Sour dough, sour dough steamed bun as well as preparation method and application of sour dough and sour dough steamed bun

Abstract

The invention provides sour dough, a sour dough steamed bun and a preparation method and application thereof, and belongs to the technical field of food manufacturing. The sour dough provided by the invention is prepared from 500 parts of wheat flour, 0.05-0.2 part of lactobacillus reuteri and 260 parts of water, and the preparation method of the sour dough comprises the following steps: mixing the wheat flour, the lactobacillus reuteri and the water according to the formula ratio, kneading to form dough, and fermenting for 6.5-10 hours under the conditions that the temperature is 33-40 DEG C and the humidity is 80%-95% to obtain the sour dough. Compared with steamed buns prepared by traditional methods and steamed buns prepared by other kinds of sour dough, the sour dough steamed buns prepared by the sour dough provided by the invention have the advantages that the specific volume is larger, the content of rapidly digestible starch is higher, the speed of hydrolyzing glucose is higher, and the sour dough steamed buns have the effect of rapidly providing energy for human bodies.

Description

Technical Field

[0001] The invention belongs to the technical field of food manufacturing and relates to sour dough, old-fashioned steamed bread and a preparation method and application thereof. Background Art

[0002] Lactobacillus reuteri is a lactic acid bacterium that naturally exists in the intestines of all vertebrates and is a probiotic. Lactobacillus reuteri has a strong ability to adhere to the intestinal mucosa, which can improve the distribution of intestinal flora and antagonize the colonization of harmful bacteria. Lactobacillus reuteri has been used in the manufacturing process of some foods such as yogurt and bread.

[0003] Chinese invention patent CN115769871A provides a method for preparing low-GI old-wheat steamed bread, comprising the following steps: S1, mixing plant lactobacillus, fermented lactobacillus, long bifidobacterium, active dry yeast powder, water and flour, kneading until uniform, and fermenting once to obtain fermented sour dough; S2, quick-freezing the fermented sour dough at -30 to -35°C; S3, taking the quick-frozen frozen sour dough, thawing it, adding water at 35 to 40°C, and then adding flour, dietary fiber and active dry yeast powder, kneading it into steamed bread dough, and fermenting once. Secondary fermentation and steaming to obtain the low GI old-style steamed bread; the mass ratio of Lactobacillus plantarum, Lactobacillus fermentation and Bifidobacterium longum is 10-20:8-15:1-3; the number of viable bacteria of Lactobacillus plantarum is not less than 300 billion CFU / g, the number of viable bacteria of Lactobacillus fermentation is not less than 300 billion CFU / g, and the number of viable bacteria of Bifidobacterium longum is not less than 100 billion CFU / g; the first fermentation is fermented at 33-38°C for 6-8h; the second fermentation is fermented at 33-38°C for 0.5-1h. The old-style steamed bread provided by this technology combines freezing technology to solve the problem of stable industrial production of sour dough, and the flavor is significantly different from ordinary yeast steamed bread, and has a lower GI value than traditional steamed bread, and has higher edible value.

[0004] Chinese invention patent CN117158532A provides a method for making freeze-dried old dough steamed bread, which uses trehalose, sodium glutamate, glycerol, and skim milk powder as freeze-drying protective agents, freeze-drying fresh old dough, crushing and sieving to make freeze-dried old flour, and using enriched flour and freeze-dried old flour as main raw materials, adding appropriate amounts of yeast, edible alkali, fungal amylase, xylanase, lipase and maltogenic amylase to make old dough steamed bread with mellow flavor, uniform texture and excellent taste. This technology solves the problem of differences caused by multi-strain fermentation and the problem of high transportation cost of wet old dough, and provides technical support for the industrial production of old dough steamed bread.

[0005] Chinese invention patent CN115669699A provides a sourdough fermentation agent dry powder and a preparation method thereof. The sourdough fermentation agent dry powder is obtained by mixing sourdough with flour paste, expanding fermentation culture, and then mixing with grain powder, drying at low temperature in stages, and crushing. The sourdough fermentation agent dry powder provided by this technology is easy to store and fully retains the activity of the strain. It not only retains the advantages of traditional sourdough fermentation, avoids the hidden danger of introducing contaminated bacteria, but also extends the shelf life of food, allows dough to form quickly, slows down the aging rate of flour-made food, and has good flavor and high nutritional quality.

