Meat particles with electrostatic field assisted gradient freeze-drying and preparation method thereof

Abstract

This invention belongs to the field of food processing technology and discloses an electrostatic field-assisted gradient freeze-dried meat granules and its preparation method. The electrostatic field-assisted gradient freeze-dried meat granules have an inner and outer double-layer gradient porous structure. The inner layer is a dense gel skeleton layer, and the outer layer is a loose porous rehydrated layer. The freeze-dried meat granules are prepared through a two-stage electrostatic field-assisted freeze-drying process. The two-stage electrostatic field treatments include: a first electrostatic field treatment, applied after the construction of the outer loose porous rehydrated layer and before the freeze-drying sublimation stage, to optimize ice crystal morphology and enhance the gradient difference between the inner and outer layers; and a second electrostatic field treatment, applied at the beginning of the freeze-drying sublimation stage, to accelerate water vapor diffusion and inhibit structural collapse. This invention constructs a dense gel skeleton layer inside the meat granules, significantly improving their toughness and resistance to breakage; and constructs a loose porous rehydrated layer on the outer layer, significantly shortening the rehydration time and resulting in a firm and elastic texture after rehydration.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to electrostatic field-assisted gradient freeze-dried meat particles and their preparation method. Background Technology

[0002] Freeze-drying (vacuum freeze-drying) technology, with its advantages of low-temperature vacuum drying, can retain the nutritional components and natural flavor of meat products to the greatest extent, and its rehydration properties are superior to traditional hot air drying. It has been widely used in instant foods such as porridge, instant noodles, and convenient soups. However, during the preparation of freeze-dried meat particles, the moisture in the material directly sublimates from ice crystals to water vapor under vacuum, resulting in a large number of porous structures inside the meat particles. While this porous structure can improve rehydration properties to some extent, it also makes the meat particles loose in texture and low in mechanical strength, making them prone to breakage during transportation, packaging, and consumption, thus making it difficult to guarantee the yield of the finished product.

[0003] To improve the aforementioned performance defects of freeze-dried meat granules, existing technologies mainly employ the following methods: First, by adding exogenous substances such as edible gums and plant proteins to improve the texture of the meat granules. While this method can fill pores and enhance mechanical strength to some extent, the introduction of exogenous substances often dilutes the inherent flavor compounds of the meat granules, leading to a weaker meat flavor and distorted taste after rehydration. Furthermore, it is difficult to simultaneously address the problems of uneven rehydration and oxidative moisture absorption. Second, by using surface spraying or impregnation to form a protective layer on the surface of the meat granules to reduce the intrusion of moisture and oxygen. However, the bonding force between the surface coating and the meat granule matrix is ​​limited, and it is prone to detachment or dissolution during rehydration, failing to fundamentally improve the physical stability of the porous structure within the meat granules. Third, by optimizing freeze-drying process parameters, such as adjusting the pre-freezing temperature, sublimation rate, or desorption temperature, an attempt is made to find a balance between rehydration properties and structural strength. However, since the distribution of ice crystals and pore structure formed by conventional freeze-drying processes are difficult to control precisely, one often ends up with the other: increasing porosity is beneficial for rehydration, but it will exacerbate the loose structure; decreasing porosity can enhance strength, but it will lead to a longer rehydration time and a harsher texture.

[0004] In recent years, electrostatic field technology has been introduced into the food processing field, mainly used for freezing and preservation of food or assisting in the thawing process. In freeze-drying applications, existing technologies mostly use electrostatic fields as a single auxiliary means to accelerate the freezing rate or shorten the drying time. However, the effects are unstable and the process reproducibility is poor. A mature technical solution that is deeply integrated with the freeze-drying process has not yet been formed, making it difficult to achieve stable industrial production.

[0005] In summary, existing freeze-dried meat particles and their preparation technologies still have the following technical defects: the meat particles have a loose structure and are easily broken; uneven water penetration during rehydration results in a soft outer layer and a hard inner layer; the porous structure has a large specific surface area, making the fat prone to oxidation and rancidity, and the product prone to moisture absorption and clumping; and the application of electrostatic fields in the freeze-drying process lacks systematicity and stability.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The present invention aims to solve at least one of the above technical problems, and provides an electrostatic field-assisted gradient freeze-dried meat granules and a preparation method thereof.

[0008] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes vacuum tumbling and in-situ gelation technology to construct a dense gel skeleton layer within meat particles, forming a three-dimensional support network. This significantly enhances the toughness and breakage resistance of the meat particles, controlling the breakage rate to below 3%. Simultaneously, through gradient quick-freezing and electrostatic field synergistic treatment, a loose, porous rehydration layer is constructed on the outer layer of the meat particles, forming directionally arranged microchannels. This significantly shortens the rehydration time, resulting in a firm and elastic texture after rehydration, free from dryness and crumbling, closely resembling fresh meat particles. This breakthrough overcomes the limitations of the disordered porous structure of traditional freeze-dried meat particles, achieving synergistic optimization of rapid outer rehydration and a strong, breakage-resistant inner layer.

