CN112136899A

CN112136899A - High-quality milk powder and preparation method thereof

Info

Publication number: CN112136899A
Application number: CN202011038978.9A
Authority: CN
Inventors: 刘秀荣
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-09-28
Filing date: 2020-09-28
Publication date: 2020-12-29

Abstract

The invention relates to the field of dairy product processing, in particular to a preparation method of high-activity milk powder, which comprises the following steps: cold concentration is adopted for milk or dairy products, low-heat energy or cold sterilization is adopted before or after the cold concentration, and finally low-temperature spraying or freeze drying is adopted to prepare the milk powder, wherein the cold concentration is preferably medium-pressure reverse osmosis concentration. The milk powder produced by the technical scheme of the invention has obvious difference in physical properties and heat-sensitive components compared with the milk powder produced by the conventional process, and the product quality is better.

Description

High-quality milk powder and preparation method thereof

Technical Field

The invention relates to the field of dairy product processing, in particular to a preparation method of high-activity milk powder.

Background

At present, the demand of infant powder and adult powder is very large in international and domestic, but the existing milk powder production process has various defects and causes great waste on nutrition. Because the existing powder spraying process needs to be produced under a thermal condition, the original taste of milk and dairy products cannot be kept, great loss is caused to active sensitive ingredients and nutritional ingredients, and the nutritional value of the milk powder is greatly reduced. The production process capable of retaining the nutrient components of the original milk to the maximum extent, retaining more natural active components and improving the nutritional value of the product is urgently needed to be developed.

The existing powder spraying process adopts a wet process, a dry process or a dry-wet mixing process, wherein the wet process is to add nutrients into liquid milk and finish powder spraying and filling for 1 time, so that the freshness and the nutritive value of milk powder can be ensured to the maximum extent; the dry process is characterized in that nutrients are added into the whole/skimmed milk powder and then subpackaged again, and the heat-sensitive nutrient components are easy to add and the process requirement is simple; the dry and wet hair mixing process is between the dry and wet hair mixing process, a wet process is adopted when a fresh milk source exists, and a dry process is adopted when the milk source does not exist, so that powder spraying is required at high temperature.

The obtained milk powder can reach the high-quality level by at least the following three aspects of performance standards.

Solubility: the solubility of the milk powder refers to the property of the milk powder which can be restored to a uniform milk state after being mixed with a certain amount of water, and refers to the final dissolution degree of the milk powder. The degree of deformation of the protein in the milk powder can be reflected to a certain degree by the solubility of the milk powder, and if the solubility of the milk powder is low, the amount of denaturation of the protein in the milk powder is large, and the protein denatured during brewing cannot be dissolved. If a powdered milk is not sufficiently soluble, it may not form a uniform final product or intermediate product, resulting in loss of solids and problems in the manufacturing process. The insoluble material is typically a deformed protein or a complex of casein/whey protein and lactose. The solubility of milk powder can be expressed by an insolubility index, the higher the insolubility index, the worse the solubility. Generally, a solubility index of 0.2 less indicates good solubility.

Wettability: wettability is a measure of the ability of a powdered milk to be wetted by water at a certain temperature. Wettability depends on the surface water absorption capacity of the milk powder agglomerates or individual particles, such as whether the particle surface is resistant to water dissolution or absorbs excess moisture to form a moisture impermeable film. The powder surface can be viewed as a complex surface with a capillary network of bridges between. The factor determining whether the milk powder can be moistened or not is the activity between the surface of the particles and the surface of water. When the particles are wetted, the material in the milk powder begins to disperse and dissolve, forming a thick milk solution around the particles. Generally, skim milk powders are easier to wet because their structure is mainly composed of amorphous lactose and proteins which are easily soluble in water. While the whole milk powder particles are often covered by a layer of fat (the proportion of free fat on the surface of the milk powder is 0.5-3 percent), so that the milk powder particles are difficult to dissolve in water. The problem that the powdered milk particles are insoluble in water caused by fat can be solved by adding a layer of surfactant (such as phospholipid) on the surface of free fat.

Dispersibility: the dispersibility of the milk powder reflects the ability of the diluted aggregated milk powder particles to be uniformly dispersed in water, i.e. the milk powder is gently stirred in the water, and the dispersion condition of the milk powder is observed. Dispersibility is an important characteristic of instant milk powder, and milk powder with good dispersibility usually has good wettability, no fine powder and good agglomeration effect.

Therefore, there is a need to develop a method for preparing milk powder with minimized loss of heat-sensitive substances, retained nutrients, and good solubility and dispersibility

Disclosure of Invention

The invention adopts the whole production process flow to be carried out at a uniform low temperature, reduces the loss of heat-sensitive substances to the maximum extent and reserves nutrient components. After the raw milk is pretreated, a cold sterilization technology (separation sterilization technology, microfiltration sterilization, micro-sieve filtration, ultraviolet sterilization, continuous ultrahigh pressure sterilization technology and the like) is combined with a pasteurization technology to carry out sterilization technology, the pasteurization heat load intensity is reduced, then a cold concentration technology (medium-pressure reverse osmosis concentration, forward osmosis concentration and high-pressure reverse osmosis concentration) is used for concentrating the raw milk, the product heat processing is reduced, the total solid content of the product reaches 30-60%, and then a cold powder spraying technology (such as low-temperature electrostatic spray drying and low-temperature air inlet temperature spraying) is carried out to prepare the high-activity whole milk powder, so that more natural active ingredients are reserved, and the nutritional value of the product is improved.

