Adsorbent with anti-oxidation and moisture absorption effects and preparation method thereof

Abstract

The invention provides an adsorbent with antioxidant and moisture absorption effects and a preparation method thereof. The preparation method comprises the following steps: preparing an emulsion, preparing a gelatin solution, preparing sol, preparing aerogel, and loading the curcumin emulsion to the aerogel. A cross-linked network of chitosan and gelatin can be used as a slow-release carrier of curcumin, curcumin is prepared into an oil-in-water emulsion and then is loaded by aerogel, after the aerogel absorbs water, the oil-in-water emulsion is easier to release, volatile oil is used as an oil phase of the emulsion, and curcumin can be carried to volatilize, so that the antibacterial and antioxidant effects are better exerted. The prepared adsorbent has excellent hygroscopicity, oxidation resistance and chemical stability, and has wide application prospects in the fields of food preservation and the like.

Description

Technical Field

[0001] The present invention belongs to the field of food technology, and particularly relates to an adsorbent with antioxidant and moisture absorption effects in air-dried meat products and a preparation method thereof. Background Art

[0002] Food aerogel is a new type of functional food material, which has low density, high porosity and biodegradability. Generally, aerogels can be used as antibacterial active substances, food insulation packaging materials and load-bearing materials with buffer protection. Food aerogels can be prepared by the complexation of polysaccharides and proteins to improve mechanical properties, maintain porous structures, reduce hydrophilicity and slow down volume shrinkage. Gelatin is a natural protein obtained by denaturing collagen, and has good biocompatibility, film-forming properties, gel stability and other characteristics, so it can be used as a food packaging material. The water absorption of proteins is proportional to their relative molecular mass, that is, the larger the molecular weight, the stronger the water absorption ability. This may be because proteins with large molecular weights have larger surface areas and more hydrophilic groups, thus being able to adsorb more water. It has been found that sheep hoof gelatin has a relatively high gel strength and may be more suitable as the natural wall material of aerogels. In addition, polysaccharides are high-quality materials that can effectively improve the thermal stability and gel strength of gelatin. It should be noted that chitosan is a polysaccharide extracted from the shells of animals, and has edibility, plasticity, adsorbability and structure-strengthening characteristics. Chitosan can strengthen the mechanical properties of gelatin and improve the three-dimensional structure stability of aerogels. At present, bio-based aerogels based on pectin, cellulose, starch, egg white protein, whey protein and plant protein have been developed and are widely used in fields such as water-absorbing materials, heat-insulating materials and as tissue engineering scaffolds. In addition, biobased aerogels can serve as a sustained-release system for bioactive substances, effectively controlling the release of active compounds such as antioxidants, antibacterial agents, antibiotics, and alkaloids, and showing great application potential in the field of food packaging. Research has shown that curcumin, a natural polyphenolic compound, has excellent antioxidant properties and can effectively extend the shelf life of meat products. However, curcumin faces some challenges in practical applications, mainly due to its deficiencies in stability and water solubility, which limit its widespread use in food packaging. Emulsifiers such as surfactants (lecithin), proteins (soy protein), or polysaccharides (gum arabic) are used to improve its low solubility and low bioavailability. The preparation of oil-in-water nanoemulsions includes high-pressure emulsification methods, microfluidics, and sonication. Through these methods, emulsions of curcumin can be prepared and encapsulated in aerogels, which can effectively solve this application limitation and realize its potential in the field of food preservation. Air-dried meat is a traditional special meat product in the northwest region of China, with a long history and unique flavor. Notably, the unique flavor stems from the local dry climate conditions, which are extremely conducive to the natural air-drying and preservation of the product. However, when transporting air-dried meat to the humid coastal cities in the east for sale, it faces severe challenges. During transportation and storage, air-dried meat is prone to absorbing moisture in the air and being invaded by microorganisms, resulting in oxidation reactions, which seriously affect the quality of the product. In food packaging, adsorbents can be used to remove excess components inside the package, such as excessive moisture, oxygen, and odors, thereby extending the shelf life of food and maintaining its quality. Currently, the main components of food adsorbents on the market are calcium oxide, silica gel, bentonite, and iron powder. These traditional adsorption materials have relatively single functions, poor preservation effects, and a potential risk of being accidentally ingested by children. Therefore, aerogel adsorbents, as a system for controlling moisture and releasing bioactive components, are expected to provide an efficient solution for extending the storage period of air-dried meat products. Summary of the Invention

[0003] Technical problems to be solved: To address the quality problems such as moisture absorption and oxidation faced by air-dried meat during transportation and sales, an adsorbent with antioxidant and moisture absorption effects needs to be prepared. To reduce the risk of accidental ingestion of the adsorbent and improve its healthiness, the adsorbent prepared by the present invention using gelatin, chitosan, curcumin, soy protein, and elsholtzia oil has the characteristics of being non-toxic and harmless, and the synergistic effect of chitosan, curcumin, and elsholtzia oil endows it with excellent moisture absorption, antibacterial, and antioxidant properties.

