CN106615117A - Stirring type fruit-flavor goat milk kefir and preparation method thereof - Google Patents

Abstract

The fruity stirred goat's milk kefir of the invention belongs to the field of dairy products. The main ingredients of fruity stirred goat milk kefir are raw milk, sugar, fruit juice, polywhey protein, pectin, and kefir starter. Fruit juice is obtained by reconcentrating concentrated fruit juice. The polymerized whey protein solution is prepared by neutral heat polymerization; two fermentations and the addition of concentrated fruit juice are used to make the three-dimensional network structure formed by the acid gel play a role in thickening, enhancing the stability of the juice and the smell of goat milk The masking function solves the difficult problem of the decline in the quality of fermented milk products caused by the addition of fruit juice in the prior art. Kefir starter is a commercial direct-injection starter composed of Lactococcus lactis, Leuconostoc, Streptococcus thermophilus, and Lactobacillus acidophilus. The fruit-flavored goat's milk kefir prepared by the present invention has the characteristics of high probiotic content, high protein content, high viscosity level, low syneresis, low goat's milk smell, unique flavor, uniform color and fine texture, etc. .

Description

A kind of fruit flavor stirring goat's milk kefir and preparation method thereof

technical field

The invention belongs to the technical field of dairy products, and in particular relates to a fruity stirred type goat milk kefir and a preparation method thereof.

Background technique

Kefir, as an ancient fermented dairy product, originated in the Caucasus region with a history of more than 1,400 years. Kefir has many health functions, such as lowering cholesterol, antibacterial, anticancer and so on. Traditional kefir is made by fermenting a leavening agent called kefir grains. Kefir grains are a microbial symbiosis system composed of lactic acid bacteria, leuconostoc, yeast and acetic acid bacteria, which symbiosis on a semi-hard granule with an irregular shape composed of viscous polysaccharides. Due to the different species of microorganisms, their metabolites are also different, which endows kefir with unique flavor characteristics. However, due to the secondary fermentation of the secondary yeast in the traditional kefir starter, the product will leak in the packaging due to the gas produced by the yeast during storage, which directly affects the quality of the product. In order to solve this problem, a commercial direct-throwing kefir starter is applied to the production and processing of kefir. It is composed of some strains isolated from traditional kefir grains. While retaining the unique flavor of traditional kefir, it also properly solves the problem of packaging leakage caused by the secondary fermentation of yeast.

As the third largest milk source in the world, goat milk plays an important role in the nutritional diet of developing countries. Compared with cow's milk, goat's milk has more short-chain fatty acids and less casein content, making it more easily absorbed by the body and less allergenic. However, the presence of more volatile short-chain fatty acids (such as C ₆ , C ₈ , and C ₁₀ ) makes goat milk products have a unique smell, and less casein content makes fermented goat milk products have low viscosity and low viscosity. Hardness, high syneresis, these defects seriously restrict the development of fermented goat milk industry.

Whey protein is a type of protein obtained by concentrating and refining the by-product whey produced in the process of cheese or casein production through a special process. According to its protein content, whey protein products are divided into whey protein isolate (WPI) and whey protein concentrate (WPC). The protein with the highest content in whey protein is β-lactoglobulin, accounting for about 50% of the total whey protein. It is a compact globular protein folded by 162 amino acids. Heat modification of whey protein under neutral conditions (pH ≈ 7) can destroy the tertiary structure of the polypeptide chain of β-lactoglobulin molecules, unfold, expose hydrophobic groups, and finally protein molecules aggregate into stable The whey protein solution polymerized but did not form a gel. During the kefir fermentation process, the pH will gradually decrease due to the influence of microbial fermentation products, so that the polymerized whey protein solution added to it will gradually approach the isoelectric point. At this time, the repulsion potential energy between molecules is not enough to maintain the stability of the system. The molecules aggregate and form a three-dimensional network. The resulting protein network can hold water through capillary forces and entrap some substances. Therefore, it can be used to enhance the hardness, viscosity and water holding capacity of kefir curd milk, and can partially cover up the smell of goat milk.

