Salted egg white gel block and preparation method thereof

Abstract

The invention belongs to the technical field of food processing, and discloses a salted egg white gel block and a preparation method thereof. The surface of the salted egg white gel block is in a compact net shape; the gel block salted egg white comprises salted egg white and a protein network formed by cross-linking glycosylated salted egg white peptide through glutamine transaminase; the glycosylated salted egg white peptide is a glycosylated compound formed by carrying out Maillard reaction on salted egg white peptide and lactose; the salted egg white gel block has the following texture characteristics: the hardness of the salted egg white gel block is 6.68 N to 11.37 N, the chewiness of the salted egg white gel block is 4.84 N to 8.00 N, and the elasticity of the salted egg white gel block is 89.68% to 100.76%. According to the method, macromolecular protein is cut into peptide fragments with proper molecular weight through trypsin enzymolysis, and a triple modification technology of lactose glycosylation modification and glutamine transaminase cross-linking is combined, so that the content of alpha-helix and beta-corner of the salted egg white peptide is reduced, the content of beta-fold is increased, amido bonds are promoted to be formed between proteins, and the salted egg white peptide is prepared. And a compact cross-linked network structure is constructed. The hardness, the elasticity and the chewiness of the salted egg white gel block are obviously improved.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to salted egg white gel blocks and their preparation method. Background Technology

[0002] Salted egg yolk products are in high demand in the food industry. The production process typically involves pickling whole eggs and then extracting the yolks, resulting in a large amount of salted egg white as a byproduct. While salted egg white is rich in protein, the high concentration of salt during pickling causes salting out and partial denaturation of the protein. Simultaneously, the pH value rises to 9.0-10.0, significantly reducing protein solubility and deteriorating its functional properties.

[0003] Currently, the high-value utilization of salted egg white mainly faces the following technical challenges: First, poor textural properties: Due to salting out and protein denaturation, the gels formed after direct thermal gelation of salted egg white generally suffer from insufficient elasticity, low hardness, and poor chewiness, resulting in a loose, crumbly texture and difficulty in forming a dense, elastic gel network structure. Second, poor water retention: Salted egg white gels are prone to water seepage during storage, leading to product dehydration and structural collapse, severely affecting the product's appearance and shelf-life stability. Third, excessive salt content leading to poor palatability: Salted egg white typically contains 8%-12% salt, making it too salty to eat directly. Traditional desalination processes (such as dialysis and ultrafiltration) are not only complex and costly but also cause protein loss, and even after desalination, it is difficult to improve its gel properties. Fourth, monotonous flavor: Salted egg white itself has a fishy smell, and the pickling process lacks precursor reactions of flavor substances, resulting in a bland flavor and lack of complexity after direct processing.

[0004] In existing technologies, the utilization of salted egg whites mainly involves simple dilution, desalination, and drying into protein powder, or adding small amounts as an ingredient to other foods, resulting in low added value. Although some studies have used enzymatic hydrolysis or chemical modification to improve the functional properties of proteins, how to directly prepare protein block products with excellent gelation properties, low salt content, and good flavor without desalination, for the specific high-salt, denatured protein system of salted egg whites, remains a pressing technical problem to be solved in this field.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The present invention aims to solve at least one of the above technical problems, and provides salted egg white gel blocks and preparation methods.

[0007] To solve the above problems, the first technical solution adopted by the present invention is as follows: The salted egg white gel block has a dense network-like surface; the salted egg white gel block contains salted egg white and a protein network formed by cross-linking of glycosylated salted egg white peptides with transglutaminase. The glycosylated salted egg white peptide is a glycosylated complex formed by salted egg white peptide and lactose through Maillard reaction; Furthermore, the salted egg white gel block possesses the following textural properties: hardness of 6.68N-11.37N, chewiness of 4.84N-8.00N, and elasticity of 89.68%-100.76%.

[0008] Preferably, the mass ratio of the glycosylated salted egg white peptide to the salted egg white is 1:(25-35).

[0009] Preferably, the salted egg white peptide is obtained by enzymatic hydrolysis of salted egg white with trypsin, and the amount of trypsin added is 1.0%-3.0% of the mass of salted egg white.

[0010] Preferably, the salted egg white gel block is subjected to brining treatment and has a salt content of 2.82%-4.65%.

