Temperature response type modified atmosphere coating material for fresh keeping of fruits and vegetables and preparation method of temperature response type modified atmosphere coating material

Abstract

The invention belongs to the technical field of fruit and vegetable preservation, and relates to a temperature response type modified atmosphere coating material for fruit and vegetable preservation and a preparation method thereof.The temperature response type modified atmosphere coating material for fruit and vegetable preservation comprises a film forming substrate and further comprises a temperature response material, the temperature response material is one or more of fatty acid, fatty alcohol or ester phase change materials; the mass fraction of the temperature response material is 1.0%-31.0%. According to the temperature response type modified atmosphere coating material for fruit and vegetable fresh-keeping, the gas permeability can be automatically adjusted along with the change of the environment temperature, so that the breathing requirements of fruits are met at different temperatures, and the optimal fresh-keeping effect is achieved; the film forming substrate and the temperature response material are biodegradable materials with good biocompatibility, and are safe and non-toxic; and the coating material is simple in preparation process, can be prepared through simple blending and emulsification, and does not need complex equipment or chemical reaction.

Description

Technical Field

[0001] This invention belongs to the field of fruit and vegetable preservation technology, and relates to a temperature-responsive modified atmosphere coating material for fruit and vegetable preservation and its preparation method. Background Technology

[0002] In the field of postharvest preservation of fruits and vegetables, low-temperature storage combined with edible coating treatment is a common method to extend shelf life. Edible coatings, such as those based on hydroxypropyl methylcellulose (HPMC), can inhibit respiration and delay senescence by regulating the exchange of O2 and CO2 gases on the fruit surface.

[0003] Among existing technologies related to fruit and vegetable coatings, Chinese invention patents CN202211181440.2 and CN202211397647.3 disclose coatings based on polysaccharides or proteins. These coatings are formed by directly spraying or coating polymer solutions onto the surface of fruits and vegetables, and after drying, they act as a polymer film, blocking gas exchange, reducing respiration intensity, and moisturizing. Furthermore, they enhance the antibacterial ability of the coating by introducing antibacterial chemical groups (such as imidazole salt groups) or directly adding antibacterial active substances (such as nisin) to the coating solution. However, these technologies mainly focus on improving the barrier properties and antibacterial and antioxidant functions of the coating, without addressing the relationship between the gas permeability of the coating and temperature.

[0004] Currently, coatings are only developed for specific scenarios, such as storage and sales, but cannot be applied to various post-harvest scenarios for fruits and vegetables. Although there are research attempts, such as Chinese invention patents CN202210459244.0 and CN202211064660.7, to improve coating performance by adding nanomaterials or active substances, none of them have achieved intelligent temperature response regulation of gas permeability.

[0005] Within the temperature range of 0℃-40℃, existing coating materials for fruit and vegetable preservation exhibit almost no temperature-responsive gas permeability, while the respiration rate of fruits is highly sensitive. When temperature fluctuations occur during cold chain storage and transportation, or when fruits and vegetables are removed from the low-temperature environment at retail, a fixed low permeability can easily lead to CO2 accumulation inside the fruit, triggering anaerobic respiration and spoilage. Conversely, when the temperature decreases, excessively high permeability may not effectively inhibit respiration, resulting in nutrient loss. Therefore, developing a coating that can respond to temperature changes and automatically adjust gas permeability is of great significance for reducing post-harvest losses and adapting to the unstable cold chain environment. Summary of the Invention

[0006] The main objective of this invention is to overcome the deficiencies in the prior art and provide a temperature-responsive modified atmosphere coating material for fruit and vegetable preservation and its preparation method.

[0007] To achieve the above objectives, the specific technical solution is as follows: This invention provides a temperature-responsive modified atmosphere coating material for preserving fruits and vegetables, comprising a film-forming matrix and a temperature-responsive material, wherein the temperature-responsive material is one or more of fatty acid, fatty alcohol, or ester phase change materials; the mass fraction of the temperature-responsive material is 1%-31%, preferably 4.3%-18.4%.

