Method for improving quality of steamed cake by fermenting whole egg liquid with lactic acid bacteria

Abstract

The invention discloses a method for improving the quality of steamed cakes through lactobacillus fermented whole egg liquid, and belongs to the field of food processing. In order to enrich existing steamed cake series products and solve the problems that the egg smell is heavy, the oil content is high and the like, the original steamed cake making process is perfected by fermenting whole egg liquid through lactic acid bacteria. The required raw materials are eggs, lactic acid bacteria, white granulated sugar, sp cake oil and low-gluten wheat flour. The fermented whole egg liquid steamed cake product can be obtained after the whole egg liquid is fermented for 16 hours at 37 DEG C by utilizing the cultured lactic acid bacteria liquid, the required raw materials are mixed, beaten and steamed in a pot for 12 minutes, and the product quality is improved under the condition that a relatively simplified and clean formula is used. The fermented whole egg liquid steamed cake prepared by the method disclosed by the invention is softer in cake body, more uniform and distinct in color, greener and healthier, has unique yogurt fragrance fermented by lactic acid bacteria, and is more popular with people.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing, and particularly relates to a method for improving the quality of steamed cakes by fermenting whole egg liquid with lactic acid bacteria. Background Art

[0002] Steamed cake is a soft, healthy, and low-fat Chinese pastry. Steamed cakes are cooked using the heat of steam, resulting in a moister, lighter flavor than oven-baked cakes. Steamed cakes are made primarily from eggs and low-gluten flour, supplemented with sugar and oil. Originating from traditional Chinese steamed pastry techniques, they have become a popular choice in recent years for both home baking and pre-packaged foods due to their ease of preparation and low fat content.

[0003] The current mainstream dietary trends are towards health, naturalness, and clean labels, and some artificial additives are often seen as "unnatural" and "unhealthy." However, during industrial steaming, the strict temperature and time controls in steaming cakes can cause the sulfides in the eggs to volatilize, resulting in a fishy odor. Furthermore, during large-scale factory production, fluctuations in steaming temperature and humidity can cause the cakes to collapse or become hard, resulting in unstable texture. Industrial production struggles to completely eliminate additives to address these two issues. Factories, driven by cost considerations, often add unhealthy additives, such as artificial flavoring to mask the eggy odor and high levels of emulsifiers and baking powder to maintain a stable texture. This goes against current dietary trends. However, consumers are not completely averse to additives; instead, they are more concerned with their necessity and safety and naturalness.

[0004] Therefore, it is extremely important to develop a green and healthy steamed cake that can not only mask the eggy smell in the steamed cake and give it a special flavor, but also stabilize its own texture characteristics while adding as few additional food additives as possible. Summary of the Invention

[0005] In order to solve the problem of strong egg smell in existing steamed cakes, the present invention provides a strain of Streptococcus thermophilus Z24, which has been deposited in the General Microbiology Center of China Culture Collection Administration of Microorganisms with a deposit number of CGMCC NO.34729 and a deposit date of May 30, 2025.

[0006] The present invention also provides a microbial agent containing the thermophilic Streptococcus Z24;

[0007] In one embodiment, the microbial agent uses the above-mentioned Streptococcus thermophilus Z24 as the main microorganism;

[0008] In one embodiment, the microbial agent contains live cells of Streptococcus thermophilus Z24, freeze-dried dry cells of Streptococcus thermophilus Z24, immobilized cells of Streptococcus thermophilus Z24, a liquid agent of Streptococcus thermophilus Z24, a solid agent of Streptococcus thermophilus Z24, or Streptococcus thermophilus Z24 in any other form.

[0009] The present invention also provides a fermented whole egg liquid, wherein the fermented whole egg liquid is obtained by fermenting with thermophilic Streptococcus Z24 or the above-mentioned microbial agent;

[0010] In one embodiment, the method for preparing the fermented whole egg liquid comprises the following steps:

[0011] (1) Egg pretreatment: After fresh eggs are cracked, the egg white and yolk are mixed by beating to make whole egg liquid;

[0012] (2) Whole egg liquid fermentation: Thermophilic Streptococcus Z24 or the above microbial agents were added at a rate of 1×10 5 ~1×10 9 The inoculum amount of CFU / g is added into the whole egg liquid prepared in (1) and fermented to obtain the obtained product.

[0013] The present invention also provides a method for improving the performance of whole egg liquid, the method comprising: fermenting the whole egg liquid with the thermophilic Streptococcus Z24 or the microbial agent;

[0014] In one embodiment, the method for preparing the fermented whole egg liquid comprises the following steps:

[0015] (1) Egg pretreatment: After fresh eggs are cracked, the egg white and yolk are mixed by beating to make whole egg liquid;

[0016] (2) Whole egg liquid fermentation: Thermophilic Streptococcus Z24 or the above microbial agents were added at a rate of 1×10 5 ~1×10 9 The inoculum amount of CFU / g is added into the whole egg liquid prepared in (1) and fermented to obtain the obtained product.

[0017] The present invention also provides a baked food, which is prepared by using the fermented whole egg liquid as a raw material;

[0018] In one embodiment, the baked food includes but is not limited to: steamed cakes, bread, biscuits, and egg tarts made with whole egg liquid fermented with lactic acid bacteria.

[0019] The present invention also provides a method for preparing a steamed cake made from whole egg liquid fermented by lactic acid bacteria, comprising the following steps:

[0020] (1) Egg pretreatment: Fresh eggs are cracked and beaten to mix the egg white and yolk to prepare whole egg liquid;

[0021] (2) Whole egg liquid fermentation: The bacterial suspension of thermophilic Streptococcus or Lactobacillus casei was prepared at a concentration of 1×10 5 ~1×10 9 The inoculum amount of CFU / g is added into the whole egg liquid prepared in (1), and fermented at 28°C to 37°C for 4 to 16 hours to obtain fermented whole egg liquid.

[0022] (3) preparing cake batter;

[0023] (4) Pour the cake batter prepared in (3) into a mold and steam it in a steamer to obtain a lactic acid bacteria fermented egg liquid steamed cake.

[0024] In one embodiment, the egg shell surface in step (1) should be disinfected and sterilized with 75% alcohol in advance.

[0025] In one embodiment, the method for preparing the bacterial suspension in step (2) is as follows: picking a single colony of Streptococcus thermophilus, inoculating it into MRS liquid culture medium, culturing it at 37°C for 20 hours, and then inoculating it into MRS liquid culture medium for a second time with an inoculum size of 2%, culturing it at 37°C for 20 hours, and centrifuging the obtained bacterial liquid to obtain a bacterial sludge precipitate, washing it twice with 0.9% sterile saline, and then redissolving it in sterile water.

[0026] In one embodiment, the concentration of the thermophilic Streptococcus suspension is 1×10 8 ~1×10 9 CFU / g.

[0027] In one embodiment, the composition of the MRS liquid culture medium is: peptone 10.0 g, Tween 80 1.0 g, beef extract 5.0 g, yeast extract 4.0 g, manganese sulfate monohydrate 0.05 g, dipotassium hydrogen phosphate 2.0 g, glucose 20.0 g, sodium acetate 5.0 g, triammonium citrate 2.0 g, magnesium sulfate heptahydrate 0.2 g, deionized water 1000 mL, pH between 6.5 and 6.8.

