Sour dough fermentation process and aleurone layer toast bread

Abstract

The invention provides a sour dough fermentation process, which comprises the following steps of: mixing and stirring wheat flour, purified water, red bean powder and pickled Chinese cabbage juice in a container to form dough, forming the dough into hydrated dough, inoculating strains, performing primary fermentation, performing secondary fermentation, and performing three-stage low-temperature cooking and forming to obtain finished sour dough. According to the sour dough fermentation process, the problems that traditional aleurone layer toast bread is rough in texture, short in shelf life and the like are solved through functional raw material integration, strain compounding regulation and control and staged gradient temperature control fermentation control, comprehensive improvement of nutrition, taste and flavor of the aleurone layer toast bread is achieved through the synergistic effect of wheat flour, red bean powder and pickled Chinese cabbage juice, and the nutritional value of the aleurone layer toast bread is improved. The market competitiveness is obvious.

Description

Technical Field

[0001] The present invention relates to the technical field of food engineering, and particularly relates to a sourdough fermentation process and a aleurone layer toast bread.

Background Art

[0002] Aleurone layer toast refers to toast made from flour containing aleurone layer components. The aleurone layer generally refers to a part of wheat grains, located between the bran and the endosperm, rich in proteins, minerals, and B vitamins. Arabinoxylan (AX) in the aleurone layer is the main cause of the rough texture of bread. Compared with ordinary toast, traditional aleurone layer toast has the following characteristics:

[0003] 1. Traditional aleurone layer toast retains the aleurone layer and thus has higher nutrition. However, arabinoxylan and crude fiber in the aleurone layer result in a rough texture and loose texture, leading to low consumer acceptance.

[0004] 2. From the perspective of the sourdough production process, arabinoxylan and cellulose in the aleurone layer are difficult to be decomposed by ordinary yeast, resulting in poor gas retention of the dough. The specific volume (volume / weight) of the bread is usually ≤ 2.8 cm 3 / g, and the honeycomb structure is uneven. A moderate specific volume makes the bread have uniform pores and good elasticity. A too low specific volume results in a strong flavor and a firm texture, but a stiff taste and a small volume.

[0005] 3. Active enzymes (such as lipase) in the aleurone layer are prone to cause rancidity, and the high fiber hygroscopicity leads to a high risk of mildew. The shelf life of commercially available products is generally ≤ 7 days.

[0006] 4. It lacks natural fermentation flavor and relies on artificial additives, which does not conform to the healthy consumption trend.

[0007] In view of this, the inventor of this case conducted in-depth research on the above problems, and thus this case was born.

Summary of the Invention

[0008] The present invention aims to solve the technical problems existing in traditional aleurone layer toast, and provides a sourdough fermentation process and an aleurone layer toast bread, aiming to improve the nutrition, taste, and extend the shelf life of the aleurone layer toast bread.

[0009] The present invention is realized as follows: A sourdough fermentation process includes the following steps:

[0010] (1) Take 100 parts of wheat flour, 60 - 70 parts of purified water, 4 - 5 parts of red bean flour, and 1 - 1.5 parts of pickled cabbage juice, mix and stir them in a container until there are no particles, forming a dough;

[0011] (2) Transfer the dough to a constant humidity box at a temperature of 25 ± 1 °C and a humidity of RH75 - 80%, and let it stand and hydrate for 25 - 30 min to form a hydrated dough;

[0012] (3) Strain inoculation: Take the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae and prepare a compound bacterial solution. Atomize and spray 3 - 5 parts of the compound bacterial solution onto the surface of the hydrated dough, and use a double - helix mixer to stir and mix evenly at a low speed for 1.5 - 2 min to form the dough to be fermented;

[0013] (4) Primary fermentation: Place the dough to be fermented in a fermentation container at 30 ± 1 °C and ferment for 8 - 10 h to naturally lower the pH to 4.2 ± 0.1;

[0014] (5) Secondary fermentation: Ferment the preliminarily fermented dough in a fermentation container at 26 ± 1 °C for 10 - 12 h to naturally lower the pH to 3.8 ± 0.1;

[0015] (6) Tertiary low - temperature aging: Place the dough after secondary fermentation in a fermentation container at 4 °C, control the humidity of the fermentation container at RH92 ± 2%, maintain the pH at 3.8 ± 0.1, and refrigerate and ferment for 24 h to form the finished sourdough.

[0016] Furthermore, in step (1), the red bean powder needs to be dry - heat treated at 80 ± 1 °C for 10 - 15 min in advance.

[0017] Furthermore, the pickled cabbage juice needs to be desalted in advance, and the salt concentration of the pickled cabbage juice ≤ 0.8%.

[0018] Furthermore, in step (1), adopt ultrasonic sorting technology to screen wheat flour with a retention rate of aleurone layer ≥ 90%, the particle size of the wheat flour is 80 - 120 mesh, and the proportion of the aleurone layer in the wheat flour is 20 - 22%.

[0019] Furthermore, in step (3), the mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae is (2 - 3):1:1.

[0020] Furthermore, in step (3), the atomization particle size of the compound bacterial solution is 50 - 70 μm.

[0021] Furthermore, the fermentation container adopts a three - stage series fermentation tank; in step (4), the humidity of the three - stage series fermentation tank is controlled at RH82 ± 2%; in step (5), the humidity of the three - stage series fermentation tank is controlled at RH82 ± 2%.

[0022] On the other hand, a kind of aleurone layer toast bread, using the finished sourdough prepared by the above - mentioned sourdough fermentation process, the baking process of the aleurone layer toast bread includes the following steps:

[0023] Step 1: Mix 100 parts of high-gluten flour, 20±1 parts of finished sourdough, 3±1 parts of trehalose, 1.5±0.1 parts of lecithin, 15±1 parts of butter, 1±0.1 parts of salt and 45±1 parts of 35°C purified water, and process with a variable-speed dough mixer to form a smooth dough with a film thickness ≤0.1 mm; place the dough in an environment of 28±1°C / RH80±2% and let it stand for 40 - 60 min until the volume expands to 1.8 - 2.0 times and a continuous air chamber structure is formed inside;

[0024] Step 2: Divide the dough into pieces; put the divided dough into a proofing box and proof for 56 - 60 min; then send it into an oven and bake and form it in stages.

[0025] Further, in Step 1, the processing with the variable-speed dough mixer is 2 min at low speed first and then 6 min at high speed.

