Lactobacillus plantarum and its application in improving stretchability of acid coagulated cheese

Abstract

The application discloses a plant lactobacillus and application thereof in improving stretchability of acid coagulated cheese. Lactiplantibacillus plantarum The plant lactobacillus is named as plant lactobacillus (Lactobacillus plantarum) B11, is preserved in China Center for Type Culture Collection, has a preservation number of CCTCC NO: M 2025778 and a preservation address of Wuhan University, No. 299, Bayi Road, Wuchang District, Wuhan City, Hubei Province. The strain provided by the application can be directionally fermented to produce viscous exocellular polysaccharide and antibacterial substances. The acid whey fermented by the strain is combined with phosphate and sodium caseinate quality improver, so that the stretchability of the acid coagulated cheese is improved, the product is inhibited from being mildewed in the airing and storage processes, and meanwhile, the product quality safety can be ensured. The problems of stretching difficulty, low product yield and easy mildewing in the airing and storage processes in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of microbial technology, and in particular to a plant lactobacillus and its application in improving the stretchability of sour curd cheese. Background Technology

[0002] As the only acid-coagulated stretch cheese in China, Rushan cheese is made by using acidic whey to cause casein to coagulate near its isoelectric point, followed by heat stretching to form a fibrous structure. It is then shaped on racks, dried, and finally yields the acid-coagulated stretch cheese product. However, during the acid coagulation process, the weak ionic bonds between casein micelles result in poor plasticity and stretchability of the coagulated material, making it prone to breakage during stretching, thus affecting product yield and quality stability. To address this issue, existing technologies have proposed improvements, such as patent CN201910710580.6, which proposes using disodium ethylenediaminetetraacetate (EDTA-2Na) as a modifier to enhance the stretchability of acid-coagulated stretch cheese. However, GB2760-2024 stipulates that EDTA-2Na cannot be used in dairy products.

[0003] Furthermore, the coagulant used in the processing of acid-coagulated stretch cheese is typically traditional naturally fermented whey, whose microbial composition is complex and difficult to control. This makes acid-coagulated stretch cheese prone to mold growth during drying and storage, severely affecting product quality and shelf life. This problem not only limits the large-scale production of acid-coagulated stretch cheese but also negatively impacts its market promotion and consumer experience.

[0004] In summary, the existing production process for acid-coagulated stretch cheese still has the following problems:

[0005] Insufficient stretchability: The ionic bonds between casein micelles are weak, resulting in poor aggregate plasticity, easy breakage during stretching, and affecting yield and quality.

[0006] Microbial control is difficult: Traditional acid coagulants have a complex microbial composition, which can easily lead to mold growth during drying and storage, reducing product quality.

[0007] Therefore, there is an urgent need to develop a new method that can both improve the stretchability of acid-coagulated cheese and reduce its mold rate during drying and storage, so as to promote the sustainable development of the acid-coagulated cheese industry.

[0008] Chinese patent application CN113755398A discloses a fermentation strain of milk fan (a type of cheese) with aroma-enhancing properties, a milk fan starter culture, and its applications. The fermentation strains provided in this invention are *Lactobacillus plantarum* ML9 and *Rhodotorula glutinis* 2-3. A milk fan starter culture is obtained by adding *Lactobacillus plantarum* ML9 and *Rhodotorula glutinis* 2-3 to traditional acidic water for fermentation. By comparing the milk fan starter culture of this invention with that fermented milk fan from traditional acidic water, the milk fan starter culture with its blended strains achieves complementary aroma-producing advantages and flavor optimization. However, the effects of this fermentation strain on the stretching properties and antibacterial activity of milk fan have not been studied. Summary of the Invention

[0009] Therefore, the purpose of this invention is to provide a strain of *Lactobacillus plantarum* and its application in improving the stretchability of sour curd cheese. The strain provided by this invention can perform directed fermentation, producing high yields of viscous extracellular polysaccharides and antibacterial substances. The fermented whey from this strain, combined with phosphate and sodium caseinate quality improvers, enhances the stretchability of sour curd cheese while inhibiting mold growth during drying and storage, and ensuring product quality and safety. This solves the problems of difficult stretching, low yield, and easy mold growth during drying and storage in the production of sour curd cheese in the prior art.

