Lactobacillus plantarum with astringency reducing function and application thereof

Abstract

The invention relates to the technical field of fermentation engineering and microorganisms, in particular to lactobacillus plantarum with an astringency reducing function and application of the lactobacillus plantarum. The lactobacillus plantarum is preserved in the China Center for Type Culture Collection on January 29, 2024, the preservation number of the lactobacillus plantarum is CCTCC NO: M 2024248, and the lactobacillus plantarum is classified and named as Lactobacillus plantarum. The lactobacillus plantarum provided by the invention has the function of improving astringency by degrading tannic acid, also has the functions of improving antioxidant activity and increasing the content of functional nutritional ingredients, and provides important strain resources and technical support for improving the flavor of functional plant products.

Description

Technical Field

[0001] The present invention relates to the technical field of microbial fermentation, and particularly relates to a Lactobacillus plantarum with a function of reducing astringency and its application. Background Art

[0002] Plant fermentation products refer to products made by processing plant raw materials through microbial fermentation technology. Such products are not only widely used in the food field, but also play an important role in the fields of health products and biological fertilizers.

[0003] Tannin is a common substance in plant fermentation products, especially products with both medicinal and edible uses. When the content is high, the taste of plant fermentation products is astringent, which affects the flavor and the development and application of products, especially the development and application of berries with high functional substance content. At present, the common technologies for reducing astringency in plant fermentation products are adding sugar for adjustment, treating with lime water, or treating with tannase. However, the process is cumbersome, the stability is poor, and it is not suitable for large-scale production.

[0004] Therefore, it is necessary to screen excellent strains with the ability to degrade tannic acid from nature. Summary of the Invention

[0005] To obtain an excellent strain with the ability to degrade tannic acid, the present invention provides a Lactobacillus plantarum with a function of reducing astringency and its application. The Lactobacillus plantarum is named L211224Ca, and was deposited at the China Center for Type Culture Collection on January 29, 2024, with the deposit number: CCTCC NO: M 2024248, and the taxonomic name is Lactobacillus plantarum. The Lactobacillus plantarum L211224Ca provided by the present invention has the function of improving astringency by degrading tannic acid, and also has the functions of enhancing antioxidant activity and increasing the content of functional nutrients, providing important strain resources and technical support for improving the flavor of functional plant products.

[0006] The present invention provides a Lactobacillus plantarum L211224Ca, which was deposited at the China Center for Type Culture Collection on January 29, 2024, with the deposit number: CCTCC NO: M 2024248, and the taxonomic name is Lactobacillus plantarum.

[0007] The Lactobacillus plantarum L211224Ca provided by the present invention has the function of improving astringency by degrading tannic acid. It can also enhance the antioxidant activity of plant fermentation products and increase the content of functional nutrients through fermentation, providing important strain resources and technical support for improving the flavor of functional plant fermentation products.

[0008] The present invention also provides a starter culture, which contains the above-mentioned Lactobacillus plantarum L211224Ca.

[0009] Further, the starter culture is a liquid starter culture or a solid starter culture;

[0010] The viable count of Lactobacillus plantarum L211224Ca in the liquid starter culture is 10 5 cfu / mL to 10 9 cfu / mL;

[0011] The viable count of Lactobacillus plantarum L211224Ca in the solid starter culture is 10 5 cfu / g to 10 9 cfu / g.

[0012] The present invention also provides an application of the above-mentioned Lactobacillus plantarum or the above-mentioned starter culture in the fermentation of plant products. The Lactobacillus plantarum L211224Ca or the starter culture is used to improve the quality of plant products. The plant products are fermented by Lactobacillus plantarum L211224Ca to obtain fermented plant products.

[0013] Further, the improvement of the quality of plant products lies in that: the Lactobacillus plantarum L211224Ca or the starter culture improves the astringency of plant products by degrading tannic acid in plant products.

[0014] Further, the improvement of the quality of plant products lies in that: the Lactobacillus plantarum L211224Ca or the starter culture increases the contents of functional nutrients flavonoids and anthocyanins in plant products.

[0015] Further, the improvement of the quality of plant products lies in that: the Lactobacillus plantarum L211224Ca or the starter culture improves the antioxidant capacity of plant products by increasing the DPPH free radical scavenging rate and ABTS free radical scavenging rate of plant products.

[0016] The tannic acid content of the fermented plant products is significantly lower than that of the unfermented plant products, resulting in a reduced astringency; the flavonoid and anthocyanin contents of the fermented plant products are significantly higher than those of the unfermented plant products; the antioxidant capacity of the fermented plant products is significantly higher than that of the unfermented plant products.

