Pressurized oxygen pretreatment method for improving meat color of frozen beef

Abstract

The invention relates to the technical field of food processing, and discloses a pressurized oxygen pretreatment method for improving the meat color of frozen beef, which comprises the following steps: selecting beef subjected to acid discharge treatment, cutting, controlling the temperature, putting into a closed pressure-resistant container, introducing oxygen for replacement, and initially pressurizing; performing pressure pulse circulation treatment in the container, synchronously starting an ultrasonic generator to perform ultrasonic treatment in a high pressure maintaining stage, and executing a periodic instantaneous exhaust program; then under-pressure supercooling locking treatment is performed, so that the beef is in an under-pressure supercooling state; and finally, releasing the pressure to normal pressure, moving out the beef, and carrying out quick freezing treatment and vacuum packaging. According to the method, pressure pulse circulation treatment is carried out on the beef subjected to initial pressure boosting in the closed pressure-resistant container, the mechanical action of pressure pulse circulation is utilized to promote oxygen to overcome mass transfer resistance, the oxygen can enter deep muscle fibers in cooperation with the cavitation effect generated by ultrasonic treatment, and the problem that the meat color distribution of the frozen beef is not uniform is solved.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to a pressurized oxygen pretreatment method for improving the color of frozen beef. Background Technology

[0002] As a major red meat product, the color of beef is a direct indicator for consumers to judge its freshness and quality. Consumers generally prefer beef products with a bright cherry-red color. The color of beef mainly depends on the state of myoglobin in the muscle tissue. When myoglobin combines with oxygen to form oxymyoglobin, the meat is bright red. However, during freezing and long-term storage, myoglobin is prone to oxidation, forming brown methemoglobin, which causes browning on the surface and inside of the beef, affecting the product's appearance and commercial value.

[0003] In existing technologies, to maintain the color of frozen beef, high-oxygen controlled packaging or high-concentration oxygen static treatment before use is often used, attempting to promote the formation of oxymyoglobin by utilizing high oxygen partial pressure. However, this static or simple surface high-oxygen treatment method has certain limitations. Due to the dense fibrous structure of muscle tissue, gas diffusion faces significant mass transfer resistance, making it difficult for oxygen to penetrate deep into the muscle layer. This easily leads to uneven color recovery in the beef, resulting in a bright red surface and browning in the center. Furthermore, prolonged exposure of beef to a simple high-concentration oxygen environment, while improving color to some extent, easily induces the oxidation of fats in the beef, leading to the accumulation of lipid peroxides and ultimately damaging the flavor. In addition, conventional freezing methods cannot effectively stabilize the spatial structure of oxymyoglobin before freezing, resulting in poor color stability during subsequent freezing and thawing processes.

[0004] Therefore, how to develop a pretreatment method that can both achieve deep and uniform oxygenation to improve meat color and effectively stabilize color and inhibit lipid oxidation is a technical problem that needs to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a pressurized oxygen pretreatment method for improving the color of frozen beef, which solves the problems in existing technologies such as the difficulty of oxygen penetrating deep into the muscle layer leading to uneven color restoration, the easy induction of lipid oxidation by simple high oxygen treatment, and poor color stability during freezing.

[0006] To address the above problems, the present invention provides the following technical solution: This invention provides a pressurized oxygen pretreatment method for improving the color of frozen beef, employing the following technical solution: A pressurized oxygen pretreatment method for improving the color of frozen beef includes the following steps: S1. Select beef that has undergone aging treatment, cut the beef, and control the core temperature of the beef to be at a low temperature. S2. Place the beef in a sealed pressure-resistant container, introduce oxygen into the sealed pressure-resistant container to replace the gas in the sealed pressure-resistant container and perform initial pressurization to obtain beef after initial pressurization. S3. The initially pressurized beef is subjected to pressure pulse cycle treatment in the sealed pressure-resistant container. The pressure pulse cycle treatment includes a high-pressure holding stage. During the high-pressure holding stage, an ultrasonic generator is simultaneously turned on to perform ultrasonic treatment on the initially pressurized beef, and a periodic instantaneous exhaust program is executed to obtain beef after pulse composite treatment. S4. Perform pressurized supercooling locking treatment on the beef after pulse composite treatment to put the beef after pulse composite treatment in a pressurized supercooling state to obtain supercooled locked beef. S5. Depressurize the sealed pressure container to normal pressure, remove the supercooled and locked beef and perform rapid freezing treatment, then vacuum seal the supercooled and locked beef to obtain a frozen beef product with stable meat color.

