Composite coating material and use thereof

Abstract

The application provides a kind of composite coating material and its application, belong to the field of crop preservation.The application provides a kind of composite coating material, by mass fraction, including the following raw materials: bleached shellac 0~5%, tea polyphenol 0~1%, grape seed extract 0~1%, fish collagen peptide 0~1%, vitamin C 0~1%, sodium carboxymethyl cellulose 0~3%, gelatin 0~1%, glycerol 1~3% and the balance of water;The mass fraction of the bleached shellac is not 0.The composite coating material of the application adopts the combination of multiple natural ingredients and has excellent preservation capacity, can effectively prolong the preservation period of fruits, improve the stability of its appearance and taste, and at the same time maintain its nutritional value and food safety.

Description

Technical Field

[0001] This invention relates to the field of crop preservation, specifically to a composite coating material and its application. Background Technology

[0002] Fruits are an important category of fresh foods rich in nutrients, possessing high nutritional value and market acceptance. However, fresh fruit tissues have high polyphenol oxidase activity, making them highly susceptible to enzymatic browning, resulting in a generally short shelf life. This significantly restricts their commercial potential and reduces consumer purchasing enthusiasm. Tropical fruits like bananas, with their easily damaged and blackened yellow peels, are particularly vulnerable to oxidation and enzymatic activity, leading to rotting and discoloration, thus shortening their shelf life and market value.

[0003] At present, most commercially available fruit and vegetable preservatives rely on chemical active ingredients to achieve functions such as inhibiting browning, anti-oxidation, and antibacterial and antiseptic properties; however, chemical preservatives generally pose food safety risks and residue problems, and can easily alter the original flavor and quality of fruits, resulting in the loss of nutrients.

[0004] Given the aforementioned limitations, developing novel preservatives that combine high safety and preservation efficacy to delay the spoilage and browning of fresh fruits, maintain their original flavor and nutritional characteristics, and extend their storage period is of significant research value and practical application demand. Summary of the Invention

[0005] This invention provides a composite coating material and its application. The composite coating material of this invention has high safety and can effectively inhibit fruit rot and reduce moisture evaporation.

[0006] This invention provides a composite coating material, comprising the following raw materials by mass fraction: Bleached shellac 0-5%, tea polyphenols 0-1%, grape seed extract 0-1%, fish collagen peptides 0-1%, vitamin C 0-1%, sodium carboxymethyl cellulose 0-3%, gelatin 0-1%, glycerin 1-3%, and the balance being water; The mass fraction of the bleached shellac is not 0.

[0007] Preferably, the raw material further includes: 0-3% ammonia water, and not 0%; The concentration of the ammonia water is 0.6 wt%.

[0008] Preferably, the pH value of the composite coating material is 7~7.5.

[0009] The present invention also provides a method for preparing the composite coating material described in the above technical solution, comprising the following steps: The raw materials for the composite coating material are mixed to obtain the composite coating material.

[0010] Preferably, when the raw material includes ammonia, the mixing includes: mixing bleached shellac with ammonia and then adding some water to dilute it to obtain a bleached shellac solution; dissolving glycerin in some water and then sequentially adding the bleached shellac solution, vitamin C, fish collagen peptides, grape seed extract, tea polyphenols, sodium carboxymethyl cellulose, gelatin, and the remaining water.

[0011] Preferably, the temperature at which the bleached shellac is mixed with ammonia is 25~65℃.

[0012] The present invention also provides the application of the composite coating material described in the above technical solution or the composite coating material prepared by the preparation method described in the above technical solution in the field of crop preservation.

[0013] Preferably, the crop includes fruit; the fruit includes bananas.

[0014] Preferably, the application includes the following steps: forming a film of the composite coating material on the surface of crops.

[0015] Preferably, the film formation includes impregnation, spraying, or coating followed by drying.

[0016] The composite coating material of this invention uses a combination of various natural ingredients to have excellent preservation capabilities. It can effectively extend the shelf life of fruits, improve their appearance and taste stability, and at the same time maintain their nutritional value and food safety.

