Method for preparing corn steamed buns through fermentation of lactobacillus plantarum and yeast

Abstract

The invention discloses a method for preparing corn steamed buns through lactobacillus plantarum and yeast fermentation, belongs to the technical field of food processing, and adopts the synergistic effect of lactobacillus plantarum JSLp-20 and saccharomycetes to shorten the fermentation time of high-proportion corn steamed buns; organic acid is generated through synergistic fermentation, starch acid hydrolysis is promoted, meanwhile, esterification reaction with alcohols is carried out to generate flavor substances such as esters, the flavor of the steamed buns is enriched, and the ageing resistance and the water binding capacity of the starch are improved; the specific volume of the prepared corn steamed bun is increased by 18.75%, the hardness, the cohesiveness and the chewiness are reduced by 3.60%, 4.00% and 5.19% respectively, the elasticity and the adhesiveness are increased by 1.14% and 57.36% respectively, the resilience is increased by one time, the total score of sensory evaluation is remarkably increased, and the prepared corn steamed bun product does not collapse or crack and has considerable texture properties.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, and in particular to a method for preparing corn steamed bread by fermenting with plant lactobacillus and yeast. Background Art

[0002] Steamed bread is one of the traditional staple foods in my country. With the increasing pursuit of healthy food by people, a wide variety of steamed bread products have appeared on the market. In the past five years, the average annual growth rate of coarse grain steamed bread has exceeded 10%, and it has become more and more popular among the public. Corn is a nutritious staple food with significant health benefits. In addition to basic nutrients such as carbohydrates, proteins and fats, it is also rich in vitamin A, vitamin E, niacin, and various trace elements such as potassium, sodium, iron, calcium, phosphorus, and magnesium. These effective ingredients help prevent cardiovascular diseases and cancer in the middle-aged and elderly. At the same time, corn is also suitable for diabetic patients. Compared with refined wheat flour, it can better meet people's pursuit of health concepts and high edible quality. However, corn flour lacks gluten protein, and the dough lacks viscosity after mixing with water, resulting in weak viscoelasticity of the dough, easy to crack, and often accompanied by small size, high hardness, rough taste and poor flavor. Problems limit the application and industrial development of corn flour in the field of flour product processing. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a method for preparing corn steamed bread by using Lactobacillus plantarum and yeast to ferment. The double-bacteria synergistic fermentation can effectively improve the texture and flavor characteristics of corn steamed bread.

[0004] A strain of Lactobacillus plantarum JSLp-20 was deposited in the General Microbiology Center of China Culture Collection Administration with the deposit number of CGMCC No.30608.

[0005] The plant lactobacillus JSLp-20 is used for preparing corn steamed bread.

[0006] A method for preparing corn steamed bread by fermenting with Lactobacillus plantarum and yeast, comprising:

[0007] 1) Add 90-100℃ hot water to corn flour and stir evenly;

[0008] 2) adding wheat flour, the activated dry powder of the Lactobacillus plantarum JSLp-20 strain according to claim 1 and active dry yeast to the corn flour prepared in step (1), stirring evenly, and kneading into a smooth dough;

[0009] 3) fermenting the dough obtained in step (2) at a temperature of 36-38° C. and a humidity of 70-75% for 50-70 minutes to obtain fermented corn dough;

[0010] 4) kneading and exhausting the fermented corn dough obtained in step (3), shaping the dough, and placing the dough at room temperature for a second proofing for 25-30 minutes;

[0011] 5) putting the corn steamed bun embryos that have been proofed twice in step (4) into a pot with cold water and steaming them to obtain corn steamed buns;

[0012] In the step (2), the weight ratio of the wheat flour to the corn flour is 1:1-2;

[0013] In step (2), auxiliary materials are also added, and the auxiliary materials include: improver, egg liquid, milk, sucrose and salt;

[0014] Based on the total weight of corn flour and wheat flour, the amount of egg liquid added is 10%, the amount of milk added is 10%, the amount of sucrose added is 1.2%, and the amount of salt added is 0.05%;

[0015] The activation of Lactobacillus plantarum JSLp-20 is performed by mixing with milk and culturing at 40° C. for 4 hours.

