Preparation method and application of sour dough with healthy efficacy

Abstract

The invention belongs to the technical field of food, and particularly relates to a preparation method and application of sour dough with a healthy effect. The sour dough consists of the following raw materials: wheat flour, lactobacillus fermentum and water in a mass ratio of 500: (0.1-0.4): 260. The sour dough provided by the invention has a remarkable inhibition effect on alpha-amylase, the specific volume and the texture of the prepared sour dough steamed bun are improved, the preparation process is simple, and the sour dough steamed bun has a wide application prospect in the aspect of reducing postprandial blood sugar rise.

Description

Technical Field

[0001] The invention belongs to the technical field of food, and in particular relates to a preparation method of sourdough with health effects and application thereof. Background Art

[0002] There are various lactobacilli in natural old dough (sour dough), and in the prior art, fermentation is used to provide unique flavor and health benefits for old dough products. However, in related studies at home and abroad, there are few comparisons of the contribution of specific bacteria to the efficacy of old dough steamed bread, and the main research species are mainly concentrated on Lactobacillus plantarum, and there are fewer studies on other species. The present invention compares 4 types of lactobacilli, including Lactobacillus plantarum, Lactobacillus fermentum, Lactobacillus reuteri and Lactobacillus rhamnosus. Among them, Lactobacillus plantarum is the most studied lactobacillus, and is often used as a starter for fermenting sour dough abroad. Through the comparison of the present invention, it is found that Lactobacillus fermentum is a probiotic that can significantly improve the health efficacy of old dough, especially in terms of the impact on starch digestion characteristics, which shows greater advantages than other species.

[0003] For example, Chinese patent CN115769871B discloses a low-GI old-style steamed bread and a preparation method thereof, the preparation method comprising: mixing Lactobacillus plantarum, Lactobacillus fermentum, Bifidobacterium longum, active dry yeast powder, water and flour and kneading them until uniform, performing a primary fermentation, quick-freezing the obtained fermented sour dough, taking out and thawing when necessary, adding water, flour, dietary fiber and active dry yeast powder, performing a secondary fermentation, and steaming. The old-style steamed bread provided by the invention solves the problem of stable industrial production of sour dough by combining freezing technology, and the flavor is significantly different from that of ordinary yeast steamed bread, and has a lower GI value than traditional steamed bread, and has a higher edible value. However, the impact of the invention on the digestion characteristics of amylase and other health effects is not clear.

[0004] Another example is Chinese patent CN104818229A, which discloses a steamed bread fermentation agent and a preparation method thereof. The steamed bread fermentation agent includes fermentation bacteria, wherein the fermentation bacteria are plant lactobacillus, fermented lactobacillus and saccharomyces cerevisiae, and the bacterial cell number ratio of the three is 1:1-10:1-10. The invention selects plant lactobacillus and fermented lactobacillus, which are dominant bacteria in traditional old dough, as representatives of lactobacillus, combines with saccharomyces cerevisiae, and adopts a lactobacillus-alcohol mother combined fermentation method, which is very representative of the bacterial phase composition of traditional old dough, is conducive to simulating the best traditional fermentation agent, and at the same time accelerates the fermentation speed, improves the acidity of the fermented dough, and then improves the taste and flavor of steamed bread, and prolongs the storage time of steamed bread. Its influence on the digestion characteristics of amylase is also not pointed out.

[0005] Another example is Chinese patent CN103814977B, which discloses a fermentation agent for old-faced steamed bread and its preparation method and application, belonging to the field of biotechnology and food. The composition of the raw materials by weight percentage is: 5.00-15.00% steamed bread yeast powder, 5.00-15.00% plant lactobacillus powder, 0.10-5.00% lactobacillus casei powder, 0.10-5.00% lactobacillus acidophilus powder, and 60.00-89.80% edible anhydrous glucose; after the bacterial powder is premixed, it is added to the glucose and then mixed to obtain the product. The amount of the fermentation agent added when making old-faced steamed bread is: 2-10g of old-faced steamed bread fermentation agent is added to every 1g of flour. The invention increases the flavor of old-faced steamed bread and improves the quality of steamed bread, thereby solving the problem of lack of fermentation agent for making old-faced steamed bread and making up for the defect that the characteristic flavor of steamed bread fermented with existing agents is not obvious. The invention also has the above problems.

