Preparation method of high DHA (docosahexaenoic acid), high phospholipid and fishy smell-free krill oil

Abstract

The invention provides a preparation method of high docosahexaenoic acid, high phospholipid and fishy smell-free krill oil, which comprises the following steps: (s1) dissolving krill powder in ethanol, and filtering to obtain filtrate; and (s2) putting the filtrate into an extraction kettle, and carrying out supercritical CO2 extraction to obtain the fishy smell-free krill oil. The preparation method disclosed by the invention is simple, efficient, simple and convenient to operate, high in product yield and easy for industrial production.

Description

Technical Field

[0001] The present invention relates to the field of food processing, and particularly to the field of a preparation method of high-DHA, high-phospholipid, and odorless krill oil. Background Art

[0002] Antarctic krill is an important crustacean living in the Antarctic Ocean. Krill oil obtained by deep processing of Antarctic krill has attracted much attention as a source of healthy lipids due to its rich nutritional components. Krill oil is rich in substances such as n-3 PUFA (polyunsaturated fatty acids), phospholipids (PL), astaxanthin, vitamins, flavonoids, and minerals. Phospholipid-type DHA and EPA in krill oil are more easily absorbed and utilized by the human body compared with triglyceride-type DHA and EPA in fish oil (Burri L, Johnsen L. Krill products: an overview of animal studies[J]. Nutrients, 2015, 7(5): 3300 - 3321.), which is of great significance for the prevention and treatment of cardiovascular diseases. In addition, krill oil also has potential effects of anti-inflammation, improving insulin sensitivity and insulin secretion to control diabetes.

[0003] However, the fishy smell of krill oil makes it difficult for consumers to accept these products, with low palatability, resulting in limited applications. It can only be made into krill oil capsule products for swallowing and cannot be directly applied in foods. The GOED organization investigated why consumers in 9 countries refused to buy products rich in EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). The results showed that up to 23% of consumers refused to buy these ω-3-rich products because of the fishy smell.

[0004] Traditional deodorization and deodorization methods such as physical adsorption, organic solvent extraction, and distillation have disadvantages such as high-temperature operation, large amounts of solvent recovery, and high losses of active ingredients, and there are problems in industrial applications. Patent 201810842218.X discloses a method for preparing deaminated low-odor krill oil. By using cation exchange resin and macroporous adsorption resin to adsorb and deodorize the krill oil extracted by ethanol, although the content of trimethylamine nitrogen is reduced by 96.88%, the odor is still relatively strong, and the physical adsorption regeneration and waste treatment costs are relatively high, the operation is relatively cumbersome, and the yield is not high. Patent 201811116201.2 discloses a method for preparing deodorized Antarctic krill oil, wherein the deodorization treatment includes: vacuum drying at a vacuum degree of 0.02-0.15 MPa and a temperature of 20-60 °C for 1-24 h to obtain deodorized Antarctic krill oil. The deodorized krill oil removes 0.5-2.5% of volatile components compared with the Antarctic krill oil before treatment, but the production efficiency of vacuum drying is not high, and there are problems such as too long drying time or too high temperature, and it is difficult to achieve high yield in industry. Patent 202110591261.5 discloses a method for preparing deaminated Antarctic krill oil. By adding a food-grade citric acid-aqueous solution to the krill oil concentrate, filtering with a titanium rod filter, and finally distilling and desolventizing to obtain deaminated Antarctic krill oil, trimethylamine oxide in the krill oil is effectively removed. However, in this patent, the reaction time of adding the citric acid aqueous solution is 8 h, which is too long. The titanium rod filter itself is prone to blockage after production, resulting in a decrease in production efficiency, and it is difficult to industrialize the overall process.

[0005] Therefore, there is an urgent need in the art for a method for preparing high-DHA, high-phospholipid, and odorless krill oil with simple operation, high recovery rate, and easy industrial production. Summary of the Invention

[0006] The object of the present invention is to provide a krill oil with high DHA, high phospholipids, and no odor and its application.

[0007] In the first aspect of the present invention, a method for preparing odorless krill oil is provided, and the preparation method includes the following steps:

[0008] (s1) Dissolve krill powder in ethanol, filter to obtain a filtrate;

[0009] (s2) Put the filtrate into an extraction kettle, perform supercritical CO2 extraction to obtain odorless krill oil.

