Preparation method and application of sodium alginate-cyperus esculentus protein / whey protein isolate dual-network gel

Abstract

The invention discloses a preparation method and application of sodium alginate-cyperus esculentus protein / whey protein isolate dual-network gel. The preparation method comprises the following steps: step 1, mixing cyperus esculentus protein, whey protein isolate and sodium alginate to prepare a compound; 2, gluconic acid-delta-lactone and calcium carbonate are added into the compound to promote gel formation, and the sodium alginate-cyperus esculentus protein / whey protein isolate composite gel subjected to acid-calcium coordinated induction is obtained. Compared with pure protein gel, the sodium alginate-cyperus esculentus protein / whey protein isolate composite gel has the advantages that the texture property, rheological property and the like of the composite gel are excellent, and the water binding capacity of the composite gel is superior to that of the pure protein gel. And the double networks have good encapsulation efficiency on curcumin, and have a better slow release effect.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of sodium alginate - tiger nut protein / isolated whey protein double - network gel, belonging to the field of food processing. Background Art

[0002] Tiger nut protein (TNP) is a protein extracted from tiger nuts. Research shows that tiger nut protein contains 18 kinds of amino acids, among which essential amino acids for humans account for 46.03%, greatly exceeding the WHO / FAO model specified value (36%) and being higher than soy protein (41.3%). It is a plant protein with high nutritional value and thus has extremely high industrial utilization value. Research shows that tiger nut protein has good emulsifying and foaming properties, but its gel properties need to be improved.

[0003] Sodium alginate is a natural anionic polysaccharide composed of 1,4 - linked α - L - guluronic acid (G - block) and β - D - mannuronic acid (M - block) residues. Sodium alginate can rapidly undergo electrostatic interaction with cations under mild conditions to form a highly tough gel with a "egg - box" - like structure. Adding sodium alginate to different protein systems can produce gel systems with different characteristic structures, and these systems have significant advantages such as good water - holding capacity and higher strength. Therefore, sodium alginate is widely used in high - protein foods to regulate the texture, structure and stability of gel - like products.

[0004] The delivery system of a single tiger nut protein - based gel is unstable to environmental stimuli during the processing and in vitro simulated digestion experiments, which to a certain extent limits its application. Based on proteins and polysaccharides, by regulating the interaction between the two polymers, the gelation mechanism and the formation conditions, a multi - scale and multi - gradient composite gel structure can be prepared, and this structure can overcome the defects of single - protein gels and form a more stable gel network. Summary of the Invention

[0005] The present invention aims to overcome the problems of low mechanical strength, poor water - holding capacity and too - fast release of bioactive components in a single tiger nut protein gel system. By constructing a sodium alginate - tiger nut protein / isolated whey protein double - network structure, the texture properties, water - holding capacity and sustained - release performance of the gel are optimized, providing an efficient and stable bioactive component delivery system for functional foods and pharmaceutical carriers.

[0006] Technical Solution

[0007] A preparation method of sodium alginate - tiger nut protein / isolated whey protein double - network gel, comprising the following steps:

[0008] 1) Prepare a composite protein solution of tiger nut protein and isolated whey protein;

[0009] 2) Heat the composite protein solution in a constant temperature water bath to obtain a pretreated composite protein solution;

[0010] 3) Add sodium alginate powder to the pretreated composite protein solution and mix evenly to obtain a polysaccharide-protein composite solution;

[0011] 4) Add calcium carbonate and glucono-δ-lactone to the polysaccharide-protein composite solution in sequence to form a double-network gel.

[0012] Further, in step 1, the tiger nut protein and the whey protein isolate are mixed at a mass ratio of 2:8, dissolved in deionized water, and stirred for 30 minutes to prepare a solution with a total protein concentration of 10%.

[0013] Further, the heating condition in step 2 is heating in a constant temperature water bath at 85 °C for 30 minutes.

[0014] Further, the addition amount of sodium alginate in step 3 is 0-0.3% of the total mass of the solution.