[0026] Further, in Step 2, the following baking stages are included:

[0027] Stage 1: Upper fire 180°C / Lower fire 200°C, steam injection for 2 s, bake for 10 min to form a hard shell layer;

[0028] Stage 2: Adjust to upper fire 160°C / lower fire 180°C and continue baking for 25 min until the center temperature reaches 96°C;

[0029] Stage 3: Turn off the lower fire, upper fire 150°C hot air circulation for 5 min to reduce the surface moisture to ≤8% to obtain the finished aleurone layer toast bread.

[0030] The advantages of the present invention are as follows:

[0031] 1. The sourdough fermentation process of the present invention solves the problems of rough texture and short shelf life of traditional aleurone layer toast bread through the integration of functional raw materials, the regulation of strain compounding, and the control of staged gradient temperature-controlled fermentation. Utilizing the synergistic effect of wheat flour, red bean flour and sauerkraut juice, it realizes the comprehensive improvement of the nutrition, taste and flavor of aleurone layer toast bread, and has significant market competitiveness.

[0032] 2. Wheat flour, as the main functional ingredient, has an aleurone layer that is rich in substances such as protein, minerals, and B vitamins. Red bean flour and pickled vegetable juice are used as auxiliary functional ingredients. Since red bean flour contains 12-15% dietary fiber, 35-40% high amylose starch, 20-22% protein, and polyphenol oxidase, the dietary fiber and high amylose starch in red bean flour can reduce the GI value of the finished bread; the polyphenol oxidase in red bean flour can promote the formation of ferulic acid and increase the content of resistant starch; pickled vegetable juice contains natural lactic acid bacteria, which can supplement the fermentation flora and inhibit miscellaneous bacteria; the organic acids (lactic acid, acetic acid) in pickled vegetables can regulate the pH and enhance the flavor complexity of the finished bread. At the same time, in the combination of red bean flour and pickled vegetable juice as auxiliary ingredients, dietary fiber and natural lactic acid bacteria can synergistically improve the gas retention property (specific volume ≥ 3.5 cm3 / g), and the combined action of ferulic acid and antibacterial peptides can extend the shelf life of the finished bread to 21-28 days.

[0033] 3. The fermentation container realizes three-stage gradient temperature control from 30°C → 26°C → 4°C, matching the optimal activity range of different strains to achieve precise regulation of the flora metabolism. In the primary fermentation stage, Lactobacillus plantarum dominates the production of lactic acid and enzymes at 30°C, and a large amount of insoluble arabinoxylan in the aleurone layer is enzymatically hydrolyzed to release soluble fiber; in the secondary fermentation stage, Lactobacillus brevis continues to metabolize sugars to produce lactic acid at 26°C, and the polyphenol oxidase in red bean flour promotes the formation of ferulic acid, and ferulic acid crosslinks with starch to form resistant starch; in the third-stage low-temperature aging stage, the strains enter the dormant state, and the ferulic acid produced by Lactobacillus brevis further crosslinks with starch molecules to form a more stable resistant starch structure. The metabolic rate of yeast decreases, but the esterase activity increases, driving the conversion of flavor precursor substances into complex flavor compounds.

[0034] 4. During the fermentation process, the process of the pH decreasing from 4.2 to 3.8 is achieved through the acid production by the metabolism dominated by Lactobacillus brevis, without the need to add additional acidic substances. This design ensures the natural acidification and functional optimization of the fermentation process through the division of labor of strains, temperature control, and the synergy of auxiliary ingredients, meeting the technical trend of "no addition" in healthy foods.

Specific Embodiments

[0035] To better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with specific embodiments.

[0036] A sourdough fermentation process includes the following steps:

[0037] (1) Take 100 parts of wheat flour, 60 - 70 parts of purified water, 4 - 5 parts of red bean flour, and 1 - 1.5 parts of pickled cabbage juice, mix and stir them in a container until there are no particles, forming a dough. The wheat flour, red bean flour, and pickled cabbage juice work together synergistically to form a triple system of nutrition - flavor - microbial community regulation. Wheat flour, as the main ingredient, has an aleurone layer, which is rich in substances such as protein, minerals, and B vitamins. Red bean flour and pickled cabbage juice, as auxiliary materials, because red bean flour contains 12 - 15% dietary fiber, 35 - 40% high amylose starch, 20 - 22% protein, and polyphenol oxidase. The dietary fiber and high amylose starch in red bean flour can reduce the GI value of the finished bread; the polyphenol oxidase in red bean flour can promote the formation of ferulic acid and increase the content of resistant starch; pickled cabbage juice contains natural lactic acid bacteria, which can supplement the fermentation flora and inhibit miscellaneous bacteria; the organic acids (lactic acid, acetic acid) in pickled cabbage can regulate the pH and enhance the flavor complexity of the finished bread. At the same time, in the combination of red bean flour and pickled cabbage juice as auxiliary materials, dietary fiber and natural lactic acid bacteria can synergistically improve the gas - holding property (specific volume ≥ 3.5 cm3 / g), and the combined action of ferulic acid and antibacterial peptides can extend the shelf life of the finished bread to 21 - 28 days.

[0038] (2) Transfer the dough to a constant - humidity box at a temperature of 25 ± 1°C and a humidity of RH75 - 80% and let it stand for hydration for 25 - 30 min to form a hydrated dough; the hydration at 25°C promotes the improvement of the dough's extensibility.

[0039] (3) Strain inoculation: Take the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae and prepare a compound bacterial liquid. Atomize and spray 3 - 5 parts of the compound bacterial liquid onto the surface of the hydrated dough, and use a double - helix mixer to stir and mix it at a low speed for 1.5 - 2 min to form a dough to be fermented. Lactobacillus plantarum and red bean flour cooperate synergistically. Dietary fiber enhances water - holding capacity, and polyphenols promote bacterial metabolism, improving the dough's extensibility. Lactobacillus brevis and pickled cabbage juice cooperate synergistically. The lactic acid bacteria in pickled cabbage juice accelerate the secondary fermentation and acidification, extending the shelf life.

[0040] (4) Primary fermentation: Place the dough to be fermented in a fermentation container at 30 ± 1°C and ferment for 8 - 10 h to make the pH naturally drop to 4.2 ± 0.1. During the primary fermentation stage, Lactobacillus plantarum generates xylanase during fermentation, decomposes the insoluble arabinoxylan in the aleurone layer, releases soluble fiber, reduces the roughness, and improves the dough's extensibility; Lactobacillus plantarum can also metabolize the hydrated dough to generate organic acids such as lactic acid and acetic acid, making the pH naturally drop to 4.2 ± 0.1; the 30°C environment optimizes the enzyme activity (such as xylanase) of Lactobacillus plantarum, accelerating fiber decomposition and acid production.

