Freeze-dried strawberry probiotic milk bean with core-shell structure and preparation method thereof
阅读说明：本技术 一种核壳结构的冻干草莓益生菌奶豆及其制备方法 (Freeze-dried strawberry probiotic milk bean with core-shell structure and preparation method thereof ) 是由 施源德 欧阳锐 康竞红 李莉鑫 项雷文 于 2021-10-08 设计创作，主要内容包括：本发明提供一种核壳结构的冻干草莓益生菌奶豆及其制备方法,本发明的方法包括如下步骤：(1)预制壁材、(2)制备芯材、(3)制备微胶囊、(4)制备保护层、(5)注模成型、(6)预冻结、(7)真空冷冻、(8)成品包装。本发明方法制备的核壳结构的冻干草莓益生菌奶豆结构口感特殊,复水率高,营养丰富且益生菌存活量多。本发明的核壳结构的冻干草莓益生菌奶豆的制备方法采用益生菌微胶囊包埋技术,使益生菌能在进入肠道之后才在肠道中缓慢释放,从而能保持益生菌的活性并有效发挥其作用。(The invention provides freeze-dried strawberry probiotic milk beans with a core-shell structure and a preparation method thereof, wherein the method comprises the following steps: (1) preparing a wall material, (2) preparing a core material, (3) preparing a microcapsule, (4) preparing a protective layer, (5) performing injection molding, (6) pre-freezing, (7) performing vacuum freezing, and (8) packaging a finished product. The freeze-dried strawberry probiotic milk bean with the core-shell structure prepared by the method has the advantages of special structural taste, high rehydration rate, rich nutrition and high survival rate of probiotics. The preparation method of the freeze-dried strawberry probiotic milk bean with the core-shell structure adopts a probiotic microcapsule embedding technology, so that probiotics can be slowly released in an intestinal tract after entering the intestinal tract, and the activity of the probiotics can be maintained and the effect of the probiotics can be effectively exerted.)
1. A preparation method of freeze-dried strawberry probiotic milk beans with a core-shell structure is characterized by comprising the following steps: the method comprises the following steps:
(1) preparing a wall material: dissolving sodium alginate in water at 70-80 ℃ to prepare a sodium alginate water solution with the concentration of 15-20 g/L, and then cooling to room temperature for later use; adding water into whey protein, stirring for 2-3 h to prepare a whey protein aqueous solution with the concentration of 15-20 g/L, centrifuging at 3000-4000 rpm for 20-30 min, taking supernatant, and mixing the obtained sodium alginate aqueous solution with the supernatant, wherein the mass ratio of the sodium alginate to the whey protein is 1-2: 1-2;
(2) preparing a core material: putting probiotics into a container, adding glycerol, fully mixing, adding olive oil, and stirring at the stirring speed of 800-1000 rpm for 20-30 min to obtain a core material; the mass ratio of the probiotics to the glycerin to the olive oil is 1-2: 12-24: 24-60 parts;
(3) preparing microcapsules: mixing and stirring the wall material prepared in the step (1) and the core material prepared in the step (2) at 300-500 rpm for 15-30 min to form a microcapsule; the mass ratio of the wall material prepared in the step (1) to the core material prepared in the step (2) is 1-3: 2-4;
(4) preparing a protective layer: adding the microcapsule prepared in the step (3) into mixed slurry consisting of skimmed milk powder and mannitol, stirring for 5-10 min, wherein the mass ratio of the microcapsule prepared in the step (3) to the mixed slurry is 3: 1-2, the mass ratio of the skimmed milk powder to the mannitol in the mixed slurry is 1-5: 1,
(5) injection molding: mixing strawberry powder, skimmed milk powder and water into mixed slurry, coating the mixed slurry on the inner wall of a mold, and injecting the material prepared in the step (4) into the mold, wherein the mass ratio of the strawberry powder to the skimmed milk powder to the water in the mixed slurry prepared from the strawberry powder, the skimmed milk powder and the water is 1: 2-4: 1;
(6) pre-freezing: pre-freezing the material subjected to injection molding in the step (5) at-40 ℃ to-50 ℃ for 8-12 hours;
(7) vacuum freezing: keeping the temperature of the bin body at-30 to-40 ℃ for 20 to 23 hours under the pressure of 0.1 to 1Pa and the temperature of a heating plate at 30 to 40 ℃;
(8) and (6) packaging a finished product.
