A flavorful peptide-based low-salt fermented soybean paste and its production process

Abstract

This application relates to the field of food fermentation technology, and discloses a flavorful peptide-based low-salt fermented soybean paste and its production process. The production process includes: preparing a thermally saturated solvated zinc source precursor by using anhydrous betaine, zinc salt, and citrate; dispersing it in brine to prepare a fermentation broth; and inoculating with koji (fermentation starter) for variable-temperature fermentation. Fermentation is divided into three stages: a controlled-temperature initiation stage to establish the microbial culture; an enzymatic hydrolysis stage where the temperature is increased and the pH drop caused by acid production triggers zinc ion release, activating neutral proteases; and a post-ripening stage where anhydrous betaine is added to reduce water activity and construct an anti-corrosion barrier. This invention improves enzymatic hydrolysis efficiency through controlled zinc ion release and utilizes betaine to achieve low-salt preservation. The resulting product has a salt content ≤8.0g / 100g, an amino acid nitrogen content ≥0.8g / 100g, a rich umami flavor, and is stable during room temperature storage.

Description

Technical Field

[0001] This invention relates to the field of food fermentation technology, specifically to a umami peptide-based low-salt fermented soybean paste and its production process. Background Technology

[0002] Traditional fermented soybean paste relies primarily on high salt concentrations (typically above 15%) to inhibit the growth of unwanted microorganisms and provide shelf life. With increasing demand for healthy diets, reducing the salt content of fermented soybean paste has become an industry trend. However, lower salt concentrations directly weaken the antimicrobial barrier of the fermentation system, making it easier for salt-tolerant spoilage microorganisms to proliferate during fermentation, leading to product rancidity or off-flavors.

[0003] To address the preservation challenges of low-salt fermentation, existing technologies primarily employ low-temperature fermentation or the addition of chemical preservatives. While low-temperature fermentation can slow the growth of unwanted microorganisms, it also significantly inhibits the activity of Aspergillus oryzae protease systems, particularly limiting the activity of neutral proteases crucial for umami flavor formation. This results in incomplete protein hydrolysis, insufficient accumulation of umami peptides and amino acids, and ultimately, a bland product flavor. Furthermore, although zinc ions are cofactors for neutral proteases, in the complex fermentation mash of soybean paste, directly added zinc ions readily form complexes with phytic acid in the raw materials, or exert non-specific inhibition on microbial growth in the early stages of fermentation, preventing effective activation of enzymes during the critical enzymatic hydrolysis phase. Therefore, how to construct an effective preservation system while reducing salinity and ensuring enzymatic hydrolysis efficiency to enhance product umami is a pressing issue in the production of low-salt soybean paste.

[0004] Therefore, this invention proposes a umami peptide-based low-salt fermented soybean paste and its production process to overcome the shortcomings of the prior art. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a flavorful peptide-based low-salt broad bean paste and its production process. This solves the problems of existing low-salt broad bean paste production processes where reduced salinity weakens the ability to inhibit unwanted bacteria, while conventional low-temperature preservation or the addition of inhibitors inhibits the activity of neutral proteases, resulting in insufficient release of flavorful substances, leading to a bland product flavor and unstable shelf life.

[0006] To address the above problems, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a flavorful peptide-based low-salt fermented soybean paste and its production process, employing the following technical solution:

[0008] A flavorful peptide-based low-salt fermented soybean paste and its production process include the following steps:

[0009] S1. Preparation of hot saturated solvated embedded zinc source precursor: Anhydrous betaine, zinc salt and citrate are mixed, water is added, and a high viscosity solvated melt is obtained under heating and shearing conditions. The high viscosity solvated melt is the hot saturated solvated embedded zinc source precursor.

[0010] S2. Preparation of compound fermentation broth: The hot saturated solvated zinc source precursor is dispersed in an aqueous solution containing sodium chloride to prepare a compound fermentation broth;

[0011] S3. Inoculation and Fermentation: Mix the prepared koji with the compound fermentation liquid and carry out fermentation;

[0012] The fermentation process includes a temperature regulation stage:

[0013] The first stage is the start-up period, where the temperature is controlled at 25℃~30℃ to inhibit the growth of miscellaneous bacteria and establish a stable microbial system.

[0014] The second stage is the enzymatic hydrolysis period, in which the temperature is raised to 35℃~40℃. The decrease in pH caused by the temperature increase and the acid production during fermentation triggers the release of zinc ions from the thermally saturated solvated zinc source precursor, thereby activating the activity of neutral protease.

[0015] The third stage is the post-ripening period, in which anhydrous betaine is added to reduce the water activity of the system and work with the acidic environment in the system to build an anti-corrosion barrier, and post-ripening is carried out at room temperature.

[0016] By adopting the above technical solution, this invention utilizes solvation encapsulation technology combined with segmented temperature-varying fermentation to resolve the contradiction between enzyme activity regulation and inhibition of contaminating microorganisms under low-salt conditions. Its specific mechanism of action is as follows:

[0017] Encapsulation stability of zinc source precursor: Anhydrous betaine acts as a hydrogen bond acceptor, forming a high-viscosity solvation system with citrate and water molecules under heating and shearing. In this system, zinc ions are stably encapsulated by the intermolecular forces formed by betaine and citrate. This structure restricts the release of zinc ions during the fermentation initiation period (first stage), preventing high concentrations of free zinc ions from inhibiting microbial growth or reacting with phytic acid in the mash for precipitation.

