An egg white protein-containing gel and preparation and use thereof

Abstract

This invention belongs to the field of food processing and protein gelation technology, specifically relating to an ovalbumin-containing gel and its preparation and application. The method involves gelling an ovalbumin-containing sample at 45℃~60℃ through the synergistic effect of acidic pH and salt ions, obtaining an ovalbumin-containing gel; wherein the salt ions are cations capable of forming solvent-sharing ion pairs with ovalbumin. Furthermore, by controlling the conditions, a transparent gel can be obtained. Under the synergistic effect of acidity and salt ions, ovalbumin can form a gel at a minimum temperature of 45℃, far lower than the traditional gelation temperature. This low-temperature condition significantly saves energy and avoids the damage to protein nutrition and flavor caused by high temperatures; furthermore, this invention applies low-temperature induced ovalbumin gelation technology to the rapid pickling of shell-bound eggs. The egg white is translucent and smooth, without an alkaline taste, and has a moderate salt content. By adjusting the pH and ion concentration of the pickling solution, the hardness, elasticity, and transparency of the egg white gel can be precisely controlled, achieving standardized production.

Description

Technical Field

[0001] This invention belongs to the field of food processing and protein gel technology, specifically relating to an ovalbumin-containing gel and its preparation and application. Background Technology

[0002] Ovalbumin (OVA) is the most abundant protein in egg white (approximately 54%). It has excellent gelling properties and is widely used in food gel products, fat substitutes, and nutrient delivery carriers. Traditional ovalbumin gels usually require heating at temperatures above 80°C to form a stable three-dimensional network structure. However, high-temperature gelation of OVA above 80°C usually leads to hardening of the egg white gel texture and loss of nutrients. The resulting gel network is coarse and uneven, mostly a stacked structure, and its gel appearance is white and opaque. Furthermore, high-temperature treatment can lead to the following problems: (1) the egg white gel texture is too hard, the taste deteriorates, and it loses its smoothness; (2) heat-sensitive nutrients are inactivated, reducing the nutritional value of the protein; (3) unpleasant flavors such as sulfur are produced during the heating process; (4) high energy consumption, which does not conform to the concept of green processing.

[0003] Current methods for preparing ovalbumin gels often employ alkali treatment, enzymatic cross-linking, or polysaccharide complexation, which can lower the gelation temperature of ovalbumin to some extent. For example, while alkali combined with salt pretreatment can form a gel at 72℃, the process is complex and leaves a residual alkaline taste. Furthermore, the heating process alters the protein structure, disrupting peptide bonds and causing protein hydrolysis. Additionally, the gel color darkens during gel formation, and the gel easily transitions to a sol, failing to maintain a stable gel morphology. While transglutaminase cross-linking can lower the gelation temperature, the enzyme is expensive, the reaction time is long, making it difficult to meet the requirements of clean labels, and the resulting gel has poor mechanical properties and often appears milky white. Acid induction is an important method for preparing functional gels. The acid-induced gelation process of proteins is basically completed in two steps. However, due to its complex operation, stringent process, and low production efficiency, the prepared gels have disadvantages such as low strength, lack of elasticity, and poor environmental tolerance, which limit its application in specific fields.

[0004] Salt ion-induced protein gelation typically requires two steps: first, heating the protein solution at a pH far from the protein's isoelectric point; then, after cooling, adding salt ions to induce gel formation. The addition of salt ions compresses the electric double layer of protein aggregates, neutralizes surface charge, and weakens electrostatic repulsion. Under van der Waals forces and hydrophobic interactions, protein molecules approach each other, macroscopically aggregating to form a gel. However, in complex solution environments, the lack of cross-linking sites in the protein network leads to a sparse gel network, making it prone to defects such as low mechanical strength, severe water separation, and poor environmental tolerance. Furthermore, even if the combined conditions induce ovalbumin to form a protein gel, the resulting gel has low transparency and a loose texture, failing to meet the requirements for high-quality appearance in food products.

