Isomaltitol-loaded bioadhesive powder hydrogel as well as preparation method and application thereof

Abstract

The invention provides isomaltitol-loaded bioadhesive powder hydrogel as well as a preparation method and application thereof, and belongs to the technical field of food preservation. The preparation method comprises the following steps: mixing and swelling isomaltitol, gelatin and sodium alginate, then carrying out heat treatment, and then preparing the isomaltitol-loaded bioadhesive powder hydrogel under the crosslinking of glutamine transaminase and glucolactone. The isomaltitol-loaded bioadhesive powder hydrogel disclosed by the invention is good in biocompatibility and relatively strong in bioadhesive force, and can be quickly attached to the surface of a wet aquatic product to realize effective combination with tissues; moreover, isomaltitol capable of obviously reducing the expression level of a pseudomonas fluorescens P15 related putrefying gene is loaded on the hydrogel, and the putrefying ability of bacteria is reduced and the generation speed of resistance of the bacteria is delayed by inhibiting the expression level of the putrefying gene regulated and controlled by quorum sensing of the bacteria, so that the antibacterial and fresh-keeping effects are achieved; the method is suitable for aquatic product preservation.

Description

Technical Field

[0001] The present invention relates to the technical field of food preservation, and particularly relates to an isomaltitol-loaded bioadhesive powder hydrogel and its preparation method and application. Background Art

[0002] In recent years, the demand for aquatic products by people has been increasing day by day. However, due to the fact that the aquaculture environment or sales environment of aquatic products is mostly flowing water at 10-20°C, and the protein content of aquatic products is rich, which is very suitable for the growth and reproduction of microorganisms. As a result, aquatic products are very likely to be contaminated by bacteria during the processes of fishing, storage and transportation. This not only reduces the nutritional value of aquatic products, but also causes potential hazards such as acute or chronic poisoning. Therefore, the demand for the preservation of aquatic products is very urgent. At present, the commonly used preservation methods for aquatic products are divided into physical preservation, chemical preservation, etc. Even with low-temperature storage, due to the existence of psychrophilic bacteria, the deterioration of aquatic products will still occur; at the same time, there are also problems such as low timeliness and potential safety hazards in preservation means such as adding preservatives. However, the surface of aquatic products is in a wet state, and traditional hydrogels are not easy to adhere to and wrap, and the demand is very large. Therefore, finding a solution that can inhibit the growth of spoilage bacteria in aquatic products and improve their food safety at the same time is of great significance for ensuring food safety and improving the competitiveness of enterprises. Summary of the Invention

[0003] The purpose of the present invention is to provide an isomaltitol-loaded bioadhesive powder hydrogel and its preparation method and application. The isomaltitol-loaded bioadhesive powder hydrogel can inhibit the expression level of spoilage genes regulated by quorum sensing, reduce the spoilage ability of bacteria and delay the generation rate of their resistance, and is suitable for application in the preservation of aquatic products.

[0004] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0005] The present invention provides a preparation method of an isomaltitol-loaded bioadhesive powder hydrogel, comprising the following steps:

[0006] Mix isomaltitol, water, gelatin and sodium alginate, and sequentially carry out water absorption and swelling and heat treatment, and defoam the obtained mixed solution by ultrasonic treatment to obtain a first product;

[0007] Mix the first product with a transglutaminase solution and carry out first cross-linking to obtain a second product;

[0008] Mix the second product with a glucono-δ-lactone solution and carry out second cross-linking to obtain a gel product;

[0009] Dry and grind the gel product in sequence to obtain the isomaltitol-loaded bioadhesive powder hydrogel.

[0010] Preferably, the mass ratio of the gelatin, sodium alginate and isomaltitol is 5:5:1-3; the mass ratio of the isomaltitol to water is 1-3:100.

[0011] Preferably, the temperature for water absorption and swelling is 4-10 °C, and the time is 3-5 h.

[0012] Preferably, the temperature for heat treatment is 60-70 °C, the time is 10-30 min; the number of times of heat treatment is 3-5 times.

[0013] Preferably, the mass ratio of transglutaminase to gelatin in the transglutaminase solution is 1:5-10; the temperature for the first crosslinking is 25-37 °C, and the time is 3-5 h.

[0014] Preferably, the mass ratio of glucono-δ-lactone to sodium alginate in the glucono-δ-lactone solution is 1:10-20; the temperature for the second crosslinking is 25-37 °C, and the time is 3-5 h.

[0015] Preferably, the mass concentration of the transglutaminase solution is 0.05-0.1 g / mL, and the mass concentration of the glucono-δ-lactone solution is 0.05-0.1 g / mL.

[0016] Preferably, the temperature for drying is 50-80 °C, and the time is 12-24 h.

