Preparation and inspection method of salmon emulsion gel for improving dysphagia

Abstract

The invention discloses a preparation and inspection method of salmon emulsion gel for improving dysphagia, relates to the technical field of preparation and inspection of protein emulsion gel, and solves the problems of dysphagia due to diet rich in protein and insufficient functional fatty acid intake of most of old people. And a salmon emulsion gel product performance verification system is not sound. On the molecular level, a large-size myofibrillar protein filament aggregate is converted into nano-sized myofibrillar micelles, the nano-sized myofibrillar micelles are dissociated in oil and are connected and aggregated with other proteins, and the molecular mechanism of the nano-sized myofibrillar micelles in the aspects of stabilization of salmon emulsion gel and thickening of texture can improve the stability of the salmon emulsion gel. The salmon emulsion gel product can be used for changing the structure and the self-assembly characteristic of protein, effective and comprehensive inspection is carried out on the salmon emulsion gel product, and the effect of improving dysphagia of the salmon emulsion gel product is strongly proved.

Description

Technical Field

[0001] The invention relates to the technical field of protein emulsion gel preparation and testing, and in particular to a method for preparing and testing a salmon emulsion gel for improving dysphagia. Background Art

[0002] Aging is a serious global problem as it is associated with many chronic diseases such as dysphagia, osteoporosis and frailty. Dysphagia is a clinical condition manifested by difficulty swallowing, which is related to the weakening of oral muscles and is common in the elderly. According to population surveys, it is estimated that nearly 20% of the population aged 50 years and above suffer from dysphagia. Elderly patients with dysphagia are more likely to suffer from long-term malnutrition and dehydration due to reduced food intake. Foods for dysphagia are usually modified from liquid to pureed to reduce the risk of choking. However, current foods for dysphagia are usually made with macromolecules extracted from raw foods, such as soy protein, whey protein, enriched starch, corn starch, gums and plant polysaccharides. These formulas usually lack bioactive compounds such as vitamins and minerals, and are difficult to stimulate appetite due to the lack of suction of the food. Therefore, it is crucial to provide these people with well-designed, safe, delicious and nutritious foods with modified textures.

[0003] Dysphagia is often associated with protein-energy malnutrition and weakness in the elderly. A diet rich in protein helps promote muscle synthesis and maintain muscle function in the elderly. Therefore, supplementing the diet with high-quality protein, such as fish protein, is a good nutritional intervention for elderly people with dysphagia. Fish protein usually has a high digestible essential amino acid score (DIAAS), is easier to digest, and helps the absorption of essential amino acids. However, compared with the recommended intake, most elderly people do not consume enough protein-rich diets due to dysphagia. In addition, polyunsaturated fatty acids (PUFAs), especially ω-3, are recommended for the elderly, which is beneficial to their cardiovascular health and immune system. However, most elderly people do not consume enough of these functional fatty acids, and the performance verification system for salmon emulsion gel products is not sound; therefore, it does not meet the existing needs. In this regard, we propose a method for improving the preparation and testing of salmon emulsion gel for dysphagia. Summary of the invention

[0004] The object of the present invention is to provide a preparation and testing method for salmon emulsion gel for improving dysphagia, so as to solve the problem of dysphagia caused by a protein-rich diet compared with the recommended intake, the problem that most elderly people do not take in enough functional fatty acids, and the problem that the performance verification system for salmon emulsion gel products is not sound.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing a salmon emulsion gel for improving dysphagia, comprising the following steps:

[0006] Step 1: Mix fresh salmon meat and ice water in a blender at a ratio of 1:3 at high speed for 1 minute, and filter the dispersion through a 60-mesh sieve;

[0007] Step 2: The obtained filtrate was pre-homogenized using a disperser at a speed of 10,000 rpm for 2 minutes;

[0008] Step 3: The dispersion is subjected to the first step of high pressure homogenization treatment for three cycles to obtain an initial protein suspension, and the protein content in the suspension is adjusted to 2.0 w / v%;

[0009] Step 4: salmon oil extracted from salmon vertebrae by cold micro-water extraction was added to the protein-based suspension to ensure that the oil volume fraction φ reached 0.3, 0.4, 0.5, 0.6 and 0.7, respectively, to obtain five samples;

[0010] Step 5: Mix the sample with a disperser at a speed of 12,000 rpm for 2 minutes to obtain emulsion gel A;

[0011] Step 6: Perform a second high-pressure homogenization on the emulsion gel A to obtain the salmon emulsion gel.

[0012] Preferably, the temperature condition of the high-pressure homogenization treatment is 4° C., and the pressure condition of the high-pressure homogenization treatment is 50 MPa.

[0013] Preferably, the salmon oil extracted from salmon spine comprises the following steps:

[0014] W1: The cleaned salmon spine was freeze-dried to reduce the moisture content, and the dried byproduct was ground in a grinder;

[0015] W2: The ground sample was rehydrated with water until the oil volume fraction φ was adjusted to 75% by volume, stirred by tangential flow with an overhead stirrer for 15 min, and then immediately centrifuged at 8000 × g for 15 min at 20 °C;

[0016] W3: Obtain the upper salmon oil and store it in a -20°C storage environment.

[0017] A method for improving the testing of salmon emulsion gel for dysphagia, comprising the following steps:

[0018] S1: The salmon emulsion gels with different φ treated by the second high pressure homogenization step were referred to as HPH0.3, HPH0.4, HPH0.5, HPH0.6 and HPH0.7, respectively, and the emulsion gel A without the second high pressure homogenization step was referred to as Un-HPH0.3, Un-HPH0.4, Un-HPH0.5, Un-HPH0.6 and Un-HPH0.7, respectively. Each emulsion gel sample was stored in a 20 ml transparent glass vial at 4°C;

[0019] S2: Color analysis of all emulsion gel samples was performed using a colorimeter, and microscopic observation and particle size analysis were performed;

[0020] S3: All emulsion gel samples were subjected to centrifugal stability testing, measured by a dispersion analyzer;

[0021] S4: The formation and dissociation of ice crystals in salmon emulsion gels were measured using differential scanning calorimetry for all emulsion gel samples;

[0022] S5: IDDSI test and rheological property test of salmon emulsion gel;

[0023] S6: Strain sweep test, viscosity shear test and frequency sweep test were performed on salmon emulsion gel;

[0024] S7: Extract the surfactant proteins from salmon emulsion gel, obtain the surface myofibrillar proteins, and analyze the morphology and interfacial rheological properties of the surface myofibrillar proteins;

[0025] S8: Repeat the above steps S1-S7 three times to calculate the mean and standard deviation of the data.

