Preparation method of anisaldehyde microcapsule / polyvinyl alcohol composite film applied to carrot preservation

Abstract

A preparation method of an anisaldehyde microcapsule / polyvinyl alcohol composite film applied to carrot preservation comprises the following steps: firstly, preparing anisaldehyde emulsion: weighing starch, slowly adding distilled water, heating under stirring until the starch is completely gelatinized, and cooling to room temperature; the preparation method comprises the following steps: weighing chitosan, adding an acetic acid solution, placing in a water bath kettle, heating under magnetic stirring at 90 DEG C until the materials are dissolved, and cooling to room temperature; uniformly mixing the two materials to serve as a wall material of the microcapsule; respectively adding anisaldehyde into the wall materials, and homogenizing the mixed solution at a high speed to obtain anisaldehyde emulsion; secondly, preparing anisaldehyde microcapsules: drying the anisaldehyde emulsion, collecting the anisaldehyde microcapsules, and storing the anisaldehyde microcapsules in a refrigerator for later use; preparing an anisaldehyde microcapsule / polyvinyl alcohol composite film: weighing polyvinyl alcohol, slowly adding distilled water, and heating while stirring; adding glycerol into the polyvinyl alcohol solution, and stirring; the anisaldehyde microcapsules are added into a polyvinyl alcohol solution, the solution is subjected to curtain coating to form a film after high-speed homogenization, and the film is dried at room temperature.

Description

Technical Field

[0001] This invention relates to the field of vegetable preservation technology, and in particular to the preparation and application technology of anisaldehyde microcapsule / polyvinyl alcohol composite film for carrot preservation. Background Technology

[0002] Carrots are susceptible to bacterial rot due to mechanical damage during post-harvest storage, which can allow pathogens to enter through the wounds. Furthermore, carrots have thin skins and are prone to wilting and becoming pithy in low humidity conditions. Therefore, post-harvest storage of carrots is a challenging task.

[0003] Currently, the main method for post-harvest storage of carrots is "cold storage + perforated polyethylene bag packaging." The cold storage temperature is controlled at 0-1℃, which is the optimal temperature range for inhibiting carrot respiration, delaying aging, and preventing sprouting and microbial growth. Simultaneously, the perforated polyethylene bag packaging after removal from cold storage achieves a balance between the four major requirements of moisture retention, disease prevention, sprout inhibition, and gas control, while also keeping costs under control. This design has become the standard packaging solution for carrot cold chains globally and is a key technological support for reducing post-harvest losses. However, polyethylene packaging not only causes white pollution but also lacks antibacterial properties. Therefore, there is an urgent need to develop an environmentally friendly packaging material with antibacterial properties.

[0004] Patent CN119552398A describes the preparation of a film using quaternary ammonium sulfonated nanocellulose, polylactic acid, and curcumin microcapsule powder, which was then applied to the preservation of spinach and strawberries. However, polylactic acid is expensive and a hydrophobic polymer, while quaternary ammonium sulfonated nanocellulose is strongly hydrophilic. When the two are mixed, the difference in polarity easily leads to weak interfacial bonding, resulting in microphase separation and reducing the uniformity and mechanical strength of the film. Patent CN119613900A describes the preparation of a composite film by adding cinnamon oil microcapsules to a mixture of polyvinyl alcohol and chitosan, which was then applied to fresh-cut fruits. However, this composite film only has antibacterial function and does not have the ability to induce resistance to achieve preservation. Patent CN118834445A describes the preparation of a microcapsule preservation film based on konjac glucomannan, in which the antibacterial components are microencapsulated litsea cubeba oil and grape seed oil. These essential oils have the drawbacks of high cost, volatility, and lack of resistance induction.

[0005] Anisaldehyde is a permitted edible flavoring agent according to the National Food Safety Standard for Use of Food Additives (GB2760-1996). On one hand, it can disrupt the integrity of fungal cell walls and reduce bacterial adhesion, exhibiting good antibacterial activity. On the other hand, anisaldehyde triggers a mitogen-activated protein kinase (MAPK) cascade reaction, activating the salicylic acid and jasmonic acid pathways, inducing resistance in vegetables, and thus extending shelf life. However, direct use of anisaldehyde can cause phytotoxicity. Therefore, microencapsulating anisaldehyde and adding it to polyvinyl alcohol not only forms antibacterial packaging materials but also extends the post-harvest shelf life of vegetables by inducing resistance.

