A high-nutrition, long-shelf-life room-temperature milk and its preparation method

Abstract

This invention discloses a high-nutrition, long-shelf-life room-temperature milk and its preparation method. The method includes milk purification, concentration, fat separation to obtain cream and skim milk, high-temperature sterilization of the cream, double-effect centrifugation sterilization of the skim milk, microfiltration sterilization of the skim milk, fat backfilling, homogenization, direct sterilization, and further homogenization. A low-temperature stabilization step is included before or after the direct sterilization step, wherein the low-temperature stabilization process is performed at 45-65℃ for 3-15 minutes. The direct sterilization is performed by steam immersion or steam injection, with a sterilization temperature of 131℃-157℃ and a sterilization time of 0.09-2 seconds. The product produced by this invention can be predicted using the Q value to determine the likelihood of bitterness. This invention achieves a longer shelf life while retaining more active substances, and does not develop bitterness within the shelf life, resulting in a better taste.

Description

Technical Field

[0001] This invention relates to the field of room temperature milk, specifically to a high-nutrition, long-shelf-life room temperature milk and its preparation method. Background Technology

[0002] High nutritional value is a consumer demand trend and also a current development trend in dairy products. More and more consumers believe that nutrition is the most important factor in evaluating the quality of food and beverages, and milk is an excellent source of nutrition. In addition to providing the nutrients needed by humans and animals, milk proteins also possess a variety of bioactive functions. In particular, whey proteins such as α-lactalbumin, β-lactoglobulin, lactoferrin, and immunoglobulins have been proven to exert multiple effects, including inhibiting pathogens, regulating immunity, promoting growth, anti-inflammation, anti-oxidation, and anti-tumor activity.

[0003] Currently, although commercially available pasteurized fresh milk can retain a high content of active substances, its shelf life is usually only 3-7 days. After the shelf life, the system will break down and taste bitter. Moreover, the short shelf life is not conducive to long-distance transportation and requires strong supply chain and cold chain transportation capabilities, so the sales range of the product is small.

[0004] Most commercially available long-shelf-life pure milk uses tubular UHT sterilization, which is generally carried out at a temperature of 137±2℃ for 4-6 seconds. The sterilization intensity is high, which can extend the shelf life of the product to 6 months at room temperature (25-35℃). However, the severe heat treatment leads to serious loss of nutrients in the milk, the appearance of a cooked taste during the shelf life, and a significant reduction in active substances.

[0005] To better avoid nutrient loss and ensure a shelf life that meets transportation requirements, the sterilization intensity is often appropriately reduced to maintain a 3-month shelf life while increasing nutrient content, thus preventing the development of bitterness or cooked taste within that period. However, in practice, it has been verified that using existing conventional processing techniques, regardless of adjustments to the sterilization intensity, even when milk stored at room temperature for 3 months meets the following high-nutrition indicators:

[0006] Protein 3.6-4.0g / 100g; furosine ≤20mg / 100g; lactulose ≤40mg / L; α-lactalbumin ≥800mg / L; β-lactoglobulin ≥1200mg / L; lactoferrin ≥5mg / kg; immunoglobulin ≥1700μg / kg. Summary of the Invention

[0007] Therefore, the technical problem to be solved by the present invention is that the existing long shelf-life room temperature milk with a shelf life of up to 3 months cannot meet the high nutritional index; and thus provides a high nutritional long shelf-life room temperature milk that meets the high nutritional index and has no bitterness during the 3-month shelf life, as well as its preparation method.

[0008] Therefore, the present invention provides the following technical solution:

[0009] A method for preparing high-nutrition, long-shelf-life room-temperature milk includes: milk purification, concentration, fat separation to extract cream and skim milk, high-temperature sterilization of cream, double-effect centrifugation sterilization of skim milk, microfiltration sterilization of skim milk, fat refilling, homogenization, direct sterilization, and homogenization.

[0010] The direct sterilization step is preceded or followed by a low-temperature stabilization step, wherein the low-temperature stabilization process involves treating the sample at 45-65°C for 3-15 minutes.

[0011] The direct sterilization method is steam immersion or steam injection sterilization, with a sterilization temperature of 131℃-157℃ and a sterilization time of 0.09-2s.

[0012] The high-nutrition, long-shelf-life room-temperature milk prepared should meet the following conditions after being stored for 3 months:

[0013] Protein 3.6-4.0g / 100g; furosine ≤20mg / 100g; lactulose ≤40mg / L; α-lactalbumin ≥800mg / L; β-lactoglobulin ≥1200mg / L; lactoferrin ≥5mg / kg; immunoglobulins ≥1700μg / kg;

[0014] Preferably, the protein content is 3.6-4.0 g / 100 g; furosine ≤16 mg / 100 g; lactulose ≤40 mg / L; α-lactalbumin ≥900 mg / L; β-lactoglobulin ≥1300 mg / L; lactoferrin ≥10 mg / kg; and immunoglobulin ≥1800 μg / kg.