[0010] To achieve the above-mentioned objectives, the present invention provides the following technical solution: a plant lactobacillus ( Lactiplantibacillus plantarum The plant lactobacillus described is named plant lactobacillus B11 and is deposited at the China Center for Type Culture Collection (CCTCC) with accession number CCTCC NO: M 2025778. The deposit address is Wuhan University, No. 299 Bayi Road, Wuchang District, Wuhan City, Hubei Province.

[0011] The present invention also provides a microbial inoculant of the aforementioned *Lactobacillus plantarum*.

[0012] The present invention also provides the application of the aforementioned *Lactobacillus plantarum* or the aforementioned microbial agent in the preparation of antibacterial products, wherein the antibacterial use is for non-therapeutic purposes, and the antibacterial effect refers to the inhibitory effect on *Escherichia coli*, *Staphylococcus aureus*, *Candida tropicalis*, or *Penicillium loudi*.

[0013] The present invention also provides the application of the *Lactobacillus plantarum* or the microbial agent in the preparation of extracellular polysaccharides, wherein the extracellular polysaccharide is a heteropolysaccharide composed of galactose, glucose and galacturonic acid; and the molar ratio of galactose, glucose and galacturonic acid is 1.8-2.2:0.8-1.2:0.25-0.4.

[0014] The present invention also provides the application of the plant lactobacillus or the microbial agent in fermented whey.

[0015] The present invention also provides the application of the plant lactobacillus or the microbial agent in improving the stretchability of acid-cured cheese.

[0016] As a further description of the above solution: the specific steps to improve the stretchability of acid-cured cheese are as follows:

[0017] Lactobacillus plantarum B11 was inoculated into sterilized whey to obtain acidic whey with a pH value ≤ 3.4.

[0018] Phosphate and sodium caseinate are added to the yogurt and heated. Then milk is added to perform acid coagulation and hot stretching in sequence to obtain curd sheets. The curd sheets are dried and shaped to obtain acid-coagulated stretched cheese.

[0019] As a preferred method, the experimental conditions for fermenting whey are as follows: fermentation at 36.5-37.5℃ for 45-70 h; the inoculum size of *Lactobacillus plantarum* in the whey is 0.8 × 10⁻⁶. 8 CFU / mL - 2.0 × 10 8 CFU / mL.

[0020] The optimal addition amounts of the compound phosphate and sodium caseinate are 0.03-0.05% and 0.05-0.07% of the milk, respectively; the mass ratio of whey to milk is 1:8-12; and the pH value of the mixture after adding milk is 4.7-4.9.

[0021] The composite phosphate is a mixture of disodium hydrogen phosphate and sodium tripolyphosphate; the mass ratio of sodium tripolyphosphate to disodium hydrogen phosphate is 5~6:5~4.

[0022] Preferably, the heating temperature is 85℃-95℃; the acid coagulation and hot stretching temperatures are 68-72℃; the thickness of the curd sheet is 0.1-0.15cm, the width is 14-16cm, and the length is 83-86cm. The yield of the curd sheet product is 11.4%.

[0023] The features of this invention are as follows: This invention screened a strain of *Lactobacillus plantarum* from soil samples in Dengchuan Town, Eryuan County, Dali City. This *Lactobacillus plantarum* B11 exhibits strong antibacterial activity, showing significant antibacterial effects against *Escherichia coli*, *Staphylococcus aureus*, *Candida tropicalis*, and *Penicillium loudi*. *Lactobacillus plantarum* B11 can synthesize viscous extracellular polysaccharides in MRS liquid medium and fermented whey, with a yield exceeding 311 mg / L. This strain can be applied to fermented whey, which can be used to process acid-coagulated stretch cheese. The antibacterial substances, such as organic acids, produced by *Lactobacillus plantarum* B11 during whey fermentation inhibit mold and yeast contamination during the drying process of acid-coagulated stretch cheese, improving product quality. Simultaneously, the viscous extracellular polysaccharides produced by *Lactobacillus plantarum* B11 during whey fermentation form complexes with casein in milk, enhancing the plasticity of the coagulant, promoting the stretching and shaping of the coagulant, and increasing product yield. In addition, this invention uses phosphate and sodium caseinate in addition to the acidic whey produced by fermentation of strain B11, which can significantly enhance the emulsification effect, improve the plasticity and stretchability of the coagulated cheese, and promote the stretching and shaping of acid-coated cheese.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) In this invention, a lactic acid bacterium that produces antibacterial organic acids and sticky extracellular polysaccharides was screened from soil samples in Dengchuan Town, Eryuan County, Dali. Through morphological and molecular biological identification, the strain was identified as *Lactobacillus plantarum* and named *Lactobacillus plantarum* B11.

