Dried egg prepared based on egg protein-sodium hyaluronate conjugate and preparation method

Abstract

The invention belongs to the technical field of dried eggs, and particularly relates to dried eggs prepared on the basis of egg protein-sodium hyaluronate conjugates and a preparation method, and the dried eggs comprise the following components in parts by weight: egg white, the egg protein-sodium hyaluronate conjugates and auxiliary materials, the preparation method of the egg protein-sodium hyaluronate conjugate comprises the following steps: hydrating yolk protein, ovalbumin and sodium hyaluronate, carrying out glycosylation treatment, cooling, drying, storing and the like, and the product has high solubility, emulsibility, foamability and thermal stability. The glycosylated and modified egg protein is then used for preparing the dried egg, the yield, hardness, color and luster and water-holding capacity of the dried egg are remarkably improved, the edible quality of the dried egg is improved, and theoretical and technical supports are provided for widening the application range of sodium hyaluronate in processing food (such as egg products).

Description

Technical Field

[0001] The invention belongs to the technical field of dried eggs, and in particular relates to a dried egg prepared based on an egg protein-sodium hyaluronate conjugate and a preparation method thereof. Background Art

[0002] Egg jerky is made from whole egg liquid through key processes such as steaming, marinating and drying, and sealing and sterilization. As a whole egg product, egg jerky is rich in nutrition and has a unique taste, and is increasingly favored by consumers. The gel formation of egg jerky depends on the thermal denaturation of egg protein and the continuous gelation of protein aggregates.

[0003] The preparation method of egg jerky is generally to add auxiliary materials to egg liquid and stir them, then put them into high temperature and high pressure, or directly steam and cook them, and stew them. In the traditional method, egg jerky is prepared by normal pressure, but there are technical problems such as rough surface, low fineness, and holes in the surface of the egg jerky, which makes the yield and quality poor.

[0004] Ovalbumin, also known as ovalbumin (OVA), is the main protein in egg white, accounting for 54% of the total protein in eggs. OVA has an isoelectric point of 4.5, is composed of 385 amino acids, has a molecular weight of about 44.3kDa, and has more α-helices and β-folds. When heated, the structure of OVA will be destroyed, exposing free sulfhydryl groups and disulfide bonds. The interaction between molecules promotes the cross-linking of proteins to form a stable gel. Livetin (LIV) is mainly found in egg yolks, accounting for about 10% of the total protein in egg yolks. There are three forms of livetin in eggs: α-livetin and β-livetin, as well as γ-livetin in egg yolks. All three proteins are water-soluble and their isoelectric points are acidic.

[0005] The research on changing the higher-order structure of proteins and improving the properties of foods by heating foods containing proteins and carbohydrates has gradually become a hot topic. Protein glycosylation can be divided into two categories: dry heat glycosylation and wet heat glycosylation according to different reaction conditions. It is essentially a carbonyl-amine condensation reaction that occurs in the primary stage of the Maillard reaction. Protein glycosylation can change the solubility, emulsification, foaming, gelling, antioxidant activity, antibacterial activity, etc. of proteins. It is favored because of its mild reaction conditions, high safety, and the fact that the grafted products exhibit a variety of functional properties.

[0006] Sodium hyaluronate (SH) is a high molecular weight linear mucopolysaccharide produced by polymerization reaction of glucuronic acid and acetylhexose as disaccharides. It contains a large number of hydroxyl groups inside its structure and can bind a large number of water molecules. Its chemical formula is (C 14 H20NO11 Na)n. Due to its good viscoelasticity, pseudoplasticity and rheological properties, SH was first used as a new material in the pharmaceutical industry, such as for medical cosmetology or treatment of ophthalmic diseases and bone and joint diseases; studies have found that sodium hyaluronate also has a certain relationship with the growth of tumor cells.

[0007] At present, research has also found that sodium hyaluronate can absorb active oxygen and eliminate free radicals, and has certain health benefits such as hydrating and beautifying. As a new resource food raw material, it has great potential for development in the food industry in the future.

[0008] The specification of Chinese patent ZL 202210445755.7 describes a method for quickly and efficiently preparing modified egg white powder and its application, which includes mixing evenly according to a certain mass ratio, adjusting the pH, and then removing the insoluble matter in the egg white solution by centrifugation.

[0009] The collected supernatant is vacuum freeze-dried to obtain a mixed powder, and the powder is rapidly dry-heated for 30-120 minutes at a certain temperature of 50-70°C, and then refrigerated at low temperature to obtain the modified egg white powder. The modified egg white powder prepared by this method has significantly improved gel strength, emulsification performance, and antioxidant properties.

[0010] However, there are still technical problems that the egg jerky prepared with such egg white powder is of low quality and has low productivity in the gelling process. Summary of the invention

[0011] In order to solve the above technical problems, the present invention provides a dried egg prepared based on egg protein-sodium hyaluronate (SH) conjugate and a preparation method thereof, wherein the glycosylated egg protein is used in the preparation of the dried egg, and the yield, hardness, color and water holding capacity of the dried egg are significantly improved, which is beneficial to greatly improve the edible quality of the dried egg; in addition, a method for preparing OS-X or LS-X by dry heat glycosylation is adopted, and the product has high solubility, emulsification, foaming and thermal stability.

[0012] The present invention solves the above technical problems by preparing a dried egg based on an egg protein-sodium hyaluronate conjugate, comprising the following components in parts by weight: egg white, an egg protein-sodium hyaluronate conjugate and auxiliary materials;

[0013] The preparation method of the egg protein-sodium hyaluronate conjugate comprises the following steps:

[0014] (1) Hydration: Disperse egg yolk protein (LIV) and / or egg white protein (OVA) in ultrapure water to prepare a dispersion with a volume concentration of 5%, then add an equal amount of sodium hyaluronate (SH), mix well, stir at room temperature for 1-3 hours, and place in a refrigerator at 3-5°C overnight to allow for full hydration;

[0015] (2) Glycosylation treatment: The powder obtained after freeze-drying the mixed solution is spread evenly on a culture dish, placed in a constant temperature and humidity incubator at 55-65° C. and a relative humidity of 75-82% for reaction for 1-24 hours, and then taken out;

[0016] (3) Cooling: Rapid cooling to terminate the reaction and obtain OS-X and / or LS-X;

[0017] (4) Drying and storage: The obtained conjugate is freeze-dried and stored at -25°C to 18°C ​​for future use.

[0018] The raw materials of LIV and OVA are different from egg white powder. Egg white powder is a powdered product formed by dehydrating egg white. LIV and OVA are the protein components in egg yolk and egg white, namely yolk globulin and ovalbumin respectively.

[0019] In the optimized solution, the amount of the egg protein-sodium hyaluronate conjugate is 0.4-0.6 g / kg based on the mass of egg white.

[0020] In a further optimized solution, the amount of the egg protein-sodium hyaluronate conjugate is 0.5 g / kg based on the mass of egg white.

[0021] When the egg white-sodium hyaluronate content is lower than 0.5g / kg, the content is small and the improvement on the quality of dried eggs is not obvious. When it is higher than 0.5g / kg, it will destroy the quality of dried eggs and affect the sensory perception.

[0022] The auxiliary materials are white sugar, salt, monosodium glutamate, marinade, and / or food preservatives.

