Method for improving water holding performance of subacid electrolyzed water composite hydrogel

Abstract

The invention provides a method for improving the water holding capacity of subacid electrolyzed water composite hydrogel, a food-grade hydrogel material and SAEW are combined to construct a slow-release composite fresh-keeping system, an SAEW-composite hydrogel system is constructed and represented, gelatin is used as a base material, tamarind polysaccharide and xanthan gum are used as auxiliary materials to prepare hydrogel-loaded SAEW, and the water holding capacity of the subacid electrolyzed water composite hydrogel is improved. Microcosmic, texture and physicochemical properties are analyzed, and a load mechanism and potential are determined. The result shows that the gelatin hydrogel SAEW has the strongest loading capacity and still has a certain concentration after being released for multiple times; the TSP and the XG are introduced, so that the absorption efficiency and the oxidation resistance are improved. According to the method, the addition amount of each material is taken as an independent variable, the SAEW load capacity is taken as a dependent variable, the optimal parameter is determined by a response surface experiment, and a verification experiment shows that the model prediction effect is good. Meanwhile, the physical dehydration treatment improves the water holding performance and the interface stability of the gel and delays the migration rate of free water.

Description

Technical Field

[0001] The present invention relates to the technical fields of food preservation materials and functional hydrogels. Specifically, it relates to a method for improving the water-holding performance of a weakly acidic electrolyzed water composite hydrogel. Background Art

[0002] As a new type of green bactericide, SAEW has the advantages of high-efficiency sterilization at low concentrations and being green and safe, showing great potential in the field of food preservation. However, SAEW faces two major problems in practical applications: its unstable chemical properties and single-use characteristics, which seriously limit the process of its industrial application. To solve the above problems, this study proposed an innovative method, that is, combining SAEW with hydrogels, and using the three-dimensional network structure of hydrogels to efficiently load and stabilize the active ingredients in SAEW, with the expectation of achieving the persistence of the bactericidal and preservation effects. However, preliminary research results show that the loading efficiency of SAEW in the hydrogel system presents a non-linear growth phenomenon, which means that the traditional single-factor optimization method is no longer applicable and it is difficult to analyze the complex mechanism of multi-component synergistic effects.

[0003] Deficiencies of the prior art:

[0004] 1. Poor chemical stability: The chemical properties of SAEW itself are unstable and it is easy to decompose, which makes it difficult to guarantee its effectiveness during storage and transportation.

[0005] 2. Single-use limitation: The current usage method of SAEW is mostly single-use, which increases the usage cost and is not conducive to large-scale popularization and application.

[0006] 3. Non-linear loading efficiency: When loading SAEW into the hydrogel system, the non-linear growth of the loading efficiency makes it impossible for traditional optimization methods to effectively analyze and optimize the synergistic effects of multi-components.

[0007] 4. Limitations of optimization methods: Single-factor optimization methods cannot handle the complex situation of multi-variable interactions and more advanced multi-factor optimization means such as the response surface method (RSM) are needed.

[0008] 5. Challenges in the preparation process: During the preparation of the hydrogel containing SAEW, there are problems such as a high effective chlorine concentration but an unsatisfactory preservation effect, and there is a contradiction between the structural stability of the aerogel and the loading efficiency.

[0009] 6. Water separation problem: There is a water separation problem in the SAEW-hydrogel system during static standing, which may lead to the non-controlled release loss of the effective chlorine component, affecting the preservation effect and stability.

[0010] 7. Technical complexity: Developing high-performance SAEW-loaded hydrogels requires comprehensive consideration of various factors, including the composition, structure, and preparation process of the hydrogels, which poses higher requirements for technology.

[0011] To address the above deficiencies, we have made improvements and proposed a method for enhancing the water retention performance of microacidic electrolyzed water composite hydrogels. Summary of the Invention

[0012] The object of the present invention is to address the problems presented in the existing background technology. To achieve the above object of the invention, the present invention provides the following technical solution: A method for enhancing the water retention performance of microacidic electrolyzed water composite hydrogels, comprising the following steps:

[0013] Step 1, Construction of the SAEW-composite hydrogel system: Using gelatin (GEL) as the base material and tamarind polysaccharide (TSP) and xanthan gum (XG) as auxiliary materials to prepare the hydrogel, and soaking the hydrogel in a microacidic electrolyzed water (SAEW) solution for loading;

[0014] Step 2, Optimization of the preparation process of the SAEW-composite hydrogel system: Using the addition amounts of GEL, TSP, and XG as independent variables and the SAEW loading capacity as the dependent variable, and using the Box-Behnken Design response surface experimental design to optimize the process parameters;

[0015] Step 3, Improving the water retention performance of the composite hydrogel: Physically dehydrating the prepared composite hydrogel.

