A composite aerogel particle fruit wax and its preparation method and application

Abstract

The present invention discloses a composite aerogel particle fruit wax and a preparation method and application thereof. The composite aerogel particle fruit wax is obtained by adding cellulose aerogel particles to a Brazilian palm-based fruit wax coating material and mixing them evenly. The cellulose aerogel particles are cellulose aerogel particles with a nanoscale pore structure. The composite aerogel particle fruit wax prepared by this method is used as a fruit and vegetable preservation coating material. The composite aerogel particle fruit wax prepared by the method of the present invention improves the permeability of oxygen and carbon dioxide by introducing nanoscale pores. Compared with traditional fruit wax, it improves the situation where fruits produce odor due to anaerobic respiration. At the same time, the gray mold barrier ability of traditional coatings is retained. The method of forming pores in situ of the invention avoids the process of secondary drilling and has a wide range of practical scenarios.

Description

Technical Field

[0001] The present invention belongs to the technical field of fruit and vegetable preservation, and particularly relates to a composite aerogel particle fruit wax and a preparation method and application thereof. Background Art

[0002] Fruits and vegetables are susceptible to spoilage during harvest and storage due to factors such as temperature, humidity, and microorganisms. Therefore, the preservation of fruits and vegetables is very important. Existing fruit wax treatment technology is an important preservation method for post-harvest fruit storage. However, the high gas barrier properties of fruit wax (carbon dioxide, oxygen permeability of about 8.6×10 -14 kg·m -1 ·s -1 ·Pa -1 , 8.3×10 -15 kg·m -1 ·s -1 ·Pa -1 ) leads to intensified anaerobic respiration of the fruit, producing acetaldehyde, ethanol and other odor components, which destroy the original flavor of the fruit; the existing storage of fruits and vegetables is carried out by increasing the air permeability of the packaging. This method mainly introduces a microporous array. However, this method can only process micropores on pre-prepared films and is not suitable for fruit wax that is directly formed in situ on the surface of the fruit. Moreover, the existing high-permeability packaging with a microporous array (pore size 8-30μm) provides a channel for the fruit to contact the external environment, which has the risk of microbial infection.

[0003] The currently disclosed technologies for preserving fruits and vegetables mainly include: 1) An edible fresh-fruit coating preservative, its preparation method, and application, CN112535207A. This invention provides an edible fresh-fruit coating preservative, its preparation method, and application. Candelilla wax, carnauba wax, and peanut oil are used as the main materials, supplemented with oleic acid, lauric acid, ammonia, and water, and an edible fruit wax coating is prepared by a hot emulsification method. This coating has the functions of maintaining the fruit's appearance, moisture retention, and freshness. However, this invention uses a large amount of wax material, and the dense wax coating can cause clogging of the fruit's stomata, resulting in increased anaerobic respiration and accumulation of odorous components. 2) A special fresh-keeping breathing film for fruits and vegetables and its preparation method, CN114854075A. This invention uses polypropylene, metallocene polypropylene, and high-melt-strength polypropylene as the main raw materials. After blow molding and drying, it is combined with a coating process to form an anti-fog and antibacterial film. To improve gas permeability, laser drilling is required on the surface of the anti-fog and antibacterial film. The additional punching step adds an extra process to the preparation of cling film, which increases the difficulty of operation and cannot be transferred to the application of fresh-keeping coating. In addition, the microporous array provides a channel for microbial infection, increasing the risk of microbial infection. 3) A breathable cling film with a nano-pectin coating, CN114097873A. The invention discloses a multi-layer breathable cling film with a nano-pectin coating, which is sequentially provided with a base film, a nano-bubble coating, a sterilization coating, and an adsorption coating. The layers work synergistically. In the fresh-keeping application, nano-bubbles are used for gas conditioning, and titanium dioxide is used for sterilization and gas regulation to extend the shelf life of fruits and vegetables. Although the invention provides a breathable and antibacterial cling film solution, it is an inedible multi-layer film and its preparation process is complicated. Titanium dioxide is used as an antibacterial substance. This raw material is harmful to consumption and brings potential food safety risks. 4) A traditional Chinese medicine fresh-keeping fruit wax, CN101836673A. This invention uses shellac, water, and maleic rosin-modified resin as its primary raw materials. It specifically incorporates bactericidal Chinese herbal extracts to enhance the bactericidal effect of the fruit wax. The extracts, which include aqueous extracts of honeysuckle, Magnolia officinalis, Scutellaria baicalensis, and Forsythia suspensa, exhibit excellent preservation. While these extracts offer a good bactericidal effect, they are chemically antimicrobial and come with an unusual flavor derived from the herbs, potentially reducing consumer acceptance. 5) ACS Nano, 2021, 15, 8742-8752, reported using chitosan and polylactic acid to create hollow microspheres via a phase separation process, with gas permeability provided by the addition of a shellac membrane. While this phase separation process was employed to prepare porous microspheres, the resulting porous microspheres exhibited a limited particle size (median diameter of 38 μm). Furthermore, the porous microspheres prepared in this paper had a relatively low pore size (average pore size of 3.6 nm), which is close to the diameter of gas molecules (approximately 0.3 nm), resulting in fewer gas exchange channels.To address these deficiencies, the present invention employs a double emulsification method to adjust the particle size distribution, and a swelling method to adjust the polymer network distribution in the gel state, thereby adjusting the pore size of the aerogel particles. Furthermore, tetrahydrofuran, a processing aid used herein, has clear physiological toxicity and is unsuitable for the production and processing of edible packaging. However, the reagents used in the aerogel processing of the present invention are highly biocompatible and suitable for the production of edible packaging. Furthermore, this prior art method fails to characterize the anaerobic respiration index used in fresh-keeping applications and fails to accurately demonstrate the improvement effect of the proposed solution on anaerobic respiration in fruit. Summary of the Invention

