A quick pickling system and method for salted duck eggs

Abstract

This invention discloses a rapid salted duck egg pickling system and method, comprising: extracting groundwater, vacuum degassing to remove dissolved oxygen and free gas, heating and maintaining a constant temperature of 40-45℃ within a safe fresh-keeping temperature range to obtain constant-temperature pure water, mixing the constant-temperature pure water with salt, preparing a first concentration of constant-temperature brine in the early stage of the total pickling cycle, and increasing the brine concentration to a second saturation state in the later stage of the total pickling cycle; loading the fresh duck eggs to be pickled into a pickling tank, and driving the constant-temperature brine prepared by S2 to circulate within the tank; monitoring and controlling the liquid level in real time during the pickling process, and when the liquid level drops and triggers the water replenishment threshold, using the waste heat generated by the heating process of S1 to preheat the replenishment water to the safe fresh-keeping temperature range before injecting it into the system; significantly improving the efficiency of the conversion of sound wave energy into microfluidic kinetic energy, fundamentally eliminating the fluid physical barrier that hinders the radial penetration of salt.

Description

Technical Field

[0001] This invention relates to a method for rapidly pickling salted duck eggs, and more particularly to a system and method for rapidly pickling salted duck eggs. Background Technology

[0002] Salted duck eggs, a traditional delicacy, are beloved by consumers for their unique taste and rich nutrition. Traditional methods of salting duck eggs, such as soaking or mud-wrapping, involve curing periods lasting weeks or even months, resulting in low production efficiency and difficulty in meeting the demands of large-scale production. To shorten curing time, several rapid curing technologies have emerged in recent years, among which methods using ultrasound and other sound waves for assisted curing have attracted widespread attention due to their ability to accelerate salt penetration. These technologies typically place duck eggs in a salt solution and use sound waves to generate cavitation effects or microjets, thereby disrupting the boundary layer on the eggshell surface and promoting salt migration into the egg.

[0003] However, existing acoustic-assisted pickling systems have an inherent drawback in practical applications: problems arising from improper pretreatment of the pickling liquid. Specifically, most existing technologies directly use untreated water to prepare the pickling liquid and then apply it directly to the pickling process after heating it to a set temperature. When the temperature rises, dissolved gases (such as oxygen and nitrogen) in the water precipitate out in large quantities due to decreased solubility, forming tiny bubbles. Because eggshells have a naturally rough microstructure and hydrophilic / hydrophobic heterogeneity, these precipitated gases easily adsorb and accumulate on the eggshell surface, gradually forming a dense microbubble shielding layer. This bubble layer adheres tightly to the outer wall of the eggshell, significantly altering the propagation path and energy distribution of sound waves in the medium. When sound waves pass through the bubble layer, severe reflection and scattering occur due to the strong acoustic impedance mismatch between the gas and liquid interfaces, resulting in a significant attenuation of the sound wave energy that should have acted on the eggshell surface, weakening or even completely suppressing the cavitation and mechanical effects of ultrasound. Ultimately, the rate of salt penetration cannot be effectively increased, making it difficult to achieve the goal of rapid pickling. Instead, it may lead to uneven pickling or prolong the pickling time, becoming a key bottleneck restricting the industrialization of this technology. Summary of the Invention

[0004] This invention overcomes the shortcomings of the prior art and provides a rapid salted duck egg pickling system and pickling method.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a method for rapidly pickling salted duck eggs, comprising the following steps:

[0006] S1: Extract groundwater, degas it under vacuum to remove dissolved oxygen and free gas, heat it and maintain it at a safe fresh temperature range of 40-45℃ to obtain constant temperature pure water.

[0007] S2: Mix constant temperature pure water with salt, prepare a constant temperature brine of the first concentration in the first part of the total pickling cycle, and increase the brine concentration to the second concentration saturation state in the second part of the total pickling cycle.

[0008] S3: Load the fresh duck eggs to be pickled into the pickling box, and drive the constant temperature brine prepared in S2 to circulate in the box;

[0009] During the cyclic pickling process, two different pickling states, the relaxation phase and the pumping phase, are periodically alternated; and during the pumping phase, the fluid in the tank is simultaneously subjected to multi-frequency alternating sweeping ultrasonic treatment.

[0010] S4: Monitor and control the liquid level in real time during the marinating process. When the liquid level drops and triggers the water replenishment threshold, use the waste heat generated by the heating process of S1 to preheat the replenishment water to the safe fresh temperature range before injecting it into the system.

[0011] In a preferred embodiment of the present invention, the temperature control parameters in S1 and S4 are as follows:

[0012] The vacuum level for vacuum degassing is -80 to -60 kPa;

[0013] A heat pump unit is used to heat the deaerated water source;

[0014] When replenishing the water source, select an underground water source with an initial temperature of 15-16℃, and let it flow through the waste heat recovery sleeve outside the heat pump unit's exhaust pipe to preheat it to a safe fresh food temperature range before injecting it.

[0015] In a preferred embodiment of the present invention, in step S2, the total pickling period is 7 days;

[0016] The first three days of the total pickling cycle are the first three days, during which the concentration of the constant-temperature brine is controlled at 10-20%.

[0017] The latter part of the total pickling cycle is from day 4 to day 7. During this period, the amount of salt dissolved is controlled to gradually increase the concentration to the second concentration, which is a saturated brine with a mass concentration of 20-30%.

[0018] In a preferred embodiment of the present invention, in S3, a sawtooth wave frequency conversion flushing method is used cyclically:

[0019] The circulation pump that drives the constant temperature brine circulation operates in a sawtooth wave frequency conversion mode, so that the flow rate of the constant temperature brine entering the pickling tank changes periodically in a sawtooth pattern between 0.5-1.5m / s, so as to generate fluid shear force to peel off the microbubbles on the surface of the duck eggshell.

[0020] In a preferred embodiment of the present invention, the periodic alternation of in S3 specifically refers to:

[0021] The relaxation phase involves evacuating the air to create a slightly negative pressure environment of -20 to -15 kPa and maintaining it for 10-15 minutes, causing the air cells inside the duck egg to expand and enlarge the micropores.

[0022] The pumping period is to restore to the standard atmospheric pressure and maintain it for 20-30 minutes, during which the external constant temperature brine is strongly rebounded under pressure and seeps into the micropores.

[0023] The diastolic and pumping phases alternate, with a time interval of 1.5-2.5 hours between two adjacent cycles.

[0024] In a preferred embodiment of the present invention, in S3, the multi-frequency alternating sweep ultrasound is:

[0025] The ultrasonic waves, which alternate between 28kHz and 40kHz, are used and activated only during the pumping phase to avoid the resonant frequency of the duck eggshell. The cavitation acoustic flow effect is also used to dissociate the lipoproteins inside the yolk.

[0026] In a preferred embodiment of the present invention, in step S3, the fresh duck eggs to be pickled are placed into a carrying tray and then sent into a pickling box via a track. The pickling status can be checked through an observation hole on the top of the box.

[0027] In a preferred embodiment of the present invention, the pickling environment temperature is maintained below the coagulation critical point of duck egg albumin while reaching the phase transition softening critical point of unsaturated fatty acids in the yolk. Combined with vacuum pressure difference and ultrasonic cavitation, the free fatty acids in the duck egg are cold-promoted to extract oil and form sand in a fresh state.

[0028] A rapid salted duck egg pickling system includes:

[0029] The pretreatment unit includes a well water pump for pumping water, a vacuum degassing tank, and a heat pump unit for heating, which are connected in sequence.

[0030] The pickling box has an internal tray for holding duck eggs and an external dual-frequency ultrasonic generator and a vacuum assembly for creating a slight negative pressure.

[0031] Built-in salt tank with a salt filling port at the top;

[0032] A circulating brine circuit is formed between the pickling box, the heat pump unit, and the built-in salt tank: water is drawn from inside the pickling box by a circulating water pump and flows sequentially into the return water pipe of the heat pump unit and the built-in salt tank, so that the salt added from the salt inlet is fully dissolved in the built-in salt tank and then flows back to the pickling box to contact the duck eggs.

[0033] In a preferred embodiment of the present invention, a liquid level adjustment module is also included:

[0034] The liquid level control module includes: a liquid level gauge installed on the side wall of the pickling tank, and a remote control center connected to the liquid level gauge signal;

[0035] When the liquid level gauge detects a drop in the liquid level due to water evaporation in the system, the remote control center automatically opens the water replenishment valve to replenish water.

[0036] The water replenishment pipeline includes a waste heat recovery sleeve that covers the outside of the heat pump unit's condenser exhaust pipe, used to preheat the groundwater during automatic water replenishment.

