Fat emulsion gel as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of food processing, and particularly relates to fat emulsion gel as well as a preparation method and application thereof. The invention provides a preparation method of fat emulsion gel. The preparation method comprises the following steps: mixing tilapia mossambica protein isolate freeze-dried powder with water, hydrating, re-mixing, and carrying out ultrasonic treatment to obtain protein dispersion liquid; mixing the flaxseed gum powder with water, cooling and hydrating to obtain a flaxseed gum aqueous solution; the protein dispersion liquid and the flaxseed gum aqueous solution are mixed, the pH value is adjusted, then mixing is conducted, and a tilapia mossambica protein isolate-flaxseed gum complex is obtained; mixing the tilapia mossambica protein isolate-flaxseed gum complex with edible vegetable oil, and emulsifying to obtain fat emulsion gel. The fat emulsion gel easy to swallow is prepared by taking the tilapia isolated protein as a construction base material, can improve dietary nutrition of people with dysphagia, and can also provide technical reference for green and high-value utilization of the tilapia isolated protein.

Description

Technical Field

[0001] The present invention relates to the technical field of food processing, and particularly relates to a fat emulsion gel, a preparation method thereof and an application thereof. Background Art

[0002] With the aggravation of population aging, chewing and swallowing disorders have become one of the main health threats faced by the elderly population. The nutritional needs of this group are particularly urgent, and easily swallowable foods can just solve their problem of nutritional intake. Therefore, the market for easily swallowable foods has emerged and shows a rapid growth trend. At present, the types of easily swallowable foods specifically for the elderly population with swallowing disorders in the market are gradually becoming rich, and the main existing forms are thickened fluids and paste foods, but they cannot meet the nutritional and sensory needs of the elderly population and lack convenience. Gel foods have become the mainstream development direction of easily swallowable foods due to their good viscoelasticity, soft appearance, convenient consumption and other advantages.

[0003] As a main raw material in modern food processing, fat can not only provide unique aroma and flavor, but also help to endow foods with a smooth texture and a shiny appearance. However, since many chronic diseases are related to excessive intake of fat, especially saturated fatty acids, it is urgent to develop fat mimetics with a structure similar to that of solid fat.

[0004] Emulsion gels are an effective method to reduce the content of solid fat in foods. Compared with traditional fats, emulsion gels contain rich polyunsaturated fatty acids, which can partially or completely replace the fats in foods to reduce calorie intake while still providing similar fat characteristics. In addition, emulsion gels meet the characteristic requirements of easily swallowable foods due to their unique semi-solid texture and ideal viscoelastic properties, and can also encapsulate specific oil-soluble nutrients to meet the personalized nutritional needs of different elderly populations. In recent years, the research on easily swallowable foods has mainly focused on the plant protein-polysaccharide emulsion gel system, and the research on the animal protein-polysaccharide emulsion gel system is relatively less. Compared with plant proteins, animal proteins have a more balanced amino acid composition and high nutritional value, and can be used as an ideal protein intake source for the elderly. Therefore, developing easily swallowable fat mimetic emulsion gel products based on animal proteins is crucial for improving the dietary nutrition of people with swallowing disorders and realizing the green and high-value utilization of animal proteins.

[0005] Based on this, the present invention is proposed. Summary of the Invention

[0006] The purpose of the present invention is to prepare an easily swallowable fat mimetic emulsion gel using tilapia protein isolate as a construction substrate, which can not only provide a technical reference for the green and high-value utilization of tilapia protein isolate, but also improve the dietary nutrition of people with swallowing disorders.

[0007] To achieve the above-mentioned invention object, the present invention provides the following technical solutions:

[0008] The present invention provides a preparation method of a fish oil emulsion gel, comprising the following steps:

[0009] (1) Mix the freeze-dried powder of tilapia myofibrillar protein and water, hydrate, mix again, and perform ultrasonic treatment to obtain a protein dispersion;

[0010] (2) Mix the flaxseed gum powder and water at 60-85°C, cool, and hydrate to obtain an aqueous flaxseed gum solution;

[0011] (3) Mix the protein dispersion and the aqueous flaxseed gum solution, adjust the pH value to 2.0-5.0 and mix again to obtain a tilapia myofibrillar protein-flaxseed gum complex;

[0012] (4) Mix the tilapia myofibrillar protein-flaxseed gum complex and an edible vegetable oil to obtain a mixture; emulsify the mixture to obtain a fish oil emulsion gel.

[0013] Preferably, in step (1), the mass-volume ratio of the freeze-dried powder of tilapia myofibrillar protein to water in the mixing is 1-7 g: 100 mL;

[0014] The mixing is magnetic stirring mixing;

[0015] The temperature of the mixing is 22-28°C;

[0016] The time of the mixing is 1-5 h;

[0017] The temperature of the hydration is 2-6°C;

[0018] The time of the hydration is 12-24 h.

[0019] Preferably, in step (1), the re-mixing is magnetic stirring mixing; the temperature of the re-mixing is 22-28°C; the time of the re-mixing is 1-3 h;

[0020] The ultrasonic treatment is high-density ultrasonic treatment; the power of the ultrasonic treatment is 100-500 W; the time of the ultrasonic treatment is 20-60 min.

[0021] Preferably, in step (2), the mass-volume ratio of the flaxseed gum powder to water in the mixing is 0.1-1.0 g: 100 mL;

[0022] The time of the mixing is 10-60 min;

[0023] The cooling is to cool to 23-27°C;

[0024] The temperature of the hydration is 2-6°C; the time of the hydration is 12-24 h;

[0025] Preferably, in step (3), the mass ratio of the protein dispersion to the flaxseed glue aqueous solution is 0.5-1.5:0.5-1.5;

[0026] The mixing is stirring; the mixing speed is 800-1500 rpm; the mixing time is 2-5 h.