[0017] The present invention provides a bioadhesive powder hydrogel loaded with isomaltitol prepared by the preparation method described in the above technical solution.

[0018] The present invention provides the application of the bioadhesive powder hydrogel loaded with isomaltitol described in the above technical solution in the fresh-keeping of aquatic products.

[0019] The present invention provides a preparation method of a bioadhesive powder hydrogel loaded with isomaltitol. Isomaltitol, gelatin and sodium alginate are mixed and crosslinked with transglutaminase and glucono-δ-lactone to obtain the bioadhesive powder hydrogel loaded with isomaltitol. The bioadhesive powder hydrogel loaded with isomaltitol prepared by the double crosslinking method of the present invention has good biocompatibility and strong bioadhesion force, can quickly adhere to the surface of wet aquatic products, and realize effective combination with tissues; moreover, the small molecule substance - isomaltitol loaded on the hydrogel has an inhibitory effect on the quorum sensing of Pseudomonas fluorescens, and can significantly reduce the expression level of the spoilage gene related to Pseudomonas fluorescens P15. Therefore, the bioadhesive powder hydrogel loaded with isomaltitol of the present invention can reduce the spoilage ability of bacteria and delay the generation speed of its resistance by inhibiting the expression level of the spoilage gene regulated by bacterial quorum sensing, so as to achieve the effect of antibacterial fresh-keeping and is suitable for application in the fresh-keeping of aquatic products.

[0020] The bioadhesive powder hydrogel loaded with isomaltitol prepared by the present invention is in powder form when not in contact with water, and can quickly restore to the gel state and adhere to the surface of an object when in contact with water during the preservation of aquatic products. Its powder state can be stored at room temperature, which is convenient for transportation and storage, and has low cost and simple preparation method.

[0021] The bioadhesive powder hydrogel loaded with isomaltitol of the present invention has excellent ability to inhibit the growth of spoilage bacteria, and can reduce its spoilage ability by inhibiting the quorum sensing of bacteria. When applied to the preservation of aquatic products, it can effectively inhibit the growth of spoilage bacteria, extend the storage time of aquatic products, and also provide a new idea for the application of hydrogels.

[0022] The bioadhesive powder hydrogel prepared by the present invention has the antifreeze property of hydrogel, can effectively protect the activity of the loaded substance at low temperature, and thus makes it a potential new food preservation material.

[0023] The bioadhesive powder hydrogel loaded with isomaltitol prepared by the present invention uses natural antibacterial components, has low cost, is non-toxic and harmless, is convenient to use, has a good effect on the preservation of aquatic products and the promotion of the development of the natural antibacterial component industry, and has remarkable economic, social and ecological benefits. Description of the Drawings

[0024] Figure 1 It is the comparison result of the addition amount of gelatin and sodium alginate and the crosslinking method on the texture properties of the hydrogel in Comparative Examples 1-7 of the present invention; among them, A is elasticity, B is resilience, C is the influence on hardness, and D is cohesiveness;

[0025] Figure 2 It is the influence of the addition amount of isomaltitol on the texture properties of the hydrogel in Examples 1-3 of the present invention; among them, A is elasticity, B is resilience, C is the influence on hardness, and D is cohesiveness;

[0026] Figure 3 It is the microscopic structure diagram of GSDH-2 (A-B) prepared in Comparative Example 4 and GSIH-2 prepared in Example 2 (C-D);

[0027] Figure 4 It is the secondary structure analysis result of different hydrogels. Among them, A is the infrared spectrum of gelatin, sodium alginate and GSDH-2 at 4000-2000 cm -1 ; B is the infrared spectrum of gelatin, sodium alginate and GSDH-2 at 2000-500 cm -1 ; C is the infrared spectrum of isomaltitol, GSDH-2 and GSIH-2 at 4000-2000 cm -1 ; D is the infrared spectrum of isomaltitol, GSDH-2 and GSIH-2 at 2000-500 cm -1FTIR spectra of isomaltulose, GSDH-2, and GSIH-2;

[0028] Figure 5 Effect of GSIH-2 prepared in Example 2 and GSDH-2 prepared in Comparative Example 4 on the pH of salmon fillets;

[0029] Figure 6 Effect of GSIH-2 prepared in Example 2 and GSDH-2 prepared in Comparative Example 4 on the water holding capacity of salmon fillets;

[0030] Figure 7 Effect of GSIH-2 prepared in Example 2 and GSDH-2 prepared in Comparative Example 4 on the texture properties of salmon fillets; where A is hardness and B is elasticity;

[0031] Figure 8 Effect of GSIH-2 prepared in Example 2 and GSDH-2 prepared in Comparative Example 4 on the total number of colonies of salmon fillets;