[0018] Environmentally responsive release and enzyme activation:

[0019] During the initiation phase (25℃~30℃), the high pH value and suitable temperature of the system help maintain the stability of the precursor structure, which is conducive to the establishment of the dominant Aspergillus oryzae community.

[0020] During the enzymatic hydrolysis phase (35℃~40℃), microbial metabolism produces acid, leading to a decrease in pH and weakening the chelating ability of citrate ions. Simultaneously, the increased temperature increases molecular thermal motion, causing the hydrogen bond network of the encapsulation system to break down. These two factors work synergistically to promote the controlled release of zinc ions from the precursor.

[0021] The released zinc ions replenish the needs of the active site of the neutral protease (zinc metalloproteinase), significantly improving its enzymatic hydrolysis efficiency of soybean protein and increasing the production of umami peptides and amino acids.

[0022] Construction of a non-salt preservative system: During the post-fermentation ripening period, the added anhydrous betaine, combined with the organic acid environment produced by fermentation, constructs a combined preservative system of "low water activity + low pH + low salt". Betaine, through strong hydration and binding with free water, reduces the water activity of the system to below the critical point for microbial growth, thereby achieving long-term preservation of the product under low-salt conditions.

[0023] Preferably, in step S1, the thermally saturated solvated zinc source precursor is made from raw materials comprising the following parts by weight: 30-40 parts of anhydrous betaine; 0.5-1.5 parts of zinc salt; 0.5-1.5 parts of citrate; 10-15 parts of water; the zinc salt is selected from one or more of zinc gluconate, zinc lactate, zinc sulfate, and zinc acetate; the citrate is selected from one or more of sodium citrate, potassium citrate, and ammonium citrate; and the molar ratio of citrate to zinc salt is 1.2:1 to 1.5:1.

[0024] By employing the above technical solution, this ratio range ensures the structural stability of the solvated melt. Excessive zinc salt or insufficient citrate will lead to incomplete zinc ion encapsulation; if the betaine ratio is too low, it will be difficult to form a high-viscosity melt, thus losing its sustained-release function. The above ratio gives the precursor suitable response characteristics to changes in pH and temperature.

[0025] Preferably, step S1 is implemented as follows: anhydrous betaine, zinc salt and citrate are mixed evenly, water is added, and the mixture is sheared and stirred at 400-600 r / min for 15-25 min at 60℃-70℃ until the system is transformed into a translucent colloidal liquid or syrupy liquid.

[0026] By adopting the above technical solution, heating provides energy in combination with high shear force, which overcomes the intermolecular force barrier, promotes the hydrogen bond rearrangement and solvation layer formation between components, and transforms the solid raw material into a uniform and stable fluid state, thus ensuring the uniform dispersion of the precursor in the fermentation broth.

[0027] Preferably, in step S2, the compound fermentation broth further includes lactate and a plant-derived antibacterial agent; the final concentration of each component in the compound fermentation broth by weight percentage is: sodium chloride 6.0%–8.0%, lactate 1.0%–2.5%, and plant-derived antibacterial agent 0.01%–0.08%; the lactate is selected from one or both of L-potassium lactate and L-sodium lactate; the plant-derived antibacterial agent is selected from one or more of clove bud extract, cinnamon extract, and rosemary extract.

[0028] By adopting the above technical solution, lactate acts as a buffer to regulate the rate of pH change; plant-derived antibacterial agents, in combination with the low-salt system, provide auxiliary antibacterial effects, especially in the early stage of fermentation (before zinc ions are released in large quantities), thus reducing the risk of early spoilage under low-salt conditions.

[0029] Preferably, in step S3, the first stage is maintained for 2 to 4 days; the second stage is maintained for 10 to 20 days, and aeration and stirring are performed daily during the second stage; the third stage of post-ripening lasts for 90 to 120 days.

[0030] By adopting the above technical solution, the first stage duration meets the requirements for microbial colonization; the second stage, through heating, aeration, and stirring, ensures sufficient enzymatic hydrolysis and oxygen supply, promoting the accumulation of enzyme products; and the third stage, with its long-term post-ripening, promotes the esterification and fusion of flavor substances.

[0031] Preferably, in step S3, the timing for adding anhydrous betaine in the third stage is: when the amino acid nitrogen content in the fermentation mash is ≥0.5g / 100g; the weight of the anhydrous betaine added in the third stage accounts for 60% to 70% of the total weight of the anhydrous betaine added in step S1 and the anhydrous betaine added in the third stage; after adding anhydrous betaine, the water activity of the fermentation system is controlled to decrease to 0.90 to 0.92.

[0032] By adopting the above technical solution and using amino acid nitrogen as an indicator, the feeding operation is ensured to be carried out after the peak of enzymatic hydrolysis, so as to avoid high concentration of betaine interfering with the early enzymatic hydrolysis. The large proportion of betaine added later is mainly used to adjust the water activity to 0.90-0.92. This range can effectively inhibit spoilage bacteria and maintain the appropriate physical properties of fermented soybean paste.

