Powdery nutritional composition suitable for premature infants and preparation method therefor

Abstract

The present invention relates to the technical field of premature infant food research, and specifically relates to a powdery nutritional composition with high protein and a high whey protein proportion and a preparation method therefor. The nutritional composition suitable for premature infants provided by the present invention contains carbohydrate, protein, fat, mineral substances, and vitamins; based on the total mass of the nutritional composition, the protein content is 3.5 g / 100 kcal or above, and whey protein accounts for 60-75% by mass of total protein; and the nutritional composition is a powdery solid. The nutritional composition can satisfy the clinical nutritional requirements of extremely premature infants / extremely low birth weight infants. Moreover, according to the preparation method for the powdery nutritional composition provided by the present invention, microfiltration technology is combined with an oil and fat online adding mode, the problems of denaturation and flocculation of a formula with high protein and a high whey protein proportion that has undergone heat treatment are overcome, pasteurization is carried out at an appropriate time on the basis of a material microorganism level for secondary sterilization so as to further reduce the microbial risk.

Description

Powdered nutritional composition suitable for premature infants and preparation method thereof Technical Field The present invention belongs to the technical field of premature infant food research, and specifically relates to a powdered nutritional composition suitable for premature infants and a preparation method thereof, and more specifically relates to a high-protein, high-whey protein powdered nutritional composition suitable for premature infants and a preparation method thereof. Background Art Premature / low birth weight babies refer to newborns with a gestational age of less than 37 weeks and a birth weight of less than 2500g. Worldwide, the incidence of premature birth is about 11%, and in my country it is about 7.1%, but the number of premature babies in my country ranks second in the world, and the incidence of premature babies has been increasing year by year in recent years. According to the gestational age of premature babies, premature babies can be further subdivided into late premature babies (gestational age 34-36 weeks), mid-preterm babies (gestational age 32-33 weeks), extremely premature babies (gestational age 28-31 weeks) and very premature babies (gestational age <28 weeks); according to the birth weight of premature babies, premature babies can be further subdivided into low birth weight babies (weight 1.5-2.5kg), extremely low birth weight babies (weight 1-1.5kg) and extremely low birth weight babies (<1kg). Since premature babies miss the critical growth period of fetal development - the late pregnancy, they have less reserves of various nutrients in their bodies after birth. At the same time, their brains, livers, kidneys, and gastrointestinal tracts are immature, and their digestion and absorption abilities are weak, which leads to the dual nutritional risks of premature babies: large nutrient requirements but difficulty in nutrient absorption. Premature babies with younger gestational age are more affected by their immaturity, and nutritional deficiencies may be more obvious in the initial adaptive stage after birth. Existing premature formulas are mostly designed based on the nutritional needs of healthy extremely premature babies / extremely low birth weight babies or mid-to-late premature babies / low birth weight babies. With the continuous improvement in the survival rate of extremely low birth weight babies with a gestational age of less than 1 kg and extremely premature babies with a gestational age of less than 28 weeks, the clinical nutritional needs of these premature babies, especially the nutritional needs of protein, have become the focus of attention. In addition to protein quantity, protein quality is also a factor that needs to be considered in clinical feeding of premature infants. Although there is no unified consensus on the protein quality requirements for premature infants, the protein quality in breast milk is the recognized gold standard. The ratio of whey protein to casein in breast milk is in a dynamic change process throughout the lactation period, ranging from 90:10 in the early lactation period (colostrum), 65:35 in transitional milk to 60:40 in mature milk and 50:50 in the late lactation period. Therefore, the fortified formula that meets the nutritional needs of premature infants with a birth weight of less than 1kg must have a protein content of 3.6g / 100kcal, and at least half of it comes from whey protein. At present, there are studies on high-protein formula milk powder for premature infants. For example, Reference 1 discloses a protein fortifier, which is used to change the protein content in premature infant nutrients, thereby making the formula or human milk suitable for the nutritional needs of very low birth weight children and extremely low birth weight children. In addition, the existing milk powder production processes include wet process, dry process and dry-wet composite process. Most of them adopt dry-wet process. The composite process includes mixing, homogenization, sterilization, concentration, spray drying, dry mixing and other processes. However, whey protein is thermally unstable and easily flocculates or precipitates when heated. Therefore, when the protein content in the formