Natural deep-eutectic solvent enhanced konjac glucomannan film as well as preparation method and application thereof

Abstract

The invention discloses a natural eutectic solvent enhanced konjac glucomannan film as well as a preparation method and application thereof, and belongs to the technical field of food packaging. The konjac glucomannan film enhanced by the natural deep eutectic solvent, provided by the invention, comprises konjac glucomannan, the natural deep eutectic solvent and gallic acid modified MXene nanoparticles; the mass ratio of the konjac glucomannan to the natural eutectic solvent to the gallic acid modified MXene nanoparticles is (850 to 950) to (50 to 250) to (10 to 40). Through the synergistic effect of all the components, the defects that KGM is insufficient in intrinsic mechanical strength, weak in antibacterial and antioxidant performance and poor in moisture resistance are overcome, the comprehensive performance of the film is remarkably improved, and the film can be used for cold-chain packaging of high-value fresh food and has environment friendliness and functional practicability.

Description

Technical Field

[0001] This invention relates to the field of food packaging technology, and in particular to a natural eutectic solvent-reinforced konjac glucomannan film, its preparation method, and its application. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Post-harvest fruits are highly susceptible to external factors such as microbial contamination, oxidation, and physical shock during storage and transportation. This is especially true for high-moisture, structurally fragile berries like raspberries, whose peels are easily damaged, leading to nutrient loss, quality decline, and a significantly shortened shelf life. Traditional preservation methods rely heavily on chemical treatments or synthetic plastic packaging, which not only have limited preservation effects but also fail to meet current requirements for green and sustainable development. Therefore, the development of packaging materials derived from natural sources and possessing both functionality and environmental friendliness has become a key research focus in the field of food preservation.

[0004] Natural polysaccharide materials are widely used in food packaging systems due to their excellent biodegradability and film-forming properties. Among them, konjac glucomannan (KGM), as an edible natural polysaccharide, possesses excellent biocompatibility and film-forming properties, making it an important choice among natural polysaccharide materials. However, KGM's inherent insufficient mechanical strength, weak antibacterial and antioxidant properties, and poor moisture resistance severely limit its application in high-performance preservation materials. To improve the performance of KGM, researchers have attempted to modify it, but existing modification methods still have significant drawbacks: while some modified KGM films have improved antibacterial and antioxidant capabilities, they have not effectively solved the problem of insufficient mechanical properties, failing to meet the protection requirements caused by physical impacts during food transportation; other modification methods involve complex chemical reactions (such as grafting reactions), resulting in low reaction efficiency and cumbersome process steps, making large-scale production and application difficult. These shortcomings mean that the practical application of KGM-based preservation materials still faces significant challenges. Summary of the Invention

[0005] In view of this, the present invention provides a konjac glucomannan film reinforced with a natural eutectic solvent, its preparation method and application. The present invention uses konjac glucomannan (KGM) as the main material, combined with gallic acid modified two-dimensional material (MXene@GA) and natural eutectic solvent (NADES) to construct a multifunctional composite film, which can endow the film with excellent mechanical properties, ultraviolet shielding, hydrophobicity and antioxidant activity.

[0006] In a first aspect, the present invention provides a konjac glucomannan film reinforced with a natural eutectic solvent, comprising konjac glucomannan, a natural eutectic solvent, and gallic acid-modified MXene nanoparticles; the mass ratio of konjac glucomannan, the natural eutectic solvent, and gallic acid-modified MXene nanoparticles is (850~950):(50~250):(10~40).

[0007] Preferably, the natural eutectic solvent includes a hydrogen bond donor and a hydrogen bond acceptor, wherein the hydrogen bond donor is selected from one or both of citric acid or caffeic acid, and the hydrogen bond acceptor is selected from one or more of glycine, L-carnitine, or aminosulfonic acid.

[0008] Furthermore, the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:(1~3); the hydrogen bond donor is citric acid and caffeic acid, and the molar ratio of citric acid to caffeic acid is 1:(0.5~2).

[0009] Preferably, in the gallic acid-modified MXene nanoparticles, the mass ratio of gallic acid to MXene is (1~2):1.

[0010] Secondly, the present invention provides a method for preparing the above-mentioned natural eutectic solvent-reinforced konjac glucomannan film, comprising the following steps: Preparation of gallic acid-modified MXene nanoparticles; Gallic acid-modified MXene nanoparticles were added to a mixture of konjac glucomannan aqueous solution and natural eutectic solvent, stirred and dispersed, and then a konjac glucomannan film reinforced with natural eutectic solvent was prepared by casting method.

