A pickling and desalting integrated method for keeping crispness of preserved vegetable

Abstract

This invention relates to the field of food processing technology and discloses an integrated pickling and desalting method for maintaining the crispness of pickled mustard tuber. The method includes: mixing high-salt pickled mustard tuber raw materials with reverse osmosis water and trehalose and cooling; adding sodium hexametaphosphate at low temperature and performing a pulsed chelation opening process involving vacuum to atmospheric pressure circulation; subsequently adding L-calcium lactate and pectin methyl esterase preparation, and soaking at a constant temperature of 15-20°C to allow the enzyme and calcium to permeate; then adding gluconate-δ-lactone, raising the temperature to 40-42°C and maintaining it at a constant temperature until the reaction is complete, and finally separating the solid and liquid phases. This invention utilizes a diffusion and reaction timing decoupling strategy, along with pulsed pressure difference and a low-temperature environment, to ensure that calcium ions and enzymes fully permeate into the tissue core before the gel reaction begins. Subsequently, in-situ solidification is induced by hot acid, constructing a uniform and dense three-dimensional network of calcium pectate in an egg-box shape throughout the entire process. This effectively solves the problem of soft inside and hard outside caused by traditional desalting processes, improving product crispness, desalting efficiency, and finished product yield.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to an integrated method for pickling and desalting pickled mustard tubers to maintain their crispness. Background Technology

[0002] Pickled mustard tuber, a traditional fermented condiment popular with consumers, is typically produced in industrial settings using a high-salt pickling-desalination process. This involves first pickling the mustard tuber with a high concentration of salt (usually above 12%), followed by desalination to create a low-salt product. However, during desalination, the rapid dissolution of salt causes drastic changes in osmotic pressure within the plant cells, easily leading to the loss of pectin and the collapse of cell wall structures, resulting in softening and loss of crispness in the product.

[0003] To address the softening problem caused by desalination, existing technologies commonly employ the addition of inorganic calcium salts such as calcium chloride, utilizing the reaction of calcium ions with pectic acid to form a gel and increase hardness. However, this traditional hardening process has significant limitations. Due to the extremely rapid reaction rate between calcium ions and pectin, and the reliance solely on concentration gradient-driven natural osmosis, calcium ions often undergo a cross-linking reaction with the surface pectin the moment they come into contact with the pickled mustard tuber, rapidly forming a dense calcium-pectin hard shell. This hardened layer not only hinders the further diffusion of calcium ions into the tissue, resulting in a product that is hard on the outside and soft on the inside with severely uneven texture, but also increases the mass transfer resistance for salt diffusion, forcing a prolonged desalination cycle.

[0004] Furthermore, the prolonged desalination and soaking process not only reduces production efficiency but also exposes the pickled mustard tuber tissue to an unprotected hypotonic environment for an extended period. This causes cells to swell due to water absorption and osmotic pressure shock, leading to significant loss of cell contents and ultimately a decrease in the yield of the finished product's solids. Simultaneously, the extended processing time exacerbates the browning reaction caused by polyphenol oxidase. Combined with the inherent metallic bitterness of traditional inorganic salts such as calcium chloride, and the sharp taste resulting from directly adding inorganic acids to adjust pH, these factors contribute to the fact that low-salt pickled mustard tubers produced using current processes fail to achieve ideal color, flavor, and overall sensory quality. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an integrated pickling and desalting method for preserving the crispness of pickled mustard tubers. This method solves the problem of uneven texture (hard outside, soft inside) and loss of overall crispness in high-salt pickled mustard tubers during desalting due to impaired penetration caused by traditional calcification processes.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for integrated pickling and desalting of pickled mustard tuber that maintains its crispness, comprising the following steps: mixing high-salt pickled mustard tuber raw materials with reverse osmosis water in a reaction vessel equipped with temperature control and stirring functions; adding trehalose; stirring to dissolve the mixture; and lowering the temperature of the mixture to 15-18°C; while maintaining the temperature at 15-18°C, adding sodium hexametaphosphate to the mixture and performing a pulse treatment involving vacuum to atmospheric pressure circulation; controlling the temperature of the mixture at 15-20°C; adding L-calcium lactate and pectin methyl esterase preparation; and performing constant-temperature soaking under these low-temperature conditions; adding gluconate-δ-lactone to the mixture; raising the temperature of the mixture to 40-42°C; and maintaining this temperature until the liquid phase salinity drops to a preset value and the pH value stabilizes; and when the liquid phase salinity drops to the preset value and the pH value stabilizes, performing solid-liquid separation to obtain the integrated pickling and desalting product that maintains the crispness of the pickled mustard tuber.