[0007] By adopting the above technical solution, and by using pressurized oxygen replacement combined with acoustic pressure coupling and pressurized subcooling technology, this invention constructs a synergistic processing mechanism of physical penetration and state locking, thereby achieving a deep improvement and stabilization of beef color.

[0008] Preferably, in step S2, the purity of the oxygen is 99.5% to 99.9%, the initial pressurization rate is 0.04 MPa / min to 0.06 MPa / min, and the pressure inside the sealed pressure-resistant container is increased to 0.3 MPa to 0.5 MPa and maintained for 10 to 14 hours.

[0009] By adopting the above technical solution, controlling the beef temperature between 0℃ and 4℃ ensures both meat freshness and facilitates the physical dissolution of oxygen. High-purity oxygen and initial gentle pressurization establish a high-concentration gradient mass transfer driving force for subsequent deep oxygenation, while avoiding mechanical damage to meat fibers caused by pressure surges.

[0010] Preferably, in step S3, the pressure pulse cycle processing includes an alternating pressurization phase, a high-pressure holding phase, a pressure release phase, and a low-pressure holding phase; the parameters of the pressure pulse cycle processing are controlled as follows: the low-pressure value of the pressure pulse cycle processing is 0.10 MPa to 0.20 MPa; the high-pressure value of the pressure pulse cycle processing is 0.30 MPa to 0.50 MPa; the pressurization rate of the pressurization phase is 0.08 MPa / min to 0.12 MPa / min; and the pressure release rate of the pressure release phase is 0.15 MPa / min to 0.25 MPa / min.

[0011] By employing the above technical solution and setting specific high and low pressure differences and circulation rates, a suitable mechanical action is constructed. If the pressure is too high or the pressurization is too rapid, it will cause excessive densification of muscle tissue, hindering oxygen entry and potentially damaging muscle fiber structure; if the pressure is too low, it will not provide sufficient driving force. This parameter range represents the optimal range for balancing mass transfer efficiency and meat texture.

[0012] Preferably, in step S3, the frequency of the ultrasonic generator is set to 20kHz to 40kHz, and the power density of the ultrasonic generator is set to 0.3W / cm². 2 ~0.5W / cm 2 .

[0013] By adopting the above technical solution, low-frequency ultrasound is selected mainly to utilize its mechanical and cavitation effects. This power density range can generate sufficient micro-disturbances to promote diffusion, while avoiding the thermal effects of high-power ultrasound that could lead to localized temperature increases and cause protein denaturation or lipid oxidation.

[0014] Preferably, in step S3, the periodic instantaneous venting procedure is executed as follows: during the high-pressure holding stage, every 30 to 60 seconds, the venting valve installed on the sealed pressure-resistant container is opened for 0.5 to 1.0 seconds, causing the pressure inside the sealed pressure-resistant container to drop instantaneously by 0.05 MPa to 0.10 MPa, and then the pressure is immediately and automatically restored to the pressure during the high-pressure holding stage.

[0015] The specific reaction mechanism achieved by employing the above technical solution is as follows: During the high-pressure holding stage, oxygen molecules are in equilibrium, diffusing into the meat. At this moment, a millisecond-level instantaneous venting occurs, causing a sudden drop in container pressure. Due to the lag in pressure transmission, the internal pressure of the meat is temporarily higher than the external pressure, leading to microscopic outward respiration and relaxation of the meat tissue. This disrupts the original gas-liquid equilibrium interface and the dense tissue layer. Immediately afterward, the system replenishes pressure, and the external pressure again becomes higher than the internal pressure. At this point, the oxygen concentration is higher, and oxygen flows at a high rate into the newly opened microchannels during the tissue relaxation. This microcirculation mechanism of relaxation impact improves oxygenation efficiency.