[0009] The first electrostatic field treatment of this invention is applied after the outer loose structure is built and before sublimation drying. By optimizing the ice crystal morphology, it strengthens the gradient difference between the inner and outer layers, inhibits the formation of large ice crystals, and protects the structural integrity of muscle cells. The second electrostatic field treatment is applied at the beginning of sublimation drying. By accelerating water vapor diffusion, it reduces mass transfer resistance and inhibits the collapse of the surface structure of the meat particles. This two-stage treatment mode is precisely adapted to the gradient freeze-drying process, which not only shortens the sublimation drying time to 8-10 hours, but also significantly improves the structural stability and appearance integrity of the product.

[0010] The inner dense gel skeleton of this invention reduces the contact area between fat and oxygen and moisture; the outer electrostatic field treatment induces mild cross-linking of proteins on the surface of meat particles, forming an ultra-thin dense layer. Combined with vacuum nitrogen-filled packaging, the product can be stored at room temperature for 6 months without obvious oxidative rancidity, and the moisture absorption rate is controlled below 6% (RH=60%, 25℃, 24h). The shelf life is extended by more than 30% compared with the prior art, and there is no need to add too many antioxidants, making it green and safe.

[0011] This invention enhances structural strength while avoiding flavor distortion caused by exogenous additives by constructing the inner gel skeleton in situ rather than using exogenous filling, and by using a specific protein-polysaccharide complex gel ratio in the outer layer (synergistic effect of soy protein isolate, wheat protein powder, konjac glucomannan and xanthan gum). After rehydration, the meat particles have a pure flavor and a sensory score of over 90 points. Attached Figure Description

[0012] Figure 1 This is a comparison diagram of the microstructure of freeze-dried beef granules prepared in Example 1 and freeze-dried beef granules prepared by conventional process. Detailed Implementation

[0013] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0014] The first embodiment of the present invention provides electrostatic field-assisted gradient freeze-dried meat particles, wherein the freeze-dried meat particles have an inner and outer double-layer gradient porous structure, wherein the inner layer is a dense gel skeleton layer and the outer layer is a loose porous rehydrated layer, and the freeze-dried meat particles are prepared by a two-stage segmented electrostatic field-assisted freeze-drying process. The two segmented electrostatic field treatments include: a first electrostatic field treatment, applied after the construction of the outer loose and porous rehydrated layer and before the freeze-drying sublimation stage, to optimize the ice crystal morphology and enhance the gradient difference between the inner and outer layers; and a second electrostatic field treatment, applied at the beginning of the freeze-drying sublimation stage, to accelerate water vapor diffusion and inhibit structural collapse.

[0015] Specifically, the aforementioned inner and outer double-layer gradient porous structure refers to the gradual increase in porosity from the center to the surface of the meat particles. The inner dense gel skeleton layer is mainly composed of muscle fibers and a protein-polysaccharide composite gel. This composite gel penetrates deep into the intercellular spaces of muscle cells to form a three-dimensional support network, which enhances the toughness and resistance to breakage of the meat particles. The outer loose porous rehydration layer consists of directionally arranged microchannels and is attached with a maltodextrin-hydroxypropyl starch-gum arabic composite layer to achieve rapid rehydration.

[0016] Through the synergistic effect of two segmented electrostatic fields, meat particles form a stable gradient porous structure during freeze-drying, thereby improving freeze-drying efficiency.

[0017] In some preferred embodiments, the protein-polysaccharide composite gel contained in the aforementioned dense gel skeleton layer is composed of 4-6 parts soy protein isolate, 1-3 parts wheat protein powder, 0.5-1.5 parts konjac glucomannan, 0.2-0.5 parts xanthan gum, and 90-93 parts water, with the addition amount being 8%-12% of the meat granules' weight. In this specific ratio, soy protein isolate and wheat protein form a dual-protein network to enhance the skeleton's toughness, while konjac glucomannan and xanthan gum synergistically enhance the gel's density and thermal stability. The synergistic effect of the dual proteins and polysaccharides can form a more stable three-dimensional support network, while avoiding the introduction of the slight astringent taste of chitosan or the faint fishy taste of gelatin, thus preserving the natural flavor of the meat granules to the greatest extent.

[0018] The aforementioned loose and porous rehydrated layer is formed by impregnation with a maltodextrin-hydroxypropyl starch-gum arabic composite solution, the mass concentration of which is 10%~15%, wherein the mass ratio of maltodextrin, hydroxypropyl starch and gum arabic is (1.2~1.6):(0.8~1.2):(0.4~0.6). Gum arabic has excellent water solubility, film-forming properties and porosity. When combined with maltodextrin and hydroxypropyl starch, it can form regularly arranged microchannels on the surface of meat particles, ensuring rapid rehydration, while improving the stability of the surface structure and reducing surface peeling during rehydration.

[0019] Through the above structural design and process preparation, the moisture content of the freeze-dried meat particles is controlled at 2.0%~3.5%, the rehydration time is ≤2.5min, the breakage rate is ≤3%, the moisture absorption rate is ≤6% after 24h of storage at 25℃ and 60% relative humidity, and there is no obvious oxidative rancidity after 6 months of storage at room temperature.