[0017] The shellac composite coating material of this invention, with its various natural components, effectively delays the discoloration and decay of bananas, extends their shelf life, and contains no chemically synthesized additives. It possesses high safety and acceptability, helping to meet consumers' demand for healthy and safe food and reducing potential risks to human health. Example results show that the composite coating material of this invention allows bananas to be stored at room temperature without any refrigeration for 30 days, achieving a 95% marketability rate, with a water loss rate of less than 15%, and maintaining essentially the same flavor and texture. It effectively reduces moisture loss, inhibits the oxidation of bananas and excessive decay caused by mold, extends shelf life, and increases commercial value.

[0018] Furthermore, compared with traditional chemically synthesized preservatives, the shellac composite coating material of this invention uses natural ingredients, reducing environmental pollution and resource consumption.

[0019] The composite coating material of the present invention is very easy to use. It can be applied to the surface of bananas by spraying, dipping or brushing. Its uniformly mixed formula and fluidity make it easy to coat and adhere to the surface of bananas, thus maintaining their freshness and taste. Attached Figure Description

[0020] Figure 1The infrared spectrum of the shellac composite coating material and raw materials in Example 7 is shown below. Figure 2 The image shows the TG-DTG diagrams of the shellac composite coating material and raw materials in Example 7. Figure 3 Scanning electron microscope images of the coating formed by the shellac composite coating material in Comparative Example 1 (left) and the coating formed by the shellac composite coating material in Example 7 (right); Figure 4 The degradation test results are shown for the film formed without shellac composite coating material in Comparative Example 1 (left) and the film formed with shellac composite coating material in Example (8) (right); Figure 5 The appearance of the banana, the banana prepared in Comparative Example 1, and the banana prepared in Example 7. Detailed Implementation

[0021] This invention provides a composite coating material, comprising the following raw materials by mass fraction: Bleached shellac 0-5%, tea polyphenols 0-1%, grape seed extract 0-1%, fish collagen peptides 0-1%, vitamin C 0-1%, sodium carboxymethyl cellulose 0-3%, gelatin 0-1%, glycerin 1-3%, and the balance being water; The mass fraction of the bleached shellac is not 0.

[0022] The composite coating material of this invention comprises 0-5% bleached shellac by mass fraction, which can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or 4.5% in specific embodiments of this invention; the bleached shellac solution contains 5% bleached shellac by mass fraction. Bleached shellac has moisturizing and preservative effects, and also acts as a film-forming agent.

[0023] The composite coating material of this invention comprises 0-1% tea polyphenols by mass fraction, which can be 0%, 0.4%, 0.6%, 0.8%, or 1% in specific embodiments of this invention. Tea polyphenols have antioxidant and antibacterial effects.

[0024] The composite coating material of this invention comprises 0-1% grape seed extract by mass fraction, which may be 0%, 0.5%, 0.6%, or 1% in specific embodiments of this invention. Grape seed extract has antioxidant and antibacterial properties.

[0025] By mass fraction, the raw materials of the composite coating material of the present invention include 0-1% fish collagen peptides, which can be 0%, 0.1%, or 1% in specific embodiments of the present invention. Fish collagen peptides can provide moisturizing effects and also play a role in film formation.

[0026] The composite coating material of this invention comprises 0-1% vitamin C by mass fraction, which may be 0%, 0.8%, or 1% in specific embodiments of this invention. Vitamin C can promote the antioxidant reaction of fruit pulp and act as an antibacterial agent.

[0027] By mass fraction, the raw materials of the composite coating material of the present invention include 0-3% sodium carboxymethyl cellulose, which can be 0%, 1%, 1.2% or 2% in specific embodiments of the present invention, and plays a role in film formation.

[0028] By mass fraction, the raw materials of the composite coating material of the present invention include 0-1% gelatin, which can be 0%, 0.6%, or 1% in specific embodiments of the present invention. Sodium carboxymethyl cellulose and gelatin can improve the viscosity of the preservative and the elasticity of the fruit pulp, and also play a role in film formation.

