A double cross-linked food gel loaded with a functional factor and a method for preparing the same

Abstract

The application discloses a kind of double crosslinking food gels of functional factor and preparation method thereof, belong to food processing technical field.The application uses protein, edible oil, kappa-carrageenan, gellan gum and the like as main gel base material, first, potassium ion is used to induce the formation protein-kappa-carrageenan or protein-gellan gum composite gel, then composite gel is immersed in acidic solution and induced to form double crosslinking protein-kappa-carrageenan or protein-gellan gum composite gel.The method can be used for the preparation of protein-kappa-carrageenan or protein-gellan gum composite hydrogel and composite emulsion gel, and double crosslinking gel can be prepared at lower protein and polysaccharide concentration, which can significantly improve the hardness of gel, reduce the swelling rate of gel, and the double crosslinking composite gel prepared can realize the co-embedding of hydrophilic and hydrophobic functional factors, significantly improve the stability and controlled release characteristics of functional factors.

Description

Technical Field

[0001] This invention relates to a double cross-linked food gel loaded with functional factors and its preparation method, belonging to the field of food processing technology. Background Technology

[0002] Gels are a common type of semi-solid food system with good stability and controllable texture and digestibility properties. They have broad application prospects in functional factor delivery, texture regulation of food matrices, and functional food development.

[0003] Proteins and polysaccharides are commonly used gel building materials, and composite gels are typically induced using methods such as salt ions, heat, acids, and enzymes. Protein-polysaccharide composite emulsion gels overcome the susceptibility of single-protein gels to environmental factors, resulting in more diverse structures and properties. However, most current protein-polysaccharide composite gels exhibit poor mechanical properties, require high gelation concentrations, have high swelling ratios, and have limited ability to protect and control the release of functional factors.

[0004] Choosing the right gel substrate and crosslinking method are key factors in determining the structure and properties of composite gels. Among them, using a double crosslinking strategy to construct composite gels with a dual network structure is an effective means to improve gel strength and reduce swelling.

[0005] Currently, dual-network composite gels are mainly prepared through chemical cross-linking, physical cross-linking, and enzymatic cross-linking methods. However, food gels prepared using dual cross-linking methods may still have defects such as low hardness and high swelling rate. For example, Yan et al. successfully prepared an arabinoxylan-soy protein isolate composite hydrogel using CaCl2 and peroxidase. When the concentrations of both arabinoxylan and soy protein isolate were 2.5 wt%, the hardness of the dual-crosslinked composite hydrogel was only 25–37 g (Food Hydrocolloids, 2020, 107, 105946). Qin et al. prepared a dual-crosslinked whey protein isolate-gellan gum composite emulsion gel using glucono delta-lactone (GDL) and CaCl2. When the concentrations of whey protein isolate and gellan gum in the gel were 3% (w / v, g / mL) and 0.3% (w / v, g / mL), respectively, the hardness of the dual-crosslinked composite emulsion gel was only 123 g (Food Chemistry, 2023, 404, 134513). Poor gel strength often fails to provide long-term protection for encapsulated functional factors. Furthermore, gels with low strength are prone to swelling and disintegration during gastrointestinal digestion, making controlled release of functional factors difficult. The successful preparation of double-crosslinked composite gels is closely related to factors such as the properties of the gel material, the type and formulation of the gelling agent, and the method of addition.

[0006] Therefore, exploring a simple and effective double cross-linking method to prepare protein-polysaccharide composite gels with high strength can improve the stability of functional factors and expand the application range of protein-polysaccharide cryogels in the food field. Summary of the Invention

[0007] [Technical Issues]

[0008] Existing double-crosslinked composite gels exhibit low strength and high swelling rates, failing to provide long-term protection for encapsulated functional factors. Furthermore, gels with lower strength are prone to swelling and disintegration during gastrointestinal digestion, making it difficult to achieve controlled release of functional factors.

[0009] [Technical Solution]

[0010] To address the aforementioned problems, the present invention aims to provide a double-crosslinked food gel loaded with functional factors and its preparation method. Specifically, it uses proteins, edible oils, κ-carrageenan, gellan gum, etc., as the main gel substrates. First, potassium ions are used to induce the formation of a protein-κ-carrageenan or protein-gellan gum composite gel. Then, the composite gel is immersed in an acidic solution to induce the formation of a double-crosslinked composite gel. This method can be used to prepare protein-κ-carrageenan or protein-gellan gum composite hydrogels and protein-κ-carrageenan or protein-gellan gum composite emulsion gels. The gel system prepared by the above method can form a food gel with high hardness and low swelling ratio at relatively low protein and polysaccharide concentrations. It can achieve co-encapsulation of hydrophilic and hydrophobic functional factors, significantly improving the stability of the encapsulated functional factors, and also has better controlled release effects.

[0011] To achieve the above objectives, the following technical solution is provided:

[0012] The first objective of this invention is to provide a method for preparing a double cross-linked food gel, wherein the method involves adding a potassium ion solution to a protein-κ-carrageenan or protein-gellan gum dispersion to prepare a protein-κ-carrageenan or protein-gellan gum composite gel, and then immersing the composite gel in an acidic solution to obtain a double cross-linked food gel.

[0013] In one embodiment, the pH value of the protein-κ carrageenan or protein-gellan gum dispersion is 6.0 to 10.0.

[0014] In one embodiment, the concentration of κ-carrageenan or gellan gum in the protein-κ-carrageenan or protein-gellan gum dispersion is 0.1% to 2.0%; preferably 0.5% to 1.5%.

[0015] In one embodiment, the potassium ion solution is one or more of KCl solution, K2SO4 solution, K2CO3 solution, and CH3COOK solution.

[0016] In one embodiment, the pH value of the acidic solution is 3.0 to 5.5.

[0017] In one embodiment, the acidic solution is one or more of GDL solution, citric acid solution, acetic acid solution, and hydrochloric acid solution.

[0018] In one embodiment, the protein-κ-carrageenan or protein-gellan gel is prepared by incubating the system with added potassium ion solution overnight at 2-4°C.

[0019] In one embodiment, the immersion time is 6 to 48 hours.