[0037] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0038] (1) This invention provides a rapid salted duck egg pickling system and pickling method. By introducing a specific vacuum degassing pretreatment in the fluid medium preparation stage, and combining it with a sawtooth wave frequency conversion flushing mechanism in the cyclic pickling process, the mass transfer properties of the medium are reconstructed from the underlying fluid dynamics and thermodynamics dimensions. The dissolved oxygen and free gas inside the water body are analyzed and extracted, reducing the irreversible adhesion work of microbubbles at the solid-liquid interface. At the same time, the elimination of the gas buffer absorption effect inside the medium causes the primary sound pressure threshold of cavitation bubble collapse to drop sharply. Based on this transformation of pure medium properties, the sawtooth wave frequency conversion flow velocity applied by the system generates continuously changing direction and strong [effects] at the boundary layer on the surface of the duck egg. The combination of local shear force and dynamic shear force completely removes the microbubbles remaining around the micropores of the eggshell. Compared with the inherent defects of existing technologies that directly heat the undated water source, resulting in a large amount of gas precipitation and the formation of a dense microbubble shielding layer on the eggshell surface, which severely attenuates the sound wave energy, this technical solution effectively eliminates the physical barrier structure, ensuring that the high-concentration salt ions are in close contact with the outer wall of the eggshell without dead angles. This not only provides a transmission channel with extremely low energy attenuation for subsequent acoustic pressure coupling intervention, but also significantly improves the efficiency of sound wave energy conversion into microfluidic kinetic energy, fundamentally eliminating the fluid physical barrier that hinders the radial penetration of salt.

[0039] (2) This invention constructs a stepped fluid solution from low to high concentration and couples it with periodically alternating micro-negative pressure relaxation, atmospheric pressure pumping, and dual-frequency sweeping ultrasonic treatment to achieve efficient permeation and lipid dissociation under safe fresh temperature conditions. In the pre-pickled stage, a gentle initial osmotic pressure difference is established using medium-low concentration brine to prevent excessive exposure of the hydrophobic groups of the surface ovalbumin. The micro-negative pressure environment mechanically stretches the micropores of the eggshell, and at the moment of atmospheric pressure rebound, a dual-frequency cavitation micro-acoustic flow that avoids the resonant frequency is used to force salt ions into the expansion channel. At the same time, the extremely high mechanical shear force of the micro-acoustic flow directly destroys the low-density lipids inside the duck egg yolk. Compared to existing technologies that use a single high-concentration brine to induce acute dehydration and shrinkage of proteins to form a dense salting-out sealing layer, or rely on destructive high-temperature thermal permeation to cause irreversible coagulation and maturation of egg white, this solution cleverly avoids the molecular cross-linking and locking reaction caused by high osmotic pressure. It maintains the continuous opening of the microscopic pores of the tissue throughout the entire processing cycle. Without damaging the initial fresh physical state of the outer egg white, this solution allows deep unsaturated fatty acids to detach from the protein binding and be released in large quantities. This significantly compresses the conventional static marinating cycle of several tens of days and gives the finished product excellent cold-induced oil extraction and sandy texture. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a planar structural diagram of a preferred embodiment of the present invention. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0043] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0044] As shown in the figure, a quick method for pickling salted duck eggs includes the following steps:

[0045] S1: Extract groundwater, degas it under vacuum to remove dissolved oxygen and free gas, heat it and maintain it at a safe fresh temperature range of 40-45℃ to obtain constant temperature pure water.

[0046] S2: Mix constant temperature pure water with salt, prepare a constant temperature brine of the first concentration in the first part of the total pickling cycle, and increase the brine concentration to the second concentration saturation state in the second part of the total pickling cycle.

[0047] S3: Load the fresh duck eggs to be pickled into the pickling box, and drive the constant temperature brine prepared in S2 to circulate in the box;

[0048] During the cyclic pickling process, two different pickling states, the relaxation phase and the pumping phase, are periodically alternated; and during the pumping phase, the fluid in the tank is simultaneously subjected to multi-frequency alternating sweeping ultrasonic treatment.

[0049] S4: Monitor and control the liquid level in real time during the marinating process. When the liquid level drops and triggers the water replenishment threshold, use the waste heat generated by the heating process of S1 to preheat the replenishment water to the safe fresh temperature range before injecting it into the system.

[0050] It should be noted that this invention addresses the technical problems of low salt penetration rate and difficulty in extracting egg white protein and yolk fat when salted duck eggs are rapidly pickled at safe fresh temperatures. It proposes a rapid pickling technology based on acoustic pressure coupling and dynamic flow field synergy. This technology involves introducing source water and performing vacuum degassing to eliminate free gas in the fluid, combined with a stepped concentration solution preparation mechanism to alleviate surface gelation resistance caused by the initial high-saturation brine. Simultaneously, during the forced brine circulation process, a periodically alternating pressure environment is used, and during the pumping phase, dual-frequency sweeping ultrasound is applied simultaneously. This utilizes the pressure difference to physically expand the eggshell micropores and, in conjunction with the ultrasonic cavitation effect, promotes deep penetration of salt molecules. Furthermore, the built-in salt tank circulation structure and waste heat recovery preheating and water replenishment mechanism maintain the dynamic stability of the internal temperature and concentration fields during the pickling process.

[0051] Compared to existing technologies, this solution effectively overcomes the technical defects of traditional high-temperature thermal infiltration, which leads to irreversible coagulation of egg white and a lengthy pickling cycle at room temperature. This solution utilizes the coupling effect of alternating pressure fields and multi-frequency ultrasonic fields to significantly improve the radial mass transfer efficiency of salt and greatly shorten the pickling cycle at temperatures below the coagulation critical point of ovalbumin. Furthermore, it effectively dissociates the lipoprotein structure inside the egg yolk through the low-frequency acoustic flow effect, thereby achieving the precipitation of free fatty acids and sand formation in fresh duck eggs. Combined with source water degassing and waste heat preheating technologies, this solution eliminates the infiltration obstacles caused by bubble shielding effect and cold shock phenomenon, further improving the stability of industrial continuous production and the overall energy utilization rate of the system.

[0052] S1: Extract groundwater, degas it under vacuum to remove dissolved oxygen and free gas, heat it and maintain it at a safe fresh temperature range of 40-45℃ to obtain constant temperature pure water.

[0053] In a preferred embodiment of the present invention, the temperature control parameters in S1 and S4 are as follows:

[0054] The vacuum level for vacuum degassing is -80 to -60 kPa;

[0055] A heat pump unit is used to heat the deaerated water source.

[0056] It should be noted that in S1, the system first extracts natural groundwater as the base medium for liquid preparation. Conventional groundwater sources contain a large amount of dissolved air. When the fluid is subsequently heated or subjected to physical vibration, these dissolved oxygen and free gases are easily released. Therefore, this scheme uses a vacuum degassing tank to treat the extracted groundwater under negative pressure. In actual industrial applications, a rotary vane vacuum pump or a water ring vacuum pump is used as the power source to reduce the pressure inside the degassing tank and maintain it in the range of -80 kPa to -60 kPa. According to the physical mechanism that the solubility of gas in a liquid is proportional to the partial pressure of gas above the liquid surface, the internal gas pressure balance of the groundwater under this negative pressure condition is broken. The dissolved oxygen and other free gases in the water quickly overflow from the liquid phase and are extracted by the vacuum system, thereby producing degassed pure water without impurity gases.

[0057] This deep degassing process solves the problem of penetration obstruction during the rapid pickling of duck eggs. If untreated water is used directly in the subsequent pickling process, the gas in the water will accumulate and precipitate in large quantities under heating and forced circulation, forming a dense layer of microbubbles on the surface of the duck eggshell. These microbubbles form a physical barrier structure, directly blocking the path of external salt ions to penetrate into the duck eggshell. At the same time, when ultrasonic treatment is applied in the subsequent process, the unremoved free gas will absorb and scatter most of the ultrasonic energy, causing the ultrasonic vibration to be unable to effectively act on the duck egg structure. By performing vacuum degassing beforehand, this solution completely eliminates the gas shielding obstruction attached to the eggshell surface, allowing the subsequently prepared brine to achieve close contact with the duck eggshell without dead angles. It also provides a pure medium with low energy attenuation for the ultrasonic transmission in the subsequent process, thereby improving the transmission and penetration efficiency of multi-frequency alternating sweep ultrasonic waves in the fluid.

[0058] After the liquid degassing process is completed, the system heats the degassed water source using an air-source heat pump unit or a water-source heat pump unit. The heat pump unit utilizes the reverse Carnot cycle physical mechanism to absorb low-grade heat energy from the outside environment and transfer it to the water through the phase change process of the refrigerant. This allows for precise temperature control of a large volume of fluid with low energy consumption. This solution sets the heating target range at 40-45℃. This temperature is obtained by calculating the critical conditions for the physical changes of the internal components of duck eggs. The critical temperature for irreversible thermal denaturation and coagulation of ovalbumin in duck egg white is around 60℃, while the temperature conditions for softening of the lipoprotein structure and precipitation of free fatty acids in duck egg yolk are above 40℃. By keeping the working environment temperature constant at 40 to 45℃, the duck egg white is ensured not to coagulate due to heat during the long pickling period of several days, maintaining the freshness of the finished product. At the same time, the fluid has sufficient molecular thermal kinetic energy, which promotes the initial softening of lipids in the egg yolk and creates conditions for subsequent precipitation and aggregation.

[0059] The above steps, through the preparation of 40-45℃ constant-temperature deaerated pure water, provide a solvent with high capacity for the addition of solid salts in S2, eliminating the problem of slow salt dissolution caused by excessively low temperature. In the sound pressure coupling pickling stage of S3, the deaerated pure water becomes a stable and efficient carrier for pressure and sound wave fields. Combined with periodic micro-negative pressure expansion and atmospheric pressure pumping, it promotes the smooth penetration of high-concentration brine through the expanded eggshell micropores. In addition, during the main heating task, the heat pump unit will inevitably release high-heat waste gas through its heat exhaust pipe. This part of the heat energy is completely absorbed by the waste heat recovery sleeve in the anti-cold shock replenishment mechanism of S4, and is used to preheat the 15℃ low-temperature well water that is replenished at any time. This avoids the sudden temperature change caused by the direct mixing of low-temperature water into the pickling box, ensures the continuous constant temperature of the pickling environment, and realizes the closed-loop use of heat energy between different steps.

