Method for extracting high-purity fish oil

Abstract

The invention discloses a method for extracting high-purity fish oil, belongs to the technical field of fish oil extraction, and aims to solve the technical problem that the extraction rate and the fish oil purity of fish oil extracted from marine fish need to be further improved in the prior art. The method comprises the following steps: cutting fresh marine fish into sections, and cleaning with water to obtain marine fish sections; the preparation method comprises the following steps: quickly cooling marine fish sections, cooling and freezing, crushing at the temperature of 3-15 DEG C to obtain marine fish meal, mixing the marine fish meal with deionized water, carrying out primary enzymolysis by using neutral enzyme to obtain neutral enzyme enzymatic hydrolysate, and carrying out secondary enzymolysis on the neutral enzyme enzymatic hydrolysate by using alkaline enzyme to obtain alkaline enzyme enzymatic hydrolysate. The enzymolysis treatment method and the degumming and deacidification method of the marine fish are optimized, so that the extraction rate of the fish oil extracted from the marine fish is increased, and the purity of the finished fish oil is also improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fish oil extraction, and particularly relates to a method for extracting high-purity fish oil. Background Art

[0002] Fish oil is rich in ω-3 polyunsaturated fatty acids (such as eicosapentaenoic acid EPA and docosahexaenoic acid DHA) and has physiological functions such as regulating blood lipid, anti-inflammatory, and promoting brain nerve development. It is widely used in the fields of health products, drugs, functional foods, and cosmetics. Due to the long-term exposure to the low-temperature and high-pressure marine environment, marine fish have evolved a high content of ω-3 polyunsaturated fatty acids in their bodies and are the main raw materials for fish oil extraction.

[0003] For example, a Chinese patent with the publication number CN103614235A discloses a method for extracting fish oil using fish heads and fish skins, which includes the following steps: freezing, coarsely grinding, and pulverizing the washed fish heads and fish skins, then homogenizing to make a homogenate, enzymatically hydrolyzing, extracting with an organic solvent, concentrating, and washing and purifying with a sodium chloride solution to obtain fish oil. Freezing, coarsely grinding, and pulverizing the fish heads and fish skins can initially damage tissue cells, facilitating the subsequent extraction of oil. Enzymatic hydrolysis further destroys cells to fully contact the organic solvent, resulting in good extraction effects. In addition, washing the concentrated crude fish oil with a sodium chloride solution can remove some soluble inorganic impurities and improve the purity of fish oil.

[0004] However, marine fish contain relatively more proteins and minerals. When using a single hydrolytic enzyme to treat fish meal, the bound fish oil in the fish meal is not released thoroughly, resulting in a fish oil extraction rate lower than 80%. Moreover, fish oil needs to undergo degumming and deacidification treatments during the preparation process. The traditional phosphoric acid degumming has insufficient phospholipid removal rate, and the residual colloid makes the fish oil turbid. During the treatment process, high temperature will cause lipid oxidation, resulting in a relatively high peroxide value of fish oil, and the purity of fish oil needs to be further improved. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for extracting high-purity fish oil to solve the technical problems that the extraction rate and purity of fish oil extracted from marine fish in the prior art need to be further improved.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A method for extracting high-purity fish oil, comprising the following steps:

[0007] S1. Cut fresh marine fish into sections, wash them with water to obtain fish sections, quickly cool and freeze the fish sections, and pulverize them in an environment with a temperature of 3-15°C to obtain fish meal;

[0008] S2. Mix the fish meal with deionized water, perform primary enzymatic hydrolysis on it using a neutral enzyme to obtain a neutral enzyme hydrolysis solution, and perform secondary enzymatic hydrolysis on the neutral enzyme hydrolysis solution using an alkaline enzyme to obtain an alkaline enzyme hydrolysis solution;

[0009] S3. Use cyclohexane as the extraction liquid to extract and separate the alkaline enzyme hydrolysate to obtain crude fish oil;

[0010] S4. Mix the crude fish oil with a supported degumming agent for degumming to prepare degummed fish oil, and then perform deacidification and decolorization treatment on the degummed fish oil to prepare the finished fish oil product.

