Method for assisting long-term frozen storage and unfreezing of prefabricated meat based on electrostatic field

Abstract

The invention relates to the technical field of food processing, in particular to a method for assisting long-term frozen storage and unfreezing of prefabricated meat based on an electrostatic field. The method comprises the following steps: pretreatment: cutting fresh beef, and pickling; pre-cooking is performed; cooking the pickled beef until the central temperature is 50 DEG C; cooling is performed; sealing the cooked beef with a sealing bag, and placing the sealed beef in a freezing chamber at-38 DEG C until the central temperature is reduced to-18 DEG C; freezing and storing; and transferring the quick-frozen prefabricated beef into a freezing chamber at-18 DEG C, and applying a high-voltage electrostatic field for long-term freezing. According to the invention, through the synergistic cooperation of a specific freezing storage mode and a corresponding unfreezing method, the juice loss in the unfreezing and cooking processes after long-term freezing storage is greatly reduced, and through the synergistic combination of pickling, low temperature, high humidity, segmented temperature control and a low-voltage electrostatic field and the evidence of experimental data, the product quality is improved. And extremely low unfreezing loss, excellent water-retaining property, nutrition and safety indexes can be realized after long-time frozen storage.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to a method for long-term freezing and thawing of pre-prepared meat based on electrostatic field-assisted freezing. Background Technology

[0002] In industrial meat production, the thawing effect of frozen pre-processed meat products directly affects subsequent processing efficiency and finished product quality. Currently, commonly used thawing methods mainly include natural air thawing, static thawing in cold storage, and hydrostatic thawing. While each has its applications, they all have significant limitations. Natural air thawing is simple to operate, but it takes a long time, and the temperature is difficult to control precisely, easily leading to excessive microbial growth and significant juice loss. While refrigerated thawing can better maintain product quality, it is too time-consuming, severely impacting production efficiency. Hydrostatic thawing, with its high heat transfer efficiency, can shorten thawing time to some extent, but it easily causes cross-contamination and color deterioration, posing food safety risks. Furthermore, while emerging thawing technologies such as microwave, radio frequency, and high-voltage electric fields show certain advantages in quality preservation, their large-scale application in industrial production is limited by factors such as complex equipment, high investment costs, and low process standardization. DENBA+ electrostatic field technology is a novel assisted defrosting method. It uses a high-voltage electrostatic field to induce resonance and activation of water molecules, thereby improving heat and mass transfer efficiency, reducing the damage of ice crystals to muscle structure, and effectively maintaining the quality of defrosted products.

[0003] DENBA+ electrostatic field technology is a novel assisted thawing method. Its principle is to generate a high-intensity (e.g., 10-25kV), low-frequency (e.g., 50Hz) alternating electrostatic field, which induces water molecules to align (dipole orientation) and activate, thereby inhibiting ice crystal growth and improving heat and mass transfer efficiency, effectively maintaining the quality of thawed products. In the actual operation of food companies, facing personnel shortages or drastic order fluctuations, factories require a highly flexible production plan. They want to be able to quickly put frozen raw materials into production without relying on complex human experience or long-term precise planning. However, this need presents a significant contradiction with the quality deterioration caused by traditional freezing technologies. Under current technology, pre-frozen meat that has been frozen for a long time generally suffers from severe juice loss, dull color, and deteriorated texture after thawing, its quality being far from that of fresh meat and unable to meet the production requirements of high-quality dishes. There is a need to find a method that can minimize the deterioration of key quality indicators such as color, flavor, and texture of pre-frozen meat during thawing, even in the case of long-term storage.

[0004] Therefore, it is necessary to invent a method for long-term freezing and thawing of pre-prepared meat based on electrostatic field assistance to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for long-term freezing and thawing of pre-prepared meat based on electrostatic field assistance. By using an electrostatic field device with specific parameters and an optimized freezing and thawing method, the dipole oscillation effect of the electrostatic field on water molecules is utilized to effectively suppress ice crystal recrystallization during freezing and juice loss during thawing. This achieves the goal of significantly reducing the deterioration of key quality indicators such as color, flavor, and texture of pre-prepared meat after long-term freezing and thawing.