[0023] The purity of the LIV, OVA and SH raw materials is ≥85%.

[0024] The ultrapure water must be neutral.

[0025] In the optimized scheme, the preparation method of the egg protein-sodium hyaluronate conjugate comprises the following steps:

[0026] (1) Hydration: Yolk protein and / or ovalbumin are dispersed in ultrapure water to prepare a dispersion with a concentration of 5% (w / v), and an equal amount of sodium hyaluronate is added. The mixture is stirred at room temperature for 2 h and placed in a refrigerator at 4°C overnight to allow for full hydration.

[0027] (2) Glycosylation treatment: The powder obtained after freeze-drying the mixed solution was spread on a culture dish and placed in a constant temperature and humidity incubator at 60° C. and relative humidity of 79% for 0, 2, 4, 6, 12, 18 and 24 hours before being taken out;

[0028] In the glycosylation reaction, temperature affects the degree of glycosylation reaction, that is, the degree of sugar grafting onto protein molecules. Too low or too high temperature will be unfavorable for grafting. The temperature range of 60 degrees is the optimal temperature range for grafting. If it exceeds or is lower than this, the grafting effect will be poor.

[0029] In terms of humidity, it can be divided into dry heat method and wet heat method according to the humidity. The glycosylation products prepared by these two methods have different functional properties. For example, studies have found that the gel prepared by the wet heat method has stronger hardness and water holding capacity, while the gel prepared by the dry heat method has better solubility and emulsification. The present invention adopts the dry heat method. The relative humidity in the present invention is saturated humidity, which provides conditions for the occurrence of glycosylation.

[0030] (3) Cooling: Rapid cooling to terminate the reaction and obtain OS-X or LS-X;

[0031] (4) Drying and storage: The obtained conjugate is freeze-dried and stored at -20°C for later use.

[0032] OS-X is the abbreviation of OVA-SH conjugate, LS-X is the abbreviation of LIV-SH conjugate, and X represents the glycosylation time.

[0033] The present invention utilizes sodium hyaluronate (SH) to undergo dry glycosylation reaction with two kinds of egg proteins, ovalbumin (OVA) and livetin (LIV) for different time lengths (0, 2h, 4h, 6h, 12h, 18h, 24h) to prepare OVA-SH or LIV-SH conjugates (OS-X or LS-X, X represents the glycosylation time).

[0034] The room temperature in step (1) is 18-25°C.

[0035] The overnight time is 8-12 hours, preferably 10 hours.

[0036] The freeze-drying temperature in step (2) is -65°C--58°C, and the time is 46-50 hours. In a further optimized solution, the freeze-drying temperature is -60°C, and the time is 48 hours.

[0037] In the rapid cooling in step (3), rapid means cooling in a -20°C refrigerator. After the reaction is completed, the mixture is placed in a -20°C refrigerator for freeze-drying for 48 hours. Rapid cooling is mainly to terminate the glycosylation reaction. If it is not cooled rapidly, the glycosylation reaction will continue.

[0038] In the step (4), the conjugate is freeze-dried at a temperature of -60°C for 48 hours.

[0039] In the step (2), the OVA is taken out after 24 hours of reaction in the incubator; and the LIV is taken out after 4 hours of reaction.

[0040] The present invention discloses a method for preparing dried egg based on egg protein-sodium hyaluronate conjugate, wherein OS-X or LS-X is used in preparing dried egg, and the method comprises the following steps:

[0041] (A) Wash and break the eggs, and take out the egg liquid for later use;

[0042] (B) Weigh the desired egg protein-sodium hyaluronate conjugate, melt it with the auxiliary materials, pour it into the egg liquid, stir for 4-8 minutes, and filter;

[0043] Filter the stirred egg liquid, and use 20 mesh (upper), 60 mesh (middle), and 80 mesh (lower) sieves to filter out the foam or fine eggshells in the product.

[0044] (C) Pour the filtered egg liquid into the mold box, cover the mold cover, and put it into the reverse pressure sterilizer for steaming; after steaming, take out the mold, place it at room temperature to cool it, then take out the product from the mold box, and place the product in clean water to wait for braising; the product is placed in clean water to prevent the surface of the product from drying out and causing the braising process to not color. If it is directly braising, it does not need to be placed in cooling water.

[0045] (D) Pour the marinade bag into a pot and heat it to 75-85°C, immerse the product in the marinade solution and heat for 8-12 minutes; after the marinating is completed, remove the product and place it in clean water for rinsing;

[0046] (E) Spread the rinsed product on a baking tray, drain the water, bake in the oven, and cool.

[0047] In the optimized solution, the back pressure sterilizer conditions in step (C) are set to 105° C., 60 min.

[0048] The oven conditions in step (E) are set to 125±5°C for 25 min.

[0049] The reverse pressure technology is used in the present invention to prepare the dried eggs, and the dried eggs produced by the reverse pressure are smoother and more delicate than the dried eggs produced by normal pressure, without any holes.

[0050] The invention adopts reverse pressure sterilization in preparing the dried eggs, which can make the texture of the dried eggs more uniform and delicate, and have a better taste.

[0051] In addition, in the present invention, the egg protein modified by glycosylation of sodium hyaluronate is used to improve the quality of dried eggs.

[0052] The dry egg product to which sodium hyaluronate glycosylated modified egg protein is added in the present invention has the technology of first preparing an egg protein-sodium hyaluronate conjugate, and then adding it to egg liquid to prepare a dry egg product with improved quality.

[0053] In the present invention, OS-X or LS-X is prepared by a dry heat glycosylation method, and the product has high solubility, emulsification, foaming and thermal stability; the glycosylated egg protein is used for the preparation of dried eggs, and the yield, hardness, color and water holding capacity of the dried eggs are significantly improved, which is conducive to the improvement of the edible quality of the dried eggs, and provides theoretical and technical support for expanding the application of SH in processed foods (such as egg products). BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 The figure shows the effect of glycosylation time on the grafting degree of OVA and LIV in the present invention (different letters indicate significant difference within the group, p < 0.05).

[0055] Figure 2 The results of SDS-PAGE analysis of the glycosylation time of OVA, OS-X, LIV and LS-X in the present invention are shown.

[0056] Figure 3 and Figure 4 This is a diagram showing the effect of glycosylation time on the intrinsic fluorescence of OVA, OS-X, LIV, and LS-X in the present invention.

[0057] Figure 5 The figure shows the effect of glycosylation time on the surface hydrophobicity of OVA, OS-X, LIV and LS-X in the present invention (different letters indicate significant differences within the groups, p < 0.05).

[0058] Figure 6 and Figure 7 This is the effect of glycosylation time on the secondary structure of OVA, OS-X, LIV, and LS-X in the present invention.

[0059] Figure 8 and Fig. 9 This is the effect of glycosylation time on the solubility of OVA, OS-X, LIV, and LS-X in the present invention.

[0060] Fig.10 and Fig.11 The figure shows the effect of glycosylation time on the emulsification of OVA, OS-X, LIV and LS-X in the present invention (different letters indicate significant differences within the groups, p < 0.05).

[0061] Fig.12 and Fig.13 The figure shows the effect of glycosylation time on the foaming properties of OVA, OS-X, LIV and LS-X in the present invention (different letters indicate significant differences within the groups, p < 0.05).