[0016] The invention provides a method for preparing corn steamed bread by using lactobacillus plantarum and yeast for fermentation. The method adopts the synergistic effect of lactobacillus plantarum JSLp-20 and yeast to shorten the fermentation time of corn steamed bread with a high proportion. The synergistic fermentation produces organic acid, promotes the acid hydrolysis of starch, and simultaneously generates esterification reaction with alcohol to generate flavor substances such as esters to enrich the flavor of steamed bread, and improves the anti-aging property and water holding capacity of starch. Moreover, the specific volume of the prepared corn steamed bread is increased by 18.75%, the hardness, cohesiveness and chewiness are respectively reduced by 3.60%, 4.00% and 5.19%, the elasticity and adhesiveness are respectively increased by 1.14% and 57.36%, the resilience is increased by 1 times, the total score of sensory evaluation is significantly increased, and the prepared corn steamed bread product does not collapse or crack, and has considerable texture properties. Instruction Manual

[0017] Figure 1 Bar graph comparing the fermentation volume changes of corn dough by yeast fermentation, standard fermentation and cooperative fermentation;

[0018] Figure 2 Bar graph comparing pH and TTA changes of corn doughs fermented by yeast and co-fermented;

[0019] Figure 3 Inversion diagram of T2 relaxation time of yeast fermentation and co-fermentation corn dough;

[0020] Figure 4 Scanning electron micrographs of yeast fermented, standard fermented, and co-fermented corn dough;

[0021] Figure 5Gas chromatogram of volatile compounds in yeast-fermented corn bread;

[0022] Figure 6 Gas chromatogram of volatile compounds in standard fermented corn steamed bread;

[0023] Figure 7 Gas chromatogram of volatile compounds in co-fermented corn steamed bread;

[0024] Figure 8 Surface morphology of corn steamed bread produced by yeast fermentation, standard fermentation and cooperative fermentation. DETAILED DESCRIPTION

[0025] Highly active dry yeast and improvers were purchased from Angel Yeast Co., Ltd.

[0026] Lactobacillus plantarum standard strain Biogreen300 was purchased from Danisco (China) Co., Ltd.

[0027] MRS culture medium is composed of 1% peptone, 1% beef extract powder, 0.4% yeast extract powder, 2% glucose, 0.108% Tween-80, 0.2% dipotassium hydrogen phosphate, 0.5% sodium acetate, 0.2% triammonium citrate, 0.02% magnesium sulfate, and 0.005% manganese sulfate. After preparation, it is sterilized at 121°C for 15 minutes.

[0028] Example 1 Screening and Identification of Lactobacillus plantarum JSLp-20

[0029] (1) Initial screening

[0030] Take 10g of naturally fermented corn sour soup dough 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 -4 Dilution 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 there are no foreign bacteria 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 15 pure colonies of short rod-shaped, Gram-positive, catalase-negative bacteria were isolated.

[0031] (2) Rescreening

[0032] The colonies obtained in the initial screening were inoculated into MRS broth culture medium and cultured at 37°C for 24 hours. The cultured bacterial solution was centrifuged at 5000r / min for 15 minutes, the supernatant was removed and sterile saline was added, and the culture was centrifuged twice. Sterile saline was added to adjust the bacterial solution concentration to an OD600 value of 12, and the bacterial suspension was placed at 4°C for use.

[0033] Weigh 50g corn flour and 50g wheat flour through an 80-mesh sieve respectively, add 43g of 90-100℃ pure water to the corn flour, mix the wheat flour into the corn flour after cooling, and stir evenly. Add auxiliary materials, fermentation agents and improvers and 3ml of the prepared bacterial suspension to form a dough. Knead the dough for 5 minutes to make a smooth corn dough. Put the dough into a constant temperature fermentation box and ferment it for 1h at a temperature of 37℃ and a humidity of 75% to obtain a primary fermented corn dough. Take it out and gently expel the bubbles in the fermented corn dough for five minutes. After the secondary fermentation for half an hour, steam it in cold water for 25 minutes. The surface of the steamed buns is smooth and flat and produces a fresh fragrance after steaming. The sensory evaluation score of ten people in the team was repeated three times to obtain the average sensory score. Six strains of bacteria that meet this indicator were selected and preserved.