[0016] Preferably, in step S3, the high-pressure holding stage is set to 3 to 5 minutes, and the low-pressure holding stage is set to 1 to 3 minutes; the process of pressurization, high-pressure holding, depressurization, and low-pressure holding is repeated 3 to 5 times.

[0017] By adopting the above technical solution, the setting of the number of cycles and the pressure holding time ensures that the treatment process can achieve the saturation of deep oxygenation without taking too long, which would lead to low production efficiency or cause side effects due to prolonged exposure to high oxygen.

[0018] Preferably, in step S4, the pressurized subcooling locking process is specifically performed as follows: adjusting and stabilizing the pressure inside the sealed pressure-resistant container to 0.20MPa to 0.25MPa; simultaneously reducing the ambient temperature inside the sealed pressure-resistant container to -3.0℃ to -2.0℃; and allowing it to stand for 10 to 20 minutes while maintaining the pressure and ambient temperature constant.

[0019] By employing the above technical solution, a pressure of 0.20 MPa to 0.25 MPa combined with a temperature of -3.0℃ to -2.0℃ represents the critical region for phase transition in the beef tissue. Under these conditions, water molecules exist in a metastable liquid phase with increased density, inhibiting the formation of ice crystal nuclei. The static treatment allows the binding reaction of myoglobin and oxygen to reach thermodynamic equilibrium under low temperature and high pressure, thus locking in the meat color.

[0020] Preferably, in step S5, the rapid freezing process is carried out in a liquid nitrogen freezer, and the core temperature of the beef is -25℃ to -15℃ when freezing is terminated. The vacuum sealing is performed using a high-barrier vacuum skin packaging material.

[0021] By employing the above technical solution, liquid nitrogen flash freezing allows the beef to rapidly pass through the maximum ice crystal formation zone, resulting in small and uniform ice crystals that do not puncture cell walls, minimizing juice loss after thawing. Vacuum-sealed packaging adheres tightly to the meat surface, effectively isolating it from external oxygen and moisture exchange under the protection of high-barrier materials, thus maintaining the good color and quality formed during the pretreatment stage.

[0022] This invention provides a pressurized oxygen pretreatment method for improving the color of frozen beef. It has the following beneficial effects: 1. This invention involves subjecting initially pressurized beef to pressure pulse circulation within a sealed pressure-resistant container, and simultaneously activating an ultrasonic generator and executing a periodic instantaneous venting procedure during the high-pressure holding phase. The mechanical action of the pressure pulse circulation forces oxygen to overcome mass transfer resistance, and the cavitation effect generated by the ultrasonic treatment forms microchannels in the tissue. Furthermore, the tissue relaxation caused by the instantaneous pressure drop during the periodic instantaneous venting procedure, coupled with the subsequent pressure boosting impact, allows oxygen to penetrate deep muscle fibers, thus improving the problem of uneven color distribution in frozen beef.

[0023] 2. This invention involves pressurized supercooling locking of beef after pulse composite treatment. By utilizing the physical property of pressure lowering the freezing point of water, the beef is kept in a pressurized supercooled state without freezing at low temperatures. This inhibits enzyme activity and oxidation reaction rate at low temperatures, while stabilizing the spatial structure of oxymyoglobin under pressure. Thermodynamic locking of meat color is achieved before rapid freezing, thus improving the color stability of beef during subsequent freezing and storage.

