Double-crosslinking food gel loaded with functional factors and preparation method of double-crosslinking food gel

Abstract

The invention discloses functional factor-loaded bi-crosslinked food gel and a preparation method thereof, and belongs to the technical field of food processing. The preparation method comprises the following steps: by taking protein, edible oil and fat, kappa-carrageenan, gellan gum and the like as main gel base materials, firstly, inducing by adopting potassium ions to form protein-kappa-carrageenan or protein-gellan gum composite gel; and dipping the composite gel in an acid solution, and inducing to form the bi-crosslinked protein-kappa-carrageenan or protein-gellan gum composite gel. The method can be used for preparing protein-kappa-carrageenan or protein-gellan gum composite hydrogel and composite emulsion gel, can be used for preparing double-crosslinking gel at lower protein and polysaccharide concentration, and can obviously improve the hardness of the gel, reduce the swelling rate of the gel and improve the stability of the gel. The prepared double-crosslinking composite gel can realize co-embedding of hydrophilic and hydrophobic functional factors, and the stability and the controlled release characteristic of the functional factors are remarkably improved.

Description

Technical Field

[0001] The invention relates to a double-crosslinked food gel loaded with functional factors and a preparation method thereof, belonging to the technical field of food processing. Background Art

[0002] Gel is a common semi-solid food system with good stability and controllable texture and digestibility. It has broad application prospects in functional factor delivery, texture control of food matrices, and development of functional foods.

[0003] Proteins and polysaccharides are commonly used gel building materials, and usually salt ions, heat, acid, enzymes and other methods are used to induce the formation of composite gels. Protein-polysaccharide composite emulsion gels overcome the defect that single protein gels are easily affected by environmental factors, forming more diverse structures and properties. However, most of the current protein-polysaccharide composite gels have poor mechanical properties, require high gelation concentrations, have high swelling rates, and have limited ability to protect functional factors and control release.

[0004] Selecting a suitable gel substrate and cross-linking method are key factors in determining the structure and properties of composite gels. Among them, adopting a double cross-linking strategy to construct a composite gel with a double network structure is an effective means to improve gel strength and reduce swelling.

[0005] At present, double network composite gels are mainly successfully prepared by chemical crosslinking, physical crosslinking, enzyme crosslinking and other methods. However, food gels prepared by the double crosslinking method may still have defects such as low hardness and high swelling rate. For example, Yan et al. successfully prepared arabinoxylan-soy protein isolate composite hydrogel using CaCl2 and peroxidase. When the concentrations of arabinoxylan and soy protein isolate were both 2.5wt%, the hardness of the double crosslinked composite hydrogel was only 25-37g (Food Hydrocolloids, 2020, 107, 105946). Qin et al. prepared a double crosslinked whey protein isolate-gellan gum composite emulsion gel using glucono δ-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 double crosslinked composite emulsion gel was only 123g (Food Chemistry, 2023, 404, 134513). Poor gel strength often cannot provide long-term protection for the embedded functional factors. In addition, low-strength gels are prone to swelling and disintegration during gastrointestinal digestion, making it difficult to achieve controlled release of functional factors. The successful preparation of double-crosslinked composite gels is closely related to factors such as the characteristics of the gel material, the type and formulation of the gelling agent, and the addition method.

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

[0007] [Technical issues]

[0008] The double cross-linked composite gel in the prior art has low strength and high swelling rate, and cannot provide long-term protection for the embedded functional factors. In addition, the low-strength gel is prone to swelling and disintegration during gastrointestinal digestion, making it difficult to achieve controlled release of the functional factors.