[0017] Further, the plant products are fermented juices of plants.

[0018] Further, the fermented juice of the plant is fermented fruit juice.

[0019] Furthermore, the fermentation process of the fruit juice is as follows: After juicing the fruit and filtering to obtain the fruit juice, add sugar for blending, sterilize it, inoculate the fermentation agent described above, and ferment at 36°C to 37°C for 46h to 48h to obtain the fermented fruit juice.

[0020] Furthermore, the fruit juice is aronia melanocarpa fruit juice or blue honeysuckle fruit juice.

[0021] Furthermore, the preparation process of the aronia melanocarpa fruit juice is as follows: After juicing the aronia melanocarpa and filtering to obtain the fruit juice, add sugar for blending, sterilize it, inoculate the fermentation agent described in claim 2, and ferment at 36°C to 37°C for 46h to 48h to obtain the fermented aronia melanocarpa fruit juice.

[0022] Furthermore, the preparation process of the blue honeysuckle fruit juice is as follows: After juicing the blue honeysuckle and filtering to obtain the fruit juice, add sugar for blending, sterilize it, inoculate the fermentation agent described in claim 2, and ferment at 36°C to 37°C for 46h to 48h to obtain the fermented blue honeysuckle fruit juice.

[0023] The present invention also provides a method for preparing fermented aronia melanocarpa fruit juice, comprising the following steps:

[0024] After juicing the aronia melanocarpa and filtering to obtain the fruit juice, add glucose accounting for 6% to 8% of the fruit juice mass for blending, sterilize it, inoculate the lactic acid bacteria fermentation agent according to the inoculation amount of 2% by mass fraction, and ferment at 36°C to 37°C for 46h to 48h to obtain the fermented aronia melanocarpa fruit juice.

[0025] The present invention also provides a method for preparing fermented blue honeysuckle fruit juice, comprising the following steps:

[0026] After juicing the blue honeysuckle and filtering to obtain the fruit juice, add glucose accounting for 2% to 3% of the fruit juice mass for blending, sterilize it, inoculate the lactic acid bacteria fermentation agent according to the inoculation amount of 2% by mass fraction, and ferment at 36°C to 37°C for 46h to 48h to obtain the fermented blue honeysuckle fruit juice.

[0027] The beneficial effects of the present invention are as follows:

[0028] The Lactobacillus plantarum L211224Ca provided by the present invention has the function of improving astringency by degrading tannic acid, and also has the functions of enhancing antioxidant activity and increasing the content of functional nutrients, providing important bacterial strain resources and technical support for improving the flavor of functional plant products.

[0029] The present invention prepares Lactobacillus plantarum L211224Ca into a bacterial concentration of 10 5 cfu / mL to 10 9The Lactobacillus plantarum starter at cfu / mL can improve the astringency of fruit juice, increase the functional nutrients (flavonoids and anthocyanins), and enhance the antioxidant capacity (DPPH radical scavenging rate and ABTS radical scavenging rate) after fermenting fruit juice. The sensory score of the black chokeberry juice fermented by Lactobacillus plantarum L211224Ca is 91 points, which is significantly higher than the sensory score of 60.25 points of the unfermented black chokeberry juice. The sensory score of the blue honeysuckle juice fermented by Lactobacillus plantarum L211224Ca is 87.2 points, which is significantly higher than the sensory score of 69.4 points of the unfermented blue honeysuckle juice. It can be seen that the isolated Lactobacillus plantarum L211224Ca of the present invention can not only degrade tannic acid in fruit juice, but also increase the contents of flavonoids and anthocyanins in fruit juice, and improve the DPPH radical scavenging rate and ABTS radical scavenging rate.

[0030] The Lactobacillus plantarum L211224Ca provided by the present invention has significant technical advantages in aspects such as astringency reduction ability, expanding application fields, and enhancing product added value, providing important strain resources and technical support for the innovative development of the astringency-reducing food-related industries.

[0031] Description of the preservation information of biological materials

[0032] L211224Ca, referred to as Lactobacillus plantarum L211224Ca in this application, was deposited at the China Center for Type Culture Collection on January 29, 2024, with the deposit number: CCTCC NO: M 2024248. The address of the depository is Wuhan University, Wuhan, China, Zip Code: 430072, and the taxonomic name is Lactobacillus plantarum L211224Ca. Description of the drawings

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0034] Figure 1 It is the identification result of the colony morphology of strain L211224Ca in the solid medium;

[0035] In the figure, A is the colony morphology of strain L211224Ca; B is the Gram staining result of strain L211224Ca.