[0004] In view of the problems existing in the prior art, the purpose of the present invention is to provide a composite aerogel particle fruit wax and a preparation method and application technical solution thereof.

[0005] The present invention is specifically implemented by the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a composite aerogel particle fruit wax. The composite aerogel particle fruit wax is obtained by adding cellulose aerogel particles having a nanoscale pore structure to a carnauba-based fruit wax coating material and mixing them uniformly. The cellulose aerogel particles are cellulose aerogel particles having a nanoscale pore structure. By adding the cellulose aerogel particles to the waxy coating, a gas-permeable microporous structure is introduced, thereby increasing the permeability. This method achieves a one-step process, allowing the in-situ formation of permeable pores in the coating.

[0007] Furthermore, the added amount of the cellulose aerogel particles is 0.1-1.00 wt% of the total mass of the carnauba-based fruit wax coating material.

[0008] Furthermore, the cellulose aerogel particles are obtained by the following steps:

[0009] 1) Swelling the microcrystalline cellulose and then dissolving it;

[0010] 2) mixing the solution from step 1) with liquid paraffin and homogenizing;

[0011] 3) taking another liquid paraffin, performing emulsification treatment, and then mixing it with the product obtained in step 2) and performing a second emulsification treatment;

[0012] 4) separating the emulsified product obtained in step 3);

[0013] 5) The separated product obtained in step 4) is sequentially subjected to washing treatment, swelling treatment, freezing and freeze-drying treatment to obtain cellulose aerogel particles.

[0014] The preparation of the cellulose aerogel particles includes a gel constant temperature swelling step before the solvent removal step in the cellulose aerogel particle preparation process, thereby obtaining a higher pore diameter.

[0015] The cellulose aerogel particles produced by this method have pores smaller than the size of microorganisms, ensuring air permeability while physically isolating them from microbial infection. This method does not require the addition of antimicrobial ingredients, thus avoiding the problems of unpleasant flavors and food hazards caused by antimicrobial substances.

[0016] Furthermore, in step 1), the microcrystalline cellulose is swollen in water at 4° C. for 24 hours and then dissolved in a solution containing 6-10 wt % NaOH and 8-12% urea at -3° C.

[0017] Furthermore, in step 2), the solution obtained in step 1) is mixed with liquid paraffin in a volume ratio of 1:10, and homogenized at 1000 rpm for 10 minutes.

