Preparation method of formula milk powder

Abstract

The invention relates to a preparation method of formula milk powder. The method comprises the following steps: mixing: mixing a base milk raw material solution, a skimmed milk raw material solution, a demineralized whey raw material solution and other optional non-temperature-sensitive components allowed to be added; a spray drying step, wherein the mixed material obtained in the mixing step is subjected to spray drying to obtain powder; wherein in the mixing step, the base milk raw material liquid is pasteurized emulsion directly from animals; the skimmed milk raw material liquid is an emulsion obtained by centrifugally degreasing animal milk; the desalted whey raw material solution is an emulsion obtained by subjecting animal milk to whey separation and whey desalination, the whey separation is performed by membrane separation, and the whey desalination is performed by membrane separation to remove salt from the whey. According to the preparation method disclosed by the invention, the denaturation rate of Maillard reaction products and whey protein in the formula milk powder is effectively reduced, and meanwhile, the reconstituability and digestion and absorption properties of the product are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of food, and relates to a preparation method of formula milk powder. More specifically, it relates to a preparation method of infant formula milk powder with excellent freshness and reconstitution properties. Background Art

[0002] Breast milk is an ideal food source to ensure the growth and development of infants. However, due to various practical factors, some infants cannot be breastfed exclusively or need to terminate breastfeeding prematurely. To ensure the normal nutritional needs of infants, formula milk powder has become the only nutritional source for breast milk substitution. However, in the production process of infant formula milk powder, multi-stage high-intensity heat treatment is required to meet the sterilization requirements. While this processing method ensures food safety, it may also have potential impacts on the nutritional value and safety of the product.

[0003] In the heat treatment process of infant formula milk powder, the Maillard reaction is one of the most representative chemical changes. The essence of this reaction is a non-enzymatic browning reaction between the carbonyl group of reducing sugars (such as lactose, galactose) and the amino group of amino acids (such as lysine, arginine). Since cow's milk itself is rich in lactose, galactose, as well as various proteins and amino acids, this type of reaction is extremely likely to occur during its processing. In the primary reaction stage, the ε-amino group of lysine combines with the reducing sugar to form a lactuloselysine complex, resulting in a significant reduction in the bioavailability of lysine. As the reaction progresses, these complexes are further oxidized to form carboxymethyllysine (also known as furosine), and this irreversible chemical modification product is called "blocked lysine". It should be noted that the content of furosine has now become an internationally recognized quantitative indicator of the heat treatment intensity of dairy products and the progress of the Maillard reaction. Research shows that the amount of Maillard reaction products (MRPs) generated in dairy products is positively correlated with the heat treatment parameters. Specifically, when the temperature increases or the heating time prolongs, the content of MRPs will show an exponential growth. For example:

[0004] The research by Wang Zhixu et al. (The influence of heat treatment process on the digestion and absorption of nutrients in infant formula powder [J]. Journal of Clinical Pediatrics, 2016, 34(03): 237-240.) shows that the Maillard reaction occurring during the heat treatment process has a significant impact on the nutritional value of proteins (especially whey proteins). The specific mechanisms are as follows: 1) Decrease in protein digestibility: The Maillard reaction modifies the amino sites of proteins through glycosylation, and the resulting steric hindrance will prevent digestive enzymes from approaching the cleavage sites of proteins, thereby reducing the sensitivity of proteins to enzymatic hydrolysis. This indicates that the structural changes of proteins caused by heat treatment may endow them with certain anti-digestive properties; 2) Decrease in lysine bioavailability: The lysine residues in whey proteins have high reactivity and are easily combined with the carbonyl groups of reducing sugars such as lactose and galactose. Whether it is the initial products of the Maillard reaction (such as lactuloselysine, fructoselysine) or the intermediate products (such as lysinoalanine), the lysine in them cannot be dissociated by digestive enzymes, resulting in a significant reduction in its bioavailability. The results of this study suggest that the heat treatment process in the production of infant formula powder may affect the digestion and absorption of proteins through the Maillard reaction, thereby reducing its nutritional value.

[0005] The research by Li Qian (Analysis of the composition of bovine whey proteins under different heat treatments and evaluation of their nutritional value [D]. Northeast Agricultural University, 2012.) shows that different heat treatment processes have a significant impact on the nutritional value of bovine whey proteins. The research data show that in commercially available demineralized whey powder treated by spray drying (inlet temperature 180°C, outlet temperature 90°C), the lysine loss rate is as high as 25.51%, which is 25 times that of whey pasteurized at 85°C / 15s and 15.28% higher than that of whey heat-treated at 95°C / 20min. This result confirms that with the increase in the intensity of heat treatment, the loss of lysine shows a significant upward trend. It is worth noting that the ineffective lysine formed during the heat treatment process (such as the bound lysine in Maillard reaction products) cannot be dissociated by digestive enzymes, and the increase in its content will directly reduce the protein nutritional value of demineralized whey powder. Since lysine is an essential amino acid for the growth and development of infants, when its content decreases, it will lead to an imbalance in the amino acid pattern of proteins, thereby reducing the bioavailability of proteins. This phenomenon is particularly crucial for infants who use formula milk powder as the sole or main protein source, and may have an adverse impact on their protein nutritional status. The results of this study suggest that during the production of infant formula milk powder, the intensity of heat treatment should be strictly controlled to maximize the retention of the nutritional value of whey proteins and ensure that infants obtain high-quality protein nutrition.

[0006] The Maillard reaction caused by overheating not only reduces the bioavailability of nutrients but also produces various potentially harmful by-products. This problem is particularly prominent in infant formula powder, where the content of Maillard reaction products is usually significantly higher than that in other dairy products. Since formula powder is the sole or main source of nutrition for non-breastfed infants, this continuous exposure to high levels of Maillard reaction products poses a food safety hazard that cannot be ignored. Although the long-term studies on the impact of Maillard reaction products on infant health are currently insufficient, several research findings deserve high attention: 1) The study by Li Y et al. (Whey protein processing influences formula-induced gut maturation in preterm pigs[J]. J Nutr, 2013, 143(12): 1934-1942.) showed that infant formula powder prepared with heat-treated whey protein affects the intestinal development of preterm piglets, specifically manifested as abnormal intestinal tissue structure, impaired function, and decreased barrier integrity, ultimately delaying the normal maturation process of the intestine. 2) The study by Mericq V et al. (Maternally transmitted and food-derived glycotoxins: a factor preconditioning the young to diabetes[J]. Diabetes Care, 2010, 33(10): 2232-2237.) found that the plasma lysinoalanine level in formula-fed infants increased significantly, and this elevated state may persist into adulthood. This continuous exposure to Maillard reaction products may increase the risk of metabolic diseases such as diabetes by increasing oxidative stress and inflammatory responses. These research findings suggest that the high-level exposure to Maillard reaction products in infant formula powder may have various adverse effects on infant growth and development, which urgently requires the high attention of the industry and researchers. To ensure the health of infants, it is necessary to further study the safety threshold of Maillard reaction products and optimize the production process to reduce their generation amount.

[0007] Whey protein is more likely to participate in the Maillard reaction and be glycated during heat treatment because its lysine residue content is significantly higher than that of casein. It is worth noting that the demineralized whey protein powder commonly added to infant formula has undergone multiple heat treatment processes including pasteurization, concentration, DSI sterilization, and spray drying during the raw material production stage. This cumulative heat treatment effect results in a significantly higher content of Maillard reaction products in infant formula than in ordinary dairy products. The research by Birlouez-Aragon I et al. (Assessment of protein glycation markers in infant formulas[J].Food Chem,2004,87(2):253-259.) provides empirical data for this. This research conducted a comparative analysis of 41 mainstream infant formulas, 7 kinds of cow's milk treated with similar heat treatment, and 7 kinds of ordinary milk powders sold in the French, Spanish, and German markets. The results showed that: 1) The content of furosine in infant formula reached 2-3 times that of cow's milk and ordinary milk powder; 2) The content of advanced glycation end products (AGEs) was 2-5 times that of the control samples; 3) Based on biochemical index estimation, the lysine loss in formula powder was about 6 times that of fresh cow's milk. These data fully illustrate that multiple heat treatments in the production process of infant formula will significantly exacerbate the Maillard reaction, thereby affecting the nutritional quality of the product. This finding has important guiding significance for optimizing the production process of infant formula.

[0008] As the basic raw material for infant formula powder, the nutritional components of cow's milk are significantly different from those of breast milk. To simulate the nutritional composition of breast milk, raw materials such as lactose powder, whey protein, and skim milk powder need to be added additionally during the production process of formula powder to adjust the protein and carbohydrate content. To meet the requirements of industrial production, storage, and transportation, whey protein is usually added in the form of demineralized whey protein powder or concentrated whey protein powder. However, this processing method may have an important impact on the nutritional value of proteins. Multiple studies have confirmed that the nutritional loss of whey protein during processing and storage cannot be ignored: 1) The research by Li Xing (Research on the digestion and absorption mechanism of milk proteins during heat treatment and storage [D]. Harbin Institute of Technology, 2021.) shows that with the increase in heat treatment intensity and the extension of storage time, although the total amount of amino acids produced by the hydrolysis of milk proteins increases, the proportion of essential amino acids decreases significantly, resulting in the destruction of amino acid balance. This change may affect the utilization efficiency of proteins by infants. 2) The research by Li Qian (Analysis of the components of whey protein in cow's milk with different heat treatments and evaluation of its nutritional value [D]. Northeast Agricultural University, 2012.) specifically points out that demineralized whey powder needs to undergo multiple heat treatments and secondary spray drying during the production process of formula powder. This repeated processing will lead to: a significant increase in protein denaturation rate, a decrease in protein solubility, partial loss of functional properties, and a decrease in in vivo digestibility; these changes not only reduce the nutritional value of demineralized whey powder but also may affect the absorption and utilization of key nutrients by infants, having a potential adverse impact on their healthy growth. This finding suggests that in the production of infant formula powder, it is necessary to optimize the processing technology to maximize the retention of the nutritional value of proteins.

[0009] Currently, the production processes of infant formula milk powder mainly include wet process, dry process, and combined wet and dry process. For example:

[0010] CN116250570B discloses a preparation method of infant formula milk powder, which adopts a dry-wet combined process. Specifically, raw materials such as raw cow milk, lactose, whole milk powder, skim milk powder, whey protein powder, demineralized whey powder, α-lactalbumin powder, and sunflower oil are processed through procedures such as batching, filtration, homogenization, cooling, concentration sterilization, spray drying, fluidized bed drying and cooling to obtain semi-finished products. On the basis of the semi-finished products, raw materials such as DHA, ARA, lactoferrin, nucleotides, and probiotics are added for dry mixing to obtain the finished product. At the same time, the production methods reported in documents CN116158469B, CN103504025A, CN115769840A, CN117898337A, and CN102283289A all use deep-processed milk raw materials as the main ingredients, including whole milk powder, demineralized whey powder, skim milk powder, etc. These raw materials have undergone multiple high-intensity heat treatments during the primary processing, resulting in the formation of Maillard reaction products. When these raw materials are used in the production of infant formula milk powder, they need to go through heat treatment procedures such as DSI sterilization, concentration, and spray drying, resulting in further accumulation of Maillard reaction products. This multi-stage and repetitive heat treatment process will cause a significant increase in the content of Maillard reaction products in the final product, which may have an adverse impact on the product quality and nutritional value.

