Probiotic directional embedding freeze-dried milk tea powder and preparation method thereof

Abstract

The application discloses a probiotic directional embedding freeze-dried milk tea powder and a preparation process thereof, and relates to the food processing technical field. The probiotic directional embedding freeze-dried milk tea powder comprises freeze-dried milk tea powder and probiotic microcapsule powder, and the mass ratio of the freeze-dried milk tea powder to the probiotic microcapsule powder is (90-95):(5-10). The probiotic microcapsule powder comprises probiotics and an embedding layer wrapped outside the probiotics, and the embedding layer comprises, from inside to outside, a sodium alginate-calcium ion gel layer, a chitosan-pectin composite film layer and an inulin layer. The probiotic directional embedding freeze-dried milk tea powder can maintain the milk tea flavor, does not need to be prepared with hot water, can effectively protect the probiotic activity and improve the survival rate of the probiotics in the stomach digestive tract.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, and in particular to a probiotic-encapsulated freeze-dried milk tea powder and its preparation method. Background Technology

[0002] Probiotic milk tea combines probiotics with milk tea, offering not only the rich flavor of milk tea but also regulating gut microbiota and promoting nutrient absorption. However, most current probiotic milk tea powders are produced using spray drying, a process that results in significant flavor loss. Furthermore, the powder requires hot water to prepare, which can heat-induced inactivation of the probiotics, leading to a less than ideal drinking experience. Additionally, directly adding probiotics to milk tea powder or encapsulating them before adding them means the probiotics are susceptible to stress from stomach acid (pH 1.5-3.5) and bile salts when entering the digestive tract, reducing their survival rate and significantly diminishing their absorption and utilization by the intestines.

[0003] Therefore, there is an urgent need for a method to prepare probiotic milk tea powder that can maintain the flavor of milk tea, requires no hot water for preparation, effectively protect the activity of probiotics, and improve the survival rate of probiotics in the gastrointestinal tract. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the purpose of this invention is to provide a probiotic-encapsulated freeze-dried milk tea powder and its preparation method, which can not only maintain the flavor and taste of milk tea, but also effectively protect the activity of probiotics and significantly improve the survival rate of probiotics in the gastrointestinal tract, thereby obtaining a probiotic freeze-dried milk tea powder product with excellent nutrition and flavor.

[0005] This invention provides the following technical solution: In a first aspect, the present invention provides a probiotic-encapsulated freeze-dried milk tea powder, comprising freeze-dried milk tea powder and probiotic microcapsule powder, wherein the mass ratio of the freeze-dried milk tea powder to the probiotic microcapsule powder is (90-95):(5-10); the probiotic microcapsule powder comprises probiotics and an encapsulation layer surrounding the probiotics, wherein the encapsulation layer comprises, from the inside out, a sodium alginate-calcium ion gel layer, a chitosan-pectin composite membrane layer, and an inulin layer.

[0006] Furthermore, the preparation method of the probiotic microcapsule powder includes the following steps: S1. Activate the probiotic strains and prepare them into bacterial sludge; S2, Sodium alginate-calcium ion gel layer encapsulation: The bacterial mud is mixed with sodium alginate solution to form a bacterial suspension, which is then added dropwise to calcium chloride solution to solidify and form a single-layer encapsulated probiotic microcapsule; S3. Chitosan-pectin composite membrane encapsulation: Single-layer encapsulated probiotic microcapsules are placed in a composite solution of chitosan and pectin for coating to obtain double-layer encapsulated probiotic microcapsules. S4. Inulin layer encapsulation: The double-layer encapsulated probiotic microcapsules are mixed and encapsulated in an inulin solution to obtain a triple-layer encapsulated probiotic microcapsule. After filtration and freeze-drying, the probiotic microcapsule powder is obtained.

[0007] Furthermore, the probiotics are a complex of Lactobacillus rhamnosus GG, Lactobacillus rhamnosus HN001, Bifidobacterium animalis subsp. lactis HN019, and Bifidobacterium breve M-16V, and the weight ratio of the four bacteria is 1:1:1:1.

[0008] Preferably, in step S1, the method for preparing the fungal sludge includes the following steps: B1. Select a quadrivalent bacterial culture (a complex of Lactobacillus rhamnosus GG, Lactobacillus rhamnosus HN001, Bifidobacterium animalis subsp. lactis HN019, and Bifidobacterium breve M-16V mixed in a mass ratio of 1:1:1:1) and inoculate the strain into 5-10 ml of MRS broth medium (0.05% L-cysteine ​​sodium hydrochloride was added to the medium beforehand) under aseptic conditions.

[0009] B2. After inoculation, place the test tube in an anaerobic environment at 37±0.5℃ for 18-24 hours. When the culture medium becomes uniformly turbid, it indicates that the strain has been successfully grown and activated, and the first-stage activated bacterial solution is obtained.

