Production method for preparing sour dough through staged fermentation of microorganisms and low-GI-value bread

Abstract

The invention provides a production method for preparing sour dough through microbial staged fermentation and low-GI-value bread, the finished sour dough is formed through acidic buffer solution preparation, functional auxiliary material pre-dispersion, main material gradient fusion, dough hydration forming, strain inoculation, primary fermentation, secondary fermentation and third-stage low-temperature ripening, and the prepared finished sour dough is used for preparing bread. The baked bread has the advantages of being low in GI value, good in taste, unique in flavor, high in nutrition and long in shelf life.

Description

Technical Field

[0001] The present invention relates to the field of food bioengineering, and specifically relates to a method for producing sourdough by microbial staged fermentation and low-GI bread.

Background Art

[0002] Traditional sourdough is a natural fermentation flavor composed of flour and water, also known as bread starter. The principle of making bread with sourdough is to use the microorganisms in the sourdough and the starch and minerals in the flour to ferment and increase the volume of the bread, while organic molecules will produce flavors.

[0003] Traditional sourdough fermentation methods mainly include single-strain fermentation, commercial yeast straight-dough process, and additive compounding method. The GI value of the sourdough prepared by single-strain fermentation is between 65 and 75. For example, when using ordinary yeast or lactic acid bacteria for single-strain fermentation, the GI value of the bread is generally higher than 70, with single metabolic products and weak flavor; the hydrolysis of fiber and starch is insufficient to break the cell walls of coarse grains, making the finished product difficult to digest and causing flatulence after eating; the production rate of dietary fiber and resistant starch is low (<5%), resulting in limited nutritional improvement. The GI value of the sourdough prepared by the commercial yeast straight-dough process is between 75 and 85. The fermentation is too fast and the gas distribution is uneven; high temperature is required to inactivate the strains, resulting in zero-active probiotics; it has a high GI value. The GI value of the sourdough prepared by the additive compounding method is between 55 and 70. It involves using chemical additives to improve the dough properties, but there are health concerns of consumers about the additives, and the additives may cover up the problem of insufficient fermentation, resulting in the lack of natural fermentation flavor and nutritional advantages of the product.

[0004] 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

[0005] The present invention aims to solve the technical problems existing in the traditional sourdough fermentation method, and provides a method for producing sourdough by microbial staged fermentation and low-GI bread. By specifically solving the defects of the traditional sourdough fermentation method, the baked bread has the advantages of low GI value, good taste, unique flavor, high nutrition, and long shelf life.

[0006] The present invention is realized as follows: A method for producing sourdough by microbial staged fermentation includes the following steps:

[0007] (1) Preparation of acidic buffer solution: Add 27-28 parts of pure water to a container, and slowly inject 2-2.5 parts of 5% concentration of food-grade acetic acid, and stir at 300-400 rpm for 2-3 min to form a buffer solution with a pH of 4.6-4.8;

[0008] (2) Pre-dispersion of functional excipients: Take 3 - 4 parts of activated oat β-glucan and sprinkle it into the buffer solution. High-speed shear at 1200 - 1500 rpm in a water bath at 40 ± 1°C for 8 - 10 min until it becomes colloidal. Add 4 - 6 parts of flaxseed powder and 5 - 8 parts of red bean powder at intervals and stir and mix until there are no particles;

[0009] (3) Gradient fusion of main ingredients: Add 2 - 5 parts of rye flour and stir at low speed for 1 - 2 min. Sieve and add 50 - 55 parts of whole wheat flour in multiple times and stir at high speed for 8 - 10 min to form dough;

[0010] (4) Dough hydration and shaping: Transfer the dough to a constant humidity box at a temperature of 25 ± 1°C and a humidity of RH75% and let it stand and hydrate for 20 - 25 min to form a hydrated dough;

[0011] (5) Strain inoculation: Take the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae and prepare a compound bacterial solution. Atomize and spray the compound bacterial solution onto the surface of the hydrated dough; Use a double - helix mixer to stir and mix at low speed for 1.5 - 2 min to form a dough to be fermented;

[0012] (6) Primary fermentation: Place the dough to be fermented in a fermentation container at 30 ± 1°C and ferment for 10 - 12 h; During this period, use intermittent dough mixing to control the PH to naturally drop to 4.2 ± 0.1;

[0013] (7) Secondary fermentation: Gradually add food - grade acetic acid with a concentration of 5% to the dough after primary fermentation, adjust the PH to 3.8 ± 0.1, and place it in a fermentation container at 26 ± 1°C for 16 - 18 h;

[0014] (8) Tertiary low - temperature aging: Place the dough after secondary fermentation in a fermentation container at 4°C and refrigerate for 24 h, maintaining the PH at 3.8 ± 0.1 to form the finished sourdough.

[0015] Further, in step (2), the red bean powder needs to be pre - treated by dry heat at a temperature of 80 ± 1°C for 10 - 15 min in advance.

[0016] Further, in step (5), the mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae is 2:1:1, and the compound bacterial solution accounts for 4 - 5% of the dough mass.

[0017] Further, in step (5), the atomization particle size of the compound bacterial solution is 50 - 80 μm.

[0018] Further, in step (6), control the oxygen content in the fermentation container to be 8 - 10%, and control the viscosity of the dough ≤ 1500 cP.

[0019] Further, in step (7), during the process of gradually adding food-grade acetic acid with a concentration of 5%, the dough is stirred at a low speed by a stirring mechanism at a speed lower than 60 rpm.

[0020] On the other hand, a low-GI bread, the GI bread is made from the finished sourdough prepared by the production method of microbial staged fermentation to prepare sourdough, and the steps are as follows:

[0021] Step 1: Mix 70 g of the finished sourdough with 144 g of high-gluten flour, 3.5 g of salt, and 90 g of warm water and knead until a smooth and elastic dough is formed.

[0022] Step 2: Place the dough in a container, cover it with plastic wrap, and conduct the first fermentation at a temperature of 35 - 45 °C for 2 - 3 hours until the dough volume doubles.

[0023] Step 3: Take out the dough after the first fermentation, gently press to exhaust the air, divide and shape it as needed; put the shaped dough into the oven for baking, the oven temperature is 180 - 220 °C, and the baking time is 25 - 30 minutes to obtain the low-GI bread.

[0024] The production method of microbial staged fermentation to prepare sourdough of the present invention has the following beneficial technical effects:

[0025] 1. Through the compounding of main materials and auxiliary materials, the synergistic metabolism of three strains of bacteria, and the control of staged fermentation, a three-dimensional breakthrough in the quality, efficiency, and functionality of sourdough has been achieved. The bread produced has a softer taste, a longer shelf life, and at the same time, the GI of the sourdough can be reduced to 52, which is much lower than that of ordinary sourdough.