[0033] Preferably, the preparation process of the koji is as follows: soaked and steamed broad beans are mixed with wheat flour, inoculated with Aspergillus oryzae Hu Niang 3.042, and cultured at 30℃~38℃ with variable temperature and ventilation for 42~48h.

[0034] By adopting the above technical solution, the standardized koji-making process provides a highly active protease system. The enzyme characteristics of Aspergillus oryzae Hu Niang 3.042 are compatible with the zinc activation strategy of this invention, thereby improving the utilization rate of raw materials.

[0035] Secondly, this invention provides a umami peptide-based low-salt fermented soybean paste, employing the following technical solution:

[0036] A umami peptide-based low-salt broad bean paste, prepared by the umami peptide-based low-salt broad bean paste production process of any one of the first aspects mentioned above.

[0037] By adopting the above technical solutions, this fermented soybean paste product achieves a balance between low salt content (salt content ≤8.0g / 100g) and high umami (amino acid nitrogen ≥0.8g / 100g). Thanks to the zinc source precursor encapsulation and release process, the product retains an appropriate amount of active zinc elements, resulting in a mellow flavor and good gloss. At the same time, relying on the low water activity environment created by betaine, the product has biological stability at room temperature and does not require the addition of chemical preservatives such as sodium benzoate.

[0038] Preferably, the umami peptide-based low-salt broad bean paste is made from the following raw materials in parts by weight: 100 parts dried broad beans; 20-30 parts wheat flour; 0.4-0.6 parts Aspergillus oryzae spore powder; 5-6 parts heat-saturated solvated zinc source precursor; 170-190 parts water; 14-18 parts sodium chloride; 4-5 parts L-lactate potassium solution; 0.08-0.12 parts eugenol; and 5-7 parts anhydrous betaine for supplementation.

[0039] By adopting the above technical solution, the functions of each raw material component are as follows:

[0040] Dried broad beans and wheat flour provide plant protein and carbohydrates, which are the material basis for the formation of umami peptides.

[0041] The dosage of the thermally saturated solvated zinc source precursor (5-6 parts) was optimized and verified, which not only provided the zinc ions required to activate neutral protease, but also controlled the total zinc content of the final product within a safe range (10-20 mg / kg), avoiding metallic odor.

[0042] The amount of sodium chloride (14-18 parts) used is significantly lower than that of traditional processes, achieving low salt content.

[0043] L-potassium lactate solution and eugenol help to create an initial antibacterial environment and adjust the flavor.

[0044] The added anhydrous betaine (5-7 parts) together with the betaine in the precursor adjusts the product's water activity to a safe storage range.

[0045] Preferably, the salt content of the umami peptide-based low-salt broad bean paste is ≤8.0g / 100g, the amino acid nitrogen content is ≥0.8g / 100g, and the total zinc content is 10-20mg / kg.

[0046] By adopting the above technical solution, the physicochemical characteristics of the product were clarified:

[0047] The salt content is ≤8.0g / 100g, which meets the low-salt food standard.

[0048] An amino acid nitrogen content ≥0.8g / 100g indicates that the protein is fully hydrolyzed and has a high content of umami substances.

[0049] The total zinc content of 10-20 mg / kg not only serves as a nutritional fortification measure, but also acts as a characteristic indicator of the process implementation in this invention, reflecting the application of zinc ion regulation technology.

[0050] This invention provides a flavorful peptide-based low-salt fermented soybean paste and its production process. It has the following beneficial effects:

[0051] 1. This invention solves the problem of enzyme activity inhibition in low-salt fermentation by constructing a thermally saturated solvated zinc source precursor and combining it with a variable temperature control process. During the fermentation initiation period, zinc ions are stably embedded in the precursor, avoiding the non-specific inhibition of microbial growth by free zinc. During the enzymatic hydrolysis period, the pH value decrease caused by temperature rise and acid production triggers the release of zinc ions from the precursor, which directionally activates the activity of neutral protease derived from Aspergillus oryzae. This mechanism significantly improves the protein hydrolysis efficiency, enabling the product to have a rich umami flavor when the amino acid nitrogen content reaches a certain level under low-salt conditions.

[0052] 2. This invention utilizes anhydrous betaine as a feeding strategy to construct a non-salt preservative barrier, solving the technical problem of easy spoilage of low-salt fermented soybean paste. By adding anhydrous betaine during the post-ripening stage, its strong hydration capacity reduces the water activity of the system. This low water activity environment and the acidic environment produced by fermentation produce a synergistic antibacterial effect, effectively inhibiting the reproduction of salt-tolerant spoilage bacteria. Thus, without adding chemical preservatives such as sodium benzoate, the biological stability of low-salt fermented soybean paste at room temperature is achieved.

[0053] 3. The solvation precursor used in this invention is prepared by heating and shearing anhydrous betaine, zinc salt, and citrate to form a high-viscosity melt with excellent structural stability. This structure effectively isolates zinc ions from components such as phytic acid in the fermentation broth, preventing premature precipitation reactions that could lead to zinc source depletion. Furthermore, this precursor exhibits specific response characteristics to temperature and pH, ensuring that zinc ions are released only during critical enzymatic hydrolysis stages, thus achieving controlled release and efficient utilization of trace elements in complex fermentation systems. Attached Figure Description

[0054] Figure 1 This is a schematic diagram illustrating the phytic acid resistance of the zinc source precursor of the present invention.