[0010] B3. Take 4 ml of the primary activated bacterial culture and inoculate it into an Erlenmeyer flask containing 200 ml of MRS medium (0.05% L-cysteine ​​sodium hydrochloride was added to the medium in advance). Place it in an anaerobic environment at 37±0.5℃ for 16-20 hours to carry out secondary strain expansion culture. B4. Measure the OD600 value at 16, 17, 18, 19 and 20 hours after incubation. Calculate the bacterial concentration based on the OD600 value. Stop culturing when the concentration reaches 3*109 CFU / g to obtain the bacterial culture medium.

[0011] B5. Dispense the bacterial culture medium into sterile centrifuge tubes and centrifuge them with the following parameters: temperature 0-4℃; speed 6000-8000 rpm; time 10-15 minutes. After centrifugation, the supernatant in the centrifuge tube is the culture medium, and the lower layer is white bacterial sludge.

[0012] B6. Discard the supernatant in the centrifuge tube, wash the bacterial sludge with pre-cooled sterile physiological saline (0.85% NaCl), with a ratio of physiological saline to bacterial sludge of 0.5:1; centrifuge again after washing (temperature 0-4℃; speed 6000-8000rpm; time 10-15 minutes); repeat the operation in B6 to finally obtain pure activated bacterial sludge.

[0013] Furthermore, in step S2, the concentration of the bacterial sludge is 3*10. 9 CFU / ml; the mass concentration of the sodium alginate solution is 2%; the molar concentration of the calcium chloride solution is 0.1 mol / L.

[0014] Preferably, in step S2, the curing parameters are: dripping speed of 5-10 ml / min; needle orifice diameter of 0.3-0.5 mm; and time of 20-30 min.

[0015] Furthermore, in step S2, after curing, the process also includes filtering with a sterile screen and rinsing with sterile water to collect the monolayer-encapsulated probiotic microcapsules and wash away excess Ca from their surface. 2+ .

[0016] Furthermore, in step S3, the method for preparing the chitosan and pectin composite solution includes the following steps: adding a pH adjuster to a chitosan solution and a pectin solution, both with a mass concentration of 5%, to adjust the pH value to 5.0-5.5, sterilizing and cooling, and then mixing the chitosan solution and the pectin solution evenly at a mass ratio of 1:1 to obtain the chitosan and pectin composite solution.

[0017] Furthermore, in step S3, after coating, the process also includes filtering with a sterile screen and rinsing with sterile water to collect the double-layered probiotic microcapsules and wash away excess solution from their surface.

[0018] Furthermore, in step S4, the mass concentration of the inulin solution is 5%.

[0019] Furthermore, in step S4, the freeze-drying includes the following steps: adding the three-layer encapsulated probiotic microcapsules to the freeze-drying protectant solution, stirring evenly and soaking for 20-30 minutes, filtering, pre-freezing at -50±10℃ for 3 hours to form small ice crystals, then performing primary drying, and then performing analytical drying to obtain probiotic microcapsule powder.

[0020] Preferably, the conditions for the primary drying are: vacuum degree 0.05 mbar, shelf temperature -10℃ to 10℃, and time 14-16 hours.

[0021] Preferably, the conditions for the analytical drying are: vacuum degree 0.01 mbar, shelf temperature 25℃-35℃, and time 4-6 hours.

[0022] Preferably, in step S4, after freeze-drying, a nitrogen-filling packaging step is further included under conditions of RH≤20%.

[0023] Furthermore, the freeze-drying protectant solution comprises the following components in parts by weight: 5 parts gum arabic, 10 parts trehalose, and 85 parts deionized water.

[0024] Furthermore, the preparation method of the freeze-dried milk tea powder includes the following steps: A1. By weight, heat 26-28 parts of refined coconut oil to 55-60℃, add 0.5-1 parts of mono- and diglyceride fatty acid esters and mix well. Then add 26-30 parts of tea infusion, 45-47 parts of raw milk and 0.5-1 parts of sucrose fatty acid esters, heat to 55-60℃ and keep warm for 5-10 minutes to obtain the mixed raw materials. A2. Homogenize the mixed raw materials once at 55-60℃, and then homogenize them a second time at 60-65℃ to obtain a mixed liquid. A3. Pre-freeze the mixture at -50±10℃ for 3 hours to form small ice crystals; then perform primary drying and subsequent analytical drying to obtain freeze-dried milk tea powder.

[0025] Preferably, in step A3, the conditions for primary drying are: vacuum degree 0.05 mbar, shelf temperature -10℃ to 10℃, and time 14-16 hours.

[0026] Preferably, in step A3, the conditions for the analytical drying are: vacuum degree 0.01 mbar, shelf temperature 25℃-35℃, and time 4-6 hours.