The invention relates to a combined comprehensive powder making technology which aims at the problem that the existing milk and dairy products serving as raw materials cannot meet the requirements of keeping the original taste, active sensitive ingredients and nutrient substances in the milk and dairy products in the milk powder production technology. Finally, the characteristics of high nutrient content and odor retention of milk and milk powder are realized.

The milk and dairy products comprise cow milk, goat milk, donkey milk, horse milk and camel milk, and also comprise dairy product stock solution formed by separating, combining and blending the milk raw materials, but not limited to other material liquid powder preparing raw materials such as animal and plant functional extracts;

wherein the cold concentration comprises forward osmosis concentration (FO), high pressure reverse osmosis concentration (RO) and medium pressure reverse osmosis concentration, but preferably adopts medium pressure reverse osmosis concentration, i.e. a step of performing reverse osmosis concentration treatment on raw milk by using a medium pressure reverse osmosis membrane; the medium-pressure reverse osmosis concentration treatment is a medium-pressure reverse osmosis concentration treatment step which is used for accurately controlling a reverse osmosis system to overcome the osmotic pressure of milk or dairy products, improve the fluidity, the working temperature and the working area.

The medium-pressure reverse osmosis concentration treatment adopts the operation that the final osmotic pressure of the last stage of the membrane is between 32 and 42bar, accurately adapts to the osmotic pressure of concentrated milk and dairy products, reduces the energy consumption increase caused by high pressure more than 42bar, and can reduce the taste change caused by mechanical influence generated by high pressure.

On the one hand, where the terminal osmotic pressure of the last stage of the membrane needs to be controlled well.

Preferably, the pressure in the medium-pressure reverse osmosis membrane treatment is controlled at 32-42bar, when the concentration value of dry matters of milk and dairy products is below 40%, the osmotic pressure gradient is freely matched, the aim of increasing the concentration of the dry matters to 40% by using the minimum pressure is achieved, and the medium-pressure reverse osmosis can reduce the manufacturing cost of the conventional high-pressure equipment.

On one hand, the working temperature in the medium-pressure reverse osmosis membrane treatment can be accurately adjusted to be 0-20 ℃, the nutrition change in the concentration process can be influenced by overhigh working temperature, and the cost can be influenced by the filtration efficiency of the reverse osmosis membrane due to influence of the temperature.

Preferably, the invention adopts low-temperature concentration, and the outlet temperature of the concentrated solution is controlled to be 10-14 ℃ by adopting a cooling device, so that the cost is effectively controlled, and active sensitive ingredients are completely reserved.

Secondly, reasonable membrane materials and membrane cores are selected in the reverse osmosis membrane treatment of the medium-pressure reverse osmosis concentration equipment. Preferably, the invention uses a coiled polyamide reverse osmosis membrane, KOCH8038 HR-VYV or the like, preferably high pressure resistant, bearing a pressure of 45bar and a flow path width of 46 mil.

The working area of the membrane in the medium-pressure reverse osmosis membrane treatment is adapted to the concentration requirement of milk and dairy products, the flux control of the medium-pressure reverse osmosis membrane is integrated, and the optimal membrane area is selected and designed according to the capacity and the treatment capacity of the production. Preferably, the flux of the medium-pressure reverse osmosis membrane is controlled to be maintained at the level of 2L/m 2/h-8L/m 2/h after the medium-pressure reverse osmosis membrane is operated for 8 hours, and the working area with the best energy production is selected, so that the mechanical energy of the membrane in the operation process and the cost for purchasing membrane materials are reduced;

preferably, the concentration equipment for treating the medium-pressure reverse osmosis membrane comprises membrane cores, membrane chambers, concentration stages, membrane groups and the like, wherein the membrane groups comprise one-stage or multi-stage concentration stages, the concentration stages comprise one or more membrane chambers, and the membrane chambers comprise 1 or more membrane cores, namely, the membrane cores, the membrane chambers, the concentration stages and the membrane groups are combined and connected in a sequence from small to large, and membrane flux is transferred to the rear section of the membrane equipment along with the running time, so that the membrane running efficiency is comprehensively guaranteed.

Preferably, the specific sequential combination connection is implemented by adopting an optimized combination mode of series-parallel-series connection. More preferably, the energy consumption is reduced by adopting a sequential combination connection mode of connecting membrane cores in series (4 branches) -connecting membrane chambers in parallel (6-8) -connecting concentration stages in series (5-6 stages) -connecting membrane groups in series (3-4 groups). More preferably, 6 grades of concentration grades are each level and are set up 1 circulating pump, and in 3 sections combination membrane groups, first 3 concentration grades of first section set up 1 force (forcing) pump, 2 concentration grades in the middle set up 1 force (forcing) pump, and 1 concentration grade sets up 1 force (forcing) pump alone at last, and accurate velocity of flow, the fluidity of pressure adaptation milk and dairy products, so can better adaptation infiltration process's pressure and flow demand.