[0011] Preferably, the stirring speed for the stirring and dispersion is 500~1200 rpm, and the stirring time is 10~40 min.

[0012] Preferably, the preparation method of the gallic acid-modified MXene nanoparticles is as follows: Gallic acid was activated by carboxylation and then mixed with MXene dispersion. The mixture was stirred, centrifuged, and dried to obtain the final product.

[0013] Further, the step of carboxyl activation of gallic acid is as follows: gallic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) are mixed and stirred in an aqueous ethanol solution for 0.5~3h.

[0014] Preferably, the concentration of the konjac glucomannan aqueous solution is 0.5~2wt%.

[0015] Thirdly, the present invention provides the application of the above-mentioned natural eutectic solvent-reinforced konjac glucomannan film or the natural eutectic solvent-reinforced konjac glucomannan film prepared by the above preparation method in food preservation.

[0016] Compared with the prior art, the present invention has achieved the following beneficial effects: (1) The konjac glucomannan film reinforced by natural eutectic solvent provided by the present invention achieves multi-component synergistic effect through the ternary composite design of konjac glucomannan (KGM), natural eutectic solvent (NADES) and gallic acid modified MXene nanoparticles (MXene@GA): NADES, as a green plasticizer and interface regulator, improves the flexibility of KGM and optimizes the interface compatibility by constructing an intramembrane hydrogen bond network; MXene@GA strengthens the mechanical strength, ultraviolet shielding and hydrophobicity of the film with its nano-reinforcing effect, while the antioxidant and antibacterial properties of gallic acid (GA) give the film material additional functional gains; the three synergistically make up for the defects of insufficient intrinsic mechanical strength, weak antibacterial and antioxidant properties and poor moisture resistance of KGM, and significantly improve the overall performance of the film.

[0017] (2) The natural eutectic solvent-reinforced konjac glucomannan film provided by the present invention can be used for cold chain packaging of high-value fresh food. Its good mechanical properties can withstand the stress in cold chain transportation, and its excellent antioxidant and antibacterial properties can inhibit food oxidation and deterioration and microbial growth. At the same time, its good hydrophobicity can reduce water penetration, providing more effective quality protection for high-value fresh food, expanding the application scenarios of natural polysaccharide-based materials in the field of high-performance packaging, and combining environmental protection and functional practicality, effectively making up for the performance shortcomings of traditional KGM-based materials in practical applications. Attached Figure Description

[0018] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation thereof. Obviously, those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0019] Figure 1 These are the UV measurement results of konjac glucomannan films from Examples 2, 6-9, and Comparative Example 1 of this invention; Figure 2 These are the UV measurement results of konjac glucomannan films from Examples 12, 15-18, and Comparative Example 1 of this invention; Figure 3 These are the UV measurement results of konjac glucomannan films from Examples 22, 24-27, and Comparative Example 1 of this invention; Figure 4 These are the antioxidant results of the konjac glucomannan films in Examples 6, 16, 27 and Comparative Example 1 of the present invention; Figure 5 These are the antibacterial results of the konjac glucomannan films of Examples 6, 16, 27 and Comparative Example 1 of the present invention; A represents the antibacterial effect against Escherichia coli (E. coli). E. coli Staphylococcus aureus ( S. aureus The antibacterial results of ) are shown, B is the antibacterial effect against yeast ( Yeast Candida albicans ( C. albicans The antibacterial results; Figure 6 These are the results of room temperature preservation of konjac glucomannan films, PE films, Parafilms, and control groups stored for different number of days in Examples 6, 16, 27, and Comparative Example 1 of the present invention. Wherein, a is the weight loss rate, b is the hardness value, c is the soluble solids (TSS) level, and d is a photograph of the actual product. Figure 7 These are the results of refrigeration preservation of konjac glucomannan films, PE films, Parafilms, and control groups stored for different numbers of days in Examples 6, 16, 27, and Comparative Example 1 of this invention. In the figures, a is the weight loss rate, b is the hardness value, c is the soluble solids (TSS) level, and d is a photograph of the actual product. Detailed Implementation

[0020] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] This invention provides a konjac glucomannan film reinforced with a natural eutectic solvent, comprising konjac glucomannan, a natural eutectic solvent, and gallic acid-modified MXene nanoparticles; the mass ratio of konjac glucomannan, natural eutectic solvent, and gallic acid-modified MXene nanoparticles is (850~950):(50~250):(10~40).