[0020] The second embodiment of the present invention provides a method for preparing electrostatically assisted gradient freeze-dried meat particles, comprising the following steps: Meat particles are mixed with protein-polysaccharide composite gel, and the composite gel is penetrated into the meat particles by vacuum tumbling. Then, the composite gel is allowed to gel in situ by low-temperature standing, resulting in pre-gelled meat particles with a dense gel skeleton layer. Pregelatinized meat particles are flash-frozen once to fix the internal dense gel skeleton layer, then surface coating treatment is performed and flash-frozen a second time to form a loose porous rehydrated layer on the surface, resulting in frozen meat particles with an inner and outer double-layer gradient porous structure. A first electrostatic field treatment was applied to frozen meat particles with an inner and outer double-layer gradient porous structure. The meat pieces that have undergone the first electrostatic field treatment are pre-frozen; The pre-frozen meat pieces are subjected to sublimation drying. A second electrostatic field treatment is applied at the beginning of the sublimation drying process, and then the sublimation drying continues until it is completed. The sublimated and dried meat particles are subjected to analytical drying to obtain freeze-dried meat particles.

[0021] Understandably, meat cubes are obtained by pre-processing raw materials. Generally, fresh livestock and poultry meat is selected, the tendons, fat and blood are removed, and it is cut into appropriately sized cubes (e.g., 5-10mm in diameter). The surface blood and free fat of the meat cubes are removed, and the water is drained for later use.

[0022] In the stage of constructing the dense gel skeleton of the inner layer, the pre-treated meat particles are mixed with a protein-polysaccharide composite gel. Vacuum tumbling is then used to allow the composite gel to penetrate into the intercellular spaces of the muscle cells within the meat particles. Subsequently, low-temperature settling allows the composite gel to gel in situ, resulting in pre-gelled meat particles with a dense gel skeleton layer. Vacuum tumbling is a commonly used marinating method in meat processing. The vacuum degree, temperature, and time parameters can be selected within a conventional range based on the performance of the equipment and the characteristics of the material, as long as sufficient penetration of the composite gel is achieved. For example, a vacuum degree of -0.08 to -0.06 MPa, a tumbling temperature of 0 to 4°C, and a tumbling time of 30 to 45 minutes are suitable; the low-temperature settling temperature is 2 to 8°C, and the time is 2 to 4 hours.

[0023] In some preferred embodiments, 0.3% to 0.5% of tea polyphenols by weight of the meat particles can be added during vacuum tumbling to inhibit the oxidation of fat inside the meat particles in advance.

[0024] The pre-gelled meat particles are then steamed and cooked at 75-85°C, and then cooled for later use. This step allows the protein-polysaccharide complex gel to undergo thermal denaturation and fixation, while simultaneously inactivating endogenous enzymes and stabilizing the quality of the meat particles.

[0025] In the outer loose and porous rehydrated layer construction stage, the pre-gelled meat particles are first quick-frozen to fix the internal dense gel skeleton layer. Then, a surface coating treatment is performed by immersing the meat particles in a maltodextrin-hydroxypropyl starch-gum arabic composite solution, allowing the composite solution to uniformly adhere to the surface of the meat particles. A second quick-freezing process is then performed, rapidly freezing the surface moisture to form fine ice crystals while preserving the internal dense gel structure, resulting in frozen meat particles with a double-layered gradient porous structure. The control of the temperature and time differences between the two quick-freezing processes, as well as the liquid nitrogen spraying rate, is crucial for constructing the gradient freezing structure and forming the internal and external temperature gradients. Specific parameters can be selected within the range of conventional quick-freezing processes based on the performance of the quick-freezing equipment and the particle size of the meat particles. For example, the temperature of the first quick-freezing is -40℃ to -30℃, and the time is 5 to 8 minutes; the temperature of the second quick-freezing is -45℃ to -35℃, and the time is 8 to 12 minutes. The surface coating treatment time is preferably such that the composite solution uniformly adheres to the surface of the meat particles, for example, immersion for 5 to 10 minutes.

[0026] Next, two segmented electrostatic field treatments are performed. The first electrostatic field treatment is applied to the frozen meat particles with the inner and outer double-layer gradient porous structure. The applied electric field strength is 10~20kV / m, the treatment time is 5~10min, and the treatment temperature is -40~-30℃. This is used to assist in the directional formation of ice crystals, enhance the gradient difference between the inner and outer layers, reduce the formation of large ice crystals, and protect the structural integrity of muscle cells. This treatment is applied before the pre-freezing treatment and is a key step in optimizing the ice crystal morphology.

[0027] Following this, a pre-freezing treatment is performed, where the meat particles that underwent the first electrostatic field treatment are pre-frozen to further solidify the gradient freezing structure. Then, the sublimation drying stage begins. The pre-frozen meat particles are placed in a freeze dryer, and a second electrostatic field treatment is applied at the initial stage of sublimation drying. The electric field strength is 5~10 kV / m, the treatment time is 2~3 hours, and the treatment temperature is -15~-10℃. This is used to accelerate the diffusion of water vapor on the surface of the meat particles, reduce mass transfer resistance, and inhibit the collapse of the surface structure. After this weak electrostatic field treatment, sublimation drying continues until completion, causing the ice crystals in the loose layer on the surface of the meat particles to sublimate into water vapor, forming a loose, porous structure. Pre-freezing and sublimation drying are standard stages in the freeze-drying process, and their parameters such as temperature, vacuum degree, and time can be selected within the standard freeze-drying process range according to the material characteristics and equipment performance.