[0024] 3. This invention rapidly freezes supercooled beef and then encapsulates it with high-barrier vacuum skin packaging material. Rapid freezing reduces mechanical damage to muscle tissue caused by ice crystals, lowers the thawing loss rate to reduce myoglobin loss with juices, and vacuum sealing isolates external oxygen and moisture, maintaining the water retention of the frozen beef product and preventing oxidative browning. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to embodiments, comparative examples, and test examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Examples 1-3: Example 1: This embodiment provides a pressurized oxygen pretreatment method for improving the color of frozen beef, including the following steps: S1. Select the longissimus dorsi muscle of cattle that has been treated with aging after slaughter, cut it into pieces of uniform thickness, and control the center temperature of the pieces to 0℃. S2. Place the meat pieces in a sealed pressure-resistant reactor, control the ambient temperature inside the reactor to 2℃, purge and replace the reactor with oxygen of 99.5% purity, and slowly increase the pressure to 0.3MPa at a rate of 0.04MPa / min, and maintain this pressure for 10 hours. S3. Perform pressure pulse circulation treatment within the reactor, setting the low-pressure value to 0.10 MPa, the high-pressure value to 0.30 MPa, the pressurization rate to 0.08 MPa / min, and the depressurization rate to 0.15 MPa / min. When the pressure rises to 0.30 MPa and enters the pressure holding stage, immediately turn on the ultrasonic generator inside the reactor, setting the frequency to 20 kHz and the power density to 0.3 W / cm³. 2Simultaneously, a periodic instantaneous venting program is activated. During the high-pressure holding period, the venting valve is opened for 0.5 seconds every 60 seconds, causing the pressure inside the vessel to drop by 0.05 MPa instantaneously. Then, the pressure is automatically restored to 0.30 MPa. The high-pressure holding time is set to 3 minutes. Then, the ultrasonic waves are turned off and the pressure is reduced to 0.10 MPa and maintained for 1 minute. The above process of pressurization, high-pressure coordinated holding, and pressure reduction is repeated 3 times. S4. After the cycle is completed, adjust and stabilize the pressure inside the vessel at 0.20MPa. At the same time, start the refrigeration system to lower the ambient temperature inside the vessel to -2.0℃. Let the beef stand for 10 minutes while maintaining constant pressure to bring it into a pressurized subcooled state. S5. After processing, quickly depressurize to atmospheric pressure, remove the meat pieces from the reactor and send them to a liquid nitrogen quick-freezing machine to freeze rapidly until the core temperature reaches -15℃. Then, use high-barrier vacuum skin packaging material to seal the frozen beef product with stable meat color.

[0027] Example 2: This embodiment provides a pressurized oxygen pretreatment method for improving the color of frozen beef, including the following steps: S1. Select the longissimus dorsi muscle of cattle after slaughter and aging treatment, cut it into pieces of uniform thickness, and control the center temperature of the pieces to 2℃. S2. Place the meat pieces in a sealed pressure-resistant reactor, control the ambient temperature inside the reactor to 2℃, purge and replace the reactor with oxygen of 99.7% purity, and slowly increase the pressure to 0.4MPa at a rate of 0.05MPa / min, and maintain this pressure for 12 hours. S3. Perform pressure pulse circulation treatment within the reactor, setting the low-pressure value to 0.15 MPa, the high-pressure value to 0.40 MPa, the pressurization rate to 0.10 MPa / min, and the depressurization rate to 0.20 MPa / min. When the pressure rises to 0.40 MPa and enters the pressure holding stage, immediately turn on the ultrasonic generator inside the reactor, setting the frequency to 28 kHz and the power density to 0.4 W / cm³. 2 Simultaneously, a periodic instantaneous venting program is activated. During the high-pressure holding period, the venting valve is opened for 0.8 seconds every 45 seconds, causing the pressure inside the vessel to drop by 0.08 MPa instantaneously. Then, the pressure is automatically restored to 0.40 MPa. The high-pressure holding time is set to 4 minutes. Then, the ultrasonic waves are turned off and the pressure is reduced to 0.15 MPa and maintained for 2 minutes. The above process of pressurization, high-pressure coordinated holding, and pressure reduction is repeated 4 times. S4. After the cycle is completed, adjust and stabilize the pressure inside the vessel at 0.22MPa. At the same time, start the refrigeration system to lower the ambient temperature inside the vessel to -2.5℃. Let the beef stand for 15 minutes while maintaining constant pressure to bring it into a pressurized subcooled state. S5. After processing, quickly depressurize to atmospheric pressure, remove the meat pieces from the reactor and send them to a liquid nitrogen quick-freezing machine to freeze rapidly until the core temperature reaches -20℃. Then, use high-barrier vacuum skin packaging material to seal the frozen beef product with stable meat color.