2. The preparation method of freeze-dried strawberry probiotic milk beans with a core-shell structure according to claim 1 is characterized in that: the relative humidity of the finished product package of the package (8) is 30-45%, and the temperature is lower than 25 ℃.
3. The preparation method of freeze-dried strawberry probiotic milk beans with a core-shell structure according to claim 1 is characterized in that: the probiotic powder is freeze-dried mixed powder of composite bifidobacteria.
4. The preparation method of freeze-dried strawberry probiotic milk beans with a core-shell structure according to claim 1 is characterized in that: after the strawberry powder, the skim milk powder and the water are mixed into mixed slurry, a 60-100-mesh screen is used for filtering and defoaming.
5. The preparation method of freeze-dried strawberry probiotic milk beans with a core-shell structure according to claim 1 is characterized in that: and (3) when the core material is prepared in the step (2), stirring and then ultrasonically dispersing for 2-3 min.
6. A freeze-dried strawberry probiotic milk bean with a core-shell structure is characterized in that: prepared by the method of any one of claims 1-5.
Technical Field
The invention relates to the technical field of food processing, in particular to freeze-dried strawberry probiotic milk beans with a core-shell structure and a preparation method thereof.
Background
The conventional milk bean processing needs to prepare milk bean molding by high-temperature baking (baking temperature is more than 100 ℃), and the milk beans obtain lower moisture, hardness and the like. Therefore, the temperature-resistant components in the traditional milk bean raw materials can be damaged, the tissue is compact, and the taste is hard. And traditional milk bean products are not suitable for consumption by young children.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides freeze-dried strawberry probiotic milk beans with a core-shell structure and a preparation method thereof. The preparation method of the freeze-dried strawberry probiotic milk bean with the core-shell structure adopts a probiotic microcapsule embedding technology, so that probiotics can be slowly released in an intestinal tract after entering the intestinal tract, and the activity of the probiotics can be maintained and the effect of the probiotics can be effectively exerted.
The invention is realized by the following technical scheme
A preparation method of freeze-dried strawberry probiotic milk beans with a core-shell structure comprises the following steps:
(1) preparing a wall material: dissolving sodium alginate in water at 70-80 ℃ to prepare a sodium alginate water solution with the concentration of 15-20 g/L, and then cooling to room temperature for later use; adding water into whey protein, stirring for 2-3 h to prepare a whey protein aqueous solution with the concentration of 15-20 g/L, centrifuging at 3000-4000 rpm for 20-30 min, taking supernatant, and mixing the obtained sodium alginate aqueous solution with the supernatant, wherein the mass ratio of the sodium alginate to the whey protein is 1-2: 1-2;
(2) preparing a core material: putting probiotics into a container, adding glycerol, fully mixing, adding olive oil, and stirring at the stirring speed of 800-1000 rpm for 20-30 min to obtain a core material; the mass ratio of the probiotics to the glycerin to the olive oil is 1-2: 12-24: 24-60 parts;
(3) preparing microcapsules: stirring the wall material prepared in the step (1) and the core material prepared in the step (2) at 300-500 rpm for 15-30 min to form a microcapsule; the mass ratio of the wall material prepared in the step (1) to the core material prepared in the step (2) is 1: 2-3: 4;
(4) preparing a protective layer: adding the microcapsule prepared in the step (3) into mixed slurry consisting of skimmed milk powder and mannitol, stirring for 5-10 min, wherein the mass ratio of the microcapsule prepared in the step (3) to the mixed slurry is 3: 1-2, the mass ratio of the skimmed milk powder to the mannitol in the mixed slurry is 1-5: 1,
(5) injection molding: mixing strawberry powder, skimmed milk powder and water into mixed slurry, coating the mixed slurry on the inner wall of a mold, and injecting the material prepared in the step (4) into the mold, wherein the mass ratio of the strawberry powder to the skimmed milk powder to the water in the mixed slurry prepared from the strawberry powder, the skimmed milk powder and the water is 1: 2-4: 1;
(6) pre-freezing: pre-freezing the material subjected to injection molding in the step (5) at-40 ℃ to-50 ℃ for 8-12 hours;
(7) vacuum freezing: keeping the temperature of the bin body at-30 to-40 ℃ for 20 to 23 hours under the pressure of 0.1 to 1Pa and the temperature of a heating plate at 30 to 40 ℃;
(8) and (6) packaging a finished product.
