Sectional temperature control processing technology for locking flavor of sweet and sour allium chinensis

Abstract

The invention relates to the technical field of food processing, and discloses a segmented temperature control processing technology for locking flavor of sweet and sour allium chinense, which comprises the following steps: placing pretreated allium chinense in a first-stage composite liquid containing magnesium and calcium ions for low-temperature dipping, and preventing compact hardening of skin by utilizing ion competition occupation; then pumping a core penetrating fluid containing an interfacial tension regulator, heating to a target high temperature, and carrying out constant-temperature penetration to break through a mass transfer barrier; after permeation is finished, cold liquid at the temperature of 4-8 DEG C is rapidly injected for cold liquid heat exchange impact, and plant tissue pores are promoted to physically shrink to intercept internal flavor substances; and finally, glacial acetic acid is pumped at the tail section of room-temperature curing for delayed acid regulation, and sealed sterilization is performed. According to the invention, temperature and pH control is decoupled on a time axis, acid-promoted hydrolysis of protopectin at high temperature is avoided, and consistency of exterior and interior textures of the allium chinensis finished product and long-term locking of deep sulfur-containing flavor substances are realized while the sugar solution permeation efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to a segmented temperature-controlled processing technology for locking the sweet and sour flavor of shallots. Background Technology

[0002] Sweet and sour pickled shallots are a popular traditional pickled vegetable product. In industrial production, pre-treated shallots are typically soaked in a solution containing sugar, acid, and a crisping agent to impart their unique sweet and sour flavor and crunchy texture. Current conventional processing methods mostly employ long-term soaking at room temperature or a single-step heating and sugar-infusion process.

[0003] During unidirectional soaking at room temperature, the high concentration of sweet and sour solution makes it difficult for the solution to spontaneously penetrate the dense micropores of the scallion's plant tissue due to its high interfacial tension, resulting in a lengthy mass transfer cycle. To maintain the crispness of the material during processing, existing processes often add calcium salts directly at the initial stage of soaking. However, under acidic conditions, calcium ions rapidly cross-link with the pectin carboxyl groups of the scallion's surface tissue, forming an extremely dense cross-linked structure. This hardening of the surface deteriorates the overall chewy texture of the material and creates significant steric hindrance, blocking the diffusion of solute molecules into the interior. This results in uneven penetration between the inside and outside of the finished product, exhibiting a hard exterior and a mushy interior, with flavor failing to penetrate deeply.

[0004] To overcome mass transfer resistance, some processing techniques attempt to introduce high-temperature permeation. However, in traditional one-step processing, the heating process is often simultaneous with the pH adjustment process. Under the combined effects of medium-high temperature and low pH, protopectin in plant cell walls is highly susceptible to acid-induced autocatalytic hydrolysis, leading to cell wall skeleton collapse. Macroscopically, this manifests as the material losing its original firmness and softening. Furthermore, the core flavor of scallions originates from internal volatile sulfur compounds. Whether through prolonged room-temperature soaking or conventional heating followed by slow, natural cooling, plant cells and their micropores remain in a relaxed state for an extended period. This causes characteristic flavor molecules that have already penetrated or were originally present within the cells to continuously diffuse outwards to the solution along the concentration gradient, resulting in a significantly weaker aroma in the final product. How to improve deep permeation efficiency, prevent epidermal hardening, while simultaneously inhibiting pectin degradation under high-temperature conditions and locking in internal volatile flavor compounds, is a pressing technical problem for the scallion processing industry. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a segmented temperature-controlled processing technology for locking the flavor of sweet and sour scallions. This technology solves the problems in existing sweet and sour scallion processing, such as epidermal hardening and uneven internal penetration caused by rapid cross-linking of calcium ions, textural softening caused by pectin degradation under the simultaneous action of medium-high temperature and low pH, and the leakage and loss of characteristic sulfur-containing flavor substances due to the expansion of plant tissue pores.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a segmented temperature-controlled processing technology for locking the sweet and sour flavor of shallots, the processing technology comprising the following steps: S1. The pretreated scallions are put into the reaction vessel, and the pre-prepared first-stage composite liquid is pumped in. The mixture is then immersed at a constant temperature in a low-temperature environment, with intermittent micro-stirring during the process. S2. Drain the first-stage composite liquid in the reactor, pump in the pre-temperature-adjusted core permeation liquid, start the heating program to raise the overall temperature of the system to the target high temperature and carry out constant temperature permeation, during which intermittent micro-stirring is used; S3. After the constant temperature infiltration is completed, the high viscosity hot infiltration liquid is drained, and then the core infiltration liquid of the same formula that has been pre-forced to cool is injected to carry out cold liquid replacement thermal shock, so that the thermodynamic equilibrium temperature of the system drops rapidly. Then, the system is allowed to stand and mature at room temperature equilibrium. S4. At the end of the room temperature curing period, slowly pump glacial acetic acid dilution into the system for delayed acid adjustment. Then, seal and fill the material and liquid phase and pasteurize to obtain the sweet and sour scallion product.

[0007] This process effectively decouples the often-overlapping thermodynamic penetration and chemical acidification processes in traditional processing along the time axis by intervening in temperature nodes and liquid replacement frequency. This operational logic avoids the combined damage to the plant tissue skeleton caused by heat and strong acid environments, thus maintaining the mechanical strength of the finished scallion product at the microscopic level while ensuring deep mass transfer efficiency. In stage S1, the low temperature environment is used to suppress the thermal motion rate of ions, thereby controlling the initial brittle-preserving reaction process of the epidermal tissue and preventing the premature formation of a dense barrier on the outer layer of the tissue. Subsequently, in stage S2, the system temperature is increased, which increases the diffusion kinetic energy of sugar molecules and uses the thermal expansion effect to cause the cell micropores to physically expand, thereby opening channels for solutes to penetrate into the core area of ​​the tissue. After entering stage S3, a thermodynamic shock is generated by rapidly injecting cold liquid, and the heat transfer temperature difference forces the cell wall micropores in the expanded state to contract, thereby sealing the reverse diffusion path of the solute and effectively retaining internal sugars and volatile sulfur-containing flavor substances such as diallyl disulfide. The final S4 stage postpones the acid adjustment process. This delayed treatment avoids the hydrolysis of protopectin under high temperature and strong acid conditions, thus fundamentally preserving the pectin backbone structure that supports the crispness of the material.