[0005] Therefore, developing a method for ovalbumin gelation that requires no complex additives, is simple in process, has a low gelation temperature, maintains the nutritional value of ovalbumin, and achieves high transparency has significant industrial value. In view of this, the present invention is proposed. The present invention aims to achieve ovalbumin gelation under low-heat induction through a simpler process, and further achieve a highly transparent ovalbumin gel. Summary of the Invention

[0006] The present invention aims to provide an ovalbumin-containing gel, its preparation and application.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing ovalbumin gel involves gelling an ovalbumin-containing sample at 45℃~60℃ through the synergistic effect of acidic pH and salt ions to obtain an ovalbumin-containing gel; wherein the salt ions are cations that can form solvent-sharing ion pairs with ovalbumin.

[0008] Furthermore, in an acidic environment below the isoelectric point (pI 4.5) of ovalbumin and in the presence of salt ions, the ovalbumin-containing sample was gelled at 45℃~60℃ to obtain an ovalbumin-containing gel; wherein the final concentration of salt ions in the gelation system was 0.01 M~0.5 M.

[0009] The cation capable of forming a solvent-sharing ion pair with ovalbumin is a monovalent cation or a magnesium ion, wherein the monovalent cation is NH4+. + Na + K + .

[0010] To go further, a) Dissolve the ovalbumin-containing sample in an aqueous solution containing a salt of a cation that can form a solvent-sharing ion pair with ovalbumin, and adjust the pH of the solution to 1-4 to obtain an ovalbumin-containing solution; wherein the final mass concentration of ovalbumin in the ovalbumin-containing solution is 1%-10%, and the final cation concentration is 0.01 M-0.5 M; b) Heat the above ovalbumin-containing solution at 45℃~60℃ for 0.5~9 h until a gel is formed; c) Cool the resulting gel to room temperature to obtain a low-heat induced high-purity ovalbumin-containing gel.

[0011] The salt containing a cation capable of forming a solvent-sharing ion pair with ovalbumin is one or more of ammonium chloride, sodium chloride, potassium chloride, and magnesium chloride.

[0012] To go further, a) Dissolve the ovalbumin-containing sample in an aqueous solution containing a salt of a cation that can form a solvent-sharing ion pair with ovalbumin, and adjust the pH of the solution to 2-3 to obtain an ovalbumin-containing solution; wherein the final mass concentration of ovalbumin in the ovalbumin solution is 1%-10%, and the final cation concentration is 0.01 M-0.5 M. b) Heat the above protein solution at 45℃~60℃ for 0.5~9 h until a gel is formed; c) Cool the resulting gel to room temperature to obtain a low-temperature induced transparent ovalbumin-containing gel.

[0013] The sample containing ovalbumin is ovalbumin or egg white.

[0014] As mentioned above, when the sample is ovalbumin, a gel is formed. a) Dissolve ovalbumin in an aqueous solution containing a salt of a cation that can form a solvent-sharing ion pair with ovalbumin, and adjust the pH of the solution to 1-4 to obtain an ovalbumin solution; wherein the final mass concentration of ovalbumin in the ovalbumin solution is 2%-10%, and the final cation concentration is 0.01 M-0.5 M. b) Heat the above ovalbumin solution at 45℃~60℃ for 0.5~10 h until a gel is formed; c) Cool the resulting gel to room temperature to obtain a low-heat induced high-purity ovalbumin gel.

[0015] When the sample is ovalbumin, a clear gel is formed. a) Dissolve ovalbumin in an aqueous solution containing a salt of a cation that can form a solvent-sharing ion pair with ovalbumin, and adjust the pH of the solution to 2-3 to obtain an ovalbumin solution; wherein the final mass concentration of ovalbumin in the ovalbumin solution is 2%-10%, and the final cation concentration is 0.01 M-0.2 M. b) Heat the above protein solution at 45℃~60℃ for 0.5~10 h until a gel is formed; c) Cool the resulting gel to room temperature to obtain a low-temperature induced transparent ovalbumin gel.

[0016] As mentioned above, when the sample is egg white, a gel is formed. a) Add a salt solution containing cations that can form solvent-sharing ion pairs with ovalbumin to the egg white, and adjust the pH of the solution to 1-4; wherein the final mass concentration of ovalbumin in the egg white solution is 1%-8%, and the final cation concentration is 0.01 M-0.5 M; b) Heat the above egg white solution at 45℃~60℃ for 0.5~10 h until a gel is formed; c) Cool the resulting gel to room temperature to obtain a low-heat induced high-purity egg white gel.