[0034] Table 1

[0035] ;

[0036] The above 6 strains were inoculated into the fermented dough and repeatedly inoculated at 37℃ for 5 times, the fermented dough volume was observed, and the flavor and taste of the steamed bread were evaluated by sensory evaluation. Finally, a lactic acid bacteria strain was selected that could maximize the steamed bread specific volume and the best flavor and taste when fermented at room temperature for 1 hour. The volume of the steamed bread was measured by the rice displacement method, and the flavor and taste were evaluated by sensory evaluation. After screening, the best strain, lactic acid bacteria JSLp-20, was obtained and stored in a -80℃ glycerol cryopreservation tube for later use.

[0037] (3) Molecular biological identification

[0038] The lactic acid bacteria JSLp-20 screened in step (2) was subjected to molecular biological identification. The genomic DNA of the lactic acid bacteria JSLp-20 was extracted and subjected to 16S rRNA sequencing, and the primers selected for sequencing were universal gene primers.

[0039] The reaction system for PCR amplification is: 1 μL of upstream primer and downstream primer, 1 μL of template, 9.5 μL of dH2O, and 12.5 μL of Mix premix. The primers are:

[0040] 27F: 5'-AGAGTTTGATCCTGGCTCAG-3';

[0041] 1541R: 5'AAGGAGGTGATCCAGCCGCA-3';

[0042] The reaction procedure is: 94°C, 5 min; 94°C, 30 s, 55°C, 20 s, 55°C, 20 s, 72°C, 1.5 min, 35 cycles; 72°C, 7 min; 4°C insulation. After PCR amplification, the sequence of the 16sDNA fragment was detected on a machine, and the sequence obtained was shown in the sequence table SEQ ID NO.1.

[0043] The sequencing results were subjected to BLAST analysis in the GenBank database of the NCBI website. The 16S rDNA sequence of the strain was 98% homologous to Lactobacillus plantarum. Combined with the morphological characteristics and physiological and biochemical test results, the strain was identified as Lactobacillus plantarum, and named Lactobacillus plantarum JSLp-20. It was deposited in the General Microbiology Center of China Culture Collection Committee on May 13, 2024, address: Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing; the deposit number is CGMCC No.30608.

[0044] The plant lactobacillus JSLp-20 has the following morphological characteristics: the colony diameter is 1.0-1.8 mm, round, smooth in surface, complete in edge, protruding in the center, milky white, and opaque; the liquid culture has no sterile film, no bubbles, turbid bacterial liquid, obvious stratification, the bacteria are not easy to be centrifuged, and there is white precipitation at the bottom; the cell morphology is rod-shaped or elliptical, the rod-shaped bacteria are 0.34 μm×2.21 μm (length×width) in size, and the elliptical bacteria are 0.52 μm×1.97 μm (length×width) in size, the cells are often arranged in a single, have no spores, and do not move.

[0045] ① After culturing the activated plant lactobacillus in liquid MRS medium for 24 hours, adjust the fermentation liquid to the same absorbance as the seed medium, inoculate it into 100mL MRS liquid medium at a 2% inoculation amount, and culture it at a constant temperature of 0-50℃ for 24 hours. During this period, take a sample every 2 hours, centrifuge it at 6000r for 5 minutes, remove the supernatant, add an equal amount of sterile saline to the supernatant, repeat 2-3 times, and shake and mix. Measure its OD value at a wavelength of 600nm. It was found that the concentration of the bacteria increased at 15℃-40℃, and the growth rate was the fastest and the concentration was the highest at 37℃. The optimal fermentation temperature is 37℃, and the suitable growth temperature is 15-40℃;

[0046] ② After culturing the activated plant lactobacillus in liquid MRS medium for 24 hours, adjust the fermentation liquid to the same absorbance as the seed medium, inoculate it into 100mL MRS liquid medium at a 2% inoculation rate, and culture it at 37°C for 24 hours. During this period, take a sample every 2 hours, centrifuge at 6000r for 5 minutes, remove the supernatant, add an equal amount of sterile saline to the supernatant, repeat 2-3 times, and shake to mix. Measure its OD value at a wavelength of 600nm. The OD600 value increases logarithmically within 8-12 hours, and then tends to stabilize. At 37°C, the logarithmic growth period of the bacteria is 8-12 (h) after inoculation, and then enters a stable growth period;

