A method for preserving meat products by composite lactic acid bacteria fermentation liquor in combination with modified atmosphere packaging

Abstract

The application discloses a meat product preservative method of composite lactic acid bacteria fermentation liquor and modified atmosphere packaging, and belongs to the technical field of food biological preservation. The existing single modified atmosphere packaging has narrow antibacterial spectrum, poor inhibition effect on Listeria and CO2-resistant yeast, and a short shelf life. The conventional lactic acid bacteria adopts dry bacterial powder, and the loss of live bacteria and metabolic antibacterial substances is large, and the lactic acid bacteria cannot be cooperated with the MAP system. The industry generally relies on chemical preservatives. The application adopts non-inactivated composite lactic acid bacteria liquid fermentation liquor, and the liquid fermentation liquor is synchronously added in a rolling process with an addition amount of 0.5% to 1.5%, and is sealed in a high-barrier packaging container, and is filled with a ternary mixed protective gas of CO2 30% to 80%, N2 15% to 65% and O2 0 to 10%. The application realizes broad-spectrum antibacterial effect through the synergistic effect of endogenous lactic acid bacteria sustained acid production and bacteriocin production and high CO2 modified atmosphere. The shelf life of the processed meat product under the condition of 0 to 10 DEG C can reach 35 to 42 days, the color and natural flavor of the meat product are completely retained, the meat product is green and safe, and the application is suitable for the industrialized production of bone processed meat such as pig fan-shaped bone and rib rack.

Description

Technical Field

[0001] This invention belongs to the field of food biological preservation technology, specifically relating to a method for preserving meat products using a compound lactic acid bacteria fermentation broth in conjunction with modified atmosphere packaging. Background Technology

[0002] Modified atmosphere packaging (MAP) creates a high-carbon dioxide, low-oxygen environment by replacing the air inside the packaging. It is currently the most widely used physical preservation method for fresh and processed meat products. This technology relies on high concentrations of CO2 to inhibit the respiratory metabolism of aerobic spoilage bacteria such as Pseudomonas, and combined with low-temperature storage, it can slow down the spoilage process of meat to some extent. However, the antibacterial effect of MAP is highly selective—the high-CO2 environment is only effective against aerobic bacteria, and its inhibitory effect on foodborne pathogens such as Listeria and Salmonella, as well as facultative anaerobes such as CO2-resistant yeasts and lactic acid bacteria, is extremely limited. These microorganisms proliferate rapidly in the later stages of refrigeration, directly leading to quality deterioration of meat products, such as souring, bloating, and stickiness. This problem is particularly prominent in bone-in processed meat: the bone sutures and soft tissue areas provide more sites for microbial attachment, and conventional modified atmosphere gases cannot evenly contact these areas, creating antibacterial "blind spots."

[0003] To compensate for the narrow antimicrobial spectrum of modified atmosphere packaging, the industry practice is to add chemical preservatives such as sodium dehydroacetate and potassium sorbate to the formula. Although chemical preservatives can inhibit the growth of facultative anaerobic bacteria to some extent, in recent years, consumers' demands for "cleanliness labels" have continued to rise, and the health controversies surrounding chemical additives have become increasingly prominent. Their use has posed a substantial constraint on the market acceptance and brand image of prepared meat products.

[0004] Against this backdrop, lactic acid bacteria bio-preservation technology has attracted attention due to its natural and safe characteristics. However, existing lactic acid bacteria preservation solutions suffer from three structural defects. First, almost all commercially available products are spray-dried bacterial powders. The high temperatures during the drying process not only kill a large number of live bacteria but also lead to a significant loss of core antibacterial metabolites such as lactic acid and bacteriocins, resulting in a substantial decrease in actual preservative efficacy compared to fermented original liquids. Second, most application solutions use single strains, resulting in a narrow antibacterial spectrum and an inability to comprehensively cover the diverse spoilage bacteria, including bacteria, yeasts, and molds, in meat products. Third, existing technologies do not systematically couple lactic acid bacteria preservation with modified atmosphere packaging (MAP), lacking precise control over the proliferation rate of lactic acid bacteria in a MAP environment. Excessive proliferation of lactic acid bacteria can lead to an excessive decrease in meat pH, excessive acid production, and flavor deterioration, making it difficult to maintain the balance between antibacterial effect and edible quality.