[0011] CN101984836A discloses a method for producing infant formula milk powder using a dry process. The process is as follows: First, lactose is mixed with vegetable oil, homogenized and emulsified, evaporated and concentrated, and spray dried to make plant fat powder. Then, the plant fat powder is mixed with whole milk powder, skim milk powder, whey protein powder, and nutrients such as ARA, DHA, lactoferrin, nucleotides, taurine, and choline through a dry mixing process. However, this method has the following potential problems: 1) Accumulation of Maillard reaction products: The deep-processed milk raw materials such as whole milk powder, skim milk powder, and whey protein powder used may undergo Maillard reaction during storage, affected by factors such as moisture content, water activity (Aw), temperature, sugar and amino acid composition. Among them, temperature and water activity are the key influencing factors - an increase in temperature will significantly accelerate the Maillard reaction, and water activity (Aw>0.3) will further promote the reaction. Therefore, with the extension of storage time, the content of Maillard reaction products in the raw materials may continue to increase, thus affecting the quality of the final product; 2) Problems of mixing uniformity and nutrient distribution: The mixing uniformity of the dry process is usually not as good as that of the wet process, which may lead to uneven distribution of nutrients (such as ARA, DHA, lactoferrin, etc.) in the finished product, thus affecting the nutritional stability and batch consistency of the product. Summary of the Invention

[0012] Problems to be Solved by the Invention

[0013] As mentioned above, formula milk powder, especially infant formula milk powder, as the sole and main food for infants in the early stage of life who are not breastfed, the quality of its nutrients is particularly important. During the production process of infant formula milk powder, repeated overheating treatment, although helpful for microbial safety and eating convenience, may reduce the digestion and utilization efficiency of nutrients such as protein, lactose, fat, and vitamins. Research shows that Maillard reaction products (MRPs) mainly come from the strong heat treatment during the production process of infant formula milk powder, and high-intensity heat treatment not only increases the degree of denaturation of whey protein but also reduces its digestibility and absorption rate in the body.

[0014] Traditional production processes usually use solid components such as skim milk powder, demineralized whey powder, and concentrated whey protein powder for mixing, homogenization, etc. to obtain the final formula milk powder, which has high efficiency. However, in the acquisition of these powder raw materials, an increase in the Maillard reaction may also occur due to multiple heat experiences or long-term storage. In addition, in the process of producing formula milk powder with liquid milk from animal milk as the raw material, although the introduction of multiple heating and spraying processes can be avoided, different heat experiences may also exist in various raw materials, especially during the separation of various liquid raw materials from animal milk.

[0015] Therefore, there are doubts about the increase in Maillard reaction products and the increase in the denaturation rate of whey protein (affecting digestion and absorption) in the above-mentioned various processing technologies of formula milk powder. As a result, not only will there be a loss of nutrition, but there is also a tendency for the product's reconstitution properties to decline (reducibility in solubility and stability). Therefore, how to reduce the heat treatment intensity during the production process of infant formula milk powder is the key to reducing Maillard reaction products and maintaining the natural structure of whey protein.

[0016] During the research process of the present invention, it was unexpectedly found that on the basis of meeting various hygienic requirements and basic nutrient formulas, by using all-liquid protein raw materials for feeding and combining mild heat treatment processes, the Maillard reaction products and the denaturation rate of whey protein in infant formula milk powder can be effectively reduced, while improving the reconstitution properties and digestion and absorption performance of the product. This technology provides an innovative solution for producing safer and more nutritious formula milk powder, especially suitable for non-breastfed infants who are sensitive to protein.

[0017] Solutions for Solving the Problems

[0018] In order to solve the above technical problems, the present invention adopts a process route of using all-liquid protein raw materials for feeding. In particular, a membrane process is used to obtain skim liquid milk and demineralized liquid whey as part of the raw materials, abandoning the traditional high-heat-treated dry powder raw materials, thereby producing infant formula milk powder with high freshness, low Maillard reaction products, and high digestibility and absorption rate.

[0019] [1]. The present invention provides a method for preparing formula milk powder, wherein the method comprises:

[0020] A step of mixing, which is a step of mixing a base milk raw material liquid, a skim milk raw material liquid, a desalted whey raw material liquid, and optionally other allowable non-temperature-sensitive components that can be added;

[0021] A step of spray drying, which is to spray dry the mixed material obtained in the mixing step to obtain a powder;

[0022] Wherein, in the mixing step:

[0023] The base milk raw material liquid is a pasteurized milk directly from an animal;

[0024] The skim milk raw material liquid is a milk obtained by centrifugally defatting animal milk;

[0025] The desalted whey raw material liquid is a milk obtained by separating whey and desalting whey from animal milk, and the whey separation is a whey separation carried out by membrane separation, and the whey desalting is to remove the salts in the whey by membrane separation;

[0026] The denaturation rate of whey protein in the formulated milk powder is 11% or less.[[ID=2l]]

[0027] [2]. The method according to [1], wherein the base milk raw material liquid, the skim milk raw material liquid, and the desalted whey raw material liquid are all from cow milk, goat milk or horse milk.

[0028] [3]. The method according to [1] or [2], wherein in the preparation of the skim milk raw material liquid: after the centrifugal defatting, the skim milk raw material liquid is obtained by one or both of pasteurization and membrane concentration.

[0029] [4]. The method according to any one of [1] to [3], wherein in the preparation of the desalted whey raw material liquid: the whey separation is carried out by microfiltration membrane treatment, and the whey desalting is carried out by electrodialysis treatment.

[0030] [5]. The method according to [4], wherein between the microfiltration membrane treatment and the electrodialysis treatment, there is also a treatment process of nanofiltration membrane to concentrate the whey liquid to be electrodialyzed.

[0031] [6]. The method according to any one of [1] to [5], wherein after the powder is obtained by spray drying, the powder is further mixed with optionally other allowable temperature-sensitive components that can be added.

[0032] [7]. The method according to any one of [1] to [6], wherein the mixing step includes a homogenization treatment.

[0033] [8]. According to the method described in any one of [1] to [7], wherein, between the step of mixing and the step of spray drying, there is also included one or both of a step of ingredient adjustment and a step of sterilization.

[0034] [9]. According to the method described in any one of [1] to [8], wherein,

[0035] the dry matter content in the skim milk raw material liquid is 9 to 25% by mass, and the fat content is 0.1% by mass or less;

[0036] the conductivity of the desalted whey raw material liquid is 1.5 mS / cm or less;

[0037] the dry matter content in the mixed material to be spray dried is 40 to 60% by mass.

[0038]

[10] . According to the method described in any one of [1] to [9], wherein, the content of furosine in the formulated milk powder is 500 mg / 100 g of protein or less.

[0039] Effects of the Invention

[0040] By implementing the above technical solutions, the present invention has achieved the following technical effects:

[0041] 1) Avoid multiple heat treatments: Adopt a process route of feeding all liquid protein raw materials. In particular, adopt a membrane process to obtain skim liquid milk and desalted liquid whey as partial raw materials, and no longer use raw materials such as skim milk powder, desalted whey powder, and concentrated whey protein powder that have undergone repeated high-temperature treatments, reduce the occurrence of Maillard reaction, and retain the natural structure of proteins to the greatest extent.

[0042] 2) Reduce whey protein denaturation: Adopt low-temperature evaporation concentration and optimize the spray drying process (such as reducing the exhaust air temperature) to reduce protein thermal denaturation; the retention degree of the natural conformation of whey protein in the product is high, and the digestion and absorption rate is significantly better than that of products of traditional processes.

[0043] 3) Reduce Maillard reaction products (MRPs): Compared with traditional processes, the content of harmful substances such as furosine in the formulated milk powder of the present invention is significantly reduced; it is closer to the protein digestion mode of breast milk and reduces potential health risks (such as metabolic burden and intestinal irritation).

[0044] 4) Improve reconstitution properties: Due to the low degree of protein denaturation, the product has better solubility and dispersibility, reduces caking phenomenon, and improves the feeding experience. Description of the Drawings

[0045] Figure 1 : Process flow chart for preparing the formulated milk powder in the embodiment of the present invention;

[0046] Figure 2 : Dissolution state evaluation criteria;

[0047] Figure 3 : Vitiligo evaluation criteria. Detailed implementation manners

[0048] The following will detail various exemplary embodiments, features, and aspects of the present invention. The term "exemplary" used herein means "serving as an example, embodiment, or illustration". Any embodiment described herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments.

[0049] In addition, for better illustration of the present invention, numerous specific details are given in the following detailed implementation manners. Those skilled in the art should understand that the present invention can be implemented without some of these specific details. In other instances, methods, means, equipment, and steps well-known to those skilled in the art are not described in detail to highlight the gist of the present invention.

[0050] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0051] In this specification, the meaning expressed by using "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process.

[0052] In this specification, the "some specific / preferred implementation manners", "other specific / preferred implementation manners", "implementation manners", etc. mentioned refer to the specific elements (e.g., features, structures, properties, and / or characteristics) related to the implementation manner described, which are included in at least one of the implementation manners described herein, and may or may not exist in other implementation manners. Additionally, it should be understood that the elements can be combined in various implementation manners in any suitable way.

[0053] In this specification, the numerical range expressed by using "numerical value A to numerical value B" refers to the range including the endpoint numerical values A and B.

[0054] In this specification, the numerical range expressed by using "above" or "below" refers to the numerical range including this number.

[0055] In this specification, the use of "optional" or "optionally" means that certain substances, components, execution steps, applied conditions, etc. are used or not used.

[0056] In this specification, the terms "comprising", "having", "including", or "containing" can be inclusive or open-ended and do not exclude additional, unrecited elements or method steps. At the same time, "comprising", "having", "including", or "containing" can also be construed as closed, excluding additional, unrecited elements or method steps.

[0057] In this specification, the term "about" can mean: a value includes the standard deviation of the error of the apparatus or method used to measure that value. The numerical ranges and parameters defining the present invention are approximate values, and the relevant values in the specific embodiments have been presented as precisely as possible herein. However, any value inherently and inevitably contains the standard deviation caused by the aforementioned test apparatus or method. Therefore, unless otherwise expressly stated, it should be understood that all ranges, amounts, values, and percentages used in the present invention are modified by "about". Herein, "about" generally means that the actual value is within ±2%, ±1%, or ±0.5% of a specific value or range.

[0058] In this specification, "solids" and "dry matter" have the same meaning and refer to the total solids in food, including soluble solids and insoluble solids.

[0059] In this specification, the "concentration multiple" mentioned refers to the weight ratio (or volume ratio) of the feed liquid before membrane filtration to the retentate in the membrane filtration separation process, where the feed liquid before membrane filtration = retentate + permeate.

[0060] In this specification, unless otherwise specified, the "conductivity" described in the present invention is the conductivity at room temperature.