[0011] The second technical solution adopted in this invention is: The preparation method of salted egg white gel blocks includes: Salted egg white was diluted and pretreated by heating, the pH was adjusted to 7.0, trypsin was added, and enzymatic hydrolysis was carried out at 37.5℃ for 2.5-3.5h. After enzyme inactivation, centrifugation and drying, salted egg white peptides were obtained. The obtained salted egg white peptides were prepared into a solution, the pH was adjusted to 6.0-8.0, lactose was added, and a wet glycosylation reaction was carried out at 80-90℃ for 2.5-3.5h. After dialysis and drying, glycosylated salted egg white peptides were obtained. Glycosylated salted egg white peptides were added to salted egg white, the pH was adjusted to 7.0-8.0, and 0.1%-0.3% of transglutaminase by total mass of salted egg white was added. The cross-linking reaction was carried out at 40-50℃ for 1.5-3.0h. The obtained cross-linked protein was subjected to degassing, cooking, braising and baking to obtain the salted egg white gel block.

[0012] Preferably, the amount of trypsin added is 1.0%-3.0% of the weight of the salted egg white.

[0013] Preferably, the mass ratio of lactose to salted egg white peptide solution is 1:(2-4), and the concentration of salted egg white peptide solution is 5 mg / ml.

[0014] Preferably, glycosylated salted egg white peptides are added to salted egg white at a mass ratio of 1:(25-35).

[0015] Preferably, the debubbling process involves ultrasonic treatment of the cross-linked protein at a power of 100W, a frequency of 22kHz, and a time of 20min.

[0016] Preferably, the cooking process involves steaming at 90°C for 30 minutes; the braising process involves braising at 90°C for 1 hour; and the baking process involves baking at 60°C for 20 minutes.

[0017] Preferably, the cooking process also includes braising and baking.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes trypsin enzymatic hydrolysis to cleave large protein molecules into peptides of suitable molecular weight. Combined with a triple modification technique involving lactose glycosylation and glutamine transaminase cross-linking, it reduces the α-helix and β-turn content and increases the β-sheet content of salted egg white peptides. Simultaneously, it promotes the formation of amide bonds between proteins, constructing a dense cross-linked network structure. This significantly improves the hardness, elasticity, and chewiness of salted egg white gel blocks, completely solving the problems of poor elasticity, low hardness, and poor chewiness after direct gelation of salted egg white.

[0019] This invention utilizes salt migration and osmotic pressure regulation during the brining process to allow salt inside the protein block to migrate outwards. After brining and drying, the salt content can be reduced to 2.0%~3.5%, reaching a palatable level. This eliminates the need for complex pre-desalting treatment, simplifies the process, avoids protein loss during desalting, and improves product yield.

[0020] In the method provided by this invention, glycosylation modification increases the number of hydrophilic groups in the protein molecule, and TG enzyme cross-linking forms a tighter gel network structure. The synergistic effect of these two processes significantly improves the water-holding capacity of the protein block, solving the problem of easy water leakage during the storage of traditional salted egg white gels and extending the product's shelf life. The Maillard reaction not only improves the functional properties of the protein but also produces a unique browning color and flavor compounds. Combined with the subsequent braising process, the product has a brown surface and a pale yellow or white interior, with a rich braising and egg aroma, no eggy smell, and a rich flavor profile. Attached Figure Description

[0021] Figure 1 A diagram illustrating the preparation process of a flavored salted egg white gel block according to a specific embodiment of the present invention; Figure 2 Thermogravimetric analysis (TGA) diagrams of salted egg white (SEW), salted egg white peptide (SEWP), and glycosylated salted egg white peptide (SEWP-L) in Example 1 are shown. Figure 3 In the middle, (a), (b), and (c) are SEM images of salted egg white (SEW), salted egg white peptide (SEWP), and glycosylated salted egg white peptide (SEWP-L) in Example 1, respectively. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The first embodiment of the present invention provides a salted egg white gel block with a dense network on its surface; the salted egg white gel block contains salted egg white and a protein network formed by cross-linking of glycosylated salted egg white peptides with transglutaminase; The glycosylated salted egg white peptide is a glycosylated complex formed by salted egg white peptide and lactose through Maillard reaction; Furthermore, the salted egg white gel block possesses the following textural properties: hardness of 6.68N-11.37N, chewiness of 4.84N-8.00N, and elasticity of 89.68%-100.76%.