[0041] (5) Secondary fermentation: The dough after primary fermentation is placed in a fermentation container at 26 ± 1 °C for 10 - 12 h to allow the pH to naturally drop to 3.8 ± 0.1. During the secondary fermentation stage, Lactobacillus brevis continues to metabolize sugars to produce lactic acid, and polyphenols in red bean powder generate ferulic acid. Ferulic acid crosslinks with starch to form resistant starch, and lactic acid further reduces the pH to 3.8 ± 0.1. Meanwhile, natural lactic acid bacteria in the pickled cabbage juice synthesize antibacterial peptides. The environment at 26 °C promotes the acid tolerance and metabolic efficiency of Lactobacillus brevis, ensuring continuous acid production at a lower pH.

[0042] (6) Tertiary low-temperature aging: The dough after secondary fermentation is placed in a fermentation container at 4 °C, and the humidity of the fermentation container is controlled at RH92 ± 2%, maintaining a pH of 3.8 ± 0.1. It is refrigerated and fermented for 24 h to form the finished sourdough. The tertiary low-temperature aging stage is a crucial period for Saccharomyces cerevisiae to synthesize flavor substances such as ethyl caproate and phenethyl alcohol. Meanwhile, during this stage, ferulic acid produced by Lactobacillus brevis further crosslinks with starch molecules to form a more stable resistant starch structure. At the same time, low temperature inhibits the activity of spoilage bacteria. In the low-temperature environment of 4 °C, the yeast metabolic rate decreases, but the esterase activity increases, driving the conversion of flavor precursor substances into complex flavor compounds. Controlling the humidity at RH92% can prevent the dough surface from cracking. Tertiary aging stabilizes the starch-gluten-fiber composite network through low temperature (4 °C) and high humidity (RH92 ± 2%), preventing fiber rebound and water loss.

[0043] The sourdough fermentation process of the present invention has at least the following beneficial technical effects:

[0044] 1. The sourdough fermentation process solves problems such as the rough texture and short shelf life of traditional aleurone layer toast bread through the integration of functional raw materials, the regulation of strain compounding, and the control of staged gradient temperature-controlled fermentation. Utilizing the synergistic effect of wheat flour, red bean powder, and pickled cabbage juice, it realizes a comprehensive improvement in nutrition, taste, and flavor, and has significant market competitiveness.

[0045] 2. The fermentation container realizes a three-stage gradient temperature control from 30 °C → 26 °C → 4 °C, matching the optimal activity range of different strains to achieve precise regulation of the microbial community metabolism. At 30 °C in the primary fermentation stage, Lactobacillus plantarum dominates the production of lactic acid and enzymes, and a large amount of insoluble arabinoxylan in the aleurone layer is enzymatically hydrolyzed to release soluble fiber. At 26 °C in the secondary fermentation stage, Lactobacillus brevis continues to metabolize sugars to produce lactic acid, and polyphenol oxidase in red bean powder promotes the production of ferulic acid. Ferulic acid crosslinks with starch to form resistant starch. In the tertiary low-temperature aging stage, the strains enter a dormant state, and ferulic acid produced by Lactobacillus brevis further crosslinks with starch molecules to form a more stable resistant starch structure. The yeast metabolic rate decreases, but the esterase activity increases, driving the conversion of flavor precursor substances into complex flavor compounds.

[0046] 3. During the fermentation process, the pH drops from 4.2 to 3.8 through the acid production by the metabolism dominated by Lactobacillus brevis, without the need to add additional acidic substances. This design ensures the natural acidification and functional optimization of the fermentation process through the division of labor among strains, temperature control, and the synergistic effect of auxiliary materials, meeting the technical trend of "no addition" in healthy foods.

[0047] Preferably, in step (1), in order to inactivate lipoxygenase and trypsin inhibitor, the red bean powder needs to be dry heat treated at a temperature of 80 ± 1°C for 10 - 15 minutes in advance.

[0048] Preferably, the sauerkraut juice needs to be desalted by dialysis membrane in advance, and the salt concentration of the sauerkraut juice ≤ 0.8%. Sodium ions cause osmotic damage to the yeast cell membrane. The salt content of sauerkraut juice is generally > 2%, which will inhibit yeast proliferation. When the salt concentration ≥ 1.5%, the fermentation rate will decrease by 40%. When performing dialysis membrane desalting treatment, the flow rate is controlled at 1.5 L / min. The desalting efficiency of dialysis membrane desalting treatment can reach over 92% and at the same time filter out solid impurities in the sauerkraut juice.

[0049] Preferably, in step (1), the retention rate of the aleurone layer of the wheat flour ≥ 90%, the particle size of the wheat flour is 80 - 120 mesh, and the aleurone layer accounts for 20 - 22% of the wheat flour. The particle size of the wheat flour is preferably 100 mesh.

[0050] Preferably, the mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae is (2 - 3):1:1. As the main strain, Lactobacillus plantarum enzymatically hydrolyzes a large amount of insoluble arabinoxylan in the aleurone layer during the primary fermentation stage, releasing soluble fiber and providing a metabolizable substrate for Lactobacillus brevis; Lactobacillus brevis dominates the acid production in the secondary fermentation stage, precisely controlling the pH to 3.8, inhibiting miscellaneous bacteria, and promoting the formation of resistant starch.

[0051] Preferably, the atomization particle size of the compound bacterial liquid is 50 - 70 μm. The particle size of 50 - 70 μm maximizes the specific surface area of the compound bacterial liquid, and the atomization technology of the compound bacterial liquid improves the uniformity of the distribution of strains. The atomization particle size of the compound bacterial liquid is preferably 60 μm.

[0052] Preferably, the fermentation container adopts a three - stage series fermentation tank; in step (4), the humidity of the three - stage series fermentation tank is controlled at RH82 ± 2%; in step (5), the humidity of the three - stage series fermentation tank is controlled at RH82 ± 2%. When refrigerated at 4°C, if the humidity < RH85%, the dough surface is prone to hardening and cracking. The control system of the three - stage series fermentation tank can monitor parameters such as temperature, oxygen content, and pH value during the reaction process in real time, realizing precise control of the reaction process. At the same time, it is more advanced and energy - saving. Compared with the traditional mechanical stirring fermentation tank, it saves 70% - 80% of electricity and reduces production costs.

