Sour soup-fermented corn noodle composite leavening agent

Abstract

The sour soup-fermented corn noodle composite leavening agent comprises lactobacillus plantarum and lactobacillus fermentum, and the thallus quantity ratio is (1-5): (1-5); the water absorption rate of the fermented corn sour soup corn noodles is increased, gelatinization is more uniform, and a more compact gel structure can be formed. The synergistically fermented noodles are low in turbidity, breaking rate, turbidity and cooking loss rate, and high in water absorption rate. The product has special flavor substances and thioethers, and the contents of aldehydes, acids, ketones and esters are increased. The color, appearance, taste, flavor and elasticity and toughness scores are improved, and the taste and flavor are superior to those of natural fermentation.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, in particular to a sour soup-fermented corn noodle composite leavening agent. Background Art

[0002] Fermented cereal foods not only increase their nutritional value, but also have a unique taste. Therefore, many countries and regions have unique traditional fermented foods. Corn sour soup noodles, a Manchu food in my country, is one of the corn foods produced by fermentation. It is also known as Tangzi or Chuan Tangzi. It has a unique taste and flavor, is rich in nutrients such as crude fiber and lactic acid bacteria, and is recognized as a healthy food.

[0003] The traditional method of making corn sour soup noodles is to wash the whole corn, put it in a container and soak it in water, put it in a cool place, and ferment it naturally at room temperature. The fermentation time is usually one month. After the fermentation is completed, the corn kernels are repeatedly rinsed with clean water to completely remove the sour smell produced by the fermentation, grind it into water surface, filter out the residue skin, and remove excess water to form water surface, which is a fine paste. In some areas, excess water is filtered and frozen for storage, but the time should not be too long, otherwise it will rot and deteriorate to produce harmful substances that endanger human health or even life. When it is ready to eat, put the prepared dough into boiling water and cook until the surface of the dough is golden. Take it out and re-knead the dough until the dough is moderately soft and hard and the surface is smooth. Put the kneaded dough in your hands and squeeze it evenly into the boiling water with a soup set. It can be eaten after cooking. The traditional method of producing corn sour soup noodles mostly relies on natural fermentation. Its production method is complicated and it is difficult to form a reasonable and large-scale industrial production. It has defects such as poor safety, unstable quality, and long production cycle. It lacks reliability and controllability in production. Under the current abundant corn production situation, in order to promote the industrial research and development of characteristic corn fermented foods, the characteristic fermentation system of sour soup and its extremely strong prebiotic functionality still have very broad development prospects. Summary of the invention

[0004] The purpose of the present invention is to solve the above problems and provide a sour soup-fermented corn noodle composite leavening agent.

[0005] Lactobacillus plantarum JSLp-30, the deposit number is CGMCC No.30607.

[0006] Lactobacillus fermentum JSLf-03, the accession number is CGMCC No.30609.

[0007] A sour soup-fermented corn noodle composite starter, comprising fermented bacteria species Lactobacillus plantarum and Lactobacillus fermentum, with a bacterial cell count ratio of 1-5:1-5;

[0008] The bacterial cell number ratio is 1:1;

[0009] The composite starter is prepared by the following method: plant lactobacillus and fermented lactobacillus are activated respectively, cultured in MRS broth medium at 37°C and 60r / min for 24h, centrifuged at 5000r / min for 15min, removed the supernatant, added with sterile physiological saline and centrifuged repeatedly for three times, mixed the two bacteria, added a sterilized freeze-drying protective agent at a ratio of 1:9, mixed well, pre-frozen with liquid nitrogen, and then freeze-dried at a pressure of 10-20Pa and a condition of -45°C to -55°C for 24-48h, ground, passed through an 80-mesh sieve, and vacuum-packed in aluminum foil bags to obtain the sour soup-fermented corn noodle composite starter;

[0010] The freeze-drying protective agent is 8% trehalose, 5% sodium L-glutamate, 10% skim milk powder, and 3% glycerol;

[0011] The plant lactobacillus is the plant lactobacillus JSLp-30; the fermented lactobacillus is the fermented lactobacillus JSLf-03.

[0012] The invention provides a sour soup-fermented corn noodle composite starter, which is fermented by the synergistic effect of Lactobacillus plantarum JSLp-30 and Lactobacillus fermentation JSLf-03. The dough breakage rate fermented by Lactobacillus fermentation JSLf-03 is low, and the acid production capacity of Lactobacillus plantarum JSLp-30 is good. The two strains are mixed with a protective agent, freeze-dried, and then ground to prepare the sour soup-fermented corn noodle composite starter.