[0007] By adopting the above technical solution, this invention solves the problems of surface hardening and internal softening caused by the excessively rapid reaction rate of calcium ions and pectin in traditional desalination processes through a control strategy that decouples diffusion and reaction timing. The specific process mechanism and innovations are as follows: The first step, low-temperature system construction and chelation pore opening: by lowering the temperature of the mixed system to 15-18℃, the activity of polyphenol oxidase and subsequently added exogenous pectin methyl esterase was initially inhibited; by utilizing the complexing ability of sodium hexametaphosphate, it preferentially binds to the bound calcium ions already present on the surface of the raw materials, opening the surface shrinkage layer that may be formed due to high salt pickling; combined with the pulse pressure change from vacuum to atmospheric pressure, the hydrodynamic effect generated by the pressure difference is used to remove interstitial gas while enhancing the mass transfer efficiency of the solid-liquid interface, thus establishing channels for the rapid penetration of subsequent substances.

[0008] The second step is low-temperature enzyme-calcium co-diffusion: Under a low-temperature environment of 15-20℃, the catalytic activity of pectin methyl esterase is inhibited, and the mixed system mainly undergoes a physical mass transfer process. Calcium ions (generated by the ionization of L-lactate calcium) and enzyme molecules diffuse into the deeper layers of the pickled mustard tuber tissue through pre-opened pore channels driven by the concentration gradient. Because the reaction is inhibited, premature formation of a gel barrier layer on the surface by calcium ions is avoided, thus achieving a uniform distribution of enzymes and calcium throughout the entire pickled mustard tuber tissue (including the pith).

[0009] The third step is in-situ curing via thermo-acid coupling: When the mixed system is heated to 40-42℃ and glucono-δ-lactone (GDL) is added, GDL decomposes upon heating to release glucono-δ-lactone, causing the pH of the mixed system to decrease slowly. Simultaneously, the heating activates the pectin methyl esterase that has already penetrated the interior. Under suitable temperature and pH conditions, the enzyme catalyzes the deesterification of methoxy groups in pectin molecules. The exposed free carboxyl groups rapidly cross-link with surrounding calcium ions, constructing a dense and uniform three-dimensional pectic acid calcium egg-box network structure in situ within the pickled mustard tuber tissue. This achieves both desalination and maintenance of overall crispness.

[0010] Preferably, the amounts of each component are as follows by weight: high-salt pickled mustard tuber raw material: 100 parts; reverse osmosis water: 150-200 parts; trehalose: 3.75-6.0 parts; sodium hexametaphosphate: 0.125-0.24 parts; L-calcium lactate: 1.0-1.8 parts; pectin methyl esterase preparation: 0.05-0.12 parts; glucono-δ-lactone: 0.5-0.9 parts.

[0011] By employing the above technical solution, the solid-liquid ratio and the proportion of functional additives were precisely controlled. The addition of trehalose adjusted the osmotic pressure of the system, and its unique hydration effect can replace water molecules in binding with cell membrane proteins, maintaining the integrity of the cell membrane structure and reducing cell rupture and solid loss during desalination. The synergistic effect of each component further optimized the reaction kinetic equilibrium.

[0012] Preferably, the high-salt pickled mustard tuber raw material is pre-cut into cubes with a side length of 30-50mm, or into slices with a size of 40mm×40mm×10mm.

[0013] By adopting the above technical solution, the geometric dimensions of the raw materials are limited, ensuring that the pulse opening and diffusion processes can reach core equilibrium within a predetermined time, thus adapting to the processing needs of products of different shapes.

[0014] Preferably, the pulse treatment is specifically performed as follows: turn on the vacuum pump to pump the pressure inside the reaction vessel to -0.03MPa to -0.04MPa and maintain it for 3-5 minutes; then quickly restore it to normal pressure and maintain it for 4-6 minutes; the vacuum to normal pressure process is repeated 3-4 times.

[0015] By adopting the above technical solution, the determined negative pressure range and circulation cycle can generate sufficient pressure difference to drive out the gas inside the tissue and introduce the external solution, while avoiding irreversible mechanical damage to plant tissue cells caused by excessive vacuum.

[0016] Preferably, the constant temperature soaking time is 60-90 minutes, and the circulation flow rate is controlled at 2-3 times the volume of the vessel per hour during the soaking process.

[0017] By adopting the above technical solution, the diffusion rate and geometric scale of enzyme and calcium ions were matched to ensure that the active ingredients had reached diffusion equilibrium before heating and solidification; the appropriate circulation flow rate maintained the concentration gradient at the solid-liquid interface and eliminated the phenomenon of local concentration polarization.

[0018] Preferably, the specific method of heating is as follows: the temperature of the mixed system is linearly increased to 40-42℃ at a rate of 0.8-1.2℃ / min; the constant temperature holding time is 90-120 minutes.

[0019] By adopting the above technical solution, controlling the linear heating rate can enable the gelation reaction to start gently, avoiding structural stress damage caused by drastic temperature changes; 40-42℃ is the optimal temperature range for pectin methyl esterase, and at this temperature, combined with the acid release characteristics of GDL, the gel network with the highest degree of cross-linking can be obtained.