[0006] Therefore, it is imperative to study a steamed bread that can significantly improve the health benefits of old dough. Summary of the invention

[0007] Based on the problems existing in the prior art, the present invention provides a preparation process of old-style steamed bread with health benefits, and clarifies the efficacy of the old-style steamed bread prepared by the invention through experiments such as α-amylase inhibition rate and in vitro starch digestion.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] In one aspect, the present invention provides a sourdough with health benefits, which comprises the following raw materials: wheat flour, lactobacillus and water.

[0010] Preferably, the mass ratio of wheat flour, lactobacillus and water in the sour dough is 500:0.1-0.4:260.

[0011] More preferably, the mass ratio of wheat flour, lactobacillus and water in the sourdough is 500:0.1-0.2:260.

[0012] Further preferably, the mass ratio of wheat flour, lactobacillus and water in the sourdough is 500:0.1:260.

[0013] Preferably, the lactobacillus in the sour dough is fermented lactobacillus, which is commercial straight-head freeze-dried bacterial powder purchased from Jinqi Bio Group Co., Ltd., and has a viable bacterial count of 150 billion CFU / g.

[0014] In another aspect, the present invention also provides a method for preparing sourdough with health benefits, comprising the following steps:

[0015] (1) Mix wheat flour, water and lactobacillus, and knead the mixture to form a dough;

[0016] (2) fermenting the dough in step (1) to obtain sourdough.

[0017] Preferably, in step (2), the fermentation temperature is 35-38° C., the humidity is 90%, and the fermentation time is 6.5 h.

[0018] Preferably, the pH of the sourdough in step (2) is 4.

[0019] On the other hand, the present invention also provides a use of sour dough with health benefits in making steamed bread.

[0020] The present invention also provides a method for preparing steamed bread with health benefits, comprising the following steps:

[0021] (1) Mix wheat flour, sourdough, yeast, alkali and water, and knead the dough to form a dough;

[0022] (2) The dough obtained in step (1) is allowed to ferment and steamed to obtain steamed buns.

[0023] Preferably, the mass ratio of the wheat flour, sourdough, yeast, alkali and water in step (1) is: 125:48-50:0.25:0.4:65.

[0024] More preferably, the mass ratio of the wheat flour, sourdough, yeast, alkali and water in step (1) is: 125:49-50:0.25:0.4:65.

[0025] Further preferably, the mass ratio of the wheat flour, sourdough, yeast, alkali and water in step (1) is: 125:50:0.25:0.4:65.

[0026] Preferably, the proofing temperature in step (2) is 36-37° C., the proofing humidity is 80%, and the proofing time is 60 min.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The lactobacillus steamed bread prepared by the present invention has simple ingredients and preparation process and is easy to produce on a large scale.

[0029] (2) The lactobacillus steamed bread prepared by the present invention has excellent taste and flavor.

[0030] (3) The lactobacillus steamed bread prepared by the present invention significantly improves the starch digestion characteristics and specific volume of the steamed bread, and has a better inhibitory effect on α-amylase.

[0031] (4) The present invention adopts commercial straight-head freeze-dried bacterial powder, which does not require expansion culture and is not only suitable for large-scale standardized production, but also meets the needs of consumers in home scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a discriminant factor DFA diagram of the electronic nose determination using Example 1 and Comparative Examples 1-2;

[0033] Figure 2 It is a principal component diagram of the electronic nose measured by application example 1 and application comparative examples 1-2;

[0034] Figure 3 Schematic diagram of the electronic tongue of Application Example 1 and Comparative Examples 1-2;

[0035] Figure 4 It is a diagram showing the in vitro digestion results of Application Example 1 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0036] The technical scheme of the present invention is clearly and completely described below with specific implementation methods. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. The materials, reagents, etc. used, if not otherwise specified, are reagents and materials available from commercial sources.

[0037]

[0038]

[0039] Example 1 A sourdough with health benefits and a method for preparing the same

[0040] It is composed of the following raw materials:

[0041] 500g wheat flour, 0.1g fermented lactobacillus with an activity of 1500CFU / g, 260g water.

