Fresh milk sterilized based on pulsed electric field and preparation method thereof

Abstract

The invention provides fresh milk sterilized based on a pulsed electric field and a preparation method of the fresh milk. The fresh milk meets the following requirements: the original protein content of the milk is more than or equal to 3.4 g / 100g and less than or equal to 4.0 g / 100g; furosine less than or equal to 10 mg / 100 g protein; lactoferrin greater than or equal to 80 mg / L; and more than or equal to 300 mg / L of immunoglobulin. The invention also provides a preparation method of the fresh milk. Microorganisms in feed liquid can be removed through pulsed electric field sterilization, bacteria, spores and other microorganisms in milk are effectively killed, the quality guarantee period of the milk is prolonged, and meanwhile more nutritional ingredients in the milk are reserved. And the matched use of the processes of pulsed electric field sterilization, a degerming separator and low-intensity pasteurization can further reduce the furosine level in the product on the basis of keeping the original shelf life stability of the product.

Description

Technical Field

[0001] This invention relates to the field of dairy processing technology, specifically to a fresh milk sterilized by pulsed electric field and its preparation method. Background Technology

[0002] Current milk product processing requires heat sterilization, such as pasteurization and ultra-high temperature (UHT) sterilization. Prolonged heating causes a significant loss of active substances in milk. Pasteurization is the most common process for fresh milk products. While pasteurization retains some active substances, dairy products obtained solely through pasteurization suffer from short shelf life and limited storage conditions. Furthermore, this process involves the production of furosine, which, if present in excessive amounts in food, may pose health risks. Summary of the Invention

[0003] To address the aforementioned technical problems, the present invention aims to provide a fresh milk sterilized using a pulsed electric field and its preparation method. This method utilizes a pulsed electric field to sterilize and remove harmful microorganisms from fresh milk, thereby extending the shelf life of the milk while retaining more of its nutrients.

[0004] To achieve the above objectives, the present invention provides fresh milk sterilized using a pulsed electric field, wherein the fresh milk meets the following requirements:

[0005] Milk native protein content ≤ 3.4g / 100g ≤ 4.0g / 100g;

[0006] Furfurylic acid content less than or equal to 10 mg / 100g protein;

[0007] Lactoferrin at a concentration of ≥80 mg / L;

[0008] Immunoglobulins at a concentration of 300 mg / L or higher.

[0009] According to a specific embodiment of the present invention, preferably, the fresh milk also meets the following requirements:

[0010] 55mg / 100g ≤ Sodium ≤ 60mg / 100g;

[0011] 120mg / 100g ≤ native calcium ≤ 130mg / 100g;

[0012] 4.5g / 100g ≤ lactose ≤ 5.5g / 100g.

[0013] The present invention also provides a method for preparing the above-mentioned fresh milk based on pulsed electric field sterilization, which includes the following steps: milk purification, degassing, homogenization, physical sterilization, pulsed electric field sterilization, and pasteurization;

[0014] The pulsed electric field sterilization includes the following steps:

[0015] The liquid milk, after physical sterilization, is then subjected to pulsed electric field sterilization. The pulsed electric field strength is 35-45 kV / cm, and the number of pulses is 1000-2000, resulting in a liquid milk treated with pulsed electric field sterilization. Pulsed electric field sterilization can remove microorganisms from the liquid milk. Specifically, the pulsed electric field acts on the microbial cells, causing them to form pores, eventually leading to cell rupture and inactivation. This effectively kills bacteria, spores, and other microorganisms in the milk, thereby extending the shelf life of the milk while retaining more of its nutrients, such as lactoferrin and immunoglobulins.

[0016] In the above-mentioned method for preparing fresh milk based on pulsed electric field sterilization, preferably, the milk purification includes the following steps:

[0017] The qualified raw milk is subjected to cooling and purification treatment at a temperature of 2-10℃. The cooled and purified raw milk is then passed through an 80-600 mesh sieve to obtain a liquid feed. This liquid feed is then centrifuged at 4000-6000 rpm to obtain the purified milk feed. In the above method for preparing fresh milk based on pulsed electric field sterilization, preferably, the degassing includes the following steps:

[0018] The milk solution after purification is degassed at 50-65°C under a degassed pressure of -0.04 bar to -0.09 bar to obtain the degassed milk solution. In the above method for preparing fresh milk based on pulsed electric field sterilization, preferably, the homogenization includes the following steps:

[0019] The degassed liquid is homogenized at 50-65°C. The homogenization pressure is adjusted by first setting the secondary pressure to 30 bar, then the primary pressure to 170-220 bar, to obtain the homogenized liquid. In the above method for preparing fresh milk based on pulsed electric field sterilization, preferably, the physical sterilization includes the following steps:

[0020] The homogenized liquid is sterilized in a sterilization separator at a temperature of 50-60℃ and a centrifugation speed of 5000-10000 rpm to improve sterilization efficiency, reduce microbial residue, preserve the nutritional components of the product, and extend the product shelf life. The sterilization separator can remove about 98% of anaerobic spore microorganisms and 95% of aerobic spore bacteria from the milk, which can cumulatively reduce the total number of bacteria in the milk by about 86% and improve product quality.

