Lactobacillus plantarum and application thereof in improving edible quality of colored brown rice

Abstract

The invention belongs to the technical field of food processing, and particularly relates to a lactic acid bacteria strain and application thereof in improving the eating quality of brown rice. The lactobacillus plantarum WL01 is preserved in China General Microbiological Culture Collection Center (CGMCC) on July 8, 2024, the preservation number is CGMCC No.31201, and the preservation address is No.3, Yard 1, Beichen West Road, Chaoyang District, Beijing. After the lactobacillus plantarum WL01 and the colored brown rice (red rice and black rice) are subjected to semi-solid state fermentation, the cooking characteristic and the eating quality of the colored brown rice are remarkably improved, and the cooking time is shortened by 18%-25%; the sensory score is improved by 25%-30%; the nutrition loss is small; the nutrition is rich; the total phenols and the total flavonoids of the fermented red rice are increased. The total phenols, combined phenols and combined flavonoids of the fermented black rice are obviously improved. And the oxidation resistance is improved to a certain extent.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing, and particularly relates to a lactic acid bacteria strain, a screening method, and a method and application thereof for improving the edible quality of brown rice. Background Art

[0002] In recent years, the prevalence of chronic diseases such as obesity and diabetes in my country has been increasing year by year. This is closely related to the excessive pursuit of refined staple foods and unbalanced dietary structure. Over-processing of grains will lead to the loss of about 80% of nutrients and more than 25% of biomass. According to the epidemic disease survey report, whole grain foods have a protective effect on chronic diseases such as cardiovascular and cerebrovascular diseases. Whole grains are rich in nutritional value and rich in dietary fiber, so the research and promotion of whole grains is of great significance.

[0003] Brown rice refers to whole grain food that is retained except for the husk, that is, rice containing cortex, endosperm and germ. It has a coarse taste, compact texture and higher nutritional value than polished white rice. Brown rice has good protein quality, is easy for the human body to digest and absorb, has less lysine content, contains more fat and carbohydrates, can provide a large amount of calories to the human body in a short time, and is gradually favored by consumers. Brown rice includes ordinary brown rice and colored brown rice. Ordinary brown rice is processed into white rice for daily consumption. Colored brown rice includes black rice, which is collectively referred to as brown rice, purple rice, red rice and other colored rice. They are all eaten in the form of brown rice, collectively referred to as brown rice. Taking black rice as an example, it is rich in anthocyanins and dietary fiber, and its endosperm, germ, pericarp and seed coat can provide many other nutrients, but its shortcomings such as difficult to cook, difficult to eat and difficult to store are not easily accepted by the public. Therefore, it is of great practical significance to improve the cooking and edible quality of brown rice and storage stability, and to study the structure-activity relationship between brown rice components.

[0004] Whole grains are an important source of dietary polyphenols, including phenolic acids, flavonoids and proanthocyanidins, which are important antioxidant active substances and have multiple biological activities. Choosing the right processing method will help increase the polyphenol content and antioxidant activity in whole grains, thereby improving the nutritional value of whole grain products. Free polyphenols can directly bind to proline-rich salivary proteins in the mouth as antioxidants and be absorbed by the human body in the stomach or small intestine. Bound polyphenols can fully exert their biological activity after intestinal digestion. The action of microorganisms or related enzymes in the large intestine will release bound polyphenols from the cell wall in the form of aglycones. The released aglycones combine with sugars to re-form glucosides, which are absorbed and utilized by the human body through glucose transporters in cells. Free flavonoids may be more beneficial in the short term, but bound flavonoids can provide more lasting effects with the help of intestinal microorganisms.

[0005] In order to improve the quality of brown rice, current domestic and foreign research usually uses physical methods (milling, high temperature fluidization, ultra-high pressure, irradiation, soaking, ultrafine grinding, etc.), biological methods (germination, addition of exogenous enzymes, biological fermentation, etc.), or physical and biological methods to treat brown rice. However, each method has certain shortcomings. The milling method significantly improves the water absorption performance of brown rice, but the nutritional loss is large. The high temperature fluidization method forms small micro-cracks on the surface of brown rice, which significantly improves the water absorption performance of brown rice, but the physical structure of brown rice grains is greatly damaged and the storage stability is reduced. The exogenous enzyme method can well improve the cooking performance of brown rice and retain important nutrients in brown rice, but it requires a lot of water, the drying process consumes a lot of energy, the investment in equipment such as tanks is high, the processing process is complicated, and the production cost of brown rice is significantly increased, which is not conducive to the expansion of the scale of brown rice production and the promotion of commercial production.

