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

Abstract

The invention discloses lactobacillus plantarum and application thereof in improving the stretchability of acid set cheese. The lactobacillus plantarum is named as lactobacillus plantarum B11 and is preserved in the China Center for Type Culture Collection, the preservation number is CCTCC NO: M 2025778, and the preservation address is Wuhan University, Wuhan University, No. 299, eight road, Wuchang District, Wuhan City, Hubei Province. The strain provided by the invention can realize directional fermentation and high yield of viscous exopolysaccharides and antibacterial substances. The acid whey fermented by the strain is combined with phosphate and a sodium caseinate quality improver, so that the stretchability of the acid coagulated stretched cheese is improved, the mildewing of the product in the airing and storage processes is inhibited, and the quality safety of the product can be ensured. The problems that in the prior art, in the acid coagulated cheese making process, stretching is difficult, the yield is low, and mildewing is prone to occurring in the airing and storing process are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of microorganisms, and in particular to a Lactobacillus plantarum and an application thereof in improving the stretchability of acid-cured cheese. Background Art

[0002] As the only acid-cured and stretched cheese in China, Rushan relies on acid whey to induce the coagulation of milk casein near its isoelectric point. This is then blanched and stretched to form a fibrous structure. The resulting cheese is then racked and air-dried to produce the acid-cured and stretched cheese. However, during the coagulation process, the weak ionic bonds between the casein micelles result in poor plasticity and stretchability, making the coagulated mass prone to breakage during stretching, thus affecting product yield and quality stability. To address this issue, existing improvements have been proposed. For example, patent number CN201910710580.6 proposes the use of disodium ethylenediaminetetraacetic acid (EDTA-2Na) as a modifier to enhance the stretchability of acid-cured and stretched cheese. However, GB2760-2024 prohibits the use of EDTA-2Na in dairy products.

[0003] Furthermore, the coagulant used in the production of acid-cured stretched cheese is typically traditional naturally fermented acid whey, which has a complex and difficult-to-control microbial composition. This makes the acid-cured stretched cheese susceptible to mold during drying and storage, seriously affecting the product's quality and shelf life. This problem not only limits the large-scale production of acid-cured stretched cheese but also negatively impacts its marketability and consumer experience.

[0004] In summary, the production process of acid-cured stretched cheese in the prior art still has the following problems: Insufficient stretchability: The ionic bond strength between casein micelles is weak, resulting in poor plasticity of the agglomerate and easy breakage when stretched, affecting production and quality.

[0005] Difficulty in controlling microorganisms: The microbial composition of traditional acid coagulants is complex, which can easily cause the product to mold during drying and storage, reducing product quality.

[0006] Therefore, it is urgent to develop a new method that can improve the stretchability of acid-cured stretched cheese and reduce its mold rate during drying and storage, so as to promote the sustainable development of the acid-cured stretched cheese industry.

[0007] The Chinese patent application with publication number CN113755398A discloses a fermented milk radish strain, a milk radish starter, and its application with a flavoring function. The fermented strains provided in this invention are Lactobacillus plantarum ML9 and Rhodotorula 2-3. The milk radish starter is obtained by adding Lactobacillus plantarum ML9 and Rhodotorula 2-3 to traditional sour water for fermentation. By comparing the milk radish starter of the present invention with milk radish fermented in traditional sour water, the milk radish starter after bacterial strain compounding can achieve the purpose of complementary aroma production and flavor optimization. However, the effect of this fermented strain on the tensile properties and antibacterial properties of milk radish has not been studied. Summary of the Invention

[0008] In view of this, the object of the present invention is to provide a plant lactobacillus and its application in improving the stretchability of acid-cured cheese. The strain provided by the present invention can be fermented in a directional manner to produce high-yield viscous extracellular polysaccharides and antibacterial substances. The acid whey after fermentation of the strain is combined with phosphate and sodium caseinate quality improvers to improve the stretchability of acid-cured stretchable cheese while inhibiting the product from becoming moldy during drying and storage, while also ensuring product quality and safety. The problem of difficulty in stretching, low yield, and easy mold formation during drying and storage in the prior art during the production of acid-cured cheese is solved.

