A method for low temperature separation of salmon by-product fish oil and protein

Abstract

The present invention relates to the technical field of deep-sea fish by-product processing, and in particular to a method for low-temperature separation of salmon by-product fish oil and protein, which comprises the following steps: drying the salmon by-product to reduce the moisture content of the material to 15-18%; crushing the material so that the oil / (oil+water) volume ratio in the crushed by-product fish paste is 65-85%, fully mixing and stirring, and obtaining fish oil and defatted protein after low-speed centrifugation and cold pressing. The present invention has simple process, easy operation, high separation efficiency, and achieves the maximum protection of the nutritional components of fish oil and the biological utilization value of fish protein and functional components in fish meal under the premise of achieving efficient separation.

Description

Technical Field

[0001] The invention relates to the technical field of deep-sea fish by-product processing, and in particular to a method for low-temperature separation of salmon by-product fish oil and protein. Background Art

[0002] Salmon, also known as salmon, is one of the raw seafood products that is deeply loved by consumers. However, the by-products produced after the fish meat is divided are as high as 50-60wt.% of the total fresh weight of the fish body, mainly including fish head, fish spine (with meat), viscera, and fish skin. Among them, the fish spine (with meat) and fish head are the main by-products after the fish meat is divided, accounting for about 14wt.% and 11wt.% of the total fresh weight of the fish body. The salmon spine and fish head contain a large amount of fat (55-65wt.%, dry basis), protein (20-30wt.%) and nutrients such as minerals and vitamins, and are high-quality raw materials for preparing high-quality fish oil and fish protein. In addition, their fish oil contains a large amount of ω-3 polyunsaturated fatty acids (over 22wt.%) such as DHA and EPA, and fat-soluble functional ingredients such as astaxanthin and vitamin D, which have high processing and utilization value. However, the salmon byproduct fish oil separation technology widely used in industry is still mainly a cooking centrifugation method, which is to grind the byproduct and heat it at 85-95°C for about 20-30min to coagulate the protein and release water and oil. However, this method not only has a low separation efficiency (generally about 72-78%), but also has a long high temperature treatment process that easily leads to the oxidation and degradation of ω-3 polyunsaturated fatty acids and astaxanthin, causing the fish oil quality to decline and protein denaturation, thereby reducing the nutritional functional characteristics of the fish oil and the biological utilization value of the protein. In addition, the heating process is prone to lipid and protein oxidation and degradation reactions, producing characteristic aldehydes and alcohols with fishy smell, making fish oil and fish protein powder have a strong unpleasant fishy smell, greatly affecting its product quality. In addition, the water phase and fish meal after the processing separation have a high moisture content, and still need to be dried additionally, which increases production costs.

[0003] In the prior art, there are many studies on the low-temperature separation technology of fish oil and protein. Among them, the enzymatic hydrolysis method is considered to have a high sustainable prospect, and the most relevant research has been carried out in recent decades. The enzymatic hydrolysis method generally requires several times the amount of water as the raw material to disperse the oil droplets and protein particles, and then the surface protein of the oil droplets is hydrolyzed by biological enzymes to release the oil. However, while the enzymatic hydrolysis is energy-consuming (40-60°C) and time-consuming (1-4h), it will also lead to the oxidation of ω-3 polyunsaturated fatty acids, resulting in a high peroxide value of fish oil and a fishy smell, and it is easy to cause excessive hydrolysis of protein and reduce the application prospects of protein. In addition, the fish oil separation efficiency of the enzymatic hydrolysis method (generally <88%) has not met expectations compared to the high cost investment of the enzyme. Although the dilute alkaline hydrolysis method has the characteristics of low temperature, it requires a large amount of water to dilute the raw materials and a large amount of alkali to adjust the pH to 9.0-11.5, but its fish oil separation efficiency is generally less than 80%, and a large amount of alkaline wastewater is generated, and subsequent wastewater treatment requires more equipment investment. New low-temperature extraction technologies, such as supercritical CO2 extraction, are limited in their industrial development due to the high cost of equipment investment involved. The traditional Soxhlet extraction solvent method is highly efficient (~100%), but the extraction temperature is as high as 80°C and the extraction time is as long as 6 hours. Combining auxiliary technologies such as microwaves and ultrasound can achieve short-term low-temperature extraction of solvent methods, but the extraction efficiency is not ideal. For example, the extraction rate of salmon spine fish oil using microwave-assisted n-hexane is less than 70%. In addition, the safety issues of solvent use are still severe. Therefore, low-temperature, fast, efficient, economical and green sustainable fish oil and fish meal separation technology still needs further research. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a low-temperature, fast, efficient, economical and green sustainable method for separating salmon by-product fish oil and protein.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0006] A method for low temperature separation of salmon by-product fish oil and protein is provided, comprising the following steps:

