Lactic acid bacteria product as well as preparation method and application thereof in food preservation

Abstract

The invention relates to a lactic acid bacteria product, a preparation method thereof and application of the lactic acid bacteria product in food preservation, and the lactic acid bacteria product comprises fermentation metabolites obtained by co-fermentation of lactobacillus plantarum, lactobacillus delbrueckii subsp. Lactis and streptococcus salivarius subsp. Thermophilus and plant extracts. The lactobacillus and the streptococcus salivarius subsp. Thermophilus are scientifically proportioned and combined, and the plant extract with a natural antibacterial effect is added, so that the antibacterial efficiency is synergistically improved, the fresh-keeping effect is enhanced, meanwhile, the nutritional value of the food can be improved, and the probiotic function is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of microbial fermentation, and in particular relates to a lactic acid bacteria product and a preparation method thereof and application in food preservation. Background Art

[0002] During the production, transportation and storage of food, it is easy to be affected by the external environment and go bad, causing foodborne diseases, food poisoning, etc. At the same time, food spoilage will cause waste of resources and bring huge economic losses to all parts of the world. Therefore, adding appropriate preservatives to food has become an inevitable process to extend the shelf life of food and ensure food quality.

[0003] At present, chemical preservatives are often used in the food processing industry to preserve food, but chemical preservatives have many disadvantages, and the use of many preservatives is subject to certain restrictions. Natural biological preservation technology is a technology that uses natural organisms and their metabolites as core raw materials, and inhibits the growth of microorganisms by adding them directly or after extraction, fermentation, enzymatic conversion, etc. Lactic acid bacteria are recognized as safe food-grade microorganisms. Lactic acid bacteria and their metabolites can not only inhibit the growth of pathogenic bacteria and extend the shelf life of products, but also have probiotic functions such as lowering blood lipids, regulating human immunity and adjusting the gastrointestinal tract, and have broad application prospects.

[0004] Since plants are abundant in sources and low in cost, plant extracts contain a wealth of chemical components, including phenols, flavonoids, aldehydes and volatile oils, which can not only achieve the preservation effect by destroying cell walls and cell membranes, inhibiting protein function or binding to genetic material, and inhibiting cell respiration, but also have health effects such as lowering blood lipids, lowering blood pressure, anti-aging, and preventing tumors. Reports have shown that plant-based preservatives have been used in many types of food, such as animal, aquatic, plant and flour-based foods.

[0005] However, the current natural biological preservation technology still has problems such as complicated fermentation technology, single antibacterial substance, narrow antibacterial spectrum and limited application scope. Summary of the invention

[0006] In view of the problems of the current natural biological preservation technology, such as complicated fermentation technology, single antibacterial substance, narrow antibacterial spectrum and limited application scope, the present invention proposes a lactic acid bacteria product and a preparation method thereof and application in food preservation. The lactic acid bacteria product of the present invention is simple to prepare, and the antibacterial substances act synergistically to improve the antibacterial efficacy and enhance the preservation effect. At the same time, the nutritional value of food can also be improved, the prebiotic function is increased, and the application scope is wide.

[0007] Specifically, the present invention provides the following technical solutions:

[0008] In a first aspect, the present invention provides a lactic acid bacteria product, characterized in that the lactic acid bacteria product comprises fermentation metabolites of co-fermentation of Lactobacillus plantarum, Lactobacillus delbrueckii subsp. lactis and Streptococcus salivarius subsp. thermophilus, and a plant extract.

[0009] Preferably, the lactic acid bacteria product is characterized in that the plant lactobacillus is a plant lactobacillus Ali.Plateau.LP.Ⅷ strain, which is deposited in China Center for Type Culture Collection (CCTCC) with a deposit number of CCTCC NO:M 2022068;

[0010] The Lactobacillus delbrueckii subsp. lactis is the Dangxiong LBⅧ strain of Lactobacillus delbrueckii subsp. lactis, which is deposited in the China Center for Type Culture Collection (CCTCC) with a deposit number of CCTCC NO: M 2023396.

[0011] The thermophilic Streptococcus salivarius subsp. thermophilus is the thermophilic Streptococcus salivarius subsp. thermophilus Jiacha.ST-685 strain, which is deposited in the China Center for Type Culture Collection (CCTCC) with a deposit number of CCTCC NO:M 20231495.

[0012] Preferably, the lactic acid bacteria product is characterized in that the plant extract is selected from one or more of Zanthoxylum bungeanum extract, Ophiopogon japonicus extract, Leonurus japonicus extract, Forsythia suspensa extract, Star anise extract and Fennel extract.

[0013] In a second aspect, the present invention provides a method for preparing the lactic acid bacteria product, characterized in that the method comprises:

[0014] (1) inoculating Lactobacillus plantarum Ali. Plateau. LP. VIII, Lactobacillus delbrueckii subspecies Dangxiong LB VIII and Streptococcus salivarius thermophilic subspecies Jiacha. ST-685 into a fermentation medium for fermentation;

[0015] (2) centrifuging the fermentation liquid obtained in step (1), taking the supernatant, and rotary evaporating the supernatant to obtain a concentrated solution;

[0016] (3) The concentrated solution obtained in step (2) and the plant extract are compounded and then inactivated.

[0017] Preferably, the method for preparing the lactic acid bacteria product is characterized in that in step (1), the viable count of Lactobacillus plantarum Ali.Plateau.LP.Ⅷ is 5×10 5 -1×10 6 CFU / g;

[0018] and / or, the viable count of Lactobacillus delbrueckii subspecies Dangxiong LBⅧ is 5×10 5 -1×10 6 CFU / g;

[0019] and / or, the viable count of Streptococcus salivarius thermophilus subspecies Jiacha.ST-685 is 5×10 5 -1×10 6 CFU / g.

[0020] Preferably, the method for preparing the lactic acid bacteria product is characterized in that, in step (1), Lactobacillus plantarum Ali.Plateau.LP.VIII, Lactobacillus delbrueckii subsp. lactis Dangxiong LBVIII and Streptococcus salivarius thermophilic subsp. Jiacha.ST-685 are each inoculated in the fermentation medium at a volume percentage of 1-5%.

[0021] Preferably, the method for preparing the lactic acid bacteria product is characterized in that in step (1), the fermentation temperature is 30-42°C;

[0022] Preferably, the fermentation time is 24-48h;

[0023] Further preferably, the fermentation medium is selected from MRS medium.

[0024] Preferably, the method for preparing the lactic acid bacteria product is characterized in that in step (2), the centrifugal speed is 6000-8000 r / min;

[0025] and / or, the centrifugation time is 10-15 min;

[0026] Preferably, the rotary evaporation temperature is 50-60°C;

[0027] Further preferably, the rotary evaporation concentration is 1 / 2-1 / 10 of the original volume.

