Fermentation method of fermented bean curd product

Abstract

The invention relates to a fermentation method of a fermented bean curd product, which ensures the quality and flavor of the product by accurately controlling raw material treatment, fermentation conditions and an after-ripening process. The method comprises the following specific steps: raw material pretreatment: selecting non-transgenic soybeans with the protein content of more than or equal to 40%, soaking, grinding and boiling to prepare bean curd blanks with the water content of less than or equal to 70%; in the primary fermentation, a complex microbial inoculant formed by mixing mucor, saccharomyces cerevisiae and lactobacillus plantarum according to a ratio of 1: 1: 0.3 is inoculated on the surface of the bean curd pehtze, and fermentation is performed for 60 hours in an environment with the temperature of 28 + / -1 DEG C and the relative humidity of 85% to form a hypha layer with the thickness of more than or equal to 1 mm; performing secondary fermentation: loading the bean curd pehtze and rice wine lees into a ceramic jar in layers according to the mass ratio of 1: 2, controlling the oxygen content to be less than or equal to 5%, performing sealed fermentation for 18 days, and turning over the pehtze once every 3 days during the period; in the after-ripening treatment, a fermentation product is transferred into a humidity control box with the humidity being 75% and the temperature being 16 DEG C, ventilation is conducted twice a day for 6 days, and the final finished product needs to meet the quality standards that the moisture content is smaller than or equal to 55%, the amino acid nitrogen content is larger than or equal to 0.8 g / 100 g, and the cover expansion and juice leakage rate is smaller than or equal to 0.8%.

Description

Technical Field

[0001] The present invention belongs to the technical field of food processing, and particularly relates to a fermentation method for fermented bean curd products, and more particularly to an industrial production method for shortening the fermentation cycle and improving product quality by optimizing the inoculum ratio and fermentation process parameters. Background Art

[0002] Fermented bean curd is a traditional fermented soy product, and its production mainly relies on the synergistic action of Mucor, yeast and lactic acid bacteria. In the traditional process, the post-fermentation stage takes more than 30 days, and it is easy to cause a relatively high rate of lid swelling and juice leakage in the finished product (usually exceeding 5%) due to uneven control of temperature and humidity, seriously affecting the product quality and shelf life. In the prior art, although the problem can be partially improved by optimizing a single strain or adjusting the salt concentration, it is difficult to balance the dual goals of shortening the cycle and reducing the juice leakage rate, and there is a lack of refined control of the co-metabolism mechanism of the strains. Therefore, there is an urgent need for an efficient and stable fermentation method for fermented bean curd to solve the above technical bottlenecks. Summary of the Invention

[0003] The present invention aims to provide a fermentation method for fermented bean curd products, which realizes the shortening of the post-fermentation cycle, the lid swelling and juice leakage rate of the finished product being less than 1%, and at the same time ensuring that the amino acid nitrogen ≥ 0.8 g / 100 g, meeting the requirements of the national standard GB2712-2014 through the synergistic action of a compound inoculum and the optimization of key process parameters.

[0004] To solve the above technical problems, the present invention provides the following technical solutions: A fermentation method for fermented bean curd products, comprising the following steps:

[0005] A. Raw material pretreatment:

[0006] Select non-genetically modified soybeans with a protein content ≥ 40%, wash them and soak them in clean water at 25-30 °C for 8-12 hours until the water absorption rate of the soybeans ≥ 120%;

[0007] When grinding the slurry, control the fineness of the slurry to be 80-100 mesh, the boiling temperature of the slurry to be 95-100 °C, and keep it for 10-15 minutes to inactivate the anti-nutritional factors;

[0008] Use glucono-δ-lactone with a mass concentration of 0.3% for coagulating the soy milk, and after coagulation, cut it into tofu cubes with a size of 3 cm × 3 cm × 1 cm, and drain the water until the water content ≤ 70%.