[0013] The pH and TTA, gelatinization characteristics, texture characteristics, crystal structure, and microstructure of corn dough during fermentation were studied. As fermentation progressed, the TTA of other groups of synergistic fermentation increased and the pH values ​​decreased; the peak viscosity, valley viscosity, final viscosity, disintegration value, and regeneration value of synergistic fermentation corn dough all decreased, and the crystallinity increased. Synergistic fermentation improved the texture characteristics of the dough and gave the dough better processing performance.

[0014] The effects of lactic acid bacteria fermentation on the cooking quality, volatile flavor substances and sensory quality of corn sour soup noodles were studied. After synergistic fermentation, the water absorption rate of noodles increased, the gelatinization was more uniform, and a denser gel structure could be formed. The turbidity, breakage rate, turbidity and cooking loss rate of the synergistic fermented noodles were low, and the water absorption rate was high. Fermentation caused corn sour soup noodles to produce unique flavor substances. Only thioethers were detected in the synergistic fermented noodles, and the content of aldehydes, acids, ketones and esters increased. The color, appearance, taste, flavor and elasticity scores of synergistic fermented corn sour soup noodles were improved, and the taste and flavor were better than those of naturally fermented corn sour soup noodles and commercially available corn sour soup noodles. Lactic acid bacteria fermentation improved the sensory quality of corn sour soup noodles. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Changes in pH of corn dough during fermentation;

[0016] Figure 2 Changes in TTA value of corn dough during fermentation;

[0017] Figure 3 RVA curve of corn dough;

[0018] Figure 4 X-ray diffraction pattern of corn dough;

[0019] Figure 5 SEM images of fermented corn sour soup noodles (magnification 1000 times);

[0020] Fig. 6 SEM images of fermented corn sour soup noodles (magnification 2000 times);

[0021] Figure 7 Gas chromatogram of volatile compounds in naturally fermented corn sour soup noodles;

[0022] Figure 8 Gas chromatogram of volatile compounds in commercially available corn sour soup noodles;

[0023] Fig. 9 Gas chromatogram of volatile compounds in corn sour soup noodles with Lactobacillus plantarum JSLp-30;

[0024] Fig.10 Gas chromatogram of volatile compounds in corn sour soup noodles fermented by Lactobacillus JSLf-03;

[0025] Fig.11 Gas chromatogram of volatile compounds in corn sour soup noodles fermented by JSLf-03 and JSLp-30. DETAILED DESCRIPTION

[0026] Example 1 Screening and Identification of Lactobacillus fermentum JSLf-03

[0027] 1. Initial screening

[0028] Take 10g of fermented sauerkraut sample from the laboratory and add it to 50ml of sterile saline, vortex mix, take 100μL and add it to 10ml of MRS broth medium, and enrich it at 37℃ for 24h. -1 -10 -4Dilution of concentration gradient. Take 100 μL of each gradient and spread it on MRS solid medium containing 3% CaCO3 (w / v), and culture it at 37°C for 24h-48h. Pick colonies with obvious calcium dissolution rings, and purify them by streaking several times until the colonies have a single morphology and no foreign bacteria are found under microscopic examination. Perform Gram staining on the purified culture strains, and observe the staining results and morphological characteristics under a microscope. A total of 10 pure colonies of Gram-positive, catalase-negative bacteria with short rod-shaped morphology were isolated.

[0029] The colonies obtained in the initial screening were inoculated into MRS broth culture medium, cultured at 37°C, 60r / min for 24h, centrifuged at 5000r / min for 15min, removed the supernatant, added sterile saline, and centrifuged repeatedly three times, and added sterile saline to adjust the concentration of the bacterial solution to an OD600 value of 12 to prepare a bacterial suspension.

