Casein-rutin gel for improving rutin bioaccessibility and preparation method thereof

Abstract

The invention discloses a casein-rutin gel and a preparation method thereof for improving the bioaccessibility of rutin, and belongs to the technical field of polyphenol gel materials. Its preparation method comprises the following steps: (1) preparing a binary composite solution with rutin and casein as raw materials, or preparing a ternary composite solution with rutin, inulin and casein as raw materials; (2) adding gluconolactone powder after defoaming the binary or ternary composite solution obtained in step (1), stirring, reacting, and obtaining. The present invention utilizes the interaction between casein, rutin and inulin to mask the antioxidant property of rutin, slows down the process of rutin being decomposed during digestion, and significantly improves the bioaccessibility of rutin; at the same time, the gel properties of casein are significantly improved by the interaction between casein, rutin and inulin, and the water holding rate, texture, microstructure and elastic rheology of the gel are improved, which provides a new idea for the application of rutin in functional foods.

Description

Technical Field

[0001] The invention relates to the technical field of polyphenol gel materials, and in particular to a casein-rutin gel capable of improving the bioaccessibility of rutin and a preparation method thereof. Background Art

[0002] Polyphenols are a class of secondary plant metabolites that are mainly found in fruits and vegetables and have multiple health benefits. Rutin, as a natural polyphenol widely found in nature, has multiple physiological functions such as antioxidant, antibacterial, anti-inflammatory, anti-cancer, hypoglycemic, hypolipidemic and capillary strengthening. However, due to its low water solubility, weak stability and limited membrane permeability, the bioavailability of rutin in the gastrointestinal tract is very limited, and the intake of rutin from natural food sources is low. Therefore, there is an urgent need for a method to improve the bioaccessibility of rutin.

[0003] The side chain groups of proteins can interact with the phenolic hydroxyl groups of polyphenols by forming hydrogen bonds, thereby improving the bioaccessibility of polyphenols. Although the interaction between polyphenols and proteins can improve the bioaccessibility of polyphenols, this interaction can also have certain negative effects. For example, the interaction between tea polyphenols and proteins can cause turbidity or even precipitation; tannins can interact with proteins to produce precipitation, and this negative effect can seriously affect the quality of the product.

[0004] How to use proteins and other substances to improve the bioaccessibility of rutin, improve the gel properties of protein while preparing gel, and ensure that the gel has excellent water holding capacity, texture, microstructure and elastic deformation behavior, is a key issue that needs to be urgently solved in improving the bioaccessibility of rutin through proteins and other substances. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a casein-rutin gel and a preparation method thereof for improving the bioaccessibility of rutin, so as to solve the problems that the existing rutin bioaccessibility is low and it is difficult to ensure excellent gel properties while improving the bioaccessibility of rutin.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] A method for preparing a casein-rutin gel for improving rutin accessibility comprises the following steps:

[0008] (1) preparing a binary composite solution using rutin and casein as raw materials;

[0009] (2) After defoaming the binary composite solution obtained in step (1), gluconolactone powder is added, stirred, and reacted to obtain the product.

[0010] The beneficial effects of the present invention are as follows: the present invention uses rutin and casein as raw materials, masks the antioxidant property of rutin through the interaction between casein and rutin, slows down the process of rutin being decomposed during digestion, and significantly improves the bioaccessibility of rutin; at the same time, the interaction between casein and rutin significantly improves the gel properties of casein, significantly improves the water holding rate, texture, microstructure and elastic rheological behavior of the prepared gel, and provides a new idea for the application of rutin in functional foods.

[0011] Furthermore, in step (1), the concentration of rutin in the binary composite solution is 0.3-0.6 mg / mL, and the concentration of casein is 20-40 mg / mL.

[0012] Preferably, in step (1), the concentration of rutin in the binary composite solution is 0.45 mg / mL, and the concentration of casein is 32.9 mg / mL.

[0013] Furthermore, in step (2), the amount of gluconolactone powder added is 1-5% of the mass fraction of the binary composite solution; the defoaming method is centrifugation at a speed of 800-1200 rpm for 30-90 s; the stirring time is 20-40 s, and the stirring speed is 400-800 rpm; the reaction temperature is 30-50°C, and the reaction time is 30-90 min.

[0014] Preferably, the amount of gluconolactone powder added in step (2) is 3% of the mass fraction of the binary composite solution; the defoaming method is centrifugation at a speed of 1000 rpm for 60 seconds; the stirring time is 30 seconds, and the stirring speed is 600 rpm; the reaction temperature is 40°C and the reaction time is 60 minutes.

[0015] A casein-rutin gel for improving the accessibility of rutin is prepared by adopting the above preparation method.

[0016] A method for preparing a casein-inulin-rutin gel for improving rutin accessibility comprises the following steps:

[0017] (A) preparing a ternary composite solution using rutin, inulin and casein as raw materials;

[0018] (B) after defoaming the ternary composite solution obtained in step (A), adding gluconolactone powder, stirring, reacting, and obtaining.

