阅读说明：本技术 一种酪乳粉及其制备方法 (Buttermilk powder and preparation method thereof ) 是由 孙颜君 徐蕴桃 刘振民 王吉栋 党慧杰 于 2020-12-29 设计创作，主要内容包括：本发明公开了一种酪乳粉的制备方法,该制备方法包括如下步骤：(1)离心稀奶油,离心结束后,收集下层水相；(2)采用酸碱调节剂调节步骤(1)中下层水相PH至5～7,再将其搅打至奶油成团,酪乳完全析出,用纱布过滤后,收集得到酪乳；(3)对步骤(2)中的酪乳进行微滤膜分离纯化,得到乳脂球膜,将乳脂球膜冷冻,再干燥,得到乳脂球膜粉末,将其置于低温保存；(4)将步骤(3)制备的乳脂球膜粉末加入酸奶中,进行发酵,发酵结束后破乳,即得。本发明的酪乳粉中膜蛋白含量高,极性脂含量高。(The invention discloses a preparation method of buttermilk powder, which comprises the following steps: (1) centrifuging the cream, and collecting the lower water phase after centrifuging; (2) adjusting the pH value of the lower-layer water phase in the step (1) to 5-7 by using an acid-base regulator, then stirring the lower-layer water phase until the lower-layer water phase is agglomerated into cream, completely separating out the buttermilk, filtering the buttermilk by using gauze, and collecting the buttermilk; (3) performing microfiltration membrane separation and purification on the buttermilk in the step (2) to obtain a buttermilk spherical membrane, freezing the buttermilk spherical membrane, drying to obtain buttermilk spherical membrane powder, and storing at low temperature; (4) and (4) adding the milk fat globule membrane powder prepared in the step (3) into the yoghourt, fermenting, and demulsifying after the fermentation is finished to obtain the milk fat globule membrane yoghourt. The casein powder of the invention has high content of membrane protein and high content of polar lipid.)

1. The preparation method of the buttermilk powder is characterized by comprising the following steps:

(1) centrifuging the cream, and collecting the lower water phase after centrifuging;

(2) adjusting the pH value of the lower-layer water phase in the step (1) to 5-7 by using an acid-base regulator, then stirring the lower-layer water phase until the lower-layer water phase is agglomerated into cream, completely separating out the buttermilk, filtering the buttermilk by using gauze, and collecting the buttermilk;

(3) performing microfiltration membrane separation and purification on the buttermilk in the step (2) to obtain a buttermilk spherical membrane, freezing the buttermilk spherical membrane, drying to obtain buttermilk spherical membrane powder, and storing at low temperature;

(4) and (4) adding the milk fat globule membrane powder prepared in the step (3) into the yoghourt, fermenting, and demulsifying after the fermentation is finished to obtain the milk fat globule membrane yoghourt.

2. The method for preparing buttermilk powder of claim 1, wherein in step (1), the centrifugation conditions are: the centrifugal force is 750 Xg-1000 Xg, the time is 10-15 min, and the temperature is 10-15 ℃.

3. The method for preparing buttermilk powder of claim 1, wherein in step (2), the whipping conditions are: the stirring speed is 800 r/min-1000 r/min, and the temperature is 10-20 ℃.

4. The method for preparing buttermilk powder of claim 1, wherein in step (2), the acid-base modifier is citric acid and sodium hydroxide; the temperature of the lower water phase is 10-20 ℃.

5. The method for preparing buttermilk powder of claim 1, wherein in step (3), the microfiltration membrane is a 0.22 μm polyethersulfone membrane.

6. The method for preparing buttermilk powder of claim 1, wherein in step (3), the conditions for microfiltration membrane separation and purification are as follows: the temperature is 5-35 ℃, the pH of the buttermilk is adjusted to 7-8 by adopting an acid-base regulator, the membrane pressure is 0.45-1 bar, and the washing and filtering times are 5 times.

7. The method for preparing buttermilk powder of claim 1, wherein in step (3), the low temperature storage is storage at-20 ℃.

8. The method of claim 1, wherein the freezing temperature in step (3) is-80 ℃.

9. The method for preparing buttermilk powder of claim 1, wherein the terminal acidity of fermentation in step (4) is from 70 to 90 ° T.

10. A buttermilk powder obtainable by the process of any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of fermented foods, and particularly relates to buttermilk powder and a preparation method thereof.

