CN113545393A

CN113545393A - Method for reducing scaling of sterilization machine, liquid dairy product and preparation method thereof

Info

Publication number: CN113545393A
Application number: CN202010325354.9A
Authority: CN
Inventors: 金磊; 王彦平; 巴根纳
Original assignee: Inner Mongolia Yili Industrial Group Co Ltd
Current assignee: Inner Mongolia Yili Industrial Group Co Ltd
Priority date: 2020-04-23
Filing date: 2020-04-23
Publication date: 2021-10-26

Abstract

The invention discloses a method for reducing scaling of a sterilization machine, a liquid dairy product and a preparation method thereof. The method for reducing scaling of the sterilization machine comprises the step of carrying out enzymolysis on milk which is not sterilized. The preparation method of the liquid dairy product comprises the following steps: performing pure milk separation on raw milk produced by a pasture to obtain skim milk and cream; mixing the filtered and sterilized skim milk with the cream subjected to the first homogenization treatment to obtain a mixed product; carrying out nanofiltration concentration on the mixed product to obtain nanofiltration concentrated milk; carrying out reverse osmosis concentration on the nanofiltration concentrated milk to obtain reverse osmosis concentrated milk; heating, homogenizing and sterilizing the reverse osmosis concentrated milk to obtain a liquid dairy product; wherein, the pasture production stage comprises the step of carrying out enzymolysis treatment on the extruded milk, or the step of carrying out enzymolysis treatment on the reverse osmosis concentrated milk. The invention designs enzymolysis before high-temperature sterilization treatment, effectively prolongs the continuous operation time of sterilization equipment, improves the production efficiency and reduces the production cost.

Description

Method for reducing scaling of sterilization machine, liquid dairy product and preparation method thereof

Technical Field

The invention relates to the technical field of dairy products. More particularly, it relates to a method for reducing scaling of a sterilization machine, and a liquid dairy product and a method for preparing the same.

Background

With regard to the production method for producing the liquid dairy product with higher milk protein content, the production and processing method of the prior art can produce and process the liquid dairy product with higher milk protein content. However, the production method of the prior art has the following problems:

first, not natural foods: in order to make the protein content of the product reach a target value, protein powder needs to be added from an external source. And further needs to add raw materials such as food additives and the like; such as the production methods provided in the chinese patent application nos. 200810100259.8 and 201610919122.

Secondly, the drinking mouthfeel of related products is poor: since sweet taste is the most popular taste for humans, it can be used to improve the palatability and certain eating properties of food products. However, some products in the prior art have relatively poor mouthfeel due to low sugar content, such as the production methods provided by the Chinese patent application with application numbers 201710792269.1, 201510914173.9 and 201811096239.8. The milk protein content of related products can reach 6.0-7.0%, but the lactose content is less than 3.0%. The concrete contents are respectively as follows: 2.0-3.0% and less than 0.5%. The lactose content in normal milk is 4.5-5.0%. Thereby influencing the overall taste of the product and further reducing the drinking experience of drinkers on the product. And the method of manufacturing application No. 201811096239.8 lacks the process steps of sterilization treatment of whey protein liquid prior to filling, and the related products lack good preservation properties.

Finally, in the prior art, although the content of milk protein can reach more than 6.0%, the phenomenon of scaling can occur in the sterilization process due to the increase of the content of protein in the liquid dairy product, the continuous operation time of the sterilization equipment is greatly shortened, and the defects of reducing the production efficiency exist.

Disclosure of Invention

In order to solve the technical problems, the invention aims to provide a method for reducing scaling of a sterilization machine, which reduces scaling in the sterilization process of liquid milk and prolongs the service time of the sterilization machine by carrying out enzymolysis on the liquid milk.

The invention also aims to provide a liquid dairy product and a preparation method thereof, and the liquid dairy product with high protein content is obtained by combining enzymolysis, nanofiltration and reverse osmosis.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method of reducing scaling in a sterilization machine, wherein the method comprises the step of subjecting unsterilized milk to enzymatic hydrolysis. Through carrying out enzymolysis on unsterilized cow milk, cholesterol and phospholipid in cow milk fat are respectively enzymolyzed into sterol ester and lysophospholipid, so that the purposes of reducing the surface tension of cow milk before sterilization and relieving the heated aggregation of protein in cow milk are achieved, and therefore, when the cow milk flows through the metal inner surface of a sterilization machine, the heat denatured protein is not easy to form scale (or called milk scale) on the heated inner surface of the sterilization machine.

After a certain period of production operation of sterilization equipment such as an ultra-high temperature sterilization machine, inevitable deposits on the inner surface of the heat exchanger adhere to the inner surface of stainless steel of the sterilization machine, and are called scaling (or milk scaling). The problem of scaling of the sterilizer is an unavoidable problem in the liquid milk production process both technically and economically for a long time. The scaling causes the pressure difference of the sterilization system to increase, the heat exchange efficiency to decrease, the energy consumption to increase, and finally the productivity to decrease and the cost to increase. Therefore, the method provided by the invention can reduce scaling, prolong the production time of each time, and further achieve the effect of reducing the cleaning frequency, thereby achieving the purposes of improving the productivity and reducing the production cost.

