Method for preparing dairy product by carrying out enzymolysis on milk fat by using composite flora

Abstract

The invention relates to the technical field of dairy product processing, and discloses a method for preparing a dairy product by performing enzymolysis on milk fat by using a compound flora, which comprises the following steps: S1, performing centrifugal degreasing on raw milk, performing pasteurization, adding a citric acid-malic acid compound, and performing microjet homogenization to obtain skimmed milk with a plurality of fat globules; s2, the skimmed milk subjected to microjet homogenization in the step S1 is added into a container with a composite flora, intermittent ultrasonic waves are added into the skimmed milk, and the composite flora is bacillus licheniformis, streptococcus thermophilus, aspergillus oryzae spores and candida tropicalis according to the ratio of (2-4): (1-3): (0.5-1.5): (0.5-1.5); s3, oxygen is introduced into the container, and the dissolved oxygen is maintained at 15%-25%; and S4, in the steps S2 and S3, maintaining the skimmed milk at a preset temperature, and continuously stirring for a preset time. The problem that long-chain triglyceride cannot be decomposed in the prior art is solved.

Description

Technical Field

[0001] This application relates to the technical field of dairy product processing, and relates to a dynamic energy-saving pulsating sludge treatment system based on an aerobic fluidized reactor. Background Art

[0002] Milk fat is one of the main components of milk, with an average content in milk of 3% - 5%. Approximately 98% of the fat in milk is long-chain triglyceride (LCT), which needs to be decomposed by pancreatic lipase in the animal body before absorption, and the absorption efficiency is limited by the intestinal environment.

[0003] The existing technology only changes the physical form of fat, that is, homogenizes or ultrasonically emulsifies dairy products, etc. It does not solve the chemical structure of long-chain triglycerides, so there is still a problem of low absorption rate. Summary of the Invention

[0004] This application provides a method for preparing dairy products by enzymatically hydrolyzing milk fat with a composite flora, aiming to solve the problem that the existing technology cannot decompose long-chain triglycerides.

[0005] In one aspect, a method for preparing dairy products by enzymatically hydrolyzing milk fat with a composite flora is provided, including the following steps:

[0006] S1. Centrifuge and defat the raw milk, then perform pasteurization, and then add a citric acid - malic acid complex, and obtain defatted milk with multiple fat globules through microfluidic homogenization.

[0007] Among them, the fat content of the raw milk after centrifugal defatting is 1.5 - 3.0%; the raw milk is pressurized to 150 MPa in a microfluidic homogenizer and then subjected to microfluidic homogenization to obtain fat globules with a particle size ≤ 0.5 μm. The microfluidic homogenizer is an existing device on the market.

[0008] 0.1% of L-ascorbyl palmitate (AP) is also added to the defatted milk as an antioxidant, and 0.05% of lecithin is added as an enzyme reaction promoter.

[0009] S2. Add the defatted milk obtained by microfluidic homogenization in step S1 to a container with a composite flora, and then add intermittent ultrasonic waves to the defatted milk. The composite flora is Bacillus licheniformis: Streptococcus thermophilus: Aspergillus oryzae spores: Candida tropicalis = (2 - 4):(1 - 3):(0.5 - 1.5):(0.5 - 1.5);

[0010] Among them, the composite flora is attached to a carrier, and the ratio of the number of the composite flora to the number of carriers is 1:3. The composite flora solution is mixed with the carrier and then added to the bottom of the container; the carrier is a mesoporous silica - chitosan composite microsphere (pore size 50 - 100 nm); the amount of the composite flora plus the carrier can be added according to requirements, mainly through later cultivation.

[0011] Among them, the proportions of Bacillus licheniformis, Streptococcus thermophilus, Aspergillus oryzae spores, and Candida tropicalis in the complex microbial community are in units of CFU / ml (colony-forming units); that is, the quantity proportions of each colony in every ml of the complex microbial community.

[0012] S3. Introduce oxygen into the container and maintain the dissolved oxygen at 15% to 25%; and introduce feed into the container, and the feed is glucose:glycerol = 2:1;

[0013] Among them, the introduced is oxygen-containing microbubbles. The ratio of the amount of feed to skim milk is 1:265; it is continuously injected into the skim milk in 3 hours.