[0019] The beneficial effects of the present invention are as follows: the present invention uses rutin, inulin and casein as raw materials, masks the antioxidant property of rutin through the interaction among casein, rutin and inulin, slows down the decomposition of rutin during digestion, and significantly improves the bioaccessibility of rutin. Compared with the binary gel system obtained by combining casein and rutin, the bioaccessibility of rutin is further improved; at the same time, through the interaction among casein, rutin and inulin, the gel properties of casein are significantly improved, and by adjusting the order of adding casein, rutin and inulin, the water holding rate, hardness, adhesion and rheology of the gel are further improved.

[0020] Furthermore, the ternary composite solution in step (A) is prepared by any of the following methods:

[0021] Method 1: First, rutin is prepared into a rutin aqueous solution, then inulin is added to form a rutin-inulin aqueous solution, then a casein PBS solution is prepared, and finally the rutin-inulin aqueous solution and the casein PBS solution are mixed and vortexed to obtain;

[0022] Method 2: First, rutin is made into a rutin aqueous solution, then a casein PBS solution is prepared, then the rutin aqueous solution and the casein PBS solution are mixed and vortexed, and finally inulin is added and vortexed continuously to obtain;

[0023] Method three: first prepare rutin into a rutin aqueous solution, then prepare a casein PBS solution, then add inulin to the casein PBS solution and vortex, finally mix with the rutin aqueous solution and continue to vortex to obtain.

[0024] The beneficial effect of adopting the above-mentioned further technical scheme is as follows: the present invention prepares a ternary composite solution of rutin, inulin and casein by three different methods, and the gels prepared by the three methods all maintain good gel properties, among which the gel prepared by method one has the strongest gel property. In addition, by adjusting the preparation method, gels with different gel properties can be obtained to meet different usage requirements.

[0025] Furthermore, the ternary composite solution in step (A) is prepared by any of the following methods:

[0026] Method 1: first dissolve rutin in water, stir at 40-80°C and 400-800 rpm for 40-80 min to obtain a rutin aqueous solution; then add inulin and stir at 40-80°C and 400-800 rpm for 40-80 min to obtain a rutin-inulin aqueous solution; then dissolve casein in PBS, stir at 400-800 rpm for 1-3 h to obtain a casein PBS solution; finally, the rutin-inulin aqueous solution and the casein PBS solution are mixed at a volume ratio of 0.8-1.2:0.8-1.2 and vortexed for 1-3 h to obtain.

[0027] Method 2: First dissolve rutin in water, stir at 400-800 rpm for 40-80 min at 40-80°C to obtain a rutin aqueous solution; then dissolve casein in PBS, stir at 400-800 rpm for 1-3 h to obtain a casein PBS solution; then blend the rutin aqueous solution and the casein PBS solution at a volume ratio of 0.8-1.2:0.8-1.2 and vortex for 40-80 min; finally, add inulin and continue vortexing for 40-80 min to obtain.

[0028] Method three: The ternary composite solution in step (1) is prepared by the following method: firstly dissolving rutin in water, stirring at 400-800 rpm for 40-80 min at 40-80°C to obtain a rutin aqueous solution; then dissolving casein in PBS, stirring at 400-800 rpm for 1-3 h to obtain a casein PBS solution; then adding inulin to the casein PBS solution and vortexing for 40-80 min; finally, blending with the rutin aqueous solution at a volume ratio of 0.8-1.2:0.8-1.2 and vortexing for 40-80 min to obtain the obtained solution.

[0029] Preferably, method 1: first dissolve rutin in water, stir at 60°C and 600 rpm for 60 minutes to obtain a rutin aqueous solution; then add inulin and stir at 60°C and 600 rpm for 60 minutes to obtain a rutin-inulin aqueous solution; then dissolve casein in PBS, stir at 600 rpm for 2 hours to obtain a casein PBS solution; finally, the rutin-inulin aqueous solution and the casein PBS solution are mixed in a volume ratio of 1:1 and vortexed for 2 hours to obtain.

[0030] Preferably, method 2: first dissolve rutin in water, stir at 600 rpm for 60 minutes at 60°C to obtain a rutin aqueous solution; then dissolve casein in PBS, stir at 600 rpm for 2 hours to obtain a casein PBS solution; then blend the rutin aqueous solution and the casein PBS solution at a volume ratio of 1:1 and vortex for 60 minutes; finally, add inulin and continue vortexing for 60 minutes to obtain.

[0031] Preferably, method three: first dissolve rutin in water, stir at 60°C and 600 rpm for 60 minutes to obtain a rutin aqueous solution; then dissolve casein in PBS, stir at 600 rpm for 2 hours to obtain a casein PBS solution; then add inulin to the casein PBS solution and vortex for 60 minutes; finally, mix with the rutin aqueous solution at a volume ratio of 1:1 and vortex for 60 minutes to obtain.

[0032] Furthermore, in the ternary composite solution, the concentration of rutin is 0.3-0.6 mg / mL, the concentration of inulin is 0.3-0.6 mg / mL, and the concentration of casein is 20-40 mg / mL.