[0017] When the sample is egg white, it forms a transparent gel. a) Add a salt solution containing cations that can form solvent-sharing ion pairs with ovalbumin to the egg white, and adjust the pH of the solution to 2-3; wherein, the final mass concentration of ovalbumin in the egg white solution is 2%-8%, and the final cation concentration is 0.01 M-0.2 M; b) Heat the above egg white solution at 45℃~60℃ for 0.5~10 h until a gel is formed; c) Cool the resulting gel to room temperature to obtain a high-purity transparent egg white gel with low heat induction.

[0018] An ovalbumin-containing gel is prepared by a method thereof, and a low-temperature ovalbumin-containing gel with uniform texture and good strength is prepared by the method thereof.

[0019] The method yields a smooth, highly transparent ovalbumin-containing gel.

[0020] An application of the ovalbumin-containing gel, specifically its application in food processing.

[0021] The application of the ovalbumin-containing gel in the preparation of low-heat or low-heat transparent egg white products includes, but is not limited to, egg white jelly, egg white pudding, egg white jelly, low-heat treated marinated egg white products, molecular gastronomy, and the application in encapsulating heat-sensitive nutrients or drugs.

[0022] Compared with the prior art, the present invention has the following significant advantages: 1. Under acidic pH conditions (such as below the isoelectric point of ovalbumin) and with the synergistic effect of salt ions of cations that can form solvent-sharing ion pairs with ovalbumin, ovalbumin can form a gel at a minimum temperature of 45°C, far below the traditional gelation temperature. This low-temperature condition significantly saves energy and avoids the damage to protein nutrition and flavor caused by high temperatures.

[0023] 2. This invention confirms that cations of different valence states, at appropriate concentrations, can synergistically interact with acidic pH levels below the isoelectric point of proteins, promoting the formation of gels from ovalbumin at 45°C to 60°C. This greatly expands the application scope and raw material selection flexibility of the method of this invention.

[0024] 3. This invention uses only food-grade acids and salts and does not introduce any non-natural ingredients, which complies with the concepts of clean labeling and green processing.

[0025] 4. This invention applies low-heat induced egg white protein gelation technology to the rapid pickling of shell-bound eggs. The egg white is translucent and smooth, without an alkaline taste, and has a moderate (adjustable) salt content. By adjusting the pH and ion concentration of the pickling solution, the hardness, elasticity, and transparency of the egg white gel can be precisely controlled, achieving standardized production. Attached Figure Description

[0026] Figure 1 The image shows the effect of self-extracted OVA powder in the example. In the image, A is OVA powder, B is SDS-PAGE gel electrophoresis, 1: self-extracted OVA in the example, 2: purchased OVA, M: Marker; C is the elution curve of self-extracted OVA in the protein purification system.

[0027] Figure 2 The images are of samples from Examples 2 and 3, and Comparative Examples 1 and 2.

[0028] Figure 3 Examples 2 and 3 (NH4) + Na + K + Mg 2+ Ca 2+ The stiffness (A) and water-holding capacity (B) of the induced ovalbumin gel.

[0029] Figure 4 Frequency scanning and differential scanning calorimetry results for Examples 2 and 4 (ovalbumin gels prepared by heating at 45°C, 50°C, 60°C, and 70°C).

[0030] Figure 5 Scanning electron microscope images of ovalbumin gels prepared by heating at 45°C, 50°C, 60°C, and 70°C in Examples 2 and 4.

[0031] Figure 6 A photograph of a low-temperature transparent ovalbumin gel (Example 5).

[0032] Figure 7 Examples 5 and 6 (NH4) + Na + K + Mg 2+ Ca 2+ Photograph of a sample of induced ovalbumin gel.

[0033] Figure 8 Examples 5 and 6 (NH4) + Na + K + Mg 2+ Ca 2+ The permeability of induced ovalbumin gel.

[0034] Figure 9 Examples 6 and Comparative Example 3 (K) + Mg 2+ Ca 2+ Scanning electron microscope images of induced ovalbumin gel and high-temperature opaque ovalbumin gel.

