Composite aerogel particle fruit wax as well as preparation method and application thereof

Abstract

The invention discloses composite aerogel particle fruit wax as well as a preparation method and application thereof, the composite aerogel particle fruit wax is obtained by adding cellulose aerogel particles into a carnauba-based fruit wax coating material and uniformly mixing, and the cellulose aerogel particles are cellulose aerogel particles with nanoscale pore structures; the composite aerogel particle fruit wax prepared by the method can be used as a fruit and vegetable fresh-keeping coating material. According to the composite aerogel particle fruit wax prepared by the method, the air permeability of oxygen and carbon dioxide is improved by introducing nanoscale pores, and compared with traditional fruit wax, the situation that fruits generate peculiar smell due to oxygen-free breathing is improved. Meanwhile, the botrytis cinerea blocking capacity of a traditional coating is reserved. According to the method for forming the pores in situ, the procedure of secondary punching is avoided, and the method has a wide practical scene.

Description

Technical Field

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

[0002] Fruits and vegetables are easily affected by factors such as temperature, humidity and microorganisms during harvesting and storage, which may cause corruption. Therefore, the preservation of fruits and vegetables is very important. The existing fruit wax treatment technology is an important preservation method for post-harvest fruit storage. However, the high gas barrier property of fruit wax (carbon dioxide, oxygen permeability is 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 the intensification of anaerobic respiration of the fruit, producing acetaldehyde, ethanol and other odor components, destroying the original flavor of the fruit; the existing means of increasing the air permeability of packaging for storage of fruits and vegetables mainly involves the introduction of microporous arrays. However, this method can only process micropores on pre-prepared films and is not suitable for fruit wax directly formed in situ on the surface of the fruit. In addition, the existing high-permeability packaging with microporous arrays (pore size 8-30μm) provides a channel for the fruit to contact the external environment, which has the risk of microbial infection.

[0003] The existing disclosed technologies for preserving fruits and vegetables mainly include: 1) An edible fresh fruit coating preservative and its preparation method and application, CN112535207A. The invention provides an edible fresh fruit coating preservative and its preparation method and application, which uses candelilla wax, carnauba wax, peanut oil as the main materials, supplemented with oleic acid, lauric acid, ammonia water and water, and prepares an edible fruit wax coating by a hot emulsification method, which has the function of maintaining the appearance of the fruit, retaining water and preserving freshness. However, the invention uses a large amount of wax material, and the dense wax coating will cause the pores of the fruit to be blocked, resulting in the aggravation of the anaerobic respiration of the fruit and the accumulation of odor components. 2) A special fresh-keeping breathing film for fruits and vegetables and its preparation method, CN114854075A. The invention is prepared with polypropylene, metallocene polypropylene, and high melt strength polypropylene as the main raw materials, and after blow molding and drying, it is combined with a coating process to form an anti-fog antibacterial film. In order to improve gas permeability, laser drilling is required on the surface of the anti-fog antibacterial film. The additional punching step adds an extra process to the preparation of the cling film, which increases the difficulty of operation and cannot be transferred to the application of the 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, and this raw material is harmful to consumption, bringing potential food safety risks. 4) A traditional Chinese medicine fresh-keeping fruit wax, CN101836673A. The invention uses shellac, water, and maleic rosin modified resin as the main raw materials, and specially adds bactericidal Chinese medicine extracts to increase the bactericidal effect of fruit wax. The Chinese medicine extracts use water extracts of Chinese medicines such as honeysuckle, Magnolia officinalis, Scutellaria baicalensis, and Forsythia suspensa, which have good preservation effects. Although Chinese medicine extracts bring good bactericidal effects, they are chemical antibacterials, accompanied by abnormal flavors derived from medicinal materials, and there is a risk of reducing consumer acceptance. 5) In "ACS Nano" 2021, 15, 8742-8752, chitosan and polylactic acid were used to prepare hollow microspheres in a phase separation manner, and gas permeability was provided in the shellac film. The porous microspheres prepared in this paper adopt a phase separation process, but the prepared porous microspheres have a limited particle size (median particle size of 38μm). In addition, the porous microspheres prepared in this paper have a lower pore size (average pore size of 3.6nm), which is closer to the diameter of gas molecules (about 0.3nm), resulting in fewer gas exchange channels.In order to solve these defects, the present invention respectively adopts a double emulsification method to adjust the particle size distribution, and adopts a swelling method to adjust the polymer network distribution in a gel state, thereby adjusting the pore size of the aerogel particles. On the other hand, tetrahydrofuran is used as a processing aid in the article, which has clear physiological toxicity and is not suitable for the production and processing of edible packaging. The reagents used in the aerogel processing of the present invention are highly biocompatible and suitable for the production of edible packaging. In addition, the method of the prior art does not characterize the anaerobic respiration index in the preservation application, and fails to accurately provide the improvement effect of the scheme in the article on the anaerobic respiration of fruits. Summary of the invention