[0026] 2. The combination of three strains of bacteria, Lactobacillus plantarum acts as a "shell-breaking expert" to decompose the cereal cell wall; Lactobacillus brevis turns ordinary starch into "anti-digestible" resistant starch; Saccharomyces cerevisiae makes the dough fluffy, soft and non-collapsing, and forms a unique flavor.

[0027] 3. In the staged fermentation: in the primary fermentation, Lactobacillus plantarum plays a leading role at a temperature of 30 °C to gently decompose cereal fiber; in the secondary fermentation, Lactobacillus brevis plays a leading role at a temperature of 25 ± 1 °C to precisely control acid production and produce resistant starch; in the third-stage low-temperature aging, Saccharomyces cerevisiae plays a leading role under low-temperature conditions of 4 °C for starch-gluten network curing, driving the formation of flavor in the final stage.

Specific Embodiment

[0028] In order to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in specific embodiments.

[0029] The present invention provides a production method of microbial staged fermentation to prepare sourdough, including the following steps:

[0030] (1) Preparation of acidic buffer: Add 27 - 28 parts of purified water into a container, and slowly inject 2 - 2.5 parts of 5% food - grade acetic acid. Stir at 300 - 400 rpm for 2 - 3 min to form a buffer solution with a pH of 4.6 - 4.8. Controlling the pH of the acetic acid buffer at 4.6 - 4.8 can inhibit miscellaneous bacteria and create a competitive advantage for lactic acid bacteria; stirring at 300 - 400 rpm forms a micro - bubble structure, which improves the subsequent dispersion efficiency of oat β - glucan.

[0031] (2) Pre - dispersion of functional excipients: Sprinkle 3 - 4 parts of activated oat β - glucan into the buffer solution, and shear at a high speed of 1200 - 1500 rpm in a water bath at 40 ± 1 °C for 8 - 10 min until it becomes colloidal. Add 4 - 6 parts of flaxseed powder and 5 - 8 parts of red bean powder at intervals and stir and mix until there are no particles. Oat β - glucan absorbs water and swells in the acidic buffer to form a hydrated colloid, which evenly wraps the flaxseed and red bean powder particles to prevent caking; the ω - 3 fatty acids in flaxseed powder can strengthen the extensibility of the dough. The addition of red bean powder can not only increase the flavor of the sourdough, but also red bean powder contains 12 - 15% dietary fiber, 35 - 40% high - amylose starch, 20 - 22% protein, and polyphenols; dietary fiber and high - amylose starch synergistically enhance the effect with β - glucan to reduce the GI value of the finished product; red bean protein forms a composite network with the gluten of whole wheat flour to optimize the flavor and structure; shearing the red bean cell wall at a high speed of 1200 - 1500 rpm can release polyphenol oxidase, and polyphenol oxidase couples with Lactobacillus brevis to produce resistant starch, enhancing the metabolic efficiency of Lactobacillus brevis and increasing the production of ferulic acid.

[0032] (3) Gradient fusion of main ingredients: Add 2 - 5 parts of rye flour and stir at a low speed for 1 - 2 min. Sieve 50 - 55 parts of whole wheat flour in multiple times and stir at a high speed for 8 - 10 min to form dough. The combination of whole wheat flour and rye flour as the main ingredients can provide diverse dietary fiber. Add rye flour first and utilize its low - gluten property to form a primary network to prevent excessive cross - linking of whole wheat flour; sieve the whole wheat flour in multiple times to control the water absorption rate of gluten and avoid local hard lumps.

[0033] (4) Dough hydration and shaping: Transfer the dough to a constant - humidity box at a temperature of 25 ± 1 °C and a humidity of RH75% and let it stand for hydration for 20 - 25 min to form a hydrated dough. A continuous protein film is formed during the self - hydration process (the film thickness is controlled at 0.8 - 1.2 mm).

[0034] (5) Inoculation of strains: Prepare a compound bacterial liquid by mixing activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae. Atomize and spray the compound bacterial liquid onto the surface of the hydrated dough; use a double - helix mixer to stir and mix at a low speed for 1.5 - 2 min to form a dough to be fermented.

[0035] Lactobacillus plantarum ferments fermentable sugars in the dough to produce lactic acid, lower the pH, and endow the product with a unique flavor. Since β-glucan mainly exists in the cereal cell wall, which has a tight structure and affects nutrient release and digestion, Lactobacillus plantarum secretes β-glucanase to break down oat β-glucan and β-glucan in the cereal cell wall into short-chain oligosaccharides (DP3-7), breaking the physical barrier and releasing the starch and protein wrapped by the cell wall, making the starch and protein more easily utilized, generating soluble dietary fiber, and enhancing the extensibility of the dough. The short-chain oligosaccharides (DP3-7) act as prebiotics to promote the metabolic activity of subsequent flora. It also creates a porous structure for subsequent starch modification, making the dough softer.

[0036] Lactobacillus brevis can hydrolyze polyphenols in the cereal cell wall to produce ferulic acid. Ferulic acid reacts with the hydroxyl groups in the starch molecules to form a stable ester bond cross-linked structure, converting ordinary starch into resistant starch, increasing the content of resistant starch, and reducing the GI value of the product. Lactobacillus brevis can also synthesize antibacterial peptides to extend the shelf life of the dough and ensure food safety.

[0037] Saccharomyces cerevisiae efficiently converts the polysaccharides released by Lactobacillus plantarum into ethanol and CO2. Ethanol inhibits miscellaneous bacteria, and CO2 makes the dough form a honeycomb structure, expanding the contact surface of the enzymatic hydrolysis reaction. At the same time, the dough can still produce esterase at a low temperature of 4°C, generating key flavor substances such as esters / aldehydes, driving the flavor synthesis in the ripening stage.

[0038] (6) Primary fermentation: Place the dough to be fermented in a fermentation container at 30±1°C and ferment for 10-12h; during this period, use intermittent dough kneading to control the pH to naturally drop to 4.2±0.1, and the viscosity ≤1500 cP. Primary fermentation activates the acid-producing system dominated by Lactobacillus plantarum to form basic flavor substances. The environment of 30±1°C helps to activate the activity of β-glucanase; the intermittent dough kneading is to rotate at 20 rpm for 10 min / stop for 20 min to prevent the settlement of the strains and make the attachment of the strains more uniform.