[0026] (2) The *Lactobacillus plantarum* B11 fermented whey provided by this invention produces high levels of antibacterial organic acids and viscous extracellular polysaccharides. Using this fermented whey to process acid-coagulated stretch cheese can improve product yield and quality stability. This invention utilizes the antibacterial organic acids produced by *Lactobacillus plantarum* B11 fermented whey to inhibit mold and yeast contamination during the drying process of acid-coagulated stretch cheese, thus improving product quality. Simultaneously, it utilizes the viscous extracellular polysaccharides produced by *Lactobacillus plantarum* B11 fermented whey to form complexes with casein in milk, enhancing the plasticity of the coagulant, promoting the stretching and shaping of the coagulant, and increasing product yield.

[0027] (3) The present invention utilizes the phosphate ions in phosphate to chelate calcium ions in milk, neutralize the electrostatic repulsion between casein micelles, thereby promoting milk gelation; at the same time, sodium caseinate is added as an emulsifier. The synergistic use of phosphate and sodium caseinate can significantly enhance the emulsification effect, emulsify the fat in milk into smaller fat particles, thereby filling the three-dimensional network structure of casein, improving the plasticity and stretchability of the coagulated mass, and promoting the stretching and shaping of acid-coagulated cheese.

[0028] The preservation information of the microorganism is as follows:

[0029] Classification and nomenclature: Lactobacillus plantarum ( Lactiplantibacillus plantarum B11;

[0030] Accession number: CCTCC NO: M 2025778;

[0031] Depository: China Center for Type Culture Collection;

[0032] Preservation period: April 14, 2025;

[0033] Address: Wuhan University, No. 299 Bayi Road, Wuchang District, Wuhan City, Hubei Province. Attached Figure Description

[0034] Figure 1 The colony morphology and Gram staining results of Lactobacillus plantarum B11 on MRS medium;

[0035] Figure 2 shows the antibacterial activity of *Lactobacillus plantarum* B11 and *Lactobacillus plantarum* B1 against *Escherichia coli*, *Staphylococcus aureus* and *Candida tropicalis*, where B11 represents *Lactobacillus plantarum* B11 and B1 represents *Lactobacillus plantarum* B1.

[0036] Figure 3 The inhibitory activity of *Lactobacillus plantarum* B11 and *Lactobacillus plantarum* B1 against *Penicillium loudi* was investigated.

[0037] Figure 4 The microstructure of the clumps obtained from traditional acid whey and whey fermented with added Lactobacillus plantarum B11 was determined. Detailed Implementation

[0038] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described in detail below with reference to specific embodiments. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0039] Example 1 Isolation and purification of bacterial strains

[0040] 10g of soil sample collected from Dengchuan Town, Eryuan County, Dali City was added to 90mL of MRS liquid medium and enriched at 37℃ for 48h. 1mL of the culture solution was then added to 9mL of physiological saline, shaken thoroughly for 30s, and serially diluted, with the highest dilution being 10⁻⁸. 8Spread 200 μL of the diluted solution onto MRS solid medium and incubate at 37°C for 48 h. Based on colony morphology, size, size and color of the calcium dissolution zone, and growth location in the medium (surface, interior, and bottom), colonies with different appearance characteristics and larger calcium dissolution zones are selected and streaked onto plates for purification. This process is repeated several times to ensure that the final plates contain colonies of the same morphology. Single colonies are then inoculated into MRS liquid medium and incubated at 37°C for 24 h for preservation and identification.

[0041] Morphological characteristics of fungal strains

[0042] like Figure 1 As shown in the left image, after culturing *Lactobacillus plantarum* B11 on MRS agar medium for 24 hours, the colonies were milky white, translucent, relatively moist, smooth, with neat edges and obvious protrusions; Figure 1 As shown in the right figure, the microscopic examination results of *Lactobacillus plantarum* B11 are as follows: it does not produce spores, its cell morphology is scattered rod-shaped, and it is a Gram-positive bacterium that stains purple.

