Preparation method of chitosan microencapsulated salt-reduced soy sauce powder
By combining freezing salt precipitation and ultrasonic treatment with chitosan microencapsulation technology, the problems of flavor loss and insufficient salt control in soy sauce powder production were solved, and the salt content of soy sauce powder was reduced, and the stability and solubility were improved, thereby extending the shelf life.
Patent Information
- Application Number
- CN202511151800.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-18
- Publication Date
- 2025-09-23
AI Technical Summary
The existing soy sauce powder production process has problems such as loss of flavor substances and nutrients, easy agglomeration, and insufficient salt control, which makes it difficult to meet the dual needs of modern consumers for flavor and health.
Ultrasound-assisted, chitosan microencapsulation and freeze-drying methods are used to reduce salt content through freeze-salting, combined with ultrasonic treatment and microencapsulation technology to retain flavor and nutrients and improve stability and solubility.
Effectively reduce the salt content of soy sauce powder, maintain flavor and nutrients, avoid flavor loss during high-temperature drying, improve the stability and solubility of soy sauce powder, and extend shelf life.
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Figure CN120678205A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of food processing, in particular to a method for preparing chitosan microencapsulated salt-reduced soy sauce powder. Background Art
[0002] Soy sauce, a traditional and important condiment, is widely used in food processing and home cooking for its unique flavor and rich nutritional profile. To meet the modern food industry's demand for convenient and quick-to-use products, soy sauce powder has emerged as a seasoning that is easy to store, transport, and use. Currently, the traditional production process for soy sauce powder primarily involves pretreatment of the raw liquid soy sauce and powdering via spray drying or hot air drying. While spray drying is highly efficient and suitable for large-scale production, the high temperature process can easily lead to the loss of volatile flavor compounds and nutrients in the soy sauce, compromising product quality. Hot air drying, while simple to operate, requires long drying times and can easily cause flavor evaporation and color change. Furthermore, soy sauce powder prepared using traditional methods is prone to clumping and suffers from deficiencies in stability, solubility, and salt control, making it difficult to meet the dual demands of modern consumers for both flavor and health. Furthermore, traditional soy sauce and its products are high in salt, and long-term consumption of high-salt foods has been linked to numerous health risks, including hypertension and cardiovascular disease. With increasing consumer health awareness and the promotion of relevant food safety policies, salt reduction has become a key research direction in the condiment industry. How to reduce the salt content while ensuring the flavor and nutritional properties of soy sauce powder has become a difficult problem that needs to be solved urgently by current technology. Summary of the Invention
[0003] In view of the above-mentioned defects of the prior art, the present invention uses ultrasound assistance, chitosan microencapsulation technology and freeze-drying method to provide a salt-reduced soy sauce powder and a preparation method thereof. This technology can effectively retain the flavor and nutritional components of soy sauce, while using the freezing salt precipitation method to reduce the salt content, and through the microencapsulation technology to improve the stability, solubility and shelf life of the soy sauce powder.
[0004] In one aspect, the present invention provides a method for preparing chitosan microencapsulated reduced-salt soy sauce powder, comprising the following steps: Step 1), cooling the soy sauce liquid to -21°C to -22°C, filtering to remove ice crystals, repeating the process several times, and collecting the mother liquor; Step 2), ultrasonically treating the mother liquor to obtain an ultrasonically treated liquid; Step 3), adjusting the pH of the ultrasonic treatment solution to 3.5-4 using HCl solution, adding chitosan solution to a chitosan concentration of 0.2-1%, to obtain a mixed solution; Step 4), stirring the mixed solution at low temperature for 45 minutes, adding NaOH to adjust the pH to 4.0-4.5, and obtaining a coagulant; Step 5), freeze-drying the coagulant, crushing and sieving to obtain the chitosan microencapsulated reduced-salt soy sauce powder.
[0005] Step 1) Salt is separated using a freeze-salt separation method. The soy sauce liquid is first cooled to approximately -21.6°C, causing water to preferentially crystallize into ice crystals. Simultaneously, salt is expelled and concentrated in the remaining liquid phase. When the salt concentration reaches supersaturation, salting-out crystals precipitate, separating the water and salt. Multiple freeze-filtration processes gradually remove water, concentrating flavor compounds and reducing the salt content in the solution. The ice crystals are then washed with deionized water at 0°C to 4°C to effectively remove salt adhering to their surfaces and improve the desalination rate.
