A method for preserving chilled beef by combining vacuum packaging and electron beam treatment

Abstract

This invention discloses a method for preserving chilled beef that integrates vacuum packaging and electron beam treatment. The method includes the following steps: cutting the chilled beef after cooling and deacidification; vacuum packaging the chilled beef; the vacuum packaging process includes: drawing a vacuum into the packaging bag containing the chilled beef, then refilling the packaging bag with nitrogen gas, and finally sealing it; irradiating the chilled beef in the packaging bag with an electron beam; and storing the irradiated chilled beef in a cold chain at 0-4°C. This preservation method does not add any chemical preservatives or preservatives throughout the entire process, and involves no high-temperature treatment. Under the constant 0-4°C cold storage conditions, the shelf life of chilled beef is extended from 7-10 days to 47-54 days, while maintaining good sensory quality and food safety. This invention is a purely physical cold sterilization and preservation method; the process is simple, industrially feasible, and effectively solves the problems of short shelf life, easy spoilage, and poor color of chilled beef.

Description

Technical Field

[0001] This invention belongs to the field of food preservation technology, specifically relating to a physical preservation method for chilled beef, and more particularly to a preservation method for chilled beef that integrates vacuum packaging and electron beam treatment. Background Technology

[0002] Chilled beef refers to fresh beef that has been rapidly cooled after slaughter and maintained at a cold chain temperature of 0-4℃ throughout the process. Its taste and nutritional value are superior to frozen beef, and market demand continues to expand. Compared to frozen beef (below -18℃), chilled beef has not undergone a freezing process, and ice crystals have not formed in the muscle tissue. Therefore, it loses less juice, has a tender texture, retains its full flavor, and has higher nutritional value, making it highly favored by consumers.

[0003] However, chilled beef faces severe quality deterioration problems during storage and distribution. Rich in nutrients such as protein, fat, and water, and with a near-neutral pH (5.5-6.5), it provides an ideal environment for microbial growth. Even under cold chain conditions of 0-4°C, psychrophilic microorganisms can still grow slowly, leading to a gradual increase in the total bacterial count on the meat surface. This triggers a series of spoilage changes, including protein decomposition, fat oxidation, pH elevation, and the accumulation of TVB-N (volatile basic nitrogen), ultimately manifesting as browning, off-odors, softening, and even the formation of slime, rendering it inedible. Due to these factors, the shelf life is typically only 7-10 days, making it difficult to meet the demands of long-distance transportation and extended sales. Therefore, extending the shelf life and maintaining the quality of chilled beef has always been a crucial issue for the meat processing industry.

[0004] Electron beam irradiation, as a purely physical cold sterilization technology, achieves sterilization and preservation by destroying the DNA of microorganisms. Compared with traditional irradiation technology that uses Co-60 to generate gamma rays, electron beam cold sterilization has significant advantages in terms of safety and ease of operation: Co-60 irradiation sources rely on the radioactive isotope (Cobalt-60), and the radiation source continuously emits rays, posing a radiation risk even after the equipment is powered off. This requires extremely high levels of shielding facilities and personnel protection, and the decommissioning of the radiation source is complex and costly. In contrast, electron beam accelerators are electrically controlled radiation sources. They generate an electron beam when powered on and radiation stops immediately after power is cut off, leaving no radioactive residue. There is no safety hazard of radiation source leakage or theft, significantly reducing potential risks to operators and the environment, and simplifying equipment maintenance and management.

[0005] However, existing irradiation preservation technology also has the following shortcomings:

[0006] (1) Lack of precise irradiation dose and limited shelf life: Some technologies use low-dose irradiation, which has limited effect on inhibiting microorganisms and makes it difficult to achieve an ultra-long shelf life;

[0007] (2) Irradiation requires freezing: Irradiation requires freezing (below -18°C), which damages the original quality of chilled meat and cannot meet consumers' demand for chilled meat;

[0008] (3) Lack of systematic understanding of the impact of electron beam treatment on the quality of chilled beef: While electron beam sterilization effectively kills microorganisms, its impact on the sensory quality of chilled beef cannot be ignored, but current research lacks a systematic and in-depth understanding of this. First, high-dose electron beam treatment induces myoglobin oxidation, causing the meat color to change from bright red to brown (a* value decreases). The degree of color deterioration at different doses and its correlation with storage time are still unclear. Second, the reactive oxygen free radicals generated by high-dose electron beams may trigger fat oxidation, producing an "irradiated" or rancid taste, especially for parts with high fat content such as sirloin and chuck, where this problem is more prominent, but current technology lacks effective control methods. In addition, high-dose electron beam treatment may cause some damage to protein structure, vitamins, and other nutrients, and the response patterns to electron beam treatment vary among different parts due to differences in fat and myoglobin content. Current technology has failed to provide a refined solution that can ensure sterilization effect while maximizing quality preservation for the differences in different parts.

[0009] Therefore, developing a simple, convenient, purely physical cold sterilization and preservation technology that does not add any preservatives or preservatives and does not involve high-temperature processing, can significantly extend the shelf life under cold conditions throughout the entire process, while maintaining the nutrition, color, and flavor of chilled beef. This technology has significant industrial value and practical application prospects. Summary of the Invention

[0010] This invention aims to overcome the shortcomings of existing technologies by providing a preservation method for chilled beef that integrates vacuum packaging and electron beam treatment. This preservation method involves no chemical preservatives or air-conditioning, and no high-temperature treatment. Through vacuum packaging, active gas regulation, and electron beam irradiation, under consistently 0-4℃ chilled conditions, the shelf life of chilled beef is extended from 7-10 days to 47-54 days, while maintaining good sensory quality and food safety. This invention is a purely physical cold sterilization and preservation method; the process is simple, industrially feasible, and effectively solves the problems of short shelf life, easy spoilage, and poor color in chilled beef.

[0011] The present invention achieves the above objectives through the following technical solutions:

[0012] This invention provides a method for preserving chilled beef that combines vacuum packaging and electron beam treatment, the method comprising the following steps:

[0013] S1. Cut the chilled fresh beef after cooling and aging, ensuring that the thickness of the chilled fresh beef does not exceed 4 cm.

[0014] S2. Vacuum packaging the chilled beef; the vacuum packaging process includes: drawing a vacuum into the packaging bag containing the chilled beef, making the internal pressure of the packaging bag ≤0.01MPa, then refilling the packaging bag with nitrogen gas, and finally sealing it; wherein the amount of nitrogen gas refilled accounts for 5%~10% of the volume of the packaging bag;

[0015] S3. Irradiate the chilled fresh beef in the packaging bag of step S2 with an electron beam of 8-10 MeV at 0-4℃; the absorbed dose of the irradiation is 1.9-5.0 kGy.

[0016] S4. The irradiated chilled beef is stored in a cold chain at 0~4℃.

[0017] In step S1 of the present invention, the cooling and acid removal can be carried out using conventional operating methods in the art, and the acid is removed by cooling at 4°C for 3 days.

[0018] In this invention, the object processed by the preservation method includes, but is not limited to, chilled beef, and may also be pork, mutton, etc.; the object processed by the preservation method is preferably beef from a specific part.

[0019] In some embodiments, in step S1, the chilled fresh beef is one or more of beef tenderloin, beef sirloin, or beef chuck; the chilled fresh beef may also be beef shank, beef brisket, beef shoulder, etc.

[0020] In this invention, chilled fresh beef is cut into beef strips / blocks / slices with a thickness not exceeding 4 cm, so that an electron beam of a specific energy can completely penetrate the beef of this thickness, thereby achieving a thorough sterilization effect.