[0006] Biofermentation is a technology that uses the metabolic process of microorganisms to produce compounds. It is a process in which microorganisms and their enzymes biochemically modify the brown rice matrix, providing a new idea for improving the quality of brown rice. Semi-solid fermentation not only broadens the matrix range of solid-state fermentation, but also has the advantages of high product concentration and low energy consumption compared to liquid fermentation.

[0007] At present, most domestic and foreign studies use a single strain or a small number of strains to solid-state ferment conventional brown rice. There are fewer studies on semi-solid fermentation of colored brown rice by lactic acid bacteria, and the effect of improving the performance of brown rice needs to be improved. Therefore, it is necessary to provide a new method to improve the edible quality of brown rice. Summary of the invention

[0008] In order to solve the technical problems that brown rice is difficult to cook, taste and store, the present invention provides a lactic acid bacteria strain and a method and application thereof for improving the edible quality of brown rice; the present invention provides technical support and basis for the research on common key technologies for processing whole-grain rice-based steamed foods and is used to prepare whole-grain brown rice foods that are better for steaming and edible.

[0009] The first object of the present invention is to provide a Lactobacillus plantarum WL01 (Lactobacillus plantarum), which has been deposited in the General Microbiology Center of China National Committee for the Preservation of Microorganisms on July 8, 2024, with a deposit number of CGMCC No. 31201, and a deposit address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing.

[0010] Lactic acid bacteria (LAB) are bacteria that can produce a large amount of lactic acid during the fermentation of available carbohydrates. They play an important role in improving the intestinal microecological environment. They have a strong ability to utilize carbohydrates during fermentation and can produce a large amount of lactic acid and enzymes such as amylase and cellulase.

[0011] The lactic acid bacteria used in the present embodiment are ten existing strains of Jiangnan University National Engineering Laboratory, numbered NO.1-NO.8, Lactobacillus acidophilus (SS) and Lactobacillus casei. Common culture media for culturing lactic acid bacteria, such as MRS culture media, can be used for culture.

[0012] The second object of the present invention is to provide a microbial agent, which contains the Lactobacillus plantarum WL01 or its culture solution, or its freeze-dried powder as described in claim 1.

[0013] The third object of the present invention is to provide a method for preparing fermented colored brown rice, comprising the steps of activating the plant lactobacillus WL01 and inoculating it into the colored brown rice, mixing the mixture evenly, performing semi-solid fermentation and drying the mixture.

[0014] The activated Lactobacillus plantarum WL01 is inoculated into brown rice containing water, mixed evenly, and then placed in a sealed container for fermentation and culture for a certain period of time in a set temperature environment. After the fermentation is completed, the brown rice is taken out and dried to obtain brown rice that is easy to steam and has good edible quality.

[0015] In some embodiments of the present invention, the colored brown rice is sterilized by soaking in water and then inoculated with Lactobacillus plantarum WL01, and the soaking conditions are: a solid-liquid ratio of 1:0.6-1.

[0016] Furthermore, in the colored brown rice, the inoculation amount of the Lactobacillus plantarum WL01 is 3.35×10 7 ~1.68×10 8 cfu / g;

[0017] In some embodiments of the present invention, the inoculation amount of Lactobacillus plantarum WL01 is 1% to 5% (w / v); preferably, the inoculation amount is 3% (v / w);

[0018] In some embodiments of the present invention, the inoculated strain is an activated third-generation strain, and the concentration of Lactobacillus plantarum WL01 is 1.86×10 9 CFU / mL;

[0019] In some embodiments of the present invention, the semi-solid fermentation temperature is 25 to 37°C;

[0020] In some embodiments of the present invention, the fermentation time is 4 to 12 hours;

[0021] In some preferred embodiments, the soaking time is 4 hours;

[0022] In some embodiments of the present invention, the drying step is to dry the colored brown rice until the moisture content is ≤14%; the drying step is to bake the fermented brown rice in a 50° C. oven until the surface is dry, and the moisture content of the brown rice is controlled to be less than 14%.