[0029] The raw materials of the composite coating material of the present invention, by mass fraction, include 1-3% glycerol, which may be 1%, 2% or 3% in specific embodiments of the present invention. Glycerol acts as a plasticizer.

[0030] The raw materials of the composite coating material of the present invention, by mass fraction, include the balance of water.

[0031] In this invention, the pH value of the composite coating material is preferably 7 to 7.5, and in specific embodiments of this invention, it can be 7.1, 7.2, 7.3 or 7.4.

[0032] The present invention also provides a method for preparing the composite coating material described in the above technical solution, comprising the following steps: The raw materials for the composite coating material are mixed to obtain the composite coating material.

[0033] In this invention, when the raw materials include ammonia, the mixing preferably includes: mixing bleached shellac with ammonia and then adding some water for dilution to obtain a bleached shellac solution; dissolving glycerin in some water and then sequentially adding the bleached shellac solution, vitamin C, fish collagen peptides, grape seed extract, tea polyphenols, sodium carboxymethyl cellulose, gelatin, and the remaining water.

[0034] In this invention, the mass fraction of bleached shellac in the bleached shellac solution is preferably 5%.

[0035] In this invention, the preferred temperature for mixing the bleached shellac with ammonia is 55°C, and the dilution is preferably carried out at room temperature.

[0036] The present invention also provides the application of the composite coating material described in the above technical solution or the composite coating material prepared by the preparation method described in the above technical solution in the field of crop preservation.

[0037] In this invention, the crop preferably includes fruit; the fruit preferably includes banana.

[0038] In this invention, the application preferably includes the following steps: forming a film on the surface of crops with a composite coating material.

[0039] In this invention, the film formation preferably includes impregnation, spraying, or coating followed by drying.

[0040] The composite coating preservation material provided by this invention uses natural edible polymers (such as polysaccharides (sodium carboxymethyl cellulose), proteins (fish collagen peptides and gelatin), lipids (bleached shellac), etc.) as the base film material, and adds edible plasticizers, film-forming agents, antibacterial agents, etc. Through the interaction between different molecules, it is prepared by coating the surface of fresh fruits and vegetables using methods such as spraying, wrapping, and dipping. This results in a functional coating material with preservation and antibacterial effects. It aims to extend the shelf life of fruits and vegetables by forming a protective edible film layer that blocks the penetration of water vapor, oxygen, or various solutes, thereby reducing the rate of spoilage during cross-regional transportation, minimizing storage losses, improving the storage performance of fruits and vegetables, and ultimately protecting their nutritional components, color, aroma, flavor, and shape.

[0041] This invention develops an edible fruit and vegetable coating preservation material with antibacterial activity, high strength, and controllability by combining natural active functional components with an integrated edible coating preparation technology. This not only provides a theoretical basis for the storage, transportation, and distribution of fresh fruits and vegetables, but also has a huge driving effect and economic value on the development of the fruit and vegetable e-commerce industry.

[0042] The following detailed description of the composite coating materials and their applications provided by the present invention, in conjunction with specific embodiments, should not be construed as limiting the scope of protection of the present invention.

[0043] Table 1 Raw materials used in the examples and comparative examples

[0044] Example 1 Preparation of bleached shellac aqueous solution: Take the raw materials according to the proportions in Table 2: Table 2 Raw materials for bleached shellac aqueous solution

[0045] The solution is prepared by the following method: First, prepare ammonia water of the relevant concentration, heat the prepared solution in a water bath to 55°C, add bleached shellac and stir for one hour until it is completely dissolved, continue to cool and stir to room temperature, add an appropriate amount of water and mix to obtain a bleached shellac solution with a bleached shellac content of 5%.

