Microcapsule wall material, lactic acid bacteria microcapsule and preparation method

Abstract

The invention belongs to the technical field of microecological preparations, and particularly provides a microcapsule wall material which comprises the following components in percentage by mass of water: 4-6% of denatured protein, 1.5-2.5% of sodium alginate and 1.5-2.5% of calcium carbonate. The protein comprises at least one of whey protein isolate and soybean protein isolate. Based on the microcapsule wall material, the invention provides the acid-resistant, cholate-resistant and heat-resistant lactic acid bacteria microcapsule and the preparation method thereof. According to the microcapsule wall material provided by the invention, the protein raw material is subjected to denaturation pretreatment and then is compounded with the sodium alginate and the calcium carbonate, so that compared with the traditional wall material sodium alginate, the microcapsule wall material provided by the invention has the advantages that the embedding rate and the stability can be improved, and the acid resistance, cholate resistance, heat resistance and storage stability of an embedded product are also greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of microecological preparations, and in particular relates to a microcapsule wall material, a lactic acid bacteria microcapsule and a preparation method thereof. Background Art

[0002] Probiotics are a type of active microorganisms that are beneficial to the host, can improve the host's microecological balance, and play a beneficial role. For probiotics to play a probiotic role, there must be enough probiotics to reach the intestines through gastric juice, and there must be enough probiotics to colonize in the intestines. However, it is relatively difficult for probiotics to pass through gastric juice directly and colonize in the intestines. Probiotics will be killed by substances such as gastric acid and bile salts in the gastrointestinal tract, which greatly reduces the number of probiotics that can colonize on the intestinal mucosa, resulting in their inability to play their probiotic role. Since probiotics are easily inactivated in low pH, high bile salt and other environments, it is necessary to improve their storage stability and resistance to gastric acid and bile salts in the preparation of probiotic preparations to ensure their high survival rate. In addition, feed factories often generate high temperatures of about 70-80°C during the process of preparing feed. Although the time is short, it will cause a certain degree of damage to lactic acid bacteria. Therefore, when lactic acid bacteria are used as feed additives, they must have a certain degree of heat resistance. Otherwise, during the processing of lactic acid bacteria-containing feed, the lactic acid bacteria will die in large numbers due to the high temperature and will not achieve the probiotic effect.

[0003] Microcapsule technology generally refers to the use of chemical and physical methods to use natural or synthetic polymers that can form a film as the capsule wall to embed and solidify tiny substances such as gases, liquids, and solids. After the microcapsules are made, they can protect the capsule core from external influences and damage, enhance the stability of the capsule core, and play a role in sustained release under certain conditions. Using microcapsule technology to embed probiotics, separate probiotics from the environment through wall materials and release them in a targeted manner, enhance the resistance and colonization effect of probiotics, is currently a key research direction in the field of probiotic preparations. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem in the prior art that lactic acid bacteria have poor acid resistance, bile salt resistance and heat resistance, which affects the effect of the action.

[0005] To this end, the present invention provides a microcapsule wall material, which includes 4-6% denatured protein, 1.5%-2.5% sodium alginate, and 1.5%-2.5% calcium carbonate based on water mass; the protein includes at least one of whey protein isolate and soy protein isolate.

[0006] Specifically, the denatured protein is prepared by the following steps: the protein is denatured at 60-65° C. for 20-40 minutes.

[0007] The present invention also provides a method for preparing the microcapsule wall material, comprising the following steps: adding sodium alginate into water, and adding denatured protein and calcium carbonate after the sodium alginate is completely dissolved, and stirring and mixing the mixture evenly.

[0008] The present invention also provides a lactic acid bacteria microcapsule, comprising lactic acid bacteria and the above-mentioned microcapsule wall material; the lactic acid bacteria are embedded in the microcapsule wall material.