[0004] Technical solution: A preparation method of an adsorbent with antioxidant and moisture absorption effects, comprising the following steps: S1. Prepare an emulsion: Dissolve soy protein in water as the aqueous phase, dissolve curcumin in vegetable oil, heat and dissolve it as the oil phase, mix the oil phase and the aqueous phase, and then perform sonication to obtain a curcumin emulsion; S2. Prepare a gelatin solution: Dissolve gelatin in water and heat it in a water bath to obtain a gelatin solution; S3. Preparation of sol: Mix the chitosan solution and the gelatin solution, adjust the pH, and continuously stir in a water bath to obtain the sol; S4. Preparation of aerogel: Pour the sol into a mold, pre-freeze it, and then freeze-dry it to obtain the aerogel; S5. Loading curcumin emulsion onto the aerogel: Dilute the curcumin emulsion prepared in S1, soak the aerogel and stir, and then dry it at a low temperature to obtain the adsorbent. Furthermore, in step S1, the molecular weight of the soy protein is less than 10 KDa, the vegetable oil is elsholtzia oil, the content of curcumin in the oil phase is 4-16 wt%, the concentration of the aqueous phase is 1-2 wt%, and the mixing ratio of the oil phase to the aqueous phase is (1-2):(8-9). Furthermore, in step S1, the temperature for heating and dissolving is 40-50 °C, and the conditions for ultrasonic treatment are a frequency of 600-800 W, an amplitude of 15-25%, and a time of 8-12 min. Furthermore, in step S2, the gelatin is rumex japonicus houtt. gelatin with a molecular weight greater than 200 KDa, the concentration of the gelatin solution is 15-25 wt%, and the temperature for heating in the water bath is 40-50 °C. Furthermore, in step S3, the concentration of the chitosan solution is 15-25 wt%, the ratio of the gelatin solution to the chitosan solution is 1:(1-4), the pH is adjusted to 7-8, the temperature for stirring in the water bath is 50-60 °C, and the time is 8-10 h. Furthermore, in step S4, the conditions for pre-freezing are freezing at 70-80 °C for 10-12 h, and the conditions for freeze-drying are a temperature of -55 °C to -65 °C and a time of 20-24 h. Furthermore, in step S5, the concentration of the diluted curcumin emulsion is 50-66 wt%, the dosage of the curcumin emulsion is 40-50 wt% of the sol, the soaking time is 8-10 h, the stirring speed is 50 rpm, and the temperature for low-temperature drying is 30-40 °C. Beneficial effects: 1. In the present invention, chitosan and gelatin can be crosslinked through chemical bonding. The amino group in chitosan reacts with the aldehyde group or carboxyl group in gelatin to form a Schiff base reaction, forming a covalent bond, thereby enhancing the structural stability of the aerogel, improving the encapsulation rate and stability of curcumin. The crosslinked network of chitosan and gelatin can serve as a sustained-release carrier for curcumin, enabling curcumin to slowly release and play a role in a specific environment; 2. Curcumin, as a natural polyphenolic compound, has excellent antioxidant properties and antibacterial activity. Chitosan itself has antibacterial properties, and in addition, elsholtzia oil also has certain antibacterial effects. The present invention utilizes the synergistic effect of the three to significantly enhance the antibacterial and antioxidant properties of the adsorbent. 3. The present invention utilizes the volatility of elsholtzia oil to increase the contact area of curcumin with the environment, enhance its antioxidant performance, and the compound of elsholtzia oil and curcumin has a synergistic effect to improve the bioavailability, which can significantly reduce the oxidation levels of lipids and proteins in air-dried meat during storage, effectively slow down the growth of microorganisms, thereby extend the shelf life of air-dried meat and ensure the taste of beef. 4. The present invention uses soy protein to increase the solubility of curcumin, increases the loading rate and encapsulation rate of curcumin in the aerogel. The low molecular weight protein has low water absorption. The present invention uses low molecular weight protein and high molecular weight gelatin to reduce the water absorption of the protein, reduce the interference of water on the encapsulation structure, and provide better protection for curcumin that is easily oxidized or degraded. The low molecular weight protein can load more target substances per unit volume and is more easily evenly dispersed in the gel network to avoid local aggregation; 5. The present invention is natural and safe. The substances used are all food-grade raw materials, which are safe and non-toxic, meeting the needs of modern consumers for healthy foods. Moreover, the preparation and application methods are simple and easy to implement, suitable for large-scale production. 6. The present invention uses sheep hoof gelatin. Compared with cowhide, sheep hoof is a by-product and has no other utilization value, so resources can be utilized more fully and reasonably. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 It is the density diagram of aerogels with different chitosan-gelatin ratios and the aerogels of Comparative Examples 5-6; Figure 2 It is the porosity diagram of aerogels with different chitosan-gelatin ratios and the aerogels of Comparative Examples 5-6; Figure 3 It is the water absorption rate diagram of aerogels with different chitosan-gelatin ratios and the aerogels of Comparative Examples 5-6; Figure 4 It is the aerogel sample diagram of Examples 4-8 and Comparative Examples 3-5; Figure 5 It is the encapsulation rate diagram of curcumin in the aerogels of Examples 4-8 and Comparative Examples 3-5; Figure 6 It is the microscopic structure diagram of the aerogels of Examples 1, 4, 8 and Comparative Examples 1, 3, 4; Figure 7 It is the change diagram of the immobilized water content of the air-dried meat samples of Examples 1-8 and Comparative Examples 1-6 during storage; Figure 8 It is the physical diagram of four groups of samples including the storage experiment blank control, commercially available adsorbent, Comparative Example 3 and Example 4; Figure 9 It is the change diagram of the bound water content of four groups of air-dried meat samples including the blank control, commercially available adsorbent, Comparative Example 3 and Example 4 during storage; Figure 10It is a comparison chart of relaxation times of air-dried meat samples before and after storage at different amplitudes; Figure 11 It is a diagram of the protein oxidation of air-dried meat samples during storage. Figure A is a diagram of the change in carbonyl content during the storage of Example 4 and Control Examples 1-6. Figure B is a diagram of the change in sulfhydryl content of four groups of air-dried meat samples, namely blank control, commercially available adsorbent, Control Example 3, and Example 4, during storage; Figure 12 It is a diagram of the lipid oxidation of air-dried meat samples during storage. Figure A is a diagram of the change in TBARS content during the storage of Example 4 and Control Examples 1-6. Figure B is a diagram of the change in TBARS content of four groups of air-dried meat samples, namely