Further, the relative humidity of the finished package (8) is 30-45%, and the temperature is lower than 25 ℃.
Further, the probiotic powder is a freeze-dried mixed powder of the complex bifidobacteria (Shandong Zhongke Jiayi bioengineering Co., Ltd. or DuPont Nutrition food ingredient (Beijing) Co., Ltd.).
Further, after the strawberry powder, the skim milk powder and the water are mixed into mixed slurry, a 60-100-mesh screen is used for filtering and defoaming.
Further, when the core material is prepared in the step (2), stirring and then performing ultrasonic dispersion for 2-3 min.
Preferably, the strawberry powder, the skim milk powder and the water are mixed into mixed slurry, and then the mixed slurry is filtered by a 60-100-mesh screen to remove bubbles.
The additive mainly comprises glycerol, olive oil, sodium alginate, lactalbumin, skimmed milk powder, mannitol and strawberry powder.
Glycerol: the water phase in the W/O core material and glycerol are used as a protective agent and an antifreeze agent in cryopreservation to prevent damage to cells due to freezing or continuous sublimation of water.
Olive oil: the oil phase in the W/O core material, namely the olive oil, is the grease which is considered to be most suitable for human nutrition so far, and the olive oil is selected mainly to have rich health care effect on human bodies.
Sodium alginate: the sodium alginate has good shape retention, gel shape and stability, and most of materials show that the sodium alginate is an excellent choice as a probiotic bacteria embedding wall material.
Whey protein: because many microporous structures exist on the surface of the sodium alginate, the embedding effect is not ideal when the sodium alginate microcapsule is used as a single microcapsule wall material, and therefore the whey protein which has extremely high nutritive value and effectively improves the survival rate of probiotics and the sodium alginate are selected to form the composite wall material.
Skim milk powder: the lyoprotectant also improves the concentration and increases the dry matter content to achieve the desired shape.
Mannitol as excipient, freeze-drying protection, and improving the disintegration temperature of the product to obtain the product with good shape and easy freeze-drying. And the sugar substitute and the flavor regulation function are realized in the experiment.
The strawberry powder is added with a proper amount of strawberry powder to improve the crisp feeling of food in mouth, and partial sour taste is added on the basis of the sweet taste of the skim milk powder and the mannitol, so that the product has proper taste and flavor. And the strawberry powder has high heat sensitivity, and the product is easy to freeze-dry.
Compared with the prior art, the invention has the following beneficial effects:
(1) the freeze-dried strawberry probiotic milk bean with the core-shell structure provided by the invention has high probiotic content, and the survival rate of the probiotics added into the milk product after processing is effectively increased;
(2) the detection proves that the freeze-dried strawberry probiotic milk beans with the core-shell structure have low water content, which indicates that the product can be well preserved at normal temperature after being packaged by the barrier material;
(3) the detection proves that the freeze-dried strawberry probiotic milk bean with the core-shell structure has low hardness and high rehydration ratio, and the product has good taste and can achieve the effect of melting in the mouth after rehydration.