[0061] In this specification, unless otherwise specified, the "normal temperature" or "room temperature" used generally refers to the temperature at 23 ± 2°C.

[0062] The present invention provides a method for preparing formula milk powder, wherein the method comprises:

[0063] A mixing step of mixing a base milk raw material liquid, a skim milk raw material liquid, a desalted whey raw material liquid, and optionally other allowable non-temperature-sensitive components that can be added;

[0064] A spray drying step of spray drying the mixed material obtained in the mixing step to obtain a powder.

[0065] Mixing Steps

[0066] In the mixing step of the present invention, a step of mixing a base milk raw material liquid, a skim milk raw material liquid, a desalted whey raw material liquid, and optionally other allowable non-temperature-sensitive components that can be added.

[0067] (Base milk raw material liquid)

[0068] In the present invention, the base milk raw material liquid is a directly animal-derived, pasteurized emulsion.

[0069] In some specific embodiments, the milk raw material of the base milk raw material liquid comes from cow milk, goat milk, mare milk or their colostrums, etc. Preferably, it can be cow milk or goat milk, and more preferably, it can be cow milk.

[0070] Specifically, the preparation process of the base milk raw material liquid is as follows:

[0071] (1) Milk raw material acceptance: Select raw cow milk that meets the standards as the raw material; in some specific embodiments, the total number of colonies of the milk raw material is controlled within the range that meets the relevant safety standards. For example, the total number of colonies of the milk raw material is controlled below 1×10 5 cfu / mL.

[0072] (2) Preheating treatment: Preheat the raw cow milk to 40 - 60 °C to optimize the subsequent milk clarification effect.

[0073] (3) Milk clarification and sterilization: Sterilize and remove impurities from the preheated raw cow milk. Typically, a milk clarifier can be used for milk clarification and sterilization.

[0074] (4) Pasteurization: Maintain at 80 - 90 °C for 10 - 20 s and quickly cool to 6 - 10 °C to ensure effective killing of pathogenic bacteria while maximizing the retention of nutrients and guaranteeing the freshness of the product.

[0075] In some specific embodiments, the dry matter content in the base milk raw material liquid is 10 - 15% by mass. For example, it can be 10% by mass, 11% by mass, 12% by mass, 13% by mass, 14% by mass, 15% by mass, etc.

[0076] (Skim milk raw material liquid)

[0077] In the present invention, the skim milk raw material liquid is an emulsion obtained by centrifugal defatting of animal milk.

[0078] In some specific embodiments, the animal milk comes from cow milk, goat milk, mare milk or their colostrums, etc. Preferably, it can be cow milk or goat milk, and more preferably, it can be cow milk.

[0079] In some embodiments, in the preparation of the skim milk raw material liquid: after centrifugal defatting, it is subjected to one or two treatments of pasteurization and membrane concentration to obtain the skim milk raw material liquid.

[0080] Specifically, the preparation process of the skim milk raw material liquid is as follows:

[0081] (1) Raw milk material acceptance: Select raw cow milk that meets the standards as the raw material; in some specific embodiments, the total number of colonies of the milk raw material is controlled within the range that meets the relevant safety standards. For example, the total number of colonies of the milk raw material is controlled below 1×10 5 cfu / mL.

[0082] (2) Preheating treatment: Preheat the above-mentioned raw cow milk to 40 - 60°C to optimize the subsequent milk clarification effect.

[0083] (3) Centrifugal defatting: Perform defatting separation on the preheated raw cow milk at a rotational speed of 4500 - 5500 r / min. Typically, a separator can be used for centrifugal defatting treatment.

[0084] (4) Pasteurization: Maintain at 80 - 90°C for 10 - 20 s and quickly cool to 6 - 10°C to ensure effective killing of pathogenic bacteria while maximizing the retention of nutrients and guaranteeing the freshness of the product.

[0085] (5) Membrane concentration: Concentrate the skim milk after pasteurization at an operating pressure of 20 - 30 bar. Typically, reverse osmosis (RO) membranes can be used for concentration treatment.

[0086] In some specific embodiments, the dry matter content in the skim milk raw material liquid is 9 - 25% by mass, preferably 15 - 20% by mass. For example, it can be 10% by mass, 12% by mass, 15% by mass, 18% by mass, 20% by mass, 22% by mass, 25% by mass, etc.; the fat content is below 0.1% by mass, preferably below 0.09% by mass, more preferably below 0.07% by mass, and further preferably below 0.06% by mass.

[0087] (Desalted whey raw material liquid)

[0088] In the present invention, the desalted whey raw material liquid is an emulsion obtained by whey separation and whey desalting of animal milk. And the whey separation is carried out by membrane separation, and the whey desalting is to remove the salts in the whey by membrane separation.

[0089] In some specific embodiments, the animal milk comes from cow milk, goat milk, horse milk or their colostrums, etc. Preferably, it can be cow milk or goat milk, and more preferably it can be cow milk.

[0090] In some specific embodiments, in the preparation of the desalted whey raw material liquid: the whey separation is carried out by microfiltration membrane treatment, and the whey desalting is carried out by electrodialysis treatment.

[0091] In some specific embodiments, between the microfiltration membrane treatment and the electrodialysis treatment, a nanofiltration membrane treatment process is further included to concentrate the whey to be subjected to electrodialysis.

[0092] Specifically, the preparation process of the desalted whey raw material liquid is as follows:

[0093] (1) Milk raw material acceptance: Select raw cow milk that meets the standards as the raw material; in some specific embodiments, the total number of colonies of the milk raw material is controlled within the range that meets the relevant safety standards. For example, the total number of colonies of the milk raw material is controlled below 1×10 5 cfu / mL.

[0094] (2) Preheating treatment: Preheat the above-mentioned raw cow milk to 40-60°C to optimize the subsequent milk clarification effect.

[0095] (3) Centrifugal defatting: Defat and separate the preheated raw cow milk at a rotational speed of 4500-5500 r / min. Typically, a separator can be used for centrifugal defatting treatment. Preferably, in the skim milk obtained after centrifugal defatting treatment, the fat content can be 0.1% by mass or less, preferably 0.09% by mass or less, more preferably 0.07% by mass or less, and further preferably 0.06% by mass or less.

[0096] (4) Pasteurization: Maintain at 80-90°C for 10-20 s and quickly cool to 6-10°C to ensure effective killing of pathogenic bacteria while maximizing the retention of nutrients and ensuring the freshness of the product.

[0097] (5) Whey separation: Microfiltration separate the skim milk after pasteurization to obtain whey.

[0098] In some embodiments, the microfiltration separation includes subjecting the skim milk after pasteurization to microfiltration membrane treatment to achieve the separation of casein and whey.

[0099] In some specific embodiments, from the perspective of balancing efficiency and separation effect, the conditions for the microfiltration separation include: the pore size of the microfiltration membrane is 0.05-0.2 μm, preferably 0.1-0.2 μm; the operating temperature is 5-20°C, preferably 10-20°C; the operating pressure is 0.1-2 bar, preferably 0.5-1.5 bar. In principle, there is no particular limitation on the material and form of the microfiltration membrane. In some preferred embodiments, the microfiltration membrane can be made of polyethersulfone; the microfiltration membrane can be further preferably a spiral wound membrane.

[0100] In addition, in the above treatment for separating casein, since microfiltration separation is used, it can also play a sterilizing role. Therefore, for the treatment of the present invention, subsequent heat sterilization treatments such as pasteurization are not necessarily required to meet the safety requirements.

[0101] (6) Nanofiltration concentration: The whey is concentrated using a nanofiltration membrane to obtain concentrated whey. In the nanofiltration concentration of the present invention, in addition to further concentrating the skimmed and de-caseinated whey, it can also play a role in removing some inorganic salts.

[0102] In some specific embodiments, the conditions for the nanofiltration concentration include: the molecular weight cut-off of the nanofiltration membrane is 100 - 500 Da, preferably 150 - 300 Da; the concentration multiple is 4 - 10 times, preferably 4 - 8 times; the operating temperature is 4 - 20 °C, preferably 8 - 20 °C. In principle, there is no particular limitation on the material of the nanofiltration membrane. In some preferred embodiments, the nanofiltration membrane can be made of polyethersulfone.

[0103] In some specific embodiments, in the concentrated whey, the solid content is 15 - 25% by mass, preferably 18 - 25% by mass; and, based on dry weight, the protein content is 10 - 20% by mass, preferably 10 - 15% by mass.

[0104] In some specific embodiments, before the nanofiltration concentration treatment, according to needs, it further includes a step of ultrafiltrating the whey. According to the proportion of raw material components, steps of ultrafiltrating to remove some lactose and minerals in the whey can be added to better ensure that the protein content of the final product meets the requirement of ≥10%.

[0105] In some specific embodiments, the conditions for the ultrafiltration include: the molecular weight cut-off of the ultrafiltration membrane is 5000 - 10000 Da; the operating temperature is 4 - 20 °C, preferably 10 - 20 °C. In principle, there is no particular limitation on the material of the ultrafiltration membrane. In some preferred embodiments, the ultrafiltration membrane can be made of polyethersulfone.

[0106] (6) Whey desalination: The concentrated whey is subjected to electrodialysis treatment until the conductivity is below 1.5 mS / cm, preferably 0.5 - 1.5 mS / cm, to obtain desalted whey.

[0107] In some specific embodiments, the conditions for the electrodialysis include: the operating temperature is 8 - 20 °C, preferably 10 - 20 °C; the initial voltage is 10 - 30 V, preferably 15 - 25 V; the operating pH is controlled at 6 - 7, preferably 6.5 - 6.8. Appropriately adjusting the pH to acidic can increase the solubility of calcium while ensuring that protein denaturation and precipitation do not occur due to too low pH, improve the operating efficiency of the electrodialysis equipment, extend the operating time, and thus reduce the cleaning difficulty of the equipment.

[0108] In some specific embodiments, in the desalted whey raw material liquid, the dry matter content is 15-25% by mass, preferably 18-25% by mass, for example, it can be 15% by mass, 16% by mass, 17% by mass, 18% by mass, 19% by mass, 20% by mass, 21% by mass, 22% by mass, 23% by mass, 24% by mass, 25% by mass, etc.; and, based on dry weight, the protein content is 10-20% by mass, preferably 10-15% by mass, for example, it can be 10% by mass, 12% by mass, 15% by mass, 18% by mass, 20% by mass, etc.

[0109] In some specific embodiments, the non-temperature-sensitive components include one or more of lactose, edible oils, oligosaccharides, vitamin supplements, mineral supplements, and nutrient supplements; the edible oils include one or more vegetable oils.

[0110] The present invention does not particularly limit the specific sources of the above non-temperature-sensitive components. For example, the finished products of each raw material can be purchased through commercial channels, or can be prepared by methods such as biological fermentation and physical purification.

[0111] In some specific embodiments, the vegetable oil is selected from one or more of soybean oil, sunflower oil, coconut oil, linseed oil, corn oil, rapeseed oil, and walnut oil, and can also be a blended oil formed by multiple oils. For example, it can be a blended oil formed by soybean oil, sunflower oil, coconut oil, and linseed oil.