[0021] Prior to this invention, existing technologies lacked specificity in the selection of vacuum packaging materials. For example, ordinary heat-shrinkable films have limited oxygen barrier properties and are difficult to effectively inhibit the fat oxidation process after irradiation. In other words, traditional high-barrier films often use polyvinylidene chloride (PVDC) coatings, which make it difficult to balance heat shrinkage and barrier properties, and microcracks are easily generated during heat shrinkage, affecting long-term sealing stability.

[0022] In specific implementations, depending on the type of chilled fresh beef, the vacuum packaging process in step S2 can be selected using a corresponding processing method:

[0023] (1) When the chilled fresh beef is beef tenderloin and / or beef chuck, the packaging bag is an EVOH high-barrier multilayer co-extruded heat-shrinkable film; after the sealing operation is completed, the packaging bag is also heat-shrinked.

[0024] (2) When the chilled fresh beef is beef sirloin, the packaging bag is a polyethylene composite film.

[0025] Among these advancements, precise matching of packaging methods to the characteristics of different parts has improved product appearance and sealing stability.

[0026] The heat-shrinking process includes immersing the packaging bag in hot water at 85-95°C for 2-5 seconds, followed immediately by cooling and shaping with cold air. After heat shrinking, the packaging bag adheres tightly to the meat surface without wrinkles or air bubbles. This heat-shrinking treatment is suitable for beef tenderloin and chuck. It reduces juice loss and prevents meat deformation, while the EVOH barrier layer significantly inhibits radiation-induced fat oxidation, especially in high-fat cuts like chuck, further improving quality stability during long-term storage.

[0027] When the packaging bag is a full polyethylene composite film, the sealing operation is sufficient; heat shrinking is unnecessary or impossible to perform to avoid the risk of fat from the bovine sirloin melting and seeping out due to high-temperature heat shrinkage, which could affect the appearance and sealing performance. Furthermore, this material does not contain polyvinylidene chloride (PVDC) or other difficult-to-recycle components, exhibiting excellent environmental performance and recyclability.

[0028] In a specific embodiment, the EVOH high-barrier multilayer co-extruded heat-shrinkable film is a co-extruded structure with five or more layers, including at least one EVOH barrier layer; the oxygen permeability of the EVOH high-barrier multilayer co-extruded heat-shrinkable film is ≤5 cm⁻¹. 3 / (m 2 •24h•0.1MPa); It can effectively inhibit the oxidation process of fat in chilled beef after irradiation; The multi-layer co-extrusion structure ensures the coordinated deformation of each layer during the heat shrinkage process, so that the packaging film fits tightly against the surface of the meat, further reducing juice seepage and improving the uniformity of electron beam irradiation.

[0029] In a specific embodiment, the all-polyethylene composite film has a multi-layer structure comprising a high-density polyethylene surface layer, a low-density polyethylene intermediate layer, and a high molecular weight polyethylene base layer; the oxygen permeability of the all-polyethylene composite film is ≤15 cm⁻¹. 3 / (m 2 ·24h·0.1MPa).

[0030] In step S2 of the present invention, the main functions of refilling with nitrogen are as follows: (1) further reducing the residual oxygen in the packaging bag and effectively inhibiting the irradiation-induced fat oxidation of high-fat parts (such as: sirloin, ribeye); (2) preventing excessive physical compression of the meat structure (especially tenderloin) by high vacuum and maintaining the original shape and juice of the meat; (3) the nitrogen environment also helps to stabilize myoglobin and improve the color in the later stage of storage.

[0031] Preferably, the amount of nitrogen refilled accounts for 6% to 8% of the volume of the packaging bag.

[0032] The purity of the nitrogen gas can be above 99.9%, so that the residual oxygen content in the packaging bag after refilling is ≤0.5%.

[0033] The nitrogen gas can be replaced by other inert gases.

[0034] In step S3 of this invention, the irradiation process is carried out at 0-4°C. At this temperature, not only can the total bacterial count be maintained at a low level and essentially eliminated after irradiation, but accelerated fat oxidation can also be prevented. If irradiation is carried out at a higher temperature, the initial total bacterial count on the surface of the meat may already be at a high level, resulting in incomplete sterilization and difficulty in achieving ultra-long shelf life standards. Simultaneously, electron beam irradiation generates free radicals. At higher temperatures, the rate of fat chain oxidation triggered by free radicals is faster, leading to a significant increase in TBARS values ​​and producing an "irradiated" or rancid taste. Furthermore, higher temperatures accelerate the oxidation rate of myoglobin, causing a more severe change in meat color from bright red to brown.

[0035] In some embodiments, in step S3, the absorbed dose of the irradiation is 2.8~3.8 kGy.

[0036] In some implementations, in step S3, the energy of the electron beam is 10 MeV; under this energy condition, the electron beam has strong penetrating power, but setting the energy of the electron beam too high will not meet the relevant food irradiation standards.

[0037] In step S3 of the present invention, preferably, the absorbed dose of the irradiation is 1.9~3.9 kGy;

[0038] In some embodiments, during step S3, the chilled beef is arranged in a single layer during the irradiation process to ensure uniform irradiation.

[0039] In this invention, by setting up visual monitoring technology on the packaging bag, consumers and the supply chain can know whether the product has experienced abnormal temperature fluctuations, so as to control the actual quality of the meat.

[0040] In some embodiments, in step S2, a time and temperature indicator and / or a freshness indicator are fixedly provided on the inner side or in the interlayer of the packaging bag; through the design of this smart packaging, the quality visualization and transparency of the entire cold chain circulation process are realized.

[0041] In a specific implementation, the time-temperature indicator includes an enzymatically catalytic irreversible indicator. Its color change cumulatively displays the equivalent temperature-time history experienced by the chilled beef during storage and transportation, providing a clear indication of its remaining shelf life. When the chilled beef begins to spoil, the alkaline gas produced causes the indicator to change color irreversibly, allowing consumers to determine its quality status without opening the bag.

[0042] In a specific embodiment, the freshness indicator includes a pH change indicator or a volatile basic nitrogen-sensitive indicator; preferably, the freshness indicator is selected from one or more of bromocresol purple and methyl red.

[0043] In a specific embodiment, the freshness indicator is coated on the inside or interlayer of the packaging bag in microencapsulation form; wherein the wall material of the microencapsulation is food-grade gum arabic.

[0044] In some embodiments, the method for preserving the beef tenderloin includes the following steps:

[0045] s1. Cut the cooled and de-acidified beef tenderloin so that the thickness of the tenderloin does not exceed 4 cm;

[0046] s2. Vacuum packaging of the beef tenderloin; the vacuum packaging process includes: drawing a vacuum into the packaging bag containing the beef tenderloin, so that the internal pressure of the packaging bag is ≤0.01MPa, then refilling the packaging bag with nitrogen, and finally sealing and heat shrinking in sequence; wherein, the amount of nitrogen refilled accounts for 5%~10% of the volume of the packaging bag; the packaging bag is an EVOH high-barrier multilayer co-extruded heat-shrinkable film;

[0047] s3. Under conditions of 0~4℃, the beef tenderloin in the packaging bag of step s2 is irradiated with an electron beam of 10MeV; the absorbed dose of the irradiation is 3.8 kGy;

[0048] s4. The irradiated beef tenderloin was stored in a cold chain at 0~4℃; after 47 days of storage, the total bacterial count of the beef tenderloin was less than 10 CFU / g.