The method provided by the invention is used for carrying out enzymolysis on cholesterol into sterol ester and phospholipid into lysophospholipid. Firstly, the sterol ester has the function of reducing the surface tension of the liquid, and after the surface tension of the milk is reduced, the sterol ester can help to prevent protein from being attached to the inner surface of the sterilizer; secondly, the lyso-phospholipid has stronger surface activity, and because of the stronger surface activity, the lyso-phospholipid not only has the function of reducing the surface tension of the liquid, but also has the function of relieving the heat aggregation among proteins in milk, so that when milk flows through the metal inner surface of the sterilization machine, the heat denatured proteins are not easy to form scale on the heated inner surface of the sterilization machine. According to a particular embodiment of the invention, the enzyme used for enzymatic hydrolysis is a glycerophospholipid cholesterol acyltransferase.

The method for reducing the scaling of the sterilization machine can reduce the scaling of milk in various sterilization treatments, such as high-temperature sterilization treatment such as UHT sterilization.

According to a specific embodiment of the present invention, the conditions of the enzymatic treatment can be controlled as follows: the enzymolysis temperature is 5-10 ℃, the dosage of enzyme is 10-30g/1000 kg, and the enzymolysis time can be controlled to be 19-24 hours based on the weight of the cow milk; or the enzymolysis temperature is 40-50 ℃, the dosage of enzyme is 5-15g/1000 kg, and the enzymolysis time can be controlled to be 15-30 minutes based on the weight of the cow milk. The invention controls the condition of enzymolysis treatment in the range, is beneficial to the preservation of milk, avoids the proliferation of microorganisms and avoids the milk deterioration in the enzymolysis process. The enzymolysis temperature is controlled within the range, so that the activity of high-temperature inhibition enzyme can be avoided, the enzymolysis is finished in a proper time, and the production efficiency is improved.

The complete production process of normal temperature liquid milk generally comprises two stages: pasture stage: milking → pasture holding (holding time < 21 hours) → transportation to the production plant (milk flow time required from milking to the production plant < 24 hours). Feeding raw materials to a factory: milk withdrawal → clean milk → standardization → ultra high temperature sterilization → sterile filling, etc. When the enzymolysis conditions of 5-10 ℃ of enzymolysis temperature and 19-24 hours of enzymolysis time are adopted, the enzymolysis step can be adjusted to the pasture stage, namely, the enzymolysis is carried out after milking and before milk purification, thus being beneficial to improving the production efficiency, not only carrying out enzymolysis, but also ensuring the circulation time of the milk from milking to a production factory. That is, the enzymolysis can be performed before the milk is purified, and the conditions of the enzymolysis treatment are as follows: the enzymolysis temperature is 5-10 ℃, the dosage of enzyme is 10-30g/1000 kg, and the enzymolysis time is 19-24 hours based on the weight of cow milk.

According to an embodiment of the present invention, the method for reducing scaling of the sterilization machine of the present invention can be performed according to the following specific steps:

after milking, carrying out enzymolysis on cow milk by using glycerophospholipid cholesterol acyltransferase, and then carrying out treatments such as milk purification, standardization, sterilization and the like, wherein the conditions of the enzymolysis treatment are as follows: the enzymolysis temperature is 5-10 ℃, the dosage of enzyme is 10-30g/1000 kg, and the enzymolysis time can be controlled to be 19-24 hours based on the weight of the cow milk;

or, after the milk is purified and standardized, the milk is subjected to enzymolysis by using glycerophospholipid cholesterol acyltransferase, and then the milk is subjected to sterilization treatment, wherein the conditions of the enzymolysis treatment are as follows: the enzymolysis temperature is 40-50 ℃, the dosage of enzyme is 5-15g/1000 kg, and the enzymolysis time can be controlled to be 15-30 minutes based on the weight of the cow milk.

The invention also provides a preparation method of the liquid dairy product, which comprises the following steps:

1) performing pure milk separation treatment on raw milk produced by a pasture to obtain skim milk and cream;

2) filtering and sterilizing skim milk, and performing first homogenization treatment on dilute cream; mixing the skim milk subjected to the filtering and bacteria reduction treatment with the cream subjected to the first homogenization treatment to obtain a mixed product;

3) carrying out nanofiltration concentration treatment on the mixed product to obtain nanofiltration concentrated milk;

4) carrying out reverse osmosis concentration treatment on the nanofiltration concentrated milk to obtain reverse osmosis concentrated milk;

5) heating, second homogenizing and sterilizing the reverse osmosis concentrated milk to obtain the liquid dairy product;

wherein, the pasture output stage in the step 1) comprises a step of carrying out enzymolysis treatment on the extruded milk, or the step 4) comprises a step of carrying out enzymolysis treatment on the obtained reverse osmosis concentrated milk.

According to a specific embodiment of the present invention, the enzyme used for the enzymatic treatment is preferably glycerophospholipid cholesterol acyltransferase; the glycerophospholipid cholesterol acyltransferase can carry out enzymolysis on cholesterol and phospholipid in milk fat, the cholesterol is subjected to enzymolysis to form sterol ester after the enzymolysis, the phospholipid is subjected to enzymolysis to form lysophospholipid, and the production time of UHT (ultra-high temperature) liquid milk can be prolonged.

According to a specific embodiment of the invention, the pasture output stage in step 1) specifically includes milking, and the raw milk is produced by temporarily storing the milked milk or performing enzymolysis treatment on the milked milk.