[0035] Figure 10 A photograph of a transparent egg white product (Example 7). Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the following detailed description of the invention is provided in conjunction with embodiments. Those skilled in the art will understand that the following embodiments are merely exemplary and not intended to limit the scope of the invention. Furthermore, in the following description, unless specific conditions are specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0037] Example 1 Egg white protein powder Separating egg whites: Use an egg separator to separate the egg whites from the yolks of fresh eggs and collect about 500 mL of egg white liquid. Use a glass rod to thoroughly beat the egg whites and mix them with twice the volume of distilled water. Stir magnetically at 4 ℃ for 2 hours to mix thoroughly (300 rpm / min).

[0038] Polyethylene glycol-8000 (PEG-8000) precipitation: After thoroughly mixing egg white and distilled water, the pH of the egg white mixture was adjusted to 6.0 with 1 mol / L HCl. 15% (w / w) PEG-8000 was added to the egg white solution, and the mixture was magnetically stirred at 4°C for 2 h to mix thoroughly, followed by precipitation for 30 min. The size exclusion effect of PEG-8000 on protein molecules precipitates some impurities. Due to its good hydrophilicity and relatively small molecular weight, ovalbumin can dissolve in the supernatant in the PEG-8000 solution, thus crudely separating it from other precipitated impurities. The supernatant was then centrifuged at 15000 g for 15 min at 4°C in a refrigerated centrifuge to obtain the supernatant of crude ovalbumin.

[0039] Isoelectric point precipitation: The isoelectric point of OVA is pI=4.5. NaCl was added to the collected supernatant to a final concentration of 0.1 mol / L. The pH of the supernatant was then adjusted to 4.5 using 1 mol / L HCl solution. After magnetic stirring at 4°C for 15 min, precipitation was allowed to occur for 30 min. The supernatant was discarded, and the precipitate was collected. The precipitate was resuspended in distilled water and dialyzed at 4°C for 48 h in a 20000 molecular weight dialysis bag to remove salts and PEG-8000. The precipitate was then lyophilized for 48 h for later use.

[0040] The OVA obtained after extraction and commercially available OVA were analyzed by electrophoresis. Both OVA powders were dissolved in deionized water, and after complete dissolution, 40 μL was added to 10 μL of denaturing electrophoresis loading buffer (4×), boiled for 6 min, and cooled to room temperature. A 4% stacking gel and a 10% separating gel were prepared using a gel electrophoresis kit, with a protein loading volume of 2 mg / mL. Sample purity was analyzed by SDS-PAGE gel electrophoresis. The voltages for the concentration and separation stages during electrophoresis were set to 100 mV and 120 mV, respectively. After electrophoresis, the gel was placed in fixative for 30 min to strengthen the gel, and then stained in staining solution for 30 min. Finally, the gel was eluted in destaining solution overnight (see [link to destaining solution]). Figure 1 ).

[0041] Depend on Figure 1 As can be seen, the OVA extraction method in this embodiment reduces extraction costs, simplifies the extraction process, and improves OVA purity. The OVA obtained after two-step precipitation extraction, dialysis for impurity removal, and freeze-drying is as follows: Figure 1 As shown in Figure A, it appears as a white powder, consistent with the appearance of commercially available OVA. The calculated yield is approximately 68%. Its purity was analyzed by SDS-PAGE gel electrophoresis. Figure 1As shown in Figure B, the OVA electrophoresis band obtained in the example is located in the same position as the sample OVA electrophoresis band, close to the 48 kDa molecular weight standard marker, consistent with the apparent molecular weight of OVA 44.5 kDa. Therefore, the OVA extracted in the example has high purity. Figure 1 As shown in C, the elution curve of OVA extracted by the protein purification system in the example is a single peak, which proves that the sample is a single component and that the OVA has not aggregated or degraded. The purity is close to 100% according to the formula.