[0062] Figure 14-15 This is the effect of glycosylation time on the thermal stability of OVA, OS-X, LIV, and LS-X in the present invention.

[0063] Fig.16 The figure shows the effect of adding OVA, LIV, SH, OS-0, LS-0, OS-24 and LS-4 in the present invention on the yield of dried egg products (different letters indicate significant differences within the groups, p < 0.05).

[0064] Fig.17 The effects of adding OVA, LIV, SH, OS-0, LS-0, OS-24 and LS-4 in the present invention on the water holding capacity of the dried egg products (different letters indicate significant differences within the groups, p < 0.05).

[0065] Fig.18 The figure shows the effect of adding OVA, LIV, SH, OS-0, LS-0, OS-24 and LS-4 in the present invention on the hardness of the dried egg product (different letters indicate significant differences within the groups, p < 0.05).

[0066] Figure 19-Figure 26 This is the effect of adding OVA, LIV, SH, OS-0, LS-0, OS-24, and LS-4 in the present invention on the microscopic morphology of dried eggs.

[0067] Fig. 27 It is a schematic diagram of the reaction of the structural formula in the grafting process of the present invention. DETAILED DESCRIPTION

[0068] The present invention is further described below in conjunction with specific embodiments:

[0069] Materials and reagents: SH, purchased from Bloomage Biotech Co., Ltd.; OVA, purchased from Dulai Reagent; LIV, purchased from Eugene Biotech and Pharmaceutical Co., Ltd.; Coomassie Brilliant Blue G-250, purchased from Beijing Solebow Technology Co., Ltd.; Tris, purchased from Beijing Solebow Technology Co., Ltd.; glycine, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; Marker, purchased from Tiangen Biochemical Technology (Beijing) Co., Ltd.; 30% acrylamide solution, 1.0 M Tris-HCl (pH 6.8), 10% (w / v) SDS, 10% ammonium persulfate, TEMED, purchased from Boster Biotech Co., Ltd.; DTNB, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0070] Instruments and equipment: Varioskan Flash microplate reader, Thermo Fisher Scientific Inc.; JY04S-3C gel imager, Beijing Junyi Oriental Electrophoresis Equipment Co., Ltd.; LHS-080 intelligent constant temperature and humidity incubator, Zhengzhou Shengyuan Instrument Co., Ltd.; TGL-16MB high-speed refrigerated centrifuge, Changsha Xiangzhi Co., Ltd.; AD500S-H high-speed shear homogenizer, Shanghai Anni Instrument Co., Ltd.; Mini Protein3 vertical electrophoresis equipment, Bio-Rad, USA; Nicolet iS10 Fourier transform infrared spectrometer, Thermo Fisher Scientific Inc.; FD-A-50 freeze dryer, Beijing Boyikang Experimental Instrument Co., Ltd.; scanning electron microscope (Thermo Fisher Quattro S), Thermo Fisher Scientific Inc.

[0071] Example 1

[0072] A dried egg prepared based on an egg protein-sodium hyaluronate conjugate is composed of the following components in parts by weight: egg white, egg protein-sodium hyaluronate conjugate and auxiliary materials, wherein the amount of egg white and egg white-sodium hyaluronate conjugate is 0.5 g / kg based on the weight of the egg white. The auxiliary materials are white sugar, salt, monosodium glutamate, halogen and / or food preservatives.

[0073] The marinade used is the "Haorenjia" brand marinade bag sold on the market, and its ingredients are: brewed soy sauce, edible salt, rapeseed oil, brown sugar syrup, white sugar, white sugar, soybean paste, chicken seasoning, edible flavors and spices, spices, monosodium glutamate, oyster sauce, angelica, rice wine, cumin, star anise, ginger, pepper, cardamom, laurel and orange peel. The following are the same.

[0074] The preparation method of egg protein-sodium hyaluronate conjugate comprises the following specific steps:

[0075] (1) Hydration: Disperse LIV and / or OVA in neutral ultrapure water to prepare a dispersion with a concentration of 5% (w / v), then add an equal amount of SH, mix well, stir at room temperature for 2 hours, and place in a refrigerator at 4°C overnight to allow it to be fully hydrated; the purity of LIV, OVA and SH raw materials should be ≥85%; the room temperature can be 25°C, and the overnight storage can be 10 hours.

[0076] (2) Glycosylation treatment: The powder obtained after freeze-drying the mixed solution was spread flat on a culture dish, placed in a constant temperature and humidity incubator at 60° C. and a relative humidity of 79%, and then taken out after reaction; the freeze-drying temperature was -60° C. and the time was 48 h;

[0077] The OVA cells were taken out from the incubator after 24 hours of reaction; the LIV cells were taken out after 4 hours of reaction.

[0078] (3) Cooling: Rapid cooling to terminate the reaction and obtain OS-X and / or LS-X;

[0079] Rapid cooling can mean that the sample is immediately placed in a -20°C refrigerator for freeze-drying for 48 hours after the reaction is completed. Rapid cooling is mainly to terminate the glycosylation reaction. If it is not cooled quickly, the glycosylation reaction will continue.

[0080] (4) Drying and storage: The obtained conjugate is freeze-dried and stored at -20°C for future use; the conjugate is freeze-dried at -60°C for 48 hours.

[0081] The OS-X or LS-X prepared in the present invention was subjected to electrophoresis to identify the structural changes of the subunits of the prepared conjugate, and the grafting degree reaction was also determined, as shown in the analysis in the subsequent test examples.

[0082] Example 2

[0083] A dried egg prepared based on egg protein-sodium hyaluronate conjugate is composed of the following components in parts by weight: egg white, egg protein-sodium hyaluronate conjugate and auxiliary materials, wherein the amount of egg white and egg white-sodium hyaluronate conjugate is 0.4 g / kg based on the weight of egg white. The auxiliary materials are white sugar, salt, monosodium glutamate, halogen and / or food preservatives.

[0084] The preparation method of egg protein-sodium hyaluronate conjugate comprises the following specific steps:

[0085] (1) Hydration: Disperse LIV and / or OVA in neutral ultrapure water to prepare a dispersion with a concentration of 5% (w / v), then add an equal amount of SH, mix well, stir at room temperature (18°C) for 3 h, and place in a refrigerator at 3°C ​​overnight to allow for full hydration; the overnight time is 12 h;

[0086] (2) Glycosylation treatment: The powder obtained after freeze-drying the mixture was spread flat on a culture dish and placed in a constant temperature and humidity incubator at 55°C and 82% relative humidity. OVA was reacted for 20 hours and then taken out; LIV was reacted for 1 hour and then taken out; the freeze-drying temperature was -65°C and the time was 46 hours;

[0087] (3) Cooling: Rapid cooling to terminate the reaction and obtain OS-X and / or LS-X; rapid means immediately placing in a -20°C refrigerator for cooling and freeze-drying for 48 hours after the reaction;

[0088] (4) Drying and storage: The obtained conjugate is freeze-dried and stored at -25°C for future use. The conjugate is freeze-dried at -60°C for 48 hours.

[0089] Example 3

[0090] A dried egg prepared based on egg protein-sodium hyaluronate conjugate is composed of the following components in parts by weight: egg white, egg protein-sodium hyaluronate conjugate and auxiliary materials, wherein the amount of egg white and egg white-sodium hyaluronate conjugate is 0.6 g / kg based on the weight of egg white. The auxiliary materials are white sugar, salt, monosodium glutamate, halogen and / or food preservatives.