[0008] This invention relates to a film-forming matrix for temperature-responsive modified atmosphere coating materials used in fruit and vegetable preservation. This matrix forms the main structure of the coating, providing basic gas barrier properties and mechanical strength, and serves as a carrier for the temperature-responsive material. The solid-liquid phase transition behavior of the temperature-responsive material can alter the free volume and molecular chain mobility within the coating, allowing the oxygen permeability (OTR) of the coating to dynamically change within the range of 10-30°C. This enables the coating material to automatically adjust its permeability in response to temperature fluctuations, thereby matching the respiration requirements of the fruit at different temperatures and achieving temperature-responsive regulation of gas permeability to achieve optimal preservation results.

[0009] Furthermore, the phase transition temperature of the temperature-responsive material is greater than 4 °C.

[0010] Furthermore, the fatty acid phase change material is one or more of oleic acid, undecanoic acid (UA), lauric acid, palmitic acid, and decanoic acid; the fatty alcohol phase change material is one or more of dodecanol and tridecanol; and the ester phase change material is a mono- or diglyceride ester.

[0011] The temperature-responsive material selected in this invention can be uniformly dispersed in the film-forming matrix; the phase change material can achieve different phase change temperature points, which can be obtained naturally.

[0012] Furthermore, the temperature-responsive material includes undecanoic acid.

[0013] This invention introduces undecanoic acid (UA), a phase change material, into a film-forming matrix. Utilizing the solid-liquid phase change that UA undergoes within a specific temperature range of 10-30°C, the microstructure of the coating is altered, thereby dynamically regulating the permeability of oxygen and carbon dioxide. As the temperature increases, UA melts, increasing chain segment mobility and gas diffusion paths, thus increasing the coating's permeability. Conversely, as the temperature decreases, UA crystallizes, reducing diffusion paths and decreasing the coating's permeability. Undecanoic acid is a common component in food fats and oils and is permitted for use as a food flavoring (FEMA 3245). The resulting coating layer can be removed by washing.

[0014] Furthermore, the film-forming matrix is ​​an edible polymer material, including cellulose, polysaccharides, proteins, or synthetic polymer materials.

[0015] Furthermore, the film-forming matrix is ​​one or more of hydroxypropyl methylcellulose (HPMC), carboxymethyl cellulose, pullulan, chitosan soy protein isolate, zein, or polyvinyl alcohol.

[0016] The film-forming matrix selected in this invention is a edible, biodegradable, safe, and film-forming polymer material.

[0017] Furthermore, the temperature-responsive modified atmosphere coating material for fruit and vegetable preservation also includes additives, which are one or more of plasticizers, emulsifiers, antioxidants, or nucleating agents.

[0018] The plasticizers used in this invention can improve the flexibility and adhesion of the coating film; the emulsifiers help stabilize the dispersion of temperature-responsive materials; the antioxidants can prevent lipid oxidation and improve the stability of the coating film; and the nucleating agents can regulate the phase change temperature of the phase change material and alleviate the supercooling phenomenon.

[0019] Furthermore, the plasticizer is glycerin, the emulsifier is Tween 80, the antioxidant is vitamin E, and the nucleating agent is an inorganic salt or nanoparticles.

[0020] In one specific embodiment of the present invention, the temperature-responsive modified atmosphere coating material for fruit and vegetable preservation includes a film-forming matrix of hydroxypropyl methylcellulose (HPMC) and a temperature-responsive material undecanoic acid (UA), wherein the mass percentage of undecanoic acid is 3.0%-31%, preferably 4.0%-18.4%.

[0021] The present invention provides a temperature-responsive modified atmosphere coating material for preserving fruits and vegetables. Under temperature fluctuation conditions (10℃ to 20℃ or 30℃), the fruits and vegetables treated with this material have a low rate of decay and can better maintain fruit firmness, titratable acid and ascorbic acid content.

[0022] The working principle of this invention for temperature-responsive modified atmosphere coating materials for fruit and vegetable preservation is as follows: Figure 1 As shown, when the ambient temperature rises, the UA dispersed in the HPMC matrix absorbs heat and undergoes a solid-liquid phase transition, changing from an ordered crystalline structure to a disordered liquid state. This process increases the mobility of polymer chain segments, expands the free volume between molecules, and provides more diffusion paths and higher diffusion rates for gas molecules (O2, CO2), thereby increasing the oxygen permeability (OTR) of the coating. Conversely, when the temperature decreases, the UA releases heat and undergoes a liquid-solid phase transition, reforming into crystals, restricting chain segment movement, reducing free volume, and thus decreasing gas permeability. This reversible change in permeability can match the trend of fruit respiration rate with temperature: providing high permeability to prevent anaerobic respiration during high-temperature, high-respiration conditions; and providing low permeability to effectively inhibit respiration consumption during low-temperature, low-respiration conditions.