[0030] 2. Rescreening

[0031] Screening of dominant bacteria in sour dough to improve the quality of corn sour soup noodles. 15 plant lactobacillus and 10 fermented lactobacillus were used as research objects. Six plant lactobacillus with strong acidification ability were screened according to the pH change rate of the fermentation liquid. The fermented dough was squeezed and added into boiling water to cook noodles. The breaking rate was observed, and four fermented lactobacillus strains that improved the viscosity of the dough were screened. Then, corn sour soup noodles were made by mixed fermentation of 6 plant lactobacillus and 4 fermented lactobacillus. The dominant yeast and lactic acid bacteria were screened according to the breaking rate, texture and total phenol content of corn sour soup noodles. Then, the optimal addition amount, ratio and fermentation time of the two were determined according to the pH, TTA and colony count of whole wheat dough. The results showed that the breaking rate of noodles made from dough fermented by fermented lactobacillus JSLf-03 was the lowest, and the acid production ability of plant lactobacillus JSLp-30 was the highest. The relative content of aldehydes in the synergistically fermented noodles was 29.82%, which was higher than that of other types of fermented noodles. Volatile flavor substances with sweet and corn aroma were added. The relative content of alcohol volatile substances in the synergistic fermented noodles was 22.22%, which was 63.53% lower than that in the market. Synergistic fermentation added volatile substances with vanilla aroma to the noodles and reduced a small amount of volatile substances with alcohol flavor. It was determined that Lactobacillus plantarum JSLp-30 and Lactobacillus plantarum JSLp-30 were the dominant bacteria in sour dough to improve the quality of corn sour soup noodles, and then the optimal addition amount of the two was determined to be 10 9 cfu / g, the best addition ratio is 1:1, and the best fermentation time is 24h.

[0032] After PCR amplification of JSLp-30, the sequence of the 16sDNA fragment was detected by the machine, and the sequence obtained was shown in the sequence table SEQID NO.2. It was named Lactobacillus plantarum JSLp-30 and was deposited in the General Microbiology Center of China Microbiological Culture Collection Committee on May 13, 2024, at the Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing; the deposit number is CGMCC No.30607.

[0033] After PCR amplification, JSLf-03 was tested for the sequence of 16sDNA fragments, and the sequence obtained was shown in the sequence table SEQID NO.1. It was named Lactobacillus fermentum JSLf-03 and was deposited in the General Microbiology Center of China Microbiological Culture Collection Committee on May 13, 2024, at the Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing; the deposit number is CGMCC No.30609.

[0034] Example 2 Preparation of Suantangzi-fermented corn noodles composite starter

[0035] The plant lactobacillus JSLp-30 and fermented lactobacillus JSLf-03 strains were activated, cultured in MRS broth medium at 37°C and 60r / min for 24h, the cultured bacterial solution was centrifuged at 5000r / min for 15min, the supernatant was removed and sterile physiological saline was added and centrifuged repeatedly for three times, 8% trehalose, 5% sodium L-glutamate, 10% skim milk powder and 3% glycerol sterilized at 121°C for 15min were added as strain freeze-drying protective agents, the plant lactobacillus sludge and the fermented lactobacillus sludge were mixed in a quantitative ratio of 1:1, and the mixed bacterial sludge and the freeze-drying protective agent were mixed in a weight ratio of 1:9 to obtain a mixture, which was pre-frozen with liquid nitrogen, and then freeze-dried at a pressure of 10-20Pa and at -45°C to -55°C for 24 to 48h, ground, sieved through an 80-mesh sieve, and vacuum-packed in aluminum foil bags to obtain a sour soup-fermented corn noodle composite starter.

[0036] Example 3 Preparation of Fermented Corn Dough

[0037] Group 1: After the corn flour was passed through an 80-mesh sieve, the corn flour and hot water were pre-gelatinized in a mass ratio of 1:1 and then cooled. The dough was kneaded to make the surface uniform and sealed and fermented at 36°C for 24 h to obtain naturally fermented corn dough.

[0038] The second group: After the corn flour was passed through an 80-mesh sieve, the corn flour and hot water were pre-gelatinized in a mass ratio of 1:1 and then cooled. A fermented Lactobacillus JSLf-03 suspension with an OD600 value of 12 was added to the mixture at a concentration of 3% of the total mass of the corn flour. The mixture was sealed and fermented for 24 hours at a fermentation temperature of 35-38°C and a fermentation humidity of 75-85% to obtain JSLf-03 fermented corn dough.

[0039] The third group: After the corn flour was passed through an 80-mesh sieve, the corn flour and hot water were pre-gelatinized in a mass ratio of 1:1 and then cooled. 3% of the total mass of the corn flour and the Lactobacillus plantarum JSLp-30 with an OD600 value of 12 and a bacterial suspension were added. The mixture was sealed and fermented for 24 hours at a fermentation temperature of 35-38°C and a fermentation humidity of 75-85%, which was the JSLp-30 fermented corn dough.

