CN115989829A - Milk and preparation method thereof - Google Patents
Milk and preparation method thereof Download PDFInfo
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- CN115989829A CN115989829A CN202111221918.5A CN202111221918A CN115989829A CN 115989829 A CN115989829 A CN 115989829A CN 202111221918 A CN202111221918 A CN 202111221918A CN 115989829 A CN115989829 A CN 115989829A
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- Dairy Products (AREA)
Abstract
The invention relates to the field of foods, in particular to milk and a preparation method thereof. The milk preparation method comprises centrifuging and sterilizing raw milk; immersing sterilized milk into steam for sterilization, and carrying out flash evaporation treatment on the sterilized milk; the method further comprises the step of carrying out passivation enzyme treatment on the sterilized milk before carrying out steam immersion sterilization on the sterilized milk; the method further comprises the step of carrying out passivation enzyme treatment on the sterilized milk before filling. The method can sufficiently deactivate and inactivate enzymes remained in milk, basically does not renaturate, avoids protein and fat decomposition in the milk after being placed for a long time at normal temperature, avoids the bad conditions of bitter taste, jellied bean curd shape, caking and the like of dairy products, and remarkably improves the quality guarantee period of the milk.
Description
Technical Field
The invention relates to the field of foods, in particular to milk and a preparation method thereof.
Background
Most of the dairy products, especially sterilized dairy products, which are commercially available at present, have been sterilized by the production and processing technology. The product prepared by the traditional pasteurized milk process has light taste, insufficient flavor and short shelf life (24 hours to 7 days) in the drinking process, and can not meet the requirements of the market for the consumption of pasteurized fresh milk products.
Thus, there is a need for an improved method of preparing milk.
Disclosure of Invention
The present inventors have found that enzymes mainly composed of proteolytic enzymes and lipolytic enzymes are produced in cow milk by the proliferation of microorganisms. The conventional milk preparation method is subjected to heat treatment, but after the milk is stored at normal temperature (for example, about 15 days), the milk product is still subjected to the defects of bitter taste, jellied bean curd, caking and the like caused by the renaturation of enzymes such as protease, lipase and the like and the decomposition of proteins and fats in the milk.
To this end, the present invention provides a milk production method that can solve at least one of the above problems.
A method of preparing milk comprising: providing raw milk; centrifugally sterilizing the raw milk to obtain sterilized milk; immersing the sterilized milk into steam for sterilization to obtain sterilized milk; the steam immersion sterilization is carried out for 0.09-2 seconds at the temperature of 131-157 ℃; carrying out flash evaporation treatment on the sterilized cow milk to obtain flash-evaporated milk; before steam immersion sterilization is carried out on the sterilized milk, the method further comprises the step of carrying out passivation enzyme treatment on the sterilized milk, wherein the passivation enzyme treatment temperature is 45-70 ℃ and the passivation enzyme treatment time is 45-65min; and/or, before filling, the method further comprises the step of carrying out passivating enzyme treatment on the milk subjected to flash evaporation treatment, wherein the passivating enzyme treatment is carried out at the temperature of 45-65 ℃ for 45-65min.
The inventor surprisingly found that the raw milk can be fully passivated and deactivated by centrifugal sterilization, milk steam immersion sterilization and flash evaporation treatment and further combined with passivation enzyme treatment, so that the residual enzymes in the milk are not renatured basically, protein and fat in the milk are prevented from being decomposed after the milk is placed for a long time at normal temperature, the defects of bitter taste, jellied bean curd shape, caking and the like of the dairy products are avoided, and the shelf life and quality of the milk are remarkably improved.
In some embodiments, the steps of inactivating the enzyme are included before steam-submerged sterilization of the sterilized milk and before filling (i.e., having been flash-treated). Thus, the enzyme in the milk can be passivated more fully, and the quality guarantee period and quality of the milk are improved better.
In some embodiments, the passivating enzyme treatment is performed after sterilization at a temperature of 50-60 ℃ for a time of 50-60 minutes.