[0006] Therefore, the purpose of this application is to develop a packaging material suitable for postharvest preservation of carrots, using anisaldehyde microcapsules as an antibacterial agent, polyvinyl alcohol as a film-forming agent, and glycerin as a plasticizer. This packaging film can extend the shelf life of carrots. Summary of the Invention

[0007] In view of the problem that existing carrot packaging materials use perforated polyethylene, the purpose of this invention is to provide a method for preparing a low-cost, environmentally friendly packaging material for carrot preservation.

[0008] To achieve this objective, the present invention adopts the following technical solution: (I) Using anisaldehyde as the core material and starch and chitosan as the wall material, anisaldehyde microcapsules were prepared by spray drying.

[0009] The preparation method of the above-mentioned anisaldehyde microcapsules includes the following steps, in parts by weight: S1: Weigh 25 parts of starch, slowly add 500 parts of distilled water, place in a water bath and heat at 90°C with magnetic stirring for 30 minutes until the starch is completely gelatinized, then cool to room temperature; weigh 5 parts of chitosan and add 500 parts of 1% acetic acid solution, place in a water bath and heat at 90°C with magnetic stirring for 30 minutes until the material dissolves, then cool to room temperature; mix the two evenly as the wall material of the microcapsules; S2: Add anisaldehyde to the wall material, and homogenize the mixture at high speed to obtain anisaldehyde emulsion.

[0010] S3: The anisaldehyde emulsion was dried using a spray dryer, and the anisaldehyde microcapsules were collected and stored in a 4°C refrigerator for later use.

[0011] Furthermore, in S1, starch refers to corn starch, specifically octenyl succinate corn starch, and the degree of substitution of octenyl succinate corn starch is between 0.0049 and 0.0198.

[0012] Furthermore, the amount of anisaldehyde added in S2 is between 2.5 and 4.5 parts.

[0013] Furthermore, the spray drying conditions in S3 are an inlet air temperature of 140–170°C and a flow rate of 100–500 mL / h.

[0014] (II) Using anisaldehyde microcapsules as an antibacterial agent, polyvinyl alcohol as a film-forming matrix, and glycerol as a plasticizer, anisaldehyde microcapsule / polyvinyl alcohol composite film was prepared by casting method.

[0015] The preparation method of the above-mentioned anisaldehyde microcapsule / polyvinyl alcohol composite film includes the following steps, in parts by weight: S1: Weigh 8 parts of polyvinyl alcohol, add 200 parts of distilled water, place in a water bath and heat for 1 hour at 90°C with magnetic stirring; add 1.6 parts of glycerol to the polyvinyl alcohol solution and stir at 50°C for 30 minutes.

[0016] S2: Add 0.25% to 1% anisaldehyde microcapsules to the above S1 polyvinyl alcohol solution, homogenize at high speed, and then cast the solution into a film.

[0017] Furthermore, the viscosity of the polyvinyl alcohol in S1 is 20-60 mPa·s.

[0018] Furthermore, the anisaldehyde microcapsules mentioned in S2 refer to the anisaldehyde addition amount in step (I) S2 being between 2.5 and 4.5 parts. Beneficial effects

[0019] 1. This invention employs microencapsulation technology to encapsulate volatile and unstable anisaldehyde, achieving stable and sustained release within a film. When applied to carrot storage, the anisaldehyde released from the film effectively inhibits carrot rot, significantly reducing the rot rate and disease incidence.

[0020] 2. This invention uses polyvinyl alcohol as a film-forming matrix, which can effectively reduce moisture evaporation during carrot storage, maintain its hardness and brittleness, and reduce wilting. Simultaneously, the polyvinyl alcohol film with added anisaldehyde microcapsules significantly improves the density of the composite film compared to traditional perforated polyethylene packaging.