[0042] The method for preparing the sourdough comprises the following steps:

[0043] (1) 500 g of wheat flour, 260 g of water and 0.1 g of fermented lactobacillus with an activity of 1500 CFU / g were mixed and kneaded to form a dough;

[0044] (2) fermenting the dough in step (1) at 37° C. and 90% humidity for 6.5 h to obtain a fermented lactobacillus sour dough.

[0045] Example 2 A sourdough with health benefits and a method for preparing the same

[0046] It is composed of the following raw materials:

[0047] 500g wheat flour, 0.4g fermented lactobacillus with an activity of 1500CFU / g, 260g water.

[0048] The method for preparing the sourdough comprises the following steps:

[0049] (1) 500 g of wheat flour, 260 g of water and 0.4 g of fermented lactobacillus with an activity of 1500 CFU / g were mixed and kneaded to form a dough;

[0050] (2) fermenting the dough in step (1) at 37° C. and 90% humidity for 6.5 h to obtain a fermented lactobacillus sour dough.

[0051] Comparative Example 1 A sourdough with health benefits and a preparation method thereof

[0052] It is composed of the following raw materials:

[0053] 500g wheat flour, 0.025g Lactobacillus rhamnosus with an activity of 6000 CFU / g, and 260g water.

[0054] (1) 500 g of wheat flour, 260 g of water and 0.025 g of Lactobacillus rhamnosus with an activity of 6000 CFU / g were mixed and kneaded to form a dough;

[0055] (2) fermenting the dough in step (1) at 37° C. and a humidity of 90% for 11 h to obtain a Lactobacillus rhamnosus sourdough.

[0056] Comparative Example 2 A sourdough with health benefits and a preparation method thereof

[0057] It is composed of the following raw materials:

[0058] 333g wheat flour, 0.01g Lactobacillus plantarum with an activity of 10000 CFU / g, 173g water.

[0059] (1) 333 g of wheat flour, 173 g of water and 0.01 g of Lactobacillus plantarum with an activity of 10,000 CFU / g were mixed and kneaded to form a dough;

[0060] (2) fermenting the dough in step (1) at 37° C. and 90% humidity for 6.5 h to obtain Lactobacillus plantarum sour dough.

[0061] Comparative Example 3 A sourdough was prepared according to the method of Example 2 in patent CN115769871B, and the specific operation steps are as follows:

[0062] 0.2 g (300 billion CFU / g) of Lactobacillus plantarum, 0.15 g (300 billion CFU / g) of Lactobacillus fermentum, 0.03 g (100 billion CFU / g) of Bifidobacterium longum, 100 g of water and 200 g of flour are mixed evenly, kneaded until the dough is uniform, and fermented once at 37° C. and 75% humidity for 8 h to obtain sourdough.

[0063] Comparative Example 4 A sourdough was prepared according to the method of Example 3 in patent CN115769871B, and the specific operation steps are as follows:

[0064] 0.1 g (300 billion CFU / g) of Lactobacillus plantarum, 0.08 g (300 billion CFU / g) of Lactobacillus fermentum, 0.01 g (100 billion CFU / g) of Bifidobacterium longum, 100 g of water and 200 g of flour are mixed evenly, kneaded until the dough is uniform, and fermented once at 37° C. and 85% humidity for 7 h to obtain sourdough.

[0065] Comparative Example 5 A sourdough was prepared according to the method of Example 3 in patent CN115812905A, and the specific operation steps are as follows:

[0066] 0.2 g (300 billion CFU / g) of Lactobacillus plantarum, 0.1 g (100 billion CFU / g) of Lactobacillus rhamnosus, 0.25 g of active dry yeast powder (Angel active dry yeast), 110 g of water and 200 g of flour are mixed evenly, kneaded until the dough is uniform, and fermented once at 37° C. and 80% humidity for 8 h to obtain fermented sour dough.

[0067] Application Examples 1-2 and Comparative Examples 1-5 A method for preparing old-style steamed bread with health benefits comprises the following steps:

[0068] (1) wheat flour, the sourdough prepared in Examples 1-2 and Comparative Examples 1-5, yeast, alkali, and water were mixed in a ratio of 125:50:0.25:0.4, and kneaded to form a dough;

[0069] (2) The dough obtained in step (1) is proofed at 35° C. and 80% humidity for 60 min, and steamed to obtain corresponding lactobacillus steamed buns.

