阅读说明：本技术 一种长货架期的常温牛奶及其制备方法 (Normal-temperature milk with long shelf life and preparation method thereof ) 是由 王秋岭 李艳君 张海斌 孙云峰 于 2019-11-28 设计创作，主要内容包括：本发明提供了一种长货架期的常温牛奶及其制备方法。该方法包括对牛奶进行物理除菌、标准化、蒸汽直接杀菌的步骤；所述标准化包括将脂肪分离,并于125-135℃进行10-15s的杀菌处理,然后再回填的过程；所述直接杀菌采用蒸汽浸入式杀菌或者蒸汽注入式杀菌的方式进行,杀菌温度为121-132℃,时间为1-4s。本发明通过对生牛乳进行物理除菌,对分离的乳脂肪进行高温杀菌,将标准化后的牛奶采用蒸汽浸入式杀菌或蒸汽注入式杀菌的方式并控制一定的参数条件进行杀菌,可以降低产品中蛋白质的变性率,减少营养物质的损失,提高产品整体风味,并且使乳产品具有较长的货架期。(The invention provides normal-temperature milk with a long shelf life and a preparation method thereof. The method comprises the steps of carrying out physical sterilization, standardization and direct steam sterilization on milk; the standardization comprises the processes of separating fat, sterilizing at the temperature of 125-135 ℃ for 10-15s, and then refilling; the direct sterilization is carried out by adopting a steam immersion sterilization or steam injection sterilization mode, the sterilization temperature is 121-132 ℃, and the time is 1-4 s. The invention can reduce the denaturation rate of protein in the product, reduce the loss of nutrient substances, improve the integral flavor of the product and enable the milk product to have longer shelf life by carrying out physical sterilization on the raw milk, carrying out high-temperature sterilization on the separated milk fat and carrying out sterilization on the standardized milk by adopting a steam immersion sterilization or steam injection sterilization mode and controlling certain parameter conditions.)

1. A preparation method of normal temperature milk with long shelf life comprises the steps of physically sterilizing and standardizing milk and directly sterilizing with steam;

wherein the standardization comprises the processes of separating fat, sterilizing at the temperature of 125-135 ℃ for 10-15s, and then refilling;

the direct sterilization is carried out by adopting a steam immersion sterilization or steam injection sterilization mode, the sterilization temperature is 121-132 ℃, and the time is 1-4 s.

2. The method for preparing according to claim 1, wherein the physical sterilization is performed by sterilizing with a sterilizing separator and/or sterilizing with a ceramic membrane microfiltration, and the temperature of the physical sterilization is 55-70 ℃.

3. The production method according to claim 1 or 2, wherein the fat separation is carried out by a centrifugal separator at 3500-5500rpm at a separation temperature of 55-70 ℃.

4. A method of production according to any one of claims 1 to 3, wherein the protein content of the separated fat is < 0.3 wt%; the fat content in the milk after fat separation was < 0.6 wt%.

5. The method according to any one of claims 1 to 4, wherein the fat obtained by the separation is sterilized by tubular sterilization or plate-and-tube sterilization.

6. The method according to any one of claims 1 to 5, wherein the standardized milk has a protein content of 3.0 to 3.5 wt% and a fat content of 0.6 to 4.0 wt%.

7. The method of any one of claims 1 to 6, wherein the method further comprises the step of flash evaporating or degassing the steam-sterilized milk; preferably, the temperature of the flash evaporation is 60-70 ℃; the degassing temperature is 60-70 ℃, and the degassing pressure is-0.07 bar to-0.09 bar.

8. The method of any one of claims 1 to 7, wherein the method further comprises the step of homogenising the flash or degassed milk; preferably, the temperature for homogenization is 60-65 ℃ and the pressure is 180-220 bar.