[0011] Further, the marine fish includes: salmon, mackerel, sardine, herring, anchovy, and the particle size of the marine fish meal is 1 - 7 mm.

[0012] Further, the primary enzymatic hydrolysis method is: mix the marine fish meal and deionized water, add neutral enzyme to the mixed system, raise the reaction temperature to 45 - 55 °C, keep the temperature for enzymatic hydrolysis for 4 - 5 h, and perform post - treatment to obtain the neutral enzyme hydrolysate.

[0013] Further, the dosage ratio of the marine fish meal to deionized water is 1 g:8 - 10 mL, the concentration of the neutral enzyme is 2800 - 3200 U / g, and the post - treatment includes: after the reaction is completed, raise the temperature of the reaction system to 80 - 85 °C, keep the temperature for 60 - 80 min, and then lower the temperature of the reaction system to room temperature to obtain the neutral enzyme hydrolysate.

[0014] Further, the secondary enzymatic hydrolysis method is: add sodium hydroxide solution to the neutral enzyme hydrolysate, adjust the pH of the system to 8 - 9, raise the temperature of the reaction system to 50 - 60 °C, add dithiothreitol and alkaline enzyme to the reaction system, keep the temperature for enzymatic hydrolysis for 3 - 4 h, and perform post - treatment to obtain the alkaline enzyme hydrolysate.

[0015] Further, the weight ratio of the neutral enzyme hydrolysate to dithiothreitol is 100:0.1 - 0.2, the concentration of the alkaline enzyme is 3500 - 4500 U / g, and the post - treatment includes: after the reaction is completed, raise the temperature of the reaction system to 80 - 85 °C, keep the temperature for 60 - 80 min, and then lower the temperature of the reaction system to room temperature to obtain the alkaline enzyme hydrolysate.

[0016] Further, the preparation method of the crude fish oil is: under the protection of an inert atmosphere, mix the alkaline enzyme hydrolysate, sodium carbonate and cyclohexane and stir for 40 - 60 min, let it stand for liquid separation to obtain the extraction liquid and the raffinate. After the raffinate is re - extracted with cyclohexane twice, combine the extraction liquids from the three extractions, perform nanofiltration, and concentrate the filtrate under reduced pressure at a temperature of 50 - 60 °C to obtain the crude fish oil.

[0017] Further, the dosage ratio of the alkaline enzyme hydrolysate, sodium carbonate and cyclohexane is 6 g:1 g:8 mL.

[0018] Further, the finished fish oil product is obtained by the following steps:

[0019] A1. Mix coconut shell carbon powder and decolorizing clay, add mixed acid thereto, and stir at room temperature for 20 - 30 min to obtain a supported degumming agent.

[0020] A2. Mix crude fish oil and the supported degumming agent and stir. Raise the temperature of the reaction system to 55 - 65 °C, stir for 25 - 30 min, and perform post - treatment to obtain degummed fish oil.

[0021] A3. Mix the degummed fish oil and a deacidifying agent. Raise the temperature of the reaction system to 40 - 45 °C, keep warm and stir for 30 - 40 min, and perform post - treatment to obtain the finished fish oil product.

[0022] Further, in step A1, the dosage ratio of the coconut shell carbon powder, decolorizing clay, and mixed acid is 5 g:3 g:5 mL, and the mixed acid is composed of 70 wt% phosphoric acid and citric acid in a weight ratio of 3:2.

[0023] Further, in step A2, the weight ratio of the crude fish oil to the supported degumming agent is 70:3, the stirring speed is 60 - 70 r / min, and the post - treatment includes: after the reaction is completed, lower the temperature of the reaction system to room temperature, set the centrifugation speed to 5000 - 6000 r / min, centrifuge for 10 min, and remove the sediment in the lower layer to obtain degummed fish oil.

