A method for improving the color of fresh meat in vacuum skin packaging

Abstract

The application discloses a method for improving color of vacuum skin packaging fresh meat, and belongs to the technical field of food preservation. The application forms a thick layer of oxygenated myoglobin on the surface of fresh meat by pressure increasing treatment in a high-oxygen environment at the front end of the vacuum skin packaging process, and inhibits the oxygen consumption of mitochondria in fresh meat, thereby solving the problem that the vacuum skin packaging fresh meat is dark purple. In combination with ice temperature control at-1 DEG C, the ability of mitochondria to compete with oxygenated myoglobin for oxygen is further limited, and the proliferation of microorganisms and lipid oxidation are significantly inhibited, thereby achieving an effective balance between meat color stability, microbial inhibition and oxidation control. In order to avoid hard switching of fresh meat from high-oxygen pressure conditions to low residual oxygen state for vacuum skin packaging, and reduce color mutation. The application further adds transition deoxygenation color stabilization treatment and controlled pressure reduction treatment after the pressure increasing color enhancement treatment step, so that the fresh meat is in a transition atmosphere close to atmospheric oxygen concentration, so as to improve the color stability of fresh meat, and reduce the risk of surface damage and local color difference.

Description

Technical Field

[0001] This invention relates to the field of food preservation technology, specifically to a method for improving the color of vacuum-packed fresh meat. Background Technology

[0002] Meat color is the most important indicator determining consumers' willingness to buy fresh meat. Most consumers use meat color as an important measure of meat freshness and hygiene. Therefore, meat color plays a crucial role in the quality evaluation and final pricing of fresh meat.

[0003] As a typical representative of fresh meat display packaging globally, vacuum skin packaging (VSP) is gaining widespread popularity in the meat consumption market due to its advantages such as high vacuum level and no juice loss caused by compression of the packaging film. It is gradually becoming the mainstream packaging method for chilled meat shelf display. However, the anaerobic environment created inside the packaging causes the myoglobin in fresh red meat such as beef to be mainly deoxymyoglobin, resulting in a dark purplish-red appearance that consumers dislike, lacking appeal. This has become a key industry problem restricting the widespread application of VSP technology.

[0004] Fresh meat has a high water content and is rich in protein, making it extremely susceptible to bacterial growth and discoloration. However, it cannot be preserved through cooking, marinating, drying, or the addition of preservatives or color-protecting agents. Instead, a delicate balance must be struck between low temperature, oxygen control, antibacterial properties, and water retention. This makes it far more challenging to process than frozen meat, processed meat, or other meat products. Therefore, improving the color of vacuum-packed fresh meat has always been a major challenge and pain point in the industry. Summary of the Invention

[0005] In view of the above-mentioned prior art, the purpose of this invention is to provide a method for improving the color of vacuum-packed fresh meat. This invention pre-treats the fresh meat before vacuum-packing, and effectively solves the problem of poor meat color in existing vacuum-packed fresh meat by staged control of gas composition and pressure.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for improving the color of vacuum-packed fresh meat includes the following steps: Fresh meat to be vacuum-packed is placed in a sealed cavity, oxygen is introduced into the sealed cavity and pressurized color enhancement treatment is performed to form an oxymyoglobin layer on the surface of the fresh meat. After processing, the pressure is released and vacuum skin packaging is completed. The product is then placed at -1°C for ice-temperature color protection.

[0007] Preferably, the purity of the oxygen introduced is 99%-100%.

[0008] Preferably, the conditions for the pressurization and color enhancement treatment are: pressurize to 0.4-0.6 MPa and maintain it, control the temperature inside the sealed cavity to 1-4℃, and treat under constant temperature and pressure conditions for 24-48 hours.

[0009] This invention places fresh meat under high-oxygen conditions and pressurizes it before vacuum skin packaging. This promotes the formation of a thicker layer of oxymyoglobin in the fresh meat, effectively solving the problem of the dark purplish-red appearance of vacuum-skin packaged fresh meat under hypoxic conditions, thus enhancing the visual appeal of vacuum-skin packaged fresh meat. Furthermore, the high-oxygen and pressurized treatment may damage or kill some microorganisms, thereby slowing down the microbial growth rate during storage and extending the product's microbial shelf life.