[0047] ③ Use dilute hydrochloric acid and sodium hydroxide to prepare MRS medium with a pH value of 2-10, sterilize at high temperature and high pressure at 121℃ for 15min, culture the activated plant lactobacillus in liquid MRS medium for 24h, adjust the fermentation liquid to the same absorbance as the seed medium, inoculate it into 100mL MRS liquid medium at a 2% inoculation amount, culture at 37℃ for 12h, centrifuge at 6000r for 5min, remove the supernatant, add sterile saline equal to the supernatant, repeat 2-3 times, and shake and mix. Measure the OD value under different pH conditions at a wavelength of 600nm. It was found that the growth concentration of the bacteria was the highest under pH6.2, and the optimal fermentation pH value of the bacteria was 6.2. The OD600 value of the bacteria increased under the condition of pH 3.5-8.0, and the pH range suitable for growth was between 3.5-8.0. When cultured at pH 6.2 for 24 hours, the pH value of the bacterial solution decreased to 3.8-4.0 with the production of acid by fermentation, and the pH value of the MRS medium decreased to 3.8-4.0 due to the production of acid by fermentation.

[0048] ④ Prepare liquid MRS medium with bile salt concentration of 0-0.6%, sterilize at high temperature and high pressure at 121℃ for 15min, culture the activated plant lactobacillus in liquid MRS medium for 24h, adjust the fermentation liquid to the same absorbance as the seed medium, inoculate it into 100mL MRS liquid medium at a 2% inoculation amount, culture at 37℃ for 12h, centrifuge at 6000r for 5min, remove the supernatant, add sterile saline equal to the supernatant, repeat 2-3 times, and shake and mix. Measure its OD value at a wavelength of 600nm. It was found that the bacterial liquid concentration of the bacteria increased under the condition of 0.4% bile salt concentration, and stopped growing at 0.5%. The bacteria can grow under the conditions of pH value of 3.5 and bile salt content of 0.4%, and has strong acid and bile salt resistance.

[0049] Example 2 Preparation of Co-fermented Corn Steamed Bread

[0050] (1) Weigh 200 g of corn flour that has been passed through an 80-mesh sieve, then add 172 g of hot water at a temperature of 90-100°C to the corn flour, stir evenly, and cool for later use.

[0051] (2) Weigh 200 g of wheat flour passed through an 80-mesh sieve, add it to the corn flour obtained in step (1), and stir evenly; weigh 0.44 g of Lactobacillus plantarum JSLp-20 dry powder, add it to 40 g of milk, and culture it at 40° C. for 3 hours; then add the activated Lactobacillus plantarum JSLp-20 together with 40 g of egg liquid, 4.8 g of sucrose, 0.2 g of salt, 2.8 g of highly active dry yeast, and 2 g of improver into the dough and knead them until the surface of the dough is smooth.

[0052] (3) fermenting the dough obtained in step (2) at a temperature of 37° C. and a humidity of 70-75% for 1 hour to obtain fermented corn dough;

[0053] (4) kneading and exhausting the fermented corn dough obtained in step (3), shaping the dough, and placing the dough at room temperature for a second proofing for 25-30 minutes;

[0054] (5) Put the corn steamed bun embryos that have been proofed twice in step (4) into a pot with cold water and steam for 25 minutes to obtain corn steamed buns.

[0055] Comparative Example 1 Preparation of Yeast Fermented Corn Steamed Bread

[0056] (1) Weigh 200 g of corn flour that has been passed through an 80-mesh sieve, then add 172 g of hot water at a temperature of 90-100°C to the corn flour, stir evenly, and cool for later use.

[0057] (2) Weigh 200 g of wheat flour passed through an 80-mesh sieve, add it to the corn flour obtained in step (1), and stir evenly; weigh 40 g of milk, 40 g of egg liquid, 4.8 g of sucrose, 0.2 g of salt, 2.8 g of highly active dry yeast, and 2 g of improver, respectively, and add them together to the dough and knead until the surface of the dough is smooth.

[0058] (3) fermenting the dough obtained in step (2) at a temperature of 37° C. and a humidity of 70-75% for 1 hour to obtain fermented corn dough;

[0059] (4) kneading and exhausting the fermented corn dough obtained in step (3), shaping the dough, and placing the dough at room temperature for a second proofing for 25-30 minutes;

[0060] (5) Put the corn steamed bun embryos that have been proofed twice in step (4) into a pot with cold water and steam for 25 minutes to obtain corn steamed buns.