[0006] During the freeze-concentration process, salt is concentrated in the mother liquor due to water crystallization. The salt in the mother liquor precipitates under low temperature and salt supersaturation conditions, thereby retaining the amino acid and sugar flavor components in the soy sauce while reducing the overall salt content, providing a better precursor system for subsequent microencapsulation.
[0007] In a preferred embodiment, step 1) further comprises heating the collected mother liquor to 4° C. to 10° C. and then stirring, which is beneficial for gentle mixing of the mother liquor and chitosan and viscosity control in subsequent steps.
[0008] Step 2) Ultrasonic treatment enhances flavor. The mother liquor collected in step 1 is treated with 20 kHz ultrasound for 30-60 minutes at a power density of 10-50 W / cm² and a temperature of 60-90°C. Ultrasonic treatment promotes molecular vibrations within the soy sauce, thereby enhancing the release of its aroma and flavor. Ultrasonic treatment effectively breaks down the macromolecular structure of the soy sauce, promoting the Maillard reaction and increasing the production of flavor components such as peptides and sugars, thereby enhancing the overall flavor profile of the soy sauce.
[0009] In step 3), an appropriate amount of HCl is first added to the sonication solution to adjust the pH to approximately 3.5–4.0, creating an acidic environment conducive to chitosan dissolution. A pH that is too low results in incomplete microencapsulation, low encapsulation efficiency, and structural instability. Increasing the pH affects binding efficiency, while a pH that is too high may prevent microcapsule formation and result in agglomeration. The charge of chitosan is determined by its amino side groups, with a pKa value of approximately 6.5. At relatively low pH values, chitosan's amino groups are protonated and soluble in water, resulting in a positive charge. However, as the pH increases, more chitosan is required to encapsulate the protein due to the decrease in chitosan charge and electrostatic repulsion, and the complex tends to precipitate at high pH values. The pH of soy sauce is originally between 4 and 4.5. Adding chitosan increases the pH, so it needs to be lowered to a lower pH beforehand. Within the pH range of 3.5-4.5, chitosan's electrostatic complexation efficiency initially increases and then decreases. Chitosan typically forms complexes with negatively charged ligands most effectively around pH 3.5. As the pH increases toward 4.5, the complexation efficiency gradually decreases. Subsequently, highly deacetylated, medium-molecular-weight chitosan is added to the acidified soy sauce solution. At this point, the solution pH rebounds. This acidic condition promotes the dissolution of chitosan, and the polycationic properties of chitosan are more pronounced under acidic conditions. This property allows chitosan to swell in acidic conditions, forming a gel that coats the core material, forming a protective film with a certain degree of softness and elasticity, facilitating the microencapsulation process.
[0010] In some embodiments, in step 3), the deacetylation degree of the chitosan is ≥85%, preferably 90%.
[0011] In step 4), under the premise of stabilizing the pH of the system, NaOH is added with sufficient stirring to form microcapsules: the mixed solution with 0.2%-1.5% chitosan added is fully stirred at low temperature (4°C to 10°C) and its pH value is monitored. The acidity is slowly reduced during the stirring process. From the initial pH 3.5 to about pH 4.0, this stirring process can ensure that the chitosan is in full contact with the components in the soy sauce liquid, because the amino groups of chitosan can be protonated under acidic conditions (amino-NH2 is converted to -NH3 + Then, gradually add NaOH dropwise to adjust the pH of the system to a stable range of 4.0-4.5. The main flavor-contributing amino acids in soy sauce are mostly negatively charged glutamic acid and small peptides. Glutamic acid electrostatically attracts chitosan, forming aggregates and a uniform microcapsule structure. Adequate stirring aids microcapsule formation and avoids uneven capsule structures, thereby improving the stability and flavor retention of the final product. Too low a pH results in incomplete microencapsulation, low encapsulation efficiency, and unstable structure. Increasing the pH affects binding efficiency, while too high a pH may prevent microcapsule formation and result in agglomeration.