[0028] In one embodiment, after the MRS liquid culture medium is dissolved, it is placed in a sterilizer at 115° C. for sterilization for 15 minutes and cooled for later use.

[0029] In one embodiment, the entire process of preparing the fermented whole egg liquid in step (2) should be performed under a sterile environment.

[0030] In one embodiment, the steamed cake batter in step (3) comprises, by weight: 80 to 180 parts of fermented whole egg liquid, 30 to 80 parts of low-gluten flour, 15 to 50 parts of white sugar, and 1.2 to 4.5 parts of sp cake oil.

[0031] In one embodiment, the steamed cake batter in step (3) comprises, by weight: 100 parts of fermented whole egg liquid, 50 parts of low-gluten flour, 30 parts of white sugar, and 2.0 parts of sp cake oil.

[0032] In one embodiment, the specific method for preparing the cake batter in step (3) is as follows: fermented whole egg liquid, white sugar, and SP cake oil are mixed and first whipped at a speed of 300-350 r / min for 10 minutes until the "8" is clearly visible and does not disappear, and the texture is as thick as a ribbon. Then, cake flour is added and whipped at a speed of 60-120 r / min for 1 minute until all ingredients are evenly mixed and the cake batter is smooth and free of particles.

[0033] In one embodiment, the mold size in step (4) is: upper base diameter of 7 cm, lower base diameter of 4.5 cm, and height of 3 cm. The cake batter is poured into the mold in an amount of 25 parts by weight.

[0034] In one embodiment, the steaming conditions in step (4) are: boil the water in advance, steam over medium heat for 12 minutes, and keep warm for 5 minutes before opening the lid.

[0035] The present invention also provides the use of the thermophilic streptococcus or the microbial agent or the fermented whole egg liquid in preparing baked foods.

[0036] Beneficial effects

[0037] The present invention provides a method for improving the quality of steamed cakes by fermenting whole egg liquid with lactic acid bacteria, which not only reduces the amount of additives used in making steamed cakes, but also improves the quality of steamed cakes, improves the stability of the quality of different batches of products, and provides an effective method for fermenting whole egg liquid to improve the flavor and nutritional value of whole egg liquid. The present invention adopts lactic acid bacteria to ferment whole egg liquid. First, the prepared bacterial suspension is used to ferment the whole egg liquid, and then the fermented whole egg liquid is used to make steamed cakes with as few additional additives as possible. The steamed cake prepared by the present invention has a large volume, better color, softer mouthfeel, better elasticity, and largely removes the eggy smell of the steamed cake, and gives it a rich and unique yogurt flavor, with a higher sensory score. The present invention achieves a comprehensive improvement in the flavor, texture, and nutrition of steamed cakes through the technical innovation of lactic acid bacteria fermentation of whole egg liquid, and provides a new idea for the development of healthy baked foods; specifically:

[0038] (1) Significantly improved flavor

[0039] A. Effectively remove the eggy odor: Lactic acid bacteria fermentation degrades sulfur compounds (such as methionine and cysteine) in egg liquid, reducing the production of unpleasant flavor substances (such as dimethyl trisulfide and 2-(ethylthio)acetophenone).

[0040] B. Imparting a unique yogurt aroma: Esters such as ethyl lactate (7.23 μg / kg), isoamyl lactate (3.12 μg / kg), and ketones such as acetoin (44.67 μg / kg) produced by fermentation impart a rich fermented milk aroma and baking aroma to the steamed cake.

[0041] C. Rich flavor layers: The synergistic effect of aldehydes (hexanal 67.49μg / kg), alcohols (octen-3-ol 17.91μg / kg) and ketones creates multi-layered flavors such as grassy, ​​floral and fruity aromas.

[0042] (2) Texture quality optimization

[0043] Improved taste: the hardness (454.44g) is 55% lower than that of comparative example 1 (1011.36g), the elasticity (0.94) and chewiness (330.48N) are better, and the taste is soft and delicate without falling off.

[0044] (3) Improved color and appearance

[0045] A. Brightness improvement: The L value of the steamed cake after fermentation reached 79.28, which was brighter than that of Comparative Example 1 (75.35).

[0046] B. Stable structure: no pudding layer, uniform internal structure, fine pores, full and symmetrical appearance (sensory score 8.65 / 9).

[0047] (4) Nutritional and health advantages

[0048] A. Increased functional ingredients: After fermentation, the umami amino acids (glutamic acid 358.50 mg / 100 g) and the total essential amino acids (662.54 mg / 100 g) are significantly increased, and polyunsaturated fatty acids (C18:3n3 6.63 mg / 100 g) are generated.

[0049] B. Reduce dependence on additives: natural fermentation replaces artificial flavors and emulsifiers, and the formula is cleaner (containing only egg liquid, flour, sugar, and SP cake oil).

[0050] Biomaterial Deposit

[0051] A strain of Streptococcus thermophilus Z24, taxonomically named Streptococcus thermophilus, was deposited in the General Microbiology Center of the China Culture Collection Administration on May 30, 2025, with the deposit number CGMCC NO.34729, and the deposit address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. DETAILED DESCRIPTION

[0052] The following describes preferred embodiments of the present invention. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0053] Unless otherwise specified, w / v or m / v in the following examples refer to g / 100ml.

[0054] The fresh eggs and related raw materials involved in the following embodiments were purchased from a local supermarket in Wuxi.

[0055] The lactic acid bacteria involved in the following examples are: Lactobacillus sanfranciscensis DSM20451T, Lactiplantibacillus plantarum M1, Lactiplantibacillus plantarum LAB2, Lactiplantibacillus plantarum LAB4, Weissella cibaria C14, Lactobacillus sakei LS8 FUA3009, all of which are deposited in the strain bank of Jiangnan University. Streptococcus thermophilus has been deposited in the General Microbiology Center of the China Culture Collection Administration.

[0056] The detection method of the steamed cake color involved in the following embodiment is as follows:

[0057] Place a handheld colorimeter close to the steamed cake skin and record the brightness (L*), redness (a*), and yellowness (b*) of the steamed cake skin or cake core.

[0058] The detection method of the steamed cake texture involved in the following embodiments is as follows:

[0059] A 12mm thick slice from the center of a steamed cake was selected for full texture analysis. A P / 25 aluminum cylindrical probe was used. Test conditions were: a trigger force of 5g, a strain of 50%, a pre-test speed of 3mm / s, a speed during the test of 1mm / s, a post-test speed of 10mm / s, a 5s interval between compressions, a sensing force of 5g, a data acquisition rate of 250pps, and the TPA test mode. Analyzed parameters included resilience, hardness, elasticity, cohesiveness, and chewiness.

[0060] The detection method of the steamed cake specific volume involved in the following embodiment is as follows:

[0061] The volume was measured using the rapeseed displacement method, and the ratio of volume to mass was recorded as the steamed cake specific volume in mL / g.

