Traditional flavor rice cake leavening agent and industrial application thereof

Abstract

The invention discloses a traditional flavor rice cake leavening agent and industrial application thereof, and belongs to the field of bioengineering technology and food preparation. The preparation method of the fermented rice cake comprises the following steps: grinding rice into powder to obtain rice flour, then blending the rice flour into rice milk, then mixing a leavening agent with the rice milk, and then performing fermentation, leavening, steaming and curing to obtain the fermented rice cake. The invention adopts safe strains for food, and is green, natural, nutritional and healthy. The prepared fermented rice cake is soft in tissue, has unique fermentation flavor, and has good sensory characteristics.

Description

Technical Field

[0001] The invention relates to a traditional flavor rice cake leavening agent and an industrial application method thereof, belonging to the fields of bioengineering technology and food preparation. Background Art

[0002] Fermented rice cake is one of the famous traditional foods. As a traditional pastry made from rice, it is ground into powder, mixed with auxiliary materials, fermented and steamed. It has a long history and profound cultural heritage. It combines the aroma of rice and the aroma of fermented wine. It has a soft and elastic taste, rich nutritional value and is easy to digest and absorb. With the technological innovation of rice cake production technology, the industrial scale production capacity of rice cake has been gradually improved, which has given the fermented rice cake market a broad development prospect to meet the needs of consumers.

[0003] The mechanism of rice cake fermentation has been explored to a certain extent, and most of the research focuses on fermentation technology, composition changes, and physicochemical properties. Studies have shown that fermentation can make rice cakes fluffy, giving the product a unique flavor and soft taste. Through the acid and enzyme production of microbial fermentation, the branched starch molecules are prone to debranching and chain breaking reactions, and the hydration capacity is enhanced, which is conducive to maintaining the moisture of the gel and maintaining a stable structure; at the same time, the straight chain starch molecules are prone to polymerization and aging during the fermentation process, which increases the strength of the formed gel network. After fermentation, the particle size of rice flour becomes smaller and tends to be consistent, which is conducive to the uniformity of gelatinization, and at the same time, a stable and delicate gel is formed, and the hardness of the product is reduced, and the elasticity and flexibility are enhanced. In addition, due to the complex composition of microorganisms in the natural fermentation state and the complex and diverse influencing factors, suitable microorganisms can be used for enhanced fermentation. While optimizing the quality of rice cakes, the quality of the product can be controlled, thereby improving the stability of industrial production.

[0004] However, there are still many problems in the rice cake production industry at this stage: most of them still maintain traditional handmade workshop production, resulting in low production efficiency, small output and single flavor; the production process mostly relies on traditional experience, and the current production of fermented rice cakes mostly adopts natural fermentation. Uncontrolled natural fermentation is very easy to be infected with bacteria, making it difficult to ensure product stability and easily causing food safety risks. Therefore, in order to develop a more efficient and stable fermented rice cake production system, it is necessary to find strains with superior characteristics in both flavor formation and antibacterial properties. Summary of the invention

[0005] Technical issues

[0006] The existing rice cake industry is mainly handmade, with low production efficiency. The fermentation process in rice cake production relies heavily on natural fermentation and traditional experience, which leads to problems such as low fermentation efficiency, unstable product quality, and single flavor. Therefore, it is necessary to provide a rice cake fermentation agent and its industrial application in order to stabilize the production of rice cakes.

[0007] Technical content

[0008] In view of the above problems, the present invention provides a traditional flavor rice cake leavening agent and its industrial application.

[0009] The first object of the present invention is to provide a Lactobacillus helveticus RS01, which has been deposited in the China Center for Type Culture Collection on July 22, 2024, with a deposit number of CCTCC M 20241668, and the depository address is Wuhan University, Wuhan, China.

[0010] The second object of the present invention is to provide a brewer's yeast (Saccharomyces cerevisiae) JM01, which has been deposited in the China Center for Type Culture Collection on July 22, 2024, with a deposit number of CCTCC M 20241667, and the depository address is Wuhan University, Wuhan, China.

[0011] The third object of the present invention is to provide a starter culture, comprising the above-mentioned Lactobacillus helveticus RS01 and Saccharomyces cerevisiae JM01.