[0053] The present invention also provides a aleurone layer toast bread, and the baking process of the aleurone layer toast bread comprises the following steps:

[0054] Step 1: Mix 100 parts of high-gluten flour, 20±1 part of finished sourdough, 3±1 part of trehalose, 1.5±0.1 part of lecithin, 15±1 part of butter, 1±0.1 part of table salt and 45±1 part of 35°C purified water, and process with a variable-speed dough mixer to form a smooth dough with a film thickness ≤0.1 mm; place the dough in an environment of 28±1°C / RH80±2% and let it stand for 40-60 min until the volume expands to 1.8-2.0 times and a continuous air chamber structure is formed inside; the processing with the variable-speed dough mixer is first at low speed for 2 min and then at high speed for 6 min.

[0055] Step 2: Divide the dough into pieces; put the divided dough into a fermentation box and proof for 56-60 min; then send it into an oven and bake and shape it in stages. The baking stages include:

[0056] Stage 1: Upper heat 180°C / lower heat 200°C, steam injection for 2 s, bake for 10 min to form a crust layer. The high-temperature steam rapidly gelatinizes the dough surface to form a crust layer, locking in the internal moisture; the high lower heat promotes caramelization at the bottom and enhances the support force.

[0057] Stage 2: Adjust to upper heat 160°C / lower heat 180°C and continue baking for 25 min until the center temperature reaches 96°C. Lower the upper heat to avoid charring of the surface, and continuous heat penetration makes the center temperature reach 96°C to ensure complete gelatinization of starch; the lower heat of 180°C maintains the bottom structure stability.

[0058] Stage 3: Turn off the lower heat, and circulate hot air at 150°C for 5 min to reduce the surface moisture to ≤8% to obtain the finished aleurone layer toast bread. The hot air circulation evenly dries the surface, and the moisture is reduced to ≤8% to extend the shelf life; turn off the lower heat to prevent excessive hardening of the bottom.

[0059] In the ingredients of the aleurone layer toast bread: High-gluten flour provides high gluten protein to form a strong gluten network, supporting the volume and honeycomb structure of the aleurone layer toast bread. The finished sourdough, as a natural leavening agent, contains metabolites of lactic acid bacteria (lactic acid, acetic acid), which reduces the pH, inhibits miscellaneous bacteria, and extends the shelf life of the aleurone layer toast bread; meanwhile, it imparts a unique sour and fragrant flavor. Trehalose, as a natural humectant, delays the aging of the aleurone layer toast bread. Lecithin, as an emulsifier, promotes the uniform distribution of water and fat, improves the ductility of the dough; combines with starch to delay aging. Butter provides the lubrication of grease, softens the gluten network, and enhances the delicate texture of the aleurone layer toast bread; the milk fat contained imparts a milky flavor. Salt can enhance the elasticity of gluten, inhibit excessive fermentation; balance sweetness and highlight the flavor level. 35°C purified water regulates the dough temperature and activates the yeast activity; 35°C is the optimal proliferation temperature of yeast (≤40°C). The combination of the finished sourdough and trehalose, the low pH of the sourdough delays starch retrogradation, and trehalose further locks in water, synergistically improving the softness of the bread; the combination of lecithin and butter, lecithin emulsifies the grease, and butter lubricates the gluten network, synergistically reducing the chewing hardness and resulting in a delicate texture.

[0060] Variable-speed dough mixer processing stage: In the low-speed dough mixing stage, the raw materials are evenly mixed to avoid damaging the initial gluten formation at high speed; in the high-speed dough mixing stage, the gluten is fully developed to form a smooth dough with a film thickness ≤ 0.1 mm (the gluten is fully extended). Standing stage: The yeast is activated in an environment of 28 ± 1°C / RH80 ± 2% to continuously produce gas, forming a continuous air chamber structure.

[0061] In the proofing stage of step two, the secondary fermentation restores the elasticity of the gluten, refines the air chamber structure, and improves the uniformity of the dough.

[0062] The aleurone layer toast bread of the present invention, through the synergistic effect of scientific ratio (synergy of high-gluten flour and sourdough), precise temperature control (baking in stages), and functional auxiliary materials (trehalose, lecithin, etc.), solves the problems of rough texture, short shelf life, and single flavor of traditional aleurone layer toast, realizes the industrial production goal of high nutrition, low GI, and long shelf life, and has significant market competitiveness.

[0063] The beneficial effects of the sourdough fermentation process of the present invention are illustrated below through several examples and comparative examples. All functional indicators in the examples and comparative examples are tested with the aleurone layer toast bread as the test object to prove the improvement effect of the sourdough fermentation process on the quality of the finished aleurone layer toast bread.

[0064] Example 1

[0065] A sourdough fermentation process includes the following steps:

[0066] (1) Take 100 parts of wheat flour, 65 parts of purified water, 4 parts of red bean flour, and 1.5 parts of pickled cabbage juice, mix and stir them in a container until there are no particles, forming a dough. The red bean flour is pre-treated by dry heat at 80 °C for 15 min. The pickled cabbage juice is pre-treated by desalination with a dialysis membrane until the salt concentration of the pickled cabbage juice ≤ 0.8%. The particle size of the wheat flour is 100 mesh, and the aleurone layer accounts for 20% of the wheat flour. In this process, the salt concentration of the pickled cabbage juice is 0.7%.

[0067] (2) Transfer the dough to a constant humidity box at a temperature of 25 °C and a humidity of RH75% and let it stand and hydrate for 30 min to form a hydrated dough.

[0068] (3) Strain inoculation: Take the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae and prepare a compound strain solution. Atomize and spray 4 parts of the compound strain solution onto the surface of the hydrated dough, and use a double-screw mixer to stir and mix evenly at a low speed for 1.5 - 2 min to form a dough to be fermented. In the compound strain solution, the mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae is 2:1:1; the atomization particle size of the compound strain solution is 60 μm.

[0069] (4) Primary fermentation: Place the dough to be fermented in a three-stage series fermentation tank at 30 °C and ferment for 9 h to make the pH naturally drop to 4.2.

[0070] (5) Secondary fermentation: Place the preliminarily fermented dough in a three-stage series fermentation tank at 26 °C and ferment for 11 h to make the pH naturally drop to 3.8.

[0071] (6) Tertiary low-temperature aging: Place the dough after secondary fermentation in a three-stage series fermentation tank at 4 °C, control the humidity at RH92%, maintain the pH at 3.8, and refrigerate and ferment for 24 h to form a finished sourdough.

[0072] Example 2

[0073] A sourdough fermentation process, including the following steps:

[0074] (1) Take 100 parts of wheat flour, 70 parts of purified water, 5 parts of red bean flour, and 1.5 parts of pickled cabbage juice, mix and stir them in a container until there are no particles, forming a dough. The red bean flour is pre-treated by dry heat at 80 °C for 15 min. The pickled cabbage juice is pre-treated by desalination with a dialysis membrane, and the salt concentration of the pickled cabbage juice ≤ 0.8%. The particle size of the wheat flour is 100 mesh, and the aleurone layer accounts for 20% of the wheat flour. In this process, the salt concentration of the pickled cabbage juice is 0.7%.