[0032] Figure 9 Effect of GSIH-2 prepared in Example 2 and GSDH-2 prepared in Comparative Example 4 on the content of total volatile basic nitrogen (TVB-N) in salmon fillets;

[0033] Figure 10 Effect of GSIH-2 prepared in Example 2 and GSDH-2 prepared in Comparative Example 4 on the content of thiobarbituric acid (TBA) in salmon fillets;

[0034] Figure 11 Effect of GSIH-2 prepared in Example 2 and GSDH-2 prepared in Comparative Example 4 on the salt solubility of myofibrillar proteins in salmon fillets. Detailed implementation manners

[0035] The present invention provides a method for preparing a bioadhesive powder hydrogel loaded with isomaltulose, comprising the following steps:

[0036] Mix isomaltulose, water, gelatin, and sodium alginate, and sequentially perform water absorption swelling and heat treatment, and degas the obtained mixture by ultrasonic treatment to obtain a first product;

[0037] Mix the first product with a transglutaminase solution and perform a first crosslinking to obtain a second product;

[0038] Mix the second product with a glucono-δ-lactone solution and perform a second crosslinking to obtain a gel product;

[0039] Dry and grind the gel product in sequence to obtain a bioadhesive powder hydrogel loaded with isomaltulose.

[0040] In the present invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well-known to those skilled in the art.

[0041] In the present invention, isomaltitol, water, gelatin and sodium alginate are mixed, and subjected to water absorption swelling and heat treatment in sequence, and the obtained mixed solution is subjected to ultrasonic defoaming to obtain a first product.

[0042] In the present invention, the mass ratio of the gelatin, sodium alginate and isomaltitol is preferably 5:5:1 - 3, more preferably 5:5:2; the mass ratio of the isomaltitol to water is preferably 1 - 3:50, more preferably 1 - 2:50.

[0043] In the present invention, the temperature of the water absorption swelling is preferably 4 - 10 °C, more preferably 4 - 6 °C, and the time is preferably 3 - 5 h, more preferably 3 - 4 h.

[0044] In the present invention, the temperature of the heat treatment is preferably 60 - 70 °C, more preferably 60 - 65 °C, and the time is preferably 10 - 30 min, more preferably 20 min; the number of times of the heat treatment is preferably 3 - 5 times, more preferably 3 times. Since gelatin will form aggregates under direct heating, making the dissolution process difficult, in the present invention, by the way of first swelling at low temperature and then heat treatment, the gelatin is dissolved more uniformly and finely in the system.

[0045] In the present invention, the heat treatment method is preferably water bath heating; after each heat treatment, the present invention preferably takes out the product, fully stirs and cools it to room temperature, and then conducts heat treatment again. After cycling 3 times, ultrasonic defoaming is carried out.

[0046] In the present invention, the ultrasonic power of the ultrasonic defoaming is preferably 320 W, and the time is preferably 1 h. After completing the ultrasonic defoaming, it is cooled to room temperature to obtain a first product.

[0047] After obtaining the first product, the present invention mixes the first product with a transglutaminase solution to carry out first crosslinking to obtain a second product.

[0048] In the present invention, the mass concentration of the transglutaminase solution is preferably 0.05 - 0.1 g / mL, more preferably 0.08 - 0.1 g / mL, the solvent used in the transglutaminase solution is preferably water; the mass ratio of the transglutaminase to the gelatin in the transglutaminase solution is preferably 1:5 - 10, more preferably 1:5.

[0049] In the present invention, the temperature of the first cross-linking is preferably 25 to 37 °C, more preferably 30 to 35 °C, the time is preferably 3 to 5 h, and more preferably 3 to 4 h. During the first cross-linking process, transglutaminase catalyzes the acyl transfer reaction of glutamine in gelatin, causing covalent cross-linking between the ε-amino group of the lysine residue side chain and the γ-formamido group of the glutamine residue side chain.

[0050] After obtaining the second product, the present invention mixes the second product with a glucono-δ-lactone solution for a second cross-linking to obtain a gel product.

[0051] In the present invention, the mass concentration of the glucono-δ-lactone solution is preferably 0.05 to 0.1 g / mL, more preferably 0.08 to 0.1 g / mL; the solvent used for the glucono-δ-lactone solution is preferably water; the mass ratio of glucono-δ-lactone to sodium alginate in the glucono-δ-lactone solution is preferably 1:10 to 20, more preferably 1:10.

[0052] In the present invention, the temperature of the second cross-linking is preferably 25 to 37 °C, more preferably 30 to 35 °C, and the time is preferably 3 to 5 h, more preferably 3 to 4 h. During the second cross-linking process, glucono-δ-lactone, as a polyhydroxy polymer, reacts with the carboxyl groups of sodium alginate, which can improve the mechanical properties of the hydrogel.