[0012] A fourth object of the present invention is to provide a method for preparing the above-mentioned leavening agent, comprising the following steps:

[0013] The Lactobacillus helveticus fermentation liquid is prepared by fermenting and culturing the Lactobacillus helveticus in a fermentation medium;

[0014] The brewer's yeast is fermented and cultured in a fermentation medium to obtain a brewer's yeast fermentation liquid;

[0015] Then the Lactobacillus helveticus fermentation liquid and the Saccharomyces cerevisiae fermentation liquid are centrifuged, and the precipitate is taken out and washed to prepare the Lactobacillus helveticus bacterial liquid and the Saccharomyces cerevisiae bacterial liquid;

[0016] The bacterial concentration in the bacterial solution is greater than or equal to 1×10 7 CFU / mL or 1×10 7 CFU / g;

[0017] Then, the Lactobacillus helveticus culture solution and the Saccharomyces cerevisiae culture solution are mixed in a mass ratio of 2 to 4:1.

[0018] In one embodiment, the bacterial concentration in the bacterial solution is 10 7 ~10 9 CFU / mL.

[0019] In one embodiment, the Lactobacillus helveticus fermentation broth is obtained by culturing Lactobacillus helveticus in MRS medium.

[0020] In one embodiment, the MRS culture medium is composed of 8-12 g of peptone, 3-7 g of beef extract powder, 2-6 g of yeast extract powder, 18-22 g of glucose, 1-3 g of dipotassium hydrogen phosphate, 1-3 g of triammonium citrate, 3-7 g of sodium acetate, 0.1-0.4 g of magnesium sulfate, 0.03-0.07 g of manganese sulfate, and 0.8-1.2 g of Tween 80 per 1000 mL of water.

[0021] In one embodiment, the preparation of the Lactobacillus helveticus fermentation broth is specifically as follows:

[0022] The above-mentioned Lactobacillus helveticus was inoculated into MRS medium and activated at 30-37°C for 16-24h;

[0023] Then, the activated strains are inoculated into MRS culture medium at an inoculation amount of 0.5-2% and cultured for at least 6 hours to obtain Lactobacillus helveticus fermentation liquid.

[0024] In one embodiment, the Saccharomyces cerevisiae fermentation broth is obtained by culturing Saccharomyces cerevisiae in YPD medium.

[0025] In one embodiment, the YPD medium is composed of 18-22 g of peptone, 18-22 g of glucose, and 8-12 g of yeast extract powder per 1000 mL of water.

[0026] In one embodiment, the preparation of the Saccharomyces cerevisiae fermentation broth is specifically as follows:

[0027] The above-mentioned Saccharomyces cerevisiae was inoculated into YPD medium and activated at 30-37°C for 16-24h;

[0028] The activated strain is then inoculated into a YPD medium at an inoculation rate of 0.5-2% and cultured for at least 2 hours to obtain a brewer's yeast fermentation liquid.

[0029] A fifth object of the present invention is to use the provided Lactobacillus helveticus, Saccharomyces cerevisiae or starter culture in the preparation of fermented food or feed.

[0030] Furthermore, the fermented food refers to fermented rice cake and / or fermented cake.

[0031] Furthermore, the feed preparation refers to mixing the grain raw materials, complete feed and water and then inoculating the strain for fermentation.

[0032] A sixth object of the present invention is to provide a method for preparing a fermented rice cake, comprising the following steps:

[0033] Rice is ground into powder to obtain rice flour, which is then mixed into rice slurry. A leavening agent and the rice slurry are then mixed, and the mixture is fermented, proofed, steamed, and cooked to obtain a fermented rice cake.

[0034] In one embodiment, the rice includes one or more of indica rice, long-grain rice, and glutinous rice.

[0035] In one embodiment, the rice milk is prepared by mixing 45-55 wt % of rice flour, 35-45 wt % of water and 8-12 wt % of sugar.

[0036] In one embodiment, the mass ratio of the leavening agent to the rice milk is 1:90-110.

[0037] In one embodiment, the fermentation is carried out at 25-37° C. and 60-80% relative humidity for 2-16 hours.

[0038] In one embodiment, the proofing is performed at 25-37° C. for 0.5-1 h.

[0039] In one embodiment, the steaming and cooking is steaming for 15 to 30 minutes.

[0040] The seventh object of the present invention is to provide a fermented rice cake, which is prepared by the above-mentioned preparation method.

