CN114557383A - Milk sterilization method with low protein denaturation rate - Google Patents
Milk sterilization method with low protein denaturation rate Download PDFInfo
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- 102000004169 proteins and genes Human genes 0.000 title claims abstract description 30
- 238000004925 denaturation Methods 0.000 title claims abstract description 23
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- 238000009928 pasteurization Methods 0.000 abstract description 15
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- CSSYQJWUGATIHM-IKGCZBKSSA-N l-phenylalanyl-l-lysyl-l-cysteinyl-l-arginyl-l-arginyl-l-tryptophyl-l-glutaminyl-l-tryptophyl-l-arginyl-l-methionyl-l-lysyl-l-lysyl-l-leucylglycyl-l-alanyl-l-prolyl-l-seryl-l-isoleucyl-l-threonyl-l-cysteinyl-l-valyl-l-arginyl-l-arginyl-l-alanyl-l-phenylal Chemical compound C([C@H](N)C(=O)N[C@@H](CCCCN)C(=O)N[C@@H](CS)C(=O)N[C@@H](CCCNC(N)=N)C(=O)N[C@@H](CCCNC(N)=N)C(=O)N[C@@H](CC=1C2=CC=CC=C2NC=1)C(=O)N[C@@H](CCC(N)=O)C(=O)N[C@@H](CC=1C2=CC=CC=C2NC=1)C(=O)N[C@@H](CCCNC(N)=N)C(=O)N[C@@H](CCSC)C(=O)N[C@@H](CCCCN)C(=O)N[C@@H](CCCCN)C(=O)N[C@@H](CC(C)C)C(=O)NCC(=O)N[C@@H](C)C(=O)N1CCC[C@H]1C(=O)N[C@@H](CO)C(=O)N[C@@H]([C@@H](C)CC)C(=O)N[C@@H]([C@@H](C)O)C(=O)N[C@@H](CS)C(=O)N[C@@H](C(C)C)C(=O)N[C@@H](CCCNC(N)=N)C(=O)N[C@@H](CCCNC(N)=N)C(=O)N[C@@H](C)C(=O)N[C@@H](CC=1C=CC=CC=1)C(O)=O)C1=CC=CC=C1 CSSYQJWUGATIHM-IKGCZBKSSA-N 0.000 description 5
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- 239000004472 Lysine Substances 0.000 description 3
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Classifications
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23C—DAIRY PRODUCTS, e.g. MILK, BUTTER OR CHEESE; MILK OR CHEESE SUBSTITUTES; MAKING THEREOF
- A23C3/00—Preservation of milk or milk preparations
- A23C3/02—Preservation of milk or milk preparations by heating
- A23C3/03—Preservation of milk or milk preparations by heating the materials being loose unpacked
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23C—DAIRY PRODUCTS, e.g. MILK, BUTTER OR CHEESE; MILK OR CHEESE SUBSTITUTES; MAKING THEREOF
- A23C9/00—Milk preparations; Milk powder or milk powder preparations
- A23C9/152—Milk preparations; Milk powder or milk powder preparations containing additives
- A23C9/1526—Amino acids; Peptides; Protein hydrolysates; Nucleic acids; Derivatives thereof
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- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
- Polymers & Plastics (AREA)
- Health & Medical Sciences (AREA)
- Biochemistry (AREA)
- Molecular Biology (AREA)
- Proteomics, Peptides & Aminoacids (AREA)
- Dairy Products (AREA)
Abstract
The invention relates to the technical field of dairy processing, and discloses a milk sterilization method with low protein denaturation rate, which comprises the following steps: pre-sterilizing milk at 62-68 ℃ for 15-20 s; detecting the pre-sterilized milk, and if the detection result does not reach the index, standardizing until the index is reached; preheating milk reaching the index to 60-65 ℃; carrying out flash evaporation sterilization on the preheated milk, controlling the temperature of an inlet heat source to be 70-85 ℃, the vacuum degree to be-0.6-0.8 MPa, the central temperature of the milk to be not more than 65 ℃, and carrying out flash evaporation sterilization for 10-15 s; and cooling the secondarily sterilized milk. The invention carries out pre-sterilization and standardization before secondary sterilization, combines flash evaporation sterilization and pasteurization during secondary sterilization, can reduce the denaturation of protein and the generation of furosine during the sterilization process while ensuring the sterilization effect, and improves the milk quality.