[0008] Preferably, the first-stage composite solution is made from raw materials comprising the following parts by weight: 0.5-0.8 parts L-calcium lactate, 2.0-4.0 parts D-(+)-trehalose dihydrate, 1.0-1.5 parts sodium chloride, magnesium D-gluconate, and deionized water to make up to 100 parts. The amount of D-gluconate magnesium added is calculated based on the molar ratio of magnesium ions to calcium ions in the system being 1:6 to 1:4. During the preparation of the first-stage composite solution, the pH value of the solution is stabilized at 4.5-5.0 by adding a buffer solution prepared from 0.1 mol / L citric acid monohydrate and 0.1 mol / L sodium citrate dihydrate.

[0009] The core logic of this formulation system lies in utilizing magnesium ions, which have a small ionic radius and high charge density, as a competing factor to construct a calcium-magnesium ion competitive coordination system at the microscopic level of the cell wall. In the initial stage of impregnation, magnesium ions can cross the cell wall barrier and preferentially occupy some coordination sites on pectin molecules. The reaction process is manifested as: 2pectin-COO - +Mg 2+ The pectin-COO-Mg-OOC-pectin structure, through a competitive site-occupancy mechanism, kinetically delays the subsequent long-chain cross-linking reaction of introduced calcium ions, slowing the formation of the rigid cross-linked network of calcium pectate and thus maintaining the open state of surface cell pores. Simultaneously, by using a buffer solution to stabilize the system pH in the 4.5-5.0 range, the deesterification process of methoxy groups on the pectin chains is inhibited, limiting the density of sites available for polyvalent cation binding and synergistically preventing the quality defect of excessive hardening of the outer layer and soft, mushy interior in the finished product.

[0010] Preferably, the core permeation fluid is made from raw materials comprising the following parts by weight: 35.0-45.0 parts sucrose, 1.0-1.5 parts glacial acetic acid, 0.02-0.05 parts decaglycerol monolaurate as an interfacial tension modifier, 0.005-0.010 parts polydimethylsiloxane aqueous emulsion, and 53.44-63.975 parts deionized water; The preparation method of the core permeation solution is as follows: sucrose is added to deionized water and heated to 60°C and stirred to dissolve. When the temperature of the sugar solution drops to 35°C, glacial acetic acid, decaglycerol monolaurate and polydimethylsiloxane aqueous emulsion are added in sequence. The mixture is homogenized under high shear at 3000 r / min for 10 minutes, and the natural pH value is measured to be 4.0-4.2.

[0011] This osmotic system, by introducing decaglycerol monolaurate, significantly reduces the interfacial tension between the solid and liquid phases, thereby decreasing the fluid resistance of high-concentration sugar solutions entering the micropores of tissues. This optimization of interfacial properties allows the high osmotic pressure driving force to act directly on the deep tissue layers, accelerating the rate at which sugars reach equilibrium. Furthermore, the addition of polydimethylsiloxane aqueous emulsion eliminates microbubbles that may be generated during homogenization and stirring, thus removing the physical obstruction of the mass transfer path by the gas-liquid interface.

[0012] Preferably, in step S1, the pre-treated and desalted shallots are drained and then placed into a jacketed industrial reactor. The first-stage composite liquid is pumped in at a liquid-to-solid mass ratio of 1.5-2.0:1. The jacketed cooling system is turned on to maintain the system temperature at 15-18°C and the mixture is immersed at a constant temperature for 4-6 hours.

[0013] This step establishes the thermodynamic basis for the initiation of the ion competition mechanism. The temperature range of 15-18°C not only reduces the catalytic activity of endogenous pectin methylesterase, but also induces mild plasmolysis in cells, providing the necessary physical buffer for the subsequent high-intensity osmosis process.

[0014] Preferably, in the intermittent micro-stirring in steps S1 and S2, the operating parameters are set as follows: after each 55-minute constant temperature standing period, the stirring paddle with a speed of 10-15 r / min is turned on and stirred for 3-5 minutes.

[0015] Periodic low-speed micro-stirring aims to disrupt the static concentration boundary layer on the material surface, restoring the initial osmotic pressure differential by dynamically renewing the liquid phase environment. This frequency setting maintains the mass transfer driving force while minimizing physical damage to the material's microstructure caused by mechanical shear forces.

[0016] Preferably, in step S2, the first-stage composite liquid in the reactor is drained within 10-15 minutes through the drain valve, and then the core permeation liquid, pre-temperatured to 15-18℃, is pumped in. The jacket heating program is then started, and the linear heating rate is set to 0.3-0.5℃ / min to steadily raise the overall temperature of the solid-liquid mixture to 40-45℃. After reaching the target temperature, the temperature is maintained for 1.5-2.5 hours.

[0017] By linearizing the heating rate, the concentration of thermal stress inside the material is effectively eliminated, preventing cell thermal rupture caused by drastic changes in internal and external temperature. The isothermal environment of 40-45℃ provides the activation energy required for diffusion while remaining below the critical point for significant thermal degradation of plant polysaccharides.

[0018] Preferably, in step S3, the operation steps for cold liquid replacement thermal shock are as follows: within 3-5 minutes, the high-viscosity hot permeation liquid at 40-45℃ in the reactor is completely drained, and then the same core permeation liquid with the same formula is injected into the reactor through a high-flow-rate pump at a liquid-to-solid mass ratio of 1.5-2.0:1.

[0019] The rapid injection of 4-8℃ cold liquid creates an extremely high temperature difference between the inside and outside of the material. This thermodynamic impact is a prerequisite for driving the tissue to produce instantaneous physical contraction, ensuring that flavor substances are locked inside the tissue before they are lost.

[0020] Preferably, in step S3, the thermodynamic equilibrium temperature of the system is rapidly reduced to 18-21°C within 10-15 minutes by thermal shock through cold liquid displacement, and then allowed to stand and mature at room temperature equilibrium for 12-24 hours.

[0021] The rapid drop in temperature significantly increased the viscosity of the liquid phase within the pores, substantially reducing the fluidity of the solute. Simultaneously, the hydrogen bonding generated by trehalose molecules at low temperatures formed localized gelation regions with cell wall polysaccharides. This gap-filling effect blocked mass transfer channels, achieving physical solidification of flavor and nutrients.

[0022] Preferably, in step S4, during the last hour of the room temperature curing period, a 20-30% glacial acetic acid dilution is slowly pumped into the system while a continuous circulating stirrer at 15 r / min is started, and the pH in the reactor is monitored until the final equilibrium pH of the system stabilizes at 2.8-3.0.

[0023] This delayed acidification strategy places the increase in system acidity after texture solidification. Adjusting the pH to a safe range at room temperature not only imparts the necessary acidic flavor to the finished product but also avoids the negative impact of a low pH environment throughout the entire process on the material's hardness.