[0049] In some embodiments, the method for preserving the bovine sirloin includes the following steps:

[0050] s1. Cut the cooled and deacidified beef sirloin so that the thickness of the sirloin does not exceed 4 cm;

[0051] s2. Vacuum packaging of the bovine sirloin; the vacuum packaging process includes: drawing a vacuum into the packaging bag containing the bovine sirloin, making the internal pressure of the packaging bag ≤0.01MPa, then refilling the packaging bag with nitrogen gas, and finally sealing it; wherein, the amount of nitrogen gas refilled accounts for 5%~10% of the volume of the packaging bag; the packaging bag is a full polyethylene composite film;

[0052] s3. Under conditions of 0~4℃, the bovine rib cage in the packaging bag of step S2 is irradiated with an electron beam of 10MeV; the absorbed dose of the irradiation is 3.8 kGy.

[0053] s4. The irradiated bovine sirloin was stored in a cold chain at 0-4°C; after 54 days of storage, the total bacterial count of the bovine sirloin was less than 10 CFU / g.

[0054] In some embodiments, the method for preserving the bovine chuck includes the following steps:

[0055] s1. Cut the cooled and deacidified beef chuck into pieces, ensuring that the thickness of the beef chuck does not exceed 4 cm;

[0056] s2. Vacuum packaging of the bovine sauerkraut; the vacuum packaging process includes: drawing a vacuum into the packaging bag containing the bovine sauerkraut, so that the internal pressure of the packaging bag is ≤0.01MPa, then refilling the packaging bag with nitrogen gas, and finally sealing and heat shrinking in sequence; wherein, the amount of nitrogen gas refilled accounts for 5%~10% of the volume of the packaging bag; the packaging bag is an EVOH high-barrier multilayer co-extruded heat-shrinkable film;

[0057] s3. Under conditions of 0~4℃, the bovine cervix in the packaging bag of step S2 is irradiated with an electron beam of 10MeV; the absorbed dose of the irradiation is 3.8 kGy;

[0058] s4. The irradiated bovine cervical mucin was stored in a cold chain at 0-4°C; after 54 days of storage, the total bacterial count of the bovine cervical mucin was less than 10 CFU / g.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] (1) The preservation method of the present invention achieves an ultra-long shelf life through the synergistic effect of "vacuum packaging, active gas conditioning and electron beam irradiation". Specifically, the preservation method of the present invention can make beef tenderloin fresh for 47 days and ribeye and chuck fresh for 54 days.

[0061] (2) The preservation method of the present invention operates and stores at 0-4℃ throughout the process without freezing, thus ensuring the original texture, flavor and nutrition of the meat and meeting consumers’ demand for high-quality chilled meat.

[0062] (3) The process of the present invention is simplified and has strong industrial applicability; the present invention does not require the addition of any chemical preservatives or antiseptics, and can achieve high-quality preservation simply through vacuum packaging, active gas regulation and electron beam treatment. The process is simple, the cost is controllable, and it is easy to apply directly to the existing chilled meat processing line without adjusting the existing production process, and has good industrialization prospects.

[0063] (4) In the preferred embodiment, the present invention integrates time and temperature indicators and freshness indicators to enable the packaging to have quality visualization function: consumers and logistics personnel can directly judge whether the product has been subjected to temperature abuse or is close to spoilage by the indicator color, which greatly improves the convenience of cold chain management and the trust in food safety. Attached Figure Description

[0064] Figure 1 This is a graph showing the change in total bacterial count of beef tenderloin over storage time under different electron beam doses.

[0065] Figure 2 This is a statistical analysis graph showing the change in pH value of beef tenderloin over storage time under different electron beam doses.

[0066] Figure 3 This is a statistical analysis graph showing the change of TVB-N value of beef tenderloin with storage time under different electron beam doses.

[0067] Figure 4 This is a statistical analysis graph showing the change of TBARS values ​​of beef tenderloin with storage time under different electron beam doses.

[0068] Figure 5 A statistical analysis of the changes in color (L* value and a* value) of beef tenderloin with storage time under different electron beam doses; Figure 5 (1) A statistical analysis graph showing the change of color L* value of beef tenderloin with storage time under different electron beam doses; Figure 5 (2) is a statistical analysis graph showing the change of color a* value of beef tenderloin with storage time under different electron beam doses.

[0069] Figure 6 This is a statistical analysis graph showing the change in moisture content of beef tenderloin over storage time under different electron beam doses.

[0070] Figure 7 A statistical analysis of the changes in fat and protein in beef tenderloin over storage time under different electron beam doses; Figure 7 (1) A statistical analysis graph showing the change of fat in beef tenderloin with storage time under different electron beam doses; Figure 7 (2) is a statistical analysis graph showing the changes in protein content of beef tenderloin with storage time under different electron beam doses.

[0071] Figure 8 This is a graph showing the change in total bacterial count of bovine lateral ribs with storage time under different electron beam doses.

[0072] Figure 9 This is a statistical analysis graph showing the change in pH value of bovine lateral ribs over storage time under different electron beam doses.

[0073] Figure 10 This is a statistical analysis of the TVB-N value of bovine lateral rib under different electron beam doses as a function of storage time.

[0074] Figure 11 This is a statistical analysis graph showing the changes in TBARS values ​​of bovine lateral ribs with storage time under different electron beam doses.

[0075] Figure 12 A statistical analysis of the changes in color (L* and a* values) of bovine lateral ribs with storage time under different electron beam doses; Figure 12 (1) A statistical analysis graph showing the change of color L* value of bovine lateral ridge with storage time under different electron beam doses; Figure 12 (2) is a statistical analysis graph showing the change of color a* value of bovine lateral rib under different electron beam doses with storage time.

[0076] Figure 13 This is a statistical analysis graph showing the change in moisture content of bovine lateral ribs over storage time under different electron beam doses.

[0077] Figure 14 A statistical analysis of the changes in fat and protein in bovine lateral loin over storage time under different electron beam doses; Figure 14 (1) A statistical analysis graph showing the changes in fat in bovine lateral rib under different electron beam doses over storage time; Figure 14 (2) is a statistical analysis graph showing the changes in protein in bovine lateral rib under different electron beam doses with storage time.

[0078] Figure 15 This is a graph showing the change in total bacterial count in bovine brain tissue over storage time under different electron beam doses.

[0079] Figure 16 This is a statistical analysis graph showing the change in pH value of bovine brain tissue over storage time under different electron beam doses.

[0080] Figure 17 This is a statistical analysis of the TVB-N value of bovine epibrain under different electron beam doses as a function of storage time.

[0081] Figure 18 This is a statistical analysis graph showing the changes in TBARS values ​​of bovine upper brain over storage time under different electron beam doses.

[0082] Figure 19A statistical analysis of the changes in color (L* and a* values) of bovine epibrain over storage time under different electron beam doses; Figure 19 (1) A statistical analysis graph showing the change of color L* value of bovine epibrain with storage time under different electron beam doses; Figure 19 (2) A statistical analysis graph showing the change of color a* value of bovine brain with storage time under different electron beam doses.

[0083] Figure 20 This is a statistical analysis graph showing the change in water content in bovine epibranchial tissue over storage time under different electron beam doses.

