Mildew-proof duck accessory vacuum nitrogen-filled package and preparation method thereof

Abstract

The invention discloses an anti-mildew duck accessory vacuum nitrogen-filled package and a preparation method thereof, and relates to the technical field of high-molecular compound processing and food packaging, in particular to a nitrogen-filled packaging system in which an antibacterial modified composite film participates, and the antibacterial modified composite film is of a three-layer structure which sequentially comprises an anti-puncture surface layer, a high-barrier middle layer and an antibacterial inner layer from outside to inside; the gas in the bag consists of nitrogen and carbon dioxide; the preparation method comprises the following steps: 1) preparing the antibacterial modified composite film; according to the method, an efficient, reliable and safe anti-mildew and quality-guaranteeing system is jointly formed through deep integration of high-strength blocking, intelligent active antibacterial, precise controlled atmosphere fresh-keeping and whole-process processing control, and the method is particularly suitable for high-value meat products such as duck accessories which are prone to rot and mildew.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of processing of high molecular compounds and food packaging, and particularly relates to a mildew-proof vacuum nitrogen-filling packaging of duck appendages and a preparation method thereof. BACKGROUND

[0002] The duck appendages are rich in protein and fat, and have a water activity of 0.85-0.90, and are easily contaminated by molds such as Aspergillus niger and Aspergillus flavus in an environment above 25 DEG C, resulting in mildew and metamorphosis, and the shelf life is usually less than 3 months. The existing preservation technology has the following defects: Limitations of vacuum packaging: although the pure vacuum environment can isolate oxygen, the pressure difference between the inside and outside of the duck appendages is greater than or equal to 0.05 MPa, which causes the meat of the duck appendages to be compressed and deformed, and cannot inhibit the growth of anaerobic molds such as Aspergillus glaucus, and the shelf life is only 2-3 months at 30 DEG C; Defects of ordinary nitrogen-filling packaging: polyethylene single-layer film is used, and the oxygen transmission rate is greater than or equal to 5 cm 3 / m 2 24h 0.1 MPa, the nitrogen leakage rate is high, and there is no active antibacterial function, and the residual oxygen in the bag is greater than or equal to 2%, which can easily cause the growth of microorganisms; Deficiency of antibacterial material: the existing antibacterial film mostly uses single nano-silver, and therefore has the risk of heavy metal migration, or uses natural plant extracts, but the antibacterial rate is less than or equal to 90%, and the compatibility of the antibacterial agent and the high molecular matrix is poor, and the agglomeration rate is greater than or equal to 30%, which affects the processing performance and the antibacterial time efficiency; Contradiction of sterilization process: although the traditional 121 DEG C high-temperature sterilization can inactivate microorganisms, it causes the oxidation of fat in the duck appendages, the acid value is greater than or equal to 3.0 mg / g, the meat is hardened, the shear force is greater than or equal to 60 N, and the flavor is seriously deteriorated. In view of the above problems, a vacuum nitrogen-filling packaging with high barrier property, active antibacterial property and compatible mild sterilization process needs to be designed to solve the technical bottleneck of mildew and quality deterioration of the duck appendages. SUMMARY

[0003] The present application aims at solving the defects in the prior art, and provides a mildew-proof vacuum nitrogen-filling packaging of duck appendages and a preparation method thereof.

[0004] In order to achieve the above-mentioned purpose, the technical scheme is as follows: The present application first provides a mildew-proof vacuum nitrogen-filling packaging of duck appendages, which comprises an antibacterial modified composite film, and is a nitrogen-filling packaging system involving the antibacterial modified composite film; The antibacterial modified composite film has a three-layer structure, and from outside to inside, it comprises an anti-puncture surface layer, a high-barrier middle layer and an antibacterial inner layer, and the total thickness is 80-120 mu m, and the mass ratio of each layer is 30:25:45; The puncture-resistant surface layer uses biaxially oriented polyethylene film as the base material, with 0.8-1.2% maleic anhydride-grafted polyethylene added by mass. The puncture-resistant surface layer uses biaxially oriented polyethylene (BOPE) film as its base material. Through longitudinal and transverse stretching and orientation, the molecular chains are arranged in a highly ordered manner, forming high strength and puncture resistance to prevent packaging damage during transportation and storage and to avoid microbial invasion. Maleic anhydride-grafted polyethylene (MAH-g-PE) is used as a compatibilizer to improve the adhesion between the surface layer and other layers, while enhancing the surface layer's chemical resistance and mechanical strength, reducing pinhole defects, and lowering the risk of microbial penetration.