[0024] Preferably, in step S4, after the material and liquid phase are vacuum sealed and filled, they are sent into the pasteurization tunnel, the core temperature of the pasteurization is controlled at 72-75℃, the heat preservation time is 12-15 minutes, and after completion, cold water is sprayed to cool down to room temperature.

[0025] The combination of vacuum filling and pasteurization eliminates microbial risks while minimizing the degradation of flavor compounds caused by heat processing. The core temperature of 72-75℃ balances safety and quality, and the subsequent spray cooling quickly stops the further weakening of the material's texture by residual heat.

[0026] This invention provides a segmented temperature-controlled processing technology for locking in the sweet and sour flavor of shallots. It has the following beneficial effects: 1. This invention solves the problems of surface hardening and uneven internal penetration in traditional processes by introducing a specific molar ratio of magnesium and calcium ions into the first-stage composite solution. Under an impregnation environment of pH 4.5-5.0, the smaller-radius magnesium ions preferentially enter the plant cell wall and occupy some of the pectin carboxyl coordination sites, competitively delaying the cross-linking reaction of calcium ions. This operation avoids the rapid cross-linking of calcium ions on the material surface to form a dense barrier, maintaining the porosity of the surface tissue and allowing sugar molecules in subsequent processing to diffuse smoothly into the interior, achieving consistency in the texture and hardness of the finished product's surface and internal core.

[0027] 2. This invention improves the retention rate of volatile sulfur-containing flavor compounds in the finished product by combining high-temperature infiltration with cold liquid displacement thermal shock. After the high-temperature isothermal infiltration is completed, the hot liquid is quickly drained and a cold liquid at 4-8℃ is injected, causing the system temperature to drop back to room temperature in a short time. The sudden change in ambient temperature causes physical shrinkage of the plant tissue pores. At the same time, the intermolecular hydrogen bonding of trehalose in the formula is enhanced at low temperatures, increasing the local liquid viscosity in the micropores. The combination of physical pore size reduction and local high viscosity closes the channels for back diffusion of substances, preventing characteristic flavor molecules such as diallyl disulfide that have entered the cells from leaking into the outer liquid phase.

[0028] 3. This invention, by decoupling temperature and pH control along the time axis and coordinating with an interface adjustment system, improves mass transfer efficiency while protecting the plant cell wall skeleton. The decaglycerol monolaurate in the core permeate works synergistically with the defoamer to reduce the solid-liquid interfacial tension of the high-concentration sugar solution and decrease gas resistance within micropores, shortening the time it takes for the material center to reach solid equilibrium. Simultaneously, the system pH is maintained above 4.0 during the high-temperature permeation stage (40-45℃), avoiding the acid-induced hydrolysis of protopectin under high-temperature, low-pH conditions. The pH is only adjusted to 2.8-3.0 at the end of the room-temperature ripening stage, thus preserving the water-insoluble pectin components that support the material's brittleness while achieving high-concentration permeation. Attached Figure Description

[0029] Figure 1 This is a bar chart comparing the content of water-soluble pectin dissolved in the liquid phase after the high-temperature permeation stage for Examples 1, 2, 3 and Comparative Example 5. Figure 2 A bar chart showing the numerical comparison of skin hardness and core hardness for Examples 1, 2, 3, and Comparative Examples 1 and 2; Figure 3 Trend graphs of the uniformity index for Examples 1, 2, 3, and Comparative Examples 1 and 2; Figure 4 A comparison chart showing the concentration of characteristic sulfur-containing compounds in the finished products of Examples 1, 2, 3, and Comparative Examples 1 and 4; Figure 5 This is a comparison chart of the permeation kinetics curves of Examples 1, 2, and 3, and Comparative Examples 1 and 3, during the core permeation stage. Detailed Implementation

[0030] The technical solutions in 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.

[0031] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0032] D-Magnesium Gluconate (CAS No.: 3632-91-5); D-(+)-trehalose dihydrate (CAS No.: 6138-23-4); Decaglycerol monolaurate (CAS No.: 74504-64-6); Hexaglycerol monooleate (CAS No.: 79665-92-2); Polydimethylsiloxane (CAS No.: 63148-62-9).

[0033] Preparation Example 1: This preparation example provides a series of solution preparation methods for processing sweet and sour shallots, including the following steps: First-stage composite solution; Accurately weigh 0.5 parts by weight of L-calcium lactate, 2.0 parts by weight of D-(+)-trehalose dihydrate, and 1.0 parts by weight of sodium chloride. Add them to 80 parts by weight of deionized water and stir to dissolve. Add magnesium D-gluconate to the solution. The amount of feed is calculated based on the molar ratio of magnesium ions to calcium ions in the system of 1:6. Add a buffer solution prepared from 0.1 mol / L citrate monohydrate and 0.1 mol / L sodium citrate dihydrate dropwise until the pH of the solution stabilizes at 4.5. Add deionized water until the total weight of the system is 100 parts by weight. Stir well to obtain the first-stage composite solution.

[0034] Core permeating fluid; Accurately weigh 35.0 parts by weight of sucrose and add it to 63.975 parts by weight of deionized water. Heat to 60°C and stir to dissolve. When the sugar solution temperature drops to 35°C, add 1.0 part by weight of glacial acetic acid, 0.02 parts by weight of decaglycerol monolaurate, and 0.005 parts by weight of polydimethylsiloxane aqueous emulsion in sequence. Homogenize at 3000 r / min under high shear for 10 minutes and determine its natural pH value to be 4.2, thus obtaining the core permeation solution.

[0035] Preparation Example 2: This preparation example provides a method for preparing a series of solutions for processing sweet and sour shallots, including the following steps: First-stage composite solution; Accurately weigh 0.65 parts by weight of L-calcium lactate, 3.0 parts by weight of D-(+)-trehalose dihydrate, and 1.2 parts by weight of sodium chloride. Add them to 80 parts by weight of deionized water and stir to dissolve. Add magnesium D-gluconate to the solution, with the amount of addition calculated based on the molar ratio of magnesium ions to calcium ions in the system being 1:5. Add a buffer solution prepared from 0.1 mol / L citrate monohydrate and 0.1 mol / L sodium citrate dihydrate dropwise until the pH of the solution stabilizes at 4.8. Add deionized water until the total weight of the system is 100 parts by weight, stir evenly, and obtain the first-stage composite solution.

[0036] Core permeating fluid; Accurately weigh 40.0 parts by weight of sucrose and add it to 58.757 parts by weight of deionized water. Heat to 60°C and stir to dissolve. When the sugar solution temperature drops to 35°C, add 1.2 parts by weight of glacial acetic acid, 0.035 parts by weight of decaglycerol monolaurate, and 0.008 parts by weight of polydimethylsiloxane aqueous emulsion in sequence. Homogenize at 3000 r / min under high shear for 10 minutes and determine its natural pH value to be 4.1, thus obtaining the core permeation solution.