[0010] After vacuum skin packaging, -1℃ ice-temperature storage can significantly slow down the rate at which mitochondria compete with oxymyoglobin for oxygen, effectively preventing the conversion of bright red oxymyoglobin to dark purple-red deoxymyoglobin. This, combined with pressurization under high oxygen conditions, has a synergistic color-preserving effect.

[0011] Furthermore, to reduce the interference of raw material differences in fresh meat on subsequent color development, the method of the present invention also includes a step of pre-treating the fresh meat before placing it in the sealed cavity.

[0012] In some preferred embodiments, the method for pre-treating fresh meat is as follows: pre-cool the cut fresh meat at 0-4°C, and select fresh meat with a pH value of 5.4-5.8; then trim the meat pieces to remove excessive free juices from the surface, so that the surface of the meat pieces is moist but without obvious liquid film accumulation.

[0013] The above pretreatment can effectively reduce the interference of raw material differences on subsequent color development and reduce the visual whitening problem caused by surface liquid film after vacuum skin packaging.

[0014] Furthermore, in order to remove some of the ambient air within the sealed cavity, reduce the initial residual oxygen, and decrease the spatial heterogeneity of residual oxygen, a controllable initial atmosphere environment is established; the method of the present invention also includes: placing the fresh meat to be vacuum-packed in the sealed cavity, and performing a pre-evacuation treatment on the sealed cavity before introducing oxygen.

[0015] In some preferred embodiments, the fresh meat to be vacuum-packed is placed in a sealed cavity and pre-evacuated to an absolute pressure of 0.6-0.8 bar.

[0016] The above pre-evacuation process removes some of the ambient air from the sealed cavity and the gaps between meat pieces, improving the efficiency of establishing a high-oxygen atmosphere and reducing the risk of browning of the meat caused by low oxygen partial pressure in the local gaps between meat pieces.

[0017] Furthermore, to avoid the abrupt transition of fresh meat from high-oxygen pressurization conditions to a low-residual-oxygen state awaiting vacuum-sealed packaging, thereby reducing color deterioration, eliminating localized residual oxygen differences, and improving meat color uniformity, the method of this invention further includes: after introducing oxygen and performing pressurization and color enhancement treatment, sequentially performing transitional deoxygenation and color stabilization treatment and controlled depressurization treatment. In some preferred embodiments, the method for transitional oxygen reduction and color stabilization treatment is as follows: after the pressurization and color enhancement treatment is completed, a premixed gas is introduced into the sealed cavity and the pressure is reduced to 0.2-0.3 MPa for 1-2 hours; so that the system transitions from high oxygen color development to low oxygen color stabilization; the composition of the premixed gas is: 20-30 vol% O2, 70-80 vol% N2; The controlled depressurization process involves reducing the pressure to atmospheric pressure at a controlled rate of 0.01 MPa / min.

[0018] Through the above-mentioned transitional deoxygenation and color stabilization treatment, a premixed gas with a concentration close to atmospheric oxygen is introduced and the pressure is simultaneously reduced slowly, so that the fresh meat is in a transitional atmosphere with a composition similar to atmospheric gas. This effectively avoids the sudden drop in meat color stability caused by the meat being quickly exposed to air after the gas pressurization and sealing cavity is opened.

[0019] Controlled depressurization can reduce problems such as localized damage to meat, pale meat color, or abnormal tissue appearance caused by rapid gas escape.

[0020] Furthermore, to more precisely control the thickness of the oxygen and myoglobin layer formed on the surface of fresh meat, the target absolute pressure for the pressurized color enhancement treatment is... P 1,set Take the larger value that satisfies the following two conditions, subject to the equipment's allowable pressure range: First, the oxygen partial pressure inside the treatment chamber should reach the minimum oxygen partial pressure required to form an oxymyoglobin layer. Secondly, the total amount of oxygen available in the free gas phase of the processing chamber should be sufficient to cover the oxygenation requirements of myoglobin within the target surface thickness range. This can be expressed as: in, P 1,set The target absolute pressure, expressed in bar or Pa; P max The maximum allowable absolute pressure of the equipment is given, and the equipment parameters are known. P min The minimum allowable control absolute pressure for the equipment is denoted as , and the equipment parameters are known. The minimum oxygen partial pressure required to form an oxymyoglobin layer can be obtained through preliminary experimental calibration. The oxygen volume fraction in the pressurized and color-enhanced gas is set and known by the gas distribution system. The oxygen supply safety factor is a preset process parameter. The molar concentration of myoglobin per unit volume of fresh meat can be obtained through detection or calibration with similar raw materials. The target oxymyoglobin layer thickness is defined as a preset process parameter. ρ is the gas constant, a known constant; T is the temperature for pressurization and color enhancement treatment, measured by a temperature sensor; ρ is the density of the fresh meat to be treated, which can be obtained through measurement or standard values; Vc is the effective volume of the treatment chamber, a known equipment parameter; m is the mass of the fresh meat to be treated, obtained by weighing; h is the average thickness of the fresh meat to be treated, obtained by measurement.