In some embodiments, the passivating enzyme treatment is performed at a temperature of 50-65℃for a period of 60-65 minutes prior to filling (i.e., having been flash-treated).
In some embodiments, the milk produced by the method of the present invention may have a lactoferrin retention of 90-100%, an immunoglobulin retention of 90-100%, an alpha-lactalbumin retention of 95-100%, and a beta-lactoglobulin retention of 95-100%, which is significantly higher than milk that has not been treated by the above methods, particularly by inactivating enzymes.
In some embodiments, the temperature of the centrifugal sterilization process is 45-65 ℃ and the rotation speed is 4500-7500rpm; optionally, the temperature of the centrifugal sterilization treatment is 50-60 ℃ and the rotating speed is 5000-6500rpm.
In the embodiment of the invention, the raw milk is subjected to centrifugal sterilization treatment at least once.
The research shows that the sterilization rate can reach 90.0-99.9% after the primary centrifugal sterilization treatment. The total number of bacterial colonies in the obtained milk is less than or equal to 1500cfu/ml, the number of spores is less than 100/ml, and the number of heat-resistant spores is less than 10/ml.
In the embodiment of the invention, the raw milk is subjected to at least two times of centrifugal sterilization treatment.
The research shows that the sterilization rate can reach 99.9-99.99% when the secondary centrifugal sterilization treatment is carried out. The total number of bacterial colonies in the obtained milk is less than or equal to 150cfu/ml, the number of spores is less than 100/ml, and the number of heat-resistant spores is less than 10/ml.
In embodiments of the invention, the parameters of the first and second centrifugal sterilization processes are the same or different.
In the embodiment of the invention, the raw milk is subjected to centrifugal sterilization treatment and partial enzymes can be removed.
In an embodiment of the invention, steam immersion sterilization: means that the clean steam (131-157 ℃) is immersed into the milk in a closed container for a very short time (0.09 s-2 s) or the milk is sterilized by the clean steam (131-157 ℃) within a very short time (0.09 s-2 s).
In some embodiments, the flash evaporation treatment means that the sterilized feed liquid is sent into a degassing system through a vacuum pump, and redundant water, oxygen, carbon dioxide, nitrogen and other gases in the milk are removed under the vacuum condition.
In some embodiments, the vacuum level at the flash treatment is from-0.06 MPa to-0.09 MPa, optionally-0.07.+ -. 0.005MPa.
In some embodiments, the temperature at the flash treatment is 65-75deg.C, optionally 65-72deg.C.
In some embodiments, an RO membrane concentration step is also included prior to steam immersion sterilization, preferably at a pressure of 30-35bar. The raw milk is passed through RO membranes having a pore size of 0.01 μm or less, for example, 0.001 to 0.01 μm, specifically, for example, 0.001 μm, 0.002 μm, 0.003 μm, 0.004 μm, 0.005 μm, 0.006 μm, 0.007 μm, 0.008 μm, 0.009 μm, 0.01 μm. Filtering off part of water by using 30-35bar pressure, and concentrating milk protein to a certain index, wherein the protein content is 3.0-6.0%.
In some embodiments, a normalization step is also included after the RO membrane concentration step and before steam immersion sterilization. The reasonable adjustment of the milk fat component of the cow and the proper adjustment of the water content in the cow milk under the condition limited by regulations can be realized through standardization; thereby increasing the total solid content and the content of fat and protein in the cow milk.
In some embodiments, a pre-heating step is also included prior to steam-submerged sterilization, typically to 50-72 ℃, optionally 60-65 ℃. The solid crystal phase of the cow milk fat in a low-temperature environment can be converted into a liquid state through preheating, preparation is made for subsequent homogenization, and meanwhile, microbial spores and heat-resistant spores contained in the cow milk can be activated, so that the cow milk fat is converted into thermolabile common microbial nutrient bodies, and the sterilization efficiency is improved.