[0036] Figure 2 It is the phylogenetic tree of strain L211224Ca based on the 16S rDNA gene.

[0037] Figure 3 For the detection of the ability of strain L211224Ca to degrade tannic acid based on the color change method.

[0038] Figure 4 It is the tannic acid standard curve.

[0039] Figure 5 It is the rutin standard curve, representing flavonoids.

[0040] Figure 6 It is the effect of fermented Aronia melanocarpa juice by strain L211224Ca on the flavonoid content during storage.

[0041] Figure 7 It is the effect of fermented Aronia melanocarpa juice by strain L211224Ca on the anthocyanin content during storage.

[0042] Figure 8 It is the effect of fermented Aronia melanocarpa juice by strain L211224Ca on the DPPH free radical scavenging rate during storage.

[0043] Figure 9 It is the effect of fermented Aronia melanocarpa juice by strain L211224Ca on the ABTS free radical scavenging rate during storage. Specific implementation manners

[0044] The following describes the specific implementation manners of the present invention in detail, but it should be understood that the protection scope of the present invention is not limited by the specific implementation manners. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are all conventional methods unless otherwise specified. The materials, reagents, etc. used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0045] Example 1: Isolation, morphological observation, physiological and biochemical characteristics, and identification of Lactobacillus plantarum L211224Ca.

[0046] 1. Strain isolation

[0047] Collect samples of homemade pickled vegetables from rural areas in Yichun City, Heilongjiang Province. Take 10 g of pickled vegetable samples and shake them in 90 mL of sterile water. Gradually dilute them according to the 10-fold serial dilution method, and select 10 -4 、10 -5 、10 -6Three gradients of sample dilutions, 100 μL of each gradient of sample dilution were respectively spread on MRS solid medium and MRS modified solid medium, repeated 3 times, then sealed and inverted and placed in a 2.5 L or 7 L anaerobic culture tank, and an anaerobic packet and an oxygen indicator were added thereto, and after sealing, it was cultured in a constant temperature incubator at 37 °C for 2 - 3 d. Randomly select single colonies with a calcium dissolution zone, pick the single colonies into MRS liquid medium, culture at 37 °C for 24 h, and streak and purify 3 times on MRS solid medium until single colonies with consistent morphology are obtained. The obtained strains were screened for the ability to degrade tannic acid, and a strain was obtained, named L211224Ca.

[0048] 2. Morphological observation

[0049] (1) Colony morphology: Streak inoculate the strain L211224Ca on an MRS solid plate and observe the colony morphology.

[0050] The results are as Figure 1 shown in A of, the strain L211224Ca was streak-cultured on MRS solid medium and cultured at 37 °C for 2 d. The colonies were round, medium-sized, convex, slightly white, moist, smooth, and the edges were neat.

[0051] (2) Gram staining

[0052] Pick the purified single colonies, stain them with a Gram staining kit, and observe the cell color and morphology under an optical microscope.

[0053] The results are as Figure 1 shown in B of, the strain L211224Ca was rod-shaped and purple under an optical microscope, and it was a Gram-positive bacterium.

[0054] 3. Physiological and biochemical characteristics

[0055] Referring to "Classification and Identification Methods of Lactic Acid Bacteria" and "Handbook of Systematic Identification of Common Bacteria", physiological and biochemical characteristic tests such as catalase test, glucose fermentation to produce acid and gas, sugar fermentation test, methyl red MR test, V-P determination, starch hydrolysis, and gelatin liquefaction were carried out on the lactic acid bacteria strains with the function of degrading tannic acid obtained by re-screening.

[0056] Results: The physiological and biochemical identification results of strain L211224Ca are shown in Table 1. As can be seen from Table 1, strain L211224Ca can ferment glucose to produce acid but not gas, and can also ferment arabinose, fructose, galactose, maltose, mannose, raffinose, trehalose, rhamnose, sucrose, and salicin to produce acid, but cannot ferment erythritol and mannitol; the result of methyl red MR test is positive; the results of catalase, starch hydrolysis, gelatin liquefaction, and V-P test are negative, which conform to the physiological and biochemical identification characteristics of the genus Lactobacillus.

[0057] Table 1 Physiological and biochemical identification results of strain L211224Ca

[0058]

[0059]

[0060] Note: "+" indicates a positive reaction, and "-" indicates a negative reaction.