[0041] Through the technical solution of the present invention, the following beneficial effects can be obtained:

[0042] 1. The Lactobacillus helveticus and Saccharomyces cerevisiae provided by the present invention are safe strains that can be used in food and are screened out from traditional starters. They are green, natural, nutritious and healthy, can be widely used in the field of fermented products, and can also be used to prepare live bacteria preparations for use in fermented rice cakes, fermented dairy products, fermented soy products and other products.

[0043] 2. The fermented rice cake prepared by the present invention has a soft texture, a unique fermented flavor and good sensory characteristics.

[0044] 3. The process for preparing the fermented rice cake of the present invention is simple to operate, suitable for industrialized and standardized production, and can stably produce high-quality fermented rice cake. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is the microscopic observation result of Lactobacillus helveticus;

[0046] Figure 2 Microscopic observation results of Saccharomyces cerevisiae;

[0047] Figure 3 The growth curves of Lactobacillus helveticus and Saccharomyces cerevisiae are shown;

[0048] Figure 4 The PCA analysis of three fermented rice cake electronic noses; DH: traditional fermented rice cake sample; JM: yeast fermented sample; Bacteria 1: isolated strains co-fermented sample. The greater the distance between samples, the greater the flavor difference between the samples. DETAILED DESCRIPTION

[0049] The present invention will be further described below through specific examples.

[0050] Deposit of biological materials:

[0051] Lactobacillus fermentum RS01 was deposited in the China Center for Type Culture Collection on July 22, 2024, with the deposit number CCTCC M 20241668. The depository address is Wuhan University, Wuhan, China.

[0052] Saccharomyces cerevisiae JM01 was deposited in the China Center for Type Culture Collection on July 22, 2024, with the deposit number CCTCC M 20241667. The depository address is Wuhan University, Wuhan, China.

[0053] Fermentation medium:

[0054] The composition of MRS medium is 10 g of peptone, 5 g of beef extract powder, 4 g of yeast extract powder, 20 g of glucose, 2 g of dipotassium hydrogen phosphate, 2 g of triammonium citrate, 5 g of sodium acetate, 0.2 g of magnesium sulfate, 0.05 g of manganese sulfate, 1 g of Tween 80 per 1000 mL of water, pH = 6.2 ± 0.02 (25°C);

[0055] The composition of YPD medium is 20 g of peptone, 20 g of glucose, and 10 g of yeast extract powder per 1000 mL of water, pH = 6.5 ± 0.2 (25°C).

[0056] Volatile substance determination method:

[0057] Flavor analysis was performed using solid phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS).

[0058] GC conditions: The chromatographic column was DB-Wax column (30m×0.25mm×0.25μm, Agilent). The injection port temperature was 250°C, the carrier gas was He, and the flow rate was 0.8mL / min. The column temperature was: the initial temperature was 40°C, the temperature was increased to 100°C at 6°C / min, and then the temperature was increased to 230°C at 10°C / min and maintained for 6min.

[0059] MS conditions: EI ionization source, electron energy 70eV, ion source temperature 200℃, scanning range 33~500amu. Compounds with a matching degree greater than 800 were screened by searching the Willery spectral library and the NIST spectral library, and then the compounds were qualitatively identified by combining the retention time, mass spectrum and retention index of the compounds.

[0060] Electronic nose measurement method:

[0061] (1) Sample preparation: The electronic nose analysis adopts the top hole extraction sampling method. Weigh 3-5g of sample into the top hole sample, shake it slightly to make the sample flat on the bottom of the tube, and let it stand for 30 minutes before sampling. Set up 3 parallels for each sample.

[0062] (2) Determination conditions: sampling time 1s / group; sensor self-cleaning time 60s; sensor zeroing time 10s; sample preparation time 5s; injection flow rate 400mL / min; analysis sampling time 120s. The original data were analyzed using principal component analysis (PCA).

[0063] pH and titratable acidity (TTA) determination method:

[0064] Take 10g of fermentation sample, add 90mL of distilled water, stir thoroughly with a magnetic stirrer, and measure the pH value with a calibrated acidometer. Titrate the solution with 0.1mol / L NaOH solution to a pH value of 8.6. TTA is the volume (mL) of NaOH solution consumed in the above step. Repeat the experiment three times, and the final result is the average of the three experiments.

[0065] Texture determination method:

[0066] The texture test mode of rice cake is TPA, and the test parameters are set as: 3mm / s before test, 1mm / s during test, 2mm / s after test, 40% compression deformation, and 3 parallel tests. The test indicators include: hardness, viscosity, elasticity, chewiness, recovery, etc.