[0084] Figure 21 A statistical analysis of the changes in fat and protein in bovine upper brain over storage time under different electron beam doses; Figure 21 (1) A statistical analysis graph showing the changes in fat in bovine epibrain over storage time under different electron beam doses; Figure 21 (2) is a statistical analysis graph showing the changes in bovine brain protein with storage time under different electron beam doses. Detailed Implementation

[0085] The present invention will be further described in detail below through preferred embodiments, but the scope of protection of the present invention is not limited thereto.

[0086] Examples 1.1-1.3

[0087] This set of embodiments discloses a method for preserving chilled fresh beef that combines vacuum packaging and electron beam treatment, including the following steps:

[0088] Step 1: Take beef tenderloin (5-7% fat content) provided by Shandong De Beef Industry Co., Ltd., which has been commercially slaughtered and cooled and aged at 4℃ for 3 days. Cut the beef tenderloin into pieces no more than 4cm thick.

[0089] Step 2: The beef tenderloin is coated with an EVOH high-barrier multilayer co-extruded heat-shrinkable film (a five-layer co-extruded structure including one EVOH barrier layer, with a thickness of 50~80µm and an oxygen permeability ≤5cm³ / (m²). 2 Vacuum heat shrink packaging is performed on materials with a pressure of 0.1 MPa (24h). Manufacturer: Global New Materials (Nantong) Co., Ltd.

[0090] The specific operation is as follows: The cut beef tenderloin is placed in a packaging bag. A microencapsulated freshness indicator (bromocresol purple: methyl red = 2:1, microcapsule wall material is gum arabic) is pre-coated onto the inside of the bag, covering an area of ​​2cm × 2cm, located in the transparent window area of ​​the packaging bag. Simultaneously, an enzyme-catalyzed time-temperature indicator label (model 3M MonitorMark) is fixed in the interlayer of the packaging bag. Then, a vacuum is drawn until the internal pressure of the bag is ≤0.01MPa, and nitrogen gas (99.9% purity) is refilled into the bag, filling it to 8% of its volume. The bag is then heat-sealed. Finally, a heat-shrink treatment is performed to ensure the film adheres tightly to the surface of the meat. The heat-shrink treatment process involves immersing the packaging bag in hot water at 85~95℃ for 2-5 seconds, followed immediately by cooling and shaping with cold air.

[0091] The freshness indicator (bromocresol purple / methyl red) fixed to the packaging bag is sensitive to alkaline gases. Under normal storage conditions of 0-4℃, the pH and TVB-N of chilled beef remain within the fresh range for a long time, and the indicator retains its initial color. If the cold chain is interrupted and the temperature rises, the ammonia produced by accelerated microbial growth will cause the indicator to change color irreversibly, providing an early warning of spoilage. In addition, the color change kinetics of the time-temperature indicator are matched with the microbial growth model, which can intuitively reflect the remaining shelf life. Therefore, this intelligent indicator design has a reliable early warning function in practical applications.

[0092] Step 3: Irradiation was performed using a 10 MeV electron beam accelerator at 0~4℃. In this set of examples, the absorbed doses of Examples 1.1, 1.2, and 1.3 were 1.9 kGy, 2.8 kGy, and 3.8 kGy, respectively. The absorbed dose of Control Example 1 was 0 kGy.

[0093] Step 4: Immediately after irradiation, return the sample to a cold storage environment of 0~4℃.

[0094] Samples from Examples 1.1, 1.2, and 1.3 and Control Example 1 were taken and tested on days 0, 7, 14, 21, 28, 33, 40, and 47, respectively. The test indicators included:

[0095] (1) Microbiological indicators: total colony count (GB 4789.2-2016);

[0096] (2) pH value, moisture (GB 5009.3-2016), TVB-N value (GB 2707-2016), protein (GB 4789.2-2025), fat (GB 4789.2-2016) and TBARS value (GB 4789.2-2016);

[0097] (3) Color: L* value (brightness) and a* value (redness) were measured using the DIGIEYE digital color measurement system (electronic eye) to measure the color of the beef surface;

[0098] (4) Sensory rating: A 5-point rating scale is used to evaluate color, smell and acceptability.

[0099] Table 1 shows the microbial indicators for Examples 1.1-1.3 and Control Example 1 (irradiation absorbed dose of 0 kGy).

[0100] Table 1

[0101]

[0102] Figure 1 This is a graph showing the change in total bacterial count of beef tenderloin over storage time under different electron beam doses. Figure 1 As shown in Table 1, for beef tenderloin, after step three electron beam cold sterilization in this embodiment, the total bacterial count in the 3.8 kGy irradiation group was still below 10 CFU / g (sterile state) at 47 days, while the total bacterial count in the untreated control group was >10 CFU / g at 12 days. 6 The CFU / g, 1.9 kGy group decomposed within 26 days (>10). 6 (CFU / g), the 2.8 kGy group had a CFU / g level below 10 at 40 days.

[0103] Table 2 shows the sensory evaluation scores of Examples 1.1-1.3 and Control Group 1 (irradiated absorbed dose of 0 kGy).

[0104] Table 2

[0105]

[0106] In Table 2, sensory evaluation was not conducted because the total bacterial count in some unirradiated groups (Control Example 1) or low-dose irradiated groups exceeded the national standard. According to the sensory evaluation results in Table 2, the 3.8 kGy irradiated group maintained acceptable levels (≥3 points out of 5) in color, odor, and acceptability scores during the 19-day storage period. Although slightly lower than the unirradiated group in the early stages of storage, it was significantly superior to the low-dose and unirradiated groups in the later stages of storage, confirming the comprehensive sensory advantages of high-dose irradiation during long-term storage.

[0107] Figure 2 This is a statistical analysis graph showing the change in pH value of beef tenderloin over storage time under different electron beam doses. Figure 2As shown, for beef tenderloin, after step three electron beam cold sterilization in this embodiment, the pH value of the 3.8 kGy group remained stable at 6.2-6.3 (fresh meat range) for 33 days; the untreated control group rose to >6.7 (spoilage level) after 19 days; the pH values ​​of the 1.9 kGy and 2.8 kGy irradiation groups remained stable at 6.2-6.3 (fresh meat range) for 33 days of storage, indicating that low and medium dose irradiation can effectively inhibit the growth of spoilage microorganisms and delay the rise in pH value.

[0108] Figure 3 This is a statistical analysis graph showing the change in TVB-N (total volatile basic nitrogen) value of beef tenderloin with storage time under different electron beam doses. Figure 3 As shown, for beef tenderloin, after step three (electron beam cold sterilization) in this embodiment, the TVB-N value in the 3.8 kGy high-dose group remained ≤15 mg / 100g for 33 days of storage, meeting national standards. In the untreated control group, the TVB-N value rose to 14.3 mg / 100g after 19 days of storage, approaching the limit of 15 mg / 100g. The TVB-N value in the 1.9 kGy irradiation group was slightly higher than the control group in the early stages of storage, but significantly lower after 26 days. The trend in the 2.8 kGy irradiation group was similar to that of the 1.9 kGy group, remaining consistently lower than the control group in the later stages.

[0109] Figure 4 This is a statistical analysis graph showing the change in TBARS (thiobarbituric acid value) of beef tenderloin with storage time under different electron beam doses. Figure 4 As shown, for beef tenderloin, after step three electron beam cold sterilization in this embodiment, the TBARS value of the 3.8 kGy high-dose group remained high during long-term storage. However, considering the color and sensory evaluation data, this oxidation level did not lead to sensory deterioration. The TBARS value of the untreated control group remained at a low level of 0.2-0.4 mg / kg throughout the storage period. The TBARS value of the 1.9 kGy irradiation group increased slightly, but the oxidation level was controllable. The TBARS value of the 2.8 kGy group reached its peak at 19 days of storage, indicating the most severe oxidation.