[0028] Preferably, the method for preparing the lactic acid bacteria product is characterized in that, in step (3), the plant extract is added to the concentrated solution at a mass percentage of 0.1-0.5%;

[0029] Preferably, the inactivation temperature is 80-100°C;

[0030] More preferably, the inactivation time is 20-30 min.

[0031] Preferably, the method for preparing the lactic acid bacteria product is characterized in that, after step (3), a drying step is further included;

[0032] Preferably, drying is selected from spray drying;

[0033] More preferably, the drying temperature is 130-190°C.

[0034] In a third aspect, the present invention provides a lactic acid bacteria product prepared by the preparation method.

[0035] In a fourth aspect, the present invention provides the use of the lactic acid bacteria product in food preservation.

[0036] Preferably, the application is characterized in that the food is selected from fruits and vegetables, baked pastries, fresh meat or pre-prepared dishes.

[0037] Preferably, the application is characterized in that the lactic acid bacteria product is added to food by soaking, spraying or as an additive.

[0038] Beneficial effects of the present invention:

[0039] The lactic acid bacteria product of the present invention improves the antibacterial efficacy and the preservation effect by scientifically combining lactobacillus and thermophilic Streptococcus salivarius and adding plant extracts with natural antibacterial effects, and can also improve the nutritional value of food and increase the probiotic function. It is suitable for a variety of application scenarios such as fruit and vegetable preservation, baked pastries, fresh meat and pre-prepared dishes.

[0040] Strain deposit information

[0041] The Streptococcus salivarius subsp. thermophilus Jiacha.ST-685 strain provided by the present invention was deposited in the China Center for Type Culture Collection (CCTCC) on August 17, 2023, with a deposit number of CCTCC NO:M 20231495, and a deposit address: Wuhan University, Wuhan, China, Postal Code: 430072; Telephone: (027)-68754052.

[0042] The Lactobacillus plantarum Ali. Plateau. LP. VIII strain provided by the present invention was deposited in the China Center for Type Culture Collection on January 13, 2022, with a deposit number of CCTCC NO: M 2022068, and a deposit address: Wuhan University, Wuhan, China, postal code: 430072; telephone: (027)-68754052. The strain has been disclosed in a patent application with publication number CN115838654A.

[0043] The Lactobacillus delbrueckii subsp. lactis Dangxiong LBⅧ strain provided by the present invention was deposited in the China Center for Type Culture Collection on March 23, 2023, with a deposit number of CCTCC NO: M 2023396, and a deposit address: Wuhan University, Wuhan, China, postal code: 430072; telephone: (027)-68754052. The strain has been disclosed in a patent application with publication number CN116948884A. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Figure 3 shows the effect of mixed culture of Lactobacillus plantarum Ali.Plateau.LP.Ⅷ, Lactobacillus delbrueckii subspecies DangxiongLBⅧ and Streptococcus salivarius thermophilic subspecies Jiacha.ST-685 on growth; A shows the effect of mixed culture of Lactobacillus plantarum Ali.Plateau.LP.Ⅷ and Streptococcus salivarius thermophilic subspecies Jiacha.ST-685 on growth; B shows the effect of mixed culture of Lactobacillus delbrueckii subspecies Dangxiong LBⅧ and Streptococcus salivarius thermophilic subspecies Jiacha.ST-685 on growth.

[0045] Figure 2 This is a diagram showing the antiseptic properties of bread in Application Example 2. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments and comparative examples, but the present invention is not limited to the following technical solution.

[0047] In some specific embodiments, the present invention provides a lactic acid bacteria product, which includes fermentation metabolites of co-fermentation of Lactobacillus plantarum, Lactobacillus delbrueckii subsp. lactis and Streptococcus salivarius subsp. thermophilus, and a plant extract.

[0048] The plant lactobacillus is the Lactobacillus plantarum Ali.Plateau.LP.Ⅷ strain, which was isolated from yak milk from herders in the Ali region of Tibet and is a natural wild strain. The strain was identified as Lactobacillus plantarum by 16S rDNA and named Lactobacillus plantarum Ali.Plateau.LP.Ⅷ. The strain was deposited in the China Center for Type Culture Collection on January 13, 2022 with a deposit number of CCTCC NO:M2022068. The strain has been disclosed in a patent application with a publication number of CN115838654A. Lactobacillus plantarum is recorded in the "List of Probiotics that Can Be Used in Health Foods" and has food safety attributes.

[0049] The lactobacillus delbrueckii subsp. lactis is the Lactobacillus delbrueckii subsp. lactis Dangxiong LBⅧ strain, which is isolated from the milk of herders in Dangxiong County, Tibet, and belongs to the natural wild strain. The strain isolation and identification method has been disclosed in the patent application with the publication number CN116948884A. Milk is a belt-shaped dairy product made from yak milk unique to northern Tibet, and has been listed in the autonomous region-level intangible cultural heritage list.

[0050] The thermophilic Streptococcus salivarius subsp. thermophilus is the thermophilic Streptococcus salivarius subsp. thermophilus Jiacha.ST-685 strain, which is screened from yogurt of herders in Jiacha County, Shannan City, Tibet, and is obtained by the following method:

[0051] 1) Take 25g of yogurt from herdsmen's home in Jiacha County, Shannan City, Tibet, and mix it with 225mL of sterile saline to obtain a uniform sample solution. The sample solution is diluted in a gradient manner and 10 -3 , 10 -4 , 10 -5 , 10 -6 The dilution of the concentration was spread on MRS medium plates for culture. After culture at 32°C for 48 hours, colonies grew on the MRS medium.

[0052] 2) Initial screening of bacterial strains

[0053] According to the standard colony characteristics of the thermophilic subspecies of Streptococcus salivarius, a single colony was picked for separation and purification in MRS medium and continued to be cultured at 37°C. The separation and purification were repeated for no less than three times to obtain purified colonies.

[0054] 3) Acid production experiment

[0055] The single colonies obtained from the initial screening of the strains were cultured on MRS medium plates containing 0.2% CaCO3. After culturing at 32°C for 48 hours, the formation of transparent circles around the colonies was observed, and single colonies with strong acid production ability and large transparent circles were selected for further separation and purification. In MRS agar medium, they usually grow into round or nearly round milky white or grayish white colonies with a smooth surface, small bacteria, and slightly irregular edges.

[0056] 4) Gram staining

[0057] The strain obtained by repeated screening was subjected to Gram staining. Gram staining was typical positive, and the strain obtained was the target strain. Under a microscope, the cells were spherical, with a diameter of about 0.5-1.0 μm, without flagella, without spores, and without movement.