[0067] Sensory evaluation method:

[0068] The preference evaluation adopts the ranking method, with 10 sensory evaluation personnel, and the specific reference is made to the GB / T 12315-2008 standard. The descriptive test evaluation score adopts a five-point system, and the specific evaluation content and evaluation criteria are shown in Table 1:

[0069] Table 1 Descriptive test evaluation method of rice cake

[0070]

[0071] Rating system (5-point preference rating): 1: dislike; 2: not too much like; 3: neither dislike nor dislike; 4: like; 5: like very much.

[0072] Example 1 Screening of fermentation strains

[0073] Fermentation samples were collected from traditional fermented rice cake shops. Accurately weigh 10 g of the sample to be tested, put it into a 250 mL Erlenmeyer flask filled with 90 mL of sterile water and small glass beads, and shake it by hand or on a shaker for 20 minutes. Then take the homogenate to make 10 -4 , 10 -5 , 10 -6 , 10 -7 , 10 -8 , 10 -9 Take 100 μL of each diluted bacterial solution and spread it on MRS and YPD culture medium plates, and culture at 30-37℃ for 40-48 hours. Observe the growth of colonies, select colonies with different morphologies as primary screening strains, inoculate them into culture medium, and culture at 30-37℃, 200r / min, with shaking for 12-16 hours. Centrifuge the culture medium at 12000r / min for 5 minutes, collect the bacterial sludge, and use it for subsequent identification of lactic acid bacteria and yeast.

[0074] Example 2 Identification and Growth Curve Determination of Lactobacillus helveticus and Saccharomyces cerevisiae Strains

[0075] (1) Identification of Lactobacillus helveticus strains

[0076] The colony phenotype of Lactobacillus helveticus RS01 is round, milky white, with neat edges, long rod-shaped bacteria under the microscope, and no spores; the physiological and biochemical characteristics are positive Gram staining microscopy and negative catalase test. The strain Lactobacillus helveticus that meets the above characteristics was inoculated into MRS medium and cultured at 37℃ overnight, and the total DNA of the bacteria was extracted as a PCR template. PCR amplification was performed using bacterial 16S rDNA universal primers 27F and 1492R. The PCR amplification conditions were: 95℃ pre-denaturation for 5min, 94℃ denaturation for 30s, 55℃ renaturation for 30s, 72℃ extension for 90s, 35 cycles; 72℃ final extension for 10min. The results of sequencing after 2% gel electrophoresis showed that the 16S rDNA of the strain had a high homology with the 16S rDNA of Lactobacillus helveticus in the GenBank database. Multiple sequence alignment analysis was performed using ClustalW 2.0 software, and finally a phylogenetic tree was constructed using MEGA 7.0 software (Neighbor-Joining method). The results showed that the phylogenetic evolutionary tree also showed a stable relationship with Lactobacillus helveticus.

[0077] Combined with the morphological characteristics, 16S rDNA sequence alignment and phylogenetic tree analysis, the strain was identified as Lactobacillus helveticus of the Lactobacillaceae family of the order Lactobacillales.

[0078] (2) Identification of Saccharomyces cerevisiae strains

[0079] The colony phenotype of Saccharomyces cerevisiae JM01 is round, milky white, smooth, and oval under a microscope. The strain Saccharomyces cerevisiae that meets the above characteristics was inoculated into YPD medium and cultured overnight at 30℃. The total DNA of the strain was extracted as a PCR template. Universal primers ITS1 and ITS4 were used for PCR amplification. The PCR amplification conditions were: 94℃ pre-denaturation for 3min, 94℃ denaturation for 30s, 55℃ renaturation for 50s, 72℃ extension for 1min, 35 cycles, and 72℃ final extension for 10min. Sequencing was performed after 2% gel electrophoresis detection. The sequencing results showed that the ITS rDNA of the strain had a very high homology with the ITS rDNA of Saccharomyces cerevisiae in the GenBank database. Then, multiple sequence alignment analysis was performed using ClustalW 2.0 software, and finally a phylogenetic tree was constructed using MEGA 7.0 software (Neighbor-Joining method). The results showed that the phylogenetic tree also showed a stable relationship with Saccharomyces cerevisiae.