[0039] (7) Secondary fermentation: Gradually add food-grade acetic acid with a concentration of 5% to the dough after the initial fermentation, adjust the pH to 3.8, and place it in a fermentation container at 26±1°C for 16-18h. Secondary fermentation precisely regulates the pH and temperature. The environment of pH 3.8 and 26±1°C helps the production of ferulic acid, increases the generation of resistant starch, and also helps to promote the synthesis of antibacterial peptides by lactic acid bacteria, inhibiting spoilage bacteria while retaining the enzyme activity. Mechanical agitation is prohibited during secondary fermentation to prevent the destruction of the formed starch-phenolic acid complex.

[0040] (8) Tertiary low-temperature ripening: Place the dough after the secondary fermentation in a fermentation container at 4°C and refrigerate for 24h, maintaining the pH at 3.8±0.1 to form the finished sourdough. Tertiary low-temperature ripening promotes the synthesis of ester / keto flavor substances and stabilizes the colloidal network.

[0041] The method for producing sourdough by microbial staged fermentation of the present invention has the following beneficial technical effects:

[0042] 1. Through the compounding of main materials and auxiliary materials, the synergistic metabolism of three strains of bacteria, and the control of staged fermentation, a three-dimensional breakthrough in the quality, efficiency, and functionality of sourdough has been achieved. The bread produced has a softer taste and a longer shelf life. At the same time, the GI of the sourdough can be reduced to 52, which is much lower than that of ordinary sourdough.

[0043] 2. The combination of three strains of bacteria: Lactobacillus plantarum acts as a "hull breaker" to decompose the cereal cell wall; Lactobacillus brevis converts ordinary starch into resistant starch in an "anti-digestible" form; Saccharomyces cerevisiae makes the dough fluffy, soft, and non-collapsing, and forms a unique flavor. Lactobacillus plantarum ferments the fermentable sugars in the dough to produce lactic acid, reducing the PH and endowing the product with a unique flavor. Since β-glucan mainly exists in the cereal cell wall, with a compact structure that affects nutrient release and digestion, Lactobacillus plantarum secretes β-glucanase to decompose the β-glucan in oat β-glucan and cereal cell walls into short-chain oligosaccharides (DP3-7), breaking the physical barrier and releasing the starch and protein wrapped by the cell wall, making the starch and protein more easily utilized, generating soluble dietary fiber, and improving the extensibility of the dough. The short-chain oligosaccharides (DP3-7) act as prebiotics to promote the metabolic activity of subsequent bacteria; they also create a porous structure for subsequent starch modification, making the dough softer. Lactobacillus brevis can hydrolyze polyphenolic substances in the cereal cell wall to generate ferulic acid, which undergoes an esterification reaction with the hydroxyl group in the starch molecule to form a stable ester bond cross-linked structure, converting ordinary starch into resistant starch, increasing the content of resistant starch, and reducing the GI value of the product. Lactobacillus brevis can also synthesize antibacterial peptides to extend the shelf life of the dough and ensure food safety. Saccharomyces cerevisiae efficiently converts the polysaccharides released by Lactobacillus plantarum into ethanol and CO2. Ethanol inhibits miscellaneous bacteria, and CO2 makes the dough form a honeycomb structure, expanding the contact surface of the enzymatic hydrolysis reaction. At the same time, the dough can still produce esterase at a low temperature of 4°C to generate key flavor substances such as esters / aldehydes, driving the flavor synthesis in the ripening stage.

[0044] 3. In the staged fermentation: Lactobacillus plantarum plays a leading role at 30°C in the primary fermentation to gently decompose cereal fibers; Lactobacillus brevis plays a leading role at 25±1°C in the secondary fermentation to precisely control acid production and produce resistant starch; Saccharomyces cerevisiae plays a leading role at a low temperature of 4°C in the tertiary low-temperature ripening for starch-gluten network solidification, driving the flavor formation in the final stage.

[0045] Preferably, in step (1), the food-grade acetic acid is natural food-grade acetic acid prepared by fermentation. Alcohol is used as the fermentation raw material and poured into the fermentation container, an appropriate amount of acetic acid bacteria is added, and factors such as temperature, humidity, and ventilation are controlled to carry out a fermentation reaction in a suitable environment. After the reaction, high-purity food-grade acetic acid is obtained through distillation and purification. Subsequently, a solvent is added to the high-purity food-grade acetic acid to prepare a 5% concentration of food-grade acetic acid.

[0046] Preferably, in step (2), since the red bean powder contains trypsin inhibitors, the red bean powder needs to be pre-treated by dry heat at a temperature of 80 ± 1 °C for 10 - 15 min.

[0047] Preferably, in step (5), the mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae is 2:1:1. The proportion of Lactobacillus plantarum ensures its dominance in the primary fermentation stage; the compound bacterial liquid accounts for 4 - 5% of the dough mass to balance the fermentation efficiency and the accumulation of metabolic by-products. If calculated based on 1000 g of hydrated dough, the content of the strains in the compound bacterial liquid is 5 - 6 g.

[0048] Preferably, in step (5), the atomization particle size of the compound bacterial liquid is 50 - 80 μm, so that the penetration depth of the bacterial liquid > 3 mm to avoid excessive acidification on the surface layer.

[0049] Preferably, in step (5), the activation method of Lactobacillus plantarum is to use MRS liquid medium and statically culture at 37 °C for 16 hours, allowing the pH value to naturally drop to 5.0, and finally measuring the viable cell count ≥ 5×10 8 CFU / mL, and storing it refrigerated at 4 °C for later use.

[0050] Preferably, in step (5), the activation method of Lactobacillus brevis is to use MRS liquid medium + 1% soluble starch, and stir at a low speed at 30 °C for 24 h. Finally, measuring the enzyme activity ≥ 150 U / mL is considered qualified, and storing it refrigerated for later use.

[0051] Preferably, in step (5), the Saccharomyces cerevisiae is cultured by shaking in ordinary YPD liquid medium at 28 °C for 10 h, and storing it refrigerated for later use.

[0052] Preferably, in step (6), the oxygen content in the fermentation container is controlled at 8 - 10% to promote the gas production and swelling structure of the yeast.

[0053] Preferably, in step (7), during the process of gradually adding 5% concentration of food-grade acetic acid, the dough is stirred at a low speed using a double-screw mixer at a speed lower than 60 rpm, which can prevent local enrichment of the acid solution resulting in a pH gradient difference, ensuring that the pH ≤ 0.1 in the entire area; at the same time, ensuring the uniformity of the colony activity.

