Degradable film material with high water vapor permeability for slowly releasing fruit ripening agent as well as preparation method and application of degradable film material

Abstract

The invention provides a degradable film material with high water vapor permeability for slowly releasing a fruit ripening agent as well as a preparation method and application of the degradable film material. The preparation method comprises the following steps: dissolving chitosan in an organic acid aqueous solution, and adjusting the pH value to 1.0-5.0; the preparation method comprises the following steps: dissolving soybean protein isolate in water, treating at 80-95 DEG C for 25-30 minutes, and adjusting the pH value to 1.0-5.0; and mixing the two solutions in proportion, adding glycerol and a plant growth regulator to prepare a degradable film material solution, carrying out ultrasonic defoaming, pouring the degradable film material solution into a mold, and drying to obtain the degradable film. The controllable and slow-release soybean protein isolate-chitosan-based degradable film material is developed by using ethephon, has good biodegradability, fracture tensile property, water vapor permeation property and ultraviolet barrier property, can conveniently, efficiently and controllably release the ripening agent, avoids the residue of ethephon in fruits, and has a good application prospect in the field of fruit maturation, fruit maturation, fruit maturation, fruit maturation, fruit maturation, fruit maturation, fruit maturation, fruit maturation, fruit maturation, fruit maturation, fruit maturation, fruit maturation and fruit maturation. The production place loss rate of the fruits is reduced, and the method has a good industrialization prospect in agricultural product storage and transportation.

Description

Technical Field

[0001] The invention relates to the technical field of slow-release materials, in particular to a high water vapor permeability degradable film material for slow-release fruit ripening agent, and a preparation method and application thereof. Background Art

[0002] Ethephon is a plant growth regulator, commonly used in the agricultural field. It can enhance the activity of enzymes, activate phosphatase and other enzymes related to fruit ripening when the fruit is ripe, and is used to accelerate the ripening and shedding of plant fruits, plant aging, and promote plant flowering and other physiological effects. Under certain conditions, ethephon can not only release ethylene itself, but also induce plants to produce ethylene, and its production can regulate, control or affect the growth and development of individuals. Ethephon is often used as a ripening agent in agricultural production by coating flower stalks, coating fruits, soaking fruits, and spraying fruits in the field. Therefore, improper operation or weak knowledge of its scientific use will lead to problems such as excessive use of ethephon and pesticide residues in the environment. In order to make it better serve human society and benefit the environment and human health, the safe and efficient use of ethephon is a technical problem that needs to be solved urgently.

[0003] In recent years, biodegradable material technology has become a research and development trend. Mixing ethephon into the material to develop a slow-release biodegradable material that is a slow-release plant growth regulator may solve the problem of ethephon residues.

[0004] Among degradable biopolymers, chitosan and soy protein isolate have good film-forming ability. Both are non-toxic, harmless, widely available and inexpensive. In addition, the complex of soy protein isolate and polysaccharide has been proven to improve the water absorption, biodegradability, tensile strength at break, water vapor permeability and UV blocking properties of the film, and therefore has broad application prospects. Summary of the invention

[0005] The purpose of the present invention is to provide a novel degradable film material with high water vapor permeability for slow-release of fruit ripening agent and a preparation method and application thereof.

[0006] In order to achieve the object of the present invention, in a first aspect, the present invention provides a method for preparing a degradable film material with high water vapor permeability for slow-release of a fruit ripening agent, comprising the following steps: (1) Dissolve chitosan in an organic acid aqueous solution and adjust the pH to 1.0-5.0; (2) Dissolve the soy protein isolate in ultrapure water, perform heat denaturation treatment at 80-95°C for 25-30 min, and adjust the pH to 1.0-5.0; (3) After mixing the above two solutions in a certain volume ratio, adding a certain amount of glycerol and plant growth regulator to prepare a degradable membrane material solution, and then ultrasonically defoaming for 5 to 10 minutes; (4) The degradable membrane material solution is poured into a mold and dried to obtain a product.