According to a specific embodiment of the invention, when the pasture production stage in step 1) includes a step of enzymolysis treatment, the enzymolysis treatment condition can be controlled to be enzymolysis treatment at 5-10 ℃ for 19-24 hours, the dosage of the enzyme is 10-30g/1000 kg, namely 10-30g of enzyme is added in each 1000 kg of raw milk to be subjected to enzymolysis treatment.

According to a particular embodiment of the invention, the net milk separation treatment in step 1) may be preceded by a step of heating the raw milk to a temperature of 50-55 ℃.

According to a specific embodiment of the present invention, when the step 4) includes a step of performing enzymolysis treatment on the obtained reverse osmosis concentrated milk, the enzymolysis treatment condition may be controlled to be enzymolysis treatment at 40-50 ℃ for 15-30 minutes, and the amount of the enzyme is 5-15g/1000 kg, that is, 5-15g of the enzyme is added to each 1000 kg of the reverse osmosis concentrated milk to be subjected to enzymolysis treatment.

According to a specific embodiment of the present invention, the filtration sterilization treatment in step 2) may be performed by membrane filtration sterilization treatment using a membrane having a pore size of 1.0 to 2.0 μm.

According to a specific embodiment of the present invention, the fat content of the mixed product obtained in step 2) is 2.0% to 3.0% (mass percent). The inventor tests and verifies that fat is reduced to 2.0-3.0%, then the protein can be concentrated to 6.0-6.5% by adopting NF and OR filtration in sequence, meanwhile, the milk fat can be controlled to be 4.0-5.0%, the fat content in the range is similar to that in normal milk, and the milk fat-reducing agent has the advantages that: because the fat content is moderate, the normal milk fat fragrance can be given to the liquid dairy product, and the phenomenon that the fat content is too high brings too greasy feeling to drinkers is avoided; meanwhile, the phenomenon that the fat floats upwards and is layered due to the high fat content in the shelf life of the liquid milk product, and the product system is unstable due to the high fat content is avoided; that is, if the fat content of the dairy product before concentration is not adjusted to 2.0% -3.0%, and membrane filtration concentration is directly performed, the fat content of the finally obtained liquid dairy product can reach 8.0% or even higher; in addition, if the milk fat content is as low as 1.5% by separating the milk fat of cow as the technical scheme provided in the Chinese invention application with the application number of 201510914173.9, the liquid dairy product prepared by the method is lack of milk flavor due to low milk fat content in the product, and the taste of the final product is greatly reduced.

According to a specific embodiment of the present invention, the nanofiltration concentration process described in step 3) is a concentration process using a Nanofiltration (NF) membrane.

According to a specific embodiment of the invention, the protein content of the nanofiltration concentrated milk obtained in step 3) is 4.0% -5.0%. The inventor tests and verifies that the lactose content in the milk is not lost when the NF membrane filtration is adopted to concentrate the protein to 4.0-5.0%; that is, the concentration is carried out by filtering with NF membrane and then concentrating with RO membrane, and the purpose is that the NF membrane is used to increase the protein content in cow's milk and the lactose content in cow's milk. Furthermore, compared with the production process of independently adopting RO membrane concentration, the production process of firstly NF concentration and then RO concentration can ensure the lactose content in the final product and greatly improve the stability of the final product.

According to a specific embodiment of the present invention, the reverse osmosis concentration treatment in the step 4) is a concentration treatment using a Reverse Osmosis (RO) membrane.

According to a specific embodiment of the invention, the reverse osmosis concentrated milk obtained in step 4) has a protein content of 6.0% to 6.5% and a lactose content of 4.90% to 5.0%. The inventor tests and verifies that the characteristics of the NF membrane are firstly utilized to simultaneously improve the contents of milk protein and lactose to a certain extent, the content of the milk protein is concentrated to 4.0-5.0%, then the RO membrane is used for concentrating, and the contents of the protein and the lactose in the milk are improved to target values, and the content of the lactose in the milk can be controlled to 8.5-9.0% when the content of the protein in the milk is concentrated to 6.0-6.5%. The treatment firstly avoids the defect that the product provided by the invention patent application with the application numbers of 201710792269.1, 201510914173.9 and 201811096239.8 has the lactose content far lower than that of 4.5-5.0% in normal cow milk, so that the taste of the product is poor. And secondly, the stability of the final product is effectively improved. Although the RO reverse osmosis membrane is singly adopted to directly concentrate the milk, the protein content of the milk can be increased to 6.0-6.5%, the lactose content can be controlled to 8.5-9.0%, but the stability of the final product is greatly reduced.

According to a specific embodiment of the present invention, the heating treatment in step 5) may be controlled to be heated to 60 to 70 ℃.

According to a specific embodiment of the present invention, the conditions of the second homogenization treatment in step 5) may be controlled to be 150-180 bar.

According to an embodiment of the present invention, the sterilization treatment conditions in step 5) may be controlled to 135-.

According to an embodiment of the present invention, the sterilization treatment in step 5) may further include a step of cooling to 20-25 ℃ and filling.

According to a specific embodiment of the present invention, the preparation method of the liquid dairy product provided by the present invention can be performed according to the following steps:

1. fat normalization: and (3) carrying out centrifugal separation process treatment on the raw milk to reduce the fat content in the milk to 2.0-3.0% so as to obtain the skim milk. The fat is firstly standardized, so that the relevant indexes of the final product can meet the target requirements.