Juice refers to the juice product obtained by pressing, centrifuging and extracting fruit. The fruit juice retains most of the nutrients in the fruit, such as various vitamins, minerals, sugar and dietary fiber. Drinking fruit juice can promote digestion, lubricate the intestines, and supplement nutrition. Since fresh juice is not easy to preserve and has high transportation costs, it is usually prepared by low-temperature vacuum concentration to obtain concentrated juice, which is then recovered by adding an equal amount of purified water later. Juice can be used in a variety of food fields, and the addition of juice to improve product flavor has become more and more popular in the market.

At present, pure fruit juice, concentrated fruit juice, jam, fruit powder, etc. are usually selected as the addition of fruit material in fruity stirred fermented dairy products, but they all have certain defects. Since the water content in the pure fruit juice is too large, its addition will reduce the solid content of the product and the fruit juice will obviously float. Although the addition of concentrated fruit juice can solve the problem of pure fruit juice, but because the pH of concentrated fruit juice is generally low, its addition may cause a sharp drop in product pH, resulting in whey precipitation and affecting the sensory properties of the product.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for preparing fruity stirred goat milk kefir. Blended goat's milk kefir has a variety of flavors by adding concentrated fruit juice. The addition of polymerized whey protein not only plays a role in thickening and increasing the stability of the juice, but also cooperates with the juice to cover up the smell of goat milk. A variety of probiotics in kefir starter can enhance the health function of the product. Finally, a fermented dairy product with unique flavor, light goat milk smell, high nutritional value and good stability was obtained.

The other two technical problems to be solved in the present invention are the preparation method of polymerized whey protein and the way of adding fruit juice. The preparation method of polymerized whey protein is relatively simple, and the relevant technology is relatively mature, but it is the first time that the present invention is used as the main thickener, fruit juice stabilizer and smell masking agent of stirred kefir. Since the water content in fruit juice is relatively high, adding pure fruit juice directly will have a greater impact on the solid content of the product. Therefore, the present invention uses concentrated fruit juice and uses goat milk kefir base material instead of water to reconstitute to prepare fruity stirred goat milk kefir. you.

The technical scheme that the present invention solves the problem is:

A fruit-flavored goat's milk kefir. The raw materials for its preparation include the following ingredients and their dosages: liquid raw milk, fruit juice accounting for 5% to 20% of the volume of the liquid raw milk, and sugar accounting for 5% to 8% of the weight of the liquid raw milk. %, polymerized whey protein accounts for 0.1% to 0.6% of the weight of liquid raw milk, pectin accounts for 0.1% to 0.3% of the weight of liquid raw milk, and kefir starter accounts for 0.005% to 0.03% of the weight of liquid raw milk; , the juice is concentrated by volume to a ratio of 1:5-10 for use.

Described fruit juice is yellow peach juice and/or strawberry juice and/or blueberry juice.

The kefir starter is made of Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. Lactis biovar. diacetylactis, Leuconostoc enterococci (Leuconostoc mesenteroides subsp.mesenteroides), Streptococcus thermophilus (Streptococcus thermonphilus), Lactobacillus acidophilus (Lactobacillus acidophilus).

The pectin is low-ester monomer pectin, and the degree of esterification is below 30%.

The fruit flavor stirring goat milk kefir of the present invention uses fruit juice as a flavor enhancer, polymerized whey protein as a thickener and juice stabilizer, pectin as an auxiliary thickener, polymerized whey protein and fruit juice A total of goat milk odor masking agent, its solid content is more than 15%, protein content is 2.50%-3.50%, fat content is 2.60%-2.90%, pH is between 4.2-4.6, good stability, no fruit juice Floating, no whey precipitation, viscosity above 1189mPa.s.

The technical scheme of the preparation method of the fruit flavor stirring type goat milk kefir of the present invention is as follows.

A method for preparing fruit-flavored goat's milk kefir, comprising the following preparation steps: concentrating fruit juice into concentrated fruit juice at a volume ratio of 1:5-10; pre-mixing sugar and pectin, adding it to liquid raw milk, Stir and heat to 50-55°C until the pectin is completely dissolved to obtain mixed raw milk; add polywhey protein to the mixed raw milk, stir and heat to 80-90°C, keep it warm for 10-20 minutes to sterilize, cool in an ice-water bath to 25-35 ℃, add kefir starter and stir evenly, ferment for 8-14 hours at 25-35℃ until the pH is lower than 4.6, break the emulsion and stir evenly to obtain goat milk kefir base material; in goat milk kefir base material Add concentrated fruit juice, stir evenly, then pack, and post-ferment at 4-6°C for 12-24 hours to obtain fruity-flavored goat's milk kefir.