[0009] [Technical solution]

[0010] In order to solve the above problems, the purpose of the present invention is to provide a double cross-linked food gel loaded with functional factors and a preparation method thereof, specifically using protein, edible oil, κ-carrageenan, gellan gum, etc. as the main gel substrate, first using potassium ions to induce the formation of protein-κ-carrageenan or protein-gellan gum composite gel, and then immersing the composite gel in an acidic solution to induce the formation of a double cross-linked composite gel. This method can be used for the preparation of protein-κ-carrageenan or protein-gellan gum composite hydrogel and protein-κ-carrageenan or protein-gellan gum composite emulsion gel. The gel system prepared by the above method can form a food gel with high hardness and low swelling rate at a lower protein and polysaccharide concentration, can achieve co-encapsulation of hydrophilic and hydrophobic functional factors, significantly improve the stability of the embedded functional factors, and have a better controlled release effect.

[0011] In order to achieve the above purpose, the technical solutions provided are as follows:

[0012] The first object of the present invention is to provide a method for preparing a double cross-linked food gel, which comprises 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 6.0-10.0.

[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 3.0-5.5.

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

[0018] In one embodiment, the protein-κ-carrageenan or protein-gellan gum composite gel is prepared by placing the system after adding potassium ion solution at 2-4° C. overnight.

[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 a protein-κ-carrageenan aqueous solution 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 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 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 specific preparation of the double cross-linked food gel comprises the following steps:

[0028] (1) mixing a heat-denatured pea protein isolate solution and vegetable oil, subjecting the mixture to high-speed shearing and high-pressure homogenization to prepare an O / W emulsion, and adding a κ-carrageenan or gellan gum aqueous solution to obtain a pea protein isolate-κ-carrageenan or pea protein isolate-gellan gum composite emulsion;

[0029] (2) adding 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 a 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 the pea protein isolate solution at a pH of 6.0 to 8.0 and 80 to 95° C. for 30 to 60 minutes.

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

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

[0034] In one embodiment, the high-speed shearing condition in step (1) is: shearing at 8000-20000 rpm for 1-2 min; and the high-pressure homogenization condition is: homogenizing 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 to 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 immersion time is 6h to 48h.

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

[0038] (1) mixing a whey protein isolate fiber solution and a κ-carrageenan or gellan gum aqueous solution, and adding a KCl solution to form a composite hydrogel;

[0039] (2) Immersing the composite hydrogel obtained in step (1) in a GDL solution to form a double-crosslinked composite hydrogel, i.e., a double-crosslinked food gel.

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

[0041] The second object of the present invention is to provide a double cross-linked food gel prepared by the above method.

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

[0043] The third object of the present invention is to provide the application of the double cross-linked food gel described above in the food field.

[0044] The fourth object of the present invention is to provide a method for preparing a double-crosslinked food gel loaded with functional factors, the method comprising 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 a double-crosslinked food gel loaded with functional factors.

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

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

[0047] (1) mixing a protein solution containing functional factors and a vegetable oil containing functional factors, subjecting the mixture to high-speed shearing and high-pressure homogenization to prepare an O / W emulsion, and adding a κ-carrageenan or gellan gum aqueous solution to obtain a protein-κ-carrageenan composite emulsion or a protein-gellan gum composite emulsion;

[0048] (2) adding 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) Immersing the composite emulsion gel obtained in step (2) in a GDL solution to form a double-crosslinked food gel loaded with functional factors, i.e., a double-crosslinked emulsion gel loaded with functional factors.

[0050] In one embodiment, the protein solution containing functional factors in step (1) is specifically a protein solution in which functional factors are added.

[0051] In one embodiment, the vegetable oil containing functional factors in step (1) is specifically vegetable oil with functional factors added thereto.

[0052] In one embodiment, the functional factors include α-tocopherol, coenzyme Q 10 , polyunsaturated fatty acids, curcumin, and resveratrol.

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

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

[0055] (2) Immersing the composite hydrogel obtained in step (1) in a GDL solution to form a double-crosslinked composite hydrogel, i.e., a double-crosslinked food gel.

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

[0057] The fifth object of the present invention is to provide a double-crosslinked food gel loaded with functional factors obtained by the above preparation method.

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

[0059] The sixth object of the present invention is to provide an application of the above-mentioned double-crosslinked food gel loaded with functional factors in the preparation of functional factor delivery systems and yogurt, jelly, candy, and fat-reduced foods.

