Fresh meat bacteria-reducing antiseptic controlled atmosphere cascade sub-normal temperature preservation method

Abstract

The invention belongs to the technical field of fresh-keeping and food, and discloses a raw fresh meat bacteria-reducing antiseptic controlled atmosphere sub-normal temperature cascade fresh-keeping method, which comprises the following steps: preparing raw materials; performing pretreatment; preparing a composite fresh-keeping solution; atomizing and spraying; performing draining; modified atmosphere packaging; and storage: storing the packaged fresh meat in an environment of 0-12 DEG C. According to the present invention, the combined bacteria reducing process combining organic acid spraying, ultraviolet irradiation and CO2 gas washing is adopted, such that the whole treatment process is mild, the color and the flavor of the fresh meat are not affected, and the surface initial bacteria amount can be rapidly reduced. Compared with traditional hypochlorous acid treatment, the risk of residues of organic chlorine compounds and other harmful substances is eradicated, and the method is a cleaner and safer processing technical path.

Description

Technical Field

[0001] This invention belongs to the field of preservation and food technology, and in particular to a modified atmosphere sub-normal temperature cascade preservation technology for fresh meat with antibacterial and preservative properties. Background Technology

[0002] The quality stability and shelf life of fresh meat are directly related to industry benefits and food safety. However, its rich nutritional matrix makes it susceptible to contamination by spoilage microorganisms throughout the entire supply chain, accompanied by problems such as oxidative deterioration and juice loss, which leads to a decrease in commodity value and an increase in safety risks. Therefore, developing technologies that take into account safety, sterilization, quality preservation, long-term freshness, and industrial adaptability has become the core demand of the industry.

[0003] Current fresh meat preservation technologies primarily rely on single-stage control, exhibiting significant shortcomings: In the sterilization stage, chemical methods easily leave harmful residues, while physical methods damage meat quality, failing to balance sterilization efficiency with quality preservation; membrane coating technology is functionally limited, lacking a synergistic design for water retention, controlled release, and antibacterial activity, making it difficult to support long-term preservation; modified atmosphere packaging suffers from performance contradictions: vacuum packaging results in dull colors, while high-oxygen packaging accelerates oxidation and is prone to collapse, and traditional mixed gas methods cannot overcome synergistic bottlenecks. More importantly, existing technological systems are fragmented and lack synergy, failing to form a complete supply chain solution. Furthermore, they are complex to operate, lack standardization, hindering industrial-scale promotion, exhibit poor preservation stability under fluctuating temperatures, have short shelf lives, and are prone to exceeding quality standards. In summary, existing technologies cannot meet the industry's core needs, making the development of a comprehensive, synergistic preservation solution an urgent industrial necessity.

[0004] The search revealed the following patent publications related to this invention: 1. Patent publication CN105309593B discloses a method for preserving and conditioning beef using a combination of compound essential oils and modified atmosphere packaging. This method involves immersing beef in a compound plant essential oil solution containing thymol, carvacrol, and other components, followed by high-oxygen modified atmosphere packaging, aiming to combine the antibacterial properties of the essential oils with the color-protecting properties of the modified atmosphere. However, this method has significant limitations: the strong characteristic flavor of the plant essential oils can mask the original flavor of the beef, affecting product acceptance; its preservation mechanism relies on essential oil adsorption and the modified atmosphere environment, failing to construct a carrier structure on the meat surface that combines stable barrier properties with the slow-release function of active ingredients, thus having a weak effect on improving juice loss.

[0005] 2. Patent publication CN110915883A discloses the preparation and preservation method of a coating preservative for chilled mutton. It uses soy protein isolate and chitosan as film-forming substrates, and combines them with lysozyme, plant essential oils (such as onion oil and Sichuan pepper oil), and black soybean flavonoids, among other natural active ingredients. A protective layer is formed through mixing and application, combined with high-concentration carbon dioxide modified atmosphere packaging. This method aims to achieve antibacterial and antioxidant effects through the synergistic effect of multiple components. However, the resulting coating is essentially a physical mixture of multiple components with a uniform film structure, and the preparation process involves multiple extraction steps, making it quite complex.