[0015] The process of double-effect centrifugation sterilization of the skim milk involves at least two centrifugation sterilization processes, with the parameters being 45-60℃, 4000-6000r / min, and a running time of 40-80s.

[0016] The microfiltration membrane for the skim milk sterilization process has a pore size of 0.8-1.0 μm, a temperature of 45-55℃, and a flow rate of 5-15 m / s.

[0017] Before separating the fat into cream and skim milk, a deoxygenation step is included. Preferably, a deoxygenation membrane is used in the deoxygenation step. Specifically, in the deoxygenation step, the oxygen concentration after deoxygenation is reduced to 1-5 ppm by membrane separation using a deoxygenation membrane.

[0018] The process of purifying the milk is as follows: first, filter the milk through a 50-150 mesh screen, and then purify it at 50-55℃ and 4000-6000rpm.

[0019] In the concentration step, the protein content after concentration reaches 3.6-4.0g / 100g, and the concentration temperature is 4-7℃.

[0020] In the fat separation step, the separation temperature is 45-60℃, and the fat content in the separated skim milk is ≤0.5g / 100g.

[0021] The parameters for high-temperature sterilization of the light cream are: 135-154℃, 0.09-3s.

[0022] The fat backfilling process involves mixing and homogenizing separately sterilized light cream and skim milk.

[0023] The homogenization temperature is 65-80℃, the total homogenization pressure is 230-280 bar, and the secondary pressure is 40-60 bar.

[0024] A high-nutrition, long-shelf-life room-temperature milk is prepared using the above-mentioned method for preparing a high-nutrition, long-shelf-life room-temperature milk.

[0025] The technical solution of this invention has the following advantages:

[0026] 1. This invention provides a method for preparing high-nutrition, long-shelf-life room-temperature milk. This method combines dual-effect centrifugation sterilization and microfiltration sterilization to significantly reduce bacterial and spore content. Specifically, dual-effect centrifugation sterilization at the front end removes 99% of bacteria and spores from the raw milk. Combined with microfiltration sterilization, this further reduces bacterial and spore content, allowing for a reduction in the intensity of direct steam sterilization. Consequently, while achieving a 3-month shelf life, more active substances in the milk can be retained. However, during the research and development process, it was found that, while meeting the 3-month shelf life requirement, room-temperature stored milk, after 3 months of storage, failed to meet the following high-nutrition indicators: protein 3.6-4.0g / 100g; furosine ≤20mg / 100g; lactulose ≤40mg / L; α-lactalbumin ≥800mg / L; β-lactoglobulin ≥1200mg / L; lactoferrin ≥5mg / kg; immunoglobulins ≥1700μg / kg. During the research, it was discovered that the reason why the shelf life could not be guaranteed was that the milk tasted bitter during storage. The inventors found that the bitter taste was caused by the production of bitter peptides after certain proteins were hydrolyzed by enzymes. To avoid the production of bitter peptides, the only way is to remove the proteins that produce bitter peptides or inactivate the enzymes that decompose proteins. The conventional method of inactivating enzymes is high-temperature inactivation, which inactivates all enzymes at the same time. The high-temperature enzyme inactivation process inevitably affects the content of active substances, making it impossible to further increase the content of active substances. As a result, the room-temperature milk prepared cannot meet the above-mentioned high nutritional index requirements. Based on the findings of the above-mentioned problems, the inventors innovatively added a low-temperature stabilization step before or after the direct sterilization step. This step effectively inactivates the enzymes that produce bitter peptides, slowing down the decomposition of proteins by the enzymes during later storage. Therefore, the sterilization intensity can be further reduced, ensuring that the product will not develop bitterness within a 3-month shelf life under a lower sterilization intensity. This achieves the requirement of a bitter taste and high nutritional value even within a long shelf life of up to 3 months. Furthermore, the room-temperature milk of this invention can predict the likelihood of bitterness in the product through the Q value.

[0027] 2. The deoxygenation technology used in the preparation method provided by this invention can reduce the oxygen concentration after deoxygenation to 1-5 ppm. This method can reduce the cooking taste caused by the sterilization process and make the product taste better. Specifically, conventional vacuum degassing methods generally have a processing temperature of 65℃-72℃, while this invention preferably uses membrane separation method (deoxygen membrane gas replacement) to reduce the oxygen concentration. The deoxygenation temperature of this method is lower, generally between 5-25℃, which has virtually no impact on the active ingredients in the product. Moreover, using a deoxygenation membrane to quantify the oxygen content allows for better control of oxygen during the product production process, thereby improving the product's taste.