[0009] The present invention also provides a method for preparing lactic acid bacteria microcapsules, comprising the following steps:

[0010] S1, preparing a lactic acid bacteria suspension and the above-mentioned microcapsule wall material, and adding a protective agent to the lactic acid bacteria suspension;

[0011] S2, mixing the lactic acid bacteria suspension added with the protective agent with the microcapsule wall material as the water phase;

[0012] S3, adding the water phase to the oil phase, mixing and emulsifying, and then dropping glacial acetic acid for pre-fixation, and then adding a sedimentation agent until the microcapsules are completely solidified and precipitated, filtering and washing to obtain the first embedded microcapsules;

[0013] S4, mixing the first embedded microcapsules with the gelatin solution, stirring to make the gelatin adhere evenly, filtering, and washing to obtain the second embedded microcapsules;

[0014] S5, mixing the secondary embedding microcapsules and the hygroscopic agent, and obtaining lactic acid bacteria microcapsules after granulation and fluidized drying.

[0015] Specifically, the volume ratio of the lactic acid bacteria suspension to the microcapsule wall material solution in the aqueous phase is 1:(6-8).

[0016] Specifically, the oil phase includes Span 80 and vegetable oil; based on the mass of the vegetable oil, the added amount of Span 80 is 0.2-0.5%.

[0017] Specifically, in the above step S3, the mass ratio of the water phase to the oil phase is 1:(1.5-2.5).

[0018] Specifically, the above step S4 is specifically as follows: mixing the first embedded microcapsules with a gelatin solution with a mass concentration of 1-2% to make the gelatin adhere evenly, filtering, and washing to obtain the second embedded microcapsules.

[0019] Specifically, during fluidized drying in step S5, the air inlet temperature is controlled to be less than 70° C., the material temperature is controlled to be less than 55° C., and the material is dried until the moisture content is less than 6% to obtain lactic acid bacteria microcapsules.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] The microcapsule wall material provided by the present invention is prepared by pre-denaturing protein raw materials and then compounding with sodium alginate and calcium carbonate. Compared with using traditional wall material sodium alginate alone, the embedding rate and stability can be improved, and the acid resistance, bile salt resistance, heat resistance and storage stability of the embedded product are also greatly improved.

[0022] The preparation method of the lactic acid bacteria microcapsule provided by the present invention is safe, simple in process, stable in quality, easy to control, and can be industrially produced. Through microencapsulation technology and fluidized bed drying technology, lactic acid bacteria are coated and granulated, the tolerance of the strain is improved, the death of lactic acid bacteria during the drying process can be reduced, and a high number of live bacteria is maintained. The double-layer encapsulation microcapsule scheme is adopted to encapsulate lactic acid bacteria in microcapsules, which increases the embedding rate and stability of Enterococcus faecium. After gastric acid treatment, the live bacteria retention rate of the final microcapsule product reaches 82.3%; after bile salt treatment, the live bacteria retention rate is 63.5%; in the heat resistance test of the wet heat box, the live bacteria retention rate can reach 85.7%; the storage stability under accelerated conditions reaches 88.6%. The microcapsule product is acid-resistant, bile-resistant, and has good heat resistance, so that the lactic acid bacteria can play a greater probiotic role in the intestine, and can also increase the storage stability of the product and extend the shelf life. DETAILED DESCRIPTION

[0023] The technical scheme in the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Although the representative embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that various modifications and changes can be made to the present invention without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the embodiments, but should be limited by the attached claims and their equivalents.

[0024] The invention provides a microcapsule wall material, which comprises 4-6% of denatured protein, 1.5%-2.5% of sodium alginate and 1.5%-2.5% of calcium carbonate based on water mass; the protein comprises at least one of whey protein isolate and soy protein isolate.

[0025] The microcapsule wall material is preferably prepared by the following steps:

[0026] (1) Denature the protein material in a water bath at 100-200 rpm / min and 60-65° C. for 20-40 min, and cool it at room temperature to obtain denatured protein for use. The protein material used includes at least one of whey protein isolate and soy protein isolate.

[0027] (2) Slowly add sodium alginate powder into water and stir rapidly until it is completely dissolved. Then add the denatured protein and calcium carbonate powder pretreated in (1) to prepare a mixture of 4-6% denatured protein, 1.5%-2.5% sodium alginate, and 1.5%-2.5% calcium carbonate, and stir to mix evenly. The mass ratio of sodium alginate to calcium carbonate is preferably 1:1.