[0053] After completing the second cross-linking, the present invention preferably rinses the obtained product 2 to 3 times with deionized water, wipes off the surface moisture with qualitative filter paper, wraps it with tin foil, and equilibrates it in an environment at 4 °C for 12 h to obtain a gel product.

[0054] After obtaining the gel product, the present invention sequentially dries and grinds the gel product to obtain an isomaltulose-loaded bioadhesive powder hydrogel.

[0055] In the present invention, the temperature of the drying is preferably 50 to 80 °C, more preferably 55 °C; the time is preferably 12 to 24 h, more preferably 12 h.

[0056] The present invention preferably cuts the gel product into 1-mm-thick slices, places them in an oven for drying and grinding to obtain an isomaltulose-loaded bioadhesive powder hydrogel.

[0057] The present invention provides an isomaltulose-loaded bioadhesive powder hydrogel prepared by the preparation method described in the above technical solution.

[0058] The present invention provides the application of the isomaltulose-loaded bioadhesive powder hydrogel described in the above technical solution in the preservation of aquatic products.

[0059] In the present invention, the preferred method of application is as follows: spraying the isomaltitol-loaded bioadhesive powder hydrogel onto the surface of aquatic products and placing them in a low-temperature environment. The present invention has no special limitation on the spraying and the spraying amount, and the required amount of powder hydrogel can be sprayed in a manner well-known in the art.

[0060] When the isomaltitol-loaded bioadhesive powder hydrogel of the present invention comes into contact with water, it quickly resumes to a gel state and adheres to the surface of aquatic products.

[0061] The technical solutions provided by the present invention will be described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0062] Example 1

[0063] Weigh 1 g of gelatin, 1 g of sodium alginate and 0.2 g of isomaltitol, add 20 mL of deionized water (the concentration of isomaltitol is 1%), stir evenly, and place it at 4 °C to absorb water and swell for 3 h; after swelling, under the condition of a 60 °C water bath, heat for 20 min, then fully stir and cool to room temperature, heat in a water bath again, and cycle three times. Carry out ultrasonic defoaming treatment at 320 W for 1 h;

[0064] Add 2 mL of transglutaminase aqueous solution (0.1 g / mL) to the defoamed product, crosslink at 37 °C for 3 h; then add 1 mL of glucono-delta-lactone aqueous solution (0.1 g / mL), crosslink at 37 °C for 3 h; after crosslinking is completed, rinse the obtained product 3 times with deionized water, wipe off the surface moisture, wrap it with tin foil, and equilibrate at 4 °C for 12 h;

[0065] After equilibration, cut the obtained hydrogel into 1-mm-thick slices, dry them in an oven at 55 °C for 12 h, and grind them to obtain the bioadhesive powder hydrogel, named GSIH-1.

[0066] Example 2

[0067] The difference between this example and Example 1 is only that: the dosage of isomaltitol is 0.4 g (the concentration of isomaltitol is 2%), and other conditions are the same as those in Example 1, to obtain the bioadhesive powder hydrogel, named GSIH-2.

[0068] Example 3

[0069] The difference between this example and Example 1 is only that: the dosage of isomaltitol is 0.6 g (the concentration of isomaltitol is 3%), and other conditions are the same as those in Example 1, to obtain the bioadhesive powder hydrogel, named GSIH-3.

[0070] Comparative Example 1

[0071] Weigh 1 g of gelatin, add 20 mL of deionized water, stir evenly, and then absorb water and swell at 4 °C for 3 h; heat the obtained mixture in a water bath at 60 °C for 20 min, take it out, stir well and cool to room temperature, heat it in a water bath again, cycle three times, and carry out ultrasonic defoaming treatment at 320 W for 1 h;

[0072] Add 2 mL of transglutaminase aqueous solution (0.1 g / mL) to the defoamed product, and crosslink at 37 °C for 3 h; take out the hydrogel, rinse it 3 times with deionized water, wipe off the surface moisture with qualitative filter paper, wrap it with tin foil and equilibrate in an environment at 4 °C for 12 h;

[0073] Cut the equilibrated hydrogel into 1-mm-thick slices, dry them in an oven at 55 °C for 12 h, and grind them to obtain a bioadhesive powder-based hydrogel, named GTH.