More preferably, the membrane flux is transferred to the later stage of the membrane equipment within 8 hours of the concentration operation, so that the membrane operation efficiency is comprehensively guaranteed.

The method of the invention adopts low heat energy sterilization or cold sterilization: the low-heat energy or cold sterilization or degerming technology can be one or a combination of several sterilization technologies, and the matching relation between the front and the back is not limited; the low-heat energy or cold sterilization or degerming technical method provided by the combined concentration method comprises the following steps: the method comprises the following steps of steam immersion sterilization, pasteurization, centrifugal sterilization, micro-sieve membrane sterilization, ultraviolet sterilization, radioactive ray irradiation sterilization, ultrasonic sterilization, discharge sterilization, high-pressure sterilization, microwave sterilization, magnetic field sterilization, electrostatic sterilization, induction electron sterilization, strong light pulse sterilization and other sterilization modes. The original odor, active sensitive ingredients and nutrient substances of the milk and the dairy products are protected through scientific and reasonable combination of different bactericides and are kept under the bactericidal action, so that the nutrient loss caused by the bactericides is improved. The combination of the multiple sterilization modes is to analyze the sterilization effect of each sterilization mode on certain types of bacteria and then combine another sterilization mode to kill other types of bacteria. For example, the combination of pasteurization and centrifugal sterilization is adopted, so that not only common bacteria and pathogenic bacteria but also heat-resistant spore bacteria and the like can be killed. According to the combination of the invention, a combination of two or three low-heat sterilization or cold sterilization modes is adopted, preferably, a combination of separation sterilization and pasteurization, a combination of separation sterilization, micro-sieve filtration and steam immersion sterilization modes, or a combination of separation sterilization, ultraviolet sterilization and microwave sterilization.

The sterilization of the invention has the advantages that: on one hand, the concentrated milk and the milk product raw material liquid can meet the requirements of microbial indexes and the requirements of retention indexes of odor, active sensitive ingredients and nutrient substances before or after concentration by adopting a low-heat energy or cold sterilization or degerming technology. On the other hand, the low-heat energy or cold sterilization method adopted for the concentrated milk and the dairy products is suitable for low-heat energy or cold sterilization or degerming with the liquid dry matter concentration of 40 percent, realizes the characteristic that the microorganism indexes of the concentrated milk and the dairy products or the products meet the indexes of pasteurization or pulverization and the like, and can be used for subsequent processing or product storage.

More preferably, a centrifugal sterilization step is adopted before or after the concentration step, and the centrifugal sterilization step is carried out as combined sterilization during other low-heat energy or cold sterilization or sterilization, wherein the sterilization temperature is 40-50 ℃; further preferably, the skim milk is filtered and sterilized by a micro-sieve membrane before the concentration step, the sterilization temperature is 40-50 ℃, and the pore diameter of the sterilization membrane is 0.5 mu m; sterilizing milk fat at 137 deg.C for 4 s, and mixing;

in another preferred embodiment, the concentration step is preceded by steam immersion sterilization at a sterilization temperature of 151 ℃ for 0.1 second, and the steam immersion sterilization at the feed liquid outlet is synchronized to remove odor generated by the sterilization. The applied milk and the milk product raw material liquid are sterilized, so that the original odor of the milk and the milk product can be kept, and meanwhile, the comprehensive retention rate of active sensitive ingredients and nutrient substances is higher than 50%.

More preferably, milk and dairy product raw material liquid is adopted to carry out ultraviolet sterilization before the concentration step, high-flux glass is adopted, the gap layer of the material liquid is 0.2-0.5mm, and the ultraviolet irradiation dose is 800J/L-1200J/L. The temperature of the milk and the milk product raw material liquid is 10-50 ℃, and the smell generated by ultraviolet sterilization is removed by adopting steam immersion sterilization at a synchronous liquid outlet. The original smell of the milk and the dairy products can be kept by sterilizing the milk and the dairy products, and the comprehensive retention rate of active sensitive ingredients and nutrient substances is higher than 60 percent.

More preferably, pasteurization is carried out at the sterilization temperature of 85 ℃ for 15S before or after the concentration step, meanwhile, the contact area and the contact time of the feed liquid and hot water in the pasteurization process are controlled in a plate type contact surface mode through a pasteurization heat exchanger device, so that the protein denaturation rate of the high-concentration liquid is reduced under the pasteurization condition, and the odor generated by pasteurization is removed through a low-temperature vacuum evaporation mode at a synchronous feed liquid outlet. The concentrated milk and the milk product can be sterilized to keep the original smell of the milk and the milk product, the problem of high feed liquid heat sterilization denaturation rate of the highly concentrated milk and the milk product is solved, and meanwhile, the comprehensive retention rate of active sensitive components and nutrient substances is higher than 50 percent.

The low-temperature powder spraying in the method of the invention adopts low-temperature electrostatic spray drying (the product temperature is approximately equal to 45 ℃) in one embodiment, and avoids adopting the traditional high-temperature spray drying 208 ℃ powder spraying (the product temperature is approximately equal to 85 ℃). In another embodiment, spray drying powder preparation at low temperature of air intake, freeze drying powder preparation and the like can be adopted.