[0062] The method for sensory evaluation of the steamed cake involved in the following embodiments is as follows:

[0063] A sensory panel of 20 trained participants (male:female ratio 1:1, aged between 22 and 30) was selected for the evaluation. The evaluation was scheduled for 4:00 PM. Samples of roughly uniform size and shape were placed on a plain white tray, randomly numbered, and presented. The panelists rated the steamed cakes on a 9-point scale based on appearance, internal structure, color, flavor, aroma, and texture. The specific criteria are shown in Table 1. Mineral water and soda crackers were provided for oral hygiene.

[0064] Table 1: Sensory evaluation criteria for steamed cakes

[0065]

[0066] The steamed cake flavor substance detection method involved in the following embodiment is as follows:

[0067] The volatile flavor compounds in steamed cakes were detected by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS): For quantitative determination, 2,4,6-trimethylpyridine was dissolved in methanol to prepare an internal standard solution, and an appropriate amount of the internal standard solution was added to the sample bottle depending on the test results. A 2g steamed cake sample was placed in a headspace extraction bottle, and a 75μm CAR / PDMS extraction head was inserted. The sample was then placed in a 60°C constant temperature water bath for extraction for 30 min. The extraction head, which had adsorbed all the volatile compounds, was removed and inserted into the injection port of a gas chromatograph-mass spectrometer for desorption at 250°C for 9 min. The capillary column model was DB-WAX 122-7032 (30m×0.25mm×0.25μm), and high-purity helium was used as the carrier gas at a flow rate of 2mL / min.

[0068] The gas chromatography-mass spectrometer (GC-MS) was programmed as follows: hold at 40°C for 3.5 minutes, then increase to 90°C at 5°C / min, and finally increase to 220°C at 12°C / min, where the temperature was held for 7 minutes. The injection port temperature was 250°C, the ionization mode was EI, the ion source temperature was 200°C, the electron energy was 70 eV, the emission current was 200 μA, and the detection voltage was 350 V. Full-scan acquisition was used, with a mass range of 33 to 495 m / z. The resulting GC-MS peaks were matched against the Wiley Library and the NIST Library. A match and purity greater than 900 were considered valid identifications. Peak areas were expressed as relative percentages.

[0069] The detection method of the egg liquid emulsification property involved in the following embodiments is as follows:

[0070] Whole egg liquid was diluted to a 0.5 mg / mL (50 mg / 100 mL) sample solution. Then, 5 mL of sunflower oil and 15 mL of the sample solution were placed in a 50 mL centrifuge tube and homogenized at 12,000 rpm for 1 minute at 25°C using a high-speed homogenizer to prepare an emulsion. 0 minutes after homogenization, 100 μL of the emulsion was aspirated from the bottom of the centrifuge tube and diluted with 5 mL of SDS solution (1 g / kg). After mixing, the absorbance of the diluted emulsion was measured at 500 nm using a UV spectrophotometer. Emulsifying activity (EA) was expressed as the absorbance measured at 500 nm after emulsion formation.

[0071] The detection method of the egg liquid foamability and foam stability involved in the following embodiments is as follows:

[0072] Whole egg liquid was diluted with ultrapure water to a 1% (w / v) sample solution. 40 mL of this diluted solution was then homogenized using a high-speed homogenizer at 12,000 rpm for 1 minute at 25°C. The foaming capacity (FC) of the sample was expressed as the ratio of the foam volume at 0 minutes after homogenization to the initial sample volume.

[0073] Foaming property FC (%) = (H1-H0) / H0×100;

[0074] Foam stability FS (%) = (H2-H0) / (H1-H0) × 100;

[0075] Record the initial height H0 (40 mL); whisk at 12,000 rpm / min for 1 minute, record the foam height H1. After standing for 30 minutes, measure the foam height H2.

[0076] The method for sensory evaluation of the fermented egg liquid involved in the following examples is as follows:

[0077] A sensory evaluation panel of 20 trained individuals (male:female ratio 1:1, aged 22-30 years) was selected. The evaluation was scheduled for 4:00 PM. Samples were placed on pure white trays, randomly numbered, and presented. The evaluators scored the fermented whole egg liquid on a 9-point scale based on its color, flavor, and texture. The specific criteria are shown in Table 2.

[0078] Table 2: Sensory evaluation criteria for fermented whole egg liquid

[0079]

[0080] The detection method of the organic acid in the egg liquid involved in the following examples is as follows:

[0081] A 1 g sample was diluted to 25 mL with ultrapure water, shaken at 25°C for 1 hour, and centrifuged at 10,000 × g for 30 minutes. The supernatant was collected, filtered through a 0.22 μm microporous filter, and analyzed using a high-performance liquid chromatograph. Column: Aminex HPX-87H (300 mm × 7.8 mm × 9 μm); mobile phase: 0.008 mol / L H₂SO₄; flow rate: 0.6 mL / min; detector wavelength: 210 nm; column temperature: 50°C; injection volume: 10 μL.

[0082] The detection method of the free amino acids in the egg liquid involved in the following embodiments is as follows:

[0083] A 1 g sample was diluted to 25 mL with 5% (w / w) trichloroacetic acid. The mixture was sonicated at 25°C for 30 min, allowed to stand for 2 h, and centrifuged at 10,000 × g for 10 min. The supernatant was collected and filtered through a 0.22 μm filter. The filtrate was analyzed by high-performance liquid chromatography. The column was an Agilent Hypersil OD column (250 mm × 4 mm × 5 μm); the column temperature was 40°C; the detection wavelength was 338 nm (262 nm for proline); the mobile phases were mobile phase A (pH = 7.2, 27.6 mmol / L sodium acetate, trimethylamine, tetrahydrofuran, 500:0.11:2.5 (v / v)); and mobile phase B (pH = 7.2, 80.9 mmol / L sodium acetate, methanol, acetonitrile, 1:2:2 (v / v)). The flow rate was 1.0 mL / min. The amino acid concentrations were determined by external standard method using 1 nmol / μL amino acid standards.

[0084] The detection method of the free fatty acids in the egg liquid involved in the following embodiments is as follows:

[0085] 1g of whole egg solution was mixed with 10mL of chloroform-methanol solution (2:1, v / v) and 1mL of internal standard (500.0mg / L C11:0 in methanol) at 150rpm / min for 24h. The mixture was filtered into a graduated test tube and evaporated in a water bath at 70°C to obtain a yellow oily liquid at the bottom. 2mL of n-hexane was added to the oily liquid to obtain a sample mixture. 6mL of n-hexane-diethyl ether (1:1, v / v) was used to equilibrate an aminopropyl separation column. The sample mixture was passed through the column and then rinsed twice with 6mL of n-hexane-diethyl ether (1:1, v / v). The eluent was discarded to elute triacylglycerides. 4mL of diethyl ether solution containing 2% formic acid was then passed through the column and the filtrate was collected. The sample was concentrated under nitrogen purge. Add 2 mL of a 14% boron trifluoride-methanol solution (boron trifluoride-ether:methanol = 1:3, v / v) to the concentrated sample and place in a 70°C water bath for 30 min. After cooling, add 2 mL of n-hexane and 2 mL of saturated saline. Extract with vortexing. The upper organic phase is aspirated and transferred to a centrifuge tube containing 1 g of anhydrous Na₂SO₄. The supernatant is analyzed by gas chromatography. Carrier gas: helium; flow rate: 1.2 mL / min; temperature program: 165°C for 10 min, then increase to 200°C at 7.4°C / min, and hold for 22 min.