[0023] In one specific embodiment of the present invention, the temperature-responsive modified atmosphere coating material for fruit and vegetable preservation includes a film-forming matrix pullulan polysaccharide, and also includes a mixture of undecanoic acid and palmitic acid as temperature-responsive materials. The mass percentage of the mixture of undecanoic acid and palmitic acid is 1%-18.4%, preferably 2.2%-4.3%; the mass ratio of undecanoic acid to palmitic acid is preferably 1:1.

[0024] The present invention provides a temperature-responsive modified atmosphere coating material for preserving fruits and vegetables. Under temperature fluctuation conditions (10℃ to 20℃ or 30℃), the fruits and vegetables treated with this material have a low rate of decay and can better maintain fruit firmness, titratable acid and ascorbic acid content.

[0025] The present invention also provides a method for preparing the above-mentioned temperature-responsive modified atmosphere coating material for fruit and vegetable preservation, wherein the components are blended to prepare an emulsion, or the emulsion is cast to form a film material.

[0026] The coating material emulsion of this invention can be evenly applied to the surface of harvested fruits and vegetables by means of dipping, spraying or brushing, and then dried by air drying or blowing to form a transparent film. It can then be packaged, stored and transported in a conventional manner. The coating can automatically play a temperature response regulation function in the subsequent cold chain or room temperature sales process.

[0027] Specifically, the preparation method of the above-mentioned temperature-responsive modified atmosphere coating material for fruit and vegetable preservation includes the following steps: (1) Disperse the film-forming matrix in deionized water, stir until there are no obvious particles, and let it stand at 3-5℃ for 10-15 hours to completely dissolve it, so as to obtain a 1.0-3.0% (w / v) aqueous solution of the film-forming matrix; (2) After heating the film-forming matrix aqueous solution and the temperature-responsive material in a water bath at 30-70℃, the temperature-responsive material is added to the film-forming matrix aqueous solution and stirred continuously at 30-70℃ for 5-7 hours to form a uniform solution or emulsion. (3) After naturally cooling to room temperature and standing to defoam, a coating solution or emulsion is obtained.

[0028] The preparation method of the present invention can easily produce a modified atmosphere coating or film material with temperature-responsive properties for the preservation of fruits and vegetables.

[0029] Compared with the prior art, the present invention has the following significant advantages: The temperature-responsive modified atmosphere coating material for fruit and vegetable preservation provided by this invention can automatically adjust its gas permeability according to changes in ambient temperature, thereby matching the respiration needs of the fruit at different temperatures and achieving the best preservation effect. Both the film-forming matrix and the temperature-responsive material are biodegradable and biocompatible, and are safe and non-toxic. Moreover, the preparation process of the coating material is simple and can be prepared by simple blending and emulsification without the need for complex equipment or chemical reactions. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram illustrating the principle of the temperature-responsive modified atmosphere coating material for fruit and vegetable preservation according to the present invention. Figure 2 These are the infrared spectra of the UA and UA / HPMC flat sheet films of this invention; Figure 3 These are the thermogravimetric curves of the UA and UA / HPMC flat sheet films of this invention; Figure 4 These are the differential thermogravimetric curves of the UA and UA / HPMC flat sheet membranes of this invention; Figure 5 These are the differential scanning calorimetry curves of the UA, HPMC, and UA / HPMC flat sheet films of this invention; Figure 6 This is the temperature-modulus curve of the UA / HPMC coating liquid of the present invention; Solid shape: energy storage modulus; Hollow shape: loss modulus; Figure 7 This is an image showing the appearance of the red mandarin orange fruit during storage at 10°C to 20°C according to the present invention; Figure 8 This is a graph showing the rate of decay of tangerine fruit during storage at 10℃ to 20℃ according to the present invention; Figure 9 This is a diagram showing the respiration rate of tangerine fruit during storage at 10℃ to 20℃ according to the present invention. Figure 10 This is an image showing the appearance of the red mandarin orange fruit during storage at 10℃ to 30℃ according to the present invention; Figure 11 This is a graph showing the rate of decay of tangerine fruit during storage at 10℃ to 30℃ according to the present invention. Figure 12 This is a diagram showing the respiration rate of tangerine fruit during storage at 10℃ to 30℃ according to the present invention. Figure 13 This is an image showing the appearance of the chili peppers during storage at 10°C to 20°C according to the present invention; Figure 14 This is a diagram showing the respiration rate of chili peppers during storage at 10°C to 20°C according to the present invention. Figure 15 This is an image showing the appearance of the chili peppers during storage at 10°C to 30°C according to the present invention; Figure 16 This is a diagram showing the respiration rate of chili peppers during storage at 10°C to 30°C according to the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0033] Unless otherwise specified in the embodiments of the present invention, the techniques or conditions described in the literature in this field or the product instructions shall be followed; if the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be purchased through legitimate channels.