[0054] The present invention also includes a low-GI bread, and the finished sourdough obtained by the production method of preparing sourdough by microbial staged fermentation is used for the GI bread, and the steps are as follows:

[0055] Step 1: Mix 70 g of the finished sourdough with 144 g of high-gluten flour, 3.5 g of salt, and 90 g of warm water and knead until a smooth and elastic dough is formed. This ratio is the optimal ratio after multiple experiments. In order to unify the production process of low-GI bread, the following examples and comparative examples all use this ratio to prepare low-GI bread.

[0056] Step 2: Place the dough in a container, cover it with plastic wrap, and conduct the first fermentation at a temperature of 35-45 °C for 2-3 hours until the volume of the dough doubles.

[0057] Step 3: Take out the dough after the first fermentation, gently press to exhaust the air, divide and shape it as needed; put the shaped dough into an oven for baking, the oven temperature is 180-220 °C, and the baking time is 25-30 minutes to obtain the low-GI bread.

[0058] The beneficial effects of the production method of preparing sourdough by microbial staged fermentation according to the present invention are described below through several examples and comparative examples. All functional indicators in the examples and comparative examples are tested with the finally baked low-GI bread to prove the improvement effect of the sourdough production method on the quality of the finished bread.

[0059] Example 1

[0060] A production method of preparing sourdough by microbial staged fermentation includes the following steps:

[0061] (1) Preparation of acidic buffer solution: Add 27-28 parts of pure water to a container, and slowly inject 2-2.5 parts of 5% food-grade acetic acid, and stir at 300-400 rpm for 2-3 min to form a buffer solution with a pH of 4.6-4.8. The specific parts of pure water and food-grade acetic acid are subject to the buffer solution with a pH of 4.6-4.8 that can actually be obtained.

[0062] (2) Predispersion of functional auxiliaries: Sprinkle 4 parts of activated oat β-glucan into the buffer solution, and perform high-speed shearing at 1200-1500 rpm in a 40 °C water bath for 8-10 min until it becomes colloidal, and add 6 parts of flaxseed powder and 8 parts of red bean powder at intervals and stir and mix until there are no particles. The red bean powder was pre-treated by dry heat at 80 °C for 15 min in advance.

[0063] (3) Gradient fusion of main materials: Add 5 parts of rye flour, stir at low speed for 1-2 min, and sieve in 55 parts of whole wheat flour in multiple times, and stir at high speed for 8-10 min to form a dough.

[0064] (4) Dough hydration and shaping: 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 20 - 25 minutes to form a hydrated dough. Spontaneous hydration forms a continuous protein film (film thickness controlled at 0.8 - 1.2 mm).

[0065] (5) Strain inoculation: Take the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae and prepare a compound bacterial solution. Atomize and spray the compound bacterial solution onto the surface of the hydrated dough; use a double - helix mixer to stir evenly at low speed for 1.5 - 2 minutes to form the dough to be fermented. The mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae is 2:1:1, and the compound bacterial solution accounts for 4% of the dough mass. The atomization particle size of the compound bacterial solution is 50 - 80 μm.

[0066] (6) Primary fermentation: Place the dough to be fermented in a fermentation container at 30°C and ferment for 12 hours, controlling the oxygen content in the fermentation container to be 8 - 10%; during this period, use intermittent dough kneading to control the PH to naturally drop to 4.2 and the viscosity ≤ 1500 cP.

[0067] (7) Secondary fermentation: Gradually add 5% - concentration food - grade acetic acid to the dough after primary fermentation, adjust the PH to 3.8, and place it in a fermentation container at 26°C for 18 hours.

[0068] (8) Tertiary low - temperature aging: Place the dough after secondary fermentation in a fermentation container at 4°C and refrigerate for 24 hours, maintaining the PH at 3.8 to form the finished sourdough.

[0069] (9) Mix 70 g of the finished sourdough with 144 g of high - gluten flour, 3.5 g of salt, and 90 g of warm water and knead until a smooth and elastic dough is formed. Place the dough in a container, cover it with plastic wrap, and conduct the first fermentation at a temperature of 40°C for 2.5 hours until the dough volume doubles. Take out the dough after the first fermentation, gently press to exhaust air, divide and shape as needed; place the shaped dough in an oven for baking at an oven temperature of 200°C for 30 minutes to obtain the low - GI bread.

[0070] Example 2

[0071] A production method for preparing sourdough by microbial staged fermentation, comprising the following steps:

[0072] (1) Preparation of acidic buffer solution: Add 27 - 28 parts of pure water to a container, and slowly inject 2 - 2.5 parts of 5% - concentration food - grade acetic acid, and stir at 300 - 400 rpm for 2 - 3 minutes to form a buffer solution with a PH of 4.6 - 4.8.

[0073] (2) Pre-dispersion of functional excipients: Sprinkle 3 parts of activated oat β-glucan into the buffer solution, and shear it at a high speed of 1200 - 1500 rpm in a 40°C water bath for 8 - 10 min until it becomes colloidal. Then, add 5 parts of flaxseed powder and 6 parts of red bean powder at intervals and stir and mix until there are no particles. The red bean powder was pre-treated by dry heat at 80°C for 10 min in advance.

[0074] (3) Gradient fusion of main ingredients: Add 3 parts of rye flour and stir at low speed for 1 - 2 min. Then, add 53 parts of whole wheat flour in multiple sieving steps and stir at high speed for 8 - 10 min to form dough.

[0075] (4) Dough hydration and shaping: Transfer the dough to a constant humidity box at 25°C and 75% relative humidity and let it stand for hydration for 20 - 25 min to form a hydrated dough. Spontaneous hydration forms a continuous protein film (film thickness controlled at 0.8 - 1.2 mm).

[0076] (5) Strain inoculation: Prepare a compound bacterial solution by mixing the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae. Atomize and spray the compound bacterial solution onto the surface of the hydrated dough; use a double - helix mixer to stir and mix at 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 is 2:1:1, and the compound bacterial solution accounts for 4% of the dough mass. The atomization particle size of the compound bacterial solution is 50 - 80 μm.

[0077] (6) Primary fermentation: Place the dough to be fermented in a fermentation container at 30°C and ferment for 10 h, controlling the oxygen content in the fermentation container to be 8 - 10%; during this period, use intermittent dough - kneading to control the pH to naturally drop to 4.1 and the viscosity ≤ 1500 cP.

[0078] (7) Secondary fermentation: Gradually add food - grade acetic acid with a concentration of 5% to the dough after primary fermentation, adjust the pH to 3.8, and place it in a fermentation container at 26°C for 16 h.

[0079] (8) Tertiary low - temperature aging: Place the dough after secondary fermentation in a fermentation container at 4°C and refrigerate for 24 h, maintaining a pH of 3.8 to form the finished sourdough.