[0091] The preparation method of egg protein-sodium hyaluronate conjugate comprises the following specific steps:

[0092] (1) Hydration: Disperse LIV and / or OVA in neutral ultrapure water to prepare a dispersion with a concentration of 5% (w / v), then add an equal amount of SH, mix well, stir at room temperature (22°C) for 1 h, and place in a refrigerator at 5°C overnight to allow for full hydration; the overnight time is 8 h;

[0093] (2) Glycosylation treatment: The powder obtained after freeze-drying the mixture was spread flat on a culture dish and placed in a constant temperature and humidity incubator at 65°C and 75% relative humidity. OVA was reacted for 10 hours and then taken out; LIV was reacted for 6 hours and then taken out. The freeze-drying temperature was -58°C and the time was 50 hours.

[0094] (3) Cooling: Rapid cooling to terminate the reaction and obtain OS-X and / or LS-X; rapid cooling means cooling in a -20°C refrigerator.

[0095] (4) Drying and storage: The obtained conjugate is freeze-dried and stored at -20°C for future use. The conjugate is freeze-dried at -60°C for 48 hours.

[0096] Example 4

[0097] A method for preparing dried egg based on egg protein-sodium hyaluronate conjugate, wherein OS-X or LS-X is used in preparing the dried egg, comprising the following steps:

[0098] (A) Wash and break the eggs, and take out the egg liquid for later use;

[0099] (B) Weigh the egg protein-sodium hyaluronate conjugate, melt it with the auxiliary materials, pour it into the egg liquid, stir it for 5 minutes, and filter it; use 20 mesh (upper), 60 mesh (middle), and 80 mesh (lower) sieves to overlap and filter out the foam or fine eggshells in the product.

[0100] (C) pouring the filtered egg liquid into a mold box, covering the mold cover, and putting it into a reverse pressure sterilizer for steaming; after the steaming is completed, taking out the mold, placing it at room temperature to cool it down, taking out the product from the mold box, and placing the product in clean water to wait for braising; the reverse pressure sterilizer condition is set to 105° C., 60 min;

[0101] (D) Pour the marinade bag into a pot and heat it to 80°C, immerse the product in the marinade solution and heat for 10 minutes; after the marinating is completed, remove the product and place it in clean water for rinsing;

[0102] (E) Spread the rinsed product on a baking tray, drain the water, and bake in an oven. Let it cool. The oven condition is set at 125±5℃ for 25min.

[0103] Example 5

[0104] The method for preparing dried eggs based on OS-X or / and LS-X is as follows:

[0105] (A) Wash and break the eggs, and take out the egg liquid for later use;

[0106] (B) Weigh the egg protein-sodium hyaluronate conjugate, melt it with the auxiliary materials, pour it into the egg liquid, stir it for 5 minutes, and filter it; use 20 mesh (upper), 60 mesh (middle), and 80 mesh (lower) sieves to overlap and filter out the foam or fine eggshells in the product.

[0107] (C) pouring the filtered egg liquid into a mold box, covering the mold cover, and putting it into a reverse pressure sterilizer for steaming; after the steaming is completed, taking out the mold, placing it at room temperature to cool it down, taking out the product from the mold box, and placing the product in clean water to wait for braising; the reverse pressure sterilizer condition is set to 105° C., 60 min;

[0108] (D) Pour the marinade bag into a pot and heat it to 80°C, immerse the product in the marinade solution and heat for 10 minutes; after the marinating is completed, remove the product and place it in clean water for rinsing;

[0109] (E) Spread the rinsed product on a baking tray, drain the water, and bake in an oven. Let it cool. The oven condition is set at 125±5℃ for 25min.

[0110] Example 6

[0111] The method for preparing dried eggs based on OS-X or / and LS-X is as follows:

[0112] (A) Wash and break the eggs, and take out the egg liquid for later use;

[0113] (B) Weigh the egg protein-sodium hyaluronate conjugate, melt it with the auxiliary materials, pour it into the egg liquid, stir it for 8 minutes, and filter it; use 20 mesh (upper), 60 mesh (middle), and 80 mesh (lower) sieves to overlap and filter out the foam or fine eggshells in the product.

[0114] (C) pouring the filtered egg liquid into a mold box, covering the mold cover, and putting it into a reverse pressure sterilizer for steaming; after the steaming is completed, taking out the mold, placing it at room temperature to cool it down, taking out the product from the mold box, and placing the product in clean water to wait for braising; the reverse pressure sterilizer condition is set to 105° C., 60 min;

[0115] (D) Pour the marinade bag into a pot and heat it to 85°C, immerse the product in the marinade solution and heat for 12 minutes; after the marinating is completed, remove the product and place it in clean water for rinsing;

[0116] (E) Spread the rinsed product on a baking tray, drain the water, and bake in an oven. Let it cool. The oven condition is set at 125±5℃ for 25min.

[0117] In the present invention, sodium hyaluronate (SH) is used to react with two kinds of egg proteins, ovalbumin (OVA) and livetin (LIV), for different time periods (0, 2h, 4h, 6h, 12h, 18h, 24h) by dry glycosylation to prepare OVA-SH or LIV-SH conjugates (OS-X or LS-X, X represents the glycosylation time). The products are analyzed by grafting degree, SDS-PAGE gel electrophoresis, intrinsic fluorescence, surface hydrophobicity, infrared, solubility, emulsification, foaming and thermal stability; and then added to dried eggs to explore their effects on the quality of dried eggs.

[0118] The results showed that OS-24 and LS-4 had the highest grafting degrees, which were 46.42% and 40.46%, respectively. The surface hydrophobicity of OS and LS decreased significantly, among which LS-4 and OS-18 had the lowest surface hydrophobicity, which were 277.98 and 49.34, respectively. The peak wavenumbers of amide I and II bands of OS and LS increased, shifting from 1645.46cm-1 (OVA) and 1652.30cm-1 (LIV) to 1648.84cm-1 (OS-24) and 1661.31cm-1 (LS-24), respectively. OS-4 and LS-18 had the highest emulsification stability index, which were 104.92 and 117.67min, respectively. OS-18 and LS-12 had the highest emulsification activity, which were 171.89m-1, respectively. 2 / g and 209.96m 2 / g; the protein denaturation temperature gradually increased from 114.6584℃(OVA) and 115.071℃(LIV) to 123.353℃(OS-24) and 124.3034℃(LS-24). The yield, hardness, color and water holding capacity of egg jerky with the addition of SH were significantly improved. The results showed that the use of glycosylated egg protein in the preparation of egg jerky is beneficial to the improvement of the edible quality of egg jerky. The research results provide theoretical and technical support for expanding the application of SH in processed foods (such as egg products).

[0119] The specific tests are as follows:

[0120] Test 1 Identification of OS-X or LS-X

[0121] Determination of degree of grafting (DG)

[0122] Via OPA method

[14] Determination of free amino content: After centrifugation, the concentration of the supernatant was adjusted to 1 mg / mL, 0.3 mL of OPA reagent A and 3.7 mL of OPA reagent B were mixed, and 200 μL of sample solution was added and mixed, and reacted at room temperature for 2 min. The OPA reagent was added with 200 μL of water as a blank, and the absorbance was measured at 340 nm using an ELISA reader. DG was calculated according to formula 1.