[0061] Comparative Example 2 Preparation of corn steamed bread fermented by co-fermentation with Lactobacillus plantarum standard

[0062] (1) Weigh 200 g of corn flour that has been passed through an 80-mesh sieve, then add 172 g of hot water at a temperature of 90-100°C to the corn flour, stir evenly, and cool for later use.

[0063] (2) Weigh 200 g of wheat flour passed through an 80-mesh sieve, add it to the corn flour obtained in step (1), and stir evenly; weigh 0.44 g of dry powder of Lactobacillus plantarum standard substance, add it to 40 g of milk, and culture it at 40° C. for 3 hours; then add the activated Lactobacillus plantarum standard substance, 40 g of egg liquid, 4.8 g of sucrose, 0.2 g of salt, 2.8 g of highly active dry yeast, and 2 g of improver into the dough and knead them until the surface of the dough is smooth.

[0064] Weigh 40g of milk, 40g of egg liquid, 4.8g of sucrose, 0.2g of salt, 2.8g of highly active dry yeast, and 2g of improver respectively, add them into the dough and knead until the surface of the dough is smooth.

[0065] (3) fermenting the dough obtained in step (2) at a temperature of 37° C. and a humidity of 70-75% for 1 hour to obtain fermented corn dough;

[0066] (4) kneading and exhausting the fermented corn dough obtained in step (3), shaping the dough, and placing the dough at room temperature for a second proofing for 25-30 minutes;

[0067] (5) Put the corn steamed bun embryos that have been proofed twice in step (4) into a pot with cold water and steam for 25 minutes to obtain corn steamed buns.

[0068] 1. Detection of corn dough fermentation ability

[0069] The method of Chevallier et al. (Chevallier S, Zúñiga R, Le-Bail A. Assessment of Bread Dough Expansion during Fermentation[J]. Food and Bioprocess Technology, 2012, 5(2): 609-617.) was slightly modified. The fermentation capacity of dough was measured by the measuring cylinder method. 100 g of the prepared dough was placed in a 500 ml measuring cylinder. The dough was compacted into the measuring cylinder to ensure that there was no gap at the bottom. The initial volume V0 was recorded. The measuring cylinder was placed in a constant temperature fermentation box (37°C, humidity 75%) for fermentation for 1 hour and the dough volume V1 was recorded. The dough expansion volume V=V1-V0.

[0070] like Figure 1As shown, the volume of the fermented corn dough prepared in step (3) of Example 2 is compared with the volume of the fermented corn dough prepared in step (3) of Comparative Example 1. The volume of the fermented corn dough in Example 2 is 20.00% larger than that of the fermented corn dough in Comparative Example 1, and the volume of the fermented corn dough in Example 2 is 9.09% larger than that of the fermented corn dough in Comparative Example 2, indicating that the fermentation effect of yeast is improved under the synergistic action of Lactobacillus plantarum, and the fermentation effect is better under the synergistic action of yeast and Lactobacillus plantarum JSLp-20.

[0071] 2. Corn dough acidification ability test

[0072] According to the second method (pH meter potentiometric titration method) in the national standard GB12456-2021, the pH and TTA values ​​of the dough were determined. Take 10g of dough sample, add 90mL of deionized water, and then let it stand and cool to room temperature after 30 minutes of magnetic stirring. Use a pH meter to measure the pH value of the sample, and then use 0.1mol / L sodium hydroxide solution to titrate the pH of the sample to 8.2, and record the volume of sodium hydroxide solution consumed as the titratable acidity (Total titratable acid, TTA) TTA value of the dough.

[0073] Referring to the method in GB5009.157-2016, 5g of fermented dough sample was weighed, a certain proportion of pure water was added for high-speed homogenization, and then placed in a 50mL centrifuge tube and centrifuged at 4000r / min for 5min. The supernatant was taken and filtered through a 0.22μm filter membrane. The lactic acid and acetic acid content in the sample was determined by HPLC. Chromatographic conditions: EcosilC18 was used, the mobile phase was methanol / water / H3PO4 (volume ratio was 97 / 3 / 0.003), the flow rate was 0.8mL / min, the column temperature was 30℃, the injection volume was 10μL, the time was set to 30min, and the detection wavelength was 210nm. The lactic acid and acetic acid standard solutions with concentrations of 0.5, 1.0, 2.0, 5.0, and 10.0mg / mL were prepared respectively. After determination under the same chromatographic conditions, the standard curve was drawn with the peak area as the vertical axis and the standard sample concentration as the horizontal axis, and the lactic acid and acetic acid content in the sample was calculated by the standard curve.