Description
Technical Field
The invention relates to the technical field of dairy processing, in particular to a milk sterilization method with low protein denaturation rate.
Background
Pasteurization, also known as pasteurization, is a low-temperature sterilization method invented by microbiology pasteur, and can better keep nutrients in food from being destroyed while killing germs due to relatively low sterilization temperature. The classical pasteurization process is to keep the temperature at 60-65 ℃ for 30min, and is widely applied to industries such as beer and the like; the other pasteurization method is to keep the temperature at 85-90 ℃ for 15-16 s, and is widely applied to the food industry.
In the existing pasteurized fresh milk production process, the pasteurization mode is generally selected to be 80-85 ℃ for 15-25 s, and the method belongs to pasteurization at a higher temperature. The selected sterilization temperature is higher and the time is longer, so that the sterilization efficiency can be better ensured, the sterilization rate of the pasteurized fresh milk is 100 percent qualified, but at the same time, the higher sterilization temperature is easy to destroy nutrient substances in the milk, the rapid loss of nutrient components such as peroxidase and lactoferrin in the milk is directly caused, and in addition, the Maillard reaction between lysine in protein and lactose is caused to generate the furfuryl amino acid. Taking lactoferrin as an example, almost complete loss is achieved after UHT sterilization, the bar killing loss rate at 85 ℃ is more than nine times, and the bar killing loss rate at 79 ℃ is reduced to about eight times. Therefore, how to accurately adjust and control the pasteurization temperature and time has important significance for improving the quality of pasteurized milk.
In the prior art, a method of precisely controlling heating time or temperature is often adopted to reduce the influence of sterilization on milk quality (nutrient substances, content of furosine, and the like) and ensure sterilization effect, for example, patent No. CN201710382008.2 improves sterilization effect by precisely controlling holding time of pasteurization, and provides a part of a reliable quality preparation guarantee system for high-quality milk. However, such a method of controlling heating conditions singly has limitations, is difficult to solve the contradiction between the sterilization effect and the milk quality, and has limited effects on improving the sterilization effect and the milk quality.
Disclosure of Invention
In order to solve the technical problem, the invention provides a milk sterilization method with low protein denaturation rate. The invention carries out pre-sterilization and standardization before secondary sterilization, combines flash evaporation sterilization and pasteurization during secondary sterilization, can reduce the denaturation of protein and the generation of furosine during the sterilization process while ensuring the sterilization effect, and improves the milk quality.
The specific technical scheme of the invention is as follows:
a method for sterilizing milk with low protein denaturation rate comprises the following steps:
(1) pre-sterilization: pre-sterilizing milk at 62-68 ℃ for 15-20 s;
(2) and (3) standardization: detecting the pre-sterilized milk, and if the detection result does not reach the index, standardizing until the index is reached;
(3) preheating: preheating milk reaching the index to 60-65 ℃;
(4) secondary sterilization: carrying out flash evaporation sterilization on the preheated milk, controlling the temperature of an inlet heat source to be 70-85 ℃, the vacuum degree to be-0.6-0.8 MPa, the central temperature of the milk to be not more than 65 ℃, and carrying out flash evaporation sterilization for 10-15 s;
(5) and (3) cooling: and cooling the secondarily sterilized milk.
In the step (1), most of microorganisms and pathogenic bacteria which are easy to propagate can be killed by pre-sterilization, so that a foundation is laid for reducing the sterilization intensity in the subsequent secondary sterilization process; the milk is standardized after the pre-sterilization, so that the influence of the pre-sterilization on the milk quality can be compensated to a certain extent.
On the basis of pre-sterilization, the secondary sterilization is carried out on the milk in the step (4), so that the microorganisms in the milk can be further reduced. And flash distillation sterilization and pasteurization are combined during secondary sterilization, the boiling temperature of the milk can be controlled between 40-60 ℃ by controlling the vacuum degree, the milk temperature is prevented from being overhigh, and the milk is in a film state in the evaporator, so that the evaporation speed is high, the heating time is short, the discharging temperature can be rapidly reduced, and by adopting the mode, the protein denaturation and the production of the furosine in the sterilization process can be reduced while the sterilization effect is ensured, and the milk quality is improved. In addition, various continuous multi-effect evaporators can be adopted for flash evaporation sterilization, particularly falling film type or plate type evaporators, and the evaporators are mainly characterized in that milk is continuously evaporated through a heater in a single pass, so that the evaporators are suitable for large-scale continuous production and are favorable for improving the labor production efficiency, ensuring the product quality and reducing the energy consumption.