[0027] Furthermore, the primary homogenization is a two-stage homogenization, with a first-stage pressure of 20-25 MPa and a second-stage pressure of 4-5 MPa. The secondary homogenization is also a two-stage homogenization, with a first-stage pressure of 20-25 MPa and a second-stage pressure of 4-5 MPa. The purpose of the first-stage homogenization is to break down large fat globules and solid particles into smaller particles, and the purpose of the second-stage homogenization is to further disperse the fine particles that have re-aggregated after the first-stage homogenization, resulting in a more uniform emulsion distribution and a more stable system. The purpose of employing secondary homogenization is to improve product stability.

[0028] Furthermore, the method for preparing the tea infusion includes the following steps: mixing tea leaves and water at a mass ratio of 1:30 for extraction, controlling the extraction temperature at 60-80℃, and the extraction time at 12-15 minutes. The extraction is carried out in a three-stage extraction mode, with each stage lasting 4-5 minutes. After extraction, the tea infusion is filtered through an 80-mesh filter and then cooled to 10-15℃ through a plate heat exchanger to obtain the tea infusion.

[0029] Furthermore, the preparation method of the raw milk includes the following steps: the milk is filtered, purified, cooled, and homogenized in sequence, and then sterilized by ultra-high temperature instantaneous treatment (UHT) for later use; the temperature of UHT is 135-145℃ and the time is 4-6 seconds. UHT sterilization can kill microorganisms while preserving the nutritional components and natural flavor of raw milk to the maximum extent.

[0030] Secondly, the present invention also discloses a method for preparing the above-mentioned probiotic-encapsulated freeze-dried milk tea powder, which includes the following steps: 1) Preparation of freeze-dried milk tea powder; 2) Preparation of probiotic microcapsule powder; 3) Mix the freeze-dried milk tea powder and probiotic microcapsule powder evenly to obtain probiotic-encapsulated freeze-dried milk tea powder.

[0031] The present invention has the following technical effects: The probiotic-encapsulated freeze-dried milk tea powder of this invention retains the flavor and texture of traditional milk tea. By effectively integrating probiotics into the freeze-dried milk tea powder, the nutritional value and health benefits of the product are enhanced. Furthermore, this probiotic-encapsulated freeze-dried milk tea powder dissolves quickly in room temperature water without the need for hot water, effectively preventing heat-induced inactivation of the probiotics. In addition, this invention uses pH-sensitive encapsulation materials for multi-layered encapsulation of the probiotics, providing multi-layered protection and effectively isolating them from the influence of stomach acid and bile salts. This significantly improves the survival rate of the probiotics in the gastrointestinal tract, ensuring precise delivery to the intestines. Detailed Implementation

[0032] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] It should be understood that, when used in this specification and the appended claims, the terms “comprising” and “including” indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0034] It should be noted that, in the following embodiments, the method for preparing tea soup includes the following steps: tea leaves and water are mixed and extracted at a mass ratio of 1:30, the extraction temperature is controlled at 70°C, the extraction time is 15 minutes, the extraction is carried out in a three-stage extraction mode, and the extraction time of each stage is 5 minutes; after the extraction is completed, the tea soup is filtered through an 80-mesh filter and then cooled to 10°C through a plate heat exchanger to obtain tea soup.

[0035] The preparation method of raw milk includes the following steps: the milk is filtered, purified, cooled, homogenized and then sterilized by ultra-high temperature instantaneous treatment (UHT) for later use; the temperature of UHT is 140℃ and the time is 5 seconds.

[0036] Example 1 A probiotic-encapsulated freeze-dried milk tea powder includes freeze-dried milk tea powder and probiotic microcapsule powder in a mass ratio of 95:5; the probiotic microcapsule powder includes probiotics and an encapsulation layer surrounding the probiotics, the encapsulation layer including, from the inside out, a sodium alginate-calcium ion gel layer, a chitosan-pectin composite membrane layer and an inulin layer.

[0037] This embodiment also provides a method for preparing the above-mentioned probiotic-encapsulated freeze-dried milk tea powder, including the following steps: Preparation of freeze-dried milk tea powder: A1. By weight, heat 27 parts of refined coconut oil to 58°C, add 0.8 parts of mono- and diglyceride fatty acid esters and mix well. Then add 28 parts of tea soup, 46 parts of raw milk and 0.8 parts of sucrose fatty acid esters, heat to 58°C and keep warm for 8 minutes to obtain the mixed raw materials. A2. The mixed raw materials are homogenized once under the conditions of first-stage homogenization pressure of 23MPa, second-stage pressure of 4.5MPa and temperature of 58℃. After that, they are homogenized a second time under the conditions of first-stage homogenization pressure of 23MPa, second-stage pressure of 4.5MPa and temperature of 62℃ to obtain a mixed liquid. A3. Pre-freeze the mixture at -60℃ for 3 hours, and simultaneously perform primary drying for 16 hours under vacuum of 0.05mbar and shelf temperature of 0℃. Then, perform desorption drying for 5 hours under vacuum of 0.01mbar and shelf temperature of 30℃ to obtain freeze-dried milk tea powder.