9. The method according to any one of claims 1 to 8, wherein the method comprises the following specific steps:

physical sterilization: physically sterilizing the raw milk by a sterilization separator and/or a ceramic membrane microfiltration sterilization mode at the temperature of 55-70 ℃;

and (3) standardization: separating fat in milk by using a centrifugal separator, wherein the rotating speed of the centrifugal separator is 3500-5500rpm, and the separation temperature is 55-70 ℃; the protein content of the separated fat is less than 0.3 wt%; the fat content in the milk after fat separation is < 0.6 wt%; sterilizing the separated fat at 135 deg.C for 10-15s by tubular sterilization or plate-changing sterilization, and refilling the fat to complete standardization, wherein the standardized milk has a protein content of 3.0-3.5 wt% and a fat content of 0.6-4.0 wt%;

direct steam sterilization: performing steam direct sterilization on the milk by adopting a steam immersion sterilization or steam injection sterilization mode, wherein the sterilization temperature is 121-;

flash evaporation or degassing: removing water vapor mixed into the milk or gas existing in the milk by a flash evaporation or degassing mode, wherein the temperature is 60-70 ℃, and the degassing pressure is-0.07 bar to 0.09 bar;

homogenizing: homogenizing the milk at 60-65 deg.C under the pressure of 180-220 bar;

and (3) cooling: and cooling the milk to obtain the normal-temperature milk with long shelf life.

10. A long shelf life ambient milk prepared by the method of any one of claims 1-9;

wherein, the normal temperature milk with long shelf life meets the following index requirements:

Technical Field

The invention relates to the field of dairy products, in particular to normal-temperature milk with a long shelf life and a preparation method thereof.

Background

Currently, commercially available dairy products processed from pure milk materials are mainly classified into two types, sterilized milk and pasteurized milk.

The pasteurized milk has weaker sterilization conditions, is generally sterilized in a tube type or plate type, is generally kept for 15s at the temperature of 72-85 ℃, is slightly heated, has more active ingredients in the milk, but cannot kill all microorganisms in the milk, so that thermophilic bacillus in the milk can survive, and has a shorter shelf life of generally only 7 days.

The sterilization condition of the sterilized milk is extremely strict, the existing UHT sterilized milk usually adopts a tubular sterilization mode, the sterilization is generally carried out for 4-6s at the temperature of 137-143 ℃, the sterilization intensity is higher, the milk is stored at normal temperature, the shelf life can reach 6 months, but the heat treatment is serious, so that the loss of nutrient components in the milk is serious, and the flavor change of the milk is large.

Disclosure of Invention

In order to solve the technical problems, the invention aims to provide the normal-temperature milk with the long shelf life and the preparation method thereof, by controlling the production process of the milk, the sensory quality of the milk is improved, the loss of nutrient components is reduced, and the shelf life of the milk is prolonged to 6 months.

In order to achieve the purpose, the invention provides a preparation method of normal-temperature milk with long shelf life, which comprises the steps of carrying out physical sterilization and standardization on the milk and directly carrying out steam sterilization;

wherein the standardization comprises the processes of separating fat, sterilizing at the temperature of 125-135 ℃ for 10-15s, and then refilling;

the direct sterilization is carried out by adopting a steam immersion sterilization or steam injection sterilization mode, the sterilization temperature is 121-132 ℃, and the time is 1-4 s.

According to a particular embodiment of the invention, the majority of spores in milk can be removed by physical sterilization. The physical sterilization can be performed by (but not limited to) sterilization by a sterilization separator and/or microfiltration by a ceramic membrane, and the temperature of the physical sterilization can be controlled to be 55-70 ℃, so that the sterilization effect is better.

According to the specific embodiment of the invention, the fat and the protein in the milk are separated through standardized treatment, a small part of spores are removed along with residues in the milk, and a part of nutrients generated by the spores are discharged along with the milk fat, wherein the bacillus thermophilus is difficult to kill in the ultrahigh-temperature instant sterilization treatment process.

According to an embodiment of the present invention, fat separation may be achieved by a centrifugal separator, the rotational speed of the separator may be controlled to 3500-5500rpm, and the separation temperature may be 55-70 ℃. Fat separation should generally be achieved to the following extent: the protein content of the separated fat is less than 0.3 wt%; the fat content in the milk after fat separation was < 0.6 wt%. The sterilization treatment of the separated fat can be performed by a tubular sterilization mode or a plate-changing sterilization mode.