[0006] 3. Patent publication CN115886060A discloses a method for preserving pork products. It employs a preservative compounded from honeysuckle extract, nisin, *Lactobacillus plantarum*, and mulberry extract. The meat is treated by soaking or spraying, followed by vacuum or high-oxygen modified packaging. This method emphasizes the broad-spectrum inhibition of various spoilage bacteria by the compound biological preservative and its synergistic effect with packaging. However, its preservation effect mainly relies on the direct adsorption or penetration of the preservative components on the meat surface, without constructing an independent anti-corrosion and preservation film layer with long-lasting physical barrier function. Therefore, it is also difficult to effectively prevent juice seepage. Furthermore, the active ingredients act through direct contact, lacking a controllable release mechanism, which may lead to insufficient persistence of the preservation effect.

[0007] The above comparison shows that the present invention patent application is fundamentally different from the aforementioned patent publications. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a modified atmosphere sub-normal temperature cascade preservation technology for fresh meat to reduce bacteria and prevent spoilage.

[0009] The technical solution adopted by this invention to solve its technical problem is: A modified atmosphere packaging technology for sterilization, preservation, and near-ambient temperature cascade preservation of fresh meat includes the following steps: Step 1: Raw material preparation: Select fresh beef, remove the surface fascia, and cut it into chunks or steaks; Step 2, Preprocessing: The beef was sprayed with an organic acid solution until it was in a dripping state, and then washed with pure CO2 gas for 1-2 minutes under ultraviolet light. Step 3: Preparation of the compound preservative solution: Solution A: 1% sodium alginate, 3% sodium lactate, 0.45% glycine and 0.02% ε-polylysine, all percentages are final mass concentrations, the solvent is water, and the mixture is prepared by mixing. Solution B: A 3% (w / w) aqueous solution of calcium propionate; Step 4: Atomized Spraying: S1 First Spray: The aqueous composite preservative liquid containing sodium alginate, sodium lactate, glycine and ε-polylysine, namely liquid A, is evenly sprayed onto the surface of the pretreated beef to form a continuous film liquid. S2 Second Spray: While liquid A is still wet, liquid B is sprayed onto its surface to trigger an ionic cross-linking reaction, thereby forming a composite gel preservation film on the surface of the beef, i.e., in-situ film formation. Step 5: Drain: Hang the beef processed in step four to drain, allowing the membrane to fully solidify and drain off excess water. Step Six: Modified Atmosphere Packaging After draining the beef in step five, pack it into modified atmosphere packaging, vacuum it, and then fill it with mixed gas. The filling time is 3 seconds and the pressure is 0.6 MPa. Step 7, Storage: Store the packaged beef at 0-12℃.

[0010] Furthermore, in step one, beef with a fat content of 15%-20% and a protein content of 18-22% is selected.

[0011] Furthermore, in step two, the organic acid is an aqueous solution obtained by mixing 1% lactic acid and 0.1% gallic acid.

[0012] Furthermore, the mixed gas in step six is: O2 55%, CO2 30%, N2 15%, where the percentages are volume concentrations.

[0013] Furthermore, in step seven, the packaged beef is stored at 12°C.

[0014] The above-described method is applied to the logistics preservation of beef.

[0015] The advantages and positive effects of this invention are as follows: 1. This invention employs a combined sterilization process that integrates organic acid spraying, ultraviolet irradiation, and CO2 gas washing. The entire process is gentle and does not affect the color and flavor of the fresh meat. It can also quickly reduce the initial bacterial count on the surface. Compared with traditional hypochlorous acid treatment, it eliminates the risk of harmful residues such as organochlorine compounds, making it a cleaner and safer processing technology.

[0016] 2. This invention proposes a multi-mechanism synergistic preservation system solution. Through a unique two-step sequential spraying process, an edible film with antibacterial, antioxidant, water-retaining, and barrier properties is prepared in situ on the surface of meat products. Based on a stable "eggshell" structure formed by the cross-linking of sodium alginate and calcium ions, the film combines physical barrier, active ingredient release, and moisture management functions. Its outer dense gel effectively blocks external contaminants and oxygen, while the inner porous network efficiently adsorbs and locks in moisture, significantly reducing juice loss. Simultaneously, this gradient structure enables intelligent controlled release of active ingredients such as sodium lactate and ε-polylysine, thus providing continuous and long-lasting antibacterial and antioxidant protection.