[0020] Preferably, the preset values ​​are that the liquid phase salinity drops to 3.0-3.5% and the pH value is stabilized at 3.6-3.8.

[0021] By adopting the above technical solution, a clear processing endpoint is set. At this point, the salinity inside and outside the mixed system has reached equilibrium, and the pH environment is suitable for the subsequent preservation and flavor presentation of the product.

[0022] Preferably, the high-salt pickled mustard tuber raw material has a center salt content of 13.5% ± 0.5% and an endogenous pectin methyl esterase activity of less than 100 U / g.

[0023] By adopting the above technical solution, the basic properties of the raw materials were clarified. The low-activity endogenous enzymes eliminated the interference of the differences in the raw materials themselves on the standardized process, ensuring that the reaction process was completely dominated by the exogenously added quantitative enzyme preparation, thus improving the controllability of the process.

[0024] Preferably, during the constant-temperature soaking process, the stirring speed is adjusted to 20-30 rpm. By adopting the above technical solution, low-speed stirring not only ensures the uniformity of heat and mass transfer in the system, but also minimizes the damage to the appearance of the pickled mustard tuber caused by mechanical shearing force.

[0025] Preferably, the specific operation of the solid-liquid separation is as follows: the salinity of the liquid phase is monitored in real time by an online conductivity meter, the liquid is drained when the preset value is reached, and the collected pickled mustard tuber material is centrifuged to dehydrate.

[0026] By adopting the above technical solution, the digital interpretation of the process endpoint is realized, avoiding quality fluctuations caused by judgment based on experience. Centrifugal dehydration further removes non-bound water adhering to the surface, which is beneficial for subsequent packaging.

[0027] This invention provides an integrated pickling and desalting method for preserving the crispness of pickled mustard tubers. It offers the following advantages: 1. This invention solves the problem of soft inner and hard outer layers in traditional processes by using a time-series decoupling strategy. It utilizes the chelating effect of sodium hexametaphosphate combined with vacuum pulses to remove surface calcium barriers, and incorporates an enzyme-calcium co-diffusion process under low-temperature conditions to ensure that calcium ions and exogenous pectin methyl esterase fully penetrate into the tissue core before the gelation reaction begins. Subsequently, in-situ rapid solidification is initiated by heating and GDL hydrolysis to produce acid, constructing a dense and uniform three-dimensional pectic acid calcium egg-box network structure throughout the pickled mustard tuber tissue, thus eliminating the hardness gradient.

[0028] 2. This invention utilizes the fluid pressure difference generated by chemical chelation pores and physical vacuum pulses to reduce the mass transfer resistance at the solid-liquid interface, shortening the desalination cycle from several hours to within 3-4 hours. Simultaneously, the trehalose introduced into the system acts as an osmotic buffer, replacing water molecules and binding to membrane proteins to maintain the integrity of the cell membrane structure. This effectively prevents cell rupture and cytoplasmic loss caused by hypotonic shocks during rapid desalination, thus maintaining a high yield of the final solids.

[0029] 3. The low-temperature pre-diffusion process employed in this invention effectively inhibits the activity of polyphenol oxidase, reduces enzymatic browning during processing, and better preserves the natural color of the raw materials. Furthermore, the use of L-calcium lactate combined with the odor-masking properties of trehalose effectively avoids the metallic bitterness associated with traditional inorganic calcium salts. The slow acidification process resulting from the hydrolysis of gluconate-δ-lactone (GDL) not only achieves uniform gelation but also produces a mild acidity that blends more seamlessly with the fermented flavor of the pickled mustard tuber, enhancing the enjoyment of consumption. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to embodiments, comparative examples, and test examples. 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] Preparation Examples 1-3: Preparation Example 1: Take out the above-mentioned high-salt pickled mustard tuber heads and quickly rinse them with clean water to remove the salt particles and impurities attached to the surface; Remove roots and old skin; It was cut into cubes with dimensions of 30mm × 30mm × 30mm using an industrial dicing machine; Drain the surface moisture, mix well, and place in a sealed bag for later use.

[0032] Preparation Example 2: The source of raw materials and pretreatment are the same as in Preparation Example 1; Adjust the cutting process to cut it into large cubes with dimensions of 50mm×50mm×50mm; Drain the surface moisture and mix well for later use.

[0033] Preparation Example 3: The source of raw materials and pretreatment are the same as in Preparation Example 1; Adjust the cutting process to cut it into slices with a thickness of 40mm×40mm×10mm; Drain the surface moisture and mix well for later use.

[0034] Examples 1-3: Example 1: This embodiment provides an integrated pickling and desalting method for maintaining the crispness of pickled mustard tuber, using the thick-sliced ​​pickled mustard tuber (40mm×40mm×10mm) obtained in Preparation Example 3 as the raw material.