[0046] Preparation of shellac composite coating material: Take the raw materials according to the proportions in Table 3: Table 3 Raw materials for shellac composite coating

[0047] The following method was used: first, dissolve glycerin in an appropriate amount of water, then add bleached shellac solution, stir and mix thoroughly, then add the remaining raw materials and mix thoroughly to obtain 100g of shellac composite coating material.

[0048] Banana coating preservation method: Coat the bananas with the prepared preservative as described above. Specifically, immerse the bananas in the prepared preservative for 3 minutes, then remove and let them air dry. Then pack them in cardboard boxes and store them at room temperature.

[0049] Example 2 The bleached shellac solution was prepared as in Example 1.

[0050] Preparation of shellac composite coating material: Prepare the raw materials according to the proportions in Table 4: Table 4 Raw materials for shellac composite coating

[0051] The following method is used: first, dissolve glycerin in an appropriate amount of water, then add bleached shellac solution, stir until fully mixed, then add the remaining raw materials and mix until uniform to obtain shellac composite coating material.

[0052] Banana coating preservation method: Coat the bananas with the prepared preservative as described above. Specifically, immerse the bananas in the prepared preservative for 3 minutes, then remove and let them air dry. Then pack them in cardboard boxes and store them at room temperature.

[0053] Example 3 The bleached shellac solution was prepared as in Example 1.

[0054] Preparation of shellac composite coating material: Prepare the raw materials according to the proportions in Table 5: Table 5 Raw materials for shellac composite coating

[0055] The following method is used: first, dissolve glycerin in an appropriate amount of water, then add bleached shellac solution, stir until fully mixed, then add the remaining raw materials and mix until uniform to obtain shellac composite coating material.

[0056] Banana coating preservation method: Coat the bananas with the prepared preservative as described above. Specifically, immerse the bananas in the prepared preservative for 3 minutes, then remove and let them air dry. Then pack them in cardboard boxes and store them at room temperature.

[0057] Example 4 The bleached shellac solution was prepared as in Example 1.

[0058] Preparation of shellac composite coating material: Prepare the raw materials according to the proportions in Table 6: Table 6 Raw materials for shellac composite coating

[0059] The following method is used: first, dissolve glycerin in an appropriate amount of water, then add bleached shellac solution, stir until fully mixed, then add the remaining raw materials and mix until uniform to obtain shellac composite coating material.

[0060] Banana coating preservation method: Coat the bananas with the prepared preservative as described above. Specifically, immerse the bananas in the prepared preservative for 1 minute, then remove and let them air dry. Then pack them in cardboard boxes and store them at room temperature.

[0061] Example 5 The bleached shellac solution was prepared as in Example 1.

[0062] Preparation of shellac composite coating material: Prepare the raw materials according to the proportions in Table 7: Table 7 Raw materials for shellac composite coating

[0063] The following method is used: first, dissolve glycerin in an appropriate amount of water, then add bleached shellac solution, stir until fully mixed, then add the remaining raw materials and mix until uniform to obtain shellac composite coating material.

[0064] Banana coating preservation method: Coat the bananas with the prepared preservative as described above. Specifically, immerse the bananas in the prepared preservative for 1 minute, then remove and let them air dry. Then pack them in cardboard boxes and store them at room temperature.

[0065] Example 6 The bleached shellac solution was prepared as in Example 1.

[0066] Preparation of shellac composite coating material: Prepare the raw materials according to the proportions in Table 8: Table 8 Raw materials for shellac composite coating

[0067] The following method is used: first, dissolve glycerin in an appropriate amount of water, then add bleached shellac solution, stir until fully mixed, then add the remaining raw materials and mix until uniform to obtain shellac composite coating material.

[0068] Banana coating preservation method: Coat the bananas with the prepared preservative as described above. Specifically, immerse the bananas in the prepared preservative for 1 minute, then remove and let them air dry. Then pack them in cardboard boxes and store them at room temperature.

[0069] Comparative Example 1 Prepare the raw materials according to the proportions in Table 9: Table 9 Raw materials for shellac composite coating

[0070] The shellac composite coating material is obtained by dissolving glycerin in an appropriate amount of water, adding the remaining raw materials, and mixing them evenly.