[0023] In some embodiments, hot air drying is used.

[0024] Furthermore, during the fermentation process, proper stirring is performed to make the fermentation process more uniform and sufficient.

[0025] In some embodiments, the activation method of Lactobacillus plantarum WL01 is: firstly activate the strain twice with MRS liquid culture medium, and culture it statically at 37° C. for 18 to 24 hours; the third generation strain is used for inoculation.

[0026] Furthermore, the colored brown rice includes but is not limited to one or a combination of red rice, black rice, and purple rice.

[0027] In a preferred embodiment, the technical solution adopted by the present invention is specifically:

[0028] (1) Activation and subculture of strains: Weigh MRS culture medium according to the proportion and add 1L water to make up the volume, sterilize at 121℃ for 15 minutes, and cool for use. Inoculate the bacterial solution stored in the glycerol tube into sterile MRS liquid culture medium at 6% (v / v). Place in a 37℃ incubator and culture for 18 to 24 hours. The first generation strain is obtained. Take the activated first generation bacterial solution and inoculate it into sterile MRS liquid culture medium at 6% (v / v). Place in a 37℃ incubator and culture for 18 to 24 hours. The second generation strain is obtained. Take the activated second generation bacterial solution and inoculate it into sterile MRS liquid culture medium at 3% (v / v). Place in a 37℃ incubator and culture for 18 to 24 hours. Centrifuge at 5000r / min for 10 minutes, remove the supernatant, add physiological saline and resuspend to make a bacterial suspension. Set aside.

[0029] (2) Inoculation and fermentation: Take the sterilized brown rice soaked at a fixed solid-liquid ratio, inoculate the third-generation strain into the raw material according to a fixed inoculum amount, mix evenly, and ferment at a fermentation temperature of 37°C for a certain period of time. During the fermentation process, shake the fermentation container intermittently.

[0030] (3) Drying the fermented brown rice at 50° C. with hot air until the surface is dry and the moisture content of the brown rice is less than 14%.

[0031] (4) drying the fermented brown rice, degassing it, and sealing and packaging it to obtain a finished product.

[0032] Another aspect of the present invention is to provide fermented colored brown rice obtained by the preparation method. The fermented brown rice is dried, degassed, sealed and packaged to obtain a finished product.

[0033] Another aspect of the present invention is to provide the use of the Lactobacillus plantarum WL01 or the microbial agent in improving the cooking quality of grains.

[0034] Compared with the prior art, the beneficial effects of the present invention are at least:

[0035] (1) The present invention first provides a Lactobacillus plantarum WL01, and provides an application of the Lactobacillus plantarum in improving the cooking quality of colored brown rice;

[0036] (2) The present invention also provides a method for improving the cooking quality and nutritional value of colored brown rice based on the plant lactobacillus WL01. After semi-solid fermentation of the plant lactobacillus WL01, the cooking characteristics and edible quality of the colored brown rice are improved, the cooking time is reduced by 18% to 25%, and the sensory score is increased by 25% to 30%.

[0037] (3) The method provided by the present invention is used to produce brown rice, and the cooking characteristics and edible quality are significantly improved. The cooking time of brown rice is greatly reduced, and the taste quality is greatly improved, the nutritional loss is small, and the nutrition is rich; the total phenols and total flavonoids of red rice are improved after fermentation. The total phenols, combined phenols, and combined flavonoids of black rice are significantly improved after fermentation, and the antioxidant properties are improved to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0039] Figure 1 Water absorption rate of brown rice after soaking;

[0040] Figure 2 The growth curves of different lactic acid bacteria. DETAILED DESCRIPTION

[0041] The present invention is further explained below in conjunction with specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. If a technician in the field makes some non-essential adjustments and improvements to the present invention based on the content of the present invention, it still belongs to the protection scope of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0042] The invention adopts semi-solid fermentation technology, performs sensory evaluation on fermented colored brown rice samples, detects pH value and optimal cooking time, performs standardization on key indicators of raw brown rice, assigns weight coefficients, obtains comprehensive scores of brown rice, and screens out optimal fermentation strains corresponding to the brown rice according to the comprehensive scores (the highest one).