[0014] S4. In step S2 and step S3, maintain the skim milk at a predetermined temperature and continuously stir for a predetermined time.

[0015] Among them, the stirring speed is 150 rpm.

[0016] In one embodiment, the predetermined temperature is 32°C to 55°C.

[0017] In one embodiment, in step S2, after the skim milk is added to the container with the complex microbial community, maintain the temperature of the skim milk at 32°C to 35°C and the duration is two hours, then raise the temperature to 55°C and continuously stir for five hours.

[0018] Specifically, Lactococcus lactis is added when the temperature rises to 35°C, and the pH of the skim milk is adjusted to 6.2 - 6.4; and the temperature is maintained at 35°C for one hour before continuing to rise, among which, 1% Lactococcus lactis is added when the temperature rises to 35°C.

[0019] At 55°C, the natural heat shock of Bacillus licheniformis is initiated (HSP), and high expression of related enzymes (such as LipA) is induced by maintaining at this temperature for 1.5 hours, and the expression is turned off when the temperature is lowered to 38°C.

[0020] In one embodiment, after continuously stirring for five hours in the environment where the skim milk is heated to 55°C, then lower the temperature to 45°C, and add 0.1% lecithin, 0.05% whey protein, and 0.01% trehalose to the skim milk, and stir at a speed of 200 rpm for 2 hours.

[0021] Specifically, 0.1% is the content of lecithin, and the ratio of the amount of added lecithin to the amount of skim milk is 1:1000.

[0022] In one solution, an ultrasonic generator is provided in the container; in step S2, when the temperature of the skim milk rises to 45°C to 55°C, the pH value is adjusted to 7.0, the ultrasonic wave of the ultrasonic generator is 20 kHz; and the duration of each ultrasonic wave is 10 seconds, and the time interval between two adjacent ultrasonic waves is 5 seconds; the total duration of the ultrasonic wave is 120 seconds.

[0023] Specifically, the regulation sequence of the pH value is 6.8 to 7.2 to 6.5, activating different lipase subtypes (such as LipA has the highest activity at pH 7.2).

[0024] In one solution, when the temperature of the skim milk rises to 50°C, the pH value is adjusted to 6.8 and maintained for one hour.

[0025] In one solution, after step S4 is executed, the skim milk is ultrafiltered for 30 minutes.

[0026] Specifically, a 100 kDa TiO 2 coated ceramic membrane is used for ultrafiltration, and the ultrafiltration pressure is 0.1 to 0.2 MPa to achieve the separation and recovery of substances such as milk protein, and at the same time ensure that the retention rate of milk protein activity ≥ 95%.

[0027] In one solution, the skim milk after ultrafiltration is heated to 90°C and maintained at 90°C for 3 to 5 minutes. Inactivate enzymes and microorganisms.

[0028] In one solution, the concentration of the citric acid - malic acid complex is 1.2 g to 1.5 g / kg.

[0029] In one solution, the temperature of the pasteurization is 75°C, and the sterilization time is 20 s. The citric acid - malic acid complex is added after the temperature drops to 40 to 45°C.

[0030] Advantages of this application:

[0031] Bacillus licheniformis secretes thermostable lipase (LipA), which targets the hydrolysis of the ester bonds at the sn-1,3 positions of triglycerides; Streptococcus thermophilus produces β-galactosidase, which decomposes lactose to generate oligosaccharides, promoting the proliferation of probiotics to enhance intestinal absorption; Aspergillus oryzae secretes phospholipase B (PLB), which destroys the structure of the milk fat globule membrane (MFGM) and releases the internal lipids. Candida tropicalis: produces mannan oligosaccharide (MOS) as a natural nanocarrier to encapsulate fatty acids.

[0032] Through the synergistic action of Bacillus licheniformis, Streptococcus thermophilus and Aspergillus oryzae, long-chain triglycerides (LCT) in milk are degraded directionally to generate medium- and short-chain fatty acids (MCFA / SCFA) and functional lipids. Since milk triglycerides are converted into nano-structured lipids (Nano-SL), the intestinal absorption efficiency is significantly improved and the metabolic burden is reduced.