[0027] Preferably, in step (3), the solution required for adjusting the pH is an HCl solution; the initial concentration of the HCl solution is 2-4 mol / L; the remixing is magnetic stirring; the remixing time is 2-4 h.

[0028] Preferably, in step (4), the addition amount of the edible vegetable oil is 50-75 wt% of the mass of the mixture;

[0029] The edible vegetable oil includes one or more of rapeseed oil, soybean oil, perilla oil, peanut oil, flaxseed oil, sunflower oil, and sesame oil.

[0030] Preferably, in step (4), the shear speed of the emulsification is 8000-12000 rpm; the shear time of the emulsification is 1-5 min.

[0031] The present invention also provides a fat emulsion gel prepared by the preparation method described above.

[0032] The present invention also provides the application of the fat emulsion gel in the preparation of foods or drugs for improving the dietary nutrition of people with dysphagia.

[0033] The beneficial effects of the present invention:

[0034] (1) The present invention uses tilapia myofibrillar protein as the construction substrate of the easy-to-swallow fat emulsion gel, which can provide a technical reference for the green and high-value utilization of tilapia myofibrillar protein;

[0035] (2) The present invention uses high-intensity ultrasound technology to treat tilapia myofibrillar protein, depolymerize large tilapia myofibrillar protein aggregates into small particles, fully expose the internal hydrophobic groups, which is beneficial to reducing the particle size of tilapia myofibrillar protein, increasing its solubility, and promoting the subsequent effective complexation with flaxseed gum;

[0036] (3) The effective complexation of flaxseed gum and tilapia myofibrillar protein in an acidic environment further improves the emulsifying ability and solubility of tilapia myofibrillar protein; tilapia myofibrillar protein and flaxseed gum form a dense oil-water interfacial film through hydrogen bonding and electrostatic interactions, effectively preventing the movement and aggregation of droplets; with the increase of the flaxseed gum concentration, the viscoelasticity and stability of the fat emulsion gel are further improved;

[0037] (4) The fat emulsion gel obtained in the present invention has a texture similar to that of cream, with a smooth and soft appearance, which can reduce the oral friction, relieve the swallowing difficulty of the elderly population, improve the dietary pleasure and quality of life; in addition, the fat emulsion gel has both the dual characteristics of emulsion and gel, presenting a good semi-solid texture and viscoelastic properties, having good extrudability and self-holding ability, and having a shape similar to that of traditional fat, which can improve the dietary nutrition of people with swallowing disorders, can achieve all or partial substitution of traditional plastic fat, and shows good application potential in healthy foods or drugs. Description of the Drawings

[0038] Figure 1 It is a graph showing the particle size, emulsifying ability test results and infrared spectrum of the tilapia myosin - flaxseed gum complex of Examples 1 - 4 and the protein dispersion of Comparative Examples 1 - 2, where A is the particle size, B is the emulsifying ability test result graph, and C is the infrared spectrum graph;

[0039] Figure 2 It is a graph showing the visual appearance and extrusion through a piping nozzle of the fat emulsion gels of Examples 1 - 4 and Comparative Examples 1 - 2, where the upper graph is the visual appearance graph and the lower graph is the extrusion through a piping nozzle graph;

[0040] Figure 3 It is a graph showing the average droplet size, droplet size distribution and zeta potential of the fat emulsion gels of Examples 1 - 4 and Comparative Examples 1 - 2, where A is the average droplet size graph, B is the droplet size distribution graph, and C is the zeta potential graph;

[0041] Figure 4 It is a micrograph of the fat emulsion gels of Examples 1 - 4 and Comparative Examples 1 - 2;

[0042] Figure 5 It is the rheological properties of the fat emulsion gels obtained in Examples 1 - 4 and Comparative Examples 1 - 2, where A is the viscosity sweep curve, B is the strain sweep curve, C is the frequency sweep curve, D is the temperature sweep curve, and E is the creep recovery curve;

[0043] Figure 6 It is the IDDSI test results of the fat emulsion gels of Examples 1 - 4 and Comparative Examples 1 - 2;

[0044] Figure 7 It is the visual appearance and micrograph of the fat emulsion gels of Examples 1 - 4 and Comparative Examples 1 - 2 after long-term storage, where A is the visual appearance graph and B is the micrograph. Detailed Embodiments

[0045] The present invention provides a method for preparing a fat emulsion gel, which comprises the following steps:

[0046] (1) Mix the freeze-dried powder of tilapia fish protein isolate with water, hydrate it, mix again, and perform ultrasonic treatment to obtain a protein dispersion;

[0047] (2) Mix the flaxseed gum powder with water at 60 - 85 °C, cool it, and hydrate it to obtain an aqueous solution of flaxseed gum;

[0048] (3) Mix the protein dispersion and the aqueous solution of flaxseed gum, adjust the pH value to 2.0 - 5.0 and mix again to obtain a tilapia fish protein isolate - flaxseed gum complex;

[0049] (4) Mix the tilapia fish protein isolate - flaxseed gum complex with edible vegetable oil to obtain a mixture; emulsify the mixture to obtain a fat emulsion gel.