In some embodiments, preheating occurs after concentration of the RO membrane and prior to steam immersion sterilization.
In some embodiments, the step of homogenizing is further included after steam-submerged sterilization. The pressure of the homogenization treatment is generally 160-220bar. Fat globules contained in cow milk can be crushed to 1-2 microns by homogenization, so that fat floating is prevented.
In some embodiments, the homogenizing is performed at a temperature of no more than 70 ℃ (e.g., no more than 65 ℃).
In some embodiments, the method further comprises the step of cooling the steam after the steam-submerged sterilization. The temperature is generally reduced to 45-65 ℃, and the enzyme can be passivated by keeping the temperature for 30-90 min.
In an embodiment of the present invention, the method further includes a filling step.
In the embodiment of the invention, the raw milk meets the milk production requirement.
In the embodiment of the invention, the raw milk is fresh milk, and is subjected to acceptance and milk purification treatment.
In the embodiment of the invention, healthy dairy cows on a large-scale pasture cultivation base are selected, and fresh milk is extracted from the breasts of the healthy dairy cows by mechanical milk extracting equipment.
In the embodiment of the invention, the fresh milk refers to natural mammary secretion extruded from normal breasts of healthy cows, and can be called as raw milk/milk or raw milk after being cooled, possibly filtered, but without sterilization, heating and milk purification, especially without pasteurization and without blending milk fat such as milk powder or cream.
In the embodiment of the invention, the acceptance comprises the steps of inspecting protein, fat, non-fat milk solids, density and acidity contained in raw and fresh milk, wherein the acceptance standard meets the national food safety standard of GB19301, and the qualified fresh milk is subjected to cold chain storage at the temperature of 2-4 ℃.
In the embodiment of the invention, the milk cleaning can adopt the prior art. For example, the method comprises passing cow milk through 100-120 mesh filter screen, removing dust, etc., purifying cow milk by centrifuge, controlling temperature to 4-8deg.C, centrifuging at 4000-7000rpm, and removing non-milk cell, etc.
In the embodiment of the invention, a centrifugal milk purifying technology is adopted; preferably, the rotation speed is 4500-5000rpm, and the treatment speed is 20-25 tons raw milk/hr. The industrial production is usually completed by adopting a centrifugal milk purifier, and slag is generally discharged once every 10-30 minutes, and the slag is discharged for 30-40kg of milk per time.
In the embodiment of the invention, the raw milk is subjected to standardization treatment, and the prior art can be adopted.
In some embodiments, the raw milk is prepared as follows:
1) The raw fresh cow milk is selected from: selecting healthy dairy cows on a large-scale pasture cultivation base, and squeezing fresh milk from the breasts of the healthy dairy cows by using mechanized milk squeezing equipment;
2) And (5) checking and accepting: checking protein, fat, non-fat milk solids, density and acidity contained in raw and fresh milk, wherein the checking and accepting standard accords with the GB19301 food safety national standard, and the qualified fresh milk is subjected to cold chain storage at 2-4 ℃;
3) Milk cleaning: sieving cow milk with 100-120 mesh sieve, removing dust, purifying with centrifuge at 4-8deg.C, and centrifuging at 4000-7000rpm to remove non-milk cell.
In some embodiments, a milk preparation method includes:
1) And (3) centrifugal sterilization:
performing centrifugal sterilization treatment on raw milk twice to obtain sterilized milk; the temperature of the centrifugal sterilization treatment is 45-65 ℃ and the rotating speed is 4500-7500rpm;
inactivating enzymes: maintaining the sterilized milk at 45-70deg.C for 45-65min;
2) Concentrating by RO membrane: filtering the raw milk by RO membrane with aperture less than or equal to 0.01 μm under 30-35bar pressure to remove part of water, concentrating to protein content of 3.0-6.0%;
3) Preheating: heating the material concentrated by the RO membrane for preheating treatment;
4) Sterilizing: steam immersing sterilization is carried out on the preheated material, the temperature is 131-157 ℃, and the sterilization is carried out for 0.09-2 seconds;
5) Flash evaporation: the sterilized feed liquid enters a degassing system through a vacuum pump, and the concentration of components in cow milk is realized under the condition of the vacuum degree of-0.06 MPa to-0.09 MPa at the temperature of 65-75 ℃; so that the redundant water in the milk and the gases such as oxygen, carbon dioxide, nitrogen and the like can be removed;
6) Homogenizing: homogenizing the milk subjected to flash evaporation treatment at 160-220bar pressure;
7) And (3) cooling and storing: cooling the homogenized material to 45-65deg.C, and maintaining for 45-65min;
8) And (5) filling.