[0006] To achieve this objective, the present invention adopts the following technical solution: A method for long-term frozen storage and thawing of pre-prepared meat based on electrostatic field assistance is provided, including the following steps; Pre-treatment: The fresh beef is cut into pieces and then marinated; Precook; steam the marinated beef until the core temperature reaches 50°C; Cooling; after steaming, seal the beef in a sealed bag and place it in a freezer at -38°C until the core temperature drops to -18°C; Frozen storage; the quick-frozen pre-prepared beef is transferred to a freezer at -18°C for long-term frozen storage; During the freezing process, an electrostatic field device that can resonate with water molecules through electrostatic waves is activated. The operating parameters of the electrostatic generator are: input voltage 200-240V, continuous stable output voltage 18-22kV, current 0.5-1.5mA, and frequency 50Hz. Thawing; The frozen meat blocks are placed in a thawing chamber equipped with a low-voltage electrostatic field and programmable temperature and humidity control, and the following six stages of temperature, humidity and wind speed conditions are executed in sequence. In each stage, the center temperature of the meat blocks and the relative humidity in the chamber are monitored in real time by sensors and closed-loop regulation is performed. Phase 1: Ambient temperature 14-18℃, relative humidity 80-99%, wind speed 1.5-2.5m / s, until the surface temperature of the meat reaches -3℃ to -1℃; Phase Two: Ambient temperature 12-15℃, relative humidity 80%~99%, wind speed 1.5~2.5m / s, until surface temperature 0℃ to 3℃ and center temperature -2℃ to -1℃; Phase 3: Ambient temperature 11-14℃, relative humidity 80%~99%, wind speed 1.0~2.0m / s, so that the core temperature rises to 0℃ to 1℃; Phase 4: Ambient temperature 10-13℃, relative humidity 80%~99%, wind speed 1.0~2.0m / s, causing the core temperature to rise to 1℃ to 2℃; Phase 5: Ambient temperature 8-12℃, relative humidity 80%~99%, wind speed 0.5~1.5m / s, to stabilize the center temperature at 2℃±0.5℃; Phase Six: Turn off the electrostatic field, maintain the ambient temperature of the thawing chamber at 6-10℃, relative humidity at 80%~99%, wind speed ≤1.0m / s, and keep the core temperature between 2℃ and 4℃, and allow it to stand at 0-4℃ for temperature uniformity. After the pre-cooked meat has been thawed, it is transferred to a 0-4℃ cold storage for further processing.

[0007] As a preferred embodiment of a method for long-term freezing and thawing of pre-prepared meat based on electrostatic field assistance, the long-term freezing time in the freezing step does not exceed 45 days.

[0008] As a preferred embodiment of a method for long-term freezing and thawing of pre-prepared meat based on electrostatic field assistance, in stage six, the pre-prepared meat is left to stand at 0-4℃ for 0.5 to 2 hours to achieve uniform temperature.

[0009] As a preferred embodiment of a method for long-term freezing and thawing of pre-prepared meat based on electrostatic field assistance, the electrostatic wave frequency generated by the electrostatic field device is the frequency that causes water molecules to resonate.

[0010] As a preferred method for long-term freezing and thawing of pre-prepared meat based on electrostatic field assistance, the beef is cut into pieces of 15cm*10cm*5cm in the pretreatment step.

[0011] As a preferred method for long-term freezing and thawing of pre-prepared meat based on electrostatic field assistance, the marinating materials in the pretreatment step are 1-2 parts of edible salt, 2-3 parts of monosodium glutamate, 1-3 parts of white sugar, 1 part of compound water-retaining agent, and 2-3 parts of rice wine, etc.

[0012] As a preferred method for long-term freezing and thawing of pre-prepared meat based on electrostatic field assistance, the marinating temperature in the pretreatment step is 0-4℃ and the time is 48-72h.

[0013] As a preferred method for long-term freezing and thawing of pre-cooked meat based on electrostatic field-assisted freezing, after pre-cooking, the meat is air-cooled for 1-3 hours and then placed in a freezer at -38°C.