[0060] S2: Mix constant temperature pure water with salt, prepare a constant temperature brine of the first concentration in the first part of the total pickling cycle, and increase the brine concentration to the second concentration saturation state in the second part of the total pickling cycle.

[0061] In a preferred embodiment of the present invention, in step S2, the total pickling period is 7 days;

[0062] The first three days of the total pickling cycle are the first three days, during which the concentration of the constant-temperature brine is controlled at 10-20%.

[0063] The latter part of the total pickling cycle is from day 4 to day 7. During this period, the amount of salt dissolved is controlled to gradually increase the concentration to the second concentration, which is a saturated brine with a mass concentration of 20-30%.

[0064] It should be noted that in S2, after receiving the constant-temperature pure water prepared in S1, the solute used is industrial-grade sodium chloride with a purity that meets food safety standards. The system guides the constant-temperature deaerated pure water into the area equipped with the salting structure through internal pipelines, and, in conjunction with an online conductivity transmitter and flow regulating valve, adjusts and monitors the concentration of salt ions inside the fluid in stages. The total duration of the entire pickling process is set to seven days. During the first three days of pickling, the system controls the dissolution ratio of sodium chloride, strictly limiting the mass concentration of the constant-temperature brine to a value range of 10%-20%.

[0065] This stepwise concentration control mechanism avoids the protein salting-out hindrance induced by high osmotic pressure during fluid mass transfer. If a fresh duck egg is directly and completely immersed in highly saturated brine, the outer layer of ovalbumin adhering to the eggshell will undergo rapid and sudden water loss under the influence of the extremely large osmotic pressure gradient. This rapid water loss causes the outer protein molecules to structurally aggregate and gel through salting-out, forming a dense physical sealing layer on the outermost surface of the egg white. This sealing layer cuts off external salt ions, allowing further... The path of salt transport to the deeper layers of the egg results in a large accumulation of salt on the surface of the duck egg, which cannot effectively reach the yolk inside. This is the core reason why the traditional single high-concentration rapid pickling method results in a tasteless interior and the inability to develop a sandy texture. In contrast, this method uses a medium-low concentration brine of 10% to 20% in the initial pickling stage to establish a relatively gentle osmotic pressure difference between the internal and external environments of the duck egg. This allows sodium and chloride ions to penetrate the micropores of the eggshell at a gentle and stable rate and be evenly distributed inside the egg white, thus ensuring the continuous opening and smooth flow of internal ion transport channels.

[0066] With the initial establishment of osmotic channels and the increase in the basic salt concentration inside the duck egg white, the system adjusts the fluid circulation logic during the later stages of pickling from the fourth to the seventh day. This allows more sodium chloride solids to dissolve into the liquid, gradually increasing the fluid's mass concentration until it reaches a near- or fully saturated state of 20%-30%. When entering the later stages of processing, the osmotic pressure difference between the inside and outside of the duck egg is widened again. At this point, the duck egg white has already absorbed an appropriate amount of salt and completed the initial balance of internal osmotic pressure. Its molecular structure has adapted to the high-concentration environment, so the outer protein no longer has the physical conditions for acute salting-out gelation. The increased fluid concentration at this time is directly converted into a strong radial mass transfer driving force, propelling a large number of subsequent salt ions along the previously established and unblocked pathways to the central region of the duck egg, significantly improving the efficiency of salt absorption by the duck egg yolk.

[0067] The dynamic solution preparation process in this step, along with the preceding and following steps, involves degassing and maintaining pure water at 40-45℃. This not only provides a high solubility limit for sodium chloride but also ensures absolute uniformity of the brine concentration after mixing by eliminating interference from microbubbles. When connecting to the subsequent acoustic-pressure coupled pickling step, the stepwise concentration change pattern and the change in mechanical pressure field produce a cumulative effect. In the early stage, when negative pressure and ultrasound are applied, the low-to-medium concentration brine, combined with physical expansion, safely opens up the physical pores of the eggshell. In the later stage, when the same forced pumping and ultrasonic permeation methods are applied, the high-concentration saturated brine is efficiently pressed into the deep tissues of the duck egg using the expanded pore structure. With the help of the internal salt tank and circulating water pump, the dynamic increase in concentration is entirely accomplished by the automatic dissolution and reflux of the fluid through the salt tank, ensuring continuous distribution and stable control of internal temperature and ion concentration throughout the seven-day processing period.

[0068] S3: Load the fresh duck eggs to be pickled into the pickling box, and drive the constant temperature brine prepared in S2 to circulate in the box;

[0069] During the cyclic pickling process, two different pickling states, the relaxation phase and the pumping phase, are periodically alternated; and during the pumping phase, the fluid in the tank is simultaneously subjected to multi-frequency alternating sweeping ultrasonic treatment.

[0070] In a preferred embodiment of the present invention, in S3, a sawtooth wave frequency conversion flushing method is used cyclically:

[0071] The circulation pump that drives the constant temperature brine circulation operates in a sawtooth wave frequency conversion mode, so that the flow rate of the constant temperature brine entering the pickling tank changes periodically in a sawtooth pattern between 0.5-1.5m / s, so as to generate fluid shear force to peel off the microbubbles on the surface of the duck eggshell.

[0072] In a preferred embodiment of the present invention, the periodic alternation of in S3 specifically refers to:

[0073] The relaxation phase involves evacuating the air to create a slightly negative pressure environment of -20 to -15 kPa and maintaining it for 10-15 minutes, causing the air cells inside the duck egg to expand and enlarge the micropores.

[0074] The pumping period is to restore to the standard atmospheric pressure and maintain it for 20-30 minutes, during which the external constant temperature brine is strongly rebounded under pressure and seeps into the micropores.

[0075] The diastolic and pumping phases alternate, with a time interval of 1.5-2.5 hours between two adjacent cycles.

[0076] In a preferred embodiment of the present invention, in S3, the multi-frequency alternating sweep ultrasound is:

[0077] The ultrasonic waves, which alternate between 28kHz and 40kHz, are used and activated only during the pumping phase to avoid the resonant frequency of the duck eggshell. The cavitation acoustic flow effect is also used to dissociate the lipoproteins inside the yolk.

[0078] In a preferred embodiment of the present invention, in step S3, the fresh duck eggs to be pickled are placed into a carrying tray and then sent into a pickling box via a track. The pickling status can be checked through an observation hole on the top of the box.

[0079] It should be noted that after the brine concentration preparation in the first and second stages of S2 is completed, the system enters the infiltration pickling operation in S3. The fresh duck eggs loaded inside the industrial support tray are automatically moved and fixed in the pressure-resistant pickling box by mechanical track. The transparent observation area reserved on the top of the pickling box allows the operator to confirm the immersion status of the internal fluid in real time. The system starts the fluid circulation pump to guide the constant temperature brine prepared in the previous process, namely S1, into the pickling box. At this time, the frequency converter inside the circulation pump starts to execute non-linear output, changing the constant fluid delivery to a sawtooth wave frequency conversion mode.

[0080] In the above mode, the brine flow rate entering the pickling tank generates high-frequency sawtooth-shaped fluctuations within the range of 0.5-1.5 m / s. This constantly abrupt and oscillating flow rate gradient generates a physical shear force that continuously changes direction and intensity at the interface between the fluid and the surface of the duck eggshell. This mechanical shear force can forcibly flush and peel away the microbubbles that remain around the tiny pores on the surface of the duck eggshell during the pickling process. This fluid flushing action, combined with the vacuum degassing operation in the previous S1 step, forms a dual protection mechanism to remove the shielding obstruction of bubbles, ensuring that the surface of the eggshell is always in an unobstructed, permeable, and open state.

[0081] While ensuring unobstructed external fluid flow, the system activates a dynamic pressure intervention mechanism inside the sealed pickling chamber. The vacuum assembly outside the pickling chamber is activated, reducing the air pressure in the internal cavity to between -20 and -15 kPa, and maintaining this slightly negative pressure state stably for 10-15 minutes. This stage is defined as the diastolic phase.

[0082] Under the aforementioned micro-negative pressure environment, the air cell inside the duck egg, which was originally in a state of normal pressure equilibrium, undergoes physical expansion due to the sudden drop in external pressure. The expansion generates an outward thrust, causing the duck egg shell structure and the attached inner membrane tissue to undergo microscopic mechanical stretching. This stretching forces the original air and water permeability micropores of the duck egg shell to be temporarily enlarged, and the originally tight tissue gaps are forcibly stretched open.

[0083] The system then shuts off the vacuum pump and opens the pressure relief valve assembly, allowing the air pressure inside the pickling chamber to quickly rise to the standard atmospheric pressure value and maintain it for 20-30 minutes. This stage is defined as the pumping period. At the moment of air pressure rebound, a huge instantaneous pressure difference is formed inside and outside the expanded eggshell micropores. The external constant-temperature brine is forced to penetrate into the micropores and membrane tissue inside the duck egg under the pressure of atmospheric pressure. The system controls this micro-negative pressure relaxation period and the atmospheric pressure pumping period to form an alternating operating cycle, and sets the time span between two adjacent operations, so that the overall tissue of the duck egg obtains sufficient stress relaxation and ion diffusion buffer time between the force expansion and rebound absorption.