[0007] The salmon by-product is dried to reduce the moisture content of the material to 15-18%; the material is crushed so that the oil / (oil+water) volume ratio of the crushed by-product fish paste is 65-85%, fully mixed and stirred, and low-speed centrifugal separation and cold pressing are performed to obtain fish oil and defatted protein.

[0008] Further, salmon by-products are fish spines and fish heads.

[0009] Furthermore, the oil / (oil+water) volume ratio in the by-product surimi is 74-75%.

[0010] Furthermore, the mixing and stirring time is 10 min.

[0011] The beneficial effects of the present invention are:

[0012] The separation process of the present invention has the advantages of low temperature, simple process, high efficiency, fast speed, green environmental friendliness and low investment cost. The entire operation process is carried out quickly at low temperature / normal temperature, so it will not cause adverse effects on nutritional components such as ω-3 polyunsaturated fatty acids, proteins, astaxanthin, vitamins, etc., significantly improves the quality of fish oil and protein, and realizes the high-value conversion of salmon by-products. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a comparison between the method of Example 1 and the traditional steaming method of Comparative Example 5 and a schematic diagram of the separation process;

[0014] Figure 2 It is a schematic diagram of fish oil separated by different methods in Example 1 and Example 2 and Comparative Example 5, Comparative Example 6, Comparative Example 11 and Comparative Example 12;

[0015] Figure 3 The stability analysis of the fish bone and fish oil separated under different internal phase fractions in Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4;

[0016] Figure 4 The stability analysis of the separated fish head fish oil under different internal phase fractions in Example 2, Comparative Example 8, Comparative Example 9 and Comparative Example 10;

[0017] Figure 5 Schematic diagram of the change in the size of the oil droplets after the fish bone and fish head oil are stirred in the embodiment;

[0018] Figure 6 The electronic nose sensor response distribution of fish oil separated in different ways in Example 1 and Example 2 and Comparative Example 5, Comparative Example 6, Comparative Example 11 and Comparative Example 12;

[0019] Figure 7 It is a comparative radar chart of the electronic nose odor response intensity of fish oil separated by different methods in Example 1 and Example 2 and Comparative Example 5, Comparative Example 6, Comparative Example 11, and Comparative Example 12;

[0020] Figure 8 It is a comparison of the lipid distribution and fatty acid composition of fish oil separated by different methods in Example 1 and Example 2;

[0021] Fig. 9 It is a comparison of the functional properties of fish bone proteins separated by different methods in Example 1, Comparative Example 5 and Comparative Example 6;

[0022] Fig.10 This is a comparison of the functional properties of fish head proteins separated by different methods in Example 2, Comparative Example 11 and Comparative Example 12. DETAILED DESCRIPTION

[0023] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0024] Example 1

[0025] The production process for separating fish oil and protein from salmon spine comprises the following steps:

[0026] (1) The salmon spine is preliminarily cleaned and cut into sections, and the moisture content of the material is reduced to 18% by freeze drying; then, the material is transferred to a grinder, crushed and mixed to obtain a by-product fish paste, and then the volume ratio of oil / (oil+water) of the whole system is adjusted by adding a small amount of water until the volume fraction of the oil phase reaches 75%, and the mixture is mixed evenly;

[0027] (2) transferring the hydrated material obtained in step (1) to a stirrer, mixing and stirring at room temperature (25° C.) for 10 min, and then centrifuging at room temperature for 15 min (2500×g) to separate a large amount of fish oil in the upper layer;

[0028] (3) The lower layer of fish cakes is bagged and cold pressed at room temperature for 2 minutes to obtain fish protein, and the extruded fish oil is filtered to obtain a small amount of fish oil.