[0005] The high-barrier middle layer is made by blending ethylene-vinyl alcohol copolymer and low-density polyethylene at a mass ratio of 7:3. The high-barrier middle layer is obtained by blending ethylene-vinyl alcohol copolymer (EVOH) and low-density polyethylene (LDPE) at a mass ratio of 7:3. Due to the hydrogen bond network formed by the hydroxyl groups in the EVOH molecular chain, its crystalline regions and hydrogen bond structure can effectively block the permeation of oxygen molecules, with an oxygen permeability ≤1.0 cm⁻¹. 3 / m 2 • 24h • 0.1MPa, thereby cutting off the oxygen source needed for the metabolism of aerobic microorganisms (such as molds and bacteria), inhibiting their growth; while LDPE provides flexibility and processability, the blending process ensures that the middle layer has both high barrier and toughness, preventing delamination, and the blending of EVOH and LDPE forms a dense structure with a water vapor permeability ≤3.5g / m 2 • 24h, to prevent moisture from entering the packaging and avoid the high humidity environment required for mold growth.

[0006] The antibacterial inner layer is based on low-density polyethylene and contains 1.0-2.0% Schiff base-modified nano zinc oxide, 0.5-1.0% kojic acid, and 0.5% antioxidant 1010.

[0007] The antibacterial inner layer substrate is low-density polyethylene (LDPE), providing good heat-sealing properties and food contact safety; Schiff base-modified nano-zinc oxide can generate reactive oxygen species, such as ·OH and H2O2, under both light and dark conditions, causing oxidative damage to microbial cell membranes, proteins, and DNA; Zn 2+ Slow release, it binds to sulfhydryl or carboxyl groups on the cell membrane, disrupting membrane integrity and causing leakage of contents; the Schiff base ligand itself can penetrate the cell membrane, interfering with enzyme activity, especially against molds such as Aspergillus niger, and bacteria such as Escherichia coli, exhibiting highly effective inhibitory effects with an antibacterial rate ≥99%; kojic acid, as a natural organic acid, can inhibit tyrosinase and metabolic enzymes of various microorganisms, interfering with mold spore germination and hyphal growth. Synergistically with nano-zinc oxide, it enhances the inhibitory effect against molds.

[0008] Preferably, the preparation method of the Schiff base modified nano zinc oxide is as follows: 10 parts of nano zinc oxide are dispersed in 85 parts of anhydrous ethanol, and under nitrogen protection, 30 parts of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane ethanol solution with a mass fraction of 10% are added dropwise, and the mixture is stirred for 1 hour; then 40 parts of ethylenediamine dihydrate acetal dihydrate ethanol solution are added dropwise, and the mixture is stirred for 2 hours; the supernatant is discarded by centrifugation, the precipitate is washed with anhydrous ethanol and deionized water, and then vacuum dried; The nano zinc oxide particles have a diameter of 20-50 nm.

[0009] Preferably, the antibacterial inner layer has an antibacterial rate of ≥99% against Aspergillus niger and Escherichia coli; and the high-barrier middle layer has a water vapor permeability of ≤3.5 g / m³. 2 24h, oxygen permeability ≤1.0cm 3 / m 2 24h 0.1MPa.

[0010] Preferably, the total residual solvent in the composite membrane is ≤5.0 mg / m³. 2 Total migration ≤10mg / dm 2 .