[0075] (2) Transfer the dough to a constant humidity box at a temperature of 25 °C and a humidity of RH75% and let it stand and hydrate for 30 min to form a hydrated dough.

[0076] (3) Strain inoculation: Take the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae and prepare a compound bacterial liquid. Atomize and spray 5 parts of the compound bacterial liquid onto the surface of the hydrated dough, and use a double - helix mixer to stir and mix evenly at a low speed for 1.5 - 2 min to form the dough to be fermented. The mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae in the compound bacterial liquid is 2:1:1; the atomization particle size of the compound bacterial liquid is 60 μm.

[0077] (4) Primary fermentation: Place the dough to be fermented in a three - stage series fermentation tank at 30 °C and ferment for 9 h to allow the pH to naturally drop to 4.2.

[0078] (5) Secondary fermentation: Place the preliminarily fermented dough in a three - stage series fermentation tank at 26 °C and ferment for 11 h to allow the pH to naturally drop to 3.8.

[0079] (6) Tertiary low - temperature aging: Place the dough after secondary fermentation in a three - stage series fermentation tank at 4 °C, control the humidity at RH92%, maintain the pH at 3.8, and refrigerate and ferment for 24 h to form the finished sourdough.

[0080] Example 3

[0081] A sourdough fermentation process includes the following steps:

[0082] (1) Take 100 parts of wheat flour, 65 parts of pure water, 4 parts of red bean flour, and 1 part of pickled cabbage juice, mix and stir in a container until there are no particles to form dough. The red bean flour is pre - heat - treated at 80 °C for 10 min. The pickled cabbage juice is pre - treated by dialysis membrane desalination, and the salt concentration of the pickled cabbage juice is ≤0.8%. The particle size of the wheat flour is 100 mesh, and the aleurone layer accounts for 20% of the wheat flour. In this process, the salt concentration of the pickled cabbage juice is 0.6%.

[0083] (2) Transfer the dough to a constant - humidity box at a temperature of 25 °C and a humidity of RH75% and let it stand and hydrate for 30 min to form the hydrated dough.

[0084] (3) Strain inoculation: Take the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae and prepare a compound bacterial liquid. Atomize and spray 3 parts of the compound bacterial liquid onto the surface of the hydrated dough, and use a double - helix mixer to stir and mix evenly at a low speed for 1.5 - 2 min to form the dough to be fermented. The mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae in the compound bacterial liquid is 2:1:1; the atomization particle size of the compound bacterial liquid is 60 μm.

[0085] (4) Primary fermentation: Place the dough to be fermented in a three - stage series fermentation tank at 30 °C and ferment for 9 h to allow the pH to naturally drop to 4.2.

[0086] (5) Secondary fermentation: Place the preliminarily fermented dough in a three - stage series fermentation tank at 26 °C and ferment for 11 h to allow the pH to naturally drop to 3.8.

[0087] (6) Tertiary low-temperature aging: The dough after secondary fermentation is placed in a tertiary series fermentation tank at 4°C, with the humidity controlled at RH92%, maintaining a pH of 3.8, and refrigerated for fermentation for 24 hours to form the finished sourdough.

[0088] Example 4

[0089] A sourdough fermentation process includes the following steps:

[0090] (1) Take 100 parts of wheat flour, 65 parts of purified water, 4 parts of red bean flour, and 1.5 parts of pickled cabbage juice, mix and stir them in a container until there are no particles to form dough. The red bean flour is pre-treated by dry heat at 80°C for 15 minutes. The pickled cabbage juice is pre-treated by desalination with a dialysis membrane, and the salt concentration of the pickled cabbage juice is ≤0.8%. The particle size of the wheat flour is 100 mesh, and the aleurone layer accounts for 20% of the wheat flour. In this process, the salt concentration of the pickled cabbage juice is 0.6%.

[0091] (2) Transfer the dough to a constant humidity box at a temperature of 25°C and a humidity of RH75% and let it stand for hydration for 30 minutes to form the hydrated dough.

[0092] (3) Strain inoculation: Take the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae and prepare a compound bacterial solution. Atomize and spray 4 parts of the compound bacterial solution onto the surface of the hydrated dough, and use a double-screw mixer to stir and mix it at a low speed for 1.5 - 2 minutes to form the dough to be fermented. In the compound bacterial solution, the mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae is 3:1:1; the atomization particle size of the compound bacterial solution is 60 μm.

[0093] (4) Primary fermentation: Place the dough to be fermented in a tertiary series fermentation tank at 30°C and ferment for 8 hours to make the pH naturally drop to 4.2.

[0094] (5) Secondary fermentation: Place the dough after preliminary fermentation in a tertiary series fermentation tank at 26°C and ferment for 10 hours to make the pH naturally drop to 3.8.

[0095] (6) Tertiary low-temperature aging: The dough after secondary fermentation is placed in a tertiary series fermentation tank at 4°C, with the humidity controlled at RH92%, maintaining a pH of 3.8, and refrigerated for fermentation for 24 hours to form the finished sourdough.

[0096] Example 5

[0097] A sourdough fermentation process includes the following steps:

[0098] (1) Take 100 parts of wheat flour, 65 parts of purified water, 4 parts of red bean flour, and 1.5 parts of pickled cabbage juice, mix and stir them in a container until there are no particles, forming a dough. The red bean flour was pre-treated by dry heat at 80 °C for 15 min. The pickled cabbage juice was pre-treated by desalination with a dialysis membrane, and the salt concentration of the pickled cabbage juice ≤ 0.8%. The particle size of the wheat flour is 100 mesh, and the aleurone layer accounts for 22% of the wheat flour. In this process, the salt concentration of the pickled cabbage juice is 0.7%.

[0099] (2) Transfer the dough to a constant humidity box at a temperature of 25 °C and a humidity of RH75% and let it stand for hydration for 30 min to form a hydrated dough.

[0100] (3) Strain inoculation: Take the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae and prepare a compound strain solution. Atomize and spray 4 parts of the compound strain solution onto the surface of the hydrated dough, and use a double-screw mixer to stir and mix evenly at a low speed for 1.5 - 2 min to form a dough to be fermented. In the compound strain solution, the mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae is 2:1:1; the atomization particle size of the compound strain solution is 60 μm.

[0101] (4) Primary fermentation: Place the dough to be fermented in a three-stage series fermentation tank at 30 °C and ferment for 9 h to make the pH naturally drop to 4.2.