[0110] Figure 5 A statistical analysis of the changes in color (L* value and a* value) of beef tenderloin with storage time under different electron beam doses; Figure 5 (1) A statistical analysis graph showing the change of color L* value of beef tenderloin with storage time under different electron beam doses; Figure 5 (2) A statistical analysis graph showing the change of color a* value of beef tenderloin with storage time under different electron beam doses. For example... Figure 5As shown in (1) and (2), for beef tenderloin, after the electron beam cold sterilization treatment in step three of this embodiment, the L* value of the 3.8 kGy high-dose group decreased over time, but the a* value showed the best stability in the later stage of storage, which was synchronized with the strong antibacterial effect. The L* value of the untreated control group gradually decreased with storage time, while the a* value was slightly higher in the early stage. The changes in L* value of the 1.9 kGy and 2.8 kGy irradiation groups were similar to those of the control group, with the a* value being slightly higher in the early stage of storage but showing no significant advantage in the later stage.

[0111] Figure 6 This is a statistical analysis graph showing the change in moisture content of beef tenderloin over storage time under different electron beam doses. (See graph for example.) Figure 6 As shown, for beef tenderloin, after step three (electron beam cold sterilization) in this embodiment, the moisture content of the 3.8 kGy high-dose group (range approximately 50-75%) showed no significant advantage compared to the medium- and low-dose groups, indicating that irradiation itself has no decisive effect on moisture content. The moisture content of the untreated control group showed a decreasing trend with storage time. The changes in moisture content in the 1.9 kGy and 2.8 kGy irradiation groups were not significantly different from those in the control group.

[0112] Figure 7 A statistical analysis of the changes in fat and protein in beef tenderloin over storage time under different electron beam doses; Figure 7 (1) A statistical analysis graph showing the change of fat in beef tenderloin with storage time under different electron beam doses; Figure 7 (2) A statistical analysis graph showing the changes in protein content in beef tenderloin over storage time under different electron beam doses. (e.g.) Figure 7 As shown in (1) and (2), for beef tenderloin, after step three electron beam cold sterilization in this embodiment, the fat content in the 3.8 kGy high-dose group also fluctuated, while the protein content remained stable. The fat content (5-7%) in the untreated control group decreased slightly, while the protein content (19-21 g / 100g) remained basically stable. The fat content in the 1.9 kGy and 2.8 kGy irradiation groups fluctuated more but decreased slightly overall, while the protein content remained stable.

[0113] The above data shows that 1.9-3.8 kGy electron beam cold sterilization combined with vacuum heat shrink packaging can effectively maintain the nutritional value, flavor, and color of beef tenderloin, while achieving efficient sterilization and inhibiting the growth of microorganisms during storage. Vacuum heat shrink packaging combined with 3.8 kGy electron beam cold sterilization can extend the shelf life of chilled beef from 7-10 days to 47 days, 2.8 kGy treatment to 40 days, and 1.9 kGy treatment to 26 days.

[0114] Examples 2.1-2.3

[0115] This set of embodiments discloses a method for preserving chilled fresh beef that combines vacuum packaging and electron beam treatment, including the following steps:

[0116] Step 1: Take beef sirloin (fat content 8-12%) provided by Shandong De Beef Industry Co., Ltd., which has been commercially slaughtered and cooled and aged at 4℃ for 3 days. Cut the beef sirloin into pieces no more than 4cm thick.

[0117] Step 2: The outer rib of the cow is made of a three-layer structure of all-polyethylene composite film (high-density polyethylene surface layer / low-density polyethylene intermediate layer / high molecular weight polyethylene base layer, with a thickness of 60~100 µm and an oxygen permeability ≤15 cm). 3 / (m 2 Vacuum packaging is performed at 0.1 MPa for 24 hours, and combined with the gas conditioning method of Example 1 (i.e., after evacuating the packaging bag, 8% nitrogen is refilled into the bag), and the indicator fixing method (directly coated on the inside of the packaging bag), this vacuum packaging does not require a heat shrinking step.

[0118] Step 3: Irradiation was performed using a 10 MeV electron beam accelerator at 0~4℃. In this set of examples, the absorbed doses of Examples 2.1, 2.2, and 2.3 were 1.9 kGy, 2.8 kGy, and 3.8 kGy, respectively. The absorbed dose of Control Example 2 was 0 kGy.

[0119] Step 4: Immediately after processing, return the sample to a refrigerated environment at 0~4℃ for storage.

[0120] Samples from Examples 2.1, 2.2, and 2.3, and Control Example 2 were sampled and tested on days 0, 7, 14, 21, 28, 33, 40, 47, and 54. The test indicators included:

[0121] (1) Microbiological indicators: total colony count (GB 4789.2-2016);

[0122] (2) pH value, moisture (GB 5009.3-2016), TVB-N value (GB 2707-2016), protein (GB 4789.2-2025), fat (GB 4789.2-2016) and TBARS value (GB 4789.2-2016);

[0123] (3) Color: L* value (brightness) and a* value (redness) were measured using the DIGIEYE digital color measurement system (electronic eye) to measure the color of the beef surface;

[0124] (4) Sensory rating: A 5-point rating scale is used to evaluate color, smell and acceptability.

[0125] Table 3 shows the microbial indicators for Examples 2.1-2.3 and Control Example 2 (irradiation absorbed dose of 0 kGy).

[0126] Table 3

[0127]

[0128] Figure 8 This is a graph showing the change in total bacterial count of bovine lateral ribs over storage time under different electron beam doses. Figure 8 As shown in Table 3, for bovine lateral rib, after step three electron beam cold sterilization in this set of examples, the 3.8 kGy irradiation group had a shelf life exceeding 54 days, with the total bacterial count still below 10 CFU / g at 54 days; the 1.9 kGy group completely failed after 47 days (reaching 10 CFU / g). 6 The 2.8kGy group (CFU / g) was able to preserve samples efficiently for up to 33 days when samples were available.

[0129] Table 4 shows the sensory evaluation scores of Examples 2.1-2.3 and Control Group 2 (irradiated absorbed dose of 0 kGy).

[0130] Table 4

[0131]

[0132] In Table 4, sensory evaluation was not conducted because the total bacterial count in some unirradiated groups (Control Example 2) exceeded the national standard. According to the sensory evaluation results in Table 4, the 3.8 kGy irradiated group maintained acceptable levels (≥3 points out of 5) in color, odor, and acceptability scores during the 33-day storage period. Although slightly lower than the unirradiated group in the early stages of storage, it was significantly superior to the unirradiated group in the later stages of storage, confirming the comprehensive sensory advantages of high-dose irradiation during long-term storage.

[0133] Figure 9 This is a statistical analysis graph showing the change in pH value of bovine lateral ribs over storage time under different electron beam doses. Figure 9 As shown, for bovine sirloin, after step three electron beam cold sterilization in this embodiment, the pH value of the 3.8 kGy group remained stable at 6.2-6.3 (fresh meat range) for 33 days; the pH values ​​of the 1.9 kGy and 2.8 kGy irradiation groups also remained stable at 6.2-6.3 (fresh meat range) for 33 days of storage, indicating that low and medium dose irradiation also has an effective pH stabilizing effect on bovine sirloin; the pH value of the untreated control group rose to 6.78 after 19 days, exceeding the spoilage level.

