Method for preparing aerogel microparticle composite fruit wax

Abstract

This invention provides a method for preparing and using aerogel microparticle composite fruit wax. [Solution] The aerogel microparticle composite fruit wax is obtained by uniformly mixing cellulose aerogel microparticles with a fruit wax coating material derived from Brazilian palm, wherein the cellulose aerogel microparticles are cellulose aerogel microparticles having a nanoscale pore structure. Furthermore, the use of the aerogel microparticle composite fruit wax prepared by the above method as a coating material for preserving fruits and vegetables is provided. [Effects] By introducing nanoscale pores, it improves the permeability of oxygen and carbon dioxide, and compared to conventional fruit waxes, it improves the situation in which fruits produce odors due to anaerobic respiration. In addition, the gray mold barrier ability of conventional coatings is maintained.

Description

[Technical Field]

[0001] This invention relates to the technology of fruit and vegetable preservation, and more specifically to aerogel microparticle composite fruit wax, and its preparation method and use. [Background technology]

[0002] Fruits and vegetables are susceptible to spoilage during harvesting and storage due to factors such as temperature, humidity, and microorganisms. Therefore, preserving fruits and vegetables is crucial, and existing fruit waxing techniques are important preservation methods for fruit after harvest. However, the high gas barrier properties of fruit wax (the permeability of carbon dioxide and oxygen is approximately 8.6 × 10⁻⁶) are problematic. -14 kg·m -1 ·s -1 ·Pa -1 , 8.3×10 -15 kg·m -1 ·s -1 ·Pa -1 This intensifies anaerobic respiration in the fruit, generating odorous components such as acetaldehyde and ethanol, which impair the fruit's original flavor. Currently, it is common practice to increase the breathability of packaging for storing fruits and vegetables. This method is mainly carried out by introducing a microporous array. However, this method can only process micropores into a pre-prepared film and is not suitable for fruit wax that forms directly on the surface of the fruit. Furthermore, highly breathable packaging using existing microporous arrays (pore size 8-30 μm) becomes a pathway for the fruit to come into contact with the external environment, posing a risk of microbial infection.

[0003] Currently disclosed fruit and vegetable preservation technologies mainly include the following: 1) The edible coating preservative for fresh fruit, its preparation method, and use described in Patent Document 1. An edible fruit wax coating is produced using candelilla wax, carnauba wax, and peanut oil as the main raw materials, with the addition of oleic acid, lauric acid, ammonia water, and water, and a heat emulsification method. This wax coating maintains the appearance of the fruit, retains moisture, and preserves freshness. However, this invention uses a large amount of wax material, and because the wax coating is dense, the stomata of the fruit become blocked, anaerobic respiration of the fruit intensifies, and odor components accumulate. 2) The breathable film for preserving fruits and vegetables and its manufacturing method described in Patent Document 2. This invention uses polypropylene, metallocene polypropylene, and high melt strength polypropylene as the main raw materials, and produces an anti-fogging and antibacterial film by blow molding and drying, and then combining it with a coating process. To improve gas permeability, it is necessary to laser perforate the surface of the anti-fogging and antibacterial film. This additional perforation step adds an extra step to the manufacturing process of the wrap film, increases the difficulty of the work, and makes it unsuitable for preservation coatings. Furthermore, the array of micropores becomes a pathway for microbial infection, increasing the risk of microbial infection. 3) A breathable wrap film with nanopectin coating as described in Patent Document 3. The present invention discloses a multilayer breathable wrap film with nanopectin coating, comprising a base film, nanobubble coating, antibacterial coating, and adsorption coating in that order. Each layer works synergistically, and in preservation applications, nanobubbles are used for gas regulation, and titanium dioxide is used for sterilization and gas regulation, thereby extending the shelf life of fruits and vegetables. The present invention provides a solution for a wrap film that combines breathability and antibacterial properties, but it is a multilayer film that is not edible, and its manufacturing process is complex. Titanium dioxide is used as the antibacterial substance, but this raw material is harmful when ingested, posing a potential food safety risk. 4) A herbal fruit preservation wax as described in Patent Document 4.This invention enhances the antibacterial effect of fruit wax by using shellac, water, and maleic acid rosin-modified resin as the main ingredients and specially adding a herbal extract with antibacterial properties. This herbal extract uses aqueous extracts of herbal medicines such as honeysuckle, magnolia, scutellaria, and forsythia, and has excellent preservative properties. Although the herbal extract has excellent antibacterial properties, this is a chemical antibacterial method and comes with a unique flavor derived from the medicinal raw materials, which carries the risk of reducing consumer acceptance. 5) Non-patent document 1 describes the production of hollow microspheres by phase separation using chitosan and polylactic acid, and imparting gas permeability by adding a shellac film. In this document, porous microspheres were produced using a phase separation process. However, the particle size of the produced porous microspheres is limited (median diameter is 38 μm). Furthermore, the porous microspheres produced in this paper have small pore sizes (average pore size 3.6 nm) close to the diameter of gas molecules (approximately 0.3 nm), resulting in fewer gas exchange channels. To address this drawback, the present invention adjusts the pore size of aerogel microparticles by adjusting the particle size distribution using a double emulsification method and the polymer network distribution in the gel state using a swelling method. On the other hand, tetrahydrofuran is used as a processing aid, but it has clear physiological toxicity and is not suitable for the production and processing of food packaging. The reagents used in the aerogel processing of the present invention are highly biocompatible and suitable for the manufacture of food packaging. Moreover, the methods of the prior art do not characterize the anaerobic respiration index for preservation purposes and do not accurately provide the improvement effect on anaerobic respiration of fruit by the solutions in the said literature. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Chinese Patent Application Publication No. 112535207 Specification [Patent Document 2] Chinese Patent Application Publication No. 114854075 Specification [Patent Document 3] Chinese Patent Application Publication No. 114097873 Specification [Patent Document 4] Chinese Patent Application Publication No. 101836673 Specification [Non-patent literature]