[0102] (5) Secondary fermentation: Place the preliminarily fermented dough in a three-stage series fermentation tank at 26 °C and ferment for 11 h to make the pH naturally drop to 3.8.

[0103] (6) Tertiary low-temperature aging: Place the dough after secondary fermentation in a three-stage series fermentation tank at 4 °C, control the humidity at RH92%, maintain the pH at 3.8, and refrigerate and ferment for 24 h to form a finished sourdough.

[0104] Comparative Example 1

[0105] A sourdough fermentation process, including the following steps:

[0106] (1) Take 104 parts of wheat flour, 65 parts of purified water, and 1.5 parts of pickled cabbage juice, mix and stir them in a container until there are no particles, forming a dough. The pickled cabbage juice was pre-treated by desalination with a dialysis membrane, and the salt concentration of the pickled cabbage juice ≤ 0.8%. The particle size of the wheat flour is 100 mesh, and the aleurone layer accounts for 20% of the wheat flour. In this process, the salt concentration of the pickled cabbage juice is 0.7%.

[0107] (2) Transfer the dough to a constant humidity box at a temperature of 25 °C and a humidity of RH75% and let it stand for hydration for 30 min to form a hydrated dough.

[0108] (3) Strain inoculation: Take the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae and prepare a compound bacterial liquid. Atomize and spray 4 parts of the compound bacterial liquid onto the surface of the hydrated dough, and use a double - screw mixer to stir and mix evenly at a low speed for 1.5 - 2 min to form the dough to be fermented. In the compound bacterial liquid, the mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae is 2:1:1; the atomization particle size of the compound bacterial liquid is 60 μm.

[0109] (4) Primary fermentation: Place the dough to be fermented in a three - stage series fermentation tank at 30 °C and ferment for 9 h to allow the pH to naturally drop to 4.2.

[0110] (5) Secondary fermentation: Place the preliminarily fermented dough in a three - stage series fermentation tank at 26 °C and ferment for 11 h to allow the pH to naturally drop to 3.8.

[0111] (6) Tertiary low - temperature aging: Place the dough after secondary fermentation in a three - stage series fermentation tank at 4 °C, control the humidity at RH92%, maintain the pH at 3.8, and refrigerate and ferment for 24 h to form the finished sourdough.

[0112] Control group 2

[0113] A sourdough fermentation process includes the following steps:

[0114] (1) Take 100 parts of wheat flour, 65 parts of pure water, and 4 parts of red bean powder and mix and stir them in a container until there are no particles, forming a dough. The red bean powder is pre - heat - treated at 80 °C for 15 min. The particle size of the wheat flour is 100 mesh, and the aleurone layer accounts for 20% of the wheat flour.

[0115] (2) Transfer the dough to a constant - humidity box at a temperature of 25 °C and a humidity of RH75% and let it stand and hydrate for 30 min to form the hydrated dough.

[0116] (3) Strain inoculation: Take the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae and prepare a compound bacterial liquid. Atomize and spray 4 parts of the compound bacterial liquid onto the surface of the hydrated dough, and use a double - screw mixer to stir and mix evenly at a low speed for 1.5 - 2 min to form the dough to be fermented. In the compound bacterial liquid, the mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae is 2:1:1; the atomization particle size of the compound bacterial liquid is 60 μm.

[0117] (4) Primary fermentation: Place the dough to be fermented in a three - stage series fermentation tank at 30 °C and ferment for 9 h to allow the pH to naturally drop to 4.2.

[0118] (5) Secondary fermentation: Place the preliminarily fermented dough in a three - stage series fermentation tank at 26 ± 1 °C and ferment for 11 h. Without the acidic environment support of the sauerkraut juice, the activity of Lactobacillus brevis is limited, the acid - production efficiency decreases, and the pH only drops to 4.0 - 4.1 and cannot reach 3.8.

[0119] (6) Tertiary low-temperature aging: The dough after secondary fermentation is placed in a tertiary series fermentation tank at 4°C, with the humidity controlled at RH92%, and refrigerated and fermented for 24h to form the finished sourdough.

[0120] Comparative Example 3

[0121] A sourdough fermentation process includes the following steps:

[0122] (1) Take 100 parts of wheat flour, 65 parts of purified water, 4 parts of red bean flour, and 1.5 parts of pickled cabbage juice, mix and stir them in a container until there are no particles to form dough. The red bean flour is pre-treated by dry heat at 80°C for 15min. The pickled cabbage juice is pre-treated by desalination with a dialysis membrane, and the salt concentration of the pickled cabbage juice is ≤0.8%. The particle size of the wheat flour is 100 mesh, and the aleurone layer accounts for 20% of the wheat flour. In this process, the salt concentration of the pickled cabbage juice is 0.7%.

[0123] (2) Transfer the dough to a constant humidity box at 25°C and RH75% and let it stand and hydrate for 30min to form the hydrated dough.

[0124] (3) Strain inoculation: Take the activated Lactobacillus plantarum and prepare it into a bacterial solution, atomize and spray 4 parts of the bacterial solution onto the surface of the hydrated dough, and use a double-screw mixer to stir and mix evenly at a low speed for 1.5 - 2min to form the dough to be fermented. The atomization particle size of the bacterial solution is 60μm.

[0125] (4) Primary fermentation: Place the dough to be fermented in a tertiary series fermentation tank at 30°C and ferment for 9h to make the PH naturally drop to 4.2.

[0126] (5) Secondary fermentation: Place the preliminarily fermented dough in a tertiary series fermentation tank at 26°C and ferment for 11h. Without the addition of Lactobacillus brevis to produce acid, the PH stagnates at about 4.2 and cannot reach 3.8.

[0127] (6) Tertiary low-temperature aging: The dough after secondary fermentation is placed in a tertiary series fermentation tank at 4°C, with the humidity controlled at RH92%, and refrigerated and fermented for 24h to form the finished sourdough.

[0128] Comparative Example 4

[0129] A sourdough fermentation process includes the following steps:

[0130] (1) Take 100 parts of wheat flour, 65 parts of purified water, 4 parts of red bean flour, and 1.5 parts of pickled cabbage juice, mix and stir them in a container until there are no particles to form dough. The red bean flour is pre-treated by dry heat at 80°C for 15min. The particle size of the wheat flour is 100 mesh, and the aleurone layer accounts for 20% of the wheat flour. In this process, the salt concentration of the pickled cabbage juice is 2.0%.

[0131] (2) Transfer the dough to a constant humidity box at a temperature of 25°C and a humidity of RH75% and let it stand for hydration for 30 minutes to form a hydrated dough.