[0016] As a preferred technical solution of the present invention, in the construction of the SAEW-composite hydrogel system, the preparation of the hydrogel is specifically as follows: Dissolve GEL, TSP, and XG in deionized water respectively, heat and stir until completely dissolved, then mix the three solutions evenly, stir and react at a certain temperature for a period of time to obtain a hydrogel precursor solution, and pour the precursor solution into a mold and cool it to form a hydrogel.

[0017] As a preferred technical solution of the present invention, in the SAEW loading in the construction of the SAEW-composite hydrogel system, the SAEW absorption time is 1.5 h, the release time is 20 min, and it is recycled 5 times.

[0018] As a preferred technical solution of the present invention, in the optimization of the preparation process of the SAEW-composite hydrogel system, the determined optimal process parameters are: the addition amount of GEL is 7%, the addition amount of TSP is 0.5%, and the addition amount of XG is 0.5%.

[0019] As a preferred technical solution of the present invention, the physical dehydration treatment is centrifugal dehydration or freeze-drying.

[0020] As a preferred technical solution of the present invention, the conditions for centrifugal dehydration are centrifugation for 10 min at a rotation speed of 3000 r / min.

[0021] As a preferred technical solution of the present invention, after the SAEW-composite hydrogel system is constructed, it further includes the steps of analyzing the microstructure, texture properties and physicochemical properties of the hydrogel, as well as the action mechanism and application of the hydrogel loaded with SAEW.

[0022] As a preferred technical solution of the present invention, the microstructure analysis is observed by a scanning electron microscope (SEM).

[0023] As a preferred technical solution of the present invention, the texture property analysis uses a texture analyzer to measure the hardness, elasticity and viscous texture properties of the hydrogel.

[0024] As a preferred technical solution of the present invention, the physicochemical property analysis measures the water holding rate and swelling rate of the hydrogel.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: The achievements obtained by the present invention in the construction, characterization and process optimization of the SAEW-composite hydrogel system have multiple beneficial effects:

[0026] Achieve continuous sterilization and preservation: The hydrogel prepared with gelatin as the base material and tamarind polysaccharide and xanthan gum as auxiliary materials can load SAEW, achieving the purpose of continuous sterilization and preservation, providing an effective way to solve the problems of poor storage stability and short action time of SAEW, and contributing to promoting its industrial application in the field of food preservation.

[0027] Clarify the loading capacity and characteristics: Determine the strongest SAEW loading capacity of the GEL hydrogel under specific absorption, release time and number of recycling times, and it still retains a certain concentration of SAEW after continuous release 8 times, providing data support for the evaluation of the usage frequency and effect in actual application. The discussion on the microstructure characterization of the composite hydrogel system and the influence mechanism of TSP and XG provides a theoretical basis for optimizing the hydrogel performance.

[0028] Improve the absorption and antioxidant capacity: The introduction of TSP and XG significantly improves the absorption efficiency and antioxidant capacity of SAEW, further enhancing the preservation effect of the composite system, and also providing a direction for subsequent research and development.

[0029] Optimize the process parameters: The optimal process parameters are determined through response surface experiments, and the verification experiments show that the model can better predict the SAEW loading capacity of the composite hydrogel, which helps to accurately control the process in actual production, improve production efficiency and product quality.

[0030] Improve water - holding performance: Aiming at the problem of easy water separation in composite hydrogels, physical dehydration treatment significantly improves the water - holding performance and interfacial stability of the gel, delays the migration rate of free water, and extends the service life and fresh - keeping effect of the composite hydrogel. Brief Description of the Drawings

[0031] Figure 1 It is a correlation diagram (a) of the simulated prediction value and the experimental value provided by the present invention and a diagram (b) of the residual error against the model prediction scatter.