[0033] Preferably, the concentration of rutin in the ternary composite solution is 0.45 mg / mL, the concentration of inulin is 0.45 mg / mL, and the concentration of casein is 32.9 mg / mL.

[0034] Furthermore, heating and / or ultrasonic treatment is performed during the preparation of the casein solution, the heating temperature is 70-100° C., the time is 20-40 min, and the ultrasonic power is 60-100 W, and the time is 10-20 min.

[0035] The beneficial effect of adopting the above-mentioned further technical scheme is as follows: the present invention further improves the gel properties of the prepared gel by adding heating and ultrasonic processes during the preparation of the casein solution, wherein the gel prepared by mixing the rutin-inulin aqueous solution with the heated but non-ultrasonicated casein solution has better water holding capacity, hardness, adhesion, rheological properties, microstructure and rutin bioaccessibility.

[0036] Preferably, heating and / or ultrasonic treatment is performed during the preparation of the casein solution, the heating temperature is 80° C., the time is 30 min, and the ultrasonic power is 80 W, and the time is 15 min.

[0037] Furthermore, in step (2), the amount of gluconolactone powder added is 1-5% of the mass fraction of the ternary composite solution.

[0038] Preferably, the amount of gluconolactone powder added in step (2) is 3% of the mass fraction of the ternary composite solution.

[0039] Furthermore, in step (2), the defoaming method is centrifugal at a speed of 800-1200 rpm for 30-90 s; the stirring time is 20-40 s, and the stirring speed is 400-800 rpm; the reaction temperature is 30-50° C., and the reaction time is 30-90 min.

[0040] Preferably, the defoaming method in step (2) is centrifugation at a speed of 1000 rpm for 60 seconds; the stirring time is 30 seconds and the stirring speed is 600 rpm; the reaction temperature is 40° C. and the reaction time is 60 minutes.

[0041] A casein-inulin-rutin gel for improving the accessibility of rutin is prepared by adopting the above-mentioned preparation method.

[0042] The present invention has the following beneficial effects:

[0043] (1) The present invention effectively increases the solubility of rutin in water solvent by adding inulin, thereby improving the bioaccessibility of rutin.

[0044] (2) The present invention utilizes the interaction between casein, rutin and inulin to mask the antioxidant property of rutin, slowing down the decomposition of rutin during digestion, and significantly improving the bioaccessibility of rutin; at the same time, the interaction between casein, rutin and inulin significantly improves the gel properties of casein, improves the water holding capacity, texture, microstructure and elastic rheology of the gel, and provides a new idea for the application of rutin in functional foods. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a graph showing the experimental results of the effect of inulin on promoting the dissolution of rutin in water solvent in Experimental Example 1;

[0046] Figure 2 This is the result of the solution stability analysis in Experiment 2, where A is the particle size and B is the potential;

[0047] Figure 3 This is a diagram showing the analysis results of the antioxidant properties of the solution in Test Example 3;

[0048] Figure 4 is a graph of the rheological analysis results of the gel in Experimental Example 5, wherein A is the change of the storage modulus with shear strain, B is the change of the loss modulus with shear stress, C is the change of the storage modulus with angular frequency, and D is the change of the loss modulus with angular frequency;

[0049] Figure 5 is a microscopic structure diagram of the gel in Experimental Example 6;

[0050] Figure 6 is the Fourier transform infrared spectrum of the gel in Experimental Example 7;

[0051] Figure 7 The rutin content and bioaccessibility in the gel in Experimental Example 8, wherein A is the rutin content of the gel before and after digestion, and B is the bioaccessibility of rutin in the gel. DETAILED DESCRIPTION

[0052] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples are only used to explain the present invention and are not used to limit the scope of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0053] Embodiment 1:

[0054] A method for preparing casein-rutin gel comprises the following steps:

[0055] (1) Preparation of rutin aqueous solution

[0056] Rutin was dissolved in warm water at 60°C, and stirred at 60°C and 600 rpm for 1 h using a magnetic stirrer to obtain a rutin aqueous solution with a concentration of 0.9 mg / mL.

[0057] (2) Preparation of heated unsonicated casein PBS solution

[0058] Casein was dissolved in PBS buffer and stirred at 600 rpm for 2 h using a magnetic stirrer, and then heated at 90° C. for 30 min to obtain a heated, non-sonicated casein PBS solution with a concentration of 65.8 mg / mL.

[0059] (3) Preparation of binary composite solution

[0060] The rutin aqueous solution and the heated non-sonicated casein PBS solution were mixed in a volume ratio of 1:1 and vortexed for 2 h using a magnetic stirrer at 600 rpm to obtain a binary composite solution.

[0061] (4) Preparation of casein-rutin gel

[0062] The binary composite solution was centrifuged at 1000 rpm for 1 min to remove bubbles in the solution, and then gluconolactone powder was added to the solution at 3% of the solution mass and stirred for 30 s. The solution was reacted at 40°C for 1 h, and the pH value of the binary composite solution gradually decreased and finally stabilized at about 4.5 to obtain casein-rutin gel.