[0009] B. Pre-fermentation:

[0010] Preparation of the compound inoculum: Mix Mucor, Saccharomyces cerevisiae and Lactobacillus plantarum in a mass ratio of 1:1:0.3, and activate them at 30 °C for 2 hours before inoculation;

[0011] The composite microbial agent was evenly inoculated on the surface of the tofu blank by the spraying method, and the inoculation amount was 2% of the mass of the tofu blank. Subsequently, it was fermented for 60 hours in an environment of 28 ± 1°C and a relative humidity of 85% until the thickness of the hyphal layer was ≥ 1 mm.

[0012] C, Post-fermentation:

[0013] Pretreatment of distiller's grains: Rice distiller's grains were selected with an alcohol content of 4% (v / v), and salt was added to a final concentration of 10%. After mixing evenly, it was sterilized;

[0014] The fermented tofu blank and distiller's grains were layered into a ceramic vat at a mass ratio of 1:2, sealed, and fermented at 22 ± 1°C for 18 days. During this period, the tofu blank was turned over every 3 days to balance the temperature, humidity, and metabolite distribution;

[0015] The oxygen content in the vat was controlled to be ≤ 5%, and an anaerobic environment was maintained by CO2 replacement.

[0016] D, Post-ripening treatment:

[0017] The post-fermentation product was transferred to a humidity-controlled box with a humidity of 75% and a temperature of 16°C, ventilated 2 times a day for 30 minutes each time, and continued for 6 days;

[0018] The moisture content of the finished product was detected to be ≤ 55%, the amino acid nitrogen was ≥ 0.8 g / 100 g, and the lid swelling and juice leakage rate was ≤ 0.8%.

[0019] Preferably: The hardness of the water used for soaking soybeans in step A was ≤ 50 mg / L.

[0020] Preferably: The protease activity of the mucor strain in step B was ≥ 5000 U / g, the lipase activity was ≥ 3000 U / g, and the inoculation amount of the composite microbial agent was 1 - 3% of the mass of the tofu blank.

[0021] Preferably: In step C, the operation of turning over the tofu blank was carried out with a sterile bamboo tool, and it was gently turned over layer by layer to avoid hyphal breakage.

[0022] Preferably: In step D, the ventilation adopted the gradient pressure reduction method, with the initial humidity of 80% gradually decreasing to 70% day by day to avoid epidermal cracking caused by sudden water loss.

[0023] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0024] 1. Synergistic effect of the composite microbial agent: Mucor dominates protein and fat decomposition, yeast produces ethanol and ester precursors, and lactic acid bacteria inhibit miscellaneous bacteria. After optimizing the ratio of the three bacteria, their metabolisms are complementary, shortening the fermentation cycle;

[0025] 2. Precise control of process parameters: Salt concentration (8 - 12%), turning-over frequency (every 3 days), and temperature and humidity gradient regulation significantly reduce the juice leakage rate;

[0026] 3. Standardized production: By quantifying indicators (such as amino acid nitrogen and moisture content), the product quality can be controlled, meeting the requirements of industrial production.

[0027] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. Brief Description of the Drawings

[0028] Figure 1 It is the preparation flow chart of a fermentation method for a fermented bean curd product of the present invention;

[0029] Figure 2 It is the technical flow chart of a fermentation method for a fermented bean curd product of the present invention;

[0030] Figure 3 It is the post-ripening treatment flow chart of a fermentation method for a fermented bean curd product of the present invention;

[0031] Figure 4 It is the post-fermentation flow chart of a fermentation method for a fermented bean curd product of the present invention;

[0032] Figure 5 It is the pre-fermentation flow chart of a fermentation method for a fermented bean curd product of the present invention;

[0033] Figure 6 It is the raw material pretreatment flow chart of a fermentation method for a fermented bean curd product of the present invention. Detailed Description of the Invention

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] It should be noted that the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only implementation manner.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs; the terms used herein in the specification of this invention are for the purpose of describing specific embodiments only and are not intended to limit the invention; the term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0037] As Figure 1 shown, the present invention relates to a fermentation method for fermented bean curd products. By precisely controlling raw material processing, fermentation conditions and post-ripening processes, the quality and flavor of the products are ensured. The specific steps include:

[0038] 1. Pretreatment of raw materials: Select non-genetically modified soybeans with a protein content of ≥40%, and make tofu blanks after soaking, grinding and boiling the soybeans, and drain the water until the water content is ≤70%.