[0055] Figure 2 This is a schematic diagram of key indicators in the fermentation process of the present invention;

[0056] Figure 3 This is a schematic diagram illustrating the shelf-life stability of the present invention;

[0057] Figure 4 This is a schematic diagram of the food safety indicators of the present invention. Detailed Implementation

[0058] 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.

[0059] 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.

[0060] Dried broad beans: commercially available, peeled, starch content ≥48%, protein content ≥26%; wheat flour: commercially available, gluten content ≥28%; Aspergillus oryzae: strain Hu Niang 3.042, commercially available soy sauce koji, spore count ≥2×10 9 CFU / g; Anhydrous betaine: CAS No. 107-43-7, purity ≥99.0%; Zinc gluconate: CAS No. 4468-02-4, zinc content 12.0%-14.0%; Sodium citrate: dihydrate, CAS No. 6132-04-3; L-potassium lactate solution: CAS No. 996-31-6, 60% aqueous solution; Eugenol: CAS No. 97-53-0, purity ≥98.0%.

[0061] Preparation Example 1: This preparation example provides a thermally saturated solvated embedded zinc source precursor, comprising the following steps:

[0062] 1. Weigh out 400g of anhydrous betaine, 8g of zinc gluconate, and 7.0g of sodium citrate (the molar ratio of sodium citrate to zinc gluconate is approximately 1.3:1).

[0063] 2. Mix the solids weighed in step 1 thoroughly and add 145g of deionized water (water accounts for 35% of the total mass of the solids).

[0064] 3. Heat the mixture to 65°C and shear and stir at 500 rpm for 18 minutes to obtain a translucent, fluid, high-viscosity syrup-like liquid;

[0065] 4. Keep the prepared liquid at 55℃ for later use.

[0066] Preparation Example 2: This preparation example provides a thermally saturated solvated embedded zinc source precursor, comprising the following steps:

[0067] 1. Weigh out 400g of anhydrous betaine, 12g of zinc gluconate, and 11g of sodium citrate (the molar ratio of sodium citrate to zinc gluconate is approximately 1.4:1).

[0068] 2. Mix the solids weighed in step 1 thoroughly and add 127g of deionized water (water accounts for 30% of the total mass of the solids).

[0069] 3. Heat the mixture to 67°C and shear and stir at 500 rpm for 20 minutes to obtain a turbid colloidal liquid with extremely high viscosity;

[0070] 4. Keep the prepared liquid at 55℃ for later use.

[0071] Preparation Example 3:

[0072] This preparation example provides a thermally saturated solvated embedded zinc source precursor, including the following steps:

[0073] 1. Weigh out 400g of anhydrous betaine, 6g of zinc gluconate, and 5g of sodium citrate (the molar ratio of sodium citrate to zinc gluconate is approximately 1.2:1).

[0074] 2. Mix the solids weighed in step 1 thoroughly and add 164g of deionized water (water accounts for 40% of the total mass of the solids).

[0075] 3. Heat the mixture to 63°C and shear and stir at 500 rpm for 15 minutes to obtain a translucent, free-flowing syrup-like liquid;

[0076] 4. Keep the prepared liquid at 55℃ for later use.

[0077] Example 1:

[0078] This embodiment provides a production process for umami peptide-based low-salt fermented soybean paste, including the following steps:

[0079] 1. Koji making: Take 10kg of dried broad beans, soak, steam, and cool them, then mix them evenly with 2.5kg of wheat flour, inoculate with 0.05kg of Aspergillus oryzae (Hu Niang 3.042) spore powder, and incubate at a constant temperature of 35℃ for 44 hours to obtain koji.

[0080] 2. Fermentation broth preparation: Take all the hot-saturated solvated zinc source precursor prepared in Example 1, and add it into 18L of cold water containing 1.6kg sodium chloride, 0.4kg L-potassium lactate solution, and 10g eugenol under stirring. Mix well to obtain a compound fermentation broth. At this time, the total salinity of the fermentation broth is about 7%.

[0081] 3. Pre-fermentation start: Mix all the koji obtained in step 1 with the compound fermentation liquid obtained in step 2, transfer it into a fermentation tank, control the fermentation temperature at 28-30℃, and maintain it for 3 days;

[0082] 4. Medium-temperature enzymatic hydrolysis: Raise the temperature of the fermenter to 38℃ and maintain fermentation for 12 days, aerating and stirring for 20 minutes daily during this period;

[0083] 5. Post-fermentation feeding: On the 16th day of fermentation, the amino acid nitrogen content was measured to be 0.55g / 100g. At this time, 600g of anhydrous betaine was added to the fermentation tank and stirred until completely dissolved.

[0084] 6. Post-fermentation: Lower the temperature of the fermentation tank to 25℃ and let it ferment for 100 days to obtain the finished soybean paste.

[0085] Example 2:

[0086] This embodiment provides a production process for umami peptide-based low-salt fermented soybean paste, including the following steps:

[0087] 1. Koji making: Take 10kg of dried broad beans, soak, steam, and cool them, then mix them evenly with 2.5kg of wheat flour, inoculate with 0.05kg of Aspergillus oryzae (Hu Niang 3.042) spore powder, and incubate at a constant temperature of 32℃ for 48 hours to obtain koji.