[0026] Preferably, the colorimeter measurement parameters include the values ​​of brightness L*, redness a* and yellowness b*;

[0027] The centrifugal stability test was performed by transferring the sample into a polycarbonate tube and collecting data at intervals of 20 seconds in a centrifuge. The sample was centrifuged for 6000 seconds to destabilize the sample, and the instability index and area percentage were calculated using LUMSEPview V6.4 software.

[0028] Preferably, microscopic observation and particle size analysis comprises the following steps:

[0029] Step 1: Dilute the homogenized salmon emulsion gel in 1% SDS solution at a ratio of 1:10 to disperse the aggregated oil droplets, and dilute the unhomogenized emulsion in ultrapure water at a ratio of 1:5;

[0030] Step 2: Use a fluorescent inverted microscope with a digital camera to observe the microstructure of the oil droplets in the salmon emulsion gel. The oil droplets are dyed red with Nile red and then dropped on a glass slide and covered with a coverslip.

[0031] Step 3: The particle size distribution of the fresh emulsion gel was determined by dynamic light scattering DLS in the range of 0.02 μm-2600 μm, with the ultrasonic power set to 35 W for 2 minutes, the stirring speed set to 1200 rpm, and the measurement shading set to 5%-20%.

[0032] Preferably, the differential scanning calorimetry measurement comprises the following steps:

[0033] Step 1: Place fresh salmon emulsion gel into an aluminum crucible and input nitrogen at a nitrogen flow rate of 20 mL / min. Cool the measuring temperature from 20°C to -30°C at a cooling rate of 5°C / min;

[0034] Step 2: After 5 min of equilibration, the sample was heated from 30 °C to 40 °C at the same flow rate and then cooled from 40 °C to 20 °C at a rate of 10 °C / min.

[0035] Preferably, the rheological property test is measured by a rheometer, the plate diameter is 40 mm, the gap distance is 1000 μm, the test sample is placed at ambient temperature for 1 hour to reach thermal equilibrium, and the test temperature is 25°C;

[0036] The strain sweep test measures viscoelasticity in the oscillatory amplitude mode within the linear viscoelastic region (LVR) at a test temperature of 25°C, a frequency of 1 Hz, and a strain range of 0.1% to 1000%;

[0037] The viscosity shear test is to place the sample on a platform with a shear rate ranging from 0.1 to 100 s-1, and evaluate the apparent viscosity by testing its response to different shear rates;

[0038] Frequency sweep tests were performed in the frequency range of 0.1 to 15 Hz to measure the storage modulus G' and loss modulus G", at a temperature of 25 °C and a strain rate of 0.5%.

[0039] Preferably, the method for extracting surfactant protein from salmon emulsion gel comprises the following steps:

[0040] E1: 20 g of fresh emulsion gel was centrifuged at 10,000 × g for 30 min at 4 °C to remove unabsorbed particles;

[0041] E2: After centrifugation, the top layer was collected, mixed with methanol at a weight-to-volume ratio of 1:2, and incubated at room temperature for 10 min;

[0042] E3: The mixture was then centrifuged at 4,700 × g for 10 min, and the top methanol phase was removed. The above process was repeated three times;

[0043] E4: After washing with methanol, the precipitate was washed three times with n-hexane and finally washed three times with ethanol. The collected precipitate was washed with 100 mM phosphate buffer at pH 7.0 containing 100 mM NaCl, 1 mM MgCl2 and 1 mM EDTA and centrifuged twice to obtain myofibrillar protein. The precipitated surfactant myofibrillar protein was dried by freeze drying.

[0044] Preferably, the analysis of the morphology and interfacial rheological properties of surface myofibrillar protein comprises the following steps:

[0045] G1: The obtained surface myofibrillar proteins were measured by FTIR, XRD, SEM, AFM and TEM, and the particle size distribution was determined by DLS;

[0046] G2: Interfacial properties were measured using an optical surface analyzer, using medium-chain triglycerides (MCT) as the oil phase. Surfactant proteins were suspended in 10 mM PBS at a concentration of 500 μg / mL and filtered through a 0.45 μm filter to remove large protein aggregates.

[0047] G3: Quantify protein concentration using the BCA protein assay kit, creating an area of ​​15 mm on the needle tip. 2 The pendant droplets were always equilibrated for 3 h before any drop area deformation was performed, and the oscillation amplitude was set to 10%. Amplitude sweeps were performed at a constant frequency of 0.05 Hz at 25 °C to obtain the interfacial tension, dilatational elastic modulus Ed', and dilatational viscous modulus Ed".

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The present invention utilizes high pressure homogenization (HPH) to convert raw salmon fillet and spine oil into an emulsion gel with high ω-3 oil content designed for patients with dysphagia. HPH improves the stability, swallowing safety and rheological viscosity of the emulsion gel containing 30-60 vol.% oil. The emulsion gel containing 50 and 60 vol.% oil exhibits excellent swallowing safety and rheological properties and can be classified as level 4 according to the IDDSI framework. The enhanced emulsion stability and gel-like texture are due to the modification of myofibrillar protein by HPH, including particle size, α-helical structure, aggregation and interface properties.

[0050] At the molecular level, HPH converts large-sized myofibrillar protein filament aggregates into nano-sized myofibrillar micelles. Nano-sized myofibrillar micelles can dissociate in oil, connect with other proteins and aggregate, revealing the molecular mechanism of HPH in stabilizing salmon emulsion gel and thickening texture. As a non-thermal physical processing technology, high-pressure homogenization HPH can be used to change the structure and self-assembly properties of proteins. When high-speed fluid passes through the narrow slit of the homogenization valve, it will generate strong shear and impact forces. These forces will destroy and mix the particles, cells or colloids in the sample, making them smaller and more evenly dispersed. The homogenization pressure will cause the protein to unfold, aggregate or form a gel, effectively improving the storage stability and taste of liquids and purified foods. In addition, the salmon emulsion gel products are effectively and comprehensively tested, which fully improves the strong evidence of the salmon emulsion gel products in improving dysphagia. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 The figure is a flow chart of the preparation of the salmon emulsion gel of the present invention;

[0052] Figure 2 It is the instability analyzer curve diagram of the salmon emulsion gel with different oil contents without HPH of the present invention;

[0053] Figure 3 It is a comparison diagram of the instability coefficient curves of the salmon emulsion gel with different oil contents without HPH of the present invention;

