A composite natto-flavored sauce and a method for preparing the same

Abstract

This invention discloses a compound natto flavored sauce and its preparation method, relating to the field of food processing technology. The natto flavored sauce is prepared from the following raw materials in parts by weight: soybeans: 75-85 parts, self-produced soybean residue: 25-35 parts, edible salt: 10-14 parts, soybean flour: 6-9 parts, Aspergillus oryzae koji extract: 0.08-0.15 parts, rice straw: 12-18 parts, with the remainder being drinking water. The soybean flour is obtained by roasting and pulverizing soybeans, and the amount of soybean flour added is 25% of the dry weight of the soybean residue. This invention uses compound soybeans and self-produced soybean residue as the main ingredients to achieve efficient utilization of by-products from soybean product processing, reduce costs, and balance economic and environmental considerations. A dual fermentation system is adopted to integrate the flavors of natto and koji, improving nutritional indicators. Raw material pretreatment removes fishy odors and enhances aroma, optimizing flavor. A segmented preparation method ensures stable and controllable fermentation, while three-stage gradient degassing and cooking processes retain nutrients. The finished product undergoes standardized post-processing, possessing both edibility and storage stability, meeting diverse needs.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to a compound natto flavored sauce and its preparation method. Background Technology

[0002] Natto-flavored sauce is a fermented soybean product that combines the unique flavor of natto with the palatability of sauce. It is made by microbial fermentation of soybeans and other legumes, and is both nutritious and flavorful. It occupies an important position in the condiment market. In the soybean product processing industry, soybeans are widely used as the core raw material in the production of various products. The optimization of fermentation process and the comprehensive utilization of raw materials have always been the core directions of research and development of soybean product sauces. Natural inoculation and artificial koji making are common methods of soybean product fermentation. Natural carriers such as rice straw are often used for the natural fermentation of natto products because they carry a variety of beneficial bacteria. Aspergillus oryzae is a commonly used strain for sauce koji making because it can efficiently decompose macromolecules in raw materials and improve the flavor and nutritional indicators of products. The application of both provides a foundation for improving the quality of fermented soybean products and also promotes the research and development of compound natto-flavored sauces.

[0003] Traditional natto flavored sauce is mostly made from soybeans alone, resulting in a limited utilization of raw materials and failing to fully utilize the byproducts generated during soybean processing. This not only wastes raw material resources but also increases overall production costs, contradicting the development concept of green processing. In some preparation methods, the combination of natural inoculation and artificial koji making is low, and the synergistic effect of the microorganisms in the fermentation system is not fully utilized, easily leading to a single flavor profile and insufficient stability of physicochemical indicators. At the same time, the parameters of traditional cooking and sterilization processes are relatively crudely controlled, easily causing the loss of nutrients in the raw materials, or affecting the flavor and storage stability of the product due to incomplete or excessive sterilization. Furthermore, the lack of refined management of conditions such as temperature, humidity, and ventilation during fermentation can easily lead to uneven fermentation and koji clumping, affecting the consistency of the final product quality. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a compound natto flavor sauce and its preparation method. Using soybeans and self-produced soybean residue as the main raw materials, combined with soybean flour, Aspergillus oryzae koji extract, rice straw, and other auxiliary materials, the sauce is prepared through raw material pretreatment, simultaneous fermentation to produce natto and koji, mixed secondary fermentation, and post-processing. The preparation process employs a dual fermentation system combining natural rice straw inoculation and artificial koji cultivation. Three-stage gradient degassing and cooking, and precise temperature, humidity, and ventilation control ensure the fermentation effect. Through aeration, stirring, and closed fermentation, continuous instantaneous sterilization, and standardized filling and cooling, a finished product with both flavor and nutrition is obtained. This invention realizes the resource utilization of soybean product by-products, optimizes the fermentation process to improve product quality stability, and ensures that the finished product meets physicochemical standards and has a long shelf life. It is suitable for industrial mass production and has both economic and environmental value.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: On the one hand, a compound natto flavored sauce is prepared from the following raw materials in parts by weight: soybeans: 75-85 parts, self-produced soybean residue: 25-35 parts, edible salt: 10-14 parts, soybean flour: 6-9 parts, Aspergillus oryzae paste koji: 0.08-0.15 parts, rice straw: 12-18 parts, and the balance being drinking water; wherein the soybean flour is obtained by roasting and pulverizing soybeans, and the amount of soybean flour added is 25% of the dry weight of soybean residue.

[0006] Furthermore, the soybean has a protein content of ≥38%, the soybean residue has a moisture content of approximately 78%, and the particle size distribution of the soybean residue meets the requirement of a 40-mesh standard sieve passing rate of ≥95%.

[0007] Furthermore, the flavor sauce is made by mixing natto and koji in a 1:1 mass ratio, then adjusting with brine and fermenting in a sealed environment; the natto is made by soaking, steaming, and naturally inoculating rice straw for solid-state fermentation; and the koji is made by fermenting cooked and cooled soybean residue, soybean flour, and Aspergillus oryzae koji through ventilation.

[0008] Furthermore, after fermentation, the flavor sauce has a moisture content of 68-70%, a salinity of 12.5-14°Bé, and an amino acid nitrogen content of 0.55-0.69g / 100g; after sterilization and bottling, the finished product has a moisture content of 70-75%, a salinity of 10.2-10.5°Bé, and an amino acid nitrogen content ≥0.5g / 100g.

[0009] Furthermore, the rice straw is in segments 30-50cm in length, without high-temperature sterilization and drying treatment, and is inoculated with natural microorganisms carried on its surface; the Aspergillus oryzae koji is premixed evenly with soybean flour to form a premixed koji for koji making.