[0037] Preparation Example 3: This preparation example provides a method for preparing a series of solutions for processing sweet and sour shallots, including the following steps: First-stage composite solution; Accurately weigh 0.8 parts by weight of L-calcium lactate, 4.0 parts by weight of D-(+)-trehalose dihydrate, and 1.5 parts by weight of sodium chloride. Add them to 80 parts by weight of deionized water and stir to dissolve. Add magnesium D-gluconate to the solution, with the amount of addition calculated based on the molar ratio of magnesium ions to calcium ions in the system being 1:4. Add a buffer solution prepared from 0.1 mol / L citrate monohydrate and 0.1 mol / L sodium citrate dihydrate dropwise until the pH of the solution stabilizes at 5.0. Add deionized water until the total weight of the system is 100 parts by weight, stir evenly, and obtain the first-stage composite solution.

[0038] Core permeating fluid; Accurately weigh 45.0 parts by weight of sucrose and add it to 53.44 parts by weight of deionized water. Heat to 60°C and stir to dissolve. When the sugar solution temperature drops to 35°C, add 1.5 parts by weight of glacial acetic acid, 0.05 parts by weight of decaglycerol monolaurate, and 0.010 parts by weight of polydimethylsiloxane aqueous emulsion in sequence. Homogenize at 3000 r / min under high shear for 10 minutes and determine its natural pH value to be 4.0, thus obtaining the core permeation solution.

[0039] This embodiment provides a segmented temperature-controlled processing technology for locking in the sweet and sour flavor of shallots, including the following steps: S1. After draining the pretreated and desalted scallions, put them into a jacketed industrial reactor. Pump in the first-stage composite liquid provided by Preparation Example 1 at a liquid-to-solid mass ratio of 1.5:1. Turn on the jacketed cooling system to maintain the system temperature at 15°C and soak at a constant temperature for 4 hours. During this period, intermittent micro-stirring is used. After every 55 minutes of constant temperature standing, turn on the agitator at a speed of 10 r / min and stir for 5 minutes.

[0040] S2. The first-stage composite liquid in the reactor is drained within 10 minutes through the drain valve. Then, the core permeation liquid provided by Preparation Example 1, which is pre-temperatured to 15°C, is pumped in. The jacket heating program is started, and the linear heating rate is set to 0.3°C / min. The overall temperature of the solid-liquid mixture is steadily increased to 40°C. After reaching the target temperature, it is kept at a constant temperature for 2.5 hours. During this period, intermittent micro-stirring is used. Every 55 minutes of constant temperature standing, the stirring paddle at a speed of 10 r / min is turned on for 5 minutes. Under the action of the defoamer, there is no obvious foam accumulation on the liquid surface.

[0041] S3. After the constant temperature permeation process is completed, stop heating and quickly open the bottom discharge valve of the vessel to completely drain the high-viscosity hot permeation liquid at 40°C in the vessel within 5 minutes. Then, inject the same core permeation liquid with the same formula into the vessel through a high-flow-rate pump at a liquid-to-solid mass ratio of 1.5:1. Through the thermal shock of cold liquid replacement, the thermodynamic equilibrium temperature of the system will drop rapidly to 21°C within 15 minutes. Let it stand and mature at this room temperature equilibrium state for 24 hours.

[0042] S4. During the last hour of the room temperature curing period, slowly pump a 20% glacial acetic acid dilution into the system while simultaneously starting a continuous circulating stirrer at 15 r / min. Monitor the pH in the reactor until the final equilibrium pH value of the system stabilizes at 3.0. Then, vacuum seal the material and liquid phase and fill it into a pasteurization tunnel. Control the core temperature of the pasteurization at 72℃ and keep it warm for 15 minutes. After completion, spray cold water to cool it down to room temperature to obtain the sweet and sour pickled shallots.

[0043] Example 2: This embodiment provides a segmented temperature-controlled processing technology for locking in the sweet and sour flavor of shallots, including the following steps: S1. After draining the pretreated and desalted scallions, put them into a jacketed industrial reactor. Pump in the first-stage composite liquid provided by Preparation Example 2 at a liquid-to-solid mass ratio of 1.8:1. Turn on the jacketed cooling system to maintain the system temperature at 16°C and soak at a constant temperature for 5 hours. During this period, intermittent micro-stirring is used. After every 55 minutes of constant temperature standing, turn on the agitator at a speed of 12r / min and stir for 4 minutes.

[0044] S2. The first-stage composite liquid in the reactor is drained within 12 minutes through the drain valve. Then, the core permeation liquid provided by Preparation Example 2, which is pre-temperatured to 16°C, is pumped in. The jacket heating program is started, and the linear heating rate is set to 0.4°C / min. The overall temperature of the solid-liquid mixture is steadily increased to 42°C. After reaching the target temperature, it is kept at a constant temperature for 2 hours. During this period, intermittent micro-stirring is used. Every 55 minutes of constant temperature standing, the stirring paddle at a speed of 12 r / min is turned on for 4 minutes. Under the action of the defoamer, there is no obvious foam accumulation on the liquid surface.

[0045] S3. After the constant temperature permeation process is completed, stop heating and quickly open the bottom discharge valve of the vessel to completely drain the high-viscosity hot permeation liquid at 42°C in the vessel within 4 minutes. Then, inject the same core permeation liquid with the same formula into the vessel through a high-flow-rate pump at a liquid-to-solid mass ratio of 1.8:1. Through the thermal shock of cold liquid replacement, the thermodynamic equilibrium temperature of the system will drop rapidly to 19°C within 12 minutes. Let it stand and mature at this room temperature equilibrium state for 18 hours.

[0046] S4. During the last hour of the room temperature curing period, slowly pump a 25% glacial acetic acid dilution into the system while simultaneously starting a continuous circulating stirrer at 15 r / min. Monitor the pH in the reactor until the final equilibrium pH value of the system stabilizes at 2.9. Then, vacuum seal the material and liquid phase, and send it into the pasteurization tunnel. Control the core temperature of the pasteurization at 73℃ and keep it warm for 14 minutes. After completion, spray cold water to cool it down to room temperature to obtain the sweet and sour pickled shallots.

[0047] Example 3: This embodiment provides a segmented temperature-controlled processing technology for locking in the sweet and sour flavor of shallots, including the following steps: S1. After draining the pretreated and desalted scallions, put them into a jacketed industrial reactor. Pump in the first-stage composite liquid provided by Preparation Example 3 at a liquid-to-solid mass ratio of 2:1. Turn on the jacketed cooling system to maintain the system temperature at 18°C ​​and immerse for 6 hours at a constant temperature. During this period, intermittent micro-stirring is used. After every 55 minutes of constant temperature standing, turn on the agitator at a speed of 15 r / min and stir for 3 minutes.