[0021] In the above-mentioned method for preparing fresh milk based on pulsed electric field sterilization, preferably, the pasteurization includes the following steps (a first low-intensity pasteurization scheme):

[0022] The liquid treated with the pulsed electric field sterilization is then subjected to low-intensity pasteurization at 62-65°C for 25-35 minutes to obtain fresh milk sterilized by pulsed electric field sterilization. In the above method for preparing fresh milk sterilized by pulsed electric field sterilization, preferably, the pasteurization includes the following steps (a second low-intensity pasteurization scheme):

[0023] The liquid material treated with the pulsed electric field sterilization was then subjected to low-intensity pasteurization at 72-75°C for 12-15 seconds to obtain fresh milk sterilized by pulsed electric field sterilization.

[0024] In the above-mentioned method for preparing fresh milk based on pulsed electric field sterilization, preferably, the pasteurization is carried out using a plate sterilizer and / or a tubular sterilizer.

[0025] The technical solution of the present invention has the following beneficial technical effects:

[0026] The pulsed electric field sterilization method used in this invention is a novel non-thermal sterilization technology that can shorten the processing time, control the temperature rise, inhibit the formation of furosine, and has a significant sterilization effect. It can effectively preserve the nutritional components and natural color, aroma, and flavor of food, and is suitable for sterilizing fresh milk.

[0027] This invention combines pulsed electric field sterilization, sterilization separation machine and low-intensity pasteurization processes to further improve the nutritional content of the product while maintaining the original shelf life stability, reduce the furosine level in the product, remove spore-like substances from the milk and extend the shelf life of the milk. Detailed Implementation

[0028] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0029] Example 1:

[0030] This embodiment provides a method for preparing fresh milk based on pulsed electric field sterilization, as follows:

[0031] (1) Cleansing milk:

[0032] Healthy dairy cows from large-scale dairy farms are selected, and fresh milk is obtained through mechanized milking equipment. The raw milk is tested for protein, fat, non-fat milk solids, pH, acidity, and total bacterial count to ensure compliance with the GB19301 national standard for raw milk. It is then stored in a cold chain environment at 2-6℃ to maintain its freshness and taste. The qualified raw milk undergoes cooling and clarification at 2℃ to ensure freshness. It is then sieved through an 80-mesh screen and centrifuged at 4000 rpm to remove bacteria, foreign matter, and other impurities.

[0033] (2) Degassing:

[0034] The purified emulsion was degassed at a temperature of 50°C and a degassed pressure of -0.09 bar.

[0035] (3) Homogeneous:

[0036] The degassed liquid was homogenized in a sterile environment at a pressure of 30 / 170 bar and a temperature of 65°C.

[0037] (4) Physical sterilization:

[0038] The sterilization separator is used to physically sterilize and separate the liquid in step (3) to further remove microorganisms from the liquid. The speed of the sterilization separator is 5000 rpm and the separation temperature is 50℃.

[0039] (5) Pulsed electric field sterilization:

[0040] The liquid in step (4) is subjected to pulsed electric field sterilization with a sterilization field strength of 35kV / cm and a pulse number of 2000.

[0041] (6) Pasteurization:

[0042] The liquid obtained in step (5) was sterilized at 62°C and kept at the sterilization temperature for 25 minutes.

[0043] (7) Filling:

[0044] The liquid obtained in step (6) is cooled to 4°C and then filled.

[0045] Example 2:

[0046] This embodiment provides a method for preparing fresh milk based on pulsed electric field sterilization, as follows:

[0047] (1) Cleansing milk:

[0048] Healthy dairy cows from large-scale dairy farms are selected, and fresh milk is obtained through mechanized milking equipment. The raw milk is tested for protein, fat, non-fat milk solids, pH, acidity, and total bacterial count to ensure compliance with the GB19301 national standard for raw milk. It is then stored in a cold chain environment at 2-6℃ to maintain its freshness and taste. The qualified raw milk undergoes cooling and clarification at 4℃ to ensure freshness. It is then sieved through an 80-mesh screen and centrifuged at 4000 rpm to remove bacteria, foreign matter, and other impurities.

[0049] (2) Degassing:

[0050] The purified emulsion was degassed at a temperature of 50°C and a degassed pressure of -0.09 bar.