[0024] Further, in step A3, the weight ratio of the degummed fish oil to the deacidifying agent is 50:1, the deacidifying agent is a 20 - 25 wt% sodium hydroxide aqueous solution, the stirring speed is 70 - 80 r / min, and the post - treatment includes: after stirring is completed, set the centrifugation speed to 5000 - 6000 r / min, centrifuge for 10 min, and remove the sediment in the lower layer to obtain the crude deacidified fish oil. Mix the crude deacidified fish oil and deionized water at a volume ratio of 10:3, stir for 20 - 30 min, set the centrifugation speed to 5000 - 6000 r / min, centrifuge for 10 min, and remove the sediment in the lower layer to obtain the finished fish oil product.

[0025] The present invention has the following beneficial effects:

[0026] 1. The method for extracting high - purity fish oil from marine fish of the present invention reduces enzyme activity and oxidation reaction by quickly cooling and freezing fish blocks, maintains the stability of raw materials, reduces the peroxide value of raw materials, then enzymatically hydrolyzes them with neutral enzyme and alkaline enzyme in sequence to promote the enzymatic hydrolysis of proteins in fish meal, thereby increasing the extraction rate of fish oil. Then, it optimizes the degumming and decolorizing method of fish oil, reduces free fatty acids and macromolecular impurities in fish oil, and improves the purity of fish oil.

[0027] 2. The method for extracting high-purity fish oil from marine fish according to the present invention can quickly freeze fish blocks by using liquid nitrogen as a cold source, reducing the freezing time. Then, the fish blocks are crushed by utilizing their brittleness in a low-temperature environment, enabling the fish meal to be quickly crushed, reducing the particle size of the fish meal, and maintaining the freshness of the fish meal raw material. A neutral enzyme combination of neutral protease and papain is used to hydrolyze highly unsaturated fats in the marine fish meal. Then, in an alkaline environment, dithiothreitol destroys the protein structure by reducing disulfide bonds, and serine protease, as an alkaline protease, destroys the lipoprotein complex to release bound lipids, thereby increasing the release rate of fish oil. When enzymatically hydrolyzing the fish meal, by optimizing the hydrolysis conditions, the enzymatic hydrolysis of marine fish meal is promoted, improving the release rate of fish oil while avoiding the oxidation and deterioration of fish oil, and increasing the extraction rate and purity of fish oil.

[0028] 3. The method for extracting high-purity fish oil from marine fish according to the present invention involves extracting the alkaline enzyme hydrolysate with cyclohexane and sodium carbonate in an argon environment. Weakly alkaline sodium carbonate reacts with free fatty acids in the hydrolysate to form soap. Cyclohexane, as a non-polar solvent, preferentially extracts fish oil containing polyunsaturated fatty acids. Nanofiltration can retain some soap or macromolecular acidic substances, while the soap and unneutralized free fatty acids remain in the aqueous phase, reducing the impurity content in the extract and increasing the extraction rate of fish oil. During the degumming process, a supported degumming agent composed of a mixed acid of phosphoric acid and citric acid, coconut shell carbon powder, and decolorizing clay is used to treat the crude fish oil. Phosphoric acid, as a strong acidic medium, protonates the hydrophilic head of phospholipids, destroying the emulsification stability of phospholipids and causing them to coagulate and precipitate from the oil phase. Citric acid chelates with calcium ions and other ions to block the bridging effect between ions and phospholipids. Using the mixed acid system of phosphoric acid and citric acid, through the dual effects of acidification + chelation, phospholipids and colloidal impurities are efficiently removed, significantly improving the purity of fish oil. Moreover, after acidifying the coconut shell carbon and decolorizing clay with the mixed acid, the adsorption efficiency for colloids and colored substances is further enhanced. At the same time, the degumming step is usually carried out at a relatively high temperature, which helps to promote the coagulation and sedimentation of impurities around the inorganic adsorbent composed of coconut shell carbon and decolorizing clay as the core, facilitating centrifugal separation. Then, sodium hydroxide reacts with free fatty acids to neutralize the free fatty acids and form saponified products. After centrifugal separation, residual saponified products and alkaline substances are removed by washing with water to further purify the fish oil and improve its purity. Detailed Embodiments

[0029] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0030] In this application, the neutral protease is selected from Hebei Jiuyu Biotechnology Co., Ltd., with an active ingredient content of 99%, a heavy metal content of 0.0001%, an enzyme activity of 100000 U / g, and an arsenic content of 0.0001%.