[0043] The lactic acid bacteria strain screening method of the present invention comprises the following steps: according to the preliminary experimental results, the brown rice is soaked and sterilized at a solid-liquid ratio of 1:0.6-1, the third-generation strain is inoculated into the raw material at a bacterial inoculation amount of 1%-5% (w / v), mixed evenly, fermented for 4-12 hours at a fermentation temperature of 25-37 DEG C to obtain a fermentation product, and the cooking time of the fermentation product is measured and a sensory evaluation is performed.

[0044] Test methods used in the examples:

[0045] Determination of water absorption by immersion:

[0046] Brown rice soaking water absorption rate % = (weight after water absorption - weight before water absorption) / weight before water absorption × 100%;

[0047] Determination of moisture content of brown rice: Take a clean aluminum box, place it in a drying oven at 101℃~105℃, heat for 4.0h, take it out and cover it, cool it in a dryer for 0.5h, weigh it, and repeat the drying until the difference between the two weights does not exceed 2mg, that is, constant weight. Grind the brown rice sample through an 80-mesh sieve, weigh 1.5g (accurate to 0.0001g), put it in an aluminum box, the sample thickness does not exceed 5mm, place it in a drying oven at 101℃~105℃, and support the box cover obliquely on the edge of the bottle. After drying for 4h, cover it and take it out, cool it in a dryer for 20~30min, and weigh it. Then put it in a drying oven at 101℃~105℃ and dry it for about 1h, take it out, cool it in a dryer for 0.5h, and weigh it again. Repeat the above operation until the difference between the two weights does not exceed 2mg, that is, constant weight.

[0048] Moisture content in the sample, X = (m1-m2) / (m1-m3)×100%

[0049] X——the moisture content in the sample, in %;

[0050] m1——The mass of the aluminum box and the sample, in grams (g);

[0051] m2——the mass of the aluminum box and the sample after drying, in grams (g);

[0052] m3——The mass of the aluminum box, in grams (g).

[0053] Determination of the optimal cooking time: Take a 250ml beaker and add about 100ml of boiled distilled water (98±1.5℃), pour in 5g of brown rice sample. After 15 minutes, take out 10 grains of rice every one minute, press with a slide to observe whether the brown rice has a white core, when at least 90% of the grains no longer have an opaque core or an uncooked center, record the time when the opaque white core no longer appears when the brown rice grains are squeezed, this time plus 2 minutes is the optimal cooking time for brown rice, to ensure that the cores of all grains have been gelatinized.

[0054] Sensory evaluation: The sensory evaluation of brown rice was conducted by a 10-person tasting panel (aged between 22 and 30 years old) who were trained to evaluate the smell, appearance, taste, palatability and texture of the cooked brown rice. The evaluation criteria were based on GB / T 15682-2008 and were modified appropriately, as shown in the following table.

[0055]

[0056]

[0057] Extraction method of phenolic compounds: accurately weigh 2.00g brown rice flour (pass 80 mesh), add 40mL 80% methanol and mix evenly, extract by ultrasonic at room temperature for 90min, centrifuge at 4000r / min for 10min, collect the supernatant, and repeat the extraction 3 times. Combine the supernatants and evaporate to dryness at 40℃ and then use 80% methanol to make up to 10mL, which is free phenol. Then add 15mL 4mol / LNaOH to the residue after extracting free phenol at room temperature and vortex for 1min in the dark, mix and stir at room temperature for hydrolysis for 1h, and adjust the pH to acidic with concentrated hydrochloric acid. Finally, add 20mL ethyl acetate to extract for 5min, centrifuge at 4000r / min for 10min, and repeat the operation 3 times. After evaporating to dryness at 45℃, use 80% methanol to make up to 10mL, which is bound phenol. Free phenol and bound phenol are stored in a 4℃ refrigerator and analyzed within one week.

[0058] Determination of total phenols (free and bound phenol content): The total phenol content was determined by the Folin-Ciocalteu method, and the total polyphenol content was expressed as gallic acid equivalent ug / g dry weight (ug GAE / g DW). Briefly, 0.2 mL of appropriately diluted sample was added with 1.5 mL of 10-fold diluted Folin phenol reagent and then 1.5 mL of 75 g / L sodium carbonate solution, mixed and kept at room temperature (25°C) in the dark for 2 h, and the absorbance was measured at 765 nm.