[0080] Combined with the morphological characteristics, ITS rDNA sequence alignment and phylogenetic tree analysis, the strain was identified as Saccharomyces cerevisiae, Saccharomycetales, Saccharomycetaceae.

[0081] (3) Determination of the growth curve of Lactobacillus helveticus strains

[0082] Select Lactobacillus helveticus and inoculate it into MRS solid medium, and incubate it at 37℃ for 24h. Inoculate the activated Lactobacillus helveticus into MRS liquid medium at a 1% inoculation rate, and incubate it at 37℃. Take samples every 2h to measure the OD600 of the fermentation liquid, and draw the growth curve of the strain accordingly. The growth curve is Figure 3As shown in the figure, it can be seen that the logarithmic growth period of Lactobacillus helveticus is 4 to 14 hours. When the culture time reaches 14 hours, the bacterial concentration tends to be saturated, and the bacterial concentration reaches 10 8 CFU / mL.

[0083] (4) Determination of growth curve of Saccharomyces cerevisiae strains

[0084] Pick out the brewer's yeast and inoculate it into the YPD medium, and let it stand for activation and culture at 30℃ for 24h. Inoculate the activated brewer's yeast into the liquid medium at a 1% inoculation rate, let it stand for culture at 30℃, take samples every 2h to measure the OD600 of the fermentation liquid, and draw the growth curve of the strain accordingly. The growth curve is Figure 3 As shown in the figure, it can be seen that the logarithmic growth period of the Saccharomyces cerevisiae strain is 2 to 8 hours. When the culture time reaches 8 hours, the strain concentration tends to be saturated, and the bacterial concentration reaches 10 8 CFU / mL.

[0085] Example 3 Preparation of combined fermented rice cake

[0086] Pick a single colony of Lactobacillus helveticus and inoculate it into MRS medium, activate it at 37°C and 200r / min for 24h, inoculate the activated bacterial solution into MRS at an inoculum amount of 1% and culture it for 10h to obtain a fermentation liquid in the logarithmic growth phase of Lactobacillus helveticus. Pick a single colony of Saccharomyces cerevisiae and inoculate it into YPD medium, activate it at 37°C and 200r / min for 24h, inoculate the activated bacterial solution into YPD at an inoculum amount of 1% and culture it for 4h to obtain a fermentation liquid in the logarithmic growth phase of yeast. Take the fermentation liquid in the logarithmic growth phase of Lactobacillus helveticus and the fermentation liquid in the logarithmic growth phase of yeast and centrifuge them respectively, remove the supernatant, rinse the precipitate with sterile water until it is colorless, and then mix it with water to obtain a fermentation liquid of Lactobacillus helveticus (10 7 CFU / mL) and yeast culture (10 7 CFU / mL).

[0087] Indica rice is ground into powder, 40% (w / w) water and 10% (w / w) white sugar are added to the rice powder to prepare rice milk, Swiss lactic acid bacteria liquid and yeast yeast liquid are mixed at a ratio of 3:1 (w / w), and then inoculated into the rice milk at a ratio of 1:100 (w / w), and fermented at 30°C and 75% relative humidity for 8h to obtain fermented rice milk, then proofed, and then steamed at 100°C for 20min to obtain the combined fermented rice cake.

[0088] Comparative Example 1

[0089] Traditional fermented rice cakes were made using commercially available traditional distiller's grains as a starter.

[0090] Indica rice is ground into powder, 40% (w / w) water and 10% (w / w) white sugar are added to the rice powder to prepare rice slurry, distiller's grains are added to the rice slurry at a ratio of 1:10 (w / w), fermented at 30° C. and 75% relative humidity for 8 h to obtain fermented rice slurry, then proofed, and then steamed at 100° C. for 20 min to obtain the traditional fermented rice cake.

[0091] Comparative Example 2

[0092] Yeast fermented rice cakes were prepared using Saccharomyces cerevisiae alone.

[0093] A single colony of Saccharomyces cerevisiae was picked and inoculated into YPD medium, and activated at 37°C and 200 r / min for 24 h. The activated bacterial solution was inoculated into YPD at an inoculum volume of 1% and cultured for 4 h to obtain a yeast fermentation solution in the logarithmic growth phase.