[0061] 4. Molecular biology identification

[0062] The genomic DNA was extracted by the CTAB method, and the DNA concentration and purity were detected by a micro ultraviolet spectrophotometer. Using the universal primers 27F and 1492R as the upstream and downstream primers respectively, PCR amplification was carried out. After the PCR reaction, the PCR products were detected by 1% agarose gel electrophoresis, placed in a gel imaging system for observation. If the electrophoresis bands of the PCR amplification products were detected around 1500 bp, they were photographed and recorded. Finally, the PCR amplification products were sent to Shanghai Sangon Biotech Co., Ltd. for sequencing. The 16S rDNA sequencing results of the strain were compared with the standard strain sequences in the NCBI database by BLAST homology alignment to determine the species of the candidate strain. The MEGA-X software was used to construct a phylogenetic tree. Through BLAST sequence alignment, it was found that the homology between strain L211224Ca and Lactobacillus plantarum was more than 99%. The gene sequences of the model strains with higher homology were selected to construct a phylogenetic tree as Figure 2 shown. Strain L211224Ca was identified as Lactobacillus plantarum.

[0063] Example 2: The ability of Lactobacillus plantarum L211224Ca to degrade tannic acid.

[0064] I. Determination of the tannic acid degradation ability of Lactobacillus plantarum L211224Ca by the color change method

[0065] Determination of the tannic acid degradation ability of Lactobacillus plantarum L211224Ca by color change method. The screening principle is to use a color-changing screening medium with tannic acid as the sole carbon source. Through the biodegradation of lactic acid bacteria, the pH in the medium decreases, causing the color of the medium to change from blue-violet to yellow-green.

[0066] 1. Preparation of the medium

[0067] MRS liquid medium: Peptone 10 g, Beef extract 10 g, Yeast extract powder 5 g, K 2 HPO 4 2 g, Ammonium citrate 2 g, Sodium acetate anhydrous 5 g, Glucose 20 g, Tween 80 1 ml, MgSO 4 .7H 2 O 0.5 g, MnSO 4 ·4H 2 O 0.25 g, Distilled water 1000 mL, pH 6.3, Sterilized at 121 °C for 20 min.

[0068] Color-changing screening medium: Tannic acid 2 g sterilized separately, Sodium nitrate 0.3 g, K 2 HPO 4 0.2 g, MgSO 4 ·7H 2 O 0.1 g, KCl 0.1 g, FeSO 4 ·7H 2 O 0.005 g, Bromophenol blue 0.01 g, Distilled water 200 mL, pH 5.0, Sterilized at 121 °C for 20 min.

[0069] 2. Preparation of the Lactobacillus plantarum starter culture:

[0070] Under sterile conditions, take the strain L211224Ca stored in the -80 °C refrigerator, inoculate it into the MRS liquid medium at an inoculation amount of 2%, activate it for two generations, centrifuge at 4 °C and 4000 r / min for 10 min, collect the cell precipitate, wash it 3 times with sterile water and then resuspend it with sterile water to obtain a cell suspension. Adjust the concentration of the cell suspension to 10 8 cfu / mL to obtain the Lactobacillus plantarum starter culture for standby.

[0071] 3. Determination of the tannic acid degradation ability by color change method

[0072] Take the strain L211224Ca stored in the -80 °C refrigerator, activate it in the MRS liquid medium, culture it at 37 °C for 24 h, activate it for two generations to restore its vitality, and obtain the activated bacterial liquid.

[0073] Absorb 3 mL of the color-changing screening culture medium into a 48-well deep-well plate, inoculate the activated bacterial solution, and inoculate it into a new color-changing screening culture medium at an inoculation amount of 2%. Conduct 3 parallel experiments, use the color-changing screening culture medium without inoculation as the negative control, and use the tannase inoculated into the color-changing screening culture medium as the positive control. After capping, incubate statically in a constant temperature incubator at 30 °C for 48 h. Observe the color change of the culture medium.

[0074] The results are as Figure 3 shown. The liquid culture medium inoculated with strain L211224Ca changed from blue-violet to yellow-green, and it was preliminarily judged that strain L211224Ca has the ability to degrade tannic acid.

[0075] II. Determination of the ability to degrade tannic acid by the content determination method

[0076] 1. Tannic acid standard curve:

[0077] Prepare a tannic acid standard solution with a concentration of 0.1 mg / mL. Take 5 10-mL tubes, add 0.2, 0.4, 0.6, 0.8, and 1.0 mL of tannic acid standard solution to them respectively. Then add 0.5 mL of Folin-Ciocalteu reagent and 1.0 mL of 75 g / L sodium carbonate solution to the 5 tubes respectively. Finally, make up the volume to the scale with distilled water, place it in the dark at room temperature for 1 h, measure the absorbance at 760 nm, repeat 3 times, take the average value, and draw the tannic acid standard curve.