[0004] In view of the problems existing in the prior art, the purpose of the present invention is to design and 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: The first aspect of the present invention provides a method for preparing a composite aerogel particle fruit wax, wherein the composite aerogel particle fruit wax is obtained by adding cellulose aerogel particles to a carnauba-based fruit wax coating material and mixing them uniformly, wherein the cellulose aerogel particles are cellulose aerogel particles having a nanoscale pore structure. By adding cellulose aerogel particles to a waxy coating, a microporous structure having gas permeability is introduced to increase the air permeability. The method realizes a one-step method to form air permeable pores in situ on the coating.

[0006] 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.

[0007] Further, the cellulose aerogel particles are obtained by the following steps: 1) Swelling the microcrystalline cellulose and then dissolving it; 2) mixing the solution of step 1) with liquid paraffin and homogenizing; 3) taking another liquid paraffin, emulsifying it, and then mixing it with the product obtained in step 2) and performing a secondary emulsification treatment; 4) separating and treating 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.

[0008] The preparation of the cellulose aerogel particles includes a gel isothermal swelling step before the solvent removal step in the preparation process of the cellulose aerogel particles, thereby obtaining a higher pore diameter.

[0009] The micropores introduced into the cellulose aerogel particles prepared by this method are smaller than the size of microorganisms, which can ensure air permeability while physically isolating microbial infection. This method does not require the addition of antibacterial ingredients, avoiding the problems of abnormal flavor and edible hazards caused by antibacterial substances.

[0010] 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.

[0011] Furthermore, 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.

[0012] Furthermore, in step 3), liquid paraffin is added with 0.5 vol% Tween 80 and 8 M acetic acid, and the mixture is emulsified for the first time at 1000 rpm using a homogenizer; after the first emulsification for 10 minutes, the mixture is mixed with the product obtained in step 2), and the mixture is emulsified for the second time at 900 rpm for 2 hours using a mechanical stirring paddle.

[0013] Furthermore, in the step 4), a 1:1 ethanol-water solution is added to the emulsified product obtained in step 3) to separate the product.

[0014] 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, and frozen with liquid nitrogen and freeze-dried for 48 hours to obtain cellulose aerogel particles.

[0015] The second aspect of the present invention provides a composite aerogel particulate fruit wax prepared by any of the above preparation methods.

[0016] The third aspect of the present invention provides the use of the composite aerogel particle fruit wax in preserving fruits and vegetables.

[0017] The fourth aspect of the present invention provides the use of the above-mentioned composite aerogel particle fruit wax in the barrier of gray mold.

[0018] 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 for 30 seconds and dry for 15 minutes.

[0019] 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, the average pore diameter reached 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; and there was no significant effect on the original mechanical properties of the fruit wax. Before the cellulose aerogel particles were embedded, the fracture strength of the fruit wax coating was 2.31±0.21MPa, and the elongation at break was 1.46±0.19%. After being embedded with 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%.