[0022] While konjac glucomannan (KGM), a natural polysaccharide, possesses biocompatibility and film-forming properties, its insufficient mechanical strength, weak antibacterial and antioxidant properties, and poor moisture resistance limit its application in high-performance food preservation materials. To overcome this limitation, this invention innovatively introduces gallic acid-modified MXene nanoparticles (MXene@GA) and a natural eutectic solvent (NADES) to form a ternary composite system. MXene, as a two-dimensional transition metal carbide / nitride material, inherently possesses excellent mechanical strengthening potential, but its surface active sites are limited and it is prone to aggregation and sedimentation. After modification with the natural polyphenolic substance gallic acid (GA), MXene@GA not only exhibits significantly improved dispersion stability, but the antioxidant and antibacterial properties of GA itself also provide additional functional gains to the membrane material. NADES, as a green solvent system formed by the self-assembly of natural small molecules through hydrogen bonds, can not only construct a stable hydrogen bond network within the membrane material to improve the flexibility of KGM, but its antibacterial and antioxidant active ingredients can also synergistically enhance the protective effect on food quality. The synergistic effect of these three components is manifested in the following ways: NADES, as a green plasticizer and interface regulator, enhances flexibility and optimizes interfacial compatibility by regulating the intramembrane hydrogen bond network; MXene@GA strengthens the membrane's barrier function (such as mechanical strength, UV shielding, and hydrophobicity) through its nano-reinforcing effect, while simultaneously releasing the bioactivity of GA; and KGM, as the matrix material, provides the basic structural support for the entire system through its film-forming properties. This ternary composite strategy not only compensates for the shortcomings of KGM's intrinsic properties but also achieves an overall improvement in the membrane's mechanical properties, moisture resistance, antibacterial properties, and antioxidant properties through the synergistic effect of functional fillers and green additives. This provides a novel sustainable material design solution for high-value fresh food cold chain packaging that combines environmental friendliness with functional expansion potential, effectively solving the problem that traditional KGM-based materials cannot meet the needs of practical applications.

[0023] In this invention, the natural eutectic solvent comprises hydrogen bond donors and hydrogen bond acceptors. The hydrogen bond donors are selected from one or both of citric acid and caffeic acid, and the hydrogen bond acceptors are selected from one or more of glycine, L-carnitine, or aminosulfonic acid. The molecular structures of these substances contain abundant polar functional groups, which can self-assemble into eutectic solvents through intermolecular hydrogen bonding. This NADES, composed of natural small molecules, not only possesses low melting point and high solubility but also exhibits biocompatibility. Its internal hydrogen bond network can interact with the hydroxyl and carboxyl groups of konjac glucomannan (KGM) molecules, thereby improving the flexibility and interfacial compatibility of the KGM membrane. Simultaneously, the antioxidant (e.g., the phenolic hydroxyl groups of caffeic acid) and antibacterial (e.g., the acidic environment of citric acid inhibiting microorganisms) components contained in the hydrogen bond acceptors and hydrogen bond donors synergistically enhance the protective function of the film for food quality.

[0024] Furthermore, the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:(1~3). This molar ratio directly affects the strength and physicochemical properties of the NADES hydrogen bond network. If the donor ratio is too high, it may lead to excessive solvent acidity or increased viscosity, affecting compatibility with KGM; if the acceptor ratio is too high, it may weaken the stability of the hydrogen bond network and reduce the plasticizing effect. The hydrogen bond donors are citric acid and caffeic acid, with a molar ratio of citric acid to caffeic acid of 1:(0.5~2). The strong acidity of citric acid enhances antibacterial properties, while the phenolic hydroxyl groups of caffeic acid improve antioxidant properties. A specific mixture of the two can balance antibacterial and antioxidant properties.

[0025] In this invention, the mass ratio of gallic acid to MXene nanoparticles modified with gallic acid is (1~2):1. MXene, as a two-dimensional nanomaterial, contains active sites such as hydroxyl (-OH) and amino (-NH2) groups on its surface. However, unmodified MXene is prone to agglomeration due to van der Waals forces, resulting in poor dispersibility. After activation by the carboxyl group, GA can covalently bind to the active sites on the MXene surface, thereby forming a "steric hindrance layer" on the MXene surface and inhibiting agglomeration. The appropriate mass ratio of the two ensures that MXene is sufficiently modified to improve dispersion stability, while also endowing the membrane material with additional antioxidant and antibacterial functions through the phenolic hydroxyl groups of GA, achieving structural enhancement and functional synergy.