[0024] The salted egg white (SEW) is a byproduct of salting duck eggs. During the pickling process, the high concentration of salt (usually about 25% saturated brine) causes protein salting out and partial denaturation. Simultaneously, the pH value rises from 7.5-8.5 in fresh eggs to 9.0-10.0, significantly reducing protein solubility and causing molecules to form dense but fragile aggregates through hydrophobic interactions. Therefore, gels formed by directly heating salted egg white generally suffer from insufficient elasticity, low hardness, poor chewiness, poor water retention, and easy water seepage.

[0025] This embodiment addresses the aforementioned problems through a triple modification mechanism of enzymatic hydrolysis, glycosylation, and cross-linking: First, trypsin hydrolysis breaks down large protein molecules into peptides of suitable molecular weight (preferably, peptides smaller than 10 kDa account for more than 60%), namely, salted egg white peptides (SEWP). Enzymatic hydrolysis not only reduces the molecular weight but, more importantly, exposes hydrophobic groups and reactive sites (such as free amino groups) within the molecule, providing reaction sites for subsequent glycosylation reactions. Simultaneously, peptides are more readily adsorbed at interfaces than intact proteins, which is beneficial for improving interfacial properties.

[0026] Secondly, the salted egg white peptide undergoes a Maillard reaction with lactose via wet glycosylation. During the reaction, the free amino groups (-NH2) in the peptide molecule react with the reducing carbonyl groups of lactose to form a Schiff base, which rearranges to form a stable glycosylated salted egg white peptide (SEWP-L). This process leads to changes in the protein's secondary structure: the content of α-helices and β-turns decreases, while the content of β-sheets increases, and the molecular structure changes from compact to relatively extended. The introduction of glycosyl groups increases the hydrophilicity of the protein molecule, improving its water-holding capacity through hydrogen bonding; simultaneously, the steric hindrance effect of the glycan chains restricts the structural unfolding of the protein at high temperatures, significantly improving its thermal stability. The microstructure of the glycosylated product exhibits a porous, sponge-like and network-like structure with a relatively smooth surface. This structural feature is beneficial for forming a uniform network during subsequent cross-linking.

[0027] Finally, through the action of transglutaminase, the gel formation process of the obtained salted egg white protein blocks is accelerated, water retention is improved, and the elasticity, hardness, and chewiness of the texture are significantly enhanced. Transglutaminase promotes the formation of amide bonds between proteins, promotes cross-linking between proteins, forms a denser gel network, improves water retention, and makes the salted egg white dried egg better in taste, more elastic, and more tender. The improved chewiness further optimizes the physical properties of the dried egg.

[0028] In this embodiment, the preferred mass ratio of the glycosylated salted egg white peptide to the salted egg white is 1:(25-35). This ratio is a key parameter for controlling the crosslinking density: when the ratio is too low (e.g., below 1:35), there are insufficient crosslinking sites, making it impossible to form a continuous and dense network structure, resulting in insufficient gel strength and poor water retention; when the ratio is too high (e.g., above 1:25), excessive crosslinking makes the gel too hard, resulting in a poor taste and increased cost.

[0029] The amount of trypsin used can be routinely adjusted by those skilled in the art based on the enzyme's specific activity, substrate protein concentration, and the molecular weight distribution of the target peptide. For example, it can be 1.0%-3.0% of the mass of salted egg white. This range ensures sufficient enzymatic hydrolysis while avoiding excessive hydrolysis that could lead to the formation of bitter peptides.

[0030] Scanning electron microscopy revealed that the gel block prepared in this embodiment possesses a dense network microstructure. This structure differs from the dense, coarse block structure of unmodified salted egg white (with salt crystals on the surface), and also from the fine particles or amorphous powder structure of salted egg white peptides after simple enzymatic hydrolysis. This dense network structure endows the product with excellent water retention, solving the problem of easy water seepage during the storage of traditional salted egg white gels.

[0031] The gel block of this embodiment has better thermal stability due to glycosylation modification, and the mass loss rate is lower than that of the untreated sample during the entire heating process, indicating that the Maillard reaction restricts the unfolding of protein structure through steric hindrance.

[0032] Regarding interfacial properties, the glycosylated egg white peptide exhibits significantly improved foaming and foam stability, as well as emulsifying activity and emulsifying stability. This is attributed to the fact that glycosylation modification increases the number of hydrophilic groups in the protein molecule, promoting adsorption at the oil-water interface; simultaneously, the protein-glycoside complex can form an interfacial layer, enhancing droplet dispersibility and stability. These improvements in interfacial properties contribute to the formation of a uniform texture in the final gel block.