[0060] Beneficial effects:

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

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

[0063] (3) The hardness of the KCl / GDL double cross-linked whey protein isolate fiber-κ-carrageenan composite emulsion gel prepared by the method of the present invention reaches 3871.9 g; compared with the composite emulsion gel prepared by a single cross-linking agent KCl or GDL, the hardness of the KCl / GDL double cross-linked composite emulsion gel is increased by 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 hardness of the KCl / GDL double cross-linked whey protein isolate fiber-κ-carrageenan composite hydrogel prepared by the method of the present invention is as high as 7764.2 g. Compared with the composite hydrogel prepared by using a single cross-linking agent KCl or GDL, the hardness of the KCl / GDL double cross-linked composite hydrogel is increased by 2.0 to 28.9 times. The double cross-linked 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 The data of free fatty acid generation of KCl, GDL, CaCl2 single cross-linked pea protein isolate-κ-carrageenan composite emulsion gel and KCl / GDL double cross-linked 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 Schematic diagram of the preparation of KCl / GDL double cross-linked protein-κ-carrageenan composite gel;

[0067] Figure 3 The appearance of different pea protein isolate-polysaccharide composite emulsions after adding KCl; (A) polysaccharide concentration is 0.25%; (B) polysaccharide concentration is 0.5%;

[0068] Figure 4The graph is a graph showing the change of the retention rate of curcumin in the KCl and GDL single cross-linked and KCl / GDL double cross-linked whey protein isolate fiber-κ-carrageenan composite emulsion gel during storage at 25°C with storage time when the κ-carrageenan concentration is 0.25%;

[0069] Figure 5 The graph is a graph showing the change of the retention rate of α-tocopherol in the KCl and GDL single cross-linked and KCl / GDL double cross-linked whey protein isolate fiber-κ-carrageenan composite emulsion gel during storage at 25°C with storage time when the κ-carrageenan concentration is 0.25%;

[0070] Figure 6 Appearance of whey protein isolate fiber-κ-carrageenan composite hydrogel formed under different induction conditions at different κ-carrageenan concentrations; (A) KCl induction, no anthocyanin added; (B) GDL induction, no anthocyanin added; (C) KCl / GDL induction, no anthocyanin added; (D) KCl / GDL induction, anthocyanin added;

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

[0072] Figure 8 The swelling rate data of whey protein isolate fiber-κ-carrageenan composite hydrogel formed by single crosslinking of KCl and GDL and double crosslinking of KCl / GDL when the concentration of κ-carrageenan is 1.0%;

[0073] Fig. 9 The data graph is a graph showing the change of the retention rate of anthocyanins in the whey protein isolate fiber-κ-carrageenan composite hydrogel formed by single crosslinking of KCl and GDL and double crosslinking of KCl / GDL during storage at 4°C with storage time when the κ-carrageenan concentration is 1.0%;

[0074] Fig.10 This is a graph showing the release rate data of anthocyanins in whey protein isolate fiber-κ-carrageenan composite hydrogels formed by single crosslinking of KCl and GDL and double crosslinking of KCl / GDL during in vitro simulated gastrointestinal digestion when the κ-carrageenan concentration is 1.0%. DETAILED DESCRIPTION

[0075] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. The following specific implementation methods further describe the present invention.