[0005] The aforementioned multiple shortcomings have resulted in the industry's current lack of a meat product preservation process that deeply synergizes liquid native compound lactic acid bacteria with ternary modified atmosphere packaging, eliminating the need for chemical preservatives throughout the entire process. This is especially true for bone-in processed meat products such as pork shoulder blades and ribs, which have complex structures and higher microbial risks; to date, there is no specific preservation solution available for industrial application. Summary of the Invention

[0006] This invention aims to provide a method for preserving meat products using a compound lactic acid bacteria fermentation broth in synergistic modified atmosphere packaging, in order to solve the technical problems of existing modified atmosphere packaging having a narrow antibacterial spectrum and relying on chemical preservatives, as well as existing lactic acid bacteria technologies having insufficient preservative efficacy and being unsuitable for complete processes of bone-in processed meat products due to the inactivation of bacterial powder, limitations of single strains, and lack of synergistic effects of modified atmosphere packaging.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for preserving meat products using a compound lactic acid bacteria fermentation broth and modified atmosphere packaging, comprising the following steps: (1) Raw material pretreatment: Clean, trim, remove lymph nodes and blood clots from livestock and poultry meat raw materials, and cut them into meat pieces of uniform size; (2) Biological endogenous preservation treatment: Add uninactivated compound lactic acid bacteria fermentation slurry to the meat product auxiliary material system. The amount added is 0.5% to 1.5% based on the total mass of meat product raw materials. Add it together with ice water and marinade into a tumbler for vacuum tumbling and mixing. The compound lactic acid bacteria fermentation slurry is a liquid native fermentation product that has not been spray dried or subjected to any inactivation treatment. (3) Synergistic modified atmosphere sealing: The tumbled meat pieces are placed into a high-barrier packaging container, the air inside the packaging is removed, a mixed protective gas is filled in, and the container is completely sealed by heat pressing; the volume composition of the mixed protective gas is: CO2 30%~80%, N2 15%~65%, O2 0~10%; (4) Cold chain storage and transportation throughout the process: sealed finished products are stored, transported and sold in a constant temperature environment of 0 to 10℃.

[0008] Furthermore, in step (2), the compound lactic acid bacteria fermentation broth is prepared by mixed fermentation of Lactobacillus plantarum, Lactobacillus sakei, and Leuconostoc mesenteroides, with a total live bacteria content ≥1.0×10⁻⁶. 9 CFU / mL, with a live cell ratio of 4:3:3 for the three strains.

[0009] Furthermore, in step (2), the amount of compound lactic acid bacteria fermentation liquid added is 0.8% to 1.2% of the total mass of the meat product raw materials.

[0010] Furthermore, the volume composition of the mixed protective gas in step (3) is: CO2 60%, N2 38%, O2 2%.

[0011] Furthermore, in step (3), the high-barrier packaging container is a PP food storage box or a composite retort pouch with an oxygen permeability ≤5cm. 3 / (m 2 • 24h • 0.1MPa), carbon dioxide transmission rate ≤ 20cm 3 / (m 2 ·24h·0.1MPa).

[0012] Furthermore, in step (1), the cut meat of livestock and poultry is pork shoulder bone, pork ribs, beef shank, beef slices, beef cubes or chicken chunks in strips of prepared meat products.

[0013] Furthermore, in step (2), the vacuum degree of vacuum tumbling is -0.09 to -0.06 MPa, the tumbling temperature is 0 to 6°C, and the tumbling time is 60 to 120 min.

[0014] Furthermore, after the mixed protective gas is filled in step (3), the residual oxygen content in the packaging is ≤0.5%.