[0050] In the present invention, in step (1), the mass - volume ratio of the freeze - dried powder of tilapia fish protein isolate to water for mixing is 1 - 7 g:100 mL, preferably 3 - 5 g:100 mL, and more preferably 4 g:100 mL;

[0051] The mixing is magnetic stirring;

[0052] The temperature of the mixing is 22 - 28 °C, preferably 24 - 26 °C, and more preferably 25 °C;

[0053] The time of the mixing is 1 - 5 h, preferably 2 - 4 h, and more preferably 3 h;

[0054] The temperature of the hydration is 2 - 6 °C, preferably 3 - 5 °C, and more preferably 4 °C;

[0055] The time of the hydration is 12 - 24 h, preferably 16 - 20 h, and more preferably 18 h;

[0056] In the present invention, in step (1), due to the poor solubility of tilapia fish protein isolate, precipitation will occur during hydration. Therefore, before ultrasonic treatment, the hydrated product needs to be remixed to avoid affecting the ultrasonic treatment effect;

[0057] The remixing is magnetic stirring; the temperature of the remixing is 22 - 28 °C, preferably 24 - 26 °C, and more preferably 25 °C; the time of the remixing is 1 - 3 h, preferably 1.5 - 2.5 h, and more preferably 2 h;

[0058] The ultrasonic treatment is high - density ultrasonic treatment; the power of the ultrasonic treatment is 100 - 500 W, preferably 200 - 400 W, and more preferably 300 W; the time of the ultrasonic treatment is 20 - 60 min, preferably 30 - 50 min, and more preferably 40 min;

[0059] Ultrasound is applied at intervals of 5 s of ultrasound followed by 5 s intervals for repeated ultrasound;

[0060] The entire ultrasound process needs to be carried out in an ice-water bath. In order to prevent the local temperature from being too high and affecting the properties of tilapia isolate protein, the ice-water bath needs to be changed 3 - 6 times, preferably 4 - 5 times, and more preferably 5 times.

[0061] In the present invention, in step (2), the mass-volume ratio of the flaxseed gum powder to water for mixing is 0.1 - 1.0 g:100 mL, preferably 0.3 - 0.8 g:100 mL, and more preferably 0.4 g:100 mL;

[0062] The mixing time is 10 - 60 min, preferably 30 - 40 min, and more preferably 35 min;

[0063] The mixing temperature is preferably 70 - 75 °C, and more preferably 72.5 °C;

[0064] The cooling is to cool to 23 - 27 °C, preferably 24 - 26 °C, and more preferably 25 °C;

[0065] The hydration temperature is 2 - 6 °C, preferably 3 - 5 °C, and more preferably 4 °C;

[0066] The hydration time is 12 - 24 h, preferably 16 - 20 h, and more preferably 18 h;

[0067] In the present invention, in step (3), the mass ratio of the protein dispersion to the aqueous flaxseed gum solution for mixing is 0.5 - 1.5:0.5 - 1.5, preferably 1:1;

[0068] The mixing is stirring mixing, preferably propeller stirring mixing; the mixing speed is 800 - 1500 rpm, preferably 1000 - 1300 rpm, and more preferably 1150 rpm; the mixing time is 2 - 5 h, preferably 3 - 4 h, and more preferably 3.5 h;

[0069] The mixing temperature is 22 - 28 °C, preferably 24 - 26 °C, and more preferably 25 °C.

[0070] In the present invention, in step (3), the pH is preferably 2.5 - 4.0, and more preferably 3.0;

[0071] The solution required for adjusting the pH is HCl solution; the initial concentration of the HCl solution is 2 - 4 mol / L, preferably 3 mol / L; the re-mixing is magnetic stirring mixing; the re-mixing time is 2 - 4 h, preferably 3 h.

[0072] In the present invention, in step (4), the addition amount of the edible vegetable oil is 50-75 wt% of the mass of the mixture, preferably 60-72 wt%, and more preferably 70 wt%.

[0073] The edible vegetable oil includes one or more of rapeseed oil, soybean oil, perilla oil, peanut oil, linseed oil, sunflower oil, and sesame oil.

[0074] In the present invention, in step (4), the shear rate of the emulsification is 8000-12000 rpm, preferably 9000-11000 rpm, and more preferably 10000 rpm; the shear time of the emulsification is 1-5 min, preferably 2-4 min, and more preferably 5 min.

[0075] The present invention also provides a fat emulsion gel prepared by the above preparation method.

[0076] The present invention also provides the application of the fat emulsion gel in the preparation of foods or drugs for improving the dietary nutrition of people with dysphagia.

[0077] The technical solutions provided by the present invention will be described in detail below with reference to the examples, but they should not be construed as limiting the protection scope of the present invention.

[0078] Example 1 A fat emulsion gel

[0079] (1) 5 g of freeze-dried tilapia myofibrillar protein and 100 mL of distilled water were magnetically stirred and mixed at 25 °C for 3 h, then transferred to a 4 °C refrigerator for 15 h of hydration. After transferring the hydrated product to 25 °C and magnetically stirring and mixing for another 2 h, it was transferred to an ultrasonic cell disruptor and ultrasonically treated at a high density for 40 min at an ultrasonic power of 300 W (ultrasonic for 5 s and then interval for 5 s for another ultrasonic treatment) to obtain a protein dispersion; during the whole ultrasonic process, the beaker containing the stirred hydrated product was placed in an ice-water bath, and the ultrasonic probe was ensured to penetrate into the middle position of the protein aqueous solution, and the ice-water bath was changed 5 times during ultrasonic treatment;

[0080] (2) 0.8 g of flaxseed gum powder and 100 mL of water were stirred and mixed in a 75 °C water bath for 40 min, then cooled to 25 °C, and then transferred to a 4 °C refrigerator for 15 h of hydration to obtain a flaxseed gum aqueous solution;

[0081] (3) The protein dispersion and the flaxseed gum aqueous solution with equal mass (mass ratio 1:1) were stirred and mixed by a propeller at 25 °C and 1100 rpm for 4 h, and then the pH value was adjusted to 3.0 with 3 mol / L HCl solution, and then continuously mixed with a magnetic stirrer for another 3 h to obtain a tilapia myofibrillar protein-flaxseed gum complex;

[0082] (4) Mix 30 g of tilapia myofibrillar protein-linseed gum complex and 70 g of edible rapeseed oil to obtain a mixture; emulsify it for 2 min at a shear rate of 12,000 rpm using a T18 high-speed disperser to obtain a fat emulsion gel.