[0005] [Non-Patent Document 1] "ACS Nano" 2021, 15, 8742-8752 [Overview of the project] [Problems that the invention aims to solve]

[0006] In response to the problems present in the prior art, the object of the present invention is to design and provide technical solutions for aerogel microparticle composite fruit wax, a method for preparing the same, and a method for using it. [Means for solving the problem]

[0007] Specifically, this invention is achieved by employing the following technical solutions.

[0008] A first aspect of the present invention provides a method for preparing an aerogel microparticle composite fruit wax, which is obtained by uniformly mixing cellulose aerogel microparticles with a Brazilian palm-derived fruit wax coating material, wherein the cellulose aerogel microparticles are nanoscale pore structures. By adding cellulose aerogel microparticles to the wax coating, a gas-permeable micropore structure is introduced, improving air permeability. This method makes it possible to form air permeable pores on the coating in a one-step manner.

[0009] Furthermore, the amount of cellulose aerogel microparticles added is 0.1 to 1.00 wt% of the total mass of the Brazilian palm-derived fruit wax coating material. Furthermore, the cellulose aerogel microparticles are Step 1) of swelling microcrystalline cellulose and then subjecting it to a dissolution treatment; Step 2) of mixing the solution from Step 1) with liquid paraffin and subjecting it to a homogenization treatment; Step 3) of separately preparing liquid paraffin, subjecting it to an emulsification treatment, and mixing it with the product obtained in Step 2) to perform a secondary emulsification treatment; Step 4) of separating the emulsified product obtained in Step 3); Step 5) of sequentially performing a washing treatment, a swelling treatment, freezing, and freeze-drying on the separated product obtained in Step 4) to obtain cellulose aerogel microparticles, which is obtained by the above steps.

[0010] In the preparation of the cellulose aerogel microparticles, a gel isothermal swelling step is added before the solvent removal step in the preparation process of the cellulose aerogel microparticles, whereby a larger pore diameter can be obtained.

[0011] The pore diameter of the micropores introduced into the cellulose aerogel microparticles prepared by this method is smaller than the size of microorganisms, so it is possible to ensure air permeability while physically isolating microorganisms from infection. Since this method does not require the addition of antibacterial components, problems such as odors and food safety risks caused by antibacterial substances can be avoided.