According to an embodiment of the present invention, the protein content of the standardized milk may be controlled to be 3.0-3.5 wt% and the fat content may be controlled to be 0.6-4.0 wt%.

The invention adopts a direct sterilization mode to sterilize the milk, the sterilization temperature is lower, the retention time is shorter, spores in the raw milk are already treated in the process of carrying out physical sterilization on the raw milk, the lower sterilization temperature is mainly used for killing pathogenic bacteria and other microorganisms in the milk, the shelf life of the prepared milk is longer, the content of thermosensitive substances is lower, and the number of aerobic spores and thermophilic spores needing to be cultured in the prepared milk can be ensured to be less than 1 CFU/ml.

Compared with the existing UHT milk sterilization process, the invention adopts steam immersion sterilization and steam injection sterilization, reduces the temperature to 121-132 ℃, shortens the holding time to 1-4s, has lower protein denaturation rate than UHT milk, has less nutrient loss, reduced cooking flavor, and fresh and sweet taste, and has longer shelf life than pasteurized milk, and the common shelf life can reach 4-6 months.

According to a particular embodiment of the invention, the method further comprises the step of flash evaporation or degassing of the directly steam sterilized milk; the water vapour mixed into the milk or the gases present in the milk itself are removed by flash evaporation or degassing. Wherein the flash evaporation temperature can be controlled to be 60-70 ℃; the degassing temperature can be controlled at 60-70 deg.C, and the degassing pressure can be controlled at-0.07 bar to-0.09 bar.

According to a particular embodiment of the invention, the method further comprises the step of homogenizing the flashed or degassed milk; the temperature of the homogenization can be controlled to be 60-65 ℃, and the pressure can be controlled to be 180-220 bar.

According to a specific embodiment of the present invention, the method provided by the present invention may comprise the following specific steps:

physical sterilization: physically sterilizing the raw milk by a sterilization separator and/or a ceramic membrane microfiltration sterilization mode at the temperature of 55-70 ℃;

and (3) standardization: separating fat in milk by using a centrifugal separator, wherein the rotating speed of the centrifugal separator is 3500-5500rpm, and the separation temperature is 55-70 ℃; the protein content of the separated fat is less than 0.3 wt%; the fat content in the milk after fat separation is < 0.6 wt%; sterilizing the separated fat at 135 deg.C for 10-15s by tubular sterilization or plate-changing sterilization, and refilling the fat to complete standardization, wherein the standardized milk has a protein content of 3.0-3.5 wt% and a fat content of 0.6-4.0 wt%;

direct steam sterilization: performing steam direct sterilization on the milk by adopting a steam immersion sterilization or steam injection sterilization mode, wherein the sterilization temperature is 121-;

flash evaporation or degassing: removing water vapor mixed into the milk or gas existing in the milk by a flash evaporation or degassing mode, wherein the temperature is 60-70 ℃, and the degassing pressure is-0.07 bar to 0.09 bar;

homogenizing: homogenizing the milk at 60-65 deg.C under the pressure of 180-220 bar;

and (3) cooling: and cooling the milk to be less than 10 ℃, and then performing aseptic filling to obtain the normal-temperature milk with the long shelf life.

The invention also provides the normal-temperature milk with long shelf life, which is prepared by the method; wherein, the normal temperature milk with long shelf life meets the following index requirements:

the normal temperature milk has low protein denaturation rate (i.e. low contents of furfuryl acid and lactulose), less loss of nutrient components, good taste, milk sensory flavor similar to that of pasteurized milk, and long shelf life similar to that of UHT milk.