[0054] Figure 4 It is a comparison diagram of the interfacial movement rate curves of salmon emulsion gels with different oil contents and HPH of the present invention;

[0055] Figure 5 It is a comparison diagram of differential thermal scanning curves of salmon emulsion gel with different oil contents and HPH of the present invention;

[0056] Figure 6 The instability analyzer curve diagram of salmon emulsion gel with different oil contents after HPH of the present invention;

[0057] Figure 7 The figure is a comparison diagram of the instability coefficient curves of salmon emulsion gels with different oil contents after HPH of the present invention;

[0058] Figure 8 This is a comparison diagram of the interfacial movement rate curves of salmon emulsion gels with different oil contents after HPH;

[0059] Fig. 9 This is a comparison diagram of differential thermal scanning curves of salmon emulsion gels with different oil contents after HPH;

[0060] Fig.10The microscopic observation pictures of the salmon emulsion gel before HPH and after HPH of the present invention;

[0061] Fig.11 This is a graph showing the change in the number of colonies during the storage of the salmon emulsion gel of the present invention;

[0062] Fig.12 It is a comparison diagram of the oscillatory strain scanning curves of the salmon emulsion gel with different oil contents and HPH of the present invention;

[0063] Fig.13 It is a comparison diagram of the frequency scanning curves of the salmon emulsion gel with different oil contents and HPH of the present invention;

[0064] Fig.14 It is a comparison diagram of viscosity shear scanning curves of salmon emulsion gel with different oil contents without HPH of the present invention;

[0065] Fig.15 This is a comparison diagram of oscillatory strain scanning curves of salmon emulsion gels with different oil contents after HPH of the present invention;

[0066] Fig.16 This is a comparison diagram of frequency scanning curves of salmon emulsion gels with different oil contents after HPH of the present invention;

[0067] Fig.17 This is a comparison diagram of viscosity shear scanning curves of salmon emulsion gels with different oil contents after HPH of the present invention;

[0068] Fig.18 This is a comparison diagram of the surface protein particle size distribution curves of Un-HPH0.6 and HPH0.6 of the present invention;

[0069] Fig.19 This is a comparison diagram of the infrared spectrum curves of Un-HPH0.6 and HPH0.6 of the present invention;

[0070] Fig. 20 It is a comparison diagram of the X-ray diffraction curves of Un-HPH0.6 and HPH0.6 of the present invention;

[0071] Fig.21 This is a SEM image of the surface protein of the salmon emulsion gel of the present invention;

[0072] Fig. 22 This is an AFM image of the surface protein of the salmon emulsion gel of the present invention;

[0073] Fig.23 This is a TEM image of the surface protein of the salmon emulsion gel of the present invention;

[0074] Fig.24 Schematic diagram of the mechanism of improving the stability and texture of salmon emulsion gel by HPH in the present invention;

[0075] Fig.25 This is a comparison diagram of the interface expansion of Un-HPH0.6 and HPH0.6 of the present invention;

[0076] Fig.26 It is a comparison diagram of the interface adsorption characteristics of Un-HPH0.6 and HPH0.6 of the present invention. DETAILED DESCRIPTION

[0077] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0078] See also Figures 1 to 6 The present invention provides an embodiment: a method for preparing a salmon emulsion gel for improving dysphagia, comprising the following steps:

[0079] Step 1: Mix fresh salmon meat and ice water in a blender at a ratio of 1:3 at high speed for 1 minute, and filter the dispersion through a 60-mesh sieve;

[0080] Step 2: The obtained filtrate was pre-homogenized using a disperser at a speed of 10,000 rpm for 2 minutes;

[0081] Step 3: The dispersion is subjected to the first step of high-pressure homogenization treatment, the temperature condition of the high-pressure homogenization treatment is 4°C, the pressure condition of the high-pressure homogenization treatment is 50 MPa, and the process is repeated three times to obtain an initial protein suspension, and the protein content in the suspension is adjusted to 2.0 w / v%;

[0082] Step 4: salmon oil extracted from salmon vertebrae by cold micro-water extraction was added to the protein-based suspension to ensure that the oil volume fraction φ reached 0.3, 0.4, 0.5, 0.6 and 0.7, respectively, to obtain five samples;

[0083] Step 5: Mix the sample with a disperser at a speed of 12,000 rpm for 2 minutes to obtain emulsion gel A;

[0084] Step 6: Perform a second high-pressure homogenization on the emulsion gel A. The temperature condition of the high-pressure homogenization treatment is 4° C., and the pressure condition of the high-pressure homogenization treatment is 50 MPa to obtain the salmon emulsion gel.

[0085] Extraction of salmon oil from salmon spine involves the following steps:

[0086] W1: The cleaned salmon spine was freeze-dried to reduce the moisture content, and the dried byproduct was ground in a grinder;

[0087] W2: The ground sample was rehydrated with water until the oil volume fraction φ was adjusted to 75% by volume, stirred by tangential flow with an overhead stirrer for 15 min, and then immediately centrifuged at 8000 × g for 15 min at 20 °C;

[0088] W3: Obtain the upper salmon oil and store it in a -20°C storage environment.

[0089] The above-mentioned test method for improving the salmon emulsion gel for dysphagia is characterized by comprising the following steps:

[0090] S1: The salmon emulsion gels with different φ treated by the second high pressure homogenization step were referred to as HPH0.3, HPH0.4, HPH0.5, HPH0.6 and HPH0.7, respectively, and the emulsion gel A without the second high pressure homogenization step was referred to as Un-HPH0.3, Un-HPH0.4, Un-HPH0.5, Un-HPH0.6 and Un-HPH0.7, respectively. Each emulsion gel sample was stored in a 20 ml transparent glass vial at 4°C;

[0091] S2: All emulsion gel samples were subjected to color analysis using a colorimeter. The colorimeter measured parameters including the values ​​of lightness L*, redness a*, and yellowness b*, and microscopic observation and particle size analysis were performed.

[0092] S3: All emulsion gel samples were subjected to centrifugal stability test, which was measured by dispersion analyzer. The centrifugal stability test was to transfer the sample into a polycarbonate tube and collect data at intervals of 20 seconds in a centrifuge. The sample was centrifuged for 6000 seconds to make it unstable, and then the instability index and area percentage were calculated using LUMSEPviewV6.4 software;

[0093] S4: The formation and dissociation of ice crystals in salmon emulsion gels were measured using differential scanning calorimetry for all emulsion gel samples;

[0094] S5: IDDSI test and rheological property test of salmon emulsion gel;

[0095] The rheological properties were tested by a rheometer with a plate diameter of 40 mm and a gap distance of 1000 μm. The test sample was placed at ambient temperature for 1 hour to reach thermal equilibrium. The test temperature was 25 °C.