[0063] Embodiment 2:

[0064] A method for preparing casein-rutin gel comprises the following steps:

[0065] (1) Preparation of rutin aqueous solution

[0066] Rutin was dissolved in warm water at 60°C, and stirred at 60°C and 600 rpm for 1 h using a magnetic stirrer to obtain a rutin aqueous solution with a concentration of 0.9 mg / mL.

[0067] (2) Preparation of heated ultrasonic casein PBS solution

[0068] Casein was dissolved in PBS buffer and stirred at 600 rpm for 2 h using a magnetic stirrer, then heated at 90°C for 30 min, and then ultrasonicated at 80 W for 15 min to obtain a heated ultrasonic casein PBS solution with a concentration of 65.8 mg / mL.

[0069] (3) Preparation of binary composite solution

[0070] The rutin aqueous solution and the heated ultrasonic casein PBS solution were mixed in a volume ratio of 1:1 and vortexed for 2 h using a magnetic stirrer at 600 rpm to obtain a binary composite solution.

[0071] (4) Preparation of casein-rutin gel

[0072] The binary composite solution was centrifuged at 1000 rpm for 1 min to remove bubbles in the solution, and then gluconolactone powder was added to the solution at 3% of the solution mass and stirred for 30 s. The solution was reacted at 40°C for 1 h. The pH value of the binary composite solution gradually decreased and finally stabilized at about 4.5 to obtain casein-rutin gel.

[0073] Embodiment 3:

[0074] A method for preparing a casein-inulin-rutin gel for improving rutin accessibility comprises the following steps:

[0075] (1) Preparation of rutin-inulin aqueous solution

[0076] Dissolve rutin in warm water at 60°C and stir the solution with a magnetic stirrer at 60°C and 600 rpm for 1 hour to obtain a rutin aqueous solution with a concentration of 0.9 mg / mL. Then, add inulin in an amount equal to that of rutin and continue stirring with a magnetic stirrer under the same conditions for 1 hour to obtain a rutin-inulin aqueous solution.

[0077] (2) Preparation of heated unsonicated casein PBS solution

[0078] Casein was dissolved in PBS buffer and stirred at 600 rpm for 2 h using a magnetic stirrer, and then heated at 90° C. for 30 min to obtain a heated, non-sonicated casein PBS solution with a concentration of 65.8 mg / mL.

[0079] (3) Preparation of ternary composite solution

[0080] The rutin-inulin aqueous solution was mixed with the heated non-sonicated casein PBS solution in a volume ratio of 1:1 and vortexed at 600 rpm for 2 h to obtain a ternary composite solution.

[0081] (4) Preparation of casein-inulin-rutin gel

[0082] The ternary composite solution was centrifuged at 1000 rpm for 1 min to remove bubbles in the solution, and then gluconolactone powder was added to the solution at 3% of the solution mass and stirred for 30 s. The solution was reacted at 40°C for 1 h. The pH value of the ternary composite solution gradually decreased and finally stabilized at about 4.5 to obtain casein-inulin-rutin gel.

[0083] Embodiment 4:

[0084] A method for preparing a casein-inulin-rutin gel for improving rutin accessibility comprises the following steps:

[0085] (1) Preparation of rutin-inulin aqueous solution

[0086] Dissolve rutin in warm water at 60°C and stir the solution with a magnetic stirrer at 60°C and 600 rpm for 1 hour to obtain a rutin aqueous solution with a concentration of 0.9 mg / mL. Then, add inulin in an amount equal to that of rutin and continue stirring with a magnetic stirrer under the same conditions for 1 hour to obtain a rutin-inulin aqueous solution.

[0087] (2) Preparation of heated ultrasonic casein PBS solution

[0088] Casein was dissolved in PBS buffer and stirred at 600 rpm for 2 h using a magnetic stirrer, then heated at 90°C for 30 min, and then ultrasonicated at 80 W for 15 min to obtain a heated ultrasonic casein PBS solution with a concentration of 65.8 mg / mL.

[0089] (3) Preparation of ternary composite solution

[0090] The rutin-inulin aqueous solution and the heated ultrasonic casein PBS solution were mixed in a volume ratio of 1:1 and vortexed at 600 rpm for 2 h to obtain a ternary composite solution.

[0091] (4) Preparation of casein-inulin-rutin gel

[0092] The ternary composite solution was centrifuged at 1000 rpm for 1 min to remove bubbles in the solution, and then gluconolactone powder was added to the solution at 3% of the solution mass and stirred for 30 s. The solution was reacted at 40°C for 1 h. The pH value of the ternary composite solution gradually decreased and finally stabilized at about 4.5 to obtain casein-inulin-rutin gel.

[0093] Embodiment 5:

[0094] A method for preparing a casein-rutin gel for improving rutin accessibility comprises the following steps:

[0095] (1) Preparation of rutin aqueous solution

[0096] Rutin was dissolved in warm water at 60°C, and stirred at 60°C and 600 rpm for 1 h using a magnetic stirrer to obtain a rutin aqueous solution with a concentration of 0.9 mg / mL.