[0051] (3) Homogeneous:

[0052] The degassed liquid was homogenized in a sterile environment at a pressure of 30 / 180 bar and a temperature of 65°C.

[0053] (4) Physical sterilization:

[0054] The sterilization separator is used to physically sterilize and separate the liquid in step (3) to further remove microorganisms from the liquid. The speed of the sterilization separator is 5000 rpm and the separation temperature is 50℃.

[0055] (5) Pulsed electric field sterilization:

[0056] The liquid in step (4) is subjected to pulsed electric field sterilization with a sterilization field strength of 35kV / cm and a pulse number of 2000.

[0057] (6) Pasteurization:

[0058] The liquid obtained in step (5) was sterilized at 65°C and kept at the sterilization temperature for 35 minutes.

[0059] (7) Filling:

[0060] The liquid obtained in step (6) is cooled to 4°C and then filled.

[0061] Example 3:

[0062] This embodiment provides a method for preparing fresh milk based on pulsed electric field sterilization, as follows:

[0063] (1) Cleansing milk:

[0064] Healthy dairy cows from large-scale dairy farms are selected, and fresh milk is obtained through mechanized milking equipment. The raw milk is tested for protein, fat, non-fat milk solids, pH, acidity, and total bacterial count to ensure compliance with the GB19301 national standard for raw milk. It is then stored in a cold chain environment at 2-6℃ to maintain its freshness and taste. The qualified raw milk undergoes cooling and clarification at 6℃ to ensure freshness. The raw milk is then sieved through a 300-mesh screen and centrifuged at 5000 rpm to remove bacteria, foreign matter, and other impurities.

[0065] (2) Degassing:

[0066] The purified emulsion was degassed at a temperature of 60°C and a degassed pressure of -0.07 bar.

[0067] (3) Homogeneous:

[0068] The degassed liquid was homogenized in a sterile environment at a pressure of 30 / 190 bar and a temperature of 60°C.

[0069] (4) Physical sterilization:

[0070] The sterilization separator is used to physically sterilize and separate the liquid in step (3) to further remove microorganisms from the liquid. The speed of the sterilization separator is 7000 rpm and the separation temperature is 55℃.

[0071] (5) Pulsed electric field sterilization:

[0072] The liquid in step (4) is subjected to pulsed electric field sterilization with a sterilization field strength of 40kV / cm and a pulse number of 1500.

[0073] (6) Pasteurization:

[0074] The liquid obtained in step (5) was sterilized at 72°C and kept at that temperature for 12 seconds.

[0075] (7) Filling:

[0076] The liquid obtained in step (6) is cooled to 4°C and then filled.

[0077] Example 4:

[0078] This embodiment provides a method for preparing fresh milk based on pulsed electric field sterilization, as follows:

[0079] (1) Cleansing milk:

[0080] Healthy dairy cows from large-scale dairy farms are selected, and fresh milk is obtained through mechanized milking equipment. The raw milk is tested for protein, fat, non-fat milk solids, pH, acidity, and total bacterial count to ensure compliance with the GB19301 national standard for raw milk. It is then stored in a cold chain environment at 2-6℃ to maintain its freshness and taste. The qualified raw milk undergoes cooling and clarification at 8℃ to ensure freshness. The raw milk is then sieved through a 300-mesh screen and centrifuged at 5000 rpm to remove bacteria, foreign matter, and other impurities.

[0081] (2) Degassing:

[0082] The purified emulsion was degassed at a temperature of 60°C and a degassed pressure of -0.07 bar.

[0083] (3) Homogeneous:

[0084] The degassed liquid was homogenized in a sterile environment at a pressure of 30 / 200 bar and a temperature of 60°C.

[0085] (4) Physical sterilization:

[0086] The sterilization separator is used to physically sterilize and separate the liquid in step (3) to further remove microorganisms from the liquid. The speed of the sterilization separator is 7000 rpm and the separation temperature is 55℃.

[0087] (5) Pulsed electric field sterilization:

[0088] The liquid in step (4) is subjected to pulsed electric field sterilization with a sterilization field strength of 40kV / cm and a pulse number of 1500.

[0089] (6) Pasteurization:

[0090] The liquid obtained in step (5) was sterilized at 72°C and kept at that temperature for 12 seconds.

[0091] (7) Filling:

[0092] The liquid obtained in step (6) is cooled to 4°C and then filled.