[0096] S6: The salmon emulsion gel was subjected to strain sweep test, viscosity shear test and frequency sweep test. The strain sweep test measured the viscoelasticity in the oscillation amplitude mode within the linear viscoelastic region (LVR). The test temperature was 25 °C, the frequency was 1 Hz, and the strain range was 0.1% to 1000%.

[0097] The viscosity shear test is to place the sample on a platform with a shear rate ranging from 0.1 to 100 s-1, and evaluate the apparent viscosity by testing its response to different shear rates;

[0098] Frequency sweep tests were performed in the frequency range of 0.1 to 15 Hz to measure the storage modulus G' and loss modulus G", the temperature was 25 °C, and the strain rate was 0.5%;

[0099] S7: Extracting the surfactant protein from the salmon emulsion gel to obtain surface myofibrillar protein. The method for extracting the surfactant protein from the salmon emulsion gel comprises the following steps:

[0100] E1: 20 g of fresh emulsion gel was centrifuged at 10,000 × g for 30 min at 4 °C to remove unabsorbed particles;

[0101] E2: After centrifugation, the top layer was collected, mixed with methanol at a weight-to-volume ratio of 1:2, and incubated at room temperature for 10 min;

[0102] E3: The mixture was then centrifuged at 4,700 × g for 10 min, and the top methanol phase was removed. The above process was repeated three times;

[0103] E4: After washing with methanol, the precipitate was washed three times with n-hexane and finally washed three times with ethanol. The collected precipitate was washed with 100 mM phosphate buffer at pH 7.0 containing 100 mM NaCl, 1 mM MgCl2 and 1 mM EDTA and centrifuged twice to obtain myofibrillar protein. The precipitated surfactant myofibrillar protein was dried by freeze drying;

[0104] The morphology and interfacial rheological properties of the surface myofibrillar protein are analyzed. The morphology and interfacial rheological properties of the surface myofibrillar protein are analyzed including the following steps:

[0105] G1: The obtained surface myofibrillar proteins were measured by FTIR, XRD, SEM, AFM and TEM, and the particle size distribution was determined by DLS;

[0106] G2: Interfacial properties were measured using an optical surface analyzer, using medium-chain triglycerides (MCT) as the oil phase. Surfactant proteins were suspended in 10 mM PBS at a concentration of 500 μg / mL and filtered through a 0.45 μm filter to remove large protein aggregates.

[0107] G3: Quantify protein concentration using the BCA protein assay kit, creating an area of ​​15 mm on the needle tip. 2The droplets were always equilibrated for 3 h before any drop area deformation was performed, and the oscillation amplitude was set to 10%. Amplitude sweeps were performed at a constant frequency of 0.05 Hz at 25 °C to obtain the interfacial tension, dilatational elastic modulus Ed', and dilatational viscous modulus Ed";

[0108] S8: Repeat the above steps S1-S7 three times to calculate the mean and standard deviation of the data.

[0109] Microscopic observation and particle size analysis include the following steps:

[0110] Step 1: Dilute the homogenized salmon emulsion gel in 1% SDS solution at a ratio of 1:10 to disperse the aggregated oil droplets, and dilute the unhomogenized emulsion in ultrapure water at a ratio of 1:5;

[0111] Step 2: Use a fluorescent inverted microscope with a digital camera to observe the microstructure of the oil droplets in the salmon emulsion gel. The oil droplets are dyed red with Nile red and then dropped on a glass slide and covered with a coverslip.

[0112] Step 3: The particle size distribution of the fresh emulsion gel was determined by dynamic light scattering DLS in the range of 0.02 μm-2600 μm, with the ultrasonic power set to 35 W for 2 minutes, the stirring speed set to 1200 rpm, and the measurement shading set to 5%-20%.

[0113] The differential scanning calorimetry measurement includes the following steps:

[0114] Step 1: Place fresh salmon emulsion gel into an aluminum crucible and input nitrogen at a nitrogen flow rate of 20 mL / min. Cool the measuring temperature from 20°C to -30°C at a cooling rate of 5°C / min;

[0115] Step 2: After 5 min of equilibration, the sample was heated from 30 °C to 40 °C at the same flow rate and then cooled from 40 °C to 20 °C at a rate of 10 °C / min.

[0116] Water seepage was observed at the bottom of the salmon protein dispersion and during storage. When the volume fraction of the oil phase reached 60% and 70%, no water seepage was observed. The high stability may be due to the repulsive effect of the oil phase, which inhibited the aggregation of proteins and then inhibited the water seepage. High-pressure homogenization (HPH) makes the emulsion gel more stable and resists water seepage. HPH can break down salmon micron-sized myofibrillar protein particles into smaller particles, thereby supporting the stability of water and oil. However, the HPH emulsion gel containing 70% oil phase failed to form a stable emulsion gel. Under such a high oil phase, the emulsion has poor fluidity when flowing through the homogenization valve and destroys the emulsion. In addition, the HPH sample remained condensed during storage and had a creamy texture. Since salmon oil is light orange-red, the color change can effectively reflect the degree of oil release in the sample, on the 1st and 7th days during storage (4°C), as shown in Table 1A and Table 1B below:

[0117] Table 1A.L*,a*,b*of the emulsion samples for different oil volumes on the 1st day.

[0118]

[0119] Table 1B.L*, a*, b* of the emulsion samples for different oil volumes on the 7th day.

[0120]

[0121] The effect of HPH treatment on the surface color of the emulsion gel is shown in Table 1A and Table 1B, respectively. On the first day, the L* value of the HPH sample was higher than that of the non-HPH sample, while the a* and b* values ​​were lower. The HPH treatment may split the oil droplets into smaller droplets, thereby reducing the red and yellow colors. After 7 days of storage, the surface color parameters (φ = 0.3-0.6) of the HPH emulsion gel did not change significantly. Therefore, it can be concluded that the 7-day storage did not cause significant oil exudation in the HPH salmon emulsion gel.