[0076] The present invention relates to a testing method

[0077] 1. Gel hardness test method

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

[0079] 2. In vitro simulated gastrointestinal digestion experiment

[0080] The INFOGEST model was used to simulate the in vitro digestion of the emulsion gel. The specific method was as follows: the gel sample was ground about 30 times in a mortar, and simulated saliva (pH 7.0) was added to the gel sample at a mass ratio of 1:1, and incubated at 37°C for 3 minutes; the pH of the digestive fluid was adjusted to 3.0, and simulated gastric fluid (pH 3.0) was added to the digestive fluid at a mass ratio of 1:1, and incubated at 37°C for 2 hours; the pH of the digestive fluid was adjusted to 7.0, and simulated intestinal fluid (pH 7.0) was added to the digestive fluid at a mass ratio of 1:1, and incubated at 37°C for 2 or 4 hours. Among them, the simulated saliva includes 15.1mmol / L KCl, 13.6mmol / L NaCl, 3.7mmol / L KH2PO4, 0.15mmol / L MgCl2(H2O)6, and 1.5mmol / L CaCl2(H2O)2; the simulated gastric fluid includes 6.9mmol / L KCl, 72.2mmol / L NaCl, 0.9mmol / L KH2PO4, 0.12mmol / L MgCl2(H2O)6, 0.15mmol / L CaCl2(H2O)2 and 2000U / mL of pepsin; the simulated intestinal fluid includes 6.8mmol / L KCl, 123.4mmol / L NaCl, 0.8mmol / LKH2PO4, 0.33mmol / L MgCl2(H2O)6, 0.6mmol / L CaCl2(H2O)2, 10mmol / L bile salts and 100U / mL of pancreatic enzymes.

[0081] 3. Determination of free fatty acids

[0082] The pH-stat method was used to determine the amount of free fatty acids released during simulated intestinal digestion. The pH values ​​of the intestinal digestive fluid at different digestion times were tested, and NaOH solution was used to titrate the pH to maintain it at 7.0. The amount of free fatty acids released was calculated using the following formula (1):

[0083]

[0084] Where: V NaOH is the volume of sodium hydroxide consumed during titration (mL), C NaOH is the molar fraction of the sodium hydroxide solution used for titration (0.1 mol / L), M Lipid is the average molecular weight of sunflower oil (880 g / mol), W Lipid is the weight of lipids initially present in the reaction vessel (g), and it is assumed that two free fatty acids are generated per triglyceride molecule by the action of lipase.

[0085] 4. Determination of swelling rate

[0086] The gel sample was completely immersed in 10 mM phosphate buffer with a pH value of 7.0. The mass of the gel was weighed every 4 hours until there was no significant change in the mass of the gel. The swelling rate of the gel was calculated using formula (2):

[0087]

[0088] Where: 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 is crushed and the functional factors are extracted. The content of the functional factors in the gel is determined by ultraviolet spectrophotometry or high performance liquid chromatography, and the retention rate and cumulative release rate of the functional factors during storage or digestion are expressed by the following formula:

[0091]

[0092] Where: C T is the content of functional factors in the gel at the beginning of storage, C i It is the content of functional factors in the gel at different storage periods.

[0093]

[0094] Where: C I is the content of functional factors in the gel at the beginning of digestion, C i It is the content of functional factors in digestive juice at different digestion periods.

[0095] Example 1

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

[0097] (1) Solution preparation

[0098] Preparation of 5% (w / v, g / mL) pea protein isolate solution: pea protein isolate was added to deionized water, the pH was adjusted to 12.0, the solution pH was adjusted to 7.0 after stirring for 1 hour, and the solution was heated at 90° C. for 30 minutes and then cooled to room temperature to obtain a 5% (w / v, g / mL) pea protein isolate solution.

[0099] Prepare 3% (w / v, g / mL) κ-carrageenan solution: add κ-carrageenan into deionized water, stir at 55° C. for 1 hour to fully dissolve it, and obtain 3% (w / v, g / mL) κ-carrageenan solution.

[0100] Prepare 25% (w / v, g / mL) GDL solution: add GDL into deionized water and stir to fully dissolve it, so as to obtain 25% (w / v, g / mL) GDL solution.

[0101] Prepare 1 mol / L CaCl2 solution: Add CaCl2 into deionized water and stir to fully dissolve it to obtain 1 mol / L CaCl2 solution.

[0102] Prepare 1 mol / L KCl solution: Add KCl into deionized water and stir to fully dissolve it to obtain 1 mol / L KCl solution.