[0017] 3. Compared with traditional vacuum packaging and 80% O2 high-oxygen modified packaging, the present invention reduces the O2 ratio to 55% and appropriately increases the CO2 concentration to achieve the same meat color as high-oxygen modified packaging. Simultaneously, it reduces the oxidation rate, slows down spoilage, and minimizes juice loss during storage. This packaging method maintains a good sales appearance while significantly improving product quality. Furthermore, the invention pre-treats fresh meat with CO2 gas, proactively addressing the problem of CO2 easily dissolving in the water and fat contained in fresh meat at low temperatures, leading to a decrease in gas concentration and potential packaging collapse, thus avoiding economic losses due to packaging issues.

[0018] 4. This invention constructs an extremely rigorous evaluation model, selects high-quality beef with high fat and protein content as the implementation object, and verifies it at 12℃. It fully demonstrates that the technical system has strong performance redundancy and temperature adaptability. Its preservation effect will be more stable and durable under more ideal low temperature conditions, solving the industry pain points of existing technologies being sensitive to temperature fluctuations and experiencing sharp performance reduction in non-standard cold chains.

[0019] 5. This invention represents a technological leap from "passive preservation" to "active quality maintenance." This technical solution can precisely control the post-cooking and biochemical processes of meat, strongly inhibiting harmful oxidation and microorganisms while guiding limited fat oxidation and protein hydrolysis that produce a pleasant flavor. This not only ensures safety but also aims to give the product a richer flavor and tender texture than deep-frozen meat, achieving a balance between freshness preservation and quality improvement.

[0020] 6. The method of this invention can effectively inhibit the growth of spoilage bacteria. The verification results at the most stringent storage temperature (12℃) show that the total bacterial count of beef on day 8 is 5.53 log CFU / g (secondary freshness). Sensory, color, texture, pH, TVB-N and other indicators are all within the range specified by national standards (the shelf life is extended by 3-4 times compared with the control group). This shows that this method can not only effectively inhibit spoilage, but also demonstrates the excellent ability to protect the flavor and nutrition of high-quality fresh meat under high-difficulty conditions. It provides a new technical paradigm for developing a flexible supply chain for high-end fresh meat and upgrading the consumer experience.

[0021] 7. The present invention is simple to operate, highly practical, standardized in process, easy to industrialize and suitable for large-scale application, providing a new technical method for the storage and preservation of fresh meat.

[0022] 8. This invention utilizes a cascade preservation technology based on sterilization technology and in-situ biofilm preservation technology. By placing fresh meat in a modified atmosphere environment, the sterilization, inhibition, and control of bacteria are achieved, resulting in good quality meat that can be preserved for 8 days at 12℃. This overcomes the problems of single treatments, such as the inability to achieve long-term antibacterial effects, color protection, and packaging collapse. It effectively inhibits the growth of spoilage bacteria (Pseudomonas and Cyclofilamentum heat-degrading bacteria). On day 8, the total bacterial count is 5.53 log CFU / g (national standard grade II freshness). Sensory, color, texture, pH, TVB-N, and other indicators are all within the range specified by national standards, extending the shelf life by 3-4 times compared to related traditional technologies. Attached Figure Description

[0023] Figure 1 This is a photograph showing the appearance of beef during storage at 12°C according to the present invention. Figure 2 This is a graph showing the effect of the combined treatment in this invention on the pH value of beef stored at 12℃. Figure 3 This is a graph showing the effect of the compound treatment in this invention on the TVB-N value of beef stored at 12℃; Figure 4 This is a graph showing the effect of the combined treatment in this invention on the TBARS value of beef stored at 12℃. Figure 5 This is a graph showing the effect of the combined treatment in this invention on the total number of microbial colonies in beef stored at 12°C. Figure 6 This is a graph showing the effect of the combined treatment in this invention on the number of Pseudomonas bacteria in beef stored at 12°C. Figure 7 This is a graph showing the effect of the combined treatment in this invention on the number of heat-dead loop mycelia in beef stored at 12°C. Figure 8 This is a graph showing the effect of three different treatment methods on the pH value of beef stored at 12°C in this invention. Figure 9This is a graph showing the effect of three different treatment methods on the TVB-N value of beef stored at 12°C in this invention. Detailed Implementation

[0024] The present invention will be further described below with reference to the embodiments. The following embodiments are descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0025] The various experimental operations involved in the specific embodiments are all conventional techniques in the field. For parts not specifically annotated in this document, those skilled in the art can refer to various commonly used reference books, scientific and technological documents or related instructions and manuals prior to the filing date of this invention to carry out the operations.