[0040] Group 4: Wash the whole corn kernels, put them into a container, soak them in water, place them in a cool place, and ferment them naturally at room temperature for one month. After fermentation, rinse the corn kernels repeatedly with clean water to completely remove the sour and smelly smell produced by the fermentation, grind them into water surface, filter out the residue and remove excess water to form water surface, which is a fine paste, and is the commercially available starter corn dough.

[0041] Group 5: After the corn flour was passed through an 80-mesh sieve, the corn flour and hot water were pre-gelatinized in a mass ratio of 1:1 and then cooled. A 1:1 bacterial suspension of fermented Lactobacillus JSLf-03 and Lactobacillus plantarum JSLp-30 with an OD600 value of 12, which was 3% of the total mass of the corn flour, was added. The mixture was sealed and fermented for 24 h at a fermentation temperature of 35-38°C and a fermentation humidity of 75-85%, which was a synergistic fermentation of corn dough by JSLf-03 and JSLp-30.

[0042] 1. pH and TTA determination

[0043] Dilute 10 g corn dough with 90 mL deionized water, put it into a beaker, place it in a high-speed homogenizer, and rotate at 5000 r / min. Homogenize for 5 minutes, let it stand for 20 minutes, take 5 mL of the supernatant, test it with a pH meter, and record the results. Take another 5 mL of the supernatant, and titrate the sample pH to 8.5 with sodium hydroxide solution (0.1 mol / L). The volume of sodium hydroxide consumed is the total titratable acidity (TTA) value of the dough.

[0044] Figure 1-2The changes of pH and TTA during the fermentation of four groups of corn dough. The changes of pH and TTA of corn dough are important indicators reflecting the fermentation state of dough. During the fermentation process, Lactobacillus plantarum JSLp-30 and Lactobacillus fermentation JSLf-03 reduce the pH of corn dough by metabolic acid production. The low pH environment can promote the interaction between protein and protease in corn dough and improve the texture characteristics of corn dough. Determining the changes of pH and TTA of corn dough at different time points can provide a reference for improving the processing quality of corn dough. During the fermentation process, the pH value of corn dough showed a continuous downward trend. The pH change trend of each fermentation group was synergistic fermentation < Lactobacillus plantarum JSLp-30 fermentation < Lactobacillus fermentation JSLf-03 fermentation < natural fermentation. The TTA change trend of each fermentation group was synergistic fermentation > Lactobacillus plantarum JSLp-30 fermentation > Lactobacillus fermentation JSLf-03 fermentation > natural fermentation. The pH value of the synergistic fermentation decreased the most compared with the other three groups, from 6.55 to 3.2; the TTA value of the synergistic fermentation increased the most compared with the other three groups, from 6.89 mL to 18.05 mL. It can be seen that Lactobacillus plantarum JSLp-30 and Lactobacillus fermentum JSLf-03 promote each other in the fermentation process, yeast promotes lactic acid bacteria to produce more lactic acid, and the acidification degree of corn dough in synergistic fermentation is significantly higher than that of other doughs; the TTA of synergistic fermentation increased by 62.65%, 17.13%, and 21.55% respectively compared with natural fermentation, JSLp-30, and JSLf-03, and the pH value decreased by 27.76%, 1.54%, and 9.34% respectively; the changes in pH and TTA values ​​of the four groups were significantly different (P<0.05).

[0045] 2. Determination of dough gelatinization characteristics

[0046] Use a precision balance to weigh 3 g of freeze-dried dough powder into a RVA-specific aluminum can, add 25 ml of distilled water, stir thoroughly to make it evenly dispersed, and place the mixture into the RVA analyzer for testing.

[0047] Test procedure: The temperature was 50 °C and the speed was 960 r / min at the beginning. After 10 s, the speed was reduced to 160 r / min and remained unchanged until the end. The temperature began to rise to 95 °C at a constant speed after 4 min. After the temperature was maintained for 2.5 min, it was cooled to 50 °C at the same speed and maintained for 2 min. The total time was 13 min.

[0048] The process of starch granules absorbing water, swelling and bursting at a specific temperature, and finally forming a sticky colloid is called gelatinization. The disintegration value is the difference between the peak viscosity and the valley viscosity, which mainly reflects the stability of the starch granule structure during the gelatinization process. A smaller disintegration value means that the structure between starch granules is more stable. After the gelatinization is completed, the temperature gradually drops and some starch molecules return to a colloidal state, which is the final viscosity. The regeneration value is the difference between the final viscosity and the valley viscosity. A larger regeneration value means that the starch has poor anti-aging properties.