[0026] This invention also provides a method for preparing the above-mentioned konjac glucomannan film reinforced by a natural eutectic solvent, comprising the following steps: Preparation of gallic acid-modified MXene nanoparticles; Gallic acid-modified MXene nanoparticles were added to a mixture of konjac glucomannan aqueous solution and natural eutectic solvent, stirred and dispersed, and then a konjac glucomannan film reinforced with natural eutectic solvent was prepared by casting method.

[0027] In this invention, the stirring speed for dispersion is 500-1200 rpm, and the stirring time is 10-40 min. A higher stirring speed is beneficial for uniformly dispersing MXene@GA nanoparticles in the KGM-NADES mixed solution.

[0028] The preparation method of the gallic acid-modified MXene nanoparticles in this invention is as follows: Gallic acid was activated by carboxylation and then mixed with MXene dispersion. The mixture was stirred, centrifuged, and dried to obtain the final product.

[0029] Further, the step of activating the carboxyl group of gallic acid is as follows: gallic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC), and N-hydroxysuccinimide (NHS) are mixed and stirred in an aqueous ethanol solution for 0.5-3 hours. This invention does not impose any particular limitation on the concentration of the aqueous ethanol solution; any concentration between 10% and 70% is acceptable, such as 10%, 20%, 30%, 40%, 50%, etc., where "%" refers to volume fraction. The carboxyl group (-COOH) in the GA molecule has low reactivity, and its direct reaction efficiency with the -OH or -NH2 groups on the MXene surface is limited. EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride), as a carbodiimide reagent, can react with the carboxyl group of GA to generate an O-acylisourea intermediate. This intermediate is unstable and easily hydrolyzed and degraded. NHS (N-hydroxysuccinimide) can react with O-acylisourea to generate a more stable N-hydroxysuccinimide ester (active ester), which significantly improves the reaction efficiency of GA with the active sites on the MXene surface, making GA more firmly bound to the MXene surface, thereby enhancing the dispersion stability and functional persistence of MXene@GA.

[0030] The present invention does not impose any special restrictions on the concentration and solvent of the MXene dispersion. The preferred concentration of the present invention is 5~20g / L; the preferred solvent of the present invention is an aqueous ethanol solution, and the preferred concentration of the aqueous ethanol solution is 10~70%.

[0031] The present invention does not impose any special limitations on the specific processes of stirring, centrifugation and drying described above; commonly used stirring, centrifugation and drying steps in the art can be used.

[0032] In this invention, the concentration of the konjac glucomannan aqueous solution is 0.5~2wt%. This concentration ensures that the film formed after casting has a suitable thickness and mechanical strength, while also ensuring that the solution has good fluidity, thereby producing a film with uniform thickness and excellent mechanical properties.

[0033] This invention does not impose any special restrictions on the preparation process of natural eutectic solvents; commonly used methods for preparing eutectic solvents in the field can be used.

[0034] This invention does not impose any special limitations on the specific process of the casting method; any casting method commonly used in the art can be used to prepare the film. For example, the mixed solution can be poured into a petri dish and dried at 40-70°C to obtain the film.

[0035] The present invention also provides the application of the above-mentioned natural eutectic solvent-reinforced konjac glucomannan film or the natural eutectic solvent-reinforced konjac glucomannan film prepared by the above preparation method in food preservation.

[0036] The konjac glucomannan film reinforced with natural eutectic solvent provided by this invention has good mechanical properties and can withstand the extrusion and impact stress during cold chain transportation. The two-dimensional sheet structure of MXene can physically block oxygen, water vapor and ultraviolet rays, thereby reducing food oxidation and light-induced deterioration. The caffeic acid, citric acid and other components in GA and NADES directly inhibit the oxidative deterioration and microbial growth of food by releasing antioxidants and antibacterial substances. The hydrogen bond network constructed by NADES and the hydrophobicity of MXene synergistically improve the moisture resistance of the film and reduce the impact of moisture penetration on food quality.

[0037] The technical solution of the present invention will be further described below with reference to specific embodiments. The present invention does not impose any special restrictions on the source of reagents used in the following embodiments; commercially available products well known to those skilled in the art can be used.