[0031] In this application, the papain is selected from Guangzhou Huayu Biotechnology Co., Ltd., with a content of 99% and a food-grade level.

[0032] In this application, the serine protease is selected from Xi'an Lavya Biotechnology Co., Ltd., with an active ingredient content of 99%, food-grade, and a CAS number of 9014-01-1.

[0033] In this application, the CAS number of dithiothreitol is 3483-12-3.

[0034] Example 1

[0035] This example provides a method for extracting high-purity fish oil, including the following steps:

[0036] Step 1. Sea fish powder preparation

[0037] Cut fresh sea fish such as salmon, mackerel, sardines, herring, and anchovies into sections, wash them with water to remove fish blood, obtain sea fish sections, place the sea fish sections in liquid nitrogen, quickly cool and freeze them, and then pulverize them at a temperature of 3°C to obtain sea fish powder with a particle size of 1-7 mm.

[0038] Step 2. Fish meal enzymolysis

[0039] Mix the neutral protease and papain in a weight ratio of 3:1 to obtain neutral enzyme for standby.

[0040] Weigh: Add 3 kg of sea fish powder and 24 L of deionized water to a stirring kettle and stir to mix. Add neutral enzyme to the stirring kettle at a concentration of 3200 U / g. Raise the temperature of the stirring kettle to 45°C and keep it for enzymatic hydrolysis for 4 h. Under argon protection, raise the temperature of the stirring kettle to 80°C and keep it for 60 min. Lower the temperature of the reaction system to room temperature to obtain a neutral enzyme hydrolysate.

[0041] Add 2 mol / L sodium hydroxide aqueous solution to the stirring kettle containing the neutral enzyme hydrolysate, adjust the pH of the system to 8, raise the temperature of the stirring kettle to 50°C, add dithiothreitol to the stirring kettle at an addition amount of 0.1 wt%, and then add serine protease to the stirring kettle at a concentration of 4500 U / g. Keep it for enzymatic hydrolysis for 3 h. Under argon protection, raise the temperature of the stirring kettle to 80°C and keep it for 60 min. Lower the temperature of the reaction system to room temperature to obtain an alkaline enzyme hydrolysate.

[0042] Step 3. Extraction and separation

[0043] Add the alkaline enzyme hydrolysate, sodium carbonate, and cyclohexane to a stirring kettle protected by argon in a ratio of 6 g:1 g:8 mL, mix and stir for 40 min, filter under pressure, let the filtrate stand for liquid separation to obtain an extract and a raffinate. The raffinate is re-extracted twice with cyclohexane at a ratio of raffinate:cyclohexane = 1:1 (vol). Combine the extracts from the three extractions and filter through a nanofiltration membrane with a pore size usually of 1 - 2 nm. The filtrate is concentrated under reduced pressure at a temperature of 50 °C to remove low-boiling substances, obtaining crude fish oil.

[0044] Step Four: Degumming of Fish Oil

[0045] Mix 70 wt% phosphoric acid and citric acid evenly in a weight ratio of 3:2 to obtain a mixed acid for standby.

[0046] Weigh 50 g of coconut shell carbon powder and 30 g of decolorizing clay, mix them evenly, add 50 mL of the mixed acid thereto, and mix at room temperature for 20 min to obtain a supported degumming agent.

[0047] Add the crude fish oil and the supported degumming agent to a reaction flask in a weight ratio of 70:3, mix and stir, set the stirring speed to 60 r / min, raise the temperature of the reaction flask to 55 °C, stir for 25 min, lower the temperature of the reaction flask to room temperature, put the reaction solution into a centrifuge tube and then place it in a centrifuge, set the centrifugation speed to 5000 r / min, centrifuge for 10 min, and remove the sediment in the lower layer to obtain degummed fish oil.