(4) The preparation method of the freeze-dried strawberry probiotic milk bean with the core-shell structure adopts a probiotic microcapsule embedding technology, so that probiotics can be slowly released in an intestinal tract after entering the intestinal tract, and the activity of the probiotics can be maintained and the effect of the probiotics can be effectively exerted.
Drawings
FIG. 1 is a 100-fold enlarged cross-sectional view of the milk bean of example 1;
fig. 2 is a 400-fold enlarged sectional view of the milk beans of example 1.
Detailed Description
The invention is further described below with reference to specific embodiments.
The freeze-dried strawberry probiotic milk beans with the core-shell structure and the preparation method thereof provided by the invention have more optional factors, and various embodiments can be designed, so that the specific embodiments are only used as an exemplary illustration of a specific implementation mode of the invention, and do not limit the scope of the invention. The following examples are chosen to illustrate the invention in order to provide a thorough understanding of the invention and to enable those skilled in the art to practice the invention. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
Example 1
A preparation method of freeze-dried strawberry probiotic milk beans with a core-shell structure comprises the following steps:
(1) preparing a wall material: dissolving sodium alginate in water at 70 deg.C to obtain sodium alginate water solution with concentration of 15g/L, and cooling to room temperature; adding water into whey protein, stirring for 2h to prepare a whey protein aqueous solution with the concentration of 15g/L, centrifuging at 3000rpm for 20min, taking supernatant, and mixing the obtained sodium alginate aqueous solution with the supernatant, wherein the mass ratio of the sodium alginate to the whey protein is 1: 1;
(2) preparing a core material: putting probiotics into a container, adding glycerol, fully mixing, adding olive oil, and stirring at the stirring speed of 800rpm for 20min to obtain a core material; the mass ratio of the probiotics to the glycerin to the olive oil is 1: 12: 24;
(3) preparing microcapsules: stirring the wall material prepared in the step (1) and the core material prepared in the step (2) at 300rpm for 30min to form a microcapsule; the mass ratio of the wall material prepared in the step (1) to the core material prepared in the step (2) is 1: 2;
(4) preparing a protective layer: adding the microcapsule prepared in the step (3) into mixed slurry consisting of skimmed milk powder and mannitol, stirring for 5min, wherein the mass ratio of the microcapsule prepared in the step (3) to the mixed slurry is 3:1, the mass ratio of the skimmed milk powder to the mannitol in the mixed slurry is 1:1,
(5) injection molding: mixing strawberry powder, skimmed milk powder and water into mixed slurry, coating the mixed slurry on the inner wall of a mold, and injecting the material prepared in the step (4) into the mold, wherein the mass ratio of the strawberry powder to the skimmed milk powder to the water in the mixed slurry prepared from the strawberry powder, the skimmed milk powder and the water is 1:2: 1;
(6) pre-freezing: pre-freezing the material subjected to injection molding in the step (5) at-40 ℃ for 12 hours;
(7) vacuum freezing: under the pressure of 0.1Pa, under the heating plate with the temperature of 30 ℃, and the temperature of the cabin body is kept for 23 hours under-30 ℃;
(8) and (6) packaging a finished product.
The relative humidity of the finished package (8) is 30% and the temperature is below 25 ℃.
The probiotic powder is lyophilized mixed powder of composite Bacillus bifidus (Shandong Zhongke Jiayi bioengineering Co., Ltd. or DuPont nutritional food ingredient (Beijing) Co., Ltd.).
The strawberry powder, the skim milk powder and the water are mixed into mixed slurry, and then the mixed slurry is filtered by a 60-mesh screen to remove bubbles.
And (3) when the core material is prepared in the step (2), stirring and then performing ultrasonic dispersion for 2 min.
The strawberry powder, the skim milk powder and the water are mixed into mixed slurry, and then the mixed slurry is filtered by a 60-mesh screen to remove bubbles.