[0014] The beneficial effects of this invention are as follows: Through a specific freezing method and a corresponding thawing method, the synergistic combination of the two greatly reduces the loss of juice during thawing and cooking after long-term freezing. Through the synergistic combination of pickling, low temperature, high humidity, segmented temperature control and low-voltage electrostatic field, and supported by experimental data, it is possible to achieve extremely low thawing loss, excellent water retention, color, nutrition and safety indicators after long-term freezing. Experiments have shown that applying an electrostatic field with a frequency of 50Hz and a voltage of 18-22kV during frozen storage can significantly inhibit the recrystallization of ice crystals through the continuous dipole oscillation of water molecules, thereby improving the distribution and water retention of moisture in beef. With prolonged frozen storage time, beef stored under electrostatic field assistance exhibits a better yield retention effect than beef stored at conventional -18℃, especially within 45 days of frozen storage, where the yield is significantly higher than that of the ordinary frozen storage group. Experiments have shown that during the thawing process, the synergistic effect of an electrostatic field of the same frequency and a low-temperature, high-humidity variable-temperature thawing method results in the lowest thawing loss (approximately 1.05%), a significant reduction in cooking loss (approximately 16.4%), excellent water retention, good color retention, L* and a* values ​​close to those of fresh meat, stable b* value, reduced shear force, improved tenderness, and low TVB-N (approximately 7.47 mg / 100g) and TBARS (approximately 0.29 mg / kg) values. Freshness and oxidative stability are significantly improved, with the highest total sulfhydryl content (approximately 1.24 μmol / g) and the lowest degree of protein oxidation. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0016] Figure 1 Changes in pH value during the storage of pre-processed beef; Figure 2 Color changes in prepared beef during frozen storage; Figure 3 Changes in cooking losses during the freezing of pre-prepared beef; Figure 4 Changes in shear force during frozen storage of pre-prepared beef; Figure 5 Changes in TVB-N during frozen storage of pre-prepared beef; Figure 6 Images of moisture distribution and H proton density during frozen storage of pre-prepared beef; Figure 7 Changes in the yield of finished products from pre-prepared beef with different freezing times; Figure 8 The effects of different thawing methods on thawing loss (a) and cooking loss (b) of pre-prepared beef; Figure 9 The effect of different thawing methods on the pH of pre-prepared beef; Figure 10 The effect of different thawing methods on the color of pre-cooked beef; Figure 11 The effect of different thawing methods on the shear force of pre-prepared beef; Figure 12 The effect of different thawing methods on TVB-N in pre-prepared beef; Figure 13 The effect of different thawing methods on pre-prepared beef TBARS; Figure 14 The effect of different thawing methods on the thiol groups in pre-processed beef. Detailed Implementation

[0017] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0018] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual images. They should not be construed as limiting the scope of this patent. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0019] Includes the following steps; Pre-treatment: Fresh beef is cut into pieces and marinated; cutting fresh beef into uniform sizes and marinating effectively inhibits bacterial growth and enhances the tenderness and juiciness of the beef; compound water-retaining agents help reduce moisture loss during subsequent cooking and improve the texture of the finished product; ensure that the beef has enhanced flavor and water retention during subsequent freezing and thawing.

[0020] Pre-cook; steam the marinated beef until the core temperature reaches 50℃; control the core temperature at 50℃ to avoid overheating and excessive protein denaturation, thereby preserving the original flavor and nutrition of the beef.