[0032] Figure 2 It is a response surface and off - line schematic diagram of the influence of different influencing factors on the SAEW - loading capacity of the composite hydrogel provided by the present invention.

[0033] Figure 3 It is a schematic diagram for characterizing the apparent morphology (a) of the composite aerogel provided by the present invention and the SAEW - loading capacity of the chlorine - containing aerogel (b) and SAEW - composite aerogel (c).

[0034] Figure 4 It is a fresh - keeping effect diagram of the SAEW - composite gel system for blueberries, strawberries and fresh - cut apples provided by the present invention.

[0035] Figure 5 It is a schematic diagram for observing the apparent morphology of the composite hydrogel before and after being treated in different ways provided by the present invention.

[0036] Figure 6 It is a schematic diagram of the SAEW - loading capacity of the composite hydrogel after being treated in different ways provided by the present invention.

[0037] Figure 7 It is a schematic diagram for observing the water - separation behavior of the composite hydrogel after being treated in different ways during 5 - day storage provided by the present invention. Detailed Embodiments

[0038] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0039] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents some embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention. It should be noted that, without conflict, the embodiments and the features and technical solutions in the embodiments of the present invention can be combined with each other. It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0040] Example 1: A method for improving the water retention performance of slightly acidic electrolyzed water composite hydrogel, comprising the following steps: Step 1, construction of the SAEW-composite hydrogel system: Using gelatin (GEL) as the base material and tamarind polysaccharide (TSP) and xanthan gum (XG) as auxiliary materials to prepare the hydrogel, and soaking the hydrogel in a slightly acidic electrolyzed water (SAEW) solution for loading;

[0041] Step 2, optimization of the preparation process of the SAEW-composite hydrogel system: Taking the addition amounts of GEL, TSP, and XG as independent variables and the SAEW loading capacity as the dependent variable, using the Box-Behnken Design response surface experimental design to optimize the process parameters;

[0042] Step 3, improving the water retention performance of the composite hydrogel: Physically dehydrating the prepared composite hydrogel.

[0043] In the construction of the SAEW-composite hydrogel system, the preparation of the hydrogel is specifically as follows: Dissolve GEL, TSP, and XG in deionized water respectively, heat and stir until completely dissolved, then mix the three solutions evenly, stir and react at a certain temperature for a period of time to obtain a hydrogel precursor solution, and pour the precursor solution into a mold and cool to form a hydrogel.

[0044] In the construction of the SAEW-composite hydrogel system, during SAEW loading, the SAEW absorption time is 1.5 h, the release time is 20 min, and it is recycled 5 times.

[0045] In the optimization of the preparation process of the SAEW-composite hydrogel system, the determined optimal process parameters are: the addition amount of GEL is 7%, the addition amount of TSP is 0.5%, and the addition amount of XG is 0.5%. The physical dehydration treatment is centrifugal dehydration or freeze-drying. The conditions for centrifugal dehydration are centrifuging at a speed of 3000 r / min for 10 min.

[0046] After the construction of the SAEW-composite hydrogel system, it also includes the steps of analyzing the microstructure, texture properties, and physicochemical properties of the hydrogel, as well as the action mechanism and application of the hydrogel loaded with SAEW. The microstructure was observed by scanning electron microscopy (SEM). The texture properties were measured using a texture analyzer to determine the hardness, elasticity, and viscous texture properties of the hydrogel. The physicochemical properties were analyzed by measuring the water holding rate and swelling rate of the hydrogel.

[0047] Experimental examples:

[0048] Materials and reagents:

[0049] The blueberries used in this invention were purchased from Fresh Fruit Chacha Store in Kunming, Yunnan Province, and the strawberry raw materials were purchased from Yuxi, Yunnan Province.

