Double-layer preservative film for prolonging shelf life of frozen beef and mutton after unfreezing and preparation method of double-layer preservative film

Abstract

The invention relates to a double-layer preservative film for prolonging the shelf life of frozen beef and mutton after unfreezing and a preparation method of the double-layer preservative film. According to the preparation method of the angelica dahurica extract-gliadin nano-particles, the angelica dahurica extract-gliadin nano-particles can be used for preparing a double-layer preservative film, and the preservative film is a natural component and is environmentally friendly and safe. The preservative film is of a double-layer structure, the mechanical performance is enhanced through the double-layer film structure, and meanwhile the preservative film has excellent oxygen and water vapor barrier performance and an antibacterial effect. According to the preservative film disclosed by the invention, slow release of active ingredients is realized by utilizing the Pycnogenin-gliadin nanoparticles, so that the antioxidant and antibacterial effects are remarkably improved, and the quality guarantee period of meat is prolonged. In addition, the preservative film does not need to be in direct contact with food in practical application, potential safety hazards of the food are further reduced, the operation process is simplified, pollution is avoided, a user can conveniently use the preservative film, the preservative film has the advantages of efficient preservation and environmental protection, and the preservative film has good application prospects and value.

Description

Technical Field

[0001] The present invention belongs to the technical field of food preservation, and more specifically relates to a double-layer fresh-keeping film for extending the shelf life of frozen beef and mutton after thawing, and a preparation method thereof. Background Art

[0002] Frozen beef and mutton, due to their ease of storage and transportation, play a crucial role in the global meat trade. However, after thawing, beef and mutton are susceptible to rapid quality degradation and a shortened shelf life due to increased microbial activity and accelerated enzyme reactions, coupled with the increased humidity during meat preservation. This process not only significantly depletes the nutritional value of the meat but also causes problems such as dulling, odor, and changes in taste, seriously impacting its quality and consumer acceptance. Furthermore, meat spoilage not only affects appearance and flavor but also poses a direct threat to food safety and consumer health. Therefore, effectively maintaining the quality of beef and mutton after thawing has become a critical issue that needs to be addressed in the meat processing industry.

[0003] Traditional plastic cling film materials such as polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) have long dominated the food cling film market due to their excellent barrier properties, mechanical strength, and cost advantages. However, these materials are difficult to degrade in the natural environment, leading to the continuous accumulation of "white pollution." Studies have shown that it takes more than 200 years for a single layer of PE film to completely degrade in soil, placing significant pressure on the ecological environment. Furthermore, microplastic particles formed by the fragmentation of plastic can accumulate through the food chain and enter the human bloodstream, inducing inflammatory reactions and cytotoxicity, posing a threat to human health. This has prompted the industry to seek environmentally friendly and sustainable packaging solutions.

[0004] Therefore, developing a green and environmentally friendly plastic wrap that can control the humidity during meat preservation, inhibit microbial growth and delay meat oxidation and deterioration has become an urgent problem to be solved in the field of food preservation. Summary of the Invention

[0005] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a Pycnogenol extract-gliadin nanoparticle, which can be used to prepare a double-layer plastic wrap. The double-layer plastic wrap can effectively block external oxygen and water vapor while regulating the humidity inside the film and releasing natural antioxidant active substances, inhibiting microbial growth and delaying fat oxidation, thereby extending the shelf life of thawed meat and maintaining its quality and commercial value during storage.

[0006] The first object of the present invention is to provide a Pycnogenol extract-gliadin nanoparticle and a preparation method and application thereof.

[0007] The second object of the present invention is to provide a composition and its application in preparing fresh-keeping film.

[0008] The third object of the present invention is to provide a fresh-keeping film and a preparation method thereof.

[0009] The fourth object of the present invention is to provide a double-layer fresh-keeping film.

[0010] The fifth object of the present invention is to provide an application of the above-mentioned fresh-keeping film or double-layer fresh-keeping film.

[0011] The above objects of the present invention are achieved by the following technical solutions:

[0012] The present invention discovers that encapsulating pycnogenol in gliadin nanoparticles can not only improve its stability and sustained-release characteristics, but also significantly enhance its application effect in meat preservation. This is expected to play a key role in extending the shelf life of thawed beef, maintaining its nutritional value and sensory quality, and promoting the development of meat preservation technology. Therefore, the present invention claims the following solutions:

[0013] The present invention provides a preparation method of pycnogenol extract-gliadin nanoparticles. The pycnogenol extract and gliadin are dissolved in an ethanol solution, and water is added to the ethanol solution under stirring conditions, and the solid is recovered to obtain pycnogenol extract-gliadin nanoparticles; wherein, the mass ratio of the pycnogenol extract to gliadin is (10-20):(50-80).

[0014] As an alternative embodiment, in the above preparation method, the mass ratio of the pycnogenol extract, gliadin, ethanol solution and water is (10-20):(50-80):(500-800):(1500-4500), and the concentration of the ethanol solution is 15-25%.

[0015] As an alternative embodiment, the concentration of the ethanol solution is 20%.

[0016] As an alternative embodiment, the preparation method of the ethanol solution is: ethanol and water are mixed in a volume ratio of 4:1.

[0017] As an alternative embodiment, in the above preparation method, by weight, 10-20 parts of pycnogenol extract and 50-80 parts of gliadin are dissolved in 500-800 parts (preferably 500 parts) of ethanol solution, and 1500-4500 parts of water are added to the ethanol solution under stirring conditions, and the solid is recovered to obtain pycnogenol extract-gliadin nanoparticles.

[0018] As an alternative embodiment, the stirring is carried out under the condition of 1500-2000 rpm by a magnetic stirrer.

[0019] As an alternative embodiment, the recovered solid is centrifuged, washed, and dried.

[0020] As an alternative embodiment, the centrifugation speed is 10,000 - 12,000 r / min and the time is 5 - 10 min; the detergent for washing is water; the drying is freeze-drying.

[0021] The present invention also provides the Pycnogenol extract - gliadin nanoparticles prepared by the above preparation method.

[0022] The present invention provides a composition, comprising the above Pycnogenol extract - gliadin nanoparticles, artemisia sphaerocephala gum, and glycerol; the mass ratio of the Pycnogenol extract - gliadin nanoparticles, artemisia sphaerocephala gum, and glycerol is (5 - 16):(2 - 8):(6:20).

[0023] As an alternative embodiment, the mass ratio of the Pycnogenol extract - gliadin nanoparticles, artemisia sphaerocephala gum, and glycerol is (5 - 13.3):(2 - 5.3):(6 - 13.3). <{

[0024] The application of the above Pycnogenol extract - gliadin nanoparticles or the above composition in the preparation of a fresh-keeping film is also within the protection scope of the present invention.