blank control, commercially available adsorbent, Control Example 3, and Example 4, during storage; Figure 13 It is a diagram of the total number of colonies of air-dried meat samples during storage. Figure A is a diagram of the change in the total number of colonies during the storage of Example 4 and Control Examples 1-6. Figure B is a diagram of the change in the total number of colonies of four groups of air-dried meat samples, namely blank control, commercially available adsorbent, Control Example 3, and Example 4, during storage. Detailed implementation manners The present invention will be further described below in conjunction with the accompanying drawings and embodiments. The following embodiments are explanations of the present invention, and the present invention is not limited to the following embodiments: Example 1 A preparation method of an adsorbent with antioxidant and moisture absorption effects, comprising the following steps: S1. Prepare an emulsion: 0.9 g of soy protein with a molecular weight of 8 KDa is dissolved in 89.1 g of water as the aqueous phase, 1.6 g of curcumin is dissolved in 8.4 g of elsholtzia oil, and heated and dissolved at 40 °C as the oil phase. The oil phase and the aqueous phase are mixed at a ratio of 1:9, and ultrasonicated at 800 W and 15% amplitude for 8 min; S2. Prepare a gelatin solution: Gelatin from sheep's hoof with a molecular weight of 200 KDa is dissolved in water and heated in a water bath at 50 °C to obtain a gelatin solution with a concentration of 20 wt%; S3. Prepare a sol: 100 g of a 20 wt% chitosan solution and 100 g of the gelatin solution are mixed, the pH is adjusted to 7, and continuously stirred in a water bath at 50 °C to obtain a sol; S4. Prepare an aerogel: Pour the sol into a mold, freeze at 80 °C for 10 h, and then lyophilize at -60 °C for 24 h to obtain an aerogel; S5. Load the curcumin emulsion onto the aerogel: Dilute 100 g of the curcumin emulsion prepared in S1 to 150 g, soak the aerogel and stir at 50 rpm, and dry at 40 °C to obtain the adsorbent. Example 2 A preparation method of an adsorbent with antioxidant and moisture absorption effects, comprising the following steps: S1. Preparation of emulsion: 0.9 g of soy protein with a molecular weight of 8 KDa is dissolved in 89.1 g of water as the aqueous phase, 1.6 g of curcumin is dissolved in 8.4 g of elsholtzia oil, heated and dissolved at 40 °C as the oil phase, the oil phase and the aqueous phase are mixed at a ratio of 1:9, and ultrasonic treatment is carried out at 800 W and 15% amplitude for 8 min; S2. Preparation of gelatin solution: Rumex japonicus Houtt. gelatin with a molecular weight of 200 KDa is dissolved in water and heated in a water bath at 50 °C to obtain a gelatin solution with a concentration of 20 wt%; S3. Preparation of sol: 134 g of a 20 wt% chitosan solution and 67 g of gelatin solution are mixed, the pH is adjusted to 7, and continuous stirring is carried out in a water bath at 50 °C to obtain a sol; S4. Preparation of aerogel: The sol is poured into a mold, frozen at 80 °C for 10 h, and then freeze-dried at -60 °C for 24 h to obtain an aerogel; S5. Loading curcumin emulsion onto aerogel: 100 g of the curcumin emulsion prepared in S1 is diluted to 150 g, the aerogel is soaked and stirred at 50 rpm, and dried at 40 °C to obtain an adsorbent. Example 3 A preparation method of an adsorbent with antioxidant and moisture absorption effects, comprising the following steps: S1. Preparation of emulsion: 0.9 g of soy protein with a molecular weight of 8 KDa is dissolved in 89.1 g of water as the aqueous phase, 1.6 g of curcumin is dissolved in 8.4 g of elsholtzia oil, heated and dissolved at 40 °C as the oil phase, the oil phase and the aqueous phase are mixed at a ratio of 1:9, and ultrasonic treatment is carried out at 800 W and 15% amplitude for 8 min; S2. Preparation of gelatin solution: Rumex japonicus Houtt. gelatin with a molecular weight of 200 KDa is dissolved in water and heated in a water bath at 50 °C to obtain a gelatin solution with a concentration of 20 wt%; S3. Preparation of sol: 150 g of a 20 wt% chitosan solution and 50 g of gelatin solution are mixed, the pH is adjusted to 7, and continuous stirring is carried out in a water bath at 50 °C to obtain a sol; S4. Preparation of aerogel: The sol is poured into a mold, frozen at 80 °C for 10 h, and then freeze-dried at -60 °C for 24 h to obtain an aerogel; S5. Loading curcumin emulsion onto aerogel: 100 g of the curcumin emulsion prepared in S1 is diluted to 150 g, the aerogel is soaked and stirred at 50 rpm, and dried at 40 °C to obtain an adsorbent. Example 4 A preparation method of an adsorbent with antioxidant and moisture absorption effects, comprising the following steps: S1. Preparation of emulsion: 0.9 g of soy protein with a molecular weight of 8 KDa is dissolved in 89.1 g of water as the aqueous phase, 1.6 g of curcumin is dissolved in 8.4 g of elsholtzia oil, heated and dissolved at 40 °C as the oil phase, the oil phase and the aqueous phase are mixed at a ratio of 1:9, and ultrasonic treatment is carried out at 800 W and 15% amplitude for 8 min; S2. Preparation of gelatin solution: Dissolve ovine hoof gelatin with a molecular weight of 200 KDa in water and heat it in a water bath at 50 °C to obtain a gelatin solution with a concentration of 20 wt%. S3. Preparation of sol: Mix 160 g of a 20 wt% chitosan solution and 40 g of the gelatin solution, adjust the pH to 7, and continuously stir in a water bath at 50 °C to obtain a sol. S4. Preparation of aerogel: Pour the sol into a mold, freeze it at 80 °C for 10 h, and then freeze-dry it at -60 °C for 24 h to obtain an aerogel. S5. Loading curcumin emulsion onto the aerogel: Dilute 100 g of the curcumin emulsion prepared in S1 to 150 g, soak the aerogel and stir at 50 rpm, and dry it at 40 °C to obtain an adsorbent. Example 5 A method for preparing an adsorbent with antioxidant and moisture absorption effects, comprising the following steps: S1. Preparation of emulsion: Dissolve 0.9 g of soy protein with a molecular weight of 8 KDa in 89.1 g of water as the aqueous phase, dissolve 1.2 g of curcumin in 8.8 g of elsholtzia oil, heat and dissolve it at 40 °C as the oil phase, mix the oil phase and the aqueous phase in a ratio of 1:9, and ultrasonicate for 8 min at 800 W and an amplitude of 15%. S2. Preparation of gelatin solution: Dissolve ovine hoof gelatin with a molecular weight of 200 KDa in water and heat it in a water bath at 50 °C to obtain a gelatin solution with a concentration of 20 wt%. S3. Preparation of sol: Mix 160 g of a 20 wt% chitosan solution and 40 g of the gelatin solution, adjust the pH to 7, and continuously stir in a water bath at 50 °C to obtain a sol. S4. Preparation of aerogel: Pour the sol into a mold, freeze it at 80 °C for 10 h, and then freeze-dry it at -60 °C for 24 h to obtain an aerogel. S5. Loading curcumin emulsion onto the aerogel: Dilute 100 g of the curcumin emulsion prepared in S1 to 150 g, soak the aerogel and stir at 50 rpm, and dry it at 40 °C to obtain an adsorbent. Example 6 A method for preparing an adsorbent with antioxidant and moisture absorption effects, comprising the following steps: S1. Preparation of emulsion: Dissolve 0.9 g of soy protein with a molecular weight of 8 KDa in 89.1 g of water as the aqueous phase, dissolve 0.8 g of curcumin in 9.2 g of elsholtzia oil, heat and dissolve it at 40 °C as the oil phase, mix the oil phase and the aqueous phase in a ratio of 1:9, and ultrasonicate for 8 min at 800 W and an amplitude of 15%. S2. Preparation of gelatin solution: Dissolve ovine hoof gelatin with a molecular weight of 200 KDa in water and heat it in a water bath at 50 °C to obtain a gelatin solution with a concentration of 20 wt%. S3. Preparation of sol: Mix 160 g of a 20 wt% chitosan solution and 40 g of a gelatin solution, adjust the pH to 7, and continuously stir in a water bath at 50 °C to obtain a sol; S4. Preparation of aerogel: Pour the sol into a mold, freeze it at 80 °C for 10 h, and then freeze-dry it at -60 °C for 24 h to obtain an aerogel; S5. Loading curcumin emulsion onto the aerogel: Dilute 100 g of the curcumin emulsion prepared in S1 to 150 g, soak the aerogel and stir at 50 rpm, and dry it at 40 °C to obtain an adsorbent. Example 7 A method for preparing an adsorbent with antioxidant and moisture absorption effects, comprising the following steps: S1. Preparation of emulsion: Dissolve 0.9 g of soy protein with a molecular weight of 8 KDa in 89.1 g of water as the aqueous phase, dissolve 0.4 g of curcumin in 9.6 g of elsholtzia oil, heat and dissolve at 40 °C as the oil phase, mix the oil phase and the aqueous phase in a ratio of 1:9, and ultrasonicate at 800 W and 15% amplitude for 8 min; S2. Preparation of gelatin solution: Dissolve rhubarb dock gelatin with a molecular weight of 200 KDa in water, and heat it in a water bath at 50 °C to obtain a 20 wt% gelatin solution; S3. Preparation of sol: Mix 160 g of a 20 wt% chitosan solution and 40 g of a gelatin solution, adjust the pH to 7, and continuously stir in a water bath at 50 °C to obtain a sol; S4. Preparation of aerogel: Pour the sol into a mold, freeze it at 80 °C for 10 h, and then freeze-dry it at -60 °C for 24 h to obtain an aerogel; S5. Loading curcumin emulsion onto the aerogel: Dilute 100 g of the curcumin emulsion prepared in S1 to 150 g, soak the aerogel and stir at 50 rpm, and dry it at 40 °C to obtain an adsorbent. Example 8 A method for preparing an adsorbent with antioxidant and moisture absorption effects, comprising the following steps: S1. Preparation of emulsion: Dissolve 0.9 g of soy protein with a molecular weight of 6 KDa in 89.1 g of water as the aqueous phase, dissolve 1.6 g of curcumin in 8.4 g of elsholtzia oil, heat and dissolve at 40 °C as the oil phase, mix the oil phase and the aqueous phase in a ratio of 1:9, and ultrasonicate at 800 W and 15% amplitude for 8 min; S2. Preparation of gelatin solution: Dissolve rhubarb dock gelatin with a molecular weight of 200 KDa in water, and heat it in a water bath at 50 °C to obtain a 20 wt% gelatin solution; S3. Preparation of sol: Mix 160 g of a 20 wt% chitosan solution and 40 g of a gelatin solution, adjust the pH to 7, and continuously stir in a water bath at 50 °C to obtain a sol; S4. Preparation of aerogel: Pour the sol into a mold, freeze it at 80 °C for 10 h, and then freeze-dry it at -60 °C for 24 h to obtain an aerogel; S5. Loading curcumin emulsion onto aerogel: Dilute 100 g of the curcumin emulsion prepared in S1 to 150 g, soak the aerogel and stir at 50 rpm, and dry at 40 °C to obtain the adsorbent. Comparative Example 1 The difference between this comparative example and Example 4 is that chitosan is not added, specifically as follows: S1. Preparation of emulsion: Dissolve 0.9 g of soy protein with a molecular weight of 8 KDa in 89.1 g of water as the aqueous phase, dissolve 1.6 g of curcumin in 8.4 g of elsholtzia oil, heat and dissolve at 40 °C as the oil phase, mix the oil phase and the aqueous phase in a ratio of 1:9, and ultrasonicate for 8 min at 800 W and 15% amplitude; S2. Preparation of gelatin solution: Dissolve rhubarb dock gelatin with a molecular weight of 200 KDa in water and heat in a water bath at 50 °C to obtain a gelatin solution with a concentration of 20 wt%; S3. Preparation of aerogel: Pour the gelatin solution into a mold, freeze at 80 °C for 10 h, and then lyophilize at -60 °C for 24 h to obtain the aerogel; S4. Loading curcumin emulsion onto aerogel: Dilute 100 g of the curcumin emulsion prepared in S1 to 150 g, soak the aerogel and stir at 50 rpm, and dry at 40 °C to obtain the adsorbent. Comparative Example 2 The difference between this comparative example and Example 4 is the ratio of chitosan to gelatin, specifically as follows: S1. Preparation of emulsion: Dissolve 0.9 g of soy protein with a molecular weight of 8 KDa in 89.1 g of water as the aqueous phase, dissolve 1.6 g of curcumin in 8.4 g of elsholtzia oil, heat and dissolve at 40 °C as the oil phase, mix the oil phase and the aqueous phase in a ratio of 1:9, and ultrasonicate for 8 min at 800 W and 15% amplitude; S2. Preparation of gelatin solution: Dissolve rhubarb dock gelatin with a molecular weight of 200 KDa in water and heat in a water bath at 50 °C to obtain a gelatin solution with a concentration of 20 wt%; S3. Preparation of sol: Mix 67 g of a 20 wt% chitosan solution and 134 g of the gelatin solution, adjust the pH to 7, and continuously stir in a water bath at 50 °C to obtain the sol; S4. Preparation of aerogel: Pour the sol into a mold, freeze at 80 °C for 10 h, and then lyophilize at -60 °C for 24 h to obtain the aerogel; S5. Loading curcumin emulsion onto aerogel: Dilute 100 g of the curcumin emulsion prepared in S1 to 150 g, soak the aerogel and stir at 50 rpm, and dry at 40 °C to obtain the adsorbent. Comparative Example 3 The difference between this comparative example and Example 4 is that curcumin is not added, specifically as follows: S1. Preparation of emulsion: 0.9 g of soy protein with a molecular weight of 8 KDa is dissolved in 89.1 g of water as the aqueous phase, and 10 g of elsholtzia oil is used as the oil phase. The oil phase and the aqueous phase are mixed at a ratio of 1:9, and ultrasonic treatment is carried out at 800 W and 15% amplitude for 8 min; S2. Preparation of gelatin solution: Rumex japonicus Houtt. gelatin with a molecular weight of 200 KDa is dissolved in water and heated in a water bath at 50 °C to obtain a gelatin solution with a concentration of 20 wt%; S3. Preparation of sol: 160 g of a 20 wt% chitosan solution and 40 g of gelatin solution are mixed, the pH is adjusted to 7, and continuous stirring is carried out in a water bath at 50 °C to obtain a sol; S4. Preparation of aerogel: The sol is poured into a mold, frozen at 80 °C for 10 h, and then freeze-dried at -60 °C for 24 h to obtain an aerogel; S5. Loading curcumin emulsion onto aerogel: 100 g of the curcumin emulsion prepared in S1 is diluted to 150 g, the aerogel is soaked and stirred at 50 rpm, and dried at 40 °C to obtain an adsorbent. Comparative Example 4 The difference between this comparative example and Example 4 is that the molecular weight of soy protein is 15 KDa, and the details are as follows: S1. Preparation of emulsion: 0.9 g of soy protein with a molecular weight of 15 KDa is dissolved in 89.1 g of water as the