[0020] The composite aerogel microparticle fruit wax prepared by the inventive method can maintain the barrier performance against Botrytis cinerea, that is, the composite fruit wax after adding cellulose aerogel microspheres still has the barrier performance against Botrytis cinerea as the traditional fruit wax coating, and can also directly form air holes in situ on the fruit surface, avoiding the process of secondary punching, and has a wide range of practical scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The particle size distribution of the cellulose aerogel particles prepared in the present invention; Figure 2 is the nitrogen adsorption curve of the cellulose aerogel particles prepared in the present invention; Figure 3 The pore distribution of the cellulose aerogel particles prepared in the present invention; Figure 4 is a scanning electron microscope image of the cellulose aerogel particles prepared in the present invention; Figure 5 are scanning electron microscope images of cellulose aerogel particles of Examples 1, 5, and 6 prepared in the present invention; Figure 6 are cross-sectional scanning electron microscope images of Example 1 and Comparative Example 1; Figure 7 is the carbon dioxide permeability of Comparative Example 1 and Examples 1-4; Figure 8 The oxygen permeability of Comparative Example 1 and Examples 1-4; Fig. 9 The mechanical properties of Comparative Example 1 and Examples 1-4; Fig.10 To test the microbial barrier properties of different materials; Fig.11 The apparent results of different treatment methods on winter jujube fruits after 6 days of storage with spraying bacteria; Fig.12 The apparent results of different treatments after 6-day storage of winter jujube fruits; Fig.13 The acetaldehyde and ethanol contents in winter jujube fruits with different treatments during storage for 6 days. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with specific embodiments to facilitate a better understanding of the present technical solution.

[0023] The carnauba-based fruit wax coating material involved in the present invention is an existing material and can be purchased commercially. In order to facilitate the experiment, the carnauba-based fruit wax coating material in the present invention is prepared by the following method (parts by weight): 1) 80 parts of carnauba wax, 20 parts of shellac and 3 parts of oleic acid are melted and mixed at 110°C; 2) 5 parts of polyethylene glycol 4000 and 1.5 parts of gelatin are dissolved in 150 parts of boiling deionized water, and then mixed with the product of step 1) and 7.5 parts of ammonia water; 3) homogenized at 110°C for 10 minutes to obtain the carnauba-based fruit wax coating material.

[0024] Example 1

[0025] The preparation method of composite aerogel particle fruit wax comprises the following steps: (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; (2) mixing the solution obtained in step (1) with liquid paraffin in a volume ratio of 1:10, and homogenizing at 1000 rpm for 10 minutes; (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); (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; (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; (6) Cellulose aerogel particles were prepared by freezing in liquid nitrogen and freeze-drying for 48 hours; (7) Adding the cellulose aerogel particles obtained in step (6) 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.

[0026] Example 2: The addition amount of aerogel particles is 0.75 wt %, and the rest is the same as Example 1.

[0027] Example 3: The addition amount of aerogel particles is 0.50wt%, and the rest is the same as Example 1.

[0028] Example 4: The addition amount of aerogel particles is 0.25 wt %, and the rest is the same as Example 1.

[0029] Example 5

[0030] The preparation method of composite aerogel particle fruit wax comprises the following steps: (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; (2) mixing the solution obtained in step (1) with liquid paraffin in a volume ratio of 1:10, and homogenizing at 1000 rpm for 10 minutes; (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 10 minutes, mix with the product of step (2); (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; (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; (6) Cellulose aerogel particles were prepared by liquid nitrogen freezing and freeze-drying for 48 hours.

[0031] Example 6

[0032] The preparation method of composite aerogel particle fruit wax comprises the following steps: (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; (2) mixing the solution obtained in step (1) with liquid paraffin in a volume ratio of 1:10, and homogenizing at 1000 rpm for 15 minutes; (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 10 minutes, mix with the product of step (2); (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; (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; (6) Cellulose aerogel particles were prepared by liquid nitrogen freezing and freeze-drying for 48 hours.

[0033] Comparative Example 1 The addition amount of aerogel particles was 0%, and the rest was the same as in Example 1.

[0034] Comparative experiment The particle size distribution of aerogel particles was characterized in 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 penetrating the wax coating.

[0035] In the specific surface area determination, the analysis was performed using a gas adsorption instrument (Autosorb-1-C, Anton Paar, USA). The nitrogen adsorption-desorption method was used. The sample was degassed at 70°C and high vacuum for 10 hours before the test. The nitrogen adsorption curve was obtained as shown in 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 distribution of cellulose aerogel particles shown in the figure 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.

