A preparation method and application of a microbial composite film for improving the flavor and quality of cured meat

Abstract

The application discloses a preparation method and application of a microbial composite film for improving the flavor and quality of cooked meat, and belongs to the technical field of meat cooking. The outer layer is an electrostatic spinning bacteria-resistant and air-permeable layer with a pore size of 0.1-0.5 microns, can intercept harmful microorganisms with a rate of 99.99%, and has an air permeability of 5 mm / s (100 Pa), so that fat oxidation and beneficial microorganism metabolism can be ensured to normally proceed; and the inner layer is a lyophilized functional bacteria loading layer fixed by a water-soluble polymer, and the microbial loading density is 10-1000 CFU / cm 2 After being in contact with the surface of meat or absorbing moisture, the functional bacteria can quickly recover and play a role in promoting cooking, directional microbial regulation of the meat cooking process is realized, and the cooking efficiency and quality are improved. The microbial composite film for improving the flavor and quality of cooked meat has the three functions of bacteria resistance, air permeability and functional bacteria loading, and is suitable for replacing traditional natural fermentation or naked cooking. The application replaces traditional natural fermentation through the synergistic effect of "bacteria resistance-air permeability-directional inoculation", shortens the cooking time by 20% or more, reduces the risk of pollution by miscellaneous bacteria, and improves the cooking efficiency and safety of meat.

Description

Technical Field

[0001] This invention belongs to the field of meat cooking technology, and particularly relates to a method for preparing and applying a microbial composite membrane for improving the flavor and quality of cooked meat. Background Technology

[0002] Meat aging is a long-standing and widely used meat processing method, playing a crucial role in the production of high-end meat products such as traditional ham and aged steaks. The core function of meat aging is to enhance tenderness, flavor, and overall quality. The aging process relies on the synergistic effects of microbial metabolism, endogenous enzymatic hydrolysis, and environmental factors such as temperature, humidity, and gas composition. This process gradually degrades proteins and fats in the meat, generating free amino acids and volatile flavor compounds, thus imparting a unique aged flavor. Traditional meat aging requires several weeks to months in a low-temperature (0-4°C), high-humidity (75%-85%), and controlled-ventilation environment, forming a microbial film on the surface and imparting a special flavor. For example, the aging process for Spanish Iberian ham is a traditional and meticulous fermentation-drying process, taking 18-36 months. However, "naked aging," which directly exposes the meat to air, presents the following long-standing challenges: 1. High risk of contamination by bacteria – Once Listeria, Salmonella, Penicillium, Aspergillus, etc., colonize, the entire piece is rendered unusable, resulting in significant economic losses; 2. The process is lengthy—lasting from weeks to months, resulting in low efficiency; 3. High salt dependence – excessive pickling for antibacterial purposes contradicts the trend of low-sodium diets; 4. Large fluctuations in quality – the natural microbial community is uncontrollable, resulting in significant fluctuations in flavor and quality.

[0003] To mitigate risks, wet aging (such as vacuum-packed steak) has been proposed. This method utilizes enzymatic hydrolysis at 0–4°C to improve tenderness and reduce the risk of contaminating microorganisms. However, because the anaerobic conditions limit the proliferation of beneficial microorganisms on the meat surface, wet aging struggles to significantly enhance flavor, limiting its effectiveness.

[0004] With advancements in materials science, nanofibers, due to their high specific surface area and controllable pore structure, are widely used in food packaging research. By electrospinning natural antibacterial agents such as nisin, tea polyphenols, and chitosan, or inorganic antibacterial agents such as nano-silver and zinc oxide, food preservation films with antibacterial release capabilities can be prepared. This type of packaging can effectively inhibit the growth of spoilage bacteria such as Escherichia coli and Staphylococcus aureus, and extend the shelf life of meat due to its excellent barrier properties. However, these nanofiber-based food preservation materials aim for "comprehensive antibacterial" effects and do not distinguish between beneficial and harmful bacteria, thus they are not suitable for meat cooking processes that rely on specific beneficial microorganisms. Most existing cooking methods still involve exposed cooking, making them highly susceptible to contamination by other microorganisms.

[0005] Therefore, there is an urgent need to develop a new type of intelligent packaging material that can effectively block the invasion of exogenous harmful microorganisms, release or load beneficial cooking bacteria on the surface of meat, and maintain a suitable breathable and moisture-permeable microenvironment to support its metabolic activities. In this way, under the premise of ensuring safety, it can reproduce or even enhance the flavor and texture of traditional cooking, providing a new technical path for meat cooking that breaks through the limitations of traditional processes. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a method for preparing and applying a microbial composite membrane for enhancing the flavor and quality of cooked meat. The microbial composite membrane of this invention, used to enhance the flavor and quality of cooked meat, is loaded with microorganisms beneficial to meat cooking and possesses synergistic antimicrobial and permeable functions. The dual-layer design and targeted microbial regulation of this invention provide a novel technical approach for meat cooking and have significant application value.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a microbial composite membrane for improving the flavor and quality of cooked meat. The microbial composite membrane includes a bacteriostatic and breathable layer and a functional bacterial loading layer. The functional bacterial loading layer is located inside the bacteriostatic and breathable layer (i.e., the functional bacterial loading layer is the side that contacts the meat when in use). The antibacterial and breathable layer is used to block the entry of external microorganisms, prevent harmful bacteria or fungi from multiplying on the surface of meat, thereby avoiding meat spoilage. At the same time, it has excellent breathability and does not affect fat oxidation and aerobic metabolism of beneficial microorganisms during the cooking process. The functional microbial support layer is loaded with freeze-dried microorganisms that are beneficial to meat cooking. After contacting the surface of the meat or absorbing moisture from the environment, the microorganisms are released to promote meat cooking.

