Lactic acid bacteria capable of reducing egg fishy smell and application of lactic acid bacteria

Abstract

The invention provides lactic acid bacteria capable of reducing the fishy smell of eggs and application of the lactic acid bacteria, the strain is Streptococcus thermophilus inm25-ST, the preservation number of the strain is CGMCC No.15446, the preservation date is March 12, 2018, the preservation unit is China General Microbiological Culture Collection Center, and the preservation address is No.3, Yard 1, Beichen West Road, Chaoyang District, Beijing. The method has the advantages that the method for reducing the hydrogen sulfide, the methyl mercaptan and the acetaldehyde by fermenting the egg milk through the streptococcus thermophilus to prepare the egg milk product not only reduces the content of the hydrogen sulfide, the methyl mercaptan and the acetaldehyde in the product, but also improves the flavor and the quality of the egg milk product.

Description

Technical Field

[0001] The invention relates to lactic acid bacteria for reducing egg odor and application thereof. Background Art

[0002] Eggs are a highly nutritious food and are a favorite among consumers. Every 100 grams of eggs contains 12.58 grams of protein, primarily ovalbumin and ovomucoid protein. These proteins contain eight essential amino acids and closely resemble the composition of human protein. The human body absorbs up to 98% of egg protein. The yolk is rich in lecithin, sterols, lutein, as well as calcium, phosphorus, iron, vitamins A and D, and B vitamins.

[0003] However, the off-flavor of processed eggs affects the quality of egg products. Research by Ren Liuyang et al. indicates that the primary source of off-flavor is the egg yolk. Research by Sang-Heee Jo et al. (2013) indicates that the primary components of the off-flavor of processed eggs are hydrogen sulfide, methyl mercaptan, and acetaldehyde. Currently, no effective methods exist to remove or reduce these three substances.

[0004] Streptococcus thermophilus, formerly known as Streptococcus thermophilus, originated from dairy products. It is an aerobic, Gram-positive bacterium that consists of two oval-shaped cocci connected in pairs to form chains about 0.7 to 0.9 μm long. Streptococcus thermophilus is considered a "generally recognized as safe (GRAS)" ingredient and is widely used in the production of some important fermented dairy products, including yogurt and cheese. Streptococcus thermophilus also has some functional activities, such as the production of exopolysaccharides, bacteriocins and vitamins. In addition, Streptococcus thermophilus can also be used as a potential beneficial bacteria. Experiments have shown that it has health effects, transport activity and certain gastrointestinal adhesion. Therefore, we need to explore the ability of different Streptococci thermophilus to produce different metabolites, not just the amount of lactic acid produced by fermentation.

[0005] Currently, relevant research is underway on egg odor removal processes. Patent: Application of Acylating Modification Reagents in Removing Egg Odor, Method for Removing Egg Odor, and Applications Thereof - CN202110670519.0. This invention relates to the effective removal of egg odor from liquid eggs and egg products using acylating modification reagents, particularly succinic anhydride and acetic anhydride, thereby further developing a method for effectively removing egg odor, providing an additional option for removing egg odor. However, it does not involve the removal of hydrogen sulfide, methyl mercaptan, and acetaldehyde by lactic acid bacteria fermentation. Patent: Application of Antioxidants and / or Metal Ion Chelators in Removing Egg Odor from Egg Products, Method for Removing Egg Odor from Egg Products - CN201711262233.9. This invention relates to the field of egg product processing, specifically the application of antioxidants and / or metal ion chelators in removing egg odor from egg products, and methods for removing egg odor from egg products. However, it does not involve the lactic acid bacteria fermentation process.

[0006] Patent: A method for preparing egg liquid for yogurt - CN2024107632 62.7. This patent involves adding a deodorizing agent, namely β-cyclodextrin, and using a vacuum deodorization process to reduce the odor of the later egg liquid fermentation product, thereby preparing a nutritious, highly fluid, and moderately flavored egg-fermented milk product. However, it does not involve the process of reducing the fishy odor through lactic acid bacteria fermentation.

[0007] The above patents all use additives to remove the fishy smell of eggs. However, using additives to improve product quality and flavor not only requires labeling on the product, but is also increasingly resisted by consumers. Summary of the Invention

[0008] In view of the above problems, the present invention provides a lactic acid bacterium for reducing eggy odor and application thereof.