[0015] Further, in step 4, 20 mM calcium carbonate (CaCO3) and 1.2% (w / w) glucono-δ-lactone (GDL) are added to the polysaccharide-protein composite solution. After stirring and mixing for 5 minutes, it is left standing at 25 °C for 24 hours to form a gel.

[0016] Beneficial effects

[0017] In the present invention, a sodium alginate-tiger nut protein / whey protein isolate double-network gel is prepared by calcium acid induction. The microstructure, texture properties, rheological properties, water holding capacity, and encapsulation efficiency of curcumin of pure protein gels and composite gels with different mass ratios are characterized and analyzed. The effect of adding sodium alginate on the double network is explored, and the differences of composite gels with different mass ratios are analyzed, providing a theoretical basis for the application of tiger nut protein to prepare composite gels.

[0018] In the present invention, a sodium alginate-tiger nut protein / whey protein isolate double-network gel is prepared by calcium acid induction. Compared with pure protein gels, the composite gels have more excellent performances in terms of hardness, chewiness, water holding capacity, rheological properties, etc. The encapsulation efficiency of curcumin of the composite gels is also better than that of pure protein gels, and it can achieve slow release in gastrointestinal simulated digestion. Description of the drawings

[0019] The attached drawings of the present invention Figure 7 sheets, wherein:

[0020] Figure 1It is the gel texture characteristic diagram a (hardness); b (viscosity); c (elasticity); d (chewiness) provided in Example 2 of the present invention;

[0021] Figure 2 It is the water holding capacity diagram of the gel provided in Example 2 of the present invention;

[0022] Figure 3 It is the modulus diagram of the gel in Example 2 of the present invention a (storage modulus); b (loss modulus);

[0023] Figure 4 It is the apparent viscosity diagram of the gel provided in Example 2 of the present invention;

[0024] Figure 5 It is the gel microstructure diagram provided in Example 2 of the present invention;

[0025] Figure 6 It is the encapsulation efficiency of curcumin in the gel provided in Example 2 of the present invention;

[0026] Figure 7 It is the release rate of curcumin in the gel in gastrointestinal simulated digestion provided in Example 2 of the present invention; Detailed implementation manners

[0027] The present invention will be further described below by way of specific examples, but the implementation manners of the present invention are not limited thereto.

[0028] Example 1: Preparation method of double-network gel

[0029] 1) Prepare a composite protein solution of tigernut protein and whey protein isolate;

[0030] 2) Heat the composite protein solution in a constant temperature water bath to obtain a pretreated composite protein solution;

[0031] 3) Add sodium alginate powder to the pretreated composite protein solution and mix evenly to obtain a polysaccharide-protein composite solution;

[0032] 4) Add calcium carbonate and glucono-δ-lactone to the polysaccharide-protein composite solution in sequence to form a double-network gel.

[0033] Example 2: Preparation of double-network gel

[0034] The preparation of the gel in this example includes the following steps:

[0035] Step 1: Weigh 0.2 g of tigernut protein and 0.8 g of whey protein isolate, add them to 10 mL of deionized water, stir at 25 °C for 30 minutes, hydrate overnight at 4 °C to fully hydrate the protein; heat in a water bath at 85 °C for 30 minutes and cool to room temperature; add 20 mM calcium carbonate (CaCO3 ) and 1.2% (w / w) glucono-δ-lactone (GDL). After stirring and mixing evenly, it was left standing at 25 °C for 24 hours to obtain a gel sample denoted as 0.

[0036] Step 2: Weigh 0.2 g of Cyperus esculentus L. protein and 0.8 g of whey protein isolate and add them to 10 mL of deionized water. Stir at 25 °C for 30 minutes, and hydrate overnight at 4 °C to fully hydrate the protein; heat in a water bath at 85 °C for 30 minutes and cool to room temperature; add 0.005 g of sodium alginate to the solution and stir magnetically at 25 °C for 2 h; add 20 mM calcium carbonate (CaCO 3 ) and 1.2% (w / w) glucono-δ-lactone (GDL). After stirring and mixing evenly, it was left standing at 25 °C for 24 hours to obtain a gel sample denoted as 0.05.