[0008] This invention is the first to propose a microbial composite membrane for enhancing the flavor and quality of cooked meat. It is a double-layered, multifunctional composite nanofiber membrane specifically designed for meat cooking, consisting of an outer antibacterial and breathable layer and an inner functional bacterial loading layer. The outer antibacterial and breathable layer is prepared through electrospinning, resulting in controllable pore size and excellent breathability. It can efficiently intercept ≥99.99% of harmful bacteria while maintaining adequate oxygen transfer, ensuring normal fat oxidation and beneficial bacterial metabolism. The inner functional bacterial loading layer introduces freeze-dried functional bacteria, fixed using water-soluble polymers. These bacteria can rapidly revive and dominate the cooking process after absorbing moisture or contacting the meat surface. Unlike existing "single-layer antibacterial membranes" or "comprehensive antibacterial packaging," the double-layered synergistic structure of this invention not only ensures the purity and stability of the cooking environment but also actively regulates the establishment of beneficial bacteria. Currently, no other design integrates "antibacterial barrier + breathability + targeted inoculation" like this invention. After applying the microbial composite membrane of this invention, the meat cooking cycle can be shortened by ≥20%, the meat weight loss rate is reduced, and the flavor consistency is significantly improved. This means that at the industrial level, it is possible to produce high-quality, low-salt, and safe cooked meat products while reducing risks and costs.

[0009] Furthermore, the load density of the freeze-dried microorganisms in the functional bacterial load layer is 10~1000 CFU / cm³. 2 .

[0010] Furthermore, the freeze-dried microorganisms are selected from freeze-dried fungi, freeze-dried fungal spores, or freeze-dried bacteria.

[0011] Furthermore, the microorganisms, namely fungi, fungal spores, or bacteria, are all in a freeze-dried dormant state and can revive and promote ripening after absorbing water or coming into contact with the surface of meat.

[0012] Furthermore, the pore size of the antibacterial and breathable layer is 0.1~0.8 μm, the thickness is 0.3~10 μm, the air permeability is not less than 5 mm / s when the test pressure difference is 100 Pa, and the interception efficiency of Bacillus atrophicus spores is not less than 99.99% when the test flow rate is 2.8 L / min for 15 minutes.

[0013] Furthermore, the raw material for preparing the antibacterial and breathable layer is a non-water-soluble polymer.

[0014] Furthermore, the non-water-soluble polymer is selected from at least one of polylactic acid (PLA), polycaprolactone (PCL), polyurethane (PU), polystyrene (PS), polyethersulfone (PES), polyvinylidene fluoride (PVDF), polyimide (PI), zein, and polyacrylonitrile (PAN).

[0015] Furthermore, the functional bacteria in the functional bacterial load layer are immobilized using a water-soluble polymer.

[0016] Furthermore, the water-soluble polymer is selected from at least one of polyvinyl alcohol (PVA), polyethylene oxide (PEO), vinylpyrrolidone (PVP), sodium alginate (SA), carboxymethyl cellulose, corn gluten, starch, guar gum, and gum arabic.

[0017] The present invention also provides a method for preparing the above-mentioned microbial composite membrane for improving the flavor and quality of cooked meat, comprising the following steps: After mixing microbial bacterial solution with water-soluble polymer solution, the mixture is loaded onto the inner side of the antibacterial and breathable layer by spraying or electrospinning, and then freeze-drying is performed to obtain the microbial composite membrane used to improve the flavor and quality of cooked meat. Alternatively, the microbial liquid can be sprayed onto the inner side of the antibacterial and breathable layer, and then the microorganisms can be fixed by spraying or electrospinning with a water-soluble polymer solution. Finally, the microbial composite membrane used to improve the flavor and quality of cooked meat can be obtained. Alternatively, the microbial liquid can be pre-freeze-dried into powder, and the powder can be distributed on the inner side of the antibacterial and breathable layer by electrostatic spraying. Then, it can be fixed by spraying with a water-soluble polymer solution or by electrostatic spinning to obtain the microbial composite membrane used to improve the flavor and quality of cooked meat.

[0018] Furthermore, the method for preparing the microbial culture is as follows: the microorganisms are dispersed in PBS buffer (pH=7.0) to obtain a viable bacterial concentration ≥1×10⁻⁶. 3 Microbial culture with a CFU / mL concentration, preferably with a viable cell concentration ≥1×10⁻⁶. 5 CFU / mL.

[0019] The present invention also provides the application of the above-mentioned microbial composite membrane for improving the flavor and quality of cooked meat in meat cooking, wherein the microbial composite membrane for improving the flavor and quality of cooked meat is covered on the surface of meat, wherein the functional bacteria loading layer side is in contact with the meat.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects: 1. This invention is the first to use nanofiber antibacterial and breathable membranes for meat cooking, breaking through the century-old tradition of "naked cooking". It effectively blocks harmful microorganisms (interception efficiency ≥99.99%) while maintaining breathability (≥5 mm / s, 100 Pa) and supporting fat oxidation and beneficial microbial metabolism.

[0021] 2. This invention features a unique dual-layer synergistic structural design. The microbial composite membrane consists of an outer antimicrobial and breathable layer and an inner functional bacterial loading layer, which work synergistically. The antimicrobial and breathable layer prevents the invasion of exogenous bacteria while providing breathability; the functional bacterial loading layer immobilizes freeze-dried beneficial bacteria with water-soluble polymers, allowing for rapid revival upon contact with the meat surface or after moisture absorption, thus directionally regulating the cooking process. Using the antimicrobial and breathable layer alone would inhibit the activity of beneficial microorganisms, while inoculating beneficial bacteria alone would make it difficult to avoid contamination by external bacteria. The dual-layer design of this invention allows the two layers to complement each other, working synergistically to ensure the safety and flavor stability of the cooking process.