[0043] Molecular biological identification of bacterial strains

[0044] 16S rDNA gene sequencing

[0045] Bacterial genomes were extracted using the TSINGKE Plant DNA Extraction Kit (Universal). Using the extracted genome as a template, PCR experiments were performed on 16S rDNA using universal bacterial primers: 27F (SEQ ID NO: 1 5 '-AGTTTGATCMTGGCTCAG -3 ') and 1492R (SEQ ID NO: 2 5 '-GGTTACCTTGTTACGACTT-3 '). The PCR products were sent to Beijing Qingke Biotechnology Co., Ltd. for sequencing. The sequencing results were compared with existing sequences in the GenBank database using BLAST in the NCBI database (www.ncbi.nlm.gov / blast) to analyze the homology between the tested strain and known strains, thus identifying the species of the selected sugar-producing strain. The 16S rDNA sequence of this strain, as shown in SEQ ID NO: 3, showed over 99% homology with the 16S rDNA sequence of *Lactobacillus plantarum*, confirming that the selected lactic acid bacterium is *Lactobacillus plantarum*. Finally, the selected strain was identified as *Lactobacillus plantarum* through morphological analysis and 16S rDNA sequencing, and named *Lactobacillus plantarum* B11. It is deposited at the China Center for Type Culture Collection (CCTCC) with accession number M 2025778.

[0046] Example 2: Antibacterial activity of Lactobacillus plantarum B11

[0047] The following examples show that *Lactobacillus plantarum* B1 was also obtained from soil samples in Dengchuan Town and identified as *Lactobacillus plantarum* by 16S rDNA sequencing.

[0048] The antibacterial activity of the strains was determined using the Oxford cup perforation method. Under aseptic conditions, four Oxford cups (10 mm deep, 8 mm wide) were placed on a clean agar plate. 2 mL of *Escherichia coli* or *Staphylococcus aureus* was injected into each cup, and agar was added to bring the volume to 20-25 mL. After the agar had completely solidified, the Oxford cups were gently removed with forceps, and 180 μL of culture medium was injected into each well. In the experimental groups, 20 μL of cell-free supernatant from *Lactobacillus plantarum* B11 and cell-free supernatant from *Lactobacillus plantarum* B1 were added, respectively. 20 μL of sterile physiological saline was used as a control. The plates were incubated at 4°C for 4 hours, then transferred to 37°C for 12 hours. The formation of inhibition zones was observed, and the diameter of the inhibition zones was measured and recorded.

[0049] Sterilized Oxford cups were placed on agar plates. A 3% (v / v) suspension of *Candida tropicalis* was inoculated into unsolidified malt extract agar medium, mixed thoroughly, and poured into the plates. After placing the plates in a clean bench for 30 minutes, the Oxford cups were removed with forceps. 200 μL of *Lactobacillus plantarum* B11 cell-free supernatant and *Lactobacillus plantarum* B1 cell-free supernatant were added to each well. For the control group, 200 μL of physiological saline was added. The malt extract agar plates were incubated at 28°C for 3 days. The size of the inhibition zone was observed and measured, with three replicates.

[0050] Cell-free supernatant of *Lactobacillus plantarum* B11 and *Lactobacillus plantarum* B12 was added to potato dextrose agar (PDA) medium, with the supernatant comprising 5% of the medium in each case. The medium was poured into plates, and after solidification, *Penicillium loudi* mycelial pellets (7 mm in diameter) were inoculated into the center of the plate using forceps. The plates were then incubated at 28°C for 6 days. A blank control was included. After 6 days, the colony diameter was measured, and three replicates were performed. The inhibition rate was calculated using the following formula:

[0051]

[0052] In the formula R 实验组 R represents the diameter of *Penicillium loudi* colonies after the addition of *Lactobacillus plantarum* B11 or *Lactobacillus plantarum* B1 cell-free supernatant; 空白组 This represents the diameter of Penicillium loudi colonies after adding 10% MRS sterile liquid culture medium.

[0053] The results are shown in Table 1 and Figure 2. Figure 3As shown, *Lactobacillus plantarum* B11 exhibited an inhibition zone diameter of 21.6 mm against *Escherichia coli*, 19.1 mm against *Staphylococcus aureus*, and 22.7 mm against *Candida tropicalis*. Its inhibition rate against *Penicillium loudi* was 76.8%, significantly higher than that of *Lactobacillus plantarum* B1. This indicates that *Lactobacillus plantarum* B11 possesses high antibacterial ability and can effectively inhibit the growth of *Escherichia coli*, *Staphylococcus aureus*, *Candida tropicalis*, and *Penicillium loudi*.

