Fermented milk whey product and preparation method thereof

Abstract

The present invention discloses a fermented milk whey product and a preparation method thereof, comprising the following steps: (1) mixing semi-solid raw milk with fermentation bacteria and forming the mixture, and then performing dry fermentation to obtain a dry fermentation product; (2) adding sodium chloride and water to the dry fermentation product and performing wet fermentation to obtain a wet fermentation product; (3) performing solid-liquid separation on the wet fermentation product to obtain fermentation product whey; and (4) sterilizing the fermentation product whey to obtain a fermented milk whey product. The method adopts a fermentation method combining dry fermentation and wet fermentation to directly ferment the semi-solid raw milk, and uses the fermentation product whey as the final product, thereby making full use of the different metabolic capabilities and modes of fermentation bacteria under different fermentation conditions, thereby significantly improving the types and contents of nutritional components in the fermented milk whey product, significantly enhancing the health-care effect, and being conducive to the large-scale promotion and application of the fermented milk whey product.

Description

Technical Field

[0001] The present invention relates to the technical field of dairy products, in particular to the field of fermented dairy products, and in particular to a fermented milk whey product and a preparation method thereof. Background Art

[0002] The yogurt market has remained at 200 billion yuan in recent years, with significant room for future growth. While there are numerous yogurt products, there are only three types: set yogurt, stirred yogurt, and drinkable yogurt. Consumers have become fatigued by decades of taste buds, and developing new fermented milk products is essential to provide consumers with a wider range of product choices.

[0003] Whey beverages are drinks made from whey protein powder or whey with appropriate ingredients through a blending, sterilization, and filling process. They are popular among young people and in fitness centers due to their health benefits, including protein supplementation, immunity enhancement, physical fitness, and weight management. However, due to limitations in raw materials, formulation, and processing technology, whey beverages have low nutritional content, a limited variety, and a significant taste difference from fermented milk, hindering their widespread adoption. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems of existing whey beverages with low nutrient content, few types and great difference in taste from fermented milk, and propose a fermented milk whey product and a preparation method thereof; the method adopts a fermentation method combining dry fermentation and wet fermentation to directly ferment semi-solid raw milk, and uses the fermentation product whey as the final product, making full use of the different metabolic capabilities and methods of fermentation bacteria under different fermentation conditions, thereby significantly improving the types and contents of nutrients in the fermented milk whey product, significantly enhancing the health care effect, and being conducive to the large-scale promotion and application of the fermented milk whey product.

[0005] In order to achieve the above object of the invention, the present invention provides a method for preparing a fermented milk whey product, comprising the following steps:

[0006] (1) mixing semi-solid raw milk with fermentation bacteria and performing dry fermentation to obtain a dry fermentation product; the semi-solid raw milk has a water content of 45-50%;

[0007] (2) adding sodium chloride and water to the dry fermentation product to perform wet fermentation to obtain a wet fermentation product;

[0008] (3) performing solid-liquid separation on the wet fermentation product to obtain fermentation product whey;

[0009] (4) sterilizing the fermentation product whey to obtain a fermented milk whey product.

[0010] The preparation method of a fermented milk whey product of the present invention not only adopts a fermentation method combining dry fermentation and wet fermentation (the existing technology only adopts one fermentation), but also fully utilizes the different metabolic abilities and methods of fermentation bacteria under different fermentation conditions, thereby significantly increasing the types of nutritional components generated by the metabolism of the fermentation bacteria. At the same time, it can also better fully ferment the components in the semi-solid raw milk, thereby increasing the yield of the fermented product and significantly improving the nutritional value of the product. The whey filtered out of the fermentation product of the semi-solid raw milk is directly used as the product (the existing technology is to ferment whey protein powder or whey as an ingredient), thereby making the obtained fermented milk whey product rich in more nutrients, and significantly enhancing its taste and health-care effects, which is conducive to the large-scale promotion and application of the fermented milk whey product.

[0011] Wherein, preferably, the semi-solid raw milk in step (1) is obtained by filtering, sterilizing, homogenizing, concentrating and drying the raw milk.

[0012] Preferably, the filtration is to filter the raw milk at a temperature of 0-20° C. using a filter membrane with a pore size of 1-80 nm; this can remove large particle impurities in the raw milk and purify the raw milk.

[0013] Preferably, the sterilization is pre-pasteurization, and the pre-pasteurization temperature is 70-85° C. and the time is 1-30 seconds; it can achieve sterilization to the greatest extent without destroying the taste and material composition of the raw milk, thereby ensuring the normal progress of the subsequent fermentation.