[0028] Furthermore, the enzyme activity test results show that the use of vacuum degassing results in a higher level of protease than the deoxygenation membrane process. This indicates that the use of deoxygenation membranes not only achieves the aforementioned deoxygenation to improve taste and increase the content of active substances, but also has a significant effect of reducing enzyme activity, thereby achieving the unexpected effect of further extending the product's shelf life at room temperature. Detailed Implementation

[0029] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0030] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0031] Example 1:

[0032] A high-nutrition, long-shelf-life, room-temperature milk is prepared as follows:

[0033] 1. Raw milk pretreatment: Raw milk is used as raw milk. It is filtered through a 50-mesh filter to remove larger impurities or foreign objects. It is then preheated to 50°C and centrifuged in a milk purifier at 4000 rpm to remove most impurities and somatic cells.

[0034] 2. Concentrate using an RO membrane to a concentration of 3.6g / 100g at a temperature of 4℃;

[0035] 3. Deoxygenation: The membrane separation method using a deoxygenation membrane is adopted. The deoxygenation membrane uses a hollow fiber membrane (Mitsubishi Rayon Corporation, MHF304KM) to remove oxygen to 1 ppm at a temperature of 5℃.

[0036] 4. Fat separation at 45℃, skim milk fat content 0.5g / 100g;

[0037] 5. High-temperature sterilization of light cream: 135℃ for 3 seconds;

[0038] 6. Dual-effect sterilization: two centrifugal sterilizers connected in series, with parameters of 45℃, 6000r / min, and a running time of 40s;

[0039] 7. Microfiltration sterilization: microfiltration membrane pore size 0.8-1.0μm, temperature 45℃, flow rate 5m / s;

[0040] 8. Fat backfilling, homogenization, 65℃, total pressure 280 bar, secondary pressure 60 bar;

[0041] 9. Low temperature stability, 45℃, 15min;

[0042] 10. Direct steam sterilization, either steam immersion or steam injection, 131℃, 2s;

[0043] 11. Homogenize, aseptically homogenize, 65°C, total pressure 280 bar, secondary pressure 60 bar;

[0044] 12. Aseptic filling: The cooled milk is aseptically filled.

[0045] Example 2:

[0046] A high-nutrition, long-shelf-life, room-temperature milk is prepared as follows:

[0047] 1. Raw milk pretreatment: Raw milk is used as raw milk. It is filtered through a 150-mesh filter to remove larger impurities or foreign objects. It is then preheated to 55°C and centrifuged in a milk purifier at 4500 rpm to remove most impurities and somatic cells.

[0048] 2. Concentrate using an RO membrane to a concentration of 4.0g / 100g at a temperature of 7℃;

[0049] 3. Deoxygenation: The membrane separation method using a deoxygenation membrane is adopted. The deoxygenation membrane uses a hollow fiber membrane (Mitsubishi Rayon Corporation, MHF304KM) to remove oxygen to 5 ppm at a temperature of 25℃.

[0050] 4. Fat separation at 60℃, skim milk fat content 0.1g / 100g;

[0051] 5. The heavy cream is sterilized at high temperature: 154℃ for 0.09 seconds.

[0052] 6. Dual-effect sterilization: two centrifugal sterilizers connected in series, with parameters of 60℃, 4000r / min, and a running time of 80s;

[0053] 7. Microfiltration sterilization: microfiltration membrane pore size 0.8-1.0μm, temperature 55℃, flow rate 15m / s;

[0054] 8. Fat backfilling, homogenization, 80℃, total pressure 230 bar, secondary pressure 40 bar;

[0055] 9. Low temperature stability, 65℃, 3 min;

[0056] 10. Direct steam sterilization, either steam immersion or steam injection, 157℃, 0.09s;

[0057] 11. Homogenize, aseptically homogenize, 80℃, total pressure 230 bar, secondary pressure 40 bar;

[0058] 12. Aseptic filling: The cooled milk is aseptically filled.

[0059] Example 3:

[0060] A high-nutrition, long-shelf-life, room-temperature milk is prepared as follows:

[0061] 1. Raw milk pretreatment: Raw milk is used as raw milk. It is filtered through a 60-mesh filter to remove larger impurities or foreign objects. It is then preheated to 53°C and centrifuged in a milk purifier at 6000 rpm to remove most impurities and somatic cells.

[0062] 2. Concentrate using an RO membrane to a concentration of 3.8g / 100g at a temperature of 5℃;

[0063] 3. Deoxygenation: The membrane separation method using a deoxygenation membrane is adopted. The deoxygenation membrane uses a hollow fiber membrane (Mitsubishi Rayon Corporation, MHF304KM) to remove oxygen to 3ppm at a temperature of 10℃.