Preferably, in step (2), the indexes are: the milk contains fat not less than 3.3wt%, protein not less than 2.95wt%, and non-fat milk solid not less than 8.2 wt%; the standardized method is to concentrate the milk to reach the index.
Preferably, before the step (1), the raw milk is filtered by a sieve of 80-100 meshes and then is purified.
Preferably, the total number of colonies in the raw milk is not more than 1X 105CFU/mL。
Preferably, prior to step (1), the elastin-like polypeptide is added to milk; the phase transition temperature of the elastin-like polypeptide is 40-55 ℃.
The elastin-like polypeptides (ELPs) are temperature-sensitive polymers, and after the elastin-like polypeptides (ELPs) are added into milk, the influence of sterilization on the quality of the milk can be reduced, and the specific mechanism is as follows: before sterilization, the milk temperature is lower than the phase transition temperature of ELPs, the ELPs are dissolved in the milk, and the polymer chain is in a stretched state; in the sterilization process, when the temperature rises above the phase transition temperature of the ELPs, the ELPs start to aggregate and are coated on the surfaces of hydrophobic proteins such as lactoferrin and immunoglobulin through hydrophobic interaction, so that the protective effect can be exerted in the sterilization process, the thermal denaturation of proteins in milk is reduced, and the generation of furfuryl acid by the reaction of lysine in the milk proteins and lactose is reduced; in the cooling process after sterilization, the ELPs are re-dissolved along with the reduction of the temperature, and the protein in the ELPs is released, so that the milk is prevented from being turbid due to the fact that the ELPs coat the protein.
In addition, the ELPs have good biocompatibility, can be naturally degraded into amino acids in vivo, are nontoxic to human bodies, and can supplement amino acids for human bodies.
Further, the elastin-like polypeptide is composed of VGVPG VGVPG GGVPG AGVPG VGVPG repeat units, and the number of the repeats is 30.
Through gene engineering, elastin-like polypeptides with various sequences can be produced in high flux, and through designing the sequences of ELPs, the ELPs with the required phase transition temperature can be obtained. For ELPs consisting of 30 VGVPG VGVPG GGVPG AGVPG VGVPG repeated sequence units, the phase transition temperature is about 41 ℃, the ELPs can be coated on the surface of milk protein in the pre-sterilization and secondary sterilization processes to play a role in protection, and when the milk is stored and drunk at room temperature, the ELPs cannot be aggregated to cause turbidity in the milk.
Furthermore, the addition amount of the elastin-like polypeptide in the milk is 0.2-0.8 mg/mL.
Preferably, in step (3), the milk is homogenized after preheating.
Preferably, in the step (5), the secondarily sterilized milk is cooled to 2-6 ℃.
Compared with the prior art, the invention has the following advantages:
(1) the pre-sterilization and the standardization are carried out before the secondary sterilization, and the flash evaporation sterilization and the pasteurization are combined during the secondary sterilization, so that the sterilization effect can be ensured, the denaturation of protein and the generation of furosine in the sterilization process can be reduced, and the milk quality can be improved;
(2) by adding the elastin-like polypeptide into the milk, the protein can be protected, and the denaturation of the protein and the generation of the furosine in the sterilization process can be reduced.
Detailed Description
The present invention will be further described with reference to the following examples.
General examples
A method for sterilizing milk with low protein denaturation rate comprises the following steps:
(1) and (4) acceptance inspection: detecting raw milk (fresh milk) to ensure that the total number of bacterial colonies is less than or equal to 1 × 105CFU/mL；
(2) And (3) filtering: filtering the milk qualified by inspection through a sieve of 80-100 meshes;
(3) cleaning milk: purifying the filtered milk by adopting a disc type device at the speed of 5t/h, and then refrigerating at the temperature of 2-6 ℃;
(4) pre-sterilization: pre-sterilizing the milk after milk purification for 15-20 s at 62-68 ℃;
(5) and (3) standardization: detecting whether the pre-sterilized milk meets the following indexes: fat content is not less than 3.3wt%, protein content is not less than 2.95wt%, and non-fat milk solid content is not less than 8.2 wt%; if the detection result does not reach the index, concentrating the milk until the index is reached;
(6) preheating: preheating milk reaching the index to 60-65 ℃;
(7) homogenizing: homogenizing the preheated milk;
(8) secondary sterilization: carrying out flash evaporation sterilization on the preheated milk, controlling the temperature of an inlet heat source to be 70-85 ℃, the vacuum degree to be-0.6-0.8 MPa, the central temperature of the milk to be not more than 65 ℃, and carrying out flash evaporation sterilization for 10-15 s;
(9) and (3) cooling: and (3) cooling the secondarily sterilized milk to 2-6 ℃ by using ice water, filling and sealing to obtain the sterilized milk.