[0059] Determination of total flavonoids content: Refer to the local standard DB43 / T 476-2008 Determination of total flavonoids in plant-derived foods. Rutin standard curve: Prepare a rutin standard solution with a mass concentration of 0.2 mg / mL, accurately draw 0, 2.00, 4.00, 6.00, 8.00, 10.00, 12.00 mL of the rutin standard solution, place them in 50 mL volumetric flasks, add 70% methanol to 20 mL, add 2 mL of 5% sodium nitrite solution, shake and place for 6 minutes, add 2 mL of 10% aluminum nitrate droplets, shake and place for 6 minutes, add 4 mL of 1 mol / L sodium hydroxide solution, and dilute to the scale with distilled water. Shake and place for 15 minutes, measure the absorbance at a wavelength of 510 nm, use the zero tube as the blank, use the rutin content (mg) as the horizontal coordinate, and use the absorbance as the vertical coordinate to draw a standard curve, and calculate the correlation coefficient.

[0060] According to the steps of drawing the rutin standard curve: take 300μL of free / bound extract, add 1.5mL ultrapure water and 90μL of 5% (m / v) NaNO2 solution, mix well, let stand in light at room temperature and react for 6 minutes. Then add 180μL of 10% AIC13·6H20 solution, mix well, let stand in the dark for 5 minutes, then add 0.6mL of 1mol / L NaOH solution, and finally add 330μL ultrapure water, and measure its absorbance at a wavelength of 510nm. The total flavonoid content is expressed as the rutin equivalent contained in 1g brown rice on a dry basis, and the unit is ug RE / g DW.

[0061] Total flavonoid content M (mg / g) = a × c × V / W;

[0062] a: dilution factor; c: flavonoid concentration (mg / mL); V: extract volume (mL); m: sample mass.

[0063] Determination of DPPH free radical scavenging ability: 1 mL of the extract solution and 2 mL of 80% DPPH·methanol solution (0.1 mmol / L) were vortexed and mixed, and reacted in the dark at room temperature for 30 minutes. At the same time, blank group, control group and test group were made. 80% methanol solution was used instead of the extract solution as the blank group, 1 mL of the sample solution and 80% methanol solution were mixed as the control group, and 1 mL of the sample solution and 2 mL of DPPH solution were used as the test group. The absorbance value was measured at 517 nm. The DPPH scavenging rate of the samples was calculated according to the formula.

[0064] DPPH free radical scavenging rate (%) = [1-(A1-A2) / A0] × 100;

[0065] A1: absorbance value of the experimental group; A2: absorbance value of the control group; A0: absorbance value of the blank group.

[0066] Determination of ABTS free radical scavenging ability: Mix 7mmol / L ABTS reagent with an equal volume of 2.45mmol / L potassium persulfate solution to form ABTS mother solution, react at 4℃ in the dark for 12-16h, and set aside. Dilute the ABTS mother solution with 80% methanol solution until the absorbance at 734nm reaches 0.7±0.02 (80% methanol solution is used as blank zero adjustment), and then obtain ABTS working solution. Mix the extract with ABTS working solution in a ratio of 1:3, incubate at room temperature in the dark with 80% methanol solution as blank for 60min, and measure the absorbance at 734nm.

[0067] ABTS free radical scavenging rate (%) = [(A0-A1) / A0] × 100;

[0068] A1: absorbance value of the test group; A0: absorbance value of the blank group.

[0069] Comprehensive score = (sensory score / highest sensory score) × 100 × 0.7 + (minimum cooking time / cooking time) × 100 × 0.3.

[0070] Example 1 (Strain Screening and Identification)

[0071] (1) Fermentation strain screening:

[0072] 1) Experimental samples and equipment: Red rice and black rice were purchased from Yangxian County, Shaanxi Province. Lactic acid bacteria were preserved by the National Engineering Laboratory of Jiangnan University.