[0021] Determine the target absolute pressure in the pressurization and color enhancement process. P 1,set Subsequently, the processing chamber preferably employs a linear pressurization method to raise the pressure to the target absolute pressure. The absolute pressure of the processing chamber at time t during the pressurization and color enhancement processing stage is... It can be represented as: in, t represents the initial absolute pressure of the sealed cavity; t is the time for pressurization; t1 is the total time for pressurization and holding.

[0022] In this invention, the pressurization treatment in the pressurization and color enhancement stage is not simply about increasing the chamber pressure, but rather aims to "form an oxygenated myoglobin layer of a predetermined thickness on the surface of the raw meat to be treated." Therefore, the target absolute pressure in the pressurization and color enhancement stage is constrained by both oxygen partial pressure and total oxygen content: on the one hand, the oxygen partial pressure within the treatment chamber needs to reach the minimum level required for myoglobin oxygenation; on the other hand, the total oxygen content in the free gas phase of the treatment chamber should be sufficient to meet the oxygenation requirements of myoglobin within the target surface thickness range.

[0023] Based on this, the present invention uses the above-mentioned target absolute pressure formula to calculate the target pressure of the pressurization and color enhancement treatment stage, and uses a linear pressurization method to raise the pressure to the target pressure within a set time, while ensuring that the total time of the pressurization and color enhancement treatment stage is not less than the minimum characteristic time required for oxygen to diffuse to the target layer thickness, thereby improving the controllability and repeatability of the formation of the surface oxygenated myoglobin layer.

[0024] The beneficial effects of this invention are: (1) It is generally believed in the industry that vacuum skin packaging (VSP) will inevitably cause the meat to turn purple due to the lack of oxygen. Moreover, for fresh meat, due to the requirements of relevant regulations, it is impossible to improve the problem of purple color caused by VSP by adding color-protecting ingredients. Therefore, it has always been a technical problem in this field.

[0025] To address this industry-wide technical challenge, this invention employs a high-oxygen environment pressurization process at the front end of the VSP process to form a thicker layer of oxymyoglobin on the surface of fresh meat and inhibit mitochondrial oxygen consumption in the fresh meat, thereby solving the problem of dark purplish-red color in vacuum-packed fresh meat. Furthermore, the -1°C ice-temperature environment further slows down the growth rate of microorganisms and the degree of lipid oxidation, thus achieving a balance between meat color stability, microbial inhibition, and oxidation control.

[0026] (2) To avoid the abrupt transition of fresh meat from high-oxygen pressurization conditions to a low-residual-oxygen state awaiting vacuum-sealed packaging, thereby reducing color abrupt changes, eliminating local residual oxygen differences, and improving the uniformity of meat color, this invention further adds a transitional deoxygenation and color stabilization treatment and a controlled depressurization treatment after the pressurization and color enhancement step. A premixed gas containing atmospheric oxygen concentration is introduced while the pressure is simultaneously and slowly reduced, placing the fresh meat in a low-oxygen transitional atmosphere with a composition similar to atmospheric conditions, thus reducing the risk of color stability deterioration. Through the controlled depressurization treatment, problems such as localized damage, whitening, or abnormal tissue appearance in fresh meat caused by rapid gas escape can be reduced.

[0027] (3) In order to more accurately control the thickness of the oxygen and myoglobin layer formed on the surface of fresh meat, the present invention also designed a target absolute pressure formula, calculates the target pressure of the pressure boosting and color enhancement treatment stage, and adopts a linear pressure boosting method to reach the target pressure within a set time, while ensuring that the total time of the pressure boosting and color enhancement treatment stage is not less than the minimum characteristic time required for oxygen to diffuse to the target layer thickness, thereby improving the controllability and repeatability of the formation of the surface oxygenated myoglobin layer. Attached Figure Description

[0028] Figure 1 Photos showing vacuum-packed steaks from each processing group after 20 days of storage.