[0080] (9) Mix 70 g of the finished sourdough with 144 g of high - gluten flour, 3.5 g of salt, and 90 g of warm water and knead until a smooth and elastic dough is formed. Place the dough in a container, cover it with plastic wrap, and conduct the first fermentation at 40°C for 2.5 h until the dough volume doubles. Take out the dough after the first fermentation, gently press it to exhaust air, divide and shape it as needed; place the shaped dough in an oven and bake at 200°C for 30 min to obtain low - GI bread.

[0081] Example 3

[0082] A method for producing sourdough by microbial staged fermentation, comprising the following steps:

[0083] (1) Preparation of acidic buffer: Add 27-28 parts of purified water into a container, and slowly inject 2-2.5 parts of 5% food-grade acetic acid, and stir at 300-400 rpm for 2-3 min to form a buffer with a pH of 4.6-4.8.

[0084] (2) Predispersion of functional accessories: Sprinkle 3.5 parts of activated oat β-glucan into the buffer, and perform high-speed shearing at 1200-1500 rpm in a 40°C water bath for 8-10 min until it becomes colloidal. Add 5 parts of flaxseed powder and 7 parts of red bean powder at intervals and stir and mix until there are no particles. The red bean powder is pre-treated by dry heat at 80°C for 12 min in advance.

[0085] (3) Gradient fusion of main materials: Add 4 parts of rye flour, stir at low speed for 1-2 min, and sieve in 52 parts of whole wheat flour in multiple batches, and stir at high speed for 8-10 min to form dough.

[0086] (4) Dough hydration and shaping: 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 20-25 min to form a hydrated dough. Spontaneous hydration forms a continuous protein film (film thickness controlled at 0.8-1.2 mm).

[0087] (5) Strain inoculation: Prepare a compound bacterial liquid by mixing activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae, and atomize and spray the compound bacterial liquid onto the surface of the hydrated dough; use a double-screw mixer to stir and mix at 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 is 2:1:1, and the compound bacterial liquid accounts for 5% of the dough mass. The atomization particle size of the compound bacterial liquid is 50-80 μm.

[0088] (6) Primary fermentation: Ferment the dough to be fermented in a fermentation container at 30°C for 11 h, and control the oxygen content in the fermentation container to be 8-10%; during this period, intermittent dough kneading is adopted to control the pH to naturally drop to 4.2, and the viscosity ≤ 1500 cP.

[0089] (7) Secondary fermentation: Gradually add 5% food-grade acetic acid to the dough after primary fermentation, adjust the pH to 3.8, and place it in a fermentation container at 26°C for 17 h.

[0090] (8) Tertiary low-temperature aging: Place the dough after secondary fermentation in a fermentation container at 4°C and refrigerate for 24 h to maintain a pH of 3.8 to form the finished sourdough.

[0091] (9) Mix 70 g of the finished sourdough with 144 g of high-gluten flour, 3.5 g of salt, and 90 g of warm water and knead until a smooth and elastic dough is formed. Place the dough in a container, cover it with plastic wrap, and let it ferment once at 40 °C for 2.5 hours until the dough volume doubles. Take out the dough after the first fermentation, gently press to exhaust air, divide and shape as needed; put the shaped dough into the oven and bake at 200 °C for 30 minutes to obtain low-GI bread.

[0092] Example 4

[0093] A production method for preparing sourdough by microbial staged fermentation includes the following steps:

[0094] (1) Preparation of acidic buffer: Add 27 - 28 parts of purified water to a container, and slowly inject 2 - 2.5 parts of 5% food-grade acetic acid, and stir at 300 - 400 rpm for 2 - 3 min to form a buffer with a pH of 4.6 - 4.8.

[0095] (2) Predispersion of functional auxiliaries: Sprinkle 4 parts of activated oat β-glucan into the buffer, and shear at a high speed of 1200 - 1500 rpm in a 40 °C water bath for 8 - 10 min until it becomes colloidal, and add 4 parts of flaxseed powder and 5 parts of red bean powder at intervals and stir and mix until there are no particles. The red bean powder was pre-treated by dry heat at 80 °C for 15 min in advance.

[0096] (3) Gradient fusion of main ingredients: Add 2 parts of rye flour, stir at low speed for 1 - 2 min, and sieve in 50 parts of whole wheat flour in multiple times, and stir at high speed for 8 - 10 min to form a dough.

[0097] (4) Dough hydration and shaping: 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 20 - 25 min to form a hydrated dough. Spontaneous hydration forms a continuous protein film (film thickness controlled at 0.8 - 1.2 mm).

[0098] (5) Strain inoculation: Prepare a compound bacterial liquid by mixing the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae, and atomize and spray the compound bacterial liquid onto the surface of the hydrated dough; use a double-screw mixer to stir and mix at low speed for 1.5 - 2 min to form a dough to be fermented. The mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae is 2:1:1, and the compound bacterial liquid accounts for 5% of the dough mass. The atomization particle size of the compound bacterial liquid is 50 - 80 μm.

[0099] (6) Primary fermentation: Ferment the dough to be fermented in a fermentation container at 30 °C for 12 h, and control the oxygen content in the fermentation container to be 8 - 10%; during this period, use intermittent dough mixing to control the pH to naturally drop to 4.2, and the viscosity ≤ 1500 cP.

[0100] (7) Secondary fermentation: Gradually add food-grade acetic acid with a concentration of 5% to the preliminarily fermented dough, adjust the pH to 3.8, and place it in a fermentation container at 26 °C for 18 h.

[0101] (8) Tertiary low-temperature aging: Place the dough after secondary fermentation in a fermentation container at 4 °C and refrigerate for 24 h, maintaining a pH of 3.8 to form the finished sourdough.

[0102] (9) Mix and knead 70 g of the finished sourdough with 144 g of high-gluten flour, 3.5 g of salt, and 90 g of warm water until a smooth and elastic dough is formed. Place the dough in a container, cover it with plastic wrap, and conduct the first fermentation at 40 °C for 2.5 hours until the dough volume doubles. Take out the dough after the first fermentation, gently press to exhaust the gas, divide and shape it as needed; place the shaped dough in the oven for baking at an oven temperature of 200 °C for 30 minutes to obtain the low-GI bread.

[0103] Comparative Example 1

[0104] A method for producing sourdough by microbial staged fermentation includes the following steps:

[0105] (1) Preparation of acidic buffer solution: Add 27 - 28 parts of pure water to a container, and slowly inject 2 - 2.5 parts of 5% food-grade acetic acid, and stir at 300 - 400 rpm for 2 - 3 min to form a buffer solution with a pH of 4.6 - 4.8.