[0009] The invention aims to achieve the following goal: a lactic acid bacteria for reducing the odor of eggs, the strain being Streptococcus thermophilus (S treptococcus thermophilus )inm25-ST, the strain preservation number is CGMCC No.15446, the preservation date is: March 12, 2018, the preservation unit is: General Microbiology Center of China Culture Collection Administration, and the preservation address is: No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing.

[0010] Application of lactic acid bacteria for reducing eggy odor in dairy products.

[0011] A starter culture prepared from lactic acid bacteria for reducing eggy odor.

[0012] Advantages of the present invention: (1) The method for reducing hydrogen sulfide, methyl mercaptan and acetaldehyde in egg and milk products by fermenting eggs and milk with thermophilic Streptococcus not only reduces the content of hydrogen sulfide, methyl mercaptan and acetaldehyde in the products, but also improves the flavor and quality of the egg and milk products; (2) It can enhance the flavor of eggs and milk, and there will be no peculiar smell in the fermented eggs and milk. It can be mixed with other products later, which means that the nutrition and flavor of eggs are retained without any safety risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Flow chart for strain screening and culture application.

[0014] Figure 2 This is the detection chart of hydrogen sulfide standard.

[0015] Figure 3 This is the detection chart of methyl mercaptan standard.

[0016] Figure 4 This is the detection chart of acetaldehyde standard. DETAILED DESCRIPTION

[0017] The present invention will be further described below with reference to specific embodiments: Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0018] Example 1, with reference to Figure 1-4 , a lactic acid bacteria that reduces the smell of eggs, the strain is Streptococcus thermophilus (S treptococcus thermophilus )inm25-ST, the strain preservation number is CGMCC No.15446, the preservation date is: March 12, 2018, the preservation unit is: General Microbiology Center of China Culture Collection Administration, and the preservation address is: No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing.

[0019] Application of lactic acid bacteria for reducing eggy odor in dairy products.

[0020] A starter culture prepared from lactic acid bacteria for reducing eggy odor.

[0021] Experimental steps: 1. Processing of raw materials From the bacterial collection, 9 glycerol tubes of different strains were taken, 100 μL was taken from each tube, and sterile saline was added to dilute the tube to 10 -1 , 10 -2 , 10 -3 , 10 -4 , 10 -5 , 10 -6 Concentration, make bacterial dilution, take 0.1 mL of each dilution and evenly spread it on M17 solid culture medium plate, culture at 37℃ for 48h, select single colonies with white colonies, raised colonies, smooth surface and neat colony edges, streak the colonies on M17 solid culture medium for secondary purification, culture at 37℃ for 48h, pick single colonies and inoculate them into liquid M17 culture medium, and name them inm21 to inm29 respectively. The screening process is as follows Figure 1 .

[0022] 2. Preliminary screening of bacterial strains The 9 strains were inoculated into M17 at 1% inoculum and cultured at 37℃ for 24h. Then, the strains were inoculated into screening medium at 1% inoculum and cultured at 37℃ for 5h. The final cell density reached 10 6 cfu / mL, to detect flavor substance indicators, The screening medium is: sterilized fresh milk (sterilization conditions 95 ℃, 15 min), cooled to room temperature and then added with hydrogen sulfide, methyl mercaptan and acetaldehyde reagents to a final concentration of (1000μg / Kg).

[0023] GCMS detection: A DB-WAX (60m´0.25mm´0.5μm) capillary column was selected.

[0024] Hydrogen sulfide: Treatment method: Take 5 mL of 1000 μg / mL hydrogen sulfide solution in water and place it in a headspace bottle. Add 2 mL of 2 mol / L HCl solution and 1 g of NaCl. Incubate in a 40°C water bath for 30 minutes. Figure 2 ).

[0025] Acetaldehyde, methyl mercaptan: Standard sample preparation method: Take 0.5 mL of 1000 μg / mL methyl mercaptan solution in water into a headspace bottle and add 0.2 g NaCl. Incubate in a 40°C water bath for 30 minutes. Figure 3 、 Figure 4 ).

[0026] GC conditions were as follows: desorption at 250°C for 5 min. Separation was performed on a DB-WAX capillary column using helium (99.99%) at a flow rate of 1.0 mL / min. The GC oven temperature was set to 32°C for 1 min, then increased to 50°C at a rate of 2°C / min and held for 10 min, and then increased to 240°C at a rate of 15°C / min and held for 5 min.