Example 2
A preparation method of freeze-dried strawberry probiotic milk beans with a core-shell structure comprises the following steps:
(1) preparing a wall material: dissolving sodium alginate in water at 80 deg.C to obtain sodium alginate water solution with concentration of 20g/L, and cooling to room temperature; adding water into the whey protein, stirring for 3h to prepare a whey protein aqueous solution with the concentration of 20g/L, centrifuging at 4000rpm for 30min, taking supernatant, and mixing the obtained sodium alginate aqueous solution with the supernatant, wherein the mass ratio of the sodium alginate to the whey protein is 1: 2;
(2) preparing a core material: putting probiotics into a container, adding glycerol, fully mixing, adding olive oil, and stirring at the stirring speed of 1000rpm for 20min to obtain a core material; the mass ratio of the probiotics to the glycerin to the olive oil is 2: 12: 60, adding a solvent to the mixture;
(3) preparing microcapsules: stirring the wall material prepared in the step (1) and the core material prepared in the step (2) at 500rpm for 15min to form microcapsules; the mass ratio of the wall material prepared in the step (1) to the core material prepared in the step (2) is 1: 4;
(4) preparing a protective layer: adding the microcapsule prepared in the step (3) into mixed slurry consisting of skimmed milk powder and mannitol, stirring for 10min, wherein the mass ratio of the microcapsule prepared in the step (3) to the mixed slurry is 3:2, the mass ratio of the skimmed milk powder to the mannitol in the mixed slurry is 5:1,
(5) injection molding: mixing strawberry powder, skimmed milk powder and water into mixed slurry, coating the mixed slurry on the inner wall of a mold, and injecting the material prepared in the step (4) into the mold, wherein the mass ratio of the strawberry powder to the skimmed milk powder to the water in the mixed slurry prepared from the strawberry powder, the skimmed milk powder and the water is 1:4: 1;
(6) pre-freezing: pre-freezing the material subjected to injection molding in the step (5) at-50 ℃ for 8 hours;
(7) vacuum freezing: under the pressure of 1Pa, under the heating plate with the temperature of 40 ℃, and the temperature of the cabin body is kept for 20 hours at minus 40 ℃;
(8) and (6) packaging a finished product.
The relative humidity of the finished package (8) is 45% and the temperature is below 25 ℃.
The probiotic powder is lyophilized mixed powder of composite Bacillus bifidus (Shandong Zhongke Jiayi bioengineering Co., Ltd. or DuPont nutritional food ingredient (Beijing) Co., Ltd.).
The strawberry powder, the skim milk powder and the water are mixed into mixed slurry, and then the mixed slurry is filtered by a 100-mesh screen to remove bubbles.
And (3) when the core material is prepared in the step (2), stirring and then performing ultrasonic dispersion for 3 min.
The strawberry powder, the skim milk powder and the water are mixed into mixed slurry, and then the mixed slurry is filtered by a 100-mesh screen to remove bubbles.
Example 3
A preparation method of freeze-dried strawberry probiotic milk beans with a core-shell structure comprises the following steps:
(1) preparing a wall material: dissolving sodium alginate in water at 75 deg.C to obtain sodium alginate water solution with concentration of 17g/L, and cooling to room temperature; adding water into the whey protein, stirring for 2.5h to prepare a 17g/L whey protein aqueous solution, centrifuging at 3500rpm for 25min, taking supernatant, and mixing the obtained sodium alginate aqueous solution with the supernatant, wherein the mass ratio of the sodium alginate to the whey protein is 2: 1;
(2) preparing a core material: putting probiotics into a container, adding glycerol, fully mixing, adding olive oil, and stirring at the stirring speed of 900rpm for 25min to obtain a core material; the mass ratio of the probiotics to the glycerin to the olive oil is 1: 24: 30, of a nitrogen-containing gas;
(3) preparing microcapsules: stirring the wall material prepared in the step (1) and the core material prepared in the step (2) at 400rpm for 16min to form microcapsules; the mass ratio of the wall material prepared in the step (1) to the core material prepared in the step (2) is 3: 4;
(4) preparing a protective layer: adding the microcapsule prepared in the step (3) into mixed slurry consisting of skimmed milk powder and mannitol, stirring for 6min, wherein the mass ratio of the microcapsule prepared in the step (3) to the mixed slurry is 3:1.5, the mass ratio of the skimmed milk powder to the mannitol in the mixed slurry is 2:1,
(5) injection molding: mixing strawberry powder, skimmed milk powder and water into mixed slurry, coating the mixed slurry on the inner wall of a mold, and injecting the material prepared in the step (4) into the mold, wherein the mass ratio of the strawberry powder to the skimmed milk powder to the water in the mixed slurry prepared from the strawberry powder, the skimmed milk powder and the water is 1:3: 1;
(6) pre-freezing: pre-freezing the material subjected to injection molding in the step (5) at-45 ℃ for 10 hours;
(7) vacuum freezing: keeping the temperature of the bin body at minus 35 ℃ for 25 hours under the pressure of 0.5Pa and the temperature of 35 ℃ under a heating plate;
(8) and (6) packaging a finished product.