[0028] As an example, the pre-freezing temperature is -30℃ to -25℃, and the holding time is 2 to 3 hours; the sublimation drying vacuum degree is -0.09 to -0.08 MPa, the temperature is -15℃ to -10℃, and the total drying time is 8 to 10 hours.

[0029] In some preferred embodiments, the electrostatic field is preferably a DC flat plate electrostatic field, and the electrode spacing is 5~10cm.

[0030] Finally, desorption drying is performed to remove residual moisture from the meat particles and further cross-link and solidify the dense gel skeleton inside, resulting in freeze-dried meat particles. In a preferred embodiment, desorption drying can employ a gradient temperature increase method to avoid structural collapse caused by a sudden temperature rise. For example, the desorption drying temperature is 35~45℃, and the drying time is 4~6 hours.

[0031] If necessary, the freeze-dried meat particles obtained above can also undergo post-processing and packaging stages. The freeze-dried meat particles are cooled to room temperature in a low-humidity workshop, broken particles are removed by screening, vacuum nitrogen-filled packaging is used, and high oxygen barrier membranes are used for sealing.

[0032] The preparation and performance of electrostatic field-assisted gradient freeze-dried meat particles are described in detail below through several specific examples.

[0033] Example 1 Raw material pretreatment: Select fresh beef, remove tendons, fat and blood stains, cut into beef cubes with a diameter of 8mm, remove surface blood and free fat, drain and set aside. Construction of the dense inner gel framework: 5 parts soy protein isolate, 2 parts wheat protein powder, 0.8 parts konjac glucomannan, 0.2 parts xanthan gum, and 92 parts water were mixed evenly to obtain a protein-polysaccharide composite gel. 10% of the protein-polysaccharide composite gel by weight of the pretreated beef granules was added to the beef granules. The vacuum degree was controlled at -0.07 MPa, the tumbling temperature was 2℃, and the tumbling time was 35 min. Subsequently, the mixture was placed in a refrigerated environment at 5℃ for 3 h to allow the protein-polysaccharide composite gel to gel in situ inside the beef granules, resulting in pre-gelled beef granules. Steaming and cooking: The pre-gelled beef is steamed and cooked at 80 ℃ and then cooled for later use; One-time quick freezing: Freeze the pre-gelled beef cubes at -40~-30℃ for 5~8 minutes to fix the shape of the meat cubes and promote the construction of a dense gel skeleton in the inner layer; Construction of the outer porous rehydration layer: A 10% (w / w) maltodextrin-hydroxypropyl starch-gum arabic composite solution (maltodextrin:hydroxypropyl starch:gum arabic = 1.5:1:0.5) was prepared. The beef granules, which had been quick-frozen once, were immersed in the composite solution for 8 minutes to ensure that the composite solution was evenly adhered to the surface of the beef granules. The beef granules were then quick-frozen again at -40℃ for 10 minutes to obtain gradient-frozen beef granules. First electrostatic field treatment: Low-voltage electrostatic field treatment was applied to gradient-frozen beef cubes with an electric field strength of 15kV / m, a treatment time of 8min, and a treatment temperature of -35℃ to assist in directional ice crystal formation and enhance the gradient difference between the inner and outer layers. Gradient sublimation drying: The gradient-frozen beef cubes after the first electrostatic field treatment are subjected to a segmented temperature-controlled sublimation drying process: the pre-freezing is completed by holding at -28℃ for 2.5h; after the pre-freezing, the sublimation drying process begins, and a second electrostatic field treatment is performed, with a weak electrostatic field applied (electrode spacing 8cm), an electric field strength of 8kV / m, a treatment time of 2.5h, and a treatment temperature of -12℃. Sublimation drying stage: After the weak electrostatic field treatment, continue to maintain the sublimation drying parameters, with a vacuum degree of -0.085MPa and a temperature controlled at -12℃. The total drying time is 9 hours (including the time for the second electrostatic field treatment). Analysis of the drying stage: The vacuum degree is kept constant, the temperature is increased to 40℃ at a rate of 5℃ / h, and dried for 5h to obtain freeze-dried beef granules with a gradient porous structure.

[0034] Comparative Experiment 1: Construction of a dense inner gel framework (used to illustrate the ratio of protein-polysaccharide composite gel) By constructing a dense inner gel framework, the fragmentation resistance, thermal stability, and moisture resistance of the meat particles are improved, and the synergy with electrostatic fields and gradient processes is enhanced. Following the preparation process of Example 1, only the formulation of the protein-polysaccharide composite gel was changed, and multiple experimental schemes were set up, as follows: Option 1: 5 parts gelatin, 2 parts soy protein isolate, 1 part chitosan, 92 parts water; Option 2: 5 parts gelatin, 2 parts soy protein isolate, 0.8 parts konjac glucomannan, 0.2 parts xanthan gum, 92 parts water; Option 3: 5 parts soy protein isolate, 2 parts wheat protein powder, 1 part chitosan, 92 parts water; Option 4: Example 1; Option 5: 5 parts soy protein isolate, 2 parts pea protein powder, 1 part chitosan, 92 parts water; Option 6: 5 parts soy protein isolate, 2 parts pea protein powder, 0.8 parts konjac glucomannan, 0.2 parts xanthan gum, 92 parts water; Control group: No soaking in gel solution.