[0078] The results are as Figure 4 shown. The regression equation of the tannic acid standard curve is y = 0.00889x + 0.009, R 2 = 0.9995, showing a good linear relationship and can be used for the calculation of tannic acid content in subsequent experiments.

[0079] 2. Determination of the degradation rate of tannic acid

[0080] Prepare a tannic acid culture solution containing a known tannic acid content, and determine the ability of L211224Ca to degrade tannic acid in it.

[0081] Preparation of the tannic acid culture solution: 10 g of tannic acid, 10 g of sucrose, 1.5 g of NH 4 Cl, 0.5 g of KCl, 1 g of K 2 HPO 4 1, 0.5 g of MgSO 4 0.5 g, 0.5 g of NaCl, 1000 mL of distilled water, natural pH, sterilize at 121 °C for 20 min.

[0082] Inoculate the previously prepared Lactobacillus plantarum starter culture into the tannic acid culture solution at a ratio of 2%, and incubate it at a constant temperature of 37°C for 48 h. Centrifuge and take the fermentation supernatant. Take 1 mL of the supernatant and place it in a centrifuge tube. Add 0.5 mL of Folin-Ciocalteu reagent and 1 mL of 75 g / L sodium carbonate solution, and supplement with 7.5 mL of distilled water to make the volume up to 10 mL. Place it in the dark at 25°C for 1 h, measure the absorbance at 760 nm, repeat 3 times, take the average value, and calculate the tannic acid content in the sample according to the regression equation of the tannic acid standard curve. And measure the tannic acid degradation rate according to the following formula.

[0083]

[0084] In the formula, A 0 is the content of tannic acid in the tannic acid culture solution without inoculation measured after 48 h; A 1 is the content of tannic acid in the tannic acid culture solution inoculated with the Lactobacillus plantarum starter culture measured after 48 h.

[0085] Result: The content of tannic acid in the tannic acid culture solution without inoculation after 48 h was 9.5 g / L, while the content of tannic acid in the tannic acid culture solution inoculated with the Lactobacillus plantarum starter culture was 6.91 g / L. It can be seen that the tannic acid degradation rate of Lactobacillus plantarum L211224Ca was 27.26%.

[0086] Example 3: The effect of strain L211224Ca on reducing the astringency of Aronia melanocarpa juice.

[0087] Aronia melanocarpa is a new resource food in recent years. During development, its astringent taste seriously affects the taste of processed products. Therefore, this example selects this plant product for verification.

[0088] 1. Preparation of Aronia melanocarpa juice without inoculation and inoculated and fermented juice

[0089] Take 100 g of Aronia melanocarpa stored at -20°C, thaw it at room temperature, select, wash it, and then juice it according to the material-liquid ratio of Aronia melanocarpa to distilled water of 1 g:2 mL. Filter it through four layers of gauze to obtain the juice, add 7% glucose by mass percentage of the juice, mix evenly to obtain Aronia melanocarpa juice. Divide 180 mL of the Aronia melanocarpa juice equally into 6 50-ml fermentation tubes, sterilize it in a constant temperature water bath at 80°C for 15 min, and let it cool to room temperature. Among them, inoculate 3 tubes with the Lactobacillus plantarum starter culture prepared in Example 2 at an inoculation amount of 2%, and the remaining 3 tubes are not inoculated with the Lactobacillus plantarum starter culture. Place all tubes at 37°C for 48 h to obtain 3 tubes of unfermented juice and 3 tubes of fermented juice respectively.

[0090] 2. Determination of tannic acid degradation rate in Aronia melanocarpa juice

[0091] According to the tannic acid content of Aronia melanocarpa being about 1% or less, the 3 tubes of unfermented juice and 3 tubes of fermented juice in this example were each diluted 50 times. Then, 1 mL was taken and placed in different centrifuge tubes, 0.5 mL of Folin-Ciocalteu reagent and 1 mL of 75 g / L sodium carbonate solution were added, and 7.5 mL of distilled water was added to make the volume up to 10 mL. It was placed in the dark at 25 °C for 1 h, and the absorbance was measured at 760 nm. The results of the 3 tubes of unfermented juice and 3 tubes of fermented juice were averaged, and the tannic acid content in the sample was calculated according to the tannic acid standard curve regression equation in Example 2.

[0092] Taking the unfermented juice of Aronia melanocarpa as a control, the tannic acid content in the fermented juice of Aronia melanocarpa was measured, and the tannic acid degradation rate of the fermented group was calculated based on the tannic acid content of the control group.