[0018] Furthermore, in step 3), liquid paraffin was added with 0.5 vol% Tween 80 and 8 M acetic acid, and the mixture was emulsified for the first time using a homogenizer at 1000 rpm; after the first emulsification for 10 minutes, the mixture was mixed with the product obtained in step 2), and the mixture was emulsified for the second time using a mechanical stirring paddle at 900 rpm for 2 hours.

[0019] Furthermore, in the step 4), a 1:1 ethanol-water solution is added to the emulsified product obtained in the step 3) to separate the product.

[0020] Furthermore, in step 5), the separated product obtained in step 4) is washed with deionized water for 6 times, swelled in deionized water at a constant temperature of 25° C. for 24-108 hours, frozen with liquid nitrogen, and freeze-dried for 48 hours to obtain cellulose aerogel particles.

[0021] The second aspect of the present invention provides a composite aerogel particle fruit wax prepared by any of the above preparation methods.

[0022] The third aspect of the present invention provides the use of the composite aerogel particle fruit wax in preserving fruits and vegetables.

[0023] The fourth aspect of the present invention provides the use of the composite aerogel particle fruit wax in blocking gray mold.

[0024] Furthermore, the specific application method is to completely immerse the fruit and vegetable products in the composite aerogel particle fruit wax, take them out and dry them at room temperature, specifically, immerse them for 30 seconds and dry them for 15 minutes.

[0025] The cellulose aerogel particles prepared by the present invention have a median particle size of 106.04 μm, a porous structure, and a specific surface area of 19.50 cm 2 / g, with an average pore diameter of 19.76nm. The carbon dioxide permeability of the composite fruit wax embedded with cellulose aerogel particles increased by 2.31 times, and the oxygen permeability increased by 2.47 times, without significantly affecting the original mechanical properties of the fruit wax. Before embedding the cellulose aerogel particles, the fracture strength of the fruit wax coating was 2.31±0.21MPa, and the elongation at break was 1.46±0.19%. After embedding the cellulose aerogel particles, the fracture strength of the composite fruit wax was 1.53±0.37MPa, and the elongation at break was 0.99±0.15%.

[0026] The composite aerogel microparticle fruit wax prepared by the inventive method can maintain barrier properties against gray mold, that is, the composite fruit wax after adding cellulose aerogel microspheres still has the gray mold barrier properties similar to traditional fruit wax coatings, and can also directly form air holes in situ on the fruit surface, avoiding the secondary punching process, and has a wide range of practical scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The particle size distribution of the cellulose aerogel particles prepared in the present invention;

[0028] Figure 2 is the nitrogen adsorption curve of the cellulose aerogel particles prepared in the present invention;

[0029] Figure 3 The pore distribution of the cellulose aerogel particles prepared in the present invention;

[0030] Figure 4 This is a scanning electron microscope image of the cellulose aerogel particles prepared in the present invention;

[0031] Figure 5 Scanning electron microscope images of cellulose aerogel particles prepared in Examples 1, 5, and 6 of the present invention;

[0032] Figure 6 are cross-sectional scanning electron microscope images of Example 1 and Comparative Example 1;

[0033] Figure 7 is the carbon dioxide permeability of Comparative Example 1 and Examples 1-4;

[0034] Figure 8 The oxygen permeability of Comparative Example 1 and Examples 1-4;

[0035] Figure 9 The mechanical properties of Comparative Example 1 and Examples 1-4;

[0036] Figure 10 To test the microbial barrier properties of different materials;

[0037] Figure 11The apparent results of different treatments on winter jujube fruits after 6 days of storage by spraying fungi;

[0038] Figure 12 The apparent results of winter jujube fruits stored for 6 days under different treatments are shown;

[0039] Figure 13 The acetaldehyde and ethanol contents of winter jujube fruits during storage for 6 days with different treatment methods. DETAILED DESCRIPTION

[0040] The present invention is further described below in conjunction with specific embodiments to facilitate a better understanding of the present technical solution.

[0041] The carnauba-based fruit wax coating material involved in the present invention is an existing material and can be purchased commercially. To facilitate experiments, the carnauba-based fruit wax coating material in the present invention was prepared using the following method (parts by weight): 1) 80 parts of carnauba wax, 20 parts of shellac, and 3 parts of oleic acid were melted and mixed at 110°C; 2) 5 parts of polyethylene glycol 4000 and 1.5 parts of gelatin were dissolved in 150 parts of boiling deionized water, and then mixed with the product of step 1) and 7.5 parts of aqueous ammonia; 3) the mixture was homogenized at 110°C for 10 minutes to obtain the carnauba-based fruit wax coating material.