[0048] Step Five: Decolorization of Fish Oil

[0049] Add the degummed fish oil and 20 wt% sodium hydroxide aqueous solution to a reaction flask in a weight ratio of 50:1, mix and stir, set the stirring speed to 70 r / min, raise the temperature of the reaction flask to 40 °C, keep stirring for 30 min, lower the temperature of the reaction flask to room temperature, put the reaction solution into a centrifuge tube and then place it in a centrifuge, set the centrifugation speed to 5000 r / min, centrifuge for 10 min, and remove the sediment in the lower layer to obtain crude degummed and deacidified fish oil. Mix the crude degummed and deacidified fish oil and deionized water in a volume ratio of 10:3, stir for 20 min, then put it into a centrifuge tube and place it in a centrifuge, set the centrifugation speed to 5000 r / min, centrifuge for 10 min, and remove the sediment in the lower layer to obtain the finished fish oil.

[0050] Example 2

[0051] This example provides a method for extracting high-purity fish oil, including the following steps:

[0052] Step One: Making Powder from Marine Fish

[0053] Cut fresh marine fish such as salmon, mackerel, sardines, herring, and anchovies into sections, wash them with water to remove fish blood, obtain marine fish sections, place the marine fish sections in liquid nitrogen, quickly cool and freeze them, and then pulverize them at a temperature of 9 °C to obtain marine fish powder with a particle size of 1-7 mm.

[0054] Step 2: Enzymatic hydrolysis of fish meal

[0055] Mix neutral protease and papain in a weight ratio of 3:1 to obtain neutral enzyme for standby;

[0056] Weigh: Add 3 kg of marine fish powder and 27 L of deionized water to a stirring kettle, stir and mix, add neutral enzyme to the stirring kettle at a concentration of 3000 U / g, raise the temperature of the stirring kettle to 50 °C, keep warm and enzymatically hydrolyze for 4.5 h, under argon protection, raise the temperature of the stirring kettle to 83 °C, keep warm for 70 min, and lower the temperature of the reaction system to room temperature to obtain neutral enzyme hydrolysate;

[0057] Add 2.5 mol / L sodium hydroxide aqueous solution to the stirring kettle containing neutral enzyme hydrolysate, adjust the pH of the system to 8.5, raise the temperature of the stirring kettle to 55 °C, add dithiothreitol to the stirring kettle at an addition amount of 0.15 wt%, and then add serine protease to the stirring kettle at a concentration of 4000 U / g, keep warm and enzymatically hydrolyze for 3.5 h, under argon protection, raise the temperature of the stirring kettle to 83 °C, keep warm for 70 min, and lower the temperature of the reaction system to room temperature to obtain alkaline enzyme hydrolysate.

[0058] Step 3: Extraction and separation

[0059] Add alkaline enzyme hydrolysate, sodium carbonate, and cyclohexane to a stirring kettle under argon protection in a ratio of 6 g:1 g:8 mL, mix and stir for 50 min, filter under pressure, let the filtrate stand for liquid separation to obtain an extract and a raffinate. The raffinate is re-extracted 2 times with cyclohexane according to the ratio of raffinate:cyclohexane = 1:1 (vol). Combine the extracts from the three extractions, filter through a nanofiltration membrane with a pore size usually of 1-2 nm, and concentrate the filtrate under reduced pressure at a temperature of 55 °C to remove low-boiling substances to obtain crude fish oil.

[0060] Step 4: Degumming of fish oil

[0061] Mix 70 wt% phosphoric acid and citric acid evenly in a weight ratio of 3:2 to obtain a mixed acid for standby;

[0062] Weigh: Mix 50 g of coconut shell carbon powder and 30 g of decolorized clay evenly, add 50 mL of the mixed acid to it, and mix at room temperature for 25 min to obtain a supported degumming agent;

[0063] Add crude fish oil and supported degumming agent to the reaction flask at a weight ratio of 70:3, mix and stir, set the stirring speed to 65 r / min, raise the temperature of the reaction flask to 60 °C, stir for 27 min, lower the temperature of the reaction flask to room temperature, load the reaction solution into a centrifuge tube and then place it in a centrifuge, set the centrifugation speed to 5500 r / min, centrifuge for 10 min, and remove the sediment at the bottom layer to obtain degummed fish oil.