[0070] Technical Effects

[0071] 1. α-Amylase inhibition assay

[0072] The specific steps are as follows:

[0073] (1) Take 0.05 g of soluble starch and mix it with deionized water until it becomes a paste. Then add 80 mL of boiling water and continue boiling for 10 min. After rapid cooling with ice water, dilute to 100 mL for later use. Add 0.1471 g of 10.2 U / mg α-amylase to 3 mL of water and vortex to mix evenly.

[0074] (2) Add 40 mL (0.5 mg / mL) of soluble starch solution into a flask and place the flask in a 37°C constant temperature shaking water bath for 5 min.

[0075] (3) 2 g of the sourdough (steamed) and white flour dough (steamed) prepared in Examples 1-2 and Comparative Examples 1-5 and 3 mL (500 U / mL) of α-amylase solution were added to the preheated Erlenmeyer flasks, respectively, and the mixture was shaken in a water bath for 30 min; the white flour dough was the blank group; and no α-amylase solution was added to the blank background group and the sample background group.

[0076] (4) Shake evenly, remove 4 mL of the suspension, inactivate the enzyme in a boiling water bath for 5 min, and then centrifuge (6000 r / min, 10 min, 4°C).

[0077] (5) Take 100 μl of supernatant, add 500 μl of water to dilute, then add 400 μl of DNS (a total of 1 ml), vortex to mix evenly, boil in a boiling water bath for 5 min, take out and cool in cold water;

[0078] (6) After vortex mixing, 500 μL was aspirated, 2 ml of water was added for dilution, vortex mixing was performed, and 200 μL of the reaction stop solution was aspirated into a 96-well plate. The absorbance at 540 nm was measured by an ELISA reader, and represented by A. The inhibition rate was calculated according to formula (1). The test was repeated 3 times in parallel, and the results are shown in Table 1.

[0079]

[0080] Table 1 Inhibition rate of α-amylase in each application example

[0081] α-Amylase inhibition rate (%) White flour dough 0a Example 1 15.13±2.32b Example 2 16.39±1.14b Comparative Example 1 7.30±5.91c Comparative Example 2 6.13±0.71c Comparative Example 3 13.08±1.49d Comparative Example 4 12.25±0.73e Comparative Example 5 7.06±2.2c

[0082] Note: Different letters in the same column indicate significant differences (p < 0.05)

[0083] It can be seen from the data in Table 1 that the inhibition rate of α-amylase by the sourdough in Examples 1-2 is significantly higher than that in Comparative Examples 1-5, which indicates that the fermented lactobacillus steamed bread obtained by the formula of the present invention can achieve better results than that obtained by other strains.

[0084] 2. Determination of specific volume

[0085] The steamed buns and ordinary white steamed buns prepared by application examples 1-2 and application comparison examples 1-5 were steamed and cooled to room temperature, and the volume of the steamed buns was measured by the millet filling method, that is, a certain volume of millet was placed in a beaker to smooth the upper contact surface, and the volume of the millet was recorded, and then a part of the millet was poured out, and the weighed steamed buns were placed in the beaker, and the millet was introduced to smooth the upper surface, and the total volume of the millet and the steamed buns was read out, and the volume of the steamed buns was obtained by subtracting the two, and the weight of the steamed buns was weighed with a balance. The specific volume of the steamed buns λ=V / m was calculated according to the following formula. In the formula: λ is the specific volume of the steamed buns, in mL / g; V is the volume of the steamed buns, in mL; m is the mass of the steamed buns, in g. The results are shown in Table 2.

[0086] Table 2 Specific volume of each application example

[0087] Specific volume (mL / g) Ordinary white steamed bread 2.13±0.03a Application Example 1 3.00±0.10b Application Example 2 3.06±0.03b Application Comparative Example 1 2.41±0.06c Application Comparative Example 2 2.50±0.05d Application Comparative Example 3 2.89±0.08e Application Comparative Example 4 2.76±0.08f Application Comparative Example 5 2.58±0.08g

[0088] Note: Different letters in the same column indicate significant differences (p < 0.05)

[0089] It can be seen from the data in Table 2 that the steamed bread prepared by using Example 1-2 has significantly improved specific volume. Compared with ordinary white steamed bread, Lactobacillus plantarum steamed bread, Lactobacillus rhamnosus steamed bread and steamed bread with a mixture of two or more lactobacilli, the fermented Lactobacillus steamed bread shows higher performance.