[0012] In step 5), freeze-drying, the microencapsulated soy sauce liquid is further frozen to -40°C to -60°C and freeze-dried, removing moisture through sublimation. The freeze-dried soy sauce powder exhibits high stability and a relatively low salt content, dissolving well in water while retaining the rich flavor of the soy sauce. The final product exhibits excellent taste and solubility, making it suitable for rapid dissolution.
[0013] In another aspect, the present invention provides chitosan microencapsulated reduced-salt soy sauce powder obtained by the above preparation method.
[0014] In a preferred embodiment, the soy sauce powder has a salt content of less than 44% and a water content of 2.5%.
[0015] In a preferred embodiment, the shelf life of the soy sauce powder (40° C., relative humidity 75%) is more than 20 months.
[0016] Technical Effects
[0017] The present invention constructs a four-step synergistic process path of "freeze-salting + ultrasonic enhancement + microencapsulation + freeze-drying", which is used for salt reduction, stabilization and efficient powderization of flavor substances such as soy sauce powder.
[0018] First, the freezing-salting separation method freezes the water in the soy sauce stock solution by lowering the temperature. The water precipitates in the form of ice crystals, while the salt is excluded and concentrated in the remaining liquid phase. When the salt concentration reaches an oversaturated state, salting-out crystals precipitate, thereby achieving the separation of water and salt. It can be filtered repeatedly and repeated many times. Combined with ultrasonic enhancement + microencapsulation. High-intensity ultrasound is used as a means to promote the maturation of soy sauce. Ultrasonic treatment promotes the interfacial effect between flavor substances and wall materials, enhances emulsification and dispersion effects, and provides a structural basis for subsequent encapsulation; chitosan microencapsulation technology efficiently encapsulates volatile and easily degradable components, improving their thermal stability and sustained-release properties. The pH of soy sauce powder is acidic, and a protonation reaction is selected under acidic conditions to form -NH3 + The chitosan exhibits excellent cationic properties, which combines with anions such as free amino acids and small peptides in soy sauce to form a stable microcapsule structure, effectively protecting the flavor components in the soy sauce. At the same time, stirring at low temperature avoids flavor loss during high-temperature drying.
[0019] The chitosan solution is mixed with soy sauce, and the pH is adjusted to form a colloid with free amino acids, small peptides, and other active and flavorful substances. The mixture is then freeze-dried. Freeze-drying removes moisture at low temperatures, preventing the damage to the soy sauce's flavor and nutrients caused by high temperatures while also minimizing the negative impact of salting-out on flavor.
[0020] Microencapsulation technology prevents soy sauce powder from clumping, allowing it to dissolve quickly in water for easy use. Meanwhile, the freeze-drying process effectively preserves flavor compounds, and the low moisture content of the soy sauce powder extends its shelf life.
[0021] Retention of flavor components: By adjusting the pH value by adding hydrochloric acid and then performing anion-cation combination microencapsulation, and ultrasonic-assisted post-ripening, the flavor components such as amino acids and sugars in the soy sauce are first released, and then effectively encapsulated with chitosan, reducing the loss of flavor components during the drying process.
[0022] Salt Reduction: The production process begins with a freeze-salt extraction method, combined with filtration during the pre-cooling process. This process reduces the salt content in the soy sauce powder. This reduction in salt increases the proportion of other flavor components and reduces water absorption. Because maltodextrin is not added during the final soy sauce powder production process, the absolute salt content in the soy sauce powder increases, but the effective salt intake is lower. This also improves storage quality and enhances the overall flavor.
[0023] Improved product stability and solubility: By eliminating maltodextrin and utilizing chitosan microencapsulation technology, the product effectively inhibits particle aggregation and antibacterial properties, preventing soy sauce powder from clumping and enabling rapid dissolution in water. Furthermore, the vacuum freeze-drying process maximizes the preservation of flavor, while the low water activity significantly extends its shelf life at room temperature.
[0024] The soy sauce produced through this process significantly improves the purity of its solids by removing maltodextrin. Consequently, the relative concentration of active ingredients like amino acid nitrogen is significantly higher than similar products, enhancing flavor intensity. While the salt content of the final soy sauce powder may appear high in dry matter, its highly concentrated nature allows for a reduced amount to achieve the same flavoring effect—actually, less salt is added to the food, truly achieving the goal of "reducing salt without sacrificing freshness." BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 The electron micrograph of the chitosan microencapsulated reduced-salt soy sauce powder prepared in Example 1 of the present invention is shown. DETAILED DESCRIPTION
[0026] The following describes several preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.