[0029] Figure 2 Effects of different treatments on the proportions of three myoglobins in vacuum-packed steaks; In the figure, MMb: metmyoglobin; DMb: deoxymyoglobin; OMb: oxymyoglobin. Detailed Implementation

[0030] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0031] To enable those skilled in the art to more clearly understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments. If specific experimental conditions are not specified in the embodiments, they are generally based on conventional conditions or conditions recommended by the reagent company; the reagents, consumables, etc. used in the following embodiments, unless otherwise specified, can be obtained commercially. Wherein: The fresh meat used came from Simmental crossbred cattle of similar age, live weight, and pre-slaughter management conditions; after the carcasses were refrigerated at 0-4℃ for 48 hours to remove acid, the pH value of the left and right halves of the carcass was measured using a portable pH meter, and the longissimus dorsi muscle with a pH value between 5.4 and 5.8 was selected. M. longissimus lumborum Remove visible fat, tendons, and connective tissue, and cut into steaks 2.54cm thick.

[0032] Example 1: A method for improving the color of vacuum-packed fresh meat The steak to be vacuum-packed is placed in a sealed cavity, and oxygen with a purity of 99%-100% is introduced into the sealed cavity and pressurized color enhancement treatment is performed to form an oxymyoglobin layer on the surface of the steak. The conditions for pressurized color enhancement treatment are: pressurize to 0.4 MPa and maintain it, control the temperature in the sealed cavity at 0-4℃, and process under constant temperature and pressure conditions for 24 hours.

[0033] After processing, depressurize and immediately complete vacuum sealing packaging, then store at -1℃.

[0034] Example 2: A method for improving the color of vacuum-packed fresh meat The steak to be vacuum-packed is placed in a sealed cavity, and oxygen with a purity of 99%-100% is introduced into the sealed cavity and pressurized color enhancement treatment is performed to form an oxymyoglobin layer on the surface of the steak. The conditions for pressurized color enhancement treatment are: pressurize to 0.4 MPa and maintain it, control the temperature in the sealed cavity at 0-4℃, and process under constant temperature and pressure conditions for 48 hours.

[0035] After processing, depressurize and immediately complete vacuum sealing packaging, then store at -1℃.

[0036] Example 3: A method for improving the color of vacuum-packed fresh meat 1. Pre-evacuation treatment: Place the steak to be vacuum-packed in a sealed cavity and pre-evacuate it to an absolute pressure of 0.6-0.8 bar.

[0037] 2. Voltage boosting and color enhancement treatment: Oxygen with a purity of 99%-100% is introduced into a pre-evacuated sealed cavity and pressurized for color enhancement, forming an oxymyoglobin layer on the surface of the steak. The conditions for pressurized for color enhancement are: pressurize to 0.4 MPa and maintain it, control the temperature in the sealed cavity to 0-4℃, and process under constant temperature and pressure conditions for 24 hours.

[0038] 3. Transitional oxygen reduction and color stabilization treatment: After the pressurization and color enhancement treatment is completed, a premixed gas is introduced into the sealed cavity and the pressure is reduced to 0.3 MPa for 1 hour; this allows the system to transition from high-oxygen color development to low-oxygen color stabilization; the composition of the premixed gas is: 20 vol% O2 and 80 vol% N2.

[0039] 4. Controlled pressure reduction treatment: After the transitional deoxygenation and color stabilization treatment was completed, the pressure was controlled to atmospheric pressure at a rate of 0.01 MPa / min.

[0040] 5. Vacuum-sealed skin packaging and storage: After controlled depressurization to atmospheric pressure, vacuum skin packaging is immediately completed, and the product is stored at -1°C.

[0041] Comparative Example 1: To simulate standard industry practices, the steaks were packaged on trays and then placed in atmospheric air at 0-4℃ for color development. After 24 hours, the steaks were immediately vacuum-sealed and stored at -1℃.

[0042] Comparative Example 2: The difference from Example 1 is that the storage temperature after vacuum skin packaging is adjusted to 4°C.

[0043] Comparative Example 3: The difference from Example 3 is that the "transitional oxygen reduction and color stabilization treatment" step is omitted; after the pressure boosting and color enhancement treatment is completed, the controlled pressure reduction treatment is carried out directly and the pressure is reduced to normal.