[0064] Step Five: Fish oil decolorization

[0065] Add degummed fish oil and 23 wt% sodium hydroxide aqueous solution to the reaction flask at a weight ratio of 50:1, mix and stir, set the stirring speed to 75 r / min, raise the temperature of the reaction flask to 43 °C, keep warm and stir for 35 min, lower the temperature of the reaction flask to room temperature, load the reaction solution into a centrifuge tube and then place it in a centrifuge, set the centrifugation speed to 5500 r / min, centrifuge for 10 min, and remove the sediment at the bottom layer to obtain crude degreased fish oil. Mix the crude degreased fish oil and deionized water at a volume ratio of 10:3, stir for 25 min, then load it into a centrifuge tube and place it in a centrifuge, set the centrifugation speed to 5500 r / min, centrifuge for 10 min, and remove the sediment at the bottom layer to obtain the finished fish oil.

[0066] Example 3

[0067] This example provides a method for extracting high-purity fish oil, including the following steps:

[0068] Step One: Sea fish powder preparation

[0069] Cut fresh sea fish such as salmon, mackerel, sardine, herring, and anchovy into sections, wash them with water to remove fish blood to obtain sea fish sections. Place the sea fish sections in liquid nitrogen for rapid cooling and freezing, and then pulverize them at a temperature of 15 °C to obtain sea fish powder with a particle size of 1 - 7 mm.

[0070] Step Two: Fish powder enzymatic hydrolysis

[0071] Mix neutral protease and papain at a weight ratio of 3:1 to obtain neutral enzyme for standby;

[0072] Weigh: Add 3 kg of sea fish powder and 30 L of deionized water to a stirring kettle for stirring and mixing. Add neutral enzyme to the stirring kettle at a concentration of 2800 U / g, raise the temperature of the stirring kettle to 55 °C, keep warm and enzymatically hydrolyze for 5 h. Under argon protection, raise the temperature of the stirring kettle to 85 °C, keep warm for 80 min, and lower the temperature of the reaction system to room temperature to obtain neutral enzyme enzymatic hydrolysate;

[0073] Add 3 mol / L sodium hydroxide aqueous solution to the stirring kettle containing neutral enzyme hydrolysis solution, adjust the pH of the system to 9, raise the temperature of the stirring kettle to 60 °C, add dithiothreitol to the stirring kettle at an addition amount of 0.2 wt%, and then add serine protease to the stirring kettle at a concentration of 3500 U / g, keep the temperature for enzymatic hydrolysis for 4 h, under the protection of argon, raise the temperature of the stirring kettle to 85 °C, keep the temperature for 80 min, and lower the temperature of the reaction system to room temperature to obtain alkaline enzyme hydrolysis solution.

[0074] Step 3: Extraction and separation

[0075] Add the alkaline enzyme hydrolysis solution, sodium carbonate and cyclohexane to the stirring kettle protected by argon in a ratio of 6 g:1 g:8 mL, mix and stir for 60 min, filter by pressure, let the filtrate stand for liquid separation to obtain an extract and a raffinate. The raffinate is re-extracted 2 times with cyclohexane according to the ratio of raffinate:cyclohexane = 1:1 (vol). Combine the extracts from the three extractions and filter through a nanofiltration membrane with a pore size usually of 1 - 2 nm. The filtrate is concentrated under reduced pressure at a temperature of 60 °C to remove low-boiling substances to obtain crude fish oil.

[0076] Step 4: Degumming of fish oil

[0077] Mix 70 wt% phosphoric acid and citric acid evenly according to a weight ratio of 3:2 to obtain a mixed acid for standby.

[0078] Weigh 50 g of coconut shell carbon powder and 30 g of decolorized clay, mix them evenly, add 50 mL of the mixed acid to it, and mix at room temperature for 30 min to obtain a supported degumming agent.