[0084] While the system is in the atmospheric pressure pumping phase and brine is seeping into the micropores in large quantities, the ultrasonic generator located outside the pickling box is simultaneously activated, releasing alternating 28kHz and 40kHz dual-frequency sweeping ultrasonic waves to the internal fluid medium. This alternating dual-frequency sweeping mode is chosen to avoid the standing wave effect generated by a single fixed-frequency ultrasonic wave in the closed cavity, thereby preventing the duck eggshells from physically oscillating and breaking due to contact with sound waves of a specific resonant frequency. When the ultrasonic waves propagate in the fluid, they trigger a violent cavitation effect, generating numerous microscopic cavitation bubbles.

[0085] The aforementioned cavitation bubbles release powerful local acoustic shear force and microjet energy upon rupture. This microacoustic energy can directly penetrate the egg white tissue and act on the central region of the yolk. The lipoprotein emulsion interface, which was originally tightly bound inside the yolk, undergoes structural dissociation under the mechanical tearing and oscillation of the microacoustic energy. This causes the unsaturated fatty acids, which are wrapped and covered by protein molecules, to break free from their bound state. This acoustic effect fills the gap in thermal kinetic energy at a temperature of 40-45℃, allowing fat components that originally required higher temperatures to melt to separate and precipitate at a safe fresh temperature.

[0086] During the aforementioned pressure-switching and sonic pumping operations, the low-concentration brine prepared in the first stage is used. This ensures that the brine absorbed in large quantities through the expanded pores is mild, avoiding the hardening of local protein tissue caused by the sudden influx of high concentrations. When the process enters the subsequent high-concentration stage, the microporous structure, which has been repeatedly stretched and has had its deep pathways safely opened, can accommodate the rapid and direct permeation of high-concentration salt ions. At the same time, since the pressure-switching operation will accelerate the evaporation of fluids on the water surface and cause local temperature fluctuations, the waste heat preheating and water replenishment mechanism introduced in the subsequent fourth step can be seamlessly connected to eliminate the abnormal pressure fluctuations caused by the drop in liquid level in real time, ensuring that the alternating cycle operation always operates continuously under environmental conditions of constant liquid level and absolute uniform temperature.

[0087] It should also be noted that the physical control mechanism of the above-mentioned multi-frequency alternating sweeping ultrasound to avoid the resonant frequency of duck eggshells, in order to overcome the objective uncertainty of the inherent resonant frequency of duck eggshells being affected by the eggshell thickness, geometric shape and size, and acoustic impedance of the immersion medium, this scheme provides a clear method for testing and calibrating the resonant frequency boundary. Before formally applying ultrasonic intervention, the sample duck eggs are suspended and fixed in a simulated pickling test chamber filled with brine of a set concentration. A broadband sound source transmitter is used to output a sweeping sound wave signal with continuously increasing frequency into the fluid medium. At the same time, a non-contact laser Doppler vibrometer is used to monitor the forced vibration displacement and velocity of the outer surface of the duck eggshell in real time. By extracting the basic value of the sound wave frequency when the amplitude of the eggshell surface increases nonlinearly, the resonant frequency distribution spectrum of this specific batch of duck eggs in the actual brine medium can be drawn.

[0088] Test results confirm that fresh duck eggs, as macroscopic ellipsoidal structures containing a fluid core, have their dominant overall structural resonance frequency and local thickness resonance frequency concentrated in the mid-to-low frequency acoustic range of 2 kHz to 20 kHz. The dual-frequency alternating sweep ultrasound of 28 kHz and 40 kHz used in this system is strictly located in the safe region to the right of the upper limit of the aforementioned measured resonance frequency. This physical design, which significantly widens the frequency difference, allows the high-frequency oscillation energy of the ultrasound to be mainly converted into microscopic cavitation acoustic flow through the water molecule medium, rather than being absorbed in large quantities by the eggshell structure through resonant coupling. This cuts off the resonance excitation source that causes eggshell fatigue and breakage at the physical acoustic level, ensuring that when changing duck eggs of different origins and specifications, those skilled in the art can safely and stably achieve the ultrasonic cavitation permeation effect without repeatedly adjusting the basic frequency of the sound wave generating equipment, without damaging the physical integrity of the eggshell.

[0089] S4: Monitor and control the liquid level in real time during the marinating process. When the liquid level drops and triggers the water replenishment threshold, use the waste heat generated by the heating process of S1 to preheat the replenishment water to the safe fresh temperature range before injecting it into the system.

[0090] In a preferred embodiment of the present invention, in S4, the temperature control parameter is:

[0091] When replenishing the water source, select an underground water source with an initial temperature of 15-16℃, and let it flow through the waste heat recovery sleeve outside the heat pump unit's exhaust pipe to preheat it to a safe fresh food temperature range before injecting it.

[0092] In a preferred embodiment of the present invention, the pickling environment temperature is maintained below the coagulation critical point of duck egg albumin while reaching the phase transition softening critical point of unsaturated fatty acids in the yolk. Combined with vacuum pressure difference and ultrasonic cavitation, the free fatty acids in the duck egg are cold-promoted to extract oil and form sand in a fresh state.

[0093] It should be noted that, because the system needs to switch between normal pressure and negative pressure repeatedly, and the hot brine itself is maintained at a temperature above 40°C, the moisture inside the tank will continue to evaporate and dissipate to the outside, causing the overall liquid level inside the pickling tank to drop. When the liquid level monitoring component set on the outside of the tank wall detects that the fluid level is lower than the set liquid replenishment standard limit, the system control center will immediately activate the water replenishment intervention mechanism.

[0094] During the above process, the system draws natural groundwater with an initial temperature between 15-16℃ as a supplementary medium. In order to avoid the thermodynamic shock caused by the direct flow of this low-temperature fluid into the main circulation system, the supplementary water is not directly discharged into the marinating tank, but is guided into the waste heat recovery pipe fittings sealed on the outside of the heat pump unit's condenser exhaust pipe. While flowing through this section of the pipe, the supplementary water absorbs the heat energy of the exhaust gas released by the heat pump unit. Relying on this physical mechanism of internal energy transfer and reuse, the temperature of the supplementary water is raised to a safe fresh food temperature range before entering the main water circuit, and then it is slowly merged into the overall circulating liquid surface.

[0095] The aforementioned temperature compensation and waste heat utilization mechanism aims to prevent local condensation and contraction reactions within the processing system. At the microscopic mass transfer level, the tiny pores of the duck eggshell after the initial pressure-switching intervention and ultrasonic permeation treatment are in a microscopic physical state of thermal expansion and channel opening. If cold well water at around 15 degrees Celsius is directly added during the liquid level replenishment stage, the temperature of the water mixing area will drop sharply. This sudden local cooling will trigger stress-induced physical contraction of the eggshell components and the internal protein membrane, causing the microscopic mass transfer channels to close instantly.

[0096] The aforementioned channel closure phenomenon caused by temperature difference completely blocks the process of salt ions continuing to penetrate into the duck egg, and it is difficult to reopen it through subsequent ordinary physical means. Through the preheating process of the waste heat recovery pipeline, the newly added water and the original constant temperature water in the box reach the same frequency state with zero temperature difference. While replenishing the total mass of fluid, it maintains the absolute stability of the thermal expansion and contraction balance at the micro level, thereby ensuring that the microporous permeation channel has the physical conditions for continuous operation. At the same time, relying on the heat dissipation of the equipment for preheating, the external power loss caused by heating the low-temperature replenishment water is directly eliminated, improving the thermal cycle efficiency of the system in long-term operation.

[0097] Through the combined operation and mutual support of all four processes mentioned above, the processing system establishes a complete closed-loop working link from medium preparation to constant environmental replenishment, maintaining the basic operating temperature of the system at 40-45℃. This temperature threshold is below the 60℃ critical point where ovalbumin, which plays a major structural role in duck egg white, denatures and coagulates. Therefore, during the seven-day processing cycle, the duck egg maintains its initial fresh protein structure without thermal coagulation. However, at the same time, this temperature limit just crosses the physical boundary where the lipids inside the duck egg yolk undergo the initial phase transition and softening.

[0098] Using the aforementioned specific temperature limits as the environmental basis for the entire processing system, the bubble-free pure medium obtained from vacuum degassing in the early stage provides conditions for high-density ion transfer. In the middle stage, combined with pressure swing physical expansion, salt is pushed into the deep layer of protein. At the same time, microfluidic ultrasonic oscillation at a specific frequency is applied to break down the lipoprotein structure wrapped in the yolk. Multiple physical energies are coupled under this gentle thermal field, allowing the softened unsaturated fatty acids to break free and be released. Without changing the fresh characteristics of the outer clear liquid, the physicochemical transformation of sand formation and oil precipitation is completed in the central area of ​​the duck egg yolk. The continuous and stable temperature system without attenuation is ensured through the end-of-stage waste heat utilization process. The close connection of each process node eliminates the energy loss and physical damage risks in traditional processing methods, constructing an efficient and continuous egg deep processing preparation procedure.