[0033] The gel block can be further processed by braising. Through salt migration and osmotic pressure adjustment during the braising process, the salt content is reduced to a palatable level of 2.82%-4.65%. Before braising, the salt content of salted egg white is usually 6%-10%. Through the osmotic effect of the braising liquid (containing spices such as star anise, ginger, Sichuan peppercorns, cinnamon, cooking wine, light soy sauce, dark soy sauce, and sugar), the internal salt migrates to the outside, achieving a palatable level without the need for complex pre-desalination treatment. This simplifies the process and avoids protein loss. Sensory evaluation verifies that the surface of the gel block is brown (due to the combined effect of Maillard reaction browning and braising coloring), and the interior is pale yellow or white, characterized by a rich braising aroma, a unique egg flavor, and no eggy smell.

[0034] It is important to note that the textural properties of the salted egg white gel block of this invention (hardness 6.68N-11.37N, chewiness 4.84N-8.00N, elasticity 89.68%-100.76%) fundamentally depend on the protein network structure constructed by the triple modification mechanism of enzymatic hydrolysis-glycosylation-crosslinking. During the crosslinking reaction stage, glycosylated salted egg white peptides and salted egg white proteins form ε-(γ-glutamyl)-lysine isopeptide bonds (amide bonds) catalyzed by transglutaminase, constructing a three-dimensional crosslinked network. The density of this covalent crosslinked network directly determines the textural properties of the final product: the higher the crosslinking density, the better the gel hardness, elasticity, and chewiness. At this point, the product's textural characteristics are essentially established. The subsequent cooking process mainly aims to further thermally denature and coagulate the proteins, fixing and stabilizing the already formed crosslinked network structure, rather than reconstructing the texture. Because the covalent crosslinks formed by TG enzyme have high thermal stability, the cooking temperature is insufficient to destroy the formed amide bonds, thus not changing the textural properties established during the crosslinking reaction stage. The braising and baking steps are post-processing conditioning steps, mainly used to reduce salt content and impart flavor, without substantially altering the already formed stable cross-linked gel network.

[0035] refer to Figure 1 The second embodiment of the present invention provides a method for preparing salted egg white gel blocks, comprising: Salted egg white was diluted and pretreated by heating, the pH was adjusted to 7.0, trypsin was added, and enzymatic hydrolysis was carried out at 37.5℃ for 2.5-3.5h. After enzyme inactivation, centrifugation and drying, salted egg white peptides were obtained. The obtained salted egg white peptides were prepared into a solution, the pH was adjusted to 6.0-8.0, lactose was added, and a wet glycosylation reaction was carried out at 80-90℃ for 2.5-3.5h. After dialysis and drying, glycosylated salted egg white peptides were obtained. Glycosylated salted egg white peptides were added to salted egg white, the pH was adjusted to 7.0-8.0, and 0.1%-0.3% of transglutaminase by total mass of salted egg white was added. The cross-linking reaction was carried out at 40-50℃ for 1.5-3.0h. The obtained cross-linked protein was subjected to degassing and cooking treatment to obtain the salted egg white gel block.

[0036] This embodiment achieves high-value utilization of salted egg white through a stepwise modification-synergistic crosslinking mechanism. First, peptides of suitable molecular weight are obtained by controlling the enzymatic hydrolysis conditions. Then, a gel network with excellent textural properties is constructed by precisely controlling the degree of glycosylation reaction and the crosslinking density.

[0037] Salted egg white needs to be diluted first (e.g., a salted egg white to water ratio of 1:7-1:10) to reduce the impact of high salt and high viscosity on enzymatic hydrolysis mass transfer. It is then pretreated by heating in a 100°C boiling water bath for 15 minutes. This step utilizes heat denaturation to moderately unfold the protein spatial structure, exposing internal cleavage sites, and simultaneously converting some salt-soluble proteins into a water-soluble state that can be recognized by trypsin. Enzymatic hydrolysis is carried out at pH 6.5-7.5 and a temperature of 35-40°C. This range is close to the optimal pH and temperature for trypsin, ensuring maximum enzyme activity. The amount of trypsin added can be routinely adjusted according to the enzyme's specific activity and substrate concentration, and can be exemplary at 1.0%-3.0% of the salted egg white mass. This range ensures sufficient hydrolysis while avoiding over-hydrolysis that could lead to the formation of bitter peptides. The hydrolysis time should be controlled between 2.5-3.5 hours. Too short a time results in insufficient hydrolysis and inadequate exposure of glycosylation sites; too long a time produces too many small peptides, affecting the strength of subsequent cross-linking networks. After enzymatic hydrolysis, the enzyme needs to be inactivated to terminate the reaction. Then, centrifuge (exemplarily 8000-10000 r / min, 15-20 min) to remove unhydrolyzed precipitates and denatured proteins. Take the supernatant and freeze-dry it to obtain salted egg white peptide powder.