2. Filtering and sterilizing: the skim milk is subjected to membrane filtration and sterilization treatment through a membrane with the pore diameter of 1.0-2.0 um. Before concentration, the number of microorganisms in the cow milk is reduced through a filtering mode, so that the microorganisms in the cow milk are prevented from being concentrated at the same time, and the heat treatment process intensity of the cow milk can be reduced without adopting a traditional pasteurization process.

3. NF concentration: and (3) carrying out nanofiltration concentration on the milk subjected to bacteria reduction to concentrate the protein content of the trapped fluid to 4.0-5.0%. The lactose in the milk can be kept as much as possible while the protein in the milk is concentrated.

4. And (3) RO concentration: and (3) continuously concentrating the milk with the feed liquid protein content of 4.0-5.0% after NF concentration by using an RO reverse osmosis membrane to concentrate the protein content of the intercepted liquid to 6.0-6.5%. The lactose content can be increased at the same time as the milk protein content is further concentrated (increased).

5. Preheating: the trapped fluid is preheated to 40-50 ℃, namely, the trapped fluid is preheated to the enzymolysis temperature.

6. Enzymolysis: adding 5-15g/1000 kg of glycerophospholipid cholesterol acyltransferase into preheated milk under the enzymolysis condition of 40-50 ℃/15-30 minutes.

7. Cooling and temporary storage: cooling the enzymolyzed cow milk to 1-6 deg.C for storage.

8. Preheating: heating the mixed raw milk to 60-70 ℃, preheating and raising the temperature to facilitate homogenization treatment.

9. Homogenizing: homogenizing the preheated milk at 150-180bar to make the milk uniform in tissue state.

10. And (3) sterilization: sterilizing homogenized cow milk at 135-.

11. Filling: and (3) aseptic filling is carried out on the sterilized milk, so that the milk is convenient to transport and sell, and the liquid dairy product with high protein content (6.0-6.5%), lactose content (8.5-9.0%) and fat content (4.0-5.0%) is finally obtained.

As another aspect of the invention, the invention also provides a liquid dairy product prepared by the preparation method. Preferably, the liquid dairy product has a protein content of 6.0-6.5%, a fat content of 4.0-5.0%, and a lactose content of 8.5-9.0%.

In the preparation method, the microbial quantity in the skim milk is reduced by filtering and bacteria reduction, the bacteria reduction method can firstly prevent the microorganisms from being concentrated at the same time during concentration, and secondly does not use a pasteurization process according to the traditional method, so that the reduction of heating treatment is realized; the nanofiltration concentration can reduce the lactose content while concentrating the protein, so that the concentration by adopting a reverse osmosis concentration process is avoided, and the lactose content is increased too high while the protein index is increased; the reverse osmosis concentration can further concentrate (improve) the protein content and simultaneously improve the lactose content; the milk product is respectively treated by nanofiltration and reverse osmosis processes, so that the content of lactose is adjusted to be in a proper range while the content of protein is increased, and the taste of the liquid milk product is improved to a certain extent on the basis of the prior art; in the enzymolysis step, cholesterol and phospholipid in the dairy product are respectively enzymolyzed into cholesterol ester and lysophospholipid, so that when the dairy product flows through the metal inner surface of the sterilization machine, the heated and denatured protein is not easy to form scale on the heated inner surface of the sterilization machine, and the problems of short ultrahigh-temperature sterilization continuous production time, low production efficiency, high production cost and the like in the conventional production of the liquid dairy product with high milk protein content are solved; in addition, the method can clean the label, and produce the liquid dairy product with higher protein content without adding any food additive, thereby maintaining the natural attribute of the food in the label ingredient column.

In addition, unless otherwise specified, any range recited herein includes any value between the endpoints and any sub-range defined by any value between the endpoints or any value between the endpoints.

The invention has the following beneficial effects:

(1) the method provided by the invention can reduce the scaling phenomenon of the sterilization machine by designing the enzymolysis process step before the sterilization treatment, thereby effectively prolonging the continuous operation time of related sterilization equipment, improving the production efficiency, reducing the production cost and solving the defect of short production time when the liquid milk with higher protein content (6.0-6.5%) is produced in the prior art.

(2) The invention adopts nanofiltration and reverse osmosis filtration processes to improve the content of protein in the liquid dairy product, thereby avoiding the use of exogenously added protein powder and food additives, keeping the natural characteristics of the product and solving the defect of stability defect of the product prepared by adopting the reverse osmosis process alone.

(3) According to the invention, tests show that the liquid dairy product with moderate lactose content and good taste can be finally obtained by properly treating the milk by adopting two membrane filtration processes of a nanofiltration membrane and a reverse osmosis membrane.

(4) According to the invention, the liquid dairy product with good preservation performance is obtained after the sterilization treatment is carried out on the related feed liquid.

(5) For the product itself: compared with the prior art, the liquid dairy product prepared by the invention has better taste and can bring better drinking experience to drinkers. For the production process: compared with the prior art, the preparation method has higher production efficiency and achieves the effect of reducing the production cost.

Drawings

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

Fig. 1 shows a schematic flow chart of a preparation method of a liquid dairy product in embodiment 1 of the invention.