[0044] Comparative Example 4: The difference from Example 3 is that the "controlled depressurization treatment" step is omitted; the pressure is released immediately after the transitional deoxygenation and color stabilization treatment is completed, and the pressure release is completed within 10 seconds.

[0045] Experimental example: 1. Test method: Steaks from the same cow were mixed thoroughly and then randomly assigned to different processing groups, as follows: Processing Group 1 (T1): Steaks were processed using the method of Example 1; Processing Group 2 (T2): The steak was processed using the method of Example 2; Processing Group 3 (T3): The steak was processed using the method of Example 3; Processing Group 4 (T4): The steaks were processed using the method described in Comparative Example 1; Processing Group 5 (T5): The steaks were processed using the method of Comparative Example 2; Processing Group 6 (T6): The steaks were processed using the method described in Comparative Example 3; Treatment Group 7 (T7): The steaks were treated using the method described in Comparative Example 4.

[0046] Samples were taken from each treatment group at 0, 10, and 20 days of storage to determine the meat color index of each vacuum-packed steak. L , a , b , C , h The content of three types of myoglobin and the total bacterial count were measured. The determination methods are as follows: (1) Determination of flesh color index: The brightness value of the steak surface was directly measured at various storage time points using a portable colorimeter (8 mm aperture, light source A, standard viewing angle 10°). （ Lightness L ）、 Redness value （ Redness a ) 、 Yellowness value （ Yellowness b ）、 Color saturation (Chroma) C ) and hue angle (Hue, h Chroma = ( a 2 + b 2 ) 1 / 2 Hue = arctan( b / a The reflectance R value was recorded between 360 and 780 nm (spectral spacing: 10 nm) and used to calculate myoglobin content. Measurements were taken at six different locations randomly selected from each steak, and the results were recorded and averaged.

[0047] (2) Determination of the content of three types of myoglobin: The relative proportions of the three myoglobins were calculated following the method of Feng et al. (2025). The relative proportions of deoxymyoglobin (DMb), oxymyoglobin (OMb), and metmyoglobin (MMb) were calculated using the following formula.

[0048] A = log (1 / R) %OMb = 100 - (%MMb + %DMb) (3) Total bacterial count determination: The determination of total bacterial count was based on the method of Yang Xiaoyin (2018) with slight modifications. Under aseptic conditions, 25 g of meat samples were randomly cut from the surface of the steak and placed in a beater bag. 225 mL of sterile peptone saline (0.85% NaCl, 0.1% peptone) was added to the beater bag, and the bag was then beat for 90 s. One mL of the mixed bacterial solution was serially diluted 10-fold. Appropriate dilutions were selected, and bacterial solutions were transferred to plate counting agar. Each dilution was performed in triplicate and incubated at 37°C for 48 h. The total bacterial count result is expressed as log CFU / g.

[0049] 2. Test Results: (1) Effects of different treatments on the color index of vacuum-packed steak: Meat color is an important indicator for evaluating the quality of fresh meat. Consumers often use color as a reference to measure the freshness and hygiene of beef. L The value is the brightness of flesh color. L The higher the value, the brighter the flesh tone; a The value is the redness value. a A higher value indicates a brighter red flesh color, which is more popular with consumers. b The value is the yellowness value. b The higher the value, the more yellow the flesh color; C The value is color saturation. C A higher value indicates a higher color saturation of the steak, and a more vibrant meat color; h The value is the hue angle. h A higher value indicates a greater hue angle in the steak. The results of measuring the color index of vacuum-packed steaks under different treatments are shown in Tables 1-5.

[0050] The results showed that, as shown in Table 1, on day 0 of storage, compared to treatment group 4 which underwent standard industrial air coloring, the steaks in treatment groups 2 and 3 had significantly lower yields. L The significantly improved color value is mainly due to the pressurized color enhancement treatment, which promotes the full oxygenation of deoxymyoglobin to form bright red oxymyoglobin. Extending the pressurized color enhancement treatment time or pre-evacuating to remove residual oxygen from the sealed cavity also helps improve the steak's shine. Furthermore, high pressure may cause subtle changes in the muscle fiber structure, increasing light scattering and thus enhancing the steak's color. L The value increased. With prolonged storage time, the value of the steaks in treatment group 3 increased. L The value was significantly higher than that of other groups of steaks, exhibiting the brightest color.