[0049] Figure 3 is the gelatinization (RVA) curve of corn dough; Table 1 is the characteristic parameters of corn dough gelatinization. Compared with the fermentation of Lactobacillus JSLf-03, Lactobacillus plantarum JSLp-30 and commercially available fermented corn dough, the peak viscosity of corn dough fermented by the synergistic leavening agent was reduced by 12.41%, 14.58% and 60.8%, respectively; the trough viscosity was reduced by 12.67%, 13.7% and 50.78%, the final viscosity was reduced by 6.61%, 7.71% and 35.21%, the disintegration value was reduced by 10.87%, 18.2% and 79.18%, and the regeneration value was reduced by 0.40%, 1.69% and 10.03%. This shows that the synergistic leavening agent fermentation is beneficial and effective for improving the anti-aging property of starch and strengthening the stability of starch granules in corn dough fermented by a single strain.

[0050] .

[0051] 3. Texture characteristics

[0052] The fermented dough was subjected to TPA test using a flat-bottom cylindrical P / 0.5 probe. Each sample was measured three times in parallel and the average value was taken.

[0053] Measurement parameters: pre-measurement speed: 1.0 mm / s; test distance 10 mm; pre-measurement speed 2.00 mm / s; measurement speed: 1.0 mm / s; post-measurement speed: 1.0 mm / s; compression dwell time: 5 s; trigger force: 5 g; compression ratio: 30%.

[0054] The texture characteristics of corn dough affect the processing characteristics and edible quality of its products. Adding lactic acid bacteria can improve the texture characteristics of corn dough and make the dough structure more compact. As can be seen from Table 2, the lowest hardness of JSLp-30 fermented dough is 2389.73N; the lowest elasticity is 0.32mm; the lowest cohesion is 0.16N; the lowest adhesiveness is 334.83N; and the lowest chewiness is 106.37N. In the process of making corn dough, there are often shortcomings such as aging and poor chewiness. Fermentation makes corn dough softer. In general, synergistic fermentation improves the texture characteristics of dough and makes the dough have better processing performance.

[0055] .

[0056] 4. Crystal structure

[0057] The starch samples from different fermentation groups were measured by X-ray diffractometer (see Figure 4 ), the test adopted the step scanning method, the specific test parameters were: test current 40 mA, tube voltage 40 kV, characteristic ray Cu-Kα target (λ=0.1543 nm), scanning diffraction angle 2θ of 5°~50°, scanning rate 5º / min, step length 0.06º, and the relative crystallinity of the sample was calculated by software JADE 5.0 (RelativeCrystallinity, RC).

[0058] Through Figure 4 From the analysis of relative crystallinity, we can know that fermentation treatment will increase the crystallinity of corn. The increase in crystallinity may be due to the change in the ratio of crystalline and non-crystalline areas of starch caused by fermentation. After fermentation, the crystal form of corn flour has not changed, but the relative crystallinity has increased. The reason may be that when the acid or enzyme hydrolyzes the starch during fermentation, the starch chains in the crystalline area of ​​the starch are closely arranged and not easily hydrolyzed by the acid or enzyme, while the amorphous area with a looser structure is weakened or damaged to a certain extent. During the fermentation process, the acid and enzyme produced by the microorganisms hydrolyze the straight-chain starch and the branched-chain starch in the amorphous area, resulting in an increase in relative crystallinity after fermentation.

[0059] 5. Analysis of the effect of synergistic fermentation of JSLf-03 and JSLp-30 on the micromorphology of corn sour soup noodles

[0060] Figure 5 The five images (a-1), (b-1), (c-1), (d-1), and (e-1) are 1000 times scanning electron microscope images of naturally fermented, commercially available, JSLp-30 fermented, JSLf-03 fermented, and co-fermented corn sour soup noodles, respectively; Figure 6 The five pictures (a-2), (b-2), (c-2), (d-2), and (e-2) are 2000 times scanning electron microscope images of corn sour soup noodles fermented by natural fermentation, commercial, JSLp-30 fermentation, JSLf-03 fermentation, and synergistic fermentation, respectively. It can be seen from the SEM image that the microscopic morphology of the naturally fermented noodles and the synergistic fermented noodles is quite different. The degree of fermentation of the naturally fermented noodles is not obvious, and the network structure shows many irregular and unevenly distributed holes. At this time, the noodles have poor elasticity, and the texture characteristics and sensory quality of the noodles are reduced. Adding lactic acid bacteria fermentation makes the connection between macromolecules such as starch and protein in the noodles tighter, and the gel network structure formed is denser, the holes are uniform and orderly, and the noodles' ability to resist extrusion is enhanced.