[0026] A modified atmosphere packaging method for preserving fresh meat at near-ambient temperature includes the following steps: Step 1: Raw material preparation: Select fresh beef, remove the surface fascia, and cut it into chunks or steaks; Step 2, Preprocessing: The beef was sprayed with an organic acid solution until it was in a droplet state, and then washed with pure CO2 gas for 1-2 minutes under ultraviolet light to obtain pretreated beef. Step 3: Preparation of the compound preservative solution: Solution A: 1% sodium alginate, 3% sodium lactate, 0.45% glycine and 0.02% ε-polylysine, all percentages are final mass concentrations, the solvent is water, and the mixture is prepared by mixing. Solution B: A 3% (w / w) aqueous solution of calcium propionate; Step 4: Atomized Spraying: S1 First Spray: The aqueous composite preservative liquid containing sodium alginate, sodium lactate, glycine and ε-polylysine, namely liquid A, is evenly sprayed onto the surface of the pretreated beef to form a continuous film liquid. S2 Second Spray: While liquid A is still wet, liquid B is sprayed onto its surface to trigger an ionic cross-linking reaction, thereby forming a composite gel preservation film on the surface of the beef, i.e., in-situ film formation. Step 5: Drain: Hang the beef processed in step four to drain, allowing the membrane to fully solidify and drain off excess water. Step Six: Modified Atmosphere Packaging After draining the beef in step five, pack it into modified atmosphere packaging, vacuum it, and then fill it with mixed gas. The filling time is 3 seconds and the pressure is 0.6 MPa. Step 7, Storage: Store the packaged beef at 0-12℃.

[0027] Furthermore, in step one, beef with a fat content of 15%-20% and a protein content of 18-22% is selected.

[0028] Furthermore, in step two, the organic acid is an aqueous solution obtained by mixing 1% lactic acid and 0.1% gallic acid.

[0029] Furthermore, the mixed gas in step six is: O2 55%, CO2 30%, N2 15%, where the percentages are volume concentrations.

[0030] Furthermore, in step seven, the packaged beef is stored at 12°C.

[0031] The above-described method is applied to the logistics preservation of beef.

[0032] Specifically, the relevant preparation and testing methods are as follows: Example 1 The specific steps of the modified atmosphere packaging and sub-ambient temperature cascade preservation technology for fresh meat, which aims to reduce bacteria and prevent spoilage, are as follows: Step 1: Raw material preparation: Select fresh beef with a fat content of 15%-20% and a protein content of 18-22%, remove the surface fascia, and cut it into pieces or steaks of a certain size. Step 2, Preprocessing: The beef was sprayed with an organic acid solution (an aqueous solution of 1% lactic acid and 0.1% gallic acid) until it reached a droplet state, and then washed with pure CO2 gas for 1-2 minutes under ultraviolet light. Step 3: Preparation of the compound preservative solution: Solution A: 1% sodium alginate, 3% sodium lactate, 0.45% glycine and 0.02% ε-polylysine, all percentages are final mass concentrations, the solvent is water, and the mixture is prepared by mixing. Solution B: A 3% (w / w) aqueous solution of calcium propionate; Step 4: Atomized Spraying: S1 First Spray: A water-based composite preservative solution (Liquid A) containing sodium alginate, sodium lactate, glycine and ε-polylysine is evenly sprayed onto the surface of the pretreated beef to form a continuous film. S2 Second Spray: While liquid A is still wet, liquid B is sprayed onto its surface to trigger an ionic cross-linking reaction, thereby forming a composite gel preservation film on the surface of the beef. Step 5: Drain: Hang the beef processed in step four to drain, allowing the membrane to fully solidify and drain off excess water. Step Six: Modified Atmosphere Packaging After draining the beef in step five, pack it into a modified atmosphere packaging (MAP), vacuum it, and then fill it with a mixed gas (O2 55%, CO2 30%, N2 15%, volume concentration) for 3 seconds at a pressure of 0.6 MPa. Step 7, Storage: Store the packaged beef at 0-12℃.