The invention also provides milk prepared by the method.
In the embodiment of the invention, the prepared milk is preserved below normal temperature, and the shelf life can reach 180 days.
Detailed Description
The following examples are illustrative of the invention and are not intended to limit the scope of the invention.
The raw milk used below is specifically as follows: healthy dairy cows on a large-scale pasture cultivation base are selected, and fresh milk is extracted from the breasts of the healthy dairy cows by mechanical milk extracting equipment. The protein, fat, non-fat milk solids, density and acidity contained in raw and fresh milk are checked, the checking and accepting standard accords with the national food safety standard GB19301, and the qualified fresh milk is stored in a cold chain at the temperature of 2 ℃. Passing the qualified milk through a filter, filtering with a 100-120 mesh filter screen, removing dust and other impurities in the milk, purifying the milk by a centrifuge, controlling the temperature to be 2 ℃, centrifuging at 4000rpm, and removing non-milk cells and other impurities in the milk. And (5) performing standardized treatment after purifying the milk to obtain raw milk.
The raw milk used below was the same batch.
Example 1
The embodiment provides milk, which is prepared by the following steps:
1) And (3) centrifugal sterilization:
performing centrifugal sterilization treatment on raw milk twice to obtain sterilized milk; the temperature of the centrifugal sterilization treatment is 45 ℃ and the rotating speed is 4500rpm;
inactivating enzymes: maintaining the sterilized milk at 45deg.C for 60min;
2) Concentrating by RO membrane: passing raw milk through RO membrane (pore size of 0.001 μm), filtering off part of water under 30bar pressure, concentrating to protein content of 3.0%;
3) Preheating: heating the concentrated material of the RO membrane to 50 ℃ for preheating treatment;
4) Sterilizing: steam immersing sterilization is carried out on the preheated material, the temperature is 157 ℃, and the sterilization is carried out for 0.09 seconds;
5) Flash evaporation: the sterilized feed liquid enters a degassing system through a vacuum pump, and the concentration of components in the cow milk is realized under the condition of the vacuum degree of-0.06 MPa at the temperature of 65 ℃; removing redundant water and gases such as oxygen, carbon dioxide, nitrogen and the like in the milk;
6) Homogenizing: homogenizing the milk subjected to flash evaporation treatment at 65 ℃ under 160bar pressure;
7) And (3) cooling and storing: cooling the homogenized material to 45 ℃, and keeping for 60min;
8) And (5) filling to obtain the milk.
Example 2
The embodiment provides milk, which is prepared by the following steps:
1) And (3) centrifugal sterilization:
performing centrifugal sterilization treatment on raw milk twice to obtain sterilized milk; the temperature of the centrifugal sterilization treatment is 50 ℃ and the rotating speed is 5000rpm;
inactivating enzymes: maintaining the sterilized milk at 50deg.C for 60min;
2) Concentrating by RO membrane: passing raw milk through RO membrane (pore size of 0.005 μm), filtering off part of water under 31bar pressure, concentrating to protein content of 3.5%;
3) Preheating: heating the concentrated material of the RO membrane to 60 ℃ for preheating treatment;
4) Sterilizing: steam immersing sterilization is carried out on the preheated material, the temperature is 150 ℃, and the sterilization is carried out for 0.25 seconds;
5) Flash evaporation: the sterilized feed liquid enters a degassing system through a vacuum pump, and the concentration of components in the cow milk is realized under the condition of the vacuum degree of-0.07 MPa at 68 ℃; removing redundant water and gases such as oxygen, carbon dioxide, nitrogen and the like in the milk;
6) Homogenizing: homogenizing the milk subjected to flash evaporation treatment at 68 ℃ by adopting 170 bar;
7) And (3) cooling and storing: cooling the homogenized material to 50deg.C, and maintaining for 60min;
8) And (5) filling to obtain the milk.