[0042] Example 1

[0043] The preparation method of composite aerogel particle fruit wax comprises the following steps:

[0044] (1) After swelling microcrystalline cellulose in water at 4°C for 24 hours, it was dissolved in a solution containing 8 wt% NaOH and 11.5 wt% urea at -3°C;

[0045] (2) The solution obtained in step (1) was mixed with liquid paraffin in a volume ratio of 1:10 and homogenized at 1000 rpm for 10 minutes;

[0046] (3) Add 0.5 vol% Tween 80 and 8 M acetic acid to liquid paraffin and perform the first emulsification using a homogenizer at 1000 rpm. After 30 minutes, mix with the product of step (2);

[0047] (4) After a second emulsification with a mechanical stirring paddle at 900 rpm for 2 hours, a 1:1 ethanol-water solution was added to separate the product;

[0048] (5) After washing with deionized water for 6 times, the sample was swelled in deionized water at a constant temperature of 25°C for 72 h;

[0049] (6) Cellulose aerogel particles were prepared by freezing in liquid nitrogen and freeze-drying for 48 hours;

[0050] (7) The cellulose aerogel particles prepared in step (6) are added to a carnauba-based traditional fruit wax coating material in an amount of 1.00 wt% of the total mass of the coating material to obtain the composite aerogel particle fruit wax.

[0051] Example 2: The addition amount of aerogel particles is 0.75 wt %, and the rest is the same as Example 1.

[0052] Example 3: The addition amount of aerogel particles is 0.50 wt %, and the rest is the same as Example 1.

[0053] Example 4: The addition amount of aerogel particles is 0.25 wt %, and the rest is the same as Example 1.

[0054] Example 5

[0055] The preparation method of composite aerogel particle fruit wax comprises the following steps:

[0056] (1) After swelling microcrystalline cellulose in water at 4°C for 24 hours, it was dissolved in a solution containing 10 wt% NaOH and 8 wt% urea at -3°C;

[0057] (2) The solution obtained in step (1) was mixed with liquid paraffin in a volume ratio of 1:10 and homogenized at 1000 rpm for 10 minutes;

[0058] (3) Add 0.5 vol% Tween 80 and 8 M acetic acid to the liquid paraffin and perform the first emulsification using a homogenizer at 1000 rpm. After 10 minutes, mix with the product of step (2);

[0059] (4) After a second emulsification at 900 rpm using a mechanical stirring paddle for 2 hours, a 1:1 ethanol-water solution was added to separate the product;

[0060] (5) After washing with deionized water for 6 times, the sample was swelled in deionized water at a constant temperature of 25°C for 24 h;

[0061] (6) Cellulose aerogel particles were prepared by freezing in liquid nitrogen and freeze-drying for 48 hours.

[0062] Example 6

[0063] The preparation method of composite aerogel particle fruit wax comprises the following steps:

[0064] (1) After swelling microcrystalline cellulose in water at 4°C for 24 hours, it was dissolved in a solution containing 6 wt% NaOH and 12 wt% urea at -3°C;

[0065] (2) The solution obtained in step (1) was mixed with liquid paraffin in a volume ratio of 1:10 and homogenized at 1000 rpm for 15 minutes;

[0066] (3) Add 0.5 vol% Tween 80 and 8 M acetic acid to the liquid paraffin and perform the first emulsification using a homogenizer at 1000 rpm. After 10 minutes, mix with the product of step (2);

[0067] (4) After a second emulsification at 900 rpm using a mechanical stirring paddle for 2 hours, a 1:1 ethanol-water solution was added to separate the product;

[0068] (5) After washing with deionized water for 6 times, the sample was swelled in deionized water at a constant temperature of 25°C for 108 h;

[0069] (6) Cellulose aerogel particles were prepared by freezing in liquid nitrogen and freeze-drying for 48 hours.

[0070] Comparative Example 1

[0071] The addition amount of aerogel particles was 0%, and the rest was the same as in Example 1.