[0094] Indica rice is ground into powder, 40% (w / w) water and 10% (w / w) white sugar are added to the rice powder to prepare rice slurry, yeast logarithmic phase bacterial liquid is inoculated into the rice slurry at a ratio of 1:100, fermented for 8 hours at 30°C and 75% relative humidity to obtain fermented rice slurry, then proofed, and then steamed at 100°C for 20 minutes to obtain the yeast fermented rice cake.

[0095] Example 4 pH detection and volatile substance analysis of fermentation samples

[0096] The fermented rice slurry after fermentation in Example 3 and Comparative Examples 1-2 was selected for pH and acidity detection, and the results are shown in Table 2. It can be found that compared with the single yeast fermentation, the pH value of the combined fermented rice slurry decreased after the fermentation, and the titrated acidity gradually increased. This shows that lactic acid bacteria metabolize and produce organic acids during the fermentation process, which give the rice cake a rich taste.

[0097] Table 2 Determination of biochemical indicators of fermentation samples

[0098]

[0099] Analysis of volatile substances in fermented rice cake:

[0100] Through GC-MS of yeast and co-fermented rice milk, it was found that the volatile substances of rice milk fermented by single yeast are mainly composed of compounds such as esters, alcohols, alkanes, and alkenes. The volatile substances of co-fermented rice cakes are mainly composed of compounds such as esters, alcohols, acids, aldehydes, and alkanes. Alcohols are the main aroma substances in the fermentation process, mainly showing fruity and floral aromas. Suitable concentrations of such substances can set off the ester aroma and promote the coordination of aroma, and are important aroma substances in fermented foods. It can be seen from the table below that the types of alcohol substances in co-fermented rice cakes are more than those in single yeast fermentation, which gives co-fermented rice cakes a variety of different flavors, such as trans-2-nonene-1-ol has a fat and violet aroma, and phenylethanol has a strong rose flavor. Most of the acid substances come from by-products of microbial metabolism, which can react with alcohol substances to form esters, thereby making the aroma of rice milk more coordinated and balanced.

[0101] In addition to the above, aldehyde compounds are also important for the aroma of rice milk. Benzaldehyde is an important volatile compound produced during the fermentation of rice milk. Aldehydes and ketones can be formed by alcohol oxidation. These compounds combined with other compounds may produce wonderful aromas that help enhance the complexity and balance of the overall aroma. The comprehensive results show that the co-fermented samples have obvious advantages in flavor.

[0102] Table 3 Determination of volatile flavor substances of yeast

[0103] Compound Relative content / % Compound Relative content / % Esters Alcohols Isoamyl acetate 0.17 Isobutanol 25.85 Ethyl hexanoate 4.89 Phenylethyl alcohol 42.75 Ethyl heptanoate 0.53 Alkanes Ethyl Caprylate 2.66 Hexamethylcyclotrisiloxane 1.02 Ethyl nonanoate 0.20 Octamethylcyclotetrasiloxane 1.57 Ethyl laurate 0.12 Decamethylcyclopentasiloxane 6.25 other Dodecamethylcyclohexasiloxane 3.61 Naphthalene 0.04 Octadecamethylcyclononasiloxane 0.24 Styrene 9.17

[0104] Table 4 Determination of volatile flavor substances in combined fermentation

[0105] Compound Relative content / % Compound Relative content / % Esters Alcohols Ethyl decanoate 0.86 Ethanol 15.45 Ethyl Caprylate 0.32 Isobutanol 0.75 Acids Phenylethyl alcohol 18.68 Acetic acid 0.92 4-Nonanol 0.20 Alkanes trans-2-nonen-1-ol 0.32 Decamethylcyclopentasiloxane 3.44 n-Amyl alcohol 41.86 Dodecamethylcyclohexasiloxane 5.36 other Tetradecamethylcycloheptasiloxane 1.65 Acetoin 2.23 Benzaldehyde 3.44

[0106] Example 5 Flavor Similarity Analysis of Fermented Rice Cake

[0107] The PCA results of the electronic nose detection of three fermented rice cakes are as follows Figure 2 As shown in the figure, the first principal component’s contribution rate is 99.009%, the second principal component’s contribution rate is 0.9525%, and the cumulative contribution rate of the two principal components exceeds 85%, which includes most of the contribution rates in PCA conversion and can better reflect multi-index information, indicating that the electronic nose detection method is significant. Figure 4 It can be seen that the flavor similarity between the rice cakes fermented by the strains and the traditional rice cake samples is higher than that of the rice cakes fermented by yeast.