[0073] 2) Activation, subculture and inoculation of strains: The strains were activated and subcultured twice with MRS liquid medium and cultured at 37°C for 18-24 hours; the lactic acid bacteria used for semi-solid fermentation included ten strains of NO.1-NO.8, Lactobacillus acidophilus (SS) and Lactobacillus casei;

[0074] 3) The third generation strain was inoculated at 3% (v / w) into the sterilized brown rice after soaking at a certain solid-liquid ratio and cultured at 37°C for 4 to 12 hours. During the fermentation process, the fermentation container was shaken intermittently. The concentration of Lactobacillus plantarum WL01 in the third generation strain was 1.86×10 9 CFU / mL.

[0075] 4) Drying: The fermented brown rice is dried at 50° C. with hot air until the surface is dry and the moisture content of the brown rice is less than 14%.

[0076] 5) Packaging: The fermented brown rice is dried, degassed, and sealed to obtain the finished product.

[0077] 6) Key evaluation indicators: Determine the cooking time of the fermented product and perform sensory evaluation. Screen the best fermentation lactic acid bacteria corresponding to each grain. The results are shown in Table 1-1 and Table 1-2:

[0078] Table 1-1 Sensory evaluation and cooking time of red rice after semi-solid fermentation by ten lactic acid bacteria

[0079]

[0080] Table 1-2 Sensory evaluation and cooking time of black rice after semi-solid fermentation by ten lactic acid bacteria

[0081]

[0082] From the results in Table 1-1 and Table 1-2, it can be seen that the comprehensive scores of red rice and black rice fermented with strain NO.1 are higher than those of untreated red rice and black rice, and the comprehensive scores are the highest among the ten strains. Therefore, the best fermentation strain for red rice and black rice is lactic acid bacteria NO.1. Fermentation with Lactobacillus plantarum WL01 can reduce the cooking time and improve its sensory quality.

[0083] (2) Identification of strains:

[0084] The best strains corresponding to each grain were identified by 16s rDNA sequencing: the prepared lactic acid bacteria genomic DNA was used as a template for PCR amplification, and PCR amplification was performed using a 50μL reaction system. Template DNA 2uL, 1.5μL of 10mmol upstream and downstream primers, 25μL of 2×Taq enzyme, and ddH2O was used to make up to 50μL. The PCR cycle parameters were: 94℃ pre-denaturation for 5min; 94℃ denaturation for 1min, 64℃ annealing for 45s, 72℃ extension for 1min, 35 cycles; 72℃ extension for 8min. 5μL of PCR product was aspirated and mixed with 1mL Loading buffer, and electrophoresed with 1.0% agarose gel at a voltage of 80V. After the electrophoresis, it was stained with ethidium bromide EB for 20-30min. After electrophoresis detection of the amplified product, it was sent to Shanghai Shenggong Bioengineering Technology Service Co., Ltd. for sequencing. The sequence obtained by sequencing was compared with the sequence in the GenBank database, and the results showed that the homology between strain No. 1 (i.e., Lactobacillus plantarum WL01) and Lactobacillus plantarum was 99.9854%, exceeding 95%, and identified to the species level. The sample was inferred to belong to the species: Lactiplantibacillus plantarum. The results showed that the best strain corresponding to red rice and black rice of the present invention was No. 1, which was Lactobacillus plantarum (i.e., Lactobacillus plantarum WL01).

[0085] Example 2 Fermentation time

[0086] (1) Activation and subculture of strains: Weigh MRS medium according to the proportion and add 1L water to make up the volume, sterilize at 121℃ for 15min, and cool for use. Inoculate the bacterial solution stored in the glycerol tube into sterile MRS liquid medium at 6% (v / v). Place in a 37℃ incubator and culture for 18-24h. The first generation strain is obtained. Take the activated first generation bacterial solution and inoculate it into sterile MRS liquid medium at 6% (v / v). Place in a 37℃ incubator and culture for 18-24h. The second generation strain is obtained. Take the activated second generation bacterial solution and inoculate it into sterile MRS liquid medium at 3% (v / v). Place in a 37℃ incubator and culture for 18-24h. Centrifuge at 5000r / min for 10min, remove the supernatant and resuspend in physiological saline to make a bacterial suspension; set aside.