[0093]

[0094] In the formula, A 0 is the tannic acid concentration of the unfermented juice; A 1 is the tannic acid concentration in the fermented juice

[0095] Results: After 48 h, the tannic acid content in the unfermented juice of Aronia melanocarpa was 3.77 g / L, while the tannic acid content in the fermented juice of Aronia melanocarpa was 2.53 g / L, and the tannic acid degradation rate of Lactobacillus plantarum L211224Ca in the Aronia melanocarpa juice was 32.89%.

[0096] Example 4: Sensory effect of Lactobacillus plantarum L211224Ca on Aronia melanocarpa juice.

[0097] 1. Sensory evaluation of fermented Aronia melanocarpa juice

[0098] A sensory evaluation panel consisting of 12 teachers and students from the College of Food Science, Shenyang Agricultural University was formed. Persons with sensitive taste and smell were selected. Taking the unfermented Aronia melanocarpa juice (CK) as a control, the fermented Aronia melanocarpa juice was subjected to sensory scoring, with color (20), tissue state (20), taste (30), and flavor (30) as evaluation items. The specific scoring criteria are shown in Table 2.

[0099] Table 2 Sensory scoring criteria for fermented Aronia melanocarpa juice

[0100]

[0101]

[0102] According to the above criteria, the fermented Aronia melanocarpa juice prepared by the present invention was subjected to sensory scoring. The results are shown in Table 3, and the comprehensive score of the fermented Aronia melanocarpa juice was 91 points.

[0103] Table 3 Comprehensive Scoring Results of Fermented Aronia melanocarpa Juice

[0104] Group Color and luster Texture Taste Flavor Comprehensive score Unfermented juice 19.25 19.25 9.50 10.75 60.25 L211224Ca fermented juice 20.00 20.00 23.00 22.00 91.00

[0105] Example 5: Fermentation by Lactobacillus plantarum L211224Ca Improves the Efficacy of Aronia melanocarpa Juice

[0106] In this example, the effects of fermentation on the contents of functional substances such as flavonoids and anthocyanins in Aronia melanocarpa juice were determined, and the improvement effect of fermentation on the antioxidant capacity of the juice was also determined.

[0107] 1. Prepare Aronia melanocarpa juice according to the method of Example 3. Inoculate Lactobacillus plantarum starter into Aronia melanocarpa juice and ferment it according to the method of Example 3. After 48 h of fermentation, collect the fermented Aronia melanocarpa juice, and the unfermented Aronia melanocarpa juice is used as a control. After the fermented juice is cooled to room temperature, both the fermentation group (fermented Aronia melanocarpa juice) and the unfermented group (unfermented Aronia melanocarpa juice) are stored at 4 °C for 28 d, and the changes in functional components and antioxidant capacity at 0 d, 7 d, 14 d, 21 d, and 28 d of storage are measured respectively.

[0108] 2. Improvement Effect of Fermentation on Flavonoids in Aronia melanocarpa Juice

[0109] Preparation of the standard curve: Slightly modified according to the method of Chen Sirui (2020). Respectively transfer 0 mL, 0.2 mL, 0.4 mL, 0.6 mL, 0.8 mL, and 1.0 mL of 0.2 mg / mL rutin standard solution into 10 mL test tubes, and successively add 0.3 mL of NaNO 2 solution (5 g / 100 mL), place for 6 min, add 0.3 mL of aluminum nitrate solution (10 g / 100 mL), place for 6 min, add 4 mL of NaOH solution (4 g / 100 mL), make up the volume to the scale with 60% ethanol solution, let stand for 15 min, and measure the absorbance value at 510 nm. Draw the rutin standard curve as Figure 5 , and the regression equation is y = 0.0053x + 0.0009, R 2 = 0.9996.

[0110] Results: As shown in Figure 6 , when Aronia melanocarpa juice was fermented with Lactobacillus plantarum L211224Ca, at 0 d of storage after fermentation, the flavonoid content was 702.58 ± 12.46 mg / L. Compared with the unfermented Aronia melanocarpa juice, the flavonoid content in the fermented Aronia melanocarpa juice increased by 2.95%. At 28 d of storage, compared with the unfermented juice, the flavonoid content in the fermented Aronia melanocarpa juice increased by 11.05%.

[0111] 3. Enhancement effect of fermentation on anthocyanins in Aronia melanocarpa juice

[0112] The anthocyanin content was detected by the pH differential method, referring to the method of Li Hongfu (2019). 1 mL of the diluted Aronia melanocarpa juice sample was respectively pipetted into 10 mL test tubes, and 9 mL of buffer solution with pH 1.0 (0.025 M hydrochloric acid - potassium chloride solution) and buffer solution with pH 4.5 (0.40 M acetic acid - sodium acetate solution) were added respectively. After placing in the dark, the absorbance values at 510 nm and 700 nm were measured respectively. The calculation formula for the total anthocyanin content is as follows.