[0014] Preferably, the homogenization pressure is 200-250 bar, and the homogenization temperature is 55-65° C.; the preferred homogenization conditions make the raw milk softer and more conducive to the concentration and drying of the raw milk.

[0015] Preferably, the concentration is carried out by combining membrane filtration and a multi-effect vacuum concentration evaporator; the concentration temperature is controlled at 55-65°C and the vacuum degree is controlled at 0.06-0.08MPa; the preferred concentration method and parameter conditions will not affect the taste and material composition of the raw milk, and the concentration speed is fast and the energy consumption is low.

[0016] Preferably, the drying is freeze-drying and drying in sequence; the preferred drying method and sequence can better achieve the drying treatment of the raw milk, and achieve rapid drying with low energy consumption without affecting the material composition of the raw milk (protein denaturation).

[0017] Preferably, the freeze-drying conditions are: pre-freezing at -40-20°C for 2-4 hours; the first drying temperature is -10-5°C for 15-25 hours; the second drying temperature is 23-28°C for 2-4 hours. The preferred freeze-drying conditions can avoid the deterioration of the components in the raw milk, and have a fast drying speed and low energy consumption.

[0018] Preferably, the drying temperature is 45-55° C.; the preferred drying temperature can avoid protein denaturation in the raw milk, and has a fast drying speed and low energy consumption.

[0019] Wherein, in step (1), the fermentation bacteria are Streptococcus thermophilus C-1 (strain collection number CGMCC 22113) and Lactobacillus fermentum DALI02 (strain collection number CGMCC 16064); preferably, among the fermentation bacteria, the weight ratio of Streptococcus thermophilus C-1 to Lactobacillus fermentum DALI02 is 3-4:2-3; the preferred fermentation bacteria composition can be combined with the fermentation method to significantly improve the fermentation effect on the semi-solid raw milk, and significantly increase the types and quantities of nutrients produced by fermentation.

[0020] Preferably, the amount of the fermentation bacteria is 1-5% of the weight of the semi-solid raw milk; the preferred amount of fermentation bacteria has a good fermentation effect and a short fermentation time.

[0021] Among them, preferably, in step (1), the dry fermentation is to form the semi-solid raw milk and then inoculate fermentation bacteria for fermentation; through dry fermentation, more types of nutrients can be produced, so that the types of nutrients contained in the product are significantly increased, and the water content in the semi-solid raw milk has a direct impact on the effect of dry fermentation.

[0022] Preferably, the shaping is to press the semi-solid raw milk into a spherical shape with a diameter of 1-3 cm; the preferred shape is more conducive to dry fermentation.

[0023] Among them, preferably, in step (1), the temperature of dry fermentation is 41-43° C. and the time is 10-14 h; the preferred fermentation conditions have good fermentation effect and short fermentation time.

[0024] Among them, preferably, in step (2), the amount of sodium chloride used is 0.5-15% of the weight of the semi-solid raw milk; the amount of water used is 3.8-4.0 times the weight of the dry fermentation product; the preferred amount of sodium chloride and water is more suitable for wet fermentation, and the amount of nutrients generated by fermentation is larger.

[0025] Among them, preferably, in step (2), the temperature of wet fermentation is 40-43° C. and the time is 6-10 h; the preferred fermentation conditions have good fermentation effect and short fermentation time.

[0026] Wherein, preferably, in step (3), the method of solid-liquid separation is filtration or pressing.

[0027] Preferably, in step (4), the sterilization temperature is 95-100°C and the time is 1-10s; preferably, the sterilization

[0028] Conditions, good sterilization effect, little impact on product quality.

[0029] In order to achieve the above object of the invention, the present invention further provides a fermented milk whey product, which is prepared by the above method.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The preparation method of the fermented milk whey product of the present invention uses the whey filtered out of the semi-solid raw material milk fermentation product directly as the product, so that the obtained fermented milk whey product is rich in more nutrients, and its taste and health care effects are significantly enhanced.

[0032] 2. The preparation method of the fermented milk whey product of the present invention adopts a fermentation method that combines dry fermentation and wet fermentation, making full use of the different metabolic capabilities and methods of fermentation bacteria under different fermentation conditions, thereby significantly increasing the types and yields of nutrients generated by the metabolism of the fermentation bacteria, and significantly improving the nutritional value of the product.