[0058] 5) Identification of strains

[0059] The isolated and purified strain was Gram-positive, H2O2 catalase-negative, acid-producing, and non-gas-producing. The 16S rDNA gene sequence was sequenced and the results were compared with the NCBI GenBank database for homology analysis. The results showed that the strain was Streptococcus salivarius thermophilic subsp.

[0060] The DNA sequence of the 16s rRNA of the thermophilic Streptococcus Jiacha.ST-685 strain is shown in SEQ ID NO: 1:

[0061] TGGCTCCAAAAGGTTACCTCACCGACTTCGGGTGTTACAAACTCTCGT

[0062] GGTGTGACGGGCGGTGTGTACAAGGCCCGGGAACGTATTCACCGCGGC

[0063] GTGCTGATCCGCGATTACTAGCGATTCCGACTTCATGTAGGCGAGTTGC

[0064] AGCCTACAATCCGAACTGAGATTGGCTTTAAGAGATTAGCTCGCCGTCA

[0065] CCGACTCGCAACTCGTTGTACCAACCATTGTAGCACGTGTGTAGCCCAG

[0066] GTCATAAGGGGCATGATGATTTGACGTCATCCCCACCTTTCCTCCGGTTTA

[0067] TTACCGGCAGTCTCGCTAGAGTGCCCAACTGAATGATGGCAACTAACAA

[0068] TAGGGGTTGCGCTCGTTGCGGGACTTAACCCAACATCTCACGACACGA

[0069] GCTGACGACAACCATGCACCACCTGTCACCGATGTACCGAAGTAACTT

[0070] TCTATCTCTAGAAATAGCATCGGGATGTCAAGACCTGGTAAGGTTCTTC

[0071] GCGTTGCTTCGAATTAAACCACATGCTCCACCGCTTGTGCGGGCCCCCG

[0072] TCAATTCCTTTGAGTTTCAACCTTGCGGTCGTACTCCCCAGGCGGAGTG

[0073] CTTAATGCGTTAGCTTCGGCACTGAATCCCGGAAAGGATCCAACACCTA

[0074] GCACTCATCGTTTACGGCGTGGACTACCAGGGTATCTAATCCTGTTCGC

[0075] TCCCCACGCTTTCGAGCCTCAGCGTCAGTTACAGACCAGAGAGCCGCT

[0076] TTCGCCACCGGTGTTCCTCCATATATCTACGCATTTCACCGCTACACATG

[0077] GAATTCCACTCTCCCCTTCTGCACTCAAGTTTGACAGTTTCCAAAGCGA

[0078] ACTATGGTTGAGCCACAGCCTTTAACTTCAGACTTATCAAACCGCCTGC

[0079] GCTCGCTTTACGCCCAATAAATCCGGACAACGCTCGGGACCTACGTATT

[0080] ACCGCGGCTGCTGGCACGTAGTTAGCCGTCCCTTTCTGGTAAGCTACCG

[0081] TCACAGTGTGAACTTTCCACTCTCACACCCGTTCTTGACTTACAACAGA

[0082] GCTTTACGATCCGAAAACCTTCTTCACTCACGCGGCGTTGCTCGGTCAG

[0083] GGTTGCCCCCATTGCCGAAGATTCCCTACTGCTGCCTCCCGTAGGAGTC

[0084] TGGGCCGTGTCTCAGTCCCAGTGTGGCCGATCACCCTCTCAGGTCGGCT

[0085] ATGTATCGTCGCCTAGGTGAGCCATTACCTCACCTACTAGCTAATACAAC

[0086] GCAGGTCCATCTTGTAGTGGAGCAATTGCCCCTTTCAAATAAATGACAT

[0087] GTGTCATCCATTGTTATGCGGTATTAGCTATCGTTTCCAATAGTTATCCCC

[0088] CGCTACAAGGCAGGTTACCTACGCGTTACTCACCCGTTCGCAACTCATC

[0089] CAAGAAGAGCAAGCTCCTCTCTTCAGCGTTCTACTTGCATGTATTAGGC

[0090] ACGCCGCCAGCGTC

[0091] The strain was deposited in the China Center for Type Culture Collection (CCTCC) on August 17, 2023, with the deposit number CCTCC NO:M20231495. The deposit address is: Wuhan University, Wuhan, China, Postal Code: 430072; Telephone: (027)-68754052.

[0092] The above three strains are all isolated from plateau dairy products and are natural and safe. Lactobacillus plantarum Ali.Plateau.LP.Ⅷ has strong acid production ability and a broad antibacterial spectrum, and has strong antibacterial ability against Escherichia coli, Staphylococcus aureus, and mold. Lactobacillus Germanus lactis subspecies Dangxiong LBⅧ has strong DPPH free radical scavenging ability and hydroxyl free radical scavenging ability, and has high antioxidant activity. Streptococcus salivarius thermophilic subspecies Jiacha.ST-685 rapidly metabolizes lactic acid, formate, CO2, etc., which can promote the growth of lactobacillus. Lactobacillus plantarum, Lactobacillus Germanus lactis subspecies, and Streptococcus salivarius thermophilic subspecies are all recorded in the "List of Edible Strains".

[0093] The lactic acid bacteria product of the present invention scientifically combines lactobacillus and thermophilic subspecies of Streptococcus salivarius that have different degrees of promoting the antiseptic and fresh-keeping functions, and adds plant extracts with natural antibacterial effects, so as to further synergistically improve the antibacterial efficacy and enhance the fresh-keeping effect. At the same time, it can improve the nutritional value of the food and increase the probiotic function.

[0094] The lactic acid bacteria product of the present invention has a wide range of applications and is suitable for a variety of application scenarios such as fruit and vegetable preservation, baked pastries, fresh meat and pre-prepared dishes. When the lactic acid bacteria product is applied to the preservation of fruits and vegetables, it can not only effectively inhibit the corruption of fruits and vegetables and extend the shelf life, but also maintain the moisture content of fruits and vegetables during the storage period and enhance the antioxidant capacity of fruits and vegetables. When the lactic acid bacteria product is applied to the preservation of baked pastries, the mildew time can be significantly extended and the texture of bread during the storage period can be improved. When the lactic acid bacteria product is applied to the preservation of pre-prepared dishes, the generation of volatile basic nitrogen and the rancidity of fats can be better controlled, and the addition of the lactic acid bacteria product will not change the flavor of the food itself.

[0095] The Lactobacillus plantarum CICC 24194 mentioned in the embodiments of the present invention is a purchased standard strain that produces class IIa bacteriocins and can be used for antibacterial performance testing and fermentation agent development.

[0096] The Lactobacillus delbrueckii subspecies lactis CICC 25164 mentioned in the examples of the present invention is a purchased standard strain.