Fig. 2 shows a schematic flow chart of a method for preparing a liquid dairy product in embodiment 3 of the invention.

Detailed Description

In order to more clearly illustrate the invention, the invention is further described below in connection with preferred embodiments. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.

In the invention, the preparation method is a conventional method if no special description is provided; the starting materials used are commercially available from published sources unless otherwise specified.

Example 1

The embodiment provides a preparation method of a liquid dairy product, the flow of which is shown in fig. 1, and the preparation method comprises the following steps:

1) milking, temporarily storing the squeezed milk to produce raw milk, preheating the raw milk to 50-55 ℃, and then carrying out pure milk separation to obtain skim milk and cream;

2) performing first homogenization treatment at 30/150bar on cream, and filtering and sterilizing skim milk by using a membrane core with a pore diameter of 1.4 μm; partially backfilling the homogenized cream and the skim milk subjected to filtering and bacteria reduction, adding the backfilled cream and the skim milk into the skim milk, and mixing the backfilled cream and the skim milk on line to obtain a mixed product, wherein the fat content of the mixed product is 2.0-2.5%;

3) carrying out NF nanofiltration concentration on the mixed product, and concentrating the protein content of the trapped fluid to 4.0-5.0%, the fat content to 2.9-3.7% and the lactose content to 5.8-6.2% to obtain nanofiltration concentrated milk;

4) concentrating the nanofiltration concentrated milk by using an RO reverse osmosis membrane, and concentrating the protein content of the trapped fluid to 6.0-6.5%, and simultaneously obtaining reverse osmosis concentrated milk with the fat content of 4.0-4.5% and the lactose content of 8.5-9.0%; heating reverse osmosis concentrated milk to 40-50 deg.C, adding glycerophospholipid cholesterol acyltransferase, wherein the addition amount is as follows: 10g/1000 kg, and the enzymolysis condition is enzymolysis for 20 minutes at 48 ℃;

5) heating the reverse osmosis concentrated milk after enzymolysis to 60-70 ℃, then carrying out 35/180bar second homogenization treatment, carrying out sterilization treatment of sterilization for 4s at 136 ℃ after the homogenization treatment, and then cooling the sterilized feed liquid to 20-25 ℃ and storing in an aseptic tank; and (3) carrying out aseptic filling on the sterilized feed liquid to obtain the liquid dairy product with the protein content of 6.0-6.5%, the fat content of 4.0-5.0% and the lactose content of 8.5-9.0%.

Example 2

The embodiment provides a preparation method of a liquid dairy product, which comprises the following steps:

2) performing first homogenization treatment at 35/180bar on cream, and filtering and sterilizing skim milk by using a membrane core with a pore diameter of 1.8 μm; then, partially backfilling the homogenized cream and the skim milk subjected to filtering and bacteria reduction, adding the backfilled cream and the skim milk into the skim milk, and mixing the backfilled cream and the skim milk on line to obtain a mixed product, wherein the fat content of the mixed product is 2.0-2.5%;

4) concentrating the nanofiltration concentrated milk by using an RO reverse osmosis membrane, concentrating the protein content of the trapped fluid to 6.0-6.5%, simultaneously, the fat content is 4.0-4.5%, and the lactose content is 8.5-9.0%, so as to obtain the reverse osmosis concentrated milk; heating reverse osmosis concentrated milk to 40-50 deg.C, adding glycerophospholipid cholesterol acyltransferase, wherein the addition amount is as follows: 5g/1000 kg, and the enzymolysis condition is enzymolysis for 30 minutes at 45 ℃;

5) heating the reverse osmosis concentrated milk after enzymolysis to 60-70 ℃, then carrying out 40/200bar second homogenization treatment, carrying out sterilization treatment of sterilization for 4s at 138 ℃ after the homogenization treatment, and then cooling the sterilized feed liquid to 20-25 ℃ and storing in an aseptic tank; and (3) carrying out aseptic filling on the sterilized feed liquid to obtain the liquid dairy product with the protein content of 6.0-6.5%, the fat content of 4.0-5.0% and the lactose content of 8.5-9.0%.

Example 3

The embodiment provides a preparation method of a liquid dairy product, the flow of which is shown in fig. 2, and the preparation method comprises the following steps:

1) milking, cooling the squeezed (leaving cow body) milk to 6 ℃, adding glycerophospholipid cholesterol acyltransferase into the cooled milk, wherein the addition amount is as follows: 15g/1000 kg, and carrying out enzymolysis for 20 hours at 6 ℃ to obtain raw milk; preheating raw milk to 50-55 ℃, and then carrying out pure milk separation to obtain skim milk and cream;

2) performing first homogenization treatment at 35/180bar on cream, and filtering and sterilizing skim milk by using a membrane core with a pore diameter of 1.4 μm; then, partially backfilling the homogenized cream and the skim milk subjected to filtering and bacteria reduction, adding the backfilled cream and the skim milk into the skim milk, and mixing the backfilled cream and the skim milk on line to obtain a mixed product, wherein the fat content of the mixed product is 2.0-2.5%;

4) concentrating the nanofiltration concentrated milk by using an RO reverse osmosis membrane, and concentrating the protein content of the trapped fluid to 6.0-6.5%, simultaneously, the fat content is 4.0-4.5%, and the lactose content is 8.5-9.0%, so as to obtain the reverse osmosis concentrated milk;

5) heating the reverse osmosis concentrated milk to 60-70 deg.C, performing 35/180bar second homogenization treatment, sterilizing at 137 deg.C for 4s, cooling to 20-25 deg.C, and storing in sterile tank; and (3) carrying out aseptic filling on the sterilized feed liquid to obtain the liquid dairy product with the protein content of 6.0-6.5%, the fat content of 4.0-5.0% and the lactose content of 8.5-9.0%.