[0033] 3. The preparation method of the fermented milk whey product of the present invention can avoid the denaturation and loss of nutrients in the raw milk by performing targeted treatment (filtration, sterilization, homogenization, concentration and drying) on ​​the raw milk, retaining the nutrients to the greatest extent, which is beneficial to increasing the content and variety of nutrients in the fermented milk whey product.

[0034] 4. The preparation method of the fermented milk whey product of the present invention can make the cooperation effect of the fermentation bacteria and the fermentation method better by optimizing the type and proportion of the fermentation bacteria, thereby increasing the fermentation utilization rate of the semi-solid raw milk, achieving better fermentation effect, and generating a larger amount and variety of nutrients through fermentation.

[0035] 5. The preparation method of the fermented milk whey product of the present invention can better ferment the semi-solid raw milk by optimizing the process parameters, and retain more nutrients in the fermented milk whey product, which is beneficial to improving the quality of the fermented milk whey product.

[0036] 6. The preparation method of the fermented milk whey product of the present invention has simple process, stable quality and good practicality, and is suitable for large-scale and industrial production of fermented milk whey products.

[0037] 7. The fermented milk whey product of the present invention has a water-like texture, a light color, a refreshing taste, is rich in nutrients, has excellent health effects, and is suitable for large-scale drinking. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is the amino acid standard sample spectrum (in the spectrum, 1 is aspartic acid, 2 is glutamic acid, 3 is serine, 4 is glycine, 5 is histidine, 6 is arginine, 7 is threonine, 8 is alanine, 9 is proline, 10 is tyrosine, 11 is valine, 12 is methionine, 13 is cystine, 14 is isoleucine, 15 is leucine, 16 is phenylalanine, and 17 is lysine);

[0039] Figure 2 This is the taste scoring result diagram in Experimental Example 4;

[0040] Figure 3 This is the odor scoring result diagram in Experimental Example 4;

[0041] Figure 4 This is the taste scoring result diagram in Experimental Example 4;

[0042] Figure 5 This is the tissue status scoring result diagram in Experimental Example 4. DETAILED DESCRIPTION

[0043] The present invention will be further described in detail below in conjunction with test examples and specific embodiments. However, this should not be understood as limiting the scope of the present invention to the following embodiments, and all technologies implemented based on the present invention fall within the scope of the present invention.

[0044] Example 1:

[0045] A fermented milk whey product, the specific preparation method of which is as follows:

[0046] (1) filtering the raw milk at a temperature of 10° C. using a filter membrane with a pore size of 40 nm, and then pre-pasteurizing (temperature of 80° C., time of 10 s) to obtain pre-pasteurized milk;

[0047] (2) homogenizing the pre-pasteurized milk obtained in step (1) (homogenization pressure: 220 bar, homogenization temperature: 60° C.);

[0048] (3) The material obtained in step (2) is concentrated by a combination of membrane filtration and a multi-effect vacuum evaporator; the concentration temperature is controlled at 60° C. and the vacuum degree is controlled at 0.07 MPa;

[0049] (4) Cooling the material obtained in step (3) and performing freeze-drying treatment (pre-freezing at -30°C for 3 hours; first-stage drying at -8°C for 20 hours; second-stage drying at 25°C for 3 hours);

[0050] (5) drying the material obtained in step (4) at 50° C. to obtain a semi-solid raw milk having a water content of 48%; and molding the semi-solid raw milk into spheres having a diameter of 2 cm.

[0051] (6) The spherical semi-solid raw milk obtained in step (5) was mixed evenly with 2% of a starter (Streptococcus thermophilus C-1 and Lactobacillus fermentum DALI02 in a weight ratio of 3:2) and subjected to dry fermentation (fermentation temperature 42° C., time 12 h);

[0052] (7) The material obtained in step (6) was mixed with sterile water (3.9 times the weight of the dry fermentation product), sodium chloride (2% of the weight of the semi-solid raw milk) was added, and wet fermentation was carried out (fermentation temperature 42°C, time 8 hours);

[0053] (8) squeezing the material obtained in step (7) to remove milk solids and filtering;

[0054] (9) The material obtained in step (8) is sterilized (temperature is 98° C., time is 3 s) to obtain a fermented milk whey product.