[0097] (2) Preparation of heated ultrasonic casein PBS solution

[0098] Casein was dissolved in PBS buffer and stirred at 600 rpm for 2 h using a magnetic stirrer, then heated at 90°C for 30 min, and then ultrasonicated at 80 W for 15 min to obtain a heated ultrasonic casein PBS solution with a concentration of 65.8 mg / mL.

[0099] (3) Preparation of ternary composite solution

[0100] The rutin-inulin aqueous solution was mixed with the heated ultrasonic casein PBS solution in a volume ratio of 1:1 and vortexed at 600 rpm for 1 h. After that, 0.45 mg of inulin was added per mL of solution, and vortexed at 600 rpm for another 1 h to obtain a ternary composite solution.

[0101] (4) Preparation of casein-inulin-rutin gel

[0102] The ternary composite solution was centrifuged at 1000 rpm for 1 min to remove bubbles in the solution, and then gluconolactone powder was added to the solution at 3% of the solution mass and stirred for 30 s. The solution was reacted at 40°C for 1 h. The pH value of the ternary composite solution gradually decreased and finally stabilized at about 4.5 to obtain casein-inulin-rutin gel.

[0103] Embodiment 6:

[0104] A method for preparing a casein-inulin-rutin gel for improving rutin accessibility comprises the following steps:

[0105] (1) Preparation of rutin aqueous solution

[0106] Rutin was dissolved in warm water at 60°C, and stirred at 60°C and 600 rpm for 1 h using a magnetic stirrer to obtain a rutin aqueous solution with a concentration of 0.9 mg / mL.

[0107] (2) Preparation of heated ultrasonic casein PBS solution

[0108] Casein was dissolved in PBS buffer and stirred at 600 rpm for 2 h using a magnetic stirrer, then heated at 90°C for 30 min, and then ultrasonicated at 80 W for 15 min to obtain a heated ultrasonic casein PBS solution with a concentration of 65.8 mg / mL.

[0109] (3) Preparation of ternary composite solution

[0110] 0.90 mg of inulin was added per mL to the heated ultrasonic casein PBS solution, and vortexed at 600 rpm for 1 h using a magnetic stirrer. It was then mixed with the rutin aqueous solution at a volume ratio of 1:1 and continued to vortex at 600 rpm for 1 h to obtain a ternary composite solution.

[0111] (4) Preparation of casein-inulin-rutin gel

[0112] The ternary composite solution was centrifuged at 1000 rpm for 1 min to remove bubbles in the solution, and then gluconolactone powder was added to the solution at 3% of the solution mass and stirred for 30 s. The solution was reacted at 40°C for 1 h. The pH value of the ternary composite solution gradually decreased and finally stabilized at about 4.5 to obtain casein-inulin-rutin gel.

[0113] Comparative Example 1:

[0114] A method for preparing casein gel comprises the following steps:

[0115] (1) Preparation of casein solution

[0116] Casein was dissolved in PBS buffer and stirred at 600 rpm for 2 h using a magnetic stirrer to obtain a 65.8 mg / mL casein solution.

[0117] (2) Preparation of casein gel

[0118] The casein solution was centrifuged at 1000 rpm for 1 min to remove bubbles in the solution, and gluconolactone powder was added to the solution at a ratio of 3% of the mass of the casein solution, stirred for 30 s, and reacted at 40°C for 1 h. The pH value of the casein solution gradually decreased and finally stabilized at about 4.5 to form a gel.

[0119] Comparative Example 2:

[0120] A method for preparing an acidic rutin turbid solution comprises the following steps:

[0121] (1) Preparation of rutin aqueous solution

[0122] Rutin was dissolved in warm water at 60°C, and stirred at 60°C and 600 rpm for 1 h using a magnetic stirrer to obtain a rutin aqueous solution with a concentration of 0.9 mg / mL.

[0123] (2) Preparation of acidic rutin turbid solution

[0124] After diluting the rutin aqueous solution by half, centrifuge at 1000 rpm for 1 min to remove bubbles in the solution, add gluconolactone powder to the solution at a ratio of 3% of the mass of the diluted rutin aqueous solution, stir for 30 s, and react at 40°C for 1 h. The pH value of the rutin aqueous solution gradually decreases and finally stabilizes at about 4.5, forming an acidic rutin turbid solution.

[0125] Comparative Example 3:

[0126] A method for preparing a rutin-inulin solution comprises the following steps:

[0127] Equal amounts of rutin and inulin were dissolved in water and stirred with a magnetic stirrer at 60°C and 600 rpm for 1 h to obtain a rutin-inulin solution with a solute mass ratio of 1:1. The concentrations of rutin and inulin in the solution were both 0.45 mg / mL.

