CN116694515A

CN116694515A - Lactobacillus helveticus AH071113 and application thereof in preparing yoghourt product by fermenting cow milk

Info

Publication number: CN116694515A
Application number: CN202310629769.9A
Authority: CN
Inventors: 黄国清; 李士玉; 肖军霞; 王志勇; 王英欣
Original assignee: Shandong Joy Biotechnology Co ltd; Qingdao Agricultural University
Current assignee: Shandong Joy Biotechnology Co ltd; Qingdao Agricultural University
Priority date: 2023-05-30
Filing date: 2023-05-30
Publication date: 2023-09-05

Abstract

The invention discloses lactobacillus helveticus AH071113 and application thereof in preparing a yoghurt product by fermenting cow milk. The invention separates and screens lactobacillus helveticus AH071113 from cow milk, which can show stronger casein hydrolysis capability in the fermentation process. The invention utilizes Lactobacillus helveticus AH071113 to ferment cow milk to prepare a yoghurt product, which comprises the steps of (1) culturing Lactobacillus helveticus and compound strain; (2) Homogenizing and sieving cow milk added with food sweetener, heating and sterilizing, and cooling to obtain emulsion; (3) Mixing the lactobacillus helveticus fermentation liquid and the compound strain fermentation liquid, adding the mixture into the emulsion, and fermenting and low-temperature after-ripening to obtain yoghourt; (4) And carrying out vacuum freeze drying treatment on the yoghurt to obtain the yoghurt powder. The invention utilizes lactobacillus helveticus AH071113 to ferment to obtain the yoghurt powder with the blood pressure reducing effect, and fills the blank of the domestic market of such products.

Description

Lactobacillus helveticus AH071113 and application thereof in preparing yoghourt product by fermenting cow milk

Technical Field

The invention belongs to the technical field of microbial fermentation, and particularly relates to lactobacillus helveticus AH071113 and application thereof in preparing a yoghurt product by fermenting cow milk.

Background

Hypertension is the most leading factor in heart disease, cerebrovascular disease, kidney disease and death, and is one of the most common chronic diseases that seriously threatens human health and affects quality of life and has caused great economic loss to society. Currently, patients suffering from hypertension are mainly treated by taking six major types of antihypertensive drugs for a long time, wherein the most commonly used drugs are angiotensin-converting enzyme (ACE) inhibitors, including captopril, alaskpride, lisinopril and the like. The medicament has good antihypertensive effect, but can produce side effect on human body and cause organism injury after long-term administration, and the ACE inhibitory peptide separated from natural food has mild efficacy and small toxic and side effect on human body, and has wide application prospect in preventing and treating hypertension.

Food-borne ACE inhibitory peptides (ACEIPs) refer to small peptides isolated from natural foods that have ACE inhibitory activity and blood pressure lowering effects. A variety of ACEIPs have been isolated and identified from a large number of proteins of diverse origin, but only a few have been used in functional food development, such as Ile-Pro-Pro (IPP), val-Pro-Pro (VPP) and Leu-Leu-Pro (LPP), derived from the milk casein sequence.

VPP and IPP are present in the casein amino acid sequence of milk, and since these two tripeptides are rich in Pro residues, a multi-enzyme system with very strong protein and polypeptide hydrolysis capacity is required to release them from casein. Among the many lactic acid bacteria, lactobacillus helveticus has been shown to have the strongest protease activity, in particular a Pro-specific enriched peptidase activity; in addition, as one of lactobacillus, lactobacillus helveticus has recognized safety and probiotic characteristics, and has the functions of reducing cholesterol, improving antioxidant activity, relieving lactose intolerance, improving digestive system and the like, so that the lactobacillus helveticus has great application potential in preparing functional dairy products for reducing blood pressure.

Due to the rapid development of society, the living standard of people is greatly improved, the proportion of dairy products in the diet life of residents is greatly increased, and the yoghourt is the most important product category in a plurality of dairy products, has various physiological effects of regulating intestines and stomach, maintaining intestinal flora of human bodies, delaying aging, promoting human development and the like on the basis of keeping the original nutritional ingredients of milk, and can meet the needs of lactose intolerant people, but the product needs refrigeration storage and has shorter shelf life. The yoghurt powder is prepared by removing about 95% of water in the yoghurt by a freeze drying method or a spray drying method, has the advantages of being capable of being stored at room temperature, convenient to carry and transport and long in shelf life on the basis of keeping the original nutritive value of the yoghurt, overcomes the limitation of the yoghurt and starts to receive attention of dairy factories. Therefore, the development of the fermented yoghurt powder which is rich in IPP and VPP and has the efficacy of reducing blood pressure based on lactobacillus helveticus has very wide application market and profound social significance.

Disclosure of Invention

The invention provides lactobacillus helveticus AH071113 and application thereof in preparing a yoghurt product by fermenting cow milk. The invention takes lactobacillus helveticus AH071113 as a fermentation strain to ferment cow milk to obtain fermented milk containing polypeptides VPP and IPP with definite in-vivo blood pressure reducing effect, and the fermented milk powder with blood pressure reducing effect is obtained through post-fermentation and vacuum freeze drying treatment.

In order to achieve the aim of the invention, the invention is realized by adopting the following technical scheme:

the invention provides a lactobacillus helveticus AH071113, which is classified and named as lactobacillus helveticus Lactobacillus helveticus and is preserved in China center for type culture collection, and the preservation number is CCTCCNO: m2023471.

Furthermore, the colony of the lactobacillus helveticus AH071113 is milky white, round, neat in edge, opaque, smooth in surface and 2-3 mm in diameter; the gram stain of the strain is positive, and the thallus is in a long rod shape.

Further, lactobacillus helveticus AH071113 has acid producing property, cholate resistance, strong protease activity and casein strong hydrolysis activity.

The invention also provides application of the lactobacillus helveticus AH071113 in preparing a yoghurt product by fermenting cow milk.

Further, the lactobacillus helveticus AH071113 fermented cow milk is used for preparing the yoghurt product as follows:

(1) Respectively culturing activated lactobacillus helveticus AH071113 and the compound strain to obtain lactobacillus helveticus fermentation liquor and compound strain fermentation liquor;

(2) Homogenizing and sieving cow milk added with food sweetener, heating and sterilizing, and cooling to obtain emulsion;

(3) Mixing the lactobacillus helveticus fermentation liquid and the compound strain fermentation liquid in the step (1), and adding the obtained mixed fermentation liquid into the emulsion in the step (2) for fermentation to obtain fermented milk;

(4) Performing low-temperature post-ripening on the fermented milk obtained in the step (3) to obtain yoghurt;

(5) And (3) performing vacuum freeze drying treatment on the yoghurt obtained in the step (3) to obtain the yoghurt powder.

Further, the culture conditions of lactobacillus helveticus AH071113 in the step (1) are as follows: the culture inoculation amount is 3% -7% (v/v), the pH of the culture medium is 4.0-8.0, the culture temperature is 35-39 ℃, and the activation time is 15-21 h.