[0054] Table 1. Antibacterial activity of Lactobacillus plantarum B11

[0055]

[0056] Note: Different superscript letters in the same column indicate significant differences. P <0.05).

[0057] Example 3: Determination of extracellular polysaccharide yield from Lactobacillus plantarum B11

[0058] Third-generation activated *Lactobacillus plantarum* B11 was inoculated into sterile fresh whey at a volume ratio of 5% and cultured at 37°C for 60 h to obtain fermentation broth. The broth was then boiled in water for 10 min to inactivate the bacteria. After cooling, it was centrifuged (4°C, 7500 rpm) for 20 min to obtain cell-free fermentation supernatant. 80% TCA was added to the supernatant to a final concentration of 4% (w / v), stirred for 3 min, and allowed to stand at 4°C for 10 h. Protein was removed by centrifugation. The supernatant was then purified to 1 / 3 and mixed with 3 times the volume of pre-cooled ethanol. Precipitation was carried out overnight at 4°C, and the precipitate was obtained by centrifugation. The precipitate was then dissolved in deionized water and dialyzed at 4°C for 48 h, with water changed every 8 h. The dialysate was lyophilized to obtain extracellular polysaccharides. The content of extracellular polysaccharides was determined using the phenol-sulfuric acid method. The same method was used to determine the content of extracellular polysaccharides in conventional acidified whey.

[0059] The results showed that the amount of extracellular polysaccharides synthesized in situ in the whey fermented by *Lactobacillus plantarum* B11 was above 311.1 mg / L, while the extracellular polysaccharide content of conventional acid whey was 66.5 mg / L, which was significantly lower than that of the whey fermented by *Lactobacillus plantarum* B11.

[0060] The monosaccharide composition of the extracellular polysaccharide synthesized from fermented whey by *Lactobacillus plantarum* B11 was determined by high performance liquid chromatography (HPLC). The results showed that the extracellular polysaccharide of *Lactobacillus plantarum* B11 was a heteropolysaccharide composed of galactose, glucose, and galacturonic acid; the molar ratio of galactose, glucose, and galacturonic acid was 2.08:1.00:0.37.

[0061] Example 4: Lactobacillus plantarum B11 fermented whey for use in sour cheese processing

[0062] (1) Take Lactobacillus plantarum B11 activated to the third generation, and add it at a volume ratio of 5% (the inoculum size of Lactobacillus plantarum is 1.0-2.0 × 10⁻⁶). 8 (CFU / mL) was inoculated into sterile fresh whey and cultured at 37°C for 60 h to obtain acid whey;

[0063] (2) Select fresh and qualified Holstein cow milk, filter it and set it aside;

[0064] (3) Heat the fermented whey with Lactobacillus plantarum B11 to 80°C and set aside;

[0065] (4) Pour the filtered milk obtained in step (2) directly into the heated whey in step (3). Adjust the pH value of the mixture of whey and milk (whey: milk = 1:10) to 4.8 by adjusting the amount of whey added. Mix thoroughly and heat slowly.

[0066] (5) Control the temperature to 70℃. After the milk coagulates into clumps, scoop out the excess whey and then heat-stretch the remaining one-third of the acidic whey.

[0067] (6) Knead the curd block by hand into an oval shape, 25cm long, and roll it around a cylindrical wooden stick. Then fix one end of the curd block to the upper drying rack. Stretch and thin the curd block by its own weight and the pulling force of your hand, and wrap it around the drying rack. Let the curd sheet wrapped on the drying rack air dry naturally. Avoid direct sunlight and air dry at room temperature for 1 day until the curd sheet hardens and takes shape.

[0068] (7) Using the same method, replace the fermented whey of Lactobacillus plantarum B11 with traditional acid whey to prepare acid-coagulated stretch cheese.

[0069] Table 2 shows that the curd state, clot elasticity, clot elongation, and product yield of the sour cheese prepared by fermenting whey with *Lactobacillus plantarum* B11 are all superior to those of sour cheese prepared by traditional fermentation. Furthermore, the mold count of the sour cheese prepared by fermenting whey with *Lactobacillus plantarum* B11 after storage at 4°C for 30 days is 1.3 × 10⁻⁶. 6 CFU / g, while the mold count of traditionally prepared whey-coated cheese stored at 4°C for 30 days is 2×10⁻⁶. 8 CFU / g.