[0112] In some specific embodiments, the oligosaccharides include one or more of galactooligosaccharides, fructooligosaccharides, isomaltooligosaccharides, and xylooligosaccharides, preferably galactooligosaccharides and fructooligosaccharides.

[0113] In some specific embodiments, the vitamin supplement is selected from one or more of vitamin A, vitamin D, vitamin E, vitamin K1, vitamin B1, vitamin B2, vitamin B6, vitamin B12, vitamin C, niacin, folic acid, pantothenic acid, biotin, and taurine, and can also be a compound vitamin formed by multiple vitamins. For example, it can be a compound vitamin formed by vitamin A, vitamin D, vitamin E, vitamin K1, vitamin B1, vitamin B2, vitamin B6, vitamin B12, vitamin C, niacin, folic acid, pantothenic acid, biotin, and taurine.

[0114] In some specific embodiments, the mineral supplement is selected from one or more of calcium citrate, calcium hydrogen phosphate, magnesium sulfate, ferric pyrophosphate, zinc sulfate, manganese sulfate, potassium iodate, copper sulfate, and sodium selenite, and can also be a compound mineral formed by multiple minerals. For example, it can be a compound mineral formed by calcium citrate, calcium hydrogen phosphate, magnesium sulfate, ferric pyrophosphate, zinc sulfate, manganese sulfate, potassium iodate, copper sulfate, and sodium selenite.

[0115] In some specific embodiments, the nutrient supplement is selected from one or more of choline chloride, lutein, inositol, and L-carnitine, and may also be a compound nutrient formed by multiple nutrients. For example, it may be a compound nutrient formed by choline chloride, lutein, inositol, and L-carnitine.

[0116] In some specific embodiments, the mixing step includes a homogenization treatment.

[0117] In some specific embodiments, the conditions for mixing include: temperature of 40 - 50 °C, pressure of -(0.4 - 0.9) bar, and time of 40 - 50 min.

[0118] In some specific embodiments, the conditions for homogenization include: temperature of 50 - 60 °C and pressure of 230 - 250 bar.

[0119] Spray Drying Steps

[0120] In the spray drying step of the present invention, the mixed material obtained in the mixing step is spray dried to obtain a powder.

[0121] In some specific embodiments, between the mixing step and the spray drying step, there is also included one or two of a composition adjustment step and a sterilization step. Among them, the composition adjustment step and the sterilization step can also be completed in one step (such as a multi-effect evaporation concentration system). Further, the sterilization method can be DSI sterilization, and the conditions for sterilization include: temperature of 85 - 97 °C and time of 5 - 15 s.

[0122] In some specific embodiments, the dry matter content in the mixed material to be spray dried is 40 - 60% by mass, for example, it can be 40% by mass, 42% by mass, 44% by mass, 46% by mass, 48% by mass, 50% by mass, 52% by mass, 54% by mass, 56% by mass, 58% by mass, 60% by mass, etc.

[0123] In some specific embodiments, the conditions for spray drying include: inlet air temperature of 120 - 190 °C and outlet air temperature of 65 - 95 °C.

[0124] In some specific embodiments, after the powder is obtained by spray drying, the powder is further mixed with optional other temperature-sensitive components that are allowed to be added.

[0125] In some specific embodiments, the temperature-sensitive components include one or more of substances such as polyunsaturated fatty acid supplements, lactoferrin, probiotics, nucleotides, etc.

[0126] In some specific embodiments, the polyunsaturated fatty acid supplement comprises arachidonic acid oil powder and / or docosahexaenoic acid oil powder.

[0127] In some specific embodiments, the arachidonic acid oil powder refers to a powder product processed from arachidonic acid oil (which can be derived from Mortierella alpina species and obtained through biologic fermentation) as the raw material, with the addition of other food raw materials and food additives as auxiliary materials, such as whey protein powder, whey powder, modified starch, maltodextrin, lactose, granulated sugar, arabic gum, starch sodium octenyl succinate, sodium caseinate, vitamin E, ascorbyl palmitate, etc. Among them, the fat content in the arachidonic acid oil powder is not less than 20% by mass, and the arachidonic acid content is not less than 10% by mass.

[0128] In some specific embodiments, the docosahexaenoic acid oil powder refers to a powder product processed from docosahexaenoic acid oil (which can be derived from Schizochytrium sp., Ulkenia sp., Crypthecodinium cohnii, etc. and obtained through biologic fermentation) as the raw material, with the addition of other food raw materials and food additives as auxiliary materials, such as whey protein powder, whey powder, modified starch, maltodextrin, lactose, granulated sugar, arabic gum, gelatin, starch sodium octenyl succinate, sodium caseinate, vitamin E, ascorbyl palmitate, etc. Among them, the fat content in the docosahexaenoic acid oil powder is not less than 20% by mass, and the docosahexaenoic acid content is not less than 7% by mass.

[0129] Other Steps

[0130] The preparation method of the present invention is not limited to the above steps. Within the scope not affecting the effects of the present invention, other steps may also be included as needed. For example, in order to improve the product reliability, the preparation method of the present invention may further include a sterile filling step and a finished product step. The sterile filling step is the step of aseptically filling the powder prepared through the above steps into a packaging container. As the packaging container, there is no particular limitation as long as it can be used in the food industry. The finished product step refers to the step of subjecting the filled product to online inspection, coding, boxing, coding, palletizing as needed and then storing it in a warehouse.

[0131] In some specific embodiments, the denaturation rate of whey protein in the formula milk powder is 11% or less, preferably 10% or less, more preferably 9.5% or less, and further preferably 9% or less.

[0132] In some specific embodiments, the content of furosine in the formula milk powder is 500 mg / 100 g of protein or less, preferably 480 mg / 100 g of protein or less, more preferably 470 mg / 100 g of protein or less, and further preferably 460 mg / 100 g of protein or less.

[0133] Example

[0134] The embodiments of the present invention will be described in detail below in conjunction with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. For those not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are followed. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0135] Example 1:

[0136] 1. Preparation of skim milk

[0137] The raw milk that has passed the acceptance inspection is first preheated to 50 °C and then enters the separator for defatting at a rotational speed of 5000 r / min. It is required that the fat content of the skim milk is <0.1%. After passing the inspection, the skim milk is pasteurized at a temperature of 85 °C for 15 s, and the outlet temperature is controlled at 6 °C.

[0138] After pasteurization, the skim milk is concentrated through an RO membrane. The operating pressure is 23 bar, the outlet dry matter is controlled at 10%, and the temperature is 6 °C. The concentrated skim milk enters the milk tank for temporary storage.

[0139] 2. Preparation of membrane desalted whey

[0140] (1) Defatting of raw milk

[0141] The raw milk that has passed the acceptance inspection is first preheated to 50 °C and then enters the separator for defatting at a rotational speed of 5000 r / min. It is required that the fat content of the skim milk is <0.1%. After passing the inspection, the skim milk is pasteurized at a temperature of 85 °C for 15 s, and the outlet temperature is controlled at 6 °C.

[0142] (2) Microfiltration separation

[0143] The above-mentioned skim milk enters the microfiltration membrane to remove casein to obtain whey. The microfiltration membrane is made of polyethersulfone, the pore size of the microfiltration membrane is 0.1 μm, the operating temperature is 10 °C, and the operating pressure is 1.0 bar.

[0144] (3) Ultrafiltration standardization

[0145] The whey obtained by microfiltration is then ultrafiltered for standardization. The ultrafiltration membrane is made of polyethersulfone, with a molecular weight cut-off of 5000 - 10000 Da. The operating temperature is 10°C, and the protein content in the outlet liquid is controlled to reach 12% of the total solids.

[0146] (4) Nanofiltration concentration

[0147] The whey after ultrafiltration standardization is further concentrated through a nanofiltration membrane. The nanofiltration membrane has a molecular weight cut-off of 100 - 500 Da, with a concentration multiple of about 4 times, and the operating temperature is 10°C. The requirement for the nanofiltration outlet is that the solids content is 15%.

[0148] (5) Electrodialysis desalination

[0149] The concentrated whey is desalted by electrodialysis until the conductivity drops to 1.0 mS / cm to obtain desalted whey. The operating temperature of electrodialysis is 10°C, the initial voltage is 20V, and the operating pH is controlled at 6.8.

[0150] 3. Preparation of pasteurized milk

[0151] The raw milk that has passed the acceptance inspection is first preheated to 50°C, then sterilized and clarified by a clarifier, followed by pasteurization at 85°C for 15 s, and the outlet temperature is controlled at 6°C.

[0152] 4. Mixing and homogenization

[0153] According to requirements, 2200 kg of pasteurized milk (270 kg of dry matter), 1700 kg of skim milk (dry matter content 10%), and 833 kg of desalted whey (dry matter content 15%) are fed into a vacuum mixer and circulated for mixing at -0.9 bar and 45°C. During the process, 130 kg of edible vegetable blended oil (soybean oil, sunflower oil, coconut oil, linseed oil), 200 kg of lactose, 75 kg of galactooligosaccharides, 6 kg of calcium citrate, 5 kg of fructooligosaccharides, 1 kg of calcium hydrogen phosphate, 3 kg of vitamin premix (vitamins A, D, E, K1, B1, B2, B6, B12, C, niacin, folic acid, pantothenic acid, biotin, taurine), 2 kg of choline chloride, 2 kg of mineral premix (magnesium sulfate, ferric pyrophosphate, zinc sulfate, manganese sulfate, potassium iodate, copper sulfate, sodium selenite), and 1 kg of nutrient premix (lutein, inositol, L-carnitine) are added. The mixing time lasts for 45 min, and then the mixed liquid is preheated to 50°C through a plate heat exchanger, homogenized at a pressure of 240 bar, and then cooled to 8°C through the plate heat exchanger for storage. The theoretical dry matter content of the above mixed liquid is 19%. Due to the presence of material head water and water top material in the production process, the actual dry matter content is 14.8%, and approximately 1.5 tons of process water enters the mixed liquid during the production process.

[0154] 5. Evaporation and Concentration

[0155] The mixed material liquid enters the evaporator for concentration. Operating conditions: DSI sterilization temperature 90°C, sterilization time 10 s, body vacuum degree -900 mbar, first-effect body temperature: 70°C, second-effect body temperature: 65°C, third-effect body temperature: 60°C, and the outlet material liquid concentration is controlled at 50%, obtaining the mixed material.

[0156] 6. Spray Drying

[0157] The mixed material is preheated to 75°C, pumped into the drying tower by a high-pressure pump for spray drying, with an inlet air temperature of 180°C and an exhaust air temperature of 75°C. After secondary drying and cooling by a dynamic fluidized bed, the semi-finished product powder is obtained and enters the powder bin for temporary storage.

[0158] 7. Dry Mixing and Packaging

[0159] Take 990 kg of semi-finished product powder, 5 kg of docosahexaenoic acid oil powder (7%), and 5 kg of arachidonic acid oil powder (10%) for dry mixing, and after completion, fill into cans.