aqueous phase, 1.6 g of curcumin is dissolved in 8.4 g of elsholtzia oil, and heated and dissolved at 40 °C as the oil phase. The oil phase and the aqueous phase are mixed at a ratio of 1:9, and ultrasonic treatment is carried out at 800 W and 15% amplitude for 8 min; S2. Preparation of gelatin solution: Rumex japonicus Houtt. gelatin with a molecular weight of 200 KDa is dissolved in water and heated in a water bath at 50 °C to obtain a gelatin solution with a concentration of 20 wt%; S3. Preparation of sol: 160 g of a 20 wt% chitosan solution and 40 g of gelatin solution are mixed, the pH is adjusted to 7, and continuous stirring is carried out in a water bath at 50 °C to obtain a sol; S4. Preparation of aerogel: The sol is poured into a mold, frozen at 80 °C for 10 h, and then freeze-dried at -60 °C for 24 h to obtain an aerogel; S5. Loading curcumin emulsion onto aerogel: 100 g of the curcumin emulsion prepared in S1 is diluted to 150 g, the aerogel is soaked and stirred at 50 rpm, and dried at 40 °C to obtain an adsorbent. Comparative Example 5 The difference between this comparative example and Example 4 is that no soy protein is added, and the details are as follows: S1. Preparation of curcumin solution: 1.6 g of curcumin is dissolved in 8.4 g of elsholtzia oil and heated and dissolved at 40 - 50 °C; S2. Preparation of gelatin solution: Rumex japonicus Houtt. gelatin with a molecular weight of 200 KDa is dissolved in water to obtain 40 g of a 20 wt% gelatin solution, 10 g of curcumin solution is added, and heated in a water bath at 50 °C, and emulsified and sheared to obtain a curcumin-gelatin emulsion; S3. Preparation of sol: 160 g of a 20 wt% chitosan solution and 50 g of curcumin-gelatin emulsion were mixed, the pH was adjusted to 7, and continuous stirring was carried out in a water bath at 50 °C to obtain a sol; S4. Preparation of aerogel: The sol was poured into a mold, frozen at 80 °C for 10 h, and then freeze-dried at -60 °C for 24 h to obtain an aerogel. Comparative Example 6 The difference between this comparative example and Example 4 is that soy protein and elsholtzia oil are not added, specifically as follows: S1. Preparation of curcumin solution: 1.6 g of curcumin was dissolved in 8.4 g of water, and the pH was adjusted to 9.0; S2. Preparation of gelatin solution: Gelatin from Rumex japonicus with a molecular weight of 200 KDa was dissolved in water to obtain 40 g of a 20 wt% gelatin solution. 10 g of curcumin solution was added, and the mixture was heated in a water bath at 50 °C and emulsified and sheared to obtain a curcumin-gelatin solution; S3. Preparation of sol: 160 g of a 20 wt% chitosan solution and 50 g of gelatin solution were mixed, the pH was adjusted to 7, and continuous stirring was carried out in a water bath at 50 °C to obtain a sol; S4. Preparation of aerogel: The sol was poured into a mold, frozen at 80 °C for 10 h, and then freeze-dried at -60 °C for 24 h to obtain an aerogel; Performance measurement: 1. Characterization of the physical properties of the aerogel adsorbent - density and porosity The density (ρ) of the aerogel was measured by the cylindrical volume method: where m represents the mass of the aerogel and V represents the volume of the aerogel. The porosity of the aerogel was measured by the water saturation method. Cubic molds (10 cm × 10 cm × 10 cm) were used to prepare aerogel samples of each group. Aerogel samples with a cubic shape were shaped so that their volume could be measured. The following formula was used to calculate the porosity (P) of the aerogel: where W1 represents the weight of the aerogel, W2 represents the weight of the sample after water absorption saturation, ρwater represents the density of water, and V represents the volume of the aerogel. As Figure 1As shown, compared with Control Example 1, the density of the aerogels in the Examples with the addition of chitosan was significantly increased (P<0.05). Moreover, the density of the aerogel was concentration-dependent on the chitosan ratio. When the ratio of gelatin to chitosan was 1:4 (Example 4), the density reached the maximum value (27.66 mg / cm3). When the proportion of gelatin was too large (Control Example 2), the density decreased. Research has shown that adding chitosan can increase the density of the composite aerogel. This may be because chitosan (poly-cation) is tightly connected to gelatin (poly-anion) through electrostatic attraction, causing the composite semi-solid gel to shrink more severely during freeze-drying, resulting in a reduction in volume. In addition, chitosan can also affect the density of the aerogel through multiple mechanisms, including increasing cationic charges, changing the original network structure of the aerogel, and regulating the physical properties of the aerogel through chemical bond formation. At the same time, the addition of protein also increases the density of the gel (Control Examples 5-6). An aerogel is a porous material with a high porosity, and this high porosity endows it with unique properties. As Figure 2 shown, the porosity of the G aerogel with the addition of chitosan was significantly higher than that of Control Example 1 (P<0.05). It shows that the addition of chitosan can strengthen the internal cross-linking of the aerogel and increase the porosity of the aerogel. This is because the network structure formed by chitosan during the gelation process locks up a large amount of air, thus forming a porous structure. In addition, as the chitosan ratio increases, the porosity also shows an upward trend (Examples 1-4). Preparing the aerogel by directly adding curcumin without adding protein will also affect the porosity (Control Examples 5-6). 2. Characterization of the physical properties of the aerogel adsorbent - water absorption rate The water absorption rate of the aerogel was measured, and the formula is as follows: where W1 represents the weight of the dry sample, and W2 represents the weight of the swollen sample. In the preparation of the aerogels in the Examples, all aerogel samples could swell extremely fast under the continuous action of water vapor. As Figure 3 shown, the water absorption rates of Examples 1-4 were significantly higher than those of the Control Examples (P<0.05). Among them, the water absorption rates of Examples 3-4 were significantly higher than those of other samples (P<0.05). Research has shown that chitosan helps to improve the water absorption rate of the aerogel. This may be because the functional groups (amino and hydroxyl groups) in chitosan and protein can form hydrogen bonds with water molecules, thus enhancing the water absorption ability of the aerogel. In addition, the increase in the porosity of the aerogel provides more adsorption sites for water molecules. 