[0020] In one embodiment, the protein-κ-carrageenan or protein-gellan gum dispersion comprises a protein-κ-carrageenan emulsion or a protein-gellan gum emulsion and an aqueous solution of protein-κ-carrageenan or a protein-gellan gum aqueous solution.

[0021] In one embodiment, the preparation of the protein-κ-carrageenan emulsion or protein-gellan gum emulsion includes: mixing a protein solution with vegetable oil to form an O / W emulsion, and then mixing the O / W emulsion with an aqueous solution of κ-carrageenan or gellan gum.

[0022] In one embodiment, the preparation of the protein-κ-carrageenan aqueous solution or the protein-gellan gum aqueous solution comprises mixing a protein solution with a κ-carrageenan or gellan gum aqueous solution.

[0023] In one embodiment, the protein is one or more of whey protein isolate fiber, whey protein isolate, pea protein isolate, casein, soy protein isolate, and muscle protein.

[0024] In one embodiment, the concentration of the protein solution is 1-5% (w / v, g / mL).

[0025] In one embodiment, the vegetable oil is one or more of soybean oil, sunflower seed oil, peanut oil, corn oil, and medium-chain fatty acid oils.

[0026] In one embodiment, the mass ratio of the protein solution to the vegetable oil is 4:1 to 9:1.

[0027] In one embodiment, the preparation of the double cross-linked food gel includes the following steps:

[0028] (1) Mix the heat-denatured pea protein isolate solution with vegetable oil, and prepare an O / W emulsion by high-speed shearing and high-pressure homogenization. Add κ-carrageenan or gellan gum aqueous solution to obtain pea protein isolate-κ-carrageenan or pea protein isolate-gellan gum composite emulsion.

[0029] (2) Add KCl solution to the pea protein isolate-κ-carrageenan or pea protein isolate-gellan gum composite emulsion obtained in step (1) to form a composite emulsion gel.

[0030] (3) The composite emulsion gel obtained in step (2) is immersed in GDL solution to form a double cross-linked food gel, namely, a double cross-linked pea protein isolate-κ-carrageenan composite emulsion gel or a pea protein isolate-gellan gum composite emulsion gel.

[0031] In one embodiment, the heat-denatured pea protein isolate solution in step (1) is obtained by treating a pea protein isolate solution at a pH of 6.0–8.0 and a temperature of 80–95°C for 30–60 minutes.

[0032] In one embodiment, the heat-denatured pea protein isolate solution in step (1) can also be a whey protein fiber isolate solution.

[0033] In one embodiment, the whey protein isolate cellulose solution is obtained by heating whey protein isolate at pH 2.0–3.0 for 5–10 hours, then dialyzing it with a dialysis bag with a molecular weight cutoff of 3500 Da for 24–72 hours, and adjusting the pH to 6.0–8.0.

[0034] In one embodiment, the high-speed shearing conditions in step (1) are: shearing at 8000-20000 rpm for 1-2 min; and the high-pressure homogenization conditions are: homogenization at 20-100 MPa for 1-5 min.

[0035] In one embodiment, the final concentration of KCl in the composite emulsion gel in step (2) is 10–30 mmol / L.

[0036] In one embodiment, the concentration of the GDL solution in step (3) is 0.5% to 3% (w / v, g / mL), the pH value is 4.0 to 5.5, and the soaking time is 6h to 48h.

[0037] In one embodiment, the preparation of the double cross-linked food gel includes the following steps:

[0038] (1) Mix whey protein cellulose isolate solution with κ-carrageenan or gellan gum aqueous solution, and add KCl solution to form composite hydrogel;

[0039] (2) The composite hydrogel obtained in step (1) is immersed in GDL solution to form a double cross-linked composite hydrogel, namely a double cross-linked food gel.

[0040] In one embodiment, the concentration of whey protein isolate fiber in step (1) is 1-5% (w / v, g / mL).

[0041] A second objective of this invention is to provide a double-crosslinked food gel prepared by the method described above.

[0042] In one embodiment, the double crosslinked food gel is a double crosslinked composite hydrogel and a double crosslinked composite emulsion gel.

[0043] A third objective of this invention is to provide the application of the aforementioned double crosslinked food gel in the food industry.

[0044] The fourth objective of this invention is to provide a method for preparing a dual cross-linked food gel loaded with functional factors. The method involves adding a potassium ion solution to a protein-κ-carrageenan or protein-gellan gum dispersion containing functional factors to prepare a protein-κ-carrageenan or protein-gellan gum composite gel, and then immersing the composite gel in an acidic solution to obtain the dual cross-linked food gel loaded with functional factors.

[0045] In one embodiment, the functional factors include α-tocopherol and coenzyme Q. 10 It contains one or more of the following: polyunsaturated fatty acids, curcumin, resveratrol, tea polyphenols, caffeic acid, ferulic acid, vitamin C, B vitamins, polypeptides, and active proteins.

[0046] In one embodiment, the preparation of the double cross-linked food gel loaded with functional factors specifically includes the following steps:

[0047] (1) A protein solution containing functional factors and a vegetable oil containing functional factors are mixed and homogenized under high speed and high pressure to prepare an O / W emulsion. An aqueous solution of κ-carrageenan or gellan gum is added to obtain a protein-κ-carrageenan composite emulsion or a protein-gellan gum composite emulsion.

[0048] (2) Add KCl solution to the protein-κ-carrageenan composite emulsion or protein-gellan gum composite emulsion obtained in step (1) to form a composite emulsion gel.

[0049] (3) The composite emulsion gel obtained in step (2) is immersed in GDL solution to form a double cross-linked food gel loaded with functional factors, namely, a double cross-linked emulsion gel loaded with functional factors.

[0050] In one embodiment, the protein solution containing functional factors mentioned in step (1) specifically involves adding functional factors to the protein solution.

[0051] In one embodiment, the vegetable oil containing functional factors mentioned in step (1) is specifically a vegetable oil in which functional factors are added.

[0052] In one embodiment, the functional factors include α-tocopherol and coenzyme Q. 10 It contains one or more of the following: polyunsaturated fatty acids, curcumin, and resveratrol.