[0097] Unless otherwise specified, the various reagents and instruments used in the examples and comparative examples of the present invention are conventional commercially available products. The source information of the instruments and reagents used in the examples and comparative examples of the present invention is shown in Table 1 below.

[0098] Table 1

[0099]

[0100]

[0101]

[0102] Example 1 Lactobacillus plantarum strain characteristics

[0103] 1. Determination of acid production capacity

[0104] The glycerol tubes of plant lactobacillus Ali.Plateau.LP.Ⅷ strain and control strain plant lactobacillus CICC 24194 were taken out from a -80°C refrigerator, thawed at room temperature, and inoculated into test tubes containing 10 mL of MRS liquid culture medium at a ratio of 2% (v / v), and statically cultured in a 37°C incubator for 12 hours to activate the strains. The activated plant lactobacillus Ali.Plateau.LP.Ⅷ strain and plant lactobacillus CICC 24194 strain were inoculated into 10 ml of MRS liquid culture medium with a pH of 6.60 after sterilization at a 2% (v / v) inoculation amount, cultured under anaerobic conditions at 37°C for 24 hours, centrifuged at 10000 r / min for 10 minutes at 4°C after culture, and the pH of the fermentation supernatant was directly measured with a pH acidometer. At the same time, the titratable acidity was determined according to the national standard GB / T5413.34-2010, and the acidity of the lactic acid bacteria fermentation broth was expressed in degrees Gilner (°T), that is, 1 mL of the fermentation broth consumed for every 100 mL was a concentration of 0.1 mol·L –1 The NaOH solution is equivalent to 1° T. The results are shown in Table 2.

[0105] Table 2 Acid production capacity of Lactobacillus plantarum

[0106]

[0107] Lactic acid bacteria produce acid during their growth, causing the pH of the fermentation liquid to decrease and the acidity to increase. Compared with the control strain Lactobacillus plantarum CICC 24194, the fermentation supernatant pH of Lactobacillus plantarum Ali.Plateau.LP.Ⅷ strain was significantly lower and the acidity was higher, indicating that it has a stronger ability to produce acid.

[0108] 2. Determination of antibacterial ability

[0109] The antimicrobial activity of the strains was determined by double-layer agar diffusion method, and Escherichia coli, Staphylococcus aureus and fungi were used as indicator bacteria.

[0110] (1) Add 10 mL of 2 g / 100 mL water agar medium to a sterile plate. After the water agar solidifies, place it in a sterile Oxford cup to prepare a water agar plate.

[0111] (2) Add 1 ml of NB agar medium cooled to 50°C with a viable count of 10 6 -10 7 The indicator bacteria Escherichia coli and Staphylococcus aureus at 10 CFU / mL were fully mixed and poured into the prepared water agar plates respectively to obtain plates containing the indicator bacteria Escherichia coli and Staphylococcus aureus respectively.

[0112] (3) Add 1 ml of PDA agar medium cooled to 50°C with a viable count of 10 6 -10 7 CFU / mL of mold, mix thoroughly and pour into the prepared water agar plate to obtain a plate containing mold.

[0113] (4) After the plate culture medium containing indicator bacteria Escherichia coli, Staphylococcus aureus and mold solidified, the Oxford cup was taken out, and 100 μL of bacterial suspension of Lactobacillus plantarum Ali.Plateau.LP.Ⅷ and Lactobacillus plantarum CICC 24194 were added to the wells, respectively, and cultured at 37°C for 24 h. The diameter of the inhibition zone was observed and measured (mm). The results are shown in Table 3.

[0114] Table 3 Antibacterial ability of Lactobacillus plantarum

[0115]

[0116] In Table 3, the antibacterial effects of Lactobacillus plantarum Ali.Plateau.LP.Ⅷ on Escherichia coli, Staphylococcus aureus, and mold were better than those of the control strain Lactobacillus plantarum CICC 24194, showing its strong antibacterial ability.

[0117] Example 2 Characteristics of Lactobacillus germanica subsp. lactis

[0118] 1. DPPH free radical scavenging activity assay

[0119] The activated Lactobacillus delbrueckii subspecies Dangxiong LBⅧ and Lactobacillus delbrueckii subspecies CICC 25164 strains were inoculated at a 2% (v / v) inoculum into 10 ml MRS liquid medium with a pH of 6.60 after sterilization, and cultured at 37°C under anaerobic conditions for 24 h. After culture, the culture was centrifuged at 10000 r / min for 10 min at 4°C, and the bacterial sludge was collected and re-dissolved with sterile physiological saline to obtain a bacterial suspension. 2 ml (OD 600The value is 0.9-1) was mixed with 1mL 0.2mmol / L DPPH-anhydrous ethanol solution, reacted at 37℃ in the dark for 30min, centrifuged at 6000r / min for 10min after the reaction, and the supernatant was taken to measure the absorbance A1 at a wavelength of 517nm; the blank group used an equal volume of anhydrous ethanol to replace the DPPH-anhydrous ethanol solution, and the control group used an equal volume of distilled water to replace the sample solution. The equal volume of distilled water-anhydrous ethanol mixture was used for blank zero adjustment. DPPH free radical is a synthetic free radical, and its alcohol solution is purple. When antioxidants are present, DPPH free radicals are scavenged, the color of its solution becomes lighter, and the absorbance at 517nm decreases. The change in its absorbance is proportional to the degree of free radical scavenging.

[0120] The DPPH free radical scavenging rate was calculated according to formula (1), and the results are shown in Table 4:

[0121]

[0122] Where: A0 is the absorbance of the blank group; A1 is the absorbance of the sample group; A2 is the absorbance of the control group.

[0123] 2. Hydroxyl Radical Scavenging Activity Assay

[0124] 1 mL of each 5 mmol / L ferrous sulfate solution, 5 mmol / L salicylic acid ethanol solution, and 3 mmol / L hydrogen peroxide solution were added to a 10 mL stoppered test tube, and 2 mL of bacterial suspension (OD 2.0) of Lactobacillus delbrueckii subsp. Dangxiong LBⅧ and Lactobacillus delbrueckii subsp. CICC 25164 were inoculated into the stoppered test tubes. 600 The value is 0.9-1), and distilled water is added to the scale to 10ml, reacted in a 37℃ water bath for 15min, and then centrifuged at 6000r / min for 10min, the supernatant is taken, and the absorbance is measured at a wavelength of 510nm. The blank group is replaced by an equal volume of distilled water instead of the sample solution. The Fenton reaction is performed using ferrous sulfate solution and hydrogen peroxide solution to generate hydroxyl radicals: H2O2+Fe 2+ = OH + H2O + Fe 3+ , add salicylic acid to the reaction system, the hydroxyl radicals generated by the Fenton reaction react with salicylic acid to generate 2,3-dihydroxybenzoic acid with special absorption at 510nm. If a substance with the function of scavenging hydroxyl radicals is added to the reaction system, the generated hydroxyl radicals will be reduced, thereby reducing the amount of colored compounds generated. Hydroxyl radicals are usually present in organisms.