[0028] The present invention also provides a lactic acid bacteria microcapsule, comprising lactic acid bacteria and the above-mentioned microcapsule wall material; the lactic acid bacteria are embedded in the microcapsule wall material.

[0029] The present invention also provides a method for preparing lactic acid bacteria microcapsules, comprising the following steps:

[0030] S1. preparing a lactic acid bacteria suspension and the above-mentioned microcapsule wall material, and adding a protective agent to the lactic acid bacteria suspension.

[0031] Based on the mass of the lactic acid bacteria suspension, the protective agent preferably includes 3-5% trehalose, 3-5% maltose, 1-2% polyvinyl pyrrolidone, 2-4% glycine, and 1-2% sodium glutamate.

[0032] Among them, trehalose is a non-reducing disaccharide with a large hydration volume. It competes for water in the protein hydration layer, making the protein structure more stable and compact, and enhancing the resistance of microorganisms to the environment. Maltose is a reducing disaccharide that can reduce oxidative damage to cells during the drying process and improve cell survival rate. Polyvinyl pyrrolidone is a good biostabilizer that can reduce damage to cells during dehydration and drying. Glycine and sodium glutamate can stabilize the pH of the cell environment during the drying process, protect the active components of the cells, and improve the survival rate of the cells during the drying process.

[0033] S2. Mix the lactic acid bacteria suspension to which the protective agent is added with the microcapsule wall material at a volume ratio of 1:(6-8) as the aqueous phase.

[0034] S3. Based on the mass of the vegetable oil, add 0.2-0.5% of Span 80 into the vegetable oil and mix well to form the oil phase. The vegetable oil is preferably one of soybean oil, rapeseed oil, cottonseed oil and palm oil.

[0035] The oil phase is stirred and then the water phase is slowly added thereto, and the mixture is thoroughly mixed and emulsified. The mass ratio of the water phase to the oil phase is preferably 1:(1.5-2.5). The stirring speed is preferably 300-450 rpm / min, and the emulsification time is preferably 5-10 min.

[0036] Then, glacial acetic acid is added dropwise for pre-fixation. The amount of glacial acetic acid added is preferably 8-10 ml, and the pre-fixation time is preferably 20-30 min.

[0037] The rotation speed is reduced to 50-100 rpm / min, and a sedimentation agent is slowly added for fixation. After the microcapsules are completely solidified and begin to settle, stirring is stopped, and the microcapsules are allowed to settle slowly. The oil phase and the water phase are separated and recovered, and the first embedded microcapsules are obtained by filtering and washing.

[0038] The sedimentation agent is preferably a calcium chloride solution with a concentration of 0.1-0.2 mol / L.

[0039] S4, mixing the first embedded microcapsules with a gelatin solution with a mass concentration of 1-2%, stirring to make the gelatin adhere evenly, preferably stirring at 150-200 rpm / min for 10-20 min, filtering and washing to obtain the second embedded microcapsules.

[0040] S5. Evenly mix the secondary embedded microcapsules and the moisture absorbent, and control the moisture content of the mixed sample to 50%-60%.

[0041] The moisture absorbent is preferably corn cob powder and diatomaceous earth. The mass ratio of the two is preferably corn cob powder: diatomaceous earth = 1: (0.5-1)

[0042] The mixed sample is made into particles, and fluidized drying is performed, the air inlet temperature is controlled to be less than 70° C., the material temperature is controlled to be less than 55° C., and the material is dried until the moisture content is less than 6%, thereby obtaining lactic acid bacteria microcapsules.

[0043] The effects of the microcapsule wall material, lactic acid bacteria microcapsule and preparation method of the present invention are studied through specific examples.

[0044] Embodiment 1:

[0045] This embodiment provides a microcapsule wall material, which is prepared by the following steps:

[0046] (1) whey protein isolate and soy protein isolate were denatured in a water bath at 150 rpm / min and 60°C for 30 min, and then cooled at room temperature to obtain denatured proteins for later use.

[0047] (2) Slowly add sodium alginate powder into water and stir rapidly until it is completely dissolved. Then add the denatured protein pretreated in (1) and calcium carbonate powder to prepare a mixture of 3% whey protein isolate, 2% soy protein isolate, 2% sodium alginate and 2% calcium carbonate based on the mass of water, stir and mix evenly to obtain a microcapsule wall material solution.