[0029] Example 2

[0030] The production process for separating fish oil and protein from salmon heads comprises the following steps:

[0031] (1) The salmon head is preliminarily cleaned and cut into sections, and the moisture content of the material is reduced to 16% by freeze drying; then, the material is transferred to a grinder, crushed and mixed to obtain a by-product fish paste, and then the volume ratio of oil / (oil+water) of the whole system is adjusted by adding a small amount of water until the volume fraction of the oil phase reaches 75%, and the mixture is mixed evenly;

[0032] (2) transferring the hydrated material obtained in step (2) to a stirrer, mixing and stirring at room temperature 25° C. for 10 minutes, and then centrifuging at room temperature for 15 minutes (2500×g) to separate a large amount of fish oil in the upper layer;

[0033] (3) The lower layer of fish cakes is bagged and cold pressed at room temperature for 2 minutes to obtain fish protein, and the extruded fish oil is filtered to obtain a small amount of fish oil.

[0034] A. Salmon by-product fish spine

[0035] Comparative Example 1

[0036] The difference between this comparative example and Example 1 is that the volume fraction of the oil phase is adjusted to 65% by controlling the moisture content after drying in step (1).

[0037] Comparative Example 2

[0038] The difference between this comparative example and Example 1 is that the volume fraction of the oil phase is adjusted to 70% by controlling the moisture content after drying in step (1).

[0039] Comparative Example 3

[0040] The difference between this comparative example and Example 1 is that the volume fraction of the oil phase is adjusted to 80% by controlling the moisture content after drying in step (1).

[0041] Comparative Example 4

[0042] The difference between this comparative example and Example 1 is that the drying process in step (1) is not performed, and based on the moisture and oil content of the raw materials, the volume fraction of the oil phase is about 35%.

[0043] Comparative Example 5

[0044] This comparative example uses the cooking and centrifugation method to separate fish oil and protein as a reference. The difference from Example 1 is that the raw material is not dried, but directly crushed with water, and then heated and centrifuged. The specific implementation steps are as follows: the salmon spine is preliminarily cleaned and cut into sections, 50% water is added, and then the material and water are transferred to a grinder at the same time, crushed and mixed to obtain a by-product fish paste slurry; then heated at 90°C for 30 minutes, centrifuged at 5000×g and 4°C for 15 minutes, and an oil phase, an aqueous phase and a sediment are obtained. Collect the upper layer of fish oil, remove the middle layer of water, and obtain the separated protein in the lower layer.

[0045] Comparative Example 6

[0046] This comparative example uses n-hexane as solvent and Soxhlet extraction method to separate fish oil and protein as a reference. First, the salmon spine is preliminarily cleaned and cut into sections, and freeze-dried to reduce the moisture content of the material to 10%; then, the material is transferred to a pulverizer, crushed and mixed to obtain a by-product, fish paste; the by-product is defatted using a Soxhlet extraction device and extracted at 80°C for 6h; the separated oil phase and solvent mixture is rotary evaporated at 45°C to remove the solvent; finally, the obtained fish oil and protein are dried at 45°C for 1h in a vacuum drying oven to remove the residual solvent.

[0047] B. Salmon by-product fish head

[0048] Comparative Example 7

[0049] The difference between this comparative example and Example 2 is that the volume fraction of the oil phase is adjusted to 65% by controlling the moisture content after drying in step (1).

[0050] Comparative Example 8

[0051] The difference between this comparative example and Example 2 is that the volume fraction of the oil phase is adjusted to 70% by controlling the moisture content after drying in step (1).

[0052] Comparative Example 9

[0053] The difference between this comparative example and Example 2 is that the volume fraction of the oil phase is adjusted to 80% by controlling the moisture content after drying in step (1).

[0054] Comparative Example 10

[0055] The difference between this comparative example and Example 2 is that the drying process in step (1) is not performed, and based on the moisture and oil content of the raw materials, the volume fraction of the oil phase is about 30%.

[0056] Comparative Example 11

[0057] This comparative example uses the cooking and centrifugation method to separate fish oil and protein as a reference. The difference from Example 2 is that the raw material is not dried, but directly crushed with water, and then heated and centrifuged. The specific implementation steps are as follows: the salmon head is preliminarily cleaned and cut into sections, 50% water is added, and then the material and water are transferred to a grinder at the same time, crushed and mixed to obtain a by-product fish paste slurry; then heated at 90°C for 30 minutes, centrifuged at 5000×g and 4°C for 15 minutes, and an oil phase, an aqueous phase and a solid phase are obtained. Collect the upper layer of fish oil, remove the middle layer of water, and obtain the separated protein of the lower layer.