[0038] Preparation of probiotic microcapsule powder; S1. Activate the probiotic strains and prepare them into bacterial sludge; S2. Sodium alginate-calcium ion gel layer encapsulation: A bacterial suspension was formed by mixing bacterial sludge with sodium alginate solution. This suspension was then added dropwise to calcium chloride solution using a 0.4mm pore size needle at a rate of 8ml / min and solidified for 25 minutes. The solution was filtered through a sterile sieve and rinsed with sterile water to obtain a single-layer encapsulated probiotic microcapsules. The concentration of the bacterial sludge was 3*10⁻⁶. 9 CFU / ml; sodium alginate solution mass concentration is 2%; calcium chloride solution molar concentration is 0.1 mol / L; S3. Chitosan-pectin composite membrane encapsulation: The single-layer encapsulated probiotic microcapsules were placed in a composite solution of chitosan and pectin for membrane encapsulation, filtered with a sterile sieve and rinsed with sterile water to obtain double-layer encapsulated probiotic microcapsules. The preparation method of the chitosan and pectin composite solution includes the following steps: adding a pH adjuster to a chitosan solution and a pectin solution, both with a mass concentration of 5%, to adjust the pH value to 5.3, sterilizing and cooling, and then mixing the chitosan solution and pectin solution evenly at a mass ratio of 1:1 to obtain the chitosan and pectin composite solution.

[0039] S4. Inulin Layer Encapsulation: The double-layer encapsulated probiotic microcapsules were mixed and encapsulated in a 5% inulin solution to obtain a triple-layer encapsulated probiotic microcapsules. After filtration, the triple-layer encapsulated probiotic microcapsules were added to a lyophilization protectant solution, stirred evenly, and soaked for 25 minutes. After filtration, they were pre-frozen at -60℃ for 3 hours, and simultaneously subjected to primary drying at a vacuum of 0.05 mbar and a shelf temperature of 0℃ for 16 hours. Then, they were desorbed and dried at a vacuum of 0.01 mbar and a shelf temperature of 30℃ for 5 hours to obtain probiotic microcapsule powder. The lyophilization protectant solution consisted of the following components in parts by mass: 5 parts gum arabic, 10 parts trehalose, and 85 parts deionized water.

[0040] Freeze-dried milk tea powder and probiotic microcapsule powder are mixed evenly to obtain probiotic-encapsulated freeze-dried milk tea powder.

[0041] In this embodiment, the method for preparing the mycelium sludge in step S1 includes the following steps: B1. Select a preservation tube containing a quadrivalent bacterial strain (a complex bacterial group consisting of Lactobacillus rhamnosus GG, Lactobacillus rhamnosus HN001, Bifidobacterium animalis subsp. lactis HN019, and Bifidobacterium breve M-16V in a mass ratio of 1:1:1:1), and inoculate the strain into 10 ml of MRS broth medium (0.05% L-cysteine ​​sodium hydrochloride was added to the medium beforehand) under aseptic conditions.

[0042] B2. After inoculation, place the test tube in an anaerobic environment at 37±0.5℃ for 20 hours. When the culture medium becomes uniformly turbid, it indicates that the strain has been successfully grown and activated, and the first-stage activated bacterial solution is obtained.

[0043] B3. Take 4 ml of the primary activated bacterial culture and inoculate it into an Erlenmeyer flask containing 200 ml of MRS medium (0.05% L-cysteine ​​sodium hydrochloride was added to the medium in advance). Place it in an anaerobic environment at 37±0.5℃ for 16 hours to carry out secondary strain expansion culture. B4. Measure the OD600 value at 16, 17, 18, 19, and 20 hours after placement. Calculate the bacterial concentration based on the OD600 value. When the concentration reaches 3*10... 9 When the concentration of CFU / g is reached, the culture is stopped, and the strain culture is obtained.

[0044] B5. Dispense the bacterial culture medium into sterile centrifuge tubes and centrifuge them with the following parameters: temperature 2℃; speed 7000 rpm; time 13 minutes. After centrifugation, the supernatant in the centrifuge tube is the culture medium, and the lower layer is white bacterial sludge.

[0045] B6. Discard the supernatant in the centrifuge tube, wash the bacterial sludge with pre-cooled sterile physiological saline (0.85% NaCl), with a ratio of physiological saline to bacterial sludge of 0.5:1; centrifuge again after washing (temperature 2℃; speed 7000rpm; time 13 minutes); repeat the above operation to finally obtain pure activated bacterial sludge.

[0046] Example 2 A probiotic-encapsulated freeze-dried milk tea powder includes freeze-dried milk tea powder and probiotic microcapsule powder in a mass ratio of 90:10; the probiotic microcapsule powder includes probiotics and an encapsulation layer surrounding the probiotics, the encapsulation layer including, from the inside out, a sodium alginate-calcium ion gel layer, a chitosan-pectin composite membrane layer and an inulin layer.