[0010] In another preferred example, the extraction is carried out at a temperature of 40-60 °C, preferably 45-55 °C.

[0011] In another preferred example, the pressure of the extraction is 10-20 MPa, preferably 13-17 MPa, such as 15 MPa.

[0012] In another preferred example, the filtration is treatment with a filter membrane of 0.1 to 1 μm.

[0013] In another preferred example, vacuum concentration treatment is also required after step (s1).

[0014] In another preferred example, the ethanol is ethanol with a volume percentage of 80 to 99%.

[0015] In another preferred example, the material-liquid ratio of krill powder to ethanol is 1:20 to 10:1 g / ml, preferably 1:5 to 1:15 g / ml, more preferably 1:6 to 1:10 g / ml, such as 1:7 g / ml.

[0016] In another preferred example, the extraction uses a single-stage separation system.

[0017] In another preferred example, the ethanol is ethanol with a volume percentage of 85 to 99%, preferably 90 to 99%, more preferably 95 to 99%.

[0018] In another preferred example, the preparation method includes the following steps:

[0019] (s1) Take krill powder, dissolve it in ethanol, filter, and obtain a filtrate;

[0020] (s2) Remove the solvent from the filtrate by rotary evaporation to obtain krill oil;

[0021] (s3) Put the krill oil into an extraction kettle, carry out supercritical CO2 extraction, and obtain odorless krill oil.

[0022] In another preferred example, the pressure of the extraction is 15 MPa.

[0023] In another preferred example, the extraction is carried out at 45 to 55 °C.

[0024] In another preferred example, the vacuum degree during the vacuum concentration is 0.01 to 0.5 Mpa, preferably 0.05 to 0.2 Mpa, such as 0.1 Mpa.

[0025] In another preferred example, the temperature during the vacuum concentration is 40 to 80 °C, preferably 50 to 70 °C, such as 60 °C.

[0026] In another preferred example, the mass-volume ratio of the filtrate to the extraction kettle is 0.01 to 1 kg / L, preferably 0.05 to 0.8 kg / L, more preferably 0.08 to 0.5 kg / L, such as 0.1 kg / L.

[0027] In another preferred example, the extraction time is 0.5 to 3 h, preferably 1 to 2 h, such as 1.5 h.

[0028] In another preferred example, the product yield of the method is ≥95%, preferably ≥96%, more preferably ≥97%.

[0029] In the second aspect of the present invention, there is provided a deodorized krill oil prepared by the preparation method as described in the first aspect of the present invention.

[0030] In another preferred example, the krill oil has one or more of the following characteristics:

[0031] (c1) The content of trimethylamine is <5 mg / kg;

[0032] (c2) The content of DHA is ≥6.3 g / 100 g;

[0033] (c3) The content of phospholipids is ≥43 g / 100 g.

[0034] In another preferred example, the content of phospholipids in the krill oil is ≥44 g / 100 g, preferably ≥45 g / 100 g.

[0035] In the third aspect of the present invention, there is provided a use of the deodorized krill oil as described in the second aspect of the present invention for preparing foods and cosmetics.

[0036] In another preferred example, the food is a functional food or a special medical purpose food.

[0037] It should be understood that within the scope of the present invention, the above technical features of the present invention and the technical features specifically described below (such as in the examples) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be repeated one by one here. Description of the Drawings

[0038] Figure 1 Shows the extraction and deodorization process flow of krill oil.

[0039] Figure 2 Shows the fluidity and separation status of krill oil under different extraction temperatures and pressures in experimental groups 1-3. T1-1 represents the krill oil in the extraction kettle at 40 °C and 12.5 MPa; T1-2 represents the krill oil in the separation kettle at 40 °C and 12.5 MPa; T2-1 represents the krill oil in the extraction kettle at 45 °C and 15 MPa; T2-2 represents the krill oil in the separation kettle at 45 °C and 15 MPa; T3-1 represents the krill oil in the extraction kettle at 55 °C and 15 MPa; T3-2 represents the krill oil in the separation kettle at 55 °C and 15 MPa; C represents the non-deodorized krill oil.

[0040] Figure 3Shows the fluidity and separation status of krill oil at different extraction temperatures and pressures in experimental groups 4 - 5. The left figure represents the krill oil in the extraction kettle at 55°C and 20 MPa; the right figure represents the krill oil in the extraction kettle at 60°C and 30 MPa.