[0006] The article "Analysis on the Diversity of Microbial Flora in Sour Dough Starter and Its Effect on the Flavor Characteristics of Steamed Bread" (Yan Bowen, doctoral dissertation from Jiangnan University) points out that the special flavor of steamed bread made from sour dough produced by using Lactobacillus reuteri as a starter is related to the short peptide compounds represented by γ-glutamyl dipeptide produced by Lactobacillus reuteri.

[0007] However, the prior art does not provide a steamed bread with a larger specific volume and faster sugar supply made from Lactobacillus reuteri old dough and a preparation process thereof. Summary of the invention

[0008] In view of this, in order to solve the problems existing in the above-mentioned prior art, the object of the present invention is to provide a sour dough, old-fashioned steamed bread and a preparation method thereof.

[0009] To achieve the above-mentioned purpose, the present invention provides a sourdough, which is made of the following ingredients by weight: 500 parts of wheat flour, 0.05-0.2 parts of Lactobacillus reuteri and 260 parts of water; the preparation method of the sourdough comprises the following steps: mixing the wheat flour, Lactobacillus reuteri and water in a formula amount, kneading the dough to form a dough, and fermenting it for 6.5-10 hours under the conditions of temperature 33-40°C and humidity 80%-95% to obtain the sourdough.

[0010] Preferably, the sourdough is made from the following ingredients by weight: 500 parts of wheat flour, 0.1 parts of Lactobacillus reuteri and 260 parts of water.

[0011] Preferably, the pH of the sourdough is ≤4.

[0012] Preferably, the temperature is 37° C., the humidity is 90%, and the fermentation time is 8.5 h.

[0013] In another aspect, the present invention provides a method for preparing the sourdough.

[0014] In another aspect, the present invention provides an old-style steamed bread, which is made from the above-mentioned sour dough or the sour dough prepared by the above-mentioned preparation method.

[0015] Preferably, the old-style steamed bread is made of the following ingredients by weight:

[0016] 125 parts of wheat flour, 45-55 parts of sourdough, 0.2-0.3 parts of yeast powder, 0.35-0.45 parts of sodium carbonate and 65 parts of water.

[0017] More preferably, the old-style steamed bread is made of the following ingredients by weight:

[0018] 125 parts of wheat flour, 50 parts of sourdough, 0.25 parts of yeast powder, 0.4 parts of sodium carbonate and 65 parts of water.

[0019] On the other hand, the present invention provides a method for preparing the above-mentioned old-style steamed bread, comprising the following steps: mixing a formula amount of wheat flour, sour dough, yeast powder, sodium carbonate and water, kneading the dough, dividing it into blocks, proofing it, and steaming it to obtain the old-style steamed bread.

[0020] More preferably, the kneading time is 8-12 minutes, the proofing temperature is 33-37° C., the proofing time is 60-90 minutes, the proofing humidity is 75%-85%, and the steaming time is 20-30 minutes.

[0021] In the last aspect, the present invention provides the use of the sour dough in preparing steamed bread with old dough.

[0022] Preferably, the old-style steamed bread can be quickly hydrolyzed.

[0023] Preferably, the old-fashioned steamed bread can quickly hydrolyze glucose.

[0024] Preferably, the old-fashioned steamed bread can quickly provide energy to the human body.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] Compared with steamed bread prepared by traditional methods and steamed bread prepared by other types of sour dough, the old-style steamed bread prepared by the sour dough provided by the present invention has a larger specific volume, a higher content of fast-digestible starch, and a faster rate of hydrolyzing glucose, thereby having the effect of quickly providing energy to the human body. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the DFA diagram of the discriminant factors of the electronic nose detecting steamed buns.

[0028] Figure 2 Principal component diagram for electronic nose detecting steamed buns. DETAILED DESCRIPTION

[0029] Terms and Claims of the Present Invention:

[0030] 1. The articles “a”, “an” and “the” include plural referents unless expressly limited to one or more referents otherwise.

[0031] 2. Numerical range: Unless otherwise expressly stated, all ranges or ratios disclosed herein will be understood to include any and all sub-ranges or sub-ratios contained therein. For example, a range or ratio of 1 to 30 stated should be considered to be included between a minimum value of 1 and a maximum value of 30, and any sub-range or sub-ratio, integer, decimal, or sub-range or sub-ratio consisting of integers or decimals including the end points.