[0047] This embodiment also provides a method for preparing the above-mentioned probiotic-encapsulated freeze-dried milk tea powder, including the following steps: Preparation of freeze-dried milk tea powder: A1. By weight, heat 26 parts of refined coconut oil to 55°C, add 0.5 parts of mono- and diglyceride fatty acid esters and mix well. Then add 26 parts of tea soup, 45 parts of raw milk and 0.5 parts of sucrose fatty acid esters, heat to 55°C and keep warm for 5 minutes to obtain the mixed raw materials. A2. The mixed raw materials are homogenized once under the conditions of first-stage homogenization pressure of 20MPa, second-stage pressure of 4MPa and temperature of 55℃. After that, they are homogenized a second time under the conditions of first-stage homogenization pressure of 25MPa, second-stage pressure of 5MPa and temperature of 60℃ to obtain a mixed liquid. A3. Pre-freeze the mixture at -55℃ for 3 hours, and simultaneously perform primary drying for 15 hours under vacuum of 0.05mbar and shelf temperature of -10℃. Then, perform desorption drying for 4 hours under vacuum of 0.01mbar and shelf temperature of 25℃ to obtain freeze-dried milk tea powder.

[0048] Preparation of probiotic microcapsule powder; S1. Activate the probiotic strains and prepare them into bacterial sludge; S2. Sodium alginate-calcium ion gel layer encapsulation: A bacterial suspension was formed by mixing bacterial sludge with sodium alginate solution. This suspension was then added dropwise to calcium chloride solution using a 0.3mm pore size needle at a rate of 8ml / min and solidified for 20 minutes. The solution was filtered through a sterile sieve and rinsed with sterile water to obtain a single-layer encapsulated probiotic microcapsules. The concentration of the bacterial sludge was 3*10⁻⁶. 9CFU / ml; sodium alginate solution mass concentration is 2%; calcium chloride solution molar concentration is 0.1 mol / L; S3. Chitosan-pectin composite membrane encapsulation: The single-layer encapsulated probiotic microcapsules were placed in a composite solution of chitosan and pectin for membrane encapsulation, filtered with a sterile sieve and rinsed with sterile water to obtain double-layer encapsulated probiotic microcapsules. The preparation method of the chitosan and pectin composite solution includes the following steps: adding a pH adjuster to a chitosan solution and a pectin solution, both with a mass concentration of 5%, to adjust the pH value to 5.0, sterilizing and cooling, and then mixing the chitosan solution and pectin solution evenly at a mass ratio of 1:1 to obtain the chitosan and pectin composite solution.

[0049] S4. Inulin Layer Encapsulation: The double-layer encapsulated probiotic microcapsules were mixed and encapsulated in a 5% inulin solution to obtain a triple-layer encapsulated probiotic microcapsules. After filtration, the triple-layer encapsulated probiotic microcapsules were added to a lyophilization protectant solution, stirred evenly, and soaked for 20 minutes. After filtration, they were pre-frozen at -60℃ for 3 hours, and simultaneously subjected to primary drying at a vacuum of 0.05 mbar and a shelf temperature of -10℃ for 15 hours. Then, they were desorbed and dried at a vacuum of 0.01 mbar and a shelf temperature of 25℃ for 4 hours to obtain probiotic microcapsule powder. The lyophilization protectant solution consisted of the following components in parts by mass: 5 parts gum arabic, 10 parts trehalose, and 85 parts deionized water.

[0050] Freeze-dried milk tea powder and probiotic microcapsule powder are mixed evenly to obtain probiotic-encapsulated freeze-dried milk tea powder.

[0051] In this embodiment, the method for preparing the mycelium sludge in step S1 includes the following steps: B1. Select a preservation tube containing a quadrivalent bacterial strain (a complex bacterial group consisting of Lactobacillus rhamnosus GG, Lactobacillus rhamnosus HN001, Bifidobacterium animalis subsp. lactis HN019, and Bifidobacterium breve M-16V in a mass ratio of 1:1:1:1), and inoculate the strain into 10 ml of MRS broth medium (0.05% L-cysteine ​​sodium hydrochloride was added to the medium beforehand) under aseptic conditions.

[0052] B2. After inoculation, place the test tube in an anaerobic environment at 37±0.5℃ for 18 hours. When the culture medium becomes uniformly turbid, it indicates that the strain has been successfully grown and activated, and the first-stage activated bacterial solution is obtained.

[0053] B3. Take 4 ml of the primary activated bacterial culture and inoculate it into an Erlenmeyer flask containing 200 ml of MRS medium (0.05% L-cysteine ​​sodium hydrochloride was added to the medium in advance). Place it in an anaerobic environment at 37±0.5℃ for 18 hours to carry out secondary strain expansion culture. B4. Measure the OD600 value at 16, 17, 18, 19, and 20 hours after placement. Calculate the bacterial concentration based on the OD600 value. When the concentration reaches 3*10... 9 When the concentration of CFU / g is reached, the culture is stopped, and the strain culture is obtained.