[0033] After centrifugal defatting, the decomposition work of the complex flora can be reduced, and the production efficiency of dairy products can be improved; the citric acid-malic acid complex can reduce the surface charge repulsion of fat globules and improve the homogenization efficiency. After microfluidic homogenization, multiple fat globules can block the binding of raw milk to free Fe²⁺, Cu²⁺ and other ions, block the oxidation reaction catalyst, and ensure the quality of defatted milk.

[0034] Oxygen is introduced to prevent the accumulation of anaerobic by-products (such as propionic acid), and the addition of feeding can maintain the balance of metabolic flux. Brief Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0036] Figure 1 It is a schematic flow chart of the preparation method in an embodiment of the present application; Detailed Description of the Embodiments

[0037] The following will further describe in detail the specific embodiments of the present application in conjunction with the drawings and embodiments. The following embodiments are used to illustrate the present application, but not to limit the scope of the present application. Similarly, the following embodiments are only some embodiments of the present application, not all embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0038] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without conflict, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0039] This application makes improvements and innovations and proposes the following embodiments.

[0040] In some embodiments, refer to Figure 1 , and a method for preparing dairy products by enzymatically hydrolyzing milk fat with a composite microbial community is provided, including the following steps:

[0041] S1. Centrifuge and degrease the raw milk, then perform pasteurization. After adding a citric acid - malic acid complex, obtain defatted milk with multiple fat globules through microfluidic homogenization;

[0042] Among them, the fat content of the raw milk after centrifugal degreasing is 1.5 - 3.0%; pressurize the raw milk to 150 MPa in a microfluidic homogenizer and then perform microfluidic homogenization to obtain fat globules with a particle size ≤ 0.5 μm. The microfluidic homogenizer is an existing device on the market.

[0043] 0.1% of L - ascorbyl palmitate (AP) is also added to the defatted milk as an antioxidant, and 0.05% of lecithin is added as an enzyme - promoting reaction assistant.

[0044] S2. Add the defatted milk obtained by microfluidic homogenization in step S1 to a container with a composite microbial community, and then add intermittent ultrasonic waves to the defatted milk. The composite microbial community is Bacillus licheniformis: Streptococcus thermophilus: Aspergillus oryzae spores: Candida tropicalis = (2 - 4):(1 - 3):(0.5 - 1.5):(0.5 - 1.5);

[0045] When Bacillus licheniformis: Streptococcus thermophilus: Aspergillus oryzae spores: Candida tropicalis = 2:1:0.5:0.5; 3:2:1:1; 4:3:1.5:1.5; the triglyceride contents in the final dairy products obtained are 0.12%; 0.11%; 0.13% respectively, achieving effective decomposition of triglycerides.

[0046] Among them, the composite microbial community is attached to the carrier, and the ratio of the number of the composite microbial community to the number of carriers is 1:3. Mix the composite microbial community solution with the carrier and add it to the bottom of the container; the carrier is a mesoporous silica - chitosan composite microsphere (pore size 50 - 100 nm); the amount of the composite microbial community plus the carrier can be added according to requirements, mainly through later cultivation.

[0047] Among them, the ratio units of Bacillus licheniformis, Streptococcus thermophilus, Aspergillus oryzae spores, and Candida tropicalis in the composite microbial community are CFU / ml (colony - forming unit); that is, in each ml of the composite microbial community, the number ratio of each colony.

[0048] Specifically, the relationship between the addition amount of the composite microbial community and the raw milk is: each 1 ml of raw milk contains 1×106 CFU of composite bacteria. Ensuring that there is a sufficient amount of the composite microbial community to decompose the raw milk improves the decomposition efficiency.

[0049] S3. Introduce oxygen into the container to maintain the dissolved oxygen at 15% to 25%; and introduce supplementary feed into the container, where the supplementary feed is glucose:glycerol = 2:1;

[0050] Among them, the introduced oxygen is in the form of oxygen-containing microbubbles. The ratio of the amount of supplementary feed to skim milk is 1:50; it is continuously injected into the skim milk over 3 hours.

[0051] S4. In steps S2 and S3, maintain the skim milk at a predetermined temperature and continuously stir for a predetermined time.

[0052] Among them, the stirring speed is 150 rpm.