[0055] Example 2:

[0056] A fermented milk whey product, the specific preparation method of which is as follows:

[0057] (1) filtering the raw milk at 20° C. using a filter membrane with a pore size of 20 nm, and then pre-pasteurizing (temperature of 70° C., time of 30 s) to obtain pre-pasteurized milk;

[0058] (2) homogenizing the pre-pasteurized milk obtained in step (1) (homogenization pressure: 200 bar, homogenization temperature: 65° C.);

[0059] (3) The material obtained in step (2) is concentrated by a combination of membrane filtration and a multi-effect vacuum evaporator; the concentration temperature is controlled at 55° C. and the vacuum degree is controlled at 0.08 MPa;

[0060] (4) Cooling the material obtained in step (3) and performing freeze-drying treatment (pre-freezing at -40°C for 3 hours; first drying at -8°C for 20 hours; second drying at 25°C for 3 hours);

[0061] (5) drying the material obtained in step (4) at 45° C. to obtain a semi-solid raw milk having a water content of 45%; and shaping the semi-solid raw milk into spheres having a diameter of 1 cm.

[0062] (6) The spherical semi-solid raw milk obtained in step (5) was mixed evenly with 2% of a starter (Streptococcus thermophilus C-1 and Lactobacillus fermentum DALI02 in a weight ratio of 4:3) and subjected to dry fermentation (fermentation temperature 41°C, time 14 h);

[0063] (7) The material obtained in step (6) was mixed with sterile water (3.8 times the weight of the dry fermentation product), sodium chloride (0.5% of the weight of the semi-solid raw milk) was added, and wet fermentation was carried out (fermentation temperature 43°C, time 6 hours);

[0064] (8) squeezing the material obtained in step (7) to remove milk solids and filtering;

[0065] (9) The material obtained in step (8) is sterilized (temperature is 95° C., time is 10 s) to obtain a fermented milk whey product.

[0066] Example 3:

[0067] A fermented milk whey product, the specific preparation method of which is as follows:

[0068] (1) filtering the raw milk at a temperature of 5° C. using a filter membrane with a pore size of 80 nm, and then pre-pasteurizing (temperature of 85° C., time of 1 s) to obtain pre-pasteurized milk;

[0069] (2) homogenizing the pre-pasteurized milk obtained in step (1) (homogenization pressure: 250 bar, homogenization temperature: 55° C.);

[0070] (3) The material obtained in step (2) is concentrated by a combination of membrane filtration and a multi-effect vacuum evaporator; the concentration temperature is controlled at 65° C. and the vacuum degree is controlled at 0.06 MPa;

[0071] (4) Cooling the material obtained in step (3) and performing freeze-drying treatment (pre-freezing at -40°C for 3 hours; first drying at -8°C for 20 hours; second drying at 25°C for 3 hours);

[0072] (5) drying the material obtained in step (4) at 45° C. to obtain a semi-solid raw milk having a water content of 50%; and shaping the semi-solid raw milk into spheres having a diameter of 1 cm;

[0073] (6) The spherical semi-solid raw milk obtained in step (5) was mixed evenly with 5% of a starter (Streptococcus thermophilus C-1 and Lactobacillus fermentum DALI02 in a weight ratio of 2:1), and dry fermentation was performed (fermentation temperature 43°C, time 10 h);

[0074] (7) The material obtained in step (6) was mixed with sterile water (4.0 times the weight of the dry fermentation product), sodium chloride (15% of the weight of the semi-solid raw milk) was added, and wet fermentation was carried out (fermentation temperature 40°C, time 8 hours);

[0075] (8) squeezing the material obtained in step (7) to remove milk solids and filtering;

[0076] (9) The material obtained in step (8) is sterilized (temperature is 95° C., time is 10 s) to obtain a fermented milk whey product.

[0077] Example 4

[0078] A fermented milk whey product, the specific preparation method of which is as follows:

[0079] (1) filtering the raw milk at a temperature of 10° C. using a filter membrane with a pore size of 40 nm, and then pre-pasteurizing (temperature of 80° C., time of 10 s) to obtain pre-pasteurized milk;

[0080] (2) homogenizing the pre-pasteurized milk obtained in step (1) (homogenization pressure: 220 bar, homogenization temperature: 60° C.);

[0081] (3) The material obtained in step (2) is concentrated by a combination of membrane filtration and a multi-effect vacuum evaporator; the concentration temperature is controlled at 60° C. and the vacuum degree is controlled at 0.07 MPa;

[0082] (4) Cooling the material obtained in step (3) and performing freeze-drying treatment (pre-freezing at -30°C for 3 hours; first-stage drying at -8°C for 20 hours; second-stage drying at 25°C for 3 hours);

[0083] (5) drying the material obtained in step (4) at 50° C. to obtain a semi-solid raw milk having a water content of 48%; and shaping the semi-solid raw milk into a cube having a side length of 2 cm;