Preferably, the milk and the milk product concentrated solution are pumped into a spraying system. The main inlet air is heated to the required temperature by a heater and then sent to the top of the drying tower. The air distributor distributes the water in the tower uniformly, the air supply is contacted with the atomized product liquid drops, and the water is evaporated rapidly within a few seconds. The evaporation itself has a cooling effect (where solid particles are generated) so that the product is not overheated. Under normal conditions, the temperature of the solid particles is about 15 ℃ lower than the air outlet temperature, so that the air inlet temperature is 120-140 ℃, the air outlet temperature is 60-70 ℃, and the solid particles are controlled below 50 ℃, so that the retention rate of active sensitive ingredients and nutrient substances in milk and dairy product powder is effectively protected, and the pollution of microorganisms is avoided.

In another preferred embodiment, the freeze-drying powder preparation method is adopted for preparing powder, a prefabricated open packaging container is used for injecting concentrated milk and milk product concentrated solution, the freeze-drying step of freezing at the temperature of 20-42 ℃ for 24-48 hours is adopted for preparing freeze-dried milk and milk product powder, then the inner part of a freeze dryer is sealed, and the single small-package freeze-dried milk and milk product powder is formed, so that the retention rate of active sensitive ingredients and nutrient substances in the milk and milk product powder is effectively protected, and the pollution of microorganisms is avoided. Or directly freeze-drying into powder by using a freeze dryer.

In another preferred embodiment, a low-temperature electrostatic spray drying powder preparation technology is adopted, so that the size and the temperature of spray-dried atomized liquid drops are relatively controllable, and the spray-dried atomized liquid drops repel each other under the electrostatic action, so that the difficulty of drying and evaporating water is reduced, namely the temperature required by water evaporation, and the degradation or denaturation of core active ingredients caused by high temperature is reduced, therefore, the air inlet temperature is 50-80 ℃, the air outlet temperature is 40-50 ℃, and the solid particles are controlled below 50 ℃, so that the retention rate of active sensitive ingredients and nutrient substances in milk and dairy powder is more effectively protected.

One particularly preferred embodiment of the present invention is as follows:

1) raw milk purification: after raw milk arrives at a factory, physical and chemical index tests are carried out on TS 12.33%, fat 3.2% and protein 3.1%, and the temperature is controlled to be 2-8 ℃ in the storage process; the storage time is strictly controlled within 8 hours; and filtering the raw milk meeting the requirements to remove physical impurities, and purifying the milk. The impurity degree after the treatment step is less than 200PPM, and the number of somatic cells is less than 200000/ml;

2) and (3) centrifugal sterilization: and after temporary storage, the raw milk enters a degerming separator for degerming at 50-55 ℃, the centrifugal force is 7000-15000N, and then the raw milk is cooled to 7 ℃ and stored, and the total solid content of the obtained raw milk is 12.35%.

In order to improve the sterilization effect, cold sterilization is usually performed by combining with microfiltration sterilization, micro-sieve filtration, ultraviolet sterilization and continuous ultrahigh pressure sterilization technologies.

3) Low-heat sterilization: and (4) carrying out pasteurization at 85 ℃ for 15 seconds after cold sterilization, and carrying out low-heat sterilization to ensure the sterilization effect. In the actual production process, a steam immersion sterilization mode (151 ℃ for 0.1 second) or ultraviolet sterilization (800J/L-1200J/L) is also adopted.

4) Concentration: the medium-pressure reverse osmosis membrane adopts a reverse osmosis membrane core with an inter-membrane flow channel of 46mil, the equipment is divided into three sections of membrane groups in 6 concentration stages, the pressure of the last section of membrane group is adjusted to 40bar, an internal circulating pump of each concentration stage is started, the surface flow rate of the membrane in each membrane chamber reaches 4-6m/s, the front and rear pressure of each membrane reaches 0.5-1bar, the pre-concentration is carried out for 20-40min, the cooling water flow in the circulating process is adjusted to control the temperature of the whole feed liquid to be below 12 ℃, the flow output to one section of membrane group under each section of membrane group is adjusted, the total output concentration ratio is controlled to be 3.3-3.5, and the dry matter of the concentrated milk reaches above 40%. The concentration step may be performed before or after sterilization.

5) Powder spraying: the low-temperature electrostatic spray drying is adopted, the air inlet temperature is 50-80 ℃, the air outlet temperature is 40-50 ℃, and the solid particles are controlled below 50 ℃, so that the retention rate of active sensitive ingredients and nutrient substances in milk and dairy product powder is effectively protected.

The milk powder produced by the technical scheme has obvious difference with the milk powder produced by the conventional process in physical properties and certain heat-sensitive components, and the product quality is obviously superior to that of the existing milk powder. The main characteristics are as follows: physical and functional characteristics: the dissolubility, the dispersibility and the wettability are better; chemical characteristics: the contents of beta-lactoglobulin (mg/mL), alpha-lactalbumin (mg/mL), lactoferrin (mg/100g protein), vitamin B12, vitamin C and vitamin B1 are higher, and particularly experiments show that the contents of beta-lactoglobulin, lactulose, lactoferrin and immunoglobulin are more than or equal to 11mg/mL, 20mg/L, 52mg/100g protein and 119mg/mL respectively, which are far higher than comparative examples, and the effects are very excellent.