[0025] The present invention provides a fresh-keeping film containing the above Pycnogenol extract - gliadin nanoparticles or the above composition (Pycnogenol extract - gliadin nanoparticles, artemisia sphaerocephala gum, and glycerol).

[0026] The present invention provides a preparation method of the above fresh-keeping film. Add the Pycnogenol extract - gliadin nanoparticles to the artemisia sphaerocephala gum solution, then add glycerol, mix well to obtain a film solution, and make the film solution into a film to obtain the fresh-keeping film.

[0027] Preferably, the mass ratio of artemisia sphaerocephala gum, Pycnogenol extract - gliadin nanoparticles, and glycerol is (2 - 8)(5 - 15):(6 - 20).

[0028] Preferably, the mass concentration of the artemisia sphaerocephala gum solution is 0.1% - 1%, more preferably 0.13% - 0.8%.

[0029] As an alternative embodiment, the preparation method is as follows: by weight, add 2 - 8 parts of artemisia sphaerocephala gum to 1000 - 1500 parts of water, heat and dissolve, then add 5 - 15 parts of Pycnogenol extract - gliadin nanoparticles, and then add 6 - 20 parts of glycerol, mix well to obtain a film solution, and make the film solution into a film to obtain the fresh-keeping film.

[0030] The present invention provides a double-layer fresh-keeping film, which comprises an outer film (barrier layer) and an inner film (active layer), and the inner film is the fresh-keeping film made of the above-mentioned pine bark extract - gliadin nanoparticles.

[0031] Optionally, for the double-layer fresh-keeping film, the outer film comprises chitosan, gelatin and glycerol.

[0032] Specifically, the outer film is prepared from chitosan, gelatin and glycerol.

[0033] More specifically, the outer film is prepared into a film solution from chitosan, gelatin, glycerol and acetic acid, and the film solution is made into a film to obtain the outer film.

[0034] As an alternative embodiment, the mass ratio of chitosan, gelatin and glycerol is (10 - 20):(30 - 60):(20 - 40).

[0035] As an alternative embodiment, for the double-layer fresh-keeping film, the outer film comprises chitosan, gelatin, glycerol and acetic acid.

[0036] As an alternative embodiment, the mass ratio of chitosan, gelatin, glycerol and acetic acid is (10 - 20):(30 - 60):(20 - 40):(1000 - 1500).

[0037] As an alternative embodiment, the mass concentration of chitosan in the film solution is 0.6% - 2%; the mass concentration of gelatin in the film solution is 2% - 6%; the mass concentration of glycerol in the film solution is 1.3 - 4%;

[0038] As an alternative embodiment, for the double-layer fresh-keeping film, by weight: 500 - 1000 parts of the outer film and 300 - 500 parts of the inner film.

[0039] As an alternative embodiment, the preparation method of the double-layer fresh-keeping film comprises the following steps:

[0040] (1) Prepare the barrier layer film solution: Add gelatin to the chitosan solution and heat to dissolve, then add glycerol and mix evenly to obtain the barrier layer film solution;

[0041] (2) Prepare the active layer film solution: Add the above-mentioned pine bark extract - gliadin nanoparticles to the artemisia sphaerocephala gum solution, then add glycerol and mix evenly to obtain the active layer film solution;

[0042] (3) Dry the barrier layer film solution obtained in step (1) into a film; then dry the active layer film solution obtained in step (2) on the barrier layer into a film to obtain the finished double-layer fresh-keeping film;

[0043] There is no chronological order between step (1) and step (2).

[0044] As an alternative embodiment, in step (1), the solvent of the chitosan solution is a 0.3-1% acetic acid solution (the solvent is water).

[0045] As an alternative embodiment, in step (1), by weight, the film-forming solution of the barrier layer contains 10-20 parts of chitosan, 30-60 parts of gelatin, 20-40 parts of glycerol, and 1000-1500 parts of acetic acid solution.

[0046] As an alternative embodiment, after adding glycerol in steps (1) and (2), ultrasonic treatment is carried out.

[0047] As an alternative embodiment, the frequency of the ultrasonic treatment is 20-25 kHz (preferably 20 kHz), the power is 800-1100 W, and the time is 5-10 min.

[0048] As an alternative embodiment, the heating temperature in step (1) is 65-75 °C.

[0049] As an alternative embodiment, in step (3), the drying treatment temperature is 40-50 °C and the time is 4-6 h.

[0050] As an alternative embodiment, the preparation method of the Pycnogenol extract is as follows: making the bark of the maritime pine into powder, taking the powder for supercritical CO2 extraction to obtain the crude Pycnogenol extract; after the crude Pycnogenol extract is rotary-evaporated to obtain the Pycnogenol concentrate, the Pycnogenol concentrate is freeze-dried to obtain the Pycnogenol powder, and sieved to 80-100 mesh to obtain the Pycnogenol extract.

[0051] Specifically, the method for supercritical CO2 extraction of the crude Pycnogenol extract is as follows: the initial pressure is 20-25 MPa, the temperature is 40-45 °C, the CO2 flow rate is 10-15 kg / h, extraction is carried out for 40-60 min to remove low-polarity impurities, then the pressure is increased to 25-30 MPa, the temperature is 45-50 °C, an entrainer (6%-12% ethanol) accounting for 5%-8% of the CO2 flow rate is added, extraction is carried out for 80-120 min, then the pressure is reduced to 8-10 MPa, the temperature is reduced to 30-35 °C to recover low-polarity impurities, and further reduced to 5-7 MPa, 20-25 °C to obtain the crude Pycnogenol extract.

[0052] Specifically, the rotary evaporation is as follows: placing the collected crude Pycnogenol extract in a rotary evaporator (temperature 40-45 °C) to distill off ethanol.

[0053] Specifically, the freeze-drying is as follows: using a freeze dryer (-50 °C to -40 °C) to freeze-dry the Pycnogenol concentrate.