[0084] (6) The spherical semi-solid raw milk obtained in step (5) was mixed evenly with 2% of a starter (Streptococcus thermophilus C-1 and Lactobacillus fermentum DALI02 in a weight ratio of 3:2) and subjected to dry fermentation (fermentation temperature 42° C., time 12 h);

[0085] (7) The material obtained in step (6) was mixed with sterile water (3.9 times the weight of the dry fermentation product), sodium chloride (2% of the weight of the semi-solid raw milk) was added, and wet fermentation was carried out (fermentation temperature 42°C, time 8 hours);

[0086] (8) squeezing the material obtained in step (7) to remove milk solids and filtering;

[0087] (9) The material obtained in step (8) is sterilized (temperature is 98° C., time is 3 s) to obtain a fermented milk whey product.

[0088] Comparative Example 1:

[0089] A fermented milk whey product, the specific preparation method of which is as follows:

[0090] (1) filtering the raw milk at a temperature of 10° C. using a filter membrane with a pore size of 40 nm, and then pre-pasteurizing (temperature of 80° C., time of 10 s) to obtain pre-pasteurized milk;

[0091] (2) homogenizing the pre-pasteurized milk obtained in step (1) (homogenization pressure: 220 bar, homogenization temperature: 60° C.);

[0092] (3) The material obtained in step (2) is concentrated by a combination of membrane filtration and a multi-effect vacuum evaporator; the concentration temperature is controlled at 60° C. and the vacuum degree is controlled at 0.07 MPa;

[0093] (4) Cooling the material obtained in step (3) and performing freeze-drying treatment (pre-freezing at -30°C for 3 hours; first-stage drying at -8°C for 20 hours; second-stage drying at 25°C for 3 hours);

[0094] (5) drying the material obtained in step (4) at 50° C. to obtain a semi-solid raw milk having a water content of 48%; and molding the semi-solid raw milk into spheres having a diameter of 2 cm.

[0095] (6) The spherical semi-solid raw milk obtained in step (5) was mixed evenly with 2% of a starter (Streptococcus thermophilus C-1 and Lactobacillus fermentum DALI02 in a weight ratio of 3:2), but the mixture was not fermented for a certain period of time, but directly proceeded to step 7;

[0096] (7) Sterile water (3.9 times the weight of the material) was added to the material obtained in step (6) and mixed, and sodium chloride (2% of the weight of the semi-solid raw milk) was added, and wet fermentation was carried out (fermentation temperature 42°C, time 20 hours);

[0097] (8) squeezing the material obtained in step (7) to remove milk solids and filtering;

[0098] (9) The material obtained in step (8) is sterilized (temperature is 98° C., time is 3 s) to obtain a fermented milk whey product.

[0099] Comparative Example 2:

[0100] A fermented milk whey product, the specific preparation method of which is as follows:

[0101] (1) filtering the raw milk at a temperature of 10° C. using a filter membrane with a pore size of 40 nm, and then pre-pasteurizing (temperature of 80° C., time of 10 s) to obtain pre-pasteurized milk;

[0102] (2) homogenizing the pre-pasteurized milk obtained in step (1) (homogenization pressure: 220 bar, homogenization temperature: 60° C.);

[0103] (3) The material obtained in step (2) is concentrated by a combination of membrane filtration and a multi-effect vacuum evaporator; the concentration temperature is controlled at 60° C. and the vacuum degree is controlled at 0.07 MPa;

[0104] (4) Cooling the material obtained in step (3) and performing freeze-drying treatment (pre-freezing at -30°C for 3 hours; first-stage drying at -8°C for 20 hours; second-stage drying at 25°C for 3 hours);

[0105] (5) drying the material obtained in step (4) at 50° C. to obtain a semi-solid raw milk having a water content of 48%; and molding the semi-solid raw milk into spheres having a diameter of 2 cm.

[0106] (6) The spherical semi-solid raw milk obtained in step (5) was mixed evenly with 2% of a starter (Streptococcus thermophilus C-1 and Lactobacillus fermentum DALI02 in a weight ratio of 3:2) and then fermented at a temperature of 42° C. for 20 h;

[0107] (7) Sterile water (3.9 times the weight of the material) was added to the material obtained in step (6) and mixed, sodium chloride (2% of the weight of the semi-solid raw milk) was added, and the bacterial strain was added, but the fermentation time was 0;

[0108] (8) squeezing the material obtained in step (7) to remove milk solids and filtering;

[0109] (9) The material obtained in step (8) is sterilized (temperature is 98° C., time is 3 s) to obtain a fermented milk whey product.