[0041] Figure 4 Shows the supercritical CO2 extraction system. Detailed implementation manner

[0042] Through extensive and in - depth research, the inventors unexpectedly discovered a method for preparing krill oil with high DHA, high phospholipids, and no fishy smell. The method has a simple process, high product yield, simple operation, and is suitable for industrial production. On this basis, the inventors completed the present invention.

[0043] Terms

[0044] Supercritical CO2 extraction

[0045] Supercritical CO2 extraction technology refers to the process of contacting supercritical carbon dioxide with the substance to be separated under supercritical conditions, so as to selectively extract components with different polarities, boiling points, and molecular weights in sequence. This technology has the characteristics of safety, environmental protection, fast extraction time, and high extraction efficiency.

[0046] Supercritical CO2 extraction technology operates under conditions close to room temperature, with lower energy consumption than general distillation, and is suitable for the separation of heat - sensitive substances and easily oxidized substances.

[0047] Supercritical CO2 extraction system

[0048] The supercritical CO2 extraction system includes (a) single - stage separation system, (b) two - stage separation system, (c) distillation + separation system ( Figure 1 ).

[0049] (a) The single - stage separation system contains an extraction kettle and a separation kettle. The material is added from the extraction kettle and flows into the separation kettle through (a1) pipeline, and then flows back to the extraction kettle through (a2) pipeline. Among them, there is a pressure reducing valve on the (a1) pipeline; there is a heat exchanger and a compressor on the (a2) pipeline.

[0050] (b) The two - stage separation system contains an extraction kettle and two separation kettles. The material is added from the extraction kettle, flows into the separation kettle through (b1) pipeline, then flows into the next - stage separation kettle through (b2) pipeline, and then flows back to the extraction kettle through (b3) pipeline. Among them, there are pressure reducing valves on the (b1) and (b2) pipelines; there is a heat exchanger and a compressor on the (b3) pipeline.

[0051] (c) The rectification + separation system contains an extraction kettle, a rectification column, and a separation kettle. The material is added to the extraction kettle and flows into the rectification column through pipeline (c1), then into the separation kettle through pipeline (c2), and then back to the extraction kettle through pipeline (c3). Among them, pressure reducing valves are installed on pipelines (c1) and (c2); a heat exchanger and a compressor are installed on pipeline (c3).

[0052] Krill oil

[0053] Krill oil is a dark red or reddish-brown transparent oily liquid prepared from krill through steps such as washing, crushing, extraction, concentration, and filtration. Krill oil is rich in phospholipid-type Omega-3 polyunsaturated fatty acids. The phospholipids in krill oil contain natural eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are anti-inflammatory fatty acids that can maintain the healthy balance of cell membranes and resist toxicity, oxidation, and inflammatory attacks. Krill oil can prevent cell inflammation and cardiovascular aging, providing strong support for heart and brain health, especially having good effects on cerebral thrombosis, sequelae of stroke, and Alzheimer's disease.

[0054] Docosahexaenoic acid

[0055] Docosahexaenoic acid, namely DHA, is an essential polyunsaturated fatty acid for the human body. DHA has the effects of assisting in the development of brain cells, anti-aging, improving blood circulation, and reducing blood lipids.

[0056] The main advantages of the present invention include:

[0057] (1) The preparation method of the present invention has a simple process, is easy to operate, and is suitable for industrial production;

[0058] (2) The krill oil of the present invention has high DHA, high phospholipids, and no fishy smell;

[0059] (3) The preparation method of the present invention has a high product yield, with the product yield higher than 95%, preferably ≥96%, and more preferably ≥97%.

[0060] The following further elaborates the present invention in combination with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The experimental methods without specific conditions noted in the following embodiments are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Unless otherwise specified, percentages and parts are calculated by weight.

[0061] General method:

[0062] Sensory evaluation method: Fifteen staff members with certain sensory discrimination abilities were selected to evaluate the sensory fishy smell intensity of the deodorized krill oil. The subjects sequentially evaluated the fishy smell of the krill oil deodorized by the control sample group, resin adsorption group, experimental group 2, and experimental group 3 methods. According to the perceived fishy smell intensity, the deodorized krill oil in each group was scored on a 5-point scale (corresponding to 5 +). The statistical data was averaged (rounded off) to obtain the fishy smell intensity of the experimental group.