[0039] 2. Pre-fermentation: Mix Mucor, Saccharomyces cerevisiae and Lactobacillus plantarum in a ratio of 1:1:0.3, inoculate on the surface of the tofu blanks, and ferment for 60 hours in an environment of 28±1°C and a relative humidity of 85% to form a mycelial layer with a thickness of ≥1 mm.

[0040] 3. Post-fermentation: Layer the tofu blanks and rice wine lees into a pottery vat according to a mass ratio of 1:2, control the oxygen content to ≤5%, seal and ferment for 18 days, and turn the blanks once every 3 days during this period.

[0041] 4. Post-ripening treatment: Transfer the fermentation product to a humidity-controlled box and conduct ventilation treatment for 6 days. The final finished product needs to meet the quality standards of a water content of ≤55%, an amino acid nitrogen content of ≥0.8 g / 100 g, and a lid swelling and leakage rate of ≤0.8%.

[0042] In addition, there are strict requirements for details such as the hardness of the soaking water (≤50 mg / L), the enzyme activity of the Mucor strain (protease ≥5000 U / g, lipase ≥3000 U / g), and the sterility of the tools for turning the blanks during the process to ensure the stability of the fermentation process and the high quality of the finished product.

[0043] In this embodiment, the pretreatment of raw materials provides a uniform tofu blank matrix for pre-fermentation through steps such as soaking, grinding and boiling. The compound microbial agent (Mucor, Saccharomyces cerevisiae, Lactobacillus plantarum) in pre-fermentation directly acts on the surface of the tofu blanks to form a mycelial layer. The tofu blank, as the fermentation matrix, is located at the core of the fermentation environment, and the compound microbial agent is evenly inoculated on its surface to ensure uniform growth of the mycelia.

[0044] By precisely controlling the soybean protein content, soaking time, and slurry fineness, the texture uniformity of the tofu blank is ensured, providing an ideal matrix for subsequent fermentation. The synergistic effect of the compound bacterium agent during the pre-fermentation significantly improves the decomposition efficiency of proteins and fats, endows the fermented bean curd with a unique flavor and texture, and at the same time avoids the problem of single flavor caused by single-strain fermentation.

[0045] After pre-fermentation, the tofu blank is mixed with distiller's grains at a mass ratio of 1:2 and loaded into a ceramic vat in layers. The distiller's grains, as the fermentation medium, come into direct contact with the tofu blank, providing alcohol and flavor substances. The tofu blank and distiller's grains are loaded in layers inside the ceramic vat, and an anaerobic environment with an oxygen content ≤ 5% is maintained through sealing and CO2 replacement. The addition of distiller's grains not only provides alcohol and flavor precursor substances but also inhibits the growth of harmful microorganisms through the anaerobic environment, significantly enhancing the aroma and flavor levels of the fermented bean curd. At the same time, the regular operation of turning the blank ensures the uniform distribution of temperature, humidity, and metabolites, avoiding over-fermentation or under-fermentation in local areas.

[0046] The post-fermentation product is transferred to a humidity-controlled box and ventilated by the gradient pressure reduction method to gradually reduce the humidity, ensuring that the moisture content of the finished product ≤ 55%, while avoiding skin cracking.

[0047] The after-ripening treatment is carried out in a humidity-controlled box, and the ventilation system is evenly distributed around the box body to ensure uniform humidity on the surface and inside of the finished product. The gradient pressure reduction ventilation method effectively avoids the problem of sudden water loss caused by traditional ventilation methods, ensuring that the surface of the finished product is smooth and the texture is uniform. At the same time, by strictly controlling indicators such as the moisture content, amino acid nitrogen, and lid swelling and leakage rate of the finished product, the stability and safety of the product are significantly improved, and the shelf life is extended.