[0088] 2. Fermentation broth preparation: Take all the hot-saturated solvated zinc source precursor prepared in Example 2, and add it into 18L of cold water containing 1.4kg sodium chloride, 0.5kg L-potassium lactate solution, and 12g eugenol under stirring. Mix well to obtain a compound fermentation broth. At this time, the total salinity of the fermentation broth is about 6.8%.

[0089] 3. Pre-fermentation start: Mix all the koji obtained in step 1 with the compound fermentation liquid obtained in step 2, transfer it into a fermentation tank, control the fermentation temperature at 28℃, and maintain it for 3 days;

[0090] 4. Medium-temperature enzymatic hydrolysis: Raise the temperature of the fermenter to 35℃ and maintain fermentation for 15 days, during which time aeration and stirring are performed for 20 minutes daily;

[0091] 5. Post-fermentation feeding: On the 19th day of fermentation, the amino acid nitrogen content was measured to be 0.50g / 100g. At this time, 600g of anhydrous betaine was added to the fermentation tank and stirred until completely dissolved.

[0092] 6. Post-fermentation: The temperature of the fermentation tank is lowered to 25℃ and allowed to ferment for 120 days to obtain the finished soybean paste.

[0093] Example 3:

[0094] This embodiment provides a production process for umami peptide-based low-salt fermented soybean paste, including the following steps:

[0095] 1. Koji making: Take 10kg of dried broad beans, soak, steam, and cool them, then mix them evenly with 2.5kg of wheat flour, inoculate with 0.05kg of Aspergillus oryzae (Hu Niang 3.042) spore powder, and incubate at a constant temperature of 36℃ for 42 hours to obtain koji.

[0096] 2. Fermentation broth preparation: Take all the hot-saturated solvated zinc source precursor prepared in Example 3, and add it into 18L of cold water containing 1.8kg sodium chloride, 0.4kg L-potassium lactate solution, and 8g eugenol under stirring. Mix well to obtain a compound fermentation broth. At this time, the total salinity of the fermentation broth is about 8%.

[0097] 3. Pre-fermentation start: Mix all the koji obtained in step 1 with the compound fermentation liquid obtained in step 2, transfer it into a fermentation tank, control the fermentation temperature at 30℃, and maintain it for 3 days;

[0098] 4. Medium-temperature enzymatic hydrolysis: Raise the temperature of the fermenter to 40℃ and maintain fermentation for 10 days, aerating and stirring for 20 minutes daily during this period;

[0099] 5. Post-fermentation feeding: On the 14th day of fermentation, the amino acid nitrogen content was measured to be 0.60g / 100g. At this time, 600g of anhydrous betaine was added to the fermentation tank and stirred until completely dissolved.

[0100] 6. Post-fermentation: The temperature of the fermentation tank is lowered to 25℃ and allowed to ferment for 90 days to obtain the finished soybean paste.

[0101] Comparative Example 1:

[0102] Compared with Example 1, the difference is that: this comparative example uses a traditional high-salt fermentation process; the fermentation broth is only 18% saline solution, without the addition of any thermally saturated solvated zinc source precursor, anhydrous betaine, L-lactate potassium solution and eugenol; the entire fermentation process is carried out at natural room temperature, and the fermentation cycle is 180 days.

[0103] Comparative Example 2:

[0104] Compared with Example 1, the difference is that the zinc source is added by simple physical mixing; that is, instead of the hot melt embedding step of Preparation Example 1, the same amount of zinc gluconate and sodium citrate powder as in Example 1 are directly dissolved in water together with sodium chloride and L-potassium lactate solution to prepare fermentation broth; the rest are the same.

[0105] Comparative Example 3:

[0106] Compared with Example 1, the difference is that the zinc source is added by premixing an aqueous solution; that is, an equal amount of zinc gluconate and sodium citrate as in Example 1 are dissolved in 10 times their mass of water to form a dilute solution, and then this dilute solution is added to the fermentation broth; the rest are the same.

[0107] Comparative Example 4:

[0108] The difference from Example 1 is that no zinc source or sodium citrate is added; otherwise, they are the same.

[0109] Comparative Example 5:

[0110] Compared with Example 1, the difference is that all anhydrous betaine is added at once in the early stage of fermentation; that is, in the fermentation liquid preparation stage of step 2, all 1000g of anhydrous betaine is dissolved into the fermentation liquid at once, and there is no subsequent feeding step; the rest are the same.

[0111] Comparative Example 6:

[0112] Compared with Example 1, the difference is that the fermentation process adopts constant temperature fermentation; that is, the pre-fermentation start-up stage is cancelled, and the entire fermentation process (except for post-ripening) is carried out at a constant temperature of 38°C; the rest are the same.

[0113] Test Example 1:

[0114] Experimental Description: This test aims to evaluate the kinetic stability of zinc source precursors prepared by hot saturated solvation encapsulation process in the presence of common chelating agents (phytic acid) in a simulated fermentation matrix for fermented soybean paste.