[0021] 3. The antibacterial agent used in this invention, anisaldehyde, is a major component of natural fennel essential oil, and its safety is higher compared to artificially synthesized chemical preservatives. Secondly, polyvinyl alcohol has good biodegradability, and as a water-soluble polymer, its casting film-forming process is mature, simple, and relatively low-cost, making it easy to scale up production. Detailed Implementation

[0022] The present invention will be further described below with reference to embodiments. These embodiments are illustrative of the present invention, but the present invention is not limited to these embodiments: Example 1: The preparation method of anisaldehyde microcapsules is as follows: S1: Weigh 25 parts of octenyl succinate corn starch, slowly add 500 parts of distilled water, place in a water bath and heat at 90°C with magnetic stirring for 30 minutes until the starch is completely gelatinized, then cool to room temperature; weigh 5 parts of chitosan and add 500 parts of 1% acetic acid solution, place in a water bath and heat at 90°C with magnetic stirring for 30 minutes until the material dissolves, then cool to room temperature; mix the two evenly as the wall material of the microcapsules; S2: Add 2.5 parts of anisaldehyde to the wall material, and homogenize the mixture at high speed to obtain anisaldehyde emulsion.

[0023] S3: The anisaldehyde emulsion was dried using a spray dryer, and the anisaldehyde microcapsules were collected and stored in a 4°C refrigerator for later use.

[0024] Example 2: The preparation method of anisaldehyde microcapsules is as follows: S1: Weigh 25 parts of octenyl succinate corn starch, slowly add 500 parts of distilled water, place in a water bath and heat at 90°C with magnetic stirring for 30 minutes until the starch is completely gelatinized, then cool to room temperature; weigh 5 parts of chitosan and add 500 parts of 1% acetic acid solution, place in a water bath and heat at 90°C with magnetic stirring for 30 minutes until the material dissolves, then cool to room temperature; mix the two evenly as the wall material of the microcapsules; S2: Add 3.0 parts of anisaldehyde to the wall material, and homogenize the mixture at high speed to obtain anisaldehyde emulsion.

[0025] S3: The anisaldehyde emulsion was dried using a spray dryer, and the anisaldehyde microcapsules were collected and stored in a 4°C refrigerator for later use.

[0026] Example 3: The preparation method of anisaldehyde microcapsules is as follows: S1: Weigh 25 parts of octenyl succinate corn starch, slowly add 500 parts of distilled water, place in a water bath and heat at 90°C with magnetic stirring for 30 minutes until the starch is completely gelatinized, then cool to room temperature; weigh 5 parts of chitosan and add 500 parts of 1% acetic acid solution, place in a water bath and heat at 90°C with magnetic stirring for 30 minutes until the material dissolves, then cool to room temperature; mix the two evenly as the wall material of the microcapsules; S2: Add 3.5 parts of anisaldehyde to the wall material, and homogenize the mixture at high speed to obtain anisaldehyde emulsion.

[0027] S3: The anisaldehyde emulsion was dried using a spray dryer, and the anisaldehyde microcapsules were collected and stored in a 4°C refrigerator for later use.

[0028] Example 4: The preparation method of anisaldehyde microcapsules is as follows: S1: Weigh 25 parts of octenyl succinate corn starch, slowly add 500 parts of distilled water, place in a water bath and heat at 90°C with magnetic stirring for 30 minutes until the starch is completely gelatinized, then cool to room temperature; weigh 5 parts of chitosan and add 500 parts of 1% acetic acid solution, place in a water bath and heat at 90°C with magnetic stirring for 30 minutes until the material dissolves, then cool to room temperature; mix the two evenly as the wall material of the microcapsules; S2: Add 4.0 parts of anisaldehyde to the wall material, and homogenize the mixture at high speed to obtain anisaldehyde emulsion.

[0029] S3: The anisaldehyde emulsion was dried using a spray dryer, and the anisaldehyde microcapsules were collected and stored in a 4°C refrigerator for later use.