Optionally, in the step (4), the elastin-like polypeptide is added into the milk after milk purification in an amount of 0.2-0.8 mg/mL before pre-sterilization; the phase transition temperature of the elastin-like polypeptide is 40-55 ℃.
Example 1
A method for sterilizing milk with low protein denaturation rate comprises the following steps:
(1) and (4) acceptance: detecting raw milk (fresh milk) to ensure that the total number of bacterial colonies is less than or equal to 1 × 105CFU/mL, somatic cell ≤ 4 × 105The number per mL, sensory index is qualified, test of 75% neutral alcohol (20 ℃) and milk is negative in a ratio of 1:1, physicochemical index is qualified, and antibiotic residue is negative;
(2) and (3) filtering: performing 100-mesh filtering on the qualified milk by using a triple filter;
(3) cleaning milk: purifying the filtered milk by adopting a disc type device at the speed of 5t/h, and pumping the milk into a storage tank with the temperature of 2 ℃ for refrigeration;
(4) pre-sterilization: pre-sterilizing the milk at 62 deg.C for 15 s;
(5) and (3) standardization: detecting whether the pre-sterilized milk meets the following indexes: fat content is not less than 3.3wt%, protein content is not less than 2.95wt%, and non-fat milk solid content is not less than 8.2 wt%; if the detection result does not reach the index, concentrating the milk by using the single-effect falling-film evaporator until the index is reached;
(6) preheating: preheating milk reaching the index to 60 ℃ by adopting a plate heat exchanger;
(7) homogenizing: carrying out secondary homogenization on the preheated milk, wherein the primary pressure is 16MPa, and the secondary pressure is 4 MPa;
(8) and (3) secondary sterilization: pumping the homogenized milk into a flash tank, controlling the temperature of an inlet heat source to be 70 ℃, the vacuum degree to be-0.6 MPa and the central temperature of the milk to be not more than 65 ℃, and carrying out flash sterilization for 15 s;
(9) and (3) cooling: and (3) cooling the secondarily sterilized milk to 2 ℃ by using ice water, filling and sealing to obtain the sterilized milk.
Example 2
A method for sterilizing milk with low protein denaturation rate comprises the following steps:
(1) and (4) acceptance: detecting raw milk (fresh milk) to ensure that the total number of bacterial colonies is less than or equal to 1 × 105CFU/mL, somatic cell less than or equal to 3X 105The number per mL, sensory index is qualified, test of 75% neutral alcohol (20 ℃) and milk is negative in a ratio of 1:1, physicochemical index is qualified, and antibiotic residue is negative;
(2) and (3) filtering: performing 100-mesh filtering on the milk qualified by acceptance by a triple filter;
(3) cleaning milk: purifying the filtered milk by adopting a disc type device at the speed of 5t/h, and pumping the milk into a storage tank at the temperature of 4 ℃ for refrigeration;
(4) pre-sterilization: pre-sterilizing the milk after milk purification at 65 ℃ for 18 s;
(5) and (3) standardization: detecting whether the pre-sterilized milk meets the following indexes: fat content is not less than 3.3wt%, protein content is not less than 2.95wt%, and non-fat milk solid content is not less than 8.2 wt%; if the detection result does not reach the index, concentrating the milk by using the single-effect falling-film evaporator until the index is reached;
(6) preheating: preheating milk reaching the index to 62 ℃ by adopting a plate heat exchanger;
(7) homogenizing: carrying out secondary homogenization on the preheated milk, wherein the primary pressure is 17MPa, and the secondary pressure is 5 MPa;
(8) secondary sterilization: pumping the homogenized milk into a flash tank, controlling the temperature of an inlet heat source to be 75 ℃, the vacuum degree to be 0.5MPa, and the central temperature of the milk to be not more than 65 ℃, and carrying out flash sterilization for 12 s;
(9) and (3) cooling: and (3) cooling the secondarily sterilized milk to 4 ℃ by using ice water, filling and sealing to obtain the sterilized milk.
