil.
Method 6. Potassium method to extract fish oil
The light alkali used in the traditional light alkali hydrolysis method to extract fish oil is a dilute solution of sodium hydroxide, and the salt is a sodium chloride solution. The process is very mature. However, the waste liquid generated during the extraction process has a high content of sodium salts and cannot be further utilized, forming new waste. According to the extraction principle of the light alkali hydrolysis process, Yang Guan’e et al. replaced sodium hydroxide and sodium chloride in the light alkali hydrolysis process with potassium hydroxide and potassium nitrate, and the extraction rate and quality of fish oil remained stable; the waste residue and waste liquid after extracting fish oil It contains a lot of amino acids and proteins, which can be further used as raw materials for high-efficiency green fertilizers, and no new waste is produced.
The extraction method is as follows: After homogenizing a certain amount of cod liver with a homogenizer, add it to a three-necked flask, add half to one and a half times the amount of water, stir in a water bath and heat up to 45-50°C, and add 40% potassium hydroxide twice Adjust the pH of the aqueous solution to 8-9, continue to stir and raise the temperature to 80-90°C, keep it warm for 30 minutes, add potassium nitrate with 4% weight of cod liver, continue to stir, salt out for 15 minutes, centrifuge while it is hot, and separate the crude fish oil.
Cod liver [water]→[45-50℃][4%KOH]→[pH8-9][80-90℃]→[30min][4%KNO3]→[15min][centrifugation]→crude fish oil
Product determination method: peroxide value-sodium thiosulfate back titration method; acid value-alkali titration method; iodine value-sodium thiosulfate titration method; saponification value-hydrochloric acid back titration method; DHA, EPA content determination-gas chromatography .
Results (n=3): The extraction rate of fish oil was 24.4%; the acid value was 2.58; the iodine value was 309; the saponification value was 178.7; the peroxide value was 0.070%; the DHA content was 19.60%.