[0093] Example 5:

[0094] This embodiment provides a method for preparing fresh milk based on pulsed electric field sterilization, as follows:

[0095] (1) Cleansing milk:

[0096] Healthy dairy cows from large-scale dairy farms are selected, and fresh milk is obtained through mechanized milking equipment. The raw milk is tested for protein, fat, non-fat milk solids, pH, acidity, and total bacterial count to ensure compliance with the GB19301 national standard for raw milk. It is then stored in a cold chain environment at 2-6℃ to maintain its freshness and taste. The qualified raw milk undergoes cooling and clarification at 10℃ to ensure freshness. The raw milk is then sieved through a 600-mesh screen and centrifuged at 6000 rpm to remove bacteria, foreign matter, and other impurities.

[0097] (2) Degassing:

[0098] The purified emulsion was degassed at a temperature of 65°C and a degassed pressure of -0.04 bar.

[0099] (3) Homogeneous:

[0100] The degassed liquid was homogenized in a sterile environment at a pressure of 30 / 210 bar and a temperature of 50°C.

[0101] (4) Physical sterilization:

[0102] The sterilization separator is used to physically sterilize and separate the liquid in step (3) to further remove microorganisms from the liquid. The speed of the sterilization separator is 10,000 rpm and the separation temperature is 60℃.

[0103] (5) Pulsed electric field sterilization:

[0104] The liquid in step (4) is subjected to pulsed electric field sterilization with a sterilization field strength of 45kV / cm and a pulse number of 1000.

[0105] (6) Pasteurization:

[0106] The liquid obtained in step (5) is sterilized at 75°C and kept at the sterilization temperature for 15 seconds.

[0107] (7) Filling:

[0108] The liquid obtained in step (6) is cooled to 4°C and then filled.

[0109] Example 6:

[0110] This embodiment provides a method for preparing fresh milk based on pulsed electric field sterilization, as follows:

[0111] (1) Cleansing milk:

[0112] Healthy dairy cows from large-scale dairy farms are selected, and fresh milk is obtained through mechanized milking equipment. The raw milk is tested for protein, fat, non-fat milk solids, pH, acidity, and total bacterial count to ensure compliance with the GB19301 national standard for raw milk. It is then stored in a cold chain environment at 2-6℃ to maintain its freshness and taste. The qualified raw milk undergoes cooling and clarification at 6℃ to ensure freshness. It is then sieved through a 600-mesh screen and centrifuged at 6000 rpm to remove bacteria, foreign matter, and other impurities.

[0113] (2) Degassing:

[0114] The purified emulsion was degassed at a temperature of 65°C and a degassed pressure of -0.04 bar.

[0115] (3) Homogeneous:

[0116] The degassed liquid was homogenized in a sterile environment at a pressure of 30 / 220 bar and a temperature of 50°C.

[0117] (4) Physical sterilization:

[0118] The sterilization separator is used to physically sterilize and separate the liquid in step (3) to further remove microorganisms from the liquid. The speed of the sterilization separator is 10,000 rpm and the separation temperature is 60℃.

[0119] (5) Pulsed electric field sterilization:

[0120] The liquid in step (4) is subjected to pulsed electric field sterilization with a sterilization field strength of 45kV / cm and a pulse number of 1000.

[0121] (6) Pasteurization:

[0122] The liquid obtained in step (5) is sterilized at 75°C and kept at the sterilization temperature for 15 seconds.

[0123] (7) Filling:

[0124] The liquid obtained in step (6) is cooled to 4°C and then filled.

[0125] Comparative Example 1:

[0126] This comparative example provides a method for preparing sterilized fresh milk as follows:

[0127] (1) Cleansing milk:

[0128] Healthy dairy cows from large-scale dairy farms are selected, and fresh milk is obtained through mechanized milking equipment. The raw milk is tested for protein, fat, non-fat milk solids, pH, acidity, and total bacterial count to ensure compliance with the GB19301 national standard for raw milk. It is then stored in a cold chain environment at 2-6℃ to maintain its freshness and taste. The qualified raw milk undergoes cooling and clarification at 2℃ to ensure freshness. It is then sieved through an 80-mesh screen and centrifuged at 4000 rpm to remove bacteria, foreign matter, and other impurities.

[0129] (2) Degassing:

[0130] The purified emulsion was degassed at a temperature of 50°C and a degassed pressure of -0.09 bar.

[0131] (3) Homogeneous:

[0132] The degassed liquid was homogenized in a sterile environment at a pressure of 30 / 170 bar and a temperature of 65°C.

[0133] (4) Physical sterilization:

[0134] The sterilization separator is used to physically sterilize and separate the liquid in step (3) to further remove microorganisms from the liquid. The speed of the sterilization separator is 5000 rpm and the separation temperature is 50℃.

[0135] (5) Direct steam sterilization:

[0136] The liquid obtained in step (4) was sterilized at 157°C for 0.16s and then cooled to 50°C.