[0032] The following non-limiting examples can enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way. The following content is merely an exemplary description of the scope of the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, which should also fall within the scope of the present invention.

[0033] The present invention is further described below by way of specific examples. The various chemical reagents used in the examples of the present invention are obtained through conventional commercial channels unless otherwise specified. Unless otherwise specified, the contents described below are all weight contents. Unless otherwise specified, it is understood that the process is carried out at room temperature.

[0034] In the following examples and comparative examples, the sources of some reagents are shown in Table 1.

[0035] Table 1

[0036] name Product Information Lactobacillus reuteri Jinqiao Biotechnology Co., Ltd. wheat flour Yihai Jiali Xiangmanyuan delicious and strong wheat flour yeast Highly active yeast (low sugar type), Angel Yeast (Yifeng) Co., Ltd. Sodium carbonate Beijing Gusong Economic and Trade Co., Ltd. Lactobacillus rhamnosus Micro-Bio (Suzhou) Co., Ltd. Lactobacillus fermentum Jinqiao Biotechnology Co., Ltd. Lactobacillus plantarum Micro-Bio (Suzhou) Co., Ltd.

[0037] In the following examples, the instruments and equipment used are shown in Table 2.

[0038] Table 2

[0039] Instrument Name factory model Dough Mixer Hauswirt HM740 Chef Machine

[0040] Example 1

[0041] A method for preparing Lactobacillus reuteri sourdough.

[0042] 500 g wheat flour, 0.1 g Lactobacillus reuteri and 260 g water were mixed. The total activity of Lactobacillus reuteri was 1.5 × 10 11 The dough was kneaded into a complete mass using a dough mixer and fermented at 37°C and 90% humidity for 8.5 h, at which time the pH of the dough dropped to 4, and the sourdough was prepared.

[0043] Example 2

[0044] A method for preparing Lactobacillus reuteri sourdough.

[0045] Compared with Example 1, the difference is that the dosage of Lactobacillus reuteri is changed to 0.05 g, and the rest is the same.

[0046] Example 3

[0047] A method for preparing Lactobacillus reuteri sourdough.

[0048] Compared with Example 1, the difference is that the dosage of Lactobacillus reuteri is changed to 0.2 g, and the rest is the same.

[0049] Example 4

[0050] A method for preparing Lactobacillus reuteri sourdough.

[0051] Compared with Example 1, the difference is that the fermentation temperature is changed to 40° C., and the rest are the same.

[0052] Example 5

[0053] A method for preparing Lactobacillus reuteri sourdough.

[0054] Compared with Example 1, the difference is that the fermentation temperature is changed to 33° C., and the rest are the same.

[0055] Example 6

[0056] A method for preparing Lactobacillus reuteri sourdough.

[0057] Compared with Example 1, the difference is that the fermentation humidity is changed to 80%, and the rest is the same.

[0058] Example 7

[0059] A method for preparing Lactobacillus reuteri sourdough.

[0060] Compared with Example 1, the difference is that the fermentation humidity is changed to 95%, and the rest is the same.

[0061] Example 8

[0062] Compared with Example 1, the difference is that the fermentation time is changed to 6.5h, and the rest are the same.

[0063] Example 9

[0064] Compared with Example 1, the difference is that the fermentation time is changed to 10 hours, and the rest are the same.

[0065] Comparative Example 1

[0066] A method for preparing a Lactobacillus rhamnosus sourdough is disclosed. Compared with Example 1, the difference is that Lactobacillus reuteri is replaced by Lactobacillus rhamnosus, as follows.

[0067] Mix 500g wheat flour, 0.025g Lactobacillus rhamnosus and 260g water. The total activity of Lactobacillus rhamnosus is 6×10 11 CFU. The dough was kneaded into a complete mass using a dough mixer and fermented at 37°C and 90% humidity for 11 h, at which time the pH of the dough dropped to 4, and the sourdough was prepared.

[0068] Comparative Example 2

[0069] A method for preparing fermented lactobacillus sourdough is disclosed. Compared with Example 1, the difference is that Lactobacillus reuteri is replaced by Lactobacillus fermentum, as described below.