[0123]

[0124] Where A0 and A1 are the absorbance values ​​of the solution before and after glycosylation, respectively.

[0125] Grafting degree analysis

[0126] Changes in the content of free amino groups can reflect the degree of protein glycosylation. Figure 1 As shown. With LIV and OVA as reference, LS-0 and OS-0 have lower grafting degrees, which may be due to the fact that SH is easily decomposed into hyaluronic acid in the solution, and hyaluronic acid will also react with amino groups at room temperature. As the glycosylation reaction time increases, the grafting degree of the protein samples generally shows a trend of first decreasing and then increasing. OS has the lowest and highest grafting degrees at 6h and 24h, respectively, and the highest can reach 46.42%. LS has the highest and lowest grafting degrees at 4h and 18h, respectively. The trend of the grafting degree decreasing in a shorter glycosylation time may be because the protein first undergoes slight denaturation at this temperature, and cross-linking occurs between proteins, which is not conducive to reaction with SH. As the dry heat reaction time increases, the protein and SH are covalently bonded, and the grafting degree gradually increases and reaches the maximum. This may be because the change in protein structure exposes more amino groups, and the probability of binding to the carbonyl group in SH increases, thereby significantly increasing the grafting degree.

[0127] The reaction schematic diagram of the structural formula in the grafting process of the present invention is as follows Fig. 27 As shown, the picture is from a paper published by this research team: Protein glycosylation a promising way to modify the functional properties and extend the application in food system.

[0128] Protein composition analysis

[0129] Protein composition was analyzed by SDS-PAGE

[15] . Use a gel kit to prepare 5% concentrated gel and 10% separation gel, respectively, for electrophoresis experiments. Dissolve the sample in 2 times loading buffer, and after fully dissolved, place it in a boiling water bath and heat it for 3 minutes. After cooling to room temperature, centrifuge the sample solution at 3000r / min for 10 minutes, take the supernatant for loading, the sample loading volume is 15μL, and the marker is 5μL. Keep the voltage constant at 120V during the electrophoresis process. After the electrophoresis is completed, use 0.25% (w / v) Coomassie Brilliant Blue R 250 staining solution to stain the gel for 50 minutes, and then decolorize it with methanol-glacial acetic acid solution. Change the decolorizing solution every 20 minutes until the bands are clear. After decolorization, take photos of the gel for analysis.

[0130] The glycosylation products were analyzed by electrophoresis. Figure 2 As shown. Proteins can undergo glycosylation reactions to form covalent bonds between their amino groups and the carbonyl groups of reducing sugars, thereby increasing their molecular weight and promoting the formation of polymers (such as dimers and trimers).

[0131] The electrophoresis results showed that compared with OVA and LIV, the electrophoretic bands of glycosylation products shifted slightly upward, indicating that OVA, LIV and SH molecules were covalently cross-linked, which increased the molecular weight of OVA and LIV and modified the protein sequences of OVA and LIV.

[0132] Compared with the traditional grafting method, the reaction sites of the glycosylation covalent cross-linking in the present invention are the free amino groups of the protein and the reducing groups (such as carbonyl groups) of the reducing sugars. The two combine to form a carbon-nitrogen bond to achieve condensation (i.e., carbonyl-amine condensation), while losing one molecule of water.

[0133] The color of the glycosylation product band becomes lighter, which may be because more insoluble products are produced after the glycosylation reaction, resulting in a lower protein concentration. In addition, a shadow band is slightly visible at the top of the glycosylation product band, which may be due to the fact that glycosylation produces products with larger molecular weights, which are blocked in the concentrated gel. Zhong Bizhen

[23] also found similar experimental phenomena when reacting glucose with OVA.

[0134] Experiment 2: Structural Characterization of OS-X or LS-X

[0135] Determination of intrinsic fluorescence spectrum

[0136] The determination was performed according to Zhou's method. The sample was dispersed in 10 mmol / L PBS (pH 7) at a concentration of 1 mg / mL, vortexed for 5 minutes, and placed in a 4°C refrigerator overnight. The sample solution was centrifuged at 10000 r / min for 10 minutes, and the supernatant was taken. The intrinsic fluorescence spectrum of the sample solution was measured using an ELISA instrument, with the excitation wavelength set to 290 nm, the emission spectrum scanning range set to 270-500 nm, and the scanning interval set to 2 nm.

[0137] The protein was analyzed by intrinsic fluorescence. Figure 3 and Figure 4 shown. Figure 3 and Figure 4 The endogenous fluorescence spectra of different samples in the range of 350-420 nm are shown. The maximum emission wavelength (λmax) of OVA is 376.2 nm, and the maximum fluorescence intensity is 2073.36. The λmax of OS-0 is 377.6 nm, and the maximum fluorescence intensity is 2721.55. This may be because although SH did not undergo glycosylation reaction with the protein, it changed the pH of the system (pH 6.1), causing the conjugation system of the OVA molecule to change, resulting in an increase in fluorescence intensity. The λmax of the glycosylated product showed a slight blue shift compared to OS-0, indicating that tryptophan is in a more hydrophobic environment. This is inconsistent with the research results of Wang Yating, Huang et al. (after the protein undergoes glycosylation reaction, the fluorescence intensity will decrease and the wavelength will red shift). It may be because after the protein structure is unfolded, the exposed tryptophan is surrounded and shielded by SH covalently bound to the protein, causing it to be in a more hydrophobic environment. The fluorescence intensity decreased to 2249.65 (OS-2), 2696.85 (OS-6), 2403.83 (OS-12), 2585.12 (OS-18), and 2556.12 (OS-24). On the one hand, the heating treatment increased the energy loss of molecular collisions, which was not conducive to the generation of fluorescence. On the other hand, when the fluorescent chromophore interacted with the solvent, the quantum yield of fluorescence might decrease.

[0138] Compared with LIV (λmax=377.9nm), the λmax of LS-0 remained unchanged, but the fluorescence intensity increased from 1558.93 to 1585.89. Compared with LS-0, the maximum emission wavelengths of LS-2 (λmax=377.6nm), LS-4 (λmax=375.9nm), and LS-12 (λmax=375.7nm) were blue-shifted. The λmax of LS-6 (λmax=378.4nm), LS-18 (λmax=378.9nm), and LS-24 (λmax=379.3nm) were red-shifted. This indicates that the molecular structure of LIV is unfolded and tryptophan is exposed to a more polar environment. The changes in fluorescence intensity and maximum emission wavelength confirm that the tertiary conformation of the protein has changed.

[0139] Surface hydrophobicity determination

[0140] The determination was carried out with reference to the method of Achouri et al. ANS was used as a fluorescent probe, and the sample was dispersed in 10 mmol / L PBS (pH 7) at a concentration of 1 mg / mL. After vortexing for 5 minutes, it was placed in a 4°C refrigerator overnight. After the sample solution was centrifuged at 10000 r / min for 10 minutes, 3 mL of the supernatant was added with 60 μL ANS (8 mmol / L, dissolved in 10 mmol / L PBS), and after thorough mixing, the fluorescence spectrum of the sample was measured under the conditions of an excitation wavelength of 290 nm, an emission wavelength of 400 to 600 nm, and a scanning interval of 2 nm. The maximum fluorescence intensity value represents the surface hydrophobicity of the sample.