[0054] B5. Dispense the bacterial culture medium into sterile centrifuge tubes and centrifuge them with the following parameters: temperature 0℃; speed 6000 rpm; time 10 minutes. After centrifugation, the supernatant in the centrifuge tube is the culture medium, and the lower layer is white bacterial sludge.

[0055] B6. Discard the supernatant in the centrifuge tube, wash the bacterial sludge with pre-cooled sterile physiological saline (0.85% NaCl), with a ratio of physiological saline to bacterial sludge of 0.5:1; centrifuge again after washing (temperature 0℃; speed 6000rpm; time 10 minutes); repeat the above operation to finally obtain pure activated bacterial sludge.

[0056] Example 3 A probiotic-encapsulated freeze-dried milk tea powder comprises freeze-dried milk tea powder and probiotic microcapsule powder in a mass ratio of 93:7; the probiotic microcapsule powder comprises probiotics and an encapsulation layer surrounding the probiotics, the encapsulation layer comprising, from the inside out, a sodium alginate-calcium ion gel layer, a chitosan-pectin composite membrane layer, and an inulin layer.

[0057] This embodiment also provides a method for preparing the above-mentioned probiotic-encapsulated freeze-dried milk tea powder, including the following steps: Preparation of freeze-dried milk tea powder: A1. By weight, heat 28 parts of refined coconut oil to 60°C, add 1 part of mono- and diglyceride fatty acid esters and mix well, then add 30 parts of tea soup, 47 parts of raw milk and 1 part of sucrose fatty acid esters, heat to 60°C and keep warm for 10 minutes to obtain the mixed raw materials. A2. The mixed raw materials are homogenized once under the conditions of first-stage homogenization pressure of 25MPa, second-stage pressure of 5MPa and temperature of 60℃. After that, they are homogenized a second time under the conditions of first-stage homogenization pressure of 20MPa, second-stage pressure of 4MPa and temperature of 65℃ to obtain a mixed liquid. A3. Pre-freeze the mixture at -50℃ for 3 hours, and simultaneously perform primary drying at a vacuum of 0.05mbar and a shelf temperature of 10℃ for 14 hours. Then, perform desorption drying at a vacuum of 0.01mbar and a shelf temperature of 35℃ for 6 hours to obtain freeze-dried milk tea powder.

[0058] Preparation of probiotic microcapsule powder; S1. Activate the probiotic strains and prepare them into bacterial sludge; S2. Sodium alginate-calcium ion gel layer encapsulation: A bacterial suspension was formed by mixing bacterial sludge with sodium alginate solution. This suspension was then added dropwise to calcium chloride solution using a 0.5mm pore size needle at a rate of 10ml / min and solidified for 30 minutes. The solution was filtered through a sterile sieve and rinsed with sterile water to obtain a single-layer encapsulated probiotic microcapsules. The concentration of the bacterial sludge was 3*10⁻⁶. 9 CFU / ml; sodium alginate solution mass concentration is 2%; calcium chloride solution molar concentration is 0.1 mol / L; S3. Chitosan-pectin composite membrane encapsulation: The single-layer encapsulated probiotic microcapsules were placed in a composite solution of chitosan and pectin for membrane encapsulation, filtered with a sterile sieve and rinsed with sterile water to obtain double-layer encapsulated probiotic microcapsules. The preparation method of the chitosan and pectin composite solution includes the following steps: adding a pH adjuster to a chitosan solution and a pectin solution, both with a mass concentration of 5%, to adjust the pH value to 5.5, sterilizing and cooling, and then mixing the chitosan solution and pectin solution evenly at a mass ratio of 1:1 to obtain the chitosan and pectin composite solution.

[0059] S4. Inulin Layer Encapsulation: The double-layer encapsulated probiotic microcapsules were mixed and encapsulated in a 5% inulin solution to obtain a triple-layer encapsulated probiotic microcapsules. After filtration, the triple-layer encapsulated probiotic microcapsules were added to a lyophilization protectant solution, stirred evenly, and soaked for 30 minutes. After filtration, they were pre-frozen at -60℃ for 3 hours, and simultaneously subjected to primary drying at a vacuum of 0.05 mbar and a shelf temperature of 10℃ for 14 hours. Then, they were desorbed and dried at a vacuum of 0.01 mbar and a shelf temperature of 35℃ for 6 hours to obtain probiotic microcapsule powder. The lyophilization protectant solution consisted of the following components in parts by mass: 5 parts gum arabic, 10 parts trehalose, and 85 parts deionized water.

[0060] Freeze-dried milk tea powder and probiotic microcapsule powder are mixed evenly to obtain probiotic-encapsulated freeze-dried milk tea powder.