[0021] Cooling; After steaming and cooking, the beef is sealed in a sealed bag and placed in a freezer at -38°C until the core temperature drops to -18°C; air cooling quickly lowers the surface temperature to prevent overcooking due to residual heat; sealed packaging prevents the beef from coming into contact with air during freezing, reducing oxidation and frostbite; quick freezing at -38°C allows the beef to pass through the ice crystal formation zone quickly, minimizing ice crystal size, protecting cell structure, reducing juice leakage during thawing, and maintaining the texture of the beef; Frozen storage: The quick-frozen pre-prepared beef is transferred to a -18℃ freezer for long-term frozen storage. During the freezing process, the DENBA+ electrostatic field device is activated. The operating parameters of its electrostatic generator are: input voltage 200-240V, continuous stable output voltage 18-22kV, current 0.5-1.5mA, and frequency 50Hz. This low-frequency, high-voltage alternating electrostatic field can cause water molecules to generate strong dipole oscillations and orientation movements, disrupting the regular growth of ice crystals and forming a fine, uniform distribution. This maximizes the protection of the integrity of muscle cells, laying the foundation for high-quality thawing after long-term frozen storage. During the freezing process, an electrostatic field device capable of resonating with water molecules through electrostatic waves is activated. Thawing: Place the frozen meat pieces into a thawing chamber equipped with a low-voltage electrostatic field (operating parameters: input voltage 200-240V, continuous stable output voltage 15-25kV, current 0.5-1.5mA, frequency 50Hz) and programmable temperature and humidity control. Sequentially execute the following six stages of temperature, humidity, and wind speed conditions, and in each stage, use sensors to monitor the center temperature of the meat pieces and the relative humidity inside the chamber in real time and perform closed-loop regulation. Phase 1; (Thawed surface) Ambient temperature 14-18℃, relative humidity 80-99%, wind speed 1.5-2.5m / s, until the surface temperature of the meat product is -3℃ to -1℃; Phase Two; (Further thawing of the surface) Ambient temperature 12-15℃, relative humidity 80%~99%, wind speed 1.5~2.5m / s, until the surface temperature is 0℃ to 3℃ and the core temperature is -2℃ to -1℃; Phase 3; (Crossing the ice crystal zone) Ambient temperature 11-14℃, relative humidity 80%~99%, wind speed 1.0~2.0m / s, causing the core temperature to rise to 0℃ to 1℃; Phase 4; (Central thawing) Ambient temperature 10-13℃, relative humidity 80%~99%, wind speed 1.0~2.0m / s, to raise the central temperature to 1℃ to 2℃; Phase 5; (Temperature Settling) Ambient temperature 8-12℃, relative humidity 80%~99%, wind speed 0.5~1.5m / s, to stabilize the center temperature at 2℃±0.5℃; Phase Six; (Low-Temperature Preservation) Turn off the electrostatic field, maintain the ambient temperature of the thawing warehouse at 6-10℃, relative humidity at 80%~99%, wind speed ≤1.0m / s, and keep the core temperature between 2℃ and 4℃, and allow it to stand at 0-4℃ to achieve uniform temperature. The meat is thawed in stages (from stage one to stage six) to gradually increase the core temperature, avoiding juice loss and texture damage caused by sudden temperature changes. An electrostatic field is continuously applied from stage one to stage five, promoting uniform melting of ice crystals and redistribution and absorption of water molecules through dipole orientation and oscillation, thereby improving thawing efficiency and reducing juice loss. After the pre-prepared meat is thawed, it is transferred to a 0-4℃ cold storage for subsequent processing. In the freezing process, the long-term freezing time shall not exceed 45 days.

[0022] In stage six, the pre-prepared meat is left to stand at 0-4°C for 0.5 to 2 hours to achieve uniform temperature.

[0023] The electrostatic wave frequency generated by the electrostatic field device is designed to induce water molecules to align (dipole orientation) and activate them, thereby inhibiting ice crystal growth and improving heat and mass transfer efficiency.

[0024] In the pretreatment step, the beef is cut into pieces measuring 15cm*10cm*5cm.

[0025] In the pretreatment step, the marinating materials are 1-2 parts salt, 2-3 parts monosodium glutamate, 1-3 parts sugar, 1 part compound water-retaining agent, and 2-3 parts rice wine, etc.

[0026] In the pretreatment step, the marinating temperature is 0-4℃ and the time is 48-72h.

[0027] After pre-cooking, air cool for 1-3 hours until the core temperature reaches 4-12℃, then place in a freezer at -38℃.

[0028] The impact of different freezing processes on beef quality; Experimental method: The pre-cooked beef was cut into 5cm*5cm*10cm pieces and placed in polyethylene plastic bags. The samples were frozen at -18℃ and DENBA+ electrostatic field assisted -18℃. Samples were taken and measured every 15 days until 60 days. Each sample was repeated three times.

[0029] like Figure 1 The figure shows the pH changes of prepared beef under different freezing methods. Throughout the storage process, the pH value of the -18D group remained lower than that of the -18 group, indicating that electrostatic field-assisted freezing has a significant advantage in maintaining the acid-base balance of pre-prepared beef.