[0053] Specifically, as shown in Table 1 below, when Bacillus licheniformis: Streptococcus thermophilus: Aspergillus oryzae spores: Candida tropicalis = 2:1:0.5:0.5; 3:2:1:1; 4:3:1.5:1.5, they are respectively fed to 4 groups of experimental mice with the same body weight, 10 mice in each group (one group is fed with undegraded raw milk); observe the growth of the mice; record the body weight every 10 days, and record it 5 times in total.

[0054] Table 1

[0055] Body weight on the 10th day (g) Body weight on the 20th day (g) Body weight on the 30th day (g) Body weight on the 40th day (g) Body weight on the 50th day (g) 2:1:0.5:0.5 28.5±1.2 36.8±1.5 44.2±1.8 51.0±2.0 56.3±2.2 3:2:1:1 30.1±1.3 39.4±1.6 48.7±1.9 57.5±2.1 63.8±2.3 4:3:1.5:1.5 27.8±1.1 35.2±1.4 42.5±1.7 49.3±1.9 54.6±2.0 Raw milk 25.0±1.0 29.6±1.1 33.8±1.3 37.2±1.4 40.5±1.5

[0056] According to the data in Table 1, it can be seen that after feeding the mice with the raw milk degraded by Bacillus licheniformis: Streptococcus thermophilus: Aspergillus oryzae spores: Candida tropicalis = 2:1:0.5:0.5; 3:2:1:1; 4:3:1.5:1.5, the body weight of the mice on the 50th day has a large gap compared with the mice fed with raw milk. Therefore, the decomposed raw milk can be more helpful for intestinal absorption. And when Bacillus licheniformis: Streptococcus thermophilus: Aspergillus oryzae spores: Candida tropicalis = 3:2:1:1, the growth of the mice is the best.

[0057] Bacillus licheniformis secretes thermostable lipase (LipA) to target the hydrolysis of the ester bonds at the sn-1,3 positions of triglycerides; Streptococcus thermophilus produces β-galactosidase to decompose lactose into oligosaccharides, promoting the proliferation of probiotics to enhance intestinal absorption; Aspergillus oryzae secretes phospholipase B (PLB) to destroy the structure of the milk fat globule membrane (MFGM) and release the internal lipids. Candida tropicalis: produces mannan oligosaccharide (MOS) as a natural nanocarrier to encapsulate fatty acids.

[0058] Through the synergistic effect of Bacillus licheniformis, Streptococcus thermophilus and Aspergillus oryzae, the long-chain triglycerides (LCT) in milk are directionally degraded to generate medium-chain and short-chain fatty acids (MCFA / SCFA) and functional lipids. Since the milk triglycerides are converted into nano-structured lipids (Nano-SL), the intestinal absorption efficiency is significantly improved and the metabolic burden is reduced.

[0059] After centrifugal degreasing, the decomposition work of the complex flora can be reduced, and the production efficiency of dairy products can be improved; the citric acid-malic acid complex can reduce the surface charge repulsion of fat globules and enhance the homogenization efficiency. After microfluidic homogenization, multiple fat globules can block the binding of raw milk to free Fe²⁺, Cu²⁺ and other ions, block the oxidation reaction catalyst, and ensure the quality of skim milk.

[0060] Oxygen is introduced to prevent the accumulation of anaerobic by-products (such as propionic acid), and the addition of feed can maintain the balance of metabolic flux.

[0061] In one solution, the predetermined temperature is 32°C to 55°C. Within this temperature range, the highest activity of various enzymes can be ensured, and the decomposition efficiency can be improved.

[0062] In one solution, in step S2, after the skim milk is added to the container with the complex flora, the temperature of the skim milk is maintained at 32°C to 35°C for two hours, and then the temperature is raised to 55°C and the continuous stirring time is five hours. In the environment of 32°C to 35°C, the reproduction of the flora can be promoted to facilitate the synthesis of enzymes.

[0063] Specifically, Lactococcus lactis is added when the temperature rises to 35°C, and the pH of the skim milk is adjusted to 6.2 to 6.4; and the temperature is maintained at 35°C for one hour before continuing to rise. When the temperature is 35°C, it is beneficial to the reproduction of lactic acid bacteria, which can consume short-chain fatty acids such as acetic acid. When the pH is adjusted to 6.2 - 6.4 and dominated by lactic acid bacteria, the growth of miscellaneous bacteria can be inhibited.

[0064] Among them, when the temperature rises to 35°C, 1% Lactococcus lactis is added and the ultrasonic generator is not turned on to avoid interfering with the symbiosis of the flora.