[0035] Component dosage: High-salt pickled mustard tuber raw material: 80 parts; Reverse osmosis water: 150 parts; Trehalose: 3.75 parts; Sodium hexametaphosphate: 0.125 parts; L-calcium lactate: 1.0 part; Pectin methyl esterase preparation (enzyme activity 30000U / g): 0.05 parts; Glucono-δ-lactone (GDL): 0.5 parts.

[0036] Preparation process steps: Step 1: Precooling and System Construction 80 parts of raw pickled mustard tuber were placed into a jacketed, temperature-controlled stainless steel reactor. 150 parts of reverse osmosis water were added. 3.75 parts of trehalose were added to the mixture, which has temperature control and stirring functions, and stirring was started to dissolve it. The jacketed cooling circulation was activated to lower the temperature of the material inside the reactor to 15°C and maintain this temperature.

[0037] Step 2: Pulse-type chelation opening While maintaining a temperature of 15°C, add 0.125 parts of sodium hexametaphosphate to the circulation line. Then, initiate the vacuum pulse program: turn on the vacuum pump to evacuate the pressure inside the vessel to -0.03 MPa within 60 seconds and maintain this pressure for 3 minutes; quickly open the vacuum release valve to restore atmospheric pressure and maintain this pressure for 5 minutes. Repeat the above vacuuming and atmospheric pressure process three times. This step takes approximately 30 minutes in total.

[0038] Step 3: Low-temperature enzyme-calcium co-diffusion Maintain the temperature inside the container at 15℃, add 1.0 part of L-calcium lactate and 0.05 parts of pectin methyl esterase preparation. Adjust the stirring speed to 20 rpm, turn on the external circulation spray, and control the circulation flow rate at twice the container volume per hour. Soak at this low temperature for 60 minutes to allow the enzyme and calcium ions to fully penetrate into the pickled mustard greens.

[0039] Step 4: Thermal Acid Coupling Curing Add 0.5 parts of glucono-δ-lactone (GDL) to the system. Switch the temperature control mode to heating and linearly increase the temperature inside the reactor to 40°C at a rate of 0.8°C per minute. Maintain this temperature at 40°C for 90 minutes. Monitor the pH value during this period; the pH value of the system should drop to 3.8 at the end of the reaction.

[0040] Step 5: Separation The reaction was stopped when the online conductivity meter showed that the liquid phase salinity dropped to 3.5% and the pH stabilized at 3.8. The liquid was drained, the pickled mustard greens were collected, and centrifuged to remove water, thus obtaining the finished product.

[0041] Example 2: This embodiment provides an integrated pickling and desalting method for maintaining the crispness of pickled mustard tuber. The standard cubic block pickled mustard tuber (30mm×30mm×30mm) obtained in Preparation Example 1 is selected as the raw material, which is the preferred embodiment.

[0042] Component dosage: High-salt pickled mustard tuber raw material: 100 parts; Reverse osmosis water: 175 parts; Trehalose: 5.0 parts; Sodium hexametaphosphate: 0.18 parts; L-calcium lactate: 1.4 parts; pectin methyl esterase preparation (30000U / g): 0.08 parts; glucono-δ-lactone (GDL): 0.7 parts.

[0043] Preparation process steps: Step 1: Precooling and System Setup. Load 100 parts of raw pickled mustard tuber into the reactor. Add 175 parts of reverse osmosis water. Add 5.0 parts of trehalose to the system and start stirring to dissolve. Start the jacket cooling circulation to lower the temperature of the material inside the reactor to 16°C and maintain it constant.

[0044] Step 2: Pulse-type chelation opening. While maintaining 16°C, add 0.18 parts of sodium hexametaphosphate. Start the vacuum pulse program: evacuate the pressure inside the vessel to -0.035 MPa and hold for 4 minutes; quickly restore to normal pressure and hold for 5 minutes. Repeat the above cycle 3 times.

[0045] Step 3: Adjust the temperature inside the reactor to 18°C ​​using low-temperature enzyme-calcium co-diffusion. Add 1.4 parts of L-calcium lactate and 0.08 parts of pectin methyl esterase preparation. Adjust the stirring speed to 25 rpm and the circulation rate to 2.5 times the reactor volume per hour. Soak under these conditions at a constant temperature for 75 minutes.

[0046] Step 4: For thermal-acid coupling curing, add 0.7 parts of glucono-δ-lactone (GDL). Switch to heating mode and raise the temperature to 41°C at a rate of 1.0°C per minute. Maintain the temperature at 41°C for 100 minutes.

[0047] Step 5: Separation When the salinity of the liquid phase reaches 3.2% and the pH stabilizes at 3.7, stop the reaction, drain the liquid, and centrifuge to obtain the finished product.