[0030] like Figure 2 As shown, the color changes of pre-cooked beef prepared using different freezing methods; Electrostatic field-assisted freezing technology has advantages in delaying the deterioration of beef color, especially in maintaining the a* value.

[0031] like Figure 3The figure shows the changes in beef cooking loss due to different freezing methods. The cooking loss of the -18D group was lower than that of the -18 group, indicating that electrostatic field-assisted freezing has a significant advantage in reducing cooking loss.

[0032] like Figure 4 As shown, the changes in shear force of pre-prepared beef under different freezing methods; Electrostatic field-assisted freezing has a clear advantage in maintaining meat quality.

[0033] like Figure 5 The figure shows the changes in volatile basic nitrogen in beef stored using different freezing methods. Electrostatic field technology has significant advantages in maintaining the freshness and quality stability of meat products.

[0034] like Figure 6 The image shows the changes in moisture distribution in beef stored for different durations of freezing. Electrostatic field-assisted freezing can improve the water-holding capacity of pre-cooked beef to some extent and slow down moisture loss.

[0035] like Figure 7 As shown, the yield of pre-frozen beef processed into braised beef varies depending on the freezing method. During long-term frozen storage, the effect of electrostatic fields on improving yield gradually weakens.

[0036] Experimental summary: (1) Compared with conventional -18℃ freezing, electrostatic field-assisted freezing significantly inhibited the increase of TVB-N content in beef (P<0.05). In addition, electrostatic field-assisted freezing can better maintain the color, cooking loss, tenderness and moisture content of beef.

[0037] (2) The water migration of beef under different freezing methods was analyzed by LF-NMR technology. The results showed that electric field-assisted freezing had a significant effect on the T21 value of water distribution (P<0.05). This indicates that electric field-assisted freezing can improve the distribution and water retention of water in beef.

[0038] (3) With the extension of freezing time, the beef frozen with electric field assistance showed better cooking rate maintenance than conventional -18℃ freezing. In particular, within 45 days of freezing, the yield of beef frozen with DENBA+ electrostatic field assistance was significantly better than that of ordinary freezing group.

[0039] Examples regarding the thawing process; 1. Sample Preparation: Marinated beef was cooked until the center temperature reached 50℃, cooled, and then quick-frozen at -38℃ until the center temperature reached -18℃, before being stored in a -18℃ freezer for 30 days. Thawing was performed as follows: the probe of a digital thermometer was inserted into the center, and thawing was stopped when the center temperature of the pre-prepared beef reached 4℃. The thawing time was recorded, and meat samples were taken for index testing.

[0040] Fresh beef (CK group); DENBA+ electrostatic field thawing (DT group): Frozen beef is placed in a DENBA+ electrostatic field-assisted low-temperature and high-humidity variable-temperature thawing chamber for thawing. Refrigerated thawing (CT group): Frozen beef was thawed in the refrigerator compartment at 4°C; Still water thawing (WT group): Frozen beef is repackaged in polyethylene vacuum packaging bags and immersed in still water for thawing. The initial water temperature is 15℃, and the water temperature is controlled at (15±1)℃. Room temperature thawing (NT group): After removing the outer packaging bag of the frozen beef, thaw it at room temperature of about 25°C; Low temperature and high humidity variable temperature thawing (LT group): Place the frozen beef in a low temperature and high humidity variable temperature thawing chamber, set the thawing parameters, insert the temperature probe into the center of the beef, and end the thawing when the center temperature is 4℃. Then transfer the thawed beef to a 0-4℃ preservation chamber.

[0041] 1. Determination of thawing loss: Weigh the beef before thawing and record the initial weight (W0). Thaw to 4℃, remove the sample, blot off excess surface moisture with filter paper, and measure the weight using the weighing method, repeating the measurement three times. The formula for calculating the thawing loss rate is:

[0042] In the formula: W0 is the weight of the sample before thawing (g); WX is the weight of the sample after thawing (g).

[0043] 2. Determination of cooking loss: Weigh the meat sample before cooking, place it in a polyethylene bag, and bathe it in an 80℃ water bath for 30 minutes. Then cool it to room temperature, wipe the surface moisture off the meat sample, and weigh it again. The cooking loss is calculated as follows:

[0044] In the formula: W0 is the initial weight (g); WX is the weight after cooking (g).