[0051] Compared to treatment group 5, at a normal refrigeration temperature of 4°C, the steak in treatment group 5... L The value decreased significantly with storage time, while -1℃ ice-temperature storage significantly improved the steak quality compared to treatment group 5. L The value indicates that a chilled environment helps maintain the brightness stability of steaks treated with pressurization and color enhancement.

[0052] Table 1: Effects of different treatments on vacuum-packed steaks L The influence of value Note: a-f This indicates that there are significant differences between different values ​​in the same column. P <0.05) x-z This indicates that there are significant differences between different values ​​in the same row. P <0.05) By processing group 3 L Compared with treatment groups 1, 6, and 7, it was found that, based on treatment group 1, adding the steps of "transitional deoxygenation and color stabilization treatment" and "controlled depressurization treatment" can synergistically improve the brightness of vacuum-packed steaks.

[0053] Table 2: Effects of different treatments on vacuum-packed steaks a The influence of value Note: a-e This indicates that there are significant differences between different values ​​in the same column. P <0.05) x-z This indicates that there are significant differences between different values ​​in the same row. P <0.05) The results showed that: beef a The color value directly reflects the degree of redness of the beef and is a core indicator for judging the color of beef. As shown in Table 2, on day 0 of storage, compared with the existing conventional air coloring (treatment group 4), the beef steaks in treatment groups 1-3... a The significant improvement is due to two main factors. First, the pressurized color-enhancing treatment promotes the dissolution and penetration of oxygen into the deep muscle layers, forming a thicker layer of oxymyoglobin. Second, the treatment causes irreversible damage to the mitochondria in beef, reducing their oxygen consumption rate and decreasing the competitive consumption of oxygen in the already formed oxymyoglobin by mitochondrial respiration, thus enhancing the steak's color development. The steaks in treatment groups 1, 2, 3, 6, and 7... a The value remained above 27 throughout the entire storage period, significantly higher than the consumer sensory acceptance threshold of 14.5, and the appearance was a bright cherry red, demonstrating excellent flesh color stability.

[0054] Steaks from processing groups 4 and 5 a The value decreased significantly with prolonged storage time and was significantly lower than that of other groups of steaks. a Value, processing group 5 steaks a The mitochondrial concentration even fell below the threshold of 14.5 towards the end of storage, demonstrating a clear defect in maintaining the bright red appearance of the beef over a long period. Furthermore, compared to ice-temperature storage, the higher storage temperature of the treated group 5 steaks resulted in stronger mitochondrial activity, leading to a faster competition for oxygen with oxymyoglobin, significantly exacerbating the defects of vacuum-packed steaks. a The value decreased. The above results indicate that surface pressure enhancement and color enhancement treatment, combined with ice-temperature storage, can impart an appealing bright red appearance to vacuum-packed steaks over a long period. Figure 1 ).

[0055] Processing of steaks in groups 3, 6, and 7 during storage a The value was consistently higher than that of the steak in treatment group 1, and the value of the steak in treatment group 3 was also higher. a The value remained at the highest level among all treatment groups. P The value <0.05 indicates that, based on treatment group 1, further adding the steps of "transitional deoxygenation and color stabilization treatment" and "controlled depressurization treatment" can synergistically improve the quality of vacuum-packed steaks. a The color stability of the meat during storage ensures a significant extension of the shelf life of vacuum-packed steaks.

[0056] Table 3: Effects of different treatments on vacuum-packed steaks b The influence of value Note: a-e This indicates that there are significant differences between different values ​​in the same column. P <0.05) x-z This indicates that there are significant differences between different values ​​in the same row. P <0.05) The results showed that, as shown in Table 3, the steaks in treatment group 3 remained relatively stable throughout. b Value outside ( P >0.05), other groups of steaks b The values ​​showed a significant decreasing trend with prolonged storage time. Notably, the values ​​of steaks in treatment groups 4 and 5... b The value was consistently significantly lower than that of steaks in treatment groups 1, 2, 3, 6, and 7. b The value also suggests that these two groups of steaks have a higher content of methemoglobin and poorer color stability.

[0057] Processing of steaks in groups 3, 6, and 7 during storage b The value was consistently higher than that of the steak in treatment group 1, indicating that by adding the steps of "transitional deoxygenation and color stabilization treatment" and "controlled depressurization treatment" on the basis of treatment group 1, the yellowness of the vacuum-packed steak could be synergistically improved.