[0071] Banana coating preservation method: Coat the bananas with the prepared preservative as described above. Specifically, immerse the bananas in the prepared preservative for 3 minutes, then remove and let them air dry. Then pack them in cardboard boxes and store them at room temperature.

[0072] Example 7 The bleached shellac solution was prepared as in Example 1.

[0073] Preparation of shellac composite coating material: Prepare the raw materials according to the proportions in Table 10: Table 10 Raw materials for shellac composite coating

[0074] The following method is used: first, dissolve glycerin in an appropriate amount of water, then add bleached shellac solution, stir until fully mixed, then add the remaining raw materials and mix until uniform to obtain shellac composite coating material.

[0075] Banana coating preservation method: Coat the bananas with the prepared preservative as described above. Specifically, immerse the bananas in the prepared preservative for 3 minutes, then remove and let them air dry. Then pack them in cardboard boxes and store them at room temperature.

[0076] Comparative Example 2 Prepare the raw materials according to the proportions in Table 11: Table 11 Raw materials for shellac composite coating

[0077] The shellac composite coating material is obtained by dissolving glycerin in an appropriate amount of water, adding the remaining raw materials, and mixing them evenly.

[0078] Banana coating preservation method: Coat the bananas with the prepared preservative as described above. Specifically, immerse the bananas in the prepared preservative for 3 minutes, then remove and let them air dry. Then pack them in cardboard boxes and store them at room temperature.

[0079] The coating obtained by air drying is brittle and easily breaks during the peeling process, which limits its performance testing and practical application.

[0080] Comparative Example 3 Prepare the raw materials according to the proportions in Table 12: Table 12 Raw materials for shellac composite coating

[0081] The shellac composite coating material is obtained by dissolving glycerin in an appropriate amount of water, adding the remaining raw materials, and mixing them evenly.

[0082] Banana coating preservation method: Coat the bananas with the prepared preservative as described above. Specifically, immerse the bananas in the prepared preservative for 3 minutes, then remove and let them air dry. Then pack them in cardboard boxes and store them at room temperature.

[0083] The resulting shellac composite coating material has high viscosity and poor leveling properties. After drying, the coating surface is uneven and prone to cracking, peeling, and breaking, which limits its practical application.

[0084] Comparative Example 4 Prepare the raw materials according to the proportions in Table 13: Table 13 Raw materials for shellac composite coating

[0085] The shellac composite coating material is obtained by mixing the raw materials evenly using the following method.

[0086] Banana coating preservation method: Coat the bananas with the prepared preservative as described above. Specifically, immerse the bananas in the prepared preservative for 3 minutes, then remove and let them air dry. Then pack them in cardboard boxes and store them at room temperature.

[0087] The coating has poor flexibility, making it difficult to coat completely, which limits its practical application.

[0088] Comparative Example 5 Prepare the raw materials according to the proportions in Table 14: Table 14 Raw materials for shellac composite coating

[0089] The shellac composite coating material is obtained by dissolving glycerin in an appropriate amount of water, adding the remaining raw materials, and mixing them evenly.

[0090] Banana coating preservation method: Coat the bananas with the prepared preservative as described above. Specifically, immerse the bananas in the prepared preservative for 3 minutes, then remove and let them air dry. Then pack them in cardboard boxes and store them at room temperature.

[0091] The coating is severely sticky and self-adhesive, with oily surface, increased size, deformation and wrinkling, which limits its performance testing and practical application.

[0092] Comparative Example 6 Prepare the raw materials according to the proportions in Table 15: Table 15 Raw materials for shellac composite coating

[0093] The following method is used: first, dissolve glycerin in an appropriate amount of water, then add bleached shellac solution, stir until fully mixed, then add the remaining raw materials and mix until uniform to obtain shellac composite coating material.