[0022] 3. This invention addresses the problems of long maturation cycles (weeks to months), high salt dependence, unstable flavor, and high risk of contamination by miscellaneous bacteria in traditional methods. Through the "bacterial inhibition-ventilation-directional inoculation" mechanism, it shortens the maturation time by ≥20%, reduces weight loss, improves flavor consistency, and reduces dependence on high-salt pickling, which is in line with the trend of low-sodium diets. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 Scanning electron microscope image of the prepared PLA antibacterial and breathable layer; Figure 2 Scanning electron microscope image of the prepared TPU antibacterial and breathable layer; Figure 3 The image shows a scanning electron microscope (SEM) image of the prepared PAN antibacterial and breathable layer. Detailed Implementation

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0027] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0028] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0029] An embodiment of the present invention provides a microbial composite membrane for improving the flavor and quality of cooked meat. The microbial composite membrane includes a bacterial barrier and a functional bacterial loading layer, wherein the functional bacterial loading layer is located inside the bacterial barrier and the functional bacterial loading layer. The antibacterial and breathable layer is used to block the entry of external microorganisms and prevent harmful bacteria or fungi from multiplying on the surface of meat, thereby avoiding meat spoilage. At the same time, it has excellent breathability and does not affect fat oxidation and the aerobic metabolism of beneficial microorganisms during the cooking process. The functional microbial support layer is loaded with freeze-dried microorganisms that are beneficial to meat maturation. After contacting the surface of the meat or absorbing moisture from the environment, the microorganisms are released to promote meat maturation.

[0030] After applying the microbial composite membrane of this invention, the meat cooking time can be shortened by more than 20%, the content of flavor substances is significantly higher than that of traditional naked cooking for the same time, the sensory score is better, the weight loss rate is reduced by about 3-5%, and the stability and consistency of cooking are greatly improved. The electrospinning and spraying processes used in this invention are mature and reliable, with good versatility and scalability, providing a safe, efficient and controllable technical solution for meat fermentation and cooking.

[0031] In an embodiment of the present invention, the loading density of freeze-dried microorganisms in the functional bacterial loading layer is 10~1000 CFU / cm³. 2 .

[0032] In embodiments of the present invention, the freeze-dried microorganisms are selected from freeze-dried fungi, freeze-dried fungal spores, or freeze-dried bacteria, and are capable of reviving and promoting ripening after absorbing water or contacting the surface of meat. Exemplarily, the microorganisms are selected from at least one of the following: freeze-dried fungi or freeze-dried fungal spores beneficial to meat ripening, including but not limited to: *Thamnidium* fungi or yeasts; freeze-dried bacteria beneficial to meat ripening, including but not limited to: lactic acid bacteria, *Lactobacillus*, or *Staphylococcus xylose*.

[0033] In the embodiments of the present invention, the pore size of the antibacterial and breathable layer is 0.1~0.8 μm, the thickness is 0.3~10 μm, the air permeability is not less than 5 mm / s when the test pressure difference is 100 Pa, and the interception efficiency of Bacillus atrophicus spores is not less than 99.99% when the test flow rate is 2.8 L / min for 15 minutes.

[0034] In embodiments of the present invention, the raw material for preparing the antibacterial and breathable layer is a non-water-soluble polymer. For example, the non-water-soluble polymer is selected from at least one of polylactic acid (PLA), polycaprolactone (PCL), polyurethane (PU), polystyrene (PS), polyethersulfone (PES), polyvinylidene fluoride (PVDF), polyimide (PI), zein, and polyacrylonitrile (PAN).

[0035] In an embodiment of the present invention, the method for preparing the antibacterial and breathable layer is as follows: at least one of the non-water-soluble polymers such as PLA, PCL, PU, ​​PS, PES, PVDF, PI, Zein and PAN is selected, dissolved in an organic solvent to obtain a solution with a mass fraction of 5-25%, and electrospinned to form a film. The product obtained by electrospinning is the antibacterial and breathable layer.

[0036] In an embodiment of the present invention, when preparing the antibacterial and breathable layer, a needle-type or needleless electrospinning machine is used for electrospinning, and the spinning temperature is controlled at 25±4℃, the relative humidity is 30~70%, and the substrate winding speed is 0.2~6 m / min.

[0037] In embodiments of the present invention, when preparing the antibacterial and breathable layer, the organic solvent is selected from acetone, ethanol, N,N-dimethylformamide or dichloromethane.

[0038] In an embodiment of the present invention, when preparing the antibacterial and breathable layer, after electrospinning, the resulting membrane material is vacuum dried at 60°C for 12 h to remove residual solvent, and then sterilized by ultraviolet ozone treatment for 30 min.

[0039] In embodiments of the present invention, a water-soluble polymer is used to immobilize the functional bacteria in the functional bacterial load layer. Exemplarily, the water-soluble polymer is selected from at least one of polyvinyl alcohol (PVA), polyethylene oxide (PEO), vinylpyrrolidone (PVP), sodium alginate (SA), carboxymethyl cellulose, corn gluten, starch, guar gum, and gum arabic. The present invention, by immobilizing functional bacteria with a water-soluble polymer, allows them to dissolve and release upon contact with meat, promoting meat maturation.