Background

The Milk Fat Globule Membrane (MFGM) is a three-layer membrane structure wrapped in the outer layer of fat droplets in cow milk, and the presence of the MFGM enables the fat droplets to be stably distributed in cow milk to form an oil-in-water emulsion state. MFGM is rich in polar lipids, such as Sphingomyelin (SM) and phospholipids such as Phosphatidylethanolamine (PE), Phosphatidylcholine (PC), Phosphatidylserine (PS), and Phosphatidylinositol (PI). The research shows that the polar lipid has the functions of regulating cholesterol metabolism, resisting inflammation and neurodegeneration and enhancing memory. The MFGM three-layer membrane structure is inlaid or surface-bound with various proteins, such as milk fat-like protein (BTN), xanthine dehydrogenase/oxidase (XDH/XO), mucus 1(MUC1), lectin 6/7(PAS 6/7), phospholipid (ADPH), cluster of differentiation 36(CD36), Fatty Acid Binding Protein (FABP) and peptone 3(PP3), and the like, and researches show that the membrane proteins have the effects of resisting apoptosis, phagocytosing apoptotic cells and improving the immunity of the organism.

Buttermilk (BM), a by-product of butter processing, is the aqueous component released during whipping of cream, and has a composition similar to skim milk, but is rich in MFGM components. The polar lipid content in BM is about 6 times that of whole milk, which can be an ideal source of MFGM. Industrially, buttermilk enriched with MFGM components has in the past typically been discarded or spray dried for use in the production of animal feed. With the increasing understanding of the structure, nutrition and health functions of MFGM, some dairy companies have begun to study methods of making MFGM and develop MFGM-rich dairy products. The buttermilk serving as a byproduct of milk fat processing is used as an MFGM source, so that the production cost can be greatly reduced, and the additional value of the buttermilk is improved.

Researches find that the traditional whipping process conditions have great influence on the content of each component of the butter milk, the conditions such as whipping speed and the like in the industry are not effectively controlled, and the problems of low yield of the butter milk, low content of related components of MFGM, poor dehydration effect of butter and the like exist in the process of producing the butter milk. Zahra Haddadian et al report that temperature and pH of whipped cream have a significant effect on membrane protein content and the activity of XO in membrane proteins, with higher temperatures and pH increasing the proportion of non-membrane proteins and significantly decreasing XO content. Meanwhile, Xuena Qu et al report that the process conditions in the cream processing process affect the composition and proportion of the MFGM protein, even change the functional properties of the MFGM protein, and centrifugation and whipping can have different effects on the components of the buttermilk. Researches show that the stirring speed can directly influence the time for reaching the solid-liquid-fat ratio, the optimal stirring speed can ensure that the moisture content in the butter is the lowest, more moisture is discharged, and more hydrophilic components are carried, the higher and lower stirring speeds can firstly cause the moisture content of the butter to be more and the texture to be soft, thus influencing the efficiency of next step of pressure refining, and secondly can influence the discharge of effective components such as butter milk yield and MFGM segments. Therefore, the research on the process for preparing the buttermilk is beneficial to obtaining the buttermilk with high yield and high MFGM component, and provides a basis for further applying to the development of functional dairy products.

The invention combines the industrial production practice, optimizes the preparation process of the buttermilk, and prepares the buttermilk product which has high yield and is rich in membrane protein and polar lipid.

Disclosure of Invention

In order to solve the problems, the invention provides the buttermilk powder rich in membrane protein and polar lipid and the preparation method thereof, and the buttermilk has high yield and is easy for industrial production. The buttermilk powder prepared by the invention can be added into various dairy products, so that the nutritional characteristics, the processing characteristics and the like of the products are improved.

In one aspect, the invention provides a preparation method of buttermilk powder, which comprises the following steps:

(1) centrifuging the cream, and collecting the lower water phase after centrifuging;

(2) adjusting the pH value of the lower-layer water phase in the step (1) to 5-7 by using an acid-base regulator, then stirring the lower-layer water phase until the lower-layer water phase is agglomerated into cream, completely separating out the buttermilk, filtering the buttermilk by using gauze, and collecting the buttermilk;

(3) performing microfiltration membrane separation and purification on the buttermilk in the step (2) to obtain a buttermilk spherical membrane, freezing the buttermilk spherical membrane, drying to obtain buttermilk spherical membrane powder, and storing at low temperature;

(4) and (4) adding the milk fat globule membrane powder prepared in the step (3) into the yoghourt, fermenting, and demulsifying after the fermentation is finished to obtain the milk fat globule membrane yoghourt.