[0122] For the centrifugal stability of salmon emulsion gel, proteins tend to aggregate during storage, leading to water seepage, while oil droplets tend to merge, leading to oil droplet separation, therefore, an accelerated stability analyzer (LUMiSizer) was used to study the potential storage stability of salmon emulsion gel. Centrifugal emulsification can lead to oil droplet merging and more severe oil droplet separation, as well as water seepage, e.g. Figure 2-Figure 9As shown, during the centrifuge (1000×g), the overall transmittance spectra of the non-high pressure homogenization (Un-HPH) and high pressure homogenization (HPH) emulsion gels showed obvious oil droplet separation due to the instability of the oil droplets, which was consistent with their appearance. The emulsions with non-high pressure treatment of 0.3-0.6 had a slight oil droplet separation layer on the top, and HPH0.3-0.6 had no oil droplet separation, indicating that the oil phase was more stable. However, they all had a water layer at the bottom from 110 mm to 130 mm. Therefore, water seepage during centrifugation can indicate the instability index.

[0123] Compared with Un-HPH0.3-0.6, the instability index of HPH0.3-0.6 was significantly reduced. The increase in emulsion stability can be attributed to the modification of protein structure and interfacial properties by high pressure shear, which improves the oil / water adsorption capacity. In addition, as the φ value increases from 0.3 to 0.6, the instability index decreases, indicating that emulsion gels with higher oil volume fraction can stabilize more water, and decreases with increasing φ value. Overall, HPH0.5 and HPH0.6 emulsions show excellent emulsion stability, and HPH0.6 has the highest stability.

[0124] The thermal stability of salmon emulsion gels was determined by differential scanning calorimetry (DSC). The crystallization temperature (Tc) and melting point (Tm) of all emulsion gels were -17 to -21 °C and 5 to 8 °C, respectively. The Tc and phase change enthalpy (ΔH) of HPH0.3-0.6 emulsion gels were lower than those of non-high pressure treated (Un-HPH0.3-0.6) emulsion gels, indicating that they have higher thermal stability.

[0125] For the microstructure and particle size of salmon emulsion gels, the stability enhancement was largely dependent on the oil droplet size, e.g. Fig.10 As shown in the figure, the oil droplets in the emulsion were observed by microscope. HPH significantly reduced the size of most oil droplets from more than 20 μm to nearly 2 μm, which is consistent with the DLS particle size distribution results. The mechanical forces generated by high-speed shear and cavitation on the emulsion gel led to the rupture of large oil droplets. In the Un-HPH0.3-0.6 emulsion gel, the oil droplets were dispersed individually. However, after high-pressure homogenization, even if dispersed in 1% SDS to reduce aggregation, the oil droplets in the HPH0.3-0.6 emulsion gel aggregated to form large flocculent particles. High-pressure homogenization can change the protein structure, such as protein unfolding and hydrophobic group exposure, which will reduce the size of protein particles, increase surface hydrophobicity, promote their electrostatic interactions, and increase emulsification and lubrication properties. The terminal region of the surface myofibrillar protein extends into the aqueous phase, which may promote a stable gel structure through steric hindrance interactions. Therefore, high-pressure homogenization effectively reduces the oil droplet size of salmon emulsion gels and promotes the aggregation of oil droplets, which has a positive effect on their storage stability.

[0126] IDDSI provides a globally recognized standard and test method for evaluating texture-modified foods for people with dysphagia. The IDDSI tests include the fork drop test, spoon tilt test, and fork pressure test, which are divided into 8 levels (0-7) from liquid beverages to semi-solid foods. The salmon emulsion gels were evaluated using the IDDSI framework. The fork drop test is used to evaluate liquid-form foods (levels 3 and 4), while the spoon tilt test evaluates the cohesion and stickiness of foods (levels 4 and 5). All Un-HPH0.3-0.6 emulsion gels exhibited a liquid consistency but failed to meet the standards of the level 3 and 4 fork drop test and spoon tilt test because they quickly dripped from the fork and stuck to the spoon. In contrast, all HPH0.3-0.6 emulsion gels were in an extremely thickened and purified state, and their cohesion was higher than that of the un-HP 0.3-0.6 emulsion gels. However, HPH0.3 and HPH0.4 were in liquid form and could not completely slide off the spoon, failing the level 4 spoon tilt test. As φ increases from 0.3 to 0.6, the viscosity increases. HPH0.5 and HPH0.6 have excellent stacking ability on a spoon, sliding down slowly when tilted without any splashing. They can also be stacked on a fork. From the fork pressure test, HPH0.5 and HPH0.6 are easily crushed under slight pressure, and the surface left by the fork has a clear pattern (passed level 4). The results combined show that HPH0.5 and HPH0.6 can be classified as level 4, that is, non-sticky and can usually be eaten with a spoon without chewing, so they are very suitable for the diet of people with dysphagia because they are easy to swallow.

[0127] For the viscoelastic testing of salmon emulsion gels, emulsion gels exhibit a range of thickening and viscoelastic behaviors when subjected to shear forces. Rheological properties are widely recognized as quantifying the oral performance and swallowability of emulsion gels. Before testing viscosity, it was necessary to evaluate the stiffness of the salmon emulsion gels. Oscillatory shear rheology (strain and frequency sweeps) was performed to obtain the storage (G') and loss (G") moduli before shearing.

[0128] In the strain sweep test, the G' of all samples was higher than G", indicating that the salmon emulsion gels exhibited elasticity-dominated behavior regardless of whether they were homogenized or not. Generally, at the same φ value, the G' and G" of the HPH0.3-0.6 emulsion gels were one order of magnitude higher than those of the non-HPH0.3-0.6 emulsion gels. In addition, G' and G" gradually increased with the increase of the oil volume fraction, that is, the mechanical strength of the emulsion gels was improved. The higher G' and G" of HPH0.3-0.6 might mean higher viscosity and hardness. When the strain reached the LVR, G' and G" began to decrease non-linearly, indicating that the network structure was damaged. Compared with the HPH0.3-0.6 emulsion gels, the non-HPH0.3-0.6 samples had a shorter viscoelastic region (LVR), indicating their brittle texture. During the oral processing and swallowing of the non-HPH0.3-0.6 emulsion gels, disordered and heterogeneous structures might occur, which would have a negative impact on the bolus adhesion during the bolus passing through the pharynx, thus increasing the swallowing risk for dysphagia patients.

[0129] In the frequency sweep test, as Figure 12-17 shown, the G' and G" of the salmon emulsion gels with frequency. Since G'>G", the emulsion gels were elastic in the range of 0.1-15 Hz. Both G' and G" increased with the increase of the oil content. This might be due to the exposure of the hydrophobic groups on the surface of salmon proteins, resulting in an increased degree of interaction between salmon proteins and oils. In addition, at the same φ value (0.3-0.6), the G' (600-5000 Pa) of the HPH0.3-0.6 emulsion gels was almost 6-8 times that of the Un-HPH0.3-0.6 emulsion gels (100-600 Pa). The salmon emulsion gels changed from liquid state to paste state after high-pressure homogenization. The possible reason was that high-pressure homogenization changed the structure of salmon proteins, improved the interfacial properties of proteins, and enhanced the emulsifying ability.