[0128] Test Example 1: Effect of inulin on the dissolution of rutin in aqueous solvent

[0129] A rutin aqueous solution with a concentration of 0.45 mg / mL was prepared, and a certain amount of inulin was added thereto, and a rutin-inulin solution was prepared according to the mass ratio of rutin to inulin of 1:0, 1:0.2, 1:0.4, 1:0.6, 1:0.8, 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8 and 1:2. After the obtained rutin-inulin solution was centrifuged, the supernatant was mixed with a methanol solution with a mass fraction of 85% in a volume ratio of 2:3, ultrasonicated at 60°C and 60W for 60 minutes, and then centrifuged at 4000g for 15 minutes, and the supernatant was filtered through a 0.22μm filter membrane and measured by high performance liquid chromatography, with a detection wavelength of 360nm, a mobile phase of methanol-water (volume ratio of 65:35), a column temperature of 25°C, an injection volume of 10μL, and a flow rate of 1mL / min. Preparation of standard curve: dilute 10 mg of rutin standard to 10 mL with anhydrous ethanol, then take 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0 mL of rutin mother solution, make up with anhydrous ethanol, pass through the membrane and then test.

[0130] The experimental results are as follows Figure 1 shown.

[0131] Depend on Figure 1 It can be seen that the solubility of rutin in water solvent is very low. The addition of inulin can significantly increase the solubility of rutin in water solvent. When the mass ratio of rutin to inulin is 1:1, the solubility of rutin in water solvent reaches the maximum, which is twice the solubility of the group without inulin.

[0132] Test Example 2: Solution Stability

[0133] The particle size of the solution was analyzed using a Malvern particle size analyzer, and the binary composite solution and ternary composite solution prepared in Examples 1-6, as well as the casein solution prepared in Comparative Example 1 were characterized. The solution was centrifuged at 9000g for 20 minutes to remove insoluble matter, and then diluted to 1:100 with 0.1 mol / L PBS to avoid multiple scattering effects. Before use, the particle size pool was rinsed with ethanol, then with distilled water, and finally with the sample. 1 mL of the composite solution was placed in the particle size pool for measurement. The ζ-potential of the solution was analyzed using a Malvern laser particle size analyzer, and the sample was processed and the curved capillary sample pool was cleaned according to the method for measuring the particle size. 1 mL of the solution was placed in the curved capillary sample pool, and the refractive index of the dispersed phase was 1.33, the absorbance was 0.01, the relative dielectric constant was 78.58, the scattering angle was 12°, and the wavelength was 671 nm.

[0134] The experimental results are as follows Figure 2 shown.

[0135] Particle size is an important factor affecting the emulsification ability of proteins. Within a certain range, the smaller the particle size, the better the emulsification performance; the higher the absolute value of the potential, the better the stability of the system. Figure 2 As shown in Figure A, the particle sizes of all examples are significantly lower than those of comparative example 1, among which the particle size of example 5 is the smallest. Figure 2 As can be seen from Figure B, the absolute values ​​of the potentials of all embodiments are significantly greater than that of Comparative Example 1, but there are no significant differences between the embodiments.

[0136] Test Example 3: Analysis of Antioxidant Properties of Solutions

[0137] A DPPH solution with a concentration of 0.1 mol / L was prepared, and then the binary composite solution and the ternary composite solution prepared in Examples 1-6, the acidic rutin turbid solution prepared in Comparative Example 2, and the rutin-inulin solution prepared in Comparative Example 3 were used as experimental objects. 0.1 mL of the test solution was mixed with 3.9 mL of the DPPH solution, and the absorbance was measured at 517 nm after the mixture was allowed to stand for 30 minutes, which was called As. 0.1 mL of 0.1 mol / L PBS buffer with a pH of 7.4 was mixed with 3.9 mL of the DPPH solution as a blank control, and the absorbance was designated as A. 0 DPPH free radical scavenging rate = 1-As / A 0 ×100%.

[0138] The experimental results are as follows Figure 3 shown.

[0139] The phenolic hydroxyl groups of polyphenols can combine with the groups of protein side chains to form hydrogen bonds to form binary complexes. The phenolic hydroxyl groups of rutin are masked during the combination process, and the phenomenon of reduced antioxidant activity is called antioxidant shielding phenomenon. The antioxidant activity of Comparative Example 3 is significantly lower than that of Comparative Example 2, indicating that the combination of rutin and inulin can consume part of the phenolic hydroxyl groups of rutin, resulting in reduced antioxidant activity. The antioxidant activity of all embodiments is significantly lower than that of Comparative Examples 2 and 3, indicating that the embodiments of the present invention have stronger antioxidant shielding ability. Among the embodiments, Example 4 has the lowest antioxidant performance, followed by Example 3, which is reduced by 86.35% and 75.68% respectively compared with Comparative Example 2. Both preparation methods are that rutin is first combined with inulin and then mixed with a heated casein solution, indicating that this method has a stronger masking effect on rutin.