[0034] Example 1 This embodiment provides a UA / HPMC temperature-responsive modified atmosphere coating material for fruit and vegetable preservation, and the preparation method is as follows: (1) Weigh 8g of HPMC powder and disperse it in 400mL of deionized water. Stir until there are no obvious particles. Let it stand at 4℃ overnight to completely dissolve it and obtain a 2% (w / v) HPMC solution. (2) Heat HPMC solution and undecanoic acid (UA) in a 40°C water bath. Take 100 μL, 500 μL and 1000 μL of UA respectively and add them to 100 mL of HPMC solution. Stir continuously at 40°C for 6 hours to form a uniform white emulsion. (3) Cool naturally to room temperature and let stand overnight to defoam, to obtain coating emulsions marked "100UA", "500UA" and "1000UA".

[0035] Example 2: The temperature-responsive modified atmosphere coating material solution for fruit and vegetable preservation provided in this embodiment is prepared by the following method: (1) Weigh 6g pullulan powder and disperse it in 400mL of deionized water. Stir until there are no obvious particles. Let it stand at 4℃ overnight to completely dissolve it and obtain a 1.5% (w / v) pullulan solution. (2) Heat pullulan polysaccharide solution and undecanoic acid and palmitic acid mixture (5:5, w / w) in a 60°C water bath respectively; take 50 μL, 100 μL and 500 μL of mixed fatty acids respectively and add them to 100 mL pullulan polysaccharide solution, and stir continuously at 60°C for 6 hours to form a uniform white emulsion. (3) Cool naturally to room temperature and let stand overnight to defoam, to obtain coating emulsions marked "100UA-2", "500UA-2" and "1000UA-2".

[0036] Application Experiment: The UA / HPMC temperature-responsive modified atmosphere coating emulsion prepared in Example 1 was applied to the preservation of tangerines: Selected tangerines of uniform size, maturity, and without damage were disinfected with a 2% (v / v) sodium hypochlorite solution for 1 minute, rinsed with deionized water, and air-dried. The fruits were then immersed in HPMC, 100UA, 500UA, and 1000UA coating solutions for 1 minute each, and then air-dried at room temperature to form a coating. Uncoated fruits served as a blank control (CK). Each fruit was individually packaged in a polyethylene (PE) bag to minimize moisture loss. All fruits were stored at 10℃ and 90%RH for 8 days, simulating a cold storage environment; subsequently, one group was transferred to 20℃ and 90%RH, and another group to 30℃ and 90%RH, until the end of the experiment. Fruit rot rate, firmness, titratable acid, ascorbic acid, and other quality indicators were periodically measured.

[0037] The rot rate was calculated by observing the appearance of the fruits in each group. Fruits with mold, lesions, or other undesirable appearance were considered rotten. The calculation formula was: Rot rate (%) = (Number of rotten fruits / Total number of fruits) × 100% Hardness was measured directly using a fruit hardness tester; The titratable acid content was determined by titrating the fruit extract with sodium hydroxide. The ascorbic acid content was determined by titration with sodium 2,6-dichlorophenolindophenol.

[0038] The UA / HPMC temperature-responsive modified atmosphere coating emulsion prepared in Example 1 was applied to the preservation of chili peppers: Peppers of uniform size, maturity, and without damage were selected and disinfected with a 2% (v / v) sodium hypochlorite solution for 1 minute, rinsed with deionized water, and air-dried. The fruits were then immersed in HPMC, 100UA, 500UA, and 1000UA coating solutions for 1 minute each, and then air-dried at room temperature to form a coating. Uncoated fruits served as a blank control (CK). Peppers were packaged in polyethylene (PE) bags to minimize moisture loss. All peppers were stored at 10℃ and 90%RH for 3 days to simulate a cold storage environment; subsequently, one group was transferred to 20℃ and 90%RH, and the other group was transferred to 30℃ and 90%RH for storage until the end of the experiment. Changes in the appearance of the peppers were recorded periodically.