[0028] Example 3: This embodiment provides a pressurized oxygen pretreatment method for improving the color of frozen beef, including the following steps: S1. Select the longissimus dorsi muscle of cattle that has been treated with aging after slaughter, cut it into pieces of uniform thickness, and control the center temperature of the pieces to 4℃. S2. Place the meat pieces in a sealed pressure-resistant reactor, control the ambient temperature inside the reactor to 2℃, purge and replace the reactor with oxygen of 99.9% purity, and slowly increase the pressure to 0.5MPa at a rate of 0.06MPa / min, and maintain this pressure for 14 hours. S3. Perform pressure pulse circulation treatment within the reactor, setting the low-pressure value to 0.20 MPa, the high-pressure value to 0.50 MPa, the pressurization rate to 0.12 MPa / min, and the depressurization rate to 0.25 MPa / min. When the pressure rises to 0.50 MPa and enters the pressure holding stage, immediately turn on the ultrasonic generator inside the reactor, setting the frequency to 40 kHz and the power density to 0.5 W / cm³. 2 Simultaneously, a periodic instantaneous venting program is activated. During the high-pressure holding period, the venting valve is opened for 1.0 second every 30 seconds, causing the pressure inside the vessel to drop by 0.10 MPa instantaneously. Then, the pressure is automatically restored to 0.50 MPa. The high-pressure holding time is set to 5 minutes. Then, the ultrasonic waves are turned off and the pressure is reduced to 0.20 MPa and maintained for 3 minutes. The above process of pressurization, high-pressure coordinated holding, and pressure reduction is repeated 5 times. S4. After the cycle is completed, adjust and stabilize the pressure inside the vessel at 0.25MPa. At the same time, start the refrigeration system to lower the ambient temperature inside the vessel to -3.0℃. Let the beef stand for 20 minutes while maintaining constant pressure to bring it into a pressurized subcooled state. S5. After processing, quickly depressurize to atmospheric pressure, remove the meat pieces from the reactor and send them into a liquid nitrogen quick-freezing machine to freeze rapidly until the core temperature reaches -25°C. Then, use high-barrier vacuum skin packaging material to seal the frozen beef product with stable meat color.

[0029] Comparative Examples 1-5: Comparative Example 1: Compared with Example 2, the difference is that steps S2 to S4 are omitted, and the beef after aging and cutting is directly subjected to rapid freezing and packaging in step S5. All other parameters and steps are the same.

[0030] Comparative Example 2: Compared with Example 2, the difference is that steps S2 to S4 are replaced by: placing the meat pieces in an environment of normal pressure (0.1MPa) and 2°C for 20 minutes and then proceeding to step S5. All other parameters and steps are the same.

[0031] Comparative Example 3: Compared with Example 2, the difference lies in step S3, where the pressure pulse cycle treatment is replaced with constant high pressure treatment, that is, the pressure inside the vessel is directly raised to 0.45MPa and kept constant. The total holding time is consistent with the total time of step S3 in Example 2, and the ultrasonic generator is not turned on during the holding period, and the instantaneous venting procedure is not executed. All other parameters and steps are the same.

[0032] Comparative Example 4: Compared with Example 2, the difference lies in step S3. Although a pressure pulse cycle is executed, the ultrasonic generator is not turned on throughout the high-pressure holding phase, and the periodic instantaneous exhaust procedure is not executed. All other parameters and steps are the same.

[0033] Comparative Example 5: Compared with Example 2, the difference is that step S4 (low temperature and high pressure steady state locking) is omitted. After the cycle of step S3 is completed, step S5 is directly depressurized and rapidly frozen. All other parameters and steps are the same.