[0050] Experimental reagents:

[0051]

[0052] Experimental methods:

[0053] Preparation of composite hydrogel and SAEW-composite hydrogel system:

[0054] Box-Behnken Design experimental design:

[0055] Based on the previous experimental research results, a Box-Behnken Design experimental design was carried out. Taking X1: GEL addition amount, X2: TSP addition amount, and X3: XG addition amount as the three independent variables, a three-factor and three-level experiment was designed, and the SAEW loading capacity was used as the evaluation index. The specific experimental design is shown in the table:

[0056]

[0057] Fresh-keeping application experiment:

[0058] Three composite systems, namely chlorine-containing composite aerogel (the hydrogel was freeze-dried after being cyclically loaded with SAEW 5 times), SAEW-composite aerogel system (the aerogel was soaked in SAEW for 1.5 h), and SAEW-composite hydrogel system (the hydrogel was soaked in SAEW for 1.5 h), were prepared as food fresh-keeping cushions (17.2 cm × 10.5 cm × 1.5 cm). Blueberries, strawberries, and fresh-cut apples were respectively placed on the above-mentioned fresh-keeping cushions for fresh-keeping experiments. The samples were stored at room temperature, and the apparent fresh-keeping effects were observed at 0, 2, 4, 6, and 8 days respectively.

[0059] Study on improving the water separation behavior of the SAEW-composite hydrogel system:

[0060] Based on the water separation phenomenon found in the previous fresh-keeping application research of the SAEW-composite hydrogel system, the present invention adopts physical dehydration and surface modification strategies to optimize the system. The experimental design includes two dimensions:

[0061] (1) In terms of water regulation, the effects of natural drying (25±2°C) and gradient temperature-controlled drying (in an incubator at 60°C) on the state of bound water inside the hydrogel were systematically investigated;

[0062] (2) In terms of structural modification, through protein cross-linking modification, transglutaminase, gluten, and zein were introduced respectively to construct a three-dimensional network reinforcement system.

[0063] The comparative analysis method was used to explore the regulation mechanism of different treatments on the water-holding performance of the hydrogel, aiming to reduce the free water migration rate of the system through multi-scale structural modification and improve the stability of the gel-solution interface. Through physical dehydration and chemical modification methods, the performance of the optimized SAEW-composite hydrogel in terms of improving the payload rate and enhancing the water-holding stability during storage was comprehensively evaluated;

[0064] Data processing and statistical analysis:

[0065] The Box-Behnken Design response surface experimental design analysis was carried out using Design-Expert 13. Data analysis was performed using SPSS Statistics 26 for analysis of variance (ANOVA) and Turkey multiple comparisons (P<0.05); the bar chart was drawn using OriginPro 2021 software;

[0066] Results and discussion:

[0067] Analysis of the experimental design results of Box-Behnken Design:

[0068] A three-factor and three-level experimental system was constructed by adopting the Box-Behnken Design experimental design. Based on the results of previous experimental studies, the addition amount of GEL (X1), the addition amount of TSP (X2), and the addition amount of XG (X3) were selected as independent variables. At the same time, the GA concentration was set at 5%, the volume was 5 mL, and the reaction temperature was 50°C. The Box-Behnken Design response surface test design was carried out with the SAEW loading capacity of the composite hydrogel prepared by each factor as the response value. 15 groups of experimental schemes (including 3 groups of center point repeated experiments) were generated by Design-Expert 13 software. The specific experimental design and measured data are shown in Table 3.

[0069] Using the data in Table 3 to carry out multiple regression fitting analysis, and then obtaining the quadratic polynomial equation: Y = 19.73 + 1.92X1 - + 5.00X2X3 - 4.7X12 - 4.03X22 Equation (3.1)

[0070] According to the model test results, the fitting test of the response surface model P = 0.0085 < 0.05 is significant; the lack-of-fit term P = 0.0523 > 0.05, indicating that the model has good predictive ability and no abnormal deviation []; the multiple correlation coefficient R 2 = 0.9010 and the adjusted determination coefficient R 2 adj = 0.8947 jointly confirm that the model can explain 89.47% of the response value variation, and the unexplained variation is controlled within 10.53% []. Analyzing the coefficients of each item in the model, it can be seen that the single-factor GEL addition amount (X1) and the interaction terms X2X3, quadratic terms X12 and X22 all reach a significant level (P < 0.05), and their influence weight rankings are X1 > X3 > X2. This may be closely related to the rheological properties and intermolecular interaction mechanisms of the composite hydrogel system. This model can be used to analyze and predict the deviation of the SAEW loading capacity of the composite hydrogel;

[0071]

[0072] Note: P < 0.05 is significant; P > 0.05 is not significant.