Example 3
The embodiment provides milk, which is prepared by the following steps:
1) And (3) centrifugal sterilization:
performing centrifugal sterilization treatment on raw milk twice to obtain sterilized milk; the temperature of the centrifugal sterilization treatment is 55 ℃ and the rotating speed is 5500rpm;
inactivating enzymes: maintaining the sterilized milk at 55deg.C for 60min;
2) Concentrating by RO membrane: passing raw milk through RO membrane (pore size of 0.006 μm), filtering off part of water under 32bar pressure, concentrating to protein content of 4.0%;
3) Preheating: heating the concentrated material of the RO membrane to 65 ℃ for preheating treatment;
4) Sterilizing: steam immersing sterilization is carried out on the preheated material, the temperature is 148 ℃, and the sterilization is carried out for 0.5 seconds;
5) Flash evaporation: the sterilized feed liquid enters a degassing system through a vacuum pump, and the concentration of components in the cow milk is realized under the condition of the vacuum degree of-0.075 MPa at 69 ℃; removing redundant water and gases such as oxygen, carbon dioxide, nitrogen and the like in the milk;
6) Homogenizing: homogenizing the flash-evaporated milk at 69 ℃ by 180 bar;
7) And (3) cooling and storing: cooling the homogenized material to 60 ℃, and keeping for 60min;
8) And (5) filling to obtain the milk.
Example 4
The embodiment provides milk, which is prepared by the following steps:
1) And (3) centrifugal sterilization:
performing centrifugal sterilization treatment on raw milk twice to obtain sterilized milk; the temperature of the centrifugal sterilization treatment is 60 ℃ and the rotating speed is 6500rpm;
inactivating enzymes: maintaining the sterilized milk at 60deg.C for 60min;
2) Concentrating by RO membrane: passing raw milk through RO membrane (pore size of 0.007 μm), filtering off part of the water under 33bar pressure, concentrating to protein content of 4.5%;
3) Preheating: heating the concentrated material of the RO membrane to 70 ℃ for preheating treatment;
4) Sterilizing: steam immersing sterilization is carried out on the preheated material, the temperature is 137 ℃, and the sterilization is carried out for 0.12 seconds;
5) Flash evaporation: the sterilized feed liquid enters a degassing system through a vacuum pump, and the concentration of components in the cow milk is realized under the condition of the vacuum degree of-0.076 MPa at the temperature of 70 ℃; removing redundant water and gases such as oxygen, carbon dioxide, nitrogen and the like in the milk;
6) Homogenizing: homogenizing the flash-evaporated milk at 70deg.C by 200 bar;
7) And (3) cooling and storing: cooling the homogenized material to 63 ℃, and keeping for 60min;
8) And (5) filling to obtain the milk.