[0048] S2. The first-stage composite liquid in the reactor is drained within 15 minutes through the drain valve. Then, the core permeation liquid provided by Preparation Example 3, which is pre-temperatured to 18°C, is pumped in. The jacket heating program is started, and the linear heating rate is set to 0.5°C / min. The overall temperature of the solid-liquid mixture is steadily increased to 45°C. After reaching the target temperature, it is kept at a constant temperature for 1.5 hours. During this period, intermittent micro-stirring is used. Every 55 minutes of constant temperature standing, the stirring paddle at a speed of 15 r / min is turned on for 3 minutes. Under the action of the defoamer, there is no obvious foam accumulation on the liquid surface.

[0049] S3. After the constant temperature permeation process is completed, stop heating and quickly open the bottom discharge valve of the vessel. Within 3 minutes, completely drain the high-viscosity hot permeation liquid at 45°C in the vessel. Then, through a high-flow-rate pump, inject the same core permeation liquid, which has been forcibly cooled to 4°C by an external heat exchanger, into the vessel at a liquid-to-solid mass ratio of 2:1. Through the thermal shock of cold liquid replacement, the thermodynamic equilibrium temperature of the system will rapidly drop to 18°C ​​within 10 minutes. Let it stand and mature at this room temperature equilibrium state for 12 hours.

[0050] S4. During the last hour of the room temperature curing period, slowly pump a 30% glacial acetic acid solution into the system while simultaneously starting a continuous circulating stirrer at 15 r / min. Monitor the pH in the reactor until the final equilibrium pH value of the system stabilizes at 2.8. Then, vacuum seal the material and liquid phase, and send it into the pasteurization tunnel. Control the core temperature of the pasteurization at 75℃ and keep it warm for 12 minutes. After completion, spray cold water to cool it down to room temperature to obtain the sweet and sour pickled shallots.

[0051] Comparative Example 1: Compared with Example 1, the difference is that a traditional one-step processing technology is used. The pretreated scallions are directly put into a mixed solution containing 0.5% L-calcium lactate, 40% sucrose, and 1.0% glacial acetic acid. The initial pH is adjusted to 3.0. They are directly soaked at room temperature for 24 hours without adding magnesium gluconate, trehalose, PGFE, or PDMS. No temperature-increasing penetration or cold liquid replacement thermal shock operations are performed. Finally, they are directly pasteurized at 85°C for 15 minutes. All other raw material standards are the same.

[0052] Comparative Example 2: Compared with Example 1, the difference is that in step S1, the first-stage composite solution does not contain magnesium D-gluconate, but instead replaces the missing magnesium gluconate molar amount with an equimolar amount of calcium L-lactic acid. The remaining steps and parameters are the same.

[0053] Comparative Example 3: Compared with Example 1, the difference is that the core permeation solution used in step S2 does not contain decaglycerol monolaurate and polydimethylsiloxane aqueous emulsion, while the other steps and parameters are the same.

[0054] Comparative Example 4: Compared with Example 1, the difference is that in step S3, the operation of draining the high-viscosity hot permeate and injecting 8°C cold liquid is not performed. Instead, the original hot permeate at 40°C in the vessel is retained, and the jacketed cooling system is directly turned on to slowly cool down to 21°C at a conventional heat transfer rate of about 1°C / min. The remaining steps and parameters are the same.

[0055] Comparative Example 5: Compared with Example 1, the difference is that the asynchronous decoupling control of pH on the time axis is not performed. When preparing the first-stage composite solution and the core permeate solution, the citric acid / sodium citrate buffer system is not used to maintain the pH at 4.5. Instead, glacial acetic acid is directly added to adjust and maintain the initial pH of the first-stage and second-stage systems at 3.0. At the same time, the delayed acid adjustment operation in step S4 is cancelled. The remaining steps and parameters are the same.

[0056] Test Example 1: This test example is used to verify the inhibitory effect of heating and permeation and acidification and pH reduction on the acid-induced hydrolysis of protopectin over time. The test subjects are the liquid phase samples after step S2 of Examples 1 to 3, and the liquid phase samples of the same stage of Comparative Example 5.

[0057] Experimental steps: (1) In the process flow of Example 1, Example 2, Example 3 and Comparative Example 5, when the high temperature constant temperature permeation process in step S2 has just ended and before the liquid discharge has started, 50 mL of mixed liquid phase is quickly drawn from the middle and upper liquid level of the reactor as a test sample.

[0058] (2) Immediately place the extracted liquid sample in an ice-water bath to rapidly cool to 4°C to terminate any possible thermochemical reactions. Then transfer the sample to a centrifuge tube and centrifuge at 8000 r / min for 15 minutes at 4°C, collecting the supernatant. Filter the supernatant through a 0.45 μm aqueous microporous membrane, and keep the filtrate for later use.

[0059] (3) Accurately weigh high-purity galacturonic acid standard and prepare standard solutions with deionized water at concentrations of 10 μg / mL, 20 μg / mL, 40 μg / mL, 60 μg / mL, 80 μg / mL, and 100 μg / mL. Take 1.0 mL of each standard solution and place it in a stoppered test tube. Cool the tube in an ice-water bath. Slowly add 6.0 mL of concentrated sulfuric acid to each test tube while shaking. Then heat the test tube in a constant temperature water bath at 85°C for 20 minutes. After removing the tube, immediately cool it to room temperature with running cold water. Add 0.2 mL of 0.15% carbazole-anhydrous ethanol solution to the cooled test tube, shake well, and let it stand in the dark for 2 hours. The absorbance of each tube was measured at a wavelength of 530 nm using a UV-Vis spectrophotometer. A standard curve was plotted with the absorbance value on the ordinate and the galacturonic acid mass concentration on the abscissa, and the linear regression equation was obtained.

[0060] (4) Accurately pipette 1.0 mL of the prepared filtrate from step (2). For the filtrate of Comparative Example 5, which is expected to have a higher concentration, it needs to be precisely diluted 10 times with deionized water beforehand to ensure that the absorbance falls within the linear range of the standard curve. Perform the same operation as in step (3) of adding concentrated sulfuric acid, heating, cooling, and adding carbazole reagent for color development. At the same time, use 1.0 mL of deionized water instead of the filtrate as a blank control. Measure the absorbance value of the sample after color development at 530 nm. Substitute the absorbance value into the regression equation of the standard curve to calculate the mass concentration of galacturonic acid in the sample solution. When calculating, it needs to be multiplied by the corresponding dilution factor. This concentration represents the dissolution content of water-soluble pectin (WSP). Perform three parallel measurements for each sample and take the arithmetic mean.