[0015] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention deeply couples the inactivated compound lactic acid bacteria liquid fermentation broth with ternary modified atmosphere packaging. On the one hand, the compound lactic acid bacteria continuously metabolize in the meat matrix to produce natural antibacterial substances such as lactic acid, bacteriocins, and hydrogen peroxide, which endogenously lowers the pH value of the meat and destroys the survival environment of facultative anaerobic pathogens (Listeria, Salmonella) and CO2-resistant yeasts. On the other hand, the high-concentration CO2 modified atmosphere environment externally blocks the respiratory metabolism of aerobic putrefactive bacteria (Pseudomonas, etc.), and the low-oxygen atmosphere simultaneously inhibits lipid oxidation and myoglobin browning. The two complement each other in terms of antibacterial targets and have a superimposed mechanism of action. Data from the examples show that the processed pork scallop bone meat using the method of this invention has a shelf life of 42 days at 4°C, which is 6 times that of single modified atmosphere treatment and 3.5 times that of single lactic acid bacteria liquid treatment, significantly better than the expectation of simple superposition of the two methods, confirming the synergistic effect of deep synergy.

[0016] (2) This invention uses a 4:3:3 ratio of live bacteria of *Lactobacillus plantarum*, *Lactobacillus sakei*, and *Leuconostoc mesenteroides* for fermentation. The three strains have clear division of labor and synergistic complementarity: *Lactobacillus plantarum* has a strong acid-producing ability, effectively inhibiting Gram-negative pathogenic bacteria and rapidly reducing the pH of meat products; *Lactobacillus sakei* produces ester aroma substances while inhibiting Gram-positive putrefactive bacteria, effectively masking the fishy smell of meat; *Leuconostoc mesenteroides* specifically inhibits CO2-resistant yeasts and molds, filling the gap in modified atmosphere packaging for yeast inhibition. The combination of the three strains enables the antibacterial spectrum to cover the entire spectrum of "bacteria + yeast + mold," solving the fundamental defect of the narrow antibacterial spectrum of single strains. Comparative verification shows that under the same modified atmosphere conditions, the shelf life of the single *Lactobacillus plantarum* group is only 22 days and yeast contamination occurs, while the shelf life of the three-strain compound group reaches 42 days and no fungi are detected.

[0017] (3) The compound lactic acid bacteria fermentation broth used in this invention is a liquid native fermentation product, which is not subjected to spray drying, freeze drying, or any high-temperature inactivation treatment throughout the entire process. Compared with commercially available spray-dried bacterial powder, this invention completely retains the activity of all live bacteria in the fermentation broth as well as heat-sensitive metabolic antibacterial products such as lactic acid, bacteriocin, acetic acid, and hydrogen peroxide. Under the same live bacteria addition conditions, the shelf life of this invention is extended by about 2.6 times (42 days vs. 16 days) compared with the spray-dried bacterial powder solution, directly verifying the irreplaceable advantage of liquid native fermentation broth in terms of preservative efficacy compared with dried bacterial powder.

[0018] (4) This invention does not add any artificial chemical preservatives such as sodium benzoate, potassium sorbate, or sodium dehydroacetate throughout the entire process. All the preservative effects come from lactic acid bacteria and their natural metabolites, which fully meets consumers' demand for "natural, low-additive, and clean label" food. It eliminates health controversies caused by chemical additives and significantly enhances the product's market competitiveness and brand premium space.

[0019] (5) This invention precisely controls the proliferation rate of lactic acid bacteria in the later stages of storage by using the moderate antibacterial effect of high concentration CO2 in the controlled atmosphere environment, so that the pH value gradually decreases to the ideal range of about 5.4 (see Example 1 final pH 5.42). This maintains the weakly acidic environment required to inhibit spoilage bacteria, and avoids excessive proliferation of lactic acid bacteria under non-controlled atmosphere conditions, which would lead to excessive pH decrease (Comparative Example 2 final pH 5.18) and thus cause the product to become too acidic and deteriorate. This achieves a precise balance between "effective antibacterial effect" and "acceptable flavor".