[0030] Example 5: The preparation method of anisaldehyde microcapsules is as follows: S1: Weigh 25 parts of octenyl succinate corn starch, slowly add 500 parts of distilled water, place in a water bath and heat at 90°C with magnetic stirring for 30 minutes until the starch is completely gelatinized, then cool to room temperature; weigh 5 parts of chitosan and add 500 parts of 1% acetic acid solution, place in a water bath and heat at 90°C with magnetic stirring for 30 minutes until the material dissolves, then cool to room temperature; mix the two evenly as the wall material of the microcapsules; S2: Add 4.5 parts of anisaldehyde to the wall material, and homogenize the mixture at high speed to obtain anisaldehyde emulsion.

[0031] S3: The anisaldehyde emulsion was dried using a spray dryer, and the anisaldehyde microcapsules were collected and stored in a 4°C refrigerator for later use.

[0032] Example 6: The preparation method of anisaldehyde microcapsules is as follows: S1: Weigh 25 parts corn starch, slowly add 500 parts distilled water, place in a water bath and heat at 90℃ with magnetic stirring for 30 minutes until the starch is completely gelatinized, then cool to room temperature; weigh 5 parts chitosan and add 500 parts 1% acetic acid solution, place in a water bath and heat at 90℃ with magnetic stirring for 30 minutes until the material dissolves, then cool to room temperature; mix the two evenly as the wall material of the microcapsules; S2: Add 3.5 parts of anisaldehyde to the wall material, and homogenize the mixture at high speed to obtain anisaldehyde emulsion.

[0033] S3: The anisaldehyde emulsion was dried using a spray dryer, and the anisaldehyde microcapsules were collected and stored in a 4°C refrigerator for later use.

[0034] The properties of the anisaldehyde microcapsules were determined, and the results are shown in Table 1. Table 1. Effects of different embodiments on encapsulation efficiency, drug loading, and particle size of anisaldehyde microcapsules The microcapsules prepared in Example 3 were selected for the next experiment. Example 7:

[0035] A method for preparing anisaldehyde microcapsule / polyvinyl alcohol composite film for carrot preservation includes the following steps, in parts by weight: S1: Weigh 8 parts of polyvinyl alcohol, slowly add 200 mL of distilled water, place in a water bath and heat for 1 hour at 90°C with magnetic stirring; S2: Add 1.6 mL of glycerol to the polyvinyl alcohol solution and stir at 50 °C for 30 min.

[0036] S3: Add 0.25% anisaldehyde microcapsules to a polyvinyl alcohol solution, homogenize at high speed, cast into a film, and dry at room temperature for 2 days. Example 8:

[0037] A method for preparing anisaldehyde microcapsule / polyvinyl alcohol composite film for carrot preservation includes the following steps, in parts by weight: S1: Weigh 8 parts of polyvinyl alcohol, slowly add 200 mL of distilled water, place in a water bath and heat for 1 hour at 90°C with magnetic stirring; S2: Add 1.6 mL of glycerol to the polyvinyl alcohol solution and stir at 50 °C for 30 min.

[0038] S3: Add 0.50% anisaldehyde microcapsules to a polyvinyl alcohol solution, homogenize at high speed, cast into a film, and dry at room temperature for 2 days. Example 9:

[0039] A method for preparing anisaldehyde microcapsule / polyvinyl alcohol composite film for carrot preservation includes the following steps, in parts by weight: S1: Weigh 8 parts of polyvinyl alcohol, slowly add 200 mL of distilled water, place in a water bath and heat for 1 hour at 90°C with magnetic stirring; S2: Add 1.6 mL of glycerol to the polyvinyl alcohol solution and stir at 50 °C for 30 min.

[0040] S3: Add 0.75% anisaldehyde microcapsules to a polyvinyl alcohol solution, homogenize at high speed, cast into a film, and dry at room temperature for 2 days.

[0041] Example 10: A method for preparing anisaldehyde microcapsule / polyvinyl alcohol composite film for carrot preservation includes the following steps, in parts by weight: S1: Weigh 8 parts of polyvinyl alcohol, slowly add 200 mL of distilled water, place in a water bath and heat for 1 hour at 90°C with magnetic stirring; S2: Add 1.6 mL of glycerol to the polyvinyl alcohol solution and stir at 50 °C for 30 min.