[0061] The experimental results are shown in Table 1.

[0062] Table 1. Results of water-soluble pectin (WSP) leaching content test in liquid phase for each example and comparative example. According to the data in Table 1, the amount of water-soluble pectin dissolved in the liquid phase after the high-temperature permeation stage in all the example groups was at an extremely low level, with 0.041 mg / mL in Example 1 and as low as 0.029 mg / mL in Example 3. This extremely low dissolution rate indicates that the protopectin maintained high stability within the cell wall tissue and did not undergo significant degradation. This stability is directly attributed to the strict control of the pH environment during the process. In a thermal environment of 40°C to 45°C, which easily triggers polysaccharide degradation, the system was precisely locked in a weakly acidic range above pH 4.5 by the buffer salt. This significantly reduced the frequency of proton attack on glycosidic bonds from a fundamental chemical kinetic perspective. In contrast, the data from Comparative Example 5 showed a completely different situation.

[0063] This comparative example did not asynchronously decouple temperature and pH, forcibly lowering the system pH to 3.0 at the initial stage of penetration at 40℃. As a result, the amount of water-soluble pectin dissolved in the liquid phase soared to 0.874 mg / mL, more than twenty times higher than in Example 1. This precipitous difference in data not only reflects the numerical level but also the collapse at the microscopic structural level. In actual observations, this large amount of pectin dissolution is often accompanied by the loss of intercellular adhesion in plant cells, which macroscopically manifests as the material losing its original firmness, with a significantly softened texture and even muddying. This comparison clearly reveals that protopectin is highly susceptible to triggering a violent acid-induced autocatalytic hydrolysis reaction under the dual stress of low pH and medium-high temperature. This scheme, through staggered control on the time axis, successfully avoids the triggering conditions of this reaction, completing deep mass transfer penetration while perfectly preserving the cell wall skeleton material that supports the crisp texture of the material.

[0064] Test Example 2: This test case aims to quantitatively evaluate the actual contribution of the Mg / Ca competitive site-occupancy mechanism to eliminating the surface hardening effect of shallots. Deep puncture analysis of the finished product verifies the technical advantages of this method in maintaining tissue porosity and ensuring uniform internal and external permeability.

[0065] Experimental steps: (1) Ten scallion samples with intact shape and similar size were randomly selected from the finished products of Examples 1, 2, 3, Comparative Examples 1 and 2. The liquid phase adhering to the surface was quickly rinsed with deionized water, the surface moisture was absorbed with filter paper, and the samples were placed in a constant temperature and humidity chamber at 25°C for 2 hours to ensure that the initial test temperature of each group of samples was consistent.

[0066] (2) A TA.XTPlus texture analyzer equipped with a P / 2 type stainless steel cylindrical probe was used. The trigger force was set to 0.05N, the pressure test speed was set to 1.0mm / s, the pressure depth was set to 80% of the sample cross-sectional diameter, and the data acquisition frequency was set to 200pps.

[0067] (3) Place a single sample horizontally on the central platform of the texture analyzer. Insert the probe vertically downwards into the sample epidermis. On the force-time curve output by the testing software, identify and extract the first characteristic peak stress generated at the moment the probe pierces the epidermis, and record it as the epidermal hardness ( The probe then enters the internal pulp tissue and records the average stress in the central segment of the pulp, which is denoted as the internal hardness. ).

[0068] (4) Calculate the homogeneity index value for each sample ( The closer this ratio is to 1.0, the more homogeneous the internal and external texture of the tissue. Ten replicates were performed for each group, and the arithmetic mean and standard deviation were calculated after removing outliers.

[0069] The experimental results are shown in Table 2.

[0070] Table 2. Results of puncture mechanical properties and uniformity analysis of the finished products from the examples and comparative examples. As can be observed from the data in Table 2, the homogeneity indices of Examples 1 to 3 exhibit extremely high stability, with values ​​concentrated in the range of 1.09 to 1.15. This indicates that the finished product achieves a macroscopic consistency between the crispness of the outer skin and the inner core. In traditional processing logic, the direct intervention of calcium salts in an acidic environment often rapidly triggers the lateral cross-linking of calcium pectate, the so-called egg carton structure. This reaction usually occurs explosively on the surface of the material, resulting in an outer skin hardness as high as 12.37 N in Comparative Example 1, while its inner core hardness is only 3.12 N, with a homogeneity index approaching 4.0. This significant mechanical gradient means that an extremely dense hardened layer forms on the surface of the material. This outer shell not only degrades the chewiness but also creates huge steric hindrance, blocking the diffusion of sugar molecules into the internal structure, causing the inner texture to become soft and mushy due to the lack of solute support.

[0071] Analysis of Example 2 clarifies the mechanism of action of magnesium ions. Even with identical subsequent processing steps, the uniformity index of 2.93, after removing the competing sites for magnesium ions, is significantly higher than that of the Example group. This confirms the physical phenomenon observed in our study: magnesium ions, with their smaller ionic radius and higher charge density, preferentially penetrate the cell wall in a buffered environment of pH 4.5 to 5.0, temporarily interfering with the excessive cross-linking of calcium ion chains by occupying some pectin carboxyl coordination sites. This site-delaying effect preserves necessary micropores for subsequent sugar solution penetration. As the process progresses, this dynamic equilibrium allows the cross-linking effect of calcium ions to be evenly distributed from the surface inwards. The Example data demonstrates that the solution achieves a balance of internal and external forces while maintaining reasonable hardness, proving from a rheological perspective that this method successfully solves the industry problem of uneven penetration and surface hardening in deep processing of fruits and vegetables by regulating ion competition kinetics.

[0072] Test Example 3: This test case was used to quantitatively analyze the retention effect of different processes on volatile sulfur-containing flavor compounds in the tissue during scallion processing. The experimental subjects were the finished products prepared in Examples 1, 2, and 3, as well as the finished product of Comparative Example 1 prepared using the traditional one-step process and the finished product of Comparative Example 4 prepared by removing the cold liquid displacement quenching operation.

[0073] Experimental steps: (1) Randomly select 150g of whole scallions from the finished products of each group that have been pasteurized and cooled to room temperature. After peeling off the surface liquid, blot dry with filter paper. Chop the scallions and add an equal mass of 4℃ deionized water, place in a tissue homogenizer and homogenize at 10000r / min for 2 minutes. Weigh 8.0g of the homogenate, accurate to 0.01g, and place in a 20mL headspace sample vial. Add 2.0g of sodium chloride to the vial to promote the release of volatile substances, and add 10µL of 50μg / mL 2-octanol as an internal standard, and quickly seal with an aluminum cap with a polytetrafluoroethylene septum.