[0099] It should also be noted that the critical point for the phase transition softening of unsaturated fatty acids in egg yolks is a thermodynamic parameter determined experimentally for a specific batch of duck eggs, as there are objective differences in the ratio of lipid components to saturated fatty acids between duck eggs of different breeds and in different spawning seasons. In order to ensure that those skilled in the art can accurately implement this technology and stably achieve the physicochemical effects of cold-induced oil extraction and sand formation, this system uses differential scanning calorimetry to determine the critical point for the phase transition softening of the batch of duck eggs before actual processing.

[0100] The specific testing method described above involves randomly selecting fresh duck eggs from the batch to be processed, extracting lipids from the yolks as test samples, placing the samples in a differential scanning calorimeter, and continuously recording the dynamic endothermic curve of heat flow rate versus temperature under a set programmed temperature rise condition. By analyzing this endothermic curve, the starting temperature of the main melting endothermic peak representing unsaturated fatty acids is calibrated as the phase transition softening critical point of that batch of duck eggs. Extensive sample test data shows that, despite differences in physical properties due to variety and season, the phase transition softening critical point of most conventional duck eggs is distributed within the range of 3°C. Between 8-42℃, the system sets a safe fresh temperature range of 40-45℃, which is a thermodynamic redundancy control range established based on the above-mentioned measured distribution law. This temperature range can ensure that the temperature of the heat transfer medium is always slightly higher than the measured endothermic peak starting point, thereby forming a positive heat transfer gradient of 2-3℃ inside the duck egg. Without triggering the irreversible thermal denaturation and coagulation of duck egg albumin at 60 degrees Celsius, it ensures that the heat is sufficient to penetrate and drive the yolk lipid molecules to undergo a moderate phase transition and softening, maintaining the kinetic conditions for the continuous precipitation and aggregation of free fatty acids in the fresh state.

[0101] A rapid salted duck egg pickling system includes:

[0102] The pretreatment unit includes a well water pump for pumping water, a vacuum degassing tank, and a heat pump unit for heating, which are connected in sequence.

[0103] The pickling box has an internal tray for holding duck eggs and an external dual-frequency ultrasonic generator and a vacuum assembly for creating a slight negative pressure.

[0104] Built-in salt tank with a salt filling port at the top;

[0105] A circulating brine circuit is formed between the pickling box, the heat pump unit, and the built-in salt tank: water is drawn from inside the pickling box by a circulating water pump and flows sequentially into the return water pipe of the heat pump unit and the built-in salt tank, so that the salt added from the salt inlet is fully dissolved in the built-in salt tank and then flows back to the pickling box to contact the duck eggs.

[0106] In a preferred embodiment of the present invention, a liquid level adjustment module is also included:

[0107] The liquid level control module includes: a liquid level gauge installed on the side wall of the pickling tank, and a remote control center connected to the liquid level gauge signal;

[0108] When the liquid level gauge detects a drop in the liquid level due to water evaporation in the system, the remote control center automatically opens the water replenishment valve to replenish water.

[0109] The water replenishment pipeline includes a waste heat recovery sleeve that covers the outside of the heat pump unit's condenser exhaust pipe, used to preheat the groundwater during automatic water replenishment.

[0110] It should be noted that the front end of this system is constructed with a pretreatment unit consisting of fluid transport and media purification devices. The fluid flows sequentially through an industrial well water pump, a vacuum degassing tank, and a heat pump unit. After the well water pump extracts the source water, it is sent to the vacuum degassing tank. The degassing tank creates a specific negative pressure physical environment inside by connecting to a rotary vane or water ring vacuum pump.

[0111] Based on the gas-liquid phase equilibrium mechanism that gas solubility decreases with decreasing pressure, dissolved air and free gases in water are forcibly desorbed and extracted, thereby preparing a pure fluid medium without free bubbles. This medium then enters a heat pump unit with either an air source or a water source system for heat exchange to reach a set constant temperature.

[0112] The treated fluid flows into the pickling tank that carries the main reaction body. The pickling tank is equipped with a tray with an array support structure to stably support the fresh duck eggs. An industrial-grade dual-frequency ultrasonic generator is mounted on the outer side wall of the tank, and a vacuum assembly for exhaust is connected to the top of the tank. The ultrasonic generator outputs multi-frequency alternating sweeping sound waves into the fluid. The mechanical force of the micro-jets released when the cavitation bubbles generated by the sound wave propagation burst physically disperses the lipoprotein molecules solidified inside the duck egg yolk. The vacuum assembly creates negative pressure by removing the internal air. Using the pressure difference between the inside and outside of the duck egg, it applies an outward mechanical expansion force to the micropores of the eggshell, establishing a widened ion permeation channel.

[0113] To facilitate smooth adjustment of salt concentration during processing, the system constructs a circulating salting fluid water circuit that runs through the main body of the equipment. This circulating water circuit uses pressure-resistant pipes to connect the bottom of the pickling tank, the return water pipe of the heat pump unit, and the built-in salt tank equipped with the upper salt inlet in series.

[0114] Throughout the entire operating cycle of the equipment, the circulating water pump continuously draws water at a constant temperature from the pickling tank, pressurizes and propels it through the heat pump unit's return water pipeline to absorb basic heat, and then injects it into the built-in salt tank. An automated feeding mechanism adds solid sodium chloride into the built-in salt tank through the salt inlet. With the continuous flushing and kinetic energy stirring of the fluid, the solid sodium chloride undergoes rapid molecular dissolution and dissociation within the confined space of the built-in salt tank, transforming the fluid into a uniformly concentrated brine medium. Subsequently, the brine flows back to the pickling tank and comes into large-area contact with the duck eggs on the tray. This circulating dissolution hardware architecture, independent of the core working chamber, physically isolates the risk of localized concentration spikes and bottom clumping caused by directly pouring large amounts of solid salt into the pickling tank. It achieves a uniform and smooth transition of the fluid from a low concentration to a high saturation state, avoiding instantaneous salt precipitation and coagulation of the duck egg surface protein caused by high salt stimulation.

[0115] To address the inevitable fluid medium evaporation loss caused by the alternating operation of continuous heating and negative pressure suction, the system incorporates a closed-loop logic liquid level regulation module on the exterior of the pickling tank. This module's hardware includes a magnetic level gauge mounted on the side wall of the pickling tank and a remote industrial control center that establishes bidirectional electrical signal communication with it. When the actual liquid level drops due to water evaporation and reaches the water replenishment trigger line calibrated by the level gauge, the level gauge immediately generates an electrical signal that is fed back to the remote control center. This center then drives the water replenishment valve to open and divert the fluid. Before the replenished fluid enters the main system, low-temperature groundwater is forcibly guided through a metal waste heat recovery sleeve encased around the condenser exhaust pipe of the heat pump unit. According to the physical mechanism of heat conduction, the waste heat emitted by the heat pump compressor during operation penetrates the metal sleeve wall and is largely absorbed by the cold groundwater source inside the sleeve. This preheats the replenished water to the same temperature as the main reaction system during its flow through the pipe before it enters the pickling tank.

[0116] Example 1:

[0117] The system first extracts natural groundwater with an initial temperature of 15°C. The water is then guided into a vacuum degassing tank, which operates under a vacuum pressure of -75 kPa. Utilizing the physical mechanism of gas-liquid phase equilibrium, dissolved oxygen and free gases mixed in with the water are forcibly desorbed and extracted, thereby producing pure degassed water free from bubble interference. The water treated by the degassing process is directly fed into the main circuit of the heat pump unit for heat exchange, heating and maintaining its temperature at a safe freshness limit of 42°C.

[0118] While the fluid medium is being prepared, the cleaned fresh duck eggs to be pickled are loaded into the carrying tray and sent into the pressure-resistant pickling box via a mechanical track. The operator can check the loading and liquid level at any time through the transparent observation hole on the top of the box. The system dynamically mixes the previously prepared 42℃ constant temperature pure water with industrial sodium chloride to prepare the solution. The total pickling cycle of the entire processing operation is 7 days.

[0119] In the early stages of the overall pickling cycle, specifically from day 1 to day 3 of processing, the system controls the salt dissolution ratio to prepare a first-concentration constant-temperature brine, maintaining its mass concentration at 15%. This low-concentration constant-temperature brine is pumped into the pickling tank by a circulating water pump, completely submerging the duck eggs on the trays and initiating initial fluid penetration.

[0120] During the continuous cyclic pickling process where duck eggs are submerged in constant-temperature brine, the circulating pump driving the fluid is set to operate in a sawtooth wave frequency conversion mode. This frequency conversion mode causes the flow rate of the constant-temperature brine entering the pickling tank to exhibit a fixed sawtooth high-frequency fluctuation between a minimum of 0.5 m / s and a maximum of 1.5 m / s. This drastic change in flow rate generates a continuously changing fluid shear force at the interface between the duck egg shell and the liquid.

[0121] While maintaining the variable frequency fluid flushing, the system periodically applies two different physical processing states to the inside of the pickling box: a relaxation phase and a pumping phase. When the system enters the relaxation phase, the external air extraction component starts working, causing the ambient air pressure inside the pickling box to drop rapidly to a slightly negative pressure state of -18 kPa, and maintaining this negative pressure environment stably for 12 minutes. Under the pull of the external low pressure, the air chamber inside the duck egg undergoes physical expansion, forcing the micropores on the eggshell surface to be stretched and expanded outward. Immediately afterwards, the system releases the negative pressure and enters the pumping phase, restoring the internal air pressure to the standard atmospheric pressure state and maintaining it for 25 minutes. Under the transient pressure action of the air pressure rebound, the external constant temperature brine is forced into the depths of the micropores that are already in the expanded state.