[0063] Extraction of krill oil in Example 1

[0064] Take 2 kg of krill powder, add ethanol with a volume percentage of 96%, the material-liquid ratio is 1:7 (g / ml), the extraction temperature is 40 °C, and stir or continuously counter-current extract for 3 h to obtain a mixed crude extract. The obtained mixed liquid was filtered through a 0.22 μm microporous membrane to obtain an ethanol crude extract of krill oil; the obtained ethanol crude extract was vacuum concentrated at 60 °C under a vacuum degree of 0.1 Mpa to obtain krill oil.

[0065] Deodorization of krill oil in Example 2

[0066] The krill oil after ethanol extraction was subjected to supercritical CO2 extraction. The separation status and fluidity of the krill oil were observed at different extraction temperatures and extraction pressures in the extraction kettle, and the supercritical CO2 extraction conditions of the krill oil with better separation status and fluidity were selected. The contents of trimethylamine, DHA, phospholipids, and fishy smell intensity of the krill oil in this group were detected.

[0067] Weigh 0.5 kg of the crude krill oil obtained in Example 1 and put it into a 5 L extraction kettle ( Figure 4 in a or b), set different temperatures and pressures (Table 1), and each separation pressure was stably separated for 1.5 h. The refined krill oil in the extraction kettle and the waste krill oil in the separation kettle were sequentially collected, and the extraction amount, color, and smell of the krill oil under each separation pressure were compared. The specific results are shown in Tables 2 and 3.

[0068] Table 1

[0069]

[0070] Comparative example

[0071] Put the ethanol crude extract oil into the extraction tank ( Figure 4 in c), preheat the supercritical CO2 to the working temperature and flow it into the extraction tank. The supercritical CO2 carries the ethanol crude extract oil into the rectification column, and the components are separated from the top of the column successively according to the solubility. After pressure reduction separation, each rectification component of the components is received for fishy smell comparison, and the component with a weaker fishy smell is selected as the target component.

[0072] In the comparative example, after passing through the rectification column ( Figure 4In c), the separated krill oil is obtained under the specific extraction and rectification conditions of an extraction temperature of 45 °C, rectification temperatures of T1 40 °C, T2 50 °C, T3 60 °C, and T4 70 °C, and an extraction pressure of 13.5 Mpa. Four components are obtained. Among them, the fourth-stage rectification product has a very strong fishy smell, while the fishy smells of the other three-stage rectification products are very weak and can be combined as a deodorized krill oil product.

[0073] The yield of krill oil under these extraction and rectification conditions is approximately 89.5%. There is little difference in the separation effect and fishy smell intensity of the krill oil in a) of the single-stage separation Figure 4 However, compared with the single-stage separation, the rectification column itself has more complex operations and more expensive equipment. Considering the cost and efficiency of actual factory operations, single-stage separation operation is selected for the deodorization of krill oil.

[0074] Test Example

[0075] The fluidity and separation status of krill oil under different extraction temperatures and pressures are shown in Table 1, Table 2, Figure 2 and Figure 3 as shown. The supercritical CO2 extraction equipment is as Figure 4 shown. Experiments found that the krill oil with a lower temperature or lower pressure (such as experimental group 1) still has a strong fishy smell and a lower extraction efficiency. Too high a temperature or too high a pressure (such as experimental groups 4 and 5) will cause the fluidity of the krill oil to deteriorate significantly, the state to become more viscous, and even become solid, affecting the processing of high-value-added functional products such as krill oil capsules. During the extraction process, it is impossible to separate supercritical CO2 from the target solute well, the number of separated substances increases significantly, and the separation effect is poor and the efficiency is low.

[0076] Table 2

[0077]

[0078]

[0079] The krill oil extracted under the conditions of experimental groups 2 and 3 with a weak fishy smell and good fluidity is taken for the determination of the contents of trimethylamine, DHA, and phospholipids and the determination of the sensory fishy smell intensity. The krill oil of the same batch without deodorization is set as the blank control group, and the krill oil of the same batch deodorized by resin adsorption is set as the positive control group.

[0080] The identification results of the contents of trimethylamine, DHA, and phospholipids and the sensory fishy smell of krill oil under different extraction temperatures and pressures are shown in Table 3.

[0081] Experiments found that no trimethylamine content (<5 mg / kg) was detected in the resin adsorption group and experimental groups 2 and 3 after the deodorization step, and the detection limit was 5 mg / kg. The krill oil after supercritical CO2 extraction (experimental groups 2 and 3) had a very high DHA retention rate, while resin adsorption would cause a slight loss of DHA.