[0094] Banana coating preservation method: Coat the bananas with the prepared preservative as described above. Specifically, immerse the bananas in the prepared preservative for 1 minute, then remove and let them air dry. Then pack them in cardboard boxes and store them at room temperature.

[0095] Replacing tea polyphenols and grape seed extract with vitamin C powder, which has similar functions, reduces the preservation effect of the coating on bananas by about 30%.

[0096] Comparative Example 7 Prepare the raw materials according to the proportions in Table 16: Table 16 Raw materials for shellac composite coating

[0097] The following method is used: first, dissolve glycerin in an appropriate amount of water, then add bleached shellac solution, stir until fully mixed, then add the remaining raw materials and mix until uniform to obtain shellac composite coating material.

[0098] Banana coating preservation method: Coat the bananas with the prepared preservative as described above. Specifically, immerse the bananas in the prepared preservative for 1 minute, then remove and let them air dry. Then pack them in cardboard boxes and store them at room temperature.

[0099] When starch with similar functions is used instead of sodium carboxymethyl cellulose, the resulting coating hardens and cracks at low temperatures, easily gelatinizes and becomes sticky at high temperatures and humidity, and its strength decreases, making it prone to breakage, which limits its performance testing and practical application.

[0100] Comparative Example 8 Prepare the raw materials according to the proportions in Table 17: Table 17 Raw materials for shellac composite coating

[0101] The following method is used: first, dissolve glycerin in an appropriate amount of water, then add bleached shellac solution, stir until fully mixed, then add the remaining raw materials and mix until uniform to obtain shellac composite coating material.

[0102] Banana coating preservation method: Coat the bananas with the prepared preservative as described above. Specifically, immerse the bananas in the prepared preservative for 1 minute, then remove and let them air dry. Then pack them in cardboard boxes and store them at room temperature.

[0103] Replacing sodium carboxymethyl cellulose with pectin, which has similar function, results in a coating that is soft, easily broken, and has poor water retention (approximately 83%) after drying, limiting its performance testing and practical application.

[0104] Comparative Example 8 Prepare the raw materials according to the proportions in Table 18: Table 18 Raw materials for shellac composite coating

[0105] The following method is used: first, dissolve polyethylene glycol in an appropriate amount of water, then add bleached shellac solution, stir until fully mixed, then add the remaining raw materials and mix until uniform to obtain shellac composite coating material.

[0106] Banana coating preservation method: Coat the bananas with the prepared preservative as described above. Specifically, immerse the bananas in the prepared preservative for 1 minute, then remove and let them air dry. Then pack them in cardboard boxes and store them at room temperature.

[0107] Replacing glycerin with polyethylene glycol (PEG200), which has a similar function, results in a coating film that has the risk of precipitation and migration after drying, limiting its practical application in the field of food preservation.

[0108] The obtained coating material was poured into a stainless steel pan, spread evenly, and dried to obtain a coating with a thickness of 0.1~0.2mm. The dried coating was then placed on a bottle containing an equal amount of water, and the total weight was recorded as W0. The coating was weighed again at intervals of 0.5 days, 1.0 days, 1.5 days, 2.0 days, 2.5 days, 3.0 days, 3.5 days, and 4.0 days, and the weight was recorded as Wi. The water retention rate (W%) of the shellac-based preservative coating was calculated according to formula (1).

[0109] Equation (1).

[0110] Table 19 Water retention rate of shellac composite coating materials

[0111] As shown in Table 19, the water retention rate data of the shellac composite coating material shows that: Example 2 could not be tested for water retention rate because the film was too brittle, and Example 3 could not form a complete film. The water retention rates of the remaining samples that could form films normally, namely Example 1, Example 4, Example 5, Example 6, Example 7, and Comparative Example 1, ranged from 87.36% to 92.09%. Among them, Example 7 had the best water retention performance (92.09%), and Example 4 had the lowest water retention rate. Overall, all the coatings in each combination had good water retention capacity. The formulation composition directly affects the film forming state and water retention effect, and thus affects its actual application effect.