Further, in the step (1), the centrifugation conditions are as follows: the centrifugal force is 750 Xg-1000 Xg, the time is 10-15 min, and the temperature is 10-15 ℃.

Further, in the step (2), the whipping conditions are as follows: the stirring speed is 800 r/min-1000 r/min, and the temperature is 10-20 ℃.

Further, in the step (2), the acid-base regulator is citric acid and sodium hydroxide; the temperature of the lower water phase is 10-20 ℃.

Further, in the step (3), the microfiltration membrane is a polyethersulfone membrane with the thickness of 0.22 μm.

Further, in the step (3), the conditions for the microfiltration membrane separation and purification are as follows: the temperature is 5-35 ℃, the pH of the buttermilk is adjusted to 7-8 by adopting an acid-base regulator, the membrane pressure is 0.45-1 bar, and the washing and filtering times are 5 times.

Further, in the step (3), the low-temperature storage is storage at-20 ℃.

Further, in the step (3), the freezing temperature is-80 ℃.

Further, in the step (4), the acidity of the fermentation end point is 70-90 degrees T.

On the other hand, the invention also provides the buttermilk powder prepared by the preparation method.

The positive progress effects of the invention are as follows:

1. can obtain the buttermilk of higher yield through above-mentioned technique, through preliminary centrifugation back, set up the whipping condition into the rotational speed again: 800-1000 r/min, temperature: 10-20 ℃, pH: 5-7, wherein the yield of the buttermilk prepared under the condition is 41.29-46.18%;

2. the method can obtain the buttermilk with high membrane protein and high polar lipid content, and the buttermilk is subjected to a centrifugation process after being stirred, wherein the membrane protein content of the buttermilk is 1.5 times that of the buttermilk stirred independently, and the polar lipid content is obviously higher than that of the buttermilk subjected to the centrifugation process after being stirred;

3. the cheese prepared by the technology can better retain bioactive substances in the cheese through freeze drying, and the nutritional value of the cheese is preserved;

4. after the buttermilk is purified and concentrated, the nutritive value and the quality of the yoghourt can be improved by applying and researching in the yoghourt, and the yoghourt has wide prospects in the development of functional dairy products.

Drawings

The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.

FIG. 1 is a schematic diagram of the difference between the preparation process of the casein milk powder and the prior art.

Detailed Description

In order to more clearly illustrate the technical solution of the present invention, the technical solution of the present invention will be further illustrated with reference to the following specific embodiments:

one of the technical schemes provided by the invention is as follows:

the invention provides a preparation method of buttermilk powder with high yield, high membrane protein content and high polar lipid content, which comprises the following components in percentage by mass: the total protein content is preferably 55% to 65%, the fat content is preferably 25% to 35%, the moisture content is preferably 3.5% to 5.5%, and the other ash component content is preferably 2.5% to 4.5%.

The preparation method comprises the following steps:

(1) centrifuging the cream, setting certain centrifugation conditions, and collecting a lower-layer water phase after centrifugation is finished;

(2) pouring the collected lower-layer water phase into a whipping vessel, setting certain whipping conditions, whipping until cream particles appear, continuing to whip until cream is agglomerated, completely separating out buttermilk, filtering with gauze, and collecting to obtain the buttermilk to be produced;

(3) separating and purifying the collected buttermilk by using a microfiltration membrane separation technology, concentrating and enriching MFGM components, freezing the concentrate at-80 ℃, and then freeze-drying to obtain solid powder for low-temperature storage;

(4) adding the prepared MFGM concentrate into the yoghourt according to a certain proportion for fermentation, and demulsifying after finishing fermentation after fermenting to a certain acidity.

It should be noted that the difference between the casein milk powder of the present application and the prior art preparation process is shown in fig. 1.

Specifically, the centrifugal conditions in the step (1) are set to be 750 Xg-1000 Xg of centrifugal force, the time is 10-15 min, and the temperature is 10-15 ℃.

And (3) setting the stirring condition in the step (2) at a rotating speed of 800 r/min-1000 r/min, a temperature of 10-20 ℃ and a pH value of 5-7.

In the step (2), citric acid and sodium hydroxide are used as acid-base regulators for regulating the pH, and the prepared concentrations are 0.1 mol/L.