Further, the activating method of lactobacillus helveticus AH071113 in the step (1) is as follows: activation and expansion culture of lactobacillus helveticus AH 071113: 100mL of MRS broth is filled into a 250mL triangular flask, the pH of a culture medium is adjusted to 6.0, sterilization is carried out, 1mL of lactobacillus helveticus AH071113 preservation bacterial liquid is sucked by a sterile suction tube and is connected into the culture medium, the culture medium is placed into a biochemical incubator for culture at 37 ℃ for 18 hours, lactobacillus helveticus AH071113 generation seed liquid is obtained, the culture medium is transferred to 2-3 generations to restore bacterial activity, and then the culture medium is transferred to an MRS culture inclined plane for preservation.

Further, the culture conditions of lactobacillus helveticus AH071113 in the step (1) are as follows: colonies were picked from the MRS culture slants with an inoculating loop in basal medium and cultured in a biochemical incubator at 37℃for 18h.

Further, the compound strain in the step (1) is one or two of streptococcus thermophilus and lactobacillus bulgaricus.

Optimally, the compound strain in the step (1) is streptococcus thermophilus and lactobacillus bulgaricus.

Further, the food sweetener in the step (2) is at least one of white granulated sugar, xylitol, glucose, fructose, lactose and maltose; the addition amount of the food sweetener is 3-9% of the mass of the cow milk.

Further, the food sweetener in the step (2) is white granulated sugar, and the adding proportion of the white granulated sugar is 5% of the mass of the cow milk.

Further, in the step (3), the fermentation temperature is 40-44 ℃ and the fermentation time is 6-12 h; the addition amount of the mixed fermentation liquor is 3-7% of the volume of the emulsion; the bacterial age of the lactobacillus helveticus AH071113 in the lactobacillus helveticus fermentation liquid is 9-15 h.

Optimally, the fermentation temperature in the step (3) is 43 ℃ and the fermentation time is 8 hours; the addition amount of the mixed fermentation liquor is 5% of the volume of the emulsion; the bacterial age of lactobacillus helveticus AH071113 in the lactobacillus helveticus fermentation liquid is 12h.

Further, in the step (3), the mixing ratio of the lactobacillus helveticus fermentation liquor and the compound strain fermentation liquor is 1:1-1:2.

Optimally, the mixing ratio of the lactobacillus helveticus fermentation liquor, the streptococcus thermophilus fermentation liquor and the lactobacillus bulgaricus fermentation liquor in the step (3) is 1:1:1.

Further, the temperature of the low-temperature after-ripening in the step (4) is 0-7 ℃ and the time is 8-24 hours.

Optimally, the low-temperature after-ripening temperature in the step (4) is 4 ℃ and the time is 12 hours.

Further, pre-freezing the fermented milk for 12 hours at the temperature of minus 80 ℃ before the vacuum freeze drying treatment in the step (5); the vacuum freeze drying time was 72h.

Further, the yogurt product has an auxiliary blood pressure lowering effect, wherein the VPP content is not less than 0.019% (w/w) and the IPP content is not less than 0.019% (w/w).

The invention also provides application of the yoghurt product in preparation of blood pressure lowering food.

Compared with the prior art, the invention has the following advantages and beneficial effects:

the invention aims at VPP and IPP with definite in-vivo blood pressure reducing effect, and provides guarantee for the blood pressure reducing effect through lactobacillus helveticus AH071113 fermentation products. At present, antihypertensive drugs for treating hypertension are mostly synthesized ACE inhibitors, which have quite a plurality of side effects on certain organs and physiological functions of human bodies, but the fermented milk powder containing VPP and IPP with antihypertensive effect, which is obtained by fermenting cow milk through lactobacillus helveticus AH071113, can be used as ACE inhibitors of natural sources for patients with hypertension, assist the patients with hypertension to reduce blood pressure daily and maintain cardiovascular health, and has quite wide application market and good industrialization prospect.

In addition, the lactobacillus helveticus AH071113 is a unique strain separated and screened from cow milk, has stronger casein hydrolyzing capacity than other lactobacillus helveticus strains in the fermentation process, and can release higher content of bioactive peptide while shortening the fermentation time of the cow milk, thereby having relatively better antihypertensive effect. The invention utilizes lactobacillus helveticus AH071113 to ferment cow milk to prepare the yoghurt powder with the blood pressure reducing effect, no report on the yoghurt powder with the blood pressure reducing effect or the yoghurt powder based on lactobacillus helveticus AH071113 is available in domestic market at present, so that the lactobacillus helveticus AH071113 has great application potential in the development and production of domestic functional yoghurt and powder.

Drawings

FIG. 1 shows the phylogenetic tree analysis of the AH071113 strain.

FIG. 2 is a colony morphology and cell morphology diagram of Lactobacillus helveticus AH 071113.

FIG. 3 is a graph showing the acid and bile salt resistant activity of Lactobacillus helveticus AH 071113.

FIG. 4 is a graph showing the protease activity and casein hydrolyzing activity of Lactobacillus helveticus AH071113 in examples 2-4 with other strains.

Fig. 5 is a schematic diagram of the preparation flow of yoghurt fermented powder.

FIG. 6 is a graph of the fermentation growth of Lactobacillus helveticus AH 071113.

FIG. 7 is a graph showing the effect of different growth conditions on the growth of Lactobacillus helveticus AH071113 in examples 5-13.

FIG. 8 is a graph showing the effect of different fermentation culture conditions on sensory scores of fermented milk in examples 5 to 13.

FIG. 9 is a graph showing the effect of different fermentation conditions on acidity of fermented milk in examples 5 to 13.

FIG. 10 is a graph showing the effect of different fermentation conditions on the colony count of fermented milk in examples 5 to 13.

FIG. 11 is a graph showing the effect of different fermentation conditions on the VPP content of fermented milk in examples 5 to 13.

FIG. 12 is a graph showing the effect of different fermentation conditions on the IPP content of fermented milk in examples 5 to 13.

FIG. 13 shows the results of different ratios of the strains in examples 14 to 17 on pH, degree of hydrolysis, OD of the fermented milk ₆₀₀ And the effect of acidity; wherein A is the pH results of the fermented milks of examples 14 to 17, B is the hydrolysis degree results of the fermented milks of examples 14 to 17, and C is the OD of examples 14 to 17 ₆₀₀ As a result, D is the acidity result of examples 14-17.

FIG. 14 shows the effect of different ratios of the strains of examples 14-17 on the final effect of the fermented milk, wherein A is the result of example 14, B is the result of example 15, C is the result of example 16, and D is the result of example 17.

FIG. 15 is a GC-MS/MS spectrum for qualitatively detecting IPP.

FIG. 16 is a GC-MS/MS spectrum for qualitatively detecting VPP.

Detailed Description

The technical scheme of the invention is further described in detail below with reference to the specific embodiments. The experimental methods in the following examples, in which specific conditions are not specified, are generally commercially available materials under conventional conditions or under conditions recommended by the manufacturer, and detailed sources are not specified.