[0053] In one embodiment, the preparation of the double cross-linked food gel loaded with functional factors specifically includes the following steps:

[0054] (1) Mix a protein solution containing functional factors with an aqueous solution of κ-carrageenan or gellan gum, and add KCl solution to form a composite hydrogel;

[0055] (2) The composite hydrogel obtained in step (1) is immersed in GDL solution to form a double cross-linked composite hydrogel, namely a double cross-linked food gel.

[0056] In one embodiment, the functional factor in step (1) includes one or more of the following: tea polyphenols, caffeic acid, ferulic acid, vitamin C, B vitamins, polypeptides, and active proteins.

[0057] The fifth objective of this invention is to provide a double cross-linked food gel loaded with functional factors obtained by the above preparation method.

[0058] In one embodiment, the bicrosslinked food gel loaded with functional factors includes a bicrosslinked emulsion gel loaded with functional factors and a bicrosslinked hydrogel.

[0059] The sixth objective of this invention is to provide an application of the above-described dual cross-linked food gel loaded with functional factors in the preparation of functional factor delivery systems and in yogurt, jelly, candy, and weight-loss foods.

[0060] Beneficial effects:

[0061] (1) The preparation of the double cross-linked food gel of the present invention is mild, simple in process, and has a wide range of applications. It can significantly improve the mechanical properties of the gel, reduce the swelling rate of the gel, enhance the protection and controlled release of functional factors, and is easy to promote and apply in industry.

[0062] (2) The KCl / GDL double crosslinked pea protein isolate-κ-carrageenan composite emulsion gel prepared by the method of the present invention has the highest hardness among all double crosslinked composite emulsion gels, reaching 4813.0g; compared with composite emulsion gels prepared by single crosslinking agents KCl, GDL or CaCl2, the KCl / GDL double crosslinked composite emulsion gel has a hardness that is 2.3 to 20.1 times higher, and the fatty acid release rate is reduced by 7.5% to 23.0% during in vitro simulated gastrointestinal digestion.

[0063] (3) The KCl / GDL double crosslinked whey protein isolate-κ-carrageenan composite emulsion gel prepared by the method of the present invention has a hardness of 3871.9g. Compared with composite emulsion gels prepared by single crosslinking agents KCl or GDL, the KCl / GDL double crosslinked composite emulsion gel has a hardness of 3.3 to 12.0 times, which can significantly improve the storage stability of the embedded functional factors α-tocopherol and curcumin.

[0064] (4) The KCl / GDL double crosslinked whey protein isolate-κ-carrageenan composite hydrogel prepared by the method of the present invention has the highest hardness of 7764.2g. Compared with composite hydrogels prepared by single crosslinking agent KCl or GDL, the KCl / GDL double crosslinked composite hydrogel has a hardness of 2.0 to 28.9 times. The double crosslinked composite hydrogel has a lower swelling rate, which can significantly improve the storage stability of the embedded functional factor anthocyanin and significantly reduce the release rate of anthocyanin in the simulated gastric digestion stage. Attached Figure Description

[0065] Figure 1 Figure 1 shows the free fatty acid production data of KCl, GDL, and CaCl2 single-crosslinked pea protein isolate-κ-carrageenan composite emulsion gel and KCl / GDL double-crosslinked pea protein isolate-κ-carrageenan composite emulsion gel at different digestion times under different κ-carrageenan concentrations; (A) κ-carrageenan concentration is 0.25%; (B) κ-carrageenan concentration is 0.50%.

[0066] Figure 2 A schematic diagram illustrating the preparation of KCl / GDL double-crosslinked protein-κ-carrageenan composite gel;

[0067] Figure 3 Images showing the appearance of different pea protein isolate-polysaccharide complex emulsions after the addition of KCl; (A) polysaccharide concentration of 0.25%; (B) polysaccharide concentration of 0.5%;

[0068] Figure 4The graph shows the change in curcumin retention rate in KCl and GDL single crosslinked and KCl / GDL double crosslinked whey protein isolate fiber-κ-carrageenan composite emulsion gels during storage at 25℃ with storage time when the κ-carrageenan concentration is 0.25%.

[0069] Figure 5 The figure shows the change in α-tocopherol retention rate in KCl and GDL single crosslinked and KCl / GDL double crosslinked whey protein isolate fiber-κ-carrageenan composite emulsion gels during storage at 25℃ with storage time when the κ-carrageenan concentration is 0.25%.

[0070] Figure 6 The images show the appearance of whey protein isolate fiber-κ-carrageenan composite hydrogels formed under different induction conditions with different κ-carrageenan concentrations; (A) KCl induction without anthocyanin; (B) GDL induction without anthocyanin; (C) KCl / GDL induction without anthocyanin; (D) KCl / GDL induction with anthocyanin.

[0071] Figure 7 The graph shows the encapsulation efficiency of anthocyanins in different whey protein isolate fiber-κ-carrageenan composite hydrogels at different κ-carrageenan concentrations.

[0072] Figure 8 The graph shows the swelling ratio of whey protein isolate fiber-κ-carrageenan composite hydrogels formed by single cross-linking of KCl and GDL and double cross-linking of KCl / GDL when the κ-carrageenan concentration is 1.0%.

[0073] Figure 9 The graph shows the changes in anthocyanin retention rate in whey protein isolate fiber-κ-carrageenan composite hydrogels formed by KCl and GDL single crosslinking and KCl / GDL double crosslinking during storage at 4℃ when the κ-carrageenan concentration is 1.0%.

[0074] Figure 10 The graph shows the release rate of anthocyanins in whey protein isolate fiber-κ-carrageenan composite hydrogels formed by single cross-linking of KCl and GDL and double cross-linking of KCl / GDL during in vitro simulated gastrointestinal digestion when the κ-carrageenan concentration is 1.0%. Detailed Implementation

[0075] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The specific embodiments described below further illustrate the present invention.