[0130] The tanδ (G" / G') value can be used to characterize the liquid or gel state of the emulsion gels. tanδ>1 indicates a dilute solution, while 0.1<tanδ<1 indicates a weak gel. Food boluses with tanδ values in the range of 0.1-1 are easier to swallow for dysphagia patients. The tanδ values of the emulsion gels of HPH0.3, HPH0.4, HPH0.5 and HPH0.6 were in the range of 0.1-0.3, indicating that they were weak emulsion gels. From the perspective of rheological properties, they were safe for dysphagia patients.

[0131] During swallowing, shear is considered to be the main deforming force applied to the food bolus. According to the National Dietary Guidelines for Dysphagia, shear is recommended as a standard for assessing swallowing thickness in patients with dysphagia. A shear rate of 50 s-1 is highly correlated with the pharyngeal force applied to the food bolus. Therefore, shear viscosity was measured in the shear rate range of 0.1 to 100 s-1 to fully evaluate the swallowability of the salmon emulsion gels. As the shear rate increased, the viscosity of the samples decreased, indicating that these emulsion gels have non-Newtonian shear thinning behavior, which is required for safe swallowing.

[0132] Thickened liquids (grades 1-4) have a strong viscosity-dependent therapeutic effect on oropharyngeal patients with severe dysphagia, with the proportion of safe swallowing increasing from 63% at 0.1 Pa×s to 95% at 1.6 Pa×s (shear at 50 s-1). The viscosities of all Un-HPH0.3-0.6 emulsion gels at a shear rate of 50 s-1 ranged from 0.14 to 0.58 Pa×s, indicating that these foods may have an incidence of unsafe swallowing exceeding 20-40%. The viscosities of HPH0.4, HPH0.5, and HPH0.6 were 2.24, 7.65, and 8.65 Pa×s, respectively, indicating that they may have a high safe swallowing rate exceeding 95%. Grade 4 commercial thickened liquids generally exhibit low shear viscosities ranging from 0.8 to 2.7 Pa×s. Recently, grade 4 dysphagia diets prepared using various colloid mixtures (1–2%) had higher shear viscosities ranging from 10–20 Pa×s at shear at 50 s−1, which are very suitable for the production of 3D printed dysphagia foods.

[0133] Based on the above investigation, it is obvious that HPH0.6 contains more ω-3 salmon oil and exhibits excellent emulsification stability, IDDSI texture, and rheological properties. Therefore, we further evaluated the relationship between storage time and cumulative colony counts of HPH0.6 at 4 °C, as shown in Figure 2. Fig.11 As shown in Figure 2, without adding any preservatives, the cumulative colony counts of HPH0.6 on the 7th, 10th, and 14th days were 5.6×10 3 CFU / g, 1.6×10 4 CFU / g and 8.1×10 4 CFU / g, according to the Chinese standard (GB10136-2015), the cumulative colony count of edible animal aquatic products reaches 5×10 4 CFU / g is the acceptable limit, which means that HPH0.6 can be eaten within 10 days.

[0134] like Figure 18-20As shown in the figure, high pressure homogenization significantly improved the physical stability of salmon emulsion gel and changed its texture and rheological properties. Due to the change in the structure of myofibrillar protein, in order to explore this phenomenon, surface myofibrillar protein was extracted and analyzed from the control group (suspension based on salmon protein), the 0.6 group without high pressure homogenization and the 0.6 group with high pressure homogenization. After high pressure homogenization, the particle size decreased. The myofibrillar protein in the control group showed a bimodal size distribution, with two main peaks of approximately 90 μm and 1200 μm, respectively. The sample after high pressure homogenization (HPH0 .6) is concentrated at about 90 μm, while the main peak of the sample Un-HPH0.6 without high-pressure homogenization is concentrated at about 90 μm, which indicates that high-pressure homogenization reduces the particle size and aggregation degree of surfactant proteins. According to the FTIR and XRD spectra, high-pressure homogenization treatment reduces the α-helix, the 9° of XRD2θ decreases, the FTIR absorption peak between 1650-1660 decreases, and the decrease in XRD intensity also indicates that the crystallinity of protein particles decreases, which is due to the fact that high-pressure homogenization treatment reduces the degree of myofibril filament structure.

[0135] like Fig.21 As shown, the protein aggregates in the control group and Un-HPH0.6 samples were fibrous and rod-shaped, consistent with the filamentous structure of fish myofibrillar protein. Between cross-links, the surface of the protein fibril aggregates was rough and there were large gaps. HPH significantly changed the morphology of myofibrillar protein. The protein aggregates of HPH0.6 showed a more granular shape with small voids between the aggregates, while the rod-shaped fibril structure disappeared. The gaps between HPH0.6 myofibrillar protein were smaller, more uniform and dense at the nanoscale, which was a sign of the transition of the protein from large fibril aggregates to small micelle aggregates.

[0136] like Fig. 22 and Fig.23 As shown, atomic force microscopy (AFM) was used to examine the surface roughness and aggregation of surface myofibrillar proteins at the nanoscale, with the control protein showing a large aggregation peak, manifested by a high root mean square roughness (Rq; 10.8 nm), average roughness (Ra; 7.22 nm), and a large surface height value (47.4 nm). After dispersion with oil, the protein Ra and surface height decreased to 2.64 and 13.3 nm, respectively. This reduction was attributed to the hydrophobic force from the oil, which inhibited the aggregation of myofibrillar filaments. The surface roughness of the HPH0.6 protein decreased to Ra = 1.59 nm in a more compact form and exhibited a more uniform small peak. This indicates that the salmon myofibrillar filaments are split into shorter and thinner aggregates.