A method for separating, screening and identifying lactobacillus helveticus AH071113, comprising the steps of:

1. separation and identification

Cow's milk was subjected to plating culture after diluted with 0.9% physiological saline in a proper gradient, while streaking was performed on the MRS solid medium plate, and the plated and streaked plate was placed in a biochemical incubator at 37℃for stationary culture for 48 hours. The single colony with smooth and opaque surface and milky white is selected for gram staining and microscopic examination, and long rod-shaped gram positive bacteria are selected and streaked and purified 2-3 times on MRS solid culture medium. And (3) picking single colonies which are streaked and purified, inoculating the single colonies to an MRS liquid culture medium, continuously culturing for 24 hours at 37 ℃, and then mixing bacterial liquid and sterilized glycerol according to the ratio of 7:3, and placing the mixed bacterial liquid and sterilized glycerol in a refrigerator at the temperature of minus 80 ℃ for preservation.

The screened strain was sent to Shanghai Biotechnology Co.Ltd for 16S RNA sequencing and homology alignment, and strain AH071113 was determined to be Lactobacillus helveticus (FIG. 1).

2. Morphological observation

Colony morphology and gram-stained cell morphology were observed for lactobacillus helveticus AH071113, and the results are shown in fig. 2. The strain has smooth surface, raised center and regular edge, and forms milky colony with diameter of 2-3 mm on MRS solid culture medium. Cells are in the form of long rods and often grow as pellets in liquid medium. The strain was inoculated into an MRS liquid medium test tube containing 0.04% bromocresol green indicator, placed in a biochemical incubator at 37℃for 12 hours, and the liquid color in the test tube turned to yellowish green.

Strain AH071113 was subjected to the strain preservation, deposit unit of lactobacillus helveticus AH 071113: china Center for Type Culture Collection (CCTCC); address: chinese university of Wuhan; preservation date: 2023, 04, 06; lactobacillus helveticus Lactobacillus helveticus AH071113 has a preservation number of CCTCC NO: m2023471.

3. Acid-resistant and bile-resistant salt

Inoculating activated lactobacillus helveticus AH071113 to the sterilized bacteria respectively with pH of 3.0, 4.0 and 5.0; the culture medium of 3% NaCl and 0.3% ox gall salt is placed in a constant temperature incubator at 37 ℃ for 6 hours, and then the viable bacteria rate is measured. As shown in FIG. 3, lactobacillus helveticus AH071113 has acid and bile salt resistant properties, and can smoothly enter the small intestine to colonise through the stomach environment of human body to perform its function.

A method for preparing yoghurt fermented powder with blood pressure reducing function by fermenting cow milk with lactobacillus helveticus AH071113, the preparation flow chart of which is shown in fig. 5, comprising the following steps:

1. activation and expansion culture of lactobacillus helveticus AH 071113: 100mL of MRS broth is filled into a 250mL triangular flask, the pH of the culture medium is adjusted to 6.0, sterilization is carried out, 1mL of lactobacillus helveticus AH071113 preservation bacterial liquid is sucked by a sterile suction tube, and is inoculated into the culture medium, and the culture medium is placed into a biochemical incubator for culture at 37 ℃ for 18 hours, so that lactobacillus helveticus AH071113 generation seed liquid is obtained.

The fermentation conditions for the second generation transfer of lactobacillus helveticus AH071113 are: 100mL of MRS broth is filled in a 250mL triangular flask, the pH is adjusted to 6.0, 5% of first-generation lactobacillus helveticus AH071113 seed solution is inoculated after sterilization, and the culture is carried out in a biochemical incubator at 37 ℃ for 12h, thus obtaining lactobacillus helveticus AH071113 fermentation broth. The fermentation curve of lactobacillus helveticus AH071113 is shown in fig. 6.

The conditions for the expansion culture of streptococcus thermophilus are as follows: colonies are picked from an MRS culture inclined plane by an inoculating loop and are cultured in a biochemical incubator at 37 ℃ for 12 hours, so as to obtain second-generation bacterial suspension. The fermentation conditions are as follows: 100mL of MRS broth is filled into a 250mL triangular flask, 5% of second-generation streptococcus thermophilus bacterial suspension is inoculated into the flask after sterilization, and the flask is placed into a biochemical incubator for culture at 37 ℃ for 9 hours, so as to obtain streptococcus thermophilus fermentation broth.

The conditions for the expansion culture of lactobacillus bulgaricus are as follows: colonies are picked from an MRS culture inclined plane by an inoculating loop and are cultured in a biochemical incubator at 37 ℃ for 18 hours, so that second-generation bacterial suspension is obtained. The fermentation conditions are as follows: 100mL of MRS broth is filled into a 250mL triangular flask, 5% of second-generation lactobacillus bulgaricus bacterial suspension is inoculated into the flask after sterilization, and the flask is placed into a biochemical incubator for culture at 37 ℃ for 13 hours, so as to obtain lactobacillus bulgaricus fermentation broth.

Wherein, the composition of each culture medium is as follows:

(1) MRS broth (g/L): 10.0 parts of peptone, 8.0 parts of beef extract powder, 4.0 parts of yeast extract powder, 20.0 parts of glucose, 2.0 parts of dipotassium hydrogen phosphate, 2.0 parts of diammonium citrate, 5.0 parts of sodium acetate, 0.2 parts of magnesium sulfate, 0.05 parts of manganese sulfate, 1.0 parts of tween 80, 1L of distilled water and 5.7+/-0.2 parts of pH.

(2) MRS slant Medium (g/L): 10.0 parts of peptone, 5.0 parts of beef extract powder, 4.0 parts of yeast extract powder, 20.0 parts of glucose, 2.0 parts of dipotassium hydrogen phosphate, 2.0 parts of diammonium citrate, 5.0 parts of sodium acetate, 0.2 parts of magnesium sulfate, 0.05 parts of manganese sulfate, 15.0 parts of agar, 1.0 part of tween 80, 1L of distilled water and 6.2+/-0.2 parts of pH.

Because lactobacillus helveticus AH071113 has extremely strong proteolytic activity and a high-efficiency proteolytic system, and can hydrolyze casein in the fermentation process to release polypeptides VPP and IPP with definite in-vivo antihypertensive effect, the polypeptide is very suitable for releasing functional polypeptides with auxiliary antihypertensive effect from casein in the fermentation process. However, the yogurt obtained by fermentation with a single lactobacillus helveticus AH071113 has poor flavor, so that it needs to be compounded with other strains to improve the flavor and taste of the yogurt.

Streptococcus thermophilus and Lactobacillus bulgaricus are the two most commonly used strains for fermentation of yogurt. Lactobacillus bulgaricus can produce protease in the fermentation process to hydrolyze protein in milk and release a large amount of free amino acids, so that the growth and reproduction of streptococcus thermophilus are promoted; formate and carbon dioxide produced by the growth of Streptococcus thermophilus can promote acid production by Lactobacillus bulgaricus. The streptococcus thermophilus, the lactobacillus bulgaricus and the lactobacillus helveticus AH071113 can be compounded and fermented to obtain the fermented milk with good flavor.