[0125] The hydroxyl radical scavenging rate was calculated according to formula (2), and the results are shown in Table 4:

[0126]

[0127] Where: A0 is the absorbance of the blank group; A1 is the absorbance of the sample group.

[0128] Table 4 Antioxidant activity of Lactobacillus germanica strains

[0129]

[0130] In Table 4, Lactobacillus germanica subspecies Dangxiong LBⅧ has strong DPPH free radical scavenging ability and hydroxyl free radical scavenging ability, and has high antioxidant activity.

[0131] Example 3 Effect of mixed culture of Lactobacillus and Streptococcus salivarius on growth

[0132] 1. Preparation of Cell-free Supernatant (CFS) of Lactobacillus plantarum, Lactobacillus germanium subsp. lactis and Streptococcus salivarius subsp. thermophilus

[0133] Lactobacillus plantarum Ali.Plateau.LP.Ⅷ, Lactobacillus germanium subsp. Dangxiong LBⅧ and Streptococcus salivarius thermophilic subsp. Jiacha.ST-685 activated for 2-3 generations were inoculated into MRS broth culture medium sterilized at high temperature, with an inoculum amount of 2% (v / v). The fermentation liquid after culturing for 12 hours was centrifuged at 10000 r / min and 4°C for 10 minutes, and the supernatant was collected and filtered through a 0.22 μm microporous filter membrane to obtain Lactobacillus plantarum Ali.Plateau.LP.Ⅷ cell-free supernatant (LP.ⅧCFS), Lactobacillus germanium subsp. Dangxiong LBⅧ cell-free supernatant (LBⅧCFS) and Streptococcus salivarius thermophilic subsp. Jiacha.ST-685 cell-free supernatant (ST685 CFS).

[0134] 2. Effect of mixed culture of Lactobacillus plantarum, Lactobacillus germanica subsp. lactis, and Streptococcus salivarius subsp. thermophilus on growth

[0135] Lactobacillus plantarum, Streptococcus salivarius thermophilus subsp. salivarius and their cell-free supernatants were inoculated into high-temperature sterilized MRS broth culture medium, including the following samples: (1) LP.Ⅷ: only inoculated with Lactobacillus plantarum Ali.Plateau.LP.Ⅷ; (2) ST685: only inoculated with Streptococcus salivarius thermophilus subsp. Jiacha.ST-685; (3) LP.Ⅷ+ST685 CFS: inoculated with Lactobacillus plantarum Ali.Plateau.LP.Ⅷ and Streptococcus salivarius thermophilus subsp. Jiacha.ST-685 cell-free supernatant; (4) LP.ⅧCFS+ST685: inoculated with Lactobacillus plantarum Ali.Plateau.LP.Ⅷ and Streptococcus salivarius thermophilus subsp. Jiacha.ST-685; (5) LPⅧ+ST685: inoculated with Lactobacillus plantarum Ali.Plateau.LP.Ⅷ and Streptococcus salivarius thermophilus subsp. Jiacha.ST-685. The total inoculation amount of each sample was 2% (v / v), in which the volume ratio of the two components in each sample was 1:1. Results are shown in Figure 1 In Figure A, it can be seen that the addition of thermophilic Streptococcus thermophilus subspecies Jiacha.ST-685 has a significant promoting effect on the growth of Lactobacillus plantarum Ali.Plateau.LP.Ⅷ, and the metabolites are closely related to the synergistic effect between the strains.

[0136] Lactobacillus germanium subsp. lactis, Streptococcus salivarius thermophilus subsp. and their cell-free supernatant were inoculated into high-temperature sterilized MRS broth medium, respectively, which included the following samples: (1) LBⅧ: only Lactobacillus germanium subsp. lactis Dangxiong LBⅧ was inoculated; (2) ST685: only Streptococcus salivarius thermophilus subsp. Jiacha.ST-685 was inoculated; (3) LBⅧ+ST685CFS: inoculated with Lactobacillus germanium subsp. lactis Dangxiong LBⅧ and cell-free supernatant of Streptococcus salivarius thermophilus subsp. Jiacha.ST-685; (4) LBⅧCFS+ST685: inoculated with Lactobacillus germanium subsp. lactis Dangxiong LBⅧ cell-free supernatant and Streptococcus salivarius thermophilus subsp. Jiacha.ST-685; (5) LBⅧ+ST685: inoculated with Lactobacillus germanium subsp. lactis Dangxiong LBⅧ and Streptococcus salivarius thermophilus subspecies Jiacha.ST-685. The total inoculation amount of each sample was 2% (v / v), wherein the ratio of the two components in each sample was 1:1. The results are shown in Figure 1 As can be seen from the figure, the addition of thermophilic Streptococcus thermophilus subsp. Jiacha.ST-685 has a significant promoting effect on the growth of Lactobacillus germanium subsp. Dangxiong LBⅧ, and the metabolites are closely related to the synergistic effect between the strains.

[0137] Lactobacillus (Lactobacillus plantarum and Lactobacillus germanica subspecies) has a strong ability to decompose protein and can produce a variety of amino acids, providing nutrients for Streptococcus thermophilus; at the same time, substances such as lactic acid, formate, and CO2 produced by the rapid metabolism of Streptococcus thermophilus can become growth stimulants for Lactobacillus, promoting the growth of Lactobacillus.

[0138] Example 4 Preparation of lactic acid bacteria products

[0139] 1. Fermentation: Take out the glycerol tubes of Lactobacillus plantarum, Lactobacillus germanium subsp. lactis and Streptococcus salivarius thermophilus subsp. from a -80°C refrigerator, melt at room temperature, and inoculate them into test tubes containing 10 mL of MRS liquid culture medium at a ratio of 2% (v / v), and culture them statically in a 37°C incubator for 12 hours for strain activation. The activated Lactobacillus plantarum Ali.Plateau.LP.Ⅷ, Lactobacillus germanium subsp. lactis Dangxiong LBⅧ and Streptococcus salivarius thermophilus subsp. Jiacha.ST-685 are inoculated into sterilized MRS culture medium at a ratio of 2% (v / v), wherein the ratio of viable bacteria of each bacterium is 2:2:1, i.e., the viable bacteria count of Lactobacillus plantarum Ali.Plateau.LP.Ⅷ is 1×10 6 CFU / g, the viable count of Lactobacillus Germanii subspecies Dangxiong LBⅧ is 1×10 6 CFU / g, the number of viable bacteria of Streptococcus salivarius thermophilic subspecies Jiacha.ST-685 was 5×10 5 CFU / g, and fermented in a 37°C incubator for 24 h to obtain the fermentation broth.