[0070] Mix 500g wheat flour, 0.1g fermented lactobacillus and 260g water. The total activity of fermented lactobacillus is 1.5×10 11 CFU. The dough was kneaded into a complete mass using a dough mixer and fermented at 37°C and 90% humidity for 6.5 h, at which time the pH of the dough dropped to 4, and the sourdough was prepared.

[0071] Comparative Example 3

[0072] A method for preparing Lactobacillus plantarum sourdough is disclosed. Compared with Example 1, the difference is that Lactobacillus reuteri is replaced by Lactobacillus plantarum, as follows.

[0073] Mix 333g wheat flour, 0.01g Lactobacillus rhamnosus and 173g water. The total activity of Lactobacillus plantarum is 10 12 CFU. The dough was kneaded into a complete mass using a dough mixer and fermented at 37°C and 90% humidity for 6.5 h, at which time the pH of the dough dropped to 4, and the sourdough was prepared.

[0074] Comparative Example 4

[0075] A method for preparing Lactobacillus reuteri sourdough.

[0076] Compared with Example 1, the fermentation temperature was changed to 25° C., the fermentation humidity was changed to 80%, and the rest were the same.

[0077] Comparative Example 5

[0078] A method for preparing Lactobacillus reuteri sourdough.

[0079] Compared with Example 1, the dosage of Lactobacillus reuteri was changed to 0.01 g, and the rest was the same.

[0080] Example 10

[0081] A method for preparing old dough steamed bread.

[0082] Put 125g wheat flour, 50g sour dough, 0.25g yeast and 0.4g sodium carbonate in a dough mixer. Set the initial speed to level 1. Slowly add 65g water while the dough mixer is mixing. After adding the water, adjust the speed to level 3 and mix the dough for 10 minutes until a complete dough is formed. Shape the dough into blocks and shape them into round or oval shapes as needed. Let it rise for 60 minutes at 35℃ and 80% humidity, then steam it for 25 minutes. After steaming, cool it naturally to room temperature to get the old dough steamed buns.

[0083] The sourdough provided by Examples 1 to 9 and Comparative Examples 1 to 5 were used to prepare sourdough steamed bread according to the above-mentioned method for preparing sourdough steamed bread. The steamed breads prepared were respectively denoted as MT1-MT9 and MTd1-MTd5.

[0084] Embodiment 11

[0085] A method for preparing old dough steamed bread.

[0086] Compared with Example 10, the only difference is that the proofing time is changed to 90 minutes, and the other conditions are the same.

[0087] The steamed bread prepared by the above method using the sourdough provided in Example 1 is recorded as MT11.

[0088] Comparative Example 6

[0089] A method for preparing old dough steamed bread.

[0090] Compared with Example 10, the difference is that the mass of sourdough used is changed to 25g, and the rest is the same.

[0091] The steamed bread prepared according to the above method is recorded as MTd6.

[0092] Comparative Example 7

[0093] A method for preparing old dough steamed bread.

[0094] Compared with Example 10, the difference is that the proofing conditions are changed to 30° C., humidity 80%, and the proofing time is 30 minutes, and the rest are the same.

[0095] The steamed bread prepared according to the above method is recorded as MTd7.

[0096] Comparative Example 8

[0097] Preparation method of white steamed bread. Compared with Example 12, the difference is that sour dough and sodium carbonate are not used. The specific preparation method is as follows:

[0098] Put 156g wheat flour and 0.25g yeast in a dough mixer, set the initial speed at gear 1, slowly add 82g water while the dough mixer is mixing, adjust the speed to gear 3 after the water is added, and mix the dough for 10 minutes until a complete dough is formed. Shape the dough into blocks, which can be round or oval as needed. Let it rise for 60 minutes at 35℃ and 80% humidity, then steam it for 25 minutes. After steaming, cool it naturally to room temperature to get the old dough steamed buns.

[0099] The steamed bread prepared according to the above method is recorded as MTd8.

[0100] Effect evaluation

[0101] 1. Specific volume of old dough steamed bread

[0102] The determination method is as follows:

[0103] After the steamed buns are cooked, they are cooled to room temperature. The volume of the buns is measured using the millet filling method, that is, a certain volume of millet is placed in a beaker to smooth the upper contact surface, the volume of the millet is recorded, and then a portion of the millet is poured out, the weighed buns are placed in a beaker, the millet is poured in to smooth the upper surface, the total volume of the millet and the buns is read, the two are subtracted to get the volume of the buns, and the weight of the buns is weighed on a scale (each bun weighs 40g). The specific volume of the buns is calculated using the following formula: λ = V / m. In the formula: λ is the specific volume of the buns, in mL / g; V is the volume of the buns, in mL; m is the mass of the buns, in g.