3. Encapsulation rate of curcumin in the aerogel adsorbent The encapsulation rate of the aerogel was tested. Curcumin was dissolved in ethanol, and the ultraviolet absorbance of the sample was measured at 424 nm to obtain a standard curve (R2 = 0.9997). The content of curcumin contained in the composite aerogel and the content of free curcumin obtained after centrifugation were measured respectively. The encapsulation rate of curcumin is crucial for ensuring its effectiveness and safety in applications. As Figure 5 shown, as the amount of curcumin added decreases (Examples 4 - 7), the encapsulation rate increases. The encapsulation rates of Comparative Examples 4 and 5 are lower than those of the examples. Both the protein content and molecular weight affect the encapsulation of curcumin. Small - molecule proteins can wrap curcumin more tightly. The encapsulation rate of Example 4 reaches the highest value (96.7 ± 1.5%), significantly higher than that of other samples (P < 0.05). At this time, the surface of the aerogel reaches the most stable structure and the best affinity. 4. Microstructure of the aerogel adsorbent The microstructure of the samples was determined by SEM. The cross - section of the freeze - dried aerogel was attached to a conductive strip, and then sputter - coated with gold. The microstructure was observed at an accelerating voltage of 5 kV and a magnification of ×300. From Figure 6 it can be observed that there are significant differences in the surface morphology of different aerogel samples. Comparative Example 1 without chitosan shows a fragmented surface similar to that of rumex japonicus houtt. gelatin, without an obvious network structure. Although chitosan was added in Comparative Example 2, there are still large pores and fragments. There are obvious morphological changes in Comparative Example 4, with obvious fractures compared to the examples. Compared with the comparative examples, the examples have a higher porosity and a denser surface network structure. 5. Antioxidant activity of the aerogel adsorbent The free - radical scavenging ability of the samples was tested using DPPH and ABTS assay kits. Curcumin has been widely proven to have excellent antioxidant properties, which can effectively scavenge free radicals and inhibit the molecular oxidation process. The DPPH free - radical and ABTS free - radical scavenging abilities of aerogels embedded with different concentrations of curcumin are shown in Table 1. The ABTS free - radical scavenging abilities of the aerogels in the examples are all significantly higher than those of the comparative examples (P < 0.05). In the test of the DPPH free - radical scavenging rate, it was also found that as the concentration of curcumin increased (Examples 4 - 8), the DPPH free - radical scavenging rate of the aerogel increased from 34.19% to 59.21%. Compared with Comparative Example 1, the chitosan used in the examples improved the solubility and dispersibility of curcumin, which is beneficial for curcumin to come into full contact with reactants such as free radicals, thereby improving the antioxidant activity. Compared with Comparative Examples 5 and 6, the curcumin in the oil phase wrapped by proteins in the examples improved its stability and thus its antioxidant ability. In Comparative Example 4, due to its large molecular weight and easy water absorption, it affects the stability of the protein wrapping, thereby reducing the antioxidant property of curcumin. Table 1 Antioxidant activities of different adsorbents 6. Influence of Aerogel Adsorbent on Air-dried Meat during Storage The aerogel adsorbent was placed in canned air-dried meat packed in PVC. Samples of canned air-dried meat were taken for testing at 0d, 30d, 60d, 90d, 120d, and 150d respectively. Samples without adsorbent were used as blank controls and compared with samples with commercially available adsorbents to comprehensively evaluate the long-term influence of different adsorbents on the storage quality of air-dried meat. 6.1 Influence of Aerogel Adsorbent on Water Distribution in Air-dried Meat during Storage The low-field nuclear magnetic resonance analyzer was used to test the water distribution in air-dried meat samples during storage at a proton resonance frequency of 23.2 MHz and a temperature of 32 °C. The samples were sheared and placed in a polytetrafluoroethylene cylindrical tube, and a 40 mm radio frequency coil was inserted to collect the CPMG decay signal. Among them, the 90° pulse (P1) was 27 μs, and the 180° pulse (P2) was 54 μs. The CPMG data was inversely processed by the SIRT algorithm. Before storage, the water in air-dried meat mainly existed in the form of bound water and immobile water, while the content of free water was relatively small. As Figure 7 shown, with the increase of storage time, the immobile water in air-dried meat samples showed an upward trend, indicating that the bound water in each group of air-dried meat was continuously lost and the water in the air was absorbed during storage. The water loss in Control Example 1 and Control Examples 4-6 was significantly higher than that in the Examples, indicating that chitosan, soybean protein, and the molecular weight of soybean protein would all affect the water absorption rate of the adsorbent. Control Example 3 in the control examples and Example 4 in the examples were preferably selected for comparison with the blank control and commercially available adsorbents, as Figure 8 shown. As Figure 9 , after 90d of storage, the content of bound water in Control Example 3 and Example 4 was significantly higher than that in the blank control group and the commercially available adsorbent group (p < 0.05). The addition of curcumin had no obvious effect on the water absorption performance. The research showed that the aerogel adsorbent could significantly maintain the low water state of air-dried meat products during long-term storage. After 150d of storage, even though the aerogels in Control Example 3 and Example 4 placed in the package adsorbed water, they still maintained a stable physical form ( Figure 10 ). This may be because the gelatin and chitosan wall materials provided support, thus maintaining the porous structure and high porosity of the aerogel. 6.2 Influence of Aerogel Adsorbent on Protein Oxidation in Air-dried Meat during Storage To evaluate the degree of protein oxidation, this study measured the carbonyl content and sulfhydryl content of proteins in air-dried meat samples at different storage times: the protein carbonyl content was determined by the dinitrophenylhydrazine (DNPH) method. Using the standard curve of bovine serum albumin, the protein concentration was calculated based on the absorbance value at 370 nm, and the results were expressed as nmol carbonyl / mg protein. The sulfhydryl content was calculated based on the absorbance value at 412 nm, combined with the molar extinction coefficient of 13,600 M -1 cm -1 and the results were expressed as nmol sulfhydryl / mg protein. The generation of carbonyl compounds is mainly due to the covalent binding of malondialdehyde, a product of lipid oxidation, to proteins. These carbonyl compounds not only cause changes in the protein structure but also further affect the texture and flavor of air-dried meat. For example Figure 11 A shows that during the 60th to 150th day of storage, the carbonyl content of the air-dried meat samples increased significantly (p < 0.05). This may be because when the malondialdehyde content accumulates to a certain amount, the reaction with proteins intensifies to form irreversible non-enzymatic