[0140] 2. Post-treatment: centrifuge the fermentation liquid at 6000r / min for 10min to obtain a supernatant; perform rotary evaporation on the supernatant at 50°C, and concentrate it to 1 / 2 of the original volume to obtain a concentrated solution; add 0.1% of the Zanthoxylum bungeanum extract to the concentrated solution at a mass percentage, mix well, and sterilize and inactivate at 80°C for 30min to obtain an inactivated solution; spray dry the sterilized and inactivated fermentation liquid at a drying temperature of 150°C to obtain a lactic acid bacteria product.

[0141] Example 5 Preparation of lactic acid bacteria products

[0142] 1. Fermentation: Take out the glycerol tubes of Lactobacillus plantarum, Lactobacillus delbrueckii subsp. lactis and Streptococcus salivarius thermophilus from a -80°C refrigerator and immediately put them into a 37°C water bath until the liquid in the glycerol tube is completely melted. Then, inoculate them into a test tube containing 10 mL of MRS liquid culture medium at a ratio of 1% (v / v) and culture them statically in a 37°C incubator for 12 hours to activate the strains. The activated Lactobacillus plantarum Ali.Plateau.LP.Ⅷ, Lactobacillus delbrueckii subsp. lactis Dangxiong LBⅧ and Streptococcus salivarius thermophilus Jiacha.ST-685 are inoculated into sterilized MRS culture medium at 1% (v / v) respectively, wherein the ratio of the live bacteria of each strain is 1:1:1, that is, the number of live bacteria of Lactobacillus plantarum Ali.Plateau.LP.Ⅷ is 1×10 6 CFU / g, the viable count of Lactobacillus delbrueckii subspecies Dangxiong LBⅧ is 1×10 6 CFU / g, the viable count of Streptococcus salivarius thermophilic subspecies Jiacha.ST-685 was 1×10 6 CFU / g, and fermented in a 30°C incubator for 48 h to obtain the fermentation broth.

[0143] 2. Post-treatment: centrifuge the fermentation liquid at 6000r / min for 10min to obtain a supernatant; perform rotary evaporation on the supernatant at 60°C, and concentrate it to 1 / 10 of the original volume to obtain a concentrated solution; add 0.5% of Ophiopogon japonicus extract to the concentrated solution at a mass percentage, mix well, and sterilize and inactivate at 100°C for 20min to obtain an inactivated solution; spray dry the sterilized and inactivated fermentation liquid at a drying temperature of 130°C to obtain a lactic acid bacteria product.

[0144] Example 6 Preparation of lactic acid bacteria products

[0145] 1. Fermentation: Take out the glycerol tubes of Lactobacillus plantarum, Lactobacillus germanium subsp. lactis and Streptococcus salivarius thermophilus from a -80°C refrigerator and immediately put them into a 37°C water bath until the liquid in the glycerol tube is completely melted, then inoculate them into a test tube containing 10 mL of MRS liquid culture medium at a ratio of 5% (v / v), and culture them statically in a 42°C incubator for 24 hours to activate the strains. The activated Lactobacillus plantarum Ali.Plateau.LP.Ⅷ, Lactobacillus germanium subsp. lactis Dangxiong LBⅧ and Streptococcus salivarius thermophilus Jiacha.ST-685 are inoculated into sterilized MRS culture medium at 5% (v / v), wherein the ratio of viable bacteria of each strain is 2:1:2, i.e., the viable bacteria count of Lactobacillus plantarum Ali.Plateau.LP.Ⅷ is 1×10 6 CFU / g, the viable count of Lactobacillus Germanii subspecies Dangxiong LBⅧ was 5×10 5CFU / g, the viable count of Streptococcus salivarius thermophilic subspecies Jiacha.ST-685 was 1×10 6 CFU / g, and fermented in a 37°C incubator for 24 h to obtain the fermentation broth.

[0146] 2. Post-treatment: centrifuge the fermentation liquid at 6000r / min for 10min to obtain a supernatant; perform rotary evaporation on the supernatant at 50°C, and concentrate it to 1 / 10 of the original volume to obtain a concentrated solution; add 0.1% of the motherwort extract to the concentrated solution at a mass percentage, mix well, and sterilize and inactivate at 80°C for 30min to obtain an inactivated solution; spray dry the sterilized and inactivated fermentation liquid at a drying temperature of 130°C to obtain a lactic acid bacteria product.

[0147] Example 7 Preparation of lactic acid bacteria products

[0148] 1. Fermentation: Take out the glycerol tubes of Lactobacillus plantarum, Lactobacillus germanium subsp. lactis and Streptococcus salivarius thermophilus from a -80°C refrigerator and immediately put them into a 37°C water bath. After the liquid in the glycerol tube is completely melted, they are inoculated into a test tube containing 10 mL of MRS liquid culture medium at a ratio of 2% (v / v), and statically cultured in a 37°C incubator for 12 hours for strain activation. The activated Lactobacillus plantarum Ali.Plateau.LP.Ⅷ, Lactobacillus germanium subsp. lactis Dangxiong LBⅧ and Streptococcus salivarius thermophilus Jiacha.ST-685 are inoculated into sterilized MRS culture medium at 2% (v / v) respectively, wherein the ratio of viable bacteria of each strain is 1:1:2, i.e., the viable bacteria count of Lactobacillus plantarum Ali.Plateau.LP.Ⅷ is 5×10 5 CFU / g, the viable count of Lactobacillus Germanii subspecies Dangxiong LBⅧ was 5×10 5 CFU / g, the viable count of Streptococcus salivarius thermophilic subspecies Jiacha.ST-685 was 1×10 6 CFU / g, and fermented in a 37°C incubator for 24 h to obtain the fermentation broth.

[0149] 2. Post-treatment: centrifuge the fermentation liquid at 8000r / min for 10min to obtain a supernatant; perform rotary evaporation on the supernatant at 60°C and concentrate it to 1 / 10 of the original volume to obtain a concentrated solution; add 0.5% of Forsythia suspensa extract to the concentrated solution at a mass percentage, mix well, sterilize and inactivate at 100°C for 20min to obtain an inactivated solution; spray dry the sterilized and inactivated fermentation liquid at a drying temperature of 130°C to obtain a lactic acid bacteria product.

[0150] Comparative Example 1

[0151] Compared with Example 1, no Zanthoxylum bungeanum extract was added, and the rest was the same as Example 1.