[0040] Embodiments of the present invention also provide a method for preparing the above-mentioned microbial composite membrane for improving the flavor and quality of cooked meat, comprising the following steps: After mixing microbial bacterial solution with water-soluble polymer solution, the mixture is loaded onto the inner side of the antibacterial and breathable layer by spraying or electrospinning, and then freeze-drying is performed to obtain a microbial composite membrane for improving the flavor and quality of cooked meat. Alternatively, the microbial liquid can be sprayed onto the inner side of the antibacterial and breathable layer, and then the microorganisms can be fixed by spraying or electrospinning with a water-soluble polymer solution. Finally, the microorganisms can be freeze-dried to obtain a microbial composite membrane for improving the flavor and quality of cooked meat. Alternatively, the microbial liquid can be pre-freeze-dried into powder, and the powder can be distributed on the inner side of the antibacterial and breathable layer by electrostatic spraying. Then, it can be fixed by spraying with a water-soluble polymer solution or by electrostatic spinning to obtain a microbial composite membrane for improving the flavor and quality of cooked meat.

[0041] In an embodiment of the present invention, the method for preparing the microbial culture is as follows: dispersing microorganisms in PBS buffer (pH=7.0) to obtain a viable bacterial concentration ≥1×10⁻⁶. 3 Microbial culture with a CFU / mL concentration, preferably with a viable cell concentration ≥1×10⁻⁶. 5 CFU / mL.

[0042] In a preferred embodiment of the present invention, the method for preparing the microbial composite membrane for enhancing the flavor and quality of cooked meat adopts any one of schemes A to C: Option A: Spraying / spinning after mixing microorganisms with water-soluble polymers ① Preparation of microbial culture: Disperse the target microorganism (such as at least one of the following: *Thamnidium* fungi, yeast, lactic acid bacteria, *Lactobacillus*, and *Staphylococcus xylose*) in PBS buffer (pH=7.0) to obtain a viable bacterial concentration ≥1×10⁻⁶. 5 Microbial culture at CFU / mL; ② Preparation of loading mixture: Mix the above microbial inoculum with 5~20wt% water-soluble polymer (such as PVA, PEO, PVP, SA, etc.) solution at a volume ratio of 0.001~0.1, and stir thoroughly to obtain the loading mixture; ③ Film Formation: Using electrostatic spraying equipment or electrospinning device, the loaded mixture is evenly applied to the inner surface of the antibacterial and breathable layer. The spraying amount is controlled at 0.01~0.5mL per square centimeter, or the final basis weight of electrospinning is controlled at 0.1~2g / m². 2 A functional bacterial load layer is formed on the inner surface of the antibacterial and breathable layer, with a microbial loading density of 10~1000 CFU / cm³. 2 A composite membrane is obtained; ④ Freeze-drying treatment: The prepared composite membrane is placed in a vacuum environment of -60℃ and ≤15Pa for freeze-drying treatment, so that the microorganisms are in a freeze-dried dormant state while retaining their activity, to obtain a microbial composite membrane for improving the flavor and quality of cooked meat.

[0043] Option B: First load microorganisms, then fix them with water-soluble polymers. ① Preparation of microbial culture: The target microorganisms were dispersed in PBS buffer (pH=7.0) to obtain a viable bacterial concentration ≥1×10⁻⁶. 3 Microbial culture at CFU / mL; ② Microbial solution spraying: Using an electrostatic sprayer or pneumatic spraying equipment, the microbial solution is evenly sprayed onto the inner surface of the antibacterial and breathable layer. The spraying amount is controlled at 0.01~0.5mL per square centimeter to ensure that the microbial loading density in the functional bacterial load layer is 10~1000 CFU / cm³. 2 Then, it is left to dry at room temperature for 3 hours to allow microorganisms to adhere evenly to the substrate surface and form a microbial layer. ③ Polymer fixation treatment: Prepare a water-soluble polymer (such as PVA, PEO, PVP, SA, etc.) solution with a concentration of 5~20wt%; A water-soluble polymer solution was uniformly applied to the surface of the microbial layer using electrostatic spraying or electrospinning, with the spraying amount controlled at 0.01~0.5 mL / cm². 2 Or the spinning weight is 0.1~2g / m 2 To achieve effective coating and fixation, a composite film is obtained; ④ Freeze-drying treatment: The composite membrane is freeze-dried at -60℃ and ≤15Pa to stabilize and quiescent the functional bacteria load layer, thus obtaining a microbial composite membrane for improving the flavor and quality of cooked meat.

[0044] Option C: First, prepare active lyophilized microbial powder, then fix it with a water-soluble polymer. ① Preparation of active freeze-dried microbial powder: The target microorganisms are freeze-dried in a vacuum environment of -60℃ and ≤15Pa to obtain stable active freeze-dried microbial powder; ② Powder spraying: Using electrostatic spraying or pneumatic spraying, the active freeze-dried microbial powder is evenly distributed onto the inner surface of the antibacterial and breathable layer, ensuring that the microbial loading density in the functional bacterial loading layer is 10~1000 CFU / cm³. 2 ; ③ Water-soluble polymer coating and fixation: Prepare a water-soluble polymer (such as PVA, PEO, PVP, SA, etc.) solution with a concentration of 5~20wt%; The active freeze-dried microbial powder is coated with a water-soluble polymer solution using spraying or electrostatic spraying methods. The coating amount is controlled at 0.01~0.5mL per square centimeter or the weight is 0.1~2g / m². 2 ; ④ Freeze-drying treatment: Dry again at -60℃ and ≤15Pa to ensure structural stability and retain microbial activity, and obtain a microbial composite membrane for improving the flavor and quality of cooked meat.

[0045] Embodiments of the present invention also provide the application of the above-mentioned microbial composite membrane for improving the flavor and quality of cooked meat in meat cooking, wherein the membrane is applied to the surface of meat, and the functional bacteria load layer side is in contact with the meat.