[0035] The meat granules prepared using the above methods were evaluated for breakage rate, moisture absorption rate, rehydration rate, and sensory evaluation. The experimental methods are as follows: (1) Breakage rate: Take the finished freeze-dried meat granules, remove obvious broken particles, and use this as the test sample. Weigh a uniform sample m0 = 100.00 g, accurate to 0.01 g. Place the sample in a 2 mm standard sieve, start the vibrating sieve machine, and vibrate for 5 min. Collect the material passing through the sieve (broken particles that pass through the 2 mm sieve openings), weigh it, and record the mass as m1. Perform the experiment in triplicate and take the arithmetic mean.

[0036] The breakage rate is calculated using the following formula: In the formula: R is the breakage rate, %; m0 is the total mass of the sample, g; m1 is the mass of the broken particles under the sieve, g.

[0037] (2) Moisture absorption rate: Take the freeze-dried meat sample to be tested and dry it in a vacuum drying oven until constant weight. After the clean and dry weighing bottle reaches constant weight, weigh it and record the mass as m0. Add 2.0000 g to 3.0000 g of sample to the weighing bottle, spread it evenly, and weigh the total mass, recording it as m1. Place the weighing bottle containing the sample in a constant temperature and humidity chamber that has been stabilized at 25 ℃ and 80% RH, let it stand for 24 h, take it out, immediately cover it, and quickly weigh the total mass, recording it as m2. Perform three parallel tests and take the average value.

[0038] The moisture absorption rate is calculated using the following formula: In the formula: W is the moisture absorption rate, %; m3 is the mass of the empty weighing bottle, g; m4 is the initial mass of the weighing bottle + sample, g; m5 is the mass of the weighing bottle + sample after absorbing moisture for 24 h, g.

[0039] (3) Sensory evaluation: A sensory evaluation group of 10 people will evaluate the freeze-dried meat pieces. The total score is 100 points (appearance integrity 25 points, color 25 points, smell 25 points, taste 25 points).

[0040] (4) Rehydration time: Accurately weigh 2.00 g of freeze-dried meat sample and place it in a dry beaker. Quickly add water preheated to 80±2℃ at a material-to-liquid ratio of 1:20, and start a stopwatch simultaneously. Rehydrate under static conditions, taking out 1-2 pieces every 10 seconds with a glass rod or tweezers, blotting off the surface moisture with filter paper, and cutting them longitudinally to observe their internal state. When all meat pieces are completely softened inside, with no white core and no hard core, stop timing immediately and record the time, which is the rehydration time. Perform three parallel measurements and take the arithmetic mean. The results are expressed in minutes (min).

[0041] (5) Texture index testing: Take 10 pieces of each sample (ensure uniform particle size to avoid abnormal particles affecting the test results); put the meat pieces into a beaker at a material-to-liquid ratio of 1:20 (g:mL), add deionized water that has been kept at a constant temperature of 80±2℃, and soak until the meat pieces are completely free of hard cores and uniformly rehydrated according to the rehydration time test method; after soaking, remove the meat pieces with tweezers, gently absorb excess water on the surface with filter paper, and immediately place them on the sample stage of the texture analyzer to test the hardness and elasticity of the sample. Probe type: 36mm cylindrical probe; test speed: 1mm / s; compression ratio: 50%; interval between two compressions: 5s; trigger force: 5g.

[0042] The experimental results are shown in Table 1. The results indicate that Scheme 4 yielded the best results, consisting of 5 parts soy protein isolate, 2 parts wheat protein powder, 0.8 parts konjac glucomannan, 0.2 parts xanthan gum, and 92 parts water. Soy protein isolate and wheat protein form a dual-protein network, enhancing the skeletal toughness; konjac glucomannan and xanthan gum synergistically enhance gel density and thermal stability; the synergistic effect of the dual proteins and polysaccharides forms a more stable three-dimensional support network. Simultaneously, it eliminates the slight astringency of chitosan and the faint fishy smell of gelatin, preserving the natural flavor of the meat pieces to the greatest extent. After rehydration, the texture is firm yet not dry, elastic, and closer to fresh meat pieces.

[0043] Table 1 Comparison of protein-polysaccharide composite gel formulations .

[0044] Comparative Experiment 2: Construction of an outer loose and porous rehydration layer (used to illustrate the proportions of the starch composite solution) Following the preparation process of Example 1, only the formulation of the starch compound solution was changed, and multiple experimental schemes were set up, as follows: Option 1: 10% maltodextrin-hydroxypropyl starch complex solution (mass ratio of maltodextrin to hydroxypropyl starch is 2:1). Option 2: Example 1; Option 3: 10% maltodextrin-modified tapioca starch-xanthan gum composite solution (maltodextrin:modified tapioca starch:xanthan gum = 1.2:1:0.3); Option 4: 10% maltodextrin-pectin-soy protein isolate complex (maltodextrin:pectin:soy protein isolate = 1:0.8:0.2); Control group: No soaking in gel solution and starch compound solution.