[0058] Table 4: Effects of different treatments on vacuum-packed steaks C The influence of value Note: a-f This indicates that there are significant differences between different values ​​in the same column. P <0.05) x-z This indicates that there are significant differences between different values ​​in the same row. P <0.05) The results showed that, as shown in Table 4, on day 0 of storage, compared with the existing conventional air coloring (treatment group 4), the steaks in treatment groups 1, 2, 3, 5, 6, and 7 had significantly different color development rates. C The values ​​were significantly improved, indicating that the pressurized color-enhancing treatment effectively promoted the binding of oxygen and myoglobin, forming a thicker layer of oxymyoglobin and thus significantly improving the color saturation of the steak. a The values ​​showed a consistent trend, with the steaks in treatment groups 4 and 5 exhibiting similar changes. C The value decreased significantly with prolonged storage time and was significantly lower than that of other groups of steaks. C The color stability is poor, and the steak cannot maintain its bright red color during anaerobic storage for a long time.

[0059] Processing of steaks in groups 3, 6, and 7 during storage C The values ​​were significantly higher than those of the steaks in treatment group 1, especially the steaks in treatment group 3, which consistently maintained the highest values. C value( P The value <0.05 indicates that, based on treatment group 1, the addition of "transitional deoxygenation and color stabilization treatment" and "controlled depressurization treatment" steps can synergistically improve the color saturation of vacuum-packed steaks, giving them a more appealing consumer appearance.

[0060] Table 5: Effects of different treatments on vacuum-packed steaks h The influence of value Note: a-c This indicates that there are significant differences between different values ​​in the same column. P <0.05) x-z This indicates that there are significant differences between different values ​​in the same row. P <0.05) The results showed that, as shown in Table 5, on day 0 of storage, the steaks in treatment group 4... h The value was significantly higher than that of the other groups of steaks, indicating a large difference in hue between the conventionally air-colored steaks and the pressurized color-enhanced steaks. This is mainly due to the brighter red color of the pressurized color-enhanced steaks. During storage, the steaks in treatment groups 4 and 5 showed... h The values ​​all showed an upward trend, and were significantly higher than those of other groups of steaks in the later stages of storage. h This value is consistent with the rapid fading of the bright red color of the steaks in the later stages of cooking. Figure 1 ).

[0061] (2) Effects of different treatments on the ratio of three myoglobins in vacuum-sealed packaged steak: Browning of meat is mainly due to the accumulation of methemoglobin caused by the oxidation of oxymyoglobin and deoxymyoglobin on the surface of beef. Therefore, the relative content of oxymyoglobin and methemoglobin on the surface of beef is an important factor affecting meat color.

[0062] The effects of different treatments on the ratio of three myoglobins in vacuum-sealed packaged steaks, such as Figure 2 As shown, in treatment groups 1, 2, 3, 6, and 7, bright red oxymyoglobin was dominant in the steaks throughout the storage period, determining the overall dominance. Figure 2 After conventional air coloring, steaks stored under anaerobic conditions experience a limited initial formation of oxymyoglobin. Mitochondrial respiration competes with oxymyoglobin for oxygen, causing it to initially transform into brownish-red methemoglobin under lower oxygen partial pressures. Ultimately, it undergoes complete deoxygenation, forming dark purplish-red deoxymyoglobin. Figure 2 This process will cause the steak to... a The value decreased significantly, which corresponds to the results in Table 2.

[0063] (3) Effects of different treatments on the total bacterial count of vacuum-packed steak: The results, as shown in Table 6, indicate that compared to steaks treated with conventional air coloring (treatment group 4), the total bacterial count of steaks treated with pressurized color enhancement was significantly lower at the same storage temperature. This suggests that the pressurized color enhancement treatment for fresh meat designed in this study not only has color-protecting properties but also antibacterial properties. This may be because the application of high-concentration, high-pressure oxygen during the pressurized color enhancement process induces the production of a large number of reactive oxygen species (ROS) within bacterial cells. These ROS attack the bacterial membrane phospholipid structure and DNA, causing bacterial damage and thus prolonging the lag phase of microbial growth and reducing its logarithmic growth rate. Furthermore, regarding the storage temperature after vacuum-packed steaks, compared to conventional 4°C refrigeration, a -1°C ice-temperature storage environment significantly extends the microbial shelf life of the packaged steaks. Notably, among all treatment groups, treatment group 3 showed the best preservation effect for vacuum-packed steaks, which may be related to the synergistic effect of the "transitional deoxygenation color stabilization treatment" combined with the "controlled depressurization treatment."