[0083] Example 2 A fat emulsion gel

[0084] The difference from Example 1 is that the addition amount of linseed gum powder in step (2) is 0.2 g, and other steps are the same as those in Example 1.

[0085] Example 3 A fat emulsion gel

[0086] The difference from Example 1 is that the addition amount of linseed gum powder in step (2) is 0.4 g, and other steps are the same as those in Example 1.

[0087] Example 4 A fat emulsion gel

[0088] The difference from Example 1 is that the addition amount of linseed gum powder in step (2) is 0.6 g, and other steps are the same as those in Example 1.

[0089] Comparative Example 1 A fat emulsion gel

[0090] (1) Magnetically stir and mix 5 g of tilapia myofibrillar protein freeze-dried powder and 100 mL of distilled water at 25 °C for 3 h, then transfer it to a 4 °C refrigerator and hydrate for 15 h. Transfer the hydrated material to 25 °C and magnetically stir and mix for another 2 h to obtain a protein dispersion;

[0091] (2) Mix 30 g of the protein dispersion and 70 g of edible rapeseed oil to obtain a mixture; emulsify it for 2 min at a shear rate of 12,000 rpm using a T18 high-speed disperser to obtain a fat emulsion gel.

[0092] Comparative Example 2 A fat emulsion gel

[0093] (1) Magnetically stir and mix 5 g of tilapia myofibrillar protein freeze-dried powder and 100 mL of distilled water at 25 °C for 3 h, then transfer it to a 4 °C refrigerator and hydrate for 15 h. Transfer the hydrated product to 25 °C and magnetically stir and mix for another 2 h, then transfer it to an ultrasonic cell disruptor and ultrasonicate for 40 min at an ultrasonic power of 300 W (ultrasonic for 5 s and then interval for 5 s to ultrasonic again) to obtain a protein dispersion; During the whole ultrasonic process, place the beaker containing the stirred hydrated product in an ice-water bath, ensure that the ultrasonic probe penetrates into the middle position of the protein aqueous solution, and change the ice-water bath 5 times during ultrasonication;

[0094] (2) Mix 30 g of the protein dispersion and 70 g of edible rapeseed oil to obtain a mixture; use a T18 high-speed disperser to emulsify at a shear rate of 12,000 rpm for 2 min to obtain a fat emulsion gel.

[0095] Experimental Example 1

[0096] 1.1 Use a Malvern nanoparticle size analyzer to measure the particle sizes of the tilapia myofibrillar protein - flaxseed gum complexes in Examples 1 - 4 and the protein dispersions in Comparative Examples 1 - 2 respectively. The results are as Figure 1 shown in A; among them, Example 1 is denoted as UTPI - 0.4% FG, Example 2 is denoted as UTPI - 0.1% FG, Example 3 is denoted as UTPI - 0.2% FG, Example 4 is denoted as UTPI - 0.3% FG, Comparative Example 1 is denoted as TPI (native tilapia myofibrillar protein), and Comparative Example 2 is denoted as UTPI;

[0097] From Figure 1 A, it can be seen that the particle size of native tilapia myofibrillar protein (TPI) is relatively large, being 1814 nm. This may be due to its poor solubility and severe aggregation of protein molecules; after high - density ultrasonic treatment, the particle size of tilapia myofibrillar protein is significantly reduced (UTPI). This may be because the cavitation effect, high - shear energy waves, and micro - flow effect generated during the ultrasonic process break the non - covalent bonds (hydrogen bonds, electrostatic interactions, hydrophobic interactions) between or within protein molecules, resulting in the decomposition of large protein aggregates into small particles; after complexing the high - density ultrasonic - treated tilapia myofibrillar protein with flaxseed gum, the particle size of the obtained tilapia myofibrillar protein - flaxseed gum complex (UTPI - FG) increases and shows a flaxseed gum concentration - dependent relationship. This may be because the introduction of flaxseed gum promotes the co - assembly of tilapia myofibrillar protein, thus leading to an increase in its particle size.

[0098] 1.2 Detection of emulsifying ability

[0099] Respectively mix 35 mL of the tilapia myofibrillar protein - flaxseed gum complexes in Examples 1 - 4 and the protein dispersions in Comparative Examples 1 - 2 (20 mg / mL) with 15 mL of edible rapeseed oil respectively, and use a T18 high - speed disperser to emulsify at a shear rate of 12,000 rpm for 2 min to obtain samples; pipette 50 μL of the sample and 5 mL of sodium dodecyl sulfate solution (SDS, 0.1%, w / v) and vortex - mix to obtain a mixed system, and measure the absorbance of the mixed system at 500 nm; after storing the sample at 25 °C for 10 min, pipette 50 μL of it and 5 mL of sodium dodecyl sulfate solution (SDS, 0.1%, w / v) and vortex - mix to obtain a mixed system, and measure the absorbance of the mixed system at 500 nm; calculate the emulsifying activity index (EAI, m of the sample according to the following formula 2 / g) and emulsion stability index (ESI, min), and the results are as Figure 1 shown in

[0100]

[0101]

[0102] Wherein, A0 is the absorbance of the sample, DF is the dilution factor (total volume of the diluted sample / volume of the sample before dilution), C is the protein concentration (20 mg / mL), is the oil phase volume fraction (30%), θ is the optical path (1 cm), ΔA is the difference between A0 and A 10 and A 10 is the absorbance of the sample after standing for 10 min.