[0106] (2) Predispersion of functional excipients: Sprinkle 4 parts of activated oat β-glucan into the buffer solution, and perform high-speed shearing at 1200 - 1500 rpm in a 40 °C water bath for 8 - 10 min until it becomes colloidal, and intermittently add 6 parts of flaxseed powder and 8 parts of red bean powder and stir and mix until there are no particles. The red bean powder was pre-treated by dry heat at 80 °C for 15 min in advance.

[0107] (3) Gradient fusion of main ingredients: Add 5 parts of rye flour and stir at low speed for 1 - 2 min, and sieve in 55 parts of whole wheat flour in multiple batches and stir at high speed for 8 - 10 min to form dough.

[0108] (4) Dough hydration and shaping: 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 20 - 25 min to form a hydrated dough. Spontaneous hydration forms a continuous protein film (film thickness controlled at 0.8 - 1.2 mm).

[0109] (5) Inoculation of strains: Take the activated Lactobacillus plantarum to prepare a bacterial solution, atomize and spray the bacterial solution onto the surface of the hydrated dough; use a double - helix mixer to stir evenly at a low speed for 1.5 - 2 min to form the dough to be fermented. The proportion of the bacterial solution in the dough mass is 4%. The atomization particle size of the bacterial solution is 50 - 80 μm.

[0110] (6) Primary fermentation: Place the dough to be fermented in a fermentation container at 30 °C and ferment for 12 h, control the oxygen content in the fermentation container to be 8 - 10%; during this period, use intermittent dough - kneading, control the pH to naturally drop to 4.2, and the viscosity ≤ 1500 cP.

[0111] (7) Secondary fermentation: Gradually add food - grade acetic acid with a concentration of 5% to the dough after primary fermentation, adjust the pH to 3.8, and place it in a fermentation container at 26 °C for 18 h.

[0112] (8) Tertiary low - temperature aging: Place the dough after secondary fermentation in a fermentation container at 4 °C and refrigerate for 24 h, maintaining a pH of 3.8 to form the finished sourdough.

[0113] (9) Mix 70 g of the finished sourdough with 144 g of high - gluten flour, 3.5 g of salt, and 90 g of warm water and knead until a smooth and elastic dough is formed. Place the dough in a container, cover it with plastic wrap, and conduct the first fermentation at 40 °C for 2.5 h until the dough volume doubles. Take out the dough after the first fermentation, gently press to exhaust air, divide and shape it as needed; put the shaped dough into the oven for baking, the oven temperature is 200 °C, and the baking time is 30 min to obtain the bread.

[0114] Comparative Example 2

[0115] A production method for preparing sourdough by microbial staged fermentation, comprising the following steps:

[0116] (1) Preparation of acidic buffer solution: Add 27 - 28 parts of pure water to a container, and slowly inject 2 - 2.5 parts of 5% food - grade acetic acid, stir at 300 - 400 rpm for 2 - 3 min to form a buffer solution with a pH of 4.6 - 4.8.

[0117] (2) Pre - dispersion of functional excipients: Take 4 parts of activated oat β - glucan and sprinkle it into the buffer solution, perform high - speed shearing at 1200 - 1500 rpm in a 40 °C water bath for 8 - 10 min until it becomes colloidal, and intermittently add 6 parts of flaxseed powder and 8 parts of red bean powder and stir and mix until there are no particles. The red bean powder is pre - treated by dry heat at 80 °C for 15 min in advance.

[0118] (3) Gradient fusion of main ingredients: Add 5 parts of rye flour, stir at a low speed for 1 - 2 min, and sieve in 55 parts of whole wheat flour in multiple batches, stir at a high speed for 8 - 10 min to form a dough.

[0119] (4) Dough hydration and shaping: Transfer the dough to a constant humidity box at 25°C and 75% relative humidity (RH) and let it stand for hydration for 20 - 25 minutes to form a hydrated dough. Spontaneous hydration forms a continuous protein film (film thickness controlled at 0.8 - 1.2 mm).

[0120] (5) Strain inoculation: Prepare a strain solution from commercial yeast, atomize and spray the strain solution onto the surface of the hydrated dough; use a double - helix mixer to stir and mix evenly at low speed for 1.5 - 2 minutes to form the dough to be fermented. The proportion of the strain solution in the dough mass is 4%. The atomization particle size of the strain solution is 50 - 80 μm.

[0121] (6) Ferment the dough to be fermented in a fermentation container at 38°C for 48 hours, control the oxygen content in the fermentation container to be 8 - 10%; during this period, use intermittent dough - kneading to form the finished sourdough.

[0122] (7) Mix 70 g of the finished sourdough with 144 g of high - gluten flour, 3.5 g of salt, and 90 g of warm water and knead until a smooth and elastic dough is formed. Place the dough in a container, cover it with plastic wrap, and conduct the first fermentation at 40°C for 2.5 hours until the dough volume doubles. Take out the dough after the first fermentation, gently press to exhaust the air, divide and shape it as needed; put the shaped dough into an oven for baking, the oven temperature is 200°C, and the baking time is 30 minutes to obtain the bread.

[0123] Comparative Example 3

[0124] A production method for preparing sourdough by microbial staged fermentation includes the following steps:

[0125] (1) Preparation of acidic buffer: Add 27 - 28 parts of pure water to a container, and slowly inject 2 - 2.5 parts of 5% - concentration food - grade acetic acid, stir at 300 - 400 rpm for 2 - 3 minutes to form a buffer with a pH of 4.6 - 4.8.

[0126] (2) Predispersion of functional auxiliaries: Sprinkle 4 parts of activated oat β - glucan into the buffer, perform high - speed shearing at 1200 - 1500 rpm in a 40°C water bath for 8 - 10 minutes until it becomes colloidal, and intermittently add 6 parts of flaxseed powder and 8 parts of red bean powder and stir and mix until there are no particles.

[0127] (3) Gradient fusion of main ingredients: Add 5 parts of rye flour, stir at low speed for 1 - 2 minutes, and sieve in 55 parts of whole wheat flour in multiple times, stir at high speed for 8 - 10 minutes to form dough.

[0128] (4) Dough hydration and shaping: The dough is transferred to a constant humidity chamber at a temperature of 25°C and a humidity of RH75% and left to stand and hydrate for 20 - 25 minutes to form a hydrated dough. Self-hydration forms a continuous protein film (film thickness controlled at 0.8 - 1.2 mm).