[0007] In the aforementioned method, the organic acid may be acetic acid.

[0008] Preferably, the organic acid aqueous solution is a 0.6-3% acetic acid aqueous solution; more preferably, the organic acid aqueous solution is a 0.6-2% acetic acid aqueous solution.

[0009] In the aforementioned method, the weight ratio of chitosan to organic acid is 1:0.4-0.8.

[0010] In the above method, the weight ratio of chitosan to soy protein isolate is 1:0.1 to 4. Preferably, the weight ratio of chitosan to soy protein isolate is 1:0.2 to 1.5; more preferably, the weight ratio of chitosan to soy protein isolate is 1:0.2 to 0.6.

[0011] In the aforementioned method, the weight ratio of chitosan to glycerol is 1:0.4-0.8.

[0012] In the aforementioned method, the plant growth regulator is ethephon.

[0013] Preferably, the weight ratio of chitosan to 40% ethephon water-repellent is 1:1.5-3.0; more preferably, the weight ratio of chitosan to 40% ethephon water-repellent is 1:1.5-2.0.

[0014] In the aforementioned method, step (4) is performed by drying at 45-65°C for 6-10 hours; preferably, drying at 45-65°C for more than 8 hours; more preferably, drying at 45-55°C for more than 8 hours.

[0015] The sustained-release degradable film material prepared by the preparation method can effectively reduce the tensile strength at break of the soy protein isolate-chitosan based sustained-release degradable material.

[0016] In a second aspect, the present invention provides a degradable film material with high water vapor permeability for slow-release of fruit ripening agent prepared according to the method.

[0017] In a third aspect, the present invention provides any of the following applications of the degradable film material: 1) Used in the field of controlled ripening of agricultural products; 2) Used in the storage and transportation of agricultural products.

[0018] By means of the above technical solution, the present invention has at least the following advantages and beneficial effects: (i) The present invention utilizes ethephon to develop a controlled sustained-release soybean protein isolate-chitosan based biodegradable packaging material, which has good biodegradability, tensile strength at break, water vapor permeability and UV blocking properties.

[0019] (ii) The preparation method of the present invention is simple and easy to implement, and has good industrialization prospects in the storage and transportation of agricultural products. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a comparison chart of the mechanical properties test of the slow-release degradable film materials of the control group of the present invention, Examples 1-3 and Comparative Examples 1-3.

[0021] Figure 2 This is a comparison chart of the ultraviolet blocking performance test of the sustained-release degradable film materials of the control group of the present invention, Examples 1-3 and Comparative Examples 1-3.

[0022] Figure 3 This is a comparison chart of the experiment of promoting the ripening of green tomatoes using the slow-release degradable film material of the control group of the present invention and Example 2. DETAILED DESCRIPTION

[0023] The invention provides a method for preparing a slow-release degradable film material for slow-release plant growth regulators.

[0024] The present invention adopts the following technical solution: The invention provides a degradable film material with high water vapor permeability for slow-release fruit ripening agent and a preparation method thereof. The preparation method comprises: adding 0.6-3% acetic acid aqueous solution to chitosan to dissolve, adjusting the pH value to 1.0-5.0; adding ultrapure water to dissolve soy protein isolate to adjust the pH value to 1.0-5.0; mixing the two solutions evenly according to a certain volume ratio, adding a certain amount of glycerol and a plant growth regulator to mix, preparing a degradable film material solution, and then ultrasonically defoaming for 5-10 minutes; finally, pouring the degradable film material solution into a mold, and drying to obtain the obtained film material.

[0025] Furthermore, the method comprises: dissolving chitosan in an organic acid aqueous solution and adjusting the pH value to 1.0-5.0; separately dissolving soy protein isolate in ultrapure water, stirring and denaturing the solution in a water bath at 80-95°C, adjusting the pH value to 1.0-5.0, mixing the two solutions in a certain volume ratio, adding a certain amount of glycerol and ethephon to the mixture, and preparing a degradable membrane material solution; and then pouring the degradable membrane material solution into a mold and drying the solution.