[0046] The microbial composite membrane of this invention consists of an outer antibacterial and breathable layer and an inner functional bacterial loading layer. The outer layer is an electrospun antibacterial and breathable layer with a pore size of 0.1~0.5 μm, which can intercept ≥99.99% of harmful microorganisms and has a breathability of ≥5 mm / s (100 Pa), ensuring the normal progress of lipid oxidation and beneficial microbial metabolism. The inner layer is a freeze-dried functional bacterial loading layer immobilized with a water-soluble polymer, with a microbial loading density of 10~1000 CFU / cm³. 2 Upon contact with the meat surface or after absorbing moisture, the microbial composite membrane can rapidly revive and promote ripening, achieving targeted microbial regulation of the meat ripening process and improving ripening efficiency and quality. This invention, used to enhance the flavor and quality of ripened meat, features a triple function of antibacterial activity, breathability, and functional microbial loading, making it suitable as a replacement for traditional natural fermentation or exposed ripening methods. Through the synergistic effect of "antibacterial activity-breathability-targeted inoculation," this invention replaces traditional natural fermentation, shortening ripening time by ≥20%, reducing the risk of contamination by other microorganisms, and improving the efficiency and safety of meat ripening.

[0047] Unless otherwise specified, the room temperature in this invention is 25±2℃.

[0048] All raw materials and reagents used in the embodiments of this invention were purchased commercially. As an example, Thanidium elegans spore suspension, Debaryomyces hansenii yeast, Staphylococcus xylosus, and Lactobacillus sakei were all purchased from Ningbo Mingzhou Biotechnology Co., Ltd.

[0049] Total volatile basic nitrogen (TVB-N) is commonly used to assess the freshness of foods such as meat and fish, because protein decomposition produces volatile substances such as ammonia and amines. The higher the TVB-N value, the more severe the spoilage.

[0050] It should be noted that all methods not described in detail in this invention are conventional practices in the field and are not the focus of this invention. For example, the specific methods such as the resuspension of spore suspension, the preparation of 10 wt% polyvinyl alcohol aqueous solution, and the preparation of water-soluble polymer solutions with a concentration of 5~20 wt% are all carried out using conventional methods.

[0051] The technical solution of the present invention will be further illustrated by the following embodiments.

[0052] Example 1 A microbial composite membrane for enhancing the flavor and quality of aged meat was prepared using Scheme A (spraying / spinning after mixing microorganisms with water-soluble polymers) and applied to dry-aged beef. The specific steps are as follows: 1.1 Preparation of the antibacterial and breathable layer Polylactic acid (PLA, Mw ≈ 100 kDa) and polycaprolactone (PCL, Mw ≈ 350 kDa) were blended at a ratio of 4:6 (w / w) and then dissolved in a dichloromethane / acetone (7:3, v / v) mixture at a total concentration of 12 wt%. Electrospinning was performed at 25 °C and 45% humidity using needles. During electrospinning, the voltage was 40 kV, the receiving distance was 20 cm, and the collection speed was 1.2 m / min. The electrospun product was then vacuum-dried at 60 °C for 12 h and sterilized with ultraviolet ozone for 30 min, yielding a product with a basis weight of 1.0 ± 0.2 g / m³. 2 The fiber membrane with a pore size of 0.80±0.13 μm is the barrier and breathable layer, denoted as PLA antibacterial breathable layer. The scanning electron microscope image is shown below. Figure 1As shown, the fiber diameter is uniformly distributed and in a non-woven morphology. The average pore size of the membrane, analyzed using ImageJ software, is 0.80 ± 0.13 μm. The membrane thickness, measured using a high-precision micrometer, is 18 μm. The air permeability, measured using the GB / T 5453-1997 method, is 35.2 mm / s (test pressure difference of 100 Pa). At a test flow rate of 2.8 L / min for 15 minutes, the interception efficiency against Bacillus atrophus spores is not less than 99.99%.

[0053] 1.2 Preparation of Functional Bacterial Loading Layer ① Preparation of microbial culture: Resuspend the Thanidium elegans spore suspension in PBS (pH=7.0) to a final concentration of 2×10⁻⁶. 7 CFU / mL was used to obtain microbial culture; ② Polymer solution: Prepare a 10 wt% polyvinyl alcohol (PVA, Mw=89 kDa) aqueous solution, sterilize at 121 ℃ for 20 min to obtain PVA aqueous solution; ③ Mixing: Mix the microbial inoculum with the PVA aqueous solution at a volume ratio of 0.05:1 and stir magnetically for 10 min to obtain the mixture; ④ Spraying: Take a 10 cm × 15 cm antibacterial and breathable layer, fix it on the electrostatic spraying table, and spray the mixture at a rate of 0.2 mL / cm. 2 The microorganisms were evenly sprayed onto the surface of the antibacterial and breathable layer (the sprayed surface is the functional layer), with the nozzle 8 cm away from the membrane surface, the voltage 12 kV, and the microbial loading density in the functional bacterial loading layer being 5 × 10⁻⁶. 2 CFU / cm 2 .

[0054] ⑤ Freeze-drying: The product obtained in step ④ is freeze-dried at -55 ℃ and 10 Pa for 18 h to obtain a microbial composite membrane for improving the flavor and quality of cooked meat.

[0055] 1.3 Beef maturation verification Take 2.5 kg of sirloin steak with a thickness of 8 cm (shear force of 68.3 N (Warner-Bratzler test method, the same below)), wipe the surface with 75% (volume fraction) alcohol, wrap it with the above-mentioned microbial composite film (functional layer facing the meat surface), and place it in a aging cabinet at 2 ℃, 80% RH (humidity), and 0.5 m / s wind speed. The control group was aged in an untreated environment.