[0058] Comparative Example 12

[0059] This comparative example uses n-hexane as solvent and Soxhlet extraction to separate fish oil and protein as a reference. First, the salmon head is preliminarily cleaned and cut into sections, and freeze-dried to reduce the moisture content of the material to 10%; then, the material is transferred to a pulverizer, crushed and mixed to obtain a by-product, fish paste; the by-product is defatted using a Soxhlet extraction device and extracted at 80°C for 6h; the separated oil phase and solvent mixture is rotary evaporated at 45°C to remove the solvent; finally, the obtained fish oil and protein are dried at 45°C for 1h in a vacuum drying oven to remove the residual solvent.

[0060] The fish oil separation efficiency of Examples 1-2 and Comparative Examples 1-12 is shown in Table 1; the quality of the fish oil of Examples 1 and 2 and Comparative Examples 5, 6, 11, and 12 is shown in Table 2; the functional properties of the proteins of Examples 1 and 2 and Comparative Examples 5, 6, 11, and 12 are compared in Table 3; the separation schematic diagram of Example 1 and Comparative Example 5 is shown in Table 3. Figure 1 .

[0061] Table 1 Comparison of fish oil and fish protein separation efficiency between the embodiment and the comparative example

[0062]

[0063]

[0064] Table 2 Comparison of fish oil quality between the embodiment and the comparative example

[0065]

[0066]

[0067] Table 3 Volatile aroma substances in fish bone oil (Headspace solid phase microextraction gas chromatography-mass spectrometry analysis HS-SPME-GC-MS)

[0068]

[0069]

[0070] ND: not detected; a The olfactory threshold refers to the second edition of the "Compilation of Olfactory Thresholds of Compounds" published by Science Press; OAV, relative odor activity value, is usually used to evaluate the volatility of odors. When OAV>1, it means that the compound has a significant odor contribution.

[0071] Table 4 Volatile aroma substances in fish head oil (Headspace solid phase microextraction gas chromatography-mass spectrometry analysis HS-SPME-GC-MS)

[0072]

[0073]

[0074]

[0075] ND: not detected; a The olfactory threshold refers to the second edition of the "Compilation of Olfactory Thresholds of Compounds" published by Science Press; OAV, relative odor activity value, is usually used to evaluate the volatility of odors. When OAV>1, it means that the compound has a significant odor contribution.

[0076] Principle of the present invention:

[0077] The present invention reduces the moisture content in the salmon by-product material by drying, so that the protein and water in the system are in a hydration interaction state rather than a flowing water or bulk water state, and the protein is easy to aggregate during the stirring process, promoting the increase of fat droplets; at the same time, the volume ratio of oil / (oil+water) in the material system needs to have a higher oil phase volume fraction The critical volume fraction of a highly inward-looking emulsion is close to 74%, so it is believed that the system also has some characteristics of a highly inward-looking emulsion, such as lipid droplet aggregation and phase separation. In this case, a large number of lipid droplets dispersed in the system are arranged relatively closely. When a stirring force is applied, lipid droplets are more likely to collide with each other, resulting in lipid droplet aggregation and enlargement (such as Figure 5 , the diameter of the oil droplets increased significantly before and after stirring). It is generally believed that the larger the lipid droplets, the more unstable they are, and the easier it is to separate the oil phase under the action of centrifugation; however, the LUMiSizer instability analyzer analysis and verification found that ( Figure 3 and Figure 4 ), when the lipid phase system fraction reaches 75%, it has lower stability than 70% and 80%, and is easier to separate, and the lipid phase is more unstable.

[0078] At the same time, tissue proteins will rearrange their structures and aggregate when hydrated and stimulated by external stirring, reducing the amount of protein particles covering the surface of the oil droplets, making it easier for the lipid droplets to aggregate and grow larger when they come into contact with each other ( Figure 5 When the lipid droplets reach a size that is easy to rupture, they are prone to rupture and phase separation during centrifugation ( Figure 3 and Figure 4 ), a clear oil phase and a bottom precipitate ( Figure 2 ), and the precipitate is cold-pressed to collect some of the residual fish oil, and finally the fish oil and protein are efficiently separated. Among them, the fish oil obtained by the method of the present invention is clearer and more transparent than that by the traditional cooking method. The traditional cooking method, such as Comparative Example 5, obtains an oil phase, an aqueous phase, and a bottom precipitate after cooking and centrifugation, while the present invention only has two phases: an oil phase and a bottom precipitate. Therefore, after the separation process, the cooking method still needs to treat the aqueous phase, such as evaporation or filtration. More importantly, the present invention is carried out at low temperature / normal temperature, and the obtained fish oil and fish protein have better quality than the traditional cooking method. The principle is that the high temperature of the traditional cooking method not only destroys the structure of the protein, but also triggers some oxidation reactions, resulting in the production or release of oxidation products and volatile odor substances, and causing protein denaturation, and reducing functional properties ( Fig. 9 and Fig.10 ).