[0038] Salted egg white peptides were prepared into a solution, and the pH was adjusted to 6.0-8.0. Lactose was added at a mass ratio of 1:(2-4) of lactose to salted egg white peptide solution (preferably 5 mg / ml). This ratio ensures sufficient contact between the reducing carbonyl group of lactose and the free amino group of the peptide. If the ratio is too low, the degree of glycosylation will be insufficient, resulting in poor improvement in hydrophilicity and thermal stability; if the ratio is too high, it will increase the burden of subsequent dialysis and may cause waste. The reaction was carried out at 80-90℃ for 2.5-3.5 h. This condition promotes the early and middle stages of the Maillard reaction, allowing the glycosyl groups to be covalently linked to the peptide chain, while avoiding over-reaction that produces bitter substances and brown pigments. After the reaction was completed, it was quickly terminated, and unreacted free lactose was removed by dialysis. After dialysis, the glycosylated salted egg white peptides were obtained by freeze-drying.

[0039] Glycosylated salted egg white peptides are mixed with salted egg white at a mass ratio of 1:(25-35), and the pH is adjusted to 7.0-8.0. This range is close to the optimal pH of transglutaminase and deviates from the original high pH (9.0-10.0) of salted egg white, which is beneficial for enzyme activity. 0.1%-0.3% transglutaminase is added, and the reaction is carried out at 40-50℃ (45℃ is an example) for 1.5-3.0 h. Under these conditions, the TG enzyme catalyzes the formation of ε-(γ-glutamyl)-lysine isopeptide bonds between protein molecules, constructing a three-dimensional network structure. The reaction time needs to be sufficient to ensure complete cross-linking, but excessive time may lead to an overly dense network and decreased elasticity.

[0040] The cross-linked protein solution needs to undergo degassing to prevent pores from affecting the texture and appearance of the product. Ultrasonic treatment can be used, utilizing the cavitation effect of ultrasound to cause bubbles to aggregate and escape. The power, frequency, and time can be adjusted according to the system viscosity and the amount of bubbles; an example is a power of 100W, a frequency of 22kHz, and a time of 20 minutes. Other physical methods such as vacuum degassing can also be used. For example, cooking can be done by steaming at 90℃ for 30 minutes, which uses heat to further denature and coagulate the protein, stabilizing the formed cross-linked network structure and simultaneously setting the product's shape. After steaming, cool and cut into appropriately sized pieces.

[0041] In a preferred embodiment, after obtaining the above-mentioned salted egg white gel blocks, they can be further subjected to braising and baking processes to obtain flavored salted egg white gel blocks. The braising temperature can be exemplarily controlled at 90°C, and the time can be adjusted according to the target salt content and flavor requirements, exemplarily 1 hour. Baking can be exemplarily performed at 60°C for 20 minutes to moderately dehydrate and dry the surface, concentrating flavor substances to form a dried egg product.

[0042] The following examples provide a detailed description of the preparation and properties of salted egg white gel blocks.

[0043] The salted egg white used in the following examples and comparative examples comes from: fresh, crack-free duck eggs are washed and dried, then completely submerged in 25% saturated brine and pickled at room temperature. The pickled duck eggs are then washed with clean water, the yolks and egg whites are separated, and the egg whites are collected to obtain the salted egg white.