[0027] Example 1: Raw materials: soy sauce concentrate, chitosan (deacetylation degree ≥ 85%), HCl (food grade), NaOH (food grade).
[0028] step: The soy sauce liquid was slowly cooled to -22°C to precipitate ice crystals, which were filtered out and removed. The filtration was repeated several times to reduce the salt content to 10% (wet weight), and the mother liquor was collected.
[0029] The mother liquor was subjected to ultrasonic treatment (20 kHz, 60°C, 60 min, 39.48 W / cm²) to obtain an ultrasonicated solution.
[0030] The pH of the ultrasonic treatment solution was adjusted to 3.5 using HCl solution, and chitosan solution was added to a chitosan concentration of 1.0% to obtain a mixed solution; The mixed solution was stirred at low temperature for 45 minutes, and NaOH was added to adjust the pH to 4.5 to obtain a coagulant; The condensate was freeze-dried (-45°C, vacuum 8 Pa, 24 hours), crushed and sieved to obtain the finished soy sauce powder (salt content 39%, water content 2.5%). The electron micrograph is shown as follows: Figure 1 shown.
[0031] Determination of the instant solubility of soy sauce powder
[0032] Determination method: Refer to solid instant tea GB / T 31740.1-2015: Take 5 g of soy sauce powder sample and dissolve it in 10 mL of pure water at 25℃±1℃. After stirring, no suspended matter or sediment is visible to the naked eye. Record the time of complete dissolution.
[0033] The shelf life of soy sauce powder was measured by accelerated test (40℃, relative humidity 75%), and the time when the soy sauce powder exceeded the shelf life was recorded.
[0034] Criteria for judging expiration of shelf life: moisture absorption and clumping, flavor loss, color change, and the generation of odor.
[0035] Specific sensory indicators: From the original brown to black, gray, or uneven color spots; Loss of sauce aroma, with a rancid, musty, or rancid taste; The powder changes from loose to hard, even to stringy and sticky; Green or white mold spots or black particles can be seen with the naked eye.
[0036] Test results: Dissolution time is 25 seconds, and the accelerated test (40°C, relative humidity 75%) shows that the shelf life can reach 20 months.
[0037] Example 2: Raw materials: soy sauce concentrate, chitosan (deacetylation degree ≥ 90%), HCl (food grade), NaOH (food grade).
[0038] step: Precooling and salt precipitation: cool the soy sauce liquid to -22℃, let it stand for 2.5 hours to precipitate ice crystals, filter out the ice crystals, and after removing the precipitated salt, the salt content is reduced to 12% (wet weight), and collect the mother liquor.
[0039] The mother liquor was subjected to ultrasonic treatment (20 kHz, 60°C, 60 min, 39.48 W / cm²) to obtain an ultrasonicated solution.
[0040] Hydrochloric acid (HCl) was added dropwise to the ultrasonic treatment solution to adjust the pH to 3.5, and then chitosan was added to a chitosan concentration of 1.5% to obtain a mixed solution.
[0041] The mixed solution was stirred at low temperature (0-5° C.) for 60 minutes, and then a NaOH solution was slowly added to adjust the pH to 4.5 to obtain a coagulant.
[0042] Freeze drying: The condensate was quickly frozen to -45°C and freeze-dried under vacuum conditions of ≤8 Pa for 24 hours. The moisture content was controlled at 2.5% and the salt content was 44%.
[0043] The dried microencapsulated soy sauce powder is crushed and sieved (100 meshes) to obtain a finished product.
[0044] The dissolution rate and shelf life of the soy sauce powder were tested using the same test method as in Example 1.
[0045] Test results: dissolution time 25 seconds; shelf life up to 20 months under accelerated test (40°C, relative humidity 75%).
[0046] Comparative Examples: To further demonstrate the superiority of the technology of the present invention, two comparative examples are provided below, in which soy sauce powder is prepared using conventional spray drying and hot air drying, respectively, and compared with the freeze drying method and chitosan microcapsule technology of the present invention.