[0137] (6) Filling:

[0138] The liquid obtained in step (5) is cooled to 4°C and then filled.

[0139] Comparative Example 2:

[0140] This comparative example provides a method for preparing sterilized fresh milk as follows:

[0141] (1) Milk Purification: Healthy dairy cows from large-scale dairy farms are selected, and fresh milk is obtained through mechanized milking equipment. The raw milk is tested for protein, fat, non-fat milk solids, pH, acidity, and total bacterial count to ensure compliance with the GB19301 "Raw Milk" national standard. It is then stored in a cold chain environment at 2-6℃ to maintain its freshness and taste. The raw milk that has passed the quality inspection is cooled and purified at 6℃ to ensure its freshness. The raw milk is sieved through a 300-mesh screen and centrifuged at 5000 rpm to remove bacteria, foreign matter, and other impurities.

[0142] (2) Degassing: The emulsified liquid is degassed at a temperature of 60°C and a degassing pressure of -0.07 bar.

[0143] (3) Fat-milk separation: The degassed liquid is separated at a temperature of 60°C and a rotation speed of 5000 rpm to obtain skim milk and cream.

[0144] (4) Physical sterilization of skim milk: The skim milk after separation is physically sterilized by using a sterilization separator and MF microfiltration in series to further remove microorganisms from the liquid. The speed of the sterilization separator is 8000 rpm and the separation temperature is 60℃. The material of the MF membrane is a ceramic membrane, the membrane temperature is 60℃, the membrane pore size is 0.8μm, and the membrane pressure is 4bar.

[0145] (5) High-temperature sterilization of light cream: The separated light cream is sterilized at 130°C for 3 seconds and then cooled to 50°C.

[0146] (6) Online mixing: The skim milk liquid that has been physically sterilized and the light cream that has been sterilized at high temperature are mixed at a mixing temperature of 55°C.

[0147] (7) Homogenization: The liquid obtained in step (6) is homogenized in a sterile environment. The homogenization pressure is 30 / 200 bar and the homogenization temperature is 60℃.

[0148] (8) Pasteurization: The liquid obtained in step (7) is sterilized at 72°C and kept at the sterilization temperature for 12 seconds.

[0149] (9) Filling: Cool the liquid obtained in step (8) to 4°C and fill it.

[0150] Comparative Example 3:

[0151] This comparative example provides a method for preparing sterilized fresh milk as follows:

[0152] (1) Milk Purification: Healthy dairy cows from large-scale dairy farms are selected, and fresh milk is obtained through mechanized milking equipment. The raw milk is tested for protein, fat, non-fat milk solids, pH, acidity, and total bacterial count to ensure compliance with the GB19301 "Raw Milk" national standard. It is then stored in a cold chain environment at 2-6℃ to maintain its freshness and taste. The raw milk that has passed the quality inspection is cooled and purified at 10℃ to ensure its freshness. The raw milk is sieved through a 600-mesh screen and centrifuged at 6000 rpm to remove bacteria, foreign matter, and other impurities.

[0153] (2) Degassing: The emulsified liquid is degassed at a temperature of 65°C and a degassing pressure of -0.04 bar.

[0154] (3) Fat-milk separation: The degassed liquid is separated at a temperature of 60°C and a rotation speed of 5000 rpm to obtain skim milk and cream.

[0155] (4) Physical sterilization of skim milk: The skim milk after separation is physically sterilized and separated using a sterilization separator to further remove microorganisms from the liquid. The speed of the sterilization separator is 8000 rpm and the separation temperature is 60℃.

[0156] (5) High-temperature sterilization of light cream: The separated light cream is sterilized at 130°C for 3 seconds and then cooled to 50°C.

[0157] (6) Online mixing: The skim milk liquid that has been physically sterilized and the light cream that has been sterilized at high temperature are mixed at a mixing temperature of 55°C.

[0158] (7) Homogenization: The liquid obtained in step (6) is homogenized in a sterile environment. The homogenization pressure is 30 / 220 bar and the homogenization temperature is 50°C.

[0159] (8) Pasteurization: The liquid obtained in step (7) is sterilized at 75°C and kept at the sterilization temperature for 15 seconds.

[0160] (9) Filling: Cool the liquid obtained in step (8) to 4°C and fill it.

[0161] Comparative Example 4:

[0162] This comparative example provides a method for preparing sterilized fresh milk as follows:

[0163] (1) Cleansing milk:

[0164] Healthy dairy cows from large-scale dairy farms are selected, and fresh milk is obtained through mechanized milking equipment. The raw milk is tested for protein, fat, non-fat milk solids, pH, acidity, and total bacterial count to ensure compliance with the GB19301 national standard for raw milk. It is then stored in a cold chain environment at 2-6℃ to maintain its freshness and taste. The qualified raw milk undergoes cooling and clarification at 2℃ to ensure freshness. It is then sieved through an 80-mesh screen and centrifuged at 4000 rpm to remove bacteria, foreign matter, and other impurities.