[0039] Experimental results: The infrared spectra of the UA and UA / HPMC flat sheet films of this invention are as follows: Figure 2 As shown, HPMC is the main matrix for film formation, and its characteristic peaks (such as the OH stretching vibration at 3442 cm⁻¹) are evident. -1 This is present in all composite membranes. Simultaneously, the four characteristic absorption peaks of UA also appeared in the composite membranes (e.g., the C=O stretching vibration peak at 1691 cm⁻¹). -1 Furthermore, the peak intensity increases with increasing UA content. Notably, UA at 1691 cm⁻¹... -1 The absorption peak at 916 cm⁻¹ underwent a blue shift, and... -1 The weakening of the out-of-plane bending vibration peak of the carboxylic acid dimer OH indicates that HPMC disrupts the intermolecular hydrogen bonds of UA and may form a new intermolecular complex with UA through hydrogen bonding or electrostatic interaction, but no chemical bonding occurs, thus preserving the phase transition properties of UA.

[0040] Thermogravimetric curves and differential thermogravimetric curves of the UA and UA / HPMC flat sheet films of the present invention are as follows: Figure 3 and Figure 4 As shown, all samples underwent three main stages of mass loss: moisture evaporation, free UA volatilization, and HPMC thermal decomposition. No volatilization peak of free UA was detected in 100UA-FF, indicating that HPMC effectively binds to and inhibits UA volatilization. Furthermore, with increasing UA content, the thermal decomposition temperature of the HPMC matrix also increased (from approximately 300℃ in HPMC-FF to approximately 350℃ in 1000UA-FF), suggesting that the interaction between UA and HPMC enhances the thermal stability of the HPMC matrix.

[0041] The differential scanning calorimetry curves of the UA, HPMC, and UA / HPMC flat sheet films of this invention are as follows: Figure 5As shown, pure HPMC exhibits no significant thermal behavior within the test temperature range, while pure UA displays two consecutive endothermic peaks, corresponding to the crystal transition from a more ordered triclinic (β-type) to a more porous hexagonal (α-type) system and the melting process of UA from crystal to liquid, respectively. In the 1000UA-FF composite film, these two phase transition peaks still exist but are separated, and both shift towards the lower temperature region (to -1.53 ​​~ 6.43 ℃ and 16.29 ~ 31.38 ℃, respectively). This indicates that the hydrophobic segments of HPMC provide more nucleation sites for UA, causing its phase transition to occur earlier, but the phase transition characteristics of UA are retained after mixing with HPMC.

[0042] The temperature-modulus curve of the UA / HPMC coating solution of this invention is as follows: Figure 6 As shown, the storage modulus (G') and loss modulus (G'') of the coating solution with added UA are both higher than those of the pure HPMC solution. This is attributed to the increase in the continuous phase of UA and the formation of the complex, which enhances the elasticity of the coating solution. Furthermore, the modulus of the pure HPMC solution remains stable with increasing temperature, while the G' and G'' of the coating solution with added UA decrease significantly between 12℃ and 27℃. This is consistent with the melting process of UA, indicating that the addition of UA imparts temperature-responsive characteristics to the coating solution.

[0043] like Figure 7 The appearance of tangerines during storage at 10℃ to 20℃ shows that at 10℃, the appearance of water spots and pitted peels may indicate chilling injury; when the temperature rises to 20℃, the appearance of brown spots and the change in peel color from bright orange to dark yellow in rotten fruit indicate possible CO2 poisoning and anaerobic respiration.

[0044] like Figure 8 The graph shows the decay rate of tangerines during storage at 10℃ to 20℃. It can be seen that on the 8th day of storage at 10℃, the CK group had the highest decay rate (23.1%), while the 100UA group had the lowest decay rate (3.45%). When the temperature rises to 20℃, the CK group has the highest decay rate (60%) on the 12th day, while the 100UA group maintains a low decay rate (48.3% on the 16th day). However, the decay rates of the 500UA and 1000UA groups increase sharply (78.6% and 96.4% respectively on the 16th day), possibly due to poisoning caused by high CO2 content.