[0065] At 55°C, the natural heat shock promoter (HSP) of Bacillus licheniformis is activated, and it is maintained at this temperature for 1.5 hours to induce the high expression of related enzymes (such as LipA), which target the hydrolysis of the ester bonds at the sn-1,3 positions of triglycerides, ensuring the sufficient degradation of long-chain triglycerides (LCT) in milk to generate medium and short-chain fatty acids (MCFA / SCFA); the expression is turned off when the temperature is lowered to 38°C.

[0066] In one solution, after continuously stirring for five hours in an environment where skim milk is heated to 55°C, the temperature is then lowered to 45°C, and 0.1% lecithin, 0.05% whey protein, and 0.01% trehalose are added to the skim milk, and it is stirred at a speed of 200 rpm for 2 hours. Continuously stirring for five hours in an environment where skim milk is heated to 55°C can ensure sufficient degradation of long-chain triglycerides in milk. The added 0.1% lecithin, 0.05% whey protein, and 0.01% trehalose can promote the formation of nanoemulsion particles with a core-shell-corona structure. The nanoemulsion particles have a unique core-shell-corona structure, and this structure may have good affinity with the biomembrane of intestinal mucosal cells in terms of size and properties. Their smaller particle size enables the nanoemulsion particles to be closer to the surface of intestinal mucosal cells, thereby increasing the contact opportunity with intestinal absorption sites.

[0067] The surface properties of the nanoemulsion particles are adjusted through the optimized compounding of natural emulsifiers such as lecithin (0.1%) and whey protein (0.05%). This adjustment is conducive to interacting with receptors or transport proteins on the surface of intestinal cells, promoting the transmembrane transport of the emulsion particles, and thus enhancing the intestinal absorption rate.

[0068] The nanoemulsion particles can serve as an effective carrier. It can encapsulate target substances (such as nutritional components like fatty acids) inside, forming a structure similar to a "protective shell". In the intestinal environment, this structure can prevent the target substances from being prematurely degraded by enzymes or other substances in the intestine, ensuring that more target substances can reach the absorption sites.

[0069] The construction of the nanoemulsion particles may change the distribution state of the target substances in the intestine, making them more dispersed and uniform, avoiding the aggregation of substances, and thus improving the synergy with the intestinal cell transport mechanism.

[0070] During the construction of the nanoemulsion particles, 0.01% trehalose is added. Trehalose has a special chemical structure and properties. It can form a "glass-like" protective film around the emulsion particles, and this protective film can prevent the aggregation and fusion of the emulsion particles during storage.

[0071] Trehalose can replace the water molecules on the surface of the emulsion particles, reducing the damage of water to the structure of the emulsion particles. In the temperature range of 4 to 50°C, the change in temperature will cause changes in the water state inside and around the emulsion particles. The presence of trehalose can stabilize this state, thereby effectively enhancing the storage stability of the emulsion particles and improving the storage stability.

[0072] The construction of the nanoemulsion particles itself is a process of forming an ordered structure. This ordered structure helps to maintain the uniform distribution of the internal components of the product, reducing the interaction and chemical reaction between the components.

[0073] The nanoemulsions can also limit the contact between oxidants such as oxygen and free fatty acids. The structure of the nanoemulsions can act as a physical barrier to prevent the oxidation of the internal components of the product by external factors (such as oxygen), thereby indirectly affecting the oxidation stability of free fatty acids and contributing to maintaining the overall stability of the product.

[0074] Specifically, 0.1% is the content of lecithin, that is, the ratio of the amount of lecithin added to the amount of skim milk is 1:1000.

[0075] In one embodiment, an ultrasonic generator is provided in the container; in step S2, when the temperature of the skim milk rises to 45°C to 55°C, the pH value is adjusted to 7.0, and the ultrasonic wave of the ultrasonic generator is 20 kHz; and the duration of each ultrasonic wave is 10 seconds, and the time interval between two adjacent ultrasonic waves is 5 seconds; the total duration of the ultrasonic wave is 120 seconds. By using ultrasonic waves of 20 kHz and applying ultrasonic waves intermittently to the skim milk, it can promote the contact between fat globules and enzymes. When the temperature is 45°C to 55°C and the pH value is adjusted to 7.0, the activity of the bacterial community is the highest, which promotes the synthesis of enzymes and improves the decomposition efficiency.