[0045] 3. pH determination: Cut 5g of meat sample into small pieces, add 45mL of ultrapure water and shake well. Insert the electrode directly into the solution and read the pH value after it stabilizes. Repeat the measurement 3 times for each sample and take the average value.

[0046] 4. Color Determination: The color of bulk braised beef was determined using a CR9 spectrophotometer according to GB / T7921-2008 "Uniform Color Space and Color Difference Formula". Measurement parameters: observation angle: standard 10°; observer / light source: D65; measurement area: 8mm². The white and black plates were calibrated before measurement. Ten points were randomly selected from the sample surface for measurement.

[0047] 5. Shear force determination: The shear force of beef was determined using a C-LM3B type muscle tenderness tester.

[0048] 6. Determination of TVB-N: The determination of TVB-N content in precooked beef is based on the automatic Kjeldahl nitrogen analyzer method in GB5009.228-2016 "National Food Safety Standard - Determination of Volatile Basic Nitrogen in Food".

[0049] 7. Determination of TBARS: The determination of TVB-N content in precooked beef was carried out in accordance with the automatic Kjeldahl nitrogen analyzer method in GB5009.228-2016 "National Food Safety Standard - Determination of Volatile Basic Nitrogen in Food".

[0050] 8. Determination of thiol groups: Perform the determination according to the kit instructions. Weigh 0.1 g of sample, add 1 mL of extraction buffer, prepare a 10% homogenate, centrifuge at 8000 rpm for 10 min at room temperature, and collect the supernatant for testing. Add 0.2 mL of sample to the control tube and 0.2 mL of standard to the blank tube, then add 0.75 mL of Reagent I and 0.5 mL of distilled water, respectively. Add 0.2 mL of sample to the test tube and 0.2 mL of standard to the test tube, then add 0.75 mL of Reagent I and 0.75 mL of Reagent II, respectively. Mix well, incubate at room temperature for 10 min, zero the instrument with double-distilled water, and measure the absorbance at 412 nm.

[0051] Results analysis: 1. Thawing Loss: The NT group experienced a 3.5% thawing loss, the CT group a 1.5% thawing loss, while the DT group had the lowest loss at only 1.05%. The electrostatic field-assisted high-humidity environment significantly reduced surface evaporation and juice loss, while dynamic temperature control effectively prevented excessive denaturation of myofibril proteins. The extremely low thawing loss indicates that the internal moisture and soluble proteins of the meat were well preserved, which is beneficial for maintaining the juiciness and nutritional value of the meat, demonstrating the significant advantage of this method in moisture retention.

[0052] 2. Cooking Loss: The cooking losses of the NT and CT groups were approximately 18.5% and 17.6%, respectively, while the cooking loss of the DT group was only 16.4%, significantly lower than the other groups. Electrostatic field assistance effectively reduces cell structure damage during thawing, making it easier to retain juices during subsequent heating. This not only significantly increases yield but also improves meat tenderness and texture. For industrial production, this method can directly improve economic efficiency and product consistency.

[0053] 3. pH value: After thawing, the pH value of the meat in the DT group remained stable at 6.37, close to the ideal range for fresh meat. The pH values ​​of the NT group and the static water thawing (WT group) decreased more significantly, possibly related to protein degradation and microbial growth. This method, through the synergistic effect of an electrostatic field and a low-temperature, high-humidity environment, slows down the decomposition reaction of proteins and amino compounds, thereby maintaining a more stable pH value and helping to enhance the water retention and flavor preservation of the meat.

[0054] 4. Color: The L* and a* values ​​of the NT group samples decreased, resulting in a duller color. The CT group was slightly better, but the DT group performed best in terms of L* and a* values, with a brighter flesh color and good redness retention. The electrostatic field combined with a high-humidity environment effectively reduced surface water loss and myoglobin oxidation, significantly inhibiting browning.

[0055] 5. Shear force: The shear force of the NT group samples was significantly higher than that of the control group, while the shear force of the DT and LT groups was closest to that of the control group, indicating that they had the lowest degree of muscle fiber breakage and protein denaturation, resulting in more tender meat. Electrostatic field assistance effectively reduced drying loss and tissue shrinkage, and combined with a staged temperature control strategy to reduce stress concentration effects, significantly improving the taste and edible quality of thawed meat products.