[0020] (6) This invention addresses the unique challenges of bone-in processed meat products such as pork ribs and spare ribs, which have numerous bone crevices, complex microbial attachment sites, and are prone to forming antibacterial blind spots using conventional modified atmosphere packaging. Through a tumbling process, the liquid bacterial solution penetrates deeply into the bone crevices and muscle tissue, achieving uniform coverage of the entire meat. The process only requires the addition of the bacterial solution during the existing tumbling process, eliminating the need for additional large-scale equipment investment. It can be directly integrated into existing processed meat production lines and is suitable for the industrial continuous mass production of all types of cut and processed meat products from pork, beef, and chicken, demonstrating significant economic benefits and promotional value. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The present invention will be further described in detail below with reference to the embodiments.

[0023] This invention provides a method for preserving meat products using a compound lactic acid bacteria fermentation broth in conjunction with modified atmosphere packaging. The core of this method lies in using an untreated, liquid, native compound lactic acid bacteria fermentation broth, which is thoroughly mixed with the meat products during the tumbling process. This allows the live bacteria and their metabolites (lactic acid, bacteriocins, acetic acid, etc.) to deeply penetrate the muscle tissue and the bone suture area of ​​bone-in meat, achieving endogenous biological antibacterial action. Simultaneously, this is combined with precise ternary mixed protective gas modified atmosphere packaging to construct a dual synergistic preservation system of "endogenous acid reduction and broad-spectrum antibacterial action + exogenous modified atmosphere physical oxygen suppression," without adding any chemical preservatives throughout the entire process.

[0024] The method of this invention can be directly connected to existing meat processing production lines without the need for large-scale equipment modification. It is suitable for the industrial continuous production of various cut and prepared meat products such as pork shoulder bones, pork ribs, beef shank, beef slices, beef cubes, and chicken chunks.

[0025] The compound lactic acid bacteria fermentation broth used in this invention is prepared by mixed fermentation of three strains: *Lactobacillus plantarum*, *Lactobacillus sakei*, and *Leuconostoc mesenteroides*. The viable cell ratio of the three strains is 4:3:3, and the total viable cell content in the resulting liquid primary fermentation slurry after fermentation is ≥1.0 × 10⁻⁶. 9 CFU / mL.

[0026] The fermentation broth is a liquid, native fermentation product that is not subjected to spray drying, freeze drying, or any high-temperature inactivation treatment throughout the entire process, so as to fully preserve the activity of live bacteria and the natural antibacterial metabolites such as lactic acid, bacteriocins, hydrogen peroxide, and acetic acid produced during the fermentation process.

[0027] The corrosion prevention method of the present invention includes the following steps in sequence: (1) Raw material pretreatment: Wash the raw materials of livestock and poultry with clean water to remove surface blood and dirt, trim and remove lymph nodes, blood clots and connective tissue, and cut them into uniform size pieces according to product specifications. The meat temperature is controlled at ≤6℃ throughout the pretreatment process. Bone-in meat products need to be fully soaked to remove blood and drained.

[0028] (2) Biological endogenous preservation treatment: Based on the total mass of meat product raw materials, add 0.5% to 1.5% (preferably 0.8% to 1.2%) of non-inactivated compound lactic acid bacteria fermentation liquid to the auxiliary material system, and put it into the tumbler along with ice water, compound marinade, water-retaining agent and other auxiliary materials. Tumble intermittently for 60 to 120 minutes under the conditions of vacuum degree of -0.06 to -0.09 MPa and temperature of 0 to 6℃, so that the bacterial liquid can penetrate evenly into the meat block.

[0029] (3) Synergistic modified atmosphere sealing: Weigh the tumbled meat pieces and fill them into high-barrier packaging containers (such as PP food storage boxes or composite retort bags with an oxygen permeability ≤5cm). 3 / (m 2 • 24h • 0.1MPa), carbon dioxide transmission rate ≤ 20cm 3 / (m 2 After evacuating the packaging by applying a 24-hour pressure of 0.1 MPa, a ternary mixed protective gas is introduced and then completely sealed by hot pressing. The volume composition of the mixed gas is: CO2 30%–80%, N2 15%–65%, O2 0–10%, preferably CO2 60%, N2 38%, and O2 2%. The residual oxygen content inside the packaging after filling is ≤0.5%.