[0061] In this embodiment, the method for preparing the mycelium sludge in step S1 includes the following steps: B1. Select a preservation tube containing a quadrivalent bacterial strain (a complex bacterial group consisting of Lactobacillus rhamnosus GG, Lactobacillus rhamnosus HN001, Bifidobacterium animalis subsp. lactis HN019, and Bifidobacterium breve M-16V in a mass ratio of 1:1:1:1), and inoculate the strain into 10 ml of MRS broth medium (0.05% L-cysteine ​​sodium hydrochloride was added to the medium beforehand) under aseptic conditions.

[0062] B2. After inoculation, place the test tube in an anaerobic environment at 37±0.5℃ for 20 hours. When the culture medium becomes uniformly turbid, it indicates that the strain has been successfully grown and activated, and the first-stage activated bacterial solution is obtained.

[0063] B3. Take 4 ml of the primary activated bacterial culture and inoculate it into an Erlenmeyer flask containing 200 ml of MRS medium (0.05% L-cysteine ​​sodium hydrochloride was added to the medium in advance). Place it in an anaerobic environment at 37±0.5℃ for 20 hours to carry out secondary strain expansion culture. B4. Measure the OD600 value at 16, 17, 18, 19, and 20 hours after placement. Calculate the bacterial concentration based on the OD600 value. When the concentration reaches 3*10... 9 When the concentration of CFU / g is reached, the culture is stopped, and the strain culture is obtained.

[0064] B5. Dispense the bacterial culture medium into sterile centrifuge tubes and centrifuge them with the following parameters: temperature 4℃; speed 8000 rpm; time 15 minutes. After centrifugation, the supernatant in the centrifuge tube is the culture medium, and the lower layer is white bacterial sludge.

[0065] B6. Discard the supernatant in the centrifuge tube, wash the bacterial sludge with pre-cooled sterile physiological saline (0.85% NaCl), with a ratio of physiological saline to bacterial sludge of 0.5:1; centrifuge again after washing (temperature 4℃; speed 8000rpm; time 15 minutes); repeat the above operation to finally obtain pure activated bacterial sludge.

[0066] To further verify the technical efficacy of the present invention, comparative examples are set up based on Example 1 as follows: Comparative Example 1 The only difference between this comparative example and Example 1 is that the probiotics were not encapsulated, and the freeze-dried milk tea powder was dried using spray drying instead of freeze drying.

[0067] The spray drying parameters are: Drying tower temperature: 90℃; Powder coating inlet air temperature: 150℃; Temperature inside the spray tower: 90℃.

[0068] Comparative Example 2 The only differences between this comparative example and Example 1 are that the encapsulation layer of the probiotic microcapsule powder is a sodium alginate-calcium ion gel layer, the preparation method of the probiotic microcapsule powder, and the freeze-drying method of the freeze-dried milk tea powder.

[0069] Specifically, in this comparative example, steps S3 and S4 are not included; that is, only the single-layer encapsulated probiotic microcapsules prepared in step S2 are used for freeze-drying preparation.

[0070] The freeze-drying method for freeze-dried milk tea powder includes the following steps: after filtering the single-layer encapsulated probiotic microcapsules, they are pre-frozen at -40℃ for 6 hours, and simultaneously dried at 0.05mbar for 24 hours to obtain probiotic microcapsule powder. The survival rate of the probiotic microcapsule powder / probiotics prepared in Examples 1-3 and Comparative Examples 1 and 2 after freeze-drying and under simulated gastric acid conditions were tested. The flavor retention of the probiotic-encapsulated freeze-dried milk tea powder was tested, and its solubility was tested in water at 40°C. Sensory evaluation of the probiotic-encapsulated freeze-dried milk tea powder was also conducted. The test results are shown in Table 1 below.

[0071] Table 1 Test results of the examples and comparative examples As shown in Table 1, the probiotic survival rate of the probiotic-encapsulated freeze-dried milk tea powder of the present invention can reach over 90%. Under simulated gastric acid conditions, the survival rate of probiotics is high, resulting in a rich milk tea flavor, short dissolution time, good condition, and a high sensory score. In contrast, the product prepared in the comparative example shows significant differences in all indicators: low probiotic survival rate, unsatisfactory survival rate under simulated gastric acid conditions, poor flavor retention, long dissolution time and incomplete dissolution, and a lower sensory score.

[0072] To further verify the technical efficacy of the present invention, the probiotic efficiency and product characteristics of the freeze-dried milk tea powder with probiotic directional encapsulation in Example 1 were tested. The test methods and test results are shown in Table 2 below.

[0073] Table 2. Test methods and results for probiotic efficiency and product characteristics. As shown in Table 2, the probiotic microcapsule powder of Example 1 of the present invention has a high encapsulation rate and a high number of live bacteria per gram of probiotic microcapsule powder, indicating that the probiotic microcapsule powder preparation process of the present invention can effectively encapsulate probiotics and ensure their activity. Furthermore, the probiotic-directed encapsulated freeze-dried milk tea powder of Example 1 of the present invention has low moisture content and water activity and good stability, indicating that the present invention can effectively achieve the drying of probiotic microcapsule powder while ensuring the activity of probiotics.