[0074] The results are as follows Figure 2As shown, the pH values ​​of fermented corn dough of Example 2, Comparative Example 1 and Comparative Example 2 were 6.02, 5.84 and 5.86 respectively, and the TTA values ​​were 2.47, 2.27 and 2.31 respectively. Compared with yeast fermented corn dough, the pH value of plant lactobacillus JSLp-20 synergistic fermented corn dough was reduced by 3.08%, and the TTA value increased by 8.81%. Compared with plant lactobacillus standard product and yeast synergistic fermentation, the pH value was reduced by 2.73%, and the TTA value increased by 6.93%. As shown in Table 1-1, yeast fermentation and standard synergistic fermentation did not produce lactic acid and acetic acid, and the lactic acid content produced by plant lactobacillus JSLp-20 synergistic yeast fermentation was 0.13mg / ml.

[0075]

[0076] 3. Detection of corn dough gelatinization characteristics

[0077] Use a precision balance to weigh 3g of freeze-dried dough powder into a RVA-specific aluminum can, pour in 25ml of distilled water, and stir thoroughly. Place the mixture into the RVA analyzer for testing. Test procedure: The temperature is 50°C at the beginning, the speed is 960 r / min, the speed drops to 160r / min after 10s and remains unchanged until the end, the temperature starts to rise to 95°C at a uniform speed after 1min, the temperature is maintained for 2.5min, and then the temperature is lowered to 50°C at the same speed, and the total time is 13min.

[0078] The results are shown in Table 2. Compared with the yeast-fermented corn dough of Comparative Example 1, the peak viscosity of the corn dough fermented by the plant lactobacillus JSLp-20 of Example 2 was reduced by 7.56%, the trough viscosity was reduced by 10.44%, the final viscosity was reduced by 12.26%, the disintegration value was reduced by 0.80%, and the regeneration value was reduced by 13.89%. Compared with the yeast-fermented corn dough of Comparative Example 2, the peak viscosity of the corn dough fermented by the plant lactobacillus standard product of Example 2 was reduced by 3.41%, the trough viscosity was reduced by 7.50%, the final viscosity was reduced by 8.67%, the disintegration value was reduced by 0.53%, and the regeneration value was reduced by 10.70%, which shows that the plant lactobacillus JSLp-20 and yeast fermentation are beneficial to improving the anti-aging property of starch and strengthening the stability of starch granules in corn dough.

[0079]

[0080] 4. Detection of moisture distribution changes in corn dough

[0081] The method of Jiang et al. (Jiang XF, Wang XT, Zhou S M. Influence of roasted flaxseed marc flour on rheological, structural, fermentation, water distribution, and migration properties of wheat dough. [J]. Journal of food science, 2023, 88 (12): 4840-4852.) was slightly modified. The moisture distribution of steamed bread dough was measured by low-field nuclear magnetic resonance (LF-NMR). 1 g of dough was placed in a nuclear magnetic resonance tube. To avoid water loss during the drying process, the tube was sealed with paraffin film. The relaxation time (T2) was measured by CPMG sequence. The measurement parameters were: number of sampling points: 200; number of echoes: 2000; number of scans: 8 times. In the obtained T2 inversion map, the T2 values ​​corresponding to different peaks were recorded as T21, T22, and T23, respectively.

[0082] The results are shown in Table 3 and Table 2. Compared with the fermented corn dough prepared in Comparative Example 1, the fermented corn dough prepared in Example 2 has a reduced total water content; the proportions of free water and weakly bound water in Example 2 are lower than those in the latter, while the proportion of bound water is higher than that in the latter. Compared with the fermented corn dough prepared in Comparative Example 2, the proportions of free water and bound water in Example 2 are higher than those in the latter, while the proportion of weakly bound water is lower than that in the latter, indicating that the water holding capacity of the reconstituted dough is weakened, the weakly bound water in the dough is converted into more tightly bound water, the degree of binding between water and starch is enhanced, and the degree of freedom of water molecules is reduced, indicating that the fermented corn dough prepared in Example 2 has a tendency to migrate weakly bound water in the dough to free water and bound water, the water holding capacity of the dough is enhanced, the dough components are more tightly bound to water molecules, and it is more conducive to forming a good gluten network.