[0045] The prepared meat granules were evaluated based on rehydration time, granule breakage rate, and sensory score. The experimental results are shown in Table 2. The results indicate that Scheme 2, namely a 10% maltodextrin-hydroxypropyl starch-gum arabic composite solution (maltodextrin:hydroxypropyl starch:gum arabic = 1.5:1:0.5), was the most effective. Gum arabic possesses excellent water solubility, film-forming properties, and porosity. When combined with the original system, it enhances the stability of the surface structure, and its hydrophilic groups accelerate water penetration. This scheme, while preserving the loose, porous structure of the outer layer and ensuring rapid rehydration, further improves moisture resistance, reduces flavor interference, and strengthens the bond with the dense gel skeleton of the inner layer, reducing surface shedding during rehydration. The rehydrated meat granules exhibit better integrity and elasticity, while avoiding the problems of being too soft and crumbly or too hard after rehydration, making them closer to fresh meat granules.

[0046] Table 2 Comparison of Starch Compound Solution Formulations .

[0047] Comparative Experiment 3: Performance Comparison of Electrostatic Field-Assisted Freeze-Dried Beef Granules Referring to the formula and process of Example 1, some processing steps were eliminated, and multiple experimental schemes were set up, as follows: Option 1: Example 1; Option 2: Perform electrostatic field treatment only once after gradient freezing; Control group 1: No electrostatic field assisted treatment; Control group 2: Traditional freeze-dried beef granules (not soaked in gel solution and starch compound solution, without electrostatic auxiliary treatment).

[0048] The prepared meat granules were tested. The results are shown in Table 3 below. The freeze-dried beef granules prepared in this example had a rehydration time of 2.0 min, a breakage rate of 2.12%, and a moisture absorption rate of 2.43%. After rehydration, the beef granules had a firm and elastic texture, without being tough or crumbly, and the flavor was close to that of fresh beef. No obvious rancid odor was observed after 6 months of storage at room temperature.

[0049] Table 3 Comparative Experiments of Electrostatic Field-Assisted Treatment .

[0050] The freeze-dried beef granules prepared in Example 1 and those prepared by a conventional process were cut perpendicular to the fiber direction and observed under an electron microscope. The results are as follows: Figure 1 As shown in the figure, the freeze-dried meat particles prepared in Example 1 have uniform pore size and a shape close to round or honeycomb, with uniform and loose gaps at the edges and an intact overall structure; while the freeze-dried meat particles prepared by traditional processes have irregular pore size and shape, fine cracks inside, more cracks at the edges, and the meat particles are more easily broken.

[0051] As can be seen from the above comparative experiments, the freeze-dried meat particles prepared by the present invention through the synergistic effect of electrostatic field and gradient porous structure construction process are significantly superior to other technologies in key performance indicators such as rehydration time, breakage rate, moisture absorption rate, freeze-drying efficiency and rehydrated taste.

[0052] Example 2 Raw material pretreatment: Select fresh pork, remove tendons, fat and blood stains, cut into pork cubes with a diameter of 5mm, remove surface blood and free fat, drain and set aside. Construction of the dense inner gel framework: 6 parts soy protein isolate, 2 parts wheat protein powder, 0.7 parts konjac glucomannan, 0.3 parts xanthan gum, and 91 parts water were mixed evenly to obtain a protein-polysaccharide composite gel. 8% of the protein-polysaccharide composite gel by weight of the pretreated pork pieces was added, and the vacuum degree was controlled at -0.08 MPa, the tumbling temperature was 0℃, and the tumbling time was 30 min. Subsequently, the mixture was placed in a refrigerated environment at 2℃ for 3 h to allow the protein-polysaccharide composite gel to gel in situ inside the pork pieces, resulting in pre-gelled pork pieces. Steaming and cooking: The pre-gelled pork is steamed and cooked at 80 ℃ and then cooled for later use; One-time quick-freezing: Pre-gelled pork particles are frozen at -40℃ for 5 minutes to fix the shape of the meat particles and promote the construction of a dense gel skeleton in the inner layer; Construction of the outer porous rehydration layer: A maltodextrin-hydroxypropyl starch-gum arabic composite solution with a mass concentration of 11% was prepared (maltodextrin:hydroxypropyl starch:gum arabic = 1.6:0.8:0.6). The pork pieces that had been quick-frozen once were placed in the composite solution and immersed for 5 minutes to allow the composite solution to adhere evenly to the surface of the pork pieces. The pork pieces were then quick-frozen again at -45℃ for 8 minutes to obtain gradient-frozen pork pieces. First electrostatic field treatment: Low-voltage electrostatic field treatment was applied to gradient-frozen pork particles with an electric field strength of 10kV / m, a treatment time of 5min, and a treatment temperature of -40℃ to assist in directional ice crystal formation and enhance the gradient difference between the inner and outer layers. Gradient sublimation drying: The gradient-frozen pork cubes after the first electrostatic field treatment are subjected to a segmented temperature-controlled sublimation drying process: the pre-freezing is completed by holding at -30℃ for 2 hours; after the pre-freezing is completed, the sublimation drying process begins, and a second electrostatic field treatment is performed, with a weak electrostatic field (electrode spacing 5cm), an electric field strength of 5kV / m, a treatment time of 2 hours, and a treatment temperature of -15℃. Sublimation drying stage: After the weak electrostatic field treatment, continue to maintain the sublimation drying parameters: vacuum degree -0.09 MPa, temperature controlled at -15℃, and total drying time 8h (including the time of the second electrostatic field treatment). Analysis of the drying stage: The vacuum degree is kept constant, the temperature is increased to 35℃ at a rate of 5℃ / h, and dried for 4h to obtain freeze-dried pork granules with a gradient porous structure.