[0090] 3. Determination of texture

[0091] After the steamed buns prepared by Application Example 1 and Application Comparative Examples 1 and 2 and ordinary white steamed buns were cooled to room temperature, the top and bottom of the steamed buns were removed, the middle part of the steamed buns was taken, and a thin slice with a thickness of 2 cm was taken for measurement using a texture analyzer. The test used the TPA mode, and the test used the SMS P / 36R probe. The parameters were set as follows: speed before the test 1mm / s, test speed 1mm / s, speed after the test 5mm / s, compression time 5s, and probe trigger force 5g. During the test, the steamed bun slices should be placed so that the center of the steamed bun and the center of the probe are on the same vertical line to avoid uneven force on the probe and affecting the correctness of the experimental results. Repeat the experiment 3 times and take the average value. The measurement results are shown in Table 3.

[0092] Table 3 Texture of each application example

[0093]

[0094] It can be seen from the data in Table 3 that the steamed buns prepared using Example 1 are lower in hardness, higher in elasticity, lower in stickiness, lower in chewiness, and higher in resilience than the steamed buns prepared using the other various fungi. These characteristics indicate that the steamed buns prepared using Example 1 are more elastic and softer and have a better taste.

[0095] 4. Electronic nose measurement

[0096] Instrument: FOX 4000 electronic nose: 18 MOS sensors, equipped with HS-100 autosampler, AG 2301 high-purity air generator, Alpha Soft 12.45 software, Alpha MOS, France.

[0097] The steamed bread prepared by using Example 1 and Comparative Examples 1 and 2 and ordinary white steamed bread were tested. The acquisition time was 120s; the data acquisition delay was 1080s; the injection volume was 5000μL; the injection speed was 1000μL / s. The parameters of the automatic sampler were: incubator 150s; incubation temperature 80℃; injector temperature 90℃. Four groups of parallel were made for each sample. The measured results are as follows: Figure 1 and Figure 2 shown.

[0098] Depend on Figure 1 and Figure 2 It can be seen that the smell of the steamed buns prepared by using Example 1 is quite special and is significantly different from the steamed buns fermented by other strains; the smells of the steamed buns prepared by using Comparative Examples 1-2 are similar.

[0099] 5. Electronic tongue measurement

[0100] The steamed bread and white steamed bread prepared in Example 1 and Comparative Examples 1 and 2 were tested and analyzed using the TS-5000Z electronic tongue (Insent, Japan). The electronic tongue data were analyzed using the Teste sensing system TS-5000Z Analysis Application software provided by the electronic tongue. The experiment was repeated 3 times and the average value was taken. The results are shown in Table 4 and Figure 3 shown.

[0101] Table 4 Electronic tongue tests for various application examples

[0102]

[0103] The larger the data, the stronger the taste. Except for sour and salty tastes, the data of other tastes below 0 are considered tasteless. It can be seen from the data in Table 4 that, considering comprehensively, the steamed buns prepared by Example 1 have the best taste.

[0104] 6. In vitro Starch Digestion Assay

[0105] (1) Digestion sample pretreatment

[0106] The steamed bread prepared in Application Example 1 and Application Comparative Examples 1 and 2 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 content quantitative kit.

[0107] (2) Reagent preparation

[0108] 2.1 Experimental Reagents

[0109] The main reagents required for the experiment are shown in Table 5.

[0110] Table 5 Main reagent materials

[0111]

[0112] 2.2 Preparation of reagent solution:

[0113] 1 mol / L CH3COONa buffer (pH 5.0): Accurately weigh 0.82 g of sodium acetate and dissolve it in 10 mL of deionized water.

[0114] 2mol / L NaOH: Accurately weigh 40g NaOH and dissolve it in a beaker. After cooling to room temperature, transfer it to a 500mL container.