[0072] Comparative experiment

[0073] The particle size distribution of aerogel particles was characterized using a laser particle size analyzer (Beckman Coulter LS13320, Coulter, USA). Figure 1 As shown, the median particle size is about 106 μm, which is larger than the thickness of the wax coating and helps to form a breathable channel through the wax coating.

[0074] The specific surface area was determined using a gas adsorption analyzer (Autosorb-1-C, Anton Paar, USA). The nitrogen adsorption-desorption method was used. Prior to testing, the sample was degassed at 70°C under high vacuum for 10 hours. The nitrogen adsorption curve was obtained as shown in the figure below. Figure 2 The specific surface area calculated using the Brunauer-Emmett-Teller (BET) theory is: 19.50 m² g -1 This shows that the particles have a loose porous structure that can provide channels for gas to pass through. Figure 3 The pore size distribution of cellulose aerogel particles shown in the paper shows an average pore size of 19 nm, which is sufficient to provide exchange channels for gas molecules (about 0.3 nm in diameter). This result is significantly different from the pore size (average pore size of 3.6 nm) reported in ACS Nano 2021, 15, 8742-8752.

[0075] Scanning electron microscopy (SEM) images of the hydrogel network were obtained using a field emission scanning electron microscope (Gemini SEM360, Zeiss, Germany). Samples were observed after a 60-second gold spray treatment. Cross-sections were observed after freezing and fracture using liquid nitrogen.

[0076] Under a scanning electron microscope, cellulose aerogel particles appear granular ( Figure 4 The pore size on its surface is in the nanometer range ( Figure 5 ), which is consistent with the results of nitrogen adsorption analysis. In addition, the scanning electron microscopy images of Examples 5 and 6 confirm that the preparation method can effectively form porous particles, and the pore sizes are different ( Figure 5 The pores are larger than the diameter of gas molecules (approximately 0.3 nanometers) but smaller than the size of microorganisms (3-5 μm). The porous structure allows gas to pass through but does not allow microorganisms to pass through.

[0077] The cross section of the aerogel microparticle composite fruit wax coating with protrusions was observed under a scanning electron microscope ( Figure 6 ), the loose porous structure of the embedded cellulose aerogel particles was retained. However, the cross-section of Comparative Example 1, which did not have embedded cellulose aerogel particles, showed a dense structure, which strongly hindered gas passage and was not conducive to the high air permeability required for fruit preservation.

[0078] The carbon dioxide permeability was determined gravimetrically. KOH was placed in a 50 mL Erlenmeyer flask and sealed with a circular film (3.60 cm radius) and 502 glue. The sealed flask was equilibrated at 25°C and 75% relative humidity for 12 hours. The mass gain over 24 hours was recorded and calculated using the following formula:

[0079]

[0080] Where: Δm (kg) is the change in bottle weight before and after the test, d (m) is the thickness of the film, A (m 2 ) is the membrane area, t (s) is the test time, and P (Pa) is the carbon dioxide pressure difference between the two sides of the membrane. Each sample was measured three times.

[0081] Oxygen permeability is calculated using a similar method, using the deoxidizer instead of KOH, according to the following formula:

[0082]

[0083] Where: Δm' (kg) is the change in bottle weight before and after the test, d (m) is the thickness of the film, A (m 2 ) is the membrane area, t (s) is the test time, and P (Pa) is the oxygen pressure difference between the two sides of the membrane. Each sample was measured three times.

[0084] The results are as follows Figure 7 and Figure 8As shown, embedding cellulose aerogel particles in a carnauba wax-based traditional fruit wax coating can enhance their gas permeability. Increasing the volume of the cellulose aerogel particles significantly increased the oxygen and carbon dioxide permeabilities. Specifically, Example 1 measured high O2 and CO2 permeabilities of 2.85×10 -13 kg·m -1 ·s -1 ·Pa -1 , 2.88×10 -14 kg·m -1 ·s -1 ·Pa -1 The oxygen and carbon dioxide gas permeabilities of Examples 2-4 increased by 2.31 and 2.47 times, respectively, compared to the control example. As the amount of cellulose aerogel particles added decreased, the oxygen and carbon dioxide permeabilities of Examples 2-4 decreased. However, the permeabilities were still higher than those of the traditional fruit wax coating in Control Example 1. This demonstrates that the addition of cellulose aerogel particles enhances gas permeability.