The invention can reduce the denaturation rate of protein in the product, reduce the loss of nutrient substances, improve the integral flavor of the product and enable the milk product to have longer shelf life by carrying out physical sterilization on the raw milk, carrying out high-temperature sterilization on the separated milk fat and carrying out sterilization on the standardized milk by adopting a steam immersion sterilization or steam injection sterilization mode and controlling certain parameter conditions. The invention ensures that the obtained product has good nutritional effect and low content of heat-sensitive substances by proper process means. The dairy product produced by the invention is a healthy dairy product meeting the needs of modern people, and has wide application prospect.

Detailed Description

The technical solutions of the present invention will be described in detail below in order to clearly understand the technical features, objects, and advantages of the present invention, but the present invention is not limited to the practical scope of the present invention.

Example 1

The embodiment provides normal-temperature milk with a long shelf life, which is prepared by the following steps:

1. the raw milk is prepared and processed in a conventional manner.

2. Preheating raw milk to 55 ℃, feeding the raw milk into a degerming separator, and removing partial spores in the raw milk to obtain the degerming milk.

3. Keeping the temperature of the sterilized milk at 55 ℃, separating the sterilized milk by a separator, wherein the rotating speed of the separator is 3500rpm, so as to obtain separated milk fat and a part containing milk protein, wherein the protein content of the separated milk fat is less than 0.3 wt%; the fat content in the milk after fat separation was < 0.6 wt%.

4. And performing tubular sterilization on the separated milk fat at 125 ℃ for 15s to obtain the sterilized milk fat.

5. Standardizing, and refilling sterilized milk fat into the milk containing milk protein to make the fat content of the milk reach 0.6% and the protein content reach 3.0%.

6. The standardized milk was heated to 75 ℃ and then introduced into a steam immersion sterilizer (Infusion sterilizer from spx corporation) to sterilize the milk at 121 ℃ for 4 seconds.

7. Degassing sterilized milk at 60 deg.C under-0.07 bar.

8. Homogenizing the degassed milk at 60 deg.C under 180 bar.

9. Cooling homogenized milk at 10 deg.C, and packaging under aseptic condition.

The normal-temperature milk with the long shelf life obtained by the embodiment has the advantages of low protein denaturation rate, less nutrient loss, long shelf life, full, smooth and fresh milk flavor, uniform tissue state and good stability, and is stored for at least 4 months at normal temperature.

Example 2

The embodiment provides normal-temperature milk with a long shelf life, which is prepared by the following steps:

1. the raw milk is prepared and processed in a conventional manner.

2. Preheating raw milk to 60 ℃, feeding the raw milk into a degerming separator, and removing partial spores in the raw milk to obtain the degerming milk.

3. Keeping the temperature of the sterilized milk at 60 ℃, separating the sterilized milk by a separator, wherein the rotating speed of the separator is 4000rpm, so as to obtain separated milk fat and a part containing milk protein, and the protein content of the separated fat is less than 0.3 wt%; the fat content in the milk after fat separation was < 0.6 wt%.

4. Subjecting the separated milk fat fraction to tubular sterilization at 130 deg.C for 12s to obtain sterilized milk fat.

5. And (4) standardizing, and refilling the sterilized milk fat into the milk containing the milk protein to ensure that the milk fat content reaches 1.5 percent and the protein content reaches 3.0 percent.

6. The standardized milk was heated to 70 ℃ and then introduced into a steam immersion sterilizer (Infusion sterilizer from spx corporation) to sterilize the milk at 125 ℃ for 3 seconds.

7. Degassing sterilized milk at 65 deg.C under-0.07 bar.

8. Homogenizing the degassed milk at 65 deg.C under 210 bar.

9. Cooling homogenized milk at 10 deg.C, and packaging under aseptic condition.

The normal-temperature milk with the long shelf life obtained by the embodiment has the advantages of low protein denaturation rate, less nutrient loss, long shelf life, full, smooth and fresh milk flavor, uniform tissue state of the product, no fat floating and good stability, and is stored for at least 4 months at normal temperature.

Example 3

The embodiment provides normal-temperature milk with a long shelf life, which is prepared by the following steps:

1. the raw milk is prepared and processed in a conventional manner.

2. Preheating raw milk to 65 ℃, feeding the raw milk into a degerming separator, and removing partial spores in the raw milk to obtain the degerming milk.