[0103] Figure 1 The results in Figure B show that both the emulsion activity index and emulsion stability index of natural tilapia protein isolate (TPI) are relatively low, indicating its poor emulsifying ability, which may be related to its low solubility in water; after high-density ultrasonic treatment of TPI to obtain UTPI, both its emulsion activity index and emulsion stability index are significantly improved, indicating that high-density ultrasonic treatment can effectively improve the emulsifying ability of TPI, which may be related to the smaller particle size and higher solubility of UTPI, thus promoting the rapid adsorption of UTPI at the oil-water interface; when introducing flaxseed gum into UTPI, the emulsion activity index and emulsion stability index of the obtained UTPI-FG complex are further improved and show a dependence on the flaxseed gum concentration, indicating that the introduction of flaxseed gum can improve the emulsifying ability of tilapia protein isolate; this may be because the tilapia protein isolate-flaxseed gum complex is more hydrophilic and easier to overcome the kinetic adsorption ability to reach the oil-water interface layer; in addition, there is a synergistic effect between tilapia protein isolate and flaxseed gum, which improves the surface activity of the UTPI-FG complex and promotes its adsorption at the two-phase interface; in addition, the introduction of flaxseed gum increases the thickness of the interface layer and the viscosity of the continuous phase, effectively preventing the aggregation of droplets and further improving the stability of the emulsion system.

[0104] 1.3 Infrared spectrometers were used to measure the infrared spectra of the tilapia protein isolate-flaxseed gum complexes in Examples 1-4 and the protein dispersions in Comparative Examples 1-2 respectively, and the results are as Figure 1 shown in

[0105] From Figure 1 Figure C, it can be seen that the absorption bands of tilapia protein isolate (TPI) and high-density ultrasonic-treated tilapia protein isolate (UTPI) at 3342 cm -1 belong to the stretching vibrations of O-H and N-H, and at 1653 cm -1, 1529 cm -1 , 1389 cm -1 and 1236 cm -1 The absorption bands at correspond to C=O stretching (amide I band), N-H stretching (amide II band), C=N stretching and N-H bending vibration (amide III band), respectively. These absorption bands are typical characteristic peaks of proteins. The broad peak at 3340 cm -1 of flaxseed gum (FG) is caused by O-H stretching vibration, while the peaks at 1653 cm -1 and 1367 cm -1 represent C=O stretching and O-H bending vibration, respectively. After complexing tilapia protein isolate treated by high-density ultrasound with flaxseed gum, the infrared spectra of all UTPI-FG complexes are quite similar to those of TPI and UTPI, and no new characteristic peaks appear, indicating that there is no chemical interaction between UTPI and FG, and they are mainly combined by non-covalent interactions. However, compared with TPI and UTPI, the peak intensity of the UTPI-FG complex at about 3342 cm -1 has changed, indicating that there may be hydrogen bond interaction between the amide group of UTPI and the hydroxyl group of FG. In addition, compared with UTPI, the absorption peak intensities of the UTPI-FG complex at 1653 cm -1 and 1236 cm -1 are significantly enhanced, which may be related to the formation of polyelectrolyte complexes due to the electrostatic interaction between partially positively charged UTPI and negatively charged FG.

[0106] Experimental Example 2

[0107] 2.1 Appearance of Fat Emulsion Gels

[0108] The visual appearance and the extrusion diagrams from the nozzle of a piping bag of the fat emulsion gels of Examples 1-4 and Comparative Examples 1-2 were photographed using a digital camera, and the results are as Figure 2 shown. Among them, Example 1 is denoted as UTPI-0.4% FG, Example 2 is denoted as UTPI-0.1% FG, Example 3 is denoted as UTPI-0.2% FG, Example 4 is denoted as UTPI-0.3% FG, Comparative Example 1 is denoted as TPI, and Comparative Example 2 is denoted as UTPI;

[0109] Figure 2The results showed that the fat emulsion gels stabilized by tilapia protein isolate-gum arabic complexes containing different concentrations of gum arabic all had a milky appearance. When the small glass bottles containing the fat emulsion gels were inverted, all the samples adhered to the bottom of the glass bottles and the system lost fluidity, indicating that a gel-like network structure was formed inside all the samples, thus presenting solid-like properties. By extruding the fat emulsion gels through a piping bag nozzle, it was found that the concentration of gum arabic had an important influence on the profile of the extruded gels. The surface of the fat emulsion gel without added gum arabic was relatively rough, the profile of the extruded gel was not clear, and the structure collapsed. After adding gum arabic, the performance of the extruded fat emulsion gels was significantly improved, with a fine and smooth texture. Moreover, with the increase in the concentration of gum arabic, the clarity of the profile of the extruded fat emulsion gels gradually increased, and they showed good viscoelasticity and self-supporting ability. This indicated that the introduction of a high concentration of gum arabic promoted the formation of the gel-like network structure in the fat emulsion gels.

[0110] 2.2 Droplet size and surface charge of fat emulsion gels

[0111] The average droplet size and droplet size distribution of the fat emulsion gels of Examples 1-4 and Comparative Examples 1-2 were measured using a laser particle size analyzer; the zeta potential of the fat emulsion gels of Examples 1-4 and Comparative Examples 1-2 was measured using a Malvern nano particle size analyzer, and the results are as Figure 3 shown;

[0112] Figure 3 A The results showed that compared with the TPI fat emulsion gel, the droplet size of the UTPI fat emulsion gel was significantly reduced. When gum arabic was introduced into the system, the droplet size of the UTPI fat emulsion gel was further reduced and showed a dependence on the gum arabic concentration. When the gum arabic concentration was 0.4 wt%, the droplet size of the UTPI-FG fat emulsion gel reached the minimum value, and its D 3,2 and D 4,3 were 1.48 μm and 2.94 μm, respectively.