[0079] Add the crude fish oil and the supported degumming agent to the reaction flask according to a weight ratio of 70:3, mix and stir, set the stirring speed to 70 r / min, raise the temperature of the reaction flask to 65 °C, stir for 30 min, lower the temperature of the reaction flask to room temperature, put the reaction solution into a centrifuge tube and then place it in a centrifuge, set the centrifugation speed to 6000 r / min, centrifuge for 10 min, and remove the sediment in the lower layer to obtain degummed fish oil.

[0080] Step 5: Decolorization of fish oil

[0081] Add degummed fish oil and 25 wt% sodium hydroxide aqueous solution to the reaction flask at a weight ratio of 50:1, mix and stir, set the stirring speed at 80 r / min, raise the temperature of the reaction flask to 45 °C, keep stirring for 40 min, lower the temperature of the reaction flask to room temperature, transfer the reaction solution to a centrifuge tube and then place it in a centrifuge, set the centrifugation speed at 6000 r / min, centrifuge for 10 min, remove the sediment in the lower layer to obtain the crude degummed fish oil. Mix the crude degummed fish oil and deionized water at a volume ratio of 10:3, stir for 30 min, transfer it to a centrifuge tube again and then place it in a centrifuge, set the centrifugation speed at 6000 r / min, centrifuge for 10 min, remove the sediment in the lower layer to obtain the finished fish oil product.

[0082] Comparative Example 1

[0083] The difference between this comparative example and Example 3 is that in Step 1, the preparation method of fish meal is as follows: Cut fresh marine fish such as salmon, mackerel, sardine, herring, and anchovy into sections, wash them with water to remove fish blood to obtain fish sections, and use a meat grinder to crush the fish sections to obtain fish meal with a particle size of 1 - 7 mm.

[0084] Comparative Example 2

[0085] The difference between this comparative example and Example 3 is that in Step 2, the neutral enzyme is neutral protease.

[0086] Comparative Example 3

[0087] The difference between this comparative example and Example 3 is that in Step 2, dithiothreitol is not added.

[0088] Comparative Example 4

[0089] The difference between this comparative example and Example 3 is that in Step 4, the mixed acid is 70 wt% phosphoric acid.

[0090] Performance test:

[0091] Refer to the standard SC / T 3502 - 2016 "Fish Oil" for the physical and chemical properties of the finished fish oil products prepared in Examples 1 - 3 and Comparative Examples 1 - 4;

[0092] Refer to the formula Determine the extraction rate of the finished fish oil products prepared in Examples 1 - 3 and Comparative Examples 1 - 4. In the formula, m1 is the mass of the finished fish oil product, and m0 is the mass of fish oil in the fish meal. The specific test results are shown in Table 1 below.

[0093] Table 1 - Data table of performance test of samples

[0094]

[0095] Data analysis:

[0096] By comparing and analyzing the data in Table 1 above, the acid value of the fish oil product prepared by the present invention is reduced to 0.42 mg KOH / g, the peroxide value is reduced to 4.25 meq / kg, the iodine value reaches 199.2 g / 100 g, the unsaponifiable matter content is reduced to 0.26%, and the extraction rate reaches 94.2%. The comprehensive performance test data of each example are better than those of the comparative examples. Therefore, the present invention optimizes the enzymatic hydrolysis method and degumming and deacidification method of marine fish, not only improving the extraction rate of fish oil from marine fish, but also improving the purity of the finished fish oil.

[0097] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for extracting high-purity fish oil, characterized in that, It includes the following steps: S1. Cut fresh sea fish into sections, wash them with water to obtain sea fish sections, quickly cool and freeze the sea fish sections, and pulverize them at a temperature of 3 - 15°C to obtain sea fish powder; S2. Mix the sea fish powder and deionized water, and perform primary enzymatic hydrolysis on it using a neutral enzyme to obtain a neutral enzyme hydrolysate. The neutral enzyme hydrolysate is subjected to secondary enzymatic hydrolysis using an alkaline enzyme to obtain an alkaline enzyme hydrolysate; S3. Use cyclohexane as an extraction solution to extract and separate the alkaline enzyme hydrolysate to obtain crude fish oil; S4. Mix the crude fish oil and a supported degumming agent for degumming to prepare degummed fish oil, and then perform deacidification and decolorization treatment on the degummed fish oil to prepare the finished fish oil product.