[0086] The detection method of the whole egg liquid flavor substances involved in the following embodiments is as follows:

[0087] The volatile flavor compounds in whole egg liquid were detected by headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS): for quantitative determination, 1 μL of cyclohexanone was dissolved in methanol to prepare 1 mL of internal standard solution, and 30 μL of the internal standard solution was added to the sample bottle. 5 g of whole egg liquid sample was placed in a headspace extraction bottle, and a 75 μm CAR / PDMS extraction head was inserted. The sample was placed in a 60°C constant temperature water bath for extraction for 30 min. The extraction head that had adsorbed the volatile compounds was removed and inserted into the injection port of a gas chromatograph-mass spectrometer, and desorbed at 250°C for 9 min. The capillary column model was DB-WAX 122-7032 (30 m × 0.25 mm × 0.25 μm), and high-purity helium was used as the carrier gas at a flow rate of 2 mL / min.

[0088] The gas chromatography-mass spectrometer (GC-MS) was programmed as follows: hold at 40°C for 4 minutes, then increase to 90°C at a rate of 5°C / min, and finally increase to 230°C at a rate of 10°C / min, where the temperature was held for 6 minutes. The injection port temperature was 250°C, the ionization mode was EI, the ion source temperature was 200°C, the electron energy was 70 eV, the emission current was 200 μA, and the detection voltage was 350 V. Full-scan acquisition was used, with a mass range of 33 to 495 m / z. The resulting GC-MS peaks were matched against the Wiley Library and the NIST Library. A match and purity greater than 900 were considered valid identifications. Peak areas were expressed as relative percentages.

[0089] The culture medium involved in the following examples is as follows:

[0090] Peptone 10.0 g, Tween 80 1.0 g, beef extract 5.0 g, yeast extract 4.0 g, manganese sulfate monohydrate 0.05 g, dipotassium hydrogen phosphate 2.0 g, glucose 20.0 g, sodium acetate 5.0 g, triammonium citrate 2.0 g, magnesium sulfate heptahydrate 0.2 g, deionized water 1000 mL, pH between 6.5 and 6.8.

[0091] Example 1: Isolation, screening and preservation of lactic acid bacteria

[0092] (1) Separation and screening 10 g of sample was taken from traditional handmade yogurt in Wuxi, Jiangsu Province, and placed in 90 mL of sterile NaCl solution (0.9%, W / V) and mixed and vortexed. -1 ~10 -5 ), from 10 -3 , 10 -4 and 10 -5 Take 100 μL of each dilution from the concentration gradient and evenly spread it on a modified MRS agar plate (as described above). Incubate anaerobically at 30°C for 48 hours and place in an anaerobic bag. After incubation, pick white colonies and isolate and purify them by multiple streaking until a single colony is obtained.

[0093] (2) Identification of strains

[0094] The whole genome DNA of the strain was extracted for 16S rDNA amplification. The amplified DNA fragments were collected and sent to the company for sequencing. The sequencing analysis results showed that the strain was Streptococcus thermophilus and was named Streptococcus thermophilus Z24.

[0095] Example 2: Preparation of fermented egg liquid

[0096] The specific steps are as follows:

[0097] (1) Egg pretreatment:

[0098] Fresh eggs are cracked and beaten to mix the egg white and yolk to make whole egg liquid;

[0099] (2) Preparation of bacterial suspension:

[0100] Single colonies of Streptococcus thermophilus Z24, Lactobacillus sanfranciscensis DSM20451T, Lactiplantibacillus plantarum M1, Lactiplantibacillus plantarum LAB2, Lactiplantibacillus plantarum LAB4, Weissella cibaria C14, and Lactobacillus sakei LS8FUA3009 were picked and inoculated into MRS liquid medium, and cultured at 37°C for 20 hours, vortexed and mixed to prepare bacterial solutions;

[0101] The prepared bacterial suspension was inoculated into MRS liquid medium at an inoculum volume of 2% (v / v) and cultured at 37°C for 20 h. The obtained bacterial suspension was centrifuged at 8000 rpm for 10 min to obtain bacterial sludge sediment, which was then washed twice with 0.9% sterile saline and resuspended in sterile water to obtain a concentration of 1×10 8 CFU / mL of bacterial suspension.

[0102] (3) Whole egg liquid fermentation:

[0103] The thermophilic Streptococcus Z24 bacterial suspension, plantarum Lactobacillus M1 bacterial suspension, plantarum Lactobacillus LAB2 bacterial suspension, plantarum LAB4 bacterial suspension, sanfranciscous DSM20451T bacterial suspension, edible sinus Weissella C14 bacterial suspension, sake Lactobacillus LS8 FUA3009 bacterial suspension prepared in step (2) were respectively added to a 1×10 8 CFU / g 蛋黄液 The inoculum amount is introduced into the whole egg liquid prepared in step (1);

[0104] The above systems were fermented at 37°C for 16 h to obtain fermented whole egg liquids prepared by different lactic acid bacteria.

[0105] Example 3: Effects of different lactic acid bacteria on fermented whole egg liquid

[0106] 1. The pH and foaming properties of the fermented whole egg liquids prepared by different lactic acid bacteria were tested respectively. The results are shown in Table 3 below:

[0107] Table 3: Results of different lactic acid bacteria

[0108] lactic acid bacteria Fermentation endpoint pH Foaming % Foam stability % Streptococcus thermophilus Z24 6.78±0.01 19.16±1.56 91.47±5.14 Lactobacillus plantarum M1 7.23±0.02 17.09±1.09 72.88±1.29 Lactobacillus plantarum LAB2 8.04±0.02 13.77±0.21 59.24±3.13 Lactobacillus plantarum LAB4 8.20±0.02 14.72±1.04 57.19±2.58 Lactobacillus sanfranciscous DSM20451T 7.98±0.09 17.91±0.98 70.99±3.09 Weissella sinusoidalis C14 7.72±0.07 13.83±1.67 52.97±2.11 Lactobacillus sakei LS8 FUA3009 8.00±0.02 15.12±1.45 61.67±4.19

[0109] The results show:

[0110] (1) The whole egg liquid fermented by thermophilic Streptococcus Z24 had the best foaming property and foam stability. Its foaming property (19.16%) and foam stability (91.47%) were significantly higher than those of other strains (p < 0.05), and the pH at the fermentation endpoint (6.78) was the lowest.

[0111] (2) The comprehensive performance of Lactobacillus plantarum M1 and Lactobacillus sanfranciscous DSM20451T was second best, with foaming properties of 17.09% and 17.91% respectively, which were close to Streptococcus thermophilus Z24, but the foam stability was lower, 72.88% and 70.99% respectively, which may be related to their neutral to alkaline pH. However, they were still better than other Lactobacillus plantarum LAB2 / LAB4 and Lactobacillus sakei.