3. Keeping the temperature of the sterilized milk at 65 ℃, separating the sterilized milk by a separator, wherein the rotating speed of the separator is 4500rpm, so as to obtain separated milk fat and a part containing milk protein, and the protein content of the separated fat is less than 0.3 wt%; the fat content in the milk after fat separation was < 0.6 wt%.

4. Subjecting the separated milk fat fraction to tubular sterilization at 132 deg.C for 12s to obtain sterilized milk fat.

5. Standardizing, and refilling sterilized milk fat into the milk containing milk protein to make the milk fat content reach 3.0% and the protein content reach 3.0%.

6. The standardized milk was heated to 70 ℃ and then introduced into a steam immersion sterilizer (Infusion sterilizer from spx corporation) to sterilize the milk at 128 ℃ for 2 seconds.

7. Degassing sterilized milk at 70 deg.C under-0.07 bar.

8. Homogenizing the degassed milk at 65 deg.C under 220 bar.

9. Cooling homogenized milk at 10 deg.C, and packaging under aseptic condition.

After 4 months at normal temperature, the normal-temperature milk with long shelf life obtained by the embodiment has normal sense, uniform tissue state, full flavor, fresh and sweet taste, fresh taste, good shelf life stability, low heat-sensitive substances and high nutritional value, can be stored for a long time at normal temperature, and has a shelf life as long as 6 months.

Example 4

The embodiment provides normal-temperature milk with a long shelf life, which is prepared by the following steps:

1. the raw milk is prepared and processed in a conventional manner.

2. Preheating the raw milk to 70 ℃, feeding the raw milk into a degerming separator, and removing partial spores in the raw milk to obtain the degerming milk.

3. Keeping the temperature of the sterilized milk at 70 ℃, separating the sterilized milk by a separator, wherein the rotating speed of the separator is 5000rpm, so as to obtain separated milk fat and a part containing milk protein, and the protein content of the separated fat is less than 0.3 wt%; the fat content in the milk after fat separation was < 0.6 wt%.

4. Subjecting the separated milk fat fraction to tubular sterilization at 135 deg.C for 10s to obtain sterilized milk fat.

5. Standardizing, and refilling sterilized milk fat into the milk containing milk protein to make the milk fat content reach 3.0% and the protein content reach 3.0%.

6. The standardized milk was heated to 70 ℃ and then introduced into a steam immersion sterilizer (Infusion sterilizer from spx corporation) to sterilize the milk at 130 ℃ for 2 seconds.

7. Degassing sterilized milk at 70 deg.C under-0.07 bar.

8. Homogenizing the degassed milk at 65 deg.C under 220 bar.

9. Cooling homogenized milk at 10 deg.C, and packaging under aseptic condition.

The stability of the long-shelf-life normal-temperature milk obtained by the embodiment is observed in the shelf life, the product has normal sense, uniform tissue state, full flavor, fresh and sweet taste, fresh taste, good shelf life stability, low heat-sensitive substances and high nutritional value, can be stored for a long time under the normal-temperature condition, and the shelf life can reach 6 months.

Example 5

The embodiment provides normal-temperature milk with a long shelf life, which is prepared by the following steps:

1. the raw milk is prepared and processed in a conventional manner.

2. Preheating the raw milk to 70 ℃, feeding the raw milk into a degerming separator, and removing partial spores in the raw milk to obtain the degerming milk.

3. Keeping the temperature of the sterilized milk at 70 ℃, separating the sterilized milk by a separator, wherein the rotating speed of the separator is 5500rpm, so as to obtain separated milk fat and a part containing milk protein, and the protein content of the separated fat is less than 0.3 wt%; the fat content in the milk after fat separation was < 0.6 wt%.

4. Subjecting the separated milk fat fraction to tubular sterilization at 135 deg.C for 10s to obtain sterilized milk fat.

5. Standardizing, and refilling sterilized milk fat into the milk containing milk protein to make the milk fat content reach 3.0% and the protein content reach 3.0%.