[0054] As an alternative embodiment, the preparation method of the Pycnogenol extract comprises the following steps:

[0055] S1. Raw material pretreatment: Using the bark of maritime pine as the raw material, crushing it and sieving it to 40 - 60 mesh;

[0056] S2. Supercritical CO2 extraction: Initial pressure 20 - 25 MPa, temperature 40 - 45 °C, CO2 flow rate 10 - 15 kg / h, extracting for 40 - 60 min to remove low - polarity impurities. Subsequently, the pressure is increased to 25 - 30 MPa, temperature 45 - 50 °C, and an entrainer (6% - 12% ethanol) accounting for 5% - 8% of the CO2 flow rate is added, and extracting for 80 - 120 min to extract the crude Pycnogenol extract;

[0057] S3. Separation: Reducing the pressure to 8 - 10 MPa, lowering the temperature to 30 - 35 °C to recover low - polarity impurities, further reducing the pressure to 5 - 7 MPa, 20 - 25 °C, and collecting the crude Pycnogenol extract;

[0058] S4. Concentration: Placing the collected crude Pycnogenol extract in a rotary evaporator (temperature 40 - 45 °C) to distill off ethanol to obtain the concentrated Pycnogenol solution;

[0059] S5. Freeze - drying: Using a freeze - dryer (-50 °C to -40 °C) to lyophilize the concentrated Pycnogenol solution to obtain Pycnogenol powder, sieving it to 80 - 100 mesh to obtain the Pycnogenol extract.

[0060] The application of the above - mentioned fresh - keeping film or the above - mentioned double - layer fresh - keeping film in food preservation or in packaged food should also be within the protection scope of the present invention.

[0061] As an alternative, the food is frozen meat, such as beef and mutton; the preservation is the preservation of frozen meat after thawing.

[0062] The present invention has the following beneficial effects:

[0063] The present invention provides a double - layer fresh - keeping film made of all - natural components, completely avoiding the use of chemical substances, and abandoning PE / PET plastics, which is more environmentally friendly and safe, reducing the impact on the environment.

[0064] The fresh - keeping film of the present invention has a double - layer structure, composed of a barrier layer and an active layer. The mechanical properties and the directional release effect are enhanced through the double - layer film structure. At the same time, it has excellent oxygen and water - vapor barrier properties and antibacterial effects. The inner layer uses artemisia sphaerocephala gum as the substrate, effectively regulating the headspace humidity in the package, alleviating the problem of water loss of meat after thawing, and maintaining the quality and taste of the meat.

[0065] The fresh-keeping film of the present invention utilizes the Pycnogenol extract - gliadin nanoparticles to achieve the slow release of active ingredients, significantly improving the antioxidant and antibacterial effects and prolonging the shelf life of meat.

[0066] The preparation process of the fresh-keeping film of the present invention is simple, has a short production cycle and is easy to operate. In practical applications, it does not need to directly contact food, can avoid the dissolution of additives (such as plasticizers) in the packaging into grease, reduce the potential food safety hazards, simplify the operation process, avoid contamination, and is convenient for users to use. It has both the advantages of high-efficiency fresh-keeping and environmental protection, and has good application prospects and value. Brief Description of the Drawings

[0067] Figure 1 pH value measurement results of meat samples treated with different fresh-keeping films in Experimental Example 1 (different lowercase letters in the figure indicate significant differences, P < 0.05).

[0068] Figure 2 TVB-N measurement results of meat samples treated with different fresh-keeping films in Experimental Example 1 (different lowercase letters in the figure indicate significant differences, P < 0.05).

[0069] Figure 3 TBARS measurement results of meat samples treated with different fresh-keeping films in Experimental Example 1 (different lowercase letters in the figure indicate significant differences, P < 0.05).

[0070] Figure 4 TBARS measurement results of meat samples treated with different fresh-keeping films in Experimental Example 4 (different lowercase letters in the figure indicate significant differences, P < 0.05). Detailed Embodiments

[0071] The present invention will be further described below in conjunction with the drawings in the specification and specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field.

[0072] Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0073] In the following examples, the preparation method of the Pycnogenol extract used includes the following steps:

[0074] S1. Raw material pretreatment: Using the bark of French coastal pine trees as raw materials, crushing and sieving them to 40 - 60 mesh;

[0075] S2. Supercritical CO2 extraction: Initial pressure is 20 - 25 MPa, temperature is 40 - 45 °C, CO2 flow rate is 10 - 15 kg / h, extract for 40 - 60 min to remove low-polarity impurities. Subsequently, increase the pressure to 25 - 30 MPa, temperature to 45 - 50 °C, add an entrainer (6% - 12% ethanol) accounting for 5% - 8% of the CO2 flow rate, and extract for 80 - 120 min to extract the crude extract of pycnogenol;

[0076] S3. Separation: Reduce the pressure to 8 - 10 MPa, lower the temperature to 30 - 35 °C to recover low-polarity impurities. Further reduce the pressure to 5 - 7 MPa and temperature to 20 - 25 °C to collect the crude extract of pycnogenol;

[0077] S4. Concentration: Place the collected crude extract of pycnogenol in a rotary evaporator (temperature 40 - 45 °C) to distill off ethanol and obtain a clear concentrated pycnogenol solution;

[0078] S5. Freeze-drying: Use a freeze dryer (-50 °C to -40 °C) to lyophilize the concentrated pycnogenol solution to obtain a light pink to brownish powder, and sieve it to 80 - 100 mesh to obtain the pycnogenol extract.

[0079] Chitosan was purchased from Sinopharm Chemical Reagent Co., Ltd., product number: 69047438.

[0080] Glycerol was purchased from Sinopharm Chemical Reagent Co., Ltd., product number: S52763.

[0081] Gliadin was purchased from Shanghai Xingye Biotechnology Co., Ltd., the CAS number of gliadin is 9007 - 90 - 3, and the structural formula is:

[0082]

[0083] Vitamin E was purchased from Shandong Qilu Biotechnology Group Co., Ltd.

[0084] Tea polyphenols were purchased from Shandong Qilu Biotechnology Group Co., Ltd.

[0085] For the experimental methods of measuring water vapor transmission rate and oxygen permeability, please refer to the specific reference "Novel multilayer chitosan / emulsion-loaded syringic acid grafted apple pectin film with sustained control release for active food packaging".

[0086] The degree of fat oxidation was evaluated using the thiobarbituric acid method. The specific method was referred to the literature "A new strategy to improve the quality of frozen chicken wings High voltage electrostatic field combined with phosphorus-free water retaining agent".

[0087] Example 1

[0088] A double-layer plastic wrap for extending the shelf life of frozen beef shanks after thawing, comprising, by weight, 500 parts of a chitosan / gelatin barrier layer and 300 parts of a Pycnogenol extract-gliadin nanoparticle / artemisia gum active layer. The steps are as follows:

[0089] (1) Preparation of Pycnogenol extract-gliadin nanoparticles: 10 parts of Pycnogenol extract and 50 parts of gliadin were dissolved in 500 parts of 20% ethanol solution to obtain a stock solution; 1500 parts of water were added to the stock solution under vigorous stirring (1500-2000 rpm) with a magnetic stirrer to obtain a Pycnogenol extract-gliadin nanoparticle suspension; the nanoparticle suspension was centrifuged at 12000 rpm for 5 minutes, and the sediment was washed three times with water and freeze-dried to obtain dry Pycnogenol extract-gliadin nanoparticles;

[0090] (2) Preparation of chitosan / gelatin barrier layer film-forming solution: 10 parts of chitosan were completely dissolved in 1000 parts of 0.3% acetic acid to obtain a chitosan solution; 30 parts of gelatin were added to the chitosan solution and heated at 70°C to dissolve, and then 20 parts of glycerol were added and stirred continuously. After ultrasonic treatment, a chitosan / gelatin barrier layer film-forming solution was obtained. The ultrasonic treatment time was 8 minutes, the ultrasonic frequency was 20 kHz, and the power was 900 W.