[0012] Furthermore, in Step 1), after swelling microcrystalline cellulose in water at 4°C for 24 hours, it is dissolved in a solution containing 6 - 10 wt% NaOH and 8 - 12% urea in an environment at -3°C.

[0013] Furthermore, in Step 2), the solution obtained in Step 1) and liquid paraffin are mixed at a volume ratio of 1:10 and homogenized at 1000 rpm for 10 minutes.

[0014] Furthermore, in the step 3), separately prepare liquid paraffin, add it to 0.5 vol% Tween 80 and 8 M acetic acid, perform the first emulsification at 1000 rpm using a homogenizer. After 10 minutes of the first emulsification, mix it with the product obtained in step 2), and perform the second emulsification at 900 rpm for 2 hours using a mechanical stirring paddle.

[0015] Furthermore, in the step 4), add an ethanol aqueous solution with a ratio of 1:1 to the emulsified product obtained in step 3) to separate the product.

[0016] Furthermore, in the step 5), wash the separated product obtained in step 4) six times with deionized water, then swell it in deionized water for 24 - 108 h under constant temperature conditions of 25 °C, freeze it with liquid nitrogen, and freeze-dry it for 48 hours to obtain cellulose aerogel microparticles.

[0017] The second aspect of the present invention provides an aerogel microparticle composite fruit wax prepared by any of the above preparation methods.

[0018] The third aspect of the present invention provides the use of the above aerogel microparticle composite fruit wax in the preservation of fruits and vegetables.

[0019] The fourth aspect of the present invention provides the use of the above aerogel microparticle composite fruit wax in the gray mold barrier.

[0020] Furthermore, the specific method of the above use is to completely immerse fruit and vegetable products in the aerogel microparticle composite fruit wax, take them out and dry them at room temperature. Specifically, they may be immersed for 30 s and dried for 15 min.

[0021] The cellulose aerogel microparticles prepared by the present invention have a median diameter of 106.04 μm, have a porous structure, and a specific surface area of 19.50 cm 2The density was / g, and the average pore size was 19.76 nm. The composite fruit wax embedded with cellulose aerogel microparticles showed a 2.31-fold increase in carbon dioxide permeability and a 2.47-fold increase in oxygen permeability, but this did not significantly affect the original mechanical properties of the fruit wax. Before embedding the cellulose aerogel microparticles, the tensile strength of the fruit wax coating was 2.31 ± 0.21 MPa and the elongation at break was 1.46 ± 0.19%. After embedding the cellulose aerogel microparticles, the tensile strength of the composite fruit wax was 1.53 ± 0.37 MPa and the elongation at break was 0.99 ± 0.15%. [Effects of the Invention]

[0022] The aerogel microparticle composite fruit wax prepared by the method of the present invention can maintain barrier performance against gray mold. That is, the composite fruit wax with added cellulose aerogel microparticles still has barrier properties against gray mold, similar to conventional fruit wax coatings, and can also form ventilation holes directly on the fruit surface in situ, avoiding the secondary puncture process, thus having a wide range of practical applications. [Brief explanation of the drawing]

[0023] [Figure 1] This is the particle size distribution of cellulose aerogel microparticles prepared according to the present invention. [Figure 2] This is the nitrogen adsorption curve of cellulose aerogel microparticles prepared according to the present invention. [Figure 3] This is the pore distribution of cellulose aerogel microparticles prepared according to the present invention. [Figure 4] This is a scanning electron microscope image of cellulose aerogel microparticles prepared according to the present invention. [Figure 5] These are scanning electron microscope images of cellulose aerogel microparticles prepared according to Examples 1, 5, and 6 of the present invention. [Figure 6] These are cross-sectional scanning electron microscope images of Example 1 and Comparative Example 1. [Figure 7]This shows the carbon dioxide permeability of Comparative Example 1 and Examples 1-4. [Figure 8] This shows the oxygen permeability of Comparative Example 1 and Examples 1-4. [Figure 9] These are the mechanical properties of Comparative Example 1 and Examples 1-4. [Figure 10] This is a test of the microbial barrier performance of various materials. [Figure 11] These are the visual results of winter jujube fruits treated with bacteria and stored for 6 days, under various treatment methods. [Figure 12] These are the visual results of winter jujube fruits after being stored for 6 days and then treated using various methods. [Figure 13] This shows the acetaldehyde and ethanol content of winter jujube fruit during 6 days of storage, using various processing methods. [Modes for carrying out the invention]

[0024] The present invention will be further described below with reference to specific examples in order to better understand the technical solutions of the present invention.