The temperature of 10-20 ℃ and the pH of 5-7 in the step (2) are set for the lower water phase obtained in the step (1), namely the temperature of the water phase before whipping, and the pH is the pH of the water phase before whipping.

And (3) continuously stirring the cream into a dough shape after the cream particles appear at the stirring end point in the step (2), and completely separating out the buttermilk at the moment.

And (3) filtering the buttermilk collected in the step (2) by using gauze, and filtering out residual butter granules.

The microfiltration membrane used in the step (3) is a 0.22 mu m polyether sulfone membrane, the microfiltration equipment system is a tangential interception system, the temperature of the microfiltration process is set to be 5-35 ℃, the pH value is set to be 7-8, the membrane pressure is set to be 0.45-1 bar, and the washing and filtering times are set to be 5 times.

In the step (3), citric acid and sodium hydroxide are used as acid-base regulators for regulating the pH, and the prepared concentrations are 0.1 mol/L.

The adding proportion of the MFGM concentrate prepared in the step (4) is 2-4% of the solid content of the raw milk (namely 0.24-0.48% of the mass of the raw milk).

Sterilizing the raw milk at 80-90 ℃ for 20-30 min before fermenting in the step (4), and adding a leaven after cooling to 42-43 ℃.

The types of the leavening agents added in the step (4) are conventional in the field, preferably Lactobacillus bulgaricus (Lactobacillus bulgaricus) and Streptococcus thermophilus (Streptococcus thermophilus), the addition amount of the leavening agents is the conventional amount for preparing fermented yoghurt in the field, 3% of leavening agents are preferably prepared, and the leavening agents are added into the raw milk according to 1 mL/kg.

The raw milk selected in the step (4) is pasteurized whole milk or pasteurized skim milk produced in factories.

And (4) adding no other additives except the MFGM concentrate and the commercial starter in the yoghourt prepared in the step (4).

And (4) judging the fermentation end point to be 70-90 DEG T according to GB541334-2010 national standard for food safety milk and dairy product acidity determination.

And (4) performing conventional process in the fermented milk preparation process under the demulsification condition in the step (4), and crushing the product uniformly in a fermentation tank by a manual moving pump when the fermented milk is cooled to 20-30 ℃.

The positive progress effects of the invention are as follows:

1. can obtain the buttermilk of higher yield through above-mentioned technique, through preliminary centrifugation back, set up the whipping condition into the rotational speed again: 800-1000 r/min, temperature: 10-20 ℃, pH: 5-7, wherein the yield of the buttermilk prepared under the condition is 41.29-46.18%;

2. the method can obtain the buttermilk with high membrane protein and high polar lipid content, and the buttermilk is subjected to a centrifugation process after being stirred, wherein the membrane protein content of the buttermilk is 1.5 times that of the buttermilk stirred independently, and the polar lipid content is obviously higher than that of the buttermilk subjected to the centrifugation process after being stirred;

3. the cheese prepared by the technology can better retain bioactive substances in the cheese through freeze drying, and the nutritional value of the cheese is preserved;

4. after the buttermilk is purified and concentrated, the nutritive value and the quality of the yoghourt can be improved by applying and researching in the yoghourt, and the yoghourt has wide prospects in the development of functional dairy products.

On the basis of the common knowledge in the field, the preferred conditions can be combined randomly to obtain the preferred embodiments of the invention. On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention. On the basis of the common knowledge in the field, the preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.

The following detailed description of the embodiments of the present invention is not intended to limit the scope of the present invention to the best mode and the scope of the present invention, and any product similar or equivalent to the present invention, which is obtained by combining the features of the present invention with other related art and the present invention, will fall within the scope of the present invention.

The experimental procedures or conditions are not shown in the examples, and the procedures or conditions of the conventional experimental procedures described in the literature in this field may be followed. The reagents or instruments used are not indicated by manufacturers, and are all conventional reagent products which can be obtained commercially.

Example 1

A preparation method of cheese powder comprises the following steps:

1. weighing 250g of fresh cream into a centrifugal barrel for centrifugation, wherein the centrifugation conditions are as follows: centrifuging at 750Xg for 10min at 15 deg.C, and collecting the lower water phase.