[0110] Comparative Example 3

[0111] A fermented milk whey product, the specific preparation method of which is as follows:

[0112] (1) filtering the raw milk at a temperature of 10° C. using a filter membrane with a pore size of 40 nm, and then pre-pasteurizing (temperature of 80° C., time of 10 s) to obtain pre-pasteurized milk;

[0113] (2) homogenizing the pre-pasteurized milk obtained in step (1) (homogenization pressure: 220 bar, homogenization temperature: 60° C.);

[0114] (3) The material obtained in step (2) was mixed evenly with 2% of a starter culture (Streptococcus thermophilus C-1 and Lactobacillus fermentum DALI02 in a weight ratio of 3:2) and fermented (fermentation temperature 42° C., time 20 h);

[0115] (4) squeezing the material obtained in step (3) to remove milk solids;

[0116] (5) The material obtained in step (4) is sterilized (temperature is 98° C., time is 3 s) to obtain a fermented milk whey product.

[0117] Comparative Example 4

[0118] A whey product, the specific preparation method of which is as follows:

[0119] (1) filtering the raw milk at a temperature of 10° C. using a filter membrane with a pore size of 40 nm, and then pre-pasteurizing (temperature of 80° C., time of 10 s) to obtain pre-pasteurized milk;

[0120] (2) performing membrane separation on the pre-pasteurized milk obtained in step (1) to collect whey;

[0121] (3) The whey obtained in step (2) was mixed evenly with 2% of a starter culture (Streptococcus thermophilus C-1 and Lactobacillus fermentum DALI02 in a weight ratio of 3:2) and fermented (fermentation temperature 42° C., time 20 h);

[0122] (4) The material obtained in step (3) is sterilized (temperature is 98° C., time is 3 s) to obtain a fermented milk whey product.

[0123] Comparative Example 5

[0124] A whey product, the specific preparation method of which is as follows:

[0125] (1) Prepare whey protein powder into 10% whey solution, add sugar and stabilizer.

[0126] (2) The material obtained in step (1) was pasteurized (temperature: 80°C, time: 10s) and homogenized (homogenization pressure: 220 bar, homogenization temperature: 60°C);

[0127] (3) The material obtained in step (2) was mixed evenly with 2% of a starter culture (Streptococcus thermophilus C-1 and Lactobacillus fermentum DALI02 in a weight ratio of 3:2) and fermented (fermentation temperature 42° C., time 20 h);

[0128] (4) filtering the material obtained in step (3);

[0129] (5) The material obtained in step (4) is sterilized (temperature is 98° C., time is 3 s) to obtain a fermented milk whey product.

[0130] Comparative Examples 6-11

[0131] Comparative Examples 6-11 are all based on Example 1, with one process parameter or condition changed to prepare fermented milk whey products. The specific differences are shown in Table 1.

[0132] Table 1 Comparative Examples 6-11 are different from Example 1

[0133]

[0134] Experimental Example 1:

[0135] Experimental project: Protein hydrolysis experiment of Streptococcus thermophilus C-1, Lactobacillus fermentum DALI02 and their combination.

[0136] Test Method: Take 5 g of sample, add 10 mL of 0.75 mol / L trichloroacetic acid and 1 mL of distilled water, mix well at room temperature, let stand for 10 minutes, centrifuge (6000 g × 10 minutes, 4°C), and filter. Take 100 μL of the filtrate and add 4 mL of OPA reagent. Use OPA reagent as a blank. Use an uninoculated fermentation sample treated in the same manner and then added with OPA reagent as a control. Incubate at room temperature for 2 minutes, then measure the absorbance at 340 nm.

[0137] The experimental results are shown in Table 2:

[0138] Table 2 Fermentation bacteria protein hydrolysis experiment

[0139]

[0140] The experimental results in Table 2 show that the protein hydrolysis ability of the two bacteria in the synergistic fermentation is significantly improved compared with the protein hydrolysis ability of the two bacteria alone. It is well known that the stronger the hydrolysis ability of the fermentation bacteria, the more types and contents of small molecule proteins and amino acids in the fermentation product.