2. Sterilization of cow milk: adding 600mL of cow milk into a 1L enamel jar, adding 5% white granulated sugar, stirring, homogenizing under 250bar, sieving, heating to 75deg.C for 20s, cooling to 43deg.C, and maintaining the temperature to obtain sterilized emulsion.

The milk used in the invention is commercially available Mongolian Niu Miejun milk, and the milk can be replaced by commercially available milk of other brands, fresh raw milk or milk powder.

Wherein, the composition of the sterilized milk used in the invention is as follows: protein 3.2 (g/100 mL), fat 3.8 (g/mL), carbohydrate 4.8 (g/mL), sodium 53 (mg/mL), calcium 100 (mg/mL).

3. Fermentation of yogurt: 200mL of the treated sterilized cow milk is inoculated into a 1L fermentation bottle, then 5 percent (v/v) of lactobacillus helveticus AH071113 with the bacterial age of 12h and fermentation liquid of streptococcus thermophilus and lactobacillus bulgaricus with proper proportion are inoculated, and the fermentation liquid is fermented for 8h in a yoghurt machine with the temperature of 43 ℃ to obtain the fermented milk.

The yogurt machine used in the invention is a Japanese Alice (iris) yogurt machine, and the yogurt machine can be replaced by other yogurt machines with adjustable temperature and time which are sold in the market.

4. Post-ripening of fermented milk: the fermented milk is placed in a refrigerator at 4 ℃ for fermentation for 10 hours.

The post-fermentation process of the yogurt is also a passivation and fermentation termination process, and the flavor substances of the passivated post-fermentation yogurt can be optimized, so that the yogurt has better use taste.

5. Vacuum freeze-drying treatment of fermented milk: the fermented milk after being after-ripened is placed in an ultralow temperature refrigerator at the temperature of minus 80 ℃ to be pre-frozen for 12 hours, and then is placed in a vacuum freeze dryer to be dried for 72 hours, so that the milky fermented milk powder with the fragrance of the yogurt, which is rich in VPP and IPP, is obtained, and the mass spectrograms of the milky fermented milk powder are shown in figures 15 and 16.

Example 1

Lactobacillus helveticus AH071113 was subjected to plating culture after diluting with a suitable gradient of 0.9% physiological saline, while streaking it on MRS solid medium plates, and the plated and streaked plates were placed in a biochemical incubator at 37 ℃ for resting culture for 48h. The coated colonies were observed under a biological microscope, and the streaked single colonies were picked up and stained with a biological microscope after gram staining treatment. The observation result of the strain is shown in figure 2, the strain AH071113 is a milky white circular colony, the edge is neat and opaque, the surface is smooth, and the diameter of the colony is 2-3 mm; the strain is positive after gram staining, and the thallus is in a long rod shape.

Example 2

100mL of MRS broth culture medium was inoculated into a 250mL Erlenmeyer flask, the pH of the broth was adjusted to 6.0, the broth was sterilized, 5mL of Lactobacillus helveticus AH071113 seed solution was aspirated by a sterile pipette, inoculated into sterilized culture medium having pH of 5.0, and cultured in a constant temperature incubator at 37℃for 18 hours. The bacterial liquid protease activity value of the process is 303U/mL, and the casein hydrolysis degree is 4.94%.

Example 3

100mL of MRS broth culture medium was inoculated into a 250mL Erlenmeyer flask, the pH of the broth was adjusted to 6.0, the broth was sterilized, 5mL of Lactobacillus helveticus CICC 6272 seed solution was aspirated by a sterile pipette, inoculated into sterilized culture medium having pH of 5.0, and cultured in a constant temperature incubator at 37℃for 18 hours. The bacterial liquid protease activity value of the process is 93U/mL, and the casein hydrolysis degree is 3.67%.

Example 4

100mL of MRS broth culture medium is inoculated into a 250mL triangular flask, the pH value of the broth is adjusted to 6.0, then the broth is sterilized, 5mL of lactobacillus helveticus CICC 20362 seed solution is sucked by a sterile suction tube, the broth is inoculated into a sterilized culture medium with the pH value of 5.0, and the broth is cultured for 18 hours in a constant temperature incubator at 37 ℃. The bacterial liquid protease activity value of the process is 188U/mL, and the casein hydrolysis degree is 3.79%.

The enzyme activities and casein hydrolyzing activities of Lactobacillus helveticus AH071113 and other Lactobacillus helveticus strain bacterial solutions of examples 2-4 are shown in FIG. 4, and according to the culture conditions of each Lactobacillus helveticus in each example, the results of the enzyme activities and casein hydrolyzing activities of Lactobacillus helveticus AH071113 and other Lactobacillus helveticus strain bacterial solutions are compared, the total protease activities and casein hydrolyzing activities of Lactobacillus helveticus AH071113 bacterial solutions are strongest, and respectively reach 303U/mL and 4.94%, so that the protein hydrolyzing activity of Lactobacillus helveticus AH071113 is superior to that of other strains, and then the Lactobacillus helveticus AH071113 has extremely strong protein hydrolyzing activity and high-efficiency protein hydrolyzing system.

Example 5

100mL of MRS broth culture medium was inoculated into a 250mL Erlenmeyer flask, the pH of the broth was adjusted to 5.0, the broth was sterilized, 4mL of Lactobacillus helveticus AH071113 seed solution was aspirated by a sterile pipette, inoculated into sterilized culture medium having pH of 5.0, and cultured in a constant temperature incubator at 36℃for 18 hours. The OD value of the bacterial liquid in the process is 1.571.

Adding 600mL of cow milk into a 1L enamel jar, homogenizing under 250bar, sieving, heating to 75deg.C for 20s, cooling to 43deg.C, and maintaining the temperature to obtain sterilized emulsion.

After scalding 1L of the fermentation cup with hot water, 200mL of the treated sterilized milk is inoculated, 8mL of the Lactobacillus helveticus AH071113 bacterial liquid cultured for 11h is sucked by a sterile suction tube, inoculated into the sterilized milk, and fermented for 8h in a yogurt machine at 42 ℃.

Fermenting the fermented milk after 8h in a refrigerator at 4 ℃ for 10h. The acidity of the fermented milk is 91 DEG T, the sensory score is 75.29, the color of the fermented milk is uniform and consistent, and the color is yellow; the tissue state is uneven and not fine, a small amount of particles are present, the sand-like feel is present, obvious whey is separated out, and the viscosity is slightly thin; the fragrance is flat and light; the fermented lactic acid has excessive taste, weak thick feel and thinner taste.

The fermented milk was centrifuged at a high speed at 10000rpm for 15min at 4℃to collect the supernatant. The supernatant is placed in an ultralow temperature refrigerator at the temperature of minus 80 ℃ to be pre-frozen for 12 hours, and then dried in a vacuum refrigerator for 3 days to obtain fermented milk powder rich in VPP and IPP, wherein the VPP content is 0.022% (w/w) and the IPP content is 0.023% (w/w).