[0036] In the measurement of scanning electron microscopy, a field emission scanning electron microscope (Gemini SEM360, Zeiss, Germany) was used to obtain the scanning electron microscope image of the hydrogel network. The sample was observed after 60 seconds of gold spraying. The cross-section sample was observed after being frozen and brittle fractured by liquid nitrogen.

[0037] 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 microscope 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 (about 0.3 nanometers) and smaller than the size of microorganisms (3-5 μm). The porous structure can provide channels for gas to pass through, but does not allow microorganisms to pass through.

[0038] The cross section with protrusions in the aerogel particle composite fruit wax coating was observed under a scanning electron microscope ( Figure 6 ), the loose porous structure of the embedded cellulose aerogel particles was retained. However, a dense structure was observed in the cross section of Comparative Example 1 where no cellulose aerogel particles were embedded, which had a strong barrier effect on the passage of gas and was not conducive to the high air permeability required for fruit preservation.

[0039] The method for determining carbon dioxide permeability is as follows: Determination based on the weight method. KOH is placed in a 50 mL conical flask and the flask mouth is sealed with a circular film (radius 3.60 cm) and 502 glue. After the sealed conical flask is placed in an environment of 25°C and 75% relative humidity for 12 hours, the mass increase within 24 hours is recorded and calculated according to the following formula:

[0040] 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.

[0041] Oxygen permeability is calculated using a similar method, using the deoxidizer instead of KOH, according to the following formula:

[0042] 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.

[0043] The results are as follows Figure 7 and Figure 8 As shown in Figure 1, embedding cellulose aerogel particles in a carnauba wax-based traditional fruit wax coating can enhance their gas permeability. Increasing the volume of cellulose aerogel particles significantly increased the oxygen permeability and carbon dioxide permeability. Specifically, Example 1 measured a higher O 2 and CO 2 The permeability is 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 the comparative example were increased by 2.31 times and 2.47 times, respectively. As the amount of cellulose aerogel particles added decreased, the oxygen and carbon dioxide permeabilities of Examples 2-4 decreased successively. However, the permeability was still higher than that of the traditional fruit wax coating in Comparative Example 1. This shows that the addition of cellulose aerogel particles has the effect of enhancing gas permeability.

[0044] The mechanical properties were tested using a Z5.0TN electronic universal testing machine from Zwick Roell, Germany. The samples were cut according to the specifications of Type 5B dumbbell specimens in the GB / T 1040.1-2018 standard, with dimensions of 2×35 mm. As Fig. 9 shown, in Examples 1-4, both the tensile strength and elongation at break decreased. The reason is that the aerogel particles have a loose and porous structure. When embedded in the wax coating, gaps are generated in the areas that should originally be filled with wax, resulting in the weakening of local mechanical properties. However, the addition of a small amount of cellulose aerogel particles does not significantly affect the mechanical properties. In Examples 1-4, the addition amount of aerogel particles did not significantly weaken the mechanical properties, and there was no significant difference in mechanical properties compared with Comparative Example 1.

[0045] The method for measuring the in vitro microbial resistance performance is as follows. The material to be tested is placed vertically in a petri dish, and a support block of potato dextrose agar medium is placed to fix the membrane sample. The culture medium is poured until it completely covers the bottom of the petri dish. Subsequently, a culture medium containing Botrytis cinerea ( Botrytis cinerea ) hyphae with a diameter of 5.0 mm is inoculated on one side of the membrane, and cultured at 25 °C and 50% relative humidity for 36 hours, and the growth range of the hyphae is observed. Materials with high microbial barrier performance will confine the hyphae to the inoculated side, while materials with weak microbial barrier performance will allow the hyphae to penetrate the material and spread on the non-inoculated side. In this experiment, the cellulose nanocrystal / polyethylene glycol 4000 membrane was used as a positive control.