Example 4

1) milking, cooling the squeezed (leaving cow body) milk to 5 ℃, adding glycerophospholipid cholesterol acyltransferase into the cooled milk, wherein the addition amount is as follows: 29g/1000 kg, and performing enzymolysis for 23 hours at 5 ℃ to obtain raw milk; preheating raw milk to 50-55 ℃, and then carrying out pure milk separation to obtain skim milk and cream;

2) performing first homogenization treatment at 30/150bar on cream, and filtering and sterilizing skim milk by using a membrane core with a pore diameter of 1.4 μm; then, partially backfilling the homogenized cream and the skim milk subjected to filtering and bacteria reduction, adding the backfilled cream and the skim milk into the skim milk, and mixing the backfilled cream and the skim milk on line to obtain a mixed product, wherein the fat content of the mixed product is 2.0-2.5%;

4) concentrating the nanofiltration concentrated milk by using an RO reverse osmosis membrane, concentrating the protein content of the trapped fluid to 6.0-6.5%, simultaneously, the fat content is 4.0-4.5%, and the lactose content is 8.5-9.0%, so as to obtain the reverse osmosis concentrated milk;

5) heating the reverse osmosis concentrated milk to 60-70 deg.C, performing 40/300bar second homogenization treatment, sterilizing at 136 deg.C for 4s, cooling to 20-25 deg.C, and storing in sterile tank; and (3) carrying out aseptic filling on the sterilized feed liquid to obtain the liquid dairy product with the protein content of 6.0-6.5%, the fat content of 4.0-5.0% and the lactose content of 8.5-9.0%.

Remarking: unless otherwise specified, the percentage contents of milk components referred to herein are mass percentages, i.e., g/100 g.

Test example 1

In order to test the difference between the method of the present invention and the prior art, the test example compares the two, and the results are shown in table 1, wherein the nutrition feeling, the color and luster of the product, the flavor of the product, the taste of the fresh milk and the preference degree of the product are evaluated by adopting the test samples of examples 1-4 and the taste test samples of the traditional process and the number of test persons of 200 respectively in an anonymous way.

TABLE 1 evaluation of products

Remarking: the detailed steps in the prior art are described in the application number: 201710792269.1, table 6 and table 7, the prior art is the same as the production method provided in example 1 of the chinese patent application.

Sensory state, thickness of precipitate, mouthfeel and flavor of the comparative samples of examples (nanofiltration prior to reverse osmosis) and comparative examples 1-3 (reverse osmosis only) were followed for 5 months at normal temperature, and the evaluation results were recorded as shown in table 2 below.

TABLE 2 comparison data table of nanofiltration + reverse osmosis process and pure reverse osmosis process samples

Comparative example 1

The comparative example provides a method for preparing a liquid dairy product, comprising the following steps:

3) concentrating the mixed product by using an RO reverse osmosis membrane, and concentrating the protein content of the trapped fluid to 6.0-6.5%, and simultaneously, obtaining reverse osmosis concentrated milk with the fat content of 4.0-4.5% and the lactose content of 8.5-9.0%; heating reverse osmosis concentrated milk to 40-50 deg.C, adding glycerophospholipid cholesterol acyltransferase, wherein the addition amount is as follows: 10g/1000 kg, and the enzymolysis condition is enzymolysis for 20 minutes at 48 ℃;

4) heating the reverse osmosis concentrated milk after enzymolysis to 60-70 ℃, then carrying out 35/180bar second homogenization treatment, carrying out sterilization treatment of sterilization for 4s at 136 ℃ after the homogenization treatment, and then cooling the sterilized feed liquid to 20-25 ℃ and storing in an aseptic tank; and (3) carrying out aseptic filling on the sterilized feed liquid to obtain the liquid dairy product with the protein content of 6.0-6.5%, the fat content of 4.0-5.0% and the lactose content of 8.5-9.0%.

Comparative example 2

3) concentrating the mixed product by an RO reverse osmosis membrane to concentrate the protein content of the trapped fluid to 6.0-6.5 percent, simultaneously, the fat content is 4.0-4.5 percent, and the lactose content is 8.5-9.0 percent to obtain reverse osmosis concentrated milk; heating reverse osmosis concentrated milk to 40-50 deg.C, adding glycerophospholipid cholesterol acyltransferase, wherein the addition amount is as follows: 5g/1000 kg, and the enzymolysis condition is enzymolysis for 30 minutes at 45 ℃;

4) heating the reverse osmosis concentrated milk after enzymolysis to 60-70 ℃, then carrying out 40/200bar second homogenization treatment, carrying out sterilization treatment of sterilization for 4s at 138 ℃ after the homogenization treatment, and then cooling the sterilized feed liquid to 20-25 ℃ and storing in an aseptic tank; and (3) carrying out aseptic filling on the sterilized feed liquid to obtain the liquid dairy product with the protein content of 6.0-6.5%, the fat content of 4.0-5.0% and the lactose content of 8.5-9.0%.