6. The standardized milk was heated to 70 ℃ and then introduced into a steam immersion sterilizer (Infusion sterilizer from spx corporation) to sterilize the milk at 132 ℃ for 1 second.

7. Degassing sterilized milk at 70 deg.C under-0.07 bar.

8. Homogenizing the degassed milk at 65 deg.C under 220 bar.

9. Cooling homogenized milk at 10 deg.C, and packaging under aseptic condition.

In the observation of the shelf life stability of the long shelf life normal temperature milk obtained by the embodiment, the product has normal sense, uniform tissue state, full flavor, fresh and sweet taste, fresh taste, good shelf life stability, low heat-sensitive substances and high nutritional value, can be stored for a long time under the normal temperature condition, and has a shelf life as long as 6 months.

Comparative example 1

The comparative example provides a common sterilized milk, the preparation method of which is as follows:

1. the raw milk is prepared and processed in a conventional manner.

2. The raw milk was heated to 65 ℃ and degassed.

3. Homogenizing the degassed milk at 65 deg.C under 220 bar.

4. Heating the homogenized milk to 70 deg.C, and sterilizing at 143 deg.C for 3s with tube or plate heater.

5. And (3) rapidly cooling the sterilized milk at the temperature of 20-25 ℃, and filling under an aseptic condition.

Comparative example 2

The present comparative example provides a pasteurized milk, the preparation method of which is as follows:

1. the raw milk is prepared and processed in a conventional manner.

2. The raw milk was heated to 65 ℃ and degassed.

3. Homogenizing the degassed milk at 65 deg.C under 220 bar.

4. Heating the homogenized milk to 70 deg.C, and sterilizing at 85 deg.C for 15s with tube or plate heater.

5. And (3) rapidly cooling the sterilized milk at 10 ℃, and filling under an aseptic condition.

Organoleptic evaluation verification of milk product with organoleptic flavor

The products produced in examples 1 to 5 and comparative examples 1 and 2 were subjected to blind tests for taste and flavor. Main sensory examination items: texture, color, taste, and flavor. Sensory and flavor scoring criteria are shown in table 1. The number of the people participating in the experiment is 30, the total score is counted, and the average score is calculated; the higher the average score, the better the representation; and gives opinions on the overall preference degree of the product, and counts the number of people who like each single product; the statistical results are reported in table 2.

TABLE 1 taste and flavor scoring criteria for milk based on high quality sensory flavors

TABLE 2 evaluation of statistical results

As can be seen from the sensory evaluation table, the products produced in the examples 1-5 by performing sterilization separation and fat-milk separation on raw milk, sterilizing and backfilling milk fat, and heating at the temperature of 125-.

Verification of contents of thermo-sensitive substances of furosine and lactulose

The contents of the furosine and the lactulose substances in the product are tested by the method of national standard (identification of reconstituted milk in NY/T939-2016 pasteurized milk and UHT pasteurized milk), and the results are shown in Table 3.

TABLE 3

As can be seen from examples 1-5 and comparative examples 1-2, the product of the invention has relatively low contents of furfuryl acid and lactulose substances, and has higher nutritional value. Comparative example 1 heat-sensitive substances were significantly higher than several other products due to the UHT process for sterilization.

Verification of shelf life stability

Shelf life test experiments were performed on the products produced in examples 1-5 and comparative examples 1 and 2. Main inspection items: sensory, pH value, total number of bacteria, shelf life 180 days. The results are shown in Table 4.

TABLE 4

From the shelf life data of examples 1-5 and comparative examples 1-2, it was shown that the product of comparative example 2 had reached the end of shelf life at day 14 of shelf life, while the products of examples 1-5 and comparative example 1 were still in the shelf life range at 180 days of shelf life, indicating that the product of the present invention had a longer shelf life. Comparative example 1 used a pasteurized milk process, while examples 1-5 used an ultra pasteurization process, but the samples of examples 1-5 reached the shelf life of the pasteurized milk, but were heated to a lesser degree than the pasteurized milk.