[0042] Example 2 Preparation of low-temperature ovalbumin gel: a) Dissolve the ovalbumin powder obtained from the above examples in 0.05M NH4Cl aqueous solution to prepare a 5% (w / v) protein solution; b) Adjust the pH of the system solution to 3 using 1 M hydrochloric acid; c) Heat the solution in a 50°C water bath for 3 hours, then remove and cool in an ice bath to obtain an ovalbumin gel (see [link to original text]). Figure 2 , 3 4).

[0043] Example 3 Compared with Example 2, the difference is that NH4Cl was replaced with KCl, NaCl, and MgCl2 of equal concentration, respectively. All other dosages, process parameters, and steps were the same as in Example 2; meanwhile, NH4Cl was replaced with CaCl2 as a control (see [link to example 2]). Figure 2 , 3 ).

[0044] Example 4 Preparation of low-temperature ovalbumin gel: a) Dissolve the ovalbumin powder obtained from the above examples in 0.05M NH4Cl aqueous solution to prepare a 5% (w / v) protein solution; b) Adjust the pH of the system solution to 3 using 1 M hydrochloric acid; c) The solution was heated in water baths at different temperatures (45℃, 50℃, and 60℃) for 3 h, then removed and cooled in an ice bath to obtain ovalbumin gel; 70℃ was used as a control (see [link to control]). Figure 4 Or 5).

[0045] Comparative Example 1 Compared with Example 2, the difference is that no ions are added, while the other dosages, process parameters, and steps are the same as in Example 2 (see Example 2). Figure 2 ).

[0046] Comparative Example 2 Compared with Example 2, the difference is that the pH is 7, while the other dosages, process parameters, and steps are the same as in Example 2 (see Example 2). Figure 2 ).

[0047] Depend on Figure 2 Different ions (NH4+) can be seen in it. + K + Na + Mg 2+ Ca 2+ Visual images of ovalbumin gels induced under low-temperature conditions. All ions synergistically induce ovalbumin gel formation in an acidic environment, but monovalent ions and Mg... 2+ The gel formed in the presence of Ca is translucent, while Ca... 2+ The induced gel was completely opaque and milky white. Gel formation failed to occur in environments lacking ions or with pH outside the specified range, indicating that under low-temperature conditions, the formation and quality of OVA gels are jointly determined by pH and ions. First, an acidic environment below the isoelectric point imparts a net positive charge to the OVA molecules, keeping them in a soluble, moderately extended conformation. This is a fundamental prerequisite for the subsequent orderly assembly of OVAs while avoiding excessive aggregation. Within this framework, appropriate ions act as key regulators, providing an environment for more uniform and complete unfolding of the OVA molecules.

[0048] The gels prepared in Examples 2-4 and Comparative Examples 1-2 were then tested. 1) Hardness test Each gel sample was prepared into a 15 mm high cylinder. Before measuring gel hardness, the cooled samples were allowed to equilibrate at room temperature for 30 min. Hardness was measured using a texture analyzer equipped with a P / 12.7 cylindrical probe in TPA mode. The measurement parameters were: pre-measurement speed 1 mm / s, test speed 0.5 mm / s, post-measurement speed 1 mm / s, compression ratio 25%, and contact force 5 g. The test was repeated three times (see [reference]). Figure 3 A).

[0049] The results are as follows Figure 3 As shown in Figure A, the hardness of the ovalbumin gel products induced by different ions varies. Among them, NH4... + The induced gel has the highest stiffness, followed by K. + Na + and Mg 2+ And Ca 2+ The induced gel was relatively weak. Overall, divalent cations exhibited a stronger electrostatic shielding effect than the optimal monovalent cations, limiting the unfolding and ordered rearrangement of ovalbumin molecules. From the microscopic model of ion-protein interaction, monovalent cations (NH4+) showed a stronger effect. + K+ Na + ) and Mg 2+ It can electrostatically interact with ovalbumin molecules in the form of "solvent-shared ion pairs," meaning that a layer of water molecules acts as a bridge between the ion and the negatively charged groups of the protein, rather than direct binding. This indirect and mild interaction mode provides moderate electrostatic shielding, promoting the orderly unfolding of ovalbumin while avoiding excessive cross-linking and disordered aggregation. In contrast, Ca... 2+ It tends to form "contact ion pairs," that is, it directly binds to protein surface groups; therefore, Ca... 2+ The disturbance to the protein hydration layer is more pronounced. Simultaneously, excessive electrostatic shielding leads to an excessive weakening of intermolecular electrostatic repulsion, causing ovalbumin to undergo uncontrolled hydrophobic aggregation before it has fully unfolded during heating. This hinders the effective formation of electrostatic crosslinks and disulfide bonds, ultimately resulting in a fragile gel structure.