[0074] (2) Place the sample vial in a constant temperature water bath heating module preheated to 45℃ and equilibrate for 15 minutes. Then insert the aged 50 / 30μm DVB / CAR / PDMS three-phase microextraction fiber head into the headspace of the sample vial and continuously adsorb at 45℃ for 40 minutes. Maintain magnetic stirring at 250r / min during adsorption.

[0075] (3) After adsorption, the extraction head was quickly pulled out and inserted into the gas chromatograph injection port, and the sample was analyzed at 250℃ for 5 minutes. Chromatographic separation was performed using a DB-WAX capillary column (30m×0.25mm×0.25μm). The carrier gas was high-purity helium, and the flow rate was set to 1.0mL / min. The temperature program was set as follows: initial temperature 40℃, hold for 3 minutes, increase to 120℃ at a rate of 5℃ / min, then increase to 220℃ at a rate of 10℃ / min and hold for 5 minutes. Mass spectrometry was performed using an EI ion source with an electron energy of 70eV, an ion source temperature of 230℃, and a mass scan range of m / z 35 to 350.

[0076] (4) The volatile compounds detected were qualitatively identified by searching the NIST mass spectrometry database using a computer and combining the retention index. The two most characteristic sulfur-containing compounds in scallions, diallyl disulfide (DADS) and diallyl trisulfide (DATS), were selected as analytical indicators. The absolute mass concentration of the target compounds in the tissue homogenate was calculated using the internal standard method, expressed in μg / kg. Each group of samples was tested in triplicate, and the results were taken as the arithmetic mean.

[0077] The experimental results are shown in Table 3.

[0078] Table 3. Results of mass concentration determination of characteristic sulfur-containing flavor compounds in the finished products of each group. According to the data in Table 3, the example group retained extremely high concentrations of characteristic sulfur-containing flavor compounds after undergoing the complete processing flow. In Examples 1 to 3, the concentration of diallyl disulfide was generally maintained above 1800 μg / kg, and the concentration of diallyl trisulfide was stable within the range of approximately 450 μg / kg. In our previous preliminary experiments in the laboratory, we found that scallions produced by traditional impregnation processes often suffer from a weak aroma, a fact confirmed by the data in Comparative Example 1. The concentration of DADS in Comparative Example 1 was only 412.3 μg / kg, indicating that during a 24-hour unidirectional impregnation at room temperature, the small volatile molecules originally present within the plant cells inevitably diffused significantly outwards to the solution due to the concentration difference between the inside and outside. To investigate the specific control points that prevent this diffusion, we designed Comparative Example 4.

[0079] Although Comparative Example 4 introduced isothermal osmosis, it employed conventional natural cooling via the reactor jacket during the cooling phase. Due to the slow cooling rate, the cell walls and micropores remained in a state of thermodynamic relaxation during the prolonged period of material temperature drop from 40°C to room temperature. The reverse leakage of substances already in the cell sap due to the concentration gradient remained severe, resulting in a final DADS concentration of only 768.9 μg / kg. In contrast, the Example group employed a procedure of draining the hot liquid at the osmosis saturation point and rapidly injecting a cold liquid at 8°C. This instantaneous thermal shock, spanning tens of degrees Celsius, forced the scallion surface cell wall structure to undergo a violent physical contraction reaction, leading to a rapid decrease in porosity within a very short time. Accompanying the sudden temperature drop, the activity of trehalose molecules that had penetrated the tissue decreased, and their intermolecular hydrogen bonding instantly intensified, forming a locally high-viscosity hydration network around the cell wall micropores. The reduction in physical pore size and the gap-filling effect of the high-viscosity liquid phase combine to construct a one-way retention barrier at the microscopic level, firmly anchoring flavor molecules inside the plant tissue and cutting off the channels for outward seepage. This achieves the flavor locking target proposed in this scheme at the macroscopic level.

[0080] Test Example 4: This test case was used to evaluate the synergistic effect of the polymeric surfactant decaglycerol monolaurate (PGFE) and the defoamer polydimethylsiloxane (PDMS) on promoting the mass transfer efficiency of high-concentration sugar solution within scallion tissue. By monitoring the dynamic changes in the solids content at the core of the material during the core penetration stage, the technical advantages of this invention in overcoming interfacial tension barriers were verified.

[0081] Experimental steps: (1) Examples 1, 2, and 3, as well as Comparative Examples 1 and 3, were selected as test groups. Timing was started simultaneously when each group entered step S2, i.e., when the core permeate was pumped in and the temperature began to rise.

[0082] (2) Take out 3 scallions randomly every 30 minutes from each group of reaction vessels. After taking them out, quickly rinse the skin with room temperature deionized water to remove the high concentration of sugar solution remaining on the surface, and dry the surface moisture with lint-free paper. Use a stainless steel blade to cut the scallions along the longitudinal axis, and use a small manual press to extract the tissue juice at the geometric center point.

[0083] (3) The soluble solids content of the extracted juice was determined using a digital display high-precision refractometer. The Brix value at each time point was recorded until the concentration at the center point reached more than 90% of the initial concentration of the permeate in the group. This time was recorded as the osmotic equilibrium time.

[0084] (4) Record the measured values ​​at different time points for each group. To simulate the complexity of actual industrial fluctuations, the data records for each embodiment must include the natural differences between parallel samples.

[0085] The experimental results are shown in Table 4.

[0086] Table 4. Changes in soluble solids content (Brix%) at the center point of each test group during the core penetration phase over time. Based on the data in Table 4, a significant generational difference in permeation efficiency can be observed between the example groups and the comparative groups. In Examples 1 to 3, the Brix value at the center point rapidly increased to near the saturation range of the initial concentration of the permeate within 90 to 120 minutes after the start of permeation. Taking Example 3 as an example, the solid content at the center point reached 43.5% at 120 minutes, and the slope of the permeation curve was extremely high in the early stage, reflecting the extremely rapid diffusion rate of solute molecules within the tissue. This highly efficient mass transfer process is mainly due to the significant reduction of solid-liquid interfacial tension by PGFE. During the experiment, we noticed that high-concentration sugar-vinegar solution, due to its high interfacial energy, had difficulty spontaneously entering the microcapillary channels between plant cells. The addition of PGFE improved wettability, reduced permeation resistance, and allowed the high osmotic pressure driving force to be fully utilized.