[0113] Anthocyanin content (mg / L) = A × M × N × 1000 / ε × 1;

[0114] In the formula: Absorbance value A = (A510 - A700)pH 1.0 - (A510 - A700)pH 4.5; M: Calculated as cyanidin - 3 - O - glucoside, the molecular weight is 449.2 g / mol; N: Sample dilution factor; ε = 26900.

[0115] The results are as Figure 7 shown. For the Aronia melanocarpa juice fermented with Lactobacillus plantarum L211224Ca, after the fermentation ended and stored for 0 d, the anthocyanin content was 673.80 ± 7.52 mg / L. Compared with the unfermented juice, the anthocyanin content increased by 6.32%. When stored for 28 d, compared with the unfermented juice, the anthocyanin content of the fermented juice increased by 5.24%. Therefore, fermenting Aronia melanocarpa juice with strain L211224Ca can increase the content of functional substances in the juice.

[0116] 4. Changes in antioxidant capacity

[0117] (1) DPPH radical scavenging rate

[0118] DPPH radical scavenging ability: Referring to the method of Wang Hui (2020) with slight modifications. 2 mL of 0.2 mmol / L DPPH - ethanol solution was added to 1 mL of the diluted Aronia melanocarpa juice sample respectively. The reaction mixture was reacted in the dark at room temperature for 30 min, and the absorbance value at 517 nm was measured. The calculation formula for the DPPH radical scavenging rate is as follows.

[0119] DPPH radical scavenging rate (%) = [1 - (A 1 - A 2 )] / A 0 × 100%;

[0120] In the formula: A 1 is the absorbance value of the Aronia melanocarpa juice sample solution with different treatment methods; A 2is the absorbance value of the reference control (absolute ethanol replaces the DPPH-ethanol solution); A 0 is the absorbance value of the blank control (distilled water replaces the sample).

[0121] The results are as Figure 8 shown. For the aronia juice fermented with strain L211224Ca, after fermentation and storage for 0 d, the DPPH radical scavenging rate increased by 12.93% compared with the unfermented juice. After storage for 28 d, the DPPH radical scavenging rate of the fermented juice was 81.10%, which was 20.82% higher than that of the unfermented juice. Therefore, fermentation with strain L211224Ca can improve the DPPH radical scavenging rate of aronia juice.

[0122] (2) ABTS radical scavenging rate

[0123] ABTS radical scavenging ability: Mix 7 mM ABTS solution and 2.45 mM K 2 SO4 solution in equal volumes, and react in the dark for 16 h to obtain the ABTS radical reaction solution. Dilute it with phosphate buffer to make the absorbance value of the diluted solution at 734 nm be 0.70 ± 0.02, which is used as the ABTS stock solution. Take 0.4 mL of the sample dilution and add 1.6 mL of the ABTS stock solution, react at room temperature in the dark for 10 min, and measure the absorbance value at 734 nm. The calculation formula for the ABTS radical scavenging activity is as follows.

[0124] ABTS radical scavenging rate (%) = [1 - (A 1 - A 2 )] / A 0 × 100%;

[0125] In the formula: A1 is the absorbance value of the aronia juice sample solution under different treatment methods; A2 is the absorbance value of the reference control (absolute ethanol replaces the ABTS stock solution); A0 is the absorbance value of the blank control (distilled water replaces the sample).

[0126] The results are as Figure 9 shown. For the aronia juice fermented with strain L211224Ca, after fermentation and storage for 0 d, the ABTS radical scavenging rate increased by 26.18% compared with the unfermented juice. After storage for 28 d, the ABTS radical scavenging rate of the fermented juice was 48.85%, which was 12.31% higher than that of the unfermented juice. Therefore, fermentation with strain L211224Ca can improve the ABTS radical scavenging rate of aronia juice.

[0127] Example 6: Effect of strain L211224Ca on blueberry juice.

[0128] I. Astringency reduction effect of strain L211224Ca on blue honeysuckle juice

[0129] 1. Preparation of un-inoculated and inoculated fermented blue honeysuckle juice

[0130] Take 120 g of blue honeysuckle stored at -20°C, select, wash, thaw naturally at room temperature and juice (material-liquid ratio is 1:1.8), adjust (glucose addition amount is 3%), filter with four layers of sterile gauze to remove the filter residue. Mix evenly to obtain the juice. Equally divide 180 mL of the juice into 6 50-ml fermentation tubes, sterilize in a constant temperature water bath at 80°C for 15 min, and cool to room temperature. Inoculate 3 of the tubes with lactic acid bacteria starter at an inoculation amount of 2% (see Example 2), and the remaining 3 tubes are not inoculated with the fermentation agent. All tubes are placed at 37°C for 48 h to obtain unfermented juice and fermented juice respectively.