[0053] Preparation of traditional freeze-dried pork granules: The pre-treated pork granules are processed using a single freezing + conventional vacuum freeze-drying process, in which the granules are directly placed into a quick-freezing machine and frozen at -35℃ without gradient, direction, or secondary freezing; in the vacuum freeze-drying stage, pre-freezing, sublimation drying and desorption drying are carried out directly without segmented temperature control, electrostatic field assistance, or structure regulation.

[0054] The performance of the freeze-dried pork granules prepared in this embodiment was compared with that of traditional freeze-dried pork granules. The results are shown in Table 4. The rehydration time was 2.3 min, the breakage rate was 2.82%, the moisture absorption rate was 3.8%, and there was no obvious rancid odor after 6 months of storage at room temperature. The hardness was 0.86 N, and the elasticity was 0.75. After rehydration, the pork granules had a delicate and chewy texture, no off-odor, and a pure flavor. The meat granules had good elasticity and chewiness without being dry or tough.

[0055] Table 4 Comparative Test of Freeze-Dried Pork Pieces .

[0056] Example 3 Raw material pretreatment: Select fresh chicken, remove tendons, fat and blood stains, cut into chicken pieces with a diameter of 10mm, remove surface blood and free fat, drain and set aside. Construction of the dense inner gel framework: 5.5 parts soy protein isolate, 3 parts wheat protein powder, 1.0 part konjac glucomannan, 0.5 parts xanthan gum, and 90 parts water were mixed evenly to obtain a protein-polysaccharide composite gel. 12% of the protein-polysaccharide composite gel by weight of the pretreated chicken pieces was added to the chicken pieces. The vacuum degree was controlled at -0.06 MPa, the tumbling temperature was 4℃, and the tumbling time was 45 min. Subsequently, the mixture was placed in a refrigerated environment at 8℃ for 4 h to allow the protein-polysaccharide composite gel to gel in situ inside the chicken pieces, resulting in pre-gelled chicken pieces. Steaming and cooking: The pre-gelled chicken is steamed and cooked at 80 ℃, then cooled for later use; One-time quick freezing: Pre-gelled chicken pieces are frozen at -30℃ for 8 minutes to fix the shape of the meat pieces and promote the construction of a dense gel skeleton in the inner layer; Construction of the outer porous rehydration layer: A 12% (w / w) maltodextrin-hydroxypropyl starch-gum arabic composite solution (maltodextrin:hydroxypropyl starch:gum arabic = 1.5:1:0.5) was prepared. Chicken pieces that had been quick-frozen once were placed in the composite solution and immersed for 10 minutes to ensure that the composite solution was evenly adhered to the surface of the chicken pieces. The chicken pieces were then quick-frozen again at -35℃ for 12 minutes to obtain gradient-frozen chicken pieces. First electrostatic field treatment: Low-voltage electrostatic field treatment was applied to the gradient-frozen chicken pieces. The electric field strength was 20kV / m, the treatment time was 10min, and the treatment temperature was -30℃. This helped to directional ice crystal formation and enhance the gradient difference between the inner and outer layers. Gradient sublimation drying: The gradient-frozen chicken pieces after the first electrostatic field treatment are subjected to a segmented temperature-controlled sublimation drying process: the chicken pieces are kept at -25℃ for 3 hours to complete the pre-freezing; after the pre-freezing, the chicken pieces enter the initial stage of sublimation drying and undergo a second electrostatic field treatment. A weak electrostatic field is applied (electrode spacing 10cm), the electric field strength is 10kV / m, the treatment time is 3 hours, and the treatment temperature is -10℃. Sublimation drying stage: After the weak electrostatic field treatment is completed, continue to maintain the sublimation drying parameters, with a vacuum degree of -0.08 MPa and a temperature controlled at -10℃. The total drying time is 10 hours (including the time for the second electrostatic field treatment). Analysis of the drying stage: The vacuum degree is kept constant, the temperature is increased to 45℃ at a rate of 5℃ / h, and dried for 6h to obtain freeze-dried chicken pieces with a gradient porous structure.

[0057] Preparation of traditional freeze-dried chicken pieces: The pre-treated chicken breast pieces are processed using a single freezing + conventional vacuum freeze-drying process, in which the meat pieces are directly placed into a quick-freezing machine and frozen at -35℃ without gradient, direction, or secondary freezing; in the vacuum freeze-drying stage, pre-freezing, sublimation drying and desorption drying are carried out directly without segmented temperature control, electrostatic field assistance, or structure regulation.