[0034] Test Example 1-3: Test Example 1: Meat Color Stability Test During Frozen Storage Experimental description: This test selected packaged meat samples prepared in Examples 1 to 3 and Comparative Examples 1 to 5 as experimental subjects. All samples were placed in a constant temperature cold storage at -18℃ for long-term frozen storage. The experiment aimed to monitor the change trend of meat color redness of frozen beef under different pretreatment processes during long-term frozen storage, thereby evaluating the color stability after the combination of pressurized oxygen treatment with acoustic pressure coupling and supercooling locking processes, and verifying the actual contribution of acoustic pressure coupling and micro-supercooling locking processes to delaying myoglobin oxidative browning.

[0035] Experimental steps: The samples were removed from the cold storage on days 7, 60, and 120 of freezing. A running water thawing method was used to raise the core temperature of the meat samples to between 0°C and 4°C. The vacuum-sealed bags were opened, and the meat samples were cut transversely along the direction perpendicular to the muscle fibers, exposing the central cut surface to air for color development. The settling time was controlled to 30 minutes.

[0036] The color of the geometric center region of the cut surface was measured using a CIE colorimeter, and the redness value a* was recorded. Three different cut surface points were selected for each measurement, and the average value was taken to reduce errors caused by local tissue differences. A higher a value indicates a more vibrant red flesh color; an a value below 10 is generally considered to be an unacceptable browning.

[0037] Table 1. Changes in redness value (a*) of frozen beef slices under different freezing times. Experimental conclusion: According to the monitoring data in Table 1, Example 2 showed better color stability during frozen storage than the comparative examples, with its redness value remaining at 19.34 on day 120 and a decay rate of 13.31%. In contrast, the redness value of Comparative Example 1 decreased more rapidly over time, and the redness values ​​of Comparative Examples 3 to 5 were also lower than those of Example 2.

[0038] Data analysis shows that the process used in Example 2 has a good color-preserving effect. On the one hand, the pressure pulse cycle combined with ultrasonic treatment promotes the penetration of oxygen into muscle tissue and increases the production of oxymyoglobin; on the other hand, the pressurized supercooling treatment in step S4 keeps the beef in a stable supercooled state under low temperature and high pressure, reducing the thermal mobility of molecules, thereby stabilizing the state of myoglobin before rapid freezing and delaying oxidative browning during subsequent frozen storage.

[0039] Test Example 2: Test of Fat Oxidation Level Experimental description: This test selected meat samples from Examples 1 to 3, and Comparative Examples 1, 3, and 4, which were frozen at -18℃ for 90 days, as experimental subjects. The experiment aimed to evaluate the impact of different processing techniques on the oxidative stability of beef lipids by measuring the thiobarbituric acid reactive substance value. The thiobarbituric acid reactive substance value mainly reflects the content of malondialdehyde, a lipid peroxidation product, and is a key indicator for evaluating the degree of oxidative rancidity of meat products. The higher the value, the more severe the degree of fat oxidation. Generally, when the value exceeds 1.0 mg / kg, the meat product will show obvious oxidative off-odor.

[0040] Experimental steps: Take thawed meat samples from each group, remove obvious external fat and connective tissue, and mince and mix the lean meat. Accurately weigh 5.00g of minced meat into a centrifuge tube, and add 25mL of 7.5% trichloroacetic acid solution containing 0.1% disodium EDTA. Extract the mixture on a shaker for 30 minutes, then centrifuge at 1600g for 5 minutes. Filter the supernatant through double-layer qualitative filter paper.

[0041] Pipette 5 mL of the filtrate into a colorimetric tube, add 5 mL of a 0.02 mol / L thiobarbituric acid solution, mix well, and heat in a 90°C water bath for 40 minutes to develop the color. After the reaction solution cools to room temperature, measure the absorbance at 532 nm using a UV-Vis spectrophotometer. Calculate the thiobarbituric acid reactant value in the sample based on the malondialdehyde standard curve, and express the result as milligrams of malondialdehyde per kilogram of meat.