[0076] The testing method involved in this invention

[0077] 1. Methods for testing gel hardness

[0078] The hardness of the gel was determined using a full texture analyzer equipped with a P-36R cylindrical test probe. The test conditions were: strain 50%, trigger force 3g, test speed 1.0mm / s, and number of cycles 2. The gel hardness was calculated using the software provided with the instrument.

[0079] 2. In vitro simulated gastrointestinal digestion experiment

[0080] The in vitro digestion of the emulsion gel was simulated using the INFOGEST model. The specific method was as follows: The gel sample was ground approximately 30 times using a mortar and pestle. Simulated saliva (pH 7.0) was added to the gel sample at a mass ratio of 1:1, and the mixture was incubated at 37°C for 3 minutes. The pH of the digestive solution was adjusted to 3.0, and simulated gastric juice (pH 3.0) was added to the digestive solution at a mass ratio of 1:1, and the mixture was incubated at 37°C for 2 hours. The pH of the digestive solution was adjusted to 7.0, and simulated intestinal juice (pH 7.0) was added to the digestive solution at a mass ratio of 1:1, and the mixture was incubated at 37°C for 2 or 4 hours. The simulated saliva contained 15.1 mmol / L KCl, 13.6 mmol / L NaCl, 3.7 mmol / L KH2PO4, 0.15 mmol / L MgCl2(H2O)6, and 1.5 mmol / L CaCl2(H2O)2; the simulated gastric juice contained 6.9 mmol / L KCl, 72.2 mmol / L NaCl, 0.9 mmol / L KH2PO4, 0.12 mmol / L MgCl2(H2O)6, 0.15 mmol / L CaCl2(H2O)2, and 2000 U / mL pepsin; and the simulated intestinal juice contained 6.8 mmol / L KCl, 123.4 mmol / L NaCl, 0.8 mmol / L KH2PO4, 0.33 mmol / L MgCl2(H2O)6, 0.6 mmol / L CaCl2(H2O)2, 10 mmol / L bile salts, and 100 U / mL pancreatic enzymes.

[0081] 3. Determination of free fatty acids

[0082] The release of free fatty acids during simulated intestinal digestion was determined using the pH-stat method. The pH of the intestinal digestive fluid at different digestion times was measured, and the pH was maintained at 7.0 by titration with NaOH solution. The release of free fatty acids was calculated using the following formula (1):

[0083]

[0084] In the formula: V NaOH To determine the volume (mL) of sodium hydroxide consumed during titration, C NaOH To determine the mole fraction (0.1 mol / L) of the sodium hydroxide solution used in the titration, M Lipid The average molecular weight of sunflower seed oil (880 g / mol), W Lipid The weight (g) of the lipids initially present in the reaction vessel is given. It is assumed that each triglyceride molecule produces two free fatty acids via lipase action.

[0085] 4. Determination of swelling ratio

[0086] The gel sample was completely immersed in 10 mM phosphate buffer solution with a pH of 7.0. The mass of the gel was measured at 4-hour intervals until there was no significant change in the mass of the gel. The swelling ratio of the gel was calculated using formula (2).

[0087]

[0088] In the formula: W1 is the mass of the gel after absorbing water, and W0 is the initial mass of the gel.

[0089] 5. Determination of functional factor content

[0090] The gel sample was broken up and the functional factors were extracted. The content of functional factors in the gel was determined by ultraviolet spectrophotometry or high performance liquid chromatography. The retention rate and cumulative release rate of functional factors during storage or digestion were expressed by the following formula:

[0091]

[0092] In the formula: C T C represents the content of functional factors in the gel at the initial stage of storage. i The content of functional factors in the gel at different storage periods.

[0093]

[0094] In the formula: C I C represents the content of functional factors in the gel at the initial stage of digestion. i The content of functional factors in digestive juices at different digestion stages.

[0095] Example 1

[0096] The preparation method of single cross-linked pea protein isolate-κ-carrageenan composite emulsion gel includes the following steps:

[0097] (1) Solution preparation

[0098] To prepare a 5% (w / v, g / mL) pea protein isolate solution: Add pea protein isolate to deionized water, adjust the pH to 12.0, stir for 1 hour, adjust the pH of the solution to 7.0, heat at 90℃ for 30 minutes, and then cool to room temperature to obtain a 5% (w / v, g / mL) pea protein isolate solution.

[0099] To prepare a 3% (w / v, g / mL) κ-carrageenan solution: Add κ-carrageenan to deionized water and stir at 55°C for 1 hour to dissolve it completely, thus obtaining a 3% (w / v, g / mL) κ-carrageenan solution.

[0100] To prepare a 25% (w / v, g / mL) GDL solution: Add GDL to deionized water and stir until fully dissolved to obtain a 25% (w / v, g / mL) GDL solution.

[0101] To prepare a 1 mol / L CaCl2 solution: Add CaCl2 to deionized water and stir until fully dissolved to obtain a 1 mol / L CaCl2 solution.

[0102] To prepare a 1 mol / L KCl solution: Add KCl to deionized water and stir until fully dissolved to obtain a 1 mol / L KCl solution.

[0103] (2) Preparation of emulsion

[0104] A 5% (w / v, g / mL) pea protein isolate solution was mixed with sunflower seed oil at a mass ratio of 9:1, sheared at 10000 r / min for 2 minutes, and then homogenized three times at 50 MPa to obtain an O / W emulsion. The O / W emulsion was then mixed with different volumes of κ-carrageenan solution and ultrapure water at 55 °C to make the final pea protein isolate-κ-carrageenan composite emulsion system contain 2.5% (w / v, g / mL) pea protein isolate, 10% (w / w) sunflower seed oil, and κ-carrageenan at concentrations of 0%, 0.25%, 0.50%, 0.75%, 1.0%, and 1.5% (w / v, g / mL).

[0105] (3) Preparation of single cross-linked composite emulsion gel

[0106] The GDL solution, CaCl2 solution or KCl solution prepared in step (1) were added to the pea protein isolate-κ-carrageenan composite emulsion obtained in step (2) and stored at 4°C overnight to form gels, which were numbered 1 to 3. The final concentration of GDL in gel 1 was 1% (w / v, g / mL), the final concentration of CaCl2 in gel 2 was 40 mmol / L, and the final concentration of KCl in gel 3 was 20 mmol / L.