[0037] Step 3: Weigh 0.2 g of Cyperus esculentus L. protein and 0.8 g of whey protein isolate and add them to 10 mL of deionized water. Stir at 25 °C for 30 minutes, and hydrate overnight at 4 °C to fully hydrate the protein; heat in a water bath at 85 °C for 30 minutes and cool to room temperature; add 0.01 g of sodium alginate to the solution and stir magnetically at 25 °C for 2 h; add 20 mM calcium carbonate (CaCO 3 ) and 1.2% (w / w) glucono-δ-lactone (GDL). After stirring and mixing evenly, it was left standing at 25 °C for 24 hours to obtain a gel sample denoted as 0.1.

[0038] Step 4: Weigh 0.2 g of Cyperus esculentus L. protein and 0.8 g of whey protein isolate and add them to 10 mL of deionized water. Stir at 25 °C for 30 minutes, and hydrate overnight at 4 °C to fully hydrate the protein; heat in a water bath at 85 °C for 30 minutes and cool to room temperature; add 0.015 g of sodium alginate to the solution and stir magnetically at 25 °C for 2 h; add 20 mM calcium carbonate (CaCO 3 ) and 1.2% (w / w) glucono-δ-lactone (GDL). After stirring and mixing evenly, it was left standing at 25 °C for 24 hours to obtain a gel sample denoted as 0.15.

[0039] Step 5: Weigh 0.2 g of Cyperus esculentus L. protein and 0.8 g of whey protein isolate and add them to 10 mL of deionized water. Stir at 25 °C for 30 minutes, and hydrate overnight at 4 °C to fully hydrate the protein; heat in a water bath at 85 °C for 30 minutes and cool to room temperature; add 0.02 g of sodium alginate to the solution and stir magnetically at 25 °C for 2 h; add 20 mM calcium carbonate (CaCO 3 ) and 1.2% (w / w) glucono-δ-lactone (GDL). After stirring and mixing evenly, it was left standing at 25 °C for 24 hours to obtain a gel sample denoted as 0.2.

[0040] Step 6: Weigh 0.2 g of Cyperus esculentus L. protein and 0.8 g of whey protein isolate and add them to 10 mL of deionized water. Stir at 25 °C for 30 minutes, and hydrate overnight at 4 °C to fully hydrate the protein; heat in a water bath at 85 °C for 30 minutes and cool to room temperature; add 0.025 g of sodium alginate to the solution and stir magnetically at 25 °C for 2 h; add 20 mM calcium carbonate (CaCO 3 ) and 1.2% (w / w) glucono-δ-lactone (GDL), stir and mix evenly, and then let stand at 25 °C for 24 hours to obtain a gel sample denoted as 0.25.

[0041] Step 7: Weigh 0.2 g of Cyperus esculentus L. protein and 0.8 g of whey protein isolate and add them to 10 mL of deionized water. Stir at 25 °C for 30 minutes, and hydrate overnight at 4 °C to fully hydrate the protein; heat in a water bath at 85 °C for 30 minutes and cool to room temperature; add 0.03 g of sodium alginate to the solution and stir magnetically at 25 °C for 2 h; add 20 mM calcium carbonate (CaCO 3 ) and 1.2% (w / w) glucono-δ-lactone (GDL), stir and mix evenly, and then let stand at 25 °C for 24 hours to obtain a gel sample denoted as 0.3.

[0042] Perform performance characterization and detailed description on the gel samples in the above steps. The specific results are as follows:

[0043] Texture properties and water-holding capacity test

[0044] Texture test: Use a texture analyzer (Brookfield CT3, TPA mode) to measure the hardness and chewiness of the gel. The test parameters are: probe diameter 5 mm, test speed 0.5 mm / s, load 4.0 g, test distance 3 mm.

[0045] The results show that the hardness of the 0.25% sodium alginate gel reaches 401.67 g and the chewiness is 6.09 mJ( Figure 1 a, 1d), which is significantly higher than the gel without added sodium alginate (hardness 232.00 g, chewiness 2.86 mJ);

[0046] Water-holding capacity test: Place the gel sample in a centrifuge tube (15 mL) with filter paper at the bottom, and then centrifuge at 6000 rpm for 10 minutes. Carefully suck out the water separated after centrifugation with a syringe and gently dry it with filter paper. Calculate WHC as the ratio of the remaining gel weight in the centrifuge tube to the initial gel weight. The calculation formula is as follows:

[0047] WHC = M 1 / M 2 × 100%

[0048] where M 1 = the mass of the gel after centrifugation; M2 = mass of the gel before centrifugation.

[0049] The WHC of 0.25% sodium alginate gel was 82.46% ( Figure 2 ), which was 16.9% higher than that of the gel without sodium alginate (70.50%).

[0050] Rheological property test

[0051] Frequency sweep: The test was carried out using a rheometer (DHR-1) at 25 °C and 1% strain.

[0052] Throughout the frequency range, G'>G” for all samples, and both G' and G” increased with the increase of frequency, indicating that the gel structure was mainly elastic. The storage modulus (G') of 0.25% sodium alginate gel reached 2850 Pa ( Figure 3 a), which was significantly higher than the loss modulus (G” = 210 Pa), indicating that the gel was dominated by an elastic network;

[0053] Shear rate sweep: The apparent viscosity of the samples was recorded in the range of 0.1 - 100 S-1.

[0054] All gel samples showed shear thinning properties, and the apparent viscosity decreased with the increase of shear rate. The addition of sodium alginate could enhance the shear thinning behavior of the composite gel, and with the increase of sodium alginate concentration, the apparent viscosity increased significantly in a concentration-dependent manner. As the sodium alginate concentration increased from 0.05% to 0.25%, the peak viscosity of the composite gel increased from 14134.9 Pa·s to 25301.4 Pa·s ( Figure 4 ), and the peak value of the gel apparent viscosity reached 25301.4 Pa·s, which was 78.9% higher than that of the gel without sodium alginate (14134.9 Pa·s);

[0055] Gel microstructure characterization

[0056] The prepared gel samples were cut into small pieces (10 mm×10 mm×5 mm), fixed with 2.5% (w / v) glutaraldehyde and freeze-dried. The freeze-dried samples were sputter-coated with gold using vacuum ion sputtering, and the microstructure of the gel samples was observed using a scanning electron microscope at 10 kV magnification of 100 times.

[0057] The gel without sodium alginate ( Figure 5 ): The microstructure showed a layered distribution, with large and irregular pores; the network cross-linking density was low and the structure was loose. The gel with 0.25% sodium alginate ( Figure 5):It presents a uniform honeycomb-like porous structure with significantly reduced pore size; the pore distribution is uniform, the network is dense and the fibers are interconnected to form a stable double-network crosslinking system. The addition of sodium alginate significantly improves the microstructure of the gel. By filling the pores of the protein network and forming a polysaccharide-protein double network, the mechanical strength and water-holding capacity of the gel are enhanced (Examples 2 and 3).

[0058] Curcumin loading and sustained-release performance

[0059] Determination of curcumin encapsulation efficiency: Disperse 1 g of the gel in 9 mL of absolute ethanol and extract by ultrasound for 20 minutes. After centrifugation (6000 rpm, 10 minutes), take the supernatant and measure the absorbance at 425 nm.

[0060] The encapsulation efficiency of the 0.25% sodium alginate gel is 92.17%( Figure 6 ), which is 15.5% higher than that of the single-protein gel (79.82%);

[0061] Gastrointestinal simulated digestion: The release rate was tested in simulated gastric juice (pH 2.5) and intestinal juice (pH 7.5). After 120 minutes of gastric digestion, the curcumin release rate was 25.44%; after 60 minutes of intestinal digestion, the release rate was 47.53%( Figure 7 ), which is significantly better than that of the single-protein gel.

[0062] The above results show that compared with the protein gel, the hardness, chewiness, water-holding capacity, and curcumin encapsulation efficiency of the double-network gel with added sodium alginate are significantly improved. The double-network gel with added sodium alginate has a stronger gel structure, and the increase in the concentration of sodium alginate can effectively enhance the characteristics of the double-network gel. It was observed by scanning electron microscopy that with the addition of sodium alginate, the pore size of the composite gel of the gel sample gradually decreased and the distribution became more uniform. The gastrointestinal simulated digestion experiment shows that the sodium alginate-protein double-network gel has a good protective effect on curcumin in the gastric simulation stage and can successfully achieve the sustained release of curcumin in the intestinal simulation stage. Therefore, the sodium alginate-separated whey protein / oleaster protein double-network gel can be used as an effective biomaterial for loading and sustained releasing bioactive components.

[0063] The above is the preferred embodiment of the present invention. The above-described embodiments are only the preferred specific embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. It should be pointed out that for those of ordinary skill in the art, without departing from the spirit and scope of the present invention, various changes and modifications can be made, and these changes and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a sodium alginate-Cyperus oleifera protein / isolated whey protein double network gel, characterized in that: The following steps are involved: 1) preparing a composite protein solution of cyperus oleifera protein and isolated whey protein; 2) heating the composite protein solution in a constant temperature water bath to obtain a pretreated composite protein solution; 3) adding sodium alginate powder to the pretreated composite protein solution and mixing them evenly to obtain a polysaccharide-protein composite solution; 4) adding calcium carbonate and glucono-δ-lactone to the polysaccharide-protein complex solution in sequence to form a double network gel.

2. The method for preparing the double network gel according to claim 1, characterized in that: Step 1) The cyperus oleifera protein and the isolated whey protein were mixed in a mass ratio of 2:8, dissolved in deionized water, and prepared into a solution with a total protein concentration of 10%.

3. The method for preparing the double network gel according to claim 1, characterized in that: The heating condition of step 2) is heating in a constant temperature water bath at 85°C for 30 minutes.

4. The method for preparing the double network gel according to claim 1, characterized in that: The amount of sodium alginate added in step 3) is 0-0.3% of the total mass of the solution.

5. The method for preparing the double network gel according to claim 1, characterized in that: In step 4), 20 mM calcium carbonate (CaCO3) and 1.2% (w / w) glucono-δ-lactone (GDL) were added, stirred and mixed evenly, and then allowed to stand at 25° C. for 24 hours to form a gel.

6. A sodium alginate-Cyperus oleifera protein / isolated whey protein double network gel, characterized in that: The double network gel is prepared according to the preparation method of any one of claims 1 to 5.

7. The use of a sodium alginate-jasper protein / isolated whey protein double network gel according to claim 6, characterized in that: Used to load biologically active ingredients.

8. The use according to claim 7, characterized in that: The double network gel achieves sustained release of curcumin during gastrointestinal digestion.

9. The application of sodium alginate-soybean protein / isolated whey protein double network gel prepared by the preparation method of claim 1 in loading curcumin, wherein the loading method comprises: Dissolving curcumin in anhydrous ethanol to prepare a curcumin solution with a concentration of 20 mg / mL; The prepared curcumin solution is added dropwise to the polysaccharide-protein complex solution in step 3) to make the final curcumin concentration in the mixed solution reach 100 μg / mL; then the mixture is placed on a magnetic stirrer in the dark at room temperature and continued to stir for 2 hours; the ethanol concentration in the final aggregate solution is ensured to be lower than 0.2% (v / v) by rotary evaporation; finally, CaCO3 with a concentration of 20 mM and GDL with a mass concentration of 1.2% are added to the mixed solution, mixed evenly, and allowed to stand at 25° C. for 24 hours to obtain a double network gel loaded with curcumin.

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