[0141] The surface hydrophobicity of the sample is Figure 5 As shown. Compared with LIV and OVA, the surface hydrophobicity of LS-0 and OS-0 is significantly reduced. This may be because SH is connected to the protein molecule through non-covalent bonds. The presence of sugar chains increases the hydroxyl groups on the protein surface and increases the number of hydrophilic groups, which reduces its hydrophobicity. When sugar and protein undergo glycosylation reaction, that is, sugar is bound to protein in the form of covalent bonds, the hydrophobicity of the protein molecule is also significantly reduced compared with LIV and OVA. This may be because during the glycosylation process, SH molecules have a surrounding and shielding effect on lysine and arginine, blocking the connection between hydrophobic amino acids and ANS probes. Mao Jihua used three hexoses (glucose, galactose, and fructose) to react with OVA for glycosylation and measured the surface hydrophobicity, and obtained similar experimental results.

[0142] Fourier transform infrared spectroscopy (FTIR) determination

[0143] Mix 2 mg of sample with 200 mg of potassium bromide and grind into powder. Press into tablets with a tablet press and place in FTIR for scanning. The scanning range is 4000-400 cm -1 , resolution 4cm-1 , the number of scans is 32 times.

[0144] The infrared absorption spectra of OVA, OS-X, LIV and LS-X are as follows: Figure 6 and Figure 7 In general, amide I (1700-1600 cm -1 )、Ⅱ(1530-1550cm -1 ) and III (1220-1330cm -1 The change in the peak position of the glycosylated protein group sample indicates that the protein structure has changed. As shown in the figure, compared with the untreated protein, the positions of the above three peaks of the glycosylated protein group sample have all changed. The reaction product at 3700cm -1 -3200cm -1 The peak at 1645.46 cm-1 became wider and stronger, which indicates that SH was covalently linked to the protein. After glycosylation, the peak positions of amide I changed from 1645.46 cm-1 to 1645.46 cm-1. -1 (OVA), 1652.30cm -1 (LIV) transferred to 1648.84cm -1 (OS-24), 1661.31cm -1 (LS-24). The increase in wave number may be due to the reaction between -NH in OVA and the carbonyl group on SH, which affects the stretching vibration of C=O, thus shifting the peak at the amide I band. The peak position of amide II shifted from 1535.06 cm -1 (OVA), 1526.19cm -1 (LIV) transferred to 1542.29cm -1 (OS-24), 1540.11cm -1 (LS-24), the amide II band belongs to the deformation vibration of NH or the stretching vibration of CN. This may be due to the carbonyl-amine condensation reaction, which affects the deformation vibration of -NH, thereby causing the peak at the amide II band to shift.

[0145] Test 3 Determination of functional properties of OS-X or LS-X

[0146] Solubility

[0147] The determination was carried out by Coomassie Brilliant Blue G250 staining method. Take 6 test tubes, prepare 0-100 μg / mL bovine serum albumin dilution solutions, take the dilutions of each concentration and add them to the Coomassie Brilliant Blue G250 solution, shake and mix, let stand for 10 minutes, measure the absorbance at a wavelength of 595 nm, and draw a standard curve. After diluting the sample to a concentration of 1 mg / mL, dissolve it in ultrapure water of pH 3, 5, 7, 9, and 11, stir and dissolve it thoroughly. Centrifuge at 8 000r / min for 15 minutes, take the supernatant and add the Coomassie Brilliant Blue G250 solution, shake and mix, and let stand for 10 minutes. Use the Coomassie Brilliant Blue G250 solution as a blank, measure the absorbance at a wavelength of 595nm, and calculate the protein solubility in the solution according to the standard curve.

[0148] Solubility is one of the important functional properties of proteins. Figure 8 and Fig. 9 As shown. In an acidic environment, the closer the pH is to 5, the lower the solubility is. This is related to the isoelectric point of the protein. The pH value affects the structure and properties of the protein by affecting its surface charge. The closer the pH value is to the isoelectric point of the protein, the less charge it carries on the surface and the lower the solubility is.

[30] When the pH value is close to 9, the solubility of some samples also shows a downward trend. This may be because the protein undergoes a certain degree of denaturation, the structure unfolds, and the internal hydrophobic groups are exposed, which enhances the hydrophobic interaction of the protein and causes aggregation between proteins. On the other hand, it may be that the Na + Under low concentration conditions, a charge shielding effect will occur, which will cause the protein to resist the influence of foreign salt ions and undergo aggregation, thereby reducing the solubility of the protein.

[31] When pH>9, the solubility increases again, probably due to Na + When the concentration reaches a certain range, it promotes the dissolution of protein.

[32] The effect of NaCl concentration on the solubility of millet protein isolate was studied. It was found that when the salt ion concentration was 0.01 mol / L, the mass concentration of millet protein isolate began to decrease, reached the lowest at 0.05 mol / L, and then began to rise again. The mass concentration of protein tended to stabilize at 0.3 mol / L. The solubility of glycosylated proteins is generally higher, which may be related to the vacuum freeze-drying treatment of the samples. The microstructure of the freeze-dried protein is flaky and has a large specific surface area.

[0149] Emulsification

[0150] Reference Zhang

[19] Method: The emulsification properties of the sample were characterized by measuring the emulsification activity index (EAI), emulsification stability index (ESI) and microstructure of the emulsion. The sample was dispersed in 10mmol / L PBS (pH7) at a concentration of 0.1% (w / v), vortexed for 5min and placed in a 4°C refrigerator overnight. Before the test, the sample solution was equilibrated at room temperature for 30min, and soybean oil was added to make the final oil phase volume fraction 10% (v / v). The mixed solution was homogenized at 12000r / min for 2min. At the 0th and 10th min after homogenization, 50μL of emulsion was taken from the bottom of the container and diluted in 0.1% (w / v) SDS solution (dilution ratio 1:100, v / v). After vortexing for 5s, its absorbance was measured at 500nm. The blank was 0.1% (w / v) SDS solution. EAI and ESI were calculated as follows:

[0151]

[0152] Where: A0 and A 10 are the absorbance values ​​of the emulsion at 0 min and 10 min, respectively; is the volume fraction of oil phase, v / v; c is the protein concentration, g / mL; θ is the optical path, 1 cm; DF is the dilution factor.

[0153] The results of Emulsification Activity Index (EAI) and Emulsion Stability Index (ESI) are as follows: Fig.10 and Fig.11 As shown. When the pH is constant (pH = 7.0, far away from pI), as the glycosylation reaction time increases, the EAI of OVA shows a trend of gradual increase, while the ESI shows a trend of first increasing and then decreasing. For glycosylated LIV, both EAI and ESI show a trend of first increasing and then decreasing. The significant increase in EAI may be due to the fact that the addition of sugar chains and heat treatment can unfold the protein structure to expose more hydrophobic groups, thereby improving the hydrophilic / hydrophobic balance of the protein itself, which is conducive to the encapsulation of oil droplets, thereby enhancing the emulsification activity of the sample. The significant increase in ESI may depend on the presence of SH, which can provide steric hindrance, prevent droplet flocculation and aggregation, and thus stabilize the emulsion. Zhou Yangying used soy protein isolate for glycosylation reaction, and the EAI and ESI of the product showed the same trend of first increasing and then decreasing.