[0033] The relevant tests are as follows: 1. The sensory effects of compound treatment on beef stored at 12℃ A sensory evaluation panel of 10 food professionals (5 men and 5 women) scored the samples every two days. A 10-point scale was used, with scores given for six aspects: color, odor, viscosity, elasticity, juice loss, and overall acceptability. The scores were calculated based on each standard and its weighting. Specific scoring criteria are shown in Table 1. Table 1 Sensory rating criteria

[0034] Table 2. Sensory evaluation results of combined treatment on beef stored at 12℃ Sensory evaluation results such as Figure 1 As shown in Table 2, the results indicate that different treatment methods have a significant impact on the quality of beef. The compound treatment group exhibited good sensory quality for the first 8 days. On day 10, a slight sour taste was observed, but no discoloration or softening was observed. On day 12, a noticeable off-odor appeared, making it unacceptable. In contrast, the control group using the traditional technology (sterile water spray washing, draining, bagging, and storage at the same temperature) showed localized discoloration on day 4, and by day 6, the surface had become sticky and had a noticeable foul odor. This demonstrates that the compound treatment has a significant effect on maintaining the quality of beef, extending the storage time of beef at 12℃ to 8 days (more than twice the storage time of the control group using the traditional technology).

[0035] 2. Effect of combined treatment on pH value of beef stored at 12℃ The pH value of food was determined according to GB 5009.237-2016, "National Food Safety Standard - Determination of pH Value in Food". A pH value between 5.8 and 6.2 indicates Grade 1 freshness, between 6.2 and 6.6 indicates Grade 2 freshness, and a pH value greater than 6.6 indicates spoiled meat. 5.0g of beef was homogenized with 50ml of potassium chloride solution, and the pH was measured using a pH meter. The pH meter was calibrated before measurement. Each measurement was taken three times, and the average value was recorded.

[0036] pH is an important physiological indicator of the quality and freshness of fresh meat. Its value gradually increases with shelf life. National standards stipulate that a pH value between 5.8 and 6.2 indicates Grade 1 freshness, a pH value between 6.2 and 6.6 indicates Grade 2 freshness, and a pH value greater than 6.6 indicates spoiled meat. Figure 2As shown, the initial pH value of the sample was 5.35. The pH value of the control group using traditional technology rapidly rose to 5.97 on day 4 and exceeded 7.01 on day 6, indicating that ordinary packaging alone could not effectively preserve freshness at this temperature. In stark contrast, the pH increase trend of the composite treatment group was significantly suppressed. Its pH value was significantly lower than that of the control group throughout the entire storage period. The pH value of the composite group was only 5.81 on day 6, 6.63 on day 10 (close to the national standard freshness threshold), and only reached 6.92 (spoilage) on day 12, effectively delaying the accumulation of alkaline substances caused by microbial activity and protein degradation. The results indicate that the composite preservation strategy adopted in this invention can play a crucial buffering and protective role under the non-ideal 12℃ storage conditions, significantly slowing down pH quality deterioration and extending the shelf life of fresh beef to 8-10 days (compared to 4-6 days for the control group). This has important application reference value for dealing with temperature fluctuations that may occur during actual distribution.

[0037] 3. Effect of compound treatment on the TVB-N value of beef stored at 12℃ The determination was performed according to GB 5009.228-2016, "National Food Safety Standard - Determination of Volatile Basic Nitrogen in Food". 10.0 g of beef was weighed into a homogenizing cup, 50 ml of perchloric acid solution was added, homogenized for 2 min, centrifuged and filtered, and 10 ml of the filtrate was accurately transferred into a digestion tube. 1.0 g of magnesium oxide was added, and the determination was performed using an automated Kjeldahl nitrogen analyzer. The 10 ml perchloric acid solution with 1 g of magnesium oxide was used as a blank control.

[0038] like Figure 3 As shown, the volatile basic nitrogen results indicate that different treatments significantly affected the TVB-N value of beef. With prolonged storage time, the TVB-N values ​​of each group showed an increasing trend. In the early storage period (0-4 days), the increase in TVB-N values ​​was relatively slow, while in the later storage period (6-12 days), the TVB-N values ​​began to increase significantly. The treatment group approached the critical point on day 10 and exceeded Grade 1 freshness on day 12, which was 2 days later than the control group.