[0160] Example 2:

[0161] 1. Preparation of Skim Milk

[0162] The raw milk that has passed the acceptance test is first preheated to 50°C, and then enters the separator for defatting at a rotational speed of 5000 r / min. It is required that the fat content of the skim milk is <0.1%. After passing the inspection, the skim milk is pasteurized at a temperature of 85°C for 15 s, and the outlet temperature is controlled at 8°C;

[0163] After pasteurization, the skim milk is concentrated through an RO membrane with an operating pressure of 23 bar, controlling the outlet dry matter at 18% and the temperature at 8°C. The concentrated skim milk enters the milk tank for temporary storage.

[0164] 2. Preparation of Membrane Desalted Whey Liquid

[0165] (1) Defatting of Raw Milk

[0166] The raw milk that has passed the acceptance test is first preheated to 50°C, and then enters the separator for defatting at a rotational speed of 5000 r / min. It is required that the fat content of the skim milk is <0.1%. After passing the inspection, the skim milk is pasteurized at a temperature of 85°C for 15 s, and the outlet temperature is controlled at 8°C.

[0167] (2) Microfiltration Separation

[0168] The above-mentioned skim milk enters the microfiltration membrane to remove casein, obtaining whey liquid; the microfiltration membrane is made of polyethersulfone, the pore size of the microfiltration membrane is 0.1 μm, the operating temperature is 15°C, and the operating pressure is 1.0 bar.

[0169] (3) Ultrafiltration standardization

[0170] The whey obtained by microfiltration is then subjected to ultrafiltration standardization. The ultrafiltration membrane is made of polyethersulfone, with a molecular weight cut-off of 5000 - 10000 Da, an operating temperature of 15 °C, and the protein content in the outlet liquid is controlled to reach 12% of the total solids.

[0171] (4) Nanofiltration concentration

[0172] The whey after ultrafiltration standardization is further concentrated through a nanofiltration membrane. The molecular weight cut-off of the nanofiltration membrane is 100 - 500 Da, the concentration multiple is about 5 times, and the operating temperature is 15 °C; the requirement for the nanofiltration outlet is that the solids content is 20%.

[0173] (5) Electrodialysis desalination

[0174] The concentrated whey is subjected to electrodialysis desalination until the conductivity drops to 1.0 mS / cm to obtain desalted whey; the operating temperature of electrodialysis is 15 °C, the initial voltage is 20 V, and the operating pH is controlled at about 6.5.

[0175] 3. Preparation of pasteurized milk

[0176] The raw cow milk that has passed the acceptance inspection is first preheated to 50 °C, then sterilized and clarified by a clarifier, followed by pasteurization at 85 °C for 15 s, and the outlet temperature is controlled at 8 °C.

[0177] 4. Mixing and homogenization

[0178] According to requirements, 2200 kg of pasteurized milk (270 kg of dry matter), 945 kg of skim milk (dry matter content of 18%), and 625 kg of demineralized whey (dry matter content of 20%) are fed into a vacuum mixer and circulated at -0.9 bar and 45 °C; during the process, 130 kg of edible vegetable oil blend (soybean oil, sunflower oil, coconut oil, linseed oil), 200 kg of lactose, 75 kg of galactooligosaccharides, 6 kg of calcium citrate, 5 kg of fructooligosaccharides, 1 kg of calcium hydrogen phosphate, 3 kg of vitamin premix (vitamins A, D, E, K1, B1, B2, B6, B12, C, niacin, folic acid, pantothenic acid, biotin, taurine), 2 kg of choline chloride, 2 kg of mineral premix (magnesium sulfate, ferric pyrophosphate, zinc sulfate, manganese sulfate, potassium iodate, copper sulfate, sodium selenite), and 1 kg of nutrient premix (lutein, inositol, L-carnitine) are added; the mixing time lasts for 45 minutes, and then the mixed liquid is preheated to 50 °C through a plate heat exchanger, homogenized at a pressure of 240 bar, and then cooled to 8 °C through a plate heat exchanger for storage; the theoretical dry matter content of the above mixed liquid is 23.6%, and due to the existence of material top water and water top material in the production process, the actual dry matter content is 17.5%, and about 1.5 tons of process water enters the mixed liquid during the production process.

[0179] 5. Evaporation and Concentration

[0180] The mixed liquid enters the evaporator for concentration, and the operating conditions are: DSI sterilization temperature of 90 °C, sterilization time of 15 s, body vacuum degree of -950 mbar, temperature of the first-effect body: 70 °C, temperature of the second-effect body: 65 °C, temperature of the third-effect body: 60 °C, and the concentration of the outlet liquid is controlled at 50% to obtain the mixed material.

[0181] 6. Spray Drying

[0182] The mixed material is preheated to 75 °C, pumped into the drying tower by a high-pressure pump for spray drying, the inlet air temperature is 180 °C, the exhaust air temperature is 75 °C, and after secondary drying and cooling by a dynamic fluidized bed, the semi-finished product powder is obtained and enters the powder silo for temporary storage.

[0183] 7. Dry Mixing and Packaging

[0184] Take 990 kg of semi-finished product powder, 5 kg of docosahexaenoic acid oil powder (7%), and 5 kg of arachidonic acid oil powder (10%) for dry mixing, and after completion, it is filled into cans.

[0185] Example 3:

[0186] 1. Skim Milk Preparation

[0187] The qualified raw milk is first preheated to 50°C and then enters the separator for defatting at a speed of 5000 r / min. The defatted milk is required to have a fat content of <0.1%. After passing the inspection, the defatted milk is pasteurized at 85°C for 15 s, and the outlet temperature is controlled at 8°C.

[0188] After pasteurization, the defatted milk is concentrated through an RO membrane at an operating pressure of 23 bar, controlling the outlet dry matter at 25% and the temperature at 8°C. The concentrated defatted milk enters the milk tank for temporary storage.

[0189] 2. Preparation of Membrane Desalted Whey

[0190] (1) Defatting of Raw Milk

[0191] The qualified raw milk is first preheated to 50°C and then enters the separator for defatting at a speed of 5000 r / min. The defatted milk is required to have a fat content of <0.1%. After passing the inspection, the defatted milk is pasteurized at 85°C for 15 s, and the outlet temperature is controlled at 8°C.

[0192] (2) Microfiltration Separation

[0193] The above defatted milk enters the microfiltration membrane to remove casein and obtain whey. The microfiltration membrane is made of polyethersulfone, with a pore size of 0.1 μm, an operating temperature of 15°C, and an operating pressure of 1.0 bar.

[0194] (3) Ultrafiltration Standardization

[0195] The whey obtained by microfiltration is further subjected to ultrafiltration standardization. The ultrafiltration membrane is made of polyethersulfone, with a retention molecular weight of 5000 - 10000 Da, an operating temperature of 15°C, and the protein content in the outlet liquid is controlled to reach 12% of the total solids.

[0196] (4) Nanofiltration Concentration

[0197] The whey after ultrafiltration standardization is further concentrated through a nanofiltration membrane. The nanofiltration membrane has a retention molecular weight of 100 - 500 Da, a concentration multiple of about 6 times, and an operating temperature of 15°C. The requirements for the nanofiltration outlet are that the solids content is 25%.

[0198] (5) Electrodialysis Desalination

[0199] The concentrated whey is subjected to electrodialysis desalination until the conductivity drops to 1.0 mS / cm to obtain desalted whey. The operating temperature of electrodialysis is 15°C, the initial voltage is 20 V, and the operating pH is controlled at 6.5.

[0200] 3. Preparation of Pasteurized Milk

[0201] The qualified raw milk is first preheated to 50°C, then sterilized and clarified by a clarifier, followed by pasteurization at 85°C for 15 s, and the outlet temperature is controlled at 8°C.

[0202] 4. Mixing and Homogenization

[0203] According to requirements, 2200 kg of pasteurized milk (270 kg of dry matter), 680 kg of skim milk (dry matter content 25%), and 500 kg of desalted whey (dry matter content 25%) are pumped into a vacuum mixer and circulated at -0.9 bar and 45°C; during the process, 130 kg of edible vegetable oil blend (soybean oil, sunflower oil, coconut oil, linseed oil), 200 kg of lactose, 75 kg of galactooligosaccharides, 6 kg of calcium citrate, 5 kg of fructooligosaccharides, 1 kg of calcium hydrogen phosphate, 3 kg of vitamin premix (vitamins A, D, E, K1, B1, B2, B6, B12, C, niacin, folic acid, pantothenic acid, biotin, taurine), 2 kg of choline chloride, 2 kg of mineral premix (magnesium sulfate, ferric pyrophosphate, zinc sulfate, manganese sulfate, potassium iodate, copper sulfate, sodium selenite), and 1 kg of nutrient premix (lutein, inositol, L-carnitine) are added; the mixing time lasts for 45 min, and then the mixed liquid is preheated to 55°C through a plate heat exchanger and homogenized at 240 bar, and then cooled to 8°C through a plate heat exchanger and stored; the theoretical dry matter content of the above mixed liquid is 26%, but due to the existence of material top water and water top material in the production process, the actual dry matter content is 18.7%, and about 1.5 tons of process water enters the mixed liquid during the production process.

[0204] 5. Evaporation and Concentration

[0205] The mixed liquid enters the evaporator for concentration. The operating conditions are: DSI sterilization temperature 90°C, sterilization time 15 s, body vacuum degree -950 mbar, first-effect body temperature: 70°C, second-effect body temperature: 65°C, third-effect body temperature: 60°C, and the outlet liquid concentration is controlled at 50% to obtain the mixed material.

[0206] 6. Spray Drying

[0207] The mixed material is preheated to 75°C, pumped into the drying tower by a high-pressure pump for spray drying, the inlet air temperature is 180°C, the exhaust air temperature is 75°C, and after secondary drying and cooling by a dynamic fluidized bed, the semi-finished product powder is obtained and stored in a powder bin.

[0208] 7. Dry Mixing and Packaging

[0209] Take 990 kg of semi-finished product powder, 5 kg of docosahexaenoic acid oil powder (7%), and 5 kg of arachidonic acid oil powder (10%) for dry mixing, and then fill into cans after completion.

[0210] Comparative Example 1:

[0211] 1. Preparation of skim milk

[0212] The raw milk that has passed the acceptance inspection is first preheated to 50°C, and then enters the separator. Skimming is carried out at a rotational speed of 5000 r / min. It is required that the fat content of the skim milk is <0.1%. After passing the inspection, the skim milk is pasteurized at a temperature of 85°C for 15 s, and the outlet temperature is controlled at 8°C;

[0213] After pasteurization, the skim milk is concentrated through the RO membrane. The operating pressure is 23 bar, the outlet dry matter is controlled at 18%, and the temperature is 8°C. The concentrated skim milk after concentration enters the milk tank for temporary storage.

[0214] 2. Preparation of enzymatically desalted whey

[0215] (1) Skimming of raw milk

[0216] The raw milk that has passed the acceptance inspection is first preheated to 50°C, and then enters the separator. Skimming is carried out at a rotational speed of 5000 r / min. It is required that the fat content of the skim milk is <0.1%. After passing the inspection, the skim milk is pasteurized at a temperature of 85°C for 15 s, and the outlet temperature is controlled at 8°C.