2. A method for extracting high-purity fish oil according to claim 1, characterized in that, The sea fish includes: Salmon, mackerel, sardine, herring, anchovy, and the particle size of the sea fish powder is 1 - 7 mm.

3. A method for extracting high-purity fish oil according to claim 1, characterized in that, The method for primary enzymatic hydrolysis is: Mix the sea fish powder and deionized water, add a neutral enzyme to the mixed system, raise the reaction temperature to 45 - 55°C, keep the temperature for enzymatic hydrolysis for 4 - 5 h, and perform post-treatment to obtain a neutral enzyme hydrolysate.

4. A method for extracting high-purity fish oil according to claim 3, characterized in that, The dosage ratio of the sea fish powder to deionized water is 1 g:8 - 10 mL, and the concentration of the neutral enzyme is 2800 - 3200 U / g.

5. A method for extracting high-purity fish oil according to claim 1, characterized in that, The method for secondary enzymatic hydrolysis is: Add a sodium hydroxide solution to the neutral enzyme hydrolysate to adjust the pH of the system to 8 - 9, raise the temperature of the reaction system to 50 - 60°C, add dithiothreitol and an alkaline enzyme to the reaction system, keep the temperature for enzymatic hydrolysis for 3 - 4 h, and perform post-treatment to obtain an alkaline enzyme hydrolysate.

6. A method for extracting high-purity fish oil according to claim 5, characterized in that, The weight ratio of the neutral enzyme hydrolysate to dithiothreitol is 100:0.1 - 0.2, and the concentration of the alkaline enzyme is 3500 - 4500 U / g.

7. A method for extracting high-purity fish oil according to claim 1, characterized in that, The preparation method of the crude fish oil is: Under the protection of an inert atmosphere, mix and stir the alkaline enzyme hydrolysate, sodium carbonate, and cyclohexane for 40 - 60 min, let it stand for liquid separation to obtain an extraction solution and a raffinate. The raffinate is re-extracted with cyclohexane 2 times, and then the extraction solutions from the three extractions are combined and nanofiltrated. The filtrate is concentrated under reduced pressure at a temperature of 50 - 60°C to obtain the crude fish oil.

8. A method for extracting high-purity fish oil according to claim 7, characterized in that, The dosage ratio of the alkaline enzyme hydrolysate, sodium carbonate, and cyclohexane is 6 g:1 g:8 mL.

9. A method for extracting high-purity fish oil according to claim 1, characterized in that, The finished fish oil product is processed by the following steps: A1. Mix coconut shell carbon powder and decolorized clay, add a mixed acid to it, and stir at room temperature for 20 - 30 min to obtain a supported degumming agent; A2. Mix and stir the crude fish oil and the supported degumming agent, raise the temperature of the reaction system to 55 - 65°C, stir for 25 - 30 min, and perform post-treatment to obtain degummed fish oil; A3. Mix the degummed fish oil and a deacidifying agent, raise the temperature of the reaction system to 40 - 45°C, keep the temperature for stirring for 30 - 40 min, and perform post-treatment to obtain the finished fish oil product.

10. A method for extracting high-purity fish oil according to claim 9, characterized in that, In step A1, the dosage ratio of the coconut shell carbon powder, the decolorizing clay, and the mixed acid is 5 g: 3 g: 5 mL, and the mixed acid is composed of 70 wt% phosphoric acid and citric acid in a weight ratio of 3:2; in step A2, the weight ratio of the crude fish oil to the supported degumming agent is 70:3, and the stirring speed is 60 - 70 r / min; in step A3, the weight ratio of the degummed fish oil to the deacidifying agent is 50:1, the deacidifying agent is a 20 - 25 wt% aqueous sodium hydroxide solution, and the stirring speed is 70 - 80 r / min.

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