[0073] To visually present the prediction effect of the model, a correlation diagram of the model prediction value and the measured value is drawn. As Figure 1 can be seen, most sample points are distributed around the diagonal, indicating that there is a close correlation between the predicted value and the experimental value of the SAEW loading capacity of the composite hydrogel under different substrate addition amounts]. A high-quality model needs to satisfy that the prediction errors of most samples are within the ±2SD interval. Regarding the distribution of the model prediction errors, all samples fall within the ±2SD range of the model, and no abnormal points appear, indicating that the experimental systematic error is within a reasonable and controllable range;

[0074] By analyzing the morphological characteristics of the three-dimensional response surface and the two-dimensional contour line, the influence of each process parameter on the SAEW loading capacity can be deeply explored ( Figure 1 ). The influence degree of different factors on the SAEW loading capacity of the composite hydrogel can be reflected by the steepness of the response surface: the steeper the surface, the greater the influence degree of the factor on the result; if the contour line presents an ellipse, it indicates that the interaction between the two factors has a more significant influence on the result. As Figure 1 shown in a, the influence of the GEL addition amount and the TSP addition amount on the SAEW loading capacity of the composite hydrogel shows a parabolic distribution, indicating that there is a non-linear coupling effect between them on the SAEW loading capacity. When the GEL addition amount is certain, the SAEW loading capacity first decreases and then increases with the increase of the TSP addition amount; when the TSP addition amount is certain, the SAEW loading capacity of the composite hydrogel first increases slightly and then increases with the increase of the GEL addition amount; As Figure 1As can be seen from the contour plot, the contour is approximately circular, which corroborates the conclusion that the X1 and X2 terms in the analysis of variance did not reach a significant level (P = 0.8836 > 0.05).

[0075] As can be seen from Figure 1 Figure b, the effects of GEL addition amount and XG addition amount on the SAEW loading capacity of the composite hydrogel show a paraboloid distribution. When the GEL addition amount is fixed, the deviation of the SAEW loading capacity of the composite hydrogel decreases unilaterally with the increase of the XG addition amount, which is contrary to the previous research speculation. This may be because the swelling performance of XG is poor. Although the low swelling property of XG can maintain the pH stability of the system, its molecular chain has strong rigidity, resulting in limited expansion of the gel network. When the XG addition amount exceeds the critical value, the specific surface area will decrease correspondingly, thus directly weakening the physical adsorption capacity of SAEW; when the XG addition amount is fixed, the deviation of the SAEW loading capacity of the composite hydrogel first decreases and then increases with the increase of the GEL addition amount. As can be seen from Figure 1 the contour plot of Figure b, the contour is circular, indicating that the fluctuation ranges of the two are very similar, and there is no significant interaction between the two factors, which is consistent with the statistical results of X1 and X3 in the regression model (P = 0.06626 > 0.05).

[0076] The effects of TSP addition amount and XG addition amount on the SAEW loading capacity of the composite hydrogel show a paraboloid distribution. When the TSP addition amount is fixed, the deviation of the SAEW loading capacity of the composite hydrogel first decreases and then increases with the increase of the XG addition amount; when the XG addition amount is fixed, the deviation of the SAEW loading capacity of the composite hydrogel first decreases and then increases with the increase of the TSP addition amount.

[0077] Verification experiment analysis: With the help of Design-expert software, the model was analyzed and predicted, and it was found that when X1 (GEL addition amount) was 7.35%, X2 (TSP addition amount) was 0.60%, and X3 (XG addition amount) was 0.63%, the response value of the model reached the maximum, which was 13.87 mg·L-1. Considering the convenience and feasibility of actual operation, the GEL addition amount was adjusted to 7%, the TSP addition amount was adjusted to 0.5%, and the XG addition amount was adjusted to 0.5%. Under these conditions, a verification experiment was carried out. The measured SAEW loading capacity of the composite hydrogel was 13.67 mg·L-1, and the deviation from the theoretical predicted value was 1.48%. Since the experimental value was close to the theoretical predicted value, it indicated that the model could better predict the SAEW loading capacity of the composite hydrogel.