Example 5
The embodiment provides milk, which is prepared by the following steps:
1) And (3) centrifugal sterilization:
performing centrifugal sterilization treatment on raw milk twice to obtain sterilized milk; the temperature of the centrifugal sterilization treatment is 65 ℃ and the rotating speed is 7000rpm;
inactivating enzymes: maintaining the sterilized milk at 65deg.C for 60min;
2) Concentrating by RO membrane: passing raw milk through RO membrane (pore size of 0.008 μm), filtering off part of water under 34bar pressure, concentrating to protein content of 5.0%;
3) Preheating: heating the concentrated material of the RO membrane to 71 ℃ for preheating treatment;
4) Sterilizing: steam immersing sterilization is carried out on the preheated material, the temperature is 144 ℃, and the sterilization is carried out for 1 second;
5) Flash evaporation: the sterilized feed liquid enters a degassing system through a vacuum pump, and the concentration of components in the cow milk is realized under the condition of the vacuum degree of-0.078 MPa at the temperature of 71 ℃; removing redundant water and gases such as oxygen, carbon dioxide, nitrogen and the like in the milk;
6) Homogenizing: homogenizing the flash-evaporated milk at 71 ℃ by 220 bar;
7) And (3) cooling and storing: cooling the homogenized material to 64 ℃, and keeping for 60min;
8) And (5) filling to obtain the milk.
Example 6
The embodiment provides milk, which is prepared by the following steps:
1) And (3) centrifugal sterilization:
performing centrifugal sterilization treatment on raw milk twice to obtain sterilized milk; the temperature of the centrifugal sterilization treatment is 65 ℃ and the rotating speed is 7500rpm;
inactivating enzymes: maintaining the sterilized milk at 70deg.C for 60min;
2) Concentrating by RO membrane: passing raw milk through RO membrane (pore size of 0.009 μm), filtering off part of the water under 35bar pressure, concentrating to protein content of 6.0%;
3) Preheating: heating the concentrated material of the RO membrane to 72 ℃ for preheating treatment;
4) Sterilizing: steam immersing sterilization is carried out on the preheated material, the temperature is 132 ℃, and the sterilization is carried out for 2 seconds;
5) Flash evaporation: the sterilized feed liquid enters a degassing system through a vacuum pump, and the concentration of components in the cow milk is realized under the condition of the vacuum degree of-0.08 MPa at the temperature of 72 ℃. Removing redundant water and gases such as oxygen, carbon dioxide, nitrogen and the like in the milk;
6) Homogenizing: homogenizing the flash-treated milk at 72 ℃ by adopting 250 bar;
7) And (3) cooling and storing: cooling the homogenized material to 65 ℃, and keeping for 60min;
8) And (5) filling to obtain the milk.
The final product obtained in the above example was tested as follows:
the results show that the milk prepared by the method of the embodiment has fresh, fragrant and thick taste, the quality of the milk reaches the commercial sterile level, and the product has the nutrition characteristics of fresh milk and the extremely low food safety risk of the sterilized milk product. The product meets the new national standard of superior quality fresh cow milk, and has commercial sterility level under the condition of having the nutrition grade of fresh cow milk product.
Comparative example 1
The comparative example provides a milk, which is prepared as follows:
1) Concentrating by RO membrane: separating partial water from raw milk by a concentrating device, and concentrating until the protein content is 3.0%;
2) Preheating: heating the concentrated milk to 55-65deg.C;
3) And (3) degassing: the preheated feed liquid enters a degassing system through a vacuum pump, and redundant water, oxygen, carbon dioxide, nitrogen and other gases in the milk are removed;
4) Homogenizing: mixing the sterilized cream with part or all of skimmed milk, homogenizing with 250 bar.
5) And (3) sterilization: sterilizing the degassed milk at 136-139 deg.C for 4-6 s;
6) And (5) storing: heat exchanging and cooling the cow milk after heat preservation and sterilization to be less than 7 ℃ through a heat exchanger, and storing the cow milk in an aseptic tank or not;
7) And (5) filling: and (3) cooling the feed liquid to be less than or equal to 25 ℃, filling the milk by a filling machine, and sealing the milk in the sterilized container to obtain the milk.
The final product obtained by this comparative example was tested as follows:
comparative example 2
This comparative example provides a milk which differs from example 1 only in that: the RO concentration process is changed into a heat treatment flash evaporation process, the flash evaporation temperature is 65-72 ℃, and the vacuum degree is-0.072 MPa.