[0152] Comparative Example 2

[0153] Compared with Example 1, Lactobacillus plantarum Ali.Plateau.LP.Ⅷ, Lactobacillus germanium subsp. lactis DangxiongLBⅧ and Streptococcus salivarius thermophilus subsp. Jiacha.ST-685 were inoculated in a sterilized MRS medium at a ratio of 6:1:2, that is, the number of live bacteria of Lactobacillus plantarum Ali.Plateau.LP.Ⅷ was 6×10 6 CFU / g, the viable count of Lactobacillus Germanii subspecies Dangxiong LBⅧ was 5×10 5 CFU / g, the viable count of Streptococcus salivarius thermophilic subspecies Jiacha.ST-685 was 1×10 6 CFU / g, and the rest are the same as in Example 1.

[0154] Experimental Example 1

[0155] 1. Determination of antibacterial ability and pH value of different lactic acid bacteria products

[0156] The antibacterial activities of the different lactic acid bacteria products prepared in Examples 4-7 and Comparative Examples 1-2 were determined by the double-layer agar diffusion method, and Escherichia coli, Staphylococcus aureus and mold were used as indicator bacteria.

[0157] (1) Add 10 mL of 2 g / 100 mL water agar medium to a sterile plate. After the water agar solidifies, place it in a sterile Oxford cup to prepare a water agar plate.

[0158] (2) Add 1 ml of NB agar medium cooled to 50°C with a viable count of 10 6 -10 7 The indicator bacteria Escherichia coli and Staphylococcus aureus at 10 CFU / mL were fully mixed and poured into the prepared water agar plates respectively to obtain plates containing the indicator bacteria Escherichia coli and Staphylococcus aureus respectively.

[0159] (3) Add 1 ml of PDA agar medium cooled to 50°C with a viable count of 10 6 -10 7 CFU / mL of mold, mix thoroughly and pour into the prepared water agar plate to obtain a plate containing mold.

[0160] (4) After the plate culture medium containing indicator bacteria Escherichia coli, Staphylococcus aureus and mold solidified, the Oxford cup was taken out, and 100 μL of different lactic acid bacteria products prepared in Examples 4-7 and Comparative Examples 1-2 were added to the wells (the lactic acid bacteria products were rehydrated to a liquid with a dry matter content of 5%), and cultured at 37° C. for 24 h. The diameter of the inhibition zone (mm) was observed and measured. The results are shown in Table 5.

[0161] The pH values ​​of the different lactic acid bacteria products prepared in Examples 4-7 and Comparative Examples 1-2 were measured using a pH meter. The results are shown in Table 5.

[0162] As shown in Table 5, the combined results of pH and inhibition zone measurements indicate that the lactic acid bacteria product obtained in Example 4 is the most preferred lactic acid bacteria product of the present invention. The compounding of lactic acid bacteria and Streptococcus salivarius thermophilus subsp. in a specific ratio and the addition of 0.1% Zanthoxylum bungeanum extract can significantly improve the antibacterial ability of the lactic acid bacteria product and enhance the preservation effect.

[0163] Table 5 pH and antibacterial ability results of different lactic acid bacteria products

[0164]

[0165] 2. Determination of the content of total reducing sugar, organic acid, protein and dietary fiber in the lactic acid bacteria prepared in Example 4

[0166] Total reducing sugar was determined according to the first method of GB5009.7-2016 “National Food Safety Standard for Determination of Reducing Sugars in Foods”; organic acid content was determined according to GB 5009.157-2016 “National Food Safety Standard for Determination of Organic Acids in Foods”; protein content was determined according to GB 5009.5-2016 “National Food Safety Standard for Determination of Protein in Foods”; dietary fiber was determined according to GB 5009.88-2014 “National Food Safety Standard for Determination of Dietary Fiber in Foods”. The determination results are shown in Table 6.

[0167] Table 6 Nutritional composition of lactic acid bacteria products

[0168]

[0169] In Table 6, the lactic acid bacteria product in Example 4 has the characteristics of low sugar, rich organic acid, protein, and dietary fiber. Applying it to food can improve the nutritional value of food and increase the probiotic function. Therefore, the lactic acid bacteria products used in the following application examples are all obtained by the composition ratio and preparation method of Example 4.

[0170] Application Example 1: Lactic acid bacteria products are used in fruit and vegetable preservation

[0171] Apples were cut into pieces (3 cm × 3 cm × 3 cm) and lettuce slices (5 cm × 5 cm) were soaked in 5% by mass of the lactic acid bacteria product prepared in Example 4 for 10 minutes, and fruits and vegetables that were not treated were used as blank controls (CK). After treatment, they were air-dried, sealed and stored at room temperature, and the indicators were measured every 5 days. The results are shown in Table 7 below.

[0172] The total colony count is determined according to the method in GB 4789.2-2016 "National Food Safety Standard - Determination of Total Colony Count for Food Microbiological Examination" and the unit is lg (CFU / mL).

[0173] The weight loss rate calculation formula is as follows:

[0174]

[0175] Where: L is the weight loss rate, %; W1 is the mass of the sample before storage, g; W2 is the mass of the sample after storage, g.

[0176] The processed fruits, vegetables and lettuce were chopped and added to pre-cooled 1% HCl-methanol solution, and then fully homogenized in a tissue homogenizer. The supernatant was extracted by centrifugation and directly colorimetric at a wavelength of 280nm. The total phenol content was expressed as the absorbance per gram of fresh weight of fruit and vegetable tissue at a wavelength of 280nm, that is, OD 280 / g. The initial total phenolic contents of apple and lettuce were 1.11 and 0.30OD, respectively. 280 / g.

[0177] Table 7 Fruit and vegetable storage period test

[0178]

[0179] After being treated with lactic acid bacteria products, the total colony count and weight loss rate of apples and lettuce decreased significantly, and the total phenol content increased slightly. This shows that the addition of lactic acid bacteria products can not only effectively inhibit the corruption of fruits and vegetables and extend the shelf life; it can also maintain the moisture content of fruits and vegetables during the storage period and enhance the antioxidant capacity of fruits and vegetables.

[0180] Application Example 2: Lactic acid bacteria products are used to preserve baked pastries

[0181] The prepared bread slices were randomly divided into packages, and 5% by mass of the lactic acid bacteria product prepared in Example 4 was sprayed on the surface. The bread without any treatment was used as a blank negative control (CK), and 1g / kg of sorbic acid was added as a positive control. The bread was sealed and stored under constant temperature and humidity conditions (temperature 35°C, humidity 85%), and the mold growth time was observed. On the third day of storage, the hardness, elasticity and viscosity of the bread were tested using a TA.XTC-18 texture analyzer and a TA / 36R column probe. The results are shown in Table 8.