[0038] In the following examples, the MXene@GA nanoparticles were prepared as follows: 0.50 g GA, 0.58 g EDC, and 0.340 g NHS were mixed and added to 20 mL of 30% ethanol solution. The mixture was stirred in an ice bath for 1 hour, followed by the addition of MXene dispersion (0.32 g MXene dissolved in 30 mL of 30% ethanol). The resulting mixture was stirred in an ice bath for 0.5 hours, followed by stirring at room temperature for 8 hours. The mixture was then centrifuged at 123,000 rpm for 10 minutes. Finally, the product was collected and freeze-dried to obtain MXene@GA nanoparticles. A 10 mg / mL MXene@GA nanoparticle dispersion was prepared by dispersing the MXene@GA nanoparticles in deionized water.

[0039] Example 1 This embodiment provides a method for preparing a konjac glucomannan film reinforced with a natural eutectic solvent.

[0040] (1) Preparation of NADES: Glycine, citric acid and caffeic acid were mixed in a molar ratio of 1:1:0.5, and then ultrapure water with a volume ratio of 1:1 to NADES was added to improve the fluidity of NADES. The mixture was stirred at 120°C for 1 h to obtain a mixture of NADES and water. (2) Thin film preparation: KGM was dissolved in deionized water and stirred at 50°C for 1 h to prepare a 1 wt% KGM aqueous solution. 0.1 g of the NADES and water mixture from step (1) was added to 90 mL of the KGM aqueous solution, and the mixture was vigorously stirred at 1000 rpm for 20 minutes to achieve uniform dispersion, thus obtaining a film-forming solution. The film-forming solution was poured into a petri dish (9 cm in diameter) and dried at 50°C for 6 h to obtain a konjac glucomannan film reinforced with a natural eutectic solvent, denoted as KG(1:1:0.5)-0.1.

[0041] Example 2 The difference between this embodiment and Example 1 is that the molar ratio of glycine, citric acid, and caffeic acid is 2:1:1. The final konjac glucomannan film reinforced with a natural eutectic solvent is denoted as KG(2:1:1)-0.1.

[0042] Example 3 The difference between this embodiment and Example 1 is that the molar ratio of glycine, citric acid, and caffeic acid is 1:2:1. The resulting konjac glucomannan film reinforced with a natural eutectic solvent is denoted as KG(1:2:1)-0.1.

[0043] Example 4 The difference between this embodiment and Embodiment 2 is that the amount of NADES and water mixture added in step (1) is 0.3g. The final natural eutectic solvent-reinforced konjac glucomannan film is denoted as KG(2:1:1)-0.3.

[0044] Example 5 The difference between this embodiment and Embodiment 2 is that the amount of NADES and water mixture added in step (1) is 0.5g. The final natural eutectic solvent-reinforced konjac glucomannan film is denoted as KG(2:1:1)-0.5.

[0045] Example 6 The difference between this embodiment and Example 2 is that 1 mL of MXene@GA nanoparticle dispersion (10 mg / mL) was added to 90 mL of KGM aqueous solution. The resulting konjac glucomannan film reinforced with a natural eutectic solvent is denoted as KG(2:1:1)-0.1-1.

[0046] Example 7 The difference between this embodiment and Example 6 is that the 10 mg / mL MXene@GA nanoparticle dispersion is 2 mL. The final konjac glucomannan film reinforced with a natural eutectic solvent is denoted as KG(2:1:1)-0.1-2.

[0047] Example 8 The difference between this embodiment and Example 6 is that the amount of MXene@GA nanoparticle dispersion added is 3 mL (10 mg / mL). The final konjac glucomannan film reinforced with natural eutectic solvent is denoted as KG(2:1:1)-0.1-3.

[0048] Example 9 The difference between this embodiment and Example 6 is that the amount of MXene@GA nanoparticle dispersion added is 4 mL (10 mg / mL). The final konjac glucomannan film reinforced with natural eutectic solvent is denoted as KG(2:1:1)-0.1-4.

[0049] Example 10 The difference between this embodiment and Example 1 is that L-carnitine is used instead of glycine. The resulting konjac glucomannan film reinforced with a natural eutectic solvent is denoted as KC(1:1:0.5)-0.1.

[0050] Example 11 The difference between this embodiment and Example 10 is that the molar ratio of L-carnitine, citric acid, and caffeic acid is 2:1:1. The resulting konjac glucomannan film reinforced with a natural eutectic solvent is denoted as KC(2:1:1)-0.1.

[0051] Example 12 The difference between this embodiment and Example 10 is that the molar ratio of L-carnitine, citric acid, and caffeic acid is 1:2:1. The resulting konjac glucomannan film reinforced with a natural eutectic solvent is denoted as KC(1:2:1)-0.1.