[0061] Example 4 Preparation of Corn Sour Soup Noodles

[0062] Take the fermented dough out of the constant temperature fermentation box, tan it into a fist-sized uniform dough, put it into a boiling water pot, scald it for 10 minutes until the surface of the dough is golden, take it out and knead it again, repeat the above operation twice, and knead the dough until the dough is uniform and the surface is smooth. Put the kneaded dough into the noodle extruder, squeeze in the noodles after the water boils, and cook for 5 minutes. When the noodles float to the surface after cooking for 5 minutes, they are cooked. Use a colander to take them out and rinse them with cold water to get the finished sour soup noodles. During the cooking process, prevent the noodles from breaking and sticking due to external forces.

[0063] Take the fermented dough out of the constant temperature fermentation box, knead it until the dough is even, put it into boiling water for 10 seconds until the surface of the dough is golden, take it out and knead it again, knead the dough until the dough is soft and hard and the surface is smooth, and repeat the above operation for the second blanching. Put the kneaded dough into the noodle extruder, and squeeze in the noodles after the water boils. Prevent the noodles from breaking and sticking due to external forces during the cooking process.

[0064] 1.1 Analysis of the effect of synergistic fermentation of JSLp-30 and JSLf-03 on the cooking quality of corn sour soup noodles

[0065] The cooking loss rate of noodles is usually regarded as an important indicator of the cooking performance of noodles. As can be seen from Table 3, the quality characteristics of the synergistically fermented noodles are significantly different from those of the naturally fermented noodles, JSLp-30 fermentation alone, JSLf-03 fermentation alone, and commercially available noodles (p<0.05). The optimal cooking time for the five types of noodles is 5 min. The breaking rate of the synergistically fermented noodles is 3.25%, which meets the requirement of noodle loss rate ≤5% in GB / T40636-2021. After synergistic fermentation, the water absorption rate of the noodles increased to 40.32%, the gelatinization was more uniform, and a denser gel structure could be formed. The chewier the noodles and the higher the quality of the noodles, the stronger the ability of the noodles to recover from deformation. The turbidity of the synergistically fermented noodles is lower than that of the individually fermented, naturally fermented, and commercially available noodles. The cooking loss rate of the synergistically fermented noodles is 4.21%, which meets the requirement of noodle cooking loss rate ≤10% in GB / T40636-2021. Compared with single fermentation, naturally fermented noodles and commercially available noodles, the breakage rate, turbidity and cooking loss rate of noodles after synergistic fermentation were significantly reduced, and the water absorption rate was significantly improved (p<0.05). It has higher steaming quality and is not easy to break.

[0066] .

[0067] 2. Determination of volatile substances in corn sour soup noodles

[0068] Using the GC-MS method, 5g of cooked corn sour soup noodles were placed in a 20ml headspace bottle and 2.0g NaCl was added. Equilibrate at 60℃ for 15min, perform solid phase microextraction (solid phase microextraction fiber: DVB / CAR / PDMS, LabTech) at 60℃ for 40min, and desorb at 250℃ for 3min before testing. Gas chromatography-mass spectrometry method: column DB-5MS (Agilent, J&W Scientific, 30m*0.25mm*0.25μm), injection port 250℃, split ratio 10:1, carrier gas is high-purity helium, flow rate is 1ml / min, heating program: 40℃ for 2min, increase to 200℃ at 6℃ / min for 0min, then increase to 300℃ at 15℃ / min for 3min. Ion source temperature 220℃, interface temperature 280℃, solvent removal time 3min, scan m / z 33-500. The mass spectra were matched by computer with those from the National Institute of Standards and Technology and Wiley Library. Compounds with a similarity percentage higher than 85% were retained for data analysis.