[0056] The properties of sirloin steak after 21 days are as follows: After 21 days, the shear force of the sirloin steak in the microbial composite membrane group was 47.1 N, while that in the control group was 53.3 N. The shear force of the microbial composite membrane group decreased by 31%, while that in the control group decreased by 22%. After 21 days, the weight loss rate of the sirloin steak in the microbial composite membrane group was 13.8%, while that in the control group was 17.4%.

[0057] Flavor compounds: The samples were tested by gas chromatography-mass spectrometry (GC-MS), and the results are shown in Table 1.

[0058] Table 1. Content of several flavor compounds (μg / kg) after 14 days of aging. As shown in Table 1, the content of key odor molecules such as hexane, 2-butanone, 3-hydroxy-2-butanone, 2,5-dimethylpyrazine, and 3-methylbutanal in the microbial composite membrane group was higher than that in the control group, and the overall sensory score was significantly better than that of the control group.

[0059] Example 2 A microbial composite membrane for enhancing the flavor and quality of aged meat was prepared using Scheme B (first loading microorganisms, then immobilizing them with water-soluble polymers). This membrane was then used for the rapid aging of Parma ham. The specific steps are as follows: 2.1 Preparation of the antibacterial and breathable layer Thermoplastic polyurethane (TPU, Lubrizol 5702) was dissolved in DMF at a concentration of 15 wt%. Electrospinning was used to form a film with a needle-free electrospinning process at a voltage of 50 kV, a receiving distance of 20 cm, a collection speed of 3 m / min, a film thickness of 4.3 μm, and a pore size of 0.31 μm. The electrospun product was vacuum dried at 60 ℃ for 12 h and sterilized with ultraviolet ozone for 30 min. This film served as the antibacterial and breathable layer, denoted as the TPU antibacterial and breathable layer. Scanning electron microscopy images are shown below. Figure 2 As shown, the fiber diameter is uniformly distributed, forming a non-woven morphology. ImageJ analysis software shows the average pore size to be 0.53 ± 0.11 μm. The membrane thickness, measured using a high-precision micrometer, is 23 μm. The air permeability, measured using GB / T 5453-1997 method, is 26.3 mm / s (test pressure difference 100 Pa). At a test flow rate of 2.8 L / min for 15 minutes, the interception efficiency against Bacillus atrophus spores is no less than 99.99%.

[0060] 2.2 Preparation of Functional Bacterial Loading Layer ① Mix Debaryomyces hansenii yeast with Staphylococcus xylosus at a 1:1 ratio, and resuspend in PBS to a final volume of 1×10⁻⁶. 4 CFU / mL was used to obtain microbial culture; ② Bacterial solution spraying: Lay the antibacterial and breathable layer flat and apply it using pneumatic spraying at a rate of 0.15 mL / cm². 2 Let it stand and dry at room temperature for 3 hours; ③ Polymer fixation: Atomized spray of an 8 wt% chitosan oligosaccharide (Mw=50 kDa) solution was used at a spraying rate of 0.25 mL / cm. 2 Film formation was assisted by hot air at 40 ℃, and the microbial loading density in the functional bacterial load layer was 1.8 × 10⁻⁶. 2 CFU / cm 2 ; ④ Freeze-drying: The membrane obtained in step ③ is freeze-dried at -60 ℃ and 15 Pa for 24 h to obtain a microbial composite membrane for improving the flavor and quality of cooked meat.

[0061] 2.3 Ham ripening verification Three kg of pig hind legs were taken, traditionally salted for 72 h, desalted in running water for 24 h, wiped with 75% (volume fraction) alcohol, wrapped in a composite film (functional layer facing inward), and aged in an environment of 15 ℃ and 75% RH. The control group was aged naked in the same environment.

[0062] The performance of the ham after 60 days was as follows: the weight loss rate of the ham in the microbial composite membrane group was 12.1%, while the weight loss rate of the ham in the control group was 14.8%.

[0063] Sensory evaluation: The marble pattern on the cut surface of the ham made of microbial composite membrane was more uniform. Free amino acids were tested by HPLC, and the results are shown in Table 2.

[0064] Table 2. Content of free amino acids (g / kg) after 60 days of maturation. The results in Table 2 show that the free amino acid content in the microbial composite membrane group was higher than that in the control group.

[0065] Example 3 A microbial composite membrane for enhancing the flavor and quality of cooked meat was prepared using scheme C (first preparing active freeze-dried microbial powder, then immobilizing it with a water-soluble polymer). This membrane was then used for the dry-cooking of lamb legs. The specific steps are as follows: 3.1 Preparation of the antibacterial and breathable layer Polyacrylonitrile (PAN, Mw=70 kDa) and polyvinylidene fluoride (PVDF, Mw=530 kDa) were dissolved in DMF at a concentration of 12 wt% (PAN:PVDF=3:1, w / w). Electrospinning was performed using a needle with a voltage of 20 kV, a receiving distance of 12 cm, and a collection speed of 0.8 m / min to obtain a fiber membrane with a thickness of 1.2 μm and a pore size of 0.18 μm. This membrane was then vacuum-dried at 60 ℃ for 12 h and sterilized with ultraviolet ozone for 30 min to obtain a bacteriostatic and breathable layer, denoted as the PAN bacteriostatic and breathable layer. The scanning electron microscope image is shown below. Figure 3 As shown, the fiber diameter is uniformly distributed, forming a non-woven morphology. ImageJ analysis software indicates the average pore size is 0.48 ± 0.09 μm. The membrane thickness, measured using a high-precision micrometer, is 21 μm. The air permeability, measured using GB / T 5453-1997 method, is 30.4 mm / s (test pressure difference 100 Pa). At a test flow rate of 2.8 L / min for 15 minutes, the interception efficiency against Bacillus atrophus spores is no less than 99.99%.