[0010] On the other hand, a method for preparing a compound natto flavored sauce, the specific steps of which are as follows: S1, Raw material pretreatment and soybean cooking: Selected soybeans are pretreated by rinsing and soaking, then sent to a cooking tank for three-stage gradient degassing and cooking. After simmering and degassing to cool down, samples are taken to confirm that the soybeans have no hard core, thus completing the soybean cooking process. Simultaneously, raw materials for koji making are prepared: Soybeans are roasted and crushed to obtain soybean powder. The soybean powder is premixed evenly with Aspergillus oryzae koji extract to obtain premixed koji for later use. Self-produced soybean residue is cooked to remove the beany smell and then cooled by an air cooler for later use. S2, Simultaneous fermentation to prepare natto and koji: Steamed soybeans are sent to a fermentation chamber with controlled temperature and humidity, and pre-treated rice straw is suspended for natural inoculation and solid-state fermentation to produce natto; at the same time, cooled soybean residue is mixed evenly with premixed koji, spread on a koji bed, and fermented in a controlled temperature and humidity environment. During the fermentation period, regular inspections are conducted and the koji is turned over to produce koji. S3, Mixed secondary fermentation: The prepared natto and koji are mixed and ground in a mass ratio of 1:1, and then salt water is added and sent to a fermentation tank with aeration, stirring and temperature control functions. Temperature is controlled, aeration and stirring are carried out in a closed fermentation, and the physicochemical indicators are monitored throughout the process until fermentation is completed. S4, Finished product post-processing: After the fermented sauce has passed the inspection, it is sterilized, hot-filled, sealed, and then cooled in a water bath to obtain the finished compound natto flavor sauce.

[0011] Furthermore, in step S1, the soybeans are soaked for 4-8 hours; drinking water with a volume of 3 times the volume of soybeans is added during soaking, the soaking environment temperature is 20-25℃, and the mixture is stirred once every 3 hours for 1 minute each time. After soaking, the moisture content of the soybeans is controlled at 60-65%. The specific operation of the three-stage gradient exhaust cooking is as follows: when the temperature inside the cooking tank rises to 95℃, the steam valve is closed and the exhaust valve is opened within 5-15 seconds, and then the exhaust valve is closed; when the temperature inside the tank is raised again to 112℃, the exhaust operation within 5-15 seconds is repeated, and then the exhaust valve is closed; when the temperature inside the tank is raised again to 122℃, the steam valve is closed and the mixture is simmered for 1 minute 50 seconds to 2 minutes 20 seconds, and then the exhaust valve is opened to release the gas. Once the temperature inside the tank drops below 100℃ and the soybeans are confirmed to have no hard core, the cooking is complete.

[0012] Furthermore, in step S2, the cooked soybeans are packaged in cleaned and disinfected fermentation baskets, with each basket containing 5 kg. After being neatly stacked, they are sent to the fermentation room. The straw is hung in the fermentation room 1-2 days in advance. The fermentation time of natto is 2.5-4 days. When making koji, the material temperature when mixing soybean residue and premixed koji is ≤35℃. The thickness of the koji bed is controlled at 20cm. In winter, the temperature of the koji room is controlled at 32-34℃, and the temperature of the koji bed material layer is controlled at 28-33℃. The ventilation volume is sufficient to completely blow through the material layer. The first turning of koji is carried out 6 hours after entering the koji bed. The second turning of koji is carried out after observing the state of the koji material at 8:00 the next day. The koji room is inspected every 2 hours. When the koji material clumps, ventilation resistance increases, or temperature distribution is uneven, the turning operation is carried out in time.

[0013] Furthermore, in step S3, after the brine is melted in the salt dissolving tank in the salt dissolving room, it is sent to the mixing tank to adjust the salinity before being lifted to the grinding room for use; all tanks are aerated and stirred through aeration pipes at the bottom of the tanks; after the brine is mixed, the moisture content of the fermentation system is ≤70%, and the salinity is 12.5-13°Bé; the temperature at the start of the fermentation tank is controlled at 25-30℃, and the temperature inside the tank is maintained at 28-32℃ during fermentation, with an aeration rate of 0.1-0.3 m³ / h. 3 / (h・m 3 The stirring speed is 20 r / min, and the fermentation time is 13-15 days.

[0014] Furthermore, in step S4, the sterilization adopts a continuous instantaneous sterilization process with a sterilization temperature of 100-120℃ and a sterilization time of 10-20 seconds. The sterilized sauce is then hot-filled and sealed. After filling, it is cooled to below 40℃ in a water bath at a cooling rate of 5℃ / minute to obtain the finished product, which has a shelf life of 18 months.

[0015] Beneficial effects Compared with existing technologies, this compound natto flavored sauce and its preparation method have the following beneficial effects: I. This invention utilizes compound soybeans and self-produced soybean residue as the main raw materials to achieve efficient resource utilization of by-products from soybean product processing. This significantly improves the comprehensive utilization rate of raw materials while reducing production costs, balancing economic efficiency and environmental friendliness. It employs a dual fermentation system combining natural inoculation with directional koji preparation using Aspergillus oryzae, blending the flavor characteristics of natto and koji to impart a rich and complex taste to the sauce. Simultaneously, relying on the synergistic effect of natural microorganisms and artificial koji, it promotes the conversion of nutrients during fermentation, improving the product's nutritional indicators such as amino acids, peptides, and nitrogen. The raw material pretreatment process deodorizes the soybean residue, effectively removing undesirable flavors. Combined with roasted soybean powder for added aroma, it further optimizes the product's flavor profile, significantly enhancing the flavor harmony and palatability of the finished product.

[0016] II. This invention achieves simultaneous fermentation of natto and koji through a segmented preparation method, followed by secondary fermentation by mixing them in proportion. This step-by-step fermentation method allows for precise control of fermentation conditions at each stage, ensuring the stability and controllability of the fermentation process and maintaining uniform physicochemical indicators of the product. The three-stage gradient degassing and cooking process, along with precise temperature, humidity, and ventilation control, ensures the cooking effect of the raw materials while avoiding nutrient loss. The continuous instantaneous sterilization process effectively sterilizes the product while preserving its flavor and nutrients to the greatest extent. The finished product undergoes a standardized post-processing procedure, maintaining suitable moisture and salinity while ensuring shelf life, giving the product both good edibility and storage stability, meeting the multiple needs of industrial production and market circulation.

[0017] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0019] Figure 1 A simplified flowchart for the overall preparation method of compound natto flavor sauce; Figure 2 Flowchart for the simultaneous fermentation of natto and koji. Detailed Implementation

[0020] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0021] Example 1: Conventional preparation method for compound natto flavor sauce.