[0009] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: a plant lactobacillus ( Lactobacillus plantarum ), the plant lactobacillus is named plant lactobacillus ( Lactobacillus plantarum ) B11, deposited in China Center for Type Culture Collection with accession number CCTCC NO: M 2025778, and the deposit address is Wuhan University, No. 299, Bayi Road, Wuchang District, Wuhan City, Hubei Province.

[0010] The present invention also provides the microbial agent of Lactobacillus plantarum.

[0011] The present invention also provides the use of the plant lactobacillus or the microbial agent in preparing an antibacterial product, wherein the antibacterial effect is used for non-therapeutic purposes, and the antibacterial effect refers to the inhibitory effect on Escherichia coli, Staphylococcus aureus, Candida tropicalis or Penicillium roqueforti.

[0012] The present invention also provides the use of the plant lactobacillus or the microbial agent in preparing extracellular polysaccharides. The extracellular polysaccharides are heteropolysaccharides composed of galactose, glucose and galacturonic acid. The molar ratio of the galactose, glucose and galacturonic acid is 1.8-2.2:0.8-1.2:0.25-0.4.

[0013] The present invention also provides application of the Lactobacillus plantarum or the microbial agent in fermenting acid whey.

[0014] The present invention also provides use of the Lactobacillus plantarum or the microbial agent in improving the stretchability of acid-curdled cheese.

[0015] As a further description of the above scheme: the specific operations for improving the stretchability of acid curd cheese are as follows: Inoculating Lactobacillus plantarum B11 into sterilized whey to prepare acid whey with a pH value of ≤3.4; Phosphate and sodium caseinate are added to acid whey and then heated, and then milk is added to perform acid coagulation and blanching and stretching in sequence to obtain curd sheets; the curd sheets are air-dried and formed to obtain acid coagulated and stretched cheese.

[0016] As a preferred method, the experimental conditions for fermenting acid whey are as follows: fermentation at 36.5°C to 37.5°C for 45h to 70h; the inoculation amount of Lactobacillus plantarum in whey is 0.8×10 8 CFU / mL-2.0×10 8 CFU / mL.

[0017] The optimal addition amounts of the composite phosphate and sodium caseinate are 0.03-0.05% and 0.05-0.07% of milk, respectively; the mass ratio of acid whey to milk is 1:8-12; and the pH value of the mixture after adding milk is 4.7-4.9; The composite phosphate is a mixture of disodium hydrogen phosphate and sodium tripolyphosphate; the mass ratio of the sodium tripolyphosphate to the disodium hydrogen phosphate is 5-6:5-4.

[0018] Preferably, the heating temperature is 85°C to 95°C; the acid coagulation and blanching temperature is 68°C to 72°C; the thickness of the curd sheet is 0.1 to 0.15 cm, the width is 14 to 16 cm, and the length is 83 to 86 cm. The yield of the milk fan product is 11.4%.

[0019] The characteristics of the present invention are as follows: The present invention screened out a strain of Lactobacillus plantarum from a soil sample in Dengchuan Town, Eryuan County, Dali City. The Lactobacillus plantarum B11 has strong antibacterial activity and has obvious antibacterial effects on Escherichia coli, Staphylococcus aureus, Candida tropicalis and Penicillium roqueforti. The Lactobacillus plantarum B11 can synthesize viscous extracellular polysaccharides in MRS liquid culture medium and fermented whey, with a yield of up to 311 mg / L or more. The strain can be applied to fermented acid whey, and the acid whey can be used to process acid-cured stretched cheese. The antibacterial substances such as organic acids produced by the fermentation of whey by Lactobacillus plantarum B11 can inhibit the contamination of mold and yeast during the drying process of acid-cured stretched cheese, thereby improving product quality. At the same time, the viscous extracellular polysaccharides produced by the fermentation of whey by Lactobacillus plantarum B11 form a complex with casein in milk, thereby improving the plasticity of the agglomerate, promoting the stretching and forming of the agglomerate, and improving the yield of the product. In addition, the present invention also uses phosphate and sodium caseinate in combination with the acid whey produced by the fermentation of strain B11, which can significantly enhance the emulsification effect, improve the plasticity and stretchability of the coagulation, and promote the stretching and forming of the acid coagulated cheese.

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention screened out a lactic acid bacterium that produces antibacterial substances, organic acids and viscous extracellular polysaccharides, from a soil sample in Dengchuan Town, Eryuan County, Dali City. The strain was identified as Lactobacillus plantarum through morphological and molecular biological identification and was named Lactobacillus plantarum B11.

[0021] (2) The whey fermented by Lactobacillus plantarum B11 provided by the present invention has a high yield of antibacterial substances, organic acids and viscous exopolysaccharides. The use of the fermented acid whey to process acid curd stretched cheese can improve the yield and quality stability of the product. The present invention utilizes the antibacterial substance organic acid produced by the fermentation of whey by Lactobacillus plantarum B11 to inhibit the contamination of mold and yeast during the drying process of acid curd stretched cheese, thereby improving the quality of the product. At the same time, the viscous exopolysaccharides produced by the fermentation of whey by Lactobacillus plantarum B11 form a complex with casein in milk, thereby improving the plasticity of the curd, promoting the stretching and forming of the curd, and improving the yield of the product.

[0022] (3) The present invention utilizes the phosphate group in phosphate to chelate the calcium ions in milk, neutralizes the electrostatic repulsion between casein micelles, and thus promotes milk gelation; at the same time, the emulsifier sodium caseinate is additionally added. The phosphate and the emulsifier sodium caseinate are used in conjunction to significantly enhance the emulsification effect, and the fat in the emulsified milk is converted into smaller fat particles, which are then filled in the three-dimensional network structure of casein, thereby improving the plasticity and stretchability of the coagulation and promoting the stretching and forming of acid-curdled cheese.

[0023] The deposit information of the microorganism is as follows: Classification name: Lactobacillus plantarum ( Lactobacillus plantarum)B11; Deposit number: CCTCC NO: M 2025778; Depository: China Center for Type Culture Collection; Deposit date: April 14, 2025; Deposit address: Wuhan University, No. 299 Bayi Road, Wuchang District, Wuhan City, Hubei Province. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The colony morphology and Gram staining results of Lactobacillus plantarum B11 on MRS medium;

[0025] FIG2 shows the antibacterial activities of Lactobacillus plantarum B11 and Lactobacillus plantarum B1 against Escherichia coli, Staphylococcus aureus and Candida tropicalis, wherein B11 represents Lactobacillus plantarum B11 and B1 represents Lactobacillus plantarum B1;

[0026] Figure 3 The inhibitory activity of Lactobacillus plantarum B11 and Lactobacillus plantarum B1 against Penicillium roqueforti;

[0027] Figure 4 The microstructure of the coagulum was obtained for conventional acid whey and whey fermented with Lactobacillus plantarum B11. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described in detail below in conjunction with specific embodiments. The description in this section is only exemplary and explanatory and should not have any limiting effect on the scope of protection of the present invention.

[0029] Example 1 Isolation and purification of bacterial strains 10 g of soil sample collected from Dengchuan Town, Eryuan County, Dali was added to 90 mL of MRS liquid culture medium and cultured at 37 °C for 48 h. Then 1 mL of culture medium was added to 9 mL of normal saline and fully shaken for 30 s. The sample was then diluted in series, with the highest dilution being 10 8 . Take 200μL of the dilution solution and spread it on MRS solid culture medium and culture it at 37℃ for 48h. Preliminarily, based on the colony morphology, size, size of the calcium-soluble circle, color, and growth position in the culture medium (surface, inside and bottom), pick colonies with different appearance characteristics and larger calcium-soluble circles for streak culture and purification. Repeat the streak purification several times using the same method to make the colonies on the final plate have the same morphology. Pick a single colony and inoculate it in MRS liquid culture medium at 37℃ for 24h for preservation and identification.

[0030] Morphological characteristics of the strain like Figure 1As shown in the left figure, after culturing Lactobacillus plantarum B11 on MRS agar medium for 24 hours, the colony morphology is milky white, translucent, relatively moist, smooth, with neat edges and obvious protrusions; Figure 1 As shown in the figure on the right, the microscopic examination results of Lactobacillus plantarum B11 are: non-spore-forming, with dispersed rod-shaped cells and purple Gram-positive bacteria.

[0031] Molecular biological identification of bacterial species 16S rDNA gene sequencing

[0032] The bacterial genome was extracted using the TSINGKE Plant DNA Extraction Kit (Universal). 16S rDNA PCR was performed using the extracted genome as a template with the universal bacterial primers 27F (SEQ ID No. 1 5'-AGTTTGATCMTGGCTCAG-3') and 1492R (SEQ ID No. 2 5'-GGTTACCTTGTTACGACTT-3'). The PCR product was sent to Beijing Qingke Biotechnology Co., Ltd. for sequencing. Sequences were compared using the BLAST tool against sequences in the NCBI database (www.ncbi.nlm.gov / blast) and GenBank. Homology was analyzed between the strain under investigation and the corresponding sequences of known strains to confirm the species of the selected sugar-producing strain. Sequencing of the 16S rDNA gene of the strain, as shown in SEQ ID No. 3, revealed over 99% homology with the 16S rDNA sequence of Lactobacillus plantarum, confirming that the selected lactic acid bacteria were Lactobacillus plantarum. Finally, the strain screened was identified as Lactobacillus plantarum through morphology and 16S rDNA sequencing and named Lactobacillus plantarum B11. Lactobacillus plantarum B11, deposited in China Center for Type Culture Collection, with the deposit number: CCTCC NO: M 2025778.

[0033] Example 2 Antibacterial activity of Lactobacillus plantarum B11 The following example Lactobacillus plantarum B1 was also screened from soil samples from Dengchuan Town and identified as Lactobacillus plantarum by 16S rDNA sequencing.

[0034] The antibacterial activity of the strains was determined using the Oxford cup punch method. Under aseptic conditions, four Oxford cups (10 mm deep, 8 mm wide) were placed on a clean plate. 2 mL of Escherichia coli or Staphylococcus aureus was injected into the plate, and agar was added to the volume to 20–25 mL. After the agar completely solidified, the Oxford cups were gently removed with tweezers. 180 μL of culture medium was then injected into each well. 20 μL of Lactobacillus plantarum B11 cell-free supernatant and Lactobacillus plantarum B1 cell-free supernatant were added to the experimental group, respectively. 20 μL of sterile saline was used as a control. The plates were incubated at 4°C for 4 hours and then transferred to 37°C for 12 hours. The formation of inhibition zones was observed, and the diameters of the inhibition zones were measured and recorded.

[0035] Place a sterilized Oxford cup on a plate and inoculate the unsolidified malt agar medium with a 3% (v / v) suspension of Candida tropicalis. Mix thoroughly and pour onto the plate. After the plate is placed in a clean bench for 30 minutes, remove the Oxford cup with tweezers and add 200 μL of Lactobacillus plantarum B11 cell-free supernatant and Lactobacillus plantarum B1 cell-free supernatant to the wells. For the control group, add 200 μL of saline. Incubate the malt agar plate at 28°C for 3 days. Observe and measure the size of the inhibition zone. Set up three replicates.

[0036] Add Lactobacillus plantarum B11 cell-free supernatant and Lactobacillus plantarum B1 cell-free supernatant to potato dextrose agar (PDA) culture medium, respectively, so that the supernatant ratio in the culture medium is 5%. Pour the culture medium into the plate. After the plate solidifies, use tweezers to pick a 7mm diameter Penicillium roqueforti cake and inoculate it into the center of the culture medium. Place the plate in a 28°C constant temperature incubator and culture for 6 days. Set up a blank control at the same time. After 6 days, measure the colony diameter. Set up three parallel groups. Calculate the inhibition rate using the following formula:

[0037] Where R 实验组 represents the diameter of Penicillium roqueforti colonies after addition of Lactobacillus plantarum B11 or Lactobacillus plantarum B1 cell-free supernatant; R 空白组 Represents the diameter of Penicillium roqueforti colonies after adding 10% MRS sterile liquid culture medium.

[0038] The results are shown in Table 1, Figure 2 and Figure 3 The inhibition zone diameters of Lactobacillus plantarum B11 against Escherichia coli were 21.6 mm, 19.1 mm against Staphylococcus aureus, and 22.7 mm against Candida tropicalis. The inhibition rate against Penicillium roqueforti was 76.8%, significantly higher than the antibacterial activity of Lactobacillus plantarum B1. This indicates that Lactobacillus plantarum B11 has a high antibacterial ability and can effectively inhibit the growth of Escherichia coli, Staphylococcus aureus, Candida tropicalis, and Penicillium roqueforti.

[0039] Table 1 Antibacterial activity of Lactobacillus plantarum B11

[0040] Note: Different shoulder letters in the same column indicate significant differences ( P <0.05).

[0041] Example 3 Determination of exopolysaccharide production of Lactobacillus plantarum B11

[0042] Third-generation activated Lactobacillus plantarum B11 was inoculated into sterile fresh whey at a 5% volume ratio and cultured at 37°C for 60 hours to obtain a fermentation broth. The fermentation broth was then inactivated by boiling in water for 10 minutes, cooled, and centrifuged at 7500 rpm at 4°C for 20 minutes to obtain a cell-free fermentation supernatant. 80% TCA was added to the supernatant to a final concentration of 4% (w / v), stirred for 3 minutes, and allowed to stand at 4°C for 10 hours. Protein was then removed by centrifugation. The supernatant was then purified to 1 / 3 the volume and mixed with 3 times the volume of pre-cooled alcohol. The mixture was precipitated overnight at 4°C and centrifuged to obtain a precipitate. The precipitate was then dissolved in deionized water and dialyzed at 4°C for 48 hours, with the water replaced every 8 hours. The dialyzate was then freeze-dried to obtain exopolysaccharides. The exopolysaccharide content was determined using the phenol-sulfuric acid method. The exopolysaccharide content of conventional acid whey was determined using the same method.

[0043] The test results showed that the amount of extracellular polysaccharides synthesized in situ in whey fermented by Lactobacillus plantarum B11 was above 311.1 mg / L, while the extracellular polysaccharide content of traditional acid whey was 66.5 mg / L, which was significantly lower than that of whey fermented by Lactobacillus plantarum B11.

[0044] High-performance liquid chromatography (HPLC) was used to determine the monosaccharide composition of exopolysaccharides synthesized by whey fermentation with Lactobacillus plantarum B11. The results showed that the exopolysaccharide of Lactobacillus plantarum B11 was a heteropolysaccharide composed of galactose, glucose, and galacturonic acid, with a molar ratio of galactose, glucose, and galacturonic acid of 2.08:1.00:0.37.

[0045] Example 4: Application of Lactobacillus plantarum B11 fermented acid whey in acid curd cheese processing (1) Take the third generation of Lactobacillus plantarum B11 and inoculate it at a volume ratio of 5% (the inoculation amount of Lactobacillus plantarum is 1.0-2.0×10 8 CFU / mL) was inoculated into sterile fresh whey and cultured at 37°C for 60 h to obtain acid whey; (2) Select fresh and qualified Holstein cow milk and filter it for later use; (3) heating the acid whey fermented by Lactobacillus plantarum B11 to 80°C and setting aside; (4) Pour the filtered milk obtained in step (2) directly into the heated acid whey in step (3), adjust the pH value of the mixture of acid whey and milk (acid whey: milk = 1:10) to 4.8 by adjusting the amount of acid whey added, mix thoroughly, and slowly stir and heat; (5) Control the temperature to 70°C, scoop out the excess whey after the milk is acidified and coagulated, and then blanch and stretch the remaining one-third of the acidified whey; (6) Knead the curd by hand into an oval block 25 cm long, and curl it on a cylindrical wooden stick. Then fix one end of the curd on the upper drying rack. The curd is stretched and thinned by its own gravity and the force of the hand, and then wrapped on the drying rack. The curd sheet wrapped on the drying rack is naturally air-dried; the drying is done away from direct sunlight and is dried at room temperature for 1 day until the curd sheet is fixed and formed. (7) The same method was used to prepare acid-curdled stretched cheese by replacing the whey fermented by Lactobacillus plantarum B11 with traditional acid whey.

[0046] As shown in Table 2, the curd state, curd elasticity, curd elongation and product yield of the acid curd cheese prepared by fermenting acid whey with Lactobacillus plantarum B11 were better than those of the acid curd cheese prepared by traditional acid whey. In addition, the mold count of the acid curd cheese prepared by fermenting acid whey with Lactobacillus plantarum B11 after storage at 4°C for 30 days was 1.3×10 6 CFU / g, while the mold count of acid curd cheese prepared from traditional acid whey stored at 4℃ for 30 days was 2×10 8 CFU / g.

[0047] Table 2 Effect of Lactobacillus plantarum B11 fermented whey on the quality improvement of acid-curdled stretched cheese

[0048] Note: The more “+” there are, the more obvious or better the degree is.

[0049] The texture characteristics of the agglomerates prepared from traditional acid whey and acid whey fermented with Lactobacillus plantarum B11 after stretching, such as hardness, viscosity, elasticity, cohesion, and chewiness, were measured using a texture analyzer. The results are shown in Table 3. The results showed that the elasticity and viscosity of the agglomerates prepared from acid whey fermented with Lactobacillus plantarum B11 after stretching were significantly higher than those of the agglomerates prepared from traditional acid whey ( p <0.05), indicating that adding Lactobacillus plantarum B11 to fermentation can improve the toughness and plasticity of the curd, which is beneficial to the stretching and forming of acid-curd cheese.

[0050] Table 3 Effects of whey fermented with Lactobacillus plantarum B11 on cheese curd texture

[0051] Note: Each component is expressed as the mean ± standard error of three parallel tests. Components with different letters in the same column indicate significant differences ( p <0.05).

[0052] Laser confocal scanning microscopy was used to observe the micromorphology of the agglomerates prepared from traditional acid whey and acid whey fermented by Lactobacillus plantarum B11, as well as the structure and distribution of proteins and fats. Green and red are the morphologies of proteins and fats under fluorescence, respectively, and black represents the voids and gaps in the whey or structure (see Figure 4 ). The casein network in the coagulum made from traditional acid whey is unevenly distributed, the casein micelle structure is loose, the casein matrix strength is weak, and the fat forms large pieces of free oil floating outside the casein micelle network. The gaps between proteins are large, and this loose gel structure also leads to quality defects such as low elasticity and viscosity of the coagulum, and loose structure. However, the casein network structure in the coagulum prepared by adding Lactobacillus plantarum B11 to ferment acid whey is uniform, and the fat globules are evenly embedded in the three-dimensional casein network. This structure gives the coagulum better elasticity and plasticity, which is conducive to the stretching and forming of acid-curdled cheese. The reason is that the extracellular polysaccharides produced by fermenting whey with Lactobacillus plantarum B11 bind to casein through electrostatic and hydrogen bonding forces to form an extracellular polysaccharide-casein complex and effectively fill the three-dimensional network structure, thereby improving the plasticity of the coagulum and promoting the stretching and forming of acid-curdled cheese.

[0053] Example 5 Application of Sodium Caseinate in Acid-Coagulated and Stretched Cheese Processing and Screening of Its Additive Amount The other steps were the same as those in Example 4, except that different amounts of sodium caseinate were added in step (4) to investigate the effects of different amounts of sodium caseinate on the stretchability of the acid curd cheese.

[0054] Results showed that the addition of sodium caseinate improved the fineness and stretchability of the curd. When sodium caseinate was added at 0.05%, 0.07%, and 0.09% of the milk content, the curds were fine and stretchable, with curd lengths of 76.1 cm, 79.4 cm, and 77.6 cm, respectively. The product yields were also high at 10.5%, 10.9%, and 10.1%, respectively. While sodium caseinate additions of 0.07% and 0.09% increased curd length, the resulting curds were relatively soft, and the curd sheets formed on the shelf easily collapsed during drying, resulting in poorly formed acid-cured stretched cheese. The addition of 0.05% sodium caseinate produced a fine, elastic curd with minimal collapse during drying, maintaining a relatively stable overall shape. Therefore, the optimal sodium caseinate addition level was determined to be 0.05%.

[0055] Table 4 Screening results of sodium caseinate addition

[0056] Note: The more “+” there are, the more obvious or better the degree is.

[0057] Example 6 Application of Phosphate in Acid-Coagulated Stretched Cheese Processing and Screening of Additives The other steps were the same as those in Example 4, except that different amounts of food additives were added in step (4). The effects of different types of food additives and their addition amounts on the stretchability of the curd cheese were investigated.

[0058] Eight different types of food additives were screened to improve the stretchability of acid-curd cheese, as shown in Table 5. The results showed that the addition of sodium tripolyphosphate and disodium hydrogen phosphate (0.05%, 0.1%, and 0.15% of the milk content) increased the elasticity of the curd and product yield, improving the curd state and the degree of collapse of the curd on the shelf. This suggests that the addition of phosphates can increase the elasticity of the curd, thereby reducing the collapse of the curd during the drying process on the shelf, and effectively maintaining the overall shape of the product.

[0059] Table 5 Food additives initial screening results

[0060] Note: More “+”s indicate a more obvious or better degree; more “-”s indicate a less obvious or worse degree.

[0061] Example 7 Application of composite phosphates in acid-cured stretched cheese processing and its ratio screening The other steps were the same as those in Example 4, except that different ratios of composite phosphates (sodium tripolyphosphate: disodium hydrogen phosphate = 2:8, 3:7, 4:6, 5:5, 8:2, 7:3, 6:4; m / m; total phosphate addition was fixed at 0.05%) were added in step (4) to investigate the effects of different ratios of composite phosphates on the stretchability of the curd cheese.

[0062] The results are shown in Table 6. When the sodium tripolyphosphate: disodium hydrogen phosphate ratio was 5:5, 7:3, and 8:2, the resulting curds were rough, loose, and irregular. The curds after stretching were hard, difficult to stretch, and had low elasticity. Curds produced with ratios of 4:6 and 3:7 had a moderate sour taste, but lacked overall elasticity, gloss, and stretchability. The curds produced with a ratio of 6:4 had a uniform texture, moderate sourness, no bitterness, and a rich frankincense. After stretching, the curds were smooth, elastic, and resistant to breakage. The curds did not collapse during drying on shelves, and the product yield reached a maximum of 10.8%. Therefore, the optimal sodium tripolyphosphate: disodium hydrogen phosphate ratio was determined to be 6:4.

[0063] Table 6 Screening results of compound phosphate ratio

[0064] Note: The more “+”, the more obvious or better the degree; the more “-”, the less obvious the degree.

[0065] Example 8 Application of sodium caseinate and compound phosphate in acid-cured stretched cheese processing and their ratio screening The results of Example 4 showed that the addition of sodium caseinate improved the smoothness and stretchability of the curd, but the curd easily collapsed during the airing process, resulting in a poorly formed product. The results of Example 7, however, showed that the addition of a composite phosphate (sodium tripolyphosphate: disodium hydrogen phosphate = 6:4) improved the elasticity and plasticity of the curd, preventing collapse during the airing process and resulting in a well-formed product. However, the tensile length of the product prepared with the phosphate addition was lower than that of the product prepared with sodium caseinate. This suggests that the combination of sodium caseinate and the composite phosphate can improve the tensile properties and elasticity of the curd. Therefore, the effects of different sodium caseinate to composite phosphate ratios on the tensile properties of the curd were investigated to determine the optimal ratio.

[0066] The other steps were the same as those in Example 4, except that different ratios of sodium caseinate to compound phosphate (3:7, 4:6, 5:5, 6:4, 7:3; the total amount of sodium caseinate and compound phosphate added was fixed at 0.1%) were added in step (4) to investigate the effects of different ratios of sodium caseinate to compound phosphate on the stretchability of the acid-curd cheese.

[0067] The results are shown in Table 7. The combined use of compound phosphate and casein yogurt can increase the elongation of the curd and product yield. This suggests that the phosphate groups in the phosphate chelate the calcium ions in the milk, neutralizing the electrostatic repulsion between casein micelles and promoting gelation. Furthermore, the addition of the emulsifier sodium caseinate significantly enhances the emulsification effect, converting the milk fat into smaller fat particles that fill the three-dimensional network of casein, improving the plasticity and stretchability of the curd and facilitating its stretchability. When the ratio of sodium caseinate to compound phosphate was 6:4, the curd had a maximum elongation of 85.4 cm. The curds did not collapse during drying on shelves, maintaining optimal overall morphology, and achieving a maximum product yield of 11.4%. Therefore, the optimal ratio of sodium caseinate to compound phosphate was determined to be 6:4.

[0068] In addition, a comparative analysis of the performance differences between curds and curd products prepared using traditional acid whey combined with an optimal sodium caseinate and complex phosphate ratio (6:4) and acid whey fermented with Lactobacillus plantarum B11 combined with an optimal sodium caseinate and complex phosphate ratio revealed that curd properties of the curds prepared using the traditional acid whey group were significantly inferior to those of the acid whey fermented with Lactobacillus plantarum B11 in terms of state integrity, elasticity, and tensile ductility. In terms of final product performance, the curd yield of the traditional acid whey group (10.3%) was approximately 9.6 percentage points lower than that of the acid whey fermented with Lactobacillus plantarum B11 (11.4%), and significant differences were also observed in the product texture and texture. These results confirm that acid whey fermented with Lactobacillus plantarum B11 has significant advantages in improving the textural properties of curds and increasing product yield.

[0069] Table 7 Screening results of the ratio of sodium caseinate to compound phosphate

[0070] Note: The more “+”, the more obvious or better the degree; the more “-”, the less obvious the degree.

[0071] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the appended claims, or equivalents thereof.

Claims

1. A plant lactobacillus ( Lactobacillus plantarum ), characterized in that, The plant lactobacillus is named plant lactobacillus ( Lactobacillus plantarum ) B11, deposited in China Center for Type Culture Collection, with the deposit number CCTCC NO: M 2025778, and the deposit address is Wuhan University, No. 299, Bayi Road, Wuchang District, Wuhan City, Hubei Province.

2. A microbial agent containing the Lactobacillus plantarum according to claim 1.

3. Use of the plant lactobacillus according to claim 1 or the microbial agent according to claim 2 in the preparation of an antibacterial product, characterized in that: The antibacterial effect is used for non-therapeutic purposes, and the antibacterial effect refers to the inhibitory effect on Escherichia coli, Staphylococcus aureus, Candida tropicalis or Penicillium roqueforti.

4. Use of the plant lactobacillus according to claim 1 or the microbial agent according to claim 2 in the preparation of exopolysaccharides, characterized in that: The extracellular polysaccharide is a heteropolysaccharide composed of galactose, glucose and galacturonic acid; the molar ratio of the galactose, glucose and galacturonic acid is 1.8-2.2:0.8-1.2:0.25-0.

4.

5. Application of the plant lactobacillus according to claim 1 or the microbial agent according to claim 2 in fermenting acid whey.

6. Use of the Lactobacillus plantarum according to claim 1 or the microbial agent according to claim 2 in improving the stretchability of acid curd cheese.

7. Use of the Lactobacillus plantarum according to claim 1 or the microbial agent according to claim 2 in improving the stretchability of acid curd cheese, characterized in that: The specific operations are as follows: Inoculating Lactobacillus plantarum B11 into sterilized whey to prepare acid whey with a pH value of ≤3.4; Phosphate and sodium caseinate are added to acid whey and heated, and then milk is added to perform acid coagulation and blanching and stretching in sequence to obtain curd sheets; the curd sheets are wound on a rack and air-dried to form acid coagulated and stretched cheese.

8. The use according to claim 7, characterized in that The experimental conditions for fermenting acid whey were as follows: fermentation at 36.5℃~37.5℃ for 45h~70h; the inoculum size of Lactobacillus plantarum in whey was 0.8×10 8 CFU / mL~2.0×10 8 CFU / mL.

9. The 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 milk, respectively; the mass ratio of acid whey to milk is 1:8-12; and the pH value of the mixture after adding milk is 4.7-4.9; The composite phosphate is a mixture of disodium hydrogen phosphate and sodium tripolyphosphate; the mass ratio of the sodium tripolyphosphate to the disodium hydrogen phosphate is 5-6:5-4.

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

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