[0131] 2. Determination of tannic acid degradation rate in blue honeysuckle juice

[0132] According to the tannic acid content range in blue honeysuckle being about within 1%, dilute the sample 50 times, use the unfermented blue honeysuckle juice as a control, measure the tannic acid content in the blue honeysuckle juice, and calculate the tannic acid degradation rate based on the tannic acid content. The calculation formula is as in Example 3.

[0133] The results show that after 48 h of fermentation, the tannic acid content in the unfermented blue honeysuckle juice is 2.65 g / L, while the tannic acid content in the fermented blue honeysuckle juice is 2 g / L, and the tannic acid degradation rate of strain L211224Ca in the blue honeysuckle juice is 24.52%.

[0134] II. Sensory evaluation of L211224Ca on blue honeysuckle juice

[0135] 1. Sensory evaluation of fermented blue honeysuckle juice

[0136] A sensory evaluation panel consisting of 12 teachers and students from the College of Food Science, Shenyang Agricultural University, selects personnel with sensitive taste and smell, and uses the unfermented blue honeysuckle juice (ck) as a control to conduct a sensory score on the fermented blue honeysuckle juice. The scoring criteria are shown in Table 3, and the scoring results are shown in Table 4.

[0137] Table 4 Sensory scores of fermented blue honeysuckle juice

[0138] Group Color and luster Texture Taste Flavor Comprehensive score Unfermented 17.4 17.7 15.2 19.1 69.4 L211224Ca fermentation 18.5 18.83 25.9 23.8 87.2

[0139] As shown in Figure 4, the sensory score of the blue honeysuckle juice fermented by L211224Ca is 87.2, which is 17.8 points higher than the sensory score of the unfermented blue honeysuckle juice.

[0140] Although the preferred embodiments of the present invention have been described, additional changes and modifications can be made to these embodiments by those skilled in the art once they learn of the basic creative concept.

[0141] Obviously, those skilled in the art can make various changes and deformations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and deformations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and deformations.

Claims

1. A strain of Lactobacillus plantarum L211224Ca, characterized in that: The Lactobacillus plantarum L211224Ca was deposited in the China Center for Type Culture Collection on January 29, 2024, with a deposit number of CCTCCNO: M 2024248 and a classification name of Lactobacillus plantarum.

2. A leavening agent, characterized in that The starter culture comprises the Lactobacillus plantarum L211224Ca described in claim 1.

3. The leavening agent according to claim 2, characterized in that The fermentation agent is a liquid fermentation agent or a solid fermentation agent; The number of viable bacteria of Lactobacillus plantarum L211224Ca in the liquid starter is 10 5 cfu / mL~10 9 cfu / mL; The number of viable bacteria of Lactobacillus plantarum L211224Ca in the solid fermentation agent is 10 5 cfu / g~10 9 cfu / g.

4. Use of the Lactobacillus plantarum L211224Ca according to claim 1 or the starter according to any one of claims 2 to 3 in the fermentation of plant products, characterized in that: The plant lactobacillus L211224Ca or the starter is used to improve the quality of plant products.

5. The use according to claim 4, characterized in that: The method for improving the quality of the plant products is that the Lactobacillus plantarum L211224Ca or the fermentation agent improves the astringency of the plant products by degrading tannic acid in the plant products.

6. The use according to claim 4, characterized in that: The method for improving the quality of plant products is that the plant lactobacillus L211224Ca or the fermentation agent increases the content of flavonoids and anthocyanins, which are functional nutrients in the plant products.

7. The use according to claim 4, characterized in that: The method for improving the quality of plant products lies in that the Lactobacillus plantarum L211224Ca or the fermentation agent improves the antioxidant capacity of the plant products by improving the DPPH free radical scavenging rate and the ABTS free radical scavenging rate of the plant products.

8. The use according to claim 4, characterized in that: The plant product is fermented juice of plants.

9. The use according to claim 8, characterized in that: The fermented juice of the plant is fermented juice.

10. The use according to claim 9, characterized in that: The fermentation process of the juice is: The fruit juice is squeezed and filtered to obtain the juice, sugar is added, the mixture is sterilized, and then the starter according to claim 2 is inoculated, and the mixture is fermented at 36° C. to 37° C. for 46 h to 48 h to obtain the fermented juice.

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