[0074] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A probiotic-encapsulated freeze-dried milk tea powder, characterized in that, The product includes freeze-dried milk tea powder and probiotic microcapsule powder, wherein the mass ratio of the freeze-dried milk tea powder to the probiotic microcapsule powder is (90-95):(5-10); the probiotic microcapsule powder includes probiotics and an encapsulation layer surrounding the probiotics, wherein the encapsulation layer comprises, from the inside out, a sodium alginate-calcium ion gel layer, a chitosan-pectin composite membrane layer, and an inulin layer.

2. The probiotic-encapsulated freeze-dried milk tea powder as described in claim 1, characterized in that, The preparation method of the probiotic microcapsule powder includes the following steps: S1. Activate the probiotic strains and prepare them into bacterial sludge; S2, Sodium alginate-calcium ion gel layer encapsulation: The bacterial mud is mixed with sodium alginate solution to form a bacterial suspension, which is then added dropwise to calcium chloride solution to solidify and form a single-layer encapsulated probiotic microcapsule; S3. Chitosan-pectin composite membrane encapsulation: Single-layer encapsulated probiotic microcapsules are placed in a composite solution of chitosan and pectin for coating to obtain double-layer encapsulated probiotic microcapsules. S4. Inulin layer encapsulation: The double-layer encapsulated probiotic microcapsules are mixed and encapsulated in an inulin solution to obtain a triple-layer encapsulated probiotic microcapsule. After filtration and freeze-drying, the probiotic microcapsule powder is obtained.

3. The probiotic-encapsulated freeze-dried milk tea powder as described in claim 2, characterized in that, The probiotics are a complex of Lactobacillus rhamnosus GG, Lactobacillus rhamnosus HN001, Bifidobacterium animalis subsp. lactis HN019, and Bifidobacterium breve M-16V, with a weight ratio of 1:1:1:

1.

4. The probiotic-encapsulated freeze-dried milk tea powder as described in claim 2, characterized in that, In step S2, the concentration of the bacterial sludge is 3*10. 9 CFU / ml; the mass concentration of the sodium alginate solution is 2%; the molar concentration of the calcium chloride solution is 0.1 mol / L.

5. The probiotic-encapsulated freeze-dried milk tea powder as described in claim 2, characterized in that, In step S3, the preparation method of the chitosan and pectin composite solution includes the following steps: adding a pH adjuster to a chitosan solution and a pectin solution, both with a mass concentration of 5%, to adjust the pH value to 5.0-5.5, sterilizing and cooling, and then mixing the chitosan solution and pectin solution evenly at a mass ratio of 1:1 to obtain the chitosan and pectin composite solution.

6. The probiotic-encapsulated freeze-dried milk tea powder as described in claim 2, characterized in that, In step S4, the mass concentration of the inulin solution is 5%.

7. The probiotic-encapsulated freeze-dried milk tea powder as described in claim 2, characterized in that, In step S4, the freeze-drying includes the following steps: adding the three-layer encapsulated probiotic microcapsules to the freeze-drying protectant solution, stirring evenly and soaking for 20-30 minutes, filtering, pre-freezing at -50±10℃ for 3 hours to form small ice crystals, then performing primary drying, and then performing analytical drying to obtain probiotic microcapsule powder.

8. The probiotic-encapsulated freeze-dried milk tea powder as described in claim 7, characterized in that, The freeze-drying protectant solution comprises the following components in parts by weight: 5 parts gum arabic, 10 parts trehalose, and 85 parts deionized water.

9. The probiotic-encapsulated freeze-dried milk tea powder as described in claim 1, characterized in that, The preparation method of the freeze-dried milk tea powder includes the following steps: A1. By weight, heat 26-28 parts of refined coconut oil to 55-60℃, add 0.5-1 parts of mono- and diglyceride fatty acid esters and mix well. Then add 26-30 parts of tea infusion, 45-47 parts of raw milk and 0.5-1 parts of sucrose fatty acid esters, heat to 55-60℃ and keep warm for 5-10 minutes to obtain the mixed raw materials. A2. Homogenize the mixed raw materials once at 55-60℃, and then homogenize them a second time at 60-65℃ to obtain a mixed liquid. A3. Pre-freeze the mixed liquid at -50±10℃ for 3 hours to form small ice crystals; then perform primary drying and subsequent analytical drying to obtain freeze-dried milk tea powder.

10. A method for preparing probiotic-encapsulated freeze-dried milk tea powder as described in any one of claims 1-9, characterized in that, Includes the following steps: Preparation of freeze-dried milk tea powder; Preparation of probiotic microcapsule powder; Freeze-dried milk tea powder and probiotic microcapsule powder are mixed evenly to obtain probiotic-encapsulated freeze-dried milk tea powder.

Images