[0025] The Brazilian palm-derived fruit wax coating material according to the present invention is a conventional material and is available commercially. In order to facilitate experiments, the Brazilian palm-derived fruit wax coating material according to the present invention is prepared by the following method (parts by weight): 1) 80 parts carnauba wax, 20 parts shellac, and 3 parts oleic acid are melted and mixed at 110°C; 2) 5 parts polyethylene glycol and 1.5 parts gelatin are dissolved in 150 parts boiling deionized water, then mixed with the product from step 1) and 7.5 parts ammonia water; 3) homogenized at 110°C for 10 minutes to obtain the Brazilian palm-derived fruit wax coating material.

[0026] [Example 1] The steps for preparing the aerogel microparticle composite fruit wax are as follows: (1) Microcrystalline cellulose was swollen in water at 4°C for 24 hours, and then dissolved at -3°C in a solution containing 8 wt% NaOH and 11.5 wt% urea. (2) The solution obtained in step (1) and liquid paraffin were mixed in a volume ratio of 1:10 and homogenized at 1000 rpm for 10 minutes. (3) 0.5 vol% Twain 80 and 8 M acetic acid were added to the liquid paraffin, and the first emulsification was performed using a homogenizer at 1000 rpm. After 30 minutes, it was mixed with the product from step (2). (4) A second emulsification was performed at 900 rpm using a mechanical stirring paddle for 2 hours, after which the product was separated by adding a 1:1 aqueous ethanol solution. (5) After washing six times with deionized water, the plants were swelled in deionized water for 72 hours under constant temperature conditions of 25°C. (6) The material was frozen with liquid nitrogen and freeze-dried for 48 hours to obtain cellulose aerogel microparticles. (7) The cellulose aerogel microparticles prepared in step (6) were added to a conventional fruit wax coating material derived from Brazilian palm in an amount of 1.00 wt% of the total mass of the coating material to obtain the aerogel microparticle composite fruit wax.

[0027] [Example 2] Except for the amount of aerogel microparticles added (0.75 wt%), the rest of the mixture was the same as in Example 1.

[0028] [Example 3] Except for the amount of aerogel microparticles added (0.50 wt%), the rest of the experiment was the same as in Example 1.

[0029] [Example 4] Except for the amount of aerogel microparticles added (0.25 wt%), the rest of the procedure was the same as in Example 1.

[0030] [Example 5] The steps for preparing the aerogel microparticle composite fruit wax are as follows: (1) Microcrystalline cellulose was swollen in water at 4°C for 24 hours, and then dissolved at -3°C in a solution containing 10 wt% NaOH and 8 wt% urea. (2) The solution obtained in step (1) and liquid paraffin were mixed in a volume ratio of 1:10 and homogenized at 1000 rpm for 10 minutes. (3) 0.5 vol% Twain 80 and 8 M acetic acid were added to the liquid paraffin, and the first emulsification was performed using a homogenizer at 1000 rpm. After 10 minutes, it was mixed with the product from step (2). (4) A second emulsification was performed at 900 rpm using a mechanical stirring paddle for 2 hours, after which the product was separated by adding a 1:1 aqueous ethanol solution. (5) After washing six times with deionized water, the plants were swelled in deionized water for 24 hours under constant temperature conditions of 25°C. (6) The material was frozen with liquid nitrogen and freeze-dried for 48 hours to obtain cellulose aerogel microparticles.