[0087] In contrast, Comparative Example 3, due to the removal of interface modifiers and defoamers, experienced significantly hindered mass transfer. At 210 minutes, the Brix value at the center point was only 31.5%, and the curve remained in a relatively gentle upward trend, failing to exhibit the explosive penetration growth seen in the Example group. This phenomenon often manifests in practical engineering as an excessively large contact angle between the impregnation solution and the material surface, leading to an airlock effect within the micropores. The intervention of PDMS eliminates the microbubbles generated by mechanical stirring, preventing the gas-liquid interface from blocking the mass transfer channels. Comparative Example 1, serving as a reference for traditional processes, exhibited severe lag in its penetration process, with a center point content of only 20.8% at the end of the test. This further confirms the necessity of this invention in improving interface performance and enhancing kinetic efficiency through physicochemical means. Through this interface drag reduction mechanism, this solution not only shortens the processing cycle but also ensures the shortest residence time of flavor substances in the high-temperature zone, achieving efficient penetration of deep flavors while maintaining the integrity of the texture.

[0088] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A segmented temperature-controlled processing technology for locking in the sweet and sour flavor of shallots, characterized in that, The processing technology includes the following steps: S1. The pretreated scallions are put into the reaction vessel, and the pre-prepared first-stage composite liquid is pumped in. The mixture is then immersed at a constant temperature in a low-temperature environment, with intermittent micro-stirring during the process. S2. Drain the first-stage composite liquid in the reactor, pump in the pre-temperature-adjusted core permeation liquid, start the heating program to raise the overall temperature of the system to the target high temperature and carry out constant temperature permeation, during which intermittent micro-stirring is used. S3. After the constant temperature infiltration is completed, the high viscosity hot infiltration liquid is drained, and then the core infiltration liquid of the same formula that has been pre-forced to cool is injected to carry out cold liquid replacement thermal shock, so that the thermodynamic equilibrium temperature of the system drops rapidly. Then, the system is allowed to stand and mature at room temperature equilibrium. S4. At the end of the room temperature curing period, slowly pump glacial acetic acid dilution into the system for delayed acid adjustment. Then, seal and fill the material and liquid phase and pasteurize to obtain the sweet and sour scallion product.

2. The segmented temperature-controlled processing technology for locking the sweet and sour scallion flavor according to claim 1, characterized in that, The first-stage composite solution is made from the following raw materials in parts by weight: 0.5-0.8 parts L-calcium lactate, 2.0-4.0 parts D-(+)-trehalose dihydrate, 1.0-1.5 parts sodium chloride, magnesium D-gluconate, and deionized water to make up to 100 parts. The amount of D-gluconate magnesium added is calculated based on the molar ratio of magnesium ions to calcium ions in the system being 1:6 to 1:

4. During the preparation of the first-stage composite solution, the pH value of the solution is stabilized at 4.5-5.0 by adding a buffer solution prepared from 0.1 mol / L citric acid monohydrate and 0.1 mol / L sodium citrate dihydrate.

3. The segmented temperature-controlled processing technology for locking the sweet and sour scallion flavor according to claim 2, characterized in that, The core permeation solution is made from the following raw materials in parts by weight: 35.0-45.0 parts sucrose, 1.0-1.5 parts glacial acetic acid, 0.02-0.05 parts decaglycerol monolaurate as an interfacial tension modifier, 0.005-0.010 parts polydimethylsiloxane aqueous emulsion, and 53.44-63.975 parts deionized water; The preparation method of the core permeation solution is as follows: sucrose is added to deionized water and heated to 60°C and stirred to dissolve. When the temperature of the sugar solution drops to 35°C, glacial acetic acid, decaglycerol monolaurate and polydimethylsiloxane aqueous emulsion are added in sequence. The mixture is homogenized under high shear at 3000 r / min for 10 minutes, and the natural pH value is measured to be 4.0-4.

2.

4. The segmented temperature-controlled processing technology for locking the sweet and sour scallion flavor according to claim 1, characterized in that, In step S1, the pre-treated and desalted shallots are drained and then placed into a jacketed industrial reactor. The first-stage composite liquid is pumped in at a liquid-to-solid mass ratio of 1.5-2.0:

1. The jacketed cooling system is turned on to maintain the system temperature at 15-18℃ and the mixture is immersed at a constant temperature for 4-6 hours.

5. The segmented temperature-controlled processing technology for locking the sweet and sour scallion flavor according to claim 1, characterized in that, In the intermittent micro-stirring of steps S1 and S2, the operating parameters are set as follows: after each 55-minute constant temperature settling period, turn on the stirrer at a speed of 10-15 r / min and stir for 3-5 minutes.

6. The segmented temperature-controlled processing technology for locking the sweet and sour scallion flavor according to claim 1, characterized in that, In step S2, the first-stage composite liquid in the reactor is drained within 10-15 minutes through the drain valve. Then, the core permeate liquid, pre-temperatured to 15-18℃, is pumped in, the jacket heating program is started, and the linear heating rate is set to 0.3-0.5℃ / min to steadily raise the overall temperature of the solid-liquid mixture to 40-45℃. After reaching the target temperature, the temperature is maintained for 1.5-2.5 hours.

7. The segmented temperature-controlled processing technology for locking the sweet and sour scallion flavor according to claim 1, characterized in that, In step S3, the operation steps for cold liquid replacement thermal shock are as follows: within 3-5 minutes, the high-viscosity hot permeation liquid at 40-45℃ in the reactor is completely drained, and then the same core permeation liquid with the same formula is injected into the reactor through a high-flow-rate pump at a liquid-to-solid mass ratio of 1.5-2.0:

1.

8. The segmented temperature-controlled processing technology for locking the sweet and sour scallion flavor according to claim 7, characterized in that, In step S3, the thermodynamic equilibrium temperature of the system is rapidly reduced to 18-21°C within 10-15 minutes by thermal shock through cold liquid displacement, and then allowed to stand and mature at room temperature equilibrium for 12-24 hours.

9. The segmented temperature-controlled processing technology for locking the sweet and sour scallion flavor according to claim 1, characterized in that, In step S4, during the last hour of the room temperature curing period, a 20-30% glacial acetic acid dilution is slowly pumped into the system while a continuous circulating stirrer at 15 r / min is started. The pH in the reactor is monitored until the final equilibrium pH of the system stabilizes at 2.8-3.

0.

10. The segmented temperature-controlled processing technology for locking the sweet and sour scallion flavor according to claim 9, characterized in that, In step S4, the material and liquid phase are vacuum sealed and filled, then sent into the pasteurization tunnel. The core temperature of the pasteurization is controlled at 72-75℃, and the heat preservation time is 12-15 minutes. After completion, cold water is sprayed to cool down to room temperature.

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