[0048] In the process, strict requirements are imposed on details such as the hardness of the soaking water, the enzyme activity of the Mucor strain, and the sterility of the turning tool. These details run through the entire fermentation process and directly affect the fermentation efficiency and the quality of the finished product. The hardness of the soaking water affects the water absorption rate of soybeans, the enzyme activity of the Mucor strain determines the efficiency of pre-fermentation, and the sterility of the turning tool ensures the hygiene of the fermentation environment. By optimizing the hardness of the soaking water and the enzyme activity of the Mucor strain, the fermentation efficiency and matrix utilization rate are significantly improved; the use of a sterile turning tool avoids contamination by miscellaneous bacteria and guarantees the stability of the fermentation process. The combined effect of these detail optimizations enhances the flavor, nutrition, and safety of the fermented bean curd, providing technical support for the modern production of traditional fermented bean curd products.

[0049] As Figure 2 shown, through the innovative fermentation process, the present invention realizes the efficient production and quality improvement of fermented bean curd products. Its core highlights include:

[0050] 1. Bacterial agent optimization: The compound bacterial agent of Mucor, Saccharomyces cerevisiae and Lactobacillus plantarum is used. After activation treatment at 30 °C and inoculation, the decomposition efficiency of protein and fat is significantly improved, endowing the fermented bean curd with a unique flavor.

[0051] 2. Environmental control: The temperature, humidity and oxygen content are strictly controlled in the pre-fermentation stage, and the anaerobic environment is maintained by CO2 replacement in the post-fermentation stage to ensure uniform hypha growth and balanced metabolite distribution.

[0052] 3. Quality monitoring: Gradient pressure reduction ventilation is used in the ripening treatment to avoid epidermal cracking caused by sudden water loss. At the same time, multi-index detection (such as amino acid nitrogen and lid swelling and juice leakage rate) is used to ensure the stability and safety of the finished product.

[0053] 4. Detail improvement: From raw material screening (such as soybean protein content ≥ 40%) to aseptic treatment of turning tools, the hygiene and efficiency of the fermentation process are guaranteed in all aspects.

[0054] In this implementation plan, the optimized ratio of the compound bacterial agent: Mucor, Saccharomyces cerevisiae and Lactobacillus plantarum are mixed according to the mass ratio of 1:1:0.3, so that the protein decomposition, alcohol fermentation and antibacterial effects are synergistic and the fermentation cycle is shortened.

[0055] Spray inoculation is used in the pre-fermentation stage (such as the PerMix spray system, atomization particle size ≤ 50 μm) to ensure uniform distribution of the bacterial agent;

[0056] CO2 replacement technology is used in the post-fermentation stage (such as the SMC gas control valve, flow rate 0.5 L / min) to maintain the anaerobic environment (O2 ≤ 5%);

[0057] Gradient pressure reduction ventilation is used in the ripening stage (such as the Siscom temperature and humidity controller, humidity 80% → 70% / day).

[0058] Among them, the quantitative index control:

[0059] Amino acid nitrogen ≥ 0.8 g / 100 g (national standard requirement ≥ 0.5 g / 100 g);

[0060] Lid swelling and juice leakage rate ≤ 0.8% (traditional process ≥ 5%).

[0061] In this implementation plan, the implementation key points and equipment / parameters are as follows:

[0062]

[0063] In one or more feasible embodiments,

[0064] Example 1:

[0065] The post-fermentation cycle is 18 days (traditional process 30 days);

[0066] The leakage rate of the swollen lid is 0.7% (5.2% for the traditional one);

[0067] The amino acid nitrogen is 0.85 g / 100 g (0.6 g / 100 g for the traditional one).