[0103] (2) Preparation of emulsion

[0104] A 5% (w / v, g / mL) pea protein isolate solution and sunflower seed oil were mixed in a mass ratio of 9:1, sheared at 10000 r / min for 2 minutes, and then homogenized 3 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., so that the final pea protein isolate-κ-carrageenan composite emulsion system contained 2.5% (w / v, g / mL) pea protein isolate, 10% (w / w) sunflower seed oil and κ-carrageenan with concentrations of 0%, 0.25%, 0.50%, 0.75%, 1.0%, and 1.5% (w / v, g / mL), respectively;

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

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

[0107] The hardness of gels 1 to 3 was measured using a full texture analyzer. The results are shown in Table 1:

[0108] Table 1 Hardness of GDL, CaCl2, and KCl single cross-linked pea protein-κ-carrageenan composite emulsion gel at different κ-carrageenan concentrations (g)

[0109]

[0110] Note: “—” indicates that 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] From the results in Table 1, it can be seen that as the concentration of κ-carrageenan gradually increases from 0.25% (w / v, g / mL) to 1.5% (w / v, g / mL), the hardness of the single-crosslinked composite emulsion gel induced by different cross-linking agents gradually increases. The hardness of the GDL composite emulsion gel increases from 171.1g to 1571.2g, the hardness of the CaCl2 composite emulsion gel increases from 43.8g to 1560.2g, and the hardness of the KCl composite emulsion gel increases from 56.2 to 1265.7g.

[0112] Example 2

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

[0114] Method 1:

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

[0116] Any two of the GDL solution, the CaCl2 solution and the KCl solution are added to the pea protein isolate-κ-carrageenan composite emulsion at a certain volume, and stored at 4°C overnight to form KCl-GDL double cross-linked pea protein isolate-κ-carrageenan composite emulsion gel; CaCl2-GDL double cross-linked pea protein isolate-κ-carrageenan composite emulsion gel; KCl-CaCl2 double cross-linked pea protein isolate-κ-carrageenan composite emulsion gel; wherein in the composite emulsion gel system, the concentration of GDL is 1% (w / v, g / mL), the concentration of CaCl2 is 40mmol / L, and the concentration of KCl is 20mmol / L.

[0117] Method 2:

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

[0119] Performance Testing

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

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

[0122]

[0123] Note: (1) “Like KCl / GDL” means that gelation is induced by KCl first and then by GDL; “KCl-GDL” means that gelation is induced by adding two cross-linking agents at the same time; “—” means that 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] It can be seen from the results in Table 2 that at the same κ-carrageenan concentration, different cross-linking agent combinations and addition methods significantly affect the hardness of the composite latex gel. Among them, in the range of κ-carrageenan concentration of 0.25% to 1.5%, the hardness of the KCl / GDL double-crosslinked composite latex gel is the highest. As the κ-carrageenan concentration increases from 0.25% to 1.5%, the hardness of the KCl / GDL double-crosslinked composite latex gel increases from 879.8g to 4813.0g, which is 3.8 to 15.6 times that of the KCl single-crosslinked composite latex gel, 2.3 to 5.1 times that of the GDL single-crosslinked composite latex gel, and 3.1 to 20.1 times that of the CaCl2 single-crosslinked composite latex gel.

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

[0127] Figure 1 The release of free fatty acids from composite emulsion gels prepared by different gelation methods during simulated gastrointestinal digestion in vitro. Figure 1 As shown in A, when the κ-carrageenan concentration was 0.25%, the fat release rate of the KCl / GDL double cross-linked composite emulsion gel after 240 minutes of simulated intestinal digestion in vitro was 26.7%, which was 10.8%, 7.6%, and 23.0% lower than that of the KCl, GDL, and CaCl2 single cross-linked composite emulsion gels, respectively. Figure 1 As shown in Figure B, when the κ-carrageenan concentration is 0.5%, the fat release rate of the KCl / GDL double cross-linked composite emulsion gel after 240 minutes of in vitro simulated intestinal digestion is 28.3%, which is 9.8%, 7.5%, and 16.7% lower than that of the KCl, GDL, and CaCl2 single cross-linked composite emulsion gels, respectively. The above results show that the composite emulsion gel prepared by the KCl / GDL double cross-linking method can effectively inhibit the rapid release of fatty acids in the early stage of digestion and achieve a sustained release effect.