[0079] Beneficial effects of the present invention:

[0080] (1) The entire process of separating salmon by-product fish oil and protein in the present invention is based on low temperature conditions and does not involve heating treatment. It can effectively retain the thermally unstable functional components in the by-products. The separated fish oil is clear and transparent, has no sediment, and has a low degree of oxidation. The quality is as high as the first-level standard of refined fish oil (Table 2), and the content of the functional factor astaxanthin is higher. No further complicated refining process is required, and the refining process generally loses active ingredients.

[0081] (2) The process of the present invention is simple and fast. The process only includes drying, crushing, fine adjustment of oil-water ratio, stirring, and centrifugation / cold pressing. The operation is easy, and the stirring and separation process is completed within 30 minutes ( Figure 1 ), and the fish oil protein separation technology can be applied on an industrial scale.

[0082] (3) The optimal efficiency of fish oil separation of the present invention reaches 94%, which is much higher than the ~75% of the cooking centrifugation method, and has significantly improved the efficiency of fish oil and protein separation technology. The fish meal protein content after separation is high (Table 1).

[0083] (4) The fish oil prepared by the present invention has a higher quality odor performance and a lower concentration of unpleasant odor compared to the traditional cooking method and solvent extraction method ( Figure 6 , Figure 7 , Table 3, Table 4). Specifically, the electronic nose response of the volatile compounds in the fish oil obtained by the solvent method and the cooking method is stronger, and the relative odor activity of the aroma substances is higher. The fish oil obtained by the solvent method has a strong gasoline smell. The traditional industry often uses the cooking method. The OAVs of the fish oil obtained by this method are much higher than the fish oil prepared by the present invention. The fishy smell is heavier and contains amine odor substances, such as 4-Amino-1-butanol and 5-Amino-1-pentanol. The fishy smell is a comprehensive manifestation of a variety of bad odors, such as rancid smell, earthy smell, fat smell, sulfur smell and sweat smell. The representative fishy smell substances detected in the embodiments of the present invention and the comparative examples mainly include hexanal, decanal, heptaldehyde, 3-methyl-butyraldehyde, 2-methyl-butyraldehyde, 1-pentan-3-ol, acetic acid and 2-ethylfuran, and the content of these substances in the comparative cooking method is significantly and nearly ten times higher than the fish oil obtained by the new technology of the embodiment. Therefore, the method of the present invention has the characteristics of reducing and behavior, and has world-leading advancedness.

[0084] (5) The fish oil prepared by the present invention has a better lipid profile. Among them, diglyceride (DG) has a better lipid-lowering function than triglyceride (TG), and the content of diglyceride in the fish oil prepared by the present invention is significantly higher than that of the fish oil obtained by the cooking method, which is more than 4 times higher ( Figure 8 ), although overall fatty acid differences were modest.

[0085] (6) The fish meal protein prepared by the present invention has a low degree of denaturation and good functional properties. Compared with the fish meal protein obtained by the traditional cooking method, it has better water and oil holding capacity, emulsification properties, higher soluble protein content, and lower crystallinity ( Fig. 9 , Fig.10 ), has a wider application prospect.

[0086] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0087] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for low temperature separation of salmon by-product fish oil and protein, characterized in that: The following steps are involved: The salmon by-product is dried to reduce the moisture content of the material to 15-18%; the material is crushed so that the oil / (oil+water) volume ratio of the crushed by-product fish paste is 74-75%, and the material is fully mixed and stirred, and then centrifuged at a low speed and cold pressed to obtain fish oil and defatted protein.

2. The method for low temperature separation of salmon by-product fish oil and protein according to claim 1, characterized in that: Salmon by-products are the spine and heads.

3. The method for low temperature separation of salmon by-product fish oil and protein according to claim 1, characterized in that: The mixing time was 10 min.

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