[0154] Foaming

[0155] Referring to the method of Ma et al.: the sample was dissolved in pH 7 PBS buffer to prepare a 0.1% (w / v) protein solution. 20 mL of protein solution was taken and the initial height H0 was recorded. After homogenization at 10000 r / min for 2 min, the height H1 was recorded. After standing for 10 min, the height H2 was recorded again. The foamability (FAI) and foam stability (FSI) of the protein solution were calculated according to formula (4) and (5):

[0156]

[0157] Where: FAI - foaming property of protein solution, %; FSI - foam stability, %.

[0158] The foaming ability and foaming stability of proteins are related to the surface tension at the air-water interface and are closely related to the protein structure. Fig.12 and Fig.13 It can be seen that after the glycosylation reaction, the FAI of the protein-sugar conjugate showed a significant downward trend, but the FSI showed an upward trend. The decrease in FAI may be because the dry glycosylation reaction changes the surface charge of the protein, and the repulsion between proteins is reduced, causing the protein to form polymers. The increase in FSI may be due to the fact that the foam formed by sugar-protein has a smaller volume, can resist disproportionation and drainage, and is resistant to excessive stirring, which can prevent the formation of insoluble aggregates with prolonged whipping and improve the foam stability of sugar-protein conjugates. On the other hand, it may be due to the presence of polymers that will adsorb at the air / water interface to form a network structure, thereby improving the stability of the foam.

[0159] Thermal stability

[0160] Refer to Wang Yifan's method: Use differential scanning calorimetry (DSC) to analyze the thermal stability of the sample. Accurately weigh 4 mg of freeze-dried sample and place it in a solid aluminum crucible and seal it. Balance it at room temperature for at least 2 hours. Heat from 20°C to 250°C at a heating rate of 5°C / min, with a nitrogen flow rate of 50mL / min, and use a sealed empty crucible as a reference. The peak temperature (Tp) and thermal denaturation enthalpy change (ΔH) are calculated based on the endothermic curve. Tp is the peak temperature of the endothermic peak, and ΔH is defined as the area under the endothermic curve. All values ​​are calculated using the General Analysis 2000 software provided by TA Instruments.

[0161] Effects of adding OVA, OS-X, LIV, and LS-X on the physical and chemical properties of dried eggs.

[0162] The thermodynamic properties of proteins were characterized by differential scanning calorimetry, and the denaturation temperatures (Tp) and thermal enthalpy changes (ΔH) of OVA, LIV, OS-X and LS-X were compared. Fig.14 and Fig.15It shows that as the glycosylation time increases, the protein denaturation temperature increases, from 114.6584℃ (OVA), 115.071℃ (LIV) to 123.353℃ (OS-24), 124.3034℃ (LS-24). The higher the denaturation temperature, the better the thermal stability of the protein. This may be due to the covalent bonding of sugar chains that improves the thermodynamic stability of the protein. ΔH also shows a similar trend to Tp. Yuan Dan

[40] used OVA and D-lactose as raw materials to prepare glycosylated products and found that the thermal denaturation temperature of OVA after glycosylation modification was significantly increased, and the corresponding denaturation enthalpy value ΔH also showed an increasing trend.

[0163] Test 4

[0164] Preparation of dried eggs

[0165] Wash and break the eggs, and take out the egg liquid for later use. Weigh SH, OS-0, LS-0, OS-24, and LS-4 (0.5g / kg, the amount to be added is determined by preliminary experiments), melt them with the auxiliary materials, pour them into the egg liquid and stir for 5 minutes. Filter the stirred egg liquid, and use 20 mesh (upper), 60 mesh (middle), and 80 mesh (lower) sieves to overlap and filter out the foam or fine eggshells in the product. Pour the filtered egg liquid into the mold box, cover the mold cover, and put it into the reverse pressure sterilizer for steaming. The reverse pressure sterilizer is set to 105℃ for 60min. After the steaming is completed, take out the mold, place it at room temperature and wait for it to cool down, then take out the product from the mold box, and place the product in clean water (to prevent the surface of the product from drying out and causing the marinade to not color. Direct marinating does not need to be placed in cooling water) and wait for marinating. Pour the marinade bag into the pot and heat it to 75-85℃, soak the product in the liquid, and heat it for 10min. After the marinating is finished, take out the product and place it in clean water to rinse off the excess soy sauce on the product. Spread the rinsed product on the baking tray, drain the water and bake it. The oven condition is set to 125±5℃, 25min, and after baking, wait for it to cool down to get the final product.

[0166] Determination of yield

[0167] The product yield is calculated as the percentage of the mass of the dried eggs after steaming, boiling and baking to the mass of the raw materials.

[0168]

[0169] Where: Y is the product yield, %; m1 is the total mass of the egg mixture after stirring (g); m2 is the mass of the dried egg after steaming, boiling and baking (g).

[0170] Egg drying rate Fig.16The dry egg yield of the blank group was 79.94%, and the yields of the other groups were all greater than 80%. The yield of the product with LIV added was significantly increased to 82.63%, which may be due to the presence of low-density lipoprotein in the protein, which can act as an emulsifier to make the eggs better emulsified and dissolved during the mixing process. The dry egg yield of the eggs with the addition of SH or glycosylated egg protein did not increase significantly, but it did not have a negative impact on the dry egg yield.

[0171] Water holding capacity determination

[0172] The centrifugation method was used for determination. During the determination, about 1 g of egg dry was evenly cut and weighed as m1, then placed in a centrifuge tube with absorbent cotton at the bottom, centrifuged at 20°C and 7500 r / min for 10 min, and the egg dry after centrifugation was weighed as m2. After that, the gel sample was placed in a 105°C oven and dried for 6 h, and weighed as m3. The WHC of egg dry was calculated as shown in formula (7).

[0173]

[0174] Where: m1 is the mass of sample gel before centrifugation (g); m2 is the mass of sample gel after centrifugation (g).

[0175] Effects of different additives on the water holding capacity of dried egg products Fig.17 As shown. Compared with the blank, except for the dried eggs with LIV and LS-4, the water holding capacity of the dried eggs in the other control groups was significantly improved (p<0.05). The water holding capacity of the dried eggs with OS-0 was as high as 95.11%, an increase of 6.85%. The increase in water holding capacity may be due to the fact that the addition of OVA and SH can improve the density and orderliness of the internal structure of the dried egg products, thereby improving the ability to fix water molecules. The water holding capacity is closely positively correlated with the texture, taste, and flavor of gel foods. The increase in water holding capacity indicates that SH or egg protein glycosylated with SH can improve important edible qualities such as the taste and flavor of dried eggs.

[0176] Color difference analysis

[0177] Cut the egg dry samples to ensure that the cross section is flat, use a colorimeter to measure the L*, a*, and b* values ​​of the sample cross section, measure each group of samples in parallel 3 times, and take the average value.

[0178] The effects of different additives on the color of dried eggs are shown in Table 1. Among them, the closer the brightness value L* is to 100, the whiter it is; when the a* value is positive, it indicates red; when the b* value is positive, it indicates yellow. The additional additives have no significant effect on the brightness value L* and the yellow-blue value b* of the dried eggs, but have a significant effect on the red-green value a* of the product. The a* value represents the saturation of the color on the red-green axis. The larger the a*, the more additional SH or egg protein glycosylated with SH can make the dried egg product brighter and help improve the color of the product.