[0027] Mass spectrometry conditions were: ion source and quadrupole temperatures of 230°C and 150°C, respectively. The quadrupole mass spectrometer was operated in 70 eV ionization mode, with a scan range of m / z 35–450. Flavor compounds were identified using the NIST 11.0 spectral search library.

[0028] Table 1 Analysis results of screening lactic acid bacteria that reduce hydrogen sulfide, methyl mercaptan and acetaldehyde

[0029] Strains inm21-ST, inm25-ST and inm27-ST with low levels of hydrogen sulfide, methyl mercaptan and acetaldehyde were selected for rescreening.

[0030] 3. Strain rescreening The lactic acid bacteria strains inm21-ST, inm25-ST, and inm27-ST that were initially screened were reactivated and cultured, and inoculated into egg and milk (egg: milk = 1:10) with a final bacterial concentration of 106 cfu / mL. The sterilization temperature was 90°C for 5 min; the fermentation temperature was 37°C for 5 h, and the egg liquid was made for sensory evaluation. The results are shown in Table 2.

[0031] Table 2 Sensory analysis of fermented egg and milk

[0032] Note: The maximum score for each indicator is 5 points, and the higher the score, the better the result.

[0033] From the results in Table 2, we can see that inm25-ST has the best sensory evaluation result. This strain is Streptococcus thermophilus (S treptococcus thermophilus ), the strain's deposit number is CGMCC No. 15446, the deposit date is March 12, 2018, and the depository is the General Microbiology Center of the China Culture Collection Administration. The deposit address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. Its gene sequence is as follows: cctggctcag gacgaacgct ggcggcgtgc ctaatacatg caagtagaac gctgaagaga ggagcttgct cttcttggat gagttgcgaa cgggtgagta acgcgtaggt aacctgcctt gtagcggggg ataactattg gaaacgatag ctaataccgc ataacaatgg atgacacatg tcatttattt gaaaggggca attgttccac tacaagatgg acctgcgttg tattagctag taggtgaggt aatggctcac ctaggcgacg atacatagcc gacctgagag ggtgatcggc cacactggga ctgagacacg gcccagactc ctacgggagg cagcagtagg gaatcttcgg caatgggggc aaccctgacc gagcaacgcc gcgtgagtga agaaggtttt cggatcgtaa agctctgttg taagtcaaga acgggtgtga gagtggaaag ttcacactgt gacggtagct taccagaaag ggacggctaa ctacgtgcca gcagccgcgg taatacgtag gtcccgagcg ttgtccggat ttattgggcg taaagcgagc gcaggcggtt tgataagtct gaagttaaag gctgtggctc aaccatagtt cgctttggaa actgtcaaac ttgagtgcag aaggggagag tggaattcca tgtgtagcgg tgaaatgcgt agatatatgg aggaacaccg gtggcgaaag cggctctctg gtctgtaact gacgctgagg ctcgaaagcg tggggagcga acaggattag ataccctggt agtccacgcc gtaaacgatg agtgctaggt gttggatcct ttccgggatt cagtgccgca gctaacgcat taagcactcc gcctggggag tacgaccgca aggttgaaac tcaaaggaat tgacgggggc ccgcacaagc ggtggagcat gtggtttaat tcgaagcaac gcgaagaacc ttaccaggtc ttgacatccc gatgctattt ctagagatag aaagttactt cggtacatcg gtgacaggtg gtgcatggtt gtcgtcagct cgtgtcgtga gatgttgggt taagtcccgc aacgagcgca acccctattg ttagttgcca tcattcagtt gggcactcta gcgagactgc cggtaataaa ccggaggaag gtggggatga cgtcaaatca tcatgcccct tatgacctgg gctacacacg tgctacaatg gttggtacaa cgagttgcga gtcggtgacg gcgagctaat ctcttaaagc caatctcagt tcggattgta ggctgcaact cgcctacatg aagtcggaat cgctagtaat cgcggatcag cacgccgcgg tgaatacgtt cccgggcctt gtacacaccg cccgtcacac cacgagagtt tgtaacaccc gaagtcggtg aggtaacctt ttggagccag ccgcctaagg tgggacagat gattggggtg aagtcgtaac aaggtaagcc gt Already disclosed in the existing patent: 201910694197.6.

[0034] Example 2, genetic stability detection of Streptococcus thermophilus inm25-ST The thermophilic Streptococcus inm25-ST from Example 1 was propagated for 10 consecutive generations in M17 liquid medium. The first, fifth, and tenth generation samples were inoculated into the screening medium, respectively. The fermentation temperature was 37°C, and the fermentation time was 5 h. Physical and chemical indicators were tested, and the methods for testing hydrogen sulfide, methyl mercaptan, and acetaldehyde contents were referred to Example 1. Eggs and milk were also fermented, and the method for rescreening was referred to Example 1. After the fermentation, sensory evaluation was performed to determine the stability of the passages. Specific data are shown in Table 3.

[0035] Table 3 Results of passage stability test

[0036] The results in Table 3 show that the fermentation performance of Streptococcus thermophilus inm25-ST strains of different generations is normal, the changes in hydrogen sulfide, methyl mercaptan and acetaldehyde contents are within 10%, the strain has good genetic stability and meets the requirements for production and use.

[0037] Example 3, Streptococcus thermophilus inm25-ST production of egg yogurt The concentration of different thermophilic Streptococcus inm25-ST was 10 4 -10 8 CFU / mL was inoculated into the screening culture medium to determine the optimal inoculation concentration. The content of hydrogen sulfide, methyl mercaptan and acetaldehyde in eggs and milk was detected according to the method described in Example 1. Thermophilic Streptococcus inm25-ST was inoculated into eggs and milk, and the concentration of inoculated fermentation bacteria was 10 4 -10 8 CFU / mL, egg yogurt was made respectively, and the fermentation index referred to the national standard GB 19302-2025 "Fermented Milk", and inm29-ST was used as the control strain. The results are shown in Table 4.

[0038] Table 4 Contents of hydrogen sulfide, methyl mercaptan and acetaldehyde in egg yogurt

[0039]

[0040] Table 5 Sensory evaluation results of egg yogurt

[0041] Note: Each assessment has a full score of 10 points, with a scoring interval of 0.1, and the comprehensive score is the sum of the values ​​of each item. The results in Tables 4 and 5 show that thermophilic Streptococcus inm25-ST can significantly reduce the content of hydrogen sulfide, methyl mercaptan and acetaldehyde in whole-grain yogurt, and the higher the inoculation amount, the lower the content of hydrogen sulfide, methyl mercaptan and acetaldehyde. However, too high or too low inoculation concentration of thermophilic Streptococcus inm25-ST will affect the sourness, sweetness and taste of yogurt. The most suitable inoculation concentration is 1.0´10 7 CFU / mL, this concentration can reduce the content of hydrogen sulfide, methyl mercaptan and acetaldehyde, and improve the flavor and taste of eggs and milk.

[0042] Example 4, Streptococcus thermophilus inm25-ST makes custard pudding The final concentration of Streptococcus thermophilus inm25-ST was 10 7 CFU / mL was used to prepare the custard pudding bacteria concentration, and another group was inoculated with inm29-ST as the control group. The preparation method of custard pudding was as follows: 30 g of white sugar, 500 mL of milk, and 50 mL of whole egg liquid were mixed evenly, and inoculated with inm25-ST. The fermentation temperature was 37°C, the fermentation time was 5 h, and then cooled at 4°C.

[0043] After the fermentation was completed, the contents of hydrogen sulfide, methyl mercaptan, and acetaldehyde were detected according to the method in Experimental Example 1. At the same time, professional tasters were asked to conduct a sensory evaluation of the custard pudding flavor. The results are recorded in Table 6.

[0044] Table 6 Detection and sensory evaluation results of hydrogen sulfide, methyl mercaptan and acetaldehyde in custard pudding

[0045] Note: Each sensory evaluation item has a full score of 10 points, with a scoring interval of 0.1, and the comprehensive score is the sum of the values ​​of each item. From the results in Table 6, we can see that the egg custard pudding 7 CFU / mL thermophilic Streptococcus inm25-ST can significantly reduce the content of hydrogen sulfide, methyl mercaptan and acetaldehyde in custard making; in addition, it can also improve the sensory evaluation of custard pudding, increase the flavor and taste of custard pudding, and make the custard pudding fragrant, sweet and sour.