[0087] (2) Inoculation and fermentation: Take the sterilized colored brown rice (red rice and black rice) soaked for 4 hours at a solid-liquid ratio of 1:0.8, inoculate the third-generation strain into the raw material at a rate of 3% (w / v), mix evenly, and ferment for a certain period of time (4h, 6h, 8h, 10h, 12h) at a fermentation temperature of 37° C. During the fermentation process, shake the fermentation container intermittently.

[0088] (3) Drying the fermented brown rice at 50° C. with hot air until the surface is dry and the moisture content is less than 14%.

[0089] Example 3 Inoculation amount

[0090] (1) Activation and subculturing of strains: Same as in Example 2.

[0091] (2) Inoculation and fermentation: The colored brown rice (red rice and black rice) that had been soaked for 4 h at a solid-liquid ratio of 1:0.8 and sterilized was inoculated with the third generation strain at a ratio of (1%, 2%, 3%, 4%, 5%) (w / v) into the raw material, mixed evenly, and fermented at a fermentation temperature of 37° C. for 8 h. During the fermentation process, the fermentation container was shaken intermittently.

[0092] (3) Drying the fermented brown rice at 50° C. with hot air until the surface is dry and the moisture content is less than 14%.

[0093] Example 4 Rice-to-Water Ratio

[0094] (1) Activation and subculturing of strains: Same as in Example 2.

[0095] (2) Inoculation and fermentation: Take the colored brown rice (red rice and black rice) that has been soaked for 4 hours and sterilized at a certain solid-liquid ratio (1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1), inoculate the third-generation strain into the raw material according to the inoculation amount (w / v) (red rice: 4%; black rice: 3%), mix well, and ferment at a fermentation temperature of 37°C for 8 hours. During the fermentation process, shake the fermentation container intermittently.

[0096] (3) Drying the fermented brown rice at 50° C. with hot air until the surface is dry and the moisture content is less than 14%.

[0097] Example 5 Fermentation Temperature

[0098] (1) Activation and subculturing of strains: Same as in Example 2.

[0099] (2) Inoculation and fermentation: Take the colored brown rice (red rice and black rice) that has been soaked for 4 hours and sterilized at a certain solid-liquid ratio (red rice 1:0.6; black rice 1:0.7), and inoculate the third-generation strain into the raw materials according to the inoculation amount (w / v) (red rice: 4%; black rice: 3%), mix them evenly, and ferment them at fermentation temperatures (25°C, 28°C, 31°C, 34, 37°C) for 8 hours. During the fermentation process, shake the fermentation container intermittently.

[0100] (3) Drying the fermented brown rice at 50° C. with hot air until the surface is dry and the moisture content is less than 14%.

[0101] Test example:

[0102] Based on the optimal strain and optimal fermentation conditions obtained in the early stage, the phenolic substances (free phenols, bound phenols, free flavonoids, bound flavonoids) and antioxidant activity of each grain before and after fermentation were explored, in order to provide technical support and basis for the research on common key technologies for processing whole-grain brown rice steamed and cooked foods and to be used for the preparation of whole-grain functional brown rice foods that are better for steaming and consumption.

[0103] Test results:

[0104] The cooking time of the brown rice obtained in Example 2-4 was measured and sensory evaluation was performed. The results are shown in Tables 2-1 to 2-4:

[0105] Table 2-1 Sensory evaluation and cooking time of brown rice after different fermentation times

[0106]

[0107] Table 2-2 Sensory evaluation and cooking time of brown rice after treatment with different inoculation amounts

[0108]

[0109] Table 2-3 Sensory evaluation and cooking time of brown rice after treatment with different rice-water ratios

[0110]

[0111] Table 2-4 Sensory evaluation and cooking time of brown rice after treatment at different fermentation temperatures

[0112]

[0113] The brown rice obtained in the example was subjected to sensory evaluation and cooking time measurement. The sensory scores and cooking time results of the brown rice are shown in Table 2 (Table 2-1 to Table 2-4). From the results, it can be seen that on the basis of screening out the bacteria, the fermentation conditions (fermentation temperature, fermentation time, inoculation amount and rice-water ratio) were optimized.