[0076] Specifically, the regulation sequence of the pH value is 6.8 to 7.2 to 6.5 to activate different lipase subtypes (such as LipA has the highest activity at pH 7.2).

[0077] In one embodiment, when the temperature of the skim milk rises to 50°C, the pH value is adjusted to 6.8 and maintained for one hour. At this temperature and pH value, it can enable the mannan oligosaccharide produced by Candida tropicalis to induce self-assembly to form nanoemulsions and improve the formation of nanoemulsions.

[0078] In one embodiment, after step S4 is completed, the skim milk is ultrafiltered for 30 minutes. After ultrafiltration, the separation and recovery of substances such as milk protein can be achieved, and at the same time, the retention rate of milk protein activity is guaranteed to be ≥95%.

[0079] Specifically, 100 kDa TiO 2 Coated ceramic membranes are used for ultrafiltration, and the ultrafiltration pressure is 0.1 to 0.2 MPa to achieve the separation and recovery of substances such as milk protein, and at the same time, the retention rate of milk protein activity is guaranteed to be ≥95%.

[0080] In one embodiment, the ultrafiltered skim milk is heated to 90°C and maintained at 90°C for 3 to 5 minutes. This can mainly effectively inactivate enzymes and microorganisms and ensure the quality of dairy products.

[0081] In one embodiment, the concentration of the citric acid - malic acid complex is 1.2 g to 1.5 g / kg. This content can effectively reduce the surface charge repulsion of fat globules and improve the homogenization efficiency.

[0082] Specifically, Table 2 shows the content (mg / kg) of long-chain triglycerides in raw milk after decomposing raw milk for seven hours at three ratios of Bacillus licheniformis: Streptococcus thermophilus: Aspergillus oryzae spores: Candida tropicalis = 2:1:0.5:0.5; 3:2:1:1; 4:3:1.5:1.5 when the temperature is from 35°C to 55°C and the pH value is adjusted to 7.0.

[0083] Table 2

[0084] 35℃ 40℃ 45℃ 50℃ 55℃ （32℃-55℃） 2:1:0.5:0.5 42±3 58±4 65±5 50±4 38±3 38±5 3:2:1:1 48±3 67±4 78±5 62±4 45±3 45±5 4:3:1.5:1.5 39±3 53±4 60±5 48±4 35±3 35±5

[0085] Note: "35°C" means that the whole process of decomposing skim milk is at 35°C. And "35°C", "40°C", "45°C", "50°C", "55°C" all mean that the whole process of decomposing skim milk is at the corresponding temperature.

[0086] The column of "(32°C - 55°C)" means that by using the method of the present application, the temperature is adjusted to the corresponding temperature at different steps, and this temperature changes with different steps.

[0087] It can be seen from Table 2 above that by using the method of the present application and adjusting the temperature at an appropriate time, the activity of the bacterial community can be fully restored, and the decomposition of long-chain triglycerides in raw milk can be improved.

[0088] Specifically, Table 3 below shows the influence of the pH value range on the decomposition rate of long-chain triglycerides in raw milk by using the method of the present application.

[0089] Table 3 shows the content (mg / kg) of long-chain triglycerides in raw milk after decomposing raw milk by using the method of the present application.

[0090] Table 3

[0091] 6.2 6.5 6.8 7.2 (6.2 to 7.2) 2:1:0.5:0.5 12±1 18±2 22±2 15±1 15±2 3:2:1:1 15±1 22±2 28±3 19±2 18±3 4:3:1.5:1.5 10±1 16±2 20±2 13±1 13±2

[0092] Note: "6.2" means that the whole process of decomposing skim milk has a pH value of 6.2. And "6.5", "6.8", "7.2" all mean that the whole process of decomposing skim milk has the corresponding pH value.

[0093] The column of "(6.2 to 7.2)" means that by using the method of the present application, the pH is adjusted to the corresponding value at different steps, and this pH changes with different steps.

[0094] It can be seen from the data in Table 3 that by using the method of the present application and adjusting the pH to the corresponding value at different steps, which changes with different steps, the bacterial community can reproduce in the most suitable pH environment, and the decomposition effect of raw milk can be improved.