[0134] Figure 10 This is a statistical analysis graph showing the change in TVB-N values ​​of bovine lateral ribs with storage time under different electron beam doses. Figure 10As shown, for bovine lateral loin, after step three electron beam cold sterilization in this embodiment, the TVB-N value of the 3.8 kGy high-dose group was significantly lower than that of the control group throughout the storage period, effectively delaying the protein spoilage process. The TVB-N value of the untreated control group exceeded the limit of 15 mg / 100g after 19 days of storage. The TVB-N values ​​of the 1.9 kGy and 2.8 kGy irradiation groups were slightly higher than those of the control group in the early stage of storage (5-12 days), but significantly lower than those of the control group after 19 days.

[0135] Figure 11 This is a statistical analysis graph showing the change of TBARS values ​​of bovine lateral ribs with storage time under different electron beam doses. Figure 11 As shown, for bovine lateral loin, after step three (electron beam cold sterilization) in this set of embodiments, the lateral loin was most sensitive to irradiation-induced lipid oxidation. All irradiation doses significantly promoted an increase in TBARS values, which intensified with storage time. The TBARS value of the 3.8 kGy group also reached a high level during long-term storage, but considering the color and sensory score data, this level of oxidation did not lead to sensory deterioration. The TBARS values ​​of the 1.9 kGy and 2.8 kGy irradiation groups also showed an increasing trend, with the oxidation level of the 2.8 kGy group falling between the two.

[0136] Figure 12 A statistical analysis of the changes in color (L* and a* values) of bovine lateral ribs with storage time under different electron beam doses; Figure 12 (1) A statistical analysis graph showing the change of color L* value of bovine lateral ridge with storage time under different electron beam doses; Figure 12 (2) A statistical analysis graph showing the change in color a* value of bovine lateral rib under different electron beam doses with storage time. For example... Figure 12 As shown in (1) and (2), for bovine lateral ribs, after the electron beam cold sterilization treatment in step three of this embodiment, the L* in the 3.8 kGy group decreased over time, but a* showed the best stability in the later stage of storage, which was highly synchronized with the antibacterial effect. The L* in the untreated control group gradually decreased with storage time, and a* deteriorated significantly in the middle and late stages of storage. The changes in L* in the 1.9 kGy and 2.8 kGy irradiation groups were similar to those in the control group, and a* decreased significantly in the early stage of storage (browning), but the stability of the low and medium dose groups was not as good as that of the 3.8 kGy group in the later stage.

[0137] Figure 13 This is a statistical analysis graph showing the change in moisture content of bovine lateral ribs over storage time under different electron beam doses. (See figure.) Figure 13As shown, for bovine lateral loin, after step three electron beam cold sterilization in this embodiment, the moisture content of the 3.8 kGy high-dose group (range approximately 60-73%) showed no significant advantage compared to the medium- and low-dose groups, indicating that irradiation itself has no decisive effect on moisture content. The moisture content of the untreated control group showed a decreasing trend with storage time. The changes in moisture content in the 1.9 kGy and 2.8 kGy irradiation groups were not significantly different from those in the control group.

[0138] Figure 14 A statistical analysis of the changes in fat and protein in bovine lateral loin over storage time under different electron beam doses; Figure 14 (1) A statistical analysis graph showing the changes in fat in bovine lateral rib under different electron beam doses over storage time; Figure 14 (2) A statistical analysis graph showing the changes in protein content in bovine lateral rib under different electron beam doses over storage time. (e.g.) Figure 14 As shown in (1) and (2), for bovine lateral rib, the fat content in the 3.8 kGy high-dose group after step three irradiation in this embodiment also fluctuated, while the protein content remained stable. The fat content (8-12%) in the untreated control group decreased slightly, while the protein content remained basically stable. The fat content data of the 1.9 kGy and 2.8 kGy irradiation groups fluctuated greatly and irregularly, but decreased slightly overall; the protein content remained stable and had no significant relationship with the irradiation dose.

[0139] The above data shows that 1.9-3.8 kGy electron beam cold sterilization combined with vacuum packaging can effectively maintain the nutritional, flavor, and color quality of beef sirloin, while achieving efficient cold sterilization and inhibiting the growth of microorganisms during storage. Vacuum packaging combined with 3.8 kGy electron beam cold sterilization can extend the shelf life of beef sirloin from 7-10 days to more than 54 days, 2.8 kGy treatment to 37 days, and 1.9 kGy treatment to 40 days.

[0140] Examples 3.1-3.3

[0141] This set of embodiments discloses a method for preserving chilled fresh beef that combines vacuum packaging and electron beam treatment, including the following steps:

[0142] Step 1: Take beef chuck (10-15% fat content) from Shandong De Beef Industry Co., Ltd., which has undergone commercial slaughter and cooling at 4℃ for 3 days to remove excess acid. Cut the beef into pieces no more than 4cm thick.

[0143] Step 2: The bovine chuck is coated with a five-layer co-extruded heat-shrinkable film with EVOH high barrier properties (including one EVOH barrier layer, with a thickness of 50~80µm and an oxygen permeability ≤5cm³ / (m²). 2 Vacuum heat shrink packaging is performed at 0.1 MPa for 24 hours.

[0144] The specific operation is as follows: The cut beef chuck is placed in a packaging bag. A microencapsulated freshness indicator (bromocresol purple: methyl red = 2:1, microcapsule wall material is gum arabic) is pre-coated onto the inside of the bag, covering an area of ​​2cm × 2cm, located in the transparent window area of ​​the packaging bag. Simultaneously, an enzyme-catalyzed time-temperature indicator label (model 3M MonitorMark) is fixed in the interlayer of the packaging bag. Then, a vacuum is drawn until the internal pressure of the bag is ≤0.01MPa, and nitrogen gas (99.9% purity) is refilled into the bag, filling it to 8% of its volume. The bag is then heat-sealed. Finally, a heat-shrink treatment is performed to ensure the film adheres tightly to the surface of the meat. The heat-shrink treatment process involves immersing the packaging bag in hot water at 85~95℃ for 2-5 seconds, followed immediately by cooling and shaping with cold air.

[0145] Step 3: Irradiation was performed using a 10 MeV electron beam accelerator at 0~4℃. In this set of examples, the absorbed doses of Examples 3.1, 3.2, and 3.3 were 1.9 kGy, 2.8 kGy, and 3.8 kGy, respectively. The absorbed dose of Control Example 3 was 0 kGy.

[0146] Step 4: Immediately after irradiation, return the sample to a cold storage environment of 0~4℃.

[0147] Samples from Examples 3.1, 3.2, and 3.3, and Control Example 3 were sampled and tested on days 0, 7, 14, 21, 28, 33, 40, 47, and 54, respectively. The test indicators included:

[0148] (1) Microbiological indicators: total colony count (GB 4789.2-2016);

[0149] (2) pH value, moisture (GB 5009.3-2016), TVB-N value (GB 2707-2016), protein (GB 4789.2-2025), fat (GB 4789.2-2016) and TBARS value (GB 4789.2-2016);

[0150] (3) Color: L* value (brightness) and a* value (redness) were measured using the DIGIEYE digital color measurement system (electronic eye) to measure the color of the beef surface;

[0151] (4) Sensory rating: A 5-point rating scale is used to evaluate color, smell and acceptability.

[0152] Table 5 shows the microbial indicators for Examples 3.1-3.3 and Control Example 3 (irradiation absorbed dose of 0 kGy).