[0048] Example 3: This embodiment provides an integrated pickling and desalting method for maintaining the crispness of pickled mustard tuber. Large pieces of pickled mustard tuber (50mm×50mm×50mm) obtained in Preparation Example 2 were selected as raw materials to verify the ultimate permeability.

[0049] Component dosage: High-salt pickled mustard tuber raw material: 120 parts; Reverse osmosis water: 200 parts; Trehalose: 6.0 parts; Sodium hexametaphosphate: 0.24 parts; L-calcium lactate: 1.8 parts; Pectin methyl esterase preparation (enzyme activity 30000U / g): 0.12 parts; Glucono-δ-lactone (GDL): 0.9 parts.

[0050] Preparation process steps: Step 1: Precooling and System Construction 120 parts of raw pickled mustard tuber were loaded into the reactor. 200 parts of reverse osmosis water were added. 6.0 parts of trehalose were added to the system and stirred until dissolved. Cooling was initiated to maintain the reactor temperature at 18°C.

[0051] Step 2: Pulse-type chelation opening Add 0.24 parts of sodium hexametaphosphate while maintaining a temperature of 18°C. Initiate a vacuum pulse program: evacuate the pressure inside the reactor to -0.04 MPa and maintain for 5 minutes; then rapidly restore to normal pressure and maintain for 5 minutes. Repeat this cycle 4 times to enhance the deep pore-opening effect under high feed rates.

[0052] Step 3: Low-temperature enzyme-calcium co-diffusion Adjust the temperature inside the reactor to 20°C, add 1.8 parts of L-calcium lactate, and simultaneously add 0.12 parts of pectin methyl esterase preparation. Adjust the stirring speed to 30 rpm and the circulation flow rate to 3 times the reactor volume per hour. Soak at a constant temperature for 90 minutes to ensure the mass exchange balance within the high-solids content system.

[0053] Step 4: Thermal Acid Coupling Curing Add 0.9 parts glucono-δ-lactone (GDL). Increase the temperature to 42°C at a rate of 1.2°C per minute. Maintain the temperature at 42°C for 120 minutes.

[0054] Step 5: Separation When the salinity of the liquid phase reaches equilibrium at 3.0% and the pH stabilizes at 3.6, the reaction is stopped, the liquid is drained, and centrifuged to obtain the final product.

[0055] Comparative Examples 1-6: Comparative Example 1: Compared with Example 2, the difference is that the traditional water soaking desalination method was used. Specifically, the raw material was soaked in water containing 0.5% calcium chloride and 0.1% citric acid, without adding trehalose, sodium hexametaphosphate, pectin methyl esterase, or glucono-δ-lactone (GDL); the entire process was carried out at room temperature (25°C) without pulse negative pressure treatment or temperature control, until the desalination endpoint was reached.

[0056] Comparative Example 2: Compared with Example 2, the difference is that in step two, sodium hexametaphosphate is not added, and vacuum pulse operation is not performed. The soaking is simply maintained, and the other steps are the same.

[0057] Comparative Example 3: Compared with Example 2, the difference is that in step three, no pectin methyl esterase preparation is added, and only the endogenous enzyme remaining in the raw materials (which is actually inactivated or has very low activity) is relied upon. The other steps are the same.

[0058] Comparative Example 4: Compared with Example 2, the difference is that the step-by-step operation is eliminated and a one-pot method is adopted. Specifically, trehalose, sodium hexametaphosphate, L-calcium lactate, pectin methyl esterase preparation, and glucono-δ-lactone (GDL) are added to the reaction vessel all at once in step one, and the temperature is directly set to 40°C and the reaction is carried out at a constant temperature until the desalination endpoint.

[0059] Comparative Example 5: Compared with Example 2, the difference is that in step four, glucono-δ-lactone (GDL) is not used, but citric acid solution is used to directly adjust the pH of the system to 3.7. The rest of the steps are the same.

[0060] Comparative Example 6: Compared with Example 2, the difference is that in step one, no trehalose was added, and only reverse osmosis water was used as the base liquid, while the other steps were the same.

[0061] Test Example 1-3: Test Example 1: Product Texture Property Test Experimental instructions and methods: This test aims to quantitatively evaluate the mechanical properties of pickled mustard tuber products processed by different techniques, mainly examining the hardness and brittleness indicators to characterize their edible quality.

[0062] Sample preparation: Samples were randomly selected from the finished products obtained in Examples 1-3 and Comparative Examples 1-6. The samples were uniformly trimmed and cut into standard cubic test blocks with dimensions of 10mm × 10mm × 10mm. Fifteen parallel samples were prepared for each group, and the test results were taken as the arithmetic mean.

[0063] Instrumentation: TA.XTPlus Texture Analyzer, equipped with a P / 5 column probe.

[0064] Test mode: Total Texture Analysis (TPA) mode.