The final product obtained by this comparative example was tested as follows:
comparative example 3
The comparative example provides a milk, the preparation method is as follows:
1) And (3) centrifugal sterilization:
performing centrifugal sterilization treatment on raw milk twice to obtain sterilized milk; the temperature of the centrifugal sterilization treatment is 65 ℃ and the rotating speed is 7500rpm;
2) And (3) milk fat separation: homogenizing at 65deg.C with a milk fat separator under 200bar pressure, separating fat from milk, and pasteurizing at 85deg.C for 15 s;
3) And (3) standardization: after pasteurization, the milk fat of the cow was adjusted to 3.1% and the protein to 3.0%;
4) (UF) membrane concentration: concentrating raw milk through UF membrane to obtain concentrated milk with protein content of 4.5% and fat content of 4.5%;
5) Temporary storage: the storage time is less than or equal to 12 hours at the temperature less than or equal to 7 ℃;
6) Sterilizing: steam immersing sterilization is carried out on the preheated material, the temperature is 154 ℃, and the sterilization is carried out for 0.25 seconds;
7) Flash evaporation: the sterilized feed liquid enters a degassing system through a vacuum pump, and the concentration of components in cow milk is realized by adopting the pressure of-0.07 MPa at the temperature of 74 ℃. Removing redundant water and gases such as oxygen, carbon dioxide, nitrogen and the like in the milk;
8) Homogenizing: homogenizing the flash-treated milk at 72 ℃ by adopting 250 bar;
9) And (3) cooling and storing: cooling the homogenized material to 25 ℃,
10 And (3) filling to obtain the milk.
Experimental example 1
The milk products prepared in examples 1-6 and comparative examples 1-3 above were evaluated, and specific scoring criteria are shown in the following table.
| Project | Scoring criteria | Full score |
| Frankincense | A score of 0-10 indicates that the attribute strength is extremely poor to excellent | 10 |
| Sweet feel | A score of 0-10 indicates that the attribute strength is extremely poor to excellent | 10 |
| Surface whiteness | A score of 0-10 indicates that the attribute strength is extremely poor to excellent | 10 |
| Burnt incense | A score of 0-10 indicates that the attribute strength is extremely poor to excellent | 10 |
| Cooking flavor | A score of 0-10 indicates that the attribute strength is extremely poor to excellent | 10 |
| Consistency in mouth | A score of 0-10 indicates that the attribute strength is extremely poor to excellent | 10 |
| Fat feel | A score of 0-10 indicates that the attribute strength is extremely poor to excellent | 10 |
| Flavor residue | A score of 0-10 indicates that the attribute strength is extremely poor to excellent | 10 |
| Comprehensive score | A score of 0-10 indicates that the attribute strength is extremely poor to excellent | 10 |
The evaluation results after standing at normal temperature for 0 days are as follows:
the evaluation results after 30 days of normal temperature standing are as follows:
the results show that the cow milk product produced by the method has stronger forward significance difference compared with cow milk products produced by conventional and other process technologies, wherein the milk flavor, sweet feeling and burnt flavor are core forward indexes.
Experimental example 2
Taking raw milk, and performing centrifugal sterilization twice at 45 ℃ and a rotating speed of 4500 rpm.
Then, passivating enzyme treatment is carried out at different temperatures, and the result is as follows:
the result shows that the active ingredients in the milk can be better preserved by adopting an enzyme deactivation (passivation) process at 55-60 ℃ for 3600 s.
Experimental example 3
Raw milk is treated according to the following table parameters respectively, and the detection results are as follows:
comparison of differently treated milk
The result shows that the detection result of the active protein of the comparative example related to the sterilized milk can show that the retention rate of the active protein is remarkably increased compared with the product of the traditional process in the product adopting the low-temperature enzyme deactivation and steam direct sterilization process, and the retention rate is stable and uniform.
While the invention has been described in detail in the general context and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that modifications and improvements can be made thereto. Accordingly, such modifications or improvements may be made without departing from the spirit of the invention and are intended to be within the scope of the invention as claimed.