[0165] (2) Degassing:

[0166] The purified emulsion was degassed at a temperature of 50°C and a degassed pressure of -0.09 bar.

[0167] (3) Homogeneous:

[0168] The degassed liquid was homogenized in a sterile environment at a pressure of 30 / 170 bar and a temperature of 65°C.

[0169] (4) Physical sterilization:

[0170] The sterilization separator is used to physically sterilize and separate the liquid in step (3) to further remove microorganisms from the liquid. The speed of the sterilization separator is 5000 rpm and the separation temperature is 50℃.

[0171] (5) Direct steam sterilization:

[0172] The liquid obtained in step (4) was sterilized at 157°C for 0.16s and then cooled to 50°C.

[0173] (6) Pasteurization:

[0174] The liquid obtained in step (5) was sterilized at 65°C and kept at the sterilization temperature for 35 minutes.

[0175] (7) Filling:

[0176] The liquid obtained in step (6) is cooled to 4°C and then filled.

[0177] Comparative Example 5:

[0178] This comparative example provides a method for preparing sterilized fresh milk as follows:

[0179] (1) Cleansing milk:

[0180] Healthy dairy cows from large-scale dairy farms are selected, and fresh milk is obtained through mechanized milking equipment. The raw milk is tested for protein, fat, non-fat milk solids, pH, acidity, and total bacterial count to ensure compliance with the GB19301 national standard for raw milk. It is then stored in a cold chain environment at 2-6℃ to maintain its freshness and taste. The qualified raw milk undergoes cooling and clarification at 2℃ to ensure freshness. It is then sieved through an 80-mesh screen and centrifuged at 4000 rpm to remove bacteria, foreign matter, and other impurities.

[0181] (2) Degassing:

[0182] The purified emulsion was degassed at a temperature of 50°C and a degassed pressure of -0.09 bar.

[0183] (3) Homogeneous:

[0184] The degassed liquid was homogenized in a sterile environment at a pressure of 30 / 170 bar and a temperature of 65°C.

[0185] (4) Pulsed electric field sterilization:

[0186] The liquid in step (3) is subjected to pulsed electric field sterilization with a sterilization field strength of 35kV / cm and a pulse number of 2000.

[0187] (5) Pasteurization:

[0188] The liquid obtained in step (4) was sterilized at 65°C and kept at the sterilization temperature for 35 minutes.

[0189] (6) Filling:

[0190] The liquid obtained in step (5) is cooled to 4°C and then filled.

[0191] Comparative Example 6:

[0192] This comparative example provides a method for preparing sterilized fresh milk as follows:

[0193] (1) Cleansing milk:

[0194] Healthy dairy cows from large-scale dairy farms are selected, and fresh milk is obtained through mechanized milking equipment. The raw milk is tested for protein, fat, non-fat milk solids, pH, acidity, and total bacterial count to ensure compliance with the GB19301 national standard for raw milk. It is then stored in a cold chain environment at 2-6℃ to maintain its freshness and taste. The qualified raw milk undergoes cooling and clarification at 2℃ to ensure freshness. It is then sieved through an 80-mesh screen and centrifuged at 4000 rpm to remove bacteria, foreign matter, and other impurities.

[0195] (2) Degassing:

[0196] The purified emulsion was degassed at a temperature of 50°C and a degassed pressure of -0.09 bar.

[0197] (3) Homogeneous:

[0198] The degassed liquid was homogenized in a sterile environment at a pressure of 30 / 170 bar and a temperature of 65°C.

[0199] (4) Physical sterilization:

[0200] The sterilization separator is used to physically sterilize and separate the liquid in step (3) to further remove microorganisms from the liquid. The speed of the sterilization separator is 5000 rpm and the separation temperature is 50℃.

[0201] (5) Pasteurization:

[0202] The liquid obtained in step (4) was sterilized at 65°C and kept at the sterilization temperature for 35 minutes.

[0203] (6) Filling:

[0204] The liquid obtained in step (5) is cooled to 4°C and then filled.

[0205] Comparative Example 7:

[0206] This comparative example provides a method for preparing sterilized fresh milk as follows:

[0207] (1) Cleansing milk:

[0208] Healthy dairy cows from large-scale dairy farms are selected, and fresh milk is obtained through mechanized milking equipment. The raw milk is tested for protein, fat, non-fat milk solids, pH, acidity, and total bacterial count to ensure compliance with the GB19301 national standard for raw milk. It is then stored in a cold chain environment at 2-6℃ to maintain its freshness and taste. The qualified raw milk undergoes cooling and clarification at 2℃ to ensure freshness. It is then sieved through an 80-mesh screen and centrifuged at 4000 rpm to remove bacteria, foreign matter, and other impurities.