[0064] Table 6: Effects of different treatments on total bacterial count (logCFU / g) of vacuum-packed steak Note: a-c This indicates that there are significant differences between different values ​​in the same column. P <0.05) x-z This indicates that there are significant differences between different values ​​in the same row. P <0.05) The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for improving the color of vacuum-packed fresh meat, characterized in that, Includes the following steps: Fresh meat to be vacuum-packed is placed in a sealed cavity, oxygen is introduced into the sealed cavity and pressurized color enhancement treatment is performed to form a bright red oxymyoglobin layer on the surface of the fresh meat. After processing, the pressure is released and vacuum skin packaging is completed. The product is then placed at -1°C for ice-temperature color protection.

2. The method for improving the color of vacuum-packed fresh meat according to claim 1, characterized in that, The purity of the oxygen introduced is 99%-100%.

3. The method for improving the color of vacuum-packed fresh meat according to claim 1, characterized in that, The conditions for pressurization and color enhancement treatment are as follows: oxygen is pressurized to 0.4-0.6 MPa and maintained, the temperature inside the sealed chamber is controlled at 1-4℃, and the treatment is carried out under constant temperature and pressure conditions for 24-48 hours.

4. The method for improving the color of vacuum-packed fresh meat according to claim 1, characterized in that, The method further includes a step of pre-treating the fresh meat before placing it in the sealed cavity; The method for pre-treating fresh meat is as follows: pre-cool the cut fresh meat at 0-4℃ and select fresh meat with a pH of 5.4-5.8; then trim the meat pieces to remove excessive free juices on the surface, so that the surface of the meat pieces is moist but without obvious liquid film accumulation.

5. The method for improving the color of vacuum-packed fresh meat according to claim 1, characterized in that, The method further includes the step of placing the fresh meat to be vacuum-packed in a sealed cavity and pre-evacuating the sealed cavity before introducing oxygen.

6. The method for improving the color of vacuum-packed fresh meat according to claim 1, characterized in that, The method further includes the steps of introducing oxygen and performing pressure-increasing color enhancement treatment, followed by a transitional oxygen reduction and color stabilization treatment and a controlled pressure reduction treatment.

7. The method for improving the color of vacuum-packed fresh meat according to claim 6, characterized in that, The method for transitional oxygen reduction and color stabilization treatment is as follows: after the pressure enhancement and color enhancement treatment is completed, a premixed gas is introduced into the sealed cavity and the pressure is reduced to 0.2-0.3 MPa for 1-2 hours; so that the gas system transitions from a high-oxygen color-developing atmosphere to a low-oxygen color-stabilizing atmosphere; the composition of the premixed gas is: 20-30 vol% O2, 70-80 vol% N2.

8. The method for improving the color of vacuum-packed fresh meat according to claim 6, characterized in that, The controlled depressurization process involves reducing the pressure to atmospheric pressure at a controlled rate of 0.01 MPa / min.

9. The method for improving the color of vacuum-packed fresh meat according to claim 1, characterized in that, The target absolute pressure of the boost color enhancement treatment P 1,set The conditions are calculated and determined based on the minimum oxygen partial pressure required for the formation of the oxymyoglobin layer and the oxygen supply conditions of the target surface layer, and must satisfy the following: in, P max The maximum absolute pressure allowed by the equipment; P min The minimum absolute control pressure allowed by the equipment; The minimum oxygen partial pressure required for the formation of an oxymyoglobin layer; The oxygen volume fraction in the pressurized and color-enhanced gas; To ensure a safety margin for oxygen supply; This represents the molar concentration of myoglobin per unit volume of fresh meat. The target is the thickness of the oxygenated myoglobin layer; It is the gas constant; The temperature for pressure-boosting and color enhancement treatment; Density of the raw meat to be processed; The effective volume of the processing cavity; m is the mass of the fresh meat to be processed; h is the average thickness of the fresh meat to be processed.

10. The method for improving the color of vacuum-packed fresh meat according to claim 9, characterized in that, The pressure for the boost color enhancement process is linearly increased according to the following relationship: in, P 0 t represents the initial absolute pressure of the sealed cavity; t is the time for pressurization; t1 is the total time for pressurization and holding.

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