[0091] (3) Preparing a film-forming solution of the active layer of Pycnogenol extract-gliadin nanoparticles / Artemisia sphaerosa gum: adding 2 parts of Artemisia sphaerosa gum to 1000 parts of water, heating and stirring at 75° C. to obtain a uniform and fine gum solution; adding 5 parts of Pycnogenol extract-gliadin nanoparticles obtained in step (1) to the gum solution and stirring, then adding 6 parts of glycerol and continuing to stir, and after ultrasonic treatment, obtaining a film-forming solution of the active layer of Pycnogenol extract-gliadin nanoparticles / Artemisia sphaerosa gum, wherein the ultrasonic treatment frequency is 20 kHz, the power is 900 W, and the time is 8 min;

[0092] (4) Preparation of double-layer fresh-keeping film: Pour 500 parts of the barrier layer film-forming solution obtained in step (2) into a petri dish and dry it at 45 °C for 5 h to form a film; then pour 300 parts of the active layer film-forming solution obtained in step (3) onto the barrier layer and dry it at 45 °C for 5 h to form a film; finally, peel off the film to obtain the finished double-layer fresh-keeping film for extending the shelf life of thawed frozen beef shanks.

[0093] The particle size of the prepared Pycnogenol extract - gliadin nanoparticles was detected using a multi-angle particle size and high-sensitivity Zeta potential analyzer to be 294.40 ± 37.57 nm.

[0094] Example 2

[0095] A double-layer fresh-keeping film for extending the shelf life of thawed frozen beef brisket, by weight, includes 500 parts of a chitosan / gelatin barrier layer and 500 parts of a Pycnogenol extract - gliadin nanoparticle / artemisia sphaerocephala Krasch gum active layer. The steps are as follows:

[0096] (1) Preparation of Pycnogenol extract - gliadin nanoparticles: Dissolve 20 parts of Pycnogenol extract and 80 parts of gliadin in 500 parts of 20% ethanol solution to obtain a stock solution; under vigorous stirring (1500 - 2000 rpm) of a magnetic stirrer, add 3000 parts of water to the stock solution to obtain a suspension of Pycnogenol extract - gliadin nanoparticles; centrifuge the nanoparticle suspension at 10000 r / min for 10 min, then wash the sediment three times with water and freeze-dry to obtain dry Pycnogenol extract - gliadin nanoparticles;

[0097] (2) Preparation of chitosan / gelatin barrier layer film-forming solution: Completely dissolve 15 parts of chitosan in 1200 parts of 0.3% acetic acid to obtain a chitosan solution; add 45 parts of gelatin to the chitosan solution and heat it to dissolve at 70 °C, then add 30 parts of glycerol and continue stirring, and after ultrasonic treatment, obtain the chitosan / gelatin barrier layer film-forming solution, with the ultrasonic treatment frequency of 20 kHz, power of 1100 W, and time of 10 min;

[0098] (3) Preparation of Pycnogenol extract - gliadin nanoparticle / artemisia sphaerocephala Krasch gum active layer film-forming solution: Add 6 parts of artemisia sphaerocephala Krasch gum to 1200 parts of water, heat and stir at 75 °C to obtain a uniform and delicate gum solution; add 10 parts of the Pycnogenol extract - gliadin nanoparticles obtained in step (1) to the gum solution and stir, then add 16 parts of glycerol and continue stirring, and after ultrasonic treatment, obtain the Pycnogenol extract - gliadin nanoparticle / artemisia sphaerocephala Krasch gum active layer film-forming solution, with the ultrasonic treatment frequency of 25 kHz, power of 800 W, and time of 10 min;

[0099] (4) Preparation of a double-layer cling film: 500 parts of the barrier layer film-forming solution obtained in step (2) were poured into a culture dish and dried at 40°C for 6 hours to form a film; then 500 parts of the active layer film-forming solution obtained in step (3) were cast on the barrier layer and dried at 40°C for 6 hours to form a film; finally, the film was peeled off to obtain a double-layer cling film product that extends the shelf life of the frozen beef brisket after thawing.

[0100] Example 3

[0101] A double-layer plastic wrap for extending the shelf life of frozen lamb legs after thawing, comprising, by weight, 1000 parts of a chitosan / gelatin barrier layer and 500 parts of a Pycnogenol extract-gliadin nanoparticle / artemisia gum active layer. The steps are as follows:

[0102] (1) Preparation of Pycnogenol extract-gliadin nanoparticles: 15 parts of Pycnogenol extract and 75 parts of gliadin were dissolved in 500 parts of 20% ethanol solution to obtain a stock solution; 4500 parts of water were added to the stock solution under vigorous stirring (1500-2000 rpm) with a magnetic stirrer to obtain a Pycnogenol extract-gliadin nanoparticle suspension; the nanoparticle suspension was centrifuged at 11000 rpm for 8 minutes, and the sediment was washed three times with water and freeze-dried to obtain dry Pycnogenol extract-gliadin nanoparticles;

[0103] (2) Preparation of chitosan / gelatin barrier layer film-forming solution: 20 parts of chitosan were completely dissolved in 1500 parts of 0.3% acetic acid to obtain a chitosan solution; 60 parts of gelatin were added to the chitosan solution and heated at 70°C to dissolve, and then 40 parts of glycerol were added and stirred continuously. After ultrasonic treatment, a chitosan / gelatin barrier layer film-forming solution was obtained. The ultrasonic treatment frequency was 20 kHz, the power was 900 W, and the time was 5 min.