[0011] This invention also proposes a method for preparing the aforementioned anti-mold duck accessory vacuum nitrogen-filled packaging, comprising the following steps: (1) Preparation of antibacterial modified composite membrane: puncture-resistant surface layer, high barrier middle layer and antibacterial inner layer were prepared respectively, and the composite was made by solvent-free composite process and cured at 50°C for 48h. (2) Meat product pretreatment: Meat products are washed, pre-cooked, braised and roasted and then set aside for use; (3) Vacuum nitrogen-filled packaging: antibacterial packaging bags are made of at least two layers of antibacterial modified composite film. After the meat products are pretreated, they are put into the bags, vacuumed, and carbon dioxide is introduced step by step for 3s and nitrogen for 10s. The oxygen content in the bag is ≤1%, and it is heat-sealed at 180℃ for 1.5s. (4) Low temperature conditioning and sterilization: sterilize at 105-110℃ for 20-25 minutes, F value 8-10, and cool to below 25℃.

[0012] Preferably, in step (1), the puncture-resistant outer layer is melt-extruded by a single screw extruder at 170-190℃ and then stretched longitudinally by 3.5 times and laterally by 4.0 times; the high-barrier middle layer is cast by a casting machine at 190-210℃; and the antibacterial inner layer is made of low-density polyethylene, Schiff base-modified nano zinc oxide, and kojic acid, and is cast by a casting machine at 150-170℃.

[0013] Preferably, in step (3), the specific process of making antibacterial packaging bags from antibacterial modified composite film includes: Unfold and fold the antibacterial modified composite film so that the antibacterial inner layers face each other. Use a heat-sealing knife to heat-seal both sides of the composite film. The heat-sealing temperature is controlled at 175-185℃, the pressure is 0.3-0.5MPa, and the time is 1.0-2.0s, forming a back-sealed cylindrical structure. Punch or cut it according to the predetermined size, and heat-seal the bottom at the same time to make a three-sided sealed pre-made packaging bag. The pre-made bags are leak-tested and the heat-sealing strength is randomly checked to ensure that there are no leaks and the heat-sealing strength is ≥2.0N / 15mm. The antibacterial packaging bag contains 95-98 vol% nitrogen, 2-5 vol% carbon dioxide, and a gas pressure of 0.02-0.03 MPa.

[0014] Preferably, in step (3), the carbon dioxide flow rate is 10 L / min and the nitrogen flow rate is 15 L / min; the heat seal strength is ≥2.0 N / 15 mm.

[0015] The present invention utilizes the aforementioned preparation method to prepare anti-mold duck offal in vacuum nitrogen-filled packaging, which can be used for packaging meat products including duck offal, aquatic products, and poultry; wherein, duck offal includes duck gizzard, duck tongue, or duck wing; aquatic products mainly include bullfrogs; and the initial microbial load of the pretreated meat products is ≤10. 2 CFU / g.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. Biaxially oriented polyethylene (BOPE) film forms a dense and high-strength network structure through molecular chain orientation. This greatly improves the puncture resistance, abrasion resistance, and impact resistance of the packaging bag, effectively preventing secondary microbial contamination caused by packaging damage during logistics and handling, and providing a stable "physical shell" for the internal system.

[0017] Ethylene-vinyl alcohol copolymer (EVOH) forms a dense "molecular sieve" structure through strong hydrogen bonds between molecular chains, exhibiting extremely high barrier properties for small molecules such as oxygen and moisture. It has an extremely low oxygen permeability (≤1.0 cm⁻¹). 3 / m 2 (24h, 0.1MPa) can maintain a low-oxygen environment inside the packaging for an extended period, fundamentally eliminating the conditions for the growth and reproduction of aerobic molds and bacteria. Low water vapor transmission rate (≤3.5g / m³). 2 • 24h) Prevents product moisture loss (drying) and external moisture intrusion, maintaining the product's optimal taste and texture, while avoiding providing the water activity required for microbial growth.