[0182] Table 8 Bread storage period test

[0183]

[0184] After adding lactic acid bacteria products, the mold time is significantly prolonged. Figure 2 At the same time, the bread has a lower hardness, higher elasticity and stickiness, which improves the problem of deterioration of texture characteristics due to starch aging during storage.

[0185] Application Example 3: Lactic acid bacteria products are used to preserve pre-prepared dishes

[0186] Fresh pork was cleaned of blood stains, sliced, and washed with distilled water. 5% by weight of the lactic acid bacteria product prepared in Example 4 was added to the pork slices, mixed evenly, and seasonings were added and stir-fried until fragrant. The pork was vacuum packed and pasteurized. A blank control experiment was performed at the same time. The total colony count, volatile basic nitrogen and acid value were measured at 7d, 14d, and 28d, respectively. The results are shown in Table 9.

[0187] The total colony count is determined according to the method in GB 4789.2-2016 "National Food Safety Standard - Determination of Total Colony Count for Food Microbiological Examination" and the unit is lg (CFU / mL).

[0188] The volatile basic nitrogen is determined by referring to the semi-micro nitrogen determination method in the National Food Safety Standard - Determination of Volatile Basic Nitrogen in Foods (GB5009.228-2016).

[0189] The acid value was determined with reference to the "Analytical Methods for Hygienic Standards of Meat and Meat Products" (GB / T5009.044-2003).

[0190] After the samples were taken out and placed at room temperature, 10 sensory evaluation personnel immediately evaluated the color, smell, taste and muscle elasticity of the meat slices, respectively, with scores between 1 and 5. The scoring details are shown in Table 10. The comprehensive score of the meat slices is 17 to 20 points for freshness, 9 to 16 points for good quality, and 8 points or less for obvious deterioration of quality. The results are shown in Table 11.

[0191] Table 9 Meat slice storage period test

[0192]

[0193] Table 10 Sensory evaluation details

[0194]

[0195] Table 11 Sensory evaluation results

[0196]

[0197]

[0198] After adding lactic acid bacteria products, the total colony count of meat slices during storage is significantly reduced, the production of volatile basic nitrogen can be better controlled, and the first-level freshness can still be maintained when stored for 28 days. The fat rancidity is rare, and the addition of lactic acid bacteria products does not affect the color, aroma and taste of the food itself.

[0199] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A lactic acid bacteria product, characterized in that: The lactic acid bacteria product comprises fermentation metabolites obtained by co-fermentation of Lactobacillus plantarum, Lactobacillus germanium subspecies lactis and Streptococcus salivarius thermophilus subspecies and plant extracts.

2. The lactic acid bacteria product according to claim 1, characterized in that The plant lactobacillus is a plant lactobacillus Ali.Plateau.LP.Ⅷ strain, which is deposited in China Center for Type Culture Collection (CCTCC) with a deposit number of CCTCC NO:M2022068. The Lactobacillus delbrueckii subsp. lactis is the Dangxiong LBⅧ strain of Lactobacillus delbrueckii subsp. lactis, which is deposited in the China Center for Type Culture Collection (CCTCC) with a deposit number of CCTCC NO: M 2023396. The thermophilic Streptococcus salivarius subsp. thermophilus is the thermophilic Streptococcus salivarius subsp. thermophilus Jiacha.ST-685 strain, which is deposited in the China Center for Type Culture Collection (CCTCC) with a deposit number of CCTCC NO:M 20231495.

3. The lactic acid bacteria product according to claim 1 or 2, characterized in that The plant extract is selected from one or more of Zanthoxylum bungeanum extract, Ophiopogon japonicus extract, Leonurus japonicus extract, Forsythia suspensa extract, Star anise extract and Fennel extract.

4. A method for preparing a lactic acid bacteria product according to any one of claims 1 to 3, characterized in that: The method comprises: (1) inoculating Lactobacillus plantarum Ali. Plateau. LP. VIII, Lactobacillus delbrueckii subspecies Dangxiong LB VIII and Streptococcus salivarius thermophilic subspecies Jiacha. ST-685 into a fermentation medium for fermentation; (2) centrifuging the fermentation liquid obtained in step (1), taking the supernatant, and rotary evaporating the supernatant to obtain a concentrated solution; (3) The concentrated solution obtained in step (2) and the plant extract are compounded and then inactivated.

5. The method for preparing a lactic acid bacteria product according to claim 4, characterized in that: In step (1), the viable count of Lactobacillus plantarum Ali.Plateau.LP.Ⅷ is 5×10 5 -1×10 6 CFU / g; and / or, the viable count of Lactobacillus delbrueckii subspecies Dangxiong LBⅧ is 5×10 5 -1×10 6 CFU / g; and / or, the viable count of Streptococcus salivarius thermophilus subspecies Jiacha.ST-685 is 5×10 5 -1×10 6 CFU / g.

6. The method for preparing a lactic acid bacteria product according to claim 4 or 5, characterized in that: In step (1), Lactobacillus plantarum Ali. Plateau. LP. VIII, Lactobacillus delbrueckii subsp. lactis Dangxiong LB VIII and Streptococcus salivarius subsp. thermophilus Jiacha. ST-685 are inoculated into the fermentation medium at a volume percentage of 1-5%.

7. The method for preparing a lactic acid bacteria product according to any one of claims 4 to 6, characterized in that: In step (1), the fermentation temperature is 30-42°C; Preferably, the fermentation time is 24-48h; Further preferably, the fermentation medium is selected from MRS medium.

8. The method for preparing a lactic acid bacteria product according to any one of claims 4 to 7, characterized in that: In step (2), the centrifugal speed is 6000-8000 r / min; and / or, the centrifugation time is 10-15 min; Preferably, the rotary evaporation temperature is 50-60°C; Further preferably, the rotary evaporation concentration is 1 / 2-1 / 10 of the original volume.

9. The method for preparing a lactic acid bacteria product according to any one of claims 4 to 8, characterized in that: In step (3), the plant extract is added to the concentrate at a mass percentage of 0.1-0.5%; Preferably, the inactivation temperature is 80-100°C; More preferably, the inactivation time is 20-30 min.

10. The method for preparing a lactic acid bacteria product according to any one of claims 4 to 9, characterized in that: The step (3) further includes a drying step; Preferably, drying is selected from spray drying; More preferably, the drying temperature is 130-190°C.

11. A lactic acid bacteria product prepared by the preparation method according to any one of claims 4 to 10.

12. Use of the lactic acid bacteria product according to any one of claims 1 to 3 or claim 11 in food preservation.

13. The use according to claim 12, characterized in that: The food is selected from vegetables, fruits, baked pastries, fresh meat or pre-prepared dishes.

14. The use according to claim 12 or 13, characterized in that: Lactic acid bacteria products are added to food by soaking, spraying or as additives.

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