[0042] S3: Add 1.0% anisaldehyde microcapsules to a polyvinyl alcohol solution, homogenize at high speed, cast into a film, and dry at room temperature for 2 days.

[0043] Comparative Example 1: The difference between this comparative example and Example 9 is that anisaldehyde microcapsules are not added, as detailed below: S1: Weigh 8 parts of polyvinyl alcohol, slowly add 200 mL of distilled water, place in a water bath and heat for 1 hour at 90°C with magnetic stirring; S2: Add 1.6 mL of glycerol to the polyvinyl alcohol solution and stir at 50 °C for 30 min.

[0044] S3: The polyvinyl alcohol solution containing glycerol was homogenized at high speed and then cast into a film, which was then dried at room temperature for 2 days.

[0045] Due to the low water vapor permeability and good tensile strength of Example 9, the composite film prepared by Example 9 and Comparative Example 1 was selected for carrot preservation, and related indicators such as weight loss rate were measured.

Claims

1. A method for preparing anisaldehyde microcapsule / polyvinyl alcohol composite film for carrot preservation, characterized in that, The steps are as follows: Step (1) Preparation of anisaldehyde emulsion: Weigh 25 g of starch, slowly add 500 mL of distilled water, place in a water bath and heat at 90 ℃ under magnetic stirring for 30 min until the starch is completely gelatinized, then cool to room temperature; weigh 5 g of chitosan and add 500 mL of 1% acetic acid solution, place in a water bath and heat at 90 ℃ under magnetic stirring for 30 min until the material dissolves, then cool to room temperature; mix the two evenly as the wall material of the microcapsules; add 2.5~4.5 g of anisaldehyde to the wall material respectively, and homogenize the mixture at high speed to obtain anisaldehyde emulsion; Step (2) Preparation of anisaldehyde microcapsules: The anisaldehyde emulsion was dried using a spray dryer, and the anisaldehyde microcapsules were collected and stored in a refrigerator at 4 ℃ for later use; the spray drying parameters were set as follows: air inlet temperature 140~170 ℃, flow rate 100~500 mL / h; Step (3) Preparation of anisaldehyde microcapsule / polyvinyl alcohol composite membrane: Weigh 8 g of polyvinyl alcohol, slowly add 200 mL of distilled water, place in a water bath and heat for 1 h under magnetic stirring at 90 ℃; add 1.6 mL of glycerol to the polyvinyl alcohol solution and stir at 50 ℃ for 30 min; add 0.25%~1% anisaldehyde microcapsules to the polyvinyl alcohol solution, homogenize at high speed, cast the solution into a film, and dry at room temperature for 2 days; Step (4) Application of anisaldehyde microcapsule / polyvinyl alcohol composite film for preservation: Freshly purchased carrots were disinfected by soaking in sodium hypochlorite, washed with tap water, air-dried, cut into round slices, and packaged in a storage box with anisaldehyde microcapsule / polyvinyl alcohol composite film. The control group was packaged with PVA film and stored at 4 ℃ for 8 days. Samples were taken every 2 days and relevant indicators were measured.

2. The method for preparing the anisaldehyde microcapsule / polyvinyl alcohol composite film for carrot preservation according to claim 1, characterized in that... The starch refers to corn starch, or octenyl succinate corn starch, wherein the degree of substitution of octenyl succinate corn starch is between 0.0049 and 0.0198.

3. The method for preparing the anisaldehyde microcapsule / polyvinyl alcohol composite film for carrot preservation according to claim 1, characterized in that... The anisaldehyde microcapsules refer to the microcapsules prepared by adding 2.5~4.5 g of anisaldehyde to the wall material in step (2).

4. The method for preparing the anisaldehyde microcapsule / polyvinyl alcohol composite film for carrot preservation according to claim 1, characterized in that... The amount of microcapsules added to the composite membrane refers to 0.25% to 1% of the dry weight of PVA in step (3).

5. The method for preparing the anisaldehyde microcapsule / polyvinyl alcohol composite film for carrot preservation according to claim 1, characterized in that... Step (4) After cutting into 2 cm thick round slices, package them in a 13 cm × 13 cm storage box using anisaldehyde microcapsule / polyvinyl alcohol composite film.

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