[0047] Comparative Example 1: Traditional spray drying method
[0048] Ingredients: Soy sauce stock (35% salt content)
[0049] step: Pretreatment: Heat the soy sauce solution to 60°C for 30 minutes to reduce the viscosity.
[0050] Spray drying: The preheated soy sauce liquid is dried in a spray dryer with an air inlet temperature of 180°C and an air outlet temperature of 80°C.
[0051] Collection and packaging: The dried soy sauce powder is collected by a cyclone separator, sieved and then packaged.
[0052] The dissolution rate and shelf life of the soy sauce powder were tested using the same test method as in Example 1.
[0053] Test results: dissolution time 25 seconds; salt content: 53%; moisture content: 3.5%.
[0054] Shelf life: 12 months under accelerated test (40℃, relative humidity 75%).
[0055] Comparative Example 2: Traditional hot air drying method
[0056] Ingredients: Soy sauce stock (35% salt content)
[0057] step: Pretreatment: Heat the soy sauce solution to 80°C for 60 minutes to reduce the viscosity.
[0058] Hot air drying: Spread the preheated soy sauce liquid evenly on the drying tray, place it in a hot air drying oven, set the temperature to 100℃, and dry it for 6 hours.
[0059] Crushing and packaging: The dried soy sauce blocks are crushed by a crusher, sieved and then packaged.
[0060] The dissolution rate and shelf life of the soy sauce powder were tested using the same test method as in Example 1.
[0061] Test results: dissolution time: 60 seconds; salt content: 53%; moisture content: 4.0%.
[0062] Shelf life: 10 months under accelerated test (40℃, relative humidity 75%).
[0063] The performance test results of the soy sauce powder of Examples 1-2 and Comparative Examples 1-2 are shown in Table 1 below.
[0064] Table 1
[0065] As can be seen from Table 1, the chitosan microencapsulated salt-reduced soy sauce powder prepared by the present invention can be quickly dissolved and used, and the salt content is reduced to below 44%, effectively extending the shelf life.
[0066] The preferred embodiments of the present invention have been described in detail above. It should be understood that numerous modifications and variations based on the concepts of the present invention are possible without inventive effort by those skilled in the art. Therefore, any technical solution that can be derived by one skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.
Claims
1. A method for preparing chitosan microencapsulated salt-reduced soy sauce powder, comprising the following steps: Step 1), cooling the soy sauce liquid to -21°C to -22°C, filtering to remove ice crystals, repeating the process several times, and collecting the mother liquor; Step 2), ultrasonically treating the mother liquor to obtain an ultrasonically treated liquid; Step 3), adjusting the pH of the ultrasonic treatment solution to 3.5-4 using HCl solution, adding chitosan solution to a chitosan concentration of 0.2%-1% to obtain a mixed solution; Step 4), stirring the mixed solution at low temperature for 45 minutes, adding NaOH to adjust the pH to 4.0-4.5, and obtaining a coagulant; Step 5), freeze-drying the coagulant, crushing and sieving to obtain the chitosan microencapsulated reduced-salt soy sauce powder.
2. The preparation method according to claim 1, wherein In step 1), the soy sauce liquid is cooled to -21.6°C.
3. The preparation method according to claim 1, wherein Step 1) further comprises heating the collected mother liquor to 4° C. to 10° C. and then stirring.
4. The preparation method according to claim 1, wherein In step 2), the ultrasonic treatment conditions are 20 kHz, the treatment time is 30-60 minutes, the power density is 10-50 W / cm², and the temperature is 60-90°C.
5. The preparation method according to claim 1, wherein In step 3), the deacetylation degree of the chitosan is ≥85%.
6. The preparation method according to claim 1, wherein In step 4), the low temperature is 4°C to 10°C.
7. The preparation method according to claim 1, wherein In step 5), freeze drying comprises freezing the coacervate to -40°C to -60°C.
8. Chitosan microencapsulated reduced-salt soy sauce powder obtained by the preparation method according to any one of claims 1 to 7.
9. The chitosan microencapsulated salt-reduced soy sauce powder according to claim 8, wherein The soy sauce powder has a salt content of less than 44% and a water content of 2.5%.
10. The chitosan microencapsulated salt-reduced soy sauce powder according to claim 8, wherein The soy sauce powder has a shelf life of more than 20 months under the conditions of 40° C. and 75% relative humidity.