Example 3
A method for sterilizing milk with low protein denaturation rate comprises the following steps:
(1) and (4) acceptance: detecting raw milk (fresh milk) to ensure that the total number of bacterial colonies is less than or equal to 1 × 105CFU/mL, somatic cell less than or equal to 3X 105The number per mL, sensory index is qualified, test of 75% neutral alcohol (20 ℃) and milk is negative in a ratio of 1:1, physicochemical index is qualified, and antibiotic residue is negative;
(2) and (3) filtering: performing 100-mesh filtering on the qualified milk by using a triple filter;
(3) cleaning milk: purifying the filtered milk by adopting a disc type device at the speed of 5t/h, and pumping the milk into a storage tank with the temperature of 6 ℃ for refrigeration;
(4) pre-sterilization: pre-sterilizing the milk at 68 deg.C for 20 s;
(5) and (3) standardization: detecting whether the pre-sterilized milk meets the following indexes: fat content is not less than 3.3wt%, protein content is not less than 2.95wt%, and non-fat milk solid content is not less than 8.2 wt%; if the detection result does not reach the index, concentrating the milk by using the single-effect falling-film evaporator until the index is reached;
(6) preheating: preheating milk reaching the index to 65 ℃ by adopting a plate heat exchanger;
(7) homogenizing: carrying out secondary homogenization on the preheated milk, wherein the primary pressure is 18MPa, and the secondary pressure is 6 MPa;
(8) secondary sterilization: pumping the homogenized milk into a flash tank, controlling the temperature of an inlet heat source to be 85 ℃, the vacuum degree to be 0.8MPa, and the central temperature of the milk to be not more than 65 ℃, and carrying out flash sterilization for 10 s;
(9) and (3) cooling: and (3) cooling the secondarily sterilized milk to 6 ℃ by using ice water, filling and sealing to obtain the sterilized milk.
Example 4
The raw milk used in this example was the same as in example 1, except that in step (4), the elastin-like polypeptide was added to the milk after the milk had been cleaned in an amount of 0.2mg/mL before pre-sterilization; the elastin-like polypeptide is composed of VGVPG VGVPG GGVPG AGVPG VGVPG repeated sequence units, the repeated times are 30 times, and the phase transition temperature is-41 ℃.
In this example, it was observed that after preheating, turbidity appeared in the milk; during the cooling process, the milk is clarified again.
Example 5
The raw milk used in this example was the same as in example 1, except that in step (4), the elastin-like polypeptide was added to the milk after the milk had been cleaned in an amount of 0.5mg/mL before pre-sterilization; the elastin-like polypeptide consists of VGVPG VGVPG GGVPG AGVPG VGVPG repeated sequence units, the repeated times are 30 times, and the phase transition temperature is-41 ℃.
In this example, it was observed that after preheating, turbidity appeared in the milk; during the cooling process, the milk is clarified again.
Example 6
The raw milk used in this example was the same as in example 1, except that in step (4), the elastin-like polypeptide was added to the milk after the milk had been cleaned in an amount of 0.8mg/mL before pre-sterilization; the elastin-like polypeptide is composed of VGVPG VGVPG GGVPG AGVPG VGVPG repeated sequence units, the repeated times are 30 times, and the phase transition temperature is-41 ℃.
In this example, it was observed that after preheating, turbidity appeared in the milk; during the cooling process, the milk is clarified again.
Comparative example 1
The raw milk used in this comparative example was the same as example 1, except that step (4) was not performed, as in example 1.
Comparative example 2
The raw milk used in this comparative example was the same as in example 1, except that in step (8), secondary sterilization was performed by pasteurization, i.e., sterilization at 70 ℃ for 10 seconds.
Test example
In examples 1 to 6 and comparative examples 1 to 2, the content of each milk protein (β -lactoglobulin, immunoglobulin and lactoferrin) in raw milk, as well as the content of arginine, the content of each milk protein and the total number of colonies in pasteurized milk were examined, and each group was tested repeatedly for 5 times, the outliers were discarded, the average value was taken, and the denaturation rate and the sterilization rate of each milk protein were calculated. The results are shown in Table 1.