[0085] Mechanical properties tests were performed using a Z5.0TN electronic universal testing machine from Zwick Roell, Germany. Samples were cut according to the 5B dumbbell specimen specifications in GB / T1040.1-2018, with dimensions of 2×35 mm. Figure 9 As shown, both tensile strength and elongation at break decreased in Examples 1-4. This is because the aerogel particles have a loose, porous structure. When embedded in the wax coating, they create gaps in areas where wax should be present, leading to localized weakening of mechanical properties. However, the addition of a small amount of cellulose aerogel particles does not significantly affect mechanical properties. In Examples 1-4, the addition of aerogel particles did not significantly weaken the mechanical properties, and the mechanical properties were not significantly different from those of Comparative Example 1.

[0086] The in vitro microbial resistance test method is as follows: the test material is placed vertically in a culture dish, and a support block of potato dextrose agar medium is placed to fix the film sample. The culture medium is poured until it completely covers the bottom of the culture dish. Then, a 5.0 mm diameter microparticle containing gray mold ( Botrytis cinerea ) culture medium containing mycelium was incubated at 25°C and 50% relative humidity for 36 hours, and the range of mycelial growth was observed. Materials with high microbial barrier properties confine mycelium to the inoculated side, while materials with weaker microbial barrier properties allow mycelium to penetrate the material and spread to the non-inoculated side. A cellulose nanocrystal / polyethylene glycol 4000 membrane was used as a positive control.

[0087] The results are as follows Figure 10As shown, Comparative Example 1 has a dense structure and can block Botrytis cinerea. No hyphae are observed on the non-inoculated side. Composite aerogel particle fruit wax, i.e. Example 1, can still achieve a barrier effect against Botrytis cinerea despite the introduction of cellulose aerogel particles and the presence of gas-permeable microporous channels. This is because its micropore size ( Figure 5 ) is much smaller than the size of gray mold. According to Table 1, the gray mold barrier efficiency of the traditional carnauba wax-based fruit wax coating reached 93.34% ± 2.32, while the composite aerogel microparticle fruit wax achieved a comparable efficiency. This indicates that the embedding of cellulose aerogel microparticles does not affect their inherent microbial resistance.

[0088] Table 1 Barrier rate of different materials to gray mold

[0089] Gray mold barrier rate of traditional fresh-keeping gel coating Gray mold barrier rate of traditional fruit wax coating Gray mold barrier rate of composite aerogel particle fruit wax coating 34.54%±11.7 93.34%±2.32 94.35%±2.17

[0090] To further evaluate the effect of incorporation of cellulose aerogel particles on the microbial barrier of the coating, the jujubes treated with distilled water coating, comparative example 1, and example 1 were sprayed with fungi and then stored at 25°C and 75% relative humidity for 6 days. Figure 11 ) and rot rate (Table 2). On the sixth day, fungal spots appeared on the surface of the uncoated jujube, while no such spots were observed in the treatments of Comparative Example 1 and Example 1 ( Figure 11 The decay rate of the uncoated group increased dramatically on the sixth day, while the decay rates of the Comparative Example 1 treatment and Example 1 remained relatively low (Table 2). These results demonstrate that Example 1 maintains the microbial barrier properties of Comparative Example 1 and is suitable for fruit preservation. This method avoids the use of preservatives, which can lead to unpleasant flavors, and meets the requirements of low-cost production.

[0091] Table 2 Decay rate of winter jujube after spraying with different materials

[0092] Uncoated decay rate (%) Decay rate of traditional fruit wax coating (%) Decay rate of fruit wax coating on composite aerogel particles (%) 0 day 0 0 0 3 days 8 0 0 6 days 56 8 4

[0093] Fruit application experiment: Winter jujube was used as a model fruit. Winter jujubes were randomly divided into three groups and soaked in pure water, comparative example 1, and example 1, respectively. They were named as no coating, traditional fruit wax coating, and composite aerogel particle fruit wax coating. They were stored in an environment of 25°C and 75% relative humidity for 6 days. According to the apparent results ( Figure 12 ), Example 1 and Comparative Example 1 had less red areas on their surfaces than the uncoated group. This indicates that Example 1 retained the original fruit appearance of Comparative Example 1.