modifications, which is an important factor leading to the rapid decline in the quality of air-dried meat. In addition, after 60 days of storage, the carbonyl content of Example 4 was significantly lower than that of the control examples. After 150 days, the carbonyl content of Control Examples 3 and 5-6 was relatively high. In Control Examples 5-6, due to the lack of protein protection, the stability of curcumin was poor. This indicates that the stability of curcumin and curcumin is very important for the antioxidant protection of air-dried meat. The attack of reactive oxygen species (ROS) on proteins in meat products promotes the oxidation reaction of sulfhydryls in proteins, resulting in a significant decrease in the total sulfhydryl content on the surface of the protein structure. As shown in Figure 11 B, during storage, the sulfhydryl content of the four groups of air-dried meat samples continuously decreased, indicating that the sulfhydryls in the air-dried meat proteins were continuously consumed due to free radical reactions. At the same time, during the storage period from 90 to 150 days, it was observed that the decline rate of the total sulfhydryl content of the air-dried meat proteins in Example 4 and Control Example 3 was significantly lower than that of the commercial adsorbent group and the blank control group (p < 0.05). This may be because the gelatin and soy protein in the aerogel compete with the proteins in the meat products, replacing the oxidation-sensitive sites in the meat products, thereby reducing the consumption rate of sulfhydryls in the air-dried meat. It is worth noting that in the later stage of storage (60 - 150 days), the decline rate of the total sulfhydryl content in Example 3 was significantly lower than that in Control Example 3 (p < 0.05). This may be because the slow-release curcumin can interact with proteins, increasing the relative content of ionic bonds and hydrogen bonds to form a stable complex, thereby protecting the protein structure. Therefore, adding curcumin aerogel in the packaging plays a crucial role in controlling the accumulation of carbonyls in air-dried meat products and maintaining the quality of meat products. 6.3 Effect of Aerogel Adsorbent on Lipid Oxidation of Air-Dried Meat during Storage In this study, the content of thiobarbituric acid reactive substances (TBARS) was used as an index. Quantitative analysis was carried out through a standard curve established using 1,1,3,3-tetraethoxypropane (TEP), and the results were expressed as milligrams of malondialdehyde (MDA) per kilogram of air-dried meat. When air-dried meat is stored, the substances produced by fat oxidation react with malondialdehyde (MDA). MDA is an index for measuring the degree of fat oxidation and combines with TBARS to form a red complex. As Figure 12 shown in A, the TBARS values of air-dried meat samples all increased with the extension of storage time, indicating that the degree of fat oxidation of air-dried meat increased continuously over time. In Control Example 5, the TBARS value increased rapidly in the early stage, which may be due to the addition of volatile oil but no protein emulsification, resulting in the rapid oxidation of volatile oil first. In Control Example 6, no volatile oil was added, and the released curcumin could only stay on the surface of the gel, restricting the exertion of its antioxidant effect. In addition, as Figure 12 shown in B, the TBARS values of Example 4, Control Example 3, and the commercial adsorbent group were all significantly lower than those of the blank control (p < 0.05). This indicates that during the storage of air-dried meat, the addition of adsorbents can significantly reduce the occurrence of fat oxidation, thereby effectively reducing the degree of fat oxidation. It should be noted that the TBARS values of Example 4 at 60d, 90d, 120d, and 150d were significantly lower than those of Control Example 3 (p < 0.05). This may be because curcumin can inhibit the activities of lipoxygenase, cyclooxygenase, and xanthine oxidase, further inhibiting fat oxidation. In addition, the TBARS values of Example 4 during storage were significantly lower than those of the commercial adsorbent (p < 0.05), proving that the curcumin-coated aerogel adsorbent is significantly more effective than commercial silica gel adsorbents in reducing fat oxidation in meat products. 6.4 Effect of Aerogel Adsorbent on Total Colony Count of Air-Dried Meat during Storage According to the method of "National Food Safety Standard Microbiological Examination of Foods - Determination of Total Colony Count" (GB 4789.2-2022) of China National Standard, the total colony count of microorganisms in four groups of air-dried meat samples during storage was determined. The total colony count is one of the important indicators for measuring the hygienic status and food processing quality of air-dried meat products. According to the China National Standard (GB 2726-2016), the detection results of the total colony count of the same batch of meat products shall not exceed 5 log CFU / g. As Figure 13 shown in A, the total colony count of air-dried meat samples showed an upward trend during storage. The antibacterial effect of Example 4 was obvious compared with the control examples. The total colony counts of Control Example 2 and Control Example 4-5 were lower than those of other groups, which may be related to the antibacterial and volatile effects of elsholtzia oil. As Figure 13As shown in Figure B, after 60 days of storage, the total number of colonies of Example 4, Control Example 3, and the commercially available adsorbent were all significantly lower than that of the blank control group (p < 0.05). The research shows that adding an adsorbent to the packaging of air-dried meat products can absorb excess moisture and oxygen in the package, thus creating an environment unfavorable for the growth of microorganisms and delaying the process of spoilage. The total number of colonies of the blank control group, the commercially available adsorbent, Control Example 3, and Example 4 exceeded 5 log CFU / g at 90, 120, 120, and 150 days respectively, reaching the storage end point. The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A preparation method of an adsorbent with antioxidant and moisture absorption effects, characterized in that, It includes the following steps: S1. Prepare the emulsion: Dissolve soy protein in water as the aqueous phase, dissolve curcumin in vegetable oil, heat and dissolve it as the oil phase, mix the oil phase and the aqueous phase, and obtain the curcumin emulsion by ultrasonic treatment; S2. Prepare the gelatin solution: Dissolve gelatin in water and heat it in a water bath to obtain the gelatin solution; S3. Prepare the sol: Mix the chitosan solution and the gelatin solution, adjust the pH, and continuously stir in a water bath to obtain the sol; S4. Prepare the aerogel: Pour the sol into a mold, pre-freeze it, and then freeze-dry it to obtain the aerogel; S5. Load the curcumin emulsion onto the aerogel: Dilute the curcumin emulsion prepared in S1, soak the aerogel and stir it, and dry it at a low temperature to obtain the adsorbent.