Drawings

Fig. 1 is a schematic diagram showing a medium-pressure reverse osmosis concentration apparatus employed in an embodiment of the present invention.

Detailed Description

To further illustrate the technical means and effects thereof, the technical solutions of the present invention are further described below with reference to the preferred embodiments of the present invention, and it should be understood that these embodiments are only used for illustrating the present invention and are not used to limit the scope of the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, and that such changes and modifications may be within the scope of the invention.

The related measurement method comprises the following steps:

1. method for determining insolubility index: mixing 10g skimmed milk powder, 13g whole milk powder or 6g whey powder (solid content should be converted if the sample is concentrated milk) with 100ml water at 24 deg.C, stirring at high speed for 90S, standing for 15min, transferring 50ml milk solution to cone with 50ml scale

Centrifuging for 5min in a centrifuge tube, pouring out supernatant, and tapering

The centrifuge tube is filled with clear water (for reading convenience), and then placed into the centrifuge for 5mi centrifugation again, and the precipitation amount (expressed in ml) is read, namely the insolubility index.

2. The method for measuring the wettability comprises the following steps: the wettability determination method recommended by the International Union of Dairy (IDF) consists in pouring 10g of skim milk powder or whole milk powder into 250mL of water at 25 ℃ and recording the wetting time of all the powders with a stopwatch. Skim milk is totally wet within 15s and may be referred to as instant; for full cream milk powder, the wettability is 30-60 s, and the full cream milk powder has better dispersibility in water.

3. The detection method of the dispersibility comprises the following steps: the international association for dairy entries (IDF) developed a detection method: the sample to be tested (25 g of skim milk powder or 34g of whole milk powder) was poured into water (250g,25 ℃) and stirred manually for 20s to disperse the milk powder into powder particles that pass through a 150 micron sieve. The amount of milk powder dissolved or dispersed after passing through the sieve can be obtained by measuring the total dry matter of the filtrate, and the dispersibility of the milk powder is expressed as a percentage. The international dairy consortium (IDF) has recognized that instant dissolution is achieved when the whole milk powder is dispersed at 85% or more or the skim milk powder is dispersed at 90% or more.

In order to avoid repetitive descriptions, specific operations employed in the steps in each example and comparative example are collectively described below:

raw milk acceptance inspection: the raw milk acceptance adopts national standards GB 19301-;

milk purification and filtration: filtering the raw milk meeting the requirement to remove physical impurities, and simultaneously carrying out separated milk purification through a duplex filter with the pore diameter of 0.50 mm.

Storage or cooling storage: cooling the filtered and purified raw milk to 7 deg.C, and storing for less than 4 hr. Simultaneously, carrying out related process index detection;

centrifugal degreasing: heating raw milk to 50 deg.C, defatting in a centrifugal separator, controlling fat content of defatted milk below 0.06% and fat content of cream at 35%;

and (3) centrifugal sterilization: the product in the former step is heated to 50-55 ℃ and enters a degerming separator for degerming, and the centrifugal force is 7000-15000N.

Pasteurization: immediately pasteurizing the product in the former step, heating to 72-85 deg.C, and holding for 15s to realize pasteurization; then cooled to 4-10 ℃.

Ultraviolet sterilization: the product of the former working procedure immediately enters an ultraviolet sterilization section, the total intensity value of ultraviolet sterilization is adjusted to 800J/L-1200J/L, and the milk in the glass interlayer is subjected to ultraviolet sterilization at the temperature of 10-50 ℃.

Steam immersion sterilization: immediately performing steam immersion sterilization on the product in the former step, and when the temperature is raised to the sterilization temperature of 140-;

and (3) sterilization by using a micro-sieve membrane: immediately performing membrane sterilization on the product obtained in the previous step by using a micro-sieve membrane with a pore diameter of 0.5 μm at a high precision and at a temperature of 40-50 ℃;

degassing: the product of the former process enters a degassing section, the temperature is adjusted to 50-70 ℃ and the vacuum degree is adjusted to-0.1 to-0.86 bar for degassing, the odor of the milk is removed, and then the temperature is adjusted to the temperature required by the next process section;

and (3) medium-pressure reverse osmosis concentration: the product of the former stage process enters medium-pressure reverse osmosis membrane treatment equipment for membrane concentration, wherein the medium-pressure reverse osmosis membrane adopts a reverse osmosis membrane core with an inter-membrane flow channel of 46mil, the equipment is divided into three sections of membrane groups by 6 stages of concentration stages, the pressure of the last section of membrane group is adjusted to 40bar, an internal circulating pump of each stage of concentration stage is started, the surface flow rate of the membrane in each membrane chamber reaches 4-6m/s, the pressure of the front and back of each membrane reaches 0.5-1bar, the pre-concentration is carried out for 20-40min, the cooling water flow in the circulating process is adjusted to control the temperature of the whole feed liquid to be below 12 ℃, the flow output to one section of membrane group under each section of membrane group is adjusted, the total output concentration ratio is controlled to be 3.3-3.5, and the dry matter of the concentrated. The medium pressure reverse osmosis concentration equipment used in particular is shown in figure 1.