[0104] The steamed bread prepared by each method was tested for specific capacity according to the above-mentioned determination method. The results are shown in Table 3.

[0105] Table 3

[0106]

[0107]

[0108] It can be seen that the steamed bread prepared from the Lactobacillus reuteri sour dough provided by the present invention has a higher specific volume.

[0109] 2. Sensory evaluation of steamed buns

[0110] Test method: 10 evaluators with food expertise and good sensory acuity were trained and selected to form an evaluation group. The steamed bread prepared in each embodiment and comparative example was subjected to sensory evaluation based on color, taste, appearance, smell, etc. The scoring criteria are shown in Table 4.

[0111]

[0112] Table 4

[0113] The steamed bread prepared by each method was subjected to sensory evaluation according to the above test method. The results are shown in Table 5.

[0114] Table 5

[0115]

[0116]

[0117] It can be seen that the steamed bread prepared with the Lactobacillus reuteri sour dough provided by the present invention has good sensory evaluation results.

[0118] 3. Texture evaluation

[0119] Test method:

[0120] After the steamed buns are cooled to room temperature, the top and bottom of the buns are removed, and a 2cm thick slice is taken from the middle of the buns. The test is measured with a texture analyzer. The test uses the TPA mode and the SMSP / 36R probe. The parameters are set as follows: 1mm / s speed before the test, 1mm / s test speed, 5mm / s speed after the test, 5s compression time, and 5g probe trigger force. During the test, the bun slices should be placed so that the center of the bun and the center of the probe are on the same vertical line to avoid uneven force on the probe and affect the correctness of the experimental results.

[0121] The texture of the steamed bread prepared by each method was tested according to the above-mentioned test method. The results are shown in Table 6.

[0122] Table 6

[0123]

[0124]

[0125] It can be seen that the texture of the steamed bread prepared with the Lactobacillus reuteri sour dough provided by the present invention is significantly softer than the white steamed bread provided by MTd8.

[0126] 4. Electronic nose detection

[0127] Test method:

[0128] Instrument: FOX 4000 electronic nose: 18 MOS sensors (sensor performance see Table 1), equipped with HS-100 automatic sample injector, AG 2301 high-purity air generator, Alpha Soft 12.45 software, Alpha MOS, France.

[0129] Acquisition time: 120 s; data acquisition delay: 1080 s; injection volume: 5000 μL; injection speed: 1000 μL / s. Autosampler parameters: incubator: 150 s; incubation temperature: 80°C; injector temperature: 90°C; 4 parallel runs for each sample.

[0130] The above method was used to detect steamed bread MT1 (Lactobacillus reuteri), MTd1 (Lactobacillus rhamnosus), MTd2 (Lactobacillus fermentum), MTd3 (Lactobacillus plantarum), and MTd8 (white steamed bread), and the discriminant factor DFA diagram was obtained as shown in the figure below: Figure 1 As shown in the figure, the principal component diagram is Figure 2 shown. Figure 1 and Figure 2 Both indicate that the smell of white steamed bread is closer to that of old-fashioned steamed bread made with Lactobacillus reuteri sour dough.

[0131] 5. In vitro starch digestion test results

[0132] 5.1. Digestion sample pretreatment

[0133] The steamed bread was freeze-dried, ground into powder, sieved with 80 mesh, sealed and dried for storage, and each digestion sample should contain about 200 mg of starch. The starch content was measured by a starch test kit.

[0134] 5.2 Reagent preparation

[0135] 5.2.1 Experimental Reagents

[0136] The information of the detection reagents used in this test experiment is shown in Table 7.

[0137] Table 7

[0138]

[0139]

[0140] 5.2.2. Preparation of reagent solution:

[0141] (1) 1 mol / L CH 3 COONa buffer (pH 5.0): Accurately weigh 0.82 g of sodium acetate and dissolve it in 10 mL of deionized water.

[0142] (2) 2 mol / L NaOH: Accurately weigh 40 g of NaOH and dissolve it in a beaker. After cooling to room temperature, transfer it to a 500 mL volumetric flask and shake to volume.