[0078] Preliminary Exploration of the Application of SAEW-Composite Gel System in Fruit Preservation: Problems Existing in the Application of SAEW-Composite Hydrogel System in the Preservation Field: To explore the preservation effect of the SAEW-composite hydrogel system after process optimization, we prepared a SAEW-hydrogel preservation cushion and used it for the preservation of fresh-cut apples. However, during storage, it was found that under the stress of fresh-cut apples, the internal SAEW in the SEAW-hydrogel preservation cushion would be extruded and precipitated, resulting in excessive moisture around the preservation cushion, which instead accelerated the decay and deterioration of fresh-cut apples. This problem greatly limits the application of the SAEW-composite hydrogel system. After consulting the literature and conducting preliminary experiments, it was found that aerogels have excellent properties such as high porosity, low density, high specific surface area, and strong adsorption [], which may provide an effective way to solve the problem of easy water precipitation in hydrogels: preparing hydrogels into aerogels by vacuum freeze-drying is expected to significantly improve their structural stability and reduce the unnecessary precipitation of SAEW during preservation. However, the loading capacity of aerogels for SAEW and its effect in actual applications still need to be further explored in depth.

[0079] Preparation of Aerogel and Analysis of Its Ability to Load SAEW: In Figure 3 a, we carried out a detailed characterization and analysis of the morphology of the aerogel. Using the preloading-freeze-drying synergistic process: First, the hydrogel loaded with SAEW 5 times was vacuum freeze-dried to obtain a chlorine-containing aerogel with a mesoporous structure; compared with the traditional method of freeze-drying first and then loading, there are great differences in their apparent morphologies. The results show that compared with the control group without SAEW loading, the surface of the aerogel in the SAEW treatment group shows a rougher texture and is accompanied by a yellowish color. This significant change can be attributed to the condensation of HClO in SAEW inside the aerogel, which in turn affects its microstructure. The penetration and reaction of HClO not only change the surface morphology of the aerogel but may also form new chemical bonding points or pore structures inside it. These changes act together on the overall morphology of the aerogel.

[0080] Furthermore, in Figure 3 b, we measured the effective chlorine concentration of the chlorine-containing aerogel and compared it with Figure 2 a and Figure 3c was compared. The results showed that the available chlorine concentration of the chlorine-containing aerogel was relatively low, which can be reasonably explained by the volatilization effect of HClO during the freeze-drying process. Although the freeze-drying technique can effectively preserve the porous structure and active components of the aerogel, during this process, as a highly volatile compound, HClO will inevitably be lost to a certain extent, resulting in a decrease in the available chlorine concentration in the final product. Despite the significant reduction in the available chlorine concentration after freeze-drying of the aerogel, we can overcome this challenge through an innovative strategy: first freeze-dry the composite hydrogel into an aerogel, and then load SAEW onto the aerogel. This method not only solves the problem of SAEW precipitation but also can improve the retention rate of available chlorine to a certain extent (as shown in Figure 3 c).

[0081] In summary, the aerogel prepared by vacuum freeze-drying solves the problem of easy water seepage of the hydrogel, but its morphology and structure have changed significantly, resulting in a decrease in the SAEW loading capacity. This not only reflects the interaction between SAEW and the aerogel substrate but also reveals the challenges that may be encountered during the freeze-drying process. Therefore, in future research, we need to further optimize the gel preparation process and the SAEW loading strategy to improve the retention rate of available chlorine and the overall performance of the gel system.

[0082] Effect of the SAEW-composite gel system on fruit preservation: To systematically verify the actual preservation efficacy of the composite system, the present invention prepared preservation cushions in different states and applied them to the preservation experiments of blueberries, strawberries, and fresh-cut apples. Blueberries showed good preservation effects due to their excellent storage resistance, while the best preservation areas for strawberries and fresh-cut apples were concentrated in the lower right corner of the figure. It is worth noting that during the experimental observation, obvious water loss occurred in the samples in the lower left corner, presumably because the excessive drying property of the aerogel matrix induced a reverse water absorption effect, that is, the matrix absorbed water from the objects to be preserved.

[0083] Comparative studies found that although the SAEW-composite hydrogel system performed better than the aerogel system in terms of the available chlorine concentration index, its overall preservation effect did not reach the expected level. This phenomenon indicates that the high water content of the hydrogel system has a dual effect: on the one hand, it provides a good loading environment for SAEW, on the other hand, it increases the risk of fruit and vegetable rot, weakening the preservation efficacy instead. This finding provides an important inspiration for the subsequent optimized design of the composite system ratio, that is, a balance needs to be sought between the preservation efficacy and the system stability.