High pressure reverse osmosis concentration (RO): the product of the former stage process enters high-pressure reverse osmosis membrane treatment equipment for membrane concentration, wherein the medium-pressure reverse osmosis membrane adopts a reverse osmosis membrane core with an inter-membrane flow channel of 46mil, the equipment is divided into four sections of membrane groups by 10 stages of concentration stages, the pressure of the last section of membrane group is adjusted to 50-60bar, an internal circulating pump of each stage of concentration stage is started, the surface flow rate of the membrane in each membrane chamber reaches 4-6m/s, the pressure of the front and the back of each membrane reaches 0.5-1bar, the pre-concentration is carried out for 20-40min, the cooling water flow in the circulating process is adjusted to control the temperature of the whole feed liquid to be below 12 ℃, the flow output to one section of membrane group under each section of membrane group is adjusted, the concentration ratio output by the whole is controlled to be 3.3-3.5, and the dry matter of the.

Forward osmosis concentration (FO): the anterior segment process product gets into the forward osmosis membrane system, and the temperature that gets into forward osmosis membrane concentrated system is 20 ℃, and the forward osmosis membrane is equipped with temperature control system, and whole journey keeps temperature 20 ℃, and the forward osmosis membrane draws liquid side velocity of flow and stoste side velocity of flow proportion is 1: and 4, the flux of the intermediate membrane swings between 0.5 and 1LMH along with the dynamic change of the system. The concentration of the extract is kept at about 9% until the concentration is finished. The used forward osmosis membrane system is a roll-type membrane, and the volume ratio of the membrane area to the feeding volume is 2: 1; the total solid content of the concentrated milk is 30-60%.

Mixing and standardizing: mixing the product obtained in the previous step with sterilized cream, and standardizing to reach the component ratio of concentrated milk; the standardized concentrated milk is stored and inspected in a storage tank by continuously cooling to 4-8 deg.C, and then rapidly filling in a filling machine or entering the next process

And (3) vacuum concentration: the product of the former process enters a vacuum concentration evaporator for heat concentration, the vacuum degree is maintained at 81-90Kpa, the milk temperature is 50-60 ℃, the vacuum degree in the last effect of the multi-effect evaporation chamber is maintained at 83.8-85Kpa, the milk temperature is 40-45 ℃, the pressure of heating steam is controlled at 0-1kg/cm2, the dry matter of the concentrated milk reaches more than 40%, and then the concentrated milk is cooled to the temperature required by the next process.

Concentrate or concentrated product: the concentrated milk enters a storage tank to be continuously cooled to 4-8 ℃ for storage and inspection, and then the concentrated milk quickly arrives at a filling machine for filling or enters the next working procedure.

Cooling: after concentration it is necessary to reduce the temperature to below 8 c and then continue to reduce and maintain the temperature in the 4-8 c storage tank.

Electrostatic spray drying: the air inlet temperature is 50-80 ℃, the air outlet temperature is 40-50 ℃, and the solid particles are controlled below 50 ℃, so that the retention rate of active sensitive ingredients and nutrient substances in milk and dairy product powder is effectively protected.

Low-temperature air inlet temperature spray drying: the method comprises the steps of injecting concentrated milk and a concentrated milk product into a prefabricated open packaging container, carrying out freeze-drying at the temperature of 20-42 ℃ for 24-48 hours to prepare freeze-dried milk and milk product powder, and then sealing the inner part of a freeze dryer to form single small-package freeze-dried milk and milk product powder, so that active sensitive ingredients and nutrient substances in the milk and milk product powder are protected more effectively.

Preparing powder by adopting a freeze drying powder preparation mode: the method comprises the steps of injecting concentrated milk and a concentrated milk product into a prefabricated open packaging container, carrying out freeze-drying at the temperature of 20-42 ℃ for 24-48 hours to prepare freeze-dried milk and milk product powder, and then sealing the inner part of a freeze dryer to form single small-package freeze-dried milk and milk product powder, so that the retention rate of active sensitive ingredients and nutrient substances in the milk and milk product powder is effectively protected, and meanwhile, the pollution of microorganisms is avoided. Or directly freeze-drying into powder by using a freeze dryer.

Conventional spray drying: the spray drying is divided into two stages, the first stage is to concentrate the pretreated milk until the milk solid content is 45-55%, and the second stage is to pump the concentrated milk into a drying tower for drying. The drying process needs a large amount of heat, the heat source is dry and hot air (inlet air), the inlet air temperature is generally 180-220 ℃, the outlet air temperature is 80-90 ℃, and the heating temperature of the powder is higher, so that the loss of nutrient components is serious and the protein denaturation is serious.

Example 1: concentrating by reverse osmosis under medium pressure, separating, sterilizing, pasteurizing, and spray drying by electrostatic method

The specific process is as follows: raw milk acceptance, milk purification by filtration, medium-pressure reverse osmosis concentration, centrifugal sterilization, degassing, pasteurization (85 ℃ for 15 seconds), chilling, and low-temperature electrostatic spray drying. The obtained product was examined, and the results are shown in table 1. The following examples and comparative examples are the same and will not be described repeatedly.