The relative humidity of the finished package (8) is 40% and the temperature is below 25 ℃.
The probiotic powder is lyophilized mixed powder of composite Bacillus bifidus (Shandong Zhongke Jiayi bioengineering Co., Ltd. or DuPont nutritional food ingredient (Beijing) Co., Ltd.).
The strawberry powder, the skim milk powder and the water are mixed into mixed slurry, and then the mixed slurry is filtered by a 80-mesh screen to remove bubbles.
And (3) when the core material is prepared in the step (2), stirring and then performing ultrasonic dispersion for 2.5 min.
The strawberry powder, the skim milk powder and the water are mixed into mixed slurry, and then the mixed slurry is filtered by a 80-mesh screen to remove bubbles.
Comparative example 1
The difference from example 2 is that corn oil is used instead of olive oil. The texture properties of the bacteria are different from those of example 2, so that the properties of the bacteria, such as water retention rate, hardness and rehydration rate, and colony count, are inferior to those of example 2.
Comparative example 2
The difference from example 2 is that after steps 1 and 2, the wall material of step 1 and the core material of step 2 are directly injection molded after ultrasonic mixing at step 3, and then steps 6, 7 and 8 are performed.
Comparative example 3
The difference from the embodiment 2 is that after the steps 1 and 2, the wall material of the step 1 and the core material of the step 2 are directly injection molded after being uniformly stirred by magnetic force, and then the steps 6, 7 and 8 are carried out.
Comparative example 4
The difference from example 2 is that (4) a protective layer is prepared: and (3) adding the microcapsules prepared in the step (3) into mixed slurry consisting of skimmed milk powder and mannitol, and stirring for 5-10 min, wherein the mass ratio of the microcapsules prepared in the step (3) to the mixed slurry is 10:3, and the mass ratio of the skimmed milk powder to the mannitol in the mixed slurry is 1-5: 1.
Comparative example 5
The method is different from the embodiment 2 in that the original step (1) of prefabricating the wall material is omitted, and the method only comprises the following steps:
(1) preparing a core material: putting probiotics into a container, adding glycerol, fully mixing, adding olive oil, and stirring at the stirring speed of 800-1000 rpm for 20-30 min to obtain a core material; the mass ratio of the probiotics to the glycerin to the olive oil is 1-2: 12-24: 24-60 parts;
(2) preparing microcapsules: stirring the core material prepared in the step (1) at 300-500 rpm for 15-30 min to form a microcapsule;
(3) preparing a protective layer: adding the microcapsules prepared in the step (2) into mixed slurry consisting of skimmed milk powder and mannitol, and stirring for 5-10 min, wherein the mass ratio of the microcapsules prepared in the step (2) to the mixed slurry is 3: 1-2, and the mass ratio of the skimmed milk powder to the mannitol in the mixed slurry is 1-5: 1;
(4) injection molding: mixing strawberry powder, skimmed milk powder and water into mixed slurry, coating the mixed slurry on the inner wall of a mold, and injecting the material prepared in the step (3) into the mold, wherein the mass ratio of the strawberry powder to the skimmed milk powder to the water in the mixed slurry prepared from the strawberry powder, the skimmed milk powder and the water is 1: 2-4: 1;
(5) pre-freezing: pre-freezing the material subjected to injection molding in the step (4) at-40 ℃ to-50 ℃ for 8-12 hours;
(6) vacuum freezing: keeping the temperature of the bin body at-30 to-40 ℃ for 20 to 23 hours under the pressure of 0.1 to 1Pa and the temperature of a heating plate at 30 to 40 ℃;
(7) and (6) packaging a finished product.