The polymerized whey protein is obtained by keeping whey protein isolate and/or concentrated whey protein at pH=7 and temperature 80-85° C. for 30 minutes, and then cooled. Specifically, it can be: according to the content of pure protein in whey protein isolate or concentrated whey protein, dissolve it in water at a mass ratio of pure protein to water of 1:10, stir magnetically for 30-60 minutes until it is completely dissolved, 4- Place it at 6°C for 10-12 hours to make it fully hydrated; use 1-3M sodium hydroxide solution to adjust the whey protein isolate solution to pH = 7, heat the water bath to 80-85°C and keep it for 30 minutes to fully denature it , cooled in an ice bath, and stored at 4-6°C until use. The prepared polymerized whey protein solution contains about 10% to 11% of the polymerized whey protein by mass.

The above-mentioned whey protein isolate has a protein content of 90% to 95% by mass, and the protein content of the concentrated whey protein is 75% to 85% by mass.

In the preparation method of the fruity stirred goat milk kefir of the present invention, the sugar is white granulated sugar and/or soft white sugar; the pectin is low-ester monomeric pectin, and the degree of esterification is 30% Below; Described kefir starter is the Kefir Mild 01 direct-throwing starter produced by Danisco (Danisco), mainly composed of Lactococcus lactis subsp.lactis, Lactococcus lactis subsp. Lactococcus lactis subsp. Lactis biovar. diacetylactis, Leuconostocmesenteroides subsp. mesenteroides, Streptococcus thermophilus, Lactobacillus acidophilus.

In the preparation method of the fruit-flavored stirred goat's milk kefir of the present invention, the fruit juice described in the fruity-flavored stirred goat's milk kefir is obtained by reconstituting the concentrated fruit juice with the goat's milk kefir base material instead of pure water.

The eating method and the consumption amount of the present invention are the same as those of eating common stirred type fermented milk products.

In the method of the present invention, the "initial fermentation" process utilizes the polymerized whey protein to cross-link with pectin and casein to form a three-dimensional network structure during the pH lowering process to play a thickening effect. However, when the concentrated fruit juice is added to the kefir base material after initial fermentation, the pH of the kefir base material will drop to a certain extent, and at this time, the uncrosslinked polymerized whey protein of the initial fermentation will produce condensation again due to the drop in pH. The gelation reaction embeds the macromolecular substances in the fruit juice, and at the same time links with the three-dimensional network structure formed earlier to form a more stable composite structure. Therefore, when adding concentrated fruit juice, the quality of the product will not decrease due to the drop in pH, but will be more stable and uniform. This greatly enhances the uniformity and stability of the final product, and avoids the problem of floating or settling fruit in fruity fermented dairy products. This new idea for the application of polymerized whey protein acid gel solves a difficult problem in the preparation of fruit-flavored stirred fermented milk products with concentrated fruit juice as the main fruit material.

At the same time, the composite structure formed by polymerized whey protein-juice material molecule-pectin-casein can combine the short-chain volatile fatty acids (such as C ₆ , C ₈ , C ₁₀ ) in goat milk and those produced by kefir starter Part of the sour taste molecules are embedded in it. Since this structure has reached the molecular level, it will not be destroyed during oral chewing, which also reduces the product's smell and the special sour taste of kefir, and enhances the taste and taste of the product. odor. It solves the special sour and muttony problems of goat milk kefir.

The product of the present invention is a fruity stirred type goat milk kefir, which uses fruit juice as a flavor enhancer, polymerized whey protein as a main thickener and juice stabilizer, and fruit juice and polymerized whey protein as a goat milk smell mask It is a new type of fermented milk product containing kefir probiotics. The raw material goat milk of this product has the characteristics of high nutritional value, easy absorption of nutrients and low allergenicity. It has the characteristics of lowering cholesterol, antibacterial and anticancer. The product of the invention has high protein content, moderate sweetness, low goat milk smell and unique flavor, and also has the characteristics of delicate texture, uniform structure, beautiful color and good taste.

The invention solves the problem in the prior art that the quality of the fermented milk product is lowered due to the addition of fruit juice, and provides a new way for the combination of the concentrated fruit juice and the stirred goat milk fermented product. In terms of the production process of the fruity stirred goat milk kefir, it has the characteristics of low cost, high stability and sensory properties.

detailed description

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that the examples are only for illustrating the present invention and are not intended to limit the scope of the present invention.