[0022] Raw material preparation: Weigh out the required raw materials according to the following proportions by weight: 80 parts soybeans, 30 parts self-produced soybean residue, 12 parts edible salt, 7.5 parts soybean flour, 0.12 parts Aspergillus oryzae koji (fermentation starter), 15 parts rice straw, and the remainder is drinking water. Soybeans with a protein content of 40% are selected. The moisture content of the self-produced soybean residue is controlled at 78%, and after sieving, the soybean residue has a 96% passing rate through a 40-mesh standard sieve. The rice straw is cut into 40cm sections and is not subjected to high-temperature sterilization or drying to retain the natural microorganisms on its surface. The soybean flour is made by cleaning and removing impurities from soybeans, roasting them, and then pulverizing them. The amount of soybean flour added is 25% of the dry weight of the soybean residue. Thoroughly mix the Aspergillus oryzae koji with the prepared soybean flour, stirring until there are no lumps, to form a premixed starter. Store it in a cool, dry place in a sealed container for later use.

[0023] S1, Raw material pretreatment and soybean cooking: Soybean pretreatment: Place the weighed soybeans into a washing device and rinse them three times with clean water to remove surface dust, impurities, and shriveled particles. After rinsing, place the soybeans in a soaking container. Add drinking water to the soaking container at three times the volume of the soybeans, control the soaking temperature at 23℃, and set the soaking time to 6 hours. Stir the soybeans every 3 hours for 1 minute each time to ensure even soaking. After soaking, check the moisture content of the soybeans and control it to 62%.

[0024] Three-stage gradient venting and cooking: Soaked soybeans are transferred to a cooking tank, which is then sealed and steam heating is initiated. When the temperature inside the cooking tank reaches 95°C, the steam valve is closed and the vent valve is opened within 10 seconds to vent the soybeans. The vent valve is then immediately closed. The steam valve is reopened to continue heating. When the temperature inside the tank reaches 112°C, the steam valve is closed and the vent valve is opened again within 10 seconds to vent the soybeans. The vent valve is then closed. Heating continues until the temperature inside the tank reaches 122°C. The steam valve is then closed, and the soybeans are steamed for 2 minutes and 10 seconds. After steaming, the vent valve is opened to vent the soybeans. Once the temperature inside the tank drops below 100°C, samples are randomly taken from different locations inside the cooking tank to observe the state of the soybeans. Once it is confirmed that the soybeans have no hard core, the cooking process is complete.

[0025] Pre-treatment of raw materials for koji making: Weigh the self-produced soybean residue and feed it into a cooking device. Heat and cook until the residue has no raw taste and the beany smell is completely removed. The cooked residue is then transferred to an air cooler to cool to room temperature. During cooling, the residue is continuously stirred to ensure even cooling. The cooled residue is then set aside. The premixed koji is kept sealed and stored in an environment at approximately 25°C for later use. Figure 1 As shown.

[0026] S2, Simultaneous fermentation to prepare natto and koji: Natto Preparation: After steaming, the soybeans are removed and packaged into 5kg portions using fermentation baskets that have been rinsed with water and sterilized at high temperature. The baskets are then neatly stacked and placed in a temperature- and humidity-controlled fermentation room. Rice straw is hung on a rack inside the fermentation room 1.5 days in advance to ensure sufficient air contact and even distribution of the natural microorganisms carried by the straw, thus naturally inoculating the soybeans. The fermentation room is kept at a stable temperature and humidity for solid-state fermentation of the soybeans for 3.5 days. The soybeans are observed daily during fermentation. Natto is ready when a thick natto film appears on the surface and a strong natto flavor is present. The natto is then transferred to a sealed container for temporary storage.

[0027] Preparation of koji (fermented soybean residue): Air-cooled soybean residue and premixed koji are added to a mixing device. The material temperature is monitored in real-time during mixing and controlled at 33℃. The mixture is stirred until the soybean residue and premixed koji are completely combined without significant stratification. The mixed material is then spread onto the koji bed, with a thickness strictly controlled at 20cm, ensuring a smooth layer. In winter, the koji room temperature is controlled at 33℃, and the koji bed material temperature is controlled at 30℃. Ventilation equipment is turned on, with an airflow sufficient to completely penetrate the material layer, ensuring adequate oxygen supply. Six hours after the material enters the koji bed, the first turning is performed, loosening and evenly mixing the material to prevent clumping. The condition of the koji is observed after 8:00 AM the following day. When white mycelium appears on the surface and the internal temperature of the material layer slightly increases, a second turning is performed. During fermentation, the fermentation chamber is inspected every 2 hours to check the temperature, humidity, and temperature of the fermentation bed material. If clumping, increased ventilation resistance, or uneven temperature distribution are observed, the fermentation material is turned over promptly. Fermentation continues until the surface of the material is covered with evenly distributed mycelium and has a rich aroma. At this point, the fermented bean curd is ready. Figure 2 As shown.

[0028] S3, mixed secondary fermentation: The prepared natto and koji (fermented soybean paste) are added to a grinding machine at a 1:1 mass ratio and ground at low speed until a fine paste-like consistency is achieved. After grinding, the paste is transferred to a mixing container. Saltwater is prepared in advance in a salt-dissolving room. Edible salt is added to the salt-dissolving tank, followed by drinking water, and stirred until the salt is completely dissolved. The dissolved saltwater is then transferred to a mixing tank, where its salinity is adjusted before being sent to the grinding room for use. The prepared saltwater is added to the ground paste and stirred until evenly mixed. After mixing, the moisture content of the fermentation system is controlled at 69%, and the salinity at 12.8°Bé. The prepared paste is then transferred to a fermentation tank equipped with aeration, stirring, and temperature control functions. The initial temperature of the fermentation tank is controlled at 28°C, and during fermentation, the internal temperature is maintained at 30°C using a temperature control system. All tanks are aerated and stirred through aeration pipes at the bottom, with an aeration rate of 0.2 cubic meters per hour per cubic meter and a stirring speed of 20 revolutions per minute. The entire fermentation process is carried out in a closed system for 14 days. During fermentation, samples are taken daily from different locations in the fermentation tank to test the physicochemical indicators of the sauce, such as moisture content, salinity, and amino acid peptide nitrogen content, to ensure a stable fermentation process.