[0217] (2) Curd filtration

[0218] According to the amount of skim milk, a quantitative Caglificio Clerici rennet (abomasum enzyme, bovine pepsin, activity 1:100000) is added at a mass ratio of 0.0045%. After mixing evenly, curdling is carried out for 40 min. After the curdling is completed, the whey is collected, filtered through a 50-μm membrane, and then treated by pasteurization to inactivate the enzyme at a temperature of 85°C for 15 s to obtain whey.

[0219] (3) Ultrafiltration standardization

[0220] The obtained whey is then subjected to ultrafiltration standardization. The ultrafiltration membrane is made of polyethersulfone, the retention molecular weight of the ultrafiltration membrane is 5000 - 10000 Da, the operating temperature is 15°C, and the protein content in the outlet liquid is controlled to reach 12% of the total solids.

[0221] (4) Nanofiltration concentration

[0222] The whey after ultrafiltration standardization is further concentrated through the nanofiltration membrane. The retention molecular weight of the nanofiltration membrane is 100 - 500 Da, the concentration multiple is about 5 times, and the operating temperature is 15°C; the requirements at the nanofiltration outlet are that the solid content is 20%.

[0223] (5) Electrodialysis desalination

[0224] The concentrated whey solution is desalted by electrodialysis until the conductivity drops to 1.0 mS / cm to obtain desalted whey. The operating temperature of electrodialysis is 15 °C, the initial voltage is 20 V, and the operating pH is controlled at 6.5.

[0225] 3. Preparation of pasteurized milk

[0226] The raw milk that has passed the acceptance inspection is first preheated to 50 °C, and then undergoes pasteurization at 85 °C for 15 s after being sterilized and clarified by a clarifier, with the outlet temperature controlled at 8 °C.

[0227] 4. Mixing and homogenization

[0228] According to requirements, 2200 kg of pasteurized milk (270 kg of dry matter), 945 kg of skim milk (dry matter content 18%), and 625 kg of desalted whey solution (dry matter content 20%) are fed into a vacuum mixer and circulated for mixing at -0.9 bar and 45 °C. During the process, 130 kg of edible vegetable oil blend (soybean oil, sunflower oil, coconut oil, linseed oil), 200 kg of lactose, 75 kg of galactooligosaccharides, 6 kg of calcium citrate, 5 kg of fructooligosaccharides, 1 kg of calcium hydrogen phosphate, 3 kg of vitamin premix (vitamin A, vitamin D, vitamin E, vitamin K1, vitamin B1, vitamin B2, vitamin B6, vitamin B12, vitamin C, niacin, folic acid, pantothenic acid, biotin, taurine), 2 kg of choline chloride, 2 kg of mineral premix (magnesium sulfate, ferric pyrophosphate, zinc sulfate, manganese sulfate, potassium iodate, copper sulfate, sodium selenite), and 1 kg of nutrient premix (lutein, inositol, L-carnitine) are added. The mixing time lasts for 45 minutes, and then the mixed liquid is preheated to 55 °C through a plate heat exchanger and homogenized at a pressure of 240 bar. After homogenization, it is cooled to 8 °C through a plate heat exchanger and stored. The theoretical dry matter content of the above mixed liquid is 23.6%. Due to the presence of material displacing water and water displacing material during the production process, the actual dry matter content is 17.5%, and approximately 1.5 tons of process water enters the mixed liquid during the production process.

[0229] 5. Evaporation and concentration

[0230] The mixed liquid enters the evaporator for concentration. The operating conditions are: DSI sterilization temperature 90 °C, sterilization time 10 s, body vacuum degree -950 mbar, temperature of the first effect body: 70 °C, temperature of the second effect body: 65 °C, temperature of the third effect body: 60 °C, and the concentration of the outlet liquid is controlled at 50% to obtain the mixed material.

[0231] 6. Spray drying

[0232] The mixed materials are preheated to 75°C and pumped into a drying tower by a high-pressure pump for spray drying. The inlet air temperature is 180°C and the outlet air temperature is 75°C. After secondary drying and cooling in a dynamic fluidized bed, semi-finished powder is obtained and enters the powder silo for temporary storage.

[0233] 7. Dry mixing and packaging

[0234] Take 990 kg of semi-finished powder, 5 kg of docosahexaenoic acid oil powder (7%), and 5 kg of arachidonic acid oil powder (10%) for dry mixing. After completion, it is filled into cans.

[0235] Comparative Example 2:

[0236] 1. Preparation of pasteurized milk

[0237] The raw milk that has passed the acceptance inspection is first preheated to 50°C, then sterilized and clarified by a milk clarifier, followed by pasteurization at 85°C for 15 s, and the outlet temperature is controlled at 8°C.

[0238] 2. Mixing and homogenization

[0239] According to requirements, 2200 kg of pasteurized milk (270 kg of dry matter) is pumped into a vacuum mixer and circulated for mixing at -0.9 bar and 45°C; during the process, 170 kg of skim milk powder, 125 kg of demineralized whey powder, 130 kg of edible vegetable blended oil (soybean oil, sunflower oil, coconut oil, linseed oil), 200 kg of lactose, 75 kg of galactooligosaccharide, 6 kg of calcium citrate, 5 kg of fructooligosaccharide, 1 kg of calcium hydrogen phosphate, 3 kg of vitamin premix (vitamin A, vitamin D, vitamin E, vitamin K1, vitamin B1, vitamin B2, vitamin B6, vitamin B12, vitamin C, niacin, folic acid, pantothenic acid, biotin, taurine), 2 kg of choline chloride, 2 kg of mineral premix (magnesium sulfate, ferric pyrophosphate, zinc sulfate, manganese sulfate, potassium iodate, copper sulfate, sodium selenite), 1 kg of nutrient premix (lutein, inositol, L-carnitine) are added; the mixing time lasts for 45 min, and then the mixed liquid is preheated to 55°C through a plate heat exchanger, homogenized at a pressure of 240 bar, and then cooled to 8°C through a plate heat exchanger and enters the wet mixing storage tank, and the volume is fixed by adding water to a dry matter content of 17.5%.

[0240] 3. Evaporation and concentration

[0241] The mixed liquid enters the evaporator for concentration. The operating conditions are: DSI sterilization temperature 90°C, sterilization time 1 s, the vacuum degree of the effect body is -950 mbar, the temperature of the first effect body is 70°C, the temperature of the second effect body is 65°C, the temperature of the third effect body is 60°C, and the concentration of the outlet liquid is controlled at 50% to obtain the mixed materials.

[0242] 4. Spray drying

[0243] The mixed materials are preheated to 75°C and pumped into a drying tower by a high-pressure pump for spray drying. The inlet air temperature is 180°C and the outlet air temperature is 75°C. After secondary drying and cooling in a dynamic fluidized bed, semi-finished powder is obtained and enters a powder bin for temporary storage.

[0244] 5. Dry mixing and packaging

[0245] Take 990 kg of semi-finished powder, 5 kg of docosahexaenoic acid oil powder (7%), and 5 kg of arachidonic acid oil powder (10%) for dry mixing, and after completion, fill into cans.

[0246] Comparative Example 3:

[0247] 1. Preparation of skim milk

[0248] The raw milk that has passed the acceptance inspection is first preheated to 50°C, then enters a separator and is defatted at a rotational speed of 5000 r / min. It is required that the fat content of the skim milk is <0.1%. After passing the inspection, the skim milk is pasteurized at a temperature of 85°C for 15 s, and the outlet temperature is controlled at 8°C;

[0249] After pasteurization, the skim milk is concentrated through an RO membrane with an operating pressure of 25 bar, controlling the outlet dry matter at 18% and a temperature of 8°C. The concentrated skim milk enters a milk tank for temporary storage.

[0250] 2. Preparation of pasteurized milk

[0251] The raw milk that has passed the acceptance inspection is first preheated to 50°C, then undergoes pasteurization at a temperature of 85°C for 15 s after being sterilized and clarified by a clarifier, and the outlet temperature is controlled at 8°C.

[0252] 3. Mixing and homogenization

[0253] According to requirements, 2200 kg of pasteurized milk (270 kg of dry matter) and 945 kg of skim milk (dry matter content 18%) are fed into a vacuum mixer and circulated for mixing at -0.9 bar and 50 °C; during the process, 125 kg of desalted whey powder, 130 kg of edible vegetable blended oil (soybean oil, sunflower oil, coconut oil, linseed oil), 200 kg of lactose, 75 kg of galactooligosaccharides, 6 kg of calcium citrate, 5 kg of fructooligosaccharides, 1 kg of calcium hydrogen phosphate, 3 kg of vitamin premix (vitamin A, vitamin D, vitamin E, vitamin K1, vitamin B1, vitamin B2, vitamin B6, vitamin B12, vitamin C, niacin, folic acid, pantothenic acid, biotin, taurine), 2 kg of choline chloride, 2 kg of mineral premix (magnesium sulfate, ferric pyrophosphate, zinc sulfate, manganese sulfate, potassium iodate, copper sulfate, sodium selenite), 1 kg of nutrient premix (lutein, inositol, L-carnitine) are added; the mixing time lasts for 45 min, and then the mixed liquid is preheated to 55 °C through a plate heat exchanger, homogenized at a pressure of 240 bar, and then cooled to 8 °C through a plate heat exchanger and enters a wet mixing storage tank, and is stored after adding water to make the dry matter content reach 17.5%.

[0254] 4. Evaporation and concentration

[0255] The mixed liquid enters the evaporator for concentration, and the operating conditions are: DSI sterilization temperature 90 °C, sterilization time 10 s, body vacuum degree -950 mbar, first-effect body temperature: 70 °C, second-effect body temperature: 65 °C, third-effect body temperature: 60 °C, and the outlet liquid concentration is controlled at 50% to obtain a mixed material.

[0256] 5. Spray drying

[0257] The mixed material is preheated to 75 °C, pumped into the drying tower by a high-pressure pump for spray drying, the inlet air temperature is 180 °C, the outlet air temperature is 75 °C, and after secondary drying and cooling by a dynamic fluidized bed, a semi-finished product powder is obtained and enters the powder bin for temporary storage.

[0258] 6. Dry mixing and packaging

[0259] Take 990 kg of semi-finished product powder, 5 kg of docosahexaenoic acid oil powder (7%), and 5 kg of arachidonic acid oil powder (10%) for dry mixing, and after completion, it is filled into cans.

[0260] Comparative example 4:

[0261] 1. Preparation of membrane desalted whey liquid

[0262] (1) Skim raw milk

[0263] The qualified raw milk is first preheated to 50°C and then enters the separator for defatting at a rotational speed of 5000 r / min. The fat content of the skim milk is required to be <0.1%. After passing the inspection, the skim milk is pasteurized at 85°C for 15 s, and the outlet temperature is controlled at 8°C.

[0264] (2) Microfiltration separation

[0265] The above-mentioned skim milk enters the microfiltration membrane to remove casein, obtaining whey; the microfiltration membrane is made of polyethersulfone, with a pore size of 0.1 μm, an operating temperature of 15°C, and an operating pressure of 1.0 bar.