[0104] (3) Preparing a film-forming solution of a Pycnogenol extract-gliadin nanoparticle / Artemisia sphaerosa gum active layer: adding 8 parts of Artemisia sphaerosa gum to 1500 parts of water, heating and stirring at 75° C. to obtain a uniform and fine gum solution; adding 15 parts of the Pycnogenol extract-gliadin nanoparticles obtained in step (1) to the gum solution and stirring, then adding 20 parts of glycerol and continuing to stir, and after ultrasonic treatment, obtaining a film-forming solution of a Pycnogenol extract-gliadin nanoparticle / Artemisia sphaerosa gum active layer, wherein the ultrasonic treatment frequency is 20 kHz, the power is 900 W, and the time is 5 min;

[0105] (4) Preparation of double-layer fresh-keeping film: Pour 1000 parts of the barrier layer film-forming solution obtained in step (2) into a petri dish, and dry it at 50 °C for 4 h to form a film; then pour 500 parts of the active layer film-forming solution obtained in step (3) onto the barrier layer, and dry it at 50 °C for 4 h to form a film; finally, peel off the film to obtain the finished double-layer fresh-keeping film for extending the shelf life of thawed frozen beef and mutton.

[0106] Example 4 Single-layer Pycnogenol extract-wheat gliadin nanoparticles / artemisia sphaerocephala Krasch gum active layer fresh-keeping film

[0107] The difference from Example 1 is that only a single-layer Pycnogenol extract-wheat gliadin nanoparticles / artemisia sphaerocephala Krasch gum active layer fresh-keeping film is prepared. Prepare the Pycnogenol extract-wheat gliadin nanoparticles / artemisia sphaerocephala Krasch gum active layer film-forming solution according to the method of Example 1, and separately prepare the Pycnogenol extract-wheat gliadin nanoparticles / artemisia sphaerocephala Krasch gum active layer.

[0108] The specific preparation method is as follows:

[0109] (1) Preparation of Pycnogenol extract-wheat gliadin nanoparticles: Dissolve 10 parts of Pycnogenol extract and 50 parts of wheat gliadin in 500 parts of 20% ethanol solution to obtain a stock solution; under vigorous stirring (1500 - 2000 rpm) of a magnetic stirrer, add 1500 parts of water to the stock solution to obtain a Pycnogenol extract-wheat gliadin nanoparticle suspension; centrifuge the nanoparticle suspension at 12000 r / min for 5 min, then wash the sediment three times with water and freeze-dry to obtain dry Pycnogenol extract-wheat gliadin nanoparticles;

[0110] (2) Preparation of Pycnogenol extract-wheat gliadin nanoparticles / artemisia sphaerocephala Krasch gum active layer film-forming solution: Add 2 parts of artemisia sphaerocephala Krasch gum to 1000 parts of water, heat and stir at 75 °C to obtain a uniform and delicate gum solution; add 5 parts of the Pycnogenol extract-wheat gliadin nanoparticles obtained in step (1) to the gum solution and stir, then add 6 parts of glycerol and continue to stir. After ultrasonic treatment, a Pycnogenol extract-wheat gliadin nanoparticles / artemisia sphaerocephala Krasch gum active layer film-forming solution is obtained. The ultrasonic treatment frequency is 20 kHz, the power is 900 W, and the time is 8 min;

[0111] (3) Preparation of fresh-keeping film: Dry the active layer film-forming solution obtained in (2) at 45 °C for 5 h to form a film; peel off the film to obtain the Pycnogenol extract-wheat gliadin nanoparticles / artemisia sphaerocephala Krasch gum active layer.

[0112] Comparative Example 1 Single-layer chitosan / gelatin barrier layer fresh-keeping film

[0113] The difference from Example 1 is that only a single-layer chitosan / gelatin barrier layer is prepared into a fresh-keeping film. Prepare the chitosan / gelatin barrier layer film-forming solution according to the method of Example 1, and separately prepare the chitosan / gelatin barrier layer.

[0114] The specific preparation method is as follows:

[0115] (1) Prepare the chitosan / gelatin barrier layer film-forming solution: 10 parts of chitosan are completely dissolved in 1000 parts of 0.3% acetic acid to obtain a chitosan solution; 30 parts of gelatin are added to the chitosan solution and dissolved by heating at 70°C, and then 20 parts of glycerol are added and stirred continuously. After ultrasonic treatment, a chitosan / gelatin barrier layer film-forming solution is obtained. The time of ultrasonic treatment is 8 min, the ultrasonic frequency is 20 kHz, and the power is 900 W;

[0116] (2) Prepare the fresh-keeping film: Pour the barrier layer film-forming solution into a petri dish and dry it at 45°C for 5 h to form a film; Peel off the film to obtain the chitosan / gelatin barrier layer.

[0117] Comparative Example 2 Vitamin E nanoparticle double-layer fresh-keeping film

[0118] Prepare the vitamin E nanoparticle double-layer fresh-keeping film. The difference from Example 3 is that vitamin E - gliadin nanoparticles replace the polyphenol-rich extract - gliadin nanoparticles, and the remaining steps are the same as those in Example 3.

[0119] The specific preparation method is as follows:

[0120] (1) Prepare vitamin E - gliadin nanoparticles: Dissolve 15 parts of vitamin E and 75 parts of gliadin in 500 parts of 20% ethanol solution to obtain a stock solution; Under vigorous stirring of a magnetic stirrer (1500 - 2000 rpm), add 4500 parts of water to the stock solution to obtain a vitamin E - gliadin nanoparticle suspension; Centrifuge the nanoparticle suspension at 11000 r / min for 8 min, then wash the sediment three times with water and freeze-dry to obtain dry vitamin E - gliadin nanoparticles;

[0121] (2) Prepare the chitosan / gelatin barrier layer film-forming solution: Dissolve 20 parts of chitosan completely in 1500 parts of 0.3% acetic acid to obtain a chitosan solution; Add 60 parts of gelatin to the chitosan solution and dissolve by heating at 70°C, then add 40 parts of glycerol and stir continuously. After ultrasonic treatment, a chitosan / gelatin barrier layer film-forming solution is obtained. The ultrasonic treatment frequency is 20 kHz, the power is 900 W, and the time is 5 min;

[0122] (3) Preparation of vitamin E - gliadin nanoparticle / artemisia sphaerocephala Krasch gum active layer film - forming solution: Add 8 parts of artemisia sphaerocephala Krasch gum to 1500 parts of water, heat and stir at 75 °C to obtain a uniform and delicate gum solution; add 15 parts of the vitamin E - gliadin nanoparticles obtained in step (1) to the gum solution and stir, then add 20 parts of glycerol and continue stirring. After ultrasonic treatment, a vitamin E - gliadin nanoparticle / artemisia sphaerocephala Krasch gum active layer film - forming solution is obtained. The ultrasonic treatment frequency is 20 kHz, the power is 900 W, and the time is 5 min;

[0123] (4) Preparation of double - layer fresh - keeping film: Pour 1000 parts of the barrier layer film - forming solution obtained in step (2) into a petri dish and dry it at 50 °C for 4 h to form a film; then pour 500 parts of the active layer film - forming solution obtained in step (3) onto the barrier layer and dry it at 50 °C for 4 h to form a film; finally, peel off the film to obtain the double - layer fresh - keeping film.