[0042] Table 2. Results of Thiobarbituric Acid Reactive Matter Value Determination in Beef Samples After 90 Days of Frozen Storage Experimental conclusion: Based on the test data analysis in Table 2, the thiobarbituric acid reactant value of Example 2 is 0.27 mg / kg, which is significantly lower than that of Comparative Example 3 and Comparative Example 4, and close to that of Comparative Example 1 under vacuum and oxygen-deficient conditions.

[0043] This result demonstrates that the process conditions in Example 2 effectively control fat oxidation. The pressurized supercooling lock-in followed by rapid freezing places the beef in a low-temperature environment, inhibiting the activity of lipid oxidases and the rate of free radical reactions. Simultaneously, the subsequent high-barrier vacuum-sealed packaging isolates external oxygen, further blocking the oxidation reaction. Therefore, this method introduces oxygen to improve meat color without causing significant fat oxidation and rancidity, thus balancing color and flavor stability.

[0044] Test Example 3: Thawing Loss and Texture Properties Test Experimental description: This test selected meat samples from Example 2, Comparative Examples 1, 3, 4, and 5, which had undergone different processing methods and were frozen for 90 days, as experimental subjects. The experiment aimed to investigate the effects of pressurized oxygen pretreatment on the physical quality of frozen beef, focusing on the thawing loss rate to characterize the water-holding capacity and cell membrane integrity of muscle tissue, and using shear force as an indicator to evaluate changes in meat tenderness. These two indicators can indirectly reflect the degree of oxidative denaturation of myofibril proteins and the mechanical damage to the muscle microstructure caused by ice crystal morphology.

[0045] Experimental steps: Thawing loss rate determination: Remove the frozen meat sample and accurately weigh it in its frozen state. Place the meat sample in a 4℃ constant temperature freezer for slow thawing until the core temperature of the meat sample reaches 0℃ to 4℃. Remove the thawed meat sample, gently blot away any blood and juices seeping from the surface with absorbent paper, and weigh it accurately again. The thawing loss rate is calculated using the formula: (Weight before freezing - Weight after thawing) / Weight before freezing × 100%. Three meat samples are selected for parallel testing in each group.

[0046] Shear force determination: Thawed meat samples were placed in a constant temperature water bath and heated until the core temperature reached 72℃. The samples were then removed and allowed to cool naturally to room temperature. Cylindrical cores with a diameter of 1.27 cm were cut parallel to the muscle fibers. A texture analyzer equipped with Warner-Bratzler shear blades was used to perform shear tests on the cores. The shearing speed was set to 200 mm / min, and the maximum force value during the shearing process was recorded. Three to five cores were drilled from each meat sample for testing, and the average value was used as the tenderness index for that sample.

[0047] Table 3. Thawing loss rate and shear force test data of beef samples after 90 days of frozen storage Experimental conclusion: Based on the data analysis in Table 3, Example 2 showed the best performance among all test groups with a thawing loss rate of 4.15% and a shear force of 44.52 N. In contrast, Comparative Example 1 had a higher thawing loss rate, indicating that conventional freezing caused greater damage to the tissue.

[0048] The superior performance of Example 2 is attributed to the multiple synergistic physical effects of this method. First, the cavitation effect generated by ultrasonic treatment improves the microstructure of muscle fibers and moderately loosens muscle bundles, which is beneficial to improving tenderness. Second, the pressurized supercooling lock in step S4 allows the beef to reach a lower temperature without freezing. Combined with the subsequent liquid nitrogen flash freezing, it promotes the formation of small and evenly distributed intracellular ice crystals, reducing the physical damage to cell membranes and protein skeletons caused by ice crystal growth, thereby effectively maintaining the water retention and tenderness of frozen beef.