[0052] Example 13 The difference between this embodiment and Embodiment 12 is that the amount of NADES and water mixture added in step (1) is 0.3g. The final natural eutectic solvent-reinforced konjac glucomannan film is denoted as KC(1:2:1)-0.3.

[0053] Example 14 The difference between this embodiment and Embodiment 12 is that the amount of NADES and water mixture added in step (1) is 0.5g. The final natural eutectic solvent-reinforced konjac glucomannan film is denoted as KC(1:2:1)-0.5.

[0054] Example 15 The difference between this embodiment and Example 12 is that 1 mL of MXene@GA nanoparticle dispersion (10 mg / mL) was added to 90 mL of KGM aqueous solution. The resulting konjac glucomannan film reinforced with a natural eutectic solvent is denoted as KC(1:2:1)-0.1-1.

[0055] Example 16 The difference between this embodiment and Example 15 is that the amount of MXene@GA nanoparticle dispersion added is 2 mL instead of 10 mg / mL. The final konjac glucomannan film reinforced with natural eutectic solvent is denoted as KC(1:2:1)-0.1-2.

[0056] Example 17 The difference between this embodiment and Example 15 is that the amount of MXene@GA nanoparticle dispersion added is 3 mL (10 mg / mL). The final konjac glucomannan film reinforced with natural eutectic solvent is denoted as KC(1:2:1)-0.1-3.

[0057] Example 18 The difference between this embodiment and Example 15 is that the amount of MXene@GA nanoparticle dispersion added is 4 mL (10 mg / mL). The final konjac glucomannan film reinforced with natural eutectic solvent is denoted as KC(1:2:1)-0.1-4.

[0058] Example 19 The difference between this embodiment and Example 1 is that glycine is replaced with aminosulfonic acid. The resulting konjac glucomannan film reinforced with a natural eutectic solvent is denoted as KS(1:1:0.5)-0.1.

[0059] Example 20 The difference between this embodiment and Example 19 is that the molar ratio of aminosulfonic acid, citric acid, and caffeic acid is 2:1:1. The resulting konjac glucomannan film reinforced with a natural eutectic solvent is denoted as KS(2:1:1)-0.1.

[0060] Example 21 The difference between this embodiment and Example 19 is that the molar ratio of aminosulfonic acid, citric acid, and caffeic acid is 1:2:1. The resulting konjac glucomannan film reinforced with a natural eutectic solvent is denoted as KS(1:2:1)-0.1.

[0061] Example 22 The difference between this embodiment and Example 20 is that the amount of NADES and water mixture added in step (1) is 0.3g. The final natural eutectic solvent-reinforced konjac glucomannan film is denoted as KS(2:1:1)-0.3.

[0062] Example 23 The difference between this embodiment and embodiment 20 is that the amount of NADES and water mixture added in step (1) is 0.5g. The final natural eutectic solvent-reinforced konjac glucomannan film is denoted as KS(2:1:1)-0.5.

[0063] Example 24 The difference between this embodiment and Example 22 is that 1 mL of MXene@GA nanoparticle dispersion (10 mg / mL) was added to 90 mL of KGM aqueous solution. The resulting konjac glucomannan film reinforced with a natural eutectic solvent is denoted as KS(2:1:1)-0.3-1.

[0064] Example 25 The difference between this embodiment and Example 23 is that the amount of MXene@GA nanoparticle dispersion added is 2 mL instead of 10 mg / mL. The final konjac glucomannan film reinforced with natural eutectic solvent is denoted as KS(2:1:1)-0.3-2.

[0065] Example 26 The difference between this embodiment and Example 23 is that the amount of MXene@GA nanoparticle dispersion added is 3 mL (10 mg / mL). The final konjac glucomannan film reinforced with natural eutectic solvent is denoted as KS(2:1:1)-0.3-3.

[0066] Example 27 The difference between this embodiment and embodiment 23 is that the amount of NADES and water mixture added in step (1) is 4 mL. The final natural eutectic solvent-reinforced konjac glucomannan film is denoted as KS(2:1:1)-0.3-4.

[0067] Comparative Example 1 The difference between this comparative example and Example 1 is that this comparative example does not contain NADES and MXene@GA nanoparticles. The specific preparation method is as follows: KGM was dissolved in deionized water and stirred at 50°C for 1 h to prepare a 1 wt% KGM aqueous solution. The KGM aqueous solution was then poured into a petri dish (9 cm in diameter) and dried at 50°C for 6 h to obtain a konjac glucomannan film, denoted as KGM.