[0026] Furthermore, the weight ratio of chitosan to organic acid is 1:0.4-0.8.

[0027] Furthermore, the organic acid is acetic acid.

[0028] The concentration of acetic acid in the acetic acid aqueous solution is 0.6~3%.

[0029] Preferably, the concentration of acetic acid is 0.6-2%.

[0030] Furthermore, the soy protein isolate aqueous solution was bathed in a water bath at 80-95°C for 30 min.

[0031] It is preferred to bathe in a water bath at 85~95℃ for 30min.

[0032] Furthermore, the pH is adjusted to 1-5.

[0033] Preferably, the pH is adjusted to 2-4.

[0034] Furthermore, the weight ratio of chitosan to soy protein isolate is 1:0.2-4.

[0035] Preferably, the weight ratio of chitosan to soy protein isolate is 1:0.2-1.5; More preferably, the weight ratio of chitosan to soy protein isolate is 1:0.2-0.6.

[0036] Under the above ratio, the comprehensive performance of the obtained sustained-release biodegradable film material reaches the best.

[0037] Furthermore, the weight ratio of chitosan to glycerol is 1:0.4-0.8.

[0038] Further, the weight ratio of chitosan to 40% ethephon water agent is 1:1.5-3.0; Preferably, the weight ratio of chitosan to 40% ethephon water-repellent is 1:1.5-2.0.

[0039] Further, drying at 45-65°C for more than 8 hours; Preferably, the drying is carried out at 45-55° C. for more than 8 hours.

[0040] The present invention also provides a degradable film material with high water vapor permeability for slow-releasing a fruit ripening agent, which is prepared by the preparation method in any one of the above technical solutions.

[0041] The invention also provides application of the high water vapor permeability degradable film material which slowly releases the fruit ripening agent in the field of controllable ripening of agricultural products.

[0042] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means known to those skilled in the art, and the raw materials used are all commercially available products. All other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0043] In the following examples, soy protein isolate was purchased from Beijing Solaibao Technology Co., Ltd., and chitosan was purchased from Beijing MacLean Technology Co., Ltd. The acid solution used to adjust the pH was 2 mol / L -1of HCl solution.

[0044] Control group This control group provides a degradable film material, and the preparation method is as follows: (1) Weigh 2 g of chitosan, add 100 mL of 1% acetic acid aqueous solution, stir evenly at room temperature, and adjust the pH to 3.0; (2) Weigh 2 g of soy protein isolate, add 100 mL of ultrapure water, stir evenly at room temperature, place in a water bath for 30 min, let the temperature drop to room temperature, and adjust the pH to 3.0; (3) The chitosan solution and the soy protein isolate solution were mixed in a volume ratio of 4:1, 0.65 g of glycerol was added, and the mixture was stirred evenly at room temperature to obtain a degradable membrane material solution.

[0045] (4) After the bubbles in the degradable membrane material solution are removed by ultrasonic treatment, the solution is added into a mold and dried to obtain a degradable membrane material, which is named as degradable membrane A.

[0046] Example 1 This embodiment provides a degradable film material, and the preparation method is as follows: (1) Weigh 2 g of chitosan, add 100 mL of 1% acetic acid aqueous solution, stir evenly at room temperature, and adjust the pH to 3.0; (2) Weigh 2 g of soy protein isolate, add 100 mL of ultrapure water, stir evenly at room temperature, place in a water bath for 30 min, let the temperature drop to room temperature, and adjust the pH to 3.0; (3) Chitosan solution and soy protein isolate solution were mixed in a volume ratio of 4:1, 0.65 g of glycerol was added, and the mixture was stirred evenly at room temperature. 0.5% of 40% ethephon water-soluble agent (based on the weight of the solution) was added and stirred evenly to obtain a slow-release biodegradable membrane material solution.