[0070] Table 2. Effects of Lactobacillus plantarum B11 fermented whey on the quality improvement of acid-coagulated stretch cheese.

[0071]

[0072] Note: The more "+" signs there are, the more pronounced or better the degree.

[0073] The textural properties of the agglomerates prepared by traditional fermented whey and whey fermented with *Lactobacillus plantarum* B11 were determined by a texture analyzer after stretching, including hardness, viscosity, elasticity, cohesiveness, and chewiness. The results are shown in Table 3. The results indicate that the agglomerates prepared by *Lactobacillus plantarum* B11 fermented whey have significantly higher elasticity and viscosity after stretching than those prepared by traditional fermented whey. p The value is <0.05, indicating that the addition of Lactobacillus plantarum B11 fermentation can improve the toughness and plasticity of the coagulated cheese, which is beneficial for stretching and shaping the sour curd cheese.

[0074] Table 3. Effects of Lactobacillus plantarum B11 fermented whey on cheese curd texture.

[0075]

[0076] Note: Each component is expressed as the mean ± standard error of three parallel trials. Different letters in the same column indicate significant differences. p <0.05).

[0077] The microstructure and protein and fat structure and distribution of coagulants prepared from conventionally fermented whey and whey fermented with Lactobacillus plantarum B11 were observed using laser confocal scanning microscopy. Green and red represent the morphology of proteins and fats under fluorescence, respectively, while black represents voids and gaps in the whey structure (see [link to study]). Figure 4 Traditionally produced whey curds exhibit uneven casein network distribution, loose casein micelle structure, and weak casein matrix strength. Large clumps of free fat float outside the casein micelle network, resulting in significant gaps between proteins. This loose gel structure leads to quality defects such as low elasticity and viscosity, and a loose structure. In contrast, whey curds prepared with added *Lactobacillus plantarum* B11 fermentation exhibit a uniform casein network structure, with fat globules evenly embedded within the three-dimensional casein network. This structure endows the curd with better elasticity and plasticity, facilitating the stretching and shaping of sourdough cheese. This is because the extracellular polysaccharides produced by *Lactobacillus plantarum* B11 fermentation bind to casein through electrostatic and hydrogen bonding forces, forming an extracellular polysaccharide-casein complex that effectively fills the three-dimensional network structure, thereby enhancing the curd's plasticity and promoting the stretching and shaping of sourdough cheese.

[0078] Example 5: Application of sodium caseinate in acid-coagulated stretch cheese processing and screening of its addition amount

[0079] The other steps are the same as those in Example 4, which uses Lactobacillus plantarum B11 to ferment whey to prepare sour cheese. The only difference is that different amounts of sodium caseinate are added in step (4) to investigate the effect of different amounts of sodium caseinate on the stretchability of sour cheese.

[0080] The results showed that adding sodium caseinate improved the smoothness and stretchability of the curd. When the sodium caseinate content was 0.05%, 0.07%, and 0.09% of the milk content, the curd exhibited high smoothness and good stretchability, with curd stretch lengths of 76.1 cm, 79.4 cm, and 77.6 cm, respectively; the product yields were also relatively high, at 10.5%, 10.9%, and 10.1%, respectively. Although the addition of 0.07% and 0.09% sodium caseinate increased the curd stretch length, the resulting curd was softer, and the curd sheets easily collapsed during drying, leading to poor shaping of the final acid-cured stretch cheese. The addition of 0.05% sodium caseinate resulted in a smooth curd texture with good elasticity, and the curd sheets showed less collapse during drying, maintaining a more stable overall shape. Therefore, the optimal addition amount of sodium caseinate was determined to be 0.05%.

[0081] Table 4 Screening results for sodium caseinate addition

[0082]

[0083] Note: The more "+" signs there are, the more pronounced or better the degree.

[0084] Example 6: Application of phosphates in acid-coagulated stretch cheese processing and its additive screening

[0085] The other steps are the same as those in Example 4, which uses Lactobacillus plantarum B11 to ferment whey to prepare sour cheese. The only difference is that different amounts of food additives are added in step (4) to investigate the effects of different types of food additives and their amounts on the stretchability of sour cheese.