[0031] [Example 6] The steps for preparing the aerogel microparticle composite fruit wax are as follows: (1) Microcrystalline cellulose was swollen in water at 4°C for 24 hours, and then dissolved at -3°C in a solution containing 6 wt% NaOH and 12 wt% urea. (2) The solution obtained in step (1) and liquid paraffin were mixed in a volume ratio of 1:10 and homogenized at 1000 rpm for 15 minutes. (3) 0.5 vol% Twain 80 and 8 M acetic acid were added to the liquid paraffin, and the first emulsification was performed using a homogenizer at 1000 rpm. After 10 minutes, it was mixed with the product from step (2). (4) A second emulsification was performed at 900 rpm using a mechanical stirring paddle for 2 hours, after which the product was separated by adding a 1:1 aqueous ethanol solution. (5) After washing six times with deionized water, the plants were swelled in deionized water for 10⁸ hours under constant temperature conditions of 25°C. (6) The material was frozen with liquid nitrogen and freeze-dried for 48 hours to obtain cellulose aerogel microparticles.

[0032] [Comparative Example 1] Except for the amount of aerogel microparticles added (0%), the rest of the setup was the same as in Example 1.

[0033] [Comparative experiment] The particle size distribution of the aerogel microparticles was characterized using a laser particle size analyzer (Beckman Coulter LS13320, Coulter, USA). As shown in Figure 1, the median diameter was approximately 10⁶ μm, which is larger than the thickness of the wax coating, and this helps to form permeable channels that penetrate the wax coating.

[0034] The specific surface area was measured using a gas adsorption apparatus (Autosorb-1-C type, Anton Paar, USA). Nitrogen adsorption-desorption was employed. The sample was degassed for 10 hours under high vacuum conditions at 70°C before testing. The resulting nitrogen adsorption curve is shown in Figure 2. The specific surface area, calculated based on the Brunauer-Emmett-Teller (BET) theory, was 19.50 m². 2 ·g -1 This indicates that the microparticles have a loosely porous structure and can provide channels for gas permeation. According to the pore distribution of the cellulose aerogel microparticles shown in Figure 3, the average pore size reaches 19 nm, which is sufficient to provide exchange channels for gas molecules (approximately 0.3 nm in diameter). This result differs significantly from the pore size (average pore size of 3.6 nm) reported in ACS Nano 2021, 15, 8742-8752.

[0035] Scanning electron microscopy (SEM) measurements were performed using a field emission scanning electron microscope (Gemini SEM360, Zeiss, Germany) to acquire scanning electron microscope images of the hydrogel network. Samples were observed 60 seconds after metal spraying. Cross-sectional samples were observed after brittle fracture by freezing with liquid nitrogen.

[0036] Scanning electron microscopy revealed that the cellulose aerogel microparticles were granular (Figure 4). The pore size on their surface was in the nanometer range (Figure 5), which is consistent with the results of nitrogen adsorption analysis. Furthermore, scanning electron microscopy images of Examples 5 and 6 confirmed that this preparation method can effectively form porous particles with different pore sizes (Figure 5). The pores are larger than the diameter of gas molecules (approximately 0.3 nanometers) and smaller than the size of microorganisms (3-5 μm). The porous structure provides channels through which gas can permeate without passing through microorganisms.

[0037] When a cross-section of the aerogel microparticle composite fruit wax coating with protrusions was observed with a scanning electron microscope (Figure 6), the loose porous structure of the embedded cellulose aerogel microparticles was maintained. In contrast, a dense structure was observed in the cross-section of Comparative Example 1, which did not have embedded cellulose aerogel microparticles, resulting in a strong effect of blocking gas passage and being unfavorable for the high permeability required for fruit preservation.

[0038] The carbon dioxide permeability was measured by gravimetric method. KOH was placed in a 50 mL Erlenmeyer flask, and the mouth of the flask was sealed with a circular film (radius 3.60 cm) and 502 adhesive. The sealed Erlenmeyer flask was left in an environment of 25°C and 75% relative humidity for 12 hours to equilibrate, and the mass increase within 24 hours was recorded and calculated according to the following formula.