[0047] (4) After the bubbles in the degradable membrane material solution are removed by ultrasonic treatment, the solution is added into a mold and dried to obtain a degradable membrane material, which is named as degradable membrane B.

[0048] Example 2 This embodiment provides a degradable film material, and the preparation method is different from that of embodiment 1 only in that: Add 1.0% of 40% ethephon water agent (by weight of solution); The degradable film material was obtained and named as degradable film C.

[0049] Example 3 This embodiment provides a degradable film material, and the preparation method is different from that of embodiment 1 only in that: Add 1.5% of 40% ethephon water agent (by solution weight); The degradable film material was obtained and named as degradable film D.

[0050] Comparative Example 1 This comparative example provides an ethephon slow-release biodegradable film material, and the preparation method is as follows: (1) Weigh 2 g of chitosan, add 100 mL of 1% acetic acid aqueous solution, stir evenly at room temperature, and adjust the pH to 3.0; (2) Weigh 2 g of soy protein isolate, add 100 mL of ultrapure water, stir evenly at room temperature, place in a water bath for 30 min, let the temperature drop to room temperature, and adjust the pH to 3.0; (3) The chitosan solution and the soy protein isolate solution were mixed in a volume ratio of 1:1, 1.3 g of glycerol was added, and the mixture was stirred evenly at room temperature. 1.0% of 40% ethephon water-soluble agent (based on the weight of the solution) was added and stirred evenly to obtain a slow-release biodegradable membrane material solution.

[0051] (4) After removing bubbles from the degradable membrane material solution by ultrasonic treatment, the solution is added into a mold and dried to obtain a degradable membrane material.

[0052] The degradable film material obtained in this comparative example is named comparative film A.

[0053] Comparative Example 2 This comparative example provides an ethephon slow-release biodegradable film material, and the preparation method is different from that of comparative example 1 only in that: The chitosan solution and the soy protein isolate solution were mixed in a volume ratio of 3:2; The degradable film material obtained in this comparative example is named comparative film B.

[0054] Comparative Example 3 This comparative example provides an ethephon slow-release biodegradable film material, and the preparation method is different from that of comparative example 1 only in that: The chitosan solution and the soy protein isolate solution were mixed in a volume ratio of 7:3; The degradable film material obtained in this comparative example is named comparative film C.

[0055] Test Example 1 Water Solubility Test (1) Cut the sustained-release membrane into small pieces of 20 mm × 20 mm, put them into a 50 mL beaker, place them in a forced air drying oven, set the temperature to 105 °C, and dry them for 24 h; (2) Take out the above slow-release film, weigh its mass (M1, g), immerse the slow-release film in deionized water for 24 hours, and stir occasionally. Then take out the film and dry it in an oven (105°C, 24 hours) to determine the final dry mass; (3) Take out the above sustained-release membrane, weigh its mass (M2, g), and calculate the water solubility. Repeat the measurement 3 times for each group.

[0056] Water solubility (%) = (M1 -M2) × 100 / M1 The test results are shown in Table 1.

[0057] Table 1 Water solubility of sustained-release membrane

[0058] The test results show that the degradation films B, C, and D have higher water solubility than the degradation film A without ethephon and the comparison films A, B, and C. The results also show that at the same ethephon addition amount (comparison films A, B, and C), as the proportion of chitosan in the film-forming liquid increases, the water absorption of the sustained-release film tends to increase, which is consistent with the properties of the chitosan film; at the same material-liquid ratio (slow-release films B, C, and D), as the ethephon content increases, the water solubility of the sustained-release film tends to decrease.

[0059] Test Example 2 Moisture absorption test (1) Cut the composite film into small pieces of 20 mm × 20 mm, accurately weigh its mass (M3, g) using an analytical balance, and place it in a constant temperature and humidity chamber at 21 °C and 76% relative humidity for 24 h.