[0083]

[0084] 5. Detection of Microscopic Morphological Changes of Corn Dough

[0085] The method of Wang et al. (Wang SQ, Lin ZY, Xia KX, et al. Dynamics of watermobility and distribution in Sur clam ( Mactra chinensis ) during dehydration and rehydration processes assessed by low-field NMR and MRI[J]. Journal of Food Measurement and Characterization, 2017, 11(3)) was slightly modified. The fermented corn dough was freeze-dried in vacuum, and freeze-dried corn dough blocks with flat cross-sections were selected for pasting. The sample surface was sprayed with gold and observed at ×500 times at an accelerating voltage of 2KV.

[0086] The results are as follows Figure 4 As shown, compared with the fermented corn dough of Comparative Examples 1 and 2, the tissue structure of the corn dough fermented by plant lactobacillus JSLp-20 and yeast in Example 2 is relatively loose, the gluten network is relatively loose, and the holes formed are fine and uniform. Some starch granules are decomposed into incomplete granules, with depressions and wrinkles. The acidic environment formed by the metabolism of lactic acid bacteria promotes acid hydrolysis of starch, which is conducive to agglomeration.

[0087] 6. Specific volume and texture change detection of corn steamed bread

[0088] According to GB / T35991-2018, the volume of corn steamed bread was measured by millet displacement method after it was steamed and cooled for 1 hour. The mass was weighed using an electronic balance (accurate to 0.1g), and each group of samples was measured three times in parallel, and then the average value was taken. The specific volume of steamed bread can be calculated by the following formula:

[0089]

[0090] The method of Yaqoob et al. (Yaqoob S, Liu H, Liu M, et al. The effect of lactic acid bacteria and co-culture on structural, rheological, and textural profile of corn dough[J]. Food Science Nutrition, 2021, 10(1): 264-271.) was slightly modified. The corn bread was taken out and cooled to room temperature, and cut into uniform slices with a thickness of about 20 mm using a cutter. The TPA test was performed using a flat-bottomed cylindrical P / 36R probe. The test parameters were: pre-test speed 1 mm / s, test speed 1 mm / s, post-test speed 1 mm / s; compression dwell time: 5 s; trigger force: 5 g; compression ratio: 50%.

[0091] The results are shown in Table 4. Compared with the yeast-fermented corn steamed bread of Comparative Example 1, the specific volume of the corn steamed bread fermented by Lactobacillus plantarum JSLp-20 in Example 2 increased by 18.75%, the hardness, cohesion and chewiness decreased by 3.60%, 4.00% and 5.19% respectively, the elasticity and adhesiveness increased by 1.14% and 57.36% respectively, and the resilience increased by 1 times. Compared with the corn steamed bread fermented by Lactobacillus plantarum standard product in Comparative Example 2, the specific volume of the corn steamed bread fermented by Lactobacillus plantarum JSLp-20 in Example 2 increased by 11.76%, the hardness, cohesion and chewiness decreased by 3.21%, 4.00% and 3.30% respectively, the elasticity and adhesiveness increased by 1.14% and 34.99% respectively, and the resilience increased by 66.67%.

[0092] ;

[0093] 7. Sensory evaluation of corn steamed buns

[0094] According to GB / T17320-2013 "Classification of Wheat Varieties Quality", a steamed bun scoring table was developed with some minor adjustments. The judging panel consisted of 10 trained members, including 5 men and 5 women. The steamed buns were scored on their shape, color, hardness, elasticity, texture, flavor and taste, with a total score of 100 points, and the final score was the average.

[0095] The results are shown in Tables 5 and 6. Compared with the yeast-fermented corn steamed buns of Comparative Example 1, the morphological score of the corn steamed buns fermented with plant lactobacillus JSLP-20 in Example 2 increased by 2.36%, the color score increased by 9.20%, the hardness score increased by 5.95%, the elasticity score increased by 5.10%, the texture structure score increased by 5.08%, the flavor and taste score increased by 6.55%, and the total score increased significantly, indicating that the overall acceptability of the corn steamed buns fermented with plant lactobacillus JSLP-20 and ink was higher than that of the yeast-fermented corn steamed buns.