[0030] (4) Cold chain storage and transportation throughout the process: sealed finished products are stored, transported and sold in a constant temperature environment of 0 to 10℃.

[0031] The following are four embodiments of the present invention.

[0032] Example 1: Preservative treatment of pig fan bones (1) Raw material pretreatment: freeze the frozen pork fan bones at 0-4℃, cut them into fan bone pieces with a thickness of 0.5-1.5cm using a bone saw, soak them in water to remove blood, and drain them until the meat temperature is ≤6℃.

[0033] (2) Biological endogenous preservation treatment: Based on the total mass of the fan ribs, weigh 0.8% of the compound lactic acid bacteria fermentation broth (the ratio of live bacteria strains is Lactobacillus plantarum: Lactobacillus sakei: Leuconostoc mesenteroides = 4:3:3, and the total live bacteria content is ≥1.0×10⁻⁶). 9 The bacterial solution (CFU / mL) was added to a tumbler along with ice water, compound marinade, and water-retaining agent. The mixture was intermittently tumbled for 105 minutes under vacuum conditions of -0.08 MPa and temperature of 4°C to allow the bacterial solution to fully penetrate the scapular muscle and suture tissue.

[0034] (3) Synergistic modified atmosphere sealing: The rolled fan bone blocks are placed into a high-barrier PP food preservation box, the air is removed and then a mixed protective gas with a volume composition of 60% CO2, 38% N2 and 2% O2 is filled in, and then it is completely sealed by hot pressing.

[0035] (4) Cold chain storage: Store the sealed finished product in a 4℃ constant temperature cold storage.

[0036] The pork fan bone processed meat products treated by the above method have a shelf life of up to 42 days at 4°C. During storage, there is no bulging, no surface mucus, no off-odor, and no foodborne pathogens such as Listeria or Salmonella are detected.

[0037] Example 2: Preservative treatment of beef tenderloin slices (thick slices) (1) Raw material pretreatment: Frozen beef shank is placed in an environment of 0 to 4℃ for slow freezing until the core temperature reaches -3℃ to -5℃. It is then sliced ​​into 3mm thick slices using a slicer and manually cut into beef slices 5cm long and 3cm wide. The temperature is maintained below 4℃ throughout the entire process.

[0038] (2) Biological endogenous preservation treatment: Based on the total mass of beef slices, weigh 0.8% of compound lactic acid bacteria fermentation liquid (strain ratio and live bacteria content are the same as in Example 1), and put it into a tumbler together with ice water, compound marinade and water-retaining agent. Tumble intermittently for 60 minutes under vacuum of -0.08MPa and temperature of 4℃.

[0039] (3) Synergistic modified atmosphere sealing: The tumbled beef slices are placed into a high-barrier PP preservation box, the air is removed and then a mixed protective gas with a volume composition of 60% CO2, 38% N2 and 2% O2 is filled in, and then it is completely sealed by heat pressing.

[0040] (4) Cold chain storage: Store the sealed finished product in a 4℃ constant temperature cold storage.

[0041] The beef slices processed using the above method have a shelf life of up to 35 days at 4°C. During storage, the meat color remains stable, there is no sour odor or mucus production, and no pathogenic bacteria are detected.

[0042] Example 3: Preservative treatment of beef brisket-flavored meat chunks (1) Raw material pretreatment: Frozen beef shank is placed in an environment of 0 to 4℃ for slow freezing until the core temperature reaches -3℃ to -5℃, and then cut into beef cubes with a length, width and height of 2cm using a pelletizer. The operating temperature is maintained below 4℃ throughout the process.

[0043] (2) Biological endogenous preservation treatment: Based on the total mass of beef granules, weigh 0.8% of compound lactic acid bacteria fermentation liquid (strain ratio and live bacteria content are the same as in Example 1), and put it into a tumbler together with ice water, compound marinade and water-retaining agent. Tumble intermittently for 75 minutes under vacuum of -0.08MPa and temperature of 4℃.