[0018] Schiff base-modified nano-zinc oxide and kojic acid form a composite antibacterial system that attacks microorganisms through multiple pathways; the Zn released by the nano-zinc oxide 2+By binding to negatively charged groups on bacterial / fungal cell membranes, the nanoparticles disrupt their integrity; simultaneously, they can also pierce the cell membrane. Nano-zinc oxide induces the production of reactive oxygen species (ROS), irreversibly oxidizing and damaging microbial proteins, lipids, and DNA. Kojic acid and Schiff base ligands can penetrate cells and specifically inhibit key enzymes (such as tyrosinase) related to microbial metabolism, especially fungal spore germination.

[0019] 2. Nitrogen gas used in nitrogen-filled packaging acts as an inert filling gas, primarily resisting external atmospheric pressure, preventing packaging collapse, and further diluting residual oxygen to solidify the oxygen-deficient environment. A small amount of CO2 (2-5%) dissolves in the moisture and fat of the food, generating weakly acidic carbonic acid, which slightly lowers the internal pH value and has a significant inhibitory effect on microorganisms, especially molds and Gram-negative bacteria. While maintaining the packaging shape, it enhances the anti-mold effect through both physical and chemical means of oxygen replacement and acidification inhibition.

[0020] 3. The high-barrier layer ensures the long-term stability of the internal controlled atmosphere environment; the stable low-oxygen environment reduces the metabolic activity of microorganisms, lessening the burden on the antimicrobial layer; the antimicrobial layer, as the last line of defense, directly kills any microorganisms that may be present or accidentally introduced. These three elements work together to achieve a synergistic anti-mold effect greater than the sum of its parts (1+1+1>3). Effective oxygen isolation significantly delays lipid oxidation and heme deterioration, preventing the product from developing a rancid taste and color deterioration. The product can better maintain its original color, flavor, texture, and nutritional components, resulting in a significantly extended shelf life.

[0021] The beneficial effects of this invention stem from its comprehensive protection design with multiple mechanisms and levels. Through the deep integration of high-strength barrier, intelligent active antibacterial, precise modified atmosphere preservation and whole-process processing control, it forms an efficient, reliable and safe anti-mold and preservation system, which is particularly suitable for high-value meat products such as duck offal that are prone to spoilage and mold. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention and related tables. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0023] Example 1: A method for preparing vacuum nitrogen-filled packaging for mold-resistant duck accessories includes the following steps: (1) Preparation of antibacterial modified composite membrane: puncture-resistant surface layer, high barrier middle layer and antibacterial inner layer were prepared respectively, and the composite was made by solvent-free composite process and cured at 50°C for 48h. (2) Duck meat pretreatment: The duck meat is washed, pre-cooked, braised and roasted and then set aside for use; (3) Vacuum nitrogen-filled packaging: antibacterial packaging bags are made of antibacterial modified composite film, carbon dioxide is introduced step by step for 3s and nitrogen for 10s, the oxygen content in the bag is ≤1%, and heat-sealed at 180℃ for 1.5s; (4) Low temperature conditioning and sterilization: sterilize at 105-110℃ for 25 minutes, F value 8-10, and cool to below 25℃.

[0024] In step (1), the puncture-resistant surface layer is made by adding 0.8% maleic anhydride-grafted polyethylene to a biaxially oriented polyethylene film, melt-extruded at 170-190℃ using a single screw extruder, and then stretching it longitudinally by 3.5 times and transversely by 4.0 times. The high-barrier middle layer is formed by blending ethylene-vinyl alcohol copolymer and low-density polyethylene at a mass ratio of 7:3 and then casting it through a casting machine at 190-210℃. The antibacterial inner layer is formed by mixing antibacterial masterbatch and low-density polyethylene at a mass ratio of 1:4 and casting it in a casting machine at 150-170℃. The antibacterial masterbatch is made by melt blending low-density polyethylene resin with 2.0% Schiff base-modified nano zinc oxide, 0.5% kojic acid, and 0.3% antioxidant 1010. From the outside to the inside, the layers are a puncture-resistant outer layer, a high-barrier middle layer, and an antibacterial inner layer, with a total thickness of 120 μm and a mass ratio of 30:25:45 for each layer.