2. Pouring the water phase collected in the step 1 into a whipping vessel for whipping, setting the whipping conditions to be 850r/min of rotating speed and 10 ℃, adjusting the pH to 5 by using 0.1mol/L of citric acid, whipping until cream particles appear, further whipping until the cream particles agglomerate, completely separating out the buttermilk at the moment, and collecting the buttermilk;

3. filtering residual cream particles by using gauze according to the buttermilk prepared in the step 2, and freeze-drying and storing the buttermilk;

4. and (3) carrying out 0.22 micron microfiltration membrane separation on the buttermilk obtained in the step (2), and setting membrane separation conditions: adjusting pH of the feed liquid to 7.5 with 0.1mol/L sodium hydroxide at a membrane pressure of 0.55bar and a temperature of 35 ℃, washing and filtering with water for 5 times, wherein the filtrate obtained in each washing is water, the pH of the feed liquid is adjusted to 7.5 with sodium hydroxide again in each time, and collecting the liquid at the interception end after membrane separation, namely the MFGM concentrate;

5. adding the MFGM concentrate obtained in the step 4 according to the proportion of 0.36 percent of fresh milk, adding a commercial leavening agent, preparing the leavening agent with the concentration of 3 percent by using sterile water, adding the raw material milk according to the proportion of 1mL/kg, fermenting at 42 ℃ until the acidity is more than or equal to 70 degrees T, and demulsifying after the fermentation is finished.

The buttermilk prepared by the steps is purified and has better hardness, viscosity and adhesiveness compared with the yoghourt added with the commercial alule MFGM-10 and the yoghourt without the MFGM concentrate, the yoghourt has more delicate texture, and the buttermilk prepared by freeze drying is frozen and dried to obtain buttermilk powder which can be stored at the temperature of minus 20 ℃ for 12 months.

Example 2

A preparation method of cheese powder comprises the following steps:

1. weighing 250g of fresh cream into a centrifugal barrel for centrifugation, setting the centrifugation condition as 750Xg of centrifugal force, the time for 10min and the temperature for 10 ℃, and collecting the lower-layer water phase after the centrifugation is finished.

2. Pouring the water phase collected in the step 1 into a whipping vessel for whipping, setting the whipping conditions to be 800r/min of rotating speed and 10 ℃, adjusting the pH to 5 by using 0.1mol/L citric acid, whipping until cream particles appear, further whipping until the cream particles are conglobated, at the moment, the butter is completely separated out, and collecting the butter;

3. filtering the residual butter granules with gauze according to the buttermilk prepared in the step 2, freeze-drying the buttermilk, and storing at-20 ℃;

4. and (3) carrying out 0.22 micron microfiltration membrane separation on the buttermilk obtained in the step (2), and setting membrane separation conditions: adjusting pH of the feed liquid to 7 with 0.1mol/L sodium hydroxide at 5 deg.C and membrane pressure of 0.45bar, washing with water for 5 times, adjusting pH of the feed liquid to 7 with sodium hydroxide, and collecting the liquid at the interception end after membrane separation to obtain MFGM concentrate;

5. adding the MFGM concentrate obtained in the step 4 according to the proportion of 0.24 percent of fresh milk, adding a commercial leavening agent, preparing the leavening agent with the concentration of 3 percent by using sterile water, adding the raw material milk according to the proportion of 1mL/kg, fermenting at 42 ℃ until the acidity is more than or equal to 70 degrees T, and demulsifying after the fermentation is finished.

The buttermilk prepared by the steps is purified and has better hardness, viscosity and adhesiveness compared with the yoghourt added with the commercial alule MFGM-10 and the yoghourt without the MFGM concentrate, the yoghourt has more delicate texture, and the buttermilk prepared by freeze drying is frozen and dried to obtain buttermilk powder which can be stored at the temperature of minus 20 ℃ for 12 months.

Example 3

A preparation method of cheese powder comprises the following steps:

1. weighing 250g of fresh cream into a centrifugal barrel for centrifugation, wherein the centrifugation condition is set as 1000Xg of centrifugal force, the time is 15min, the temperature is 15 ℃, and after the centrifugation is finished, collecting the lower-layer water phase.