[0266] (3) Ultrafiltration standardization

[0267] The whey obtained by microfiltration is then subjected to ultrafiltration standardization. The ultrafiltration membrane is made of polyethersulfone, with a cut-off molecular weight of 5000 - 10000 Da, an operating temperature of 15°C, and the protein content in the outlet liquid is controlled to reach 12% of the total solids.

[0268] (4) Nanofiltration concentration

[0269] The whey after ultrafiltration standardization is further concentrated through a nanofiltration membrane. The cut-off molecular weight of the nanofiltration membrane is 100 - 500 Da, the concentration multiple is about 5 times, and the operating temperature is 15°C; the requirement for the nanofiltration outlet is that the solids content is 20%.

[0270] (5) Electrodialysis desalination

[0271] The concentrated whey is subjected to electrodialysis desalination until the conductivity drops to 1.0 mS / cm, obtaining desalted whey; the operating temperature of electrodialysis is 15°C, the initial voltage is 20 V, and the operating pH is controlled at 6.5.

[0272] 2. Preparation of pasteurized milk

[0273] The qualified raw milk is first preheated to 50°C, then sterilized and clarified by a clarifier, and then pasteurized at 85°C for 15 s, with the outlet temperature controlled at 8°C.

[0274] 3. Mixing and homogenization

[0275] According to requirements, 2200 kg of pasteurized milk (270 kg of dry matter) and 625 kg of demineralized whey (20% dry matter content) are pumped into a vacuum mixer and circulated for mixing at -0.9 bar and 45 °C; during the process, 170 kg of skim milk powder, 130 kg of edible vegetable blended oil (soybean oil, sunflower oil, coconut oil, linseed oil), 200 kg of lactose, 75 kg of galactooligosaccharides, 6 kg of calcium citrate, 5 kg of fructooligosaccharides, 1 kg of calcium hydrogen phosphate, 3 kg of vitamin premix (vitamin A, vitamin D, vitamin E, vitamin K1, vitamin B1, vitamin B2, vitamin B6, vitamin B12, vitamin C, niacin, folic acid, pantothenic acid, biotin, taurine), 2 kg of choline chloride, 2 kg of mineral premix (magnesium sulfate, ferric pyrophosphate, zinc sulfate, manganese sulfate, potassium iodate, copper sulfate, sodium selenite), and 1 kg of nutrient premix (lutein, inositol, L-carnitine) are added; the mixing time lasts for 45 minutes, and then the mixed liquid is preheated to 55 °C through a plate heat exchanger, homogenized at a pressure of 240 bar, cooled to 8 °C through a plate heat exchanger after homogenization, and enters a wet mixing storage tank, and is stored by adding water to make the dry matter content reach 17.5%.

[0276] 4. Evaporation and concentration

[0277] The mixed liquid enters the evaporator for concentration. The operating conditions are: DSI sterilization temperature 90 °C, sterilization time 10 s, body vacuum degree -950 mbar, first-effect body temperature: 70 °C, second-effect body temperature: 65 °C, third-effect body temperature: 60 °C, and the outlet liquid concentration is controlled at 50% to obtain a mixed material.

[0278] 5. Spray drying

[0279] The mixed material is preheated to 75 °C, pumped into the drying tower by a high-pressure pump for spray drying, with an inlet air temperature of 180 °C and an outlet air temperature of 75 °C. After secondary drying and cooling in a dynamic fluidized bed, a semi-finished product powder is obtained and enters the powder silo for temporary storage.

[0280] 6. Dry mixing and packaging

[0281] Take 990 kg of semi-finished product powder, 5 kg of docosahexaenoic acid oil powder (7%), and 5 kg of arachidonic acid oil powder (10%) for dry mixing, and after completion, fill into cans.

[0282] Comparative example 5:

[0283] 1. Preparation of skim milk

[0284] The qualified raw milk is first preheated to 50°C and then enters a separator for defatting at a rotational speed of 5000 r / min. The defatted milk is required to have a fat content of <0.1%. After passing the inspection, the defatted milk is pasteurized at 85°C for 15 s, and the outlet temperature is controlled at 8°C.

[0285] After pasteurization, the defatted milk is concentrated through an RO membrane at an operating pressure of 25 bar, with an outlet dry matter content of 8.4% and a temperature of 8°C. The concentrated defatted milk enters a milk tank for temporary storage.

[0286] 2. Preparation of Membrane Desalted Whey

[0287] (1) Defatting of Raw Milk

[0288] The qualified raw milk is first preheated to 50°C and then enters a separator for defatting at a rotational speed of 5000 r / min. The defatted milk is required to have a fat content of <0.1%. After passing the inspection, the defatted milk is pasteurized at 85°C for 15 s, and the outlet temperature is controlled at 8°C.

[0289] (2) Microfiltration Separation

[0290] The above defatted milk enters a microfiltration membrane to remove casein, obtaining whey. The microfiltration membrane is made of polyethersulfone, with a pore size of 0.1 μm, an operating temperature of 15°C, and an operating pressure of 1.0 bar.

[0291] (3) Ultrafiltration Standardization

[0292] The whey obtained by microfiltration is then subjected to ultrafiltration standardization. The ultrafiltration membrane is made of polyethersulfone, with a retention molecular weight of 5000 - 10000 Da, an operating temperature of 15°C, and the protein content in the outlet liquid is controlled to reach 12% of the total solids.

[0293] (4) Nanofiltration Concentration

[0294] The whey after ultrafiltration standardization is further concentrated through a nanofiltration membrane. The nanofiltration membrane has a retention molecular weight of 100 - 500 Da, a concentration multiple of about 2.5 times, and an operating temperature of 15°C. The requirements for the nanofiltration outlet are a solids content of 10%.

[0295] (5) Electrodialysis Desalination

[0296] The concentrated whey is subjected to electrodialysis desalination until the conductivity drops to 1.0 mS / cm, obtaining desalted whey. The operating temperature of electrodialysis is 15°C, the initial voltage is 20 V, and the operating pH is controlled at 6.5.

[0297] 3. Preparation of Pasteurized Milk

[0298] The qualified raw milk is first preheated to 50°C, then sterilized and clarified by a clarifier, followed by pasteurization at 85°C for 15 s, and the outlet temperature is controlled at 8°C.

[0299] 4. Mixing and Homogenization

[0300] According to requirements, 2200 kg of pasteurized milk (270 kg of dry matter), 2023 kg of skim milk (dry matter content 8.4%), and 1250 kg of desalted whey (dry matter content 10%) are fed into a vacuum mixer and circulated at -0.9 bar and 45°C; during the process, 130 kg of edible vegetable oil blend (soybean oil, sunflower oil, coconut oil, linseed oil), 200 kg of lactose, 75 kg of galactooligosaccharides, 6 kg of calcium citrate, 5 kg of fructooligosaccharides, 1 kg of calcium hydrogen phosphate, 3 kg of vitamin premix (vitamins A, D, E, K1, B1, B2, B6, B12, C, niacin, folic acid, pantothenic acid, biotin, taurine), 2 kg of choline chloride, 2 kg of mineral premix (magnesium sulfate, ferric pyrophosphate, zinc sulfate, manganese sulfate, potassium iodate, copper sulfate, sodium selenite), and 1 kg of nutrient premix (lutein, inositol, L-carnitine) are added; the mixing time lasts for 45 min, and then the mixed liquid is preheated to 55°C through a plate heat exchanger and homogenized at 240 bar, and then cooled to 8°C through a plate heat exchanger and stored; the theoretical dry matter content of the above mixed liquid is 15.9%, and due to the presence of water at the top of the material and water displacing the material during the production process, the actual dry matter content is 12.8%, and about 1.5 tons of process water enters the mixed liquid during the production process.

[0301] 5. Evaporation Concentration and Spray Drying

[0302] The mixed liquid enters the evaporator for concentration, and the operating conditions are: DSI sterilization temperature 90°C, sterilization time 10 s, vacuum degree of the effective body -950 mbar, temperature of the first-effect effective body: 70°C, temperature of the second-effect effective body: 65°C, temperature of the third-effect effective body: 60°C, and the concentration of the outlet liquid is controlled at 50%.

[0303] Since the current concentration of the imported feed liquid is only 12.8%, to achieve the target of 40% for the outlet feed liquid concentration, it is necessary to reduce the feed rate of the evaporator and increase the pressure of the heat pump. Although the evaporation intensity can be enhanced to increase the amount of water evaporated per unit time, it will lead to an increase in system energy consumption. At the same time, the reduction in the feed rate results in a decrease in the input amount of dry matter, and then the amount of material at the evaporator outlet decreases synchronously, which cannot match the normal production of the drying tower and cannot ensure continuous operation. If the concentration of the outlet feed liquid of the evaporator is reduced to ensure the matching of the outlet amount of the evaporator and the feed amount of the drying tower, the concentration of the material entering the drying tower is too low. To achieve the drying effect and ensure continuous production, it is necessary to increase the inlet air temperature, but this will also lead to: the material is subjected to a large heat treatment intensity, the component particles are very fine, and the product has poor reconstitution properties.

[0304] Comparative Example 6:

[0305] 1. Preparation of skim milk

[0306] The qualified raw milk is first preheated to 50 °C and then enters the separator for defatting at a rotation speed of 5000 r / min. The fat content of the skim milk is required to be <0.1%. After passing the inspection, the skim milk is subjected to pasteurization at a temperature of 85 °C for 15 s, and the outlet temperature is controlled at 8 °C.

[0307] The pasteurized skim milk is concentrated by an RO membrane at an operating pressure of 25 bar, with a dry matter content of 28% at the outlet and a temperature of 8 °C. The concentrated skim milk enters the milk tank for temporary storage.

[0308] 2. Preparation of membrane desalted whey

[0309] (1) Defatting of raw milk

[0310] The qualified raw milk is first preheated to 45 °C and then enters the separator for defatting at a rotation speed of 5000 r / min. The fat content of the skim milk is required to be <0.1%. After passing the inspection, the skim milk is subjected to pasteurization at a temperature of 85 °C for 15 s, and the outlet temperature is controlled at 8 °C.

[0311] (2) Microfiltration separation

[0312] The above-mentioned skim milk enters the microfiltration membrane to remove casein, obtaining whey; the microfiltration membrane is made of polyethersulfone, the pore size of the microfiltration membrane is 0.1 μm, the operating temperature is 15 °C, and the operating pressure is 1.0 bar.

[0313] (3) Ultrafiltration standardization

[0314] The whey obtained by microfiltration is further subjected to ultrafiltration standardization. The ultrafiltration membrane is made of polyethersulfone, the retention molecular weight of the ultrafiltration membrane is 5000 - 10000 Da, the operating temperature is 15 °C, and the protein content in the outlet liquid is controlled to reach 12% of the total solids.

[0315] (4) Nanofiltration Concentration

[0316] The whey liquid after ultrafiltration standardization is further concentrated through a nanofiltration membrane. The molecular weight cut-off of the nanofiltration membrane is 100 - 500 Da, the concentration multiple is about 7 times, and the operating temperature is 15 °C. The requirement for the nanofiltration outlet is that the solid content is 28%.