[0025] In step (3), the specific process of making antibacterial packaging bags from antibacterial modified composite film includes: Unfold and fold the antibacterial modified composite film so that the antibacterial inner layers face each other. Use a heat-sealing knife to heat-seal both sides of the composite film. Control the heat-sealing temperature at 175-185℃, the pressure at 0.3-0.5MPa, and the time at 1.0-2.0s to form a back-sealed cylindrical structure. Punch or cut the film according to the predetermined size, and simultaneously heat-seal the bottom to make a three-sided sealed pre-made packaging bag. Perform leak testing and heat-sealing strength testing on the pre-made bags to ensure that there are no leaks and the heat-sealing strength is ≥2.0N / 15mm.

[0026] In step (3), the carbon dioxide flow rate is 10 L / min and the nitrogen flow rate is 15 L / min; the heat seal strength is ≥2.0 N / 15 mm.

[0027] Example 2: The preparation method is the same as in Example 1, but in step (1), the puncture-resistant surface layer is made by adding 1.0% maleic anhydride grafted polyethylene to a biaxially oriented polyethylene film, melt extruding it at 170-190℃ using a single screw extruder, and then stretching it longitudinally by 3.5 times and transversely by 4.0 times. The high-barrier middle layer is formed by blending ethylene-vinyl alcohol copolymer and low-density polyethylene at a mass ratio of 7:3 and then casting it through a casting machine at 190-210℃. The antibacterial inner layer is formed by mixing antibacterial masterbatch and low-density polyethylene at a mass ratio of 1:4 and casting it in a casting machine at 150-170℃. The antibacterial masterbatch is made by melt blending low-density polyethylene resin with 1.5% Schiff base-modified nano zinc oxide, 0.75% kojic acid, and 0.3% antioxidant 1010. From the outside in, the layers are arranged as follows: puncture-resistant outer layer, high-barrier middle layer, and antibacterial inner layer, with a total thickness of 100 μm and a mass ratio of 30:25:45 for each layer.

[0028] In step (3), the carbon dioxide flow rate is 10 L / min and the nitrogen flow rate is 15 L / min; the heat seal strength is ≥2.0 N / 15 mm.

[0029] Example 3: The preparation method is the same as in Example 1, but in step (1), the puncture-resistant surface layer is made by adding 1.2% maleic anhydride grafted polyethylene to a biaxially oriented polyethylene film, melt extruding it at 170-190℃ using a single screw extruder, and then stretching it longitudinally by 3.5 times and transversely by 4.0 times. The high-barrier middle layer is formed by blending ethylene-vinyl alcohol copolymer and low-density polyethylene at a mass ratio of 7:3 and then casting it through a casting machine at 190-210℃. The antibacterial inner layer is formed by mixing antibacterial masterbatch and low-density polyethylene at a mass ratio of 1:4 and casting it in a casting machine at 150-170℃. The antibacterial masterbatch is made by melt blending low-density polyethylene resin with 1.0% Schiff base-modified nano zinc oxide, 1.0% kojic acid, and 0.3% antioxidant 1010. From the outside in, the layers are arranged as follows: puncture-resistant outer layer, high-barrier middle layer, and antibacterial inner layer, with a total thickness of 80 μm and a mass ratio of 30:25:45 for each layer.

[0030] In step (3), the carbon dioxide flow rate is 10 L / min and the nitrogen flow rate is 15 L / min; the heat seal strength is ≥2.0 N / 15 mm.