[0074] Comparative Example 2

[0075] Weigh 1 g of sodium alginate, add 20 mL of deionized water, stir evenly, and then absorb water and swell at 4 °C for 3 h; heat the obtained mixture in a water bath at 60 °C for 20 min, take it out, stir well and cool to room temperature, heat it in a water bath again, cycle three times, and carry out ultrasonic defoaming treatment at 320 W for 1 h;

[0076] Add 1 mL of glucono-δ-lactone aqueous solution (0.1 g / mL) to the defoamed product for crosslinking for 3 h; take out the hydrogel, rinse it 2 - 3 times with deionized water, wipe off the surface moisture with qualitative filter paper, wrap it with tin foil and equilibrate in an environment at 4 °C for 12 h;

[0077] Cut the equilibrated hydrogel into 1-mm-thick slices, dry them in an oven at 55 °C for 12 h, and grind them to obtain a bioadhesive powder-based hydrogel, named SGH.

[0078] Comparative Example 3

[0079] Weigh 2 g of gelatin and 1 g of sodium alginate, add 20 mL of deionized water, stir evenly, and then absorb water and swell at 4 °C for 3 h; heat the obtained mixture in a water bath at 60 °C for 20 min, take it out, stir well and cool to room temperature, heat it in a water bath again, cycle three times, and carry out ultrasonic defoaming treatment at 320 W for 1 h;

[0080] Add 2 mL of transglutaminase aqueous solution (0.1 g / mL) to the defoamed product, and crosslink at 37 °C for 3 h; then add 1 mL of glucono-δ-lactone aqueous solution (0.1 g / mL) for crosslinking for 3 h; take out the hydrogel, rinse it 3 times with deionized water, wipe off the surface moisture with qualitative filter paper, wrap it with tin foil and equilibrate in an environment at 4 °C for 12 h;

[0081] The balanced hydrogel was cut into 1-mm-thick slices, dried in an oven at 55 °C for 12 h, and ground to obtain a bioadhesive powder-based hydrogel named GSDH-1.

[0082] Comparative Example 4

[0083] Weigh 1 g of gelatin and 1 g of sodium alginate, add 20 mL of deionized water, stir well, and allow it to absorb water and swell at 4 °C for 3 h; heat the resulting mixture in a water bath at 60 °C for 20 min, take it out, stir well and cool to room temperature, then heat it in a water bath again for three cycles, and perform ultrasonic defoaming treatment at 320 W for 1 h;

[0084] Add 2 mL of an aqueous solution of transglutaminase (0.1 g / mL) to the defoamed product and crosslink at 37 °C for 3 h; then add 1 mL of an aqueous solution of glucono-δ-lactone (0.1 g / mL) and crosslink for 3 h; take out the hydrogel, rinse it 3 times with deionized water, wipe off the surface moisture with qualitative filter paper, wrap it with tin foil and equilibrate it in an environment at 4 °C for 12 h;

[0085] The balanced hydrogel was cut into 1-mm-thick slices, dried in an oven at 55 °C for 12 h, and ground to obtain a bioadhesive powder-based hydrogel named GSDH-2.

[0086] Comparative Example 5

[0087] Weigh 1 g of gelatin and 2 g of sodium alginate, add 20 mL of deionized water, stir well, and allow it to absorb water and swell at 4 °C for 3 h; heat the resulting mixture in a water bath at 60 °C for 20 min, take it out, stir well and cool to room temperature, then heat it in a water bath again for three cycles, and perform ultrasonic defoaming treatment at 320 W for 1 h;

[0088] Add 2 mL of an aqueous solution of transglutaminase (0.1 g / mL) to the defoamed product and crosslink at 37 °C for 3 h; then add 1 mL of an aqueous solution of glucono-δ-lactone (0.1 g / mL crosslink for 3 h; take out the hydrogel, rinse it 3 times with deionized water, wipe off the surface moisture with qualitative filter paper, wrap it with tin foil and equilibrate it in an environment at 4 °C for 12 h;

[0089] The balanced hydrogel was cut into 1-mm-thick slices, dried in an oven at 55 °C for 12 h, and ground to obtain a bioadhesive powder-based hydrogel named GSDH-3.

[0090] Comparative Example 6

[0091] Weigh 1 g of sodium alginate, add 20 mL of deionized water, stir evenly, and allow it to absorb water and swell at 4 °C for 3 h; heat the obtained mixture in a water bath at 60 °C for 20 min, take it out, stir well and cool to room temperature, then heat it in a water bath again for three cycles, and perform ultrasonic defoaming treatment at 320 W for 1 h; take out the hydrogel, rinse it 3 times with deionized water, wipe off the surface moisture with qualitative filter paper, wrap it with tin foil and equilibrate it in an environment at 4 °C for 12 h;

[0092] Cut the equilibrated hydrogel into 1-mm-thick slices, place them on tin foil and dry them in an oven at 55 °C for 12 h, then grind them to obtain a bioadhesive powder-based hydrogel, named SH.