[0143] (3) 2 mol / L HCl: In a fume hood, measure 16.67 mL of concentrated hydrochloric acid (mass fraction 37%) and add water to make up to 100 mL.

[0144] (4) pH 8.0 phosphate buffer: accurately weigh 6.78 g of Na 2 HPO 4 12H 2 O and 0.17 g of NaH 2 PO 4 ·2H 2 O, add water to make up to 100 mL.

[0145] (5) L-leucine standard solution: Accurately weigh 50 mg of L-leucine and add water to make up to 100 mL.

[0146] 5.2.3 Preparation of simulated digestion electrolyte solution

[0147] The electrolyte preparation for oral cavity, stomach and small intestine is shown in Table 8.

[0148] Table 8

[0149] Oral electrolytes Gastric electrolytes Small Intestinal Electrolytes Deionized water (mL) 500 1000 1000 NaCl(g) - 3.1 5.4 KCl(g) 0.562 1.1 0.65 CaCl(g) - 0.15 - NaHCO(g) 0.571 0.6 - KHPO(g) 0.252 - - <![CDATA[MgCl(H 2 O)(g)]]> 0.015 - - <![CDATA[(NH 4 )CO(g)]]> 0.003 - - <![CDATA[CaCl 2 (H 2 O)(g)]]> 0.11 - 0.33 pH 7.0 2.0 7.0

[0150] 5.2.4. Preparation of simulated digestive fluid

[0151] (1) Simulated oral fluid

[0152] Take 100 mL of oral electrolyte solution and add 7500 U of salivary amylase (>5 U / mg) to prepare 75 U / mL simulated oral fluid. Stir magnetically at room temperature for 10 min and adjust the pH of the solution to 7.0 with 2 mol / L NaOH.

[0153] (2) Simulated gastric fluid

[0154] a. Solid samples

[0155] Take 100mL of gastric electrolyte solution and add 2×10 5 U pepsin (> 250U / mg) was prepared into 2000U / mL simulated gastric fluid, and 5mL of CH 3 COONa buffer (1 mol / L, pH 5.0) was added and magnetically stirred at room temperature for 10 min, and the pH of the solution was adjusted to 2.0 with 2 mol / L HCl.

[0156] b. Liquid samples

[0157] Take 100mL of gastric electrolyte solution and add 4×10 5 U pepsin (> 250U / mg) was prepared into 4000U / mL simulated gastric fluid, and 5mL of CH 3 COONa buffer (1 mol / L, pH 5.0) was added and magnetically stirred at room temperature for 10 min, and the pH of the solution was adjusted to 2.0 with 2 mol / L HCl.

[0158] (3) Simulated intestinal fluid

[0159] Pancreatic juice: Weigh 0.4 g pancreatin (4×USP) and dissolve it in 50 mL deionized water to prepare 0.8% pancreatic juice. Stir magnetically at room temperature for 10 min.

[0160] Bile solution: Weigh 1.79 g of No. 3 bile salt and dissolve it in 100 mL of deionized water to prepare a 40 mM bile salt solution. Dissolve evenly at room temperature for later use.

[0161] Simulated intestinal fluid: Take 50 mL of small intestinal electrolyte solution, 100 mL of bile salt solution (40 mM) and 50 mL of pancreatic juice (0.8%), prepare them in a volume ratio of 1:2:1, add 50000 U of pancreatic lipase to 250 U / mL, stir magnetically at room temperature for 10 min, and adjust the pH of the solution to 7.0 with 2 mol / L NaOH.

[0162] 5.3. In vitro simulated digestion experiment

[0163] This in vitro simulated digestion experiment refers to the existing method and is slightly adjusted. The digestion sample should contain about 200 mg of starch, and the amount of starch to simulated oral fluid is 1:1 (w / w), the volume ratio of simulated gastric fluid to simulated intestinal fluid is 1:1 (v / v, 10mL+10mL), and 2 mol / L HCl or 2 mol / L NaOH is used to adjust the pH of the simulated digestive fluid.