[0209] (2) Degassing:

[0210] The purified emulsion was degassed at a temperature of 50°C and a degassed pressure of -0.09 bar.

[0211] (3) Homogeneous:

[0212] The degassed liquid was homogenized in a sterile environment at a pressure of 30 / 170 bar and a temperature of 65°C.

[0213] (4) Physical sterilization:

[0214] The sterilization separator is used to physically sterilize and separate the liquid in step (3) to further remove microorganisms from the liquid. The speed of the sterilization separator is 5000 rpm and the separation temperature is 50℃.

[0215] (5) Pulsed electric field sterilization:

[0216] The liquid in step (4) is subjected to pulsed electric field sterilization with a sterilization field strength of 60kV / cm and a pulse number of 2000.

[0217] (6) Pasteurization:

[0218] The liquid obtained in step (5) was sterilized at 62°C and kept at the sterilization temperature for 25 minutes.

[0219] (7) Filling:

[0220] The liquid obtained in step (6) is cooled to 4°C and then filled.

[0221] Product experimental technology results:

[0222] Table 1

[0223]

[0224]

[0225] The physicochemical indicators of the samples are shown in Table 1. The protein content of the raw milk is 3.0-3.4g / 100g, the sodium content is 50-60mg / 100g, the calcium content is 100-130mg / 100g, and the lactose content is 4.5-6.0g / 100g. As can be seen from Table 1, the protein content of Examples 1 to 6, which used pulsed electric field sterilization, is higher than that of Comparative Examples 1 to 7, and the protein content, sodium content, calcium content, and lactose content are still within the same range as those of the raw milk.

[0226] Table 2

[0227] sample pH Acidity / °T Fresh milk 6.80 13.4 Example 1 6.78 14.8 Example 2 6.77 14.9 Example 3 6.77 15.1 Example 4 6.76 15.0 Example 5 6.78 14.8 Example 6 6.77 14.9 Comparative Example 1 6.70 15.8 Comparative Example 2 6.70 15.8 Comparative Example 3 6.72 15.5 Comparative Example 4 6.68 16.0 Comparative Example 5 6.66 16.2 Comparative Example 6 6.67 16.1 Comparative Example 7 6.66 16.2

[0228] The pH and acidity measurement results of the samples are shown in Table 2. The pH of Examples 1 to 6 was between 6.76 and 6.78, and the acidity was between 14.8 and 15.1°T. In contrast, the pH of Comparative Examples 1 to 7 was between 6.66 and 6.72, and the acidity was between 15.5 and 16.2°T. After sterilization treatment with a pulsed electric field with specific parameters, the pH of Examples 1 to 6 increased significantly compared to Comparative Examples 1 to 7, and the acidity decreased significantly. During the heat treatment, some lactose in the raw milk degrades to produce organic acids, which affects the shelf life and quality of the product.

[0229] Table 3

[0230]

[0231] The content of active substances in the samples is shown in Table 3. Samples from Examples 1 to 6 have higher levels of nutritionally active substances, and the furosine content is controlled to be ≤10 mg / 100g protein. In contrast, samples from Comparative Examples 1 to 7 have furosine content ≥10 mg / 100g protein, with Comparative Example 4 having the highest furosine content at 17.0 mg / 100g protein. The immunoglobulin content in samples from Examples 1 to 6 is between 300-330 mg / L, while the immunoglobulin content in Comparative Examples 1 and 4 is extremely low, exceeding the instrument's detection range. Excessive temperature during the processing of raw milk can severely affect the content of active proteins and furosine in the final sample, thereby reducing the nutritional value of the product.

[0232] Table 4

[0233]

[0234] Table 5

[0235]

[0236]

[0237] The taste and flavor scoring criteria for milk are shown in Table 4. The test participants were 30 people. Thirteen milk samples were placed in front of each person. Each person tasted each sample in turn. Between tasting any two samples, each person rinsed their mouth with water for 30 seconds to remove the taste of the previous sample. After tasting, each person scored the samples according to Table 4. The average score of the samples was taken as the final result. As can be seen from the flavor evaluation table in Table 5, the milk obtained by applying pulsed electric field sterilization, pasteurization, and sterilization separation machine (Examples 1-6, Comparative Examples 1-7) showed that Examples 1-6 effectively enhanced the milk aroma and improved the taste compared to Comparative Examples 1-7. Comparative Example 1, due to the use of direct steam injection sterilization, destroyed the volatile components in the fresh milk, reduced the generation of aroma substances, and had a weak milk aroma, which seriously affected the taste. Comparative Example 2, using MF membrane sterilization and separation sterilization of skim milk and cream, decomposed the volatile substances in the milk, weakening the taste. Comparative Example 3, using pasteurization and separation sterilization of skim milk and cream, reduced the generation of a large number of aroma substances in the fresh milk, resulting in a weak milk aroma and seriously affecting the taste. It can be seen that unsuitable sterilization methods, sterilization parameters, and unsuitable sterilization processes can all affect the milk aroma content.