[0029] S4, Post-finishing processing: After fermentation, the sauce underwent comprehensive physicochemical testing. The results showed a moisture content of 69%, a salinity of 13°Bé, and an amino acid peptide nitrogen content of 0.62 grams per 100 grams. After passing the tests, sterilization was performed. A continuous, instantaneous sterilization process was used, where the sauce was fed into the sterilization equipment at a controlled temperature of 110°C for 15 seconds, ensuring even distribution without any omissions. Immediately after sterilization, the sauce was hot-filled into sterilized packaging containers, which were then sealed tightly to prevent leakage. The sealed product was then transferred to a water bath and cooled to below 40°C at a rate of 5°C per minute. After cooling, the final product was a compound natto-flavored sauce. The finished product was tested and found to have a moisture content of 72%, a salinity of 10.3°Bé, and an amino acid peptide nitrogen content of 0.55 grams per 100 grams. The finished product should be stored in a sealed container in a cool, dry, and dark environment. The shelf life is 18 months.

[0030] Example 2: The effect of different ingredient ratios on the quality of compound natto flavored sauce.

[0031] Raw material preparation: Three experimental groups with different raw material ratios were set up. In all experimental groups, the amount of soybean flour added was 25% of the dry weight of soybean residue. The rice straw was cut into 35cm pieces and was not subjected to high-temperature sterilization and drying treatment. The soybean protein content was 39%. The moisture content of the self-produced soybean residue was 78%, and the passing rate through a 40-mesh standard sieve was 95%. Aspergillus oryzae koji and soybean flour were mixed evenly to prepare a premixed koji. The specific raw material ratios for each experimental group are as follows: Experimental Group 1: 75 parts soybeans, 25 parts self-produced soybean residue, 10 parts edible salt, 6.25 parts soybean flour, 0.08 parts Aspergillus oryzae koji, 12 parts rice straw, and the remainder was drinking water.

[0032] Experimental Group 2: 85 parts soybeans, 35 parts self-produced soybean residue, 14 parts edible salt, 8.75 parts soybean flour, 0.15 parts Aspergillus oryzae koji, 18 parts rice straw, and the remainder was drinking water.

[0033] Experimental Group 3: 80 parts soybeans, 32 parts self-produced soybean residue, 11 parts edible salt, 8 parts soybean flour, 0.1 parts Aspergillus oryzae koji, 16 parts rice straw, and the remainder was drinking water.

[0034] Preparation method: All three experimental groups were prepared according to the complete steps in Example 1: raw material pretreatment and soybean cooking, simultaneous fermentation to prepare natto and koji, mixed secondary fermentation, and finished product post-processing. The soybean soaking temperature was controlled at 22℃, and the moisture content after soaking was controlled at 60%. The operating parameters of the three-stage gradient exhaust cooking were completely consistent with those in Example 1. The natto fermentation time was 3 days, and the rice straw was hung in the fermentation room one day in advance for natural inoculation. During the fermentation of the koji, the temperature of the koji bed material layer was controlled at 28℃, and the ventilation volume was determined to completely blow through the material layer. The turning operation was carried out according to the time nodes and requirements of Example 1. During the mixed secondary fermentation, the moisture content of the fermentation system was controlled at 68%, the salinity was controlled at 12.5°Bé, the temperature of the fermentation tank was 25℃, the temperature inside the tank was maintained at 28℃ during the fermentation process, the aeration volume was 0.1 cubic meters per hour per cubic meter, the stirring speed was 20 revolutions per minute, and the fermentation time was 13 days. The sterilization adopted a continuous instantaneous sterilization process with a sterilization temperature of 100℃ and a sterilization time of 20 seconds. After filling, the temperature was cooled to below 40℃ at a cooling rate of 5℃ per minute.

[0035] Finished product quality inspection: After the three experimental groups of compound natto flavored sauce were prepared, all the finished products were subjected to uniform physicochemical index testing. The test items included the moisture content, salinity, and amino acid peptide nitrogen content of the sauce after fermentation, as well as the moisture content, salinity, and amino acid peptide nitrogen content of the finished product after sterilization and filling. The test results are shown in the table below.

[0036] The test results show that all three experimental groups with different raw material ratios were able to produce composite natto-flavored sauce that met the preparation requirements, with all physicochemical indicators within reasonable ranges. Experimental group one had a relatively small amount of raw materials added, resulting in the lowest moisture content, salinity, and amino acid peptide nitrogen content in the fermented sauce among the three groups. The finished product also had correspondingly lower indicators, a relatively mild natto flavor and soy sauce aroma, and a bland taste. Experimental group two had the largest amount of raw materials added, resulting in the highest moisture content, salinity, and amino acid peptide nitrogen content in the fermented sauce among the three groups. The finished product also had relatively high indicators, a rich natto flavor, a mellow soy sauce aroma, and a slightly salty taste. Experimental group three had a moderate raw material ratio, resulting in moderate physicochemical indicators in both the fermented sauce and the finished product. The natto flavor and soy sauce aroma were well integrated, the taste was mellow and moderate, and the overall quality was superior. Different raw material ratios directly affect the physicochemical indicators and flavor of the finished product. The raw material ratios can be adjusted according to different market demands and taste preferences.

[0037] Example 3: The effect of soybean steaming and simmering time on the quality of compound natto flavor sauce.

[0038] Raw material preparation: The raw materials are weighed according to the following proportions: 80 parts soybeans, 30 parts self-produced soybean residue, 12 parts edible salt, 7.5 parts soybean flour, 0.12 parts Aspergillus oryzae koji (fermentation starter), 15 parts rice straw, and the remainder is drinking water. The soybean protein content is 40%, the self-produced soybean residue has a moisture content of 78%, and a 96% pass rate through a 40-mesh standard sieve. The rice straw is cut into 40cm sections and does not undergo high-temperature sterilization or drying. The soybean flour is made from roasted and ground soybeans, and the amount added is 25% of the dry weight of the soybean residue. The Aspergillus oryzae koji is mixed evenly with the soybean flour to prepare a premixed starter, which is then sealed for later use.

[0039] Raw material pretreatment and differentiated cooking: Soybean pretreatment: Rinse soybeans repeatedly with clean water to remove impurities, then place them in a soaking container and add drinking water three times the volume of the soybeans. Control the soaking temperature at 25°C and soak for 6 hours, stirring for 1 minute every 3 hours. After soaking, check the moisture content of the soybeans and control it at 65%.