[0048] Embodiment 2:

[0049] This embodiment provides an Enterococcus faecium microcapsule based on the microcapsule wall material prepared in Example 1, which is prepared by the following steps.

[0050] S1. Prepare Enterococcus faecium suspension: Take the fermentation liquid of Enterococcus faecium from the tank, filter it through a plate and frame to obtain bacterial mud. Rinse the bacterial mud twice with pH 7.0 PBS buffer, add physiological saline and stir evenly, and use the MRS plate culture counting method to measure the viable number of Enterococcus faecium to 310 billion cfu / ml, which is set aside.

[0051] Based on the mass of the Enterococcus faecium suspension, 4% trehalose, 4% maltose, 1.5% polyvinyl pyrrolidone, 3% glycine and 1.5% sodium glutamate were added as protective agents to the Enterococcus faecium suspension, and the mixture was stirred and mixed evenly.

[0052] Preparation of microcapsule wall material solution: denature whey protein isolate and soy protein isolate in a water bath at 150 rpm / min and 60°C for 30 min, cool at room temperature, and obtain denatured protein for use. Slowly add sodium alginate powder into water and stir rapidly until completely dissolved. Then add denatured protein and calcium carbonate powder, and prepare a mixture of 3% whey protein isolate, 2% soy protein isolate, 2% sodium alginate, and 2% calcium carbonate based on the mass of water, stir and mix evenly to obtain a microcapsule wall material solution.

[0053] S2. Mix the lactic acid bacteria suspension to which the protective agent is added with the microcapsule wall material solution at a volume ratio of 1:7 as the aqueous phase.

[0054] S3. Based on the mass of the vegetable oil, add 0.4% of Span 80 into the soybean oil and mix well to form the oil phase.

[0055] 5 kg of oil phase was added to a 10 L fermenter, and the oil phase was stirred at a speed of 400 rpm / min. Then, 2.5 kg of water phase was slowly added thereto, and the mixture was thoroughly mixed and emulsified for 8 min.

[0056] Slowly add 9 ml of glacial acetic acid to the fermenter for pre-fixation for 30 minutes.

[0057] The rotation speed was reduced to 50 rpm / min, and a 0.1 mol / L calcium chloride solution was slowly added as a precipitant for fixation. After the microcapsules were completely solidified and began to settle, stirring was stopped and the microcapsules were allowed to settle slowly. The oil phase and the water phase were separated and recovered, and the microcapsules were washed twice with deionized water after filtering to obtain the first embedded microcapsules.

[0058] S4. The first embedded microcapsules were mixed with a gelatin solution with a mass concentration of 1.5%, stirred at 150 rpm / min for 15 min to allow the gelatin to adhere evenly, filtered, and washed twice with deionized water to obtain secondary embedded microcapsules.

[0059] S5. Slowly add the secondary embedding microcapsules and the desiccant into the mixing granulator and mix them evenly, and control the moisture content of the mixed sample to be 55%. The desiccant includes corn cob powder and diatomaceous earth in a mass ratio of 1:1.

[0060] The mixed sample is granulated by a screw extruder, added to a centrifugal pill-making machine, and spheronized to prepare spherical microcapsule particles, which are placed in a fluidized bed for fluidized drying. The inlet air temperature is controlled to be less than 70°C and the material temperature is less than 55°C. The material is dried until the moisture content is less than 6%, and then packaged in bags to obtain Enterococcus faecium microcapsules.

[0061] Test the number of viable bacteria, embedding rate, acid resistance, alkali resistance, heat resistance, and accelerated storage stability.

[0062] (1) Detect the encapsulation rate of Enterococcus faecium in the wet microcapsules encapsulated twice in S4.

[0063] Method: Take 1g of microcapsules and place them in a conical flask, add 99ml of 0.06mol / L sodium citrate solution. Shake at 37℃ constant temperature at 200rpm / min for 60min to completely dissolve the microcapsules. Take 1ml of the dissolved bacterial solution and dilute it 10 times in a gradient step with sterile saline, then take an appropriate amount of the dilution to spread on the MRS plate, culture at 37℃ for 24h, count the colonies, and calculate the number of viable bacteria in the microcapsules.