[0031] Based on this, the following design was also created: Comparative Example 1: The formulation and experimental method are the same as in Example 2, but maleic anhydride-grafted polyethylene is not added to the puncture-resistant surface layer; Comparative Example 2: The formulation and experimental methods are the same as in Example 2, but Schiff base-modified nano zinc oxide is not added to the antibacterial inner layer; Comparative Example 3: The formulation and experimental method were the same as in Example 2, but kojic acid was not added to the antibacterial inner layer; Comparative Example 4: The formulation and experimental method were the same as in Example 2, but 5% by mass of maleic anhydride-grafted polyethylene was added to the puncture-resistant surface layer. Comparative Example 5: The formulation and experimental methods are the same as in Example 2, but 5% by mass of Schiff base is added to modify nano zinc oxide in the antibacterial inner layer; Comparative Example 6: The formulation and experimental method were the same as in Example 2, but 5% kojic acid was added to the antibacterial inner layer; For each embodiment and comparative example, the tensile strength / elongation at break, puncture resistance, oxygen permeability, water vapor permeability, antibacterial rate, mildew resistance, heat seal strength, and total organic molecule migration of the packaging bag of the present invention were tested according to GB / T 1040.3-2006, GB / T 21302-2007, GB / T1038-2000, GB / T 16928-1997, GB / T 31402-2015, GB / T 26113-2010, and GB 31604.8-2021. The corresponding results are shown in Table 1. Table 1. Performance test data of packaging bags

[0032] Data Analysis: Data shows that the tensile strength of the three examples ranged from 40.0 to 44.0 MPa, and the elongation at break ranged from 310% to 330%, exhibiting excellent strength and toughness. Example 1, with the largest total thickness (120 μm), had the highest tensile strength. Compared to Comparative Example 1 (without maleic anhydride-grafted polyethylene), its tensile strength (38.0 MPa) and elongation at break (300%) were significantly lower than those of Example 2 (42.0 MPa, 320%). This demonstrates that maleic anhydride-grafted polyethylene, acting as a compatibilizer and reinforcing agent, effectively improved the intermolecular chain forces of biaxially oriented polyethylene, enhancing the macroscopic mechanical properties of the material. However, although the tensile strength of Comparative Example 4 (with 5% maleic anhydride added) slightly increased to 45.0 MPa, the elongation at break dropped sharply to 250%, indicating that excessive addition led to increased brittleness and impaired flexibility, which was detrimental to the impact resistance of the packaging.

[0033] Puncture resistance directly relates to whether the packaging can withstand the puncture of sharp objects such as duck bones. The puncture resistance of Examples 1-3 ranged from 62-68 N, also positively correlated with thickness and additive content. The puncture resistance of Comparative Example 1 plummeted to 45 N, a decrease of over 30%, clearly demonstrating that maleic anhydride-grafted polyethylene is indispensable for forming a tough, puncture-resistant surface layer. The puncture resistance of Comparative Example 4 (60 N) was also lower than that of the examples with normal additive amounts, further confirming the principle of "too much of a good thing." Excessive additives disrupt the continuity of the matrix resin, thus reducing the material's toughness and puncture resistance.

[0034] The oxygen permeability in the three embodiments was between 0.6 and 1.0 cm. 3 / m 2 • 24h • 0.1MPa, water vapor transmission rate is 4.8-5.6g / m³ 2 • After 24 hours, all samples met the requirements for high-barrier packaging. Example 1, being the thickest, exhibited the best barrier properties. Example 3, being the thinnest, showed a slight decrease in barrier properties, but still maintained an excellent level. The barrier performance data of all comparative examples were very close to those of the corresponding examples (such as Comparative Examples 1-6 and Example 2), indicating that the barrier performance is mainly determined by the high-barrier middle layer (EVOH / LDPE blend). As long as the structure and formulation of this layer remain unchanged, adjustments to trace components in other layers have minimal impact on the overall barrier properties of the packaging. This highlights the rationality and effectiveness of functional layering design in multi-layer composite structures.

[0035] All three embodiments exhibited an antibacterial rate exceeding 99.3% and a mold resistance rating of 0 (mold-free), demonstrating outstanding performance. This is attributed to the composite antibacterial system composed of Schiff base-modified nano-zinc oxide and kojic acid in the antibacterial inner layer. Nano-zinc oxide disrupts microbial structures by generating reactive oxygen species and releasing zinc ions through photocatalysis, while kojic acid effectively inhibits mold growth; the two may have a synergistic effect.