[0113] Figure 3 B The results showed that the droplet size of all fat emulsion gels presented a multi-peak distribution; however, with the increase in the gum arabic concentration, the position of the largest peak in the droplet size distribution gradually shifted to the left and reached the minimum value when the gum arabic concentration was 0.4 wt%, which was consistent with Figure 3 the analysis results of the droplet size in A.

[0114] Figure 3The C results showed that the zeta potentials of both the TPI fat emulsion gel and the UTPI fat emulsion gel were negative, which might be due to the pH of the system being higher than the isoelectric point of tilapia myofibrillar protein. The acidic amino acids in the protein molecular structure dissociated, releasing negative charges. When different concentrations of flaxseed gum were introduced into the system, the potential value of the fat emulsion gel changed from negative to positive. This might be because the acidic environment of the system caused more dissociation of the basic amino acids in the protein molecular structure, neutralizing the negative charges dissociated by the acidic amino acids, thus making the surface of the fat emulsion gel droplets carry positive charges. In addition, with the increase in the concentration of flaxseed gum, the absolute value of the zeta potential of the UTPI-FG fat emulsion gel decreased slightly. This might be because the introduction of a high concentration of flaxseed gum covered or inserted on the surface of tilapia myofibrillar protein, increasing the thickness and compactness of the oil-water interface layer, and thus leading to a downward trend in its surface charge amount.

[0115] 2.3 Microstructure of fat emulsion gels

[0116] The optical microscope was used to analyze the microstructure of the fat emulsion gels of Examples 1-4 and Comparative Examples 1-2. The results are as Figure 4 shown;

[0117] Figure 4 The results showed that the droplets in the TPI fat emulsion gel, UTPI fat emulsion gel, and UTPI-FG fat emulsion gel were all closely packed together, squeezing and deforming each other, thus filling the entire system space. Among them, some adjacent droplets shared the same interface layer, forming a gel-like network structure. This might be the main reason for the semi-solid texture and self-supporting gel-like characteristics of the fat emulsion gel. In addition, the droplet size of the UTPI-FG fat emulsion gel was significantly lower than that of the TPI fat emulsion gel and the UTPI fat emulsion gel. With the increase in the concentration of flaxseed gum, the droplet size of the UTPI-FG fat emulsion gel further decreased and reached the minimum value when the concentration of flaxseed gum was 0.4 wt%, which was consistent with the analysis results of the fat emulsion gel droplet size.

[0118] 2.4 Rheological properties of fat emulsion gels

[0119] The rheological properties of the fat emulsion gels of Examples 1-4 and Comparative Examples 1-2 were analyzed using a rheometer: Viscosity sweep test: Measure at a shear rate of 0-100 s -1Apparent viscosity of the fat emulsion gel at that time; Strain sweep test: Measure the storage modulus (G') and loss modulus (G") of the fat emulsion gel at strains from 0 to 100%; Frequency sweep test: Measure the storage modulus (G') and loss modulus (G") of the fat emulsion gel at frequencies from 0.1 to 10 Hz; Temperature sweep test: Measure the storage modulus (G') and loss modulus (G") of the fat emulsion gel at temperatures from 20 to 70 °C; Creep recovery test: Apply a stress of 10 Pa to all fat emulsion gels for 300 s, then remove the stress and recover for 300 s, and analyze the strain values of the emulsion gels to analyze their ability to resist deformation; The measurement results are as Figure 5 shown;

[0120] For the viscosity sweep test ( Figure 5 A), the apparent viscosities of all fat emulsion gels gradually decreased with the increase of shear rate, showing typical shear-thinning behavior, which is one of the common characteristics of concentrated emulsion gels; In addition, compared with TPI fat emulsion gels and UTPI fat emulsion gels, the apparent viscosity of UTPI-FG fat emulsion gels was significantly increased and showed a dependence on the concentration of flaxseed gum, which may be because the introduction of high-concentration flaxseed gum in the system increased the viscosity of the aqueous phase and the viscoelasticity of the interfacial layer; At higher flaxseed gum concentrations, the droplet size of the fat emulsion gel was smaller, and the number of droplet interactions per unit volume increased, resulting in a higher apparent viscosity of the UTPI-FG fat emulsion gel.

[0121] For the strain sweep test ( Figure 5 B), within the linear viscoelastic region, the storage modulus (G') of all fat emulsion gels was greater than the loss modulus (G"), showing a dominant elastic gel behavior. Compared with TPI fat emulsion gels and UTPI fat emulsion gels, UTPI-FG fat emulsion gels had a higher G'; In addition, when the concentration of flaxseed gum increased from 0.1 wt% to 0.4 wt%, the G' of UTPI-FG fat emulsion gels showed a gradually increasing trend, indicating that the gel strength of the fat emulsion gel could be improved by increasing the concentration of flaxseed gum.

[0122] The influence of the incorporation of flaxseed gum on the viscoelastic properties of the fat emulsion gel was further analyzed by the frequency sweep test ( Figure 5C), within the entire test frequency range, the G' of all fat emulsion gel samples was greater than G'', indicating that all fat emulsion gels exhibited gel-like behavior dominated by elasticity; in addition, the G' of all fat emulsion gel samples showed a slight frequency dependence, indicating that all fat emulsion gels had a certain ability to resist deformation; compared with TPI fat emulsion gel and UTPI fat emulsion gel, the UTPI-FG fat emulsion gel had a higher G', and G' gradually increased with the increase in the concentration of flaxseed gum, indicating that the incorporation of flaxseed gum could improve the strength of the fat emulsion gel, which might be due to the bridging flocculation of tilapia protein isolate-flaxseed gum complexes between two adjacent droplets; in addition, the fat emulsion gel containing a high concentration of flaxseed gum had a smaller droplet size, which was also one of the reasons for its higher G'.