[0115] bottle, dilute to volume and shake well.

[0116] 2mol / L HCl: In a fume hood, measure 16.67mL of concentrated hydrochloric acid (mass fraction 37%) and add water to make up to 100mL.

[0117] pH 8.0 phosphate buffer: Accurately weigh 6.78 g Na2HPO4·12H2O and 0.17 g NaH2PO4·2H2O and add water to make up to 100 mL.

[0118] L-Leucine standard solution: Accurately weigh 50 mg of L-leucine and add water to make up to 100 mL.

[0119] 2.3 Preparation of simulated digestion electrolyte solution

[0120] The electrolyte preparation for oral cavity, stomach and small intestine is shown in Table 6.

[0121] Table 6 Electrolyte solution preparation

[0122] 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 — <![CDATA[NaHCO3(g)]]> 0.571 0.6 — <![CDATA[KH2PO4(g)]]> 0.252 — — <![CDATA[MgCl2(H2O)6(g)]]> 0.015 — — <![CDATA[(NH4)2CO3(g)]]> 0.003 — — <![CDATA[CaCl(H2O)2(g)]]> 0.11 — 0.33 pH 7.0 2.0 7.0

[0123] 2.4 Preparation of simulated digestive fluid

[0124] Simulated oral fluid

[0125] 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.

[0126] Simulated gastric fluid

[0127] a. Solid samples

[0128] Take 100mL of gastric electrolyte solution and add 2×10 5 U pepsin (>250U / mg) was prepared into 2000U / mL simulated gastric fluid, 5mL CH3COONa buffer (1mol / L, pH 5.0) was added, magnetic stirring was performed at room temperature for 10min, and the pH of the solution was adjusted to 2.0 with 2mol / LHCl.

[0129] b. Liquid samples

[0130] Take 100mL of gastric electrolyte solution and add 4×10 5 U pepsin (>250U / mg) was added to prepare 4000U / mL simulated gastric fluid, 5mL CH3COONa buffer (1mol / L, pH 5.0) was added, magnetic stirring was performed at room temperature for 10min, and the pH of the solution was adjusted to 2.0 with 2mol / LHCl.

[0131] Simulated intestinal fluid

[0132] 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.

[0133] 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 it evenly at room temperature for later use.

[0134] 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.

[0135] (3) In vitro simulated digestion experiment

[0136] The digestion sample should contain about 200 mg of starch, and the dosage 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). 2mol / L HCl or 2mol / L NaOH is used to adjust the pH of the simulated digestive fluid.

[0137] 3.1 Preliminary experiments on simulated digestion

[0138] 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. (HCI) ; Then, 10 mL of simulated intestinal fluid was added to the gastric juice mixed digestive fluid (the volume ratio of gastric juice mixture: intestinal fluid was 1:1. For samples that were not digested orally, such as protein samples, 20 mL of simulated intestinal fluid could be added to the gastric juice mixture), the pH value was measured after mixing evenly, and the pH of the digestive mixture was adjusted to 7.0 with 2 mol / L NaOH. The volume of 2 mol / L NaOH required, V (NaOH) .

[0139] 3.2 In vitro simulated digestion of starch samples

[0140] 3.2.1 Simulated oral digestion

[0141] Accurately weigh an appropriate amount of digestion sample (containing about 200 mg starch or 200 mg digestible and available carbohydrate) 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 to adjust the pH to 2.0 and vortex to mix to stop the simulated oral digestion.

[0142] 3.2.2 Simulated gastric digestion

[0143] The entire oral digestion mixture was transferred to the dissolution cup of the drug dissolution apparatus, 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 was immediately added to adjust the pH to 7.0 to stop the simulated gastric digestion.

[0144] 3.2.3 Simulated small intestinal digestion

[0145] 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.

[0146] (4) Glucose content determination

[0147] Taking the steamed bread and white steamed bread prepared by starch digestion application example 1 and application comparative examples 1 and 2 as examples, in order to draw the hydrolysis curve of starch in digestion steamed bread, the DNS method or amyloglucosidase-high performance liquid chromatography method was used to measure the glucose concentration in the samples collected at each digestion time, and the starch hydrolysis rate of the steamed bread prepared by digestion application example 1 and application comparative examples 1 and 2 and ordinary white steamed bread was calculated. Starch hydrolysis rate (%)

[0148] =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. 120min is the amount of glucose produced when 120 min of simulated intestinal digestion is performed, and TS is the total starch content in the sample. The experiment was repeated three times, and the average value was taken. The calculated results are shown in Table 7.