[0064] Embedding rate = total number of live bacteria in microcapsules after embedding / total number of live bacteria before embedding × 100%

[0065] (2) Acid resistance test

[0066] Method: Take 1g of dried S5 Enterococcus faecium microcapsules and place them in a conical flask containing 50ml of prepared artificial gastric juice. Shake at 37℃, 150rpm / min, and keep constant temperature for 2h. Then collect the microcapsules by centrifugation and add 99ml of 0.06mol / L sodium citrate solution. Shake at 37℃ constant temperature and 200rpm / min for 60min to completely dissolve the microcapsules. Take 1ml of the dissolved bacterial solution and dilute it step by step with sterile saline in a 10-fold gradient. Then take an appropriate amount of the dilution to spread on the MRS plate, culture at 37℃ for 24h, count the colonies, and calculate the number of live bacteria in the microcapsules treated with artificial gastric juice.

[0067] Acid resistance = total number of live bacteria before artificial gastric juice treatment / total number of live bacteria after artificial gastric juice treatment × 100%

[0068] (3) Bile salt resistance test

[0069] Method: Take 1g of dried S5 Enterococcus faecium microcapsules and place them in a conical flask containing 50ml of 0.3% pig bile salt, and shake at 37℃, 150rpm / min, for 3h. Then collect the microcapsules by centrifugation and add 99ml of 0.06mol / L sodium citrate solution. Shake at 37℃ constant temperature, 200rpm / min for 60min to completely dissolve the microcapsules. Take 1ml of the dissolved bacterial solution and dilute it step by step with sterile saline, then take an appropriate amount of the dilution to spread on the MRS plate, culture at 37℃ for 24h, count the colonies, and calculate the number of viable bacteria in the microcapsules treated with pig bile salt.

[0070] Bile salt resistance = total number of live bacteria in the sample before bile salt treatment / total number of live bacteria in the sample after bile salt treatment × 100%

[0071] (4) Heat resistance test

[0072] Method: Take 5g of dried microcapsules of Enterococcus faecium from S5, spread them on a plate, place them in a wet heat box at 85℃ and 95% humidity for 5min, take them out immediately, rinse the bacteria on the plate with 495ml of 0.06mol / L sodium citrate solution, and collect the bacteria in a triangular flask. Shake them in a 37℃ constant temperature shaker at 200rpm / min for 60min to completely dissolve the microcapsules. Take 1ml of the dissolved bacterial solution and dilute it 10 times in a gradient step by step with sterile saline, then take an appropriate amount of the dilution and spread it on an MRS plate, culture it at 37℃ for 24h, count the colonies, and calculate the number of live bacteria in the microcapsules treated with pig bile salt.

[0073] Heat resistance = total number of live bacteria before sample heat box treatment / total number of live bacteria after sample heat box treatment × 100%

[0074] (5) Accelerated storage stability testing

[0075] Method: A certain amount of S5 dried Enterococcus faecium microcapsules were vacuum-sealed in aluminum foil bags and placed in a 45℃ constant temperature incubator for 30 days. Then 1g was taken into a triangular flask and 99ml of 0.06mol / L sodium citrate solution was added. The microcapsules were completely dissolved in a 37℃ constant temperature shaker at 200rpm / min for 60min. 1ml of the dissolved bacterial solution was diluted 10 times in a stepwise gradient with sterile saline, and then an appropriate amount of the dilution was spread on an MRS plate, cultured at 37℃ for 24h, and the colonies were counted. The number of viable bacteria after vacuuming and storing at 45℃ for 30 days was calculated.

[0076] Accelerated stability, with the viable bacteria retention rate after vacuuming at 45°C for 30 days as the indicator.

[0077] Live bacteria retention rate = total live bacteria count before accelerated storage of the sample / total live bacteria count after accelerated storage of the sample × 100%

[0078] The test results are shown in Table 1.