[0093] Comparative Example 7

[0094] Weigh 1 g of gelatin, add 20 mL of deionized water, stir evenly, and allow it to absorb water and swell at 4 °C for 3 h; heat the obtained mixture in a water bath at 60 °C for 20 min, take it out, stir well and cool to room temperature, then heat it in a water bath again for three cycles, and perform ultrasonic defoaming treatment at 320 W for 1 h; take out the hydrogel, rinse it 3 times with deionized water, wipe off the surface moisture with qualitative filter paper, wrap it with tin foil and equilibrate it in an environment at 4 °C for 12 h;

[0095] Cut the equilibrated hydrogel into 1-mm-thick slices, place them on tin foil and dry them in an oven at 55 °C for 12 h, then grind them to obtain a bioadhesive powder-based hydrogel, named GH.

[0096] Performance test

[0097] 1) Figure 1 This is the comparison result of the addition amount of gelatin and sodium alginate and the cross-linking method on the texture characteristics of the hydrogel in Comparative Examples 1-7 of the present invention. Among them, A is elasticity, B is resilience, C is the influence on hardness, and D is cohesiveness; hardness is an important index reflecting the mechanical properties of the hydrogel material, indicating the compressive ability of the hydrogel, but it is also difficult to apply for preservation if the hardness is too high, and it is appropriate to be between 200 and 300; cohesiveness reflects the ability of the hydrogel to adhere to the material surface, and good cohesiveness is the basis for the application of the hydrogel; resilience reflects the ability of the hydrogel to restore its original or partial shape and function after being subjected to an external force; good elasticity can avoid the fracture of the hydrogel during application. Due to the lack of strength of traditional hydrogels, they are prone to permanent fracture, and their internal structure is simple and lacks special functions, which limits their application. From Figure 1 Comparisons show that when the mass fraction ratio of gelatin to sodium alginate is 1:1 and the double cross-linking agents act together, the prepared hydrogel has the best performance.

[0098] 2) Figure 2Effects of the addition amount of isomaltitol on the texture properties of hydrogels in Examples 1-3 of the present invention; among them, A is elasticity, B is resilience, C is the effect on hardness, and D is cohesiveness. The prepared hydrogels were tested for their hardness, resilience, elasticity and cohesiveness using a texture analyzer (TA-XT-PLUS). Texture analyzer parameter settings: P / 0.5 type probe, pre-test rate 3 mm / s, test rate 1 mm / s, post-test rate 1 mm / s, compression deformation rate 50%, and the interval time between two tests of the probe is 2 s. From Figure 2 It can be seen that as the concentration of isomaltitol increases, the hardness of the hydrogel first increases and then decreases, the cohesiveness shows a downward trend, and the resilience and elasticity show an upward trend. This may be because hydrogen bonds are formed between isomaltitol dissolved in water and the gel network, enhancing the intermolecular interaction and making some mechanical properties of the hydrogel stronger. Comparing with the texture parameters of the hydrogel (GSDH-2) prepared with the optimal ratio, the concentration of 2% isomaltitol was selected as the optimal addition amount (GSIH-2).

[0099] 3) Figure 3 Microscopic structure diagrams (C-D) of GSDH-2 (A-B) prepared in Comparative Example 4 and GSIH-2 prepared in Example 2 at different magnifications. From Figure 3 It can be observed that both of them show pore structures, indicating that they have great application potential in the aspect of cargo slow release. Compared with GSDH-2, GSIH-2 shows a more uniform and dense three-dimensional structure, and the addition of isomaltitol increases the elasticity of the hydrogel.

[0100] 4) The secondary structures of gelatin, sodium alginate, isomaltitol, GSDH-2 and GSIH-2 were characterized by Fourier transform infrared spectroscopy analysis, and the results are shown in Figure 4 . Figure 4 Secondary structure analysis diagrams of different powder hydrogels. A is the infrared spectra of gelatin, sodium alginate and GSDH-2 at 4000-2000 cm -1 ; B is the infrared spectra of gelatin, sodium alginate and GSDH-2 at 2000-500 cm -1 ; C is the infrared spectra of isomaltitol, GSDH-2 and GSIH-2 at 4000-2000 cm -1 ; D is at 2000-500 cm -1FTIR spectra of isomaltulose, GSDH-2 and GSIH-2. As can be seen from A and B (gelatin, sodium alginate and GSDH-2), compared with pure gelatin and sodium alginate, the absorption peaks of GSDH-2 shifted at multiple positions in the spectrum, indicating that a double-crosslinked network structure was formed inside the isomaltulose-free hydrogel. As can be seen from C and D (GSIH-2, GSDH-2 and isomaltulose), compared with GSDH-2 and isomaltulose, the absorption peaks of GSIH-2 shifted at multiple positions in the spectrum, indicating that isomaltulose was successfully incorporated into the crosslinked network of the hydrogel.