[0149] 4.1 DNS method for determination of glucose content

[0150] Drawing of glucose standard curve

[0151] 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.

[0152] Glucose concentration measurement

[0153] 1 mL of supernatant was taken into a 15 mL graduated test tube, 2 mL of DNS reagent was added, and the mixture was cooled with ice water immediately after boiling water bath for 5 min. The solution was supplemented to 15 mL with deionized water, mixed evenly, and the absorbance value was measured at a wavelength of 540 nm. Each sample was measured in parallel 3 times, and the glucose concentration in the steamed bread prepared by the application example 1 and the application comparative examples 1 and 2 and the ordinary white steamed bread at each digestion time was calculated according to the glucose standard curve, and the hydrolysis rate was calculated. The experiment was repeated three times and the average value was taken. The results are shown in Table 8.

[0154] Table 7 Starch hydrolysis rate

[0155]

[0156]

[0157] Table 8 Hydrolysis rate at different time points

[0158]

[0159] The starch hydrolysis rate simulates the increase in blood sugar after a meal. Therefore, the lower the content of fast-digestible starch and the higher the content of slow-digestible starch and resistant starch, the more helpful it is to alleviate the rapid increase in blood sugar after a meal. Figure 4 It can be seen that, overall, the application of Example 1 shows great advantages in alleviating the increase in postprandial blood sugar.

[0160] 7. Human sensory evaluation

[0161] Ten evaluators with food expertise and good sensory acuity were trained and selected to form an evaluation group, and sensory evaluation was performed on the steamed bread prepared in Example 1 and Comparative Examples 1 and 4 based on color, taste, appearance, and smell. The scoring criteria are shown in Table 9. The scoring results are shown in Table 10.

[0162] Table 9 Sensory scoring criteria for steamed bread

[0163]

[0164]

[0165] Table 10 Sensory evaluation of steamed bread

[0166]

[0167] It can be seen from Table 10 that the comprehensive score of Application Example 1 is the highest.

[0168] It can be seen that the steamed bread prepared by using the lactobacillus formula disclosed in the present invention has better efficacy and a simpler formula compared with the prior art.

Claims

1. A sourdough with health benefits, characterized in that: The invention is composed of the following raw materials: wheat flour, fermented lactobacillus and water, and the mass ratio of the three is 500:0.1-0.4:

260.

2. The sourdough according to claim 1, characterized in that The fermented lactobacillus in the sour dough has a viable bacterial count of 150 billion CFU / g.

3. The sourdough according to any one of claims 1 to 2, characterized in that The method for preparing sourdough comprises the following steps: (1) mixing wheat flour, water and lactobacillus, and kneading to obtain dough; (2) fermenting the dough in step (1) to obtain sourdough.

4. The preparation method according to claim 3, characterized in that: The fermentation temperature in step (2) is 36° C.-37° C., the humidity is 90%, and the fermentation time is 6.5 h.

5. The preparation method according to claim 4, characterized in that: The pH of the sourdough in step (2) is 4.

6. Use of the sourdough according to any one of claims 1 to 2 or the sourdough prepared by the preparation method according to any one of claims 3 to 5 in preparing pasta.

7. The use according to claim 6, characterized in that: The pasta is steamed bread.

8. The use according to claim 7, characterized in that: The steamed bread is prepared according to the following preparation method: (1) mixing wheat flour, sourdough, yeast, alkali and water, and kneading to obtain dough; (2) The dough obtained in step (1) is allowed to ferment and steamed to obtain steamed buns.

9. The use according to claim 8, characterized in that: The mass ratio of the wheat flour, sourdough, yeast, alkali and water in step (1) is 125:50:0.25:0.4:

65.

10. The use according to claim 8, characterized in that: The proofing temperature in step (2) is 35-37° C., the proofing humidity is 80%, and the proofing time is 60 min.

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