[0044] (3) Synergistic modified atmosphere sealing: The tumbled beef cubes are placed into a high-barrier PP preservation box, the air is removed and then a mixed protective gas with a volume composition of 60% CO2, 38% N2 and 2% O2 is filled in, and then it is completely sealed by heat pressing.

[0045] (4) Cold chain storage: Store the sealed finished product in a 4℃ constant temperature cold storage.

[0046] The beef granules processed using the above method have a shelf life of up to 37 days at 4°C. During storage, the granules are distinct, without stickiness, bulging, or off-odors, and no pathogens were detected.

[0047] Example 4: Preservative treatment of pork rib sections (1) Raw material pretreatment: Cut frozen pork ribs into rib sections with a length of 4cm, a width of 1.5cm and a thickness of unlimited by a cutting machine. Soak them in clean water to thaw and remove blood. Drain until the meat temperature is ≤6℃.

[0048] (2) Biological endogenous preservation treatment: Based on the total mass of the rib section, weigh 0.5% of the compound lactic acid bacteria fermentation liquid (strain ratio and live bacteria content are the same as in Example 1), and put it into the tumbler together with ice water, compound pickling material and water-retaining agent. Tumble intermittently for 90 minutes under vacuum of -0.08MPa and temperature of 4℃.

[0049] (3) Synergistic modified atmosphere sealing: The tumbled rib sections are placed into a high-barrier PP food storage box, the air is removed and then a mixed protective gas with a volume composition of 60% CO2, 38% N2 and 2% O2 is filled in, and then it is completely sealed by hot pressing.

[0050] (4) Cold chain storage: Store the sealed finished product in a 4℃ constant temperature cold storage.

[0051] The pork ribs processed using the above method have a shelf life of up to 42 days at 4°C. During storage, there is no bloating, sourness, stickiness, or off-odor, and no pathogenic bacteria were detected.

[0052] It should be added that, in other alternative embodiments, the mixed protective gas can also be prepared in proportions such as 80% CO2, 20% N2, and 0% O2, or 30% CO2, 60% N2, and 10% O2, all of which can achieve the purpose of extending shelf life.

[0053] To systematically verify the synergistic effect between the "liquid composite bacterial strain" and the "ternary modified atmosphere" in this invention, and the superiority of "liquid native" over "spray-dried bacterial powder" and "composite bacterial strain" over "single bacterial strain", the following comparative examples were set up, using the pig fan bone product of Example 1 as a representative: Comparative Example 1 (Single modified atmosphere, no lactic acid bacteria): No lactic acid bacteria fermentation liquid was added, and the remaining modified atmosphere packaging process (CO2 60%, N2 38%, O2 2%, high barrier PP box) and tumbling parameters were the same as in Example 1; Comparative Example 2 (Compound Bacterial Liquid, No Modified Atmosphere): Add 0.8% compound lactic acid bacteria fermentation liquid (same as Example 1), tumble and do not perform modified atmosphere sealing, but only seal in a non-high barrier packaging under normal air environment, the rest is the same as Example 1; Comparative Example 3 (spray-dried compound bacterial powder, modified atmosphere): The number of viable bacteria was equal to 1.0 × 10⁻⁶. 9 Commercially available spray-dried compound lactic acid bacteria powder (CFU / g) with strain ratios the same as in Example 1 was used to replace the liquid fermentation broth. The amount added was calculated based on the number of live bacteria, and the remaining modified atmosphere and process parameters were the same as in Example 1. Comparative Example 4 (single liquid strain, modified atmosphere): only an equal amount (0.8%) of Lactobacillus plantarum single liquid fermentation broth (excluding Lactobacillus sakei and Leuconostoc mesenteroides) was used, and the remaining modified atmosphere and process parameters were the same as in Example 1.

[0054] The products of Example 1 and each comparative example were stored simultaneously at 4°C in the dark. Samples were taken every 3 days to determine the total bacterial count (according to GB4789.2-2022) and pH value (according to GB5009.237), and sensory evaluation (color, odor, mucus, and box swelling) was performed concurrently. A total bacterial count ≥10 was considered acceptable. 6 The earliest point at which CFU / g or sensory indicators reach unacceptable levels (significant rancidity, sliminess, or box swelling) is considered the end of the shelf life. Three parallel samples were set up for each group, and the results were averaged. See Table 1 for details.