Comparative example 3

3) concentrating the mixed product by using an RO reverse osmosis membrane, and concentrating the protein content of the trapped fluid to 6.0-6.5%, meanwhile, the fat content is 4.0-4.5%, and the lactose content is 8.5-9.0%, so as to obtain reverse osmosis concentrated milk;

4) heating the reverse osmosis concentrated milk to 60-70 deg.C, performing 35/180bar second homogenization treatment, sterilizing at 137 deg.C for 4s, cooling to 20-25 deg.C, and storing in sterile tank; and (3) carrying out aseptic filling on the sterilized feed liquid to obtain the liquid dairy product with the protein content of 6.0-6.5%, the fat content of 4.0-5.0% and the lactose content of 8.5-9.0%.

Test example 2

Taking an ultra-high temperature sterilization machine with the production capacity of 18 tons/hour as an example, the ultra-high temperature sterilization machine is used for sterilizing liquid milk with the protein content of 3.0-3.5%. The time for which continuous production is possible is 10 hours. The time for continuous production was 4 hours when sterilizing liquid milk with protein content of 6.0-6.5%, see table 3; the daily cleaning energy consumption (cost) of 3.0-3.5% protein content cow milk is shown in table 4, and the daily cleaning energy consumption (cost) of 6.0-6.5% protein content cow milk is shown in table 5. A comparison of the process of the present invention and the prior art is made and the results are shown in tables 6 and 7.

TABLE 3 protein content and production time (washing time)

The data show that the continuous production running time of the sterilization machine is greatly shortened along with the increase of the protein content of the liquid dairy product.

TABLE 43.0-3.5% protein content cow milk daily cleaning energy consumption (cost) calculation table

Energy project

Energy consumption per hour

Each time of cleaning

Daily cleaning

Used for daily cleaning

Unit price of

Daily cleaning cost

Consumption of water

4T/h

2h

2 times (one time)

4×4＝16T

10 yuan/T

160 yuan

Power consumption

150kw/h

2h

2 times (one time)

150×4＝600kw

0.6 yuan/degree

360 yuan

Gas consumption

1.5T/h

2h

2 times (one time)

1.5×4＝6T

300 yuan/T

1800 Yuan

Total up to

/

2320 element

TABLE 56.0-6.5% protein content cow milk daily cleaning energy consumption (cost) calculation table

Energy project

Energy consumption per hour

Each time of cleaning

Daily cleaning

Used for daily cleaning

Unit price of

Daily cleaning cost

Consumption of water

4T/h

2h

4 times (twice)

4×8＝32T

10 yuan/T

320 Yuan

Power consumption

150kw/h

2h

4 times (twice)

150×8＝1200kw

0.6 yuan/degree

720 yuan

Gas consumption

1.5T/h

2h

4 times (twice)

1.5×8＝12T

300 yuan/T

3600 yuan

Total up to

/

4640 yuan

And (3) displaying data: the daily cleaning cost is increased by 0.232 ten thousand yuan after the protein content is increased from 3.0-3.5% to 6.0-6.5%. The cleaning cost is increased by over 80 ten thousand yuan each year. Moreover, the production efficiency is reduced: the production time is reduced from the previous 20 hours/day to 16 hours/day. Reduction in throughput: at 4 hours per day, 18T/hour, 72 tons, yield reduction per year: 2.5 ten thousand tons.

TABLE 6 comparative table of time for ultra-high temperature production of examples and prior art

Item	Example 1	Example 2	Example 3	Example 4	Prior Art
						UHT continuous production time	7.2	6.9	7.3	7.0	4.2
UHT continuous production time	6.8	7.0	7.0	7.5	3.9
						UHT continuous production time	7.5	7.3	7.2	6.9	4.0
UHT continuous production time	7.0	7.6	7.8	7.3	3.8
						UHT continuous production time	7.3	7.4	6.9	6.9	4.1

Table 7 production time (cleaning time) comparison data of the present invention and the prior art

The above data show that the number of washes per day is reduced by 1 in the method of the invention compared to the prior art. The required cleaning time was reduced by two hours. The corresponding cleaning cost is reduced by 1160 yuan every day, and the production time is increased by 2 hours. (in the prior art, the production time per day is 4 multiplied by 4 to 16 hours, and the cleaning time of 8 hours is 24 hours in the whole day, the production time per day is 7 multiplied by 2 to 4 hours in the case of 18 hours, and the cleaning time of 6 hours in the case of 24 hours in the whole day).

Taking an ultra-high temperature sterilization machine of 18 tons/hour as an example, the production cost is reduced, and the production efficiency is improved. The cost of cleaning energy consumption is saved by more than 40 ten thousand yuan throughout the year, and the yield is increased by 1.29 ten thousand tons.