Claims (10)
1. A method of preparing milk comprising:
providing raw milk;
centrifugally sterilizing the raw milk to obtain sterilized milk;
immersing the sterilized milk into steam for sterilization to obtain sterilized milk; the steam immersion sterilization is carried out for 0.09-2 seconds at the temperature of 131-157 ℃; and
carrying out flash evaporation treatment on the sterilized cow milk to obtain flash-evaporated milk;
before steam immersion sterilization is carried out on the sterilized milk, the method further comprises the step of carrying out passivation enzyme treatment on the sterilized milk, wherein the passivation enzyme treatment temperature is 45-70 ℃ and the passivation enzyme treatment time is 45-65min; and/or the number of the groups of groups,
the method also comprises the step of carrying out passivating enzyme treatment on the milk subjected to flash evaporation treatment, wherein the passivating enzyme treatment is carried out at the temperature of 45-65 ℃ for 45-65min.
2. A method of preparing milk according to claim 1, characterized in that the step of inactivating enzyme is included before steam-submerged sterilization of the sterilized milk and before filling.
3. A milk preparation method according to claim 1 or 2, characterized in that the passivating enzyme treatment performed after sterilization is performed at a temperature of 50-60 ℃ for a time of 50-60min; and/or the number of the groups of groups,
the temperature of the enzyme passivation treatment is 50-65 ℃ and the time is 60-65min before filling.
4. A milk preparation method according to any one of claims 1-3, wherein the temperature of the centrifugal sterilization treatment is 45-65 ℃ and the rotation speed is 4500-7500rpm; optionally, the temperature of the centrifugal sterilization treatment is 50-60 ℃ and the rotating speed is 5000-6500rpm.
5. A milk preparation method according to any one of claims 1-4, wherein the raw milk is subjected to at least one centrifugal sterilization treatment; preferably, the raw milk is subjected to at least a secondary centrifugal sterilization treatment.
6. A method of preparing milk according to any one of claims 1 to 5, further comprising an RO membrane concentration step prior to steam immersion sterilization; preferably, the pore diameter of the RO membrane is less than or equal to 0.01 mu m; preferably, the pressure at the concentration of the RO membrane is 30-35bar.
7. A method of preparing milk according to any one of claims 1 to 6, further comprising the step of preheating to 50-72 ℃ prior to steam-submerged sterilization; optionally preheating to 60-65deg.C.
8. A milk preparation method according to any one of claims 1-7, further comprising a step of homogenizing after steam-submerged sterilization; alternatively, the pressure of the homogenisation treatment is between 160 and 220bar.
9. A milk preparation method according to any one of claims 1 to 8, comprising:
1) And (3) centrifugal sterilization:
performing centrifugal sterilization treatment on raw milk twice to obtain sterilized milk; the temperature of the centrifugal sterilization treatment is 45-65 ℃ and the rotating speed is 4500-7500rpm;
inactivating enzymes: maintaining the sterilized milk at 45-70deg.C for 45-65min;
2) Concentrating by RO membrane: filtering the raw milk by RO membrane with aperture less than or equal to 0.01 μm under 30-35bar pressure to remove part of water, concentrating to protein content of 3.0-6.0%;
3) Preheating: heating the material concentrated by the RO membrane for preheating treatment;
4) Sterilizing: steam immersing sterilization is carried out on the preheated material, the temperature is 131-157 ℃, and the sterilization is carried out for 0.09-2 seconds;
5) Flash evaporation: the sterilized feed liquid enters a degassing system through a vacuum pump, and the concentration of components in cow milk is realized under the condition of the vacuum degree of-0.06 MPa to-0.09 MPa at the temperature of 65-75 ℃;
6) Homogenizing: homogenizing the milk subjected to flash evaporation treatment at 160-220bar pressure;
7) And (3) cooling and storing: cooling the homogenized material to 45-65deg.C, and maintaining for 45-65min;
8) And (5) filling.
10. Milk, characterized in that it is prepared by the method according to any one of claims 1 to 9.
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