[0128] In summary, if Figure 2 As shown, the preparation method of the KCl / GDL double cross-linked protein-κ-carrageenan composite gel is to firstly use potassium ions to induce the formation of protein-κ-carrageenan composite gel, and then immerse the composite gel in an acidic solution to form a double cross-linked composite gel.

[0129] Example 3

[0130] The preparation method of the KCl / GDL double cross-linked composite emulsion gel in method 2 of Example 2 is referred to, except that κ-carrageenan is replaced with gellan gum of the same concentration, and 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 gel hardness of the KCl / GDL double cross-linked pea protein isolate-gellan gum composite emulsion prepared in Example 3 was measured. The results are shown in Table 3:

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

[0135]

[0136] Note: 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).

[0137] As shown in Table 3, at the same gellan gum concentration, the hardness of the KCl / GDL double cross-linked composite emulsion gel is the highest, reaching 4269.8 g, which is 3.0 to 12.9 times that of the KCl single cross-linked composite emulsion gel and 2.2 to 3.4 times that of the GDL single cross-linked composite emulsion gel. The above results show that the preparation method of the KCl / GDL double cross-linked gel is also applicable to the pea protein isolate-gellan gum composite emulsion gel system.

[0138] Comparative Example 1

[0139] The preparation method of the KCl / GDL double-crosslinked composite emulsion gel in Method 2 of Example 2 was referred to, with the only difference being that κ-carrageenan was replaced with gum arabic, pectin, sodium alginate, pullulan, hydroxypropyl methylcellulose, xanthan gum, octenyl succinate starch, and chitosan of the same concentration, and the other parameters and conditions were the same.

[0140] like Figure 3 As shown in the figure, in the pea protein isolate-polysaccharide composite emulsion system, when the polysaccharide concentration is 0.25% to 0.5%, using any polysaccharide of gum arabic, pectin, sodium alginate, pullulan, hydroxypropyl methylcellulose, xanthan gum, octenyl succinate starch, and chitosan to replace κ-carrageenan, KCl could not be used to induce the formation of a self-supporting gel.

[0141] Example 4

[0142] The preparation method of the KCl / GDL double-crosslinked composite emulsion gel in method 2 of Example 2 was referred to, except that the pea protein isolate was replaced with casein, whey protein isolate, and soy protein isolate of the same concentration, respectively, and the other parameters and conditions were the same.

[0143] Performance Testing

[0144] 1. The gel hardness of the KCl / GDL double cross-linked protein-κ-carrageenan composite emulsion prepared in Example 4 was measured. The results are shown in Table 4-6:

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

[0146]

[0147] Note: 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).

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

[0149]

[0150] Note: 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).

[0151] Table 6 Hardness of soy protein isolate-κ-carrageenan composite emulsion gel induced by KCl, GDL, and KCl / GDL at different κ-carrageenan concentrations (g)

[0152]

[0153] Note: 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).

[0154] It can be seen from Tables 4-6 that at the same κ-carrageenan concentration, the hardness of the KCl / GDL double-crosslinked composite emulsion gel in different protein-κ-carrageenan composite emulsion gel systems is the highest. Among them, the maximum hardness of KCl / GDL double cross-linked casein-κ-carrageenan composite emulsion gel is 4431.8g, which is 4.5-20.4 times of KCl single cross-linked composite emulsion gel and 2.3-4.2 times of GDL single cross-linked composite emulsion gel; the maximum hardness of KCl / GDL double cross-linked whey protein isolate-κ-carrageenan composite emulsion gel is 4924.1g, which is 4.9-20.5 times of KCl single cross-linked composite emulsion gel and 3.5-5.9 times of GDL single cross-linked composite emulsion gel; the maximum hardness of KCl / GDL double cross-linked soy protein isolate-κ-carrageenan composite emulsion gel is 4621.2g, which is 3.8-14.1 times of KCl single cross-linked composite emulsion gel and 2.3-4.8 times of GDL single cross-linked composite emulsion gel. The above results show that the KCl / GDL double cross-linking 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 fiber-κ-carrageenan composite emulsion gel loaded with curcumin and α-tocopherol comprises the following steps:

[0157] (1) heating a 2% (w / v, g / mL) whey protein isolate solution at pH 2.0 and 90° C. with stirring for 6 hours, dialyzing for 72 hours using a dialysis bag with a molecular cutoff of 3500 Da, and adjusting the pH value to 7.0 to obtain a whey protein isolate fiber solution; dissolving curcumin in dimethyl sulfoxide, and adding the solution to the whey protein isolate fiber solution to prepare a whey protein isolate fiber-curcumin complex, wherein the concentration of curcumin is 100 μg / mL; and adding α-tocopherol to sunflower seed oil so that the concentration of α-tocopherol in the sunflower seed oil is 10% (w / w);

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

[0159] (3) adding KCl solution and GDL solution to the emulsion system in step (2) respectively, and storing them at 4° C. overnight to form KCl single cross-linked composite emulsion gel, wherein the final concentration of KCl is 20 mmol / L; and GDL single cross-linked composite emulsion gel, wherein the final concentration of GDL is 0.2% (w / v, g / mL);

[0160] (4) The KCl single cross-linked composite latex gel in step (3) was immersed in a 1% (w / v, g / mL) GDL solution for 6 h to form a KCl / GDL double cross-linked composite latex gel.

[0161] Performance measurement

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

[0163] Table 7 Hardness of whey protein isolate fiber-κ-carrageenan composite emulsion gel induced by KCl, GDL, and KCl / GDL at different κ-carrageenan concentrations (g)

[0164]

[0165] Note: “—” indicates that 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] It can be seen from Table 7 that at the same κ-carrageenan concentration, the hardness of the KCl / GDL double cross-linked composite emulsion gel is the highest, reaching 3871.9 g, which is 4.3 to 12.0 times that of the KCl single cross-linked composite emulsion gel and 3.3 to 5.7 times that of the GDL single cross-linked composite emulsion gel. The above results show that the preparation method of the KCl / GDL double cross-linked gel is also applicable to the whey protein isolate fiber-κ-carrageenan composite emulsion gel system.

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

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

[0169]

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

[0171] As shown in Table 8, the encapsulation rates of α-tocopherol and curcumin in the double-crosslinked composite emulsion gels with different κ-carrageenan concentrations were all above 98%, indicating that the double-crosslinked composite emulsion had good 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 change with storage time. Figure 4 As shown in the figure, after storage at 25°C for 14 days, the retention rate of curcumin in the KCl / GDL double cross-linked composite latex gel was 79.21%, and the retention rates of curcumin in the KCl and GDL single cross-linked composite latex gels were 38.94% and 59.42%, respectively. Figure 5 As shown in the figure, after 14 days of storage at 25°C, the retention rate of α-tocopherol in the KCl / GDL double cross-linked composite emulsion gel was 95.69%, which was 7.07% and 3% higher than that of the KCl or GDL single cross-linked composite emulsion gel, respectively. The above results show that the KCl / GDL double cross-linked composite emulsion gel can significantly improve the storage stability of α-tocopherol and curcumin.

[0173] Example 5

[0174] A method for preparing a proanthocyanidin-loaded whey protein isolate fiber-κ-carrageenan composite hydrogel comprises the following steps:

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

[0176] (2) adding KCl solution and GDL solution to the whey protein isolate fiber-κ-carrageenan solution in the above step (1), respectively, and storing at 4°C overnight to form KCl single cross-linked composite hydrogel, wherein the final concentration of KCl is 20 mmol / L; GDL single cross-linked composite hydrogel, wherein the final concentration of GDL is 0.35% (w / v, g / mL);

[0177] (3) The KCl single cross-linked composite hydrogel in the above step (2) was immersed in a 1% (w / v, g / mL) GDL solution for 6 h to form a KCl / GDL double cross-linked composite hydrogel.