[0036] The data from Comparative Example 2 (without nano zinc oxide) and Comparative Example 3 (without kojic acid) are highly revealing. Comparative Example 2 showed an antibacterial rate decrease to 85% and a mildew resistance level of 2; Comparative Example 3 showed an antibacterial rate decrease to 90% and a mildew resistance level of 1. This indicates that: 1) both antibacterial agents are indispensable, and neither can achieve optimal results when used alone; 2) nano zinc oxide may contribute slightly more to the overall antibacterial rate than kojic acid, while kojic acid plays a more crucial role in specific mildew prevention.

[0037] It is worth noting that although the antibacterial rates (99.8%, 99.7%) and antifungal grades (Grade 0) of Comparative Example 5 (5% nano zinc oxide) and Comparative Example 6 (5% kojic acid) did not improve, their total organic molecule migration rates surged to 5.0 and 4.5 mg / dm³, respectively. 2The levels far exceed safety standards. This indicates that blindly increasing the dosage of antibacterial agents after reaching an effective antibacterial concentration not only fails to improve the effect but also poses serious food safety risks.

[0038] All experimental groups achieved a heat seal strength of ≥2.0 N / 15 mm, ranging from 2.3 to 2.6 N / 15 mm. This indicates that the solvent-free lamination process and heat seal parameters (180℃, 1.5 s) used in this study are stable and reliable. The heat seal strength of Comparative Examples 5 and 6 decreased slightly, possibly because the excessive small-molecule antibacterial agent formed a weak boundary layer at the heat seal interface, slightly interfering with the thermal fusion bonding of the polyethylene chains.

[0039] Total organic molecule migration is the gold standard for measuring the safety of food contact materials. The migration amounts in Examples 1-3 were between 2.0 and 2.3 mg / dm³. 2 The levels were within the range that fully complied with food safety regulations. However, the migration levels in comparatives 4, 5, and 6 were significantly increased (3.0-5.0 mg / dm³). 2 The increased migration in Comparative Example 4 was due to excessive maleic anhydride-grafted polyethylene and its hydrolysis products; Comparative Examples 5 and 6 were directly due to excessively high levels of antimicrobial agents. The amount of functional additives used must be strictly controlled within safe thresholds; otherwise, the packaging itself will become a source of contamination.

[0040] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A vacuum nitrogen-filled packaging for mold-resistant duck accessories, characterized in that, Including antibacterial modified composite films; The antibacterial modified composite membrane has a three-layer structure, consisting of a puncture-resistant outer layer, a high-barrier middle layer, and an antibacterial inner layer from the outside to the inside, with a total thickness of 80-120 μm and a mass ratio of 30:25:45 for each layer. The puncture-resistant surface layer uses biaxially oriented polyethylene film as the base material, with 0.8-1.2% maleic anhydride-grafted polyethylene added by mass. The high-barrier middle layer is made by blending ethylene-vinyl alcohol copolymer and low-density polyethylene at a mass ratio of 7:

3. The antibacterial inner layer is based on low-density polyethylene and contains 1.0-2.0% Schiff base-modified nano zinc oxide, 0.5-1.0% kojic acid, and 0.5% antioxidant 1010.

2. The vacuum nitrogen-filled packaging for mold-resistant duck accessories according to claim 1, characterized in that, The preparation method of the Schiff base modified nano zinc oxide is as follows: 10 parts of nano zinc oxide are dispersed in 85 parts of anhydrous ethanol. Under nitrogen protection, 30 parts of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane ethanol solution with a mass fraction of 10% are added dropwise, and the mixture is stirred for 1 hour; then 40 parts of ethylenediamine dihydrate ethylenediamine dihydrate ethanol solution with a mass fraction of 5% are added dropwise, and the mixture is stirred for 2 hours; the supernatant is discarded by centrifugation, and the precipitate is washed with anhydrous ethanol and deionized water and dried under vacuum. The nano zinc oxide particles have a diameter of 20-50 nm.