[0045] like Figure 9 The respiration rate graph of tangerine fruit during storage at 10℃ to 20℃ shows that the respiration rate drops sharply during the first eight days of storage at 10℃, and rises when the temperature is increased to 20℃; the respiration rate of the 100UA group remains stable and is the lowest, which helps to reduce the rot rate.

[0046] like Figure 10The appearance of tangerines during storage at 10℃ to 30℃ shows that, during storage at 30℃, the coated fruit develops more brown spots and darkens in color, indicating that it may have suffered more severe CO2 poisoning and anaerobic respiration.

[0047] like Figure 11 The graph shows the rot rate of tangerines stored at 10℃ to 30℃. It can be seen that in the early stage of storage at 30℃ (day 12), the rot rate of the 100UA group was the lowest (27.6%). However, after long-term storage (day 16), the rot rate of all coating groups was higher than that of the CK group (50%). Among them, the 1000UA group had the highest rot rate (92.9%), while the 100UA group had a relatively lower rot rate (62.1%). This indicates that the coating may exacerbate rot at high temperatures.

[0048] like Figure 12 The respiration rate graph of tangerines stored at 10℃ to 30℃ shows that the respiration rate increases when the temperature rises to 30℃, but the respiration rate of the 100UA group remains stable and is the lowest, which helps it resist the effects of rising temperature in the early stages. In summary, tangerines treated with 100UA coating have the lowest rot rate under fluctuating temperature conditions (10℃ to 20℃ or 30℃) and can better maintain fruit firmness, titratable acid, and ascorbic acid content.

[0049] like Figure 13 The appearance of chili peppers stored at 10℃ to 20℃ shows that different UA content coating treatments have significant differences in their effect on preserving the appearance of chili peppers during storage. The appearance quality of chili peppers in the HPMC group gradually declined with the extension of storage time; the chili peppers in the 100UA group maintained the best appearance throughout the entire storage period, with the least rot and quality deterioration.

[0050] like Figure 14This diagram shows the respiration rate of chili peppers during storage at 10℃ to 20℃. It can be seen that there are significant differences in respiration rates among the different treatment groups. Under 10℃ storage conditions, the respiration rates of all treatment groups remained at relatively low levels. The 100UA group showed the most stable respiration rate, consistently remaining at the lowest range, indicating its effective inhibition of chili pepper respiration. In contrast, the HPMC and 1000UA groups exhibited larger fluctuations in respiration rates, especially showing a significant upward trend in the later stages of storage. When the storage temperature rose to 20℃, the respiration rates of all treatment groups increased, but the differences became more pronounced. The 100UA group maintained the lowest respiration rate with the smallest increase, indicating that the coating effectively mitigated the increased respiration caused by temperature rise. The high-concentration 500UA and 1000UA treatment groups showed the most significant increases in respiration rates, especially in the later stages of storage, significantly higher than other groups. This may be due to the high UA concentration reducing the coating's permeability, leading to CO2 accumulation and enhanced anaerobic respiration. The respiration rate of the HPMC group fell between that of the 100UA group and the high-concentration UA ​​group. Overall, the 100UA coating performed best in maintaining the respiration stability of chili peppers and effectively slowed down the fruit senescence process.

[0051] like Figure 15 The images show the appearance of chili peppers stored at temperatures ranging from 10°C to 30°C. It can be seen that the preservation effects of different treatment groups varied significantly under high-temperature storage conditions. In the initial stage of storage at 10°C (Day 3), all treatment groups maintained good appearance quality. When the temperature rose to 30°C and the storage time increased, the appearance changes of each treatment group showed significant differences: the HPMC group showed obvious softening and spoilage in the middle and later stages of storage (Days 9-15). The 100UA group maintained the best appearance and the least degree of spoilage throughout the entire storage period. These appearance changes indicate that the 100UA coating provides the best protection for chili peppers under high-temperature conditions.