[0056] 6. TVB-N: The DT group had the lowest TVB-N value, at only 7.47 mg / 100g, far below the national limit. This method effectively inhibited the generation of volatile alkaline nitrogen caused by microorganisms and enzymatic reactions through the combined effects of electrostatic field and low temperature and high humidity environment, indicating that the thawed meat still maintains excellent freshness and food safety.

[0057] 7. TBARS: The NT group had the highest TBARS, followed by the CT group, while the DT group had the lowest at only 0.29 mg / kg. This indicates that the electrostatic field-assisted low-temperature and high-humidity environment effectively slowed down lipid peroxidation, reducing off-flavors and flavor deterioration. The significant reduction in TBARS values ​​demonstrates the outstanding effect of this method in improving product storage stability and sensory quality.

[0058] 8. Thiol content: The DT group had the highest total thiol content, reaching 1.24 μmol / g, significantly better than the other groups. The total thiol contents of the CT, LT, and WT groups were 1.06 μmol / g, 1.12 μmol / g, and 1.01 μmol / g, respectively, while the NT group had the lowest total thiol content, at only 0.50 μmol / g. This indicates that DENBA+ electrostatic field-assisted thawing can effectively inhibit protein oxidation and maintain thiol stability. Its mechanism of action may be related to the electrostatic field mitigating protein conformational damage and oxidative stress during thawing, thereby better preserving the nutritional quality and processing characteristics of meat products.

[0059] refer to Figures 8 to 14Compared with traditional thawing methods such as room temperature, still water, and refrigeration, the method provided in this invention has the following advantages: 1. Lowest thawing loss (approximately 1.05%), significantly reduced cooking loss (approximately 16.4%), and excellent water retention; 2. The color is well maintained, and the L* and a* values ​​are close to those of fresh meat, while the b* value is stable; 3. Shear force is reduced, tenderness is improved, and the values ​​of TVB-N (approximately 7.47 mg / 100g) and TBARS (approximately 0.29 mg / kg) are both low, indicating significant improvement in freshness and oxidative stability; 4. It has the highest total sulfhydryl content (approximately 1.24 μmol / g) and the lowest degree of protein oxidation; 5. The process is highly feasible and suitable for continuous industrial production.

[0060] This invention, through a specific freezing method and a corresponding thawing method, works synergistically to greatly reduce the loss of juice during thawing and cooking after long-term freezing. Through the synergistic combination of pickling, low temperature, high humidity, segmented temperature control, and low-voltage electrostatic field, and supported by experimental data, it can achieve extremely low thawing loss, excellent water retention, color, nutrition, and safety indicators after long-term freezing. Experiments have shown that applying an electrostatic field with a frequency of 50Hz and a voltage of 18-22kV during frozen storage can significantly inhibit the recrystallization of ice crystals through the continuous dipole oscillation of water molecules, thereby improving the distribution and water retention of moisture in beef. With prolonged frozen storage time, beef stored under electrostatic field assistance exhibits a better yield retention effect than beef stored at conventional -18℃, especially within 45 days of frozen storage, where the yield is significantly higher than that of the ordinary frozen storage group. Experiments have shown that during the thawing process, the synergistic effect of an electrostatic field of the same frequency and a low-temperature, high-humidity variable-temperature thawing method resulted in the lowest thawing loss (approximately 1.05%), significantly reduced cooking loss (approximately 16.4%), excellent water retention, good color retention, L* and a* values ​​close to those of fresh meat, stable b* value, reduced shear force, improved tenderness, and lower TVB-N (approximately 7.47 mg / 100g) and TBARS (approximately 0.29 mg / kg) values. This significantly improved freshness and oxidative stability, the highest total sulfhydryl content (approximately 1.24 μmol / g), and the lowest degree of protein oxidation.

[0061] It should be stated that the above-described specific embodiments are merely preferred embodiments of the present invention and the technical principles employed. Those skilled in the art should understand that various modifications, equivalent substitutions, and variations can be made to the present invention. However, such variations, as long as they do not depart from the spirit of the present invention, should be within the scope of protection of the present invention. Furthermore, some terminology used in this specification and claims is not limiting, but merely for ease of description.