[0112] 2. Conduct sensory evaluation on the fermented whole egg liquid after fermentation

[0113] The results are shown in Table 4.

[0114] Table 4: Sensory evaluation of fermented whole egg liquid

[0115]

[0116] The results showed that Streptococcus thermophilus Z24 scored >8.5 on all three indicators, with its mild acid production significantly improving flavor and texture. The second-best strains, Lactobacillus sanfranciscous DSM20451T and Lactobacillus plantarum M1, scored >7.0 on flavor. Lactobacillus plantarum LAB2, LAB4, and Weissella sinusoidalis C14 had a strong fishy smell and low sensory scores.

[0117] Finally, three strains with relatively superior performance were obtained: fermented whole egg liquid prepared from the bacterial suspensions of Streptococcus thermophilus Z24, Lactobacillus plantarum M1, and Lactobacillus sanfranciscous DSM20451T.

[0118] Example 4: Effects of different fermentation conditions

[0119] 1. Based on Example 2 (the added strain is Streptococcus thermophilus Z24), the fermentation time in step (3) is changed to 12 h, and the remaining steps are consistent with Example 2 to prepare fermented whole egg liquid -12 h.

[0120] 2. Based on Example 2 (the added strain is Streptococcus thermophilus Z24), the fermentation time in step (3) is changed to 8h, and the remaining steps are consistent with Example 2 to prepare fermented whole egg liquid -8h.

[0121] 3. On the basis of Example 2 (the added strain is Streptococcus thermophilus Z24), the fermentation time in step (3) is changed to 4h, and the remaining steps are consistent with Example 2 to prepare fermented whole egg liquid-4h.

[0122] Comparative Example 1: Whole egg liquid is not fermented

[0123] On the basis of Example 2, step (2) and step (3) are omitted, and the remaining steps are consistent with Example 1. The specific steps are that fresh eggs are cracked and beaten to mix the egg white and yolk to prepare whole egg liquid.

[0124] Example 5: Detection of the performance of different groups of whole egg liquid

[0125] The fermented whole egg liquids prepared at different fermentation times using Streptococcus thermophilus Z24 in Example 4 were tested, and the whole egg liquids of each group were named Streptococcus thermophilus-16h (Example 2), Streptococcus thermophilus-12h, Streptococcus thermophilus-8h, and Streptococcus thermophilus-4h, respectively.

[0126] The whole egg liquid obtained in Comparative Example 1 was used as a control. The performance of the whole egg liquids of different groups was tested, and the results are as follows:

[0127] (1) Determination of the emulsification properties of whole egg liquid

[0128] The results of emulsification test of fermented whole egg liquid are shown in Table 5.

[0129] Table 5: Measurement results of the emulsification of whole egg liquid

[0130]

[0131] The results showed that the emulsifying properties of the fermented whole egg liquid prepared by fermenting for 16 hours and 12 hours using Streptococcus thermophilus Z24 were 0.71±0.09 and 0.76±0.05, respectively; they also showed excellent emulsifying properties, and their values ​​were significantly higher than those of the comparative example groups. This excellent emulsifying property may be mainly due to the moderate hydrolysis and reorganization of the protein structure during the fermentation process, which enables the protein molecules to more effectively form a stable interfacial film at the oil-water interface. A higher emulsifying index indicates that a more uniform and stable emulsification system can be formed during the baking process, which will directly translate into a more delicate organizational structure and more uniform pore distribution of the baked product. In contrast, the emulsifying performance of the comparative example 1 group is obviously insufficient, which may lead to quality defects such as rough texture and uneven structure in the final product. The present invention significantly improves the emulsifying properties of the whole egg liquid, which is of great relevance for obtaining baked products with ideal texture characteristics.

[0132] (2) Determination of foaming properties and foam stability of whole egg liquid

[0133] The foamability and foam stability of the fermented egg liquid according to the present invention are measured as shown in Table 6.

[0134] Table 6: Measurement results of foaming property and foam stability of whole egg liquid

[0135]

[0136] The results show:

[0137] Fermentation time is positively correlated with foaming properties. The foaming properties of the 16h fermentation group were 19.16%, significantly higher than those of the other groups (p < 0.05), and 3.28 times that of Comparative Example 1, indicating that long-term fermentation (12-16h) can significantly improve the foaming ability of egg liquid. The foaming properties of the 4h and 8h groups were similar, but both were significantly higher than those of the blank group, indicating that short-term fermentation still has a certain effect. The foam stability of the 16h group (91.47%) was significantly higher than that of Comparative Example 1, followed by the 12h group (84.16%). There was no significant difference in the stability of the 4h and 8h groups compared with the blank group (p > 0.05), and the data of the 4h group fluctuated greatly, indicating that the stability required ≥ 12h fermentation to be significantly improved.

[0138] The fermented whole egg liquid prepared by fermenting for 16 hours using Streptococcus thermophilus Z24 not only has a strong foaming ability, but also has a foam stability of up to 91.47%, indicating that the bubble structure produced has a strong resistance to rupture and can effectively maintain the structural integrity of the cake during the steaming and cooling process. This excellent foaming property is mainly due to the moderate hydrolysis and reorganization of the protein structure during the fermentation process, as well as the generation of surfactants, which work together to improve the stability of the gas-liquid interface. The fermentation conditions created by the present invention significantly improve the foaming ability and foam stability of the whole egg liquid, which is a key technical feature for obtaining steamed cakes with ideal fluffiness, uniform pore structure and delicate taste, and is also an important advantage of the present invention compared to traditional processes.

[0139] (3) Determination of organic acids in whole egg liquid

[0140] The organic acid content in the fermented whole egg liquid of the present invention is shown in Table 7:

[0141] Table 7: Determination of organic acids in whole egg liquid (mg / 100g)

[0142]

[0143] The results showed that the fermented whole egg liquid prepared by fermenting with Streptococcus thermophilus Z24 for 16 hours exhibited the most prominent organic acid profile, with a total organic acid content of 189.25±8.32 mg / 100g, significantly higher than that of the other groups. Lactic acid (152.46±6.14 mg / 100g) was particularly prominent, exceeding that of Comparative Example 1 (1.85±0.01 mg / 100g) by 82.4 times. This high lactic acid content not only imparts a mild sour flavor and a refreshing taste to the product, but also interacts with amino acids to produce aromatic compounds such as pyrazines, significantly enhancing the flavor complexity of the product.

[0144] Meanwhile, the citric acid content (21.91 ± 1.77 mg / 100 g) and malic acid content (13.32 ± 0.49 mg / 100 g) of the fermented egg liquid prepared by fermenting thermophilic streptococcus Z24 for 16 h are also maintained at a higher level, and the synergistic effect of these organic acids makes the product present a rich sour taste. By contrast, the total amount of organic acid of Comparative Example 1 is obviously on the low side, and especially lactic acid is obviously lower, causing the product to lack the unique sour and fragrant flavor of fermentation. It is worth noting that although the total acid amount of the fermented egg liquid prepared by fermenting thermophilic streptococcus Z24 for 4 h is lower (53.29 ± 2.16 mg / 100 g), its citric acid content (40.02 ± 1.66 mg / 100 g) is significantly higher than other groups, which may give the product a more distinct fruit acid feature. The present invention significantly increases the content of organic acids, especially lactic acid, by regulating the fermentation time. This not only improves the taste balance of the product, but more importantly provides a key acidic environment for the subsequent Maillard reaction, which plays a decisive role in forming the unique flavor characteristics of the product.