[0179] Table 1 Effects of different additives on the color of dried egg products

[0180]

[0181] Note: Different letters indicate significant differences within the groups (p<0.05).

[0182] Gel hardness

[0183] Fig.18 The effect of different additives on the hardness of dried egg products is shown. The hardness of dried eggs with added OVA and SH was significantly improved compared with the blank group, by 43.54% and 65.55% respectively. The increase in hardness may be due to the addition of SH, which increases the soluble solid content in the dried eggs, and other macromolecules and sugars in the eggs may have cross-linked to form a new pore structure, resulting in an increase in hardness. Zhang

[41] et al. prepared glycine-carbohydrate by dry heat method and added it to whole soybean tofu. They found that when glycine-carbohydrate conjugate was used as part of the raw material, the yield, hardness and gel strength of whole soybean tofu were significantly improved. Studies have reported that OVA can significantly promote the gel properties of egg white.

[23] Therefore, adding additional OVA to increase the OVA content in the egg liquid can also increase the hardness of the gel.

[0184] Determination of texture properties

[0185] The whole texture profile analysis (TPA) of dried egg products was performed with a 12mm diameter round hole sampler. The samples were processed into a Φ12mm×10mm cylinder. The P / 36R cylindrical probe was used for testing. The test conditions were: pre-test speed 1.00mm / s; test speed 5.00mm / s; post-test speed 5.00mm / s, compression distance 5.00mm; test time 5s; trigger force 5g. Three parallels were measured for each group of samples, and the results were averaged.

[0186] Microscopic morphology observation and analysis

[0187] The microstructure of the samples was observed using a scanning electron microscope. The samples were cut into small pieces of 2 mm × 2 mm × 2 mm, fixed in 0.1 mol / L phosphate buffer (containing 25% glutaraldehyde by mass, pH 7), placed at 4 ° C for 24 hours, washed with 0.1 mol / L phosphate buffer, and then dehydrated step by step using 60%, 70%, 80%, 90% and 100% ethanol solutions by volume. After dehydration, the samples were vacuum freeze-dried. After the samples were dried, gold was sprayed, and the microstructure of the samples was observed using a scanning electron microscope at a voltage of 15 kV.

[0188] The microstructure observed by SEM is as follows Figure 19-Figure 26 As shown, the observation scale of each group is 50, 100, and 200 μm, respectively. The microscopic morphology of the blank group is dense, without obvious large pores, the surface is uneven, and the micropores are unevenly distributed. The surface of the product with the addition of LIV, OVA, and OS-24 becomes loose and porous. The surface of the product with the addition of SH and OS-0 is flat, the micropores are more evenly distributed, and the overall morphology is greatly improved compared with the blank. This may be because the addition of SH and OS-0 allows the product to capture more water molecules, and the increase in water content plays a positive role in the dissolution of macromolecules such as proteins and sugars, making the gel formation more continuous and dense. In the microscopic morphology pictures of products containing LS-0, OS-0 and LS-4, more obvious pores can be observed, and the overall appearance becomes slightly loose and uneven compared with the control. This may be because the addition of LS-0, OS-0, and LS-4 has a certain hindering effect on the mutual binding between proteins, thereby causing the discontinuous formation of the gel.

[0189] For the above data processing, Microsoft Office Excel 2019 software was used to perform statistical analysis on the experimental data; SPSS23.0 was used to perform correlation and significance analysis (p<0.05) in single-factor experiments; and Origin 21 software was used to draw graphs.

[0190] The above implementation / test examples are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A dried egg prepared based on egg protein-sodium hyaluronate conjugate, characterized in that: The invention comprises the following components in parts by weight: egg white, egg protein-sodium hyaluronate conjugate and auxiliary materials; The preparation method of the egg protein-sodium hyaluronate conjugate comprises the following steps: (1) Hydration: Disperse egg yolk protein and / or egg white protein in ultrapure water to prepare a dispersion with a volume concentration of 5%, then add an equal amount of sodium hyaluronate, mix well, stir at room temperature for 1-3 hours, and place in a refrigerator at 3-5°C overnight to fully hydrate; (2) Spread the powder obtained after freeze-drying the mixture in a culture dish, place it in an incubator at 55-65° C. and a relative humidity of 75-82% for 1-24 hours, and then take it out; (3) Cooling: Rapid cooling to terminate the reaction and obtain OS-X and / or LS-X; (4) Drying and storage: The obtained conjugate is freeze-dried and stored at -25°C to 18°C ​​for later use.

2. The dried egg prepared based on the egg protein-sodium hyaluronate conjugate according to claim 1, characterized in that: Calculated based on the mass of egg white, the amount of the egg protein-sodium hyaluronate conjugate is 0.4-0.6 g / kg.

3. The dried egg prepared based on the egg protein-sodium hyaluronate conjugate according to claim 2, characterized in that: Calculated based on the mass of egg white, the amount of the egg protein-sodium hyaluronate conjugate is 0.5 g / kg.

4. A dried egg prepared based on egg protein-sodium hyaluronate conjugate according to any one of claims 1-3, characterized in that: The freeze-drying temperature in step (2) is -65°C to 58°C, and the time is 46-50 hours.

5. A dried egg prepared based on egg protein-sodium hyaluronate conjugate according to any one of claims 1-3, characterized in that: In the rapid cooling in step (3), rapid means cooling in a -20°C refrigerator for 48 hours.

6. A dried egg prepared based on egg protein-sodium hyaluronate conjugate according to any one of claims 1-3, characterized in that: In the step (4), the conjugate is freeze-dried at a temperature of -60°C and a drying time of 48 hours.

7. A dried egg prepared based on egg protein-sodium hyaluronate conjugate according to any one of claims 1-3, characterized in that: In the step (2), the OVA is taken out after 24 hours of reaction in the incubator; and the LIV is taken out after 4 hours of reaction.

8. A method for preparing dried egg based on egg protein-sodium hyaluronate conjugate according to any one of claims 1-3, characterized in that: The following steps are involved: (A) Wash and break the eggs, and take out the egg liquid for later use; (B) weighing, melting with auxiliary materials, pouring into egg liquid, stirring for 4-8 minutes, and filtering; (C) pouring the filtered egg liquid into a mold box, covering the mold cover, and putting it into a back-pressure sterilizer for steaming; after the steaming is completed, taking out the mold, placing it at room temperature until it cools down, taking out the product from the mold box, and placing the product in clean water to wait for brine; (D) Pour the marinade bag into a pot and heat it to 75-85°C, immerse the product in the marinade solution and heat for 8-12 minutes; after the marinating is completed, remove the product and place it in clean water for rinsing; (E) Spread the rinsed product on a baking tray, drain the water, bake in the oven, and cool.

9. The method for preparing dried egg based on egg protein-sodium hyaluronate conjugate according to claim 8, characterized in that: In the step (C), the back pressure sterilizer condition is set to 105° C. for 60 min.

10. The method for preparing dried egg based on egg protein-sodium hyaluronate conjugate according to claim 8, characterized in that: In the step (E), the oven condition is set to 125±5° C. for 25 min.

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