[0044] Example 1 SEW was stirred thoroughly, filtered to remove air bubbles, and diluted 1:9. It was then heated in a boiling water bath at 100℃ for 15 minutes to adjust the pH of the salted egg white to 7.0. 1.5% trypsin (w / w, based on the weight of the salted egg white) was added, and the mixture was enzymatically hydrolyzed at 37℃ for 3 hours. After hydrolysis, the enzyme was inactivated, the mixture was centrifuged, and the supernatant was freeze-dried to obtain SEWP. Lactose was added to a 5 mg / ml SEWP solution at a mass ratio of 1:3.2, and the mixture was reacted at 90℃ for 3 hours. The pH was adjusted to 7 to promote the Maillard reaction. The reaction was terminated after the reaction was complete to obtain the glycosylated complex. The complex was dialyzed and freeze-dried to obtain SEWP-L. SEWP-L was added to salted egg white at a mass ratio of 1:30, the pH of the glycosylated salted egg white was adjusted to 7, and 0.3% transglutaminase (TG enzyme) was added at a mass ratio. The mixture was reacted at 45℃ for 2 hours to promote protein cross-linking. The cross-linked proteins were treated with ultrasound to remove air bubbles. The salted egg whites, after removing air bubbles, are steamed until solidified. After cooling and cutting into pieces, they are then braised (the braising spice recipe is: 3.5% star anise, 3.5% ginger slices, 3.5% Sichuan peppercorns, 3.5% cinnamon, 2% cooking wine, 2% light soy sauce, 0.4% dark soy sauce, and 3% sugar, based on the total weight of the braising liquid). The braising temperature is 90℃, and the braising time is 1 hour. The braised salted egg white blocks are then baked to obtain salted egg white tofu.

[0045] Example 2 Compared to Example 1, the only difference was that SEW was diluted 1:7, 1.0% trypsin was added, and the enzymatic hydrolysis reaction was carried out for 2.5 hours. The pH was adjusted to 6, lactose was added at a ratio of 1:2, and the reaction was carried out at 80°C for 2.5 hours. The pH of the glycosylated salted egg white was adjusted to 7, and the obtained SEWP-L was added to the salted egg white at a mass ratio of 1:25. 0.1% transglutaminase was added at a mass ratio, and the reaction was carried out at 40°C for 1.5 hours. The final baking time was 15 minutes. All other dosages, process parameters, and steps were the same as in Example 1.

[0046] Example 3 Compared to Example 1, the only difference was that SEW was diluted 1:10, 3.0% trypsin was added, and the enzymatic hydrolysis reaction was carried out for 3.5 hours. The pH was adjusted to 8, lactose was added at a ratio of 1:4, and the reaction was carried out at 90°C for 3.5 hours. The pH of the glycosylated salted egg white was adjusted to 8, and the obtained SEWP-L was added to the salted egg white at a mass ratio of 1:35. 0.3% transglutaminase was added at a mass ratio, and the reaction was carried out at 50°C for 3 hours. The final baking time was 30 minutes. All other dosages, process parameters, and steps were the same as in Example 1.

[0047] Comparative Example 1 Compared to Example 1, the only difference is that the glycosylation treatment is omitted, i.e., the step of adding lactose to SEWP to carry out the Maillard reaction to obtain SEWP-L is omitted, and SEWP is directly mixed with salted egg white. All other dosages, process parameters and steps are the same as in Example 1.

[0048] Comparative Example 2 Compared to Example 1, the only difference is that the order of the TG enzyme cross-linking step and the glycosylation step is switched. Specifically, SEWP is cross-linked with salted egg white under the action of transglutaminase, and then subjected to Maillard reaction with lactose to obtain the glycosylated complex. All other amounts and processes are the same as in Example 1.

[0049] Comparative Example 3 Compared to Example 1, the only difference is that the TG enzyme is omitted; instead, SEWP-L is added to the salted egg white at a mass ratio of 1:3, and then the protein is cross-linked using ultrasound. All other dosages and processes are the same as in Example 1.

[0050] Comparative Example 4 Compared to Example 1, the difference lies in the direct use of fresh egg whites, eliminating the enzymatic hydrolysis, glycosylation treatment, and TG enzyme cross-linking steps. All other quantities and processes remain the same as in Example 1. The specific method is as follows: Whisk the egg whites until smooth and filter them through cheesecloth. Use ultrasound to treat the egg whites and remove air bubbles. Steam the egg whites until they solidify, cool, cut into pieces, and then braise at 90℃ for 1 hour. Remove the braised egg white pieces and bake them in a 60℃ oven for 20 minutes to obtain dried egg white.

[0051] Comparative Example 5 Compared with Comparative Example 4, the only difference is that the fresh egg whites are replaced with the salted egg whites used in Example 1. The rest of the processing is exactly the same as Comparative Example 4.