[0107] The hardness of gels 1–3 was determined using a full texture analyzer, and the results are shown in Table 1.

[0108] Table 1. Hardness (g) of GDL, CaCl2, and KCl monocrosslinked pea protein-κ-carrageenan composite emulsion gels at different κ-carrageenan concentrations.

[0109]

[0110] Note: "—" indicates that a self-supporting gel cannot be formed under this condition; different lowercase letters represent significant differences between data in the same row, and different uppercase letters represent significant differences between data in the same column (P<0.05).

[0111] As shown in Table 1, as the concentration of κ-carrageenan gradually increased from 0.25% (w / v, g / mL) to 1.5% (w / v, g / mL), the hardness of the single crosslinked composite emulsion gels induced by different crosslinking agents gradually increased. The hardness of the GDL composite emulsion gel increased from 171.1 g to 1571.2 g, the hardness of the CaCl2 composite emulsion gel increased from 43.8 g to 1560.2 g, and the hardness of the KCl composite emulsion gel increased from 56.2 g to 1265.7 g.

[0112] Example 2

[0113] The preparation method of double crosslinked pea protein isolate-κ-carrageenan composite emulsion gel includes the following steps:

[0114] Method 1:

[0115] The double crosslinked composite emulsion gel was prepared according to the method of Example 1, except that two crosslinking agents were added in different ways in step (3) to obtain the double crosslinked pea protein isolate-κ-carrageenan composite emulsion gel; the specific preparation method is as follows:

[0116] Two of the following solutions—GDL, CaCl2, and KCl—were added simultaneously in a certain volume to a pea protein isolate-κ-carrageenan composite emulsion and stored overnight at 4°C, respectively, to form KCl-GDL double-crosslinked pea protein isolate-κ-carrageenan composite emulsion gels; CaCl2-GDL double-crosslinked pea protein isolate-κ-carrageenan composite emulsion gels; and KCl-CaCl2 double-crosslinked pea protein isolate-κ-carrageenan composite emulsion gels. In each composite emulsion gel system, the concentration of GDL was 1% (w / v, g / mL), the concentration of CaCl2 was 40 mmol / L, and the concentration of KCl was 20 mmol / L.

[0117] Method 2:

[0118] Following the method described in Example 1, single-crosslinked composite emulsion gels were first prepared, gels 1 to 3; then, they were respectively immersed in 1% (w / v, g / mL) GDL solution, 40 mmol / L CaCl2 solution, and 20 mmol / L KCl solution, and stored overnight at 4°C to form KCl / GDL double-crosslinked pea protein isolate-κ-carrageenan composite emulsion gels; GDL / KCl double-crosslinked pea protein isolate-κ-carrageenan composite emulsion gels; CaCl2 / GDL double-crosslinked pea protein isolate-κ-carrageenan composite emulsion gels; GDL / CaCl2 double-crosslinked pea protein isolate-κ-carrageenan composite emulsion gels; KCl / CaCl2 double-crosslinked pea protein isolate-κ-carrageenan composite emulsion gels; and CaCl2 / KCl double-crosslinked pea protein isolate-κ-carrageenan composite emulsion gels.

[0119] Performance testing

[0120] 1. The hardness of the double-crosslinked pea protein isolate-κ-carrageenan composite emulsion gel prepared in Example 2 was determined, and the results are shown in Table 2:

[0121] Table 2. Hardness (g) of pea protein isolate-κ-carrageenan composite emulsion gel under different κ-carrageenan concentrations and preparation methods.

[0122]

[0123] Note: (1) "e.g. KCl / GDL" means that gelation is induced first by KCl and then by GDL; "KCl-GDL" means that two crosslinking agents are added at the same time to induce gelation; "—" means that a self-supporting gel cannot be formed under this condition.

[0124] (2) Different lowercase letters represent significant differences between different data in the same row, and different uppercase letters represent significant differences between different data in the same column (P<0.05).

[0125] Table 2 shows that, at the same κ-carrageenan concentration, different crosslinking agent formulations and addition methods significantly affect the hardness of the composite emulsion gel. Among them, the KCl / GDL double-crosslinked composite emulsion gel exhibits the highest hardness within the κ-carrageenan concentration range of 0.25%–1.5%. As the κ-carrageenan concentration increases from 0.25% to 1.5%, the hardness of the KCl / GDL double-crosslinked composite emulsion gel increases from 879.8 g to 4813.0 g, which is 3.8–15.6 times that of the KCl single-crosslinked composite emulsion gel, 2.3–5.1 times that of the GDL single-crosslinked composite emulsion gel, and 3.1–20.1 times that of the CaCl2 single-crosslinked composite emulsion gel.

[0126] 2. An in vitro experiment was conducted on the release of free fatty acids during simulated gastrointestinal digestion of pea protein isolate-κ-carrageenan composite emulsion gel. The results are as follows: Figure 1 As shown:

[0127] Figure 1 Composite emulsion gels prepared using different gelation methods were used to simulate the release of free fatty acids during gastrointestinal digestion in vitro. For example... Figure 1 As shown in Figure A, when the κ-carrageenan concentration was 0.25%, the fat release rate of the KCl / GDL double crosslinked composite emulsion gel was 26.7% after 240 minutes of simulated intestinal digestion in vitro, which was reduced by 10.8%, 7.6%, and 23.0% compared to the KCl, GDL, and CaCl2 single crosslinked composite emulsion gels, respectively. Figure 1 As shown in Figure B, when the κ-carrageenan concentration was 0.5%, the fat release rate of the KCl / GDL double-crosslinked composite emulsion gel was 28.3% after 240 minutes of simulated intestinal digestion in vitro, which was reduced by 9.8%, 7.5%, and 16.7% compared to the KCl, GDL, and CaCl2 single-crosslinked composite emulsion gels, respectively. These results indicate that the composite emulsion gel prepared using the KCl / GDL double-crosslinking method can effectively inhibit the rapid release of fatty acids in the early stages of digestion, achieving a sustained-release effect.