[0101] 5) According to the formula, swelling ratio = (W 2 - W 1 ) / W 1 × 100% (where W 1 is the initial weight and W 2 is the weight after water absorption); natural degradation rate = (W a - W b ) / W a (where W a is the initial weight and W b is the weight after degradation). The swelling properties and natural degradation ability of GSDH-2 and GSIH-2 were tested at 4 °C and different pH values, and the results are shown in Table 1.

[0102] The swelling property can reflect the water absorption ability of the hydrogel material and, to a certain extent, reflect the crosslinking situation inside the hydrogel material. The impact of the hydrogel on the environment was evaluated by analyzing the natural degradation ability.

[0103] Table 1 shows the swelling properties and natural degradation ability of the hydrogels GSDH-2 and GSIH-2

[0104]

[0105] Among them, a - c represent significant differences (p < 0.05).

[0106] The results in Table 1 show that the addition of isomaltulose enhanced the crosslinking of the hydrogel, formed a denser gel network, increased the swelling property of the hydrogel, and at the same time, GSIH-2 had good natural degradation ability and would not cause adverse effects on the environment during application.

[0107] 6) Aquatic products are prone to spoilage during cold storage transportation and storage because of the presence of specific spoilage bacteria such as Pseudomonas fluorescens in refrigerated aquatic products. It can grow and reproduce at low temperatures and produce extremely heat-resistant proteases and lipases, causing food spoilage and deterioration. Therefore, Pseudomonas fluorescens was used as the inoculated bacterium to test the fresh-keeping performance of the hydrogel.

[0108] Cultivate the Pseudomonas fluorescens P15 bacterial liquid until it reaches 10 8 CFU / mL. Take an appropriate amount of the bacterial liquid and centrifuge it at 8000 r / min for 10 min at 4°C. Discard the supernatant, resuspend the precipitate with sterile normal saline, and dilute it to obtain a bacterial suspension of 10 5 CFU / mL. Quickly wipe the fresh salmon slices of the same batch with similar morphological size, state, and quality with 75% alcohol, then immerse them in the bacterial suspension for 5 s and take them out. Wrap them separately with 3 g of GSIH-2 and GSDH-2, put them into a sterile sampling bag, and store them at 4°C. Sample every 3 days, using the fish meat without wrapped hydrogel as a blank control, and measure various indicators (see Figures 5 to 11 ).

[0109] Refer to the method in the national food safety standard Determination of pH value of foods GB 5009.237-2016 for pH determination, and the results are shown in Figure 5 ; Figure 5 The effects of GSIH-2 prepared in Example 2 and GSDH-2 prepared in Comparative Example 4 on the pH of salmon slices. Generally speaking, the pH of fish shows a trend of first decreasing and then increasing after death. The decrease in pH in the early stage of refrigeration is mainly due to the decomposition of glycogen in the fish body to produce acidic substances such as lactic acid, and the accumulation of inorganic phosphorus generated by ATP degradation will also cause a decrease in pH; in the middle and late stages of refrigeration, the proteins and peptides in the fish body are decomposed by proteases produced by microorganisms to generate alkaline compounds such as indole and biogenic amines, resulting in an increase in pH. Figure 5 The results of

[0110] Figure 6 show that Example 2 inhibited the production of Pseudomonas fluorescens P15 protease and delayed the spoilage of salmon.

[0111] Figure 7 The effects of GSIH-2 prepared in Example 2 and GSDH-2 prepared in Comparative Example 4 on the water holding capacity of salmon slices. Since the hydrogel has good water absorption and moisture retention properties, wrapping it on the surface of the fish slices can reduce the evaporation of water on the surface of the fish slices, thereby reducing the cell rupture caused by water loss on the surface of the fish slices. Isomaltulose further inhibits the decomposition of proteins in the fish meat by Pseudomonas fluorescens P15 on this basis, maintains the ordered network structure of proteins, and further delays the decline of the water holding capacity of salmon slices.

[0111] Figure 7 The effects of GSIH-2 prepared in Example 2 and GSDH-2 prepared in Comparative Example 4 on the texture properties of salmon slices. Among them, A is hardness and B is elasticity. Figure 7 The results of

[0112] The total number of colonies was determined according to the method in GB4789.2-2016; Figure 8 The effects of GSIH-2 prepared in Example 2 and GSDH-2 prepared in Comparative Example 4 on the total number of colonies of salmon fillets; Figure 8 The results showed that the total number of colonies of salmon fillets showed an upward trend during refrigeration. This was because isomaltitol regulated the QS behavior of Pseudomonas fluorescens P15 without killing it, thereby reducing its spoilage ability. Compared with Comparative Example 4, the total number of colonies of the salmon fillets in Example 2 decreased slightly.