[0060] (2) Take out the composite film, weigh it immediately (M4, g), and calculate the moisture absorption rate. Repeat the measurement 3 times for each group.

[0061] Moisture absorption rate (%) = (M4-M3) × 100 / M3 The test results are shown in Table 2.

[0062] Table 2 Moisture absorption rate of sustained-release membrane

[0063] The test results show that compared with the comparison films A, B and C, the degradation films B, C and D have lower moisture absorption rate, and the moisture absorption rate gradually increases with the increase of ethephon content. Under the treatment conditions of 0.5~1.5% ethephon, the moisture absorption rate is 2.40~3.06%; under the same ethephon addition amount (comparison films A, B and C), the moisture absorption rate gradually decreases with the increase of chitosan content.

[0064] Test Example 3 Mechanical Properties Test The film was cut into small pieces of 10 mm × 50 mm, and its tensile strength (TS) and elongation at break (EB) were measured using a texture analyzer. The test speed was 50 mm / min, the clamp distance was 30 mm, and the measurement was repeated 4 times for each group of films.

[0065] TS=F / (d×W) Where: TS—tensile strength (N / mm 2); F—maximum tension when the membrane breaks (N; d—membrane thickness (mm); W—membrane width (mm); Elongation at break calculation formula: EB = (L-L0) × 100 / L0 Where: EB is the elongation at break (%); L is the distance between the marking lines when the film breaks (mm); L0 is the distance between the original marking lines of the film (mm).

[0066] The test results are as follows Figure 1 As shown, Figure 1 The comparison diagram shows the mechanical properties of the degradation films prepared by different methods. The results show that ethephon has a great influence on the mechanical properties of chitosan-soy protein isolate film, and the tensile strength of degradation films B, C, and D is higher than that of comparison films A, B, and C. And under the same material-liquid ratio, with the increase of ethephon, the tensile strength and elongation at break both show a trend of first increasing and then decreasing, reaching the maximum value at 1.0%, with a tensile strength of 20.34MPa and an elongation at break of 129%. The results also show that under the same ethephon addition amount, with the increase of chitosan content, the tensile strength shows an increasing trend, and the elongation at break shows a trend of first decreasing and then increasing, with the lowest being 65%.

[0067] Test Example 4 Ultraviolet blocking performance test The film was cut into small pieces of 10 mm×40 mm and scanned in the range of 325-700 nm using an ultraviolet spectrophotometer to determine the light transmittance of the film.

[0068] The test results are as follows Figure 2 As shown, the degradation films B, C, D with added ethephon and the comparison films A, B, C all have good UV blocking properties.

[0069] Test Example 5 Water Vapor Transmission Rate Test (1) Measure the thickness of the film with a vernier caliper (L, mm); (2) Take a 20 mL glass beaker and calculate the area of ​​the beaker mouth, i.e. the effective penetration area (A, m 2 ), and add 10mL of distilled water thereto; (3) Cover the mouth of the cup with a film, weigh the sealed cups, and then place them in an anhydrous calcium chloride desiccator at 24°C and 20% RH.

[0070] (4) Weigh every 1 hour (Δt, h) to obtain the mass of water permeation (Δm, g), and weigh 6 times. Calculate the water vapor permeability coefficient (WVP, gm -1 s -1 Pa -1 ).

[0071] The water transported through the membrane and adsorbed by the desiccant was measured periodically from the weight loss over 24 h in the glass permeation cell. The WVP of the membrane was determined by the following formula: WVP= WVTR(L / △P)=△m·L / (A·△t·△P) WVTR is the water vapor transmittance through the film (g / m 2 ·h), L is the film thickness (mm), m / △t is the slope of the cup weight loss curve (measured within 0.0001g) over time (g / h), A is the film area exposed on the cup (m 2 ), △P is the water vapor partial pressure difference on both sides of the membrane, 2.33282 kPa.