[0065] Parameter settings: Pre-measurement velocity: 2.0 mm / s; Test speed: 1.0 mm / s; Post-measurement velocity: 1.0 mm / s; Strain ratio: 50%; Trigger force: 5g; Interval between two compressions: 5 seconds.

[0066] Indicator definition: Hardness (N): The maximum peak force during the first compression cycle, characterizing the ability to resist deformation.

[0067] Brittleness (N): The force value of the first fracture peak that appears during the first compression. If there is no obvious yield peak, it indicates that the sample is tough or soft, and the value is 0 or recorded as not detected.

[0068] Chewing performance (mJ): A comprehensive energy consumption index calculated from hardness, cohesiveness, and elasticity.

[0069] Test results: Detailed test data is shown in the table below. Table 1. Summary of Total Texture Analysis (TPA) Test Data for Each Sample Group Results Analysis and Conclusions: Based on the data in Table 1 and the technical principles of this invention, the analysis is as follows: Overall strengthening effect analysis: The hardness and brittleness indices of Example Groups (1-3) were superior to those of the comparative examples. Among them, Example 2 performed best, with a brittleness value of 25.34 N, which is about 6 times that of the traditional process (Comparative Example 1). This indicates that the combined process of chelation pore opening, enzyme-calcium co-diffusion, and in-situ gelation can effectively reconstruct the plant tissue skeleton under low-salt conditions.

[0070] The Importance of Mass Transfer Channels (Analysis of Comparative Example 2): After removing sodium hexametaphosphate and the vacuum pulse step, Comparative Example 2 showed a hardness value of 21.04 N, seemingly a small decrease, but its brittleness value was only 11.56 N, with a coefficient of variation (CV) as high as 12.33%. Mechanistically, the lack of epidermal chelating pores makes it difficult for external calcium ions and enzyme molecules to penetrate the dense epidermal layer and enter the medulla, resulting in only superficial hardening on the surface while the internal tissue remains soft. This hard-on-the-outer-skin, soft-on-the-core structure leads to indistinct overall brittle fracture characteristics and poor chewability.

[0071] The necessity of constructing a chemically cross-linked network using exogenous enzymes (analysis of Comparative Example 3): Comparative Example 3 relied solely on physically permeated calcium ions, without the addition of exogenous pectin methyl esterase, and its hardness was only 18.23 N. This confirms that the endogenous enzymes in the raw materials cured with high salt for a long time have been essentially inactivated. The introduction of exogenous enzymes catalyzed the deesterification reaction of high-methoxyl pectin, and the resulting free carboxyl groups formed a more chemically bonded eggshell-structured gel network with the permeated calcium ions, thus contributing additional structural strength.

[0072] Effectiveness of spatiotemporal decoupling control (analysis of Comparative Examples 4 and 5): Comparative Example 4, using a one-pot method, had the highest coefficient of variation (15.60%), indicating extremely poor product uniformity. This is because the enzymatic reaction rate at high temperatures is much greater than the diffusion rate, leading to rapid surface gelation and closure of mass transfer channels, while the interior failed to harden effectively. Comparative Example 5 used citric acid for direct acidification, causing the system pH to rapidly drop to the enzyme's inactivation range. The enzyme became inactive before it could exert its catalytic effect, hence all mechanical properties were lower than those of the examples.

[0073] Cell-protective effect of trehalose (analysis of Comparative Example 6): Comparative Example 6 lacked trehalose; although its hardness was still acceptable, its brittleness value was lower than that of the Example. This indicates that under the osmotic pressure impact of rapid desalination, the lack of dielectric protection from trehalose leads to partial cell membrane rupture and tissue collapse, reducing the material's tendency to undergo brittle fracture.

[0074] In summary, this invention achieves uniform hardening of the pickled mustard tuber tissue from the surface to the interior by stepwise regulating mass transfer and reaction kinetics, thus solving the softening problem caused by traditional desalination processes.

[0075] Test Example 2: Calcium Ion Permeability Uniformity Test Experimental instructions and methods: This test aims to examine the spatial distribution of calcium ions within plant tissues. By measuring the difference in calcium content between the surface and core regions, it verifies the effectiveness of the chelation-opening and low-temperature diffusion steps of this invention in eliminating mass transfer resistance.

[0076] Sample source: The desalination products prepared by Example 2, Comparative Example 2 (without chelation pores) and Comparative Example 4 (one-pot method / without time control) were selected.

[0077] Sampling strategy: Surface sample: Tissue with a thickness of 0-2 mm from the outer surface of the sample is cut from six sides using a stainless steel slicer.

[0078] Core sample: Tissue within a 5mm × 5mm × 5mm area at the geometric center of the sample is cut.

[0079] Pretreatment: The collected wet sample was dried to constant weight in an oven at 105℃ and then pulverized through a 60-mesh sieve. 0.5g of the dry powder was accurately weighed, and 10mL of concentrated nitric acid and 2mL of perchloric acid were added. The mixture was then wet digested on a hot plate until the solution was clear and transparent, and the volume was adjusted to 50mL.