[0066] 3.2 Preparation of Functional Bacterial Loading Layer ① Preparation of active freeze-dried microbial powder: The compound strain (Lactobacillus sakei and Debaryomyces hansenii in a ratio of 3:1) was cultured to the late logarithmic stage, collected by centrifugation, freeze-dried at -60 ℃ and 15 Pa for 48 h, and pulverized through a 100-mesh sieve to obtain active freeze-dried powder (microbial survival rate >85%). ② Powder spraying: The active freeze-dried microbial powder is uniformly deposited on the inner side of the antibacterial and breathable layer by electrostatic spraying (voltage 25 kV, powder feeding rate 0.5 g / min), and the loading density of microorganisms in the functional bacterial loading layer is controlled to be 8×10. 2 CFU / cm 2 ; ③ Polymer Coating: The active lyophilized microbial powder was coated using a 6 wt% gelatin / sodium alginate solution (mass ratio 7:3) via electrostatic spraying at a coating volume of 0.3 mL / cm². 2 This forms a continuous coating layer; ④ Freeze-drying: freeze-dry again at -55 ℃ and 10 Pa for 20 h to ensure that the active freeze-dried microbial powder is fixed and has no loss of activity, and obtain a microbial composite membrane for improving the flavor and quality of cooked meat.

[0067] 3.3 Verification of lamb leg cooking Two kg of boneless lamb leg (shear force 33.8 N) was wiped with 75% (volume fraction) alcohol, tightly wrapped with a microbial composite film (functional layer facing inward), and placed in a curing oven at 1 ℃ and 85% RH. The control group was cured naked under the same conditions.

[0068] The performance of lamb leg after 21 days is as follows: Physicochemical indicators: The pH of lamb legs in the microbial composite membrane group decreased from 5.8 to 5.3, while the pH in the control group decreased to 5.4; the TVB-N (total volatile basic nitrogen) in the microbial composite membrane group was 11.2 mg / 100 g, significantly lower than the 14.7 mg / 100 g in the control group; the shear force of the microbial composite membrane was 24.0 N, a decrease of 29%; the shear force of the control group was 26.5 N, a decrease of 21.6%. The tenderness of the lamb legs in the microbial composite membrane group was significantly improved.

[0069] Flavor: The muttony smell of the microbial composite membrane was significantly reduced. The samples were tested by gas chromatography-mass spectrometry (GC-MS), and the results are shown in Table 3.

[0070] Table 3. Content of several flavor compounds (μg / kg) after 14 days of aging. The results in Table 3 show that the fat content in the lamb legs of the microbial composite membrane group was significantly reduced, proving the significant effect of cooking on fat decomposition.

[0071] Comparative Example 1 1. Preparation of antibacterial and breathable membrane Similar to section “3.1” in Example 3, PAN∶PVDF=3∶1 (w / w) electrospinning was used to obtain a fiber membrane with a thickness of 1.2 μm, a pore size of 0.18 μm, and an air permeability of 30.4 mm / s (100 Pa). After vacuum drying at 60 ℃ for 12 h, it was sterilized by ultraviolet ozone for 30 min and then put into use.

[0072] 2. Wrapping and cooking the lamb leg As in Example 3, Section 3.3, 2 kg of boneless lamb leg (shear force 33.8 N, Warner-Bratzler test method) was taken, the surface was wiped with 75% (volume fraction) alcohol, tightly wrapped with a sterile and breathable membrane, and placed in a curing chamber at 1 ℃ and 85% RH. The control group was cured under the same conditions.

[0073] 3. Physicochemical properties: In Comparative Example 1, the pH of a lamb leg cooked with an antibacterial and breathable membrane decreased from 5.8 to 5.4; TVB-N was 10.9 mg / 100 g; and the shear force was 27.2 N, a decrease of 19.5%. Flavor: The samples were tested using gas chromatography-mass spectrometry (GC-MS), and the results are shown in Table 4.

[0074] Comparative Example 1 used a single-layer antibacterial and breathable membrane to mature lamb legs under the same conditions. Compared with the control group matured under bare conditions, the pH did not change significantly, but the decrease in shear force and the content of flavor compounds were slightly less. Compared with lamb legs matured using a microbial composite membrane, the pH did not change significantly, but the decrease in shear force and the content of flavor compounds were significantly reduced. This is because the antibacterial membrane blocked all external bacteria from participating in the maturation process, thus shielding the maturation process from the effects of microorganisms. Simultaneously, the lamb legs matured using the single-layer antibacterial and breathable membrane had a lower TVB-N content because the membrane shielded the growth of harmful microorganisms and inhibited the production of TVB-N.

[0075] Comparative Example 2 1. Preparation of functional bacterial loaded membranes Similar to section 3.2 of Example 3, the substrate is ordinary medical polypropylene nonwoven fabric (25g / m2) that does not intercept bacteria. ① Preparation of active freeze-dried microbial powder: The compound strain (Lactobacillus sakei and Debaryomyces hansenii in a ratio of 3:1) was cultured to the late logarithmic stage, collected by centrifugation, freeze-dried at -60 ℃ and 15 Pa for 48 h, and pulverized through a 100-mesh sieve to obtain active freeze-dried powder (microbial survival rate >85%). ② Powder spraying: The active freeze-dried microbial powder is uniformly deposited onto the nonwoven fabric using electrostatic spraying (voltage 25 kV, powder feeding rate 0.5 g / min), controlling the microbial loading density in the functional bacterial load layer to be 8 × 10⁻⁶. 2 CFU / cm 2 ; ③ Polymer Coating: The active lyophilized microbial powder was coated using a 6 wt% gelatin / sodium alginate solution (mass ratio 7:3) via electrostatic spraying at a coating volume of 0.3 mL / cm². 2 This forms a continuous coating layer; ④ Freeze-drying: freeze-dry again at -55 ℃ and 10 Pa for 20 h to ensure that the active freeze-dried microbial powder is fixed and has no loss of activity, and obtain functional bacterial loaded membrane.