[0079] Comparative Example 1:

[0080] This comparative example provides a live Enterococcus faecium preparation, which is prepared by similar steps to Example 2, except that whey protein isolate and soy protein isolate are not denatured when preparing the microcapsule wall material solution in step S1.

[0081] The embedding rate, acid resistance, bile salt resistance, heat resistance and accelerated storage stability of the obtained live Enterococcus faecium preparation were tested, and the results are shown in Table 1.

[0082] Comparative Example 2:

[0083] This comparative example provides a live Enterococcus faecium preparation, which is prepared by similar steps to Example 2, except that whey protein isolate and soy protein isolate are not added when preparing the microcapsule wall material solution in step S1.

[0084] The embedding rate, acid resistance, bile salt resistance, heat resistance and accelerated storage stability of the obtained live Enterococcus faecium preparation were tested, and the results are shown in Table 1.

[0085] Comparative Example 3:

[0086] This comparative example provides a live Enterococcus faecium preparation, which is prepared by similar steps to Example 2, except that in step S1, no protective agent is added to the Enterococcus faecium suspension.

[0087] The embedding rate, acid resistance, bile salt resistance, heat resistance and accelerated storage stability of the obtained live Enterococcus faecium preparation were tested, and the results are shown in Table 1.

[0088] Comparative Example 4:

[0089] This comparative example provides a live Enterococcus faecium preparation, which is prepared by similar steps to Example 2, except that no secondary gelatin embedding is performed, and the microcapsules embedded for the first time are directly granulated and dried.

[0090] The embedding rate, acid resistance, bile salt resistance, heat resistance and accelerated storage stability of the obtained live Enterococcus faecium preparation were tested, and the results are shown in Table 1.

[0091] Comparative Example 5:

[0092] This comparative example provides a live Enterococcus faecium preparation, which is prepared by similar steps to Example 2, except that during fluidized drying in step S5, the inlet air temperature is controlled to be less than 80°C, the material temperature is less than 65°C, and the material is dried until the moisture content is less than 6%.

[0093] The embedding rate, acid resistance, bile salt resistance, heat resistance and accelerated storage stability of the obtained live Enterococcus faecium preparation were tested, and the results are shown in Table 1.

[0094] Comparative Example 6:

[0095] This comparative example provides a live Enterococcus faecium preparation, which is prepared using the following steps.

[0096] S1. Take the fermentation liquid of Enterococcus faecium and put it into a tank, filter it through a plate and frame to obtain bacterial mud. Rinse the bacterial mud twice with PBS buffer at pH 7.0. Add a certain amount of desiccant, mix it evenly, and control the moisture content of the mixed sample to 55%. The desiccant includes corn cob powder and diatomaceous earth in a mass ratio of 1:1.

[0097] S2. The sample mixed in S1 is granulated by a screw extruder.

[0098] S3. Add the material prepared in S2 into a centrifugal pill-making machine and roll it into a ball to prepare microcapsule particles that are approximately spherical.

[0099] S4, placing the material prepared in S3 into a fluidized bed for fluidized drying, controlling the air inlet temperature to be less than 70°C and the material temperature to be less than 55°C, drying until the material moisture is less than 6%, and then bagging and packaging to obtain a live Enterococcus faecium preparation.

[0100] The acid resistance, bile salt resistance, heat resistance and accelerated storage stability of the obtained live Enterococcus faecium preparation were tested, and the results are shown in Table 1.

[0101] Comparative Example 7:

[0102] Preparation of Enterococcus faecium suspension: Take the fermentation liquid of Enterococcus faecium in a tank, filter it through a plate and frame to obtain bacterial mud. Rinse the bacterial mud twice with PBS buffer of pH 7.0, add a certain amount of physiological saline, stir evenly, and use the MRS plate culture counting method to measure the viable number of Enterococcus faecium to be 310 billion cfu / ml, which is set aside.

[0103] The acid resistance, bile salt resistance and heat resistance of the obtained Enterococcus faecium suspension were tested, and the results are shown in Table 1.

[0104] Table 1 Performance test results

[0105]

[0106]

[0107] As can be seen from Table 1, by using the method provided by the present invention to perform two microencapsulation of Enterococcus faecium and combining it with fluidized bed drying, the acid resistance, bile resistance and heat resistance of the live Enterococcus faecium preparation product can be better improved, and the storage stability can also be improved to extend the shelf life of the product.