[0145] (4) Determination of free amino acids in whole egg liquid

[0146] The free amino acid content in the fermented whole egg liquid is shown in Table 8:

[0147] Table 8: Determination of free amino acids in whole egg liquid (mg / 100g)

[0148]

[0149] The results show:

[0150] The total essential amino acid content of Streptococcus thermophilus Z24 fermentation groups after 16 and 12 hours was 640.61 mg / 100 g and 646.11 mg / 100 g, respectively, significantly higher than the control group's 627.32 mg / 100 g. Leucine (Leu) reached 137.92 mg / 100 g in the 16-hour group, a 5.3% increase over the control group. The 4-hour group had the highest total essential amino acid content, reaching 662.54 mg / 100 g, with isoleucine (Ile) particularly high, 8.0% higher than the control group. Notably, methionine (Met) content decreased with increasing fermentation time, reaching the highest level in the 8-hour group at 50.00 mg / 100 g, a 16.9% increase over the 16-hour group.

[0151] Glutamic acid (Glu), the primary umami amino acid, reached its highest level in the 16-hour fermentation group, reaching 294.50 mg / 100 g, a 19.2% increase over the control group. Aspartic acid (Asp) levels were higher in all fermentation groups, reaching 146.51 mg / 100 g in the 12-hour fermentation group, a 9.1% increase. The total umami amino acid content reached 722.21 mg / 100 g in the 16-hour fermentation group, a 10.1% increase over the control group. This explains the material basis for the enhanced flavor of fermented egg liquid.

[0152] The total amino acid content showed a U-shaped trend over fermentation time, with higher levels in the 4-hour group (1543.65 mg / 100 g) and the 16-hour group (1560.59 mg / 100 g), while the 8-hour group had the lowest level, at 1432.24 mg / 100 g. Arginine (Arg) content was highest in the 12-hour group, 19.6% higher than the control group. Total amino acid content was higher in all fermentation groups than in the control group, with the 16-hour group showing an 8.6% increase. The essential amino acid / total amino acid ratio reached 42.0% in the 12-hour group, compared to 43.7% in the control group, indicating that fermentation improved amino acid balance. Tyrosine (Tyr) content was highest in the 12-hour group (104.48 mg / 100 g), 7.7% higher than the control group, which is important for protein synthesis. The 12-hour fermentation process achieved a good balance between total essential amino acid content (646.11 mg / 100 g) and umami amino acid content (705.29 mg / 100 g), making it the optimal process. For the highest total amino acid content, a 16-hour fermentation process is recommended.

[0153] (5) Determination of free fatty acids in whole egg liquid

[0154] Table 9 is the result of determination of free fatty acid content in fermented whole egg liquid:

[0155] Table 9: Determination results of free fatty acids in whole egg liquid

[0156]

[0157] The results show:

[0158] Fermentation using Streptococcus thermophilus Z24 revealed that C16:0 (palmitic acid) and C18:0 (stearic acid) were the highest in all groups, accounting for over 70% of the total fatty acids. The C16:0 content in the 16-hour fermentation group (52.55 mg / 100 g) was significantly lower than that in the 4-hour group (68.01 mg / 100 g), but higher than that in the 8-hour group (38.89 mg / 100 g), demonstrating a nonlinear effect of fermentation time on saturated fatty acid content. Notably, unsaturated fatty acids such as C18:1 (oleic acid) and C18:2 (linoleic acid) were generally higher in the fermentation groups than in the control group. In particular, the C18:1 content in the 12-hour fermentation group (13.10 mg / 100 g) was 34% higher than that in the control group (9.77 mg / 100 g). Medium-chain fatty acids C12:0 and C13:0 were detected in all fermentation groups, with the 12h group showing the highest C12:0 content at 2.50mg / 100g. The long-chain polyunsaturated fatty acid C18:3n3 (α-linolenic acid) was only present in the 8h (2.93mg / 100g) and 4h (7.65mg / 100g) groups, indicating that shorter fermentations are more conducive to the release of n-3 fatty acids. Of particular note, the C17:0 (heptadecanoic acid) content decreased with prolonged fermentation time, reaching 9.76mg / 100g in the 16h group, significantly lower than both the 4h group (16.98mg / 100g) and the control (17.14mg / 100g). All fermentation groups exhibited a richer fatty acid profile, particularly the 12-hour fermentation group, where seven fatty acids, including C12:0, C13:0, C16:0, C17:0, C18:0, C18:1, and C18:2, were detected, compared to only five in the control group. Nutritionally, the elevated unsaturated fatty acids in the fermentation groups (e.g., C18:2, reaching 8.56 mg / 100 g in the 8-hour fermentation group, a 110% increase compared to the control group) have higher bioactivity value.

[0159] (6) Determination of flavor substances in whole egg liquid

[0160] The flavor substances of the fermented whole egg liquid of the present invention are shown in Table 10:

[0161] Table 10: Determination results of volatile flavor substances in whole egg liquid

[0162]

[0163]

[0164]

[0165] The results show:

[0166] Changes in characteristic flavor substances:

[0167] The 16-hour fermentation group produced a high level of acetoin, reaching 30.83 μg / kg, nearly 100 times higher than the control group. This is a key contributor to the characteristic flavor of fermented dairy products. Furthermore, the 16-hour group also showed significantly higher levels of phenylacetaldehyde (1.12 μg / kg) and D-limonene (7.36 μg / kg), giving the product a distinctive aromatic character. Notably, the 8-hour fermentation group also produced benzonitrile (1.45 μg / kg) and benzoic acid (3.32 μg / kg), unique components that may contribute to the distinctive flavor.

[0168] The 16-hour group showed significantly higher levels of octanal (3.76 μg / kg) and decanal (6.64 μg / kg) than the other groups. These substances contribute to a refreshing citrus and fatty aroma. (Z)-2-heptenal (1.23 μg / kg) and (E)-2-nonenal (1.10 μg / kg), both characteristic of the control group, were either undetectable or reduced in the fermentation group, suggesting that the fermentation process alters lipid oxidation pathways. Acetic acid was highest in the 8-hour group (29.14 μg / kg), 16% higher than in the 16-hour group. The 16-hour group also showed significantly higher levels of 2-ethyl-1-hexanol (11.72 μg / kg) and 2,6-dimethylcyclohexanol (5.15 μg / kg) than in the control group. These substances contribute to a sweet and woody aroma. Furthermore, the control group had significantly higher levels of 1-butanol (14.60 μg / kg) and 1-pentanol (10.59 μg / kg) than the fermentation group.