[0082] The phospholipid retention rate of experimental group 3 is higher than that of other experimental groups.

[0083] For the sensory identification of fishy smell in four groups, the intensity of fishy smell is as follows: control sample group > resin adsorption group > experimental group 2 > experimental group 3. The fishy smell intensity of the krill oil extracted under the conditions of experimental group 3 is the weakest.

[0084] Table 3

[0085]

[0086] Note: The fewer the "+", the lighter the fishy smell. The detection limit of trimethylamine is 5mg / kg

[0087] Shelf life experiment: The krill oil extracted by supercritical CO2 under the conditions of experimental group 3 was stored in a sealed state at 4°C and 25°C for 3 months, and there was no obvious increase in fishy smell. The fishy smell increased slightly after accelerating at 45°C for 3 months, but it was still much better than the control sample group and the resin adsorption group. It is recommended to store it in a sealed state at low temperature or normal temperature.

[0088] To sum up, when supercritical CO2 extraction is carried out on the crude extracted krill oil, when the temperature of the extraction kettle is 55°C and the extraction pressure is 15MPa, the krill oil has good fluidity, high separation degree, high yield (96.2%), no trimethylamine detected, high DHA and phospholipid content, no obvious fishy smell, and the fishy smell intensity remains unchanged after storage at 4°C for 1 month.

[0089] Discussion

[0090] This study explored the appropriate process conditions for applying supercritical CO2 extraction technology to the deodorization of krill oil. According to different extraction temperatures and extraction pressures, experimental groups were set (40°C, 12.5MPa; 45°C, 15MPa; 55°C, 15MPa; 55°C, 20MPa; 60°C, 30MPa). Taking the fluidity and separation status of krill oil as the primary screening conditions, the better conditions (45°C, 15MPa; 55°C, 15MPa) were screened out. Further, the determination of trimethylamine, DHA, and phospholipid content and the identification of fishy smell intensity were carried out. Considering various indicators comprehensively, 55°C, 15MPa was selected as the optimal extraction condition.

[0091] This study systematically compared for the first time the content of nutritional components and the degree of reduction of fishy smell intensity of krill oil under different extraction conditions, and found that the deodorization effect is strong and the retention rate of nutritional components is high under the conditions of 55°C and 15MPa, which is the best extraction condition. Specifically, (1) The krill oil has good fluidity, high separation degree, and high product yield. (2) Trimethylamine was not detected. (3) The retention rates of DHA and phospholipid content are high. (4) The fishy smell intensity is significantly reduced.

[0092] The present invention can be applied to the development of functional foods, foods for special medical purposes, and cosmetics related to krill oil and its intensive processing.

[0093] All documents mentioned in the present invention are cited herein by reference as if each individual document was cited by reference. In addition, it should be understood that after reading the above teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Claims

1. A preparation method of odorless krill oil, characterized in that, The preparation method comprises the following steps: (S1) Dissolve krill powder in ethanol, filter to obtain a filtrate; (S2) Put the filtrate into an extraction kettle, carry out supercritical CO2 extraction to obtain odorless krill oil.

2. The preparation method according to claim 1, characterized in that, The extraction is carried out at a temperature of 40 - 60 °C.

3. The preparation method according to claim 1, characterized in that, The pressure of the extraction is 10 - 20 MPa.

4. The preparation method according to claim 1, characterized in that, The filtration is carried out by using a filter membrane with a pore size of 0.1 - 1 μm.

5. The preparation method according to claim 1, characterized in that, Vacuum concentration treatment is also required after step (S1).

6. The preparation method according to claim 1, characterized in that, The ethanol is ethanol with a volume percentage of 80 - 99%.

7. The preparation method according to claim 1, characterized in that The extraction adopts a single-stage separation system.

8. An odorless krill oil prepared by the preparation method according to any one of claims 1 - 8.

9. The odorless krill oil according to claim 8, characterized in that, The odorless krill oil has one or more of the following characteristics: (C1) The content of trimethylamine < 5 mg / kg; (C2) The content of DHA ≥ 6.3 g / 100 g; (C3) The content of phospholipids ≥ 43 g / 100 g.

10. Use of the odorless krill oil according to claim 8 or 9, characterized in that, It is used for preparing foods and cosmetics.

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