[0039] 4. Effect of combined treatment on the TBARS value of beef stored at 12℃ Weigh 5.0g of beef, mince it, and add 50ml of 7.5% (w / v) trichloroacetic acid (containing 0.1% EDTA·Na2). Extract by shaking for 30min, filter twice with double-layered filter paper, and take 5ml of the filtrate. Add 5ml of 0.02mol / L TBA solution, heat in a 100℃ water bath for 40min, cool to room temperature, and centrifuge for 5min. Take the supernatant, add 5ml of chloroform, allow to stand for separation, and measure the absorbance of the supernatant at 532nm and 600nm. The trichloroacetic acid mixture serves as a blank control. The calculation formula is as follows: In the formula: 155 is the molar absorptivity; A532 and A600 are the absorbances of the supernatant at 532 and 600 nm, respectively. like Figure 4 As shown, TBARS (thiobarbituric acid reactants) value is an important indicator for evaluating the degree of fat oxidation in meat, reflecting the accumulation of lipid peroxidation products. Throughout the storage period, the TBARS value of the combined treatment group was consistently significantly lower than that of the control group (P<0.05). By the end of storage, day 12, the TBARS value of the conventional technology control group rose sharply to 0.581 mg / kg, indicating severe lipid oxidative rancidity; while the value of the combined treatment group was only 0.370 mg / kg, a decrease of 36.3% compared to the control group, effectively maintaining the degree of oxidation at a low level. This result indicates that the combined treatment can significantly delay the fat oxidation process in fresh beef, effectively extend its shelf life, and provide a reliable technical basis for quality assurance of meat products under non-constant low-temperature environments.

[0040] 5. Effects of combined treatment on microorganisms in beef stored at 12℃ The method was modified slightly according to GB 4789.2-2022 "National Food Safety Standard - Microbiological Examination of Food: Determination of Total Colony Count". 5.0 g of sample was placed in a sterile homogenizing cup, and 45 ml of sterile physiological saline was added. After homogenization, 1 ml of the homogenate was serially diluted 10-fold. 100 μl of each of the 1-3 suitable dilutions was evenly spread onto different selective culture media and plated. Each dilution was performed in triplicate. The culture conditions for different microorganisms were as follows: total colony count was cultured on plate counting agar at 37°C for 48 h; *Streptomycin-thallousacetate-acidione* was cultured on STAA (Streptomycin-thallousacetate-acidione) selective medium at 25°C for 48 h; *Pseudomonas* culture was cultured on CFC (Centrimide-fucidin-cephaloridine) selective medium at 25°C for 48 h.

[0041] like Figures 5 to 7As shown, microbial proliferation is the core factor in the spoilage of fresh meat, and the total bacterial count reflects the overall contamination level. *Pseudomonas* and *Avira thermophila* are the main spoilage bacteria. By analyzing the total bacterial count, *Pseudomonas* count, and *Avira thermophila* count, this study focused on evaluating the inhibitory effect of the combined preservation treatment on beef microorganisms under 12℃ storage conditions. In the conventional technology control group, the number of microorganisms showed explosive growth, with the total bacterial count and *Pseudomonas* count reaching 7.11 and 7.54 log CFU / g, respectively, on day 4. In contrast, the combined treatment group showed significant and sustained inhibition of the growth of all indicator bacteria. On day 4, its total bacterial count (3.92 log CFU / g) and *Pseudomonas* count (3.78 log CFU / g) were both approximately 3.3 orders of magnitude lower than the control group at the same time point. Notably, the numbers of *Pseudomonas* and *Avira thermophila* remained significantly lower than the control group throughout the entire 12℃ storage period, indicating that the combined effect of the preservative solution and modified atmosphere packaging may have a selective and strong inhibitory effect on these specific spoilage bacteria. Meanwhile, the total bacterial count in the composite treatment group reached the spoilage threshold (6.16 log CFU / g) on ​​day 10, while both Pseudomonas and Cyclofilariae exceeded the limit on day 12, indicating that the method of the present invention can extend the shelf life of beef to about 8 days, which is nearly twice as long as the 4-day shelf life of the traditional technology control group.

[0042] 6. Comparison of the effects of three different treatments on pH and TVB-N in beef The comparison results of pH and TVB-N values ​​under organic acid combined with air washing sterilization pretreatment are as follows: (The original text appears to be incomplete and contains errors. A more accurate translation would require the full context.) Figure 8 and Figure 9 The specific processing methods are as follows: Single plastic wrap treatment is the same as steps one to five in Example 1, after which the beef is drained and directly placed into a plastic bag and sealed, and stored at 12°C; Single modified atmosphere treatment: the pre-treated beef is placed into a modified atmosphere package, vacuumed and then filled with a mixed gas (O2 55%, CO2 30%, N2 15%, volume concentration), the filling time is 3s and the pressure is 0.6MPa, and then stored at 12°C; Composite treatment is the same as steps one to seven in Example 1; The control group is sterile water spray washing, drained and directly placed into a plastic bag and sealed, and stored at the same temperature.