[0064] 4. Fat separation at 55℃, skim milk fat content 0.3g / 100g;

[0065] 5. High-temperature sterilization of light cream: 137℃ for 2 seconds;

[0066] 6. Dual-effect sterilization: two centrifugal sterilizers connected in series, with parameters of 54℃, 6000r / min, and a running time of 60s;

[0067] 7. Microfiltration sterilization: microfiltration membrane pore size 0.8-1.0μm, temperature 50℃, flow rate 10m / s;

[0068] 8. Fat backfilling, homogenization, 65℃, total pressure 240 bar, secondary pressure 45 bar;

[0069] 9. Direct steam sterilization, either steam immersion or steam injection, 140℃, 2s;

[0070] 10. Low temperature stability, 50℃, 10min;

[0071] 11. Homogenize, aseptically homogenize, 75°C, total pressure 230 bar, secondary pressure 40 bar;

[0072] 12. Aseptic filling: The cooled milk is aseptically filled.

[0073] Example 4:

[0074] A high-nutrition, long-shelf-life, room-temperature milk is prepared as follows:

[0075] 1. Raw milk pretreatment: Raw milk is used as raw milk. It is filtered through a 110-mesh filter to remove larger impurities or foreign objects. It is then preheated to 52°C and centrifuged in a milk purifier at 5500 rpm to remove most impurities and somatic cells.

[0076] 2. Concentrate using an RO membrane to a concentration of 3.9g / 100g at a temperature of 8℃;

[0077] 3. Deoxygenation: The membrane separation method using a deoxygenation membrane is adopted. The deoxygenation membrane uses a hollow fiber membrane (Mitsubishi Rayon Corporation, MHF304KM) to remove oxygen to 4 ppm at a temperature of 15℃.

[0078] 4. Fat separation at 50℃, skim milk fat content 0.4g / 100g;

[0079] 5. The heavy cream is sterilized at high temperature: 145℃ for 0.09 seconds.

[0080] 6. Dual-effect sterilization: two centrifugal sterilizers connected in series, with parameters of 56℃, 5500r / min, and a running time of 60s;

[0081] 7. Microfiltration sterilization: microfiltration membrane pore size 0.8-1.0μm, temperature 47℃, flow rate 8m / s;

[0082] 8. Fat backfilling, homogenization, 75℃, total pressure 260 bar, secondary pressure 55 bar;

[0083] 9. Direct steam sterilization, either steam immersion or steam injection, 150℃, 0.09s;

[0084] 10. Low temperature stability, 65℃, 4min;

[0085] 11. Homogenize, aseptically homogenize, 70°C, total pressure 240 bar, secondary pressure 45 bar;

[0086] 12. Aseptic filling: The cooled milk is aseptically filled.

[0087] Example 5:

[0088] A high-nutrition, long-shelf-life, room-temperature milk is prepared as follows:

[0089] 1. Raw milk pretreatment: Raw milk is used as raw milk. It is filtered through a 90-mesh filter to remove larger impurities or foreign objects. It is then preheated to 54°C and centrifuged in a milk purifier at 5000 rpm to remove most impurities and somatic cells.

[0090] 2. Concentrate using an RO membrane to a concentration of 3.7g / 100g at a temperature of 6℃;

[0091] 3. Deoxygenation: The membrane separation method using a deoxygenation membrane is adopted. The deoxygenation membrane uses a hollow fiber membrane (Mitsubishi Rayon Corporation, MHF304KM) to remove oxygen to 2ppm at a temperature of 20℃.

[0092] 4. Fat separation at 53℃, skim milk fat content 0.2g / 100g;

[0093] 5. High-temperature sterilization of light cream: 140℃ for 1 second;

[0094] 6. Dual-effect sterilization: two centrifugal sterilizers connected in series, with parameters of 55℃, 5700r / min, and a running time of 60s;

[0095] 7. Microfiltration sterilization: microfiltration membrane pore size 0.8-1.0μm, temperature 51℃, flow rate 9m / s;

[0096] 8. Fat backfilling, homogenization, 70℃, total pressure 250 bar, secondary pressure 50 bar;

[0097] 9. Direct steam sterilization, either steam immersion or steam injection, 145℃, 1s;

[0098] 10. Low temperature stability, 55℃, 5min;

[0099] 11. Homogenize, aseptically homogenize, 70°C, total pressure 250 bar, secondary pressure 50 bar;

[0100] 12. Aseptic filling: The cooled milk is aseptically filled.

[0101] Example 6:

[0102] A high-nutrition, long-shelf-life, room-temperature milk is prepared as follows:

[0103] 1. Raw milk pretreatment: Raw milk is used as raw milk. It is filtered through a 90-mesh filter to remove larger impurities or foreign objects. It is then preheated to 54°C and centrifuged in a milk purifier at 5000 rpm to remove most impurities and somatic cells.