Example 2: separating, sterilizing, pasteurizing, concentrating by reverse osmosis at medium pressure, and spray drying at low temperature

The specific process is as follows: raw milk acceptance inspection, milk purification filtration, centrifugal sterilization, degassing, pasteurization (85 ℃ for 15 seconds), medium-pressure reverse osmosis, refrigeration, low-temperature air inlet spray drying

Example 3: separating, sterilizing, filtering with micro sieve, pasteurizing, concentrating by reverse osmosis under medium pressure, and freeze drying to obtain powder

The specific process is as follows: checking raw milk, filtering to remove pure milk, centrifuging to remove bacteria, micro-sieving, degassing, pasteurizing (85 deg.C, 15 s), reverse osmosis at medium pressure, refrigerating, and lyophilizing

Example 4: RO cold concentration method, separation sterilization, micro filtration sterilization, pasteurization, and electrostatic spray drying

The specific process is as follows: raw milk acceptance, milk purification by filtration, RO (reverse osmosis) -centrifugal sterilization, micro-sieve filtration, degassing, pasteurization (85 ℃ for 15 seconds), and electrostatic spray drying.

Example 5: concentrating by medium-pressure reverse osmosis, separating and sterilizing, filtering with micro-sieve, steam-immersed sterilization, and electrostatic spray drying

The specific process is as follows: raw milk acceptance, milk purification by filtration, medium-pressure reverse osmosis concentration, centrifugal sterilization, micro-sieve filtration, steam immersion sterilization (151 ℃ for 0.1 second), and electrostatic spray drying

Example 6: separating and sterilizing, micro-sieve filtering, steam immersion type sterilization, FO cold concentration method, and spray drying at low temperature

The specific process is as follows: checking and accepting raw milk, filtering and purifying milk, performing centrifugal sterilization, performing micro-sieve filtration, performing steam immersion sterilization (151 ℃ for 0.1 second), performing FO-chilling, and performing spray drying at low-temperature air inlet temperature.

Example 7: separating, sterilizing, ultraviolet sterilizing, microwave sterilizing, medium-pressure reverse osmosis concentrating, and electrostatic spray drying

The specific process is as follows: checking and accepting raw milk, filtering and purifying milk, centrifugally sterilizing, performing ultraviolet sterilization, performing microwave sterilization, performing medium-pressure reverse osmosis concentration, refrigerating, and performing electrostatic spray drying.

Example 8: the medium-pressure reverse osmosis concentration method comprises separating and sterilizing, ultraviolet sterilizing, steam immersion sterilizing, and freeze drying to obtain powder

The specific process is as follows: checking and accepting raw milk, filtering and purifying milk, concentrating by medium-pressure reverse osmosis, performing centrifugal sterilization, performing ultraviolet-steam immersion sterilization (151 ℃ for 0.1 second), and freeze-drying to prepare powder.

Example 9: centrifugal sterilization, ultraviolet sterilization, pasteurization, FO cold concentration method, spray drying at low temperature of air inlet temperature and preparing powder

The specific process is as follows: checking and accepting raw milk, filtering and purifying the milk, centrifugally sterilizing, performing ultraviolet sterilization, pasteurizing (85 ℃ for 15 seconds), FO cooling, and performing spray drying at low-temperature air inlet temperature.

Comparative example 1: adopts the traditional wet powder spraying process (thermal concentration, thermal sterilization and thermal spraying powder)

The specific process is as follows: checking and accepting raw milk, filtering and purifying milk, vacuum concentrating, refrigerating, UHT-conventional spray drying

Comparative example 2: hot concentration, cold sterilization and hot spraying powder

The specific process is as follows: raw milk acceptance, milk purification by filtration, vacuum concentration, chilling, centrifugal sterilization, ultraviolet sterilization, conventional spray drying, comparative example 3: hot concentration, cold sterilization and cold powder spraying

The specific process is as follows: checking and accepting raw milk, filtering and purifying milk, vacuum concentrating, refrigerating, centrifugally sterilizing, ultraviolet sterilizing and electrostatic spray drying

Comparative example 4: hot concentration, hot sterilization and cold powder spraying

The specific process is as follows: checking and accepting raw milk, filtering and purifying milk, vacuum concentrating, refrigerating, UHT-electrostatic spray drying.

Comparative example 5: separating sterilization, ultraviolet sterilization, microwave sterilization, medium-pressure reverse osmosis concentration, and conventional spray drying

The specific process is as follows: checking and accepting raw milk, filtering and purifying milk, centrifugally sterilizing, performing ultraviolet sterilization, performing microwave sterilization, performing medium-pressure reverse osmosis concentration, refrigerating, and performing conventional spray drying.

The powders obtained in the above examples and comparative examples were tested and the experimental data are as follows:

the milk powder has high nutritive value and the indexes of high active ingredients comprise beta-lactoglobulin, lactulose, furosine, lactoferrin and immunoglobulin, namely, the higher the content of the ingredients is, the higher the nutritive value of the milk powder is; and the data in examples 1-9 are much higher than the data in comparative examples 1-4. Wherein, in the comparative example 1, the conventional technology adopted by all the milk powder on the market at present almost all the nutrient components of the produced milk powder are lost, and the quality of the milk powder is not good. Comparative examples 2, 3, 4 and 5 show that the three steps need to adopt a cold method to finally ensure that the nutrient components of the flour are retained to the maximum extent, so that the quality of the flour is good, otherwise, the quality of the flour is poor due to the heating mode in one link.