[0141] Experimental Example 2:

[0142] Experimental project: Determine the types, quantities and total contents of amino acids in the nutritional ingredients of the whey products prepared in Examples 1-4 and Comparative Examples 1-11;

[0143] Determination method: High performance liquid chromatography (chromatogram of amino acids see Figure 1 )

[0144] Chromatographic conditions: Mobile phase A: Dissolve 2.72g sodium acetate and 180µl triethylamine in 1L ultrapure water, adjust the pH to 7.20 with 1% glacial acetic acid, add 3.0ml tetrahydrofuran (THF), mix, and filter through a 0.22µm aqueous membrane. Degas and store at 4°C in the dark. Mobile phase B: Dissolve 2.72g sodium acetate in water to 200ml, adjust the pH to 7.20 with 1% glacial acetic acid, add 400ml acetonitrile and 400ml methanol, degas, and use. Chromatographic column: C18, column temperature: 40°C. Injection volume: 20µl.

[0145] Sample pretreatment: 10 ml of sample was centrifuged at 4 °C for 30 min with a centrifugal force of 9000 g. The supernatant was taken and made up to 25 ml, and then filtered through glass wool to obtain a water-soluble extract. The sample solution was then derivatized.

[0146] Derivatization conditions: 250 μL of sample solution, 100 μL (2 mol / L) KHCO₃, and 200 μL of 4 g / L dansyl chloroacetone were placed in an 80-90°C water bath for 40 min. The reaction was terminated by adding 200 μL of 1 mol / L HCl, followed by cooling and high-speed centrifugation at 12,000 rpm for 10 min. The supernatant was sampled and assayed.

[0147] Measurement results: See Table 3 and Table 4.

[0148] Table 3 Determination of the types and quantities of amino acids in the whey products of the embodiments and comparative examples

[0149]

[0150] Table 4 Determination of the total content of amino acids (corresponding amounts of amino acids detected in Table 4) in the whey products of the examples and comparative examples

[0151]

[0152] As shown in Tables 3 and 4, Examples 1-4 contain 17 amino acid species and a total content of nearly 400 mg / 100 g. The comparative examples all contain fewer than 17 amino acid species and a total amino acid content of less than 360 mg / 100 g. These differences are significant in terms of both the number of amino acid species and the amino acid content.

[0153] Experimental Example 3:

[0154] Experimental project: Determine the flavor content in the whey products of Examples 1-4 and Comparative Examples 1-11;

[0155] Experimental methods:

[0156] (1) Collection and detection of flavor substances

[0157] In this experiment, a 50 / 30 micron DVB / CPR / PDMS extraction head was used to enrich the samples, with three parallels in each group. The volatile flavor substances were then detected and analyzed using GC-MS technology.

[0158] (2) Extraction and determination conditions of flavor substances

[0159] Chromatographic conditions: He carrier gas, flow rate 1.0 mL / min; splitless injection, inlet temperature 250°C. A temperature program was used: starting at 35°C, holding for 5 min, then increasing to 140°C at a rate of 5°C / min, holding for 2 min, then increasing to 250°C at a rate of 10°C / min, and holding for 3 min.

[0160] Mass spectrometry conditions: full scan mode; EI ion source; electron energy 70 eV; ion source temperature 230 °C; mass scan range m / z 35-500; no solvent delay.

[0161] SPME extraction conditions: 50℃ equilibrium for 60min

[0162] Desorption conditions: desorption at 250 °C for 3 min.

[0163] (3) Qualitative and quantitative analysis

[0164] Qualitative method: Automated comparison was performed using the NIST11 standard library carried by the Masshunter workstation. Substances with a match rate ≥ 85% were selected as identification results. At the same time, retention indices (RI) were determined according to the Vandendol method. Volatile flavor compounds in the samples were re-identified based on the RI values ​​reported in the literature. The RI value calculation formula is as follows:

[0165]

[0166] Where: RT (Z) , RT (Z+1) and RT (X) are the retention times of n-alkanes with carbon atoms of Z, Z+1 and analyte X, and RT (Z) <RT (X) <RT (Z+1) .

[0167] Quantitative method: Add 50 μL of 0.01 μg / L internal standard 1,2-dichlorobenzene solution to 5 mL of fermentation sample. The concentration of each flavor component in the sample can be calculated by substituting it into formula (2):

[0168]

[0169] Where: C i -The concentration of each flavor compound in the test sample, in micrograms per liter (μg / L);

[0170] C s -1,2-dichlorobenzene concentration in micrograms per liter (μg / L);

[0171] A i —The chromatographic peak area corresponding to the analyte in the sample;

[0172] A S —Chromatographic peak area of ​​internal standard.

[0173] (4) Aroma activity value evaluation method

[0174] Based on the quantitative analysis of the volatile flavor compounds in the sample, the aroma activity value (OAV), a physical quantity that can characterize the contribution rate of the flavor compounds, was calculated using the flavor threshold of each flavor compound in water as a reference.