[0128] In summary, such as Figure 2 As shown, the preparation method of KCl / GDL double crosslinked protein-κ-carrageenan composite gel is to first induce the formation of protein-κ-carrageenan composite gel with potassium ions, and then impregnate the composite gel in an acidic solution to form a double crosslinked composite gel.

[0129] Example 3

[0130] The preparation method of KCl / GDL double crosslinked composite emulsion gel in Method 2 of Example 2 is the same, except that κ-carrageenan is replaced with gellan gum of the same concentration. All other parameters and conditions are the same.

[0131] Performance testing

[0132] like Figure 3 As shown, Figure 3 A. When the gellan gum concentration is 0.25%, KCl cannot induce the formation of pea protein isolate-gellan gum composite emulsion gel. Figure 3 B. When the gellan gum concentration reaches 0.5%, KCl can induce the formation of pea protein isolate-gellan gum composite emulsion gel.

[0133] The hardness of the KCl / GDL double-crosslinked pea protein isolate-gellan gel composite emulsion prepared in Example 3 was determined, and the results are shown in Table 3:

[0134] Table 3. Hardness (g) of pea protein isolate-gellan gum composite emulsion gels induced by KCl, GDL, and KCl / GDL at different gellan gum concentrations.

[0135]

[0136] Note: Different lowercase letters indicate significant differences between different data in the same row, and different uppercase letters indicate significant differences between different data in the same column (P<0.05).

[0137] Table 3 shows that, at the same gellan gum concentration, the KCl / GDL double-crosslinked composite emulsion gel exhibits the highest hardness, reaching 4269.8 g, which is 3.0–12.9 times that of the KCl single-crosslinked composite emulsion gel and 2.2–3.4 times that of the GDL single-crosslinked composite emulsion gel. These results indicate that the KCl / GDL double-crosslinked gel preparation method is also applicable to the pea protein isolate-gellan gum composite emulsion gel system.

[0138] Comparative Example 1

[0139] The preparation method of KCl / GDL double crosslinked composite emulsion gel in Method 2 of Example 2 is the same, except that κ-carrageenan is replaced with gum arabic, pectin, sodium alginate, pullulan, hydroxypropyl methylcellulose, xanthan gum, octenyl succinic acid starch, and chitosan of the same concentration. All other parameters and conditions are the same.

[0140] like Figure 3 As shown, in the pea protein isolate-polysaccharide complex emulsion system, when the polysaccharide concentration is 0.25% to 0.5%, replacing κ-carrageenan with any of the following polysaccharides—gum arabic, pectin, sodium alginate, pullulan, hydroxypropyl methylcellulose, xanthan gum, octenyl succinate starch, or chitosan—cannot induce the formation of a self-supporting gel using KCl.

[0141] Example 4

[0142] The preparation method of KCl / GDL double crosslinked composite emulsion gel in Method 2 of Example 2 is the same, except that the pea protein isolate is replaced with casein, whey protein isolate and soy protein isolate of the same concentration. All other parameters and conditions are the same.

[0143] Performance testing

[0144] 1. The hardness of the KCl / GDL double-crosslinked protein-κ-carrageenan composite emulsion gel prepared in Example 4 was determined, and the results are shown in Tables 4-6:

[0145] Table 4. Stiffness (g) of casein-κ-carrageenan composite emulsion gels induced by KCl, GDL, and KCl / GDL at different κ-carrageenan concentrations.

[0146]

[0147] Note: Different lowercase letters indicate significant differences between data in the same row, and different uppercase letters indicate significant differences between data in the same column (P<0.05).

[0148] Table 5. Stiffness (g) of whey protein isolate-κ-carrageenan composite emulsion gels induced by KCl, GDL, and KCl / GDL at different κ-carrageenan concentrations.

[0149]

[0150] Note: Different lowercase letters indicate significant differences between data in the same row, and different uppercase letters indicate significant differences between data in the same column (P<0.05).

[0151] Table 6. Stiffness (g) of soybean protein isolate-κ-carrageenan composite emulsion gels induced by KCl, GDL, and KCl / GDL at different κ-carrageenan concentrations.

[0152]

[0153] Note: Different lowercase letters indicate significant differences between data in the same row, and different uppercase letters indicate significant differences between data in the same column (P<0.05).

[0154] As shown in Table 4-6, under the same κ-carrageenan concentration, the KCl / GDL double crosslinked composite emulsion gel has the highest hardness among different protein-κ-carrageenan composite emulsion gel systems. The highest hardness of the KCl / GDL double-crosslinked casein-κ-carrageenan composite emulsion gel was 4431.8 g, which is 4.5–20.4 times that of the KCl single-crosslinked composite emulsion gel and 2.3–4.2 times that of the GDL single-crosslinked composite emulsion gel. The highest hardness of the KCl / GDL double-crosslinked whey protein isolate-κ-carrageenan composite emulsion gel was 4924.1 g, which is 4.9–20.5 times that of the KCl single-crosslinked composite emulsion gel and 3.5–5.9 times that of the GDL single-crosslinked composite emulsion gel. The highest hardness of the KCl / GDL double-crosslinked soy protein isolate-κ-carrageenan composite emulsion gel was 4621.2 g, which is 3.8–14.1 times that of the KCl single-crosslinked composite emulsion gel and 2.3–4.8 times that of the GDL single-crosslinked composite emulsion gel. These results indicate that the KCl / GDL double-crosslinking method can be used to prepare different protein-κ-carrageenan composite emulsion gel systems.

[0155] Example 4

[0156] A method for preparing a double-crosslinked whey protein isolate-κ-carrageenan composite emulsion gel loaded with curcumin and α-tocopherol, comprising the following steps:

[0157] (1) A 2% (w / v, g / mL) whey protein isolate solution was heated with stirring at pH 2.0 and 90℃ for 6 hours, and dialyzed for 72 hours using a dialysis bag with a molecular weight cutoff of 3500 Da. The pH was then adjusted to 7.0 to obtain a whey protein cellulose isolate solution. Curcumin was dissolved in dimethyl sulfoxide and added to the whey protein cellulose isolate solution to prepare a whey protein cellulose isolate-curcumin complex, wherein the concentration of curcumin was 100 μg / mL. α-Tocopherol was added to sunflower seed oil to make the concentration of α-tocopherol in the sunflower seed oil 10% (w / w).