[0069] During the fermentation process, lactic acid bacteria metabolize and produce a large number of compounds such as aldehydes, alcohols, ketones, esters, acids and hydrocarbons, which play an important role in the formation of noodle flavor substances. The volatile substances produced by corn sour soup noodles were determined by GC-MS. Table 4 shows the classification and statistical results of volatile flavor substances; Table 5 is a summary of volatile flavor substances; Figure 5 This is the gas chromatogram of volatile substances in naturally fermented corn sour soup noodles; Figure 6 This is the gas chromatogram of volatile substances in commercially available fermented corn sour soup noodles; Figure 7 Gas chromatogram of volatile substances in naturally fermented corn sour soup noodles; Figure 8 This is the gas chromatogram of volatile substances in commercially available fermented corn sour soup noodles; Fig. 9 The gas chromatogram of volatile substances in corn sour soup noodles fermented by Lactobacillus plantarum JSLp-30; Fig.10 This is the gas chromatogram of volatile substances in corn sour soup noodles fermented by Lactobacillus fermentum JSLf-03; Fig.11 This is the gas chromatogram of volatile substances in corn sour soup noodles fermented by JSLp-30 and JSLf-03. There are 39 volatile substances in naturally fermented noodles; there are 36 volatile substances in commercially fermented noodles; there are 36 volatile substances in noodles fermented by JSLp-30; there are 33 volatile substances in noodles fermented by JSLf-03; there are 35 volatile substances in noodles fermented by JSLp-30 and JSLf-03; fermentation makes corn sour soup noodles produce unique flavor substances.

[0070] There were 39 volatile substances in naturally fermented noodles; 36 volatile substances in commercially fermented noodles; 36 volatile substances in JSLp-30 fermented noodles; 33 volatile substances in JSLf-03 fermented noodles; 35 volatile substances in JSLp-30 and JSLf-03 co-fermented noodles; fermentation made corn sour soup noodles produce unique flavor substances. Thioethers were only detected in JSLf-03 and co-fermented corn sour soup noodles. Aldehydes are the main flavor components of noodles and the main products of lipid oxidation and decomposition. The relative content of aldehydes in co-fermented noodles was 29.82%, which was higher than that of other types of fermented noodles, and volatile flavor substances with sweet and corn aroma were added. The relative content of alcohol volatile substances in co-fermented noodles was 22.22%, which was 63.53% less than that of commercial noodles. The synergistic fermentation added volatile substances with vanilla aroma to the noodles and reduced a small amount of volatile substances with alcohol flavor. The relative content of acidic volatile substances increased from 13.2% to 32.59%. The synergistic fermentation gave the corn sour soup noodles a unique sour taste. Ketones and esters also affected the formation of the aroma of corn sour soup noodles, giving the noodles a buttery aroma.

[0071] . ;

[0072] .

[0073] 3. Sensory quality determination

[0074] A sensory evaluation was conducted on corn sour soup noodles. The sensory evaluation team consisted of 10 trained personnel (5 males and 5 females). According to the sensory scoring standard of GB / T25005-2010 with slight modifications, a sensory evaluation was conducted on the color, appearance, taste, flavor, and elasticity of the corn sour soup noodles. The final score was the average value. .

[0075] As can be seen from Table 7, after the sensory evaluation team scored, the total sensory scores of naturally fermented noodles, JSLf-03 fermented noodles, JSLp-30 fermented noodles, commercial noodles, and synergistic fermented noodles were 67, 70, 72.5, 77, and 82.5, respectively. The total sensory score of synergistic fermented noodles was significantly higher than that of other noodles. At the same time, studies have shown that synergistic fermentation can activate biological enzymes in dough, improve the antioxidant activity of dough, and the enzyme activity related to the extracellular polysaccharide content will also be affected by the growth and metabolism of lactic acid bacteria, which has a great impact on the sensory quality of food. The color, appearance, taste, flavor and elasticity of synergistic fermented corn sour soup noodles are improved, and the taste and flavor are better than those of naturally fermented corn sour soup noodles and commercial corn sour soup noodles. Lactic acid bacteria fermentation improves the sensory quality of corn sour soup noodles.

[0076] .