[0096] ;

[0097] ;

[0098] 8. Detection of changes in volatile flavor substances in corn steamed bread

[0099] The flavor components of steamed bread were analyzed by GC-MS (Cao Y, Zhang H, Yang Z, et al. Influence of the fermentation time and potato pulp addition on the technological properties and volatile compounds of wheat dough and steamed bread [J]. LWT - Food Science and Technology, 2020, 128: 109377.). 2 g corn steamed bread was placed in a 20 mL headspace bottle, the sample was equilibrated in a 60 ° C water bath for 15 min, and then heated in a 60 ° C water bath for extraction for 60 min. Then the extraction head was inserted into the injection port for 5 min. A HP-5MS column (30m × 0.25mm × 0.25μm) was used, the column temperature was 40 ° C for 2 min, increased to 80 ° C at 2 ° C / min, then increased to 120 ° C at 8 ° C / min, and finally increased to 220 ° C at 5 ° C / min and maintained for 4 min. The ionization energy and scanning range were 70 eV and 40-350 m / z, respectively. The temperature of the ion source was set at 250°C. The mass spectra were matched by computer with those from the National Institute of Standards and Technology and the Wiley Library. Compounds with a similarity percentage higher than 80% were retained for data analysis.

[0100] The results are shown in Table 7. The fermented corn steamed bread prepared in Example 2 has 15 more kinds of volatile flavor substances than the fermented corn steamed bread prepared in Example 1, and 15 more kinds of volatile flavor substances than the fermented corn steamed bread prepared in Example 2. Among them, the main volatile flavor substances that form the corn aroma are n-hexanal and caprylic aldehyde. The content of caprylic aldehyde in the synergistically fermented corn steamed bread is increased by 1.21%, which increases its corn aroma. It is also rich in various esters, such as ethyl acetate, ethyl caprylate, ethyl caprylate, etc., which enriches the flavor of the corn steamed bread.

[0101] .

Claims

1. A strain of Lactobacillus plantarum JSLp-20, deposited in the General Microbiology Center of China Microbiological Culture Collection Administration, with the deposit number of CGMCC No.30608.

2. Use of the Lactobacillus plantarum JSLp-20 described in claim 1 in preparing corn steamed bread.

3. A method for preparing corn steamed bread by using Lactobacillus plantarum and yeast for fermentation, comprising: 1) Add 90-100℃ hot water to corn flour and stir evenly; 2) adding wheat flour, the activated dry powder of the Lactobacillus plantarum JSLp-20 strain according to claim 1 and active dry yeast to the corn flour prepared in step (1), stirring evenly, and kneading into a smooth dough; 3) fermenting the dough obtained in step (2) at a temperature of 36-38° C. and a humidity of 70-75% for 50-70 minutes to obtain fermented corn dough; 4) kneading and exhausting the fermented corn dough obtained in step (3), shaping the dough, and placing the dough at room temperature for a second proofing for 25-30 minutes; 5) Put the corn steamed bun embryos that have been proofed twice in step (4) into a pot with cold water and steam them to obtain corn steamed buns.

4. The method for preparing corn steamed bread by using Lactobacillus plantarum and yeast fermentation according to claim 3, characterized in that: The weight ratio of the wheat flour to the corn flour in the step (2) is 1:1-2.

5. The method for preparing corn steamed bread by using Lactobacillus plantarum and yeast fermentation according to claim 4, characterized in that: In the step (2), auxiliary materials are also added, and the auxiliary materials include: improver, egg liquid, milk, sucrose and salt.

6. The method for preparing corn steamed bread by using Lactobacillus plantarum and yeast fermentation according to claim 5, characterized in that: Based on the total weight of corn flour and wheat flour, the amount of egg liquid added is 10%, the amount of milk added is 10%, the amount of sucrose added is 1.2%, and the amount of salt added is 0.05%.

7. The method for preparing corn steamed bread by using Lactobacillus plantarum and yeast fermentation according to claim 6, characterized in that: The activation of Lactobacillus plantarum JSLp-20 is performed by mixing with milk and culturing at 40° C. for 4 hours.

8. The method for preparing corn steamed bread by using plant lactobacillus and yeast for fermentation according to claim 1, 2, 3, 4, 5, 6 or 7, characterized in that: The weight ratio of the wheat flour to the corn flour in the step (2) is 1:1.

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