[0039] [Mathematics 1] (Carbon dioxide permeability)=(Δm×d) / (A×t×P) Here, Δm (kg) is the change in flask weight before and after the test, d (m) is the film thickness, and A (m) is the change in flask weight before and after the test. 2 ) represents the membrane area, t(s) is the test time, and P(Pa) is the difference in carbon dioxide pressure between the two sides of the membrane. Each sample was measured three times.

[0040] Oxygen permeability was calculated using a similar method with an oxygen scavenger instead of KOH, according to the following formula.

[0041] [Math 2] (Oxygen permeability)=(Δm'×d) / (A×t×P) Here, Δm'(kg) is the change in flask weight before and after the test, d(m) is the film thickness, and A(m) is the change in flask weight before and after the test. 2 ) represents 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.

[0042] The results are shown in Figures 7 and 8, and embedding cellulose aerogel microparticles in a conventional carnauba wax-based fruit wax coating can improve its gas permeability. Increasing the volume of the cellulose aerogel microparticles significantly improves oxygen and carbon dioxide permeability. Specifically, in Example 1, the oxygen and carbon dioxide permeability were 2.85 × 10⁻⁶, respectively. ―13 kg·m -1 ·s -1 ·Pa -1 and 2.88 × 10 ―14 kg·m -1 ·s -1 ·Pa -1 The permeability was high, 2.31 times and 2.47 times higher, respectively, than that of the comparative example's oxygen permeability and carbon dioxide gas permeability. In Examples 2-4, the oxygen and carbon dioxide permeability decreased sequentially as the amount of cellulose aerogel microparticles added decreased sequentially. However, the permeability was higher than that of the conventional fruit wax coating in Comparative Example 1. This indicates that the addition of cellulose aerogel microparticles has the effect of increasing gas permeability.

[0043] A Z5.0TN electronic universal tester manufactured by Zwick Roell GmbH in Germany was used for testing the mechanical properties. Samples were cut to a size of 2 × 35 mm according to the specifications for 5B dumbbell test specimens in the GB / T 1040.1-2018 standard. As shown in Figure 9, both tensile strength and elongation at break decreased in Examples 1-4. This is because aerogel microparticles have a loose porous structure, and when embedded in a wax coating, gaps are created in the areas where the wax should be filled, weakening the local mechanical properties. However, the addition of a small amount of cellulose aerogel microparticles did not have a significant effect on the mechanical properties. In Examples 1-4, the amount of aerogel microparticles added did not significantly weaken the mechanical properties, and there was no significant difference in mechanical properties compared to Comparative Example 1.

[0044] The in vitro microbial resistance measurement method is as follows: The test material was placed vertically in a culture dish, and the film sample was fixed using a support block of potato dextrose agar. The culture medium was poured in until the bottom of the dish was completely covered. Subsequently, a culture medium containing hyphae of the gray mold fungus (Botrytis cinerea) with a diameter of 5.0 mm was inoculated onto one side of the membrane, and the culture was incubated at 25°C and 50% relative humidity for 36 hours, and the extent of hyphae growth was observed. Materials with high microbial barrier performance confined the hyphae to the inoculated side, while materials with weak microbial barrier performance allowed the hyphae to penetrate the material and spread to the uninoculated side. In this experiment, cellulose nanocrystalline / polyethylene glycol 4000 membrane was used as a positive control.

[0045] The results are shown in Figure 10. Comparative Example 1 had a dense structure and was able to act as a barrier against gray mold, and no hyphae were observed on the uninoculated side. In the aerogel microparticle composite fruit wax, i.e., Example 1, cellulose aerogel microparticles were introduced and have gas-permeable microporous channels, yet it was still possible to achieve a barrier against gray mold. This is because its micropore size (Figure 5) is much smaller than that of gray mold. According to Table 1, the gray mold barrier rate of conventional carnauba wax-based fruit wax coatings reached 93.34% ± 2.32, while the aerogel microparticle composite fruit wax was comparable. This indicates that the embedding of cellulose aerogel microparticles does not affect the inherent physical resistance to microorganisms.