[0052] Experimental Example 1 (1) The foaming properties and foam stability of salted egg white (SEW), salted egg white peptide (SEWP), and glycosylated salted egg white peptide (SEWP-L) in Example 1 were determined according to the standard GB / T 7462-2020 "Determination of foaming properties of surfactants" (modified Ross-Miles). The results are shown in Table 1. The results show that the glycosylation reaction can promote foaming ability. The Maillard reaction causes the α-helix structure inside the protein to unfold, exposing additional hydrophobic groups. The non-covalent interaction between lactose and salted egg white protein at the air-water interface leads to rapid adsorption at the interface. The resistance of the entire system to foam breakage and collapse is enhanced, thereby enhancing foaming properties. A more uniform and complete interfacial film is formed at the air-water interface. Moreover, the introduction of lactose increases the viscosity of the system, making the formed foam more stable, thus enhancing foam stability.

[0053] Table 1 .

[0054] (2) The emulsifying activity and emulsifying stability of salted egg white (SEW), salted egg white peptide (SEWP), and glycosylated salted egg white peptide (SEWP-L) in Example 1 were determined according to the classical turbidimetric method of Pearce et al. (1978), and the emulsifying performance test specifications in the national standard GB / T22493-2022 "Soybean Protein Powder" were also followed. The results are shown in Table 2. The results show that the improvement in emulsifying performance may be due to the glycosylation modification increasing the number of hydrophilic groups in the protein molecules, which promotes their adsorption capacity at the oil-water interface. On the other hand, the protein-carbohydrate complex can form an interfacial layer, which can enhance the dispersibility and stability of droplets and effectively prevent the coagulation of oil droplets in the emulsion. The poor emulsifying properties of salted egg white are due to Na + Cl - It has a shielding effect on the surface charge of proteins, which weakens the interaction between proteins and water.

[0055] Table 2 .

[0056] (3) The lipophilic and hydrophilic abilities of salted egg white (SEW), salted egg white peptide (SEWP), and glycosylated salted egg white peptide (SEWP-L) in Example 1 were determined. The results are shown in Table 3.

[0057] Table 3 .

[0058] (4) The thermal stability of the salted egg white (SEW), salted egg white peptide (SEWP), and glycosylated salted egg white peptide (SEWP-L) in Example 1 was analyzed. The results are as follows: Figure 2As shown in the figure. The results show that SEW, SEWP, and SEWP-L exhibit different weight loss stages in the thermal stability range of 100–600 °C. SEW has two weight loss stages: the first stage occurs between 30–380 °C, and the second stage occurs between 380–600 °C. At high temperatures, the protein backbone breaks down, and the protein side chain groups decompose, resulting in significant mass loss. SEWP has three weight loss stages: the first stage is between 30–180 °C, where the mass loss is mainly due to the loss of free and bound water in the sample; the second stage is between 180–260 °C; and the third stage is between 260–600 °C. The mass loss in these two stages may be caused by the rapid dehydration of peptide bonds and the breaking of covalent bonds between C=O, CN, CO, etc., at high temperatures. SEWP-L exhibits three weight loss phases: the first phase occurs between 30 and 200 °C, resulting in mass loss due to the release of bound water; the second phase occurs between 200 and 320 °C; and the third phase occurs between 320 and 600 °C, during which the peptide chains and lactose molecules gradually decompose. Throughout the process, SEWP-L shows the lowest mass loss rate and exhibits better thermal stability, indicating that the Maillard reaction can significantly improve the thermal stability of proteins. This may be because glycosylation restricts the unfolding of protein structures through steric hindrance.

[0059] (5) Scanning electron microscopy was performed on the salted egg white (SEW), salted egg white peptide (SEWP), and glycosylated salted egg white peptide (SEWP-L) from Example 1. The microstructures of freeze-dried SEW, SEWP, and SEWP-L are shown at 500x magnification. The results are as follows: Figure 3 As shown in the figure, SEW exhibits a dense, coarse blocky or sheet-like structure with salt crystals on the surface; SEWP presents as finer particles, fragments, or amorphous powder, with a more dispersed and irregular overall morphology; SEWP-L exhibits a porous, sponge-like, network-like structure with a relatively smooth surface and a more dense network structure. During the Maillard reaction, the protein structure changes, and the interactions of hydrogen bonds, hydrophobic forces, and electrostatic repulsion increase the total force required to form a three-dimensional network structure, thus SEWP-L forms a dense network structure. Scanning electron microscopy results are similar to those obtained from infrared spectroscopy and circular dichroism spectroscopy, both indicating a structural change in SEWP-L and the Maillard reaction between SEWP and lactose.