[0129] (5) Strain inoculation: The activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae are taken and formulated into a compound bacterial liquid, which is atomized and sprayed onto the surface of the hydrated dough; a double-screw mixer is used to stir and mix evenly at a low speed for 1.5 - 2 minutes to form a dough to be fermented. The mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae is 2:1:1, and the compound bacterial liquid accounts for 4% of the dough mass. The atomization particle size of the compound bacterial liquid is 50 - 80 μm.

[0130] (6) Primary fermentation: The dough to be fermented is placed in a fermentation container at 30°C and fermented for 12 hours, controlling the oxygen content in the fermentation container to be 8 - 10%; during this period, intermittent dough kneading is adopted to control the PH to naturally drop to 4.2 and the viscosity ≤ 1500 cP.

[0131] (7) Secondary fermentation: The dough after primary fermentation is gradually added with 5% concentration of food-grade acetic acid to adjust the PH to 3.8, and placed in a fermentation container at 26°C for 18 hours.

[0132] (8) Tertiary low-temperature aging: The dough after secondary fermentation is placed in a fermentation container at 4°C and refrigerated for 24 hours, maintaining the PH at 3.8 to form a finished sourdough.

[0133] (9) Mix 70 g of the finished sourdough with 144 g of high-gluten flour, 3.5 g of salt, and 90 g of warm water and knead until a smooth and elastic dough is formed. Place the dough in a container, cover it with plastic wrap, and conduct the first fermentation at a temperature of 40°C for 2.5 hours until the dough volume doubles. Take out the dough after the first fermentation, gently press to exhaust air, divide and shape as needed; place the shaped dough in an oven and bake at an oven temperature of 200°C for 30 minutes to obtain bread.

[0134] Control Example 4

[0135] A method for producing sourdough by microbial staged fermentation includes the following steps:

[0136] (1) Preparation of acidic buffer solution: Add 27 - 28 parts of pure water to a container, and slowly inject 2 - 2.5 parts of 5% concentration of food-grade acetic acid, and stir at 300 - 400 rpm for 2 - 3 minutes to form a buffer solution with a PH of 4.6 - 4.8.

[0137] (2) Pre-dispersion of functional excipients: Sprinkle 4 parts of activated oat β-glucan into the buffer solution, and perform high-speed shearing at 1200 - 1500 rpm in a 40°C water bath for 8 - 10 min until it becomes colloidal. Intermittently add 6 parts of flaxseed powder and 8 parts of red bean powder and stir and mix until there are no particles. The red bean powder was previously pretreated by dry heat at 80°C for 15 min.

[0138] (3) Gradient fusion of main ingredients: Add 5 parts of rye flour and stir at low speed for 1 - 2 min. Sieve and add 55 parts of whole wheat flour in multiple times and stir at high speed for 8 - 10 min to form dough.

[0139] (4) Dough hydration and shaping: 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 20 - 25 min to form a hydrated dough. Spontaneous hydration forms a continuous protein film (the film thickness is controlled at 0.8 - 1.2 mm).

[0140] (5) Strain inoculation: Prepare a compound bacterial solution by mixing the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae. Atomize and spray the compound bacterial solution onto the surface of the hydrated dough; use a double-screw mixer to stir and mix evenly at 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 is 1:2:1, and the compound bacterial solution accounts for 4% of the dough mass. The atomization particle size of the compound bacterial solution is 50 - 80 μm.

[0141] (6) Primary fermentation: Place the dough to be fermented in a fermentation container at 30°C and ferment for 12 h, controlling the oxygen content in the fermentation container to be 8 - 10%; during this period, use intermittent dough kneading to control the PH to naturally drop to 4.2 and the viscosity ≤ 1500 cP.

[0142] (7) Secondary fermentation: Gradually add food-grade acetic acid with a concentration of 5% to the dough after primary fermentation, adjust the PH to 3.8, and place it in a fermentation container at 26°C for 18 h.

[0143] (8) Tertiary low-temperature aging: Place the dough after secondary fermentation in a fermentation container at 4°C and refrigerate for 24 h, maintaining the PH at 3.8 to form the finished sourdough.

[0144] (9) Mix 70 g of the finished sourdough with 144 g of high-gluten flour, 3.5 g of salt, and 90 g of warm water and knead until a smooth and elastic dough is formed. Place the dough in a container, cover it with plastic wrap, and perform the first fermentation at 40°C for 2.5 hours until the dough volume doubles. Take out the dough after the first fermentation, gently press to exhaust air, divide and shape as needed; place the shaped dough in an oven and bake at an oven temperature of 200°C for 30 minutes to obtain bread.

[0145] Control Example 5

[0146] A method for producing sourdough by microbial staged fermentation, comprising the following steps:

[0147] (1) Preparation of acidic buffer: Add 27 - 28 parts of pure water to a container, and slowly inject 2 - 2.5 parts of 5% food-grade acetic acid, and stir at 300 - 400 rpm for 2 - 3 min to form a buffer with a pH of 4.6 - 4.8.

[0148] (2) Predispersion of functional excipients: Sprinkle 4 parts of activated oat β-glucan into the buffer, and perform high-speed shearing at 1200 - 1500 rpm in a 40°C water bath for 8 - 10 min until it becomes colloidal. Intermittently add 6 parts of flaxseed powder and 8 parts of red bean powder and stir and mix until there are no particles. The red bean powder was previously pretreated by dry heat at 80°C for 15 min.

[0149] (3) Gradient fusion of main ingredients: Add 5 parts of rye flour, stir at low speed for 1 - 2 min, and sieve in 55 parts of whole wheat flour in multiple batches, and stir at high speed for 8 - 10 min to form dough.

[0150] (4) Dough hydration and shaping: 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 20 - 25 min to form a hydrated dough. Spontaneous hydration forms a continuous protein film (film thickness controlled at 0.8 - 1.2 mm).

[0151] (5) Strain inoculation: Take the activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae and prepare a compound bacterial liquid. Atomize and spray the compound bacterial liquid onto the surface of the hydrated dough; use a double-screw mixer to stir and mix evenly at 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 is 2:1:1, and the compound bacterial liquid accounts for 4% of the dough mass. The atomization particle size of the compound bacterial liquid is 50 - 80 μm.

[0152] (6) Primary fermentation: Place the dough to be fermented in a fermentation container at 30°C and ferment for 12 h, controlling the oxygen content in the fermentation container to be 8 - 10%; during this period, use intermittent dough mixing to control the pH to naturally drop to 4.2, and the viscosity ≤ 1500 cP.