Example 1

The fruit juice in this example is yellow peach juice, and concentrated into concentrated fruit juice at a concentration ratio of 1:7. The specific amount of concentrated fruit juice added is: if the amount of fruit juice added to the prepared fruity stirred goat milk kefir is liquid 15% of the volume of raw milk, liquid raw milk is calculated for every 500mL, 75mL of yellow peach juice should be added, calculated according to the concentration ratio of 1:7, which is equivalent to adding 10.71mL of concentrated yellow peach juice.

The polymerized whey protein is prepared through the following steps: 10.8g of whey protein isolate (92% protein content) is dissolved in 100mL of water, magnetically stirred for 60min, and placed at 4°C for 12h to fully hydrate it. The whey protein solution was adjusted to pH = 7 with 1M sodium hydroxide solution, heated in a water bath at 85°C for 30 minutes, cooled in an ice-water bath, and stored at 4°C until use.

Fruity Stirred Goat Milk Kefir is made by mixing liquid raw milk, sugar, pectin, and polywhey protein for initial fermentation, adding concentrated yellow peach juice (concentration ratio: 1:7), and then post-fermenting.

The preparation method of the fruit flavor stirring type goat milk kefir in this embodiment has the following process steps:

Add the pre-mixture to the liquid raw milk and mix and stir → stir and heat to 50°C until the pectin is fully dissolved → add polywhey protein → heat to 80°C for 10 minutes to sterilize → cool → add kefir starter → ferment at 25°C until the pH is low In 4.6 → demulsification → add concentrated yellow peach juice → sub-packaging → post-fermentation at 4°C for 24 hours → store the finished product at 4°C.

Specifically, 7.5% (37.5g) of white granulated sugar and 0.1% (0.5g) of pectin were pre-mixed and added to liquid raw milk (500mL) and stirred evenly, stirred and heated to 50°C until the pectin was completely dissolved. Add 20mL of the prepared polymerized whey protein solution (the polymerized whey protein contained in it accounts for 0.4% of the liquid raw milk) into the raw milk mixture, stir and heat to 80°C for 10min, then cool to 25°C, add 0.02 % (0.1g) kefir starter and stir evenly, initially ferment at 25°C until its pH is lower than 4.6, break the emulsion and stir evenly, add concentrated yellow peach juice (10.71mL), divide it after stirring evenly, and put it in Ferment at 4°C for 24 hours to obtain the finished product, and store at 4°C.

Example 2

The fruit juice in this example is strawberry juice, and it is concentrated into concentrated fruit juice at a concentration ratio of 1:8. The specific amount of concentrated fruit juice added is: if the amount of fruit juice added to the prepared fruity-flavored goat milk kefir is liquid raw material For 10% of the milk volume, 50mL of strawberry juice should be added for every 500mL of liquid raw milk, which is equivalent to adding 6.25mL of concentrated strawberry juice according to the concentration ratio of 1:8.

The polymerized whey protein is prepared through the following steps: dissolving 10.8g of whey protein isolate (with a protein content of 92%) in 100mL of water, magnetic stirring for 60min, and placing it at 4°C for 10h to fully hydrate it. The whey protein solution was adjusted to pH = 7 with 3M sodium hydroxide solution, heated in a water bath at 80°C for 30 minutes, cooled in an ice-water bath, and stored at 4°C until use.

Fruity Stirred Goat Milk Kefir is made by mixing liquid raw milk, sugar, pectin, and polywhey protein for pre-fermentation, adding concentrated strawberry juice (the concentration ratio is 1:8), and then post-fermenting.

The preparation method of the fruit flavor stirring type goat milk kefir of this embodiment is to make according to the following process steps:

Add the premixed liquid raw milk to dissolve and stir well → heat and stir to 55°C → add polywhey protein solution → heat to 85°C and keep warm for 15 minutes → cool → add kefir starter → ferment at 28°C until the pH is lower than 4.6 → Demulsification → adding concentrated strawberry juice → subpackaging → post-fermentation at 4°C for 12 hours → store the finished product at 4°C.