[0076] 2. Wrapping and cooking the lamb leg As in Example 3, Section 3.3, 2 kg of boneless lamb leg (shear force 33.8 N, Warner-Bratzler test method) was taken, the surface was wiped with 75% (volume fraction) alcohol, tightly wrapped with a functional bacterial loading film, and placed in a curing oven at 1 ℃ and 85% RH. The control group was cured under the same conditions.

[0077] 3. Physicochemical properties: In the comparative example, the pH of the two lamb legs cooked with the antibacterial and breathable membrane decreased from 5.8 to 5.3; the TVB-N was 13.9 mg / 100 g; and the shear force was 24.3 N, a decrease of 28.1%. Flavor: The samples were tested using gas chromatography-mass spectrometry (GC-MS), and the results are shown in Table 4.

[0078] Table 4. Content of several flavor compounds (μg / kg) after 14 days of aging. Comparative Example 2 used a functional microbial-supported membrane to age lamb legs under the same conditions. There was no significant difference compared to the control group aged without food; pH remained unchanged, but the decrease in shear force and the content of flavor compounds increased significantly. Compared to lamb legs aged with the microbial composite membrane, pH remained unchanged, and the decrease in shear force and the content of flavor compounds were comparable. This indicates the promoting effect of beneficial microorganisms in the functional microbial-supported membrane on aging. Meanwhile, Comparative Example 2 had a higher TVB-N content compared to lamb legs aged with a single-layer antibacterial and breathable membrane used in Comparative Example 1, but not significantly different from the control group aged without food. This is because the lack of a protective membrane allowed harmful microorganisms to partially multiply on the meat surface. However, compared to the control group aged without food, Comparative Example 2 had a slightly lower TVB-N content. This is because the beneficial microorganisms supported by the functional microbial-supported membrane formed a dominant microbial community on the meat surface, relatively reducing the proliferation of harmful microorganisms.

[0079] The above comparative examples demonstrate that the antibacterial and breathable membrane in the microbial composite membrane intercepts harmful bacteria, and the microbial load layer promotes meat cooking. The two work synergistically to improve the quality of meat cooking.

[0080] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A microbial composite membrane for enhancing the flavor and quality of cooked meat, characterized in that, The microbial composite membrane includes a bacterial barrier and air-permeable layer and a functional bacterial loading layer; The antibacterial and breathable layer is used to block external microorganisms from entering and prevent harmful bacteria or fungi from multiplying on the surface of meat. The functional microbial support layer is loaded with freeze-dried microorganisms that are beneficial to the cooking of meat; The load density of the freeze-dried microorganisms in the functional bacterial support layer is 10~1000 CFU / cm³. 2 ; The freeze-dried microorganisms are selected from freeze-dried fungi, freeze-dried fungal spores, or freeze-dried bacteria; The pore size of the antibacterial and breathable layer is 0.1~0.8 μm, the thickness is 0.3~10 μm, and the air permeability is not less than 5 mm / s when the test pressure difference is 100 Pa. The raw material for preparing the antibacterial and breathable layer is a non-water-soluble polymer; The functional bacteria in the functional bacterial load layer were immobilized using a water-soluble polymer.

2. The microbial composite membrane for enhancing the flavor and quality of cooked meat according to claim 1, characterized in that, The non-water-soluble polymer is selected from at least one of polylactic acid, polycaprolactone, polyurethane, polystyrene, polyethersulfone, polyvinylidene fluoride, polyimide, zein, and polyacrylonitrile.

3. The microbial composite membrane for enhancing the flavor and quality of cooked meat according to claim 1, characterized in that, The water-soluble polymer is selected from at least one of polyvinyl alcohol, polyethylene oxide, vinylpyrrolidone, sodium alginate, carboxymethyl cellulose, corn gluten, starch, guar gum, and gum arabic.

4. A method for preparing a microbial composite membrane for improving the flavor and quality of cooked meat as described in any one of claims 1 to 3, characterized in that, Includes the following steps: After mixing microbial bacterial solution with water-soluble polymer solution, the mixture is loaded onto the inner side of the antibacterial and breathable layer by spraying or electrospinning, and then freeze-drying is performed to obtain the microbial composite membrane used to improve the flavor and quality of cooked meat. Alternatively, the microbial liquid can be sprayed onto the inner side of the antibacterial and breathable layer, and then the microorganisms can be fixed by spraying or electrospinning with a water-soluble polymer solution. Finally, the microbial composite membrane used to improve the flavor and quality of cooked meat can be obtained. Alternatively, the microbial liquid can be pre-freeze-dried into powder, and the powder can be distributed on the inner side of the antibacterial and breathable layer by electrostatic spraying. Then, the microorganisms can be fixed by spraying with a water-soluble polymer solution or by electrospinning to obtain the microbial composite membrane used to improve the flavor and quality of cooked meat.

5. The application of a microbial composite membrane for enhancing the flavor and quality of cooked meat as described in any one of claims 1 to 3 in meat cooking.

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