[0046] [Table 1]

[0047] To further evaluate the effect of cellulose aerogel microparticle formulation on the microbial barrier of the coating, fungi were sprayed onto jujubes treated with distilled water coating, Comparative Example 1, and Example 1, and then stored at 25°C and 75% relative humidity for 6 days. The surface morphology of the fruit (Figure 11) and spoilage rate (Table 2) were characterized. On day 6, fungal spots appeared on the surface of the uncoated jujubes, whereas no such spots were observed in the treatments of Comparative Example 1 and Example 1 (Figure 11). The spoilage rate in the uncoated group increased sharply on day 6, but the spoilage rates remained relatively low in the treatments of Comparative Example 1 and Example 1 (Table 2). These results indicate that Example 1 maintains the microbial barrier performance of Comparative Example 1 and is suitable for fruit preservation. This method avoids the use of preservatives, avoids odors caused by preservatives, and meets the requirements for low-cost production.

[0048] [Table 2]

[0049] Experiment on application to fruit: Winter jujube was used as a model fruit. Winter jujubes were randomly divided into three groups and immersed in pure water, Comparative Example 1, and Example 1, respectively. These were named uncoated, conventional fruit wax coating, and aerogel microparticle composite fruit wax coating. They were stored at 25°C and 75% relative humidity for 6 days. According to the appearance results (Figure 12), Example 1 and Comparative Example 1 showed less red area on the surface compared to the uncoated group. This indicates that Example 1 retains the original fruit appearance maintenance ability of Comparative Example 1.

[0050] The accumulation of alcohol odor is a typical characteristic of post-harvest aging of jujube fruit, with acetaldehyde and ethanol being the main volatile compounds causing the odor. After storing the above jujube fruit for 6 days, the acetaldehyde and ethanol content was measured (Figure 13). During storage, in all groups, the levels of ethanol and acetaldehyde gradually increased over time. Among these, conventional fruit wax coatings, due to their dense coating, hindered the normal respiration process of the fruit, resulting in significantly higher accumulation of acetaldehyde and ethanol compared to the uncoated group. On the other hand, in the aerogel microparticle composite fruit wax with high gas permeability, the levels of acetaldehyde and ethanol were significantly lower than in the conventional fruit wax coating group, with accumulation values ​​decreasing by 34.79% and 15.81%, respectively. This reduction in volatile compounds helps minimize the accumulation of alcohol odor during fruit storage. These results indicate that Example 1 has higher oxygen and carbon dioxide permeability than Comparative Example 1 and is more suitable for fruit preservation.

[0051] (Note) (Note 1) A method for preparing an aerogel microparticle composite fruit wax, The aerogel microparticle composite fruit wax is obtained by uniformly mixing cellulose aerogel microparticles with a fruit wax coating material derived from Brazilian palm, wherein the cellulose aerogel microparticles are cellulose aerogel microparticles having a nanoscale pore structure. The cellulose aerogel microparticles are Step 1) involves swelling the microcrystalline cellulose and then dissolving it, Step 2) involves mixing the solution from Step 1) with liquid paraffin and homogenizing it, Step 3) involves preparing liquid paraffin separately, emulsifying it, and then mixing it with the product obtained in step 2) to perform a secondary emulsification process. Step 4) involves separating the emulsified product obtained in Step 3), A method for preparing aerogel microparticle composite fruit wax, characterized by the following steps: step 4) washing, swelling, freezing, and freeze-drying the separated product obtained in step 5) to obtain cellulose aerogel microparticles.

[0052] (Note 2) The method for preparing an aerogel microparticle composite fruit wax according to Appendix 1, characterized in that the amount of cellulose aerogel microparticles added is 0.1 to 1.00 wt% of the total mass of the Brazilian palm-derived fruit wax coating material.

[0053] (Note 3) A method for preparing an aerogel microparticle composite fruit wax as described in Appendix 1, characterized in that, in step 1), 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 an environment of -3°C.

[0054] (Note 4) The method for preparing an aerogel microparticle composite fruit wax as described in Appendix 1, characterized in that in step 2), the solution obtained in step 1) and liquid paraffin are mixed in a volume ratio of 1:10 and homogenized at 1000 rpm for 10 minutes.