[0080] Determination method: Calcium content was determined by flame atomic absorption spectrophotometry (FAAS). Instrument parameters: wavelength 422.7 nm, slit width 0.7 nm, lamp current 10 mA, air-acetylene flame.

[0081] Evaluation index: Calculation of calcium distribution evenness coefficient ( The calculation formula is as follows: In the formula, The calcium content of the medullary core (mg / kg) Surface calcium content (mg / kg). The closer the value is to 1, the more uniform the penetration. The smaller the value, the more obvious the concentration gradient or surface crusting phenomenon.

[0082] Test results: The spatial distribution data of calcium in each group of samples are shown in the table below.

[0083] Table 2. Results of calcium content distribution in different spatial levels of pickled mustard tuber tissue. Results Analysis and Conclusions: Based on the data in Table 2 and the chemical mass transfer mechanism, the analysis is as follows: Validation of mass transfer channel opening mechanism: Distribution uniformity coefficient of Example 2 A value of 0.874 indicates that calcium ions have accumulated at a high concentration in the core tissue region. In contrast, Comparative Example 2 (removal of sodium hexametaphosphate and vacuum pulse) showed a significantly lower concentration. The value was only 0.296. This difference confirms that the chelating and stripping effect of sodium hexametaphosphate on the surface pectin calcium, combined with the pressure difference flow generated by the vacuum pulse, effectively destroyed the dense epidermal barrier layer formed by high-salt pickling, reducing the interfacial mass transfer resistance for external substances to enter the interior. Without this step, calcium ions would mainly remain in the superficial layer and would not be able to penetrate deeper.

[0084] Reaction kinetic control verification: Comparative Example 4 showed extreme distribution differences, with the surface layer calcium content reaching as high as 5678.1 mg / kg, while the core layer was only 642.5 mg / kg. The value was as low as 0.113. This is because direct heating without low-temperature pre-diffusion caused rapid activation of the pectin methyl esterase in the surface contact layer, catalyzing the deesterification of the surface pectin and instantaneously cross-linking with the high concentration of calcium ions. This reaction formed a dense calcium pectate gel shielding layer on the sample surface, blocking the channels for calcium ions to diffuse inward.

[0085] Conclusion: Example 2 has high... The data strongly supports the diffusion-first, reaction-later technical approach of this invention. By using a low-temperature environment in step three to inhibit enzyme activity and maintain channel openness, it is ensured that calcium ions and enzyme molecules have completed homogeneous filling within the tissue before the gelation reaction begins, thereby achieving full-domain hardening of the final product.

[0086] Example 3: Test Example 3: Desalination Efficiency and Yield Test Experimental instructions and methods: This test aims to examine the economics and efficiency of different processing technologies in industrial production, with a focus on desalination kinetics and the yield (mass retention) of solid materials.

[0087] Sample grouping: The process of Example 2 (preferred group), Comparative Example 1 (traditional water soaking), Comparative Example 2 (no chelation opening) and Comparative Example 6 (no trehalose) was monitored.

[0088] Desalination endpoint determination: The unified termination criterion is a reduction in liquid phase salinity to 3.5% (mass fraction). Real-time monitoring is performed using an online conductivity meter, and the chloride ion content is verified using the Mohr method (AgNO3 titration). Test process: Accurately weigh 5.00 kg of each group of raw materials (recorded as...). ).

[0089] Desalination is carried out according to their respective process parameters.

[0090] Record the total time required from the start of feeding to reaching the desalination endpoint (including auxiliary operation time).

[0091] After reaching the endpoint, remove the solid material, drain it under standard gravity for 10 minutes, and weigh the final wet weight (recorded as ). ). Calculation formula: Finished product yield (%) Test results: The desalination time and material yield data for each process group are recorded in the table below.

[0092] Table 3. Monitoring data on desalination efficiency and finished product yield for each group of processes. Results Analysis and Conclusions: Based on the data in Table 3 and the principles of mass transfer, the analysis is as follows: Improved mass transfer kinetics: The total desalination time in Example 2 was 3.25 hours, lower than 9.50 hours in Comparative Example 1 and 6.80 hours in Comparative Example 2. Sodium hexametaphosphate-mediated chelation removed the epidermal calcium barrier, and combined with the fluid pressure difference generated by the vacuum pulse, established low-resistance solute diffusion channels within the tissue. In contrast, Comparative Example 2 lacked an active pore-opening step, relying solely on concentration gradient-driven natural permeation, resulting in a significantly reduced desalination efficiency.