[0164] 5.3.1. Simulated digestion pre-experiment

[0165] The amount of HCl or NaOH used was determined by simulated digestion pre-experiments to maintain the required pH for each simulated digestion environment. About 200 mg of simulated oral fluid was mixed with 10 mL of simulated gastric fluid, and the pH value of the digestion mixture was measured after vortexing. The pH of the oral and gastric digestion mixture was adjusted to 2.0 with 2 mol / L HCl, and the volume V of 2 mol / L HCl required was recorded. HCl ; Then add 10mL of simulated intestinal fluid to the gastric juice mixed digestive fluid (the volume ratio of gastric juice mixture: intestinal fluid is 1:1. For samples such as protein samples that are not digested orally, 20mL of simulated intestinal fluid can be added to the gastric juice mixture), mix well and measure the pH value, and adjust the pH of the digestive mixture to 7.0 with 2mol / L NaOH, and record the volume V of 2mol / L NaOH required NaOH .

[0166] 5.3.2. In vitro simulated digestion of starch samples

[0167] 5.3.2.1. Simulated oral digestion Accurately weigh an appropriate amount of digestion sample (containing about 200 mg starch or 200 mg digestible and available carbon) and place it in a stoppered centrifuge tube. Add simulated oral fluid at a ratio of 1:1 (w / w) and mix evenly. Oscillate at 200 rpm and 37°C for 2 min. Immediately add 2 mol / L HCl (V HCl ) was adjusted to pH 2.0 and vortexed to stop oral simulated digestion.

[0168] 5.3.2.2. Simulated gastric digestion

[0169] The oral digestion mixture was transferred to the dissolution cup of the drug dissolution instrument, and 10 mL of simulated gastric fluid was added to each cup. The mixture was shaken and incubated at 200 rpm and 37 °C for 1 h, and then 2 mol / L NaOH (V NaOH ) The pH was adjusted to 7.0 to stop gastric simulated digestion.

[0170] 5.3.2.3. Simulated small intestinal digestion

[0171] Then, 10 mL of simulated small intestinal fluid was added to the digestion system, and the shaking incubation was continued at 200 rpm and 37 °C for 3 h. 500 μL of the sample digestion fluid was aspirated at digestion times of 0, 20, 40, 60, 90, 120, 150, and 180 min, respectively. 4500 μL of anhydrous ethanol was immediately added or a boiling water bath was used for 10 min to inactivate the enzyme. After centrifugation at 5000 rpm for 5 min, the supernatant was taken for subsequent glucose content detection.

[0172] 5.4. Determination of glucose content

[0173] Taking starch digestion samples as an example, in order to draw the hydrolysis curve of starch in the digestion samples, the DNS method or amyloglucosidase-HPLC method is used to determine the glucose concentration in the samples collected at each digestion time. The starch hydrolysis rate of the digestion samples, as well as the contents of rapidly digestible starch, slowly digestible starch and resistant starch in the samples are calculated according to the following formula.

[0174] Starch hydrolysis rate (%) = 0.9 × Gt / TS × 100, fast digestible starch hydrolysis rate (%) = 0.9 × Gt / TS × 100 20min / TS×100, hydrolysis rate of slowly digestible starch (%) = 0.9×(G 120min -G 20min ) / TS×100, hydrolysis rate of resistant starch (%) = (TS-0.9×G 120min ) / TS×100, where 0.9 is the mass conversion coefficient of starch and glucose, Gt is the amount of glucose produced when the intestinal digestion time is t, and G 20min G is the amount of glucose produced in 20 min of simulated intestinal digestion. 120minis the amount of glucose produced during 120 min of simulated intestinal digestion, and TS is the total starch content in the sample.

[0175] 5.4.1. Determination of glucose content by DNS method

[0176] (1) Drawing of glucose standard curve

[0177] Prepare a glucose standard stock solution with a concentration of 1 mg / mL, add 0, 0.2, 0.4, 0.6, 0.8, and 1.0 mL to the test tubes respectively, and add deionized water to make up to 1 mL, prepare glucose standard working solutions with concentration gradients of 0, 0.2, 0.4, 0.6, 0.8, and 1.0 mg / mL respectively; then add 2 mL of DNS reagent, boil in a water bath for 5 min, immediately cool with ice water, make up to 15 mL with deionized water, and mix well; measure the absorbance value at a wavelength of 540 nm, and draw a standard curve with the concentration of glucose solution as the horizontal axis and the absorbance value as the vertical axis.