[0052] like Figure 16 This diagram shows the respiration rate of chili peppers stored at temperatures ranging from 10°C to 30°C. It reveals significant differences in respiration rates among the different treatment groups under varying temperature conditions. At 10°C, the respiration rates of all treatment groups remained relatively low. The 100UA group exhibited the most stable respiration rate, remaining within the lowest range, indicating its effective inhibition of chili pepper respiration at low temperatures. When the storage temperature rose to 30°C, the respiration rates of all treatment groups increased significantly, but the differences between treatment groups became more pronounced. The 100UA group maintained the lowest respiration rate with the smallest increase, demonstrating that the coating effectively mitigated the increased respiration caused by high temperatures. The 100UA coating performed best during variable-temperature storage from 10°C to 30°C, effectively inhibiting chili pepper respiration and delaying fruit senescence.

[0053] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A temperature-responsive modified atmosphere coating material for preserving fruits and vegetables, comprising a film-forming matrix, characterized in that, It also includes temperature-responsive materials, which are one or more of fatty acid, fatty alcohol, or ester phase change materials; the mass fraction of the temperature-responsive materials is 1.0% to 31.0%.

2. The temperature-responsive modified atmosphere coating material for fruit and vegetable preservation according to claim 1, characterized in that, The fatty acid phase change material is one or more of oleic acid, undecanoic acid, lauric acid, palmitic acid, and decanoic acid; the fatty alcohol phase change material is one or more of dodecanol and tridecanol; the ester phase change material is a mono- or diglyceride ester, and preferably the temperature-responsive material includes undecanoic acid.

3. The temperature-responsive modified atmosphere coating material for fruit and vegetable preservation according to claim 1 or 2, characterized in that, The film-forming matrix is ​​an edible polymer material, including one or more of cellulose, polysaccharide, protein, or synthetic polymer materials.

4. The temperature-responsive modified atmosphere coating material for fruit and vegetable preservation according to claim 3, characterized in that, The film-forming matrix is ​​one or more of hydroxypropyl methylcellulose, carboxymethyl cellulose, pullulan, chitosan soy protein isolate, zein, or polyvinyl alcohol.

5. The temperature-responsive modified atmosphere coating material for fruit and vegetable preservation according to any one of claims 1, 2, or 4, characterized in that, The temperature-responsive modified atmosphere coating material for fruit and vegetable preservation also includes additives, which are one or more of plasticizers, emulsifiers, antioxidants, or nucleating agents.

6. The temperature-responsive modified atmosphere coating material for fruit and vegetable preservation according to claim 5, characterized in that, The plasticizer is glycerin, the emulsifier is Tween 80, the antioxidant is vitamin E, and the nucleating agent is an inorganic salt or nanoparticles.

7. The temperature-responsive modified atmosphere coating material for fruit and vegetable preservation according to any one of claims 1, 2, or 4, characterized in that, It includes a film-forming matrix of hydroxypropyl methylcellulose and a temperature-responsive material undecanoic acid, wherein the mass percentage of undecanoic acid is 3.0%-31%, preferably 4.0%-18.4%.

8. The temperature-responsive modified atmosphere coating material for fruit and vegetable preservation according to any one of claims 1, 2, or 4, characterized in that, The film-forming matrix includes pullulan polysaccharide, and a temperature-responsive mixture of undecanoic acid and palmitic acid, wherein the mass percentage of the undecanoic acid and palmitic acid mixture is 1.0%-18.4%, preferably 2.2%-4.3%; and the mass ratio of undecanoic acid to palmitic acid is preferably 1:

1.

9. A method for preparing a temperature-responsive modified atmosphere coating material for fruit and vegetable preservation as described in any one of claims 1 to 8, characterized in that, The components are blended to prepare an emulsion, or the emulsion is cast to form a film material.

10. The method for preparing a temperature-responsive modified atmosphere coating material for fruit and vegetable preservation according to claim 9, characterized in that, Includes the following steps: (1) Disperse the film-forming matrix in deionized water, stir until there are no obvious particles, and let it stand at 3-5℃ for 10-15 hours to completely dissolve it, so as to obtain a 1.0-3.0% (w / v) aqueous solution of the film-forming matrix; (2) After heating the film-forming matrix aqueous solution and the temperature-responsive material in a water bath at 30-70℃, the temperature-responsive material is added to the film-forming matrix aqueous solution and stirred continuously at 30-70℃ for 5-7 hours to form a uniform solution or emulsion. (3) After naturally cooling to room temperature and standing to defoam, the coating emulsion is obtained.

Images