[0104] 2. Concentrate using an RO membrane to a concentration of 3.7g / 100g at a temperature of 6℃;

[0105] 3. Vacuum degassing, with a vacuum degree of -0.065MPa and a temperature of 65℃.

[0106] 4. Fat separation at 53℃, skim milk fat content 0.2g / 100g;

[0107] 5. High-temperature sterilization of light cream: 140℃ for 1 second;

[0108] 6. Dual-effect sterilization: two centrifugal sterilizers connected in series, with parameters of 55℃, 5700r / min, and a running time of 60s;

[0109] 7. Microfiltration sterilization: microfiltration membrane pore size 0.8-1.0μm, temperature 51℃, flow rate 9m / s;

[0110] 8. Fat backfilling, homogenization, 70℃, total pressure 250 bar, secondary pressure 50 bar;

[0111] 9. Direct steam sterilization, either steam immersion or steam injection, 145℃, 1s;

[0112] 10. Low temperature stability, 55℃, 5min;

[0113] 11. Homogenize, aseptically homogenize, 70°C, total pressure 250 bar, secondary pressure 50 bar;

[0114] 12. Aseptic filling: The cooled milk is aseptically filled.

[0115] Comparative Example 1:

[0116] A type of pasteurized milk, the preparation method of which is as follows:

[0117] 1. The raw milk is purified by cooling at 2°C to obtain a liquid mixture;

[0118] 2. The obtained liquid is preheated to 55°C for 5 seconds and degassed at 55°C with a degassed pressure of -0.04 MPa.

[0119] 3. The degassed liquid is centrifuged at 55℃ to remove fat, resulting in light cream and skim milk. The fat content of the light cream is 45g / 100g, and the fat content of the skim milk is ≤0.06g / 100g.

[0120] 4. Sterilize the obtained cream at 115℃ for 15 seconds, then cool it to 30℃ for 10 seconds.

[0121] 5. Remove the spores from the obtained skim milk using a sterilization separator at 55°C. The centrifugal force is 5000g. The resulting liquid is then filtered through a 0.5μm MF microfiltration system to remove microorganisms from the skim milk. The filtration pressure is 4 bar and the filtration temperature is 55°C.

[0122] 6. Mix the filtrates from steps (4) and (5) online at a mixing temperature of 55°C. Homogenize at 55°C at a homogenization pressure of 230 bar. After 10 seconds, raise the temperature to 72°C. After 15 seconds of tubular sterilization at 72°C, lower the temperature to 2°C after 30 seconds and fill the container to obtain the product.

[0123] Comparative Example 2:

[0124] A type of room-temperature milk, prepared as follows:

[0125] 1. Raw milk pretreatment: Raw milk is used as raw milk. It is filtered through a 50-mesh filter to remove larger impurities or foreign objects. It is then preheated to 50°C and centrifuged in a milk purifier at 4000 rpm to remove most impurities and somatic cells.

[0126] 2. Concentrate using an RO membrane to a concentration of 3.6g / 100g at a temperature of 4℃;

[0127] 3. Deoxygenation: The membrane separation method using a deoxygenation membrane is adopted. The deoxygenation membrane uses a hollow fiber membrane (Mitsubishi Rayon Corporation, MHF304KM) to remove oxygen to 1 ppm at a temperature of 5℃.

[0128] 4. Fat separation at 45℃, skim milk fat content 0.5g / 100g;

[0129] 5. High-temperature sterilization of light cream: 135℃ for 3 seconds;

[0130] 6. Microfiltration sterilization: microfiltration membrane pore size 0.8-1.0μm, temperature 45℃, flow rate 5m / s;

[0131] 7. Fat backfilling, homogenization, 65℃, total pressure 280 bar, secondary pressure 60 bar;

[0132] 8. Stable at low temperatures, 45℃, 15min;

[0133] 9. Direct steam sterilization, either steam immersion or steam injection, 131℃, 2s;

[0134] 10. Homogenize, aseptically homogenize, 65°C, total pressure 280 bar, secondary pressure 60 bar;

[0135] 11. Aseptic filling: The cooled milk is aseptically filled.

[0136] Comparative Example 3:

[0137] A type of room-temperature milk, prepared as follows:

[0138] 1. Raw milk pretreatment: Raw milk is used as raw milk. It is filtered through a 150-mesh filter to remove larger impurities or foreign objects. It is then preheated to 55°C and centrifuged in a milk purifier at 4500 rpm to remove most impurities and somatic cells.