[0108] Example 6 Fermented Rice Cake Quality Evaluation

[0109] The texture characteristics of steamed rice cakes include hardness, elasticity, chewiness and other indicators, which are important indicators for measuring the quality of steamed rice cakes. High-quality steamed rice cakes generally have moderate hardness, greater elasticity, good chewiness and greater resilience. Comparing the effects of different strains on the quality of rice cakes, according to the data in Table 5, the combined fermented rice cakes have good elasticity and resilience, moderate hardness, and their texture properties are close to traditional fermented rice cakes, which are better than yeast fermented rice cakes. In terms of overall flavor preference, the flavor preference score of yeast fermented rice cakes is 3.85, which is significantly lower than that of traditional fermented rice cakes and combined fermented rice cakes. Therefore, the comprehensive sensory quality and texture quality show that the quality of combined fermented rice cakes is better.

[0110] Table 5 Quality evaluation of fermented rice cake

[0111]

[0112] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A Lactobacillus helveticus RS01, characterized in that The Lactobacillus helveticus is deposited in China Center for Type Culture Collection with a deposit number of CCTCC M 20241668.

2. A Saccharomyces cerevisiae JM01, characterized in that: The brewer's yeast is deposited in China Center for Type Culture Collection with a deposit number of CCTCC M 20241667.

3. A leavening agent, characterized in that The starter culture comprises Lactobacillus helveticus RS01 and Saccharomyces cerevisiae JM01 as described above.

4. The method for preparing the leavening agent according to claim 3, characterized in that: The following steps are involved: Fermenting the Lactobacillus helveticus described in claim 1 in a fermentation medium to obtain a Lactobacillus helveticus fermentation liquid; Fermenting the brewer's yeast according to claim 2 in a fermentation medium to obtain a brewer's yeast fermentation liquid; Then the Lactobacillus helveticus fermentation liquid and the Saccharomyces cerevisiae fermentation liquid are centrifuged, and the precipitate is taken out and washed to prepare the Lactobacillus helveticus bacterial liquid and the Saccharomyces cerevisiae bacterial liquid; The bacterial concentration in the bacterial solution is greater than or equal to 1×10 7 CFU / mL or 1×10 7 CFU / g; Then, the Lactobacillus helveticus culture solution and the Saccharomyces cerevisiae culture solution are mixed in a mass ratio of 2 to 4:

1.

5. The preparation method according to claim 4, characterized in that: The Lactobacillus helveticus fermentation liquid is obtained by culturing Lactobacillus helveticus in an MRS culture medium; the MRS culture medium is composed of 8-12g of peptone, 3-7g of beef extract powder, 2-6g of yeast extract powder, 18-22g of glucose, 1-3g of dipotassium hydrogen phosphate, 1-3g of triammonium citrate, 3-7g of sodium acetate, 0.1-0.4g of magnesium sulfate, 0.03-0.07g of manganese sulfate and 0.8-1.2g of Tween 80 per 1000mL of water.

6. The preparation method according to claim 4, characterized in that: The brewer's yeast fermentation liquid is obtained by culturing brewer's yeast in a YPD culture medium; the YPD culture medium is composed of 18-22g of peptone, 18-22g of glucose and 8-12g of yeast extract powder per 1000mL of water.

7. Use of the Lactobacillus helveticus described in claim 1, the Saccharomyces cerevisiae described in claim 2, the starter described in claim 3 and / or the starter prepared by the preparation method described in any one of claims 4 to 6 in the preparation of fermented food or feed.

8. A method for preparing fermented rice cake, characterized in that: The following steps are involved: Rice is ground into powder to obtain rice flour, which is then mixed into rice slurry. The leavening agent described in claim 3 and / or the leavening agent prepared by the preparation method described in any one of claims 4 to 6 is mixed with the rice slurry, and then fermented, proofed, steamed and cooked to obtain fermented rice cake.

9. The preparation method according to claim 8, characterized in that: The rice milk is prepared by mixing 45-55wt% of rice flour, 35-45wt% of water and 8-12wt% of sugar; the mass ratio of the leavening agent to the rice milk is 1:90-110.

10. The preparation method according to claim 9, characterized in that: The fermentation is carried out at 25-37° C. and 60-80% relative humidity for 2-16 hours; the proofing is carried out at 25-37° C. and 0.5-1 hour; and the steaming and maturation is carried out by steaming for 15-30 minutes.

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