[0093] The water-retention and weight-gain mechanism of trehalose: The yield of the finished product in Example 2 reached 94.20%, while the yield of Comparative Example 6, which lacked trehalose, was only 79.60%. During rapid desalination (salinity decreased from 13% to 3.5% within 3 hours), cells faced severe hypotonic shock. Data from Comparative Example 6 showed that the lack of osmotic buffers led to excessive water absorption, swelling, and rupture of cells, resulting in cytoplasmic loss and tissue collapse, thus reducing the yield. Trehalose maintains the integrity of the cell membrane structure by replacing water molecules and binding to membrane proteins, reducing the loss of soluble solids.

[0094] Water-locking effect of gel network: Compared with Comparative Example 1 (86.40%), the calcium pectate-egg carton three-dimensional network structure constructed in this invention not only improves hardness but also enhances the physical binding capacity of the matrix for water molecules. This chemically cross-linked network restricts the release of free water, enabling the product to maintain a high quality yield even after undergoing hot acid treatment.

[0095] In summary, the technical solution of this invention significantly shortens the process cycle while improving product yield, and has advantages for industrial production.

Claims

1. A method for integrating pickling and desalting of pickled mustard tuber to maintain its crispness, characterized in that, Includes the following steps: High-salt pickled mustard tuber raw material and reverse osmosis water are placed in a reaction vessel with temperature control and stirring functions and mixed. Trehalose is added, stirring is started to dissolve, and the temperature of the mixed system is lowered to 15-18℃. Sodium hexametaphosphate was added to the mixture while maintaining a temperature of 15-18°C, and pulse treatment of vacuum to atmospheric pressure cycling was performed. The temperature of the mixture is controlled at 15-20℃, and L-calcium lactate and pectin methyl esterase preparation are added. The mixture is then soaked at a constant temperature under these low-temperature conditions. Add gluconate-δ-lactone to the mixture, raise the temperature of the mixture to 40-42°C, and maintain this temperature until the liquid phase salinity drops to a preset value and the pH value stabilizes. When the salinity of the liquid phase drops to the preset value and the pH value stabilizes, solid-liquid separation is achieved, resulting in a finished product that integrates pickling and desalination while maintaining the crispness of the pickled mustard tuber.

2. The integrated pickling and desalting method for maintaining the crispness of pickled mustard tuber according to claim 1, characterized in that, The amounts of each component by weight are as follows: High-salt pickled mustard tuber raw material: 80-120 parts; Reverse osmosis water: 150-200 parts; Trehalose: 3.75-6.0 parts; Sodium hexametaphosphate: 0.125-0.24 parts; L-calcium lactate: 1.0-1.8 parts; Pectin methyl esterase preparation: 0.05-0.12 parts; Glucono-δ-lactone: 0.5-0.9 parts.

3. The integrated pickling and desalting method for maintaining the crispness of pickled mustard tuber according to claim 1, characterized in that, The high-salt pickled mustard tuber raw material is pre-cut into cubes with a side length of 30-50mm, or into slices with a size of 40mm×40mm×10mm.

4. The integrated pickling and desalting method for maintaining the crispness of pickled mustard tuber according to claim 1, characterized in that, The specific operation of the pulse treatment is as follows: turn on the vacuum pump to pump the pressure inside the reaction vessel to -0.03MPa to -0.04MPa and maintain it for 3-5 minutes; then quickly restore it to normal pressure and maintain it for 4-6 minutes; the vacuum to normal pressure process is repeated 3-4 times.

5. The integrated pickling and desalting method for maintaining the crispness of pickled mustard tuber according to claim 1, characterized in that, The constant temperature soaking time is 60-90 minutes, and the circulation flow rate is controlled at 2-3 times the volume of the vessel per hour during the soaking process.

6. The integrated pickling and desalting method for maintaining the crispness of pickled mustard tuber according to claim 1, characterized in that, The specific method of heating is as follows: the temperature of the mixed system is linearly increased to 40-42℃ at a rate of 0.8-1.2℃ / min; the constant temperature holding time is 90-120 minutes.

7. The integrated pickling and desalting method for maintaining the crispness of pickled mustard tuber according to claim 1, characterized in that, The preset values ​​are that the liquid phase salinity drops to 3.0-3.5% and the pH value stabilizes at 3.6-3.

8.

8. The integrated pickling and desalting method for maintaining the crispness of pickled mustard tuber according to claim 1, characterized in that, The salt content of the high-salt pickled mustard tuber raw material is 13.5%±0.5%, and the endogenous pectin methyl esterase activity is less than 100U / g.

9. The integrated pickling and desalting method for maintaining the crispness of pickled mustard tuber according to claim 1, characterized in that, During the constant temperature soaking process, the stirring speed is adjusted to 20-30 rpm.

10. The integrated pickling and desalting method for maintaining the crispness of pickled mustard tuber according to claim 1, characterized in that, The specific operation of the solid-liquid separation is as follows: the salinity of the liquid phase is monitored in real time by an online conductivity meter, the liquid is drained when the preset value is reached, and the collected pickled mustard tuber material is centrifuged to dehydrate.

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