Specifically, 7% (35g) of white granulated sugar and 0.2% (1g) of pectin were mixed in advance and slowly added to liquid raw milk (500mL), stirred and heated to 55°C until the pectin was completely dissolved, and then prepared in this example 15mL of the polymerized whey protein solution (the polymerized whey protein contained in it accounts for 0.3% of the liquid raw milk) was added to the raw milk mixture, stirred and heated to 85°C for 15min, then cooled to 28°C, and 0.01% ( 0.05g) kefir starter and stir evenly, initially ferment at 28°C until the pH is lower than 4.6, break the emulsion and stir evenly, add concentrated strawberry juice (6.25mL), after stirring evenly, subpackage, after 4°C Ferment for 12 hours to obtain the finished product, and store at 4°C.

Example 3

The fruit juice in this example is blueberry juice, and it is concentrated into concentrated fruit juice at a concentration ratio of 1:10. The specific amount of concentrated fruit juice added is: if the amount of fruit juice added to the prepared fruity stirred goat milk kefir is liquid raw materials 5% of the milk volume, liquid raw milk is calculated for every 500mL, then 25mL of blueberry juice should be added, calculated according to the concentration ratio of 1:10, which is equivalent to adding 2.5mL of concentrated blueberry juice.

The polymerized whey protein is prepared through the following steps: 12.5g of concentrated whey protein (80% protein content) is dissolved in 100mL of water, magnetically stirred for 45min, and placed at 4°C for 10h to fully hydrate it. The whey protein solution was adjusted to pH = 7 with 1M sodium hydroxide solution, heated in a water bath at 85°C for 30 minutes, cooled in an ice-water bath, and stored at 4°C until use.

Fruity Stirred Goat Milk Kefir is made by mixing liquid raw milk, sugar, pectin, and polywhey protein for initial fermentation, adding concentrated blueberry juice (concentration ratio: 1:10), and then post-fermenting.

The preparation method of the fruit flavor stirring type goat milk kefir of this embodiment is to make according to the following process steps:

Add the pre-mixture into liquid raw milk to dissolve and stir evenly→heat and stir to 50°C→add polywhey protein solution→heat to 85°C and keep warm for 15min→cool→add kefir starter→ferment at 30°C until the pH is lower than 4.6→ Demulsification → adding concentrated blueberry juice → subpackaging → post-fermentation at 4°C for 12 hours → store the finished product at 4°C.

Specifically, 6.5% (32.5g) white granulated sugar and 0.3% (1.5g) pectin are pre-mixed and added to liquid raw milk (500mL) and stirred evenly, stirred and heated to 50°C until the pectin is completely dissolved, and this 10mL of the polymerized whey protein solution prepared in the example (the polymerized whey protein contained in it accounts for 0.2% of the liquid raw milk) was added to the raw milk mixture, the temperature was raised to 80°C and kept for 10min, then cooled to 31°C, and 0.005% (0.025g) kefir starter and stir evenly, initially ferment at 31°C until the pH is lower than 4.6, break the emulsion and stir evenly, add 2.5mL of concentrated blueberry juice, after stirring evenly, subpackage, and post-ferment at 4°C The finished product was obtained within 24 hours and stored at 4°C.

The analysis items and method of the product of embodiment 1～3 are as follows:

(1) Physical and chemical indicators: use the national standard method to analyze its total solid content, ash, protein, fat, and carbohydrates.

(2) Stability: analyze its viscosity (Brookfield viscometer), pH, and measure syneresis (Beckman centrifuge);

(3) Kefir starter: sourced from the manufacturer (Danisco);

(4) Sensory analysis: the product of the present invention is tested in terms of acceptability and liking; at the same time, the product of the present invention is descriptively analyzed, and the main characteristics of the product are determined according to appearance and color, taste, flavor, tissue state and overall acceptability ; All sensory analyzes were performed by a trained professional team of 12 students in food science; data analysis was performed by ANOVA and chi-square test using SPSS version 21.0.

The technical index results obtained by product analysis are shown in Table 1 and Table 2.