[0055] Example 1 (Invention) 42 5.42 5.88 Bright red color, firm texture, and no off-odor Not detected Comparative Example 1 (Controlled Atmosphere Only) 7 6.15 7.92 Sticky surface, strong sour smell, dull meat color Listeria was detected. Comparative Example 2 (bacterial culture only) 12 5.18 7.35 pH excessively low, slightly acidic smell, surface moist. No pathogenic bacteria were detected, but yeast was detected. Comparative Example 3 (Sprayed Bacterial Powder + Modified Atmosphere) 16 5.78 7.01 Dark in color and has a slight odor A small amount of lactic acid bacteria was detected. Comparative Example 4 (Single-strain liquid + modified atmosphere) 22 5.61 6.54 Slightly sticky surface, with slight oxidation of fat. Yeast was detected The results show: (1) The shelf life of Example 1 of the present invention is 42 days, which is 6 times that of Comparative Example 1 (single modified atmosphere) and 3.5 times that of Comparative Example 2 (single bacterial culture, no modified atmosphere). Comparative Example 1 spoiled after 7 days of storage due to stickiness and sour smell, which proved that single modified atmosphere is ineffective against facultative anaerobic bacteria (lactic acid bacteria, yeast); Comparative Example 2 relied solely on the acid production of lactic acid bacteria to inhibit bacteria, and due to the lack of a modified atmosphere barrier, aerobic Pseudomonas proliferated in large quantities after 12 days. The expected value of simply adding the two (7+12=19 days) is much lower than the 42 days of Example 1, which fully demonstrates that the "endogenous biological acid reduction and broad-spectrum antibacterial + exogenous modified atmosphere physical oxygen suppression" of the present invention has a significant synergistic effect, rather than a simple superposition of the two methods.

[0056] (2) The shelf life of Comparative Example 3 (spray-dried bacterial powder + modified atmosphere) was only 16 days, far shorter than the 42 days of Example 1. Although the amount of live bacteria added and the modified atmosphere parameters were the same for both, the high temperature during the spray drying process (inlet air temperature of about 160-180°C) resulted in the loss of a large amount of heat-sensitive metabolites such as bacteriocins and organic acids. At the same time, the live bacteria were severely damaged, and their colonization and acid production capabilities were greatly reduced. This result directly verifies the irreplaceable technical advantage of the "liquid original fermentation broth" used in this invention—complete preservation of live bacteria activity and all metabolic antibacterial products, with an antiseptic effect that is about 1.6 times higher than that of bacterial powder (42 / 16=2.6, after considering the contribution of the basic modified atmosphere, the contribution of liquid original fermentation broth is much higher than that of dry powder).

[0057] (3) Comparative Example 4 (single Lactobacillus plantarum liquid + modified atmosphere packaging) had a shelf life of 22 days, which was better than the powder group, but significantly shorter than Example 1. Sensory data showed that Comparative Example 4 developed a sticky surface at 22 days, and subsequent microbial identification indicated yeast contamination, while in Example 1, yeast was still under control at 42 days. This is because Leuconostoc mesenteroides specifically inhibits yeast and mold, and Lactobacillus sakei inhibits Gram-positive spoilage bacteria while producing ester aroma. The combination of the three strains covers a broad spectrum of "bacteria + yeast", while a single strain has a narrow antibacterial spectrum and cannot fully cover the diverse spoilage bacteria in meat products.

[0058] (4) It is worth mentioning that the shelf-life pH of Comparative Example 2 (only bacterial liquid without modified atmosphere) dropped to 5.18, which was significantly lower than 5.42 of Example 1. This indicates that the excessive proliferation and acid production of lactic acid bacteria in the environment without modified atmosphere led to the meat becoming too acidic and deteriorating. The modified atmosphere environment (high CO2) of the present invention moderately slowed down the reproduction rate of lactic acid bacteria, so that the pH dropped slowly. This maintained the weakly acidic environment required for antibacterial activity and avoided the destruction of the meat flavor by excessive acidification, thus achieving a dynamic balance between "antibacterial activity" and "flavor protection".