[0153] Table 5

[0154]

[0155] Figure 15 This is a graph showing the change in total bacterial count in bovine epibranchial tissue over storage time under different electron beam doses. Figure 15 As shown in Table 5, for bovine cerumen, after the electron beam cold sterilization treatment in step three of this set of embodiments, 3.8 kGy was the only long-term effective dose for bovine cerumen, and the total bacterial count remained below 10 after 54 days of storage. CFU / g, shelf life exceeding 54 days; the total bacterial count in the low-to-medium dose groups (1.9 kGy and 2.8 kGy) increased to 10 after 40-47 days of storage. 6 CFU / g or higher poses a risk of failure.

[0156] Table 6 shows the sensory evaluation scores of Examples 3.1-3.3 and Control Group 3 (irradiated absorbed dose of 0 kGy).

[0157] Table 6

[0158]

[0159] In Table 6, sensory evaluation was not conducted because the total bacterial count in some unirradiated groups (Control Example 3) exceeded the national standard. According to the sensory evaluation results in Table 6, the 3.8 kGy irradiated group maintained acceptable levels (≥3 points out of 5) in color, odor, and acceptability scores during the 26-day storage period. Although slightly lower than the unirradiated group in the early stages of storage, it was significantly superior to the unirradiated group and the low-dose group in the later stages of storage, confirming the comprehensive sensory advantages of high-dose irradiation during long-term storage.

[0160] Figure 16 This is a statistical analysis graph showing the change in pH value of bovine epibranchial tissue over storage time under different electron beam doses. (See figure.) Figure 16 As shown, for bovine chuck, after step three electron beam cold sterilization in this embodiment, the pH value of the 3.8 kGy group remained stable at 6.2-6.3 (fresh meat range) for 33 days; the pH values ​​of the 1.9 kGy and 2.8 kGy irradiation groups also remained stable at 6.2-6.3 (fresh meat range) for 33 days of storage, indicating that low and medium dose irradiation also has an effective pH stabilizing effect on bovine chuck; the pH value of the untreated control group rose to 6.78 after 19 days, exceeding the spoilage level.

[0161] Figure 17 This is a statistical analysis graph showing the change in TVB-N values ​​of bovine epibrain over storage time under different electron beam doses. Figure 17As shown, for bovine cerum, after step three electron beam cold sterilization in this embodiment, the TVB-N value of the 3.8 kGy high-dose group was significantly lower than that of the control group after 19 days, effectively delaying the protein spoilage process. The TVB-N value of the untreated control group was close to the limit standard of 15 mg / 100g after 19 days of storage. The TVB-N values ​​of the 1.9 kGy and 2.8 kGy irradiation groups were slightly higher than those of the control group in the early stage of storage (5-12 days), but also showed a trend of being lower than those of the control group in the later stage.

[0162] Figure 18 This is a statistical analysis graph showing the change in TBARS values ​​of bovine epibrain over storage time under different electron beam doses. Figure 18 As shown, for bovine cerebrum, after step three (electron beam cold sterilization) in this embodiment, the TBARS values ​​fluctuated significantly, with no clear pattern among the irradiation groups, but the overall trend was upward. The TBARS values ​​in the 3.8 kGy group also showed an upward trend during long-term storage, but considering the color and sensory evaluation data, this oxidation level did not lead to sensory deterioration. The TBARS values ​​in the 1.9 kGy and 2.8 kGy irradiation groups also showed an upward trend, with no significant differences between the dose groups.

[0163] Figure 19 A statistical analysis of the changes in color (L* and a* values) of bovine epibrain over storage time under different electron beam doses; Figure 19 (1) A statistical analysis graph showing the change of color L* value of bovine epibrain with storage time under different electron beam doses; Figure 19 (2) A statistical analysis graph showing the change in color a* value of bovine epibrain with storage time under different electron beam doses. For example... Figure 19 As shown in (1) and (2), for bovine cerebrum, after the electron beam cold sterilization treatment in step three of this embodiment, the L* value of the 3.8 kGy high-dose group decreased over time, and the stability of the a* value in the later stage of storage was highly correlated with the antibacterial effect. The L* value of the untreated control group gradually decreased with storage time, and the a* value decreased significantly in the early stage of storage. The changes in L* value of the 1.9 kGy and 2.8 kGy irradiation groups were similar to those of the control group, and the a* value decreased significantly in the early stage of irradiation, but the stability of the medium and low dose groups in the later stage was not as good as that of the 3.8 kGy group.

[0164] Figure 20 This is a statistical analysis graph showing the change in water content in bovine epibranchial tissue over storage time under different electron beam doses. Figure 20As shown, for bovine cervical mucosa, the moisture content (range approximately 45-75%) in the 3.8 kGy high-dose group after step three electron beam treatment in this embodiment fluctuated greatly, but did not match the stable changes in microorganisms and pH data, proving that moisture content is mainly determined by muscle characteristics and experimental variations, not by direct irradiation. The moisture content of the untreated control group showed a decreasing trend with storage time. The changes in moisture content in the 1.9 kGy and 2.8 kGy irradiation groups were not significantly different from those in the control group.

[0165] Figure 21 A statistical analysis of the changes in fat and protein in bovine upper brain over storage time under different electron beam doses; Figure 21 (1) A statistical analysis graph showing the changes in fat in bovine epibrain over storage time under different electron beam doses; Figure 21 (2) A statistical analysis graph showing the changes in bovine brain protein over storage time under different electron beam doses. (e.g.) Figure 21 As shown in (1) and (2), for bovine cerebrum, the fat content in the 3.8 kGy high-dose group after electron beam treatment in step three of this embodiment also fluctuated, while the protein content remained stable, showing no significant relationship with the irradiation dose. The fat content (10-15%) in the untreated control group fluctuated, while the protein content remained basically stable. The fat content data in the 1.9 kGy and 2.8 kGy irradiation groups fluctuated greatly and irregularly (e.g., within the same group, it could range from 18.2 g / 100g to 33.7 g / 100g at 12 days), indicating that irradiation had a certain impact on fat content; the protein content remained stable, showing no significant relationship with the irradiation dose.

[0166] The above data shows that 1.9-3.8 kGy electron beam cold sterilization combined with vacuum heat shrink packaging can effectively maintain the nutritional, flavor, and color quality of bovine sirloin, while achieving efficient cold sterilization and inhibiting the growth of microorganisms during storage. Vacuum heat shrink packaging combined with 3.8 kGy electron beam cold sterilization can extend the shelf life of bovine sirloin from 7-10 days to more than 54 days, 2.8 kGy treatment to 40 days, and 1.9 kGy treatment to 33 days.

[0167] The total bacterial count results in Tables 1, 3, and 5 show that the 3.8 kGy electron beam irradiation dose used in this invention exhibits significant antibacterial advantages in different cuts of beef: the total bacterial count of beef tenderloin remained below 10 CFU / g after 47 days of storage, and the total bacterial count of beef sirloin remained below 10 CFU / g after 54 days. 4 CFU / g, bovine cervical mucin showed a total bacterial count below 10 after 54 days. 4 CFU / g, while the total bacterial count in the low- and medium-dose groups (1.9 kGy, 2.8 kGy) had increased to 10 after 40–47 days of storage. 6Above CFU / g, spoilage and failure to keep food fully demonstrate the "leapfrog" preservation effect of using 3.8 kGy as the dose threshold.

[0168] The sensory evaluation results in Tables 2, 4 and 6 show that the color, odor and acceptability scores of the 3.8 kGy irradiated group remained at an acceptable level (≥3 points, out of 5) during the 26-day storage period.