[0050] 2) Water holding capacity measurement Accurately weigh 1 g of each gel sample and place it in a 50 ml centrifuge tube. Centrifuge at 6000 rpm for 20 min. Wipe off the water that has separated from the gel surface during centrifugation and weigh the remaining gel. Calculate the water-holding capacity of the sample based on the difference in mass before and after centrifugation (see [reference]). Figure 3 B).

[0051] The results are as follows Figure 3 As shown in Figure B, the water-holding capacity results exhibit a similar trend to the hardness results: the water-holding capacity of ovalbumin gels induced by monovalent cations is significantly higher than that of gels induced by divalent cations. From a mechanical property perspective, ovalbumin gels induced by monovalent cations have higher hardness, indicating that their network structure is more compact and ordered. This dense network can more effectively retain water through capillary action and resist the extrusion of water by external forces during centrifugation, thus resulting in a significantly higher water-holding capacity than that induced by Ca. 2+ Induced loose gel network. Notably, in divalent cations, Mg... 2+ The induced gel water-holding capacity (67.3±1.7%) was lower than that of monovalent cations, but still slightly higher than that of Ca. 2+ (65.7±2.6%). This difference can be explained by the effect of ions on the degree of protein unfolding. Mg 2+ Although it is also a divalent cation, its electrostatic shielding strength is between that of Ca. 2+ The inhibitory effect on OVA development between monovalent cations and Ca is greater. 2+ The Mg is weak, therefore it retains relatively more exposed hydrophilic groups, making Mg 2+ The induced gel is slightly better than Ca in terms of water retention capacity. 2+ Induced gel.

[0052] As can be seen from the above, under the acidic pH and low-temperature conditions described in this invention, all cations can induce ovalbumin to form a self-supporting gel, and the hardness and water-holding capacity of the gel vary depending on the type of ion. Generally speaking, monovalent cations and Mg... 2+ The induced gel exhibits superior mechanical properties, while Ca... 2+ The induced gel properties were relatively low. This indicates that cations capable of forming solvent-sharing ion pairs with ovalbumin—including monovalent cations (NH4+)—are more likely to be involved. + K + Na + ) and Mg 2 + —The moderate electrostatic shielding provided, combined with the acidic environment and low-temperature conditions, is more conducive to the orderly unfolding of ovalbumin and the formation of a three-dimensional network structure, thereby obtaining a high-strength, low-temperature ovalbumin gel.

[0053] 3) Rheological testing Before determining the rheological properties of each gel, the cooled samples were equilibrated at room temperature for 30 min. Frequency scanning of the gel samples was performed using a rheometer equipped with a 35 mm parallel plate, ranging from 1 to 10 Hz, with the strain fixed at 1%. The results are as follows: Figure 4 As shown in Figure A, the gels formed at various temperatures all exhibited stable network structures, and the storage modulus increased with increasing heating temperature, indicating that the gel strength is temperature-dependent. Notably, under the combined induction of acid and ions, OVA can successfully gel at a minimum temperature of 45°C, which significantly reduces the temperature of OVA heat-induced gelation, thus promoting protein structure stability and alleviating protein denaturation.

[0054] 4) Differential scanning calorimetry Small amounts of each gel were sealed in a dedicated aluminum crucible, with an empty crucible serving as a control. The aluminum crucible lids were tightened and perforated before being placed in a simultaneous thermal analyzer for testing. Heating was performed from 25 °C to 200 °C at a rate of 10 °C / min, with a nitrogen flow rate of 50 mL / min. Results are as follows: Figure 4 As shown in Figure B, the thermal denaturation temperature of the OVA gel gradually increased from 72.92℃ to 81.73℃ as the temperature decreased from 70℃ to 50℃. This indicates that lowering the temperature helps improve the thermal stability of the ovalbumin gel. The gel formed at 45℃ had a thermal denaturation temperature slightly lower than 50℃, which may be related to its longer processing time. The results suggest that appropriately lowering the heating temperature can prevent excessively rapid denaturation of OVA, which may contribute to more ordered and stable self-assembly of protein molecules, thereby improving the thermal stability of the gel network.