[0124] Comparative Example 3 Tea polyphenol nanoparticle double - layer fresh - keeping film

[0125] The preparation of the tea polyphenol nanoparticle double - layer fresh - keeping film is different from that of Example 3 in that: tea polyphenol - gliadin nanoparticles are used instead of pine bark extract - gliadin nanoparticles, and the remaining steps are the same as those in Example 3.

[0126] The specific preparation method is as follows:

[0127] (1) Preparation of tea polyphenol - gliadin nanoparticles: Dissolve 15 parts of tea polyphenols and 75 parts of gliadin in 500 parts of 20% ethanol solution to obtain a stock solution; under vigorous stirring (1500 - 2000 rpm) of a magnetic stirrer, add 4500 parts of water to the stock solution to obtain a tea polyphenol - gliadin nanoparticle suspension; centrifuge the nanoparticle suspension at 11000 r / min for 8 min, then wash the sediment three times with water and freeze - dry to obtain dry tea polyphenol - gliadin nanoparticles;

[0128] (2) Preparation of chitosan / gelatin barrier layer film - forming solution: Completely dissolve 20 parts of chitosan in 1500 parts of 0.3% acetic acid to obtain a chitosan solution; add 60 parts of gelatin to the chitosan solution and dissolve it by heating at 70 °C, then add 40 parts of glycerol and continue stirring. After ultrasonic treatment, a chitosan / gelatin barrier layer film - forming solution is obtained. The ultrasonic treatment frequency is 20 kHz, the power is 900 W, and the time is 5 min;

[0129] (3) Preparation of tea polyphenol - gliadin nanoparticle / artemisia sphaerocephala krasch gum active layer film - forming solution: Add 8 parts of artemisia sphaerocephala krasch gum to 1500 parts of water, heat and stir at 75 °C to obtain a uniform and delicate gum solution; add 15 parts of the tea polyphenol - gliadin nanoparticles obtained in step (1) to the gum solution and stir, then add 20 parts of glycerol and continue stirring. After ultrasonic treatment, a tea polyphenol - gliadin nanoparticle / artemisia sphaerocephala krasch gum active layer film - forming solution is obtained. The ultrasonic treatment frequency is 20 kHz, the power is 900 W, and the time is 5 min;

[0130] (4) Preparation of double - layer fresh - keeping film: Pour 1000 parts of the barrier layer film - forming solution obtained in step (2) into a petri dish and dry it at 50 °C for 4 h to form a film; then pour 500 parts of the active layer film - forming solution obtained in step (3) onto the barrier layer and dry it at 50 °C for 4 h to form a film; finally, peel off the film to obtain the double - layer fresh - keeping film.

[0131] Comparative Example 4 Pycnogenol extract double - layer fresh - keeping film

[0132] The preparation of Pycnogenol extract double - layer fresh - keeping film is different from that of Example 3 in that: Pycnogenol extract is used instead of Pycnogenol extract - gliadin nanoparticles, and the remaining steps are the same as those in Example 3.

[0133] The specific preparation method is as follows:

[0134] (1) Preparation of chitosan / gelatin barrier layer film - forming solution: Completely dissolve 20 parts of chitosan in 1500 parts of 0.3% acetic acid to obtain a chitosan solution; add 60 parts of gelatin to the chitosan solution and heat and dissolve it at 70 °C, then add 40 parts of glycerol and continue stirring. After ultrasonic treatment, a chitosan / gelatin barrier layer film - forming solution is obtained. The ultrasonic treatment frequency is 20 kHz, the power is 900 W, and the time is 5 min;

[0135] (2) Preparation of Pycnogenol extract / artemisia sphaerocephala krasch gum active layer film - forming solution: Add 8 parts of artemisia sphaerocephala krasch gum to 1500 parts of water, heat and stir at 75 °C to obtain a uniform and delicate gum solution; add 15 parts of Pycnogenol extract to the gum solution and stir, then add 20 parts of glycerol and continue stirring. After ultrasonic treatment, a Pycnogenol extract / artemisia sphaerocephala krasch gum active layer film - forming solution is obtained. The ultrasonic treatment frequency is 20 kHz, the power is 900 W, and the time is 5 min;

[0136] (3) Preparation of double - layer fresh - keeping film: Pour 1000 parts of the barrier layer film - forming solution obtained in step (1) into a petri dish and dry it at 50 °C for 4 h to form a film; then pour 500 parts of the active layer film - forming solution obtained in step (2) onto the barrier layer and dry it at 50 °C for 4 h to form a film; finally, peel off the film to obtain the double - layer fresh - keeping film.

[0137] Comparative Example 5 Vitamin E double - layer fresh - keeping film

[0138] To prepare a vitamin E double-layer fresh-keeping film, the difference from Example 3 is that vitamin E is used instead of the extract of Pinus sylvestris var. mongolica Litv.-gliadin nanoparticles, and the remaining steps are the same as those in Example 3.

[0139] The specific preparation method is as follows:

[0140] (1) Prepare the chitosan / gelatin barrier layer film-forming solution: Completely dissolve 20 parts of chitosan in 1500 parts of 0.3% acetic acid to obtain a chitosan solution; add 60 parts of gelatin to the chitosan solution and dissolve it by heating at 70°C, then add 40 parts of glycerol and continue stirring. After ultrasonic treatment, a chitosan / gelatin barrier layer film-forming solution is obtained. The ultrasonic treatment frequency is 20 kHz, the power is 900 W, and the time is 5 min;

[0141] (2) Prepare the vitamin E / artemisia sphaerocephala Krasch gum active layer film-forming solution: Add 8 parts of artemisia sphaerocephala Krasch gum to 1500 parts of water, heat and stir at 75°C to obtain a uniform and delicate gum solution; add 15 parts of vitamin E to the gum solution and stir, then add 20 parts of glycerol and continue stirring. After ultrasonic treatment, a vitamin E / artemisia sphaerocephala Krasch gum active layer film-forming solution is obtained. The ultrasonic treatment frequency is 20 kHz, the power is 900 W, and the time is 5 min;

[0142] (3) Prepare the double-layer fresh-keeping film: Pour 1000 parts of the barrier layer film-forming solution obtained in step (1) into a petri dish and dry it at 50°C for 4 h to form a film; then pour 500 parts of the active layer film-forming solution obtained in step (2) onto the barrier layer and dry it at 50°C for 4 h to form a film; finally, peel off the film to obtain the double-layer fresh-keeping film.