[0058] The performance of the freeze-dried chicken pieces prepared in this embodiment and the traditional freeze-dried chicken pieces were compared. The results are shown in Table 5. The freeze-dried chicken pieces prepared in Example 3 had a rehydration time of 1.8 min, a breakage rate of 2.9%, a moisture absorption rate of 3.74%, and no obvious rancid odor after 6 months of storage at room temperature. The hardness was 0.82 N and the elasticity was 0.72. After rehydration, the chicken pieces had a tender and elastic texture, a rich flavor, and no dryness.

[0059] Table 5 Comparative Test of Freeze-Dried Chicken Pieces .

[0060] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. Electrostatic field assisted gradient freeze meat pellets, characterized in that, The freeze-dried meat particles have a double-layer gradient porous structure, with the inner layer being a dense gel skeleton layer and the outer layer being a loose porous rehydrated layer. The freeze-dried meat particles are prepared by a two-stage segmented electrostatic field-assisted freeze-drying process. The two segmented electrostatic field treatments include: a first electrostatic field treatment, applied after the construction of the outer loose and porous rehydrated layer and before the freeze-drying sublimation stage, to optimize the ice crystal morphology and enhance the gradient difference between the inner and outer layers; and a second electrostatic field treatment, applied at the beginning of the freeze-drying sublimation stage, to accelerate water vapor diffusion and inhibit structural collapse.

2. The electrostatic field-assisted gradient freeze meat pellets of claim 1, wherein, The dense gel skeleton layer is composed of muscle fibers and protein-polysaccharide composite gel; the protein-polysaccharide composite gel is composed of 4-6 parts soy protein isolate, 1-3 parts wheat protein powder, 0.5-1.5 parts konjac glucomannan, 0.2-0.5 parts xanthan gum and 90-93 parts water, and the amount added is 8%-12% of the weight of meat particles.

3. The electrostatic field-assisted gradient freeze meat pellets of claim 1, wherein, The loose and porous rehydration layer is formed by impregnation with a maltodextrin-hydroxypropyl starch-gum arabic composite solution; the mass concentration of the composite solution is 10%~15%, wherein the mass ratio of maltodextrin, hydroxypropyl starch and gum arabic is (1.2~1.6):(0.8~1.2):(0.4~0.6).

4. The method for preparing electrostatic field-assisted gradient freeze-dried meat particles as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Meat particles are mixed with protein-polysaccharide composite gel, and the composite gel is penetrated into the meat particles by vacuum tumbling. Then, the composite gel is allowed to gel in situ by low-temperature standing, resulting in pre-gelled meat particles with a dense gel skeleton layer. Pregelatinized meat particles are flash-frozen once to fix the internal dense gel skeleton layer, then surface coating treatment is performed and flash-frozen a second time to form a loose porous rehydrated layer on the surface, resulting in frozen meat particles with an inner and outer double-layer gradient porous structure. A first electrostatic field treatment was applied to frozen meat particles with an inner and outer double-layer gradient porous structure. The meat pieces that have undergone the first electrostatic field treatment are pre-frozen; The pre-frozen meat pieces are subjected to sublimation drying. A second electrostatic field treatment is applied at the beginning of the sublimation drying process, and then the sublimation drying continues until it is completed. The sublimated and dried meat particles are subjected to analytical drying to obtain freeze-dried meat particles.

5. The preparation method according to claim 4, characterized in that, The electric field strength of the first electrostatic field treatment is 10~20kV / m, the treatment time is 5~10min, and the treatment temperature is -40℃~-30℃; the electric field strength of the second electrostatic field treatment is 5~10kV / m, the treatment time is 2~3h, and the treatment temperature is -15℃~-10℃.

6. The preparation method according to claim 4, characterized in that, The pre-freezing temperature is -30℃ to -25℃, and the holding time is 2 to 3 hours; the sublimation drying vacuum degree is -0.09 to -0.08 MPa, the temperature is -15℃ to -10℃, and the total drying time is 8 to 10 hours; the desorption drying temperature is 35 to 45℃, and the drying time is 4 to 6 hours.

7. The preparation method according to claim 4, characterized in that, The first quick-freezing temperature is -40℃ to -30℃, and the time is 5 to 8 minutes; the second quick-freezing temperature is -45℃ to -35℃, and the time is 8 to 12 minutes.

8. The preparation method according to claim 4, characterized in that, The surface coating treatment involves immersing the surface in a maltodextrin-hydroxypropyl starch-gum arabic composite solution for 5-10 minutes.

9. The preparation method according to claim 4, characterized in that, The vacuum tumbling process is performed at a vacuum level of -0.08 to -0.06 MPa, a tumbling temperature of 0 to 4°C, and a tumbling time of 30 to 45 minutes; the low-temperature settling process is performed at a temperature of 2 to 8°C for 2 to 4 hours.

10. The preparation method according to claim 4, characterized in that, During the vacuum tumbling process, 0.3% to 0.5% of tea polyphenols by weight of the meat particles are added; the electrostatic field is a DC flat plate electrostatic field with an electrode spacing of 5 to 10 cm.

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