[0055] 5) Microscopic morphology observation The prepared gel samples were pre-frozen in liquid nitrogen and then freeze-dried in a vacuum freeze dryer. The freeze-dried samples were then sputter-coated with gold, and the microstructure of the hydrogels was observed using a scanning electron microscope. The results of ovalbumin gelation at different temperatures are shown below. Figure 5 As shown, ovalbumin gels formed at 45–60°C exhibit sheet-like characteristics and are highly ordered. However, as the temperature rises to 70°C, the high temperature alters the gel formation pattern. Excessive hydrophobic drive and covalent cross-linking disrupt the force balance, causing the gelation mode to change from ordered, slow assembly to disordered, rapid aggregation, resulting in a honeycomb-like porous structure.

[0056] Example 5 Preparation of clear ovalbumin gel: a) Dissolve the ovalbumin powder obtained in Example 1 in 0.05M NH4Cl aqueous solution to prepare a 5% (w / v) protein solution.

[0057] b) Adjust the pH of the solution to 2 using 1 M hydrochloric acid.

[0058] c) Heat the solution in a 60°C water bath for 0.5 h, then remove and cool in an ice bath to obtain a clear ovalbumin gel (see [link to original text]). Figure 6 , 7 8).

[0059] Example 6 Compared with Example 5, the difference is that NH4Cl was replaced with KCl, NaCl, and MgCl2 of equal concentration, respectively. All other dosages, process parameters, and steps were the same as in Example 5; NH4Cl was replaced with CaCl2 as a control (see [link to example 5]). Figure 7 , 8 、9).

[0060] The actual product of low-temperature transparent ovalbumin gel is as follows: Figure 6 As can be seen, the gel has high transparency, and the grid in the background can be clearly seen through the gel. Figure 6 For different ions (NH4) + K + Na + Mg 2+ Ca 2+ Visual images of NH4-induced clear ovalbumin gels, showing the presence of NH4. + K + Na + and Mg 2+ The induced gels all exhibited high transparency, but there were some differences in transparency between different ions, ranging from 60% to 80%. In comparison, Ca... 2+ The induced gel cannot be transparent; it can only be a milky white gel.

[0061] Comparative Example 3 Preparation of conventional high-temperature ovalbumin gel: a) Dissolve the ovalbumin powder in phosphate buffer (0.05 M, pH 7) to prepare a 5% (w / v) protein solution.

[0062] b) Heat the solution in a 90°C water bath for 0.5 h, then remove and cool in an ice bath to obtain an opaque ovalbumin gel (see [link to original text]). Figure 9 ).

[0063] Then, the different gels prepared in Examples 5-6 and Comparative Example 3 were tested. 1) Light transmittance test Each gel sample was prepared in a disposable plastic cuvette, which was then placed in a cuvette with an optical path length of 1 cm. The transmittance of the samples was measured at 600 nm using a UV spectrophotometer. The results are as follows: Figure 8 As shown, different ions not only affect the stiffness of ovalbumin gels, but also exhibit differentiated effects on light transmittance. NH4+ + and K + The induced ovalbumin gel exhibited high transmittance, approaching 80%, and Mg... 2+ Its light transmittance is as high as 60%; while Ca 2+ It has the lowest light transmittance, almost completely opaque. This result is consistent with... Figure 7 The visual observations are highly consistent.

[0064] 2) Microscopic morphological observation The prepared gel samples were pre-frozen in liquid nitrogen and then freeze-dried in a vacuum freeze dryer. The freeze-dried samples were then sputter-coated with gold, and the microstructure of the hydrogels was observed using a scanning electron microscope. Results of different ion-induced transparent ovalbumin gels and conventional high-temperature gels are shown below. Figure 9 As shown, the transparent ovalbumin gel network exhibits a channel-like layered structure, which facilitates light transmission. Among them, K... + The induced gel network has the smoothest surface. In contrast, the ovalbumin gel formed by conventional high-temperature heating has a stacked structure and lacks an ordered lamellar arrangement, which is the main reason for its opacity.