[0046] Example 5: Preparation of Phoenix Yogurt with Thermophilus Streptococcus inm25-ST The final concentration of Streptococcus thermophilus inm25-ST was 10 7 Phoenix yogurt was inoculated with a concentration of 100 CFU / mL. Another group inoculated with inm29-ST was used as a control group. Phoenix milk was prepared by mixing 160g of milk, 16g of egg yolk liquid, and 20g of white sugar (optional). The mixture was stirred evenly and sterilized at 90°C for 5 minutes. The mixture was then cooled to 37°C and inoculated with thermophilic Streptococcus inm25-ST. The fermentation temperature was 37°C and the fermentation time was 5 hours. After fermentation, the hydrogen sulfide, methyl mercaptan, and acetaldehyde contents of the Phoenix yogurt were tested according to the method in Experimental Example 1. Professional tasters were also invited to conduct a sensory evaluation of the Phoenix yogurt flavor. The results are recorded in Table 7.

[0047] Table 7 Sensory evaluation results of Phoenix yogurt test and croissant

[0048] Note: Each sensory evaluation item has a full score of 10 points, with a scoring interval of 0.1, and the comprehensive score is the sum of the values ​​of each item. From the results in Table 7, we can see that 10 7 CFU / mL thermophilic Streptococcus inm25-ST was used to make Phoenix yogurt, which could significantly reduce the content of hydrogen sulfide, methyl mercaptan and acetaldehyde in Phoenix yogurt; in addition, it could also improve the sensory evaluation of Phoenix milk, increase the aroma, enhance the flavor and taste, and make Phoenix milk fragrant, sweet and sour.

[0049] Example 6: Preparation of Ginger Egg Yogurt with Streptococcus thermophilus inm25-ST The final concentration of Streptococcus thermophilus inm25-ST was 10 7 The inoculation concentration of ginger egg milk was prepared at a dose of CFU / mL, and another group of inoculated inm29-ST was taken as the control group. The preparation method of ginger egg milk was as follows: 180g fresh milk, 18g whole egg liquid or egg yolk, 12g ginger juice, sterilization temperature 90℃, time 5 min, cooling to 37℃, adding thermophilic Streptococcus inm25-ST, fermentation temperature 37℃, fermentation time 5h.

[0050] After the fermentation was completed, the contents of hydrogen sulfide, methyl mercaptan, and acetaldehyde in the ginger egg yogurt were detected according to the method in Experimental Example 1. At the same time, professional tasters were asked to perform sensory evaluation on the flavor. The results are recorded in Table 8.

[0051] Table 8 Ginger egg yogurt flavor detection and sensory evaluation results

[0052] Note: Each sensory evaluation item has a full score of 10 points, with a scoring interval of 0.1, and the comprehensive score is the sum of the values ​​of each item. From the results in Table 8, we can see that 10 7 CFU / mL thermophilic Streptococcus inm25-ST was used to make ginger egg yogurt, which can significantly reduce the content of hydrogen sulfide, methyl mercaptan and acetaldehyde; in addition, it can also improve the flavor of ginger yogurt, increase the aroma, reduce the spicy taste of ginger, and make the ginger yogurt fragrant, sweet and sour.

[0053] Based on the results of the above examples, the thermophilic Streptococcus inm25-ST (S treptococcus thermophilus ), used in egg and milk fermentation to remove fishy odor, without changing the existing process, can significantly improve the quality of related egg and milk products by reducing the content of hydrogen sulfide, methyl mercaptan and acetaldehyde, while also improving the aroma and taste of egg and milk products, significantly improving the quality of egg and milk products.

[0054] The above-described embodiments merely represent several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the scope of the present invention. Therefore, the scope of protection of the patent for this invention shall be subject to the appended claims.

Claims

1. A lactic acid bacterium for reducing egg odor, characterized in that: The strain is Streptococcus thermophilus (S treptococcus thermophilus )inm25-ST, the strain preservation number is CGMCC No.15446, the preservation date is: March 12, 2018, the preservation unit is: General Microbiology Center of China Culture Collection Administration, and the preservation address is: No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing.

2. Use of the lactic acid bacteria for reducing egg odor according to claim 1 in dairy products.

3. A starter culture prepared from lactic acid bacteria for reducing egg odor.

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