[0046] The results are as Fig.10 shown. Due to its dense structure, Comparative Example 1 can block Botrytis cinerea, and no hyphae were observed on the non-inoculated side. The composite aerogel particle fruit wax, namely Example 1, although introducing cellulose aerogel particles and having microporous channels through which gas can pass, can still achieve the blocking effect on Botrytis cinerea. The reason is that its micropore size ( Figure 5 ) is much smaller than the size of Botrytis cinerea. According to Table 1, the Botrytis cinerea blocking rate of the carnauba wax-based traditional fruit wax coating reaches 93.34%±2.32, which is comparable to that of the composite aerogel particle fruit wax. This shows that the embedding of cellulose aerogel particles does not affect its original microbial physical resistance ability.

[0047] Table 1 Blocking rates of different materials against Botrytis cinerea Barrier rate of gray mold in traditional fresh-keeping gel coating Traditional fruit wax coating gray mold barrier rate Barrier rate of Botrytis cinerea on composite aerogel particle fruit wax coating 34.54%±11.7 93.34%±2.32 94.35%±2.17 To further evaluate the influence of the incorporation of cellulose aerogel particles on the microbial barrier of the coating, distilled water coating treatment, Comparative Example 1 treatment, and Example 1 treatment jujubes were subjected to fungal spraying treatment, and then stored at 25 °C and 75% relative humidity for 6 days. The surface morphology ( Fig.11 ) and decay rate (Table 2) of the fruits were characterized. On the sixth day, fungal spots appeared on the surface of the uncoated jujubes, while no such spots were observed in the Comparative Example 1 treatment and Example 1 treatment ( Fig.11 ). The decay rate of the uncoated group increased sharply on the sixth day, while the decay rates of the comparative example 1 treatment and Example 1 remained relatively low (Table 2). These results show that Example 1 maintains the microbial barrier performance of the comparative example 1 and is suitable for fruit preservation. This method avoids the use of preservatives, avoids abnormal flavors caused by preservatives, and meets the needs of low-cost production.

[0048] Table 2 Decay rate of winter jujube after spraying with different materials No coating decay rate (%) Traditional fruit wax coating decay rate (%) 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 Fruit application experiment: Winter jujube was used as a model fruit. Winter jujube was randomly divided into 3 groups, and soaked in pure water, comparative example 1, and example 1, and named as no coating, traditional fruit wax coating, and composite aerogel particle fruit wax coating. It was stored in an environment of 25°C and 75% relative humidity for 6 days. According to the apparent results ( Fig.12 ), the surfaces of Example 1 and Comparative Example 1 have less red areas than the uncoated group. This shows that Example 1 retains the original fruit appearance maintenance ability of Comparative Example 1.

[0049] The accumulation of alcohol odor is a typical feature of postharvest aging of jujube fruits. Acetaldehyde and ethanol are the main volatile compounds that cause off-odor. After the jujube fruits were stored for six days, the contents of acetaldehyde and ethanol ( Fig.13 ). During storage, the levels of ethanol and acetaldehyde in all groups gradually increased over time. Among them, the traditional fruit wax coating hindered the normal breathing process of the fruit due to the dense coating, 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 into a carnauba-based fruit wax coating material and mixing them evenly. The cellulose aerogel particles are cellulose aerogel particles with nano-scale pore structures.

2. The method for preparing a composite aerogel particle fruit wax according to claim 1, characterized in that: 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, characterized in that: The cellulose aerogel particles are obtained by the following steps: 1) Swelling the microcrystalline cellulose and then dissolving it; 2) mixing the solution of step 1) with liquid paraffin and homogenizing; 3) taking another liquid paraffin, emulsifying it, and then mixing it with the product obtained in step 2) and performing a secondary 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.

4. The method for preparing a composite aerogel particle fruit wax according to claim 3, characterized in that: 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.

5. The method for preparing a composite aerogel particle fruit wax according to claim 3, characterized in that: 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.

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

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

8. The method for preparing a composite aerogel particle fruit wax according to claim 3, characterized in that: 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.

9. The composite aerogel particulate fruit wax prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the composite aerogel particle fruit wax as claimed in claim 9 in preserving fruits and vegetables.

11. Use of the composite aerogel particle fruit wax as claimed in claim 9 in barrier against Botrytis cinerea.

12. The use according to claim 10, 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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