[0143] Comparative Example 6 Tea polyphenol double-layer fresh-keeping film

[0144] To prepare a tea polyphenol double-layer fresh-keeping film, the difference from Example 3 is that tea polyphenols are used instead of the extract of Pinus sylvestris var. mongolica Litv.-gliadin nanoparticles, and the remaining steps are the same as those in Example 3

[0145] The specific preparation method is as follows:

[0146] (1) Prepare the chitosan / gelatin barrier layer film-forming solution: Completely dissolve 20 parts of chitosan in 1500 parts of 0.3% acetic acid to obtain a chitosan solution; add 60 parts of gelatin to the chitosan solution and dissolve it by heating at 70°C, then add 40 parts of glycerol and continue stirring. After ultrasonic treatment, a chitosan / gelatin barrier layer film-forming solution is obtained. The ultrasonic treatment frequency is 20 kHz, the power is 900 W, and the time is 5 min;

[0147] (2) Preparation of the film-forming solution for the tea polyphenol / artemisia sphaerocephala Krasch gum active layer: Add 8 parts of artemisia sphaerocephala Krasch gum to 1500 parts of water, heat and stir at 75 °C to obtain a uniform and delicate gum solution; add 15 parts of tea polyphenols to the gum solution and stir, then add 20 parts of glycerol and continue stirring. After ultrasonic treatment, a film-forming solution for the tea polyphenol / artemisia sphaerocephala Krasch gum active layer is obtained. The ultrasonic treatment frequency is 20 kHz, the power is 900 W, and the time is 5 min;

[0148] (3) Preparation of the double-layer fresh-keeping film: Pour 1000 parts of the barrier layer film-forming solution obtained in step (1) into a petri dish and dry it at 50 °C for 4 h to form a film; then pour 500 parts of the active layer film-forming solution obtained in step (2) onto the barrier layer and dry it at 50 °C for 4 h to form a film; finally, peel off the film to obtain the double-layer fresh-keeping film.

[0149] Comparative Example 7 Double-layer fresh-keeping film without antioxidant

[0150] Preparation of a double-layer fresh-keeping film without antioxidant, the difference from Example 3 is that no antioxidant is added to the active layer film-forming solution, and the other steps are the same as those in Example 3.

[0151] The specific preparation method is as follows:

[0152] (1) Preparation of the chitosan / gelatin barrier layer film-forming solution: Completely dissolve 20 parts of chitosan in 1500 parts of 0.3% acetic acid to obtain a chitosan solution; add 60 parts of gelatin to the chitosan solution and heat and dissolve it at 70 °C, then add 40 parts of glycerol and continue stirring. After ultrasonic treatment, a chitosan / gelatin barrier layer film-forming solution is obtained. The ultrasonic treatment frequency is 20 kHz, the power is 900 W, and the time is 5 min;

[0153] (2) Preparation of the artemisia sphaerocephala Krasch gum active layer film-forming solution: Add 8 parts of artemisia sphaerocephala Krasch gum to 1500 parts of water, heat and stir at 75 °C to obtain a uniform and delicate gum solution, then add 20 parts of glycerol and continue stirring. After ultrasonic treatment, an artemisia sphaerocephala Krasch gum active layer film-forming solution is obtained. The ultrasonic treatment frequency is 20 kHz, the power is 900 W, and the time is 5 min;

[0154] (3) Preparation of the double-layer fresh-keeping film: Pour 1000 parts of the barrier layer film-forming solution obtained in step (1) into a petri dish and dry it at 50 °C for 4 h to form a film; then pour 500 parts of the active layer film-forming solution obtained in step (2) onto the barrier layer and dry it at 50 °C for 4 h to form a film; finally, peel off the film to obtain the double-layer fresh-keeping film.

[0155] Experimental Example 1

[0156] I. Experimental method

[0157] The fresh-keeping films prepared in Example 1, the fresh-keeping films prepared in Example 4, the commercially available fresh-keeping films, and the fresh-keeping films of Comparative Example 1 were cut into appropriate sizes. For the double-layer fresh-keeping film of Example 1, with the chitosan / gelatin barrier layer facing outward and the pine bark extract - gliadin nanoparticles / artemisia sphaerocephala krasch gum active layer facing inward, it was tightly covered on the open mouth of the fresh-keeping box containing thawed beef shanks; while for the single-layer fresh-keeping films of the positive control PE fresh-keeping film, Example 4, and Comparative Example 1, any side was covered on the open mouth of the fresh-keeping box containing thawed beef shanks. Using the commercially available fresh-keeping film treatment (covering the open mouth of the fresh-keeping box with the commercially available fresh-keeping film) as the positive control, and not covering the open mouth of the fresh-keeping box with a fresh-keeping film as the negative control. Each treatment was stored at 4°C for fresh-keeping.

[0158] During storage, the acid produced by bacteria decomposing proteins causes the pH value in the meat tissue to increase; the proteins in the meat are decomposed by enzymes and bacteria, generating volatile nitrogen-containing substances such as ammonia and amines. The content of these substances is measured by total volatile basic nitrogen (TVB-N); the degree of lipid oxidation is usually expressed by the TBARS value. The higher the TBARS value, the more severe the oxidation degree of the food, thus reflecting the deterioration of the meat quality.

[0159] Therefore, the pH value, total volatile basic nitrogen (TVB-N), and TBARS of the beef shanks after 0, 2, 4, and 6 days of fresh-keeping storage were measured to evaluate the fresh-keeping effect of the meat. Specifically, 3 g of chopped beef shank samples were added to 27 ml of deionized water. After shearing with a shearer for 30 s, the supernatant was taken after centrifuging at 10000 g for 10 min using a centrifuge. The pH value of the supernatant was measured using a pH meter. The samples were processed for distillation using an automatic Kjeldahl apparatus and titrated with 0.01 mol / L HCl to obtain TVB-N. The degree of fat oxidation was evaluated by the thiobarbituric acid method.

[0160] II. Experimental Results

[0161] The pH value measurement results of the meat samples treated with different fresh-keeping films are as Figure 1 shown, the TVB-N measurement results are as Figure 2 shown, and the TBARS measurement results are as Figure 3 shown. The results show that: the treatment with the fresh-keeping film of Example 1 can significantly reduce the changes in the pH value, TVB-N, and TBARS of the beef shank samples at each test time point, and the fresh-keeping effect is significantly better than that of the control, Example 4, and Comparative Example 1, indicating that the double-layer fresh-keeping film of Example 1 has a good effect on fresh-keeping meat. In addition, the treatment with the fresh-keeping film of Example 4 is significantly better than that of the commercially available PE fresh-keeping film.