[0040] Differential Three-Stage Gradient Exhaust Cooking: Soaked soybeans were placed in a cooking tank for three-stage gradient exhaust cooking. The exhaust operations after the first two temperature increases were consistent with Example 1, i.e., exhaust was completed within 10 seconds when the temperature reached 95℃ and 112℃. After the third temperature increase to 122℃, three experimental groups with different simmering times were set up, with the remaining operations being the same, as detailed below: Experimental Group 1: After closing the steam valve, the simmering time is 2 minutes. After simmering, open the exhaust valve to release the gas. Wait for the temperature inside the tank to drop below 100℃ and check that the soybeans have no hard core before cooking.

[0041] Experimental Group 2: After closing the steam valve, the simmering time was 2 minutes and 10 seconds, which was the same as the simmering time in Example 1. After simmering, the steam was released and the temperature was lowered. After checking that the soybeans had no hard core, the cooking was completed.

[0042] Experiment Group 3: After closing the steam valve, the simmering time is 2 minutes and 20 seconds. After simmering, the steam is released to cool down. After checking that the soybeans have no hard core, the cooking is complete.

[0043] Pretreatment of raw materials for koji making: After cooking the self-produced soybean residue to remove the beany smell, it is cooled to room temperature by an air cooler for later use. The premixed koji is kept sealed and placed in a cool place for later use.

[0044] Subsequent preparation methods: The preparation of natto, preparation of koji, mixed secondary fermentation, and post-processing of the finished product in all three experimental groups were carried out according to the steps and parameters of Example 1. The natto fermentation time was 4 days, and the straw was hung in the fermentation room 2 days in advance. During the koji fermentation, the room temperature was 34℃, the koji bed material temperature was 33℃, and the turning operation was carried out according to the requirements of Example 1. During the mixed secondary fermentation, the moisture content of the fermentation system was 70%, the salinity was 13°Bé, the temperature at the fermentation tank was 30℃, the temperature inside the tank was maintained at 32℃, the aeration rate was 0.3 cubic meters per hour per cubic meter, the stirring speed was 20 revolutions per minute, and the fermentation time was 15 days. Sterilization was carried out using a continuous instantaneous sterilization process at a sterilization temperature of 120℃ for 10 seconds, and the product was cooled to below 40℃ in a water bath after filling.

[0045] Finished product quality inspection: After the finished products of the three experimental groups were prepared, the sensory quality and physicochemical indicators of the finished products were tested. The sensory quality was mainly evaluated for the intensity of natto flavor, the fineness of the sauce, and the smoothness of the taste. The physicochemical indicators were mainly tested for the amino acid peptide nitrogen content. The test results are shown in the table below.

[0046] The test results show that the steaming time of soybeans significantly affects the quality of the compound natto flavored sauce. In Experiment 1, the steaming time was too short. Although the soybeans had no hard core, they were not fully cooked internally, resulting in slightly uneven inoculation and reproduction of microorganisms during subsequent natto fermentation. This led to insufficient natto flavor development, resulting in a milder flavor. Furthermore, the undercooked soybeans caused a slight grainy texture in the sauce after grinding, resulting in poor smoothness and a lower amino acid peptide nitrogen content compared to the other two groups. Experiment 2, with an appropriate steaming time, resulted in fully cooked soybeans without any mushy texture. Microorganisms multiplied evenly during natto fermentation, leading to a fully developed natto flavor. The ground sauce was smooth and free of grains, with a high level of amino acid peptide nitrogen content, making it the best overall quality. Experiment 3, with an excessively long steaming time, resulted in overly soft soybeans. This caused a slight rancidity reaction during natto fermentation, leading to a rancid taste in the finished natto. The overly soft soybeans also made the sauce too viscous, resulting in a greasy texture, and a decrease in amino acid peptide nitrogen content. Therefore, during the soybean steaming process, the optimal simmering time after the third temperature increase to 122℃ is 2 minutes and 10 seconds. At this time, the soybeans will be steamed to the best effect, which can lay a good foundation for subsequent fermentation and the quality of the finished product.

[0047] Example 4: The effect of natto fermentation time on the quality of compound natto flavored sauce.

[0048] Raw material preparation: The raw materials are weighed according to the following proportions: 80 parts soybeans, 30 parts self-produced soybean residue, 12 parts edible salt, 7.5 parts soybean flour, 0.12 parts Aspergillus oryzae koji (fermentation starter), 15 parts rice straw, and the remainder is drinking water. The soybeans contain 39% protein, the self-produced soybean residue has a moisture content of 78%, and a 95% pass rate through a 40-mesh standard sieve. The rice straw is cut into 40cm pieces and does not undergo high-temperature sterilization or drying. The soybean flour is made from roasted and ground soybeans, and is added at 25% of the dry weight of the soybean residue. The Aspergillus oryzae koji is thoroughly mixed with the soybean flour to prepare a premixed starter, which is then sealed for later use.

[0049] Raw material pretreatment and soybean cooking: After rinsing the soybeans with clean water, place them in a soaking container, add three times the volume of drinking water, control the soaking temperature at 23°C, and soak for 6 hours, stirring for 1 minute every 3 hours. After soaking, the moisture content should be controlled at 62%. Transfer the soaked soybeans to a cooking tank and cook them according to the three-stage gradient exhaust cooking process described in Example 1. After the third heating to 122°C, simmer for 2 minutes and 10 seconds, exhaust the gas, and cool to ensure the soybeans have no hard core, thus completing the cooking process. Cook the self-produced soybean residue to remove the beany smell, then cool it to room temperature using an air cooler for later use. Keep the premixed starter in a sealed state for later use.

[0050] Differentiated Natto Fermentation Time Settings: After steaming, the soybeans were divided into 5kg portions and placed into sterilized fermentation baskets. These baskets were then placed in a temperature- and humidity-controlled fermentation room. Rice straw was hung in the fermentation room 1.5 days in advance for natural inoculation. Four experimental groups with different natto fermentation times were set up. The koji (fermentation starter) was prepared according to the process and parameters of Example 1 to ensure sufficient fermentation. The specific experimental group settings are as follows: Experimental Group 1: Natto fermentation time was 3 days, and the natto was collected for later use after fermentation.

[0051] Experimental Group 2: The fermentation time of natto was 3.5 days. After the fermentation was completed, the natto was collected for later use.