[0140] Test Example 4: Gel water holding capacity and texture analysis

[0141] The gels prepared in Examples 1-6 and Comparative Example 1 were used for experiments. A certain amount of sample gel was weighed into a 10 mL centrifuge tube and weighed as Ma. The centrifuge tube containing the gel was centrifuged at 4000 g for 15 min and then taken out and weighed as Mb. The water holding capacity of the gel = Mb / Ma×100%.

[0142] The experimental results are shown in Table 1.

[0143] Table 1 Water holding capacity and texture of gel

[0144]

[0145]

[0146] As can be seen from the results of Table 1, the water holding rates of all embodiments are significantly higher than those of Comparative Example 1, and there are significant differences between the embodiments, wherein the water holding rate of Embodiment 3 is the highest, 28.56% higher than that of Comparative Example 1; Embodiment 1 is second, 19.85% higher than that of Comparative Example 1, indicating that the combination of rutin or rutin-inulin with heated casein solution without ultrasound is more conducive to the formation of casein gel properties. The hardness and adhesion of all embodiments are also significantly higher than those of Comparative Example 1, and there are significant differences between the embodiments, wherein the hardness and adhesion of Embodiment 3 are the highest, and Embodiment 1 is second, 55% and 44% higher than the hardness of Comparative Example 1, respectively, and the adhesion is 2 times and 1.56 times higher than that of Comparative Example 1, respectively. Both groups are gels formed by heating casein without ultrasound and combining rutin or rutin-inulin, which are significantly higher than the heated ultrasound casein treatment group.

[0147] Test Example 5: Gel Rheology Analysis

[0148] The gels prepared in Examples 1-6 and Comparative Example 1 were used for experiments. A PP25 parallel plate was selected for the experiment. The gap between the plates was 1 mm and the plate was balanced at 25°C for 30 min. Strain amplitude scanning: The linear viscoelastic region of the gel sample was obtained by placing the gel sample on the rheometer. The scanning strain was 0.01-100%, the angular frequency was 1 rad / s, and the temperature was 25°C. Frequency scanning: The constant strain was 0.3%, and the measurement was carried out at an angular frequency of 0.1-100 rad / s to observe the storage modulus G′, loss modulus G″, and the difference between G′ and G″ of the sample. G′ and G″ represent the elastic modulus and viscous modulus, respectively.

[0149] The experimental results are as follows Figure 4 shown.

[0150] Depend on Figure 4 It can be seen that with the increase of angular frequency, the storage modulus G' and loss modulus G" of all embodiments are greater than those of comparative example 1, among which G' and G" of embodiment 3 present the largest values, followed by embodiment 4, and G' is always greater than G", indicating that the gels of embodiments 3 and 4 have better elastic rheological behavior.

[0151] Test Example 6: Gel Microstructure Analysis

[0152] The gels prepared in Examples 1-6 and Comparative Example 1 were tested. The gel samples were fixed with 10 mL of glutaraldehyde (mass fraction of 2.5%, solvent of 10 mmol / L PBS, pH = 6.8) for 24 h, and then washed with 0.1 mol / L PBS (pH = 6.8) for 3 times, each for 10 min. The gel samples were dehydrated 3 times in 50%, 70%, 80%, 90% and 100% ethanol by mass fraction, and washed for 10 min. After replacement with 100% ethanol: n-butanol (volume ratio of 1:1) and n-butanol for 15 min, they were dried in a freeze drying device for 48 h. The microstructure of the gel was determined by scanning electron microscopy, and the microstructure of the gel samples was observed at an accelerating voltage of 10 kV.

[0153] The experimental results are as follows Figure 5 shown.

[0154] Depend on Figure 5 It can be seen that compared with Comparative Example 1, the "macroporous" structures of Examples 1 and 2 are reduced and turned into "net" structures with a more compact structure; Example 3 changes from a "net" structure to a dense "surface" structure, with almost no pores visible and a denser structure; Examples 4 and 5 present dense "net" structures; The structure of Example 6 is similar to that of Comparative Example 1, both of which are in the shape of "holes".

[0155] Experimental Example 7: Gel Fourier Transform Infrared Spectroscopy and Secondary Structure Content Analysis

[0156] The gels prepared in Examples 1-6 and Comparative Example 1 were used for experiments. The gel samples were freeze-dried, 2 mg of gel powder and 200 mg of potassium bromide were weighed and ground evenly to form transparent sheets. The freeze-dried samples were scanned in transmission mode with a resolution of 4 cm -1 OMNIC 8.0 and PeakFit V 4.12 software were used to analyze the 4000-500cm -1 The infrared spectra were recorded and analyzed.

[0157] The experimental results are as follows Figure 6 And as shown in Table 2.

[0158] Table 2 Secondary structure content of gel

[0159]

[0160]

[0161] Depend on Figure 6 As shown in Figure B, compared with Comparative Example 1, all examples have a higher -1 The absorption peaks in the region all undergo red shift, and the hydrogen bonding effect is enhanced, among which Example 3 has the strongest hydrogen bonding effect, followed by Example 4. As can be seen from Table 2, the ordered structure content of all examples is higher than that of Comparative Example 1, among which Example 3 has the highest ordered structure content, which is 30.29% higher than that of Comparative Example 1, and Example 4 is the second, which is 20.69% higher than that of Comparative Example 1, significantly higher than other examples.