[0084] However, the hydrogel system faces the technical bottleneck of easy water separation in practical applications, which severely restricts the expansion of its application scenarios. Although attempts to use aerogel alternatives effectively solve the water separation problem, the SAEW loading capacity has decreased significantly. To address this issue, subsequent research will focus on the coordinated optimization of the gel preparation process and the SAEW loading strategy, aiming to simultaneously improve the loading efficiency and retention rate of available chlorine, enhance the comprehensive performance of the gel system, and provide an intelligent carrier solution with both stability and high efficiency for the food preservation field.

[0085] Based on the water separation phenomenon of the SAEW-composite hydrogel system discovered in the previous fresh-keeping application research, the present invention adopts physical dehydration and surface modification strategies to optimize the system. By using the comparative analysis method, the regulation mechanism of different treatment groups on the water retention performance of the hydrogel is explored, and the best treatment method is obtained, aiming to reduce the free water migration rate of the system through multi-scale structure modification and improve the stability of the gel-solution interface.

[0086] Through preliminary pre-experiments, it was found that the natural air-drying process can obtain the best treatment effect under the condition of 48 hours, while the hot air drying process only needs 2 hours to reach the performance balance point under the constant temperature condition of 60 °C. There are significant differences in the process sequence among different treatment groups: the water control group (including natural air-drying and hot air drying) adopts the process flow of "dehydration first and then loading", and the SAEW loading performance is evaluated after the dehydration treatment; while the structure modification group adopts the innovative process path of "loading first and then modification", and its SAEW loading performance is detected after the surface modification.

[0087] Figure 5 Revealed the regulation law of different modification processes on the SAEW loading efficiency of the composite hydrogel. The experimental data show that the SAEW loading rate of the composite hydrogel after using the physical dehydration method (natural air-drying and hot air drying) reaches 14.67 ± 0.03 mg·L-1, which is 69.19%-175.18% higher than that of the protein modification group. The possible reason for the speculation is that the dense network structure formed by chemical modification has a significant steric hindrance effect on the diffusion and release of HClO molecules. The loading capacity of the 50 °C heat treatment group is relatively low, which may be closely related to the volatilization loss of active ingredients under the thermodynamic equilibrium condition.

[0088] Figure 6Systematic observations clearly revealed the significant regulatory effect of different modification processes on the water drainage behavior of hydrogels. In the unmodified control group, surface wetting occurred on the second day of storage. By the third day, obvious water accumulation had appeared at the bottom of the gel, and the water drainage phenomenon was more severe on the fifth day. Although the gluten treatment group delayed the water drainage process, surface wetting was still observed on the fifth day. In sharp contrast, no obvious water drainage occurred in the natural air-drying group and the hot air drying group throughout the storage period. The underlying mechanism can be attributed to the fact that the physical dehydration process promotes the shrinkage of the gel pores, forcing SAEW to preferentially fill the internal pores. This pore filling mechanism not only increases the water absorption capacity of the gel but also fundamentally changes the water drainage kinetics, effectively avoiding the occurrence of the water drainage phenomenon.

[0089] Based on the response surface method, the present invention constructed an optimization model for the preparation process of GEL / TSP / XG composite hydrogels. Taking the addition amounts of the three substrates as independent variables and the SAEW loading capacity as the response value, a significant quadratic polynomial model was established (P = 0.0085, R 2 adj = 0.8947). Verification experiments showed that the SAEW loading amount under the optimal process parameters reached 13.67 mg·L-1, with a deviation rate from the predicted value lower than 1.48%, confirming the engineering applicability of the model. Subsequently, aiming at the water drainage problem of hydrogels in the preservation of fresh-cut apples, the present invention innovatively adopted a preloading-freeze-drying process to prepare chlorine-containing aerogels, but the freeze-drying process would cause the volatilization of HClO and a decrease in the available chlorine concentration. Therefore, the present invention proposed a "freeze-dry first and then load" strategy to improve the retention rate of available chlorine, but the loading capacity still needed to be optimized. Comparative experiments showed that the hydrogel had a high available chlorine concentration but limited preservation effect, and the aerogel structure was stable but with insufficient loading efficiency. Subsequent research will focus on the optimization of the gel process and the innovation of the loading strategy. By regulating the cross-linking density, pore distribution, and developing a synergistic loading technology, a composite system with both bactericidal efficacy and stability will be constructed. To improve the water drainage behavior, two technical paths of physical drying process optimization and surface protein modification were studied and compared. It was found that the natural air-drying process could maintain the integrity of the network skeleton while reducing the water content by controlling the dehydration time, and could also improve the loading capacity, showing multiple advantages. The present invention innovatively established a "structure-function-process" collaborative optimization model, providing theoretical support and practical solutions for the industrial application of hydrogel functional materials.