[0065] Example 7 Preparation of transparent egg white gel: a) After homogenizing the fresh egg whites, add 0.5 M NH4Cl solution and stir to dissolve.

[0066] b) Adjust the pH of the solution to 3 using 1 M hydrochloric acid.

[0067] c) Heat the solution in a 50°C water bath for 0.5 h, then remove and cool in an ice bath to obtain a transparent egg white gel (see [link]). Figure 10 ).

[0068] Depend on Figure 10 As can be seen, after low-heat treatment, egg products with fully gelled egg white and high transparency can be obtained. This transparent egg white gel is uniformly pale yellow, free of bubbles and flocculent matter, with a smooth and uniform surface, excellent light transmittance, and the yolk inside is clearly visible.

Claims

1. A method for preparing an ovalbumin-containing gel, characterized in that: By leveraging the synergistic effect of acidic pH and salt ions, ovalbumin-containing samples are gelled at 45℃~60℃ to obtain ovalbumin-containing gels; wherein, the salt ions are cations that can form solvent-sharing ion pairs with ovalbumin.

2. The method for preparing ovalbumin-containing gel according to claim 1, characterized in that: In an acidic environment below the isoelectric point (pI 4.5) of ovalbumin, and in the presence of salt ions, the ovalbumin-containing sample was gelled at 45℃~60℃ to obtain an ovalbumin-containing gel; wherein the final concentration of salt ions in the gelation system was 0.01 M~0.5 M.

3. The method for preparing ovalbumin-containing gel according to claim 1 or 2, characterized in that: The cation capable of forming a solvent sharing ion pair with ovalbumin is a monovalent cation or a magnesium ion, wherein the monovalent cation is NH4 + , Na + , K + .

4. The method for preparing ovalbumin-containing gel according to any one of claims 1-3, characterized in that: a) Dissolve the ovalbumin-containing sample in an aqueous solution containing a salt of a cation that can form a solvent-sharing ion pair with ovalbumin, and adjust the pH of the solution to 1-4 to obtain an ovalbumin-containing solution; wherein the final mass concentration of ovalbumin in the ovalbumin-containing solution is 1%-10%, and the final cation concentration is 0.01 M-0.5 M; b) Heat the above ovalbumin-containing solution at 45℃~60℃ for 0.5~9 h until a gel is formed; c) Cool the resulting gel to room temperature to obtain a low-heat induced high-purity ovalbumin-containing gel.

5. The method for preparing ovalbumin-containing gel according to claim 4, characterized in that: The salt containing a cation capable of forming a solvent-sharing ion pair with ovalbumin is one or more of ammonium chloride, sodium chloride, potassium chloride, and magnesium chloride.

6. The method for preparing ovalbumin-containing gel according to claim 4, characterized in that: a) Dissolve the ovalbumin-containing sample in an aqueous solution containing a salt of a cation that can form a solvent-sharing ion pair with ovalbumin, and adjust the pH of the solution to 2-3 to obtain an ovalbumin-containing solution; wherein the final mass concentration of ovalbumin in the ovalbumin solution is 1%-10%, and the final cation concentration is 0.01 M-0.5 M. b) Heat the above protein solution at 45℃~60℃ for 0.5~9 h until a gel is formed; c) Cool the resulting gel to room temperature to obtain a low-temperature induced transparent ovalbumin-containing gel.

7. The method for preparing ovalbumin-containing gel according to claim 1, characterized in that: The sample containing ovalbumin is ovalbumin or egg white.

8. A gel containing ovalbumin prepared by the method of claim 1, characterized in that: A low-temperature ovalbumin-containing gel with uniform texture and good strength was prepared according to the method described in claim 1.

9. The ovalbumin-containing gel according to claim 8, characterized in that: The method yields a smooth, highly transparent ovalbumin-containing gel.

10. An application of the ovalbumin-containing gel according to claim 8 or 9, characterized in that, Application of the ovalbumin-containing gel in food processing.

Images