[0158] (2) The whey protein isolate-curcumin complex obtained in step (1) was mixed with sunflower seed oil containing α-tocopherol at a mass ratio of 4:1, sheared at 10000 r / min for 3 minutes, and then homogenized three times at 50 MPa to obtain an O / W emulsion; the O / W emulsion was mixed with different volumes of κ-carrageenan solution and ultrapure water at 55°C so that the final system contained 1.0% (w / v, g / mL) whey protein isolate, 10% (w / w) sunflower seed oil and 0.25% to 1.50% (w / v, g / mL) κ-carrageenan;

[0159] (3) Add KCl solution and GDL solution to the emulsion system in step (2) respectively, and store at 4°C overnight to form KCl monocrosslinked composite emulsion gel, with a final KCl concentration of 20 mmol / L; and GDL monocrosslinked composite emulsion gel, with a final GDL concentration of 0.2% (w / v, g / mL).

[0160] (4) The KCl monocrosslinked composite emulsion gel from step (3) is immersed in 1% (w / v, g / mL) GDL solution for 6 hours to form KCl / GDL bicrosslinked composite emulsion gel.

[0161] Performance testing

[0162] 1. The hardness of the composite emulsion gel prepared in Example 4 was measured, and the results are shown in Table 7:

[0163] Table 7. Stiffness (g) of whey protein isolate cellulose-κ-carrageenan composite emulsion gels induced by KCl, GDL, and KCl / GDL at different κ-carrageenan concentrations.

[0164]

[0165] Note: "—" indicates that a self-supporting gel cannot be formed under this condition; different lowercase letters represent significant differences between data in the same row, and different uppercase letters represent significant differences between data in the same column (P<0.05).

[0166] Table 7 shows that, at the same κ-carrageenan concentration, the KCl / GDL double-crosslinked composite emulsion gel exhibits the highest hardness, reaching 3871.9 g, which is 4.3–12.0 times that of the KCl single-crosslinked composite emulsion gel and 3.3–5.7 times that of the GDL single-crosslinked composite emulsion gel. These results indicate that the KCl / GDL double-crosslinked gel preparation method is also applicable to the whey protein isolate-κ-carrageenan composite emulsion gel system.

[0167] 2. The encapsulation efficiency and storage stability of the composite emulsion prepared in Example 4 were determined, and the results are shown in Table 8. Figures 4-5 As shown:

[0168] Table 8. Encapsulation efficiency of curcumin and α-tocopherol in KCl / GDL double-crosslinked whey protein isolate cellulose-κ-carrageenan composite emulsion gel.

[0169]

[0170] Note: Different lowercase letters indicate significant differences (P < 0.05) between data points in the same row.

[0171] As shown in Table 8, the encapsulation rates of α-tocopherol and curcumin in the double cross-linked composite emulsion gels with different κ-carrageenan concentrations were all above 98%, indicating that the double cross-linked composite emulsion has excellent co-encapsulation performance of functional factors.

[0172] Figure 4 and Figure 5 The retention rates of curcumin and α-tocopherol in different composite emulsion gels changed with storage time. Figure 4 As shown, after 14 days of storage at 25℃, the retention rate of curcumin in the KCl / GDL double crosslinked composite emulsion gel was 79.21%, while the retention rates of curcumin in the KCl and GDL single crosslinked composite emulsion gels were 38.94% and 59.42%, respectively. Figure 5 As shown, after 14 days of storage at 25℃, the retention rate of α-tocopherol in the KCl / GDL double crosslinked composite emulsion gel was 95.69%, which was 7.07% and 3% higher than that of the KCl or GDL single crosslinked composite emulsion gel, respectively. These results indicate that the KCl / GDL double crosslinked composite emulsion gel can significantly improve the storage stability of α-tocopherol and curcumin.

[0173] Example 5

[0174] A method for preparing a whey protein isolate-κ-carrageenan composite hydrogel loaded with proanthocyanidins includes the following steps:

[0175] (1) A 5% (w / v, g / mL) whey protein isolate solution was heated at pH 2.0 and 90℃ with stirring for 6 h, and dialyzed for 72 h using a dialysis bag with a molecular weight cutoff of 3500 Da. The pH was then adjusted to 7.0 to obtain a whey protein cellulose isolate solution. Proanthocyanidins and κ-carrageenan were then added to obtain a whey protein cellulose isolate-κ-carrageenan solution system. In the final system, the concentration of whey protein cellulose isolate was 1% (w / v, g / mL), the concentration of proanthocyanidins was 90 mg / mL, and the concentration of κ-carrageenan was 0.25% to 2.0% (w / v, g / mL).

[0176] (2) Add KCl solution and GDL solution to the whey protein isolate cellulose-κ-carrageenan solution in step (1) above, and store at 4°C overnight to form KCl monocrosslinked composite hydrogel with a final KCl concentration of 20 mmol / L and GDL monocrosslinked composite hydrogel with a final GDL concentration of 0.35% (w / v, g / mL).

[0177] (3) The KCl monocrosslinked composite hydrogel from step (2) above is immersed in 1% (w / v, g / mL) GDL solution for 6 hours to form KCl / GDL double crosslinked composite hydrogel.

[0178] Performance testing

[0179] The hardness of the composite hydrogel prepared in Example 5 was measured, and the results are shown in Table 9:

[0180] Table 9. Hardness (g) of KCl, GDL, and KCl / GDL whey protein isolate-κ-carrageenan composite hydrogels at different κ-carrageenan concentrations.

[0181]

[0182] Note: "—" indicates that a self-supporting gel cannot be formed under this condition; different lowercase letters (ad) represent significant differences between data in the same row, and different uppercase letters (AC) represent significant differences between data in the same column (P<0.05).