[0139] 2. Concentrate using an RO membrane to a concentration of 4.0g / 100g at a temperature of 7℃;

[0140] 3. Deoxygenation: The membrane separation method using a deoxygenation membrane is adopted. The deoxygenation membrane uses a hollow fiber membrane (Mitsubishi Rayon Corporation, MHF304KM) to remove oxygen to 5 ppm at a temperature of 25℃.

[0141] 4. Fat separation at 60℃, skim milk fat content 0.1g / 100g;

[0142] 5. The heavy cream is sterilized at high temperature: 154℃ for 0.09 seconds.

[0143] 6. Dual-effect sterilization: two centrifugal sterilizers connected in series, with parameters of 60℃, 4000r / min, and a running time of 80s;

[0144] 7. Microfiltration sterilization: microfiltration membrane pore size 0.8-1.0μm, temperature 55℃, flow rate 15m / s;

[0145] 8. Fat backfilling, homogenization, 80℃, total pressure 230 bar, secondary pressure 40 bar;

[0146] 9. Direct steam sterilization, either steam immersion or steam injection, 157℃, 0.09s;

[0147] 10. Homogenize, aseptically homogenize, 80℃, total pressure 230 bar, secondary pressure 40 bar;

[0148] 11. Aseptic filling: The cooled milk is aseptically filled.

[0149] Comparative Example 4:

[0150] A high-nutrition, long-shelf-life, room-temperature milk is prepared as follows:

[0151] 1. Raw milk pretreatment: Raw milk is used as raw milk. It is filtered through a 110-mesh filter to remove larger impurities or foreign objects. It is then preheated to 52°C and centrifuged in a milk purifier at 5500 rpm to remove most impurities and somatic cells.

[0152] 2. Concentrate using an RO membrane to a concentration of 3.9g / 100g at a temperature of 8℃;

[0153] 3. Deoxygenation: The membrane separation method using a deoxygenation membrane is adopted. The deoxygenation membrane uses a hollow fiber membrane (Mitsubishi Rayon Corporation, MHF304KM) to remove oxygen to 4 ppm at a temperature of 15℃.

[0154] 4. Fat separation at 50℃, skim milk fat content 0.4g / 100g;

[0155] 5. The heavy cream is sterilized at high temperature: 145℃ for 0.09 seconds.

[0156] 6. Dual-effect sterilization: two centrifugal sterilizers connected in series, with parameters of 56℃, 5500r / min, and a running time of 60s;

[0157] 7. Microfiltration sterilization: microfiltration membrane pore size 0.8-1.0μm, temperature 47℃, flow rate 8m / s;

[0158] 8. Fat backfilling, homogenization, 75℃, total pressure 260 bar, secondary pressure 55 bar;

[0159] 9. Direct steam sterilization, either steam immersion or steam injection, 148℃, 2.5s;

[0160] 10. Homogenize, aseptically homogenize, 70°C, total pressure 240 bar, secondary pressure 45 bar;

[0161] 11. Aseptic filling: The cooled milk is aseptically filled.

[0162] Experimental Example

[0163] 1. Analysis of indicator components after 3 months of storage at room temperature, and tracking of system and taste during room temperature storage.

[0164] The contents of protein, heat-sensitive substances, and bioactive substances in room-temperature milk obtained in the examples and comparative examples were detected after 3 months of storage at room temperature. The system and taste of the room-temperature milk during the storage process were also tracked. The results are shown in Table 1 below:

[0165] Table 1

[0166]

[0167] The results above show that the samples in Examples 1-6, after being stored at room temperature for 3 months, all met the requirements of the process and product design for protein, heat-sensitive substances (furfurine, lactulose), and bioactive substances (α-lactalbumin, β-lactoglobulin, lactoferrin, immunoglobulins). The system remained stable at room temperature for 3 months without developing a bitter taste. However, in Example 6, although the content of each component met the requirements of the process and product design, and no bitter taste developed during its shelf life, the lack of a deoxygenation process meant that residual oxygen in the raw milk participated in oxidation reactions during production and storage, leading to a fatty oxidation taste after 2.5 months, affecting palatability.

[0168] Comparative Example 1 used a combination of centrifugal sterilization and microfiltration sterilization, but only single-effect centrifugal sterilization, lacking deoxygenation and low-temperature stabilization processes. Samples produced using this process developed a noticeable bitter taste after 42 days, far short of the required 3-month shelf life at room temperature. Comparative Example 2, while employing low-temperature stabilization, relied solely on microfiltration instead of a combination of centrifugal and microfiltration sterilization, significantly reducing sterilization effectiveness. Bitterness appeared after two months, presumably due to enzyme decomposition of proteins by microorganisms. Comparative Example 3, without low-temperature stabilization, developed bitterness after 2 months at room temperature. Comparative Example 4, without low-temperature stabilization but with increased sterilization intensity, maintained a normal taste and did not develop bitterness for 3 months. However, after 3 months at room temperature (25-35℃), the levels of bioactive substances in the sample were significantly lower than in Examples 1-6. In summary, the results of Comparative Examples 1-3 show that none of them meet the requirements of system stability and no bitter taste at room temperature for 3 months of shelf life; although Comparative Example 4 can meet the requirements of system stability and no bitter taste at room temperature for 3 months of shelf life, the bioactive substances do not meet the design requirements.