[0077] The dominant bacteria suitable for growing and producing acid in cornmeal were isolated, screened and identified from naturally fermented foods, and made into a composite fermentation agent for sour soup and fermented corn noodles. The pH and TTA, gelatinization characteristics, texture characteristics, crystal structure and microstructure of corn dough during fermentation were studied. As fermentation progressed, the TTA of other groups of synergistic fermentation increased and the pH values ​​decreased respectively; there were significant differences in the changes in pH and TTA values ​​of the four groups. Compared with other fermented corn doughs, the peak viscosity, trough viscosity, final viscosity, disintegration value and regeneration value of corn dough fermented with synergistic fermentation agents were all reduced, which shows that synergistic fermentation is beneficial and effective for improving the anti-aging property of starch and strengthening the stability of starch granules in corn dough fermented with a single strain of bacteria. Adding lactic acid bacteria can improve the texture characteristics of corn dough and make the dough structure more compact. The lowest hardness of JSLp-30 fermented dough was 2389.73N; the lowest elasticity was 0.32mm; the lowest cohesion was 0.16N; the lowest adhesiveness was 334.83N; the lowest chewiness was 106.37N. In the process of making corn dough, there are often shortcomings such as aging and poor chewiness. Fermentation makes corn dough softer. In general, synergistic fermentation improves the texture characteristics of dough and makes the dough have better processing properties. Fermentation treatment will increase the crystallinity of corn. The increase in crystallinity may be due to the change in the ratio of crystalline and non-crystalline regions of starch caused by fermentation. After fermentation, the crystal form of corn flour did not change but the relative crystallinity increased. The microscopic morphology of naturally fermented noodles and synergistically fermented noodles is quite different. The fermentation degree of naturally fermented noodles is not obvious, and the network structure shows more irregular and unevenly distributed holes. The addition of lactic acid bacteria fermentation makes the connection between macromolecules such as starch and protein in noodles tighter, and the gel network structure formed is denser, the holes are uniform and orderly, and the noodles have enhanced anti-extrusion ability.

[0078] The effects of lactic acid bacteria fermentation on the cooking quality, volatile flavor substances, and sensory quality of corn sour soup noodles were studied. After synergistic fermentation, the water absorption rate of noodles increased, the gelatinization was more uniform, and a denser gel structure could be formed. The chewier the noodles, the higher the quality of the noodles. The turbidity of synergistic fermented noodles was lower than that of single fermentation, natural fermentation noodles, and commercial noodles. Compared with single fermentation, natural fermentation noodles, and commercial noodles, the breakage rate, turbidity, and cooking loss rate of synergistic fermented noodles were significantly reduced, and the water absorption rate was significantly improved. The noodles had higher cooking quality and were not easy to break. Fermentation produced unique flavor substances in corn sour soup noodles. Thioethers were only detected in synergistic fermented noodles, and the content of aldehydes, acids, ketones, and esters increased, giving the noodles vanilla and butter aromas; the alcohol content decreased, reducing the volatile substances with alcohol flavor. The total sensory score of synergistic fermented noodles was significantly higher than that of other noodles. The color, appearance, taste, flavor and elasticity scores of the synergistically fermented corn sour soup noodles were improved, and the taste and flavor were better than those of naturally fermented corn sour soup noodles and commercially available corn sour soup noodles. Lactic acid bacteria fermentation improved the sensory quality of corn sour soup noodles.

Claims

1. Lactobacillus plantarum JSLp-30, deposited with CGMCC No.30607.

2. Lactobacillus fermentum JSLf-03, accession number is CGMCC No.30609.

3. A composite leavening agent for sour soup and fermented corn noodles, characterized in that: It includes fermentation bacteria species Lactobacillus plantarum and Lactobacillus fermentum, and the bacterial count ratio is 1-5:1-5.

4. The sour soup-fermented corn noodle composite leavening agent according to claim 3, characterized in that: The bacterial cell number ratio is 1:

1.

5. The sour soup-fermented corn noodle composite leavening agent according to claim 4, characterized in that: The preparation method is as follows: plant lactobacillus and fermented lactobacillus are activated respectively, cultured in MRS broth medium at 37°C and 60r / min for 24h, centrifuged at 5000r / min for 15min, removed the supernatant, added with sterile physiological saline and centrifuged repeatedly for three times, mixed the two bacteria, added with a sterilized freeze-drying protective agent at a ratio of 1:9, mixed evenly, pre-frozen with liquid nitrogen, and then freeze-dried at a pressure of 10-20Pa and a condition of -45°C to -55°C for 24 to 48h, ground, passed through an 80-mesh sieve, and vacuum-packed in aluminum foil bags to obtain a sour soup-fermented corn noodle composite starter.

6. The sour soup-fermented corn noodle composite leavening agent according to claim 5, characterized in that: The freeze-drying protective agent is 8% trehalose, 5% sodium L-glutamate, 10% skimmed milk powder and 3% glycerol.

7. The sour soup-fermented corn noodle composite leavening agent according to claim 3, 4, 5 or 6, characterized in that: The plant lactobacillus is the plant lactobacillus JSLp-30 described in claim 1; the fermented lactobacillus is the fermented lactobacillus JSLf-03 described in claim 2.

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