Table 1 Product Characteristics: Physicochemical and Microbiological Indexes

Example 1 sample Example 2 sample Example 3 sample Ash (%) 0.68±0.01 0.73±0.02 0.76±0.02 Fat(%) 2.64±0.12 2.75±0.09 2.64±0.11 Total solids (%) 19.64±0.79 18.22±1.12 20.06±0.87 protein(%) 3.56±0.12 3.31±0.22 3.10±0.15 carbohydrate(%) 12.76±0.26 11.43±0.76 13.56±0.29 pH 4.45±0.01 4.45±0.04 4.47±0.02 Viscosity (mPa.s) 1626.08±161.04 1385.38±100.04 1786.23±68.12 Syneresis (%) 1.13±0.09 0.90±0.05 0.50±0.02 Lactobacillus acidophilus (Log CFU/mL) 10 ¹⁰ 10 ¹⁰ 10 ¹⁰ Escherichia coli not detected not detected not detected mold and yeast not detected not detected not detected

Table 2 Product Features (5-point scale)

Example 1 sample Example 2 sample Example 3 sample overall acceptability 3.80±0.20 4.83±0.23 3.28±1.06 appearance and color 4.65±0.35 4.37±0.96 3.03±0.76 smell 4.67±0.33 4.42±1.15 4.63±0.25 flavor 3.77±0.25 3.54±1.10 3.79±1.01 organizational status 4.02±0.21 3.21±0.78 3.01±0.96

The analysis results of physicochemical and microbiological properties showed that the fruity-flavored goat milk kefir had high protein content, high viscosity, moderate pH and low syneresis. The content of Lactobacillus acidophilus in the final product was as high as 10 ¹⁰ Log CFU/mL, and no harmful bacteria such as Escherichia coli, mold and yeast were detected.

The results of the sensory evaluation showed that the fruity-flavored goat's milk kefir had a strong taste with a unique flavor of kefir, and the goat's milk had a low smell and a more obvious fruity taste. The product has a pure color and a uniform and delicate texture, which can be considered as a good stirred fermented dairy product.

Claims (6)

1. A fruit-flavored goat's milk kefir, the raw materials for its preparation include the following ingredients and their dosages: liquid raw milk, fruit juice accounting for 5% to 20% of the volume of the liquid raw milk, and sugar accounting for 5% of the weight of the liquid raw milk ～8%, polymerized whey protein accounts for 0.1%～0.6% of the weight of liquid raw milk, pectin accounts for 0.1%～0.3% of the weight of liquid raw milk, and kefir starter accounts for 0.005%～0.03% of the weight of liquid raw milk ; Wherein, the fruit juice is concentrated to a ratio of 1:5-10 by volume for use. 2. The fruity stirred goat's milk kefir according to claim 1, wherein the fruit juice is yellow peach juice and/or strawberry juice and/or blueberry juice. 3. A method for preparing the fruity stirred goat milk kefir according to claim 1, comprising the following preparation steps: concentrating the fruit juice into concentrated fruit juice in a volume ratio of 1:5 to 10; mixing sugar and pectin in advance, adding Add the liquid raw milk, stir and heat to 50-55°C until the pectin is completely dissolved to obtain the mixed raw milk; add the polymerized whey protein into the mixed raw milk, stir and heat to 80-90°C, keep it warm for 10-20min to sterilize, and freeze Cool in a water bath to 25-35°C, add kefir starter and stir evenly, start fermentation at 25-35°C for 8-14 hours until the pH is lower than 4.6, break the emulsion and stir evenly to obtain goat milk kefir base material; Concentrated fruit juice is added to the kefir base material, stirred evenly, then packaged, and then fermented at 4-6° C. for 12-24 hours to obtain the fruit-flavored stirred goat milk kefir. 4. The method for preparing fruity-flavored goat's milk kefir according to claim 3, wherein the fruit juice is yellow peach juice and/or strawberry juice and/or blueberry juice. 5. according to the preparation method of the described fruit flavor stirring type goat's milk kefir of claim 3 or 4, it is characterized in that, described polymerized whey protein, is according to the pure in whey protein isolate or concentrated whey protein For protein content, dissolve in water at a mass ratio of pure protein to water of 1:10, stir magnetically for 30-60 minutes until it dissolves completely, and place it at 4-6°C for 10-12 hours to fully hydrate it; use 1-3M Adjust the whey protein isolate solution to pH = 7 with a sodium hydroxide solution, raise the temperature in a water bath to 80-85°C and keep it warm for 30 minutes to fully denature it, cool it in an ice bath, and store it at 4-6°C. 6. The method for preparing fruity stirred goat milk kefir according to claim 5, characterized in that, the whey protein isolate has a protein content of 90% to 95% by mass, and the concentrated whey The protein content in the protein is 75% to 85% by mass.