[0072] The test results are shown in Table 3.

[0073] Table 3 Water vapor permeability of degradable films The test results show that the water vapor permeability of the degradation films B, C, and D is higher than that of the degradation film A and the comparison films A, B, and C prepared with soy protein isolate-chitosan alone. And under the same material-liquid ratio, with the increase of ethephon, the water vapor permeability shows an increasing trend. The results also show that under the same ethephon addition amount, with the increase of chitosan content, the water vapor permeability shows an increasing trend.

[0074] Test Example 6 Tomato Ripening Test Combination Figure 3 It can be seen that: on the third day of storage, the tomatoes treated with the ethephon film changed from green to white and yellowish, and the color change was more obvious than that of the control group, indicating that the tomatoes in the film-treated group entered the color change period faster than the tomatoes in the control group; on the fifth day of storage, the tomatoes treated with the ethephon film entered the ripening period, and the color change was more significant. Some samples had completely turned red, while the vast majority of tomatoes in the control group were still green; on the seventh day of storage, the color change of the tomatoes treated with the ethephon film was more obvious, and there were still tomatoes in the white ripening period in the control group, and the color was still green. The overall maturity difference affected the processing quality of tomatoes. The fruit ripening film of the present invention has a strong ripening effect and can effectively accelerate the ripening of tomatoes. It can be seen from the figure that with the change of storage days, the color of the tomatoes treated with the ethephon film changes faster, which can achieve the effect of accelerating the ripening of tomatoes.

[0075] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a high water vapor permeability degradable film material for slow-release fruit ripening agent, characterized in that: The following steps are involved: (1) Dissolve chitosan in an organic acid aqueous solution and adjust the pH to 1.0-5.0; (2) Dissolve the soy protein isolate in ultrapure water, perform heat denaturation treatment at 80-95°C for 25-30 min, and adjust the pH to 1.0-5.0; (3) After mixing the above two solutions in a certain volume ratio, adding a certain amount of glycerol and plant growth regulator to prepare a degradable membrane material solution, and then ultrasonically defoaming for 5 to 10 minutes; (4) The degradable membrane material solution is poured into a mold and dried to obtain a product.

2. The method according to claim 1, characterized in that: The organic acid is acetic acid; Preferably, the organic acid aqueous solution is a 0.6% to 3% acetic acid aqueous solution; More preferably, the organic acid aqueous solution is a 0.6% to 2% acetic acid aqueous solution.

3. The method according to claim 2, characterized in that The weight ratio of chitosan to organic acid is 1:0.4~0.

8.

4. The method according to claim 1, characterized in that: The weight ratio of chitosan to soy protein isolate is 1:0.1~4. Preferably, the weight ratio of chitosan to soy protein isolate is 1:0.2-1.5; More preferably, the weight ratio of chitosan to soy protein isolate is 1:0.2-0.

6.

5. The method according to claim 1, characterized in that The weight ratio of chitosan to glycerol is 1:0.4~0.

8.

6. The method according to claim 1, characterized in that The plant growth regulator is ethephon.

7. The method according to claim 6, characterized in that The weight ratio of chitosan to 40% ethephon water agent is 1:1.5~3.0; Preferably, the weight ratio of chitosan to 40% ethephon water-repellent is 1:1.5-2.

0.

8. The method according to any one of claims 1 to 7, characterized in that: Step (4) drying at 45-65°C for 6-10 hours; Preferably, drying at 45-65°C for more than 8 hours; More preferably, the mixture is dried at 45-55° C. for more than 8 h.

9. A degradable film material with high water vapor permeability for slow-release of fruit ripening agent prepared by the method according to any one of claims 1 to 8.

10. Any of the following uses of the sustained-release degradable film material according to claim 9: 1) Used in the field of controlled ripening of agricultural products; 2) Used in the storage and transportation of agricultural products.

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