[0113] The TVB-N content was determined according to the method in GB5009.228-2016. Figure 9 The effects of GSIH-2 prepared in Example 2 of the present invention and GSDH-2 prepared in Comparative Example 4 on the content of total volatile basic nitrogen (TVB-N) in salmon fillets; The main components of TVB-N are ammonia and amine and other basic nitrogen-containing substances produced by the decomposition of proteins during the spoilage process. Under specific conditions, they can volatilize into the air to form total volatile basic nitrogen, which is one of the important indicators reflecting the freshness and quality of food. The higher the content of TVB-N, the more amino acids in the fish are destroyed, and the lower the nutritional value of the fish. Figure 9 The results showed that Example 2 could significantly delay the increase of TVB-N during the refrigeration of salmon fillets.

[0114] Figure 10 The effects of GSIH-2 prepared in Example 2 of the present invention and GSDH-2 prepared in Comparative Example 4 on the content of thiobarbituric acid (TBA) in salmon fillets. During refrigeration, the unsaturated fatty acids in salmon fillets can spontaneously oxidize with oxygen to generate small molecule substances such as aldehydes and ketones. Among them, malondialdehyde (MDA) can react with thiobarbituric acid to form a red complex. Therefore, the oxidation degree of fat is indirectly represented by measuring the content of malondialdehyde. Figure 10 The results showed that Example 2 reduced the contact level between unsaturated fatty acids and oxygen in salmon fillets and delayed the rate of fat oxidation; Isomaltitol could combine with free radicals, making the free radicals lose their oxidation ability, thereby playing an antioxidant role and further delaying the oxidation degree of the fat in salmon fillets during refrigeration.

[0115] Refer to the method described in the prior art [Zhang Xiaoli. Research on the Preservation Effect of AOB and Steady-State ClO -2 on Tilapia and Its Products [D]. Shanghai Ocean University, 2017.] to test the salt solubility; Figure 11Effects of GSIH-2 prepared in Example 2 of the present invention and GSDH-2 prepared in Comparative Example 4 on the salt solubility of myofibrillar protein in salmon fillets. During refrigeration, the salmon fillets are affected by microorganisms and endogenous enzymes, and the intact structure of myofibrillar protein is damaged. The exposed sulfhydryl groups are oxidized to disulfide bonds, resulting in protein denaturation and aggregation, reducing the solubility of myofibrillar protein in the fish fillets. Figure 11 The results show that Example 2 can significantly delay the decrease in the salt solubility of myofibrillar protein in salmon fillets during refrigeration, indicating that isomaltitol reduces the damage to the spatial structure of myofibrillar protein in salmon fillets by Pseudomonas fluorescens P15, keeping the myofibrillar protein in good salt solubility.

[0116] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing an isomalt-loaded bioadhesive powder hydrogel, comprising the following steps: Mixing isomalt, water, gelatin and sodium alginate, subjecting the mixture to water absorption and swelling and heat treatment in sequence, and subjecting the resulting mixture to ultrasonic defoaming to obtain a first product; The first product is mixed with a transglutaminase solution, and a first cross-linking is performed to obtain a second product; The second product is mixed with a gluconolactone solution and subjected to a second cross-linking to obtain a gel product; The gel product is dried and ground in sequence to obtain isomalt-loaded bioadhesive powder hydrogel.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the gelatin, sodium alginate and isomalt is 5:5:1-3; the mass ratio of isomalt to water is 1-3:

100.

3. The preparation method according to claim 1, characterized in that: The water absorption and swelling process is performed at a temperature of 4 to 10° C. and for a time of 3 to 5 hours.

4. The preparation method according to claim 1, characterized in that: The temperature of the heat treatment is 60-70° C., the time is 10-30 min, and the number of times of the heat treatment is 3-5 times.

5. The preparation method according to claim 1, characterized in that: The mass ratio of glutamine aminotransferase to gelatin in the glutamine aminotransferase solution is 1:5-10; the temperature of the first cross-linking is 25-37° C., and the time is 3-5 hours.

6. The preparation method according to claim 1, characterized in that: The mass ratio of gluconolactone to sodium alginate in the gluconolactone solution is 1:10-20; the temperature of the second cross-linking is 25-37° C., and the time is 3-5 hours.

7. The preparation method according to claim 1, characterized in that: The mass concentration of the glutamine aminotransferase solution is 0.05-0.1 g / mL, and the mass concentration of the gluconolactone solution is 0.05-0.1 g / mL.

8. The preparation method according to claim 1, characterized in that: The drying temperature is 50-80° C. and the drying time is 12-24 hours.

9. The isomalt-loaded bioadhesive powder hydrogel prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the isomalt-loaded bioadhesive powder hydrogel according to claim 9 in the preservation of aquatic products.

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