[0090] The above embodiments are only used to illustrate the present invention and do not limit the technical solutions described in the present invention. Although this specification has described the present invention in detail with reference to the above respective embodiments, the present invention is not limited to the above specific embodiments. Therefore, any modification or substitution of the present invention; and all technical solutions and their improvements that do not depart from the spirit and scope of the invention are covered by the scope of the claims of the present invention.

Claims

1. A method for improving the water-holding performance of slightly acidic electrolyzed water composite hydrogel, characterized in that, It includes the following steps: Step 1, Construction of SAEW-composite hydrogel system: Using gelatin (GEL) as the base material, and tamarind polysaccharide (TSP) and xanthan gum (XG) as auxiliary materials to prepare the hydrogel, and soaking the hydrogel in slightly acidic electrolyzed water (SAEW) solution for loading; Step 2, Optimization of the preparation process of SAEW-composite hydrogel system: Taking the addition amounts of GEL, TSP and XG as independent variables and the SAEW loading capacity as the dependent variable, using Box-Behnken Design response surface experimental design to optimize the process parameters; Step 3, Improving the water retention performance of the composite hydrogel: Conducting physical dehydration treatment on the prepared composite hydrogel.

2. The method for improving the water holding performance of the slightly acidic electrolyzed water composite hydrogel according to claim 1, wherein In the construction of the SAEW-composite hydrogel system, the preparation of the hydrogel is specifically as follows: Dissolve GEL, TSP and XG in deionized water respectively, heat and stir until completely dissolved, then mix the three solutions evenly, stir and react at a certain temperature for a period of time to obtain a hydrogel precursor solution, pour the precursor solution into a mold, and cool and form to obtain the hydrogel.

3. The method for improving the water retention performance of the slightly acidic electrolyzed water composite hydrogel according to claim 1, characterized in that, In the construction of the SAEW-composite hydrogel system, during SAEW loading, the SAEW absorption time is 1.5 h, the release time is 20 min, and it is recycled 5 times.

4. The method for improving the water retention performance of the slightly acidic electrolyzed water composite hydrogel according to claim 1, characterized in that In the optimization of the preparation process of the SAEW-composite hydrogel system, the determined optimal process parameters are: the addition amount of GEL is 7%, the addition amount of TSP is 0.5%, and the addition amount of XG is 0.5%.

5. The method for improving the water retention performance of the slightly acidic electrolyzed water composite hydrogel according to claim 1, characterized in that, The physical dehydration treatment is centrifugal dehydration or freeze-drying.

6. The method for improving the water retention performance of the slightly acidic electrolyzed water composite hydrogel according to claim 5, characterized in that The conditions for the centrifugal dehydration are centrifuging at a speed of 3000 r / min for 10 min.

7. The method for improving the water retention performance of the slightly acidic electrolyzed water composite hydrogel according to claim 1, characterized in that After the construction of the SAEW-composite hydrogel system, it also includes steps of analyzing the microstructure, texture characteristics and physicochemical characteristics of the hydrogel, the action mechanism and application of the hydrogel loaded with SAEW.

8. The method for improving the water holding performance of the slightly acidic electrolyzed water composite hydrogel according to claim 7, characterized in that The microstructure analysis is observed by scanning electron microscope (SEM).

9. The method for improving the water retention performance of the slightly acidic electrolyzed water composite hydrogel according to claim 7, characterized in that, The texture characteristics analysis uses a texture analyzer to measure the hardness, elasticity and viscous texture characteristics of the hydrogel.

10. The method for improving the water retention performance of the slightly acidic electrolyzed water composite hydrogel according to claim 7, wherein The physicochemical characteristics analysis measures the water retention rate and swelling rate of the hydrogel.

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