[0169] 16-hour fermentation produced a more diverse spectrum of volatile substances, particularly forming a variety of unique ketones (such as acetophenone 2.86μg / kg) and alcohols. 8-hour fermentation exhibited intermediate characteristics, with some substances (such as phenol 4.98μg / kg) reaching peak levels. 2,4-di-tert-butylphenol (2.28μg / kg) and 4-methylhexan-2-one (8.21μg / kg) detected in the control group completely disappeared in the fermentation group. The 16-hour fermentation process performed outstandingly in forming characteristic flavor substances (such as acetoin and D-limonene), making it suitable for products requiring a rich fermented aroma. 8-hour fermentation can retain some of the characteristics of the raw materials while also producing a unique combination of flavor substances.

[0170] Example 6: Preparation of steamed cake

[0171] The steamed cake was prepared using the whole egg liquid prepared in Example 2: fermented whole egg liquid (Streptococcus thermophilus Z24), fermented whole egg liquid (Lactobacillus plantarum M1), and fermented whole egg liquid (Lactobacillus sanfranciscous DSM20451T), as well as the fermented whole egg liquid-12h, fermented whole egg liquid-8h, and fermented whole egg liquid-4h prepared in Example 3, comprising the following steps:

[0172] (1) Preparation of cake batter: Clean the mixing bowl to avoid any oil stains or water contamination. Pour 100 parts of fermented whole egg liquid, 30 parts of white sugar, and 2.0 parts of sp cake oil into the mixing bowl and mix. First, beat at 350 r / min for 10 minutes until the "8" is clear and does not disappear, and the texture is as thick as a ribbon. Then add 50 parts of low-gluten flour and beat at 60 r / min for 1 minute. All ingredients are mixed evenly and the cake batter is smooth and free of particles.

[0173] (2) Steaming the cake: Pour the prepared cake batter into a mold with a size of 7 cm in upper base diameter, 4.5 cm in lower base diameter, and 3 cm in height, with 25 parts of cake batter per mold. Boil the water in advance, steam over medium heat for 12 minutes, keep warm for 5 minutes, and then open the lid to prepare the lactic acid bacteria fermented egg liquid steamed cake.

[0174] The steamed cake-Streptococcus thermophilus Z24, steamed cake-Lactobacillus plantarum M1, steamed cake-Lactobacillus sanfranciscous DSM20451T, steamed cake-fermented whole egg liquid-12h, steamed cake-fermented whole egg liquid-8h, and steamed cake-fermented whole egg liquid-4h were prepared respectively.

[0175] Comparative Example 2: Preparation of Steamed Cake Using Whole Egg Liquid Without Fermentation

[0176] The specific steps are as follows:

[0177] (1) Egg pretreatment: Fresh eggs are cracked and beaten to mix the egg white and yolk to prepare whole egg liquid;

[0178] (2) Prepare cake batter: Clean the mixing bowl to avoid any oil or water stains. Pour 100 parts of whole egg liquid, 30 parts of white sugar, and 2.0 parts of sp cake oil into the mixing bowl and mix. First, beat at 350 r / min for 10 minutes until the "8" is clear and does not disappear, and the texture is as thick as a ribbon. Then add 50 parts of low-gluten flour and beat at 60 r / min for 1 minute. All ingredients are mixed evenly and the cake batter is smooth and free of particles.

[0179] (3) Steaming the cake: Pour the prepared cake batter into a mold with a top base diameter of 7 cm, a bottom base diameter of 4.5 cm, and a height of 3 cm. Each mold should contain 25 parts of cake batter by weight. Boil the water in advance, steam over medium heat for 12 minutes, keep warm for 5 minutes, and then remove the lid to prepare the steamed cake.

[0180] Example 7: Detection of Steamed Cake Index

[0181] (1) Determination of color of steamed cake

[0182] Table 11 is the colorimetric test results of steamed cakes;

[0183] Table 11: Color measurement results of steamed cake

[0184]

[0185] The results show:

[0186] The L of steamed cake in steamed cake-thermophilic Streptococcus-16h group and steamed cake-thermophilic Streptococcus-12h group * The value is the highest, and the color of the steamed cake skin is the brightest. * The value is the smallest among all groups, indicating that the lactic acid bacteria fermentation used in the article can improve the brightness of steamed cakes. * The value is the smallest in each group. Compared with comparative example 2, the yellowness b * The values ​​were all decreased, and the b of the method of the present invention (steamed cake-thermophilic streptococcus) was * The value was smaller than that of the other groups, indicating that the steamed cakes made with Lactobacillus casei fermented whole egg liquid were less yellowish and more attractive. The color change showed that the steamed cakes made with Lactobacillus casei fermented whole egg liquid were brighter, improving the product's appearance. Fermenting the whole egg liquid with Lactobacillus casei for 12 hours and 16 hours significantly increased the brightness of the steamed cakes.

[0187] (2) Determination of steamed cake texture

[0188] Generally speaking, the greater the hardness, stickiness and chewiness, the worse the taste of the steamed cake, the lower the softness, and the lack of the soft taste. The test results are shown in Table 12.

[0189] Table 12: Texture test results of steamed cake

[0190]

[0191] As can be seen from Table 12, the difference of each group steamed cake in hardness, elasticity, glutinousness and chewiness.Compared with Comparative Example 2, the hardness, glutinousness and chewiness of the cake prepared by adopting method of the present invention (steamed cake-thermophilus streptococcus) all obviously decline, have given the feature that steamed cake mouthfeel is smooth and soft.And lactobacillus fermented egg liquid also has positive effect on the elasticity of steamed cake product (except Comparative Example 2), increases elasticity and makes steamed cake under the prerequisite with more suitable hardness and sponginess, avoids the mouthfeel of entrance to be thin and soft, and is more difficult for cracking.Wherein the improvement effect of embodiment 1 is particularly obvious, and the steamed cake texture that promptly steamed after lactobacillus casei fermented egg liquid 16h is best.

[0192] (3) Determination of specific volume of steamed cake

[0193] The results are shown in Table 13.

[0194] Table 13: Specific volume determination results of steamed cake

[0195]

[0196]

[0197] Table 13 shows that the specific volume of the steamed cake-thermophilus-16h group increased significantly. Under the same 12-h fermentation time, the specific volume ranked from highest to lowest: steamed cake-thermophilus-12h > steamed cake-Lactobacillus plantarum > steamed cake-Lactobacillus sanfranciscous. This indicates that the lactic acid bacteria's effect on steamed cake volume increases from strongest to weakest: Streptococcus thermophilus > Lactobacillus plantarum > Lactobacillus sanfranciscous.

[0198] (4) Sensory evaluation of steamed cake

[0199] The sensory scores of the steamed cakes are shown in Table 14.