[0068] Comparative example (traditional process):

[0069] Single Mucor fermentation, without controlling the O2 content, and the turning interval is 5 days, resulting in uneven metabolism and a high leakage rate.

[0070] 4. Industrial application adaptability

[0071] Equipment adaptation: The spray inoculation system (PerMix) and the constant temperature fermentation box (Binder) can be docked with the automated production line, increasing the production capacity by 30%;

[0072] Parameters can be extended: The strain ratio (0.5 - 1.5 for yeast) and the post-fermentation temperature (20 - 25 °C) can both stably achieve the target indicators.

[0073] Conclusion: Through the innovation of the bacterial agent ratio and precise process control, combined with standardized equipment (such as SMC gas valves and ESPEC humidity control boxes), the present invention realizes the high efficiency, low loss, and high quality of sufu production, and has the value of industrial promotion.

[0074] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.

Claims

1. A fermentation method for fermented bean curd products, characterized in that, It includes the following steps: A. Raw material pretreatment: Select non-genetically modified soybeans with a protein content of ≥40%, soak them in clean water at 25 - 30°C for 8 - 12 hours after washing until the water absorption rate of soybeans is ≥120%; When grinding the slurry, control the fineness of the slurry to be 80 - 100 mesh, and the boiling temperature of the slurry to be 95 - 100°C for 10 - 15 minutes to inactivate anti-nutritional factors; Use glucono-δ-lactone with a mass concentration of 0.3% for coagulating the soy milk. After coagulation, cut it into tofu blanks of 3 cm × 3 cm × 1 cm, and drain the water until the water content is ≤70%. B. Pre-fermentation: Compound bacterium agent preparation: Mix Mucor, Saccharomyces cerevisiae and Lactobacillus plantarum according to the mass ratio of 1:1:0.3, and activate them at 30°C for 2 hours before inoculation; Use the spraying method to evenly inoculate the compound bacterium agent on the surface of the tofu blank, and the inoculation amount is 2% of the mass of the tofu blank. Then ferment it in an environment of 28±1°C and a relative humidity of 85% for 60 hours until the thickness of the mycelium layer is ≥1 mm. C. Post-fermentation: Rice wine lees pretreatment: Select rice wine lees with an alcohol content of 4% (v / v), add salt to a final concentration of 10%, mix evenly and then sterilize; Layer the fermented tofu blanks and rice wine lees into earthen jars according to the mass ratio of 1:2, seal them and ferment at 22±1°C for 18 days. During this period, turn the blanks once every 3 days to balance the temperature, humidity and metabolite distribution; Control the oxygen content in the jar to be ≤5%, and maintain an anaerobic environment by CO2 replacement. D. Post-ripening treatment: Transfer the post-fermentation product to a humidity-controlled box with a humidity of 75% and a temperature of 16°C, ventilate it twice a day, each time for 30 minutes, and continue for 6 days; Detect that the water content of the finished product is ≤55%, the amino acid nitrogen is ≥0.8 g / 100 g, and the lid swelling and juice leakage rate is ≤0.8%.

2. The fermentation method of a fermented bean curd product according to claim 1, characterized in that: The hardness of the water used for soaking soybeans in step A is ≤50 mg / L.

3. A fermentation method for fermented bean curd products according to claim 1, characterized in that: In step B, the protease activity of the Mucor strain is ≥5000 U / g, the lipase activity is ≥3000 U / g, and the inoculation amount of the compound bacterium agent is 1 - 3% of the mass of the tofu blank.

4. A fermentation method of fermented bean curd products according to claim 1, characterized in that: In step C, the blank turning operation uses a sterile bamboo tool, and turn the blanks layer by layer gently to avoid breaking the mycelium.

5. A fermentation method for fermented bean curd products according to claim 1, characterized in that: In step D, the ventilation adopts the gradient pressure reduction method, and the initial humidity of 80% is gradually reduced to 70% day by day to avoid epidermal cracking caused by sudden water loss.

Images