[0059] In summary, the comparative experiments described above systematically demonstrated the scientific validity and advanced nature of the technical solution of this invention from four dimensions: "synergistic effect of modified atmosphere", "necessity of liquid native environment", "broad-spectrum nature of compound strains" and "controllability of fermentation rate".

[0060] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0061] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preserving meat products using a compound lactic acid bacteria fermentation broth in conjunction with modified atmosphere packaging, characterized in that, The steps are as follows: (1) Raw material pretreatment: Clean, trim, remove lymph nodes and blood clots from livestock and poultry meat raw materials, and cut them into meat pieces of uniform size; (2) Biological endogenous preservation treatment: Add uninactivated compound lactic acid bacteria fermentation slurry to the meat product auxiliary material system. The amount added is 0.5% to 1.5% based on the total mass of meat product raw materials. Add it together with ice water and marinade into a tumbler for vacuum tumbling and mixing. The compound lactic acid bacteria fermentation slurry is a liquid native fermentation product that has not been spray dried or subjected to any inactivation treatment. (3) Synergistic modified atmosphere sealing: The tumbled meat pieces are placed into a high-barrier packaging container, the air inside the packaging is removed, a mixed protective gas is filled in, and the container is completely sealed by heat pressing; the volume composition of the mixed protective gas is: CO2 30%~80%, N2 15%~65%, O2 0~10%; (4) Cold chain storage and transportation throughout the process: sealed finished products are stored, transported and sold in a constant temperature environment of 0 to 10℃.

2. The method for preserving meat products using a composite lactic acid bacteria fermentation broth in synergistic modified atmosphere packaging according to claim 1, characterized in that: The compound lactic acid bacteria fermentation broth in step (2) is prepared by mixed fermentation of Lactobacillus plantarum, Lactobacillus sakei, and Leuconostoc mesenteroides, with a total live bacteria content ≥1.0×10⁻⁶. 9 CFU / mL, with a live cell ratio of 4:3:3 for the three strains.

3. The method for preserving meat products using a composite lactic acid bacteria fermentation broth in synergistic modified atmosphere packaging according to claim 2, characterized in that, The amount of compound lactic acid bacteria fermentation liquid added in step (2) is 0.8% to 1.2% of the total mass of meat product raw materials.

4. The method for preserving meat products using a composite lactic acid bacteria fermentation broth in synergistic modified atmosphere packaging according to claim 1, characterized in that: The volume composition of the mixed protective gas in step (3) is: CO2 60%, N2 38%, O2 2%.

5. The method for preserving meat products using a composite lactic acid bacteria fermentation broth in synergistic modified atmosphere packaging according to claim 1, characterized in that: In step (3), the high-barrier packaging container is a PP food storage box or a composite retort pouch with an oxygen permeability ≤5cm. 3 / (m 2 • 24h • 0.1MPa), carbon dioxide transmission rate ≤ 20cm 3 / (m 2 ·24h·0.1MPa).

6. The method for preserving meat products using a composite lactic acid bacteria fermentation broth in synergistic modified atmosphere packaging according to claim 1, characterized in that: In step (1), the cut meat of livestock and poultry is pork shoulder bone, pork ribs, beef shank, beef slices, beef cubes or chicken chunks in strips.

7. The method for preserving meat products using a composite lactic acid bacteria fermentation broth and modified atmosphere packaging according to claim 1, characterized in that: The vacuum degree of the vacuum tumbling in step (2) is -0.09 to -0.06 MPa, the tumbling temperature is 0 to 6℃, and the tumbling time is 60 to 120 min.

8. The method for preserving meat products using a composite lactic acid bacteria fermentation broth in synergistic modified atmosphere packaging according to claim 1, characterized in that: After the mixed protective gas is filled in step (3), the residual oxygen content in the packaging is ≤0.5%.