[0052] Experimental Group 3: The fermentation time of natto was 4 days. After fermentation, the natto was collected for later use.

[0053] Experimental Group 4: The fermentation time of natto was 2.5 days. After fermentation, the natto was collected for later use.

[0054] Mixed secondary fermentation and finished product post-processing: In all four experimental groups, the prepared natto and koji were ground in a 1:1 mass ratio using a grinding machine until a fine paste was formed. Then, prepared brine was added, controlling the moisture content of the fermentation system to 70% and the salinity to 13°Bé. The prepared paste was then transferred to a fermentation tank at an initial temperature of 30°C. During fermentation, the tank temperature was maintained at 32°C, with an aeration rate of 0.3 cubic meters per hour per cubic meter and a stirring speed of 20 revolutions per minute. Fermentation was carried out in a sealed environment for 14 days. After fermentation, the qualified paste was subjected to a continuous instantaneous sterilization process at 115°C for 12 seconds. After sterilization, the paste was hot-filled, sealed, and cooled to below 40°C at a rate of 5°C per minute to obtain the finished product.

[0055] Finished product quality inspection: After the finished products of the four experimental groups were prepared, sensory evaluation and physicochemical index testing were carried out on the finished products. The sensory evaluation included the characteristic flavor of natto, the overall flavor harmony, and the taste. The physicochemical index testing included the amino acid peptide nitrogen content. The test results are shown in the table below.

[0056] The fermentation time of natto directly determines the degree to which its characteristic flavor is formed, thus affecting the overall quality of the compound natto flavor sauce. Experimental group four, with a fermentation time of only 2.5 days, did not complete the fermentation process, resulting in almost no formation of the characteristic natto flavor. The finished product only had a soy sauce aroma, with a monotonous overall flavor and the lowest amino acid peptide nitrogen content among the three groups, indicating the worst quality. Experimental group one, with a fermentation time of 3 days, had insufficient fermentation, a weak characteristic flavor, and only average integration with the soy sauce koji flavor, resulting in a bland taste and average performance across all indicators. Experimental group two, with a fermentation time of 3.5 days, had fully fermented natto, resulting in a prominent characteristic flavor without any off-odors. It integrated well with the soy sauce aroma of the koji, resulting in a harmonious overall flavor, a mellow and moderate taste, and the highest amino acid peptide nitrogen content, indicating the best overall quality. Experimental group three, with a fermentation time of 4 days, had over-fermented natto, exhibiting a slight rancidity reaction. This led to an overly strong and rancid natto flavor, severely masking the soy sauce aroma, resulting in poor overall flavor harmony, a sour taste in the finished product, and a decline in quality. Therefore, the optimal fermentation time for natto is 3.5 days. At this time, the natto is fully fermented, its characteristic flavor is well formed, and it can be perfectly integrated with the flavor of the koji, thus improving the overall quality of the finished product.

[0057] Example 5: The effect of aeration rate during secondary fermentation on the quality of compound natto flavored sauce. Raw material preparation: The raw materials are weighed according to the following proportions: 80 parts soybeans, 30 parts self-produced soybean residue, 12 parts edible salt, 7.5 parts soybean flour, 0.12 parts Aspergillus oryzae koji (fermentation starter), 15 parts rice straw, and the remainder is drinking water. The soybeans contain 40% protein, the self-produced soybean residue has a moisture content of 78%, and a 96% pass rate through a 40-mesh standard sieve. The rice straw is cut into 40cm pieces and does not undergo high-temperature sterilization or drying. The soybean flour is made from roasted and ground soybeans, and is added at 25% of the dry weight of the soybean residue. The Aspergillus oryzae koji is mixed evenly with the soybean flour to prepare a premixed starter, which is then sealed for later use.

[0058] Preparation of Natto and Koji: Soybeans were pretreated and cooked according to the raw material pretreatment and soybean cooking process described in Example 1. The soaking temperature was 23℃, and the moisture content after soaking was 62%. After three-stage gradient degassing and cooking, it was confirmed that the soybeans had no hard core. The cooked soybeans were packaged and fermented. Rice straw was hung for inoculation 1.5 days in advance, and fermentation was carried out for 3.5 days to produce natto. Self-produced soybean residue was cooked, air-cooled, and mixed with premixed koji at a mixing temperature of 33℃. The koji bed was 20cm thick. In winter, the koji room temperature was 33℃, and the material layer temperature was 30℃. The koji was turned and fermented as required to produce sauce koji, ensuring that the quality of both natto and sauce koji met the preparation requirements.

[0059] Mixed grinding and differentiated secondary fermentation: The prepared natto and koji were added to a grinding device at a 1:1 mass ratio and ground into a fine paste. After grinding, prepared brine was added, and the moisture content and salinity of the fermentation system in all experimental groups were controlled at 69% and 12.8°Bé, respectively. After thorough mixing, the mixture was transferred to a fermentation tank equipped with aeration, stirring, and temperature control functions. Three experimental groups with different aeration rates were set up. The inlet temperature of the fermentation tanks in all experimental groups was 28°C, and the internal temperature of the tanks was maintained at 30°C during fermentation. The stirring speed was 20 revolutions per minute, and the fermentation time was 14 days. The specific experimental group settings are as follows: Experimental group 1: Aeration rate of 0.1 cubic meters per hour per cubic meter.

[0060] Experimental Group 2: The aeration rate was 0.2 cubic meters per hour per cubic meter, consistent with the parameters of Example 1.

[0061] Experimental group 3: Aeration rate of 0.3 cubic meters per hour per cubic meter.

[0062] Post-processing of finished products: After the fermentation of the three experimental groups was completed, the physicochemical indicators of the sauce were tested. After passing the test, a continuous instantaneous sterilization process was adopted, with a sterilization temperature of 110℃ and a sterilization time of 15 seconds. After sterilization, the sauce was hot-filled and sealed, and cooled to below 40℃ at a cooling rate of 5℃ per minute to obtain the finished compound natto flavor sauce.

[0063] Finished product quality inspection: After the three experimental groups completed the preparation of the finished products, the physicochemical indicators of the fermented sauce and the finished product were tested. The main tests were the amino acid peptide nitrogen content of the fermented sauce, the amino acid peptide nitrogen content of the finished product, and the flavor intensity of the finished product. The test results are shown in the table below.