[0122] During the same period of the pumping phase, the system simultaneously activates the dual-frequency ultrasonic generator, outputting sweeping ultrasonic waves that alternate between 28kHz and 40kHz to the fluid inside the chamber. This specific dual-frequency alternation mode avoids the inherent resonant frequency of the fragile duck eggshell. The cavitation acoustic flow effect generated by the ultrasonic waves in the fluid directly penetrates the inside of the duck egg, dissociating the lipoprotein structure solidified deep in the yolk through mechanical vibration. The system controls the relaxation phase and the pumping phase to be executed continuously as a complete operating cycle, with a 2-hour time interval between adjacent cycles to allow for free diffusion of internal ions.

[0123] With the completion of the initial low-concentration clearing process, the pickling process enters the latter stage, from day 4 to day 7. At this point, the system actively increases the amount of salt dissolved in the built-in salt tank, raising the fluid concentration from the previous low level to a second concentration of 25% (by mass) saturated brine. This highly saturated, temperature-controlled brine, flowing through the internal pores that were fully opened and where no protein salting-out occurred during the previous three days, rapidly delivers high-density sodium and chloride ions to the core area of ​​the duck egg yolk, achieving efficient ion accumulation and deep penetration.

[0124] During the 7-day processing cycle, the system continuously monitors the liquid level inside the pickling tank in real time using a level gauge. When the natural evaporation of the constant-temperature hot water causes the liquid level to drop and touch the bottom water replenishment threshold, the control system automatically draws in groundwater with an initial temperature of 15°C for fluid compensation.

[0125] To eliminate the risk of sudden temperature drop and pore closure caused by direct injection of cold water, the underground water source is guided to flow through a waste heat recovery sleeve wrapped around the outside of the heat pump unit's condenser exhaust pipe. After fully absorbing the waste heat from the equipment's exhaust, the supplementary water source is precisely preheated to 42°C before entering the pickling tank, and then slowly injected into the main system, achieving seamless compensation for both liquid level and temperature field.

[0126] Example 2:

[0127] A method for rapidly pickling salted duck eggs, the overall process steps of which are the same as those in Example 1, the only difference being the ultrasonic frequency parameter applied during the atmospheric pressure pumping period. In this example, the ultrasonic generator is turned on synchronously during the atmospheric pressure pumping period, but the ultrasonic waves output to the fluid in the chamber are set to a constant frequency of 40kHz single-frequency ultrasonic waves, thus eliminating the dual-frequency alternating sweep working mode.

[0128] Example 3:

[0129] A method for rapidly pickling salted duck eggs, the overall process steps of which are the same as those in Example 1, the only difference being the ultrasonic frequency parameter applied during the atmospheric pressure pumping period. In this example, the ultrasonic generator is turned on synchronously during the atmospheric pressure pumping period, but the ultrasonic waves output to the fluid in the chamber are set to a constant frequency of 40kHz single-frequency ultrasonic waves, thus eliminating the dual-frequency alternating sweep working mode.

[0130] Real-time example 4:

[0131] A method for rapidly pickling salted duck eggs is provided. The overall process steps are the same as those in Example 1. The only difference between the two is the pressure control parameters of the vacuum degassing process. In this example, when the system degasses the groundwater source, the pressure control target inside the vacuum degassing tank is changed to -40 kPa, so that the dissolved gas extraction operation can be completed under relatively low vacuum conditions.

[0132] Example 5:

[0133] A method for rapidly pickling salted duck eggs, the overall process steps of which are the same as those in Example 1, the only difference between the two is the fluid control mode in the circulating pickling process. In this example, the circulating pump that drives the constant temperature brine circulation is set to a constant output mode, so that the flow rate of the constant temperature deaerated brine entering the pickling box is kept constant at 1.0 m / s, without generating periodic changes in fluid shear force.

[0134] Example 6:

[0135] A method for rapidly pickling salted duck eggs, the overall process steps are the same as in Example 1, the only difference is the target temperature parameter of the water replenishment and preheating process. In this example, when the replenished underground water flows through the waste heat recovery sleeve outside the heat pump unit's exhaust pipe, the system reduces the heat absorbed by adjusting the water flow speed, and sets the preheating target temperature to 30°C. Then, the 30°C fluid is injected into the main system.

[0136] Example 7:

[0137] A method for rapidly pickling salted duck eggs has the same overall process steps as in Example 1. The only difference between the two is the target temperature parameter in the water replenishment and preheating process. In this example, when the replenished underground water flows through the waste heat recovery sleeve, the system extends the residence time of the fluid in the sleeve to allow it to absorb more waste heat from the equipment exhaust, and sets the preheating target temperature to 45°C. Then, the 45°C fluid is injected into the main system.

[0138] Comparative Example 1:

[0139] A method for pickling salted duck eggs, the overall process steps are the same as in Example 1, the only difference is the parameter setting of concentration preparation and physical permeation promotion means. In this comparative example, a saturated brine with a constant mass concentration of 25% is directly prepared in the brine preparation process and is used throughout the 7-day pickling cycle, eliminating the step-by-step concentration change mechanism.

[0140] Meanwhile, during the cyclic marinating process, the internal environmental pressure of the marinating tank is always maintained at standard atmospheric pressure, eliminating the alternation between the micro-negative pressure relaxation period and the atmospheric pressure pumping period, and the ultrasonic generator is not activated during the entire cycle.

[0141] Comparative Example 2:

[0142] A method for pickling salted duck eggs, the overall process steps are the same as in Example 1. The only difference is the concentration strategy of the brine. In this comparative example, the stepwise change from low concentration at the beginning to high concentration at the end is eliminated. The concentration of the brine is directly kept constant at 25%, and the total processing time is maintained for 7 days. In the cyclic pickling process, the pressure alternation operation is still exactly the same as in Example 1, as well as the 28kHz and 40kHz dual-frequency alternating sweep ultrasonic treatment.

[0143] Comparative Example 3:

[0144] A method for pickling salted duck eggs, the overall process steps are the same as those in Example 1. The only difference between the two is the setting of the source water pretreatment and fluid flushing parameters. In this comparative example, after the groundwater source is extracted, the heat pump unit is used directly for heating, eliminating the operation step of vacuum degassing to remove dissolved oxygen and free gas.

[0145] Meanwhile, in the circulating pickling process, the circulating pump that drives the constant temperature brine circulation operates in a fixed frequency mode, so that the constant temperature brine flow rate entering the pickling tank is kept constant at 1.0m / s, eliminating the need for sawtooth wave frequency conversion flow rate changes.

[0146] Comparative Example 4:

[0147] A method for pickling salted duck eggs, the overall process steps are the same as those in Example 1, the only difference is the setting of the source water pretreatment process. In this comparative example, after the system extracts the groundwater source, it is directly sent to the heat pump unit for heating without any negative pressure treatment, thus eliminating the vacuum degassing process.

[0148] However, in the circulating pickling process, the system still retains the sawtooth wave frequency conversion mode of the circulating pump, so that the flow rate of the brine entering the pickling tank changes periodically in a sawtooth pattern between 0.5m / s and 1.5m / s.

[0149] Comparative Example 5:

[0150] A method for pickling salted duck eggs has the same overall process steps as in Example 1. The only difference between the two is the temperature compensation in the liquid level control process. In this comparative example, when the liquid level drops due to water evaporation and water replenishment is triggered, the system directly extracts groundwater with an initial temperature of 15°C and injects it directly into the pickling tank. Subsequently, the water is reheated by the heat pump unit through the main circulating water circuit, eliminating the need to preheat the replenished water source using the waste heat recovery sleeve.

[0151] Experiment 1:

[0152] In the course of this experiment, fresh duck egg samples of consistent quality and age were first selected and grouped. Then, according to the parameter combinations specified in the various embodiments and comparative examples, the duck egg samples were placed into an experimental pickling system equipped with fluid circulation, vacuum suction, and ultrasonic emission components. A degassed water source maintained at a constant temperature of 42 degrees Celsius was uniformly injected. Based on this, sodium chloride solid was added according to the set constant brine concentration or a stepped-variable concentration for each group. Simultaneously, the system's set alternating program of micro-negative pressure and normal pressure was activated, and the ultrasonic generator at a specific frequency was turned on or off. After the set seven-day pickling cycle was completed, the duck egg samples from each group were taken out for laboratory testing to obtain various microscopic characterization data reflecting the underlying mechanisms.

[0153] To detect the hydrophobic group exposure index of surface ovalbumin, researchers carefully peeled the shell of the test duck egg under constant temperature conditions and extracted the outermost layer of ovalbumin tissue closely adhering to the inner membrane of the shell as the protein sample to be tested. After centrifugation and purification, the protein sample was prepared into a protein solution of fixed concentration, and a quantitative amount of aniline naphthalenesulfonic acid fluorescent probe solution was added for a light-protected reaction. The probe molecule can specifically bind to the hydrophobic region exposed by the dehydration folding of the protein macromolecule. Subsequently, the reaction solution was placed in a fluorescence spectrophotometer, and its emission spectrum was scanned under a specific ultraviolet excitation wavelength, and the peak relative fluorescence intensity was recorded. By calculating the ratio of probe binding amount to protein concentration, the hydrophobic group exposure index was derived. This value directly quantifies the degree of acute salting out and molecular cross-linking lock-in of the outermost protein.