Example 6

100mL of MRS broth culture medium was inoculated into a 250mL Erlenmeyer flask, the pH of the broth was adjusted to 5.5, the broth was sterilized, 5mL of Lactobacillus helveticus AH071113 seed solution was aspirated by a sterile pipette, inoculated into sterilized culture medium having pH of 5.5, and cultured in a constant temperature incubator at 36℃for 18 hours. The OD value of the bacterial liquid in the process is 1.701.

After scalding 1L of the fermentation cup with hot water, 200mL of the treated sterilized milk is inoculated, 10mL of the lactobacillus helveticus AH071113 bacterial liquid cultured for 11h is sucked by a sterile suction tube, inoculated into the sterilized milk, and fermented for 8h in a yoghurt machine at 43 ℃.

Fermenting the fermented milk after 8h in a refrigerator at 4 ℃ for 10h. The acidity of the fermented milk is 80 DEG T, the sensory score is 76.14, the color of the fermented milk is uniform and consistent, and the color is milky; the tissue state is uniform and fine, small particles are arranged, no bubbles exist, slightly whey is separated out, and the hardness is egg-thick and firm; the fragrance is flat and light; the fermented lactic acid has poor taste, fine texture and slightly astringent taste.

The fermented milk was centrifuged at a high speed at 10000rpm for 15min at 4℃to collect the supernatant. The supernatant is placed in an ultralow temperature refrigerator at the temperature of minus 80 ℃ to be pre-frozen for 12 hours, and then dried in a vacuum refrigerator for 3 days to obtain fermented milk powder rich in VPP and IPP, wherein the content of the VPP is 0.029% (w/w) and the content of the IPP is 0.021% (w/w).

Example 7

100mL of MRS broth culture medium was inoculated into a 250mL Erlenmeyer flask, the pH of the broth was adjusted to 6.0, the broth was sterilized, 6mL of Lactobacillus helveticus AH071113 seed solution was aspirated by a sterile pipette, inoculated into sterilized culture medium having pH of 6.0, and cultured in a constant temperature incubator at 36℃for 18 hours. The OD value of the bacterial liquid in the process is 1.835.

After scalding 1L of the fermentation cup with hot water, 200mL of the treated sterilized milk is inoculated, 12mL of the Lactobacillus helveticus AH071113 bacterial liquid cultured for 11h is sucked by a sterile suction tube, inoculated into the sterilized milk, and fermented for 8h in a yoghurt machine at 44 ℃.

Fermenting the fermented milk after 8h in a refrigerator at 4 ℃ for 10h. The acidity of the fermented milk obtained in this process was 92℃T and the organoleptic score was 74.57. The color of the fermented milk is uniform and consistent, and the color is yellow; the tissue state is uneven, a small amount of particles are present, the tissue state is rough, and a small amount of whey is separated out; the fragrance is slightly odorous; the fermented milk has pure cow milk taste, weak sour taste and slightly astringent taste.

The fermented milk was centrifuged at a high speed at 10000rpm for 15min at 4℃to collect the supernatant. The supernatant is placed in an ultralow temperature refrigerator at the temperature of minus 80 ℃ to be pre-frozen for 12 hours, and then dried in a vacuum refrigerator for 3 days to obtain fermented milk powder rich in VPP and IPP, wherein the VPP content is 0.032% (w/w) and the IPP content is 0.021% (w/w).

Example 8

100mL of MRS broth culture medium was inoculated into a 250mL Erlenmeyer flask, the pH of the broth was adjusted to 5.0, the broth was sterilized, 6mL of Lactobacillus helveticus AH071113 seed solution was aspirated by a sterile pipette, inoculated into sterilized culture medium having pH of 5.0, and cultured in a constant temperature incubator at 37℃for 18 hours. The OD value of the bacterial liquid in the process is 1.679.

After scalding 1L of the fermentation cup with hot water, 200mL of the treated sterilized milk is inoculated, 8mL of the Lactobacillus helveticus AH071113 bacterial liquid cultured for 12h is sucked by a sterile suction tube, inoculated into the sterilized milk, and fermented for 8h in a yogurt machine at 43 ℃.

Fermenting the fermented milk after 8h in a refrigerator at 4 ℃ for 10h. The acidity of the fermented milk in this process was 75°t and the organoleptic score was 73.86. The color of the fermented milk is uneven, and the color is yellowish; the tissue state is uneven and fine, small particles are arranged, small bubbles are arranged, whey is separated out, and the viscosity is too thin; the fragrance is slightly odorous; the fermented milk has bad sour taste, fine texture and bad taste.

The fermented milk was centrifuged at a high speed at 10000rpm for 15min at 4℃to collect the supernatant. The supernatant is placed in an ultralow temperature refrigerator at the temperature of minus 80 ℃ to be pre-frozen for 12 hours, and then dried in a vacuum refrigerator for 3 days to obtain fermented milk powder rich in VPP and IPP, wherein the content of the VPP is 0.026% (w/w) and the content of the IPP is 0.021% (w/w).

Example 9

100mL of MRS broth culture medium was inoculated into a 250mL Erlenmeyer flask, the pH of the broth was adjusted to 5.5, the broth was sterilized, 4mL of Lactobacillus helveticus AH071113 seed solution was aspirated by a sterile pipette, inoculated into sterilized culture medium having pH of 5.5, and cultured in a constant temperature incubator at 37℃for 18 hours. The OD value of the bacterial liquid in the process is 1.759.

After scalding 1L of the fermentation cup with hot water, 200mL of the treated sterilized milk is inoculated, 10mL of the lactobacillus helveticus AH071113 bacterial liquid cultured for 12h is sucked by a sterile suction tube, inoculated into the sterilized milk, and fermented for 8h in a yoghurt machine at 44 ℃.

Fermenting the fermented milk after 8h in a refrigerator at 4 ℃ for 10h. The acidity of the fermented milk obtained in this process was 77℃T and the organoleptic score was 78.00. The color of the fermented milk is uniform and consistent, and the color is milky; the tissue state is uniform and fine, no large particles or bubbles exist, a small amount of whey is separated out, and the viscosity is proper; the fragrance is flat and light; the fermented milk has excessive sour taste, fine and smooth texture and weak thick feel.

The fermented milk was centrifuged at a high speed at 10000rpm for 15min at 4℃to collect the supernatant. The supernatant is placed in an ultralow temperature refrigerator at the temperature of minus 80 ℃ to be pre-frozen for 12 hours, and then dried in a vacuum refrigerator for 3 days to obtain fermented milk powder rich in VPP and IPP, wherein the VPP content is 0.037% (w/w) and the IPP content is 0.029% (w/w).

Example 10

100mL of MRS broth culture medium was inoculated into a 250mL Erlenmeyer flask, the pH of the broth was adjusted to 6.0, the broth was sterilized, 5mL of Lactobacillus helveticus AH071113 seed solution was aspirated by a sterile pipette, inoculated into sterilized culture medium having pH of 6.0, and cultured in a constant temperature incubator at 37℃for 18 hours. The OD value of the bacterial liquid in the process is 1.894.