[0115] The experimental steps are as follows:

[0116] Take 100 mL each of the compound fermentation broth prepared in step 2 of Example 1 (experimental group), the compound fermentation broth prepared in step 2 of Comparative Example 2 (control group A), and the compound fermentation broth prepared in step 2 of Comparative Example 3 (control group B), place them in beakers, add a magnetic stir bar, and stir at low speed at room temperature.

[0117] Using deionized water as a blank reference, the initial absorbance of the three solutions was measured and recorded at a wavelength of 600 nm using a spectrophotometer.

[0118] Using a 10 mL microburette, add approximately 1 mL of 1% (w / v) sodium phytate aqueous solution dropwise to each beaker. After stirring for 1 minute, take a sample and measure its absorbance at 600 nm.

[0119] Continue adding and recording data until the absorbance readings of each group of solutions tend to stabilize.

[0120] The experimental data are shown in Table 1:

[0121] Table 1: Test data on the phytic acid resistance of zinc source precursors

[0122]

[0123] Conclusion: Combined with the appendix Figure 1 And as shown in Table 1;

[0124] Comparing the data of control group A and control group B, when the volume of sodium phytate added was 3.1 mL, the absorbance of the latter (0.145) was lower than that of the former (0.342), indicating that the pre-chelation treatment in aqueous solution can improve the stability of the zinc source.

[0125] Comparing the experimental group and control group B, when the volume of sodium phytate added reached 7.2 mL, the absorbance of control group B had increased to 0.462, while the absorbance of the experimental group was only 0.028. This result shows that the hot saturated solvation embedding process of the present invention can more effectively delay the precipitation of zinc source by phytic acid compared with conventional aqueous solution pre-chelation.

[0126] The reason for this phenomenon is that the solvation system formed by high concentrations of betaine under heating conditions constitutes a physical layer with steric hindrance after encapsulating the citrate-zinc complex. This structure kinetically hinders the contact and reaction between the external phytic acid molecules and the internal zinc complex, thereby maintaining the stability and bioavailability of the zinc source in a matrix containing natural chelating agents.

[0127] Test Example 2:

[0128] Experimental Description: This test aims to quantitatively evaluate the impact of the technical solution of this invention on the fermentation process and final product quality of fermented soybean paste. By dynamically monitoring key biochemical indicators (protease activity, amino acid nitrogen) during the fermentation cycle and quantitatively analyzing the core flavor compounds (umami peptides, free glutamic acid) in the final product, the effect of this invention in promoting protein degradation and improving the efficiency of flavor compound formation is verified.

[0129] The experimental steps are as follows:

[0130] 1. Samples from Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 4 and Comparative Example 5 were collected on day 5, day 15, day 30, day 60 of fermentation and after the end of fermentation for subsequent index determination.

[0131] 2. Neutral protease activity was determined using the Folin-phenol reagent method; casein was used as the substrate, and the reaction was carried out at pH 7.5 and 40℃. The absorbance of the hydrolysis products at 680 nm was measured. The enzyme activity unit (U / g) was defined as the amount of enzyme that catalyzes the production of 1 μg of tyrosine per minute per gram of sample under specific conditions.

[0132] 3. The amino acid nitrogen (AAN) content was determined by formaldehyde titration according to GB-5009.235 standard.

[0133] 4. The content of umami peptides (molecular weight <3000Da) in the final product was determined by high performance liquid chromatography (HPLC). The test target was the component of the water-soluble extract of the sample after ultrafiltration.

[0134] 5. The content of free glutamic acid (Glu) in the final product was determined using an automated amino acid analyzer.

[0135] The experimental data are shown in Table 2:

[0136] Table 2: Key indicators and final product quality data for each group during fermentation.

[0137]

[0138] Conclusion: Combined with the appendix Figure 2 The data in Table 2 show the impact of different processes on the fermentation process and the final product.

[0139] Comparing the neutral protease activities of Example 1, Comparative Example 2, and Comparative Example 4 on day 15 of fermentation (812.6, 416.9, and 380.2 U / g, respectively), the results showed that the addition of zinc was a factor in increasing enzyme activity. However, the hot saturated solvation encapsulation process used in this invention had a better activation effect on protease than simple physical mixing. This high protease activity obtained in the early stage of fermentation directly led to higher protein degradation efficiency, as reflected in the consistently leading amino acid nitrogen accumulation rate of Example 1.

[0140] The comparison of data from Example 1 and Comparative Example 5 reveals the effect of the staged feeding strategy. On the 5th day of fermentation, the protease activity of Comparative Example 5 (all betaine added at once) was only 85.2 U / g, which was lower than 345.1 U / g in Example 1. This is because the excessively high osmotic pressure in the early stage of fermentation inhibited the growth and enzyme production of Aspergillus oryzae. Therefore, maintaining a low osmotic pressure in the early stage of fermentation and feeding after the protein has been effectively degraded is a technical prerequisite for ensuring normal start-up and efficient fermentation.

[0141] In terms of final product quality, the content of umami peptides (1568 mg / 100g) and free glutamic acid (951 mg / 100g) in Example 1 was higher than that in all comparative examples. In particular, compared with Comparative Example 1, which used traditional high-salt long-cycle fermentation, the present invention obtained a higher content of flavor substances while shortening the fermentation cycle by about 36% and having a lower salinity. This shows that the process combination of the present invention provides sufficient precursors for the generation of flavor substances in the later stage through efficient enzymatic hydrolysis in the early stage, and ultimately achieves the goals of low salt, enhanced umami, and high efficiency.