Claims

1. A pressurized oxygen pretreatment method for improving the color of frozen beef, characterized in that, Includes the following steps: S1. Select beef that has undergone aging treatment, cut the beef, and control the center temperature of the beef to be at a low temperature. S2. Place the beef in a sealed pressure-resistant container, introduce oxygen into the sealed pressure-resistant container to replace the gas in the sealed pressure-resistant container and perform initial pressurization to obtain beef after initial pressurization. S3. The initially pressurized beef is subjected to pressure pulse cycle treatment in the sealed pressure-resistant container. The pressure pulse cycle treatment includes a high-pressure holding stage. During the high-pressure holding stage, an ultrasonic generator is simultaneously turned on to perform ultrasonic treatment on the initially pressurized beef, and a periodic instantaneous exhaust program is executed to obtain beef after pulse composite treatment. S4. Perform pressurized supercooling locking treatment on the beef after pulse composite treatment to put the beef after pulse composite treatment in a pressurized supercooling state to obtain supercooled locked beef. S5. Depressurize the sealed pressure container to normal pressure, remove the supercooled and locked beef and perform rapid freezing treatment, then vacuum seal the supercooled and locked beef to obtain a frozen beef product with stable meat color.

2. The pressurized oxygen pretreatment method for improving the color of frozen beef according to claim 1, characterized in that, In step S2, the purity of the oxygen is 99.5% to 99.9%, the initial pressurization rate is 0.04 MPa / min to 0.06 MPa / min, and the pressure inside the sealed pressure-resistant container is increased to 0.3 MPa to 0.5 MPa and maintained for 10 to 14 hours.

3. The pressurized oxygen pretreatment method for improving the color of frozen beef according to claim 1, characterized in that, In step S3, the pressure pulse cycle processing includes an alternating pressurization phase, a high-pressure holding phase, a pressure relief phase, and a low-pressure holding phase. The parameters for the pressure pulse cyclic processing are controlled as follows: The low pressure value of the pressure pulse cycle treatment is 0.10 MPa to 0.20 MPa; The high pressure value of the pressure pulse cycle treatment is 0.30 MPa to 0.50 MPa; The pressurization rate during the pressurization phase is 0.08 MPa / min to 0.12 MPa / min, and the depressurization rate during the depressurization phase is 0.15 MPa / min to 0.25 MPa / min.

4. The pressurized oxygen pretreatment method for improving the color of frozen beef according to claim 1, characterized in that, In step S3, the frequency of the ultrasonic generator is set to 20kHz to 40kHz, and the power density of the ultrasonic generator is set to 0.3W / cm². 2 ~0.5W / cm 2 .

5. The pressurized oxygen pretreatment method for improving the color of frozen beef according to claim 1, characterized in that, In step S3, the periodic instantaneous exhaust procedure is executed as follows: During the high-pressure holding stage, the exhaust valve on the sealed pressure-resistant container is opened for 0.5 to 1.0 seconds every 30 to 60 seconds, causing the pressure inside the sealed pressure-resistant container to drop by 0.05 MPa to 0.10 MPa instantly, and then the pressure is automatically restored to the pressure of the high-pressure holding stage.

6. The pressurized oxygen pretreatment method for improving the color of frozen beef according to claim 3, characterized in that, In step S3, the high-pressure holding phase is set to 3 to 5 minutes, and the low-pressure holding phase is set to 1 to 3 minutes; the process of pressurization, high-pressure holding, depressurization, and low-pressure holding is repeated 3 to 5 times.

7. The pressurized oxygen pretreatment method for improving the color of frozen beef according to claim 1, characterized in that, In step S4, the specific execution method of the pressurized undercooling locking process is as follows: Adjust and stabilize the pressure inside the sealed pressure vessel to 0.20 MPa to 0.25 MPa; Simultaneously, the ambient temperature inside the sealed pressure-resistant container is reduced to -3.0℃ to -2.0℃; Allow the mixture to stand for 10 to 20 minutes while maintaining constant pressure and ambient temperature.

8. The pressurized oxygen pretreatment method for improving the color of frozen beef according to claim 1, characterized in that, In step S5, the rapid freezing process is carried out in a quick-freezing machine, and the core temperature of the beef is -25℃ to -15℃ when freezing is completed. The vacuum sealing is performed using high-barrier vacuum skin packaging material.

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