[0153] (7) Secondary fermentation: Gradually add 5% food-grade acetic acid to the dough after primary fermentation, adjust the pH to 3.8, and place it in a fermentation container at 26°C for 36 h to form the finished sourdough.

[0154] (8) Mix 70 g of the finished sourdough with 144 g of high-gluten flour, 3.5 g of salt, and 90 g of warm water and knead until a smooth and elastic dough is formed. Place the dough in a container, cover it with plastic wrap, and conduct the first fermentation at a temperature of 40 °C for 2.5 hours until the dough volume doubles. Take out the dough after the first fermentation, gently press to exhaust air, divide and shape as needed; put the shaped dough into the oven and bake at an oven temperature of 200 °C for 30 minutes to obtain bread.

[0155] Table 1 Parameter comparison of low-GI breads prepared in each example and comparative example

[0156]

[0157] Conclusion:

[0158] 1. By comparing Examples 1-4, Comparative Examples 1 and 2, it can be seen that the synergistic action of three strains and staged fermentation can significantly reduce the GI value of bread (52 vs. traditional 65-85) and increase the resistant starch content (13.1% vs. traditional <5%).

[0159] 2. By comparing Comparative Examples 3 and 4, it can be seen that the pretreatment of red beans and the control of the strain ratio directly affect the production of ferulic acid and the fermentation efficiency. Trypsin inhibitors in the unpretreated red bean powder are not inactivated, inhibiting the metabolic activity of Lactobacillus brevis, resulting in a reduction in the synthesis of antibacterial peptides and a shortened shelf life. An excessive proportion of Lactobacillus brevis leads to an early drop in pH, inhibiting the activity of yeast. Therefore, the imbalance of the strain ratio mainly affects the fermentation uniformity and the generation of resistant starch, but the synthesis of antibacterial peptides still exists, and the reduction in the shelf life of Comparative Example 4 is relatively small.

[0160] 3. By comparing Comparative Example 5, it can be seen that the generation of resistant starch mainly depends on the action of Lactobacillus brevis in the secondary fermentation stage (the cross-linking of ferulic acid and starch), and the core function of the third-stage low-temperature aging is to stabilize the starch-gluten network and drive the synthesis of flavor substances. The third-stage low-temperature aging does not significantly increase the resistant starch content, but it has a decisive role in flavor and shelf life.

[0161] 4. In this case, by specifically solving the defects of the traditional method, the comprehensive advantages of low-GI, high-nutrition, and long shelf life of baked bread are achieved.

[0162] Although the specific implementation manners of the present invention are 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 method for producing sourdough by microbial staged fermentation, characterized in that: It includes the following steps: (1) Preparation of acidic buffer: Add 27 - 28 parts of purified water into a container, and slowly inject 2 - 2.5 parts of 5% food - grade acetic acid, stir at 300 - 400 rpm for 2 - 3 min to form a buffer solution with a pH of 4.6 - 4.8; (2) Pre - dispersion of functional excipients: Sprinkle 3 - 4 parts of activated oat β - glucan into the buffer solution, and shear at a high speed of 1200 - 1500 rpm in a water bath at 40 ± 1 °C for 8 - 10 min until it becomes colloidal. Intermittently add 4 - 6 parts of flaxseed powder and 5 - 8 parts of red bean powder and stir and mix until there are no particles; (3) Gradient fusion of main ingredients: Add 2 - 5 parts of rye flour, stir at a low speed for 1 - 2 min, and sieve 50 - 55 parts of whole wheat flour in multiple times, then stir at a high speed for 8 - 10 min to form a dough; (4) Dough hydration and forming: Transfer the dough to a constant - humidity box at a temperature of 25 ± 1 °C and a humidity of RH75% and let it stand for hydration for 20 - 25 min to form a hydrated dough; (5) Strain inoculation: Prepare a compound bacterial solution by mixing activated Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae. Atomize and spray the compound bacterial solution onto the surface of the hydrated dough; use a double - helix mixer to stir and mix at a low speed for 1.5 - 2 min to form a dough to be fermented; (6) Primary fermentation: Place the dough to be fermented in a fermentation container at 30 ± 1 °C and ferment for 10 - 12 h; during this period, use intermittent dough - kneading to control the pH to naturally drop to 4.2 ± 0.1; (7) Secondary fermentation: Gradually add 5% food - grade acetic acid to the dough after the primary fermentation, adjust the pH to 3.8 ± 0.1, and place it in a fermentation container at 26 ± 1 °C for 16 - 18 h; (8) Tertiary low - temperature aging: Place the dough after the secondary fermentation in a fermentation container at 4 °C and refrigerate for 24 h, maintaining the pH at 3.8 ± 0.1 to form a finished sourdough.

2. The method for producing sourdough by microbial staged fermentation according to claim 1, characterized in that: In step (2), the red bean powder needs to be pre - treated by dry heat at a temperature of 80 ± 1 °C for 10 - 15 min in advance.

3. The method for producing sourdough by microbial staged fermentation according to claim 1, characterized in that: In step (5), the mass ratio of Lactobacillus plantarum, Lactobacillus brevis, and Saccharomyces cerevisiae is 2:1:1, and the compound bacterial solution accounts for 4 - 5% of the dough mass.

4. The method for producing sourdough by microbial staged fermentation according to claim 1, characterized in that: In step (5), the atomization particle size of the compound bacterial solution is 50 - 80 μm.

5. The method for producing sourdough by microbial staged fermentation according to claim 1, characterized in that: In step (6), control the oxygen content in the fermentation container to be 8 - 10%, and control the viscosity of the dough ≤ 1500 cP.

6. The method for producing sourdough by microbial staged fermentation according to claim 1, characterized in that: In step (7), during the process of gradually adding 5% food - grade acetic acid, the dough is stirred at a low speed by a stirring mechanism at a speed lower than 60 rpm.

7. A low-GI bread, characterized in that: The GI - value bread is made from the finished sourdough prepared by the method of producing sourdough through staged fermentation of the microorganism described in any one of claims 1 - 6. The steps are as follows: Step 1: Mix 70 g of the finished sourdough with 144 g of high - gluten flour, 3.5 g of salt, and 90 g of warm water and knead until a smooth and elastic dough is formed. Step 2: Place the dough in a container, cover it with plastic wrap, and conduct a primary fermentation at a temperature of 35 - 45 °C for 2 - 3 hours until the dough volume doubles. Step 3: Take out the dough after the first fermentation, gently press it to exhaust air, divide and shape it as needed; put the shaped dough into the oven for baking, the oven temperature is 180 - 220 °C, and the baking time is 25 - 30 minutes to obtain low-GI bread.

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