3. The anti-mildew duck accessory vacuum nitrogen-filled packaging according to claim 1, characterized in that, The antibacterial inner layer has an antibacterial rate of ≥99% against Aspergillus niger and Escherichia coli; the high-barrier middle layer has a water vapor permeability of ≤3.5g / m³. 2 24h, oxygen permeability ≤1.0cm 3 / m 2 24h 0.1MPa.

4. The anti-mildew duck accessory vacuum nitrogen-filled packaging according to claim 1, characterized in that, The total residual solvent in the composite membrane is ≤5.0 mg / m³. 2 Total migration ≤10mg / dm 2 .

5. A method for preparing vacuum nitrogen-filled packaging for mold-resistant duck accessories, characterized in that, Includes the following steps: (1) Preparation of antibacterial modified composite membrane: puncture-resistant surface layer, high barrier middle layer and antibacterial inner layer were prepared respectively, and the composite was made by solvent-free composite process and cured at 50°C for 48h. (2) Meat product pretreatment: Meat products are washed, pre-cooked, braised and roasted and then set aside for use; (3) Vacuum nitrogen-filled packaging: antibacterial packaging bags are made of at least two layers of antibacterial modified composite film. After the meat products are pretreated, they are put into the bags, vacuumed, and carbon dioxide is introduced step by step for 3s and nitrogen for 10s. The oxygen content in the bag is ≤1%, and it is heat-sealed at 180℃ for 1.5s. (4) Low temperature conditioning and sterilization: sterilize at 105-110℃ for 20-25 minutes, F value 8-10, and cool to below 25℃.

6. The preparation method of vacuum nitrogen-filled packaging for anti-mildew duck accessories according to claim 5, characterized in that, In step (1), the puncture-resistant outer layer is melt-extruded by a single screw extruder at 170-190℃ and then stretched longitudinally by 3.5 times and laterally by 4.0 times; the high-barrier middle layer is cast by a casting machine at 190-210℃; the antibacterial inner layer is made of low-density polyethylene, Schiff base modified nano zinc oxide, and kojic acid, and is cast by a casting machine at 150-170℃.

7. The preparation method of vacuum nitrogen-filled packaging for anti-mildew duck accessories according to claim 5, characterized in that, In step (3), the specific process of making antibacterial packaging bags from antibacterial modified composite film includes: Unfold and fold the antibacterial modified composite film so that the antibacterial inner layers face each other. Use a heat-sealing knife to heat-seal both sides of the composite film. The heat-sealing temperature is controlled at 175-185℃, the pressure is 0.3-0.5MPa, and the time is 1.0-2.0s, forming a back-sealed cylindrical structure. Punch or cut it according to the predetermined size, and heat-seal the bottom at the same time to make a three-sided sealed pre-made packaging bag. The pre-made bags are leak-tested and the heat-sealing strength is randomly checked to ensure that there are no leaks and the heat-sealing strength is ≥2.0N / 15mm. The antibacterial packaging bag contains 95-98 vol% nitrogen, 2-5 vol% carbon dioxide, and a gas pressure of 0.02-0.03 MPa.

8. The method for preparing a vacuum nitrogen-filled packaging for mold-resistant duck accessories according to claim 5, characterized in that, In step (3), the carbon dioxide flow rate is 10 L / min and the nitrogen flow rate is 15 L / min; the heat seal strength is ≥2.0 N / 15 mm.

9. A vacuum nitrogen-filled packaging for mold-resistant duck accessories prepared by the preparation method according to any one of claims 5-8, characterized in that, It can be used for packaging meat products including duck offal, aquatic products, and poultry; duck offal includes duck gizzard, duck tongue, or duck wing; aquatic products mainly include bullfrogs; the initial microbial load of the pre-treated meat products is ≤10. 2 CFU / g.

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