[0200] Table 14: Sensory scores of steamed cakes

[0201]

[0202] The results showed that both the steamed cake-thermophilus-16h group and the steamed cake-thermophilus-12h group achieved satisfactory results in terms of appearance, internal structure, color, flavor, odor, and texture. Sensory scorers described both groups as having a plump and bright appearance, uniform internal structure, and fine pores. Their texture was delicate, soft, and chewy, with no eggy odor. The steamed cake-thermophilus-16h group had a distinct yogurt aroma. This suggests that Lactobacillus casei imparts a unique yogurt flavor to the whole egg liquid after 16 hours of fermentation. The steamed cake from Comparative Example 2, on the other hand, had a yellowish crust and was smaller in size, contained a pudding layer, had a strong eggy odor, and lacked softness. Overall, the steamed cake from the steamed cake-thermophilus-16h group was the most popular.

[0203] (5) Determination of flavor substances in steamed cakes

[0204] The results of the determination of volatile flavor substances in steamed cakes are shown in Table 15.

[0205] Table 15: Determination results of volatile flavor compounds in steamed cakes

[0206]

[0207]

[0208]

[0209] The results showed that aldehydes (such as hexanal, nonanal, and octanal) were the most abundant in all samples (especially hexanal, reaching a maximum of 67.49 μg / kg), and are the primary flavor contributors to steamed cakes, potentially imparting aromas such as grassy and fatty notes. Alcohols (such as 1-hexanol, octen-3-ol, and (E)-oct-2-en-1-ol) and ketones (such as 6-methylhept-5-en-2-one) were next most abundant, potentially contributing to floral, fruity, and mushroom aromas. Esters (such as ethyl L-lactate and ethyl octanoate) and phenols (such as phenol) were present at lower levels but may contribute to flavor modifications, such as sweet and smoky notes.

[0210] The contents of most substances in Comparative Example 2 were significantly lower than those in the Examples. However, the presence of 2-acetylthiazole (a sulfur heterocyclic compound) and 2-(methylmercapto)benzothiazole (a sulfur-containing compound) in Comparative Example 2 may contribute to the eggy flavor of the steamed cake. The content of lactic acid ester compounds (such as L-ethyl lactate and isoamyl lactate) in the Steamed Cake - Streptococcus thermophilus - 16h group was significantly higher than in the other groups, giving it a unique yogurt and sweet flavor.

[0211] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A strain of Streptococcus thermophilus, characterized in that: It has been deposited in the General Microbiology Center of China Culture Collection Administration, with the deposit number CGMCC NO.34729 and the deposit date of May 30, 2025.

2. A microbial agent, characterized in that: Containing the thermophilic Streptococcus CGMCC NO.34729 according to claim 1; Preferably, the microbial agent uses the thermophilic Streptococcus described in claim 1 as the main microorganism; Preferably, the microbial agent contains live cells of Streptococcus thermophilus, freeze-dried dry cells of Streptococcus thermophilus, immobilized cells of Streptococcus thermophilus, liquid agent of Streptococcus thermophilus, solid agent of Streptococcus thermophilus strain, or Streptococcus thermophilus strain in any other form.

3. A fermented whole egg liquid, characterized in that: Obtained by fermentation with the thermophilic Streptococcus CGMCC NO.34729 according to claim 1 or the microbial agent according to claim 2; Preferably, the method for preparing the fermented whole egg liquid comprises the following steps: (1) Egg pretreatment: After fresh eggs are cracked, the egg white and yolk are mixed by beating to make whole egg liquid; (2) Whole egg liquid fermentation: The thermophilic Streptococcus described in claim 1 or the microbial agent described in claim 2 was added at a rate of 1×10 5 ~1×10 9 The inoculum amount of CFU / g is added into the whole egg liquid prepared in (1) and fermented to obtain the obtained product.

4. A method for improving the performance of whole egg liquid, characterized in that, The method is to obtain the product by fermenting the thermophilic Streptococcus CGMCC NO.34729 according to claim 1 or the microbial agent according to claim 2; Preferably, the method for preparing the fermented whole egg liquid comprises the following steps: (1) Egg pretreatment: After fresh eggs are cracked, the egg white and yolk are mixed by beating to make whole egg liquid; (2) Whole egg liquid fermentation: The thermophilic Streptococcus CGMCC No. 34729 described in claim 1 or the microbial agent described in claim 2 was added at a rate of 1×10 5 ~1×10 9 The inoculum amount of CFU / g whole egg liquid was inoculated into the whole egg liquid prepared in (1) for fermentation.

5. A baked food, characterized in that The baked food is prepared by using the fermented whole egg liquid according to claim 3 as a raw material; Preferably, the baked food includes but is not limited to: steamed cakes, bread, biscuits and egg tarts made with whole egg liquid fermented by lactic acid bacteria.

6. A method for improving the quality of steamed cakes made with lactic acid bacteria fermented egg liquid, characterized in that: The method comprises the following steps: (1) Egg pretreatment: Fresh eggs are cracked and beaten to mix the egg white and yolk to prepare whole egg liquid; (2) Whole egg liquid fermentation: The thermophilic Streptococcus CGMCC No. 34729 described in claim 1 or the microbial agent described in claim 2 was added at a rate of 1×10 5 ~1×10 9 The inoculum amount of CFU / g whole egg liquid is added into the whole egg liquid prepared in (1), and fermented at a temperature of 28° C. to 37° C. for 4 to 16 hours to obtain fermented whole egg liquid; (3) Prepare cake batter: Mix the fermented whole egg liquid, low-gluten flour, white sugar, and SP cake oil until the cake batter is smooth and free of particles; (4) Pour the cake batter prepared in (3) into a mold and steam it in a steamer to obtain a lactic acid bacteria fermented egg liquid steamed cake.

7. The method according to claim 6, characterized in that In step (3), the added amounts of the raw materials, in parts by weight, are: 80-180 parts of fermented whole egg liquid, 30-80 parts of low-gluten flour, 15-50 parts of white sugar, and 1.2-4.5 parts of sp cake oil; Preferably, 100 parts of fermented whole egg liquid, 50 parts of low-gluten flour, 30 parts of white sugar, and 2.0 parts of sp cake oil.

8. The method according to claim 6 or 7, characterized in that In step (3), the specific method for preparing the cake batter is as follows: the fermented whole egg liquid, white sugar and sp cake oil are mixed, and the mixture is first beaten at a speed of 300-350 r / min for 10 min until the "8" figure is clear and does not disappear and the texture is as thick as a ribbon; then the low-gluten flour is added and the mixture is beaten at a speed of 60-120 r / min for 1 min until all the ingredients are evenly mixed and the cake batter is smooth and free of particles.

9. The method according to any one of claims 6 to 8, characterized in that: In step (2), the thermophilic Streptococcus is added in the form of a bacterial suspension; Preferably, the preparation method of the bacterial suspension is as follows: picking a single colony of Lactobacillus casei, inoculating it into MRS liquid culture medium, culturing it at 25-37°C for 16-24 hours, then transferring it to MRS liquid culture medium with an inoculum amount of 0.2-2.0%, culturing it at 25-37°C for 16-24 hours to obtain a bacterial liquid, obtaining a bacterial precipitate by centrifugation, rinsing it twice with sterile saline, and then redissolving it in sterile water.

10. Use of the thermophilic Streptococcus CGMCC NO.34729 according to claim 1 or the microbial agent according to claim 2 or the fermented whole egg liquid according to claim 3 in preparing baked goods.

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