[0123] Temperature sweep results ( Figure 5 D) showed that during the entire heating process, the G' and G'' of all fat emulsion gel samples did not change significantly, indicating that the fat emulsion gel system had good thermal stability, and during the entire programmed temperature increase process, the gel-like network structure inside the system remained intact.

[0124] For the creep recovery test ( Figure 5 E), compared with TPI fat emulsion gel and UTPI fat emulsion gel, the strain value of the UTPI-FG fat emulsion gel decreased significantly. In addition, with the increase in the concentration of flaxseed gum, the strain value of the UTPI-FG fat emulsion gel gradually decreased.

[0125] The self-supporting ability of the fat emulsion gel was mainly reflected in its G' and yield stress. The above results showed that the fat emulsion gel containing 0.4 wt% flaxseed gum had good anti-deformation ability.

[0126] 2.5 Swallowing performance test of fat emulsion gel

[0127] The fork compression test, fork drop test, and fork tilt test in the International Dysphagia Diet Standard (IDDSI) were used to analyze the swallowing performance of the fat emulsion gels of Examples 1-4 and Comparative Examples 1-2. The results are as Figure 6 shown;

[0128] The force exerted by the tongue during swallowing was approximately 17 kPa, similar to the force generated by applying pressure on a fingernail.

[0129] Figure 6The results showed that during the application of pressure, no whitening of the nails was observed for any of the fat emulsion gel samples, indicating that all samples could be crushed and deformed with slight pressure, making them easy for patients to swallow and considered ideal foods for dysphagia patients; after the fork was removed, clear outlines remained on the surfaces of all fat emulsion gel samples, indicating that these fat emulsion gels had weak fluidity and could be eaten with a fork, spoon or chopsticks; in the fork dripping test, all fat emulsion gel samples could be piled up on the fork, and no sample continuously flowed or dripped from the fork tip, indicating that all fat emulsion gel samples belonged to IDDSI solid food level 4 - puree type or above; in the TPI fat emulsion gel, a small amount of fish - tail shape formed under the fork, indicating that its gel texture was soft, while this phenomenon did not occur in the UTPI fat emulsion gel and UTPI - FG fat emulsion gel samples; the fork tilting test showed that all fat emulsion gel samples had sufficient cohesiveness to maintain their shape on the spoon and were likely to fall off easily when the spoon was gently turned to one side, with only a small amount of sample remaining on the tilted spoon, which was beneficial for safe swallowing by dysphagia patients; according to the IDDSI standard, the fat emulsion gels based on Examples 1 - 4 could be classified as level 5 chopped and moistened dysphagia diets.

[0130] 2.6 Storage stability of fat emulsion gels

[0131] Digital cameras were used to take visual appearance pictures of the fat emulsion gels of Examples 1 - 4 and Comparative Examples 1 - 2 after storage at 25°C for 15 days, and the microscopic structures of the fat emulsion gels after storage were collected by means of an optical microscope. The results are as Figure 7 shown;

[0132] Figure 7 The results showed that from the visual appearance of the TPI fat emulsion gel ( Figure 7 A), after the fat emulsion gel samples were stored at room temperature for 15 days, slight oil floating appeared on the surface; from the microscopic structure of the fat emulsion gel ( Figure 7In terms of B), partial aggregation of droplets occurred in the system, the droplet size was large, and the internal gel-like network structure was damaged, indicating poor storage stability of the TPI fat emulsion gel; compared with the TPI fat emulsion gel, the droplet size of the UTPI fat emulsion gel decreased slightly, and the internal gel-like network structure was relatively intact. However, compared with the fresh UTPI fat emulsion gel, the droplet size of the stored fat emulsion gel increased slightly, and the internal network structure was relatively loose; in contrast, after long-term storage at room temperature, the UTPI-FG fat emulsion gel containing different concentrations of flaxseed gum showed no obvious change in droplet size and no obvious aggregation compared with the fresh fat emulsion gel. The droplets in the system were relatively evenly distributed, and the internal gel-like network structure remained intact, indicating good storage stability of the UTPI-FG fat emulsion gel.

[0133] As can be seen from 2.1 to 2.6, the combination of high-density ultrasonic technology and flaxseed gum can construct fat emulsion gels with good viscoelastic properties, extrusion properties and self-supporting ability, which can partially replace traditional plastic fats and meet the international standards of easy-to-swallow foods. It effectively realizes the green and high-value utilization of tilapia protein isolate and provides a technical reference for the development of new easy-to-swallow foods.

[0134] Example 5 A fat emulsion gel

[0135] (1) Mix 6 g of tilapia protein isolate freeze-dried powder and 100 mL of distilled water by magnetic stirring at 24 °C for 2 h, then transfer it to a 5 °C refrigerator and hydrate for 20 h. Transfer the hydrated product to 26 °C and mix by magnetic stirring for another 1.5 h, then transfer it to an ultrasonic cell disruptor and perform high-density ultrasonic treatment at an ultrasonic power of 200 W for 50 min (ultrasonic for 5 s and then interval for 5 s to perform ultrasonic again) to obtain a protein dispersion; during the whole ultrasonic process, place the beaker containing the stirred hydrated product in an ice-water bath, ensure that the ultrasonic probe penetrates into the middle position of the protein aqueous solution, and replace the ice-water bath 6 times during ultrasonic treatment;

[0136] (2) Mix 0.8 g of flaxseed gum powder and 100 mL of water in a 60 °C water bath by stirring for 50 min, then cool to 25 °C, transfer it to a 5 °C refrigerator and hydrate for 20 h to obtain a flaxseed gum aqueous solution;

[0137] (3) Mix the protein dispersion and the flaxseed gum aqueous solution with equal mass (mass ratio 1:1) by a propeller at 24 °C and 1400 rpm for 4 h, adjust the pH value to 4.0 with 3 mol / l HCl solution, and continue to mix with a magnetic stirrer for another 4 h to obtain a tilapia protein isolate-flaxseed gum complex;

[0138] (4) Mix 30 g of tilapia myofibrillar protein-linseed gum complex and 60 g of perilla oil to obtain a mixture; emulsify it for 5 min at a shear rate of 8000 rpm using a T18 high-speed disperser to obtain a fat emulsion gel.