[0108] The addition of composite protein materials can increase the embedding rate of live bacteria in Enterococcus faecium microcapsules, and also greatly improve the acid resistance, bile resistance, heat resistance, and storage stability of the product. Adding a composite protective agent to the suspension of Enterococcus faecium and then embedding it in microcapsules can reduce the death of bacteria during fluidized drying, increase the yield of live bacteria in the product, and also greatly improve the acid resistance, bile resistance, heat resistance, and storage stability of the product. Using gelatin to perform secondary microencapsulation of Enterococcus faecium can increase the yield of live bacteria in the product, and also greatly improve the acid resistance, bile resistance, heat resistance, and storage stability of the product. During the fluidized bed drying process, controlling the appropriate drying temperature can reduce the death of Enterococcus faecium during the drying process and increase the yield of live bacteria in the product.

[0109] The above examples are merely illustrative of the present invention and do not constitute a limitation on the protection scope of the present invention. All designs that are the same or similar to the present invention fall within the protection scope of the present invention.

Claims

1. A microcapsule wall material, characterized in that: The invention comprises 4-6% of denatured protein, 1.5%-2.5% of sodium alginate and 1.5%-2.5% of calcium carbonate based on the mass of water; the protein comprises at least one of whey protein isolate and soy protein isolate.

2. The microcapsule wall material according to claim 1, characterized in that: The denatured protein is prepared by the following steps: the protein is denatured at 60-65° C. for 20-40 minutes.

3. The method for preparing a microcapsule wall material according to any one of claims 1 to 2, characterized in that: The following steps are involved: Add sodium alginate into water, and after it is completely dissolved, add denatured protein and calcium carbonate, and stir to mix evenly.

4. A lactic acid bacteria microcapsule, characterized in that: The microcapsule comprises lactic acid bacteria and the microcapsule wall material according to any one of claims 1 to 2; the lactic acid bacteria are embedded in the microcapsule wall material.

5. A method for preparing lactic acid bacteria microcapsules, characterized in that: The following steps are involved: S1, preparing a lactic acid bacteria suspension and the microcapsule wall material according to any one of claims 1 to 2, and adding a protective agent to the lactic acid bacteria suspension; S2, mixing the lactic acid bacteria suspension added with the protective agent with the microcapsule wall material as the water phase; S3, adding the water phase to the oil phase, mixing and emulsifying, and then dropping glacial acetic acid for pre-fixation, and then adding a sedimentation agent until the microcapsules are completely solidified and precipitated, filtering and washing to obtain the first embedded microcapsules; S4, mixing the first embedded microcapsules with the gelatin solution, stirring to make the gelatin adhere evenly, filtering, and washing to obtain the second embedded microcapsules; S5, mixing the secondary embedding microcapsules and the hygroscopic agent, and obtaining lactic acid bacteria microcapsules after granulation and fluidized drying.

6. The method for preparing lactic acid bacteria microcapsules according to claim 5, characterized in that: The volume ratio of the lactic acid bacteria suspension to the microcapsule wall material solution in the aqueous phase is 1:(6-8).

7. The method for preparing lactic acid bacteria microcapsules according to claim 5, characterized in that: The oil phase includes Span 80 and vegetable oil; based on the mass of the vegetable oil, the added amount of Span 80 is 0.2-0.5%.

8. The method for preparing lactic acid bacteria microcapsules according to claim 5, characterized in that: The mass ratio of the water phase to the oil phase in step S3 is 1:(1.5-2.5).

9. The method for preparing lactic acid bacteria microcapsules according to claim 5, characterized in that: In the step S4, the microcapsules embedded for the first time are mixed with a gelatin solution having a mass concentration of 1-2%.

10. The method for preparing lactic acid bacteria microcapsules according to claim 5, characterized in that: In step S5, during fluidized drying, the air inlet temperature is controlled to be less than 70° C., the material temperature is controlled to be less than 55° C., and the material is dried until the moisture content is less than 6% to obtain lactic acid bacteria microcapsules.

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