[0142] Test Example 3:

[0143] Experimental Description: This test consists of two parts; the first part uses electronic tongue and gas chromatography-mass spectrometry (GC-MS) to objectively and quantitatively characterize the flavor profile of the final product; the second part evaluates the control effect of this invention on the microbial stability of the product under low-salt conditions through accelerated shelf-life experiments.

[0144] The experimental steps are as follows:

[0145] The final products of Example 1, Comparative Example 1, Comparative Example 4 and Comparative Example 6 were used as the test samples.

[0146] The water-soluble extracts of each group of samples were analyzed by electronic tongue, and the response values ​​of the umami, saltiness and body thickness sensors were recorded using a TS-5000Z electronic tongue.

[0147] The volatile compounds in each sample were analyzed and the contents of ethyl acetate and isovaleric acid were quantified using headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS).

[0148] After aliquoting the samples, they were placed in a 37°C constant temperature incubator for accelerated storage. Samples were taken on days 0, 30, 60, and 90 of storage, and the total bacterial count and pH value of the samples were determined according to the corresponding standard methods.

[0149] The experimental data are shown in Tables 3 and 4:

[0150] Table 3: Electronic tongue and GC-MS flavor compound analysis data of the final product

[0151]

[0152] Table 4: Accelerated Shelf Life Stability Test Data

[0153]

[0154] Conclusion: Combined with the appendix Figure 3 With appendix Figure 4 And the data in Table 3 are shown below:

[0155] The electronic tongue analysis data in Table 3 show that the umami response value (11.8) and body response value (9.6) of Example 1 are higher than those of the comparative examples, while its saltiness response value (6.5) is significantly lower than that of the high-salt comparative example 1 (14.2). The GC-MS analysis results show that the ethyl acetate content (315.4 μg / kg) of Example 1 is at a high level, while the content of the representative off-flavor substance isovaleric acid (15.2 μg / kg) is much lower than that of comparative example 6 (176.9 μg / kg). These data indicate that the sample obtained by the technical solution of the present invention has advantages in umami and body, while having moderate saltiness, and effectively inhibits the generation of off-flavor substances that may be caused by isothermal fermentation (comparative example 6), thus ensuring the harmony of the flavor profile.

[0156] Table 4 shows that the accelerated storage data indicates that the total bacterial count of the sample in Example 1 remained at a low level (<300 CFU / g) and the pH value remained stable during the 90-day storage period, with microbial stability comparable to that of the high-salt Comparative Example 1. In contrast, Comparative Examples 4 and 6, which were also low-salt systems, showed a rapid increase in the total bacterial count and a significant decrease in pH value after 30 days, indicating microbial spoilage. These results demonstrate that the composite antibacterial system of the present invention (potassium L-lactic acid and anhydrous betaine added later) can effectively control microbial growth and ensure the shelf-life stability of the product under low-salt conditions.

[0157] Test Example 4:

[0158] Experimental Description: This test aims to comprehensively evaluate the food safety of the low-salt broad bean paste prepared by this invention from two dimensions: physicochemical hazards (biogenic amines, heavy metals) and biological hazards (pathogenic bacteria, fungal toxins). The focus is on whether the addition of zinc source leads to excessive heavy metals, and whether the antibacterial system of this invention can effectively inhibit the accumulation of biogenic amines and the growth of pathogenic bacteria that are easily generated during low-salt fermentation.

[0159] The experimental steps are as follows:

[0160] The final products of Example 1, Comparative Example 1, Comparative Example 4 and Comparative Example 6 were used as the test samples.

[0161] The biogenic amine content of each group of samples was detected by high performance liquid chromatography (HPLC), and histamine, tyramine and total biogenic amine were quantitatively analyzed.

[0162] According to GB-5009.22 standard, the content of aflatoxin B1 in the sample was determined by immunoaffinity chromatography-high performance liquid chromatography; the number of Staphylococcus aureus in the sample was detected according to GB-4789.10 Method II.

[0163] The total zinc residue in the sample was determined by inductively coupled plasma mass spectrometry (ICP-MS) in accordance with GB-5009.14 standard.

[0164] The experimental data are shown in Table 5:

[0165] Table 5: Test data of key food safety indicators for final products

[0166]

[0167] Note: ND indicates not detected or below the detection limit.

[0168] Conclusion: Based on the data in Table 5:

[0169] The test data in Table 5 show that the total amount of biogenic amines in the sample of Example 1 was 58.9 mg / kg, and the histamine content was 12.4 mg / kg. This value is close to that of Comparative Example 1 (42.6 mg / kg) of traditional high-salt fermentation, and significantly lower than that of Comparative Example 4 (153.4 mg / kg) without zinc source and Comparative Example 6 (289.5 mg / kg) of isothermal fermentation. Low-salt environments usually lead to enhanced activity of microbial decarboxylases, resulting in the accumulation of biogenic amines. The data of Example 1 show that the introduced zinc ions, while activating proteases, inhibited the activity of amino acid decarboxylases. Combined with the variable-temperature fermentation process, this blocked the metabolic pathway of amino acid conversion into harmful biogenic amines.