[0178] Performance measurement

[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 of KCl, GDL, KCl / GDL whey protein isolate fiber-κ-carrageenan composite hydrogel at different κ-carrageenan concentrations (g)

[0181]

[0182] Note: “—” indicates that 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] From the results in Table 9, it can be seen that when the concentration of κ-carrageenan is 0.25% to 2.0%, the KCl / GDL double-crosslinked composite hydrogel has the highest hardness, 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 measurement

[0185] Figure 6 The appearance of different whey protein isolate fiber-κ-carrageenan composite hydrogels, A is KCl single cross-linked composite hydrogel, B is GDL single cross-linked composite hydrogel, C is KCl / GDL double cross-linked composite hydrogel, and D is KCl / GDL double cross-linked composite hydrogel loaded with anthocyanin. It can be seen from the results in the figure that except for the condition of κ-carrageenan concentration of 0.25%, GDL cannot induce the formation of composite hydrogels, while the others can form self-supporting composite hydrogels.

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

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

[0188] Fig. 9 The retention rate of proanthocyanidins in different composite hydrogels during storage at 4°C. Fig. 9As shown, after 14 days of storage, the retention rate of proanthocyanidins in the KCl / GDL double-crosslinked composite hydrogel was 63.84%, which was 25.38% and 18.31% higher than that of the KCl or GDL single-crosslinked composite hydrogel, respectively.

[0189] Fig.10 To simulate the release of proanthocyanidins from different composite hydrogels during gastrointestinal digestion in vitro. Fig.10 As shown in the data, in the in vitro simulated gastrointestinal digestion process, KCl / GDL double cross-linked composite hydrogel can effectively reduce the release rate and amount of proanthocyanidins in the simulated gastric digestion stage. The release amount is 38.69%, which is 40.62% and 31.66% lower than that of KCl or GDL single cross-linked composite hydrogel, respectively, indicating that KCl / GDL double cross-linked composite hydrogel can play a significant sustained-release role.

[0190] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a double cross-linked food gel, characterized in that: The preparation method comprises the following steps: adding potassium ion solution to a protein-κ-carrageenan or protein-gellan gum dispersion to prepare a composite gel of the protein-κ-carrageenan or protein-gellan gum, and then immersing the composite gel in an acidic solution to obtain a double cross-linked food gel.

2. The preparation method according to claim 1, characterized in that: The concentration of κ-carrageenan or gellan gum in the protein-κ-carrageenan or protein-gellan gum dispersion is 0.1% to 2.0%.

3. The preparation method according to claim 1, characterized in that: The potassium ion solution is one or more of KCl solution, K2SO4 solution, K2CO3 solution, and CH3COOK solution.

4. The preparation method according to claim 1, characterized in that: The acidic solution is one or more of a GDL solution, a citric acid solution, an acetic acid solution, and a hydrochloric acid solution.

5. The preparation method according to claim 1, characterized in that: The protein-κ-carrageenan or protein-gellan gum dispersion includes a protein-κ-carrageenan emulsion or a protein-gellan gum emulsion and a protein-κ-carrageenan aqueous solution or a protein-gellan gum aqueous solution.

6. Double cross-linked food gel obtained by the preparation method according to any one of claims 1 to 5.

7. Use of the double cross-linked food gel according to claim 6 in the food field.

8. A method for preparing a double-crosslinked food gel loaded with functional factors, characterized in that: The method comprises the steps of adding a potassium ion solution into 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, and then immersing the composite gel in an acidic solution to obtain a double-crosslinked food gel loaded with the functional factors.

9. The double-crosslinked food gel loaded with functional factors obtained by the preparation method according to claim 8.

10. Use of the double-crosslinked food gel loaded with functional factors according to claim 9 in the preparation of functional factor delivery systems and yogurt, jelly, candy, and fat-reducing foods.

Images