[0086] Eight different types of food additives were screened to improve the stretchability of sour curd cheese, as shown in Table 5. The results showed that adding sodium tripolyphosphate and disodium hydrogen phosphate compound phosphate at milk content of 0.05%, 0.1%, and 0.15% improved the elasticity of the curd and the product yield, as well as the curd state and the degree of collapse of the curd during shelf drying. This indicates that adding phosphates can increase the elasticity of the curd, thereby reducing the degree of collapse of the curd during shelf drying and allowing the overall shape of the product to be well maintained.

[0087] Table 5 Initial Screening Results of Food Additives

[0088]

[0089] Note: More "+" signs indicate a more pronounced or better degree; more "-" signs indicate a less pronounced or worse degree.

[0090] Example 7: Application and formulation screening of compound phosphates in acid-coagulated stretched cheese processing

[0091] The other steps are the same as those in Example 4, which uses Lactobacillus plantarum B11 to ferment whey to prepare sour cheese. The only difference is that in step (4), different ratios of compound phosphate (sodium tripolyphosphate: disodium hydrogen phosphate = 2:8, 3:7, 4:6, 5:5, 8:2, 7:3, 6:4; m / m; total phosphate addition is fixed at 0.05%) are added to explore the effect of different ratios of compound phosphate on the stretchability of sour cheese.

[0092] The results are shown in Table 6. When the ratio of sodium tripolyphosphate to disodium hydrogen phosphate was 5:5, 7:3, and 8:2, the resulting curd blocks were rough, loose, and irregular. After stretching, the curd blocks were hard, difficult to stretch, and had low elasticity. The curd blocks obtained at ratios of 4:6 and 3:7 had a moderate acidity, but the overall elasticity, gloss, and stretching effect of the curd blocks were lacking. The curd blocks obtained at a ratio of 6:4 had a uniform texture, a moderate acidity, no bitterness, and a rich milky aroma. After stretching, the curd blocks were smooth, had good elasticity, and were not easily broken. The curd blocks did not collapse during the drying process on the rack, and the product yield was the highest at 10.8%. Therefore, the optimal ratio of sodium tripolyphosphate to disodium hydrogen phosphate was determined to be 6:4.

[0093] Table 6 Screening Results of Compound Phosphate Ratios

[0094]

[0095] Note: More "+" signs indicate a more pronounced or better degree; more "-" signs indicate a less pronounced degree.

[0096] Example 8: Application and ratio screening of sodium caseinate and complex phosphate in acid-coagulated stretch cheese processing

[0097] The results of Example 4 showed that adding sodium caseinate improved the smoothness and stretchability of the curd, but the curd was prone to collapse during the drying process, resulting in poor final product shape. In contrast, the results of Example 7 showed that adding a complex phosphate (sodium tripolyphosphate: disodium hydrogen phosphate = 6:4) improved the elasticity and plasticity of the curd. The curd did not collapse during the drying process, and the final product had better shape. However, the product with the added phosphate had a lower stretch length than the product with the added sodium caseinate. This suggests that the combined use of sodium caseinate and complex phosphate can improve the stretchability and elasticity of the curd. Therefore, the effect of different ratios of sodium caseinate to complex phosphate on the stretchability of the curd was investigated to determine the optimal ratio.

[0098] The other steps are the same as those in Example 4, which uses Lactobacillus plantarum B11 to ferment whey to prepare sour cheese. The only difference is that in step (4), different ratios of sodium caseinate and compound phosphate are added (3:7, 4:6, 5:5, 6:4, 7:3; the total amount of sodium caseinate and compound phosphate added is fixed at 0.1%) to explore the effect of different ratios of sodium caseinate and compound phosphate on the stretchability of sour cheese.

[0099] The results are shown in Table 7. The combined use of compound phosphate and casein yogurt can improve the clot stretching length and product yield, indicating that the phosphate ions in the phosphate chelate calcium ions in milk, neutralizing the electrostatic repulsion between casein micelles and thus promoting milk gelation. Simultaneously, the addition of sodium caseinate, an emulsifier, significantly enhances the emulsification effect through the synergistic use of phosphate and sodium caseinate. This emulsifies milk fat into smaller fat particles, which fill the three-dimensional network structure of casein, improving the plasticity and stretchability of the clot and promoting its stretching and shaping. When the ratio of sodium caseinate to compound phosphate is 6:4, the highest clot stretching length is 85.4 cm. During the drying process, the formed clots did not collapse, maintaining the optimal overall product shape, and the highest product yield was 11.4%. Therefore, the optimal ratio of sodium caseinate to compound phosphate is determined to be 6:4.