[0170] Regarding microbiological and toxin indicators, neither aflatoxin B1 nor Staphylococcus aureus was detected in the sample of Example 1; in contrast, Staphylococcus aureus was detected in Comparative Example 4 (8.5 × 10⁻⁶). 2 The CFU / g ratio was positive, and Staphylococcus aureus and aflatoxin B1 (3.8 μg / kg) were detected in Comparative Example 6. This confirmed the effectiveness of the segmented non-salt barrier system constructed by L-lactate and anhydrous betaine: in the early stage, L-lactate combined with low temperature inhibited the growth of toxin-producing fungi, and in the later stage, the high osmotic pressure generated by betaine inhibited the growth of pathogenic bacteria.

[0171] In terms of physicochemical indicators, the total zinc content in Example 1 was 18.4 mg / kg, which is within the safe range recommended for use of food fortifiers and did not cause excessive heavy metal residues. In summary, the present invention effectively controls the risks of biogenic amines, pathogenic bacteria and fungal toxins by reducing salt content through metabolic regulation and antibacterial barrier technology.

[0172] 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 production process for a flavorful peptide-based low-salt fermented soybean paste, characterized in that, Includes the following steps: S1. Preparation of hot saturated solvated embedded zinc source precursor: Mix 30-40 parts by weight of anhydrous betaine, 0.5-1.5 parts by weight of zinc salt and 0.5-1.5 parts by weight of citrate evenly, add 10-15 parts by weight of water, and shear and stir at 400-600 r / min for 15-25 min at 60℃-70℃ until the system is transformed into a translucent colloidal liquid or syrupy liquid to obtain a high viscosity solvated melt, which is the hot saturated solvated embedded zinc source precursor; S2. Preparation of compound fermentation broth: The hot saturated solvated zinc source precursor is dispersed in an aqueous solution containing sodium chloride to prepare a compound fermentation broth; S3. Inoculation and Fermentation: Mix the prepared koji with the compound fermentation liquid and carry out fermentation; The fermentation process includes a temperature regulation stage: The first stage is the start-up period, where the temperature is controlled at 25℃~30℃ to inhibit the growth of miscellaneous bacteria and establish a stable microbial system. The second stage is the enzymatic hydrolysis period, in which the temperature is raised to 35℃~40℃. The decrease in pH caused by the temperature increase and the acid production during fermentation triggers the release of zinc ions from the thermally saturated solvated zinc source precursor, thereby activating the activity of neutral protease. The third stage is the post-ripening period, in which anhydrous betaine is added. The weight of the anhydrous betaine added in the third stage accounts for 60% to 70% of the total weight of the anhydrous betaine added in step S1 and the anhydrous betaine added in the third stage. This reduces the water activity of the system and works with the acidic environment in the system to form an anti-corrosion barrier, allowing the post-ripening to take place at room temperature.

2. The production process of a flavorful peptide-based low-salt fermented soybean paste according to claim 1, characterized in that, In step S1, the zinc salt is selected from one or more of zinc gluconate, zinc lactate, zinc sulfate, and zinc acetate; the citrate is selected from one or more of sodium citrate, potassium citrate, and ammonium citrate; and the molar ratio of the citrate to the zinc salt is 1.2:1 to 1.5:

1.

3. The production process of a flavorful peptide-based low-salt fermented soybean paste according to claim 1, characterized in that, In step S2, the compound fermentation broth further includes lactate and plant-derived antibacterial agent; the final concentration of each component in the compound fermentation broth by weight percentage is: sodium chloride 6.0%–8.0%, lactate 1.0%–2.5%, and plant-derived antibacterial agent 0.01%–0.08%; the lactate is selected from one or both of L-potassium lactate and L-sodium lactate; the plant-derived antibacterial agent is selected from one or more of clove bud extract, cinnamon extract, and rosemary extract.

4. The production process of a flavorful peptide-based low-salt fermented soybean paste according to claim 1, characterized in that, In step S3, the first stage is maintained for 2 to 4 days; the second stage is maintained for 10 to 20 days, and aeration and stirring are performed daily during the second stage; the post-ripening time of the third stage is 90 to 120 days.

5. The production process of a flavorful peptide-based low-salt fermented soybean paste according to claim 1, characterized in that, In step S3, the timing for adding anhydrous betaine in the third stage is when the amino acid nitrogen content in the fermentation mash is ≥0.5g / 100g; after adding anhydrous betaine, the water activity of the fermentation system is controlled to decrease to 0.90-0.

92.

6. The production process of a flavorful peptide-based low-salt fermented soybean paste according to claim 1, characterized in that, The preparation process of the koji is as follows: soaked and steamed broad beans are mixed with wheat flour, inoculated with Aspergillus oryzae Hu Niang 3.042, and cultured at 30℃~38℃ with variable temperature and ventilation for 42~48h.

7. A umami-rich peptide-based low-salt fermented soybean paste, characterized in that, It is prepared by the production process of umami peptide-based low-salt broad bean paste as described in any one of claims 1-6.

8. The umami peptide-based low-salt fermented soybean paste according to claim 7, characterized in that, The umami peptide-based low-salt broad bean paste has a salt content of ≤8.0g / 100g, an amino acid nitrogen content of ≥0.8g / 100g, and a total zinc content of 10-20mg / kg.

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