2. Pouring the water phase collected in the step 1 into a whipping vessel for whipping, setting the whipping conditions to be 1000r/min of rotating speed and 20 ℃, adjusting the pH to 7 by using 0.1mol/L of sodium hydroxide, whipping until cream particles appear, further whipping until the cream particles agglomerate, at the moment, the butter is completely separated out, and collecting the butter;

3. filtering the residual butter granules with gauze according to the buttermilk prepared in the step 2, freeze-drying the buttermilk, and storing at-20 ℃;

4. and (3) carrying out 0.22 micron microfiltration membrane separation on the buttermilk obtained in the step (2), and setting membrane separation conditions: adjusting pH of feed liquid to 8 with 0.1mol/L sodium hydroxide at membrane pressure of 1bar and temperature of 35 deg.C, washing with water for 5 times, adjusting pH of feed liquid to 8 with sodium hydroxide, and collecting the liquid at the interception end after membrane separation;

5. adding the MFGM concentrate obtained in the step 3 according to the proportion of 0.48 percent of fresh milk, adding a commercial leavening agent, preparing the leavening agent with the concentration of 3 percent by using sterile water, adding the raw material milk according to the proportion of 1mL/kg, fermenting at 42 ℃ until the acidity is more than or equal to 70 degrees T, and demulsifying after the fermentation is finished.

The buttermilk prepared by the steps is purified and has better hardness, viscosity and adhesiveness compared with the yoghourt added with the commercial alule MFGM-10 and the yoghourt without the MFGM concentrate, the yoghourt has more delicate texture, and the buttermilk prepared by freeze drying is frozen and dried to obtain buttermilk powder which can be stored at the temperature of minus 20 ℃ for 12 months.

Example 4

A preparation method of cheese powder comprises the following steps:

1. weighing 250g of fresh cream, centrifuging in a centrifuge bucket under the centrifugal condition of 900Xg for 13min at 12 ℃, and collecting the lower-layer water phase after centrifuging;

2. pouring the water phase collected in the step 1 into a whipping vessel for whipping, setting the whipping conditions to be 900r/min of rotating speed and 15 ℃, adjusting the pH to 6 by using 0.1mol/L citric acid, whipping until cream particles appear, further whipping until the cream particles agglomerate, at the moment, the butter is completely separated out, and collecting the butter;

3. filtering the residual butter granules with gauze according to the buttermilk prepared in the step 2, freeze-drying the buttermilk, and storing at-20 ℃;

4. and (3) carrying out 0.22 micron microfiltration membrane separation on the buttermilk obtained in the step (2), and setting membrane separation conditions: adjusting pH of the feed liquid to 7.5 with 0.1mol/L sodium hydroxide at 20 deg.C and membrane pressure of 0.75bar, washing with water for 5 times, adjusting pH of the feed liquid to 7.5 with sodium hydroxide, and collecting the liquid at the interception end after membrane separation to obtain MFGM concentrate;

5. adding the MFGM concentrate obtained in the step 3 according to the proportion of 0.3 percent of fresh milk, adding a commercial leavening agent, preparing the leavening agent with the concentration of 3 percent by using sterile water, adding the raw material milk according to the proportion of 1mL/kg, fermenting at 42 ℃ until the acidity is more than or equal to 70 degrees T, and demulsifying after the fermentation is finished.

The buttermilk prepared by the steps is purified and has better hardness, viscosity and adhesiveness compared with the yoghourt added with the commercial alule MFGM-10 and the yoghourt without the MFGM concentrate, the yoghourt has more delicate texture, and the buttermilk prepared by freeze drying is frozen and dried to obtain buttermilk powder which can be stored at the temperature of minus 20 ℃ for 12 months.

Comparative example 1

The preparation method of the comparative example is the same as that of example 1, except that only the whipping process is performed in the steps 1 and 2, the centrifugation process before whipping is omitted, the whipping parameters are the same as those in the step 1 of example 1, the cream is whipped until cream particles appear, the whipping is continued until the cream is agglomerated, the buttermilk is completely separated out, and the buttermilk is collected after being filtered by gauze.

Comparative example 2

The preparation method of the comparative example is the same as that of example 1, except that the steps 1 and 2 are performed with the same whipping parameters as those of step 2, and then the centrifugation process is performed with centrifugal parameters set to 3000Xg at 15 ℃ for 10min, and after the centrifugation is finished, the lower aqueous phase is collected and filtered by gauze and then collected.

Comparative example 3

The preparation method of this comparative example is the same as that of example 1, except that the whipping speed in step 1 is set to 700r/min, the temperature of the cream is set to 30 ℃, and the pH is adjusted to 4 with 0.1mol/L citric acid; setting membrane separation conditions in the step 3: the feed solution pH was adjusted to 5.5 with 0.1mol/L citric acid at a membrane pressure of 0.25bar and a temperature of 50 ℃.