[0112] Example 7: Infrared spectra of shellac composite coating material and raw materials are shown below. Figure 1 As shown.

[0113] Figure 1 The infrared spectrum of the shellac composite coating material and raw materials in Example 7 is shown.

[0114] Depend on Figure 1 It can be seen that the shellac composite coating material integrates the characteristic peaks of the raw materials, 3000-3600 cm⁻¹. -1 The hydroxyl peak is contributed by tea polyphenols, bleached shellac, grape seed extract, and sodium carboxymethyl cellulose, forming a superimposed broad peak. Bleached shellac retains the peak at 1650-1750 cm⁻¹. -1 The characteristic absorption peak of α,β-unsaturated ketones is observed at 1030 cm⁻¹, and tea polyphenols exhibit this characteristic absorption peak at 1030 cm⁻¹. -1 The absorption peak of COC at 575 cm⁻¹ -1 The absorption peak of CO and the 2365 cm⁻¹ in grape seed extract. -1 The characteristic absorption peak of the alkyne group is observed at 1000-1200 cm⁻¹. -1 The CO peak at this location integrates the characteristic peaks of sodium carboxymethyl cellulose. During material formation, the 3000-3600 cm⁻¹ peak... -1 hydroxyl peak and 1600 cm -1 The nearby carbonyl peaks showed a significant enhancement, which is likely due to intermolecular hydrogen bonds. The results indicate that the functional group structure of the shellac composite coating material conforms to the expected changes in material preparation compared to the raw materials, and the intensity of the absorption peaks also reflects the presence of intermolecular hydrogen bonds.

[0115] Figure 2 The image shows the TG-DTG diagram of the shellac composite coating material and raw materials in Example 7.

[0116] Depend on Figure 2It was observed that bleached shellac exhibited an endothermic peak at 360℃, and its corresponding main decomposition process was consistent with the decomposition behavior observed in TG-DTG. The shellac-free composite coating material showed a weak endothermic peak at 190℃, possibly due to the weak interaction between residual moisture and the sodium carboxymethyl cellulose matrix. In contrast, the shellac composite coating material showed a significant high-temperature endothermic peak at 440℃, exceeding the decomposition temperatures of both bleached shellac and shellac-free composite coating materials. This indicates that when the bleached shellac content is high, the intermolecular hydrogen bonds formed between it and sodium carboxymethyl cellulose can significantly improve the material's thermal stability. Furthermore, TG-DTG analysis showed that the preservative coating material underwent multi-step decomposition, proving that the addition of bleached shellac can slow down the thermal decomposition of the coating and improve its thermal stability.

[0117] Figure 3 Scanning electron microscope images of the coating formed by the shellac composite coating material in Comparative Example 1 (left) and the coating formed by the shellac composite coating material in Example 7 (right).

[0118] The microstructure, size, and elemental composition and distribution of some raw materials and coating materials with different ratios were characterized by SEM. Figure 3 It can be seen from the comparison that with the addition of bleached shellac, the surface cracks and pore size of the coating were significantly improved. The increase in surface cracks in the coating will enhance the water migration of fruit tissue and increase the respiration intensity of fruit by increasing the gas exchange area.

[0119] The obtained coating material was poured into a stainless steel pan, spread evenly, and then dried to obtain a coating with a thickness of 0.1~0.2 mm. The coating was measured at three random locations using an optical transmittance meter. The average value of the three measurements was taken as the final visible light transmittance and ultraviolet and infrared light blocking rate. The results are shown in Tables 20~22.

[0120] Table 20 Visible light transmittance of coatings obtained in Examples 1-7 and Comparative Example 1

[0121] Table 21 UV blocking efficiency of coatings obtained in Examples 1-7 and Comparative Example 1

[0122] Table 22 Infrared blocking rates of coatings obtained in Examples 1-7 and Comparative Example 1

[0123] Tests show that the visible light transmittance of the shellac composite coating material is 50.6±0.7, which facilitates observation of the preservation status and avoids quality degradation caused by excessive light transmission; its ultraviolet blocking rate is 99.0±0.6, effectively blocking ultraviolet rays and reducing the impact of photo-oxidation on preserved fruits, thus extending shelf life; its infrared blocking rate is 7.6±0.4, which helps reduce the light energy limitation of fruit photosynthesis and respiration while delaying yellowing and water loss.