[0132] (3) Strain inoculation: Take the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae and prepare a compound bacterial liquid. Atomize and spray 4 parts of the compound bacterial liquid onto the surface of the hydrated dough, and use a double-screw mixer to stir and mix evenly at a low speed for 1.5 - 2 minutes to form a dough to be fermented. In the compound bacterial liquid, the mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae is 2:1:1; the atomization particle size of the compound bacterial liquid is 60 μm.

[0133] (4) Primary fermentation: Place the dough to be fermented in a three-stage series fermentation tank at 30°C and ferment for 9 hours. If the salt concentration is too high, the activities of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae will decrease, and the acid production ability will drop significantly, causing the pH to only drop to 4.5 - 4.6.

[0134] (5) Secondary fermentation: Place the preliminarily fermented dough in a three-stage series fermentation tank at 26°C and ferment for 11 hours. The metabolism of Lactobacillus brevis is inhibited, and the pH cannot drop below 4.0.

[0135] (6) Tertiary low-temperature aging: Place the dough after secondary fermentation in a three-stage series fermentation tank at 4°C, control the humidity at RH92%, and refrigerate and ferment for 24 hours to form a finished sourdough.

[0136] Control group 5

[0137] A sourdough fermentation process, comprising the following steps:

[0138] (1) Take 100 parts of wheat flour, 65 parts of purified water, 4 parts of red bean flour, and 1.5 parts of pickled cabbage juice, mix and stir in a container until there are no particles to form a dough. The red bean flour is pre-treated by dry heat at 80°C for 15 minutes. The pickled cabbage juice is pre-treated by dialysis membrane desalination, and the salt concentration of the pickled cabbage juice is ≤0.8%. The particle size of the wheat flour is 100 mesh, and the aleurone layer accounts for 20% of the wheat flour. In this process, the salt concentration of the pickled cabbage juice is 0.7%.

[0139] (2) Transfer the dough to a constant humidity box at a temperature of 25°C and a humidity of RH75% and let it stand for hydration for 30 minutes to form a hydrated dough.

[0140] (3) Strain inoculation: Take the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae and prepare a compound bacterial liquid. Atomize and spray 4 parts of the compound bacterial liquid onto the surface of the hydrated dough, and use a double-screw mixer to stir and mix evenly at a low speed for 1.5 - 2 minutes to form a dough to be fermented. In the compound bacterial liquid, the mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae is 2:1:1; the atomization particle size of the compound bacterial liquid is 60 μm.

[0141] (4) Primary fermentation: Place the dough to be fermented in a three-stage series fermentation tank at 30 °C and ferment for 9 h to allow the pH to naturally drop to 4.2.

[0142] (5) Secondary fermentation: Place the preliminarily fermented dough in a three-stage series fermentation tank at 26 °C and ferment for 35 h to allow the pH to naturally drop to 3.8, forming the finished sourdough.

[0143] Comparative Example 6

[0144] A sourdough fermentation process includes the following steps:

[0145] (1) Take 100 parts of wheat flour, 65 parts of pure water, 4 parts of red bean flour, and 1.5 parts of pickled cabbage juice, mix and stir them in a container until there are no particles, forming dough. The red bean flour is pre-treated by dry heat at 80 °C for 15 min. The pickled cabbage juice is pre-treated by dialysis membrane desalination until the salt concentration of the pickled cabbage juice ≤ 0.8%. The particle size of the wheat flour is 100 mesh, and the aleurone layer accounts for 20% of the wheat flour. In this process, the salt concentration of the pickled cabbage juice is 0.7%.

[0146] (2) Transfer the dough to a constant humidity box at a temperature of 25 °C and a humidity of RH75% and let it stand and hydrate for 30 min to form a hydrated dough.

[0147] (3) Strain inoculation: Take the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae and prepare a compound bacterial liquid. Atomize and spray 4 parts of the compound bacterial liquid onto the surface of the hydrated dough, and use a double-screw mixer to stir and mix evenly at a low speed for 1.5 - 2 min to form the dough to be fermented. In the compound bacterial liquid, the mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae is 1:2:1; the atomization particle size of the compound bacterial liquid is 60 μm.

[0148] (4) Primary fermentation: Place the dough to be fermented in a three-stage series fermentation tank at 30 °C and ferment for 9 h. The proportion of Lactobacillus plantarum is too low (1 part), resulting in a decrease in the decomposition efficiency of arabinoxylan, insufficient lactic acid production, and the pH naturally dropping to 4.4. At the same time, the fiber decomposition is insufficient and the gas-holding property decreases, resulting in a specific volume of only 2.7 cm 3 / g.

[0149] (5) Secondary fermentation: Place the preliminarily fermented dough in a three-stage series fermentation tank at 26 °C and ferment for 11 h. Due to the premature activity of Lactobacillus brevis, a high proportion of Lactobacillus brevis (2 parts) produces acid in the primary fermentation stage, lacking sufficient fiber decomposition substrates, and the metabolic efficiency is limited. The pH naturally drops to 4.0. The unqualified pH inhibits the activity of polyphenol oxidase, insufficient production of ferulic acid and antibacterial peptides, a decrease in the production amount of resistant starch (4.5%), and a shorter shelf life (15 days).

[0150] (6) Tertiary low-temperature aging: The dough after secondary fermentation is placed in a tertiary series fermentation tank at 4°C, with the humidity controlled at RH92%, and refrigerated and fermented for 24 hours to form the finished sourdough.

[0151] Table 1 Comparison of various parameters of each example and comparative example

[0152]

[0153] Note: The sensory scoring criteria are mainly comprehensively judged through dimensions such as appearance, smell, taste, flavor, and tissue structure. This score is obtained by selecting at least 50 people to score each dimension of the bread baked from each example and comparative example.

[0154] Conclusion:

[0155] 1. In Examples 1-5, the red bean powder (4-5 parts) is cross-linked by dietary fiber and ferulic acid, increasing the resistant starch content to 10-12.5% (only 3.8% in Comparative Example 1), and reducing the GI value to 52-56 (66 in Comparative Example 1); the polyphenol oxidase in the red bean powder is metabolically coupled with Lactobacillus brevis, increasing the production of ferulic acid and significantly extending the shelf life to 23-27 days (only 14 days in Comparative Example 1); this shows that the red bean powder plays a core role in the sourdough fermentation process of the present invention.