[0137] The surface myofibrillar proteins of the control, non-HPH0.6, and HPH0.6 were also observed by transmission electron microscopy, and the proteins from the control formed a large protein aggregate at more than 6 μm, while the proteins from non-HPH0.6 showed filament aggregates with a length of about 3 μm. Myosin and actin filaments (or sarcomeres) are usually about 2.5 μm in length. In contrast, the proteins from HPH0.6 formed smaller aggregates at both the micrometer (about 1 μm) and nanometer scales. These observations are consistent with the results of atomic force microscopy, that is, high-pressure homogenization reduced the size of protein aggregates, and their shape was no longer filamentous, but a more loose aggregate state. High-pressure homogenization with oil can break up myofibrillar fibril aggregates and break them into subprotein species. These smaller units can then aggregate in the aqueous phase to form different forms, depending on the hydrophobicity they are exposed to. The cavitation and shear forces generated by the high-pressure homogenization treatment may promote hydrophobic adsorption to oil molecules and destroy the electrostatic and hydrophobic interactions between protein molecules. Therefore, the high-pressure homogenization treatment effectively reduces protein aggregation and size.

[0138] like Fig.25 and 26 As shown, for the aggregation and interfacial properties of surface proteins, the interfacial properties of surface proteins are mainly determined by nanoparticles, and micro-sized protein aggregates are removed by filtration through a 0.45 μm filter. Nano-sized protein particles were observed by transmission electron microscopy (TEM). The nano-sized particles of the control group and HPH0.6 showed a chain-like coiled-coil fibril structure. The filtrates all showed aggregate fibrils with chain lengths exceeding 2 μm and chain widths below 0.45 μm. The nano-sized particles of HPH0.6 were about 400 nm in diameter, spherical, and evenly distributed, which may be protein micelles.

[0139] The interfacial properties of the nanomyofibril protofilaments of the control group and Un-HPH0.6 were compared with the myofibrillar micelles of HPH0.6. The interfacial tension of the nanomyofibril micelles of the nanomyofibril protofilaments was lower than that of the myofibrillar protofilaments of the control group and Un-HPH0.6. This indicates that more nanomyofibril micelles are adsorbed on the oil / water interface. The dilation elastic modulus (Ed') is one order of magnitude higher than the viscous modulus (Ed''), indicating that the elastic component dominates the dilation response. The elastic modulus of the nanomyofibril micelles of HPH0.6 is higher than that of the myofibrillar protofilaments of the control group and Un-HPH0.6, which means that the interface stiffness is higher and the interface is stronger. This is due to the smaller size of the myofibrillar micelles, which also exposes the hydrophobic region. In addition, the myofibrillar micelles may dissociate at the interface. Therefore, the oil droplet of HPH0.6 is more stable at the interface than the oil droplet of Un-HPH0.6.

[0140] Based on the results and viewpoints in the above sections, Fig.24As shown, a schematic diagram of the mechanism of improved stability and texture by HPH is proposed. The myofibrillar protein of salmon is mainly myosin, which has a molecular weight of about 200 kilodaltons.

[0141] The fish muscle myosin molecule contains a long α-helical tail and two pear-shaped heads. The tail is 155 nm long and 2 nm in diameter, while the head axis is about 20 nm long and 6 nm wide, exhibiting a radius of rotation of 80-90 nm. Therefore, the diameter of a single myosin molecule is likely to be 160-180 nm. Since the nanoparticles in HPH0.6 are almost spherical with a diameter of about 400 nm, we propose that myosin molecules assemble into nanomicelles of two length scales. The HPH treatment reduces the α-helix and exposes the internal hydrophobic regions of the protein. When exposed to water, the protein is likely to aggregate into a spherical shape due to hydrophobic-driven interactions. In non-HPH0.6, more than half of the oil droplets are dispersed in a large size of 20 μm, while most of the oil droplets in HPH0.6 are much smaller (<4 μm). It is worth noting that surfactant myofibrillar proteins should be an order of magnitude smaller than oil droplets, which suggests that surfactant proteins in non-HPH0.6 and HPH0.6 should be smaller than 2 μm and 400 nm, respectively, which is consistent with the sizes of fibrils and micelles observed by transmission electron microscopy.

[0142] In non-HPH0.6 emulsion gels, individual myofibrillar protein molecules, each about 160–180 nm long, aggregate to form silk fiber units of about 2.5 μm, which may further aggregate to form large fibril aggregates. The oil droplets stabilized by the fibril structure are poorly stable, while the cohesive interactions between protein fibrils are too low to form thick structures.

[0143] From a molecular perspective, high-pressure homogenization destroys the structure of fibril aggregates, reduces α-helices, and exposes the internal hydrophobic regions of myofibrillar proteins, which will assemble into nano-sized micelle structures (about 400 nanometers) under the aggregation of hydrophobic heads to prevent the hydrophobic heads from contacting water. Protein micelles may dissociate at the oil interface. The surface proteins in the oil droplets of HPH0.6 may be myofibrillar protein monomers, whose hydrophobic heads are attached to the oil interface and the long tails extend into the aqueous phase. Therefore, the oil droplets of HPH0.6 are much more stable. Compared with HPH0.3-0.4, the system of HPH0.6 is more compact and the oil droplets are more closely arranged. Since HPH unfolds the protein tails to a certain extent, the tails in the aqueous phase are likely to promote the aggregation of oil droplets through electrostatic forces and steric interactions between oil droplets, which helps to form a gel-like structure and increase the cohesive rheology and viscosity of the emulsion gel.

Claims

1. A method for preparing a salmon emulsion gel for improving dysphagia, characterized in that: The steps include: Step 1: Mix fresh salmon meat and ice water in a blender at a ratio of 1:3 at high speed for 1 minute, and filter the dispersion through a 60-mesh sieve; Step 2: The obtained filtrate was pre-homogenized using a disperser at a speed of 10,000 rpm for 2 minutes; Step 3: The dispersion is subjected to the first step of high pressure homogenization treatment for three cycles to obtain an initial protein suspension, and the protein content in the suspension is adjusted to 2.0 w / v%; Step 4: salmon oil extracted from salmon vertebrae by cold micro-water extraction was added to the protein-based suspension to ensure that the oil volume fraction φ reached 0.3, 0.4, 0.5, 0.6 and 0.7, respectively, to obtain five samples; Step 5: Mix the sample with a disperser at a speed of 12,000 rpm for 2 minutes to obtain emulsion gel A; Step 6: Perform a second high-pressure homogenization on the emulsion gel A to obtain the salmon emulsion gel.

2. The method for preparing the salmon emulsion gel for improving dysphagia according to claim 1, characterized in that: The temperature condition of the high-pressure homogenization treatment is 4° C., and the pressure condition of the high-pressure homogenization treatment is 50 MPa.