[0055] (Note 5) The method for preparing an aerogel microparticle composite fruit wax as described in Appendix 1, characterized in that, in step 3) above, liquid paraffin is prepared separately, added to 0.5 vol% Twain 80 and 8 M acetic acid, and the first emulsification is performed at 1000 rpm using a homogenizer, and after 10 minutes of the first emulsification, it is mixed with the product obtained in step 2), and the second emulsification is performed at 900 rpm for 2 hours using a mechanical stirring paddle.

[0056] (Note 6) The method for preparing an aerogel microparticle composite fruit wax according to Appendix 1, characterized in that, in step 4), a 1:1 aqueous ethanol solution is added to the emulsified product obtained in step 3) to separate the product.

[0057] (Note 7) The method for preparing aerogel microparticle composite fruit wax according to Appendix 1, characterized in that, in step 5), the separation product obtained in step 4) is washed six times with deionized water, then swelled in deionized water under constant temperature conditions of 25°C for 24 to 108 hours, frozen with liquid nitrogen, and freeze-dried for 48 hours to obtain cellulose aerogel microparticles.

[0058] (Note 8) Aerogel microparticle composite fruit wax prepared by the preparation method described in any one of the appendices 1 to 7.

[0059] (Note 9) Use of the aerogel microparticle composite fruit wax described in Appendix 8 for the preservation of fruits and vegetables.

[0060] (Note 10) Use of the aerogel microparticle composite fruit wax described in Appendix 8 in a gray mold barrier.

[0061] (Note 11) The use described in Appendix 9 is characterized by completely immersing fruit and vegetable products in an aerogel microparticle composite fruit wax, removing them, and drying them at room temperature.

Claims

1. A method for preparing an aerogel microparticle composite fruit wax, The aerogel microparticle composite fruit wax is obtained by uniformly mixing cellulose aerogel microparticles with a fruit wax coating material derived from Brazilian palm, wherein the cellulose aerogel microparticles are cellulose aerogel microparticles having a nanoscale pore structure. The cellulose aerogel microparticles are Step 1) involves swelling the microcrystalline cellulose and then dissolving it, Step 2) involves mixing the solution from step 1) with liquid paraffin and performing a homogenization process, Step 3) involves preparing liquid paraffin separately, emulsifying it, and then mixing it with the product obtained in step 2) to perform a secondary emulsification process. Step 4) involves separating the emulsified product obtained in step 3), A method for preparing aerogel microparticle composite fruit wax, characterized by the following steps: step 4) washing treatment, swelling treatment, freezing and freeze-drying treatment sequentially on the separated product obtained in step 5) to obtain cellulose aerogel microparticles; and step 5) obtaining the aerogel microparticle composite fruit wax by the above method.

2. The method for preparing an aerogel microparticle composite fruit wax according to claim 1, characterized in that the amount of cellulose aerogel microparticles added is 0.1 to 1.00 wt% of the total mass of the Brazilian palm-derived fruit wax coating material.

3. A method for preparing an aerogel microparticle composite fruit wax according to claim 1, characterized in that, in step 1), 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 an environment of -3°C.

4. The method for preparing an aerogel microparticle composite fruit wax according to claim 1, characterized in that in step 2), the solution obtained in step 1) and liquid paraffin are mixed in a volume ratio of 1:10 and homogenized at 1000 rpm for 10 minutes.

5. The method for preparing an aerogel microparticle composite fruit wax according to claim 1, characterized in that, in step 3), liquid paraffin is prepared separately, added to 0.5 vol% Twain 80 and 8 M acetic acid, and the first emulsification is performed at 1000 rpm using a homogenizer, and after 10 minutes of the first emulsification, it is mixed with the product obtained in step 2), and the second emulsification is performed at 900 rpm for 2 hours using a mechanical stirring paddle.

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

7. The method for preparing aerogel microparticle composite fruit wax according to claim 1, characterized in that, in step 5), the separation product obtained in step 4) is washed six times with deionized water, then swelled in deionized water under constant temperature conditions of 25°C for 24 to 108 hours, frozen with liquid nitrogen, and freeze-dried for 48 hours to obtain cellulose aerogel microparticles.

Images