[0100] Furthermore, by comparing and analyzing the performance differences of cheese curds and cheese products prepared by traditional yogurt fermentation with the optimal sodium caseinate to compound phosphate ratio (6:4) and by *Lactobacillus plantarum* B11 fermentation with the same optimal sodium caseinate to compound phosphate ratio, the results showed that: in terms of curd characteristics, the cheese curds prepared by the traditional yogurt fermentation group were significantly lower than those prepared by the *Lactobacillus plantarum* B11 fermentation group in terms of integrity, elasticity, and tensile extensibility; in terms of final product performance, the yield of cheese curds in the traditional yogurt fermentation group (10.3%) was about 9.6 percentage points lower than that in the *Lactobacillus plantarum* B11 fermentation group (11.4%), and there were also significant differences in product texture and structure. These results confirm that *Lactobacillus plantarum* B11 fermentation yogurt has significant advantages in improving the textural properties of cheese curds and increasing product yield.

[0101] Table 7. Screening results of sodium caseinate to complex phosphate ratio

[0102]

[0103] Note: More "+" signs indicate a more pronounced or better degree; more "-" signs indicate a less pronounced degree.

[0104] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A Lactiplantibacillus (Lactobacillus) plantarum strain, characterized in that, Lactiplantibacillus plantarum The plantarum lactiplantibacillus is named as plantarum lactiplantibacillus B11, preserved in China Center for Type Culture Collection, with a preservation number of CCTCC NO: M2025778 and a preservation address of Wuhan University, No. 299, Bayi Road, Wuchang District, Wuhan City, Hubei Province. ​ 2. A microbial inoculant containing the plantarum lactiplantibacillus of claim 1.

3. Use of the Lactobacillus plantarum according to claim 1 or the microbial inoculant according to claim 2 for the manufacture of an antibacterial product, characterized in that, The bacteriostasis is for non-therapeutic purposes, and refers to the inhibition of Escherichia coli, Staphylococcus aureus, Candida tropicalis or Penicillium roqueforti.

4. Use of the Lactobacillus plantarum according to claim 1 or the microbial inoculant according to claim 2 for the preparation of exopolysaccharides, characterized in that, The exopolysaccharide is a heteropolysaccharide composed of galactose, glucose and galacturonic acid; and the molar ratio of the galactose, glucose and galacturonic acid is 1.8-2.2:0.8-1.2:0.25-0.

4.

5. The plantarum lactiplantibacillus of claim 1 or the microbial inoculant of claim 2 is applied in fermented acid whey.

6. The plantarum lactiplantibacillus of claim 1 or the microbial inoculant of claim 2 is applied in improving the stretchability of acid coagulated cheese.

7. Use of Lactobacillus plantarum according to claim 1 or microbial inoculant according to claim 2 for improving the stretchability of acid coagulated cheese, characterized in that, The specific operation is as follows: The plantarum lactiplantibacillus B11 is inoculated into sterilized whey to prepare acid whey with a pH value of ≤3.4; After the addition of composite phosphate and sodium caseinate to the acid whey and heating, milk is added to sequentially perform acid coagulation and hot stretching, and then curd pieces are obtained; the curd pieces are wound on a rack to dry and form into acid coagulated stretched cheese; the composite phosphate is a mixture of disodium hydrogen phosphate and sodium tripolyphosphate.

8. Use according to claim 7, characterized in that, The experimental conditions for the fermentation of acid whey are as follows: fermentation at 36.5-37.5°C for 45-70 h; inoculum of Lactobacillus plantarum in whey of 0.8 x 10 8 CFU / mL-2.0 x 10 8 CFU / mL.

9. Use according to claim 7, characterized in that, The optimal addition amounts of the composite phosphate and sodium caseinate are 0.03-0.05% and 0.05-0.07% of the milk, respectively; the mass ratio of the acid whey to the milk is 1:8-12; and the pH value of the mixture after the addition of the milk is 4.7-4.9; The mass ratio of the sodium tripolyphosphate to the disodium hydrogen phosphate is 5-6:5-4.

10. Use according to claim 7, characterized in that, The heating temperature is 85-90°C; the acid coagulation and hot stretching temperature is 68-72°C, the thickness of the curd pieces is 0.1-0.15 cm, the width is 14-16 cm, and the length is 83-86 cm.

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