[0154] To determine the average expansion rate of effective micropores in the eggshell inner membrane, eggshell slices containing the inner membrane tissue were extracted. To prevent physical dehydration from causing membrane structure shrinkage and deformation, the samples were quickly immersed in liquid nitrogen for in-situ structural freeze fixation. Subsequently, they were transferred to a vacuum freeze dryer to remove internal moisture. The surface of the dried membrane structure sample was then vacuum sputtered with gold and placed inside the vacuum chamber of a field emission scanning electron microscope for microscopic morphology observation. Using the matching microscopic morphology image analysis system, the edges of micropores in the inner membrane region were identified and the cross-sectional area of ​​the pores was calculated. This measurement data was compared with the baseline value of the inner membrane pore area of ​​an uncured blank duck egg to obtain the average area increase rate of the membrane pores under alternating air pressure stretching.

[0155] Data on the radial migration flux of free sodium ions were obtained by combining ion mass monitoring with physical size conversion. Within a set pickling time period, radial cutting was performed along the equator of the duck egg, and a clear liquid tissue sample was extracted at a specific penetration depth. The sample was then subjected to microwave digestion, and the absolute mass of sodium in the test solution was precisely quantified using inductively coupled plasma mass spectrometry. Based on the radial penetration cross-sectional area of ​​the extracted tissue, the penetration time, and the increase in the number of sodium ions per molar, the absolute number of sodium ions migrating from the outside to the inside per unit cross-sectional area per unit time was derived using the mass transfer flux calculation formula. This method quantifies the ion transfer efficiency under the synergy of multiple physical fields.

[0156] To obtain the dissociation rate parameters of low-density lipoprotein (LDL) interface in egg yolks, semi-solid material from the center of the pickled duck egg yolk was extracted as the analytical base solution and injected into a pre-prepared density gradient centrifugation solution for ultracentrifugation. The purified LDL layer was separated based on the difference in mass and density. The separated extract was sent to a dynamic light scattering instrument to measure the hydrodynamic particle size distribution changes caused by the destruction of the outer encapsulated protein by ultrasonic shear force. Simultaneously, high-performance liquid chromatography (HPLC) was used to quantitatively determine the total amount of free lipid components escaping through the destroyed interface. The percentage relationship between this total amount of free lipids and the total mass of lipids in the original encapsulated state was calculated. This was used as a specific dissociation rate indicator to measure the success of ultrasonic cavitation flow in destroying the emulsified interface and releasing deep free fatty acids, as shown in Table 1.

[0157] Table 1

[0158] <![CDATA[Surface ovalbumin hydrophobic group exposure index (H0)*]]> Average expansion rate of effective micropores in eggshell inner membrane (%) <![CDATA[Free Na⁺ microscopic radial migration flux (μmol / (cm 2 ·s))]]> Egg yolk low-density lipoprotein (LDL) interfacial dissociation rate (%) Comparative Example 1 185.6 1.2 0.08 5.4 Comparative Example 2 412.3 12.5 0.35 32.8 Example 1 45.2 48.6 2.85 94.2 Example 2 98.5 45.3 2.15 88.6 Example 3 48.8 35.4 1.76 65.4

[0159] As shown in Table 1, the high-concentration saline solution, under the combined effect of mechanical and physical osmosis-enhancing methods, generates a transient high osmotic pressure infusion effect, causing acute dehydration of the outer ovalbumin layer closely attached to the inner side of the duck eggshell. This dehydration process causes a large number of hydrophobic groups of protein molecules to be exposed, triggering abnormal cross-linking and folding of molecular chains, and thus forming a dense salting-out closed network in the surface tissue of the duck egg. This irreversible closed structure at the microscopic level directly counteracts the mechanical tensile stress exerted by the external micro-negative pressure on the eggshell pores, inhibits the effective expansion of the inner membrane micropores, and physically isolates and blocks the microscopic radial migration flux of external sodium ions into the interior of the duck egg.

[0160] By introducing a synergistic intervention mechanism of stepped fluid concentration control and acoustic pressure coupling, the system inputs low-to-medium concentration brine in the pre-processing stage, establishing a gentle initial osmotic pressure gradient between the inner and outer tissues of the duck egg. This specific pressure difference condition controls the exposure index of hydrophobic groups of surface ovalbumin, inhibits the surface cross-linking and denaturation reaction of protein molecules, and maintains the original permeability of surface cells and membrane structures. Under the condition of avoiding the formation of salting-out cross-linking networks, the periodic micro-negative pressure tensile stress can be effectively transmitted to the micropores of the eggshell and inner membrane, increasing the average physical expansion rate of micropores. After the internal micropore channels are mechanically expanded and maintained in an open state, the high-saturation concentration brine input in the post-processing stage provides radial mass transfer driving force. Combined with the ultrasonic cavitation effect applied by the system to change the hydration radius parameter of sodium ions, the micro-radial migration flux of sodium ions inside the pores is increased, realizing the efficient transfer of ions to the deeper tissues.

[0161] Furthermore, by introducing a dual-frequency alternating sweep ultrasonic output mode, the standing wave interference effect in the fluid medium is eliminated, and a cavitation micro-acoustic flow in a continuously changing state is excited inside the fluid. This dynamic micro-acoustic flow outputs continuous hydrodynamic shear stress in a constant temperature environment of 42°C. This shear stress penetrates the outer layer of the duck egg and acts directly on the low-density lipoprotein structure in the yolk region. By applying high-frequency mechanical shear force, the emulsification interface of the low-density lipoprotein is destroyed, and the structural encapsulation of the internal fat components by the protein macromolecules is released. This achieves the physical dissociation of lipids in a fresh environment and establishes a physical pathway for fat desorption and ion transfer at the underlying biochemical reaction level.

[0162] Experiment 2:

[0163] This experiment was conducted in a constant-temperature fluid dynamics test chamber. The internal environment of the chamber was 45°C and it was equipped with transparent optical observation components to cooperate with external optical measurement equipment. Before the test, fresh duck eggs with consistent surface micromorphology were selected as test samples and fixed on a fixture in the center of the test chamber. For different test groups, the system first extracted natural well water. In the example group, the fluid was guided into a vacuum degassing tank. By setting the pumping parameters of the industrial vacuum pump, constant negative pressure environments of -40 kPa and -75 kPa were established for pretreatment to change the initial free gas content in the water. This step was omitted in the comparative group.

[0164] The treated fluid was injected into the test chamber and circulated in a controlled manner by a programmable variable frequency water pump. In the control group with a constant flow rate, the water pump maintained a stable speed output. In the test group with a variable flow rate, the water pump controller introduced a sawtooth wave control program, which caused the fluid to undergo periodic abrupt changes in the range of 0.5-1.5 m / s. Under this fluid movement state, the system synchronously activated a dual-frequency ultrasonic generator to apply acoustic intervention to the fluid, thereby constructing a complete simulated pickling microenvironment.

[0165] During the fluid circulation and acoustic pressure intervention process, various microscopic physical indicators are collected and calculated in real time through in-situ detection equipment. For the indicator of dissolved oxygen supersaturation in the fluid medium, a high-precision optical dissolved oxygen sensor is connected in series in the fluid loop. This sensor measures the actual dissolved oxygen concentration inside the water body under thermal field intervention in real time and calculates the ratio with the theoretical saturated dissolved oxygen concentration at 42℃ to obtain the supersaturation data, thereby measuring the thermodynamic trend of gas evolution inside the fluid.

[0166] To obtain the local Reynolds number of the eggshell boundary layer, the experiment introduced particle image velocimetry technology. During the test, micron-sized tracer particles with extremely high flow characteristics were seeded into the circulating fluid. A high-speed camera and a sheet light source laser were used to continuously record the movement trajectory of the particles in the microscopic boundary region on the surface of the duck eggshell. By processing the continuous image sequence with a cross-correlation algorithm, the real transient fluid shear stress and velocity vector distribution in the solid-liquid interface region were obtained. Then, combined with the fluid kinematic viscosity and the characteristic length of the duck eggshell surface, the local Reynolds number was calculated by deriving fluid dynamics formulas, which accurately reflects the physical disturbance intensity of the fluid scouring state.

[0167] To determine the irreversible adhesion work of microbubbles at the solid-liquid interface, the experiment used a contact angle measuring instrument with a constrained bubble method in conjunction with a dynamic surface tension meter. In a set fluid and temperature environment, a precision sample introduction component automatically released microbubbles of standard volume onto the surface of a duck eggshell. A high-resolution imaging system was used to capture the geometric contour of the bubbles adhering to the eggshell surface and to accurately read the contact angle value formed between the bubbles and the solid phase interface. Simultaneously, the liquid-gas surface tension data of the fluid medium after different degassing treatments were acquired. The above values ​​were substituted into Young's equation and the thermodynamic calculation model of adhesion work to derive the minimum physical energy barrier required for the bubbles to completely detach from the solid phase surface, i.e., the value of the irreversible adhesion work.