After scalding 1L of the fermentation cup with hot water, 200mL of the treated sterilized milk is inoculated, 12mL of the lactobacillus helveticus AH071113 bacterial liquid cultured for 12h is sucked by a sterile suction tube, inoculated into the sterilized milk, and fermented for 8h in a yogurt machine at 42 ℃.

Fermenting the fermented milk after 8h in a refrigerator at 4 ℃ for 10h. The acidity of the fermented milk obtained in this process was 84℃T and the organoleptic score was 72.57. The color of the fermented milk is uneven, and the color is yellowish; poor curdlan in tissue state, bubbles, severe precipitation of whey and infirm; the fragrance is flat and light; the fermented milk has too heavy sour taste and slightly astringent taste.

The fermented milk was centrifuged at a high speed at 10000rpm for 15min at 4℃to collect the supernatant. The supernatant is placed in an ultralow temperature refrigerator at the temperature of minus 80 ℃ to be pre-frozen for 12 hours, and then dried in a vacuum refrigerator for 3 days to obtain fermented milk powder rich in VPP and IPP, wherein the VPP content is 0.021% (w/w) and the IPP content is 0.019% (w/w).

Example 11

100mL of MRS broth culture medium was inoculated into a 250mL Erlenmeyer flask, the pH of the broth was adjusted to 5.0, the broth was sterilized, 5mL of Lactobacillus helveticus AH071113 seed solution was aspirated by a sterile pipette, inoculated into sterilized culture medium having pH of 5.0, and cultured in a constant temperature incubator at 38℃for 18 hours. The OD value of the bacterial liquid in the process is 1.653.

After scalding 1L of the fermentation cup with hot water, 200mL of the treated sterilized milk is inoculated, 8mL of the lactobacillus helveticus AH071113 bacterial liquid cultured for 13h is sucked by a sterile suction tube, inoculated into the sterilized milk, and fermented for 8h in a yoghurt machine at 44 ℃.

Fermenting the fermented milk after 8h in a refrigerator at 4 ℃ for 10h. The acidity of the fermented milk obtained in this process was 89℃T and the organoleptic score was 76.43. The color of the fermented milk is uniform and consistent, and the color is yellow; the tissue state is uneven, a small amount of particles are present, the tissue state is rough, and a small amount of whey is separated out; the fragrance is slightly odorous; the fermented milk has pure cow milk taste, poor sour taste, and slightly astringent taste.

The fermented milk was centrifuged at a high speed at 10000rpm for 15min at 4℃to collect the supernatant. The supernatant is placed in an ultralow temperature refrigerator at the temperature of minus 80 ℃ to be pre-frozen for 12 hours, and then dried in a vacuum refrigerator for 3 days to obtain fermented milk powder rich in VPP and IPP, wherein the content of the VPP is 0.031% (w/w) and the content of the IPP is 0.032% (w/w).

Example 12

100mL of MRS broth culture medium was inoculated into a 250mL Erlenmeyer flask, the pH of the broth was adjusted to 5.5, the broth was sterilized, 6mL of Lactobacillus helveticus AH071113 seed solution was aspirated by a sterile pipette, inoculated into sterilized culture medium having pH of 5.5, and cultured in a constant temperature incubator at 38℃for 18 hours. The OD value of the bacterial liquid in the process is 1.720.

After scalding 1L of the fermentation cup with hot water, 200mL of the treated sterilized milk is inoculated, 10mL of the lactobacillus helveticus AH071113 bacterial liquid cultured for 13h is sucked by a sterile suction tube, inoculated into the sterilized milk, and fermented for 8h in a yogurt machine at 42 ℃.

Fermenting the fermented milk after 8h in a refrigerator at 4 ℃ for 10h. The acidity of the fermented milk obtained in this process was 87℃T and the organoleptic score was 75.00. The color of the fermented milk is uniform and consistent, and the color is yellow; the tissue state is uniform and not fine, small particles are arranged, no bubbles exist, a small amount of whey is separated out, the hardness is weak, and the viscosity is thin; the fragrance is flat and light; the fermented milk has heavy sour taste, thick texture, weak sense and slightly astringent taste.

The fermented milk was centrifuged at a high speed at 10000rpm for 15min at 4℃to collect the supernatant. The supernatant is placed in an ultralow temperature refrigerator at the temperature of minus 80 ℃ to be pre-frozen for 12 hours, and then dried in a vacuum refrigerator for 3 days to obtain fermented milk powder rich in VPP and IPP, wherein the content of the VPP is 0.019% (w/w) and the content of the IPP is 0.021% (w/w).

Example 13

100mL of MRS broth culture medium was inoculated into a 250mL Erlenmeyer flask, the pH of the broth was adjusted to 6.0, the broth was sterilized, 4mL of Lactobacillus helveticus AH071113 seed solution was aspirated by a sterile pipette, inoculated into sterilized culture medium having pH of 6.0, and cultured in a constant temperature incubator at 38℃for 18 hours. The OD value of the bacterial liquid in the process is 1.870.

After scalding 1L of the fermentation cup with hot water, 200mL of the treated sterilized milk is inoculated, 12mL of the lactobacillus helveticus AH071113 bacterial liquid cultured for 13h is sucked by a sterile suction tube, inoculated into the sterilized milk, and fermented for 8h in a yoghurt machine at 43 ℃.

Fermenting the fermented milk after 8h in a refrigerator at 4 ℃ for 10h. The acidity of the fermented milk obtained in this process was 88℃T and the organoleptic score was 79.57. The color of the fermented milk is uniform and consistent, and the color is milky; the tissue state is uniform and fine, large particles and bubbles are avoided, a small amount of whey is separated out, and the hardness is in the shape of an egg thick soup and is firm; the yoghurt fragrance exists; the fermented milk has slightly heavy sour taste, fine texture and thick feel of sour milk.

The fermented milk was centrifuged at a high speed at 10000rpm for 15min at 4℃to collect the supernatant. The supernatant is placed in an ultralow temperature refrigerator at the temperature of minus 80 ℃ to be pre-frozen for 12 hours, and then dried in a vacuum refrigerator for 3 days to obtain fermented milk powder rich in VPP and IPP, wherein the VPP content is 0.041% (w/w) and the IPP content is 0.039% (w/w).

The results of the OD value, the sensory score, the acidity, the colony count and the VPP and IPP content of the Lactobacillus helveticus AH071113 strain fluid of examples 5 to 13 are shown in FIG. 7, FIG. 8, FIG. 9, FIG. 10, FIG. 11 and FIG. 12, respectively, and the results of the OD value, the sensory score, the acidity and the colony count of the fermented milk and the VPP and IPP content of the Lactobacillus helveticus AH071113 strain fluid are compared according to the culture conditions of the Lactobacillus helveticus AH071113 strain and the fermentation conditions of the fermented milk in each example, so that the optimal culture conditions of the Lactobacillus helveticus AH071113 strain are the inoculation amount of 5%, the initial culture medium pH value of 6.0 and the culture temperature of 37 ℃. Comparing the flavor and taste result of the fermented milk with the sensory scores of the fermented milk, and obtaining the optimal fermentation condition of the fermented milk, namely 13 hours of inoculation bacteria age of lactobacillus helveticus AH071113, 5% of inoculation amount and 43 ℃ of fermentation temperature.