[0114] The phenolic substances (free phenol, bound phenol, free flavonoids, bound flavonoids) and antioxidant activity of the brown rice obtained in the embodiment and the comparative example were measured (① red rice: Lactobacillus plantarum WL01, 8h, 4%, 1:0.6, 31°C; ② black rice: Lactobacillus plantarum WL01, 8h, 3%, 1:0.7, 31°C), and the results are shown in Table 3-1:

[0115] Table 3-1 Phenolic substances (free phenols, bound phenols, free flavonoids, bound flavonoids) and antioxidant activity of brown rice before and after fermentation

[0116]

[0117] From the results in Table 3, it can be seen that on the basis of the best strain and the best fermentation conditions obtained in the early stage, the phenolic substances (free phenol, bound phenol, free flavonoids, bound flavonoids) and antioxidant activity of each grain before and after fermentation. After fermentation, the total phenol of red rice increased from 1342.09 to 1854.59μg GAE / g DW, and the total flavonoids increased from 1938.08 to 1985.65μg TE / g DW. After fermentation, the total phenol of black rice increased from 2758.26 to 2847.93μg GAE / g DW, the bound phenol increased from 775.45 to 907.35; the bound flavonoids increased from 682.99 to 1234.64μg TE / g DW. And the antioxidant properties were all improved to a certain extent. It shows that the brown rice produced by the production process of the present invention is better than that of unfermented rice, and is easy to industrialize, which greatly promotes the basic consumption of brown rice and brings good social and economic benefits.

[0118] After fermentation with the screened Lactobacillus plantarum WL01, the cooking characteristics and edible quality of the colored brown rice were improved; during the fermentation process, Lactobacillus plantarum WL01 can produce amylase, protease, cellulase and pectinase, which destroy the integrity of the cell wall of the brown rice cortex, making it easier for water to enter the interior of the brown rice, shortening the cooking time of the brown rice. In addition, the crude fiber of the brown rice cortex is degraded to varying degrees, and the structure is destroyed. During the cooking process, water can migrate to the interior faster, enhancing the binding effect of starch and water, and quickly gelatinizing, thereby making the texture of the brown rice soft and effectively improving the taste quality of the brown rice.

[0119] It should be understood that the above detailed embodiments of the present disclosure are only for the purpose of illustrating or explaining the principles of the present disclosure, rather than limiting the present invention. Therefore, any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present disclosure should be included in the protection scope of the present invention.

[0120]

Claims

1. A Lactobacillus plantarum WL01 (Lactobacillus plantarum), which has been deposited in the General Microbiology Center of China National Microbiological Culture Collection Committee on July 8, 2024, with a deposit number of CGMCC No. 31201, and a deposit address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing.

2. A microbial agent, characterized in that: The microbial agent contains the Lactobacillus plantarum WL01 or its culture solution, or its freeze-dried powder according to claim 1.

3. A method for preparing fermented colored brown rice, characterized in that: The activated Lactobacillus plantarum WL01 is inoculated into the colored brown rice, mixed evenly, and dried after semi-solid fermentation.

4. The method for preparing fermented colored brown rice according to claim 3, characterized in that: The colored brown rice was sterilized by soaking in water and then inoculated with Lactobacillus plantarum WL01. The soaking condition was: the solid-liquid ratio was 1:0.6-1.

5. The method for preparing fermented colored brown rice according to claim 3, characterized in that: In the colored brown rice, the inoculation amount of the plant lactobacillus WL01 is 3.35×10 7 ~1.68×10 8 cfu / g; and / or, semi-solid fermentation temperature 25-37°C; And / or, the fermentation time is 4 to 12 hours.

6. The method for preparing fermented colored brown rice according to claim 3, characterized in that: The colored brown rice is dried to a moisture content of ≤14% in the drying step.

7. The method for preparing fermented colored brown rice according to claim 3, characterized in that: The activation method is as follows: firstly activate the strain twice with MRS liquid culture medium, and culture it statically at 37°C for 18 to 24 hours; the third generation strain is used for inoculation.

8. The method for preparing fermented colored brown rice according to claim 3, characterized in that: The colored brown rice includes but is not limited to one or a combination of red rice, black rice, and purple rice.

9. Fermented colored brown rice obtained by the preparation method according to claims 3-8.

10. Use of the Lactobacillus plantarum WL01 according to claim 1 or the microbial agent according to claim 2 in improving the cooking quality of grains.

Images