[0060] Experimental Example 2 (1) Sensory evaluation was performed on the final samples prepared in the above examples and comparative examples. Evaluation criteria: Total sensory score = color × 0.2 + odor × 0.2 + shape × 0.2 + texture × 0.2 + taste × 0.2; Appearance: 20. The shape is intact, without microbubbles, the texture is smooth and uniform, and the thickness is moderate. Color: 20. Surface is brown, interior is pale yellow or white, and the color is uniform. Aroma: 20. Rich in savory aroma with a unique egg flavor, and no fishy smell. Texture: 20. It has a certain degree of elasticity and firmness; Taste: 20. Moderately salty and mild, with a palatable umami, sweet or other flavor, without bitterness, sourness or other unpleasant taste.

[0061] The results are shown in Table 4.

[0062] Table 4 Sensory evaluation table of samples prepared in the examples and comparative examples .

[0063] (2) The final samples prepared in the above examples and comparative examples were subjected to texture determination. The test method was as follows: The TS.XT.Plus texture analyzer and P / 36R probe were used to measure the parameters of each sample. The main parameters measured were elasticity, hardness, cohesion, resilience, and chewiness. The measurement conditions were as follows: pre-measurement speed 2 mm / s, test speed 2 mm / s, post-measurement speed 5 mm / s; sample compression ratio 50%, time 5 s, and trigger force 5 gf.

[0064] The test results are shown in Table 5.

[0065] Table 5. Texture parameters of samples prepared in the examples and comparative examples. .

[0066] (3) The salt content of the samples before and after brining and after drying in the above examples and comparative examples was tested, and the results are shown in Table 6.

[0067] Table 6. Salt content of the examples and comparative samples (unit: %) .

[0068] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. Salted egg white gel block, characterized in that, Its surface has a dense network structure; the gel block of salted egg white contains a protein network formed by cross-linking of salted egg white and glycosylated salted egg white peptides with transglutaminase; The glycosylated salted egg white peptide is a glycosylated complex formed by salted egg white peptide and lactose through Maillard reaction; Furthermore, the salted egg white gel block possesses the following textural properties: hardness of 6.68N-11.37N, chewiness of 4.84N-8.00N, and elasticity of 89.68%-100.76%.

2. The salted egg white gel block as described in claim 1, characterized in that, The mass ratio of the glycosylated salted egg white peptide to the salted egg white is 1:(25-35).

3. The salted egg white gel block as described in claim 1, characterized in that, Salted egg white peptides are obtained by enzymatic hydrolysis of salted egg white with trypsin, and the amount of trypsin added is 1.0%-3.0% of the mass of salted egg white.

4. The salted egg white gel block as described in claim 1, characterized in that, The salted egg white gel block is subjected to brining treatment, and its salt content is 2.82%-4.65%.

5. A method for preparing salted egg white gel blocks, characterized in that, include: Salted egg white was diluted and pretreated by heating, the pH was adjusted to 7.0, trypsin was added, and enzymatic hydrolysis was carried out at 37.5℃ for 2.5-3.5h. After enzyme inactivation, centrifugation and drying, salted egg white peptides were obtained. The obtained salted egg white peptides were prepared into a solution, the pH was adjusted to 6.0-8.0, lactose was added, and a wet glycosylation reaction was carried out at 80-90℃ for 2.5-3.5h. After dialysis and drying, glycosylated salted egg white peptides were obtained. Glycosylated salted egg white peptides were added to salted egg white, the pH was adjusted to 7.0-8.0, and 0.1%-0.3% of transglutaminase by total mass of salted egg white was added. The cross-linking reaction was carried out at 40-50℃ for 1.5-3.0h. The obtained cross-linked protein was subjected to degassing and cooking treatment to obtain the salted egg white gel block.

6. The preparation method according to claim 5, characterized in that, The amount of trypsin added is 1.0%-3.0% of the weight of the salted egg white.

7. The preparation method according to claim 5, characterized in that, The mass ratio of lactose to salted egg white peptide solution is 1:(2-4), and the concentration of salted egg white peptide solution is 5mg / ml.

8. The preparation method according to claim 5, characterized in that, Glycosylated salted egg white peptides were mixed with salted egg white at a mass ratio of 1:(25-35).

9. The preparation method according to claim 5, characterized in that, The cooking process involves steaming at 90°C for 30 minutes; the braising process involves braising at 90°C for 1 hour; and the baking process involves baking at 60°C for 20 minutes.

10. The preparation method according to claim 5, characterized in that, After cooking, it also includes braising and baking.

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