[0238] Regarding the cooked flavor, when using the same batch of fresh milk, pulsed electric field sterilization showed a significant improvement in flavor. This is because using pulsed electric field sterilization at a lower temperature reduces the impact of prolonged high temperatures on the milk's flavor and structure, resulting in less cooked flavor and thus minimizing flavor changes caused by the sterilization process. Furthermore, specific pulsed electric field sterilization parameters allow the milk to produce more milky aroma components and fewer cooked flavor components. In terms of preference, the level of preference is mainly related to the ratio of milky aroma to cooked flavor. The preference for Examples 1 to 6 was significantly higher than that for Comparative Examples 1 to 7.

[0239] Table 6

[0240]

[0241] The total bacterial count was determined according to GB 4789.2 "National Food Safety Standard - Microbiological Examination of Food - Total Bacterial Count". Table 6 shows the effect of different sterilization methods on the microorganisms of the samples. It can be seen that the milk products of Examples 1 to 6 of this invention had very low total bacterial counts on day 42. While ensuring the product's taste, this significantly improved the biosafety of the milk products and extended their shelf life. Overall, the process in Example 1 yielded the best milk quality, with a relatively high content of nutritionally active substances, ensuring high nutritional activity and biosafety, and effectively extending the product's shelf life.

Claims

1. Fresh cow milk based on pulsed electric field sterilization, wherein, The fresh milk meets the following requirements: Milk native protein content ≤ 3.4g / 100g ≤ 4.0g / 100g; Furfurylic acid content less than or equal to 10 mg / 100g protein; Lactoferrin at a concentration of ≥80 mg / L; Immunoglobulins at a concentration of 300 mg / L or higher.

2. The method for preparing fresh cow milk based on the pulsed electric field sterilization according to claim 1, comprising the steps of: Milk purification, degassing, homogenization, physical sterilization, pulsed electric field sterilization, pasteurization; The pulsed electric field sterilization includes the following steps: The liquid material after physical sterilization is subjected to pulsed electric field sterilization with a pulsed electric field strength of 35-45kV / cm and a pulse number of 1000-2000 to obtain the liquid material after pulsed electric field sterilization.

3. The preparation method according to claim 2, wherein, The milk purification process includes the following steps: The raw milk that has passed the test is cooled and purified. The cooled and purified raw milk is then passed through an 80-600 mesh sieve to obtain a liquid. The liquid is then centrifuged at a speed of 4000-6000 rpm to obtain a purified liquid.

4. The preparation method according to claim 3, wherein, The temperature of the cooled milk is 2-10℃.

5. The method of making according to any one of claims 2-4, wherein, The degassing process includes the following steps: The emulsion solution after the purification process is degassed at 50-65°C and the degassed pressure is -0.04 bar to -0.09 bar to obtain the emulsion solution after the degassed step.

6. The method of making according to any one of claims 2 or 5, wherein, The homogenization process includes the following steps: The degassed liquid is homogenized at 50-65°C. The homogenization pressure is adjusted by first setting the secondary pressure to 30 bar and then the primary pressure to 170-220 bar to obtain the homogenized liquid.

7. The method of making according to any one of claims 2 or 6, wherein, The physical sterilization process includes the following steps: The homogenized liquid is sterilized by a sterilization separator at a temperature of 50-60℃ and a centrifugation speed of 5000-10000rpm to obtain the liquid after physical sterilization treatment.

8. The production method according to claim 2, wherein The pasteurization process includes the following steps: The liquid material treated with the pulsed electric field sterilization was then subjected to low-intensity pasteurization at 62-65°C for 25-35 minutes to obtain fresh milk sterilized by pulsed electric field sterilization.

9. The production method according to claim 2, wherein, The pasteurization process includes the following steps: The liquid material treated with the pulsed electric field sterilization was then subjected to low-intensity pasteurization at 72-75°C for 12-15 seconds to obtain fresh milk sterilized by pulsed electric field sterilization.

10. The production method according to claim 9, wherein The pasteurization is performed using a plate sterilizer and / or a tubular sterilizer.

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