[0064] The aeration rate during the secondary fermentation process directly affects the oxygen content in the fermentation system, which in turn affects the metabolic activity of microorganisms, ultimately impacting the quality of the finished product. In Experiment 1, the aeration rate was 0.1 cubic meters per hour per cubic meter. Insufficient oxygen supply led to a slower metabolic rate of microorganisms and lower production of flavor compounds and amino acid peptide nitrogen. This resulted in lower amino acid peptide nitrogen content in both the fermented sauce and the finished product, with a weak natto and soy sauce flavor, and an overall poor flavor profile. In Experiment 2, the aeration rate was 0.2 cubic meters per hour per cubic meter. The oxygen content in the fermentation system was moderate, and the activity of microorganisms was optimal. The metabolic process was thorough, resulting in a large production of flavor compounds and amino acid peptide nitrogen. The amino acid peptide nitrogen content in both the fermented sauce and the finished product was the highest among the three groups. The finished product had a rich natto and soy sauce flavor with excellent integration, resulting in the best overall quality. In the experimental group, the aeration rate for the three-stage fermentation was 0.3 cubic meters per hour per cubic meter. This excessive oxygen supply inhibited the activity of some beneficial microorganisms and oxidized some characteristic flavor compounds of natto, resulting in a decrease in the amino acid peptide nitrogen content of the fermented sauce. The finished product had a slightly stronger soy sauce aroma and a slightly weaker natto flavor, with overall flavor harmony being average. Therefore, the optimal aeration rate for mixed two-stage fermentation is 0.2 cubic meters per hour per cubic meter.

[0065] Example 6: The effect of sterilization process parameters on the quality of compound natto flavored sauce.

[0066] Raw material preparation: The raw materials are weighed according to the following proportions: 80 parts soybeans, 30 parts self-produced soybean residue, 12 parts edible salt, 7.5 parts soybean flour, 0.12 parts Aspergillus oryzae koji (fermentation starter), 15 parts rice straw, and the remainder is drinking water. The soybeans contain 39% protein, the self-produced soybean residue has a moisture content of 78%, and a 95% pass rate through a 40-mesh standard sieve. The rice straw is cut into 40cm pieces and does not undergo high-temperature sterilization or drying. The soybean flour is made from roasted and ground soybeans, and is added at 25% of the dry weight of the soybean residue. The Aspergillus oryzae koji is mixed evenly with the soybean flour to prepare a premixed starter, which is then sealed for later use.

[0067] Preliminary preparation method: The raw material pretreatment, soybean cooking, natto and koji preparation, and mixed secondary fermentation were carried out according to the complete process of Example 1. The soybeans were soaked at 23°C with a moisture content of 62%, and after three-stage gradient degassing and cooking, there was no hard core. The natto fermented for 3.5 days, and the koji fermented until the mycelium was uniform. The natto and koji were mixed and ground in a 1:1 ratio, and after adding brine, the fermentation system had a moisture content of 69% and a salinity of 12.8°Bé. The fermentation tank inlet temperature was 28°C, the tank internal temperature was 30°C, the aeration rate was 0.2 cubic meters per hour per cubic meter, the stirring speed was 20 revolutions per minute, and the fermentation lasted for 14 days. After fermentation, the sauce was tested, and the results showed a moisture content of 69%, a salinity of 13°Bé, and an amino acid peptide nitrogen content of 0.62 grams per 100 grams, which met the standards and was ready for sterilization.

[0068] Differentiated sterilization process settings: The qualified sauces were divided into four experimental groups, all of which adopted a continuous instantaneous sterilization process with different sterilization temperatures and times. After sterilization, all experimental groups were immediately hot-filled and sealed, and then cooled to below 40°C at a cooling rate of 5°C per minute. The specific sterilization parameters were set as follows: Experimental group 1: Sterilization temperature 100℃, sterilization time 20 seconds.

[0069] Experimental Group 2: Sterilization temperature 110℃, sterilization time 15 seconds, consistent with the parameters of Example 1.

[0070] Experimental Group 3: Sterilization temperature 120℃, sterilization time 10 seconds.

[0071] Experimental group four: sterilization temperature 105℃, sterilization time 18 seconds.

[0072] Finished product quality inspection: After the finished products of the four experimental groups were prepared, multiple quality tests were conducted on the finished products, including sterilization effect, flavor retention, taste, and amino acid peptide nitrogen content. The sterilization effect was considered qualified if there was no deterioration after being stored at room temperature for 3 months. The test results are shown in the table below.

[0073] All four experimental groups achieved effective sterilization using the same sterilization parameters, and the finished products showed no spoilage after three months of storage at room temperature. However, different sterilization temperatures and times significantly affected the flavor retention, texture, and amino acid peptide nitrogen content of the finished products. Experimental group three, with a sterilization temperature as high as 120℃ and a sterilization time of only 10 seconds, rapidly decomposed some flavor compounds in the sauce, especially the characteristic flavor compounds of natto, resulting in a weaker natto flavor. The high temperature also caused slightly more moisture loss, leading to a drier texture and a slight decrease in amino acid peptide nitrogen content. Experimental groups one and four, with relatively lower sterilization temperatures, exhibited better flavor retention and a smoother texture, but compared to experimental group two, the complete flavor retention was slightly worse, and the amino acid peptide nitrogen content was also slightly lower. Experimental group two used a sterilization temperature of 110℃ and a sterilization time of 15 seconds. These parameters effectively and rapidly kill harmful microorganisms in the sauce while avoiding the decomposition of flavor compounds and moisture loss caused by excessively high temperatures and prolonged sterilization times. The finished product fully retains the natto flavor and soy sauce aroma, exhibiting excellent fusion, a rich and smooth taste, and the highest levels of amino acid peptide nitrogen content, resulting in the best overall quality. Therefore, the optimal continuous instantaneous sterilization process parameters for compound natto flavored sauce are a sterilization temperature of 110℃ and a sterilization time of 15 seconds.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A compound natto flavored sauce, characterized in that, It is prepared from the following raw materials in parts by weight: soybeans: 75-85 parts, self-produced soybean residue: 25-35 parts, edible salt: 10-14 parts, soybean flour: 6-9 parts, Aspergillus oryzae koji: 0.08-0.15 parts, rice straw: 12-18 parts, and the balance is drinking water; the soybean flour is obtained by roasting and grinding soybeans, and the amount of soybean flour added is 25% of the dry weight of soybean residue.