[0178] (2) Glucose concentration measurement

[0179] Pipette 1mL of supernatant into a 15mL graduated test tube, add 2mL of DNS reagent, boil in water for 5min and immediately cool in ice water, add deionized water to make up the solution to 15mL, mix well, and measure the absorbance at 540nm. Each sample was measured 3 times in parallel, and the glucose concentration in the sample at each digestion time was calculated according to the glucose standard curve, and the hydrolysis rate was calculated.

[0180] 5.5. Test results

[0181] 5.5.1 Contents of fast-digestible starch, slow-digestible starch and resistant starch in different steamed breads

[0182] The contents of fast-digestible starch, slow-digestible starch and resistant starch in the steamed bread prepared in each example and comparative example were detected by the method provided in 5.4.

[0183] After calculation, the contents of the three starches in the steamed bread prepared in each embodiment and comparative example are shown in Table 9.

[0184] Table 9

[0185] Group Fast digestible starch (%) Slowly digestible starch (%) Resistant starch (%) MT1 48.34 28.51 23.15 MT2 39.46 22.89 37.65 MT3 31.86 20.00 48.14 MT4 33.04 23.22 43.74 MT5 33.92 27.40 38.68 MT6 40.32 27.96 31.72 MT7 30.53 27.90 41.57 MT8 36.15 25.43 38.42 MT9 31.06 30.56 38.38 MT11 36.86 30.56 32.58 MTd1 18.86 21.16 59.98 MTd2 13.51 22.20 64.29 MTd3 22.88 21.71 55.41 MTd4 29.83 23.02 47.15 MTd5 28.38 21.76 49.86 MTd6 32.63 21.99 45.38 MTd7 31.97 20.30 47.73 MTd8 33.54 28.59 37.87

[0186] It can be seen that the content of fast-digestible starch in the old-style steamed bread prepared with Lactobacillus reuteri is significantly increased.

[0187] 5.5.2 Starch hydrolysis rate of different steamed bread at different time points

[0188] The starch hydrolysis rates of the steamed bread prepared in each embodiment and comparative example at different time points were measured. The experimental results are shown in Table 10.

[0189] Table 10

[0190]

[0191] It can be seen that the hydrolysis rate of the old-fashioned steamed bread prepared with Lactobacillus reuteri is significantly improved, and it has the function of quickly replenishing glucose.

[0192] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A sourdough, characterized in that Made from the following ingredients by weight: 500 parts of wheat flour, 0.05-0.2 parts of Lactobacillus reuteri and 260 parts of water; The method for preparing the sourdough comprises the following steps: The formula amount of wheat flour, Lactobacillus reuteri and water are mixed, kneaded to form dough, and fermented for 6.5-10 hours under the conditions of temperature of 33-40° C. and humidity of 80%-95% to obtain sour dough.

2. The sourdough according to claim 1, characterized in that Made from the following ingredients by weight: 500 parts of wheat flour, 0.1 parts of Lactobacillus reuteri and 260 parts of water.

3. The sourdough according to claim 1, characterized in that The pH of the sourdough is ≤4.

4. The sourdough according to claim 1, characterized in that The temperature is 37° C., the humidity is 90%, and the fermentation time is 8.5 h.

5. A method for preparing sourdough according to any one of claims 1 to 4.

6. A steamed bread made from old dough, characterized in that: The method is prepared by using the sourdough described in any one of claims 1 to 4 or the sourdough prepared by the preparation method described in claim 5.

7. The old-style steamed bread according to claim 6, characterized in that: The following ingredients are included by weight: 125 parts of wheat flour, 45-55 parts of sourdough, 0.2-0.3 parts of yeast powder, 0.35-0.45 parts of sodium carbonate and 65 parts of water.

8. The old-style steamed bread according to claim 7, characterized in that: Includes the following ingredients: 125 parts of wheat flour, 50 parts of sourdough, 0.25 parts of yeast powder, 0.4 parts of sodium carbonate and 65 parts of water.

9. The method for preparing the old-style steamed bread according to any one of claims 6 to 8, characterized in that: The following steps are involved: The formulated amount of wheat flour, sour dough, yeast powder, sodium carbonate and water are mixed, kneaded, divided into blocks, proofed and steamed to obtain old dough steamed buns.

10. Use of the sour dough according to any one of claims 1 to 4 in preparing old-style steamed bread.

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