The indexes for representing the quality of the milk powder comprise solubility (insolubility index), dispersibility and wettability; the higher the insolubility index, the more denatured the protein in the product and the poorer the solubility of the product. The lower the wettability index, the more water soluble the product. The dispersibility is an important characteristic of the instant milk powder, the dispersibility index is high, the dispersibility of the product is better, the milk powder usually has good wettability, no fine powder is generated, and the agglomeration effect is good. The data in examples 1-10 and comparative examples 1-4 are very clear to yield the effect.

The index for representing the digestion and absorption conditions of the milk powder is the content of free amino acid, and an in vitro simulated digestion experiment is carried out, so that the content of the free amino acid can directly reflect the digestion and absorption conditions of the product, and the higher the content is, the better the digestion and absorption rate is.

Claims

1. A preparation method of high-activity milk powder is characterized by comprising the following steps: cold concentration is adopted for milk or dairy products, low heat energy or cold sterilization is adopted before or after the cold concentration, and finally low-temperature spraying or freeze drying is adopted to prepare the milk powder.

2. The method of claim 1, wherein the milk or dairy product is selected from cow's milk, goat's milk, donkey's milk, horse's milk, and camel's milk, and the milk raw materials are separated, combined, and blended to form a dairy stock solution.

3. The method of claim 1, wherein the low-heat or cold sterilization is selected from one or more of steam immersion sterilization, pasteurization, centrifugal sterilization, micro-sieve membrane sterilization, ultraviolet sterilization, radiation sterilization, ultrasonic sterilization, electric discharge sterilization, high-pressure sterilization, microwave sterilization, magnetic field sterilization, electrostatic sterilization, induction electron sterilization, and intense light pulse sterilization, preferably two or three of them, preferably a combination of separation sterilization and pasteurization, a combination of separation sterilization, micro-sieve filtration, and steam immersion sterilization, or a combination of separation sterilization, ultraviolet sterilization, and microwave sterilization.

4. The method of claim 1, wherein the cold concentration is performed by medium pressure reverse osmosis concentration, preferably wherein the final permeate pressure of the last stage of the membrane is maintained at 32-42bar, the operating temperature is controlled at 0-20 ℃, and the outlet temperature of the concentrate is controlled at 10-14 ℃ by a cooling device.

5. The preparation method according to claim 4, wherein the medium-pressure reverse osmosis membrane concentration equipment comprises a membrane core, membrane chambers, concentration stages and a membrane group, the membrane group comprises one or more concentration stages, the concentration stages comprise one or more membrane chambers, and the membrane chambers comprise one or more membrane cores, namely, the membrane core-membrane chamber-concentration stage-membrane group is connected in a sequential combination manner from small to large.

6. The concentration method according to claim 5, wherein the combination connection mode is a sequential combination connection mode of membrane core series-membrane chamber parallel-concentration stage series-membrane group series, more preferably, a sequential combination connection mode of 4 membrane cores series-6-8 membrane chamber parallel-5-6 concentration stage series-3-4 membrane group series; further preferably, 1 circulating pump is arranged at each of 6 stages of concentration stages, 1 pressurizing pump is arranged at the first 3 concentration stages in the first stage, 1 pressurizing pump is arranged at the middle 2 concentration stages in the 3 sections of combined membrane groups, and 1 pressurizing pump is independently arranged at the last 1 concentration stage; preferably, the flux control of the medium-pressure reverse osmosis membrane still maintains the level of 2L/m 2/h-8L/m 2/h after running for 8 hours.

7. The method of claim 1, wherein the low temperature spray is selected from the group consisting of low temperature electrostatic spray drying, low temperature air inlet spray drying, and freeze drying to produce a powder.

8. The method according to any one of claims 1 to 5, wherein the specific steps include raw milk acceptance-filtered clean milk-medium pressure reverse osmosis concentration-centrifugal sterilization-degassing-pasteurization (preferably 85 ℃, 15 seconds) -chilling-low temperature electrostatic spray drying.

9. The method according to any one of claims 1 to 5, comprising the steps of:

1) raw milk purification: filtering raw milk to remove physical impurities, and purifying the milk;

2) and (3) centrifugal sterilization: entering a degerming separator for degerming at the temperature of 50-55 ℃, wherein the centrifugal force is 7000-15000N;

3) low-heat sterilization: pasteurizing at 85 deg.C for 15s after cold sterilization; or carrying out ultraviolet sterilization by adopting steam immersion sterilization at 151 ℃ for 0.1 second or under the condition of 800J/L-1200J/L;

4) concentration: a medium pressure reverse osmosis membrane, which is carried out before or after low heat sterilization;

5) powder spraying: the low-temperature electrostatic spray drying is adopted, the air inlet temperature is 50-80 ℃, the air outlet temperature is 40-50 ℃, and the solid particles are controlled below 50 ℃.

10. The process according to any one of claims 1 to 9, wherein the high-activity milk powder obtained by the process has a beta-lactoglobulin content of 11mg/mL or more, a lactulose content of 20mg/L or more, a lactoferrin content of 52mg/100g protein or more, and an immunoglobulin content of 119mg/mL or more.