Example 5

1) milking, cooling the squeezed (leaving cow body) milk to 5 ℃, adding glycerophospholipid cholesterol acyltransferase into the cooled milk, wherein the addition amount is as follows: 20g/1000 kg, and carrying out enzymolysis for 20 hours (namely 1320 minutes) at the temperature of 6 ℃ to obtain raw milk; preheating raw milk to 50-55 ℃, and then carrying out pure milk separation to obtain skim milk and cream;

Example 6

4) concentrating the nanofiltration concentrated milk by using an RO reverse osmosis membrane, concentrating the protein content of the trapped fluid to 6.0-6.5%, simultaneously, the fat content is 4.0-4.5%, and the lactose content is 8.5-9.0%, so as to obtain the reverse osmosis concentrated milk; heating reverse osmosis concentrated milk to 40-50 deg.C, adding glycerophospholipid cholesterol acyltransferase, wherein the addition amount is as follows: 10g/1000 kg, and the enzymolysis condition is enzymolysis for 30 minutes at 45 ℃;

Comparative example 4

The comparative example provides a method for preparing a liquid dairy product, wherein the enzymolysis temperature is 2 ℃, and the rest is the same as that of the example 5.

Comparative example 5

The comparative example provides a method for preparing a liquid dairy product, wherein the enzymolysis temperature is 60 ℃, and the rest is the same as that of the example 6.

Test example 3 comparative test of the Effect of enzymatic hydrolysis parameters on the continuous UHT-running time

The enzymatic hydrolysis conditions and UHT continuous running time for examples 5-6 and comparative examples 4-5 are shown in Table 8.

TABLE 8

As can be seen from the contents of Table 8, the continuous UHT running time can be greatly prolonged by the method of the present invention, which shows that the fouling of UHT sterilization can be reduced and the continuous running time can be prolonged by the method of the present invention, which is helpful for reducing the production cost.

It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.

Claims

1. A method of reducing scaling in a sterilization machine, wherein the method comprises the step of subjecting unsterilized milk to enzymatic hydrolysis.

2. The method for reducing scaling of a sterilization machine as recited in claim 1, wherein the enzyme used for enzymatic hydrolysis is glycerophospholipid cholesterol acyltransferase.

3. A method of reducing fouling in a sterilization machine as claimed in claim 1 or 2, wherein said sterilization comprises high temperature sterilization, preferably UHT sterilization.

4. A method of reducing fouling in a sterilization machine as claimed in any one of claims 1 to 3, wherein said enzymatic treatment is carried out under conditions selected from: the enzymolysis temperature is 5-10 ℃, the dosage of enzyme is 10-30g/1000 kg, and the enzymolysis time is preferably 19-24 hours based on the weight of the cow milk; or the enzymolysis temperature is 40-50 ℃, the dosage of enzyme is 5-15g/1000 kg, and the enzymolysis time is preferably 15-30 minutes based on the weight of the cow milk.

5. The method of reducing scaling of a sterilizer as set forth in any one of claims 1 to 4, wherein the enzymatic hydrolysis is carried out prior to milk purification and the conditions of the enzymatic hydrolysis treatment are: the enzymolysis temperature is 5-10 ℃, the dosage of enzyme is 10-30g/1000 kg, based on the weight of cow milk, and the enzymolysis time is preferably 19-24 hours.

6. A preparation method of a liquid dairy product comprises the following steps:

7. The method for preparing a liquid dairy product according to claim 6, wherein the enzyme used in the enzymatic treatment is glycerophospholipid cholesterol acyltransferase.

8. The method for preparing a liquid dairy product according to claim 6 or 7, wherein the pasture production stage in step 1) comprises milking, and the extruded milk is temporarily stored or subjected to enzymolysis to produce raw milk.

9. The method for preparing the liquid dairy product according to claim 8, wherein when the pasture production stage in the step 1) includes an enzymolysis treatment step, the enzymolysis treatment is carried out at 5-10 ℃ for 19-24 hours, and the amount of enzyme is 10-30g/1000 kg based on the weight of the raw milk.

10. The method for preparing a liquid dairy product according to claim 7 or 8, wherein when the step 4) comprises a step of performing enzymolysis treatment on the obtained reverse osmosis concentrated milk, the enzymolysis treatment is performed at 40-50 ℃ for 15-30 minutes, and the amount of enzyme is 5-15g/1000 kg based on the weight of the reverse osmosis concentrated milk.

11. The method of producing a liquid dairy product according to any one of claims 6-10, wherein the fat content of the product mixture obtained in step 2) is between 2.0% and 3.0%.

12. The method for preparing a liquid dairy product according to any one of claims 6-11, wherein the filtration sterilization treatment in step 2) is membrane filtration sterilization treatment using a membrane with a pore size of 1.0-2.0 μm.

13. The method of producing a liquid dairy product according to any of claims 6-12, wherein the nanofiltration concentrated milk obtained in step 3) has a protein content of 4.0-5.0%.

14. The method for preparing a liquid dairy product according to any one of claims 6-13, wherein the reverse osmosis concentrated milk obtained in step 4) has a protein content of 6.0-6.5% and a lactose content of 8.5-9.0%.

15. The method for preparing a liquid dairy product according to any of claims 6-14, wherein the conditions of the sterilization treatment in step 5) are 135-;

preferably, the heating treatment in step 5) is carried out under conditions of heating to 60-70 ℃;

preferably, the conditions of the second homogenization treatment in step 5) are 150-180 bar.

16. A liquid dairy product obtained by the method of any one of claims 6-15;

preferably, the liquid dairy product has a protein content of 6.0-6.5%, a fat content of 4.0-5.0%, and a lactose content of 8.5-9.0%.