[0317] (5) Electrodialysis Desalination

[0318] The concentrated whey liquid is subjected to electrodialysis desalination until the conductivity drops to 1.0 mS / cm to obtain desalted whey. The operating temperature of electrodialysis is 15 °C, the initial voltage is 20 V, and the operating pH is controlled at 6.5.

[0319] 3. Preparation of Pasteurized Milk

[0320] The raw milk that has passed the acceptance inspection is first preheated to 50 °C, then sterilized and clarified by a milk clarifier, followed by pasteurization at 85 °C for 15 s, and the outlet temperature is controlled at 8 °C.

[0321] 4. Mixing and Homogenization

[0322] According to requirements, 2200 kg of pasteurized milk (270 kg of dry matter), 607 kg of skim milk (dry matter content 28%), and 446 kg of desalted whey liquid (dry matter content 28%) are fed into a vacuum mixer and circulated for mixing at -0.9 bar and 45 °C. During the process, 130 kg of edible vegetable blended oil (soybean oil, sunflower oil, coconut oil, linseed oil), 200 kg of lactose, 75 kg of galactooligosaccharides, 6 kg of calcium citrate, 5 kg of fructooligosaccharides, 1 kg of calcium hydrogen phosphate, 3 kg of vitamin premix (vitamins A, D, E, K1, B1, B2, B6, B12, C, niacin, folic acid, pantothenic acid, biotin, taurine), 2 kg of choline chloride, 2 kg of mineral premix (magnesium sulfate, ferric pyrophosphate, zinc sulfate, manganese sulfate, potassium iodate, copper sulfate, sodium selenite), and 1 kg of nutrient premix (lutein, inositol, L-carnitine) are added. The mixing time lasts for 45 min, and then the mixed liquid is preheated to 55 °C through a plate heat exchanger and homogenized at a pressure of 240 bar. After homogenization, it is cooled to 8 °C through a plate heat exchanger and stored. The theoretical dry matter content of the above mixed liquid is 27.9%. Due to the presence of material top water and water top material during the production process, the actual dry matter content is 21%, and approximately 1.5 tons of process water enters the mixed liquid during the production process.

[0323] 5. Evaporation Concentration and Spray Drying

[0324] The mixed liquid enters the evaporator for concentration. Operating conditions: DSI sterilization temperature 90°C, sterilization time 10 s, body vacuum -950 mbar, temperature of the first-effect body: 70°C, temperature of the second-effect body: 65°C, temperature of the third-effect body: 60°C, and the concentration of the outlet liquid is controlled at 50%.

[0325] During the processing of infant formula milk powder, it is found that when the dry matter content in the mixed liquid reaches 21%, although it can meet the normal production requirements of the evaporation concentration and spray drying processes, the following problems exist in the DSI sterilization process: Due to the slightly higher material concentration (dry matter content > 20%), the insulation pipe is prone to coking during long-term operation at high temperature, which affects the quality and safety of the product, and the quality index of furosine in the obtained product also increases. The reason may be that during the DSI sterilization process of the mixed liquid with too high a concentration entering the evaporator, due to the relatively high concentrations of protein and carbohydrates, the heat treatment intensity is high, resulting in a relatively intense Maillard reaction. At the same time, there are a series of problems such as high energy consumption, long production time, and shortened service life of the nanofiltration membrane during the nanofiltration concentration of the defatted milk and demineralized whey liquid with too high a concentration.

[0326] Test Examples

[0327] 1. Protein, furosine, and lysine contents

[0328] For the protein, lysine, and furosine in the raw materials and products of each example and each comparative example, the protein content is detected by the first method in GB 5009.5, the furosine content is detected with reference to the draft for soliciting opinions of the "National Food Safety Standard - Determination of Furosine in Dairy Products", and the amino acid content is detected with reference to GB 5009.124. The results are shown in Table 1.

[0329] 2. Denaturation rate of whey protein

[0330] The denaturation rate of whey protein in the finished products of each example and each comparative example is measured (the results are shown in Table 1). The theoretical value of whey protein is calculated based on the proportion of whey protein in cow's milk and milk raw materials and the dosage of each protein raw material, so as to calculate the denaturation rate of whey protein in the finished product. The detection method uses the Kjeldahl method. First, the finished milk powder is reconstituted at a certain ratio, centrifuged at about 4°C to remove fat, and then centrifuged with 1 mol / L hydrochloric acid solution to remove the precipitate. The obtained supernatant (undenatured whey protein solution) is reacted with a catalyst and distilled. After adding boric acid to the distillate, it is titrated with hydrochloric acid. The content of undenatured whey protein is calculated based on the amount of acid consumed, and the denaturation rate is calculated using the difference in the whey protein content between the mixed liquid and the finished powder. The calculation formula is as follows:

[0331]

[0332] Table 1:

[0333]

[0334] 3. Evaluation of Product Dispensability

[0335] Detection of dissolution state: Prepare the product according to the corresponding reconstitution ratio and water temperature. After allowing the reconstituted milk liquid to stand for 1 min, immerse 3 / 4 of a clean microbiological slide into the reconstituted milk, stir vigorously back and forth for 5 s (do not draw circles), then vertically remove the slide, tilt it at about 60° and hold for 10 s. Then dry the back and bottom of the slide, and under a well-lit black background, compare it with the standard version (as shown in Figure 2 ). The reading time should not exceed 30 s. If the result is between two standards, record 0.5 unit.

[0336] Detection of white spots: Prepare the product according to the corresponding reconstitution ratio and water temperature. After standing for 5 min, carefully tilt the beaker, slowly rotate the beaker one full circle, then gently place it on the tabletop with the beaker upright. After 30 s, compare the beaker wall with the standard (as shown in Figure 3 ). If the result is between two standards, record 0.5 unit.

[0337] Product dispensability score = dissolution state × 0.5 + white spots × 0.5. The higher the final score, the better the dispensability (see Table 2).

[0338] Table 2:

[0339] Groups Dissolution State Score White Spot Score Comprehensive Score Example 1 4 5 4.5 Example 2 5 5 5 Example 3 5 5 5 Comparative Example 1 5 5 5 Comparative Example 2 2.5 2 2.25 Comparative Example 3 3 2.5 2.75 Comparative Example 4 3 3.5 3.25 Comparative Example 5 2 4 3 Comparative Example 6 4 3.5 3.75

[0340] Currently, raw materials such as skim milk powder, demineralized whey powder, and concentrated whey protein powder used in the production process of infant formula milk powder often need to go through a long storage period from production to actual use, ranging from several months to one to two years. During storage, these raw materials will inevitably undergo a series of complex chemical and biological changes. However, limited by existing technical means, it is difficult to comprehensively monitor these changes, resulting in the freshness of the raw materials not being fully guaranteed. In contrast, using all-liquid protein feeding can completely avoid the storage period of powdered protein raw materials. This process effectively solves the problem of nutrient loss caused by multiple heat treatments and long-term storage in the production of traditional infant formula milk powder, thus providing infants with fresher, safer, and more easily absorbable nutritional products, which is beneficial to the growth and development of infants.

[0341] The present invention provides a method for preparing formula milk powder, which significantly improves the product quality through raw material system selection and process optimization. The specific technical solution is as follows:

[0342] (1) Raw material system selection

[0343] Adopt a process route of feeding with all liquid protein raw materials. In particular, adopt a membrane process to obtain defatted liquid milk and desalted liquid whey as partial raw materials, and abandon the traditional high-temperature treatment of dry powder raw materials. This innovative solution has the following advantages: 1) Avoid multiple high-temperature treatments in the raw material production process, significantly reducing the degree of Maillard reaction; 2) Reduce protein thermal denaturation and maintain the natural conformation of whey protein; 3) Eliminate the quality uncertainty brought by long-term storage of powdered raw materials.

[0344] (2) Process optimization and control

[0345] 1) By precisely controlling the dry matter content of desalted whey liquid and defatted milk, optimize energy consumption while ensuring process continuity;

[0346] 2) Adopt mild heat treatment parameters to maximize the retention of nutrients;

[0347] 3) Adopt an integrated process of vacuum mixing - evaporation concentration - spray drying to ensure product freshness.

[0348] (3) Product quality improvement

[0349] The content of Maillard reaction products (such as furosine) in the product is reduced, the retention rate of essential amino acids (lysine) is increased, the denaturation rate of whey protein is controlled below 11%, the product is evenly dispersed, without caking phenomenon, and has good reconstitutability.

[0350] It should be noted that although the technical solution of the present invention is introduced with specific examples, those skilled in the art can understand that the present invention should not be limited thereto.

[0351] The embodiments of the present invention have been described above. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to technologies in the market, or to enable other ordinary skilled in the art in this technical field to understand the disclosed embodiments.

Claims

1. A preparation method of formula milk powder, characterized in that, The method includes: a mixing step of mixing a base milk raw material liquid, a skim milk raw material liquid, a desalted whey raw material liquid, and optionally other allowable non-temperature-sensitive components that can be added; a spray drying step of spray drying the mixed material obtained in the mixing step to obtain a powder; wherein, in the mixing step: the base milk raw material liquid is a directly animal-derived, pasteurized emulsion; the skim milk raw material liquid is an emulsion obtained by centrifugally defatting animal milk; the desalted whey raw material liquid is an emulsion obtained by separating whey and desalting whey from animal milk, and the whey separation is carried out by membrane separation, and the whey desalting is to remove the salts in the whey by membrane separation; the denaturation rate of whey protein in the formulated milk powder is 11% or less.

2. The method according to claim 1, wherein The base milk raw material liquid, the skim milk raw material liquid, and the desalted whey raw material liquid are all derived from cow milk, goat milk or horse milk.

3. The method according to claim 1 or 2, characterized in that, In the preparation of the skim milk raw material liquid: after the centrifugal defatting, it is obtained by one or two treatments of pasteurization and membrane concentration to obtain the skim milk raw material liquid.

4. The method according to any one of claims 1 to 3, characterized in that, In the preparation of the desalted whey raw material liquid: the whey separation is carried out by microfiltration membrane treatment, and the whey desalting is carried out by electrodialysis treatment.

5. The method according to claim 4, wherein Between the microfiltration membrane treatment and the electrodialysis treatment, a nanofiltration membrane treatment process is further included to concentrate the whey liquid to be electrodialyzed.

6. The method according to any one of claims 1 to 5, characterized in that, After the spray drying to obtain the powder, the powder is further mixed with optionally other allowable temperature-sensitive components that can be added.

7. The method according to any one of claims 1 to 6, characterized in that The mixing step includes a homogenization treatment.

8. The method according to any one of claims 1 to 7, characterized in that, Between the mixing step and the spray drying step, one or two of a composition adjustment step and a sterilization step are further included.

9. The method according to any one of claims 1 to 8, characterized in that the dry matter content in the skim milk raw material liquid is 9 to 25% by mass, and the fat content is 0.1% by mass or less; the conductivity in the desalted whey raw material liquid is ​ 10. The method according to any one of claims 1 to 9, characterized in that ​

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