TABLE 1
As can be seen from table 1:
(1) compared with comparative example 1, the bacterial colony number of the sterilized milk obtained in example 1 is obviously less, and the content of each milk protein in the sterilized milk is less different from that in comparative example 1, which shows that the milk is pre-sterilized before secondary sterilization, so that the sterilization effect can be effectively improved, and the influence on the protein is less.
(2) Compared with the comparative example 2, the bacterial colony number of the sterilized milk obtained in the example 1 is obviously less, and the denaturation rate of each milk protein and the content of the furosine in the sterilized milk are obviously lower, which shows that compared with the traditional pasteurization, the pasteurization and the flash sterilization are combined, so that the sterilization effect can be effectively improved, and the denaturation of the protein and the generation of the furosine are reduced.
(3) Compared with the example 1, the denaturation rate of each milk protein and the content of the furosine in the sterilized milk in the examples 4-6 are obviously lower, which shows that the denaturation of the protein and the generation of the furosine in the sterilization process can be reduced by adding the elastin-like polypeptide into the milk before sterilization; in addition, no obvious turbidity phenomenon is observed in the sterilized milk obtained in the examples 4-6, which shows that the milk is not turbid due to the addition of the ELPs. The reason is that: in the sterilization process, when the temperature rises above the phase transition temperature of the ELPs, the ELPs start to aggregate and are coated on the surfaces of hydrophobic proteins such as lactoferrin and immunoglobulin through hydrophobic interaction, so that the protective effect can be exerted in pre-sterilization, preheating and secondary sterilization, the thermal denaturation of the proteins in the milk is reduced, and the generation of the furfuryl amino acid by the reaction of lysine in the milk proteins and lactose is reduced; in the cooling process after sterilization, the ELPs are re-dissolved along with the reduction of the temperature, and the protein in the ELPs is released, so that the milk is prevented from being turbid due to the fact that the ELPs coat the protein.
The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, alterations and equivalents of the above embodiments according to the technical spirit of the present invention are still within the protection scope of the technical solution of the present invention.
Claims (10)
1. A method for sterilizing milk with low protein denaturation rate is characterized by comprising the following steps:
(1) pre-sterilization: pre-sterilizing milk at 62-68 ℃ for 15-20 s;
(2) and (3) standardization: detecting the pre-sterilized milk, and if the detection result does not reach the index, standardizing until the index is reached;
(3) preheating: preheating milk reaching the index to 60-65 ℃;
(4) and (3) secondary sterilization: carrying out flash evaporation sterilization on the preheated milk, controlling the temperature of an inlet heat source to be 70-85 ℃, the vacuum degree to be-0.6-0.8 MPa, the central temperature of the milk to be not more than 65 ℃, and carrying out flash evaporation sterilization for 10-15 s;
(5) and (3) cooling: and cooling the secondarily sterilized milk.
2. The sterilization method according to claim 1, wherein in the step (2), the indexes are: the milk has fat content of not less than 3.3wt%, protein content of not less than 2.95wt%, and non-fat milk solid content of not less than 8.2 wt%.
3. The sterilization method according to claim 1, wherein in the step (2), the milk is concentrated to reach the target value by the standardized method.
4. The sterilization method according to claim 1, wherein the raw milk is filtered through a 80-100 mesh sieve before the step (1), and then the raw milk is cleaned.
5. The sterilization method according to claim 4, wherein the total number of colonies in said starting milk is not more than 1X 105CFU/mL。
6. The sterilization method according to claim 1 or 4, wherein prior to step (1), the elastin-like polypeptide is added to the milk; the phase transition temperature of the elastin-like polypeptide is 40-55 ℃.
7. The bactericidal method of claim 6, wherein the elastin-like polypeptide is comprised of VGVPG VGVPG GGVPG AGVPG VGVPG repeat units, and the number of repeats is 30.
8. The sterilization method according to claim 6, wherein the addition amount of the elastin-like polypeptide in milk is 0.2-0.8 mg/mL.
9. The sterilization method as claimed in claim 1, wherein in the step (3), the milk is homogenized after preheating.
10. The sterilization method according to claim 1, wherein in the step (5), the secondarily sterilized milk is cooled to 2 to 6 ℃.
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