[0068] Test case 1. Tensile property testing Tensile properties were tested on the films of Examples 1-27 and Comparative Example 1, and the test results are summarized in Table 1.

[0069] Table 1. Tensile property test results of the films of Examples 1-27 and Comparative Example 1

[0070] As can be seen from Table 1, the tensile strength of the konjac glucomannan films reinforced with natural eutectic solvents in the examples is generally higher than that of the KGM films. In the examples where glycine, L-carnitine, and sulfamic acid are used as hydrogen bond acceptors and MXene@GA nanoparticles are added, the konjac glucomannan films reinforced with natural eutectic solvents in Examples 6 (KG(2:1:1)-0.1-1), 16 (KC(1:2:1)-0.1-2), and 27 (KS(2:1:1)-0.3-4) exhibit the highest tensile strength and elongation at break exceeding 50%, demonstrating excellent mechanical properties.

[0071] 2. Ultraviolet Measurement The konjac glucomannan films reinforced with natural eutectic solvents in Examples 2, 6-9, 12, 15-18, 22, and 24-27, as well as the konjac glucomannan film in Comparative Example 1, were subjected to UV-Vis measurements. The test results... Figure 1 , Figure 2 and Figure 3 As shown in the figure, the film of the embodiment has a stronger UV resistance compared to the konjac glucomannan film of Comparative Example 1.

[0072] 3. Antioxidant effect The antioxidant capacity of the natural eutectic solvent-reinforced konjac glucomannan films of Examples 6 (KG(2:1:1)-0.1-1, KG), 16 (KC(1:2:1)-0.1-2, KC), and 27 (KS(2:1:1)-0.3-4, KS), as well as the konjac glucomannan film (KGM) of Comparative Example 1, was evaluated by DPPH and ABTS free radical scavenging rate tests. The test results are as follows: Figure 4 As shown, the antioxidant capacity of the film was significantly improved after adding NADES and MXene@GA nanoparticles.

[0073] 4. Antibacterial effect The antibacterial rates of the konjac glucomannan films reinforced with natural eutectic solvents in Examples 6 (KG(2:1:1)-0.1-1, KG), 16 (KC(1:2:1)-0.1-2, KC), and 27 (KS(2:1:1)-0.3-4, KS) and the konjac glucomannan film (KGM) in Comparative Example 1 were tested using the plate count method. The antibacterial rates of the materials against bacteria (Escherichia coli) were determined using microbial growth curves. E. coli Staphylococcus aureus S. aureus ) and fungi (yeast) Yeast Candida albicans C. albicans The antibacterial effect of ) was tested, and the results are as follows: Figure 5As shown in the figure, the antibacterial ability of the film was significantly improved after adding NADES and MXene@GA nanoparticles.

[0074] 5. Preservation effect Given that the konjac glucomannan films reinforced with natural eutectic solvents of Examples 6 (KG(2:1:1)-0.1-1, KG), 16 (KC(1:2:1)-0.1-2, KC), and 27 (KS(2:1:1)-0.3-4, KS) possess antibacterial, antioxidant, and good mechanical properties, their potential for extending the shelf life of raspberries was further evaluated. Raspberries were placed in disposable storage boxes, and the nanocomposite film was sealed with tape to ensure direct contact between the film and the fruit. Subsequently, the raspberries were stored at room temperature (RT) and 4°C for 15 days, and their appearance and quality were continuously monitored. The results were compared with those of the control group (no film), the polyethylene (PE) film treatment group, and the Parafilm film treatment group. Figure 6 and Figure 7 As shown.

[0075] Multiple factors, including respiration, transpiration, oxidation, and microbial activity, contribute to the deterioration of raspberry quality during storage, significantly reducing its commercial value. Weight fluctuations in raspberries during storage are negatively correlated with storage time. Notably, KG, KC, and KS nanocomposite films exhibit strong antibacterial activity, effectively inhibiting microbial growth. After 15 days of storage, the weight loss rate of raspberries packaged with KC and KS nanocomposite films was significantly lower than that of the control and KGM groups: reduced by 33.84% and 30.35% respectively at room temperature, and by 3.21% and 3.13% respectively at 4℃; in contrast, the weight loss rates of the control groups were 51.08% and 42.11% at room temperature, and 8.73% and 5.89% respectively at 4℃.