[0169] 2. Taste preference test

[0170] Preference rating tests were conducted on the products from Examples 5 and 6 after being stored at room temperature for 3 months. A total of 50 people participated in the test. The rating rules are shown in Table 2, and the test results (number of participants) are shown in Table 3.

[0171] Table 2

[0172]

[0173] Table 3

[0174]

[0175] The test results above show that after 3 months of storage at room temperature, the sample produced using the process of Example 5 scored 354, while the sample produced using the process of Example 6 scored 81. The consumer preference test results indicate that using a deoxidizing film significantly improves the product's taste over its shelf life.

[0176] Vacuum degassing typically operates at 65℃-72℃, while deoxygenation membrane deoxygenation operates at a lower temperature, typically 5-25℃. Based on the data from Examples 5 and 6 in Table 1, it can be seen that the deoxygenation membrane used in Example 5 has virtually no impact on the active ingredients in the product. Compared to vacuum degassing, the active ingredient content in the product is higher. Furthermore, using a deoxygenation membrane to quantify the oxygen content allows for better control over the oxygen content during the product manufacturing process.

[0177] 3. Prediction of bitter substances

[0178] According to the rule proposed by Ney (1979), the hydrophobicity of a peptide (expressed as a Q value) can be used to predict its bitterness. The average hydrophobicity Q of a peptide is calculated by dividing the sum of the hydrophobicities of the amino acid side chains by the number of amino acid residues in the peptide. This principle suggests that a Q value higher than 1400 cal / mol is considered bitter.

[0179] Existing research has found that bitter peptides in cow's milk mainly originate from the hydrolysis of milk proteins. Nielsen et al. studied the peptide β-CNf(208-222), which has a mass of 1668.52 Da and a Q value of 1730 cal / mol. Their study showed that the peptide β-CNf(208-222) increases during the storage of UHT milk products, and this peptide has been confirmed to cause bitterness in milk.

[0180] 3.1 Detection of protease activity in the finished product

[0181] The protease activity of the finished products of Examples 1-6 and Comparative Examples 1-4 was detected by GB / T 23527 method for detecting enzyme activity in protease preparations. The results are shown in Table 4.

[0182] 3.2 The peptide β-CN f(208-222) in the finished products of Examples 1-6 and Comparative Examples 1-4 after offline and room temperature storage for 3 months was detected using the following detection methods:

[0183] Peptide profiling was performed using liquid chromatography-electrospray ionization tandem mass spectrometry ion trap.

[0184] Milk samples were diluted with 0.05 M NH4HCO3 (60 mL: 140 mL) and reduced by adding 10 mL of dithioerythritol (DTE) dissolved in 0.05 M NH4HCO3 (10 mg / mL). The samples were incubated at 60 °C for 10 min and then cooled to room temperature. The reduced milk samples were then added to 10 mL of iodoacetamide dissolved in 0.05 M NH4HCO3 (50 mg / mL) and incubated at 37 °C in the dark for 30 min. The milk was then precipitated with 1 M HCl and centrifuged at 18,500 × g for 5 min at 22 °C. The supernatant was filtered through a 10 kDa cutoff filter membrane (14,000 × g, 4 °C for 15 min). The peptide solution (10 mL) was loaded onto an Aeris Peptide C18 column (250 mm × 2.1 mm, 3.6 mm particle size, Phenomenex, Torrance, CA, USA) directly connected to an Agilent LC 1200 series superion trap (Bruker Daltonics, Frederikssund, Denmark). The LC eluent was initially set to 98% A (0.1% formic acid) and 2% B (0.1% formic acid solution in 80% acetonitrile) for 5 min, then increased to 40% B over 75 min, then increased to 80% B for another 5 min, and then held constant for 5 min. Mass scans in MS mode were set to 400–1800 m / z, and in MS / MS mode to 150–1800 m / z. Spectra were analyzed using Data Analysis and Biotools software (Bruker Daltonics).

[0185] The results of protease activity and the intensity of peptide β-CN f(208-222) in the chromatogram at different time points during the offline and room temperature shelf life are shown in Table 4 below.