[0156] 2. The dehydrochlorinated sauerkraut juice (salt concentration ≤ 0.8%) ensures yeast activity, with a specific volume stability ≥ 3.3 cm3 / g (the specific volume is only 2.3 cm3 / g when the salt concentration in Comparative Example 4 is 2.0%); the natural lactic acid bacteria in the sauerkraut juice supplement the fermentation flora, inhibit miscellaneous bacteria, and extend the shelf life to 23-27 days (the shelf life is 17 days without sauerkraut juice in Comparative Example 2); this shows the necessity of desalting the sauerkraut juice.

[0157] 3. The strain ratio (2-3):1:1 ensures that Lactobacillus plantarum dominates the decomposition of dietary fiber (the specific volume in Example 2 is 3.7 cm3 / g), Lactobacillus brevis precisely controls the acidity (pH 3.8 ± 0.1), and Saccharomyces cerevisiae synthesizes flavor substances (sensory score ≥ 8.4); the three-stage gradient temperature control (30°C → 26°C → 4°C) optimizes the metabolism of the flora, increasing the specific volume by 30% (the specific volume in Example 2 is 3.7 cm3 / g vs 2.5 cm3 / g in Comparative Example 3); this shows the importance of strain compounding and staged fermentation.

[0158] 4. The aleurone layer retention rate of 20-22% provides rich nutrition, but staged fermentation is required to break the fiber structure (the specific volume in Example 5 is 3.3 cm 3 / g, much larger than ≤ 2.8 cm 3 / g in the traditional process); this shows the synergistic effect of the aleurone layer and the fermentation process.

[0159] 5. Comparative example 5 lacks the third-stage aging process, has only the lactic acid flavor of primary fermentation, lacks the fruity and wheat aroma layers after aging, has a reduced content of flavor substances, and the sensory score is only 7.0.

[0160] 6. The sourdough fermentation process of the present invention, through the synergistic effect of red bean powder, pickled cabbage juice, strain compounding and staged fermentation, systematically solves the problems of rough texture, short shelf life and single flavor of traditional aleurone layer toast, improves the nutrition of aleurone layer toast bread (low GI value of 52 - 56, high resistant starch of 10 - 12.5%), improves the taste (specific volume of 3.3 - 3.8 cm 3 / g, sensory score of 8.4 - 8.8), and has the comprehensive advantage of extending the shelf life (23 - 27 days), meeting the needs of the healthy food market.

[0161] Although the specific implementation manners of the present invention have been described above, those skilled in the art should understand that the specific embodiments we described are illustrative rather than used to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be covered by the scope protected by the claims of the present invention.

Claims

1. A sourdough fermentation process, characterized in that: The steps include: (1) 100 parts of wheat flour, 60-70 parts of purified water, 4-5 parts of red bean powder, and 1-1.5 parts of sauerkraut juice are mixed and stirred in a container until there are no particles, thereby forming a dough; (2) transferring the dough to a constant humidity chamber at a temperature of 25±1° C. and a humidity of 75-80% and allowing it to stand for 25-30 minutes to form a hydrated dough; (3) Inoculation of bacterial strains: Activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae are mixed into a composite bacterial solution, and 3-5 portions of the composite bacterial solution are atomized and sprayed onto the surface of the hydrated dough, and a double-helix mixer is used to stir and mix at a low speed for 1.5-2 minutes to form a dough to be fermented; (4) Primary fermentation: Place the dough to be fermented in a fermentation container at 30±1°C for 8-10 hours to allow the pH to naturally drop to 4.2±0.1; (5) Secondary fermentation: The dough after primary fermentation is fermented in a fermentation container at 26±1°C for 10-12 h to allow the pH to naturally drop to 3.8±0.1; (6) Three-stage low-temperature maturation: The second-fermented dough is placed in a fermentation container at 4°C, the humidity of the fermentation container is controlled at RH92±2%, and the pH is maintained at 3.8±0.

1. It is refrigerated and fermented for 24 hours to form a finished sourdough.

2. The sourdough fermentation process according to claim 1, wherein: In step (1), the red bean powder is first subjected to dry heat treatment at 80±1°C for 10-15 minutes.

3. The sourdough fermentation process according to claim 1, wherein: The sauerkraut juice needs to be desalted in advance, and the salt concentration of the sauerkraut juice is ≤0.8%.

4. The sourdough fermentation process according to claim 1, wherein: In step (1), ultrasonic sorting technology is used to screen wheat flour with a endosperm retention rate of ≥90%, the wheat flour particle size is 80-120 mesh, and the endosperm accounts for 20-22% of the wheat flour.

5. The sourdough fermentation process according to claim 1, wherein: In step (3), the mass ratio of Lactobacillus plantarum, Lactobacillus brevis and Saccharomyces cerevisiae is (2-3): 1:

1.

6. The sourdough fermentation process according to claim 1, wherein: In step (3), the atomized particle size of the composite bacterial solution is 50-70 μm.

7. The sourdough fermentation process according to claim 1, wherein: The fermentation container is a three-stage series fermentation tank; in step (4), the humidity of the three-stage series fermentation tank is controlled at RH82±2%; in step (5), the humidity of the three-stage series fermentation tank is controlled at RH82±2%.

8. A kind of aleurone toast bread, which is a finished sourdough made by the sourdough fermentation process according to any one of claims 1 to 7, characterized in that: The baking process of the aleurone toast bread comprises the following steps: Step 1: 100 parts of high-gluten flour, 20±1 parts of finished sourdough, 3±1 parts of trehalose, 1.5±0.1 parts of lecithin, 15±1 parts of butter, 1±0.1 parts of salt and 45±1 parts of 35°C purified water are mixed and processed by a variable speed dough mixer to form a smooth dough with a film thickness of ≤0.1 mm; the dough is placed in an environment of 28±1°C / RH80±2% and allowed to stand for 40-60 minutes until the volume expands to 1.8-2.0 times and a continuous air chamber structure is formed inside; Step 2: Divide the dough into pieces; put the divided dough into a fermentation box to rise for 56-60 minutes; then put it into the oven and bake it in stages.

9. The process for baking aleurone toast bread according to claim 8, characterized in that: In step 1, the variable speed dough mixer is first at low speed for 2 minutes and then at high speed for 6 minutes.

10. The process for baking aleurone toast bread according to claim 8, characterized in that: In step 2, the following baking stages are included: Stage 1: upper heat 180℃ / lower heat 200℃, steam spray 2s, bake for 10min to form a hard shell layer; Stage 2: Adjust the upper heat to 160℃ / lower heat to 180℃, continue baking for 25 minutes, and the center temperature reaches 96℃; Stage 3: Turn off the lower fire, circulate the upper fire hot air at 150°C for 5 minutes to reduce the surface moisture to ≤8%, and obtain the finished endosperm toast bread.

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