[0175] It can be substituted into formula (2) to calculate:

[0176]

[0177] Where: OAV i —aroma activity value of flavor compound i;

[0178] C i —The concentration of volatile flavor compounds in the sample in micrograms per liter (μg);

[0179] OT i —Odor threshold of the flavor compound tested in water.

[0180] Test results: See Table 5 (“-” means not detected)

[0181] Table 5 OAV values ​​of flavor substances in whey products of Examples and Comparative Examples

[0182]

[0183] Result analysis: The type, content and threshold of each volatile substance in the sample jointly determine its overall flavor. The aroma activity value (OAV) refers to the ratio of the concentration of the aroma component to its aroma threshold in water, which can accurately evaluate the contribution of a single aroma component to the overall flavor. Generally, substances with OAV>1 are identified as key flavor compounds in the sample, which have an important contribution to the overall flavor, while components with 0.1<OAV<1 have an important modifying effect on the overall flavor of the sample. Components with OAV<0.1 have a weaker effect on the overall flavor of the sample. The key volatile flavor substances of the product at the end of fermentation and during storage include n-valeraldehyde and ethyl acetate. The flavor compound with an important modifying effect is 2-nonanol. Among them, n-valeraldehyde has a refreshing aromatic taste, ethyl acetate has the flavor of orange peel, and 2-nonanol has a creamy aroma. As can be seen from the above table, the OAV values ​​of Examples 1-4 of the three key flavor substances are significantly higher than those of the control example.

[0184] Experimental Example 4

[0185] The samples were subjected to sensory evaluation every 7 days. The evaluation team consisted of 20 food professional sensory personnel. The 20 evaluators received two sensory evaluation trainings before the evaluation. They scored the samples according to the evaluation criteria. The specific sensory evaluation reference standards are shown in Table 6 below:

[0186] Table 6 Sensory evaluation scoring standards

[0187]

[0188] The sensory quality of a sample is an important indicator of its overall quality. At present, the sensory analysis of related products in China is usually evaluated through four aspects: taste, flavor, smell, and texture. For samples during the storage period, sensory evaluation is conducted every 7 days. The experimental results are as follows: Figure 2-5 As shown in the results, the sensory evaluation scores of the smell and taste of the Example during the storage period were significantly higher than those of the other groups (P < 0.05).

Claims

1. A method for preparing a fermented milk whey product, characterized in that: The following steps are involved: (1) After semi-solid raw milk and fermentation bacteria are mixed and formed, dry fermentation is performed to obtain a dry fermentation product; the fermentation bacteria are Streptococcus thermophilus C-1 and Lactobacillus fermentum DALI02; the water content of the semi-solid raw milk is 45-50%; the semi-solid raw milk is obtained by filtering, sterilizing, homogenizing, concentrating and drying the raw milk; the strain preservation number of Streptococcus thermophilus C-1 is CGMCC 22113, and the strain preservation number of Lactobacillus fermentum DALI02 is CGMCC 16064; (2) adding sodium chloride and water to the dry fermentation product to perform wet fermentation to obtain a wet fermentation product; (3) performing solid-liquid separation on the wet fermentation product to obtain fermentation product whey; (4) The fermentation product whey is sterilized to obtain a fermented milk whey product.

2. The preparation method according to claim 1, characterized in that In the fermentation bacteria, the weight ratio of Streptococcus thermophilus C-1 to Lactobacillus fermentum DALI02 is 3-4:2-3.

3. The preparation method according to claim 1, characterized in that The amount of the fermentation bacteria used is 1-5% of the weight of the semi-solid raw milk.

4. The preparation method according to claim 1, characterized in that In step (1), the molding is to press the semi-solid raw milk into a spherical shape with a diameter of 1-3 cm.

5. The preparation method according to claim 1, characterized in that In step (1), the dry fermentation temperature is 41-43°C and the time is 10-14 hours.

6. The preparation method according to claim 1, characterized in that In step (2), the amount of sodium chloride used is 0.5-15% of the weight of the semi-solid raw milk; the amount of water used is 3.8-4.0 times the weight of the dry fermentation product.

7. The preparation method according to claim 1, characterized in that In step (2), the temperature of wet fermentation is 40-43°C and the time is 6-10 hours.

8. The preparation method according to claim 1, characterized in that In step (4), the sterilization temperature is 95-100°C and the time is 1-10s.

9. A fermented milk whey product, characterized in that It is prepared by the preparation method according to any one of claims 1 to 8.

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