[0076] Furthermore, the KC and KS nanocomposite films effectively limited water migration, thereby reducing nutrient loss during storage. These films also played a role in maintaining fruit firmness (an important indicator of freshness). The KG, KC, and KS films acted as a protective barrier, slowing the softening process of raspberries and helping to maintain their structural integrity. After 4 days of storage at room temperature, the firmness values ​​of the control and KGM groups of raspberries dropped sharply from 0.69 N and 0.68 N to 0.31 N and 0.29 N, respectively. In contrast, after 9 and 12 days of storage under refrigeration (4°C), the firmness values ​​of the samples coated with the nanocomposite films (0.35 N, 0.38 N, and 0.32 N) remained significantly higher than those of the control and KGM groups (0.17 N and 0.18 N), confirming their superior ability to maintain fruit quality.

[0077] Soluble solids (TSS) and pH are key indicators reflecting fruit flavor and ripeness. During storage, raspberries utilize soluble sugars and other nutrients to maintain metabolic activity, leading to a gradual decrease in TSS levels. After 12 days of storage at room temperature, a significant decrease in TSS was observed (KG: 6.0%, KC: 4.47%, KS: 7.03%). Similarly, after 12 days of storage under refrigeration (4°C), a significant decrease in TSS was also observed (KG: 8.8%, KC: 8.7%, KS: 8.5%). Despite these changes, the experimental film effectively reduced the respiration rate of raspberries under both storage conditions. Microbial growth was observed on control group raspberries after only 4 days at room temperature. However, at the end of the storage period at 4°C, no significant microbial growth was observed in any of the seven raspberry samples. After 9 days of storage at room temperature, control group raspberries were completely covered by microbial colonies, while the KG and KS groups maintained a higher proportion of intact fruit and had better visual quality. Even after being stored at 4°C for 9 days, the raspberry pulp in the experimental group remained in good condition, highlighting the important role of KG, KC and KS nanocomposite films in extending shelf life and maintaining fruit quality through their comprehensive antibacterial, antioxidant and gas regulation effects.

[0078] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A konjac glucomannan film reinforced with a natural eutectic solvent, characterized in that, The product comprises MXene nanoparticles modified with konjac glucomannan, a natural eutectic solvent, and gallic acid; the mass ratio of konjac glucomannan, a natural eutectic solvent, and gallic acid-modified MXene nanoparticles is (850~950):(50~250):(10~40).

2. The konjac glucomannan film reinforced with a natural eutectic solvent as described in claim 1, characterized in that, The natural eutectic solvent includes a hydrogen bond donor and a hydrogen bond acceptor, wherein the hydrogen bond donor is selected from one or both of citric acid or caffeic acid, and the hydrogen bond acceptor is selected from one or more of glycine, L-carnitine, or aminosulfonic acid.

3. The konjac glucomannan film reinforced with a natural eutectic solvent as described in claim 2, characterized in that, The molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:(1~3); the hydrogen bond donor is citric acid and caffeic acid, and the molar ratio of citric acid to caffeic acid is 1:(0.5~2).

4. The konjac glucomannan film reinforced with a natural eutectic solvent as described in claim 1, characterized in that, In the gallic acid-modified MXene nanoparticles, the mass ratio of gallic acid to MXene is (1~2):

1.

5. The method for preparing the konjac glucomannan film reinforced with a natural eutectic solvent as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Preparation of gallic acid-modified MXene nanoparticles; Gallic acid-modified MXene nanoparticles were added to a mixture of konjac glucomannan aqueous solution and natural eutectic solvent, stirred and dispersed, and then a konjac glucomannan film reinforced with natural eutectic solvent was prepared by casting method.

6. The preparation method according to claim 5, characterized in that, The stirring speed for the dispersion is 500~1200 rpm, and the stirring time is 10~40 min.

7. The preparation method according to claim 5, characterized in that, The preparation method of the gallic acid-modified MXene nanoparticles is as follows: Gallic acid was activated by carboxylation and then mixed with MXene dispersion. The mixture was stirred, centrifuged, and dried to obtain the final product.

8. The preparation method according to claim 7, characterized in that, The steps for carboxyl activation of gallic acid are as follows: gallic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide are mixed and stirred in an aqueous ethanol solution for 0.5-3 hours.

9. The preparation method according to claim 5, characterized in that, The concentration of the konjac glucomannan aqueous solution is 0.5~2wt%.

10. The application of the konjac glucomannan film reinforced with natural eutectic solvent as described in any one of claims 1 to 4, or the konjac glucomannan film reinforced with natural eutectic solvent prepared by the preparation method described in any one of claims 5 to 9, in food preservation.

Images