Claims

1. A method for long-term frozen storage and thawing of pre-prepared meat based on electrostatic field assistance, characterized by: The method comprises the following steps: Preprocessing: cutting fresh beef and marinating; Pre-cooking; Steaming the marinated beef to a core temperature of 50℃; Cooling: after sealing the steamed beef in a sealed bag, it is placed in a freezer at -38℃ until the core temperature is reduced to -18℃; Freezing: the frozen pre-prepared beef is transferred to a long-term freezing room at -18℃; In the freezing step, an electrostatic field device capable of resonating with water molecules through electrostatic waves is turned on, and the working parameters of the electrostatic generator are as follows: input voltage 200-240V, continuous stable output voltage 18-22kV, current 0.5-1.5mA, frequency 50Hz; Thawing: the frozen beef is placed in a thawing room equipped with a low-pressure electrostatic field and programmable temperature and humidity control, and the following six stages of temperature and humidity, air speed conditions are executed in turn, and the core temperature of the beef and the relative humidity in the room are monitored in real time by sensors and adjusted in a closed loop during each stage. Stage one: the environmental temperature is 14-18℃, the relative humidity is 80-99%, and the wind speed is 1.5-2.5m / s, until the surface temperature of the meat product is -3℃ to -1℃; Stage two: the environmental temperature is 12-15℃, the relative humidity is 80%~99%, and the wind speed is 1.5~2.5m / s, until the surface temperature is 0℃ to 3℃ and the core temperature is -2℃ to -1℃; Stage three: the environmental temperature is 11-14℃, the relative humidity is 80%~99%, and the wind speed is 1.0~2.0m / s, so that the core temperature rises to 0℃ to 1℃; Stage four: the environmental temperature is 10-13℃, the relative humidity is 80%~99%, and the wind speed is 1.0~2.0m / s, so that the core temperature rises to 1℃ to 2℃; Stage five: the environmental temperature is 8-12℃, the relative humidity is 80%~99%, and the wind speed is 0.5~1.5m / s, so that the core temperature stabilizes at 2℃±0.5℃; Stage six: the electrostatic field is turned off, the environmental temperature of the thawing room is 6-10℃, the relative humidity is 80%~99%, the wind speed is ≤1.0m / s, the core temperature is maintained at 2℃ to 4℃, and the temperature is kept uniform at 0-4℃; After the thawing of the pre-prepared meat is completed, it is transferred to a 0-4℃ preservation room for subsequent processing.

2. The method for long-term frozen storage and thawing of pre-prepared meat based on electrostatic field assistance according to claim 1, characterized in that: In the freezing step, the long-term freezing time is not more than 45 days.

3. The method of long-term freezing and thawing of pre-prepared meat based on electrostatic field assistance according to claim 2, characterized by the fact that: In stage six, the pre-prepared meat is kept at a temperature of 0-4℃ for 0.5-2 hours.

4. The method for long-term frozen storage and thawing of pre-prepared meat based on electrostatic field assistance according to claim 3, characterized in that: The frequency of the electrostatic waves generated by the electrostatic field device is the frequency that causes the water molecules to resonate.

5. The method of long-term freezing and thawing of preformed meat based on electrostatic field assistance according to claim 3, characterized by the fact that: In the preprocessing step, the size of the cut beef is 15cm*10cm*5cm.

6. The method for long-term frozen storage and thawing of pre-prepared meat based on electrostatic field assistance according to claim 5, characterized in that: In the preprocessing step, the marinating materials are 1-2 parts of edible salt, 2-3 parts of monosodium glutamate, 1-3 parts of sugar, 1 part of compound water-retaining agent, 2-3 parts of yellow rice wine, etc.

7. The method of long-term freezing and thawing of preformed meat based on electrostatic field assistance according to claim 6, characterized by the fact that: In the preprocessing step, the marinating temperature is 0-4℃, and the time is 48-72h.

8. The method of long-term freezing and thawing of preformed meat based on electrostatic field assistance according to claim 7, characterized by the fact that: After pre-cooking is completed, air cooling is performed for 1-3h, and after the core temperature is cooled to 4-12℃, it is placed in a freezer at -38℃.

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