[0183] As shown in Table 9, when the concentration of κ-carrageenan is 0.25% to 2.0%, the KCl / GDL double crosslinked composite hydrogel has the highest hardness, reaching up to 7764.2 g, which is 2.0 to 28.9 times that of the KCl or GDL single crosslinked composite hydrogel.

[0184] Performance testing

[0185] Figure 6 The images show the appearance of different whey protein isolate fiber-κ-carrageenan composite hydrogels. A is a KCl monocrosslinked composite hydrogel, B is a GDL monocrosslinked composite hydrogel, C is a KCl / GDL double crosslinked composite hydrogel, and D is a KCl / GDL double crosslinked composite hydrogel loaded with anthocyanins. The results show that, except for the condition where GDL cannot induce the formation of composite hydrogels at a κ-carrageenan concentration of 0.25%, all others can form self-supporting composite hydrogels.

[0186] Figure 7 The encapsulation efficiency of anthocyanins by different hydrogels. For example... Figure 7 As shown, when the concentration of κ-carrageenan reaches 0.50% or higher, the encapsulation rate of anthocyanins in the KCl / GDL double crosslinked composite hydrogel is higher than 94%, which is significantly higher than that of the KCl or GDL single crosslinked composite hydrogel.

[0187] Figure 8 The swelling ratios of different whey protein isolate-κ-carrageenan composite hydrogels are shown. Figure 8 As shown, the KCl / GDL double crosslinked composite hydrogel has the lowest swelling rate at 19.65%, which is 41.59% and 35.96% lower than that of the KCl or GDL single crosslinked composite hydrogel, respectively.

[0188] Figure 9 This shows the changes in proanthocyanidin retention rates in different composite hydrogels during storage at 4℃. For example... Figure 9As shown, after 14 days of storage, the proanthocyanidin retention rate in the KCl / GDL double crosslinked composite hydrogel was 63.84%, which was 25.38% and 18.31% higher than that in the KCl or GDL single crosslinked composite hydrogel, respectively.

[0189] Figure 10 To simulate the release of proanthocyanidins from different composite hydrogels during in vitro gastrointestinal digestion. For example... Figure 10 As shown, during in vitro simulated gastrointestinal digestion, the KCl / GDL dual crosslinked composite hydrogel can effectively reduce the release rate and amount of proanthocyanidins in the simulated gastric digestion stage, with a release amount of 38.69%, which is 40.62% and 31.66% lower than that of KCl or GDL single crosslinked composite hydrogel, respectively. This indicates that the KCl / GDL dual crosslinked composite hydrogel can play a significant sustained-release role.

[0190] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for preparing a double cross-linked food gel, characterized in that, The preparation method involves adding potassium ion solution to a protein-κ-carrageenan or protein-gellan gum dispersion to prepare a protein-κ-carrageenan or protein-gellan gum composite gel, and then immersing the composite gel in an acidic solution to obtain a double cross-linked food gel. The potassium ion solution is one or more of KCl solution, K2SO4 solution, K2CO3 solution, and CH3COOK solution; The concentration of κ-carrageenan in the protein-κ-carrageenan dispersion is 0.25%~2.0%; The concentration of gellan gum in the protein-gellan gum dispersion is 0.5%~1.5%; The acidic solution is gluconic acid δ. GDL lactone solution; The protein-κ-carrageenan dispersion is a protein-κ-carrageenan emulsion or a protein-κ-carrageenan aqueous solution; The protein-gellan gum dispersion is a protein-gellan gum emulsion or a protein-gellan gum aqueous solution; The preparation of the protein-κ-carrageenan emulsion or protein-gellan gum emulsion includes: mixing a protein solution with vegetable oil to form an O / W emulsion, and then mixing the O / W emulsion with an aqueous solution of κ-carrageenan or gellan gum. The preparation of the protein-κ-carrageenan aqueous solution or the protein-gellan gum aqueous solution includes: mixing a protein solution with a κ-carrageenan or gellan gum aqueous solution; The protein is one or more of the following: whey protein isolate, whey protein isolate, pea protein isolate, casein, soy protein isolate, and muscle protein. The concentration of the protein solution is 1–5% w / v, g / mL.

2. The double cross-linked food gel obtained by the preparation method according to claim 1.

3. The application of the double cross-linked food gel according to claim 2 in the food industry.

4. A method for preparing a double-crosslinked food gel loaded with functional factors, characterized in that, The method involves adding a potassium ion solution to a protein-κ-carrageenan or protein-gellan gum dispersion containing functional factors to prepare a protein-κ-carrageenan composite gel or a protein-gellan gum composite gel. The composite gel is then immersed in an acidic solution to obtain a double-crosslinked food gel loaded with functional factors. The potassium ion solution is one or more of KCl solution, K2SO4 solution, K2CO3 solution, and CH3COOK solution. The concentration of κ-carrageenan in the protein-κ-carrageenan dispersion is 0.25%~2.0%; The concentration of gellan gum in the protein-gellan gum dispersion is 0.5%~1.5%; The acidic solution is gluconic acid δ. GDL lactone solution; The protein-κ-carrageenan dispersion is a protein-κ-carrageenan emulsion or a protein-κ-carrageenan aqueous solution; The protein-gellan gum dispersion is a protein-gellan gum emulsion or a protein-gellan gum aqueous solution; The preparation of the protein-κ-carrageenan emulsion or protein-gellan gum emulsion includes: mixing a protein solution with vegetable oil to form an O / W emulsion, and then mixing the O / W emulsion with an aqueous solution of κ-carrageenan or gellan gum. The preparation of the protein-κ-carrageenan aqueous solution or the protein-gellan gum aqueous solution includes: mixing a protein solution with a κ-carrageenan or gellan gum aqueous solution; The protein is one or more of the following: whey protein isolate, whey protein isolate, pea protein isolate, casein, soy protein isolate, and muscle protein. The concentration of the protein solution is 1–5% w / v, g / mL.

5. The double cross-linked food gel loaded with functional factors obtained by the preparation method of claim 4.

6. The application of the dual cross-linked food gel loaded with functional factors as described in claim 5 in the preparation of functional factor delivery systems and in yogurt, jelly, candy, and weight-loss foods.

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