[0162] Experimental Example 8: Analysis of the bioaccessibility of rutin in gel

[0163] The acidic rutin turbid liquid obtained in Comparative Example 2 and the gels prepared in Examples 1-6 were used for experiments.

[0164] Preparation of gastric digestive juice: weigh 0.5 g NaCl, 1.75 mL HCl and 0.8 g pepsin and dissolve them in distilled water, make the volume to 250 mL, and adjust the pH of the gastric digestive juice to 1.20 with 0.1 mol / L hydrochloric acid solution.

[0165] Preparation of intestinal digestive juice: weigh 0.30 mol / L CaCl 2 , 30.72mmol / L NaCl, 5mg / mL bile salt and 8mg / mL pancreatic enzyme, make up to 250mL, and adjust the pH of the simulated intestinal digestive fluid to 7.00 with 1mol / L NaOH solution.

[0166] Weigh 4g of the sample to be tested and place it in a conical flask, add 10mL of simulated gastric digestion solution, adjust the pH to 2.00 with 0.5mol / L NaOH solution, and place the conical flask in a constant temperature water bath at 37℃, 110rpm for 2h. Cool in an ice water bath for 10min to terminate gastric digestion. Adjust the pH of the gastric digestion solution to 7.00 with 1mol / L NaOH, then add 20mL of simulated intestinal digestion solution and digest at 37℃, 370rpm for 2h, cool in an ice water bath for 10min to terminate intestinal digestion.

[0167] Extraction of rutin in gel sample before digestion: Weigh 4g gel and dissolve it in 30mL pure water, stir evenly. Mix the gel solution with methanol in a ratio of 1:2, sonicate at 60W, sonicate for 60min, sonicate at 60℃, centrifuge at 4000g for 15min after sonication, and take the supernatant as the solution before digestion.

[0168] Extraction of rutin after digestion: The digested solution was mixed with 85% methanol by mass in a volume ratio of 1:2, and the supernatant was extracted after ultrasonication and centrifugation.

[0169] The experimental results are as follows Figure 7 shown.

[0170] Depend on Figure 7 It can be seen that the rutin content in the gels of all examples before and after digestion is significantly higher than that of comparative example 2, among which the rutin content in the gels of example 3 before and after digestion is the highest, followed by example 4. The bioaccessibility of rutin in the gels of all examples is significantly higher than that of comparative example 2, among which the bioaccessibility of rutin in the gel of example 3 is the highest, which is 5.83 times higher than that of comparative example 2; example 4 is second, which is 5.14 times higher than that of comparative example 2. Both groups are the way in which rutin is first combined with inulin and then mixed with the heated casein solution, indicating that this method has a stronger protective effect on rutin and the bioaccessibility of rutin is higher.

[0171] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a casein-inulin-rutin gel for improving rutin accessibility, characterized in that: The following steps are involved: (A) preparing a ternary composite solution using rutin, inulin and casein as raw materials; (B) removing bubbles from the ternary composite solution obtained in step (A), adding gluconolactone powder, stirring, and reacting to obtain; Wherein, the ternary composite solution in step (A) is prepared by any of the following methods: Method 1: First, rutin is prepared into a rutin aqueous solution, then inulin is added to form a rutin-inulin aqueous solution, then a casein PBS solution is prepared, and finally the rutin-inulin aqueous solution and the casein PBS solution are mixed and vortexed to obtain; Method 2: First, rutin is made into a rutin aqueous solution, then a casein PBS solution is prepared, then the rutin aqueous solution and the casein PBS solution are mixed and vortexed, and finally inulin is added and vortexed continuously to obtain; Method 3: First, rutin is made into a rutin aqueous solution, then a casein PBS solution is prepared, then inulin is added to the casein PBS solution and vortexed, and finally mixed with the rutin aqueous solution and vortexed continuously to obtain; The concentration of rutin in the ternary composite solution is 0.3-0.6 mg / mL, the concentration of inulin is 0.3-0.6 mg / mL, and the concentration of casein is 20-40 mg / mL; In any one of the methods 1, 2 and 3, the casein PBS solution is heated and / or ultrasonically treated during preparation, the heating temperature is 70-100° C., the time is 20-40 min, and the ultrasonic power is 60-100 W, and the time is 10-20 min.

2. The method for preparing the casein-inulin-rutin gel for improving rutin accessibility according to claim 1, characterized in that: In the step (B), the added amount of gluconolactone powder is 1-5% of the mass fraction of the ternary composite solution; the defoaming method is centrifugation at a speed of 800-1200rpm for 30-90s; the stirring time is 20-40s, and the stirring speed is 400-800rpm; the reaction temperature is 30-50℃, and the reaction time is 30-90min.

3. A casein-inulin-rutin gel for improving rutin accessibility, characterized in that: The method is prepared according to claim 1 or 2.

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