Comparative example 6
The difference from example 2 is that the steps (6) of pre-freezing and (7) of vacuum freezing are changed to oven-drying. Oven drying conditions were as follows:
(1) under normal pressure conditions: the pressure of the frozen material is 100000 Pa;
(2) heating plate temperature: the heating temperature of the material spreading plate is 100 ℃;
(3) temperature in the cabin: the temperature in the bin where the material spreading plate is located is 100 ℃;
(4) and (3) preparing a finished product: the finished product is packaged at normal temperature and normal pressure.
Evaluation of Experimental Effect
1. Sensory rating (full score 30 points)
TABLE 1 sensory evaluation index System
According to the examples of the invention and the comparison documents, the flavor, mouthfeel and texture were organoleptically scored, and the samples were randomly offered to 10 trained persons for tasting and identification, and scored according to table 1.
2. The rehydration ratio is as follows: weighing a certain mass of freeze-dried strawberry probiotic milk beans with the core-shell structure and a product m of a comparison file1(g) Soaking in a centrifuge tube containing distilled water at constant temperature of 20 deg.C for 1h, centrifuging at 4000r/min for 30min, and weighing precipitate m2(g) M represents the rehydration ratioAfter centrifugation/mBefore centrifugation；
3. Hardness: the measurement parameters were as follows: the probe is a cylinder with the diameter of 20mm, the downward moving speed is 1mm/s, the compression rate is 50%, the upward moving speed after pressing is 5.00mm/s, the retention time is 5s, and the texture instrument attribute 'brittleness' is defined as the pressure peak value of the first extrusion of the sample. The measurements of each experimental treatment group were repeated three times, and the measurement results were averaged.
4. Determination of bifidobacteria: the measurement was carried out by the plate colony counting method of "food microbiological test- -lactic acid bacteria test" in GB4789.35-2016, and the measurement of each experimental treatment group was repeated three times, and the measurement results were averaged.
As can be seen from table 2, compared with the conventional milk beans, the freeze-dried strawberry probiotic milk beans with the core-shell structure of the embodiment of the invention can improve the rehydration rate to 4.44, and improve the flavor, taste and tissue state of the milk beans; the hardness and water binding capacity of milk beans can be respectively reduced to 29.9N and 1.04 percent, and the number of the active probiotics is more than 1.0x106 cfu/g; compared with a comparative example, the freeze-dried strawberry probiotic milk bean with the core-shell structure has the advantages of better flavor, mouthfeel and tissue state, higher rehydration rate and lower hardness and water retention.
TABLE 2 sensory scores and comparison of important indices
Fig. 1 is a 100-fold enlarged cross-sectional view of a freeze-dried strawberry probiotic milk bean of the core-shell structure of example 1; fig. 2 is a 400-fold enlarged cross-sectional view of the freeze-dried strawberry probiotic milk beans of the core-shell structure of example 1. As can be seen from the picture in fig. 1, the hot air drying damages the structure of the milk beans and the holes have uneven sizes; and after the freeze drying technology treatment, the holes are uniform. The reason for this is probably that the vacuum freeze drying process causes the dissolved bean ice crystals to sublimate directly to form a porous structure, so that the structure of the sample before treatment can be better maintained, and the sensory quality is better.
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