[0168] To obtain the primary sound pressure threshold for cavitation bubble collapse, researchers suspended a broadband hydrophone assembly close to the duck egg test sample. When the alternating frequency sweep ultrasonic wave was activated, the hydrophone captured the acoustic emission signal generated inside the fluid in real time. The system performed fast Fourier transform spectrum analysis on the captured signal sequence and continuously monitored the abrupt inflection point of the broadband white noise signal. The lowest ultrasonic source emission pressure value recorded by the system when the inflection point of this secondary acoustic distortion was generated was determined as the primary sound pressure threshold for exciting the microscopic cavitation jet. Various in-situ detection methods worked together to complete the objective data extraction of the mechanical and acoustic properties of the underlying medium under complex conditions, as detailed in Table 2.

[0169] Table 2

[0170] Dissolved oxygen supersaturation (σ) in fluid medium Local Reynolds number (Re) of the eggshell boundary layer Irreversible adhesion work of microbubbles at the solid-liquid interface (mJ / m²) Primary sound pressure threshold (MPa) for cavitation bubble collapse Comparative Example 3 1.85 1250 114.6 0.82 Comparative Example 4 1.92 3450 108.2 0.85 Example 1 0.05 4280 12.4 0.15 Example 4 0.66 3860 45.8 0.42 Example 5 0.08 1320 15.6 0.18

[0171] As shown in Table 2, under the constraint of not changing the total amount of dissolved gas inside the water body, simply applying mechanical frequency conversion flushing to the fluid faces the bottom-layer obstacle of irreversible gas adhesion at the solid-liquid interface. When the undegassed well water is heated and operated at 42℃, the dissolved oxygen supersaturation index inside the fluid medium increases, and a large amount of gas is released. If frequency conversion mechanical flow velocity is forcibly superimposed for flushing at this time, i.e., Comparative Example 4, although the local Reynolds number of the eggshell boundary layer is increased to 3450, indicating that the fluid is in a state of strong turbulent disturbance, the irreversible adhesion work of microbubbles at the solid-liquid interface is still as high as 108.2 mJ / m². This high adhesion work value indicates that the dissolved gas rich in the water body generates an extremely strong surface tension network at the solid-liquid interface. The fluid shear force cannot overcome this adhesion work resistance, resulting in the generated secondary microbubbles firmly adhering to the eggshell surface.

[0172] Meanwhile, the presence of a large amount of dissolved gas acts as an acoustic buffer, absorbing the kinetic energy of sound wave oscillations. This forces the collapse of the cavitation bubble required to excite the cavitation microjets, resulting in a primary sound pressure threshold as high as 0.85 MPa, which inhibits the effective conversion of ultrasonic energy.

[0173] By introducing a deep degassing pretreatment with specific negative pressure parameters, this scheme reconstructs the thermodynamic properties of the fluid medium at the molecular level. Under deep degassing conditions, i.e., in Example 1, the dissolved oxygen supersaturation of the fluid medium is forcibly reduced to 0.05, eliminating the driving force for gas molecule precipitation under heating conditions. With the removal of a large amount of free gas and dissolved oxygen, the surface tension of the fluid at the solid-liquid interface decreases, and the irreversible adhesion work of microbubbles drops sharply to 12.4 mJ / m².

[0174] Based on the aforementioned changes in medium properties, the application of sawtooth wave frequency conversion scouring pushes the local Reynolds number of the fluid boundary layer to 4280. The resulting shear force directly exceeds the already significantly reduced adhesion resistance limit, completely stripping away any remaining sporadic bubbles. Furthermore, due to the loss of gas buffer absorption within the medium, the acoustic properties of the medium change. The cavitation bubble collapse primary sound pressure threshold drops precipitously to 0.15 MPa. This extremely low excitation sound pressure threshold allows low-power sweeping ultrasound to propagate without resistance in the pure medium, and to excite a large amount of secondary micro-acoustic flow with strong penetrating power deep within the medium. Deep degassing alters the medium's interfacial energy and acoustic impedance properties, while frequency conversion scouring provides dynamic shear kinetic energy. The combination of these two factors completely breaks down the physical barriers of gas shielding and energy attenuation at the microfluidic level.

[0175] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for rapidly pickling salted duck eggs, characterized in that, Includes the following steps: S1: Extract groundwater, degas it under vacuum to remove dissolved oxygen and free gas, heat it and maintain it at a safe fresh temperature range of 40-45℃ to obtain constant temperature pure water. S2: Mix constant temperature pure water with salt, prepare a constant temperature brine of the first concentration in the first part of the total pickling cycle, and increase the brine concentration to the second concentration saturation state in the second part of the total pickling cycle. S3: Load the fresh duck eggs to be pickled into the pickling box, and drive the constant temperature brine prepared in S2 to circulate in the box; During the cyclic pickling process, two different pickling states, the relaxation phase and the pumping phase, are periodically alternated; and during the pumping phase, the fluid in the tank is simultaneously subjected to multi-frequency alternating sweeping ultrasonic treatment. S4: Monitor and control the liquid level in real time during the marinating process. When the liquid level drops and triggers the water replenishment threshold, use the waste heat generated by the heating process of S1 to preheat the replenishment water to the safe fresh temperature range before injecting it into the system.

2. The method for rapidly pickling salted duck eggs according to claim 1, characterized in that: In S1 and S4, the temperature control parameters are: The vacuum level for vacuum degassing is -80 to -60 kPa; A heat pump unit is used to heat the deaerated water source; When replenishing the water source, select an underground water source with an initial temperature of 15-16℃, and let it flow through the waste heat recovery sleeve outside the heat pump unit's exhaust pipe to preheat it to a safe fresh food temperature range before injecting it.

3. The method for rapidly pickling salted duck eggs according to claim 1, characterized in that: In S2, the total pickling period is 7 days; The first three days of the total pickling cycle are the first three days, during which the mass concentration of the first concentration of constant-temperature brine is controlled at 10-20%. The latter part of the total pickling cycle is from day 4 to day 7. During this period, the amount of salt dissolved is controlled to gradually increase the concentration to the second concentration, which is a saturated brine with a mass concentration of 20-30%.

4. The method for rapidly pickling salted duck eggs according to claim 1, characterized in that: In step S3, a sawtooth wave frequency conversion flushing method is used cyclically: The circulation pump that drives the constant temperature brine circulation operates in a sawtooth wave frequency conversion mode, so that the flow rate of the constant temperature brine entering the pickling tank changes periodically in a sawtooth pattern between 0.5-1.5m / s, so as to generate fluid shear force to peel off the microbubbles on the surface of the duck eggshell.

5. The method for rapidly pickling salted duck eggs according to claim 1, characterized in that: In S3, the periodic alternation specifically refers to: The relaxation phase involves evacuating the air to create a slightly negative pressure environment of -20 to -15 kPa and maintaining it for 10-15 minutes, causing the air cells inside the duck egg to expand and enlarge the micropores. The pumping period is to restore to the standard atmospheric pressure and maintain it for 20-30 minutes, during which the external constant temperature brine is strongly rebounded under pressure and seeps into the micropores. The diastolic and pumping phases alternate, with a time interval of 1.5-2.5 hours between two adjacent cycles.

6. The method for rapidly pickling salted duck eggs according to claim 1, characterized in that: In S3, the multi-frequency alternating sweep ultrasound is: The ultrasonic waves, which alternate between 28kHz and 40kHz, are used and activated only during the pumping phase to avoid the resonant frequency of the duck eggshell. The cavitation acoustic flow effect is also used to dissociate the lipoproteins inside the yolk.

7. The method for rapidly pickling salted duck eggs according to claim 1, characterized in that: In step S3, the fresh duck eggs to be pickled are placed into a carrying tray and then fed into the pickling box via a track. The pickling status can be checked through an observation hole on the top of the box.

8. The method for rapidly pickling salted duck eggs according to claim 1, characterized in that: By maintaining the pickling environment temperature below the critical point of coagulation of duck egg albumin, while reaching the critical point of phase transition softening of unsaturated fatty acids in the yolk, and combining vacuum pressure difference and ultrasonic cavitation, the free fatty acids in the duck egg are cold-promoted to extract oil and form a sandy texture in a fresh state.

9. A rapid pickling system for salted duck eggs, based on the pickling method according to any one of claims 1-8, characterized in that, include: The pretreatment unit includes a well water pump for pumping water, a vacuum degassing tank, and a heat pump unit for heating, which are connected in sequence. The pickling box has an internal tray for holding duck eggs and an external dual-frequency ultrasonic generator and a vacuum assembly for creating a slight negative pressure. A built-in salt tank, with a salt inlet at the top of the built-in salt tank; A circulating brine circuit is formed between the pickling box, the heat pump unit, and the built-in salt tank: water is drawn from inside the pickling box by a circulating water pump and sequentially enters the return water pipe of the heat pump unit and the built-in salt tank, so that the salt added from the salt inlet is fully dissolved in the built-in salt tank and then flows back to the pickling box to contact the duck eggs.

10. The rapid pickling system for salted duck eggs according to claim 9, characterized in that: It also includes a liquid level control module: The liquid level adjustment module includes: a liquid level gauge installed on the side wall of the pickling tank, and a remote control center connected to the liquid level gauge via signal. When the liquid level gauge detects a drop in the liquid level due to water evaporation in the system, the remote control center automatically opens the water replenishment valve to replenish water. The water replenishment pipeline includes a waste heat recovery sleeve covering the outside of the heat pump unit's condenser exhaust pipe, which is used to preheat the groundwater with waste heat during automatic water replenishment.

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