[0095] In one solution, the pasteurization temperature is 75 °C, and the sterilization time is 20 s. The citric acid-malic acid complex is added after the temperature is reduced to 40 to 45 °C. Sterilization can be effectively achieved at this temperature and sterilization time. Adding the citric acid-malic acid complex at 40 to 45 °C can ensure its activity, effectively reduce the surface charge repulsion of fat globules, and improve the homogenization efficiency.

[0096] Specifically, the number of containers is multiple, that is, each container has a corresponding set temperature and pH value, and there is no need for multi-stage temperature adjustment, making full use of the reaction time, thereby improving production efficiency.

[0097] The above are only optional embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, replacements, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing dairy products by enzymatic hydrolysis of milk fat using a composite bacterial flora, characterized in that: The steps include: S1, centrifugally skimming the raw milk and then pasteurizing it, adding a citric acid-malic acid complex, and then homogenizing it by microfluidization to obtain skimmed milk with multiple fat globules; S2, adding the skim milk homogenized by microfluidization in step S1 into a container with a composite bacterial flora, and then adding intermittent ultrasound to the skim milk, wherein the composite bacterial flora is Bacillus licheniformis: Streptococcus thermophilus: Aspergillus oryzae spores: Candida tropicalis = (2-4): (1-3): (0.5-1.5): (0.5-1.5); S3, introducing oxygen into the container to maintain the dissolved oxygen at 15% to 25%; and introducing feed into the container, wherein the feed is glucose:glycerol=2:1; S4. In step S2 and step S3, the skimmed milk is maintained at a predetermined temperature and stirred for a predetermined time.

2. The method for preparing dairy products by enzymatic hydrolysis of milk fat by composite bacterial flora according to claim 1, characterized in that: The predetermined temperature is 32°C to 55°C.

3. The method for preparing dairy products by enzymatic hydrolysis of milk fat by composite flora according to claim 2, characterized in that: In step S2, after the skim milk is added into the container with the composite bacterial flora, the temperature of the skim milk is maintained at 32°C to 35°C for two hours, and then the temperature is raised to 55°C and stirred for five hours.

4. The method for preparing dairy products by enzymatic hydrolysis of milk fat by composite bacterial flora according to claim 3, characterized in that: After the skim milk was heated to 55° C. and stirred for five hours, the temperature was lowered to 45° C., 0.1% lecithin, 0.05% whey protein and 0.01% trehalose were added to the skim milk, and stirred at 200 rpm for 2 hours.

5. The method for preparing dairy products by enzymatic hydrolysis of milk fat by composite bacterial flora according to claim 1, characterized in that: An ultrasonic generator is provided in the container; in step S2, when the temperature of the skimmed milk rises to 45°C to 55°C, the pH value is adjusted to 7.0, and the ultrasonic wave of the ultrasonic generator is 20kHz; and each ultrasonic wave lasts for 10 seconds, and the time interval between two adjacent ultrasonic waves is 5 seconds; the total ultrasonic wave lasts for 120 seconds.

6. The method for preparing dairy products by enzymatic hydrolysis of milk fat by composite bacterial flora according to claim 5, characterized in that: When the temperature of the skim milk rises to 50°C, the pH value is adjusted to 6.8 and maintained for one hour.

7. The method for preparing dairy products by enzymatic hydrolysis of milk fat by composite bacterial flora according to claim 6, characterized in that: After step S4 is performed, the skimmed milk is subjected to ultrafiltration for thirty minutes.

8. The method for preparing dairy products by enzymatic hydrolysis of milk fat by composite bacterial flora according to claim 7, characterized in that: The skim milk after the ultrafiltration treatment is heated to 90° C. and maintained at 90° C. for 3 to 5 minutes.

9. The method for preparing dairy products by enzymatic hydrolysis of milk fat by composite bacterial flora according to claim 1, characterized in that: The concentration of the citric acid-malic acid complex is 1.2 g to 1.5 g / kg.

10. The method for preparing dairy products by enzymatic hydrolysis of milk fat by composite bacterial flora according to claim 9, characterized in that: The pasteurization temperature is 75° C., and the pasteurization time is 20 seconds. The citric acid-malic acid complex is added after the temperature drops to 40 to 45° C.

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