Comparative example 4

The preparation method of the comparative example is the same as that of example 1, except that the stirring speed in step 1 is set to 1500r/min, the temperature of the cream is set to 5 ℃, and the pH is adjusted to 8 by 0.1mol/L sodium hydroxide; setting membrane separation conditions in the step 3: the feed was adjusted to pH 4 with 0.1mol/L citric acid at a membrane pressure of 1.25bar and a temperature of 60 ℃.

Comparative example 5

This comparative example was prepared in the same manner as example 1, except that the MFGM concentrate was added in an amount of 0.12% of the starting milk in step 4.

Comparative example 6

This comparative example was prepared in the same manner as example 1, except that the MFGM concentrate was added in step 4 in an amount of 1.5% of the starting milk.

Effect example 1

The yields and the methods for determining the total lipid, total protein content and relative amounts of membrane protein and polar lipid of the buttermilk prepared in examples 1, 2, 3, 4 and comparative examples 1, 2, 3, 4 are as follows:

measuring total lipid by a GB 5009.6-2016 method;

the total protein is determined by a first method of GB 5009.5-2016;

the total ash content is measured by a GB 5009.4-2016 method;

performing qualitative detection of lipid by high performance liquid chromatography-mass spectrometry (HPLC-MS), and performing relative quantitative analysis of lipid according to peak height; qualitative analysis was performed by SDS-PAGE and relative quantitative analysis was performed using ImageLab software.

The results are shown in tables 1, 2 and 3.

The initial centrifugation and the whipping can take account of the advantages of relatively high content of membrane protein and polar lipid.

TABLE 1 buttermilk yield data

	Buttermilk yield (%)
		Example 1	46.18
Example 2	41.29
		Example 3	42.83
Example 4	45.87
		Comparative example 3	31.9
Comparative example 4	34.1

TABLE 2 Total buttermilk fat, Total protein, Total Ash data

	Fat (g/100g)	Protein (g/100g)	Ash content (g/100g)
				Example 1	3.89	2.86	0.62
Comparative example 1	2.07	2.93	0.63
				Comparative example 2	0.592	2.96	0.64

Note: the data in table 2 are the results of the buttermilk solution test, before drying.

TABLE 3 relative content data of membrane proteins and polar lipids

Note: the data in Table 3 are not absolute contents, have no specific units, and are only relative quantitative results

Effect example 2

The removal rates of casein and whey proteins (i.e., MFGM concentrate purity) from buttermilk after membrane separation in examples 1, 2, 3, 4 and comparative examples 3, 4 were evaluated and the results are shown in table 4.

TABLE 4 removal rate of casein and whey protein in Casein milk

Effect example 3

The different MFGM concentrates and the different amounts added in examples 1, 2, 3 and comparative examples 5, 6 were evaluated with respect to the hardness, the viscosity and the adhesiveness of the yoghurts prepared.

Setting parameters of a TA-XT physical tester: the measurement mode is as follows: pressing down; the descending speed of the probe is 1.0mm/s before measurement, the testing speed is 1.0mm/s, the return speed of the probe is 1mm/s after measurement, the testing distance is 20mm, and the induction force is 1.0 g. Three replicates were run for each yogurt sample and the results are shown in table 5.

In the course of increasing the amount of the MFGM concentrate, the respective indices tend to increase, but when the amount of the MFGM concentrate is increased to a certain level, the results tend to be gentle, and when the amount of the MFGM concentrate is increased, it is meaningless.

TABLE 5 yogurt texture test results

In conclusion, based on the optimization of the milk yield and the research of a comparative test on the way of preparing the milk, the invention obtains that the dilute cream is stirred at the stirring speed of 800-1000 r/min, the temperature of 10-20 ℃ and the pH of 5-7 after the initial centrifugation of 750-1000 x g, and the precipitated water phase milk is finally frozen, dried and stored. The method is a technical route suitable for producing the high-yield, high-membrane protein and high-polarity buttermilk powder, is favorable for improving the additional value of the buttermilk, has good adding effect in the yoghourt, can increase the viscosity of the yoghourt, is finer and smoother, and lays a foundation for the development of the buttermilk in functional dairy products.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.