[0169] As can be seen from the above embodiments, the preservation method of the present invention achieves excellent preservation results by employing differentiated vacuum packaging methods for three cuts of beef: tenderloin, sirloin, and chuck (tenderloin and chuck are vacuum heat-shrink packaged, while sirloin is vacuum packaged), combined with 3.8 kGy electron beam irradiation treatment at 0–4°C and cold chain storage throughout the entire process. The present invention does not add any chemical preservatives or preservatives, achieving a simple, convenient, and purely physical cold sterilization and preservation process without high-temperature treatment. Experimental data shows that this method can preserve beef tenderloin for up to 47 days and beef sirloin and chuck for up to 54 days, with the total bacterial count consistently below 10 during the storage period. 4 CFU / g (below 10 CFU / g for some parts), TVB-N value ≤15 mg / 100g, pH value stable within the fresh range of 5.8–6.3, stable protein content, and good sensory quality. This invention effectively solves the problems of short shelf life, easy spoilage, reliance on chemical additives, and complex processes in existing technologies for chilled beef, and has significant prospects for industrial application and market promotion value.

[0170] The embodiments described above are merely preferred embodiments, and are described in detail, but the scope of protection of this invention is not limited thereto. Any improvements or variations made by those skilled in the art based on this invention should fall within the scope of protection of this invention.

Claims

1. A method for preserving chilled beef that combines vacuum packaging and electron beam treatment, characterized in that, The preservation method includes the following steps: S1. Cut the chilled fresh beef after cooling and aging, ensuring that the thickness of the chilled fresh beef does not exceed 4 cm. S2. Vacuum packaging the chilled beef; the vacuum packaging process includes: drawing a vacuum into the packaging bag containing the chilled beef, making the internal pressure of the packaging bag ≤0.01MPa, then refilling the packaging bag with nitrogen gas, and finally sealing it; wherein the amount of nitrogen gas refilled accounts for 5%~10% of the volume of the packaging bag; S3. Irradiate the chilled fresh beef in the packaging bag of step S2 with an electron beam of 8-10 MeV at 0-4℃; the absorbed dose of the irradiation is 1.9-5.0 kGy. S4. The irradiated chilled beef is stored in a cold chain at 0~4℃.

2. The preservation method as described in claim 1, characterized in that, In step S1, the chilled fresh beef is one or more of beef tenderloin, beef sirloin, or beef chuck.

3. The preservation method as described in claim 2, characterized in that, Based on the different types of chilled fresh beef, the vacuum packaging process in step S2 satisfies any one of the following conditions: When the chilled fresh beef is beef tenderloin and / or beef chuck, the packaging bag is an EVOH high-barrier multilayer co-extruded heat-shrinkable film; after the sealing operation is completed, the packaging bag is also heat-shrinked. When the chilled fresh beef is beef sirloin, the packaging bag is a polyethylene composite film.

4. The preservation method as described in claim 3, characterized in that, The EVOH high-barrier multilayer co-extruded heat-shrinkable film has a co-extruded structure with five or more layers, including at least one EVOH barrier layer; the oxygen permeability of the EVOH high-barrier multilayer co-extruded heat-shrinkable film is ≤5 cm⁻¹. 3 / (m 2 ·24h·0.1MPa); The all-polyethylene composite film has a multi-layer structure comprising a high-density polyethylene surface layer, a low-density polyethylene intermediate layer, and a high-molecular-weight polyethylene base layer; the oxygen permeability of the all-polyethylene composite film is ≤15 cm⁻¹. 3 / (m 2 ·24h·0.1MPa).

5. The preservation method as described in claim 1, characterized in that, Step S3 satisfies at least one of the following conditions: The absorbed dose of the irradiation is 2.8~3.8 kGy; The energy of the electron beam is 10 MeV; During the irradiation process, each of the chilled beef pieces is placed in a single layer.

6. The preservation method as described in claim 1, characterized in that, The packaging bag is fixedly provided with a time and temperature indicator and / or a freshness indicator on the inner side or in the interlayer.

7. The preservation method as described in claim 6, characterized in that, The packaging bag meets at least one of the following conditions: The time-temperature indicator includes an enzyme-catalyzed irreversible indicator; The freshness indicator includes a pH change indicator or a volatile basic nitrogen-sensitive indicator; The freshness indicator is coated in microencapsulated form on the inside or interlayer of the packaging bag.

8. The preservation method as described in claim 2, characterized in that, The method for preserving beef tenderloin includes the following steps: s1. Cut the cooled and de-acidified beef tenderloin so that the thickness of the tenderloin does not exceed 4 cm; s2. Vacuum packaging of the beef tenderloin; the vacuum packaging process includes: drawing a vacuum into the packaging bag containing the beef tenderloin, so that the internal pressure of the packaging bag is ≤0.01MPa, then refilling the packaging bag with nitrogen, and finally sealing and heat shrinking in sequence; wherein, the amount of nitrogen refilled accounts for 5%~10% of the volume of the packaging bag; the packaging bag is an EVOH high-barrier multilayer co-extruded heat-shrinkable film; s3. Under conditions of 0~4℃, the beef tenderloin in the packaging bag of step s2 is irradiated with an electron beam of 10MeV; the absorbed dose of the irradiation is 3.8 kGy; s4. The irradiated beef tenderloin was stored in a cold chain at 0~4℃; after 47 days of storage, the total bacterial count of the beef tenderloin was less than 10 CFU / g.

9. The preservation method as described in claim 2, characterized in that, The method for preserving the beef loin includes the following steps: s1. Cut the cooled and deacidified beef sirloin so that the thickness of the sirloin does not exceed 4 cm; s2. Vacuum packaging of the bovine sirloin; the vacuum packaging process includes: drawing a vacuum into the packaging bag containing the bovine sirloin, making the internal pressure of the packaging bag ≤0.01MPa, then refilling the packaging bag with nitrogen gas, and finally sealing it; wherein, the amount of nitrogen gas refilled accounts for 5%~10% of the volume of the packaging bag; the packaging bag is a full polyethylene composite film; s3. Under conditions of 0~4℃, the bovine rib cage in the packaging bag of step S2 is irradiated with an electron beam of 10MeV; the absorbed dose of the irradiation is 3.8 kGy. s4. The irradiated bovine sirloin was stored in a cold chain at 0-4°C; after 54 days of storage, the total bacterial count of the bovine sirloin was less than 10 CFU / g.

10. The preservation method as described in claim 2, characterized in that, The method for preserving beef chuck includes the following steps: s1. Cut the cooled and deacidified beef chuck into pieces, ensuring that the thickness of the beef chuck does not exceed 4 cm; s2. Vacuum packaging of the bovine sauerkraut; the vacuum packaging process includes: drawing a vacuum into the packaging bag containing the bovine sauerkraut, so that the internal pressure of the packaging bag is ≤0.01MPa, then refilling the packaging bag with nitrogen gas, and finally sealing and heat shrinking in sequence; wherein, the amount of nitrogen gas refilled accounts for 5%~10% of the volume of the packaging bag; the packaging bag is an EVOH high-barrier multilayer co-extruded heat-shrinkable film; s3. Under conditions of 0~4℃, the bovine cervix in the packaging bag of step S2 is irradiated with an electron beam of 10MeV; the absorbed dose of the irradiation is 3.8 kGy; s4. The irradiated bovine cervical mucin was stored in a cold chain at 0-4°C; after 54 days of storage, the total bacterial count of the bovine cervical mucin was less than 10 CFU / g.

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