[0139] Example 6 A fat emulsion gel

[0140] (1) Mix 3 g of freeze-dried tilapia myofibrillar protein powder and 100 mL of distilled water by magnetic stirring at 26 °C for 4 h, then transfer it to a 3 °C refrigerator for 24 h of hydration. Transfer the hydrated product to 25 °C and stir it magnetically for another 3 h, then transfer it to an ultrasonic cell disruptor and perform high-density ultrasound at an ultrasonic power of 500 W for 40 min (ultrasonic for 5 s and then interval for 5 s and ultrasonic again). During the whole ultrasonic process, place the beaker containing the stirred hydrated product in an ice-water bath, ensure that the ultrasonic probe penetrates into the middle position of the protein aqueous solution, and change the ice-water bath 4 times during ultrasonic treatment;

[0141] (2) Mix 0.8 g of linseed gum powder and 100 mL of water by stirring in an 80 °C water bath for 30 min, then cool it to 25 °C, transfer it to a 3 °C refrigerator for 24 h of hydration to obtain a linseed gum aqueous solution;

[0142] (3) Mix the protein dispersion and the linseed gum aqueous solution in equal mass (mass ratio 1:1) by stirring with a propeller at 26 °C and 800 rpm for 3 h, then adjust the pH value to 2.0 using 3 mol / l HCl solution and continue to mix with a magnetic stirrer for another 2 h to obtain a tilapia myofibrillar protein-linseed gum complex;

[0143] (4) Mix 30 g of tilapia myofibrillar protein-linseed gum complex and 50 g of linseed oil to obtain a mixture; emulsify it for 3 min at a shear rate of 10000 rpm using a T18 high-speed disperser to obtain a fat emulsion gel.

[0144] As can be seen from the above examples, the present invention provides a fat emulsion gel and its preparation method and application. The present invention uses tilapia myofibrillar protein as a construction substrate to prepare an easily swallowable fat emulsion gel, which can not only provide a technical reference for the green and high-value utilization of tilapia myofibrillar protein, but also improve the dietary nutrition of people with swallowing disorders.

[0145] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a fat emulsion gel, characterized in that, It includes the following steps: (1) Mix the freeze-dried powder of tilapia protein isolate and water, hydrate, mix again, and perform ultrasonic treatment to obtain a protein dispersion; (2) Mix the flaxseed gum powder and water at 60 - 85 °C, cool, and hydrate to obtain an aqueous solution of flaxseed gum; (3) Mix the protein dispersion and the aqueous solution of flaxseed gum, adjust the pH value to 2.0 - 5.0 and mix again to obtain a tilapia protein isolate - flaxseed gum complex; (4) Mix the tilapia protein isolate - flaxseed gum complex and edible vegetable oil to obtain a mixture; emulsify the mixture to obtain a fat emulsion gel.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass - volume ratio of the freeze-dried powder of tilapia protein isolate to water for mixing is 1 - 7 g:100 mL; The mixing is magnetic stirring; The temperature of the mixing is 22 - 28 °C; The time of the mixing is 1 - 5 h; The temperature of the hydration is 2 - 6 °C; The time of the hydration is 12 - 24 h.

3. The preparation method according to claim 2, wherein In step (1), the re - mixing is magnetic stirring; the temperature of the re - mixing is 22 - 28 °C; the time of the re - mixing is 1 - 3 h; The ultrasonic treatment is high - density ultrasonic treatment; the power of the ultrasonic treatment is 100 - 500 W; the time of the ultrasonic treatment is 20 - 60 min.

4. The preparation method according to claim 3, characterized in that, In step (2), the mass - volume ratio of the flaxseed gum powder to water for mixing is 0.1 - 1.0 g:100 mL; The time of the mixing is 10 - 60 min; The cooling is to cool to 23 - 27 °C; The temperature of the hydration is 2 - 6 °C; the time of the hydration is 12 - 24 h.

5. The preparation method according to claim 4, characterized in that, In step (3), the mass ratio of the protein dispersion to the aqueous solution of flaxseed gum for mixing is 0.5 - 1.5:0.5 - 1.5; The mixing is stirring; the speed of the mixing is 800 - 1500 rpm; the time of the mixing is 2 - 5 h.

6. The preparation method according to claim 5, characterized in that, In step (3), the solution required for adjusting the pH is HCl solution; the initial concentration of the HCl solution is 2 - 4 mol / L; the re - mixing is magnetic stirring; the time of the re - mixing is 2 - 4 h.

7. The preparation method according to claim 6, characterized in that, In step (4), the addition amount of the edible vegetable oil is 50 - 75 wt% of the mass of the mixture; The edible vegetable oil includes one or more of rapeseed oil, soybean oil, perilla oil, peanut oil, flaxseed oil, sunflower oil, and sesame oil.

8. The preparation method according to claim 7, wherein In step (4), the shear speed of the emulsification is 8000 - 12000 rpm; the shear time of the emulsification is 1 - 5 min.

9. A fat emulsion gel prepared by the preparation method according to any one of claims 1 - 8.

10. Use of the fat emulsion gel according to claim 9 in the preparation of foods or drugs for improving the dietary nutrition of people with dysphagia.

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