Example 14

100mL of MRS broth culture medium was inoculated into a 250mL Erlenmeyer flask, the pH of the broth was adjusted to 6.0, the broth was sterilized, 5mL of Lactobacillus helveticus AH071113 seed solution was aspirated by a sterile pipette, inoculated into sterilized culture medium having pH of 6.0, and cultured in a constant temperature incubator at 37℃for 18 hours.

100mL of MRS broth culture medium was inoculated into a 250mL Erlenmeyer flask, 5mL of Lactobacillus bulgaricus seed solution was pipetted into the culture medium, and the culture was performed in a constant temperature incubator at 37℃for 13 hours.

Adding 600mL of cow milk into a 1L enamel jar, adding 30g of white granulated sugar, stirring uniformly, homogenizing under 250bar, sieving, heating to 75deg.C for 20s, cooling to 43deg.C, and maintaining the temperature to obtain sterilized emulsion.

Scalding 1L fermentation cup with hot water, inoculating 200mL of treated sterilized milk, sucking 5mL of Lactobacillus helveticus AH071113 bacterial liquid cultured for 11h with a sterile straw, sucking 5mL of Lactobacillus bulgaricus bacterial liquid cultured for 13h with a sterile straw, inoculating into sterilized milk, and fermenting in a yogurt machine at 43 ℃ for 8h.

Fermenting the fermented milk after 8h in a refrigerator at 4 ℃ for 10h. The fermented milk obtained by the process has uniform and consistent color, and the color is milky white; the tissue state is uniform and fine, no large particles, no bubbles and whey are separated out, and the hardness is egg-thick soup-like and firm; the fragrance is flat and light; the fermented milk has pure cow milk taste, has weak sour taste, fine and smooth texture and slightly astringent taste.

Example 15

100mL of MRS broth culture medium was inoculated into a 250mL Erlenmeyer flask, 5mL of Streptococcus thermophilus seed solution was pipetted into the culture medium, and the culture was performed in a constant temperature incubator at 37℃for 9 hours.

Scalding 1L fermentation cup with hot water, inoculating 200mL of treated sterilized milk, sucking 5mL of the Lactobacillus helveticus AH071113 bacterial liquid cultured for 11h with a sterile straw, sucking 5mL of the Streptococcus thermophilus bacterial liquid cultured for 9h with a sterile straw, inoculating into sterilized milk, and fermenting in a yogurt machine at 43 ℃ for 8h.

Fermenting the fermented milk after 8h in a refrigerator at 4 ℃ for 10h. The fermented milk obtained by the process has uniform and consistent color, and the color is milky white; the tissue state is uniform and fine, no large particles or bubbles exist, slightly whey is separated out, the hardness is poor, the structure is not firm and the structure can flow; the fragrance is flat and light; the fermented milk has fine and smooth taste, high sweetness, poor sourness and weak thick feel.

Example 16

After scalding 1L of the fermentation cup with hot water, 200mL of the treated sterilized milk is inoculated, 3.5mL of the Lactobacillus helveticus AH071113 bacterial liquid cultured for 11h is sucked by a sterile suction pipe, 3.5mL of the Streptococcus thermophilus bacterial liquid cultured for 9h is sucked by a sterile suction pipe, 3.5mL of the Lactobacillus bulgaricus bacterial liquid cultured for 13h is sucked by a sterile suction pipe, and the mixture is inoculated into the sterilized milk and fermented for 8h in a yogurt machine at 43 ℃.

Fermenting the fermented milk after 8h in a refrigerator at 4 ℃ for 10h. The fermented milk obtained by the process has uniform and consistent color, and the color is milky white; the tissue state is uniform and fine, no large particles, no bubbles, no whey precipitation, the hardness is egg custard, and the structure is firm; the yoghourt has faint scent and proper sweetness; the fermented milk has fine and smooth texture and sweet and sour taste.

Example 17

Scalding 1L fermentation cup with hot water, inoculating 200mL of treated sterilized milk, sucking 5mL of the Streptococcus thermophilus bacterial liquid cultured for 9h with a sterile straw, sucking 5mL of the Lactobacillus bulgaricus bacterial liquid cultured for 13h with a sterile straw, inoculating into sterilized milk, and fermenting in a yogurt machine at 43 ℃ for 8h.

Fermenting the fermented milk after 10h in a refrigerator at 4 ℃ for 8h. The fermented milk obtained by the process has uniform and consistent color, and the color is milky white; the tissue state is uniform and fine, no large particles or bubbles exist, slightly whey is separated out, the hardness is slightly poor, and the tissue is not firm and flowable; the fragrance is flat and light; the fermented milk has fine and smooth texture, slightly high sweetness and insufficient sour taste.

The pH, degree of hydrolysis, and OD of the fermented milks of examples 14 to 17 ₆₀₀ And the acidity is shown in fig. 13, and the effect diagram of the fermented milk is shown in fig. 14, according to the compounding ratio of lactobacillus helveticus AH071113, streptococcus thermophilus and lactobacillus bulgaricus in each embodiment, the sensory evaluation effect of the fermented milk is finally obtained, the color, texture, tissue state and flavor of the fermented milk obtained when two strains are simultaneously compounded with lactobacillus helveticus AH071113 are better, and the compounding optimal ratio of the three is 1:1:1.

Example 18

Adding 600mL of cow milk into a 1L enamel jar, adding 30g of white granulated sugar and 20g of strawberry powder, uniformly stirring, homogenizing under 250bar, sieving, heating to 75 ℃ for 20s, cooling to 43 ℃ and preserving heat to obtain the sterilizing emulsion.

After scalding 1L of the fermentation cup with hot water, 200mL of the treated sterilized milk is inoculated, 3mL of the Lactobacillus helveticus AH071113 bacterial liquid cultured for 11h is sucked by a sterile suction pipe, 6mL of the Streptococcus thermophilus bacterial liquid cultured for 9h is sucked by a sterile suction pipe, 4mL of the Lactobacillus bulgaricus bacterial liquid cultured for 13h is sucked by a sterile suction pipe, and the sterilized milk is inoculated, and fermented for 8h in a yogurt machine at 43 ℃.

Fermenting the fermented milk after 10h in a refrigerator at 4 ℃ for 8h. The fermented milk obtained by the process has uniform color and pink color; the tissue state is uniform and fine, no large particles, no bubbles, no whey precipitation, the hardness is egg custard, and the structure is firm; the sweet taste is proper, and the sour milk and the strawberry are fragrant; the fermented milk has fine and smooth texture and sweet and sour taste.