2. The compound natto flavored sauce according to claim 1, characterized in that, The soybeans have a protein content of ≥38%, the soybean residue has a moisture content of approximately 78%, and the particle size distribution of the soybean residue meets the requirement of a ≥95% passing rate through a 40-mesh standard sieve.

3. The compound natto flavored sauce according to claim 1, characterized in that, The flavor sauce is made by mixing natto and koji in a 1:1 mass ratio, then adjusting with brine and fermenting in a sealed environment. The natto is made by soaking, steaming, and naturally inoculating rice straw for solid-state fermentation. The koji is made by fermenting cooked and cooled soybean residue, soybean flour, and Aspergillus oryzae koji through ventilation.

4. The compound natto flavored sauce according to claim 1, characterized in that, After fermentation, the flavor sauce has a moisture content of 68-70%, a salinity of 12.5-14°Bé, and an amino acid nitrogen content of 0.55-0.69g / 100g; after sterilization and bottling, the finished product has a moisture content of 70-75%, a salinity of 10.2-10.5°Bé, and an amino acid nitrogen content ≥0.5g / 100g.

5. The compound natto flavored sauce according to claim 1, characterized in that, The rice straw is in segments 30-50cm in length, without high-temperature sterilization and drying treatment, and is inoculated with natural microorganisms carried on its surface; the Aspergillus oryzae koji is mixed evenly with soybean flour in advance to form a premixed koji for koji making.

6. A method for preparing a compound natto flavored sauce, the method being used to prepare the compound natto flavored sauce according to any one of claims 1-5, characterized in that, The specific steps of this preparation method are as follows: S1, Raw material pretreatment and soybean cooking: Selected soybeans are pretreated by rinsing and soaking, then sent to a cooking tank for three-stage gradient degassing and cooking. After simmering and degassing to cool down, samples are taken to confirm that the soybeans have no hard core, thus completing the soybean cooking process. Simultaneously, raw materials for koji making are prepared: Soybeans are roasted and crushed to obtain soybean powder. The soybean powder is premixed evenly with Aspergillus oryzae koji extract to obtain premixed koji for later use. Self-produced soybean residue is cooked to remove the beany smell and then cooled by an air cooler for later use. S2, Simultaneous fermentation to prepare natto and koji: Steamed soybeans are sent to a fermentation chamber with controlled temperature and humidity, and pre-treated rice straw is suspended for natural inoculation and solid-state fermentation to produce natto; at the same time, cooled soybean residue is mixed evenly with premixed koji, spread on a koji bed, and fermented in a controlled temperature and humidity environment. During the fermentation period, regular inspections are conducted and the koji is turned over to produce koji. S3, Mixed secondary fermentation: The prepared natto and koji are mixed and ground in a mass ratio of 1:1, and then salt water is added and sent to a fermentation tank with aeration, stirring and temperature control functions. Temperature is controlled, aeration and stirring are carried out in a closed fermentation, and the physicochemical indicators are monitored throughout the process until fermentation is completed. S4, Finished product post-processing: After the fermented sauce has passed the inspection, it is sterilized, hot-filled, sealed, and then cooled in a water bath to obtain the finished compound natto flavor sauce.

7. The method for preparing a compound natto flavored sauce according to claim 6, characterized in that, In step S1, the soybeans are soaked for 4-8 hours. During soaking, three times the volume of drinking water is added. The soaking environment temperature is 20-25℃. The soybeans are stirred every 3 hours for 1 minute each time. After soaking, the moisture content of the soybeans is controlled at 60-65%. The specific operation of the three-stage gradient exhaust cooking is as follows: When the temperature inside the cooking tank reaches 95℃, the steam valve is closed and the exhaust valve is opened within 5-15 seconds, then the exhaust valve is closed. When the temperature inside the tank is raised to 112℃, the exhaust operation within 5-15 seconds is repeated, then the exhaust valve is closed. When the temperature inside the tank is raised again to 122℃, the steam valve is closed and the soybeans are simmered for 1 minute 50 seconds to 2 minutes 20 seconds, then the exhaust valve is opened to release the gas. Once the temperature inside the tank drops below 100℃ and the soybeans are confirmed to have no hard core, the cooking process is complete.

8. The method for preparing a compound natto flavored sauce according to claim 6, characterized in that, In step S2, the cooked soybeans are packaged in cleaned and disinfected fermentation baskets, with each basket containing 5 kg. After being neatly stacked, they are sent to the fermentation room. The straw is hung in the fermentation room 1-2 days in advance. The fermentation time of natto is 2.5-4 days. When making koji, the material temperature when mixing soybean residue and premixed koji is ≤35℃. The thickness of the koji bed is controlled at 20cm. In winter, the temperature of the koji room is controlled at 32-34℃, and the temperature of the koji bed material layer is controlled at 28-33℃. The ventilation volume is based on completely blowing through the material layer. The first turning of koji is carried out 6 hours after entering the koji bed. The second turning of koji is carried out after observing the state of the koji material at 8:00 the next day. The koji room is inspected every 2 hours.

9. The method for preparing a compound natto flavored sauce according to claim 6, characterized in that, In step S3, the brine is melted in the salt dissolving tank in the salt dissolving room, then sent to the mixing tank to adjust the salinity, and finally lifted to the grinding room for use; all tanks are aerated and stirred through aeration pipes at the bottom of the tanks; after brine mixing, the moisture content of the fermentation system is ≤70%, and the salinity is 12.5-13°Bé; the temperature at the start of the fermentation tank is controlled at 25-30℃, and the temperature inside the tank is maintained at 28-32℃ during fermentation, with an aeration rate of 0.1-0.3 m³ / h. 3 / (h・m 3 The stirring speed is 20 r / min, and the fermentation time is 13-15 days.

10. The method for preparing a compound natto flavored sauce according to claim 6, characterized in that, In step S4, the sterilization adopts a continuous instantaneous sterilization process with a sterilization temperature of 100-120℃ and a sterilization time of 10-20 seconds. After sterilization, the sauce is hot-filled and sealed. After filling, it is cooled to below 40℃ in a water bath at a cooling rate of 5℃ / minute to obtain the finished product, which has a shelf life of 18 months.

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