[0124] 10 ml of the shellac composite coating solution from Comparative Example 1 and Example 7 was poured into a stainless steel pan, shaken to spread it evenly, and allowed to dry at room temperature. The film was then peeled off, cut, and placed in natural soil. The dimensional changes of the film were observed and recorded by photographing to evaluate its degradation effect. The results are as follows: Figure 4 As shown.

[0125] Figure 4 The degradation results are shown for the film formed by Comparative Example 1 without shellac composite coating material (left) and the film formed by Example (8) with shellac composite coating material (right).

[0126] from Figure 4 It can be seen that the shellac composite coating material exhibits outstanding degradation ability, completely degrading in approximately 27 days compared to the non-shellac composite coating material. This indicates that the shellac composite coating material not only ensures the stability of the coating function during the shelf life but also verifies its complete degradability in nature.

[0127] Figure 5 The appearance of the banana, the banana prepared in Comparative Example 1, and the banana prepared in Example 7.

[0128] Depend on Figure 5 It can be seen that the control group (i.e., bananas) developed brown spots on day 3, and by day 5, the brown spot coverage reached 25% of the entire banana peel. At this point, experimental group 1 (without shellac composite coating material treatment) only began to show brown spots, while experimental group 2 (shellac composite coating material treatment group) had not yet shown any brown spots. After a storage period of 9 days, the brown spot coverage in the control group was close to 100%, while the brown spot coverage in experimental group 1 did not exceed 25%, and experimental group 2 began to show a small number of brown spots. Compared to the control group and experimental group 1, the brown spot coverage in experimental group 3 remained below 30%, and its color retention was significantly better than other systems.

[0129] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite coating material, characterized in that, By mass fraction, it includes the following raw materials: Bleached shellac 0-5%, tea polyphenols 0-1%, grape seed extract 0-1%, fish collagen peptides 0-1%, vitamin C 0-1%, sodium carboxymethyl cellulose 0-3%, gelatin 0-1%, glycerin 1-3%, and the balance being water; The mass fraction of the bleached shellac is not 0.

2. The composite coating material according to claim 1, characterized in that, The raw materials also include, by mass fraction: 0-3% ammonia water, and not 0%; The concentration of the ammonia water is 0.6 wt%.

3. The composite coating material according to claim 1, characterized in that, The pH value of the composite coating material is 7~7.

5.

4. The method for preparing the composite coating material according to any one of claims 1 to 3, characterized in that, Includes the following steps: The raw materials for the composite coating material are mixed to obtain the composite coating material.

5. The preparation method according to claim 4, characterized in that, When the raw materials include ammonia, the mixing includes: mixing bleached shellac with ammonia and then adding some water to dilute it to obtain a bleached shellac solution; dissolving glycerin in some water and then sequentially adding the bleached shellac solution, vitamin C, fish collagen peptides, grape seed extract, tea polyphenols, sodium carboxymethyl cellulose, gelatin, and the remaining water.

6. The preparation method according to claim 5, characterized in that, The temperature at which the bleached shellac is mixed with ammonia is 25~65℃.

7. The application of the composite coating material according to any one of claims 1 to 3 or the composite coating material prepared by the preparation method according to any one of claims 4 to 6 in the field of crop preservation.

8. The application according to claim 7, characterized in that, The crops include fruits; the fruits include bananas.

9. The application according to claim 7, characterized in that, The application includes the following steps: forming a film on the surface of crops with a composite coating material.

10. The application according to claim 9, characterized in that, The film formation includes impregnation, spraying, or coating followed by drying.

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