[0162] Experimental Example 2

[0163] I. Experimental Method

[0164] The plastic food wraps prepared in Example 2, the plastic food wraps prepared in Example 4, commercially available plastic food wraps, and the plastic food wraps of Comparative Example 1 were cut into appropriate sizes. For the double-layer plastic food wrap of Example 2, with the chitosan / gelatin barrier layer facing outward and the pine bark extract - gliadin nanoparticles / artemisia sphaerocephala gum active layer facing inward, it was tightly covered on the open mouth of the fresh-keeping box containing thawed sirloin; while for the single-layer plastic food wraps of the positive control PE plastic food wrap, Example 4, and Comparative Example 1, any side was covered on the open mouth of the fresh-keeping box containing thawed sirloin. Treating with commercially available plastic food wraps (covering the open mouth of the fresh-keeping box with commercially available plastic food wraps) was used as the positive control, and not covering the open mouth of the fresh-keeping box with a plastic food wrap was used as the negative control. Each treatment was stored at 4 °C for freshness preservation.

[0165] In addition, the mechanical properties of the plastic food wraps of Example 2, 4, and Comparative Example 1 were measured.

[0166] II. Experimental Results

[0167] The experimental results proved that the plastic food wraps prepared in Example 2 and the plastic food wraps prepared in Example 4 had significantly better effects on preserving thawed sirloin than the positive control, negative control, and the plastic food wrap treatment of Comparative Example 1.

[0168] The mechanical properties of the plastic food wraps of Example 2, 4, and Comparative Example 1 were measured, and the measurement results are shown in Table 1. The results showed that compared with Example 4 and Comparative Example 1, the plastic food wrap of Example 2 had a higher tensile strength, indicating that it was more durable.

[0169] Table 1 Mechanical properties of the plastic food wrap obtained in Example 2

[0170]

[0171] Note: Different lowercase letters in the same column indicate significant differences (p < 0.05)

[0172] Experimental Example 3

[0173] I. Experimental Method

[0174] The plastic food wraps prepared in Example 3, the plastic food wraps of Example 4, commercially available plastic food wraps, and the plastic food wraps of Comparative Example 1 were cut into appropriate sizes. For the double-layer plastic food wrap of Example 3, with the chitosan / gelatin barrier layer facing outward and the pine bark extract - gliadin nanoparticles / artemisia sphaerocephala gum active layer facing inward, it was tightly covered on the open mouth of the fresh-keeping box containing thawed lamb leg meat; while for the single-layer plastic food wraps of the positive control PE plastic food wrap, Example 4, and Comparative Example 1, any side was covered on the open mouth of the fresh-keeping box containing thawed lamb leg meat. Treating with commercially available plastic food wraps (covering the open mouth of the fresh-keeping box with commercially available plastic food wraps) was used as the positive control, and not covering the open mouth of the fresh-keeping box with a plastic food wrap was used as the negative control. Each treatment was stored at 4 °C for freshness preservation.

[0175] In addition, the water vapor transmission rate and oxygen permeability of the fresh-keeping films of Examples 3 and 4 and Comparative Example 1 were measured.

[0176] II. Experimental Results

[0177] The experimental results prove that the fresh-keeping effects of the fresh-keeping films prepared in Example 3 and Example 4 on thawed lamb legs are significantly better than those of the positive control, negative control, and the fresh-keeping film of Comparative Example 1.

[0178] The measurement results of the water vapor transmission rate and oxygen permeability of the fresh-keeping films of Examples 3 and 4 and Comparative Example 1 are shown in Table 2. The results show that the fresh-keeping film of Comparative Example 1 has excellent water vapor and oxygen barrier properties. The water vapor transmission rate of Example 3 is higher than that of Example 4, and the oxygen transmission rate has no significant difference from that of Comparative Example 1. This indicates that Example 3 has the advantages of high water vapor and oxygen barrier properties of the barrier layer at the same time.

[0179] Table 2 Water vapor transmission rate and oxygen permeability of different fresh-keeping films

[0180]

[0181] Note: Different lowercase letters in the same column indicate significant differences (p<0.05)

[0182] Experimental Example 4

[0183] The TBARS values of the meat treated with the fresh-keeping films of Example 3 and Comparative Examples 2-7 were measured, and the measurement results are as Figure 4 shown. The results show that during the preparation of the fresh-keeping film, directly adding antioxidant components can all play a role in inhibiting the increase of TBARS. There is no significant difference in the effect of preventing fat oxidation between the treatments of Comparative Examples 4-6, indicating that there is no significant difference in the treatment effects of adding extracts of pine bark, vitamin E, or tea polyphenols.

[0184] However, after preparing them into nanoparticles, the treatment effect of the fresh-keeping film prepared from the extract of pine bark and gliadin nanoparticles is significantly better than that of other antioxidant nanoparticles, indicating that the combination of the extract of pine bark and gliadin nanoparticles has unique advantages in delaying lipid oxidation.

[0185] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent substitution methods and are all included in the protection scope of the present invention.

Claims

1. A preparation method of a pine bark extract - gliadin nanoparticle, characterized in that, Dissolve the pine bark extract and gliadin in an ethanol solution, add water to the ethanol solution under stirring conditions, and recover the solid to obtain pine bark extract-gliadin nanoparticles; wherein, the mass ratio of the pine bark extract to gliadin is (10-20):(50-80).

2. The preparation method according to claim 1, wherein The mass ratio of the pine bark extract, gliadin, ethanol solution and water is (10-20):(50-80):(500-800):(1500-4500), and the concentration of the ethanol solution is 15-25%.

3. Pine bark extract-gliadin nanoparticles prepared by the preparation method according to claim 1 or 2.

4. A composition, characterized in that, It includes the pine bark extract-gliadin nanoparticles according to claim 3, artemisia sphaerocephala gum and glycerol; the mass ratio of the pine bark extract-gliadin nanoparticles, artemisia sphaerocephala gum and glycerol is (5-16):(2-8):(6:20).

5. Use of the pine bark extract-gliadin nanoparticles according to claim 3 or the composition according to claim 4 in the preparation of food wrap.

6. A cling film, characterized in that, Containing the pine bark extract-gliadin nanoparticles according to claim 3 or the composition according to claim 4.

7. The preparation method of the fresh-keeping film according to claim 6, characterized in that, Add the pine bark extract-gliadin nanoparticles to the artemisia sphaerocephala gum solution, then add glycerol, mix evenly to obtain a film solution, and make the film solution into a film to obtain it.

8. A double-layer plastic food wrap, characterized in that, It includes an outer layer film and an inner layer film, and the inner layer film is the food wrap according to claim 6.

9. The double-layer plastic food wrap according to claim 8, wherein, The outer layer film includes chitosan, gelatin and glycerol.

10. Use of the food wrap according to claim 6 or the double-layer food wrap according to any one of claims 8-9 in food preservation or in packaging food.

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