Example 19

Fermenting the fermented milk after 10h in a refrigerator at 4 ℃ for 8h. And adding various fruits into the fermented yoghourt, and cutting into pieces, coconut grains and the like.

Example 20

The fermented milk obtained in example 16 was centrifuged at high speed at 10000rpm at 4℃for 15min, and the supernatant was collected. And (3) placing the supernatant in an ultralow temperature refrigerator at the temperature of minus 80 ℃, pre-freezing for 12 hours, and then drying in a vacuum refrigerator for 3 days to obtain freeze-dried powder.

Weighing a small amount of freeze-dried powder, placing the freeze-dried powder into a 5mL centrifuge tube, adding a proper amount of methanol for dissolution, then centrifuging at a high speed for 15min at a centrifugation speed of 10000rpm at a temperature of 4 ℃, and collecting supernatant; placing the supernatant in a clean plate, and evaporating the supernatant in a water bath at 70 ℃; then re-dissolving with acetonitrile reagent, sucking 1mL of the solution into a liquid phase bottle through 0.22 mu L of organic filter membrane by using a disposable syringe, and carrying out ultra-high resolution mass spectrometry.

The results of the ultra-high resolution mass spectrometry are shown in fig. 15-16, and according to the analysis of the high resolution secondary mass spectrograms of the standard products VPP and IPP, in the process of fermenting cow milk, lactobacillus helveticus AH071113 can hydrolyze casein to release polypeptides VPP and IPP with definite blood pressure reducing effect, and further show that the yoghurt with auxiliary blood pressure reducing effect can be obtained by fermenting cow milk through lactobacillus helveticus AH 071113.

Example 21

The fermented milk obtained in the example 16 is taken and placed into a centrifuge tube with the volume of 100mL, covered with a preservative film, perforated, placed into an ultralow temperature refrigerator with the temperature of-80 ℃ for pre-freezing for 12 hours, and then dried in a vacuum freezer for 3 days to obtain fermented milk freeze-dried powder, namely yoghurt powder with the auxiliary blood pressure reducing effect.

In summary, the pH of the initial medium has a relatively maximal effect on the growth of Lactobacillus helveticus AH071113, and Lactobacillus helveticus AH071113 is not acid-resistant during the growth process, and if the pH of the growth medium is too small, i.e. too acidic, it inhibits the growth or even does not grow of Lactobacillus helveticus AH071113, so that it is necessary to provide a suitable initial medium pH.

The influence of the fermentation temperature on the sensory score of the fermented milk is relatively large, the fermentation time is correspondingly increased when the fermentation temperature is too low, the fermentation time is too long, the strain fermentation is unbalanced, and the casein is not good in structure when solidified, so that the fermented yoghourt is poor in taste, and the fermentation is slow and is easy to cause mixed bacteria pollution so that the fermentation is failed. And when the fermentation temperature is too high, the activity of the fermentation strain is inhibited, and even the lactobacillus is killed, so that the fermentation of the yoghurt fails. It is therefore necessary to provide a suitable fermentation temperature for lactobacillus helveticus AH071113 and the built-up strain.

In addition, the fermentation temperature has relatively large influence on the content of VPP and IPP in the fermented milk, the fermentation time can be correspondingly prolonged when the fermentation temperature is too low, and the strain can cause insufficient nutrition in the too long fermentation process, so that the content of VPP and IPP in the fermented milk is lower due to the utilization of polypeptide VPP and IPP released during casein hydrolysis. However, too high a fermentation temperature can inhibit the activity of the fermented strain and even kill part of the lactic acid bacteria, so that the hydrolysis activity of the strain is weakened, and the casein cannot be hydrolyzed more to release active polypeptide, and the content of VPP and IPP in the fermented milk is low. Therefore, it is particularly important to provide a proper fermentation temperature for lactobacillus helveticus AH071113 and the compound strain.

The flavor of the fermented milk can be effectively improved by adding streptococcus thermophilus, lactobacillus bulgaricus and lactobacillus helveticus AH071113 to compound the fermented milk. The yogurt obtained by fermenting the lactobacillus helveticus AH071113 has poor taste and bad flavor, and needs to be compounded with other strains to improve the flavor and taste of the yogurt. The lactobacillus bulgaricus can increase the aroma of the fermented milk, the streptococcus thermophilus can increase the consistency of the fermented milk, compared with the lactobacillus bulgaricus and lactobacillus bulgaricus which are respectively single and are compounded and fermented with lactobacillus helveticus AH071113, the fermented milk obtained by compounding the two strains with lactobacillus helveticus AH071113 has better flavor, and the optimal ratio is 1:1:1.

Fruit powder, essence or fruit dices with different flavors are added into the fermented yoghourt with the after-fermentation ripeness to prepare fermented milk with different flavors, so that the flavor of the fermented milk is richer.

The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be apparent to one skilled in the art that modifications may be made to the technical solutions described in the foregoing embodiments, or equivalents may be substituted for some of the technical features thereof; such modifications and substitutions do not depart from the spirit and scope of the corresponding technical solutions.

Claims

1. The lactobacillus helveticus AH071113 is characterized in that the lactobacillus helveticus AH071113 is classified and named as lactobacillus helveticus Lactobacillus helveticus, and is preserved in China Center for Type Culture Collection (CCTCC) NO: m2023471.

2. Use of lactobacillus helveticus AH071113 as claimed in claim 1 for preparing a yoghurt product from fermented milk.

3. Use according to claim 2, characterized in that the step of preparing a yoghurt product by fermenting cow's milk with lactobacillus helveticus AH071113 is as follows:

4. The use according to claim 3, wherein the culture conditions of lactobacillus helveticus AH071113 in step (1) are: the inoculation amount is 3% -7% (v/v), the pH of the culture medium is 4.0-8.0, the culture temperature is 35-39 ℃, and the activation time is 15-21 h.

5. The use according to claim 3, wherein the compound strain in step (1) is one or both of streptococcus thermophilus and lactobacillus bulgaricus.

6. The use according to claim 3, wherein the food sweetener in step (2) is at least one of white granulated sugar, xylitol, glucose, fructose, lactose, maltose; the addition amount of the food sweetener is 3-9% of the mass of the cow milk.

7. The use according to claim 3, wherein the fermentation temperature in step (3) is 40-44 ℃ and the fermentation time is 6-12 hours; the addition amount of the mixed fermentation liquor is 3% -7% of the volume of the emulsion; the bacterial age of the lactobacillus helveticus AH071113 in the lactobacillus helveticus fermentation liquid is 9-15 h.

8. The use according to claim 3, wherein the mixing ratio of lactobacillus helveticus fermentation broth and the compound strain fermentation broth in the step (3) is 1:1-1:2.

9. Use according to claim 3, characterized in that the yoghurt product has an auxiliary antihypertensive effect, wherein the tripeptide Val-Pro is not less than 0.019% (w/w) and the tripeptide Ile-Pro is not less than 0.019% (w/w).

10. Use of a yoghurt product as claimed in claim 9 in the manufacture of a blood pressure lowering food product.