[0043] like Figure 8 As shown, different treatment methods have significantly different effects on the pH value of beef. Preservative treatment and modified atmosphere packaging can both delay the rise in the pH value of beef, but the effect is limited. The combined treatment, through the dual barrier of chemical antibacterial and physical atmosphere modification, can most effectively inhibit microbial activity and the action of endogenous enzymes in meat, extending the shelf life of the product to nearly twice that of a single treatment method.

[0044] like Figure 9As shown, different preservation treatments exhibited significantly different inhibitory effects on the accumulation of TVB-N (volatile basic nitrogen) in beef. Both preservative treatment and modified atmosphere packaging (MAP) could delay the rise in TVB-N to some extent, but in the later stages of storage (day 8 for the preservative group and day 6 for the MAP group), both single-treatment groups approached or exceeded the spoilage limit of 15 mg / 100g. The combined treatment group showed a significant synergistic preservation effect, with its TVB-N value not reaching the limit until day 12. This indicates that the combined treatment, through a dual-action mechanism, extended the safe shelf life of the product by at least 6 days compared to the control group, reaching 1.5 times the preservation time of the single optimal treatment (preservative group), making it an effective method for ensuring meat quality under storage conditions of 0℃-12℃.

[0045] In summary, the combined sterilization pretreatment technology and in-situ biofilm preservation technology, which place fresh meat in a modified atmosphere environment, resulted in a cascade preservation technology that maintained good quality for 8 days at 12℃. This effectively inhibited the growth of spoilage bacteria (Pseudomonas and Cyclofilamentosa), with a total bacterial count of 5.53 log CFU / g on day 8 (national standard grade II freshness). Sensory properties, color, texture, pH, and TVB-N were all within the range specified by national standards, extending the shelf life by 3-4 times compared to the control group using related traditional technologies.

[0046] Although embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments.

Claims

1. A method for cascaded preservation of fresh meat at sub-normal temperature with modified atmosphere packaging for sterilization and preservation, characterized in that: Includes the following steps: Step 1: Raw material preparation: Select fresh beef, remove the surface fascia, and cut it into chunks or steaks; Step 2, Preprocessing: The beef was sprayed with an organic acid solution until it was in a droplet state, and then washed with pure CO2 gas for 1-2 minutes under ultraviolet light to obtain pretreated beef. Step 3: Preparation of the compound preservative solution: Solution A: 1% sodium alginate, 3% sodium lactate, 0.45% glycine and 0.02% ε-polylysine, all percentages are final mass concentrations, the solvent is water, and the mixture is prepared by mixing. Solution B: A 3% (w / w) aqueous solution of calcium propionate; Step 4: Atomized Spraying: S1 First Spray: The aqueous composite preservative liquid containing sodium alginate, sodium lactate, glycine and ε-polylysine, namely liquid A, is evenly sprayed onto the surface of the pretreated beef to form a continuous film liquid. S2 Second Spray: While liquid A is still wet, liquid B is sprayed onto its surface to trigger an ionic cross-linking reaction, thereby forming a composite gel preservation film on the surface of the beef, i.e., in-situ film formation. Step 5: Drain: Hang the beef processed in step four to drain, allowing the membrane to fully solidify and drain off excess water. Step Six: Modified Atmosphere Packaging After draining the beef in step five, pack it into modified atmosphere packaging, vacuum it, and then fill it with mixed gas. The filling time is 3 seconds and the pressure is 0.6 MPa. Step 7, Storage: Store the packaged beef at 0-12℃.

2. The method according to claim 1, characterized in that: In step one, select beef with a fat content of 15%-20% and a protein content of 18-22%.

3. The method according to claim 1, characterized in that: In step two, the organic acid is an aqueous solution obtained by mixing 1% lactic acid and 0.1% gallic acid.

4. The method according to claim 1, characterized in that: The mixed gas in step six is: O2 55%, CO2 30%, N2 15%, and the percentages are volume concentrations.

5. The method according to any one of claims 1 to 4, characterized in that: In step seven, the packaged beef is stored at 12°C.

6. The application of the method as described in any one of claims 1 to 5 in the logistics preservation of beef.

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