2. The preparation method of an adsorbent with antioxidant and moisture absorption effects according to claim 1, characterized in that: In the step S1, the molecular weight of the soy protein is less than 10KDa, the vegetable oil is elsholtzia oil, the content of curcumin in the oil phase is 4-16wt%, the concentration of the aqueous phase is 1-2wt%, and the mixing ratio of the oil phase and the aqueous phase is (1-2):(8-9).

3. The preparation method of an adsorbent with antioxidant and moisture absorption effects according to claim 1, characterized in that: In the step S1, the temperature for heating and dissolving is 40-50°C, and the conditions for ultrasonic treatment are a frequency of 600-800W, an amplitude of 15-25%, and a time of 8-12min.

4. The preparation method of an adsorbent with antioxidant and moisture absorption effects according to claim 1, characterized in that: In the step S2, the gelatin is rumex japonicus houtt. gelatin with a molecular weight greater than 200KDa, the concentration of the gelatin solution is 15-25wt%, and the temperature for heating in the water bath is 40-50°C.

5. The preparation method of an adsorbent having antioxidant and moisture absorption effects according to claim 1, characterized in that: In the step S3, the concentration of the chitosan solution is 15-25wt%, the ratio of the gelatin solution to the chitosan solution is 1:(1-4), adjust the pH to 7-8, the temperature for stirring in the water bath is 50-60°C, and the time is 8-10h.

6. The preparation method of an adsorbent with antioxidant and moisture absorption effects according to claim 1, characterized in that: In the step S4, the conditions for pre-freezing are freezing at 70-80°C for 10-12h, and the conditions for freeze-drying are a temperature of -55°C to -65°C and a time of 20-24h.

7. The preparation method of an adsorbent with antioxidant and moisture absorption effects according to claim 1, characterized in that: In the step S5, the concentration of the diluted curcumin emulsion is 50-66wt%, the dosage of the curcumin emulsion is 40-50wt% of the sol, the soaking time is 8-10h, the stirring speed is 50rpm, and the temperature for low-temperature drying is 30-40°C.

8. An adsorbent with antioxidant and moisture absorption effects prepared by the preparation method according to any one of claims 1-7.

9. Application of the adsorbent with antioxidant and moisture absorption effects obtained according to any one of claims 1-8 in air-dried meat products.

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