[0186] Table 4

[0187]

[0188] Based on the activity test results of the protease at different time points during its shelf life at room temperature, the protease activity in the products of Examples 1-6 and Comparative Example 4 at the time of production was ≤362U / 100mL, which corresponds to the result that the taste was normal and no bitterness was produced after 3 months at room temperature. However, the protease activity of Comparative Examples 1-3 was >362U / 100mL, and bitterness was produced during the shelf life. Therefore, it can be inferred that if the protease activity of the samples at the time of production was ≤362U / 100mL, bitterness would not be produced after 3 months at room temperature. In addition, Example 6 used vacuum degassing, and Examples 1-5 used deoxygenation membranes. The protease activity after production was higher due to vacuum degassing than that after deoxygenation membranes. This indicates that the use of deoxygenation membranes not only achieves the purpose of deoxygenation to improve taste and increase the content of active substances, but also has a significant effect on reducing enzyme activity, thereby further extending the shelf life of the product at room temperature.

[0189] The detection results of peptide β-CN f(208-222) show that: in Examples 1-6 and Comparative Example 4, peptide β-CN f(208-222) was not detected in the samples after 3 months of storage at room temperature and below the detection limit. In Comparative Examples 1-3, it was not detected at the detection limit, but the intensity of β-CN f(208-222) gradually increased during the 3 months of storage at room temperature, which corresponds to the phenomenon of bitterness in the samples. Furthermore, since peptide β-CN f(208-222) was not detected in the samples of Examples 1-6 after 1 month of storage at room temperature, while it was present in the chromatograms of Comparative Examples 1-3, it can be inferred that if peptide β-CN f(208-222) is not detected in the samples after 1 month of storage at room temperature, it will not produce bitterness after 3 months of storage at room temperature.

[0190] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing high-nutrition, long-shelf-life, room-temperature milk, characterized in that, include: The process involves: milk purification, concentration, fat separation to produce cream and skim milk, high-temperature sterilization of cream, double-effect centrifugation sterilization of skim milk, microfiltration sterilization of skim milk, fat refilling, homogenization, direct sterilization, and homogenization. The direct sterilization step is preceded or followed by a low-temperature stabilization step, wherein the low-temperature stabilization process involves treating the sample at 45-65°C for 3-15 minutes. The direct sterilization is a steam immersion or steam injection sterilization, with a sterilization temperature of 131℃-157℃ and a sterilization time of 0.09-2s. The process of sterilizing skim milk by double centrifugation involves at least two centrifugation processes.

2. The preparation method according to claim 1, characterized in that, The parameters for centrifugal sterilization are 45-60℃, 4000-6000r / min, and a running time of 40-80s; The microfiltration membrane for the skim milk sterilization process has a pore size of 0.8-1.0 μm, a temperature of 45-55℃, and a flow rate of 5-15 m / s.

3. The preparation method according to claim 1 or 2, characterized in that, Before the fat is separated into cream and skim milk, a deoxygenation step is also included, after which the oxygen concentration is 1-5 ppm.

4. The preparation method according to claim 3, characterized in that, The deoxygenation process uses a deoxygenation membrane.

5. The preparation method according to claim 1 or 2, characterized in that, The process of purifying the milk is as follows: first, filter the milk through a 50-150 mesh screen, and then purify it at 50-55℃ and 4000-6000rpm.

6. The preparation method according to claim 1 or 2, characterized in that, In the concentration step, the protein content after concentration reaches 3.6-4.0g / 100g, and the concentration temperature is 4-7℃.

7. The preparation method according to claim 1 or 2, characterized in that, In the fat separation step, the separation temperature is 45-60℃, and the fat content in the separated skim milk is ≤0.5g / 100g.

8. The preparation method according to claim 1 or 2, characterized in that, The parameters for high-temperature sterilization of the light cream are: 135-154℃, 0.09-3s.

9. The preparation method according to claim 1 or 2, characterized in that, The fat backfilling process involves mixing separately sterilized light cream and skim milk.

10. The preparation method according to claim 1 or 2, characterized in that, The homogenization temperature is 65-80℃, the total homogenization pressure is 230-280 bar, and the secondary pressure is 40-60 bar.

11. A high-nutrition, long-shelf-life, room-temperature milk, characterized in that, The milk was prepared using the method described in any one of claims 1-10, which provides a high-nutrition, long-shelf-life, room-temperature milk.

12. The high-nutrition, long-shelf-life, room-temperature milk according to claim 11, characterized in that, The aforementioned high-nutrition, long-shelf-life room-temperature milk, when stored at room temperature for 3 months, contains the following components: protein 3.6-4.0g / 100g; furosine ≤20mg / 100g; lactulose ≤40mg / L; α-lactalbumin ≥800mg / L; β-lactoglobulin ≥1200mg / L; lactoferrin ≥5mg / kg; and immunoglobulins ≥1700μg / kg.

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