3. The method for preparing the salmon emulsion gel for improving dysphagia according to claim 2, characterized in that: Extraction of salmon oil from salmon spine involves the following steps: W1: The cleaned salmon spine was freeze-dried to reduce the moisture content, and the dried byproduct was ground in a grinder; W2: The ground sample was rehydrated with water until the oil volume fraction φ was adjusted to 75% by volume, stirred by tangential flow with an overhead stirrer for 15 min, and then immediately centrifuged at 8000 × g for 15 min at 20 °C; W3: Obtain the upper salmon oil and store it in a -20°C storage environment.

4. A method for testing the salmon emulsion gel for improving dysphagia according to any one of claims 1 to 3, characterized in that: The steps include: S1: The salmon emulsion gels with different φ treated by the second high pressure homogenization step were referred to as HPH0.3, HPH0.4, HPH0.5, HPH0.6 and HPH0.7, respectively, and the emulsion gel A without the second high pressure homogenization step was referred to as Un-HPH0.3, Un-HPH0.4, Un-HPH0.5, Un-HPH0.6 and Un-HPH0.7, respectively. Each emulsion gel sample was stored in a 20 ml transparent glass vial at 4°C; S2: Color analysis of all emulsion gel samples was performed using a colorimeter, and microscopic observation and particle size analysis were performed; S3: All emulsion gel samples were subjected to centrifugal stability testing, measured by a dispersion analyzer; S4: The formation and dissociation of ice crystals in salmon emulsion gels were measured using differential scanning calorimetry for all emulsion gel samples; S5: IDDSI test and rheological property test of salmon emulsion gel; S6: Strain sweep test, viscosity shear test and frequency sweep test were performed on salmon emulsion gel; S7: Extract the surfactant proteins from salmon emulsion gel, obtain the surface myofibrillar proteins, and analyze the morphology and interfacial rheological properties of the surface myofibrillar proteins; S8: Repeat the above steps S1-S7 three times to calculate the mean and standard deviation of the data.

5. The method for testing the salmon emulsion gel for improving dysphagia according to claim 4, characterized in that: The colorimeter measurement parameters include the values ​​of brightness L*, redness a* and yellowness b*; The centrifugal stability test was performed by transferring the sample into a polycarbonate tube and collecting data at intervals of 20 seconds in a centrifuge. The sample was centrifuged for 6000 seconds to destabilize the sample, and the instability index and area percentage were calculated using LUMSEPview V6.4 software.

6. The method for testing the salmon emulsion gel for improving dysphagia according to claim 4, characterized in that: Microscopic observation and particle size analysis include the following steps: Step 1: Dilute the homogenized salmon emulsion gel in 1% SDS solution at a ratio of 1:10 to disperse the aggregated oil droplets, and dilute the unhomogenized emulsion in ultrapure water at a ratio of 1:5; Step 2: Use a fluorescent inverted microscope with a digital camera to observe the microstructure of the oil droplets in the salmon emulsion gel. The oil droplets are dyed red with Nile red and then dropped on a glass slide and covered with a coverslip. Step 3: The particle size distribution of the fresh emulsion gel was determined by dynamic light scattering DLS in the range of 0.02 μm-2600 μm, with the ultrasonic power set to 35 W for 2 minutes, the stirring speed set to 1200 rpm, and the measurement shading set to 5%-20%.

7. The method for testing the salmon emulsion gel for improving dysphagia according to claim 4, characterized in that: The differential scanning calorimetry measurement comprises the following steps: Step 1: Place fresh salmon emulsion gel into an aluminum crucible and input nitrogen at a nitrogen flow rate of 20 mL / min. Cool the measuring temperature from 20°C to -30°C at a cooling rate of 5°C / min; Step 2: After 5 min of equilibration, the sample was heated from 30 °C to 40 °C at the same flow rate and then cooled from 40 °C to 20 °C at a rate of 10 °C / min.

8. The method for testing the salmon emulsion gel for improving dysphagia according to claim 4, characterized in that: The rheological properties test was carried out by a rheometer, the plate diameter of which was 40 mm, the gap distance was 1000 μm, the test sample was placed at ambient temperature for 1 hour to reach thermal equilibrium, and the test temperature was 25°C; The strain sweep test measures viscoelasticity in the oscillatory amplitude mode within the linear viscoelastic region (LVR) at a test temperature of 25°C, a frequency of 1 Hz, and a strain range of 0.1% to 1000%; The viscosity shear test is to place the sample on a platform with a shear rate ranging from 0.1 to 100 s-1, and evaluate the apparent viscosity by testing its response to different shear rates; Frequency sweep tests were performed in the frequency range of 0.1 to 15 Hz to measure the storage modulus G' and loss modulus G", at a temperature of 25 °C and a strain rate of 0.5%.

9. The method for testing the salmon emulsion gel for improving dysphagia according to claim 4, characterized in that: The method for extracting surfactant proteins from salmon emulsion gel comprises the following steps: E1: 20 g of fresh emulsion gel was centrifuged at 10,000 × g for 30 min at 4 °C to remove unabsorbed particles; E2: After centrifugation, the top layer was collected, mixed with methanol at a weight-to-volume ratio of 1:2, and incubated at room temperature for 10 min; E3: The mixture was then centrifuged at 4,700 × g for 10 min, and the top methanol phase was removed. The above process was repeated three times; E4: After washing with methanol, the precipitate was washed three times with n-hexane and finally washed three times with ethanol. The collected precipitate was washed with 100 mM phosphate buffer at pH 7.0 containing 100 mM NaCl, 1 mM MgCl2 and 1 mM EDTA and centrifuged twice to obtain myofibrillar protein. The precipitated surfactant myofibrillar protein was dried by freeze drying.

10. The method for testing the salmon emulsion gel for improving dysphagia according to claim 9, characterized in that: The analysis of the morphology and interfacial rheological properties of surface myofibrillar proteins includes the following steps: G1: The obtained surface myofibrillar proteins were measured by FTIR, XRD, SEM, AFM and TEM, and the particle size distribution was determined by DLS; G2: Interfacial properties were measured using an optical surface analyzer, using medium-chain triglycerides (MCT) as the oil phase. Surfactant proteins were suspended in 10 mM PBS at a concentration of 500 μg / mL and filtered through a 0.45 μm filter to remove large protein aggregates. G3: Quantify protein concentration using the BCA protein assay kit, creating an area of ​​15 mm on the needle tip. 2 The pendant droplets were always equilibrated for 3 h before any drop area deformation was performed, and the oscillation amplitude was set to 10%. Amplitude sweeps were performed at a constant frequency of 0.05 Hz at 25 °C to obtain the interfacial tension, dilatational elastic modulus Ed', and dilatational viscous modulus Ed".

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