[0094] The accumulation of alcoholic odor is a typical characteristic of postharvest aging of jujube fruits. Acetaldehyde and ethanol are the main volatile compounds that cause the odor. After the jujube fruits were stored for six days, the acetaldehyde and ethanol contents were measured ( Figure 13). During storage, the levels of ethanol and acetaldehyde in all groups gradually increased over time. Among them, the traditional fruit wax coating, due to its dense coating, hindered the normal respiratory process of the fruit, resulting in significantly higher accumulation of acetaldehyde and ethanol than the uncoated group. In contrast, the composite aerogel microparticle fruit wax with higher gas permeability had significantly lower levels of acetaldehyde and ethanol than the traditional fruit wax coating group, with accumulation reduced by 34.79% and 15.81%, respectively. This reduction in volatile compounds helps to minimize the accumulation of alcohol odor during fruit storage. These results show that Example 1 has higher oxygen and carbon dioxide permeability than Comparative Example 1 and is more suitable for fruit preservation.

Claims

1. A method for preparing a composite aerogel particle fruit wax, characterized in that: The composite aerogel particle fruit wax is obtained by adding cellulose aerogel particles to a carnauba-based fruit wax coating material and mixing them evenly, wherein the cellulose aerogel particles are cellulose aerogel particles having a nano-scale pore structure; The cellulose aerogel particles are obtained by the following steps: 1) Swelling the microcrystalline cellulose and then dissolving it; 2) mixing the solution from step 1) with liquid paraffin and homogenizing; 3) taking another liquid paraffin, performing emulsification treatment, and then mixing it with the product obtained in step 2) and performing a second emulsification treatment; 4) separating the emulsified product obtained in step 3); 5) The separated product obtained in step 4) is sequentially subjected to washing treatment, swelling treatment, freezing and freeze-drying treatment to obtain cellulose aerogel particles.

2. The method for preparing a composite aerogel particle fruit wax according to claim 1, wherein: The added amount of the cellulose aerogel particles is 0.1-1.00 wt% of the total mass of the carnauba-based fruit wax coating material.

3. The method for preparing a composite aerogel particle fruit wax according to claim 1, wherein: In the step 1), the microcrystalline cellulose is swollen in water at 4° C. for 24 hours and then dissolved in a solution containing 6-10 wt % NaOH and 8-12% urea at -3° C.

4. The method for preparing a composite aerogel particle fruit wax according to claim 1, wherein: In the step 2), the solution obtained in the step 1) is mixed with liquid paraffin in a volume ratio of 1:10, and homogenized at 1000 rpm for 10 minutes.

5. The method for preparing a composite aerogel particle fruit wax according to claim 1, wherein: In step 3), liquid paraffin was added with 0.5 vol% Tween 80 and 8 M acetic acid, and the mixture was emulsified for the first time using a homogenizer at 1000 rpm. After the first emulsification for 10 minutes, the mixture was mixed with the product obtained in step 2), and the mixture was emulsified for the second time using a mechanical stirring paddle at 900 rpm for 2 hours.

6. The method for preparing a composite aerogel particle fruit wax according to claim 1, wherein: In the step 4), a 1:1 ethanol-water solution is added to the emulsified product obtained in the step 3) to separate the product.

7. The method for preparing a composite aerogel particle fruit wax according to claim 1, wherein: In the step 5), the separated product obtained in the step 4) is washed with deionized water for 6 times, swelled in deionized water at a constant temperature of 25° C. for 24-108 hours, frozen with liquid nitrogen, and freeze-dried for 48 hours to obtain cellulose aerogel particles.

8. The composite aerogel particulate fruit wax prepared by any one of the preparation methods of claims 1 to 7.

9. Use of the composite aerogel particle fruit wax according to claim 8 in preserving fruits and vegetables.

10. Use of the composite aerogel particle fruit wax according to claim 8 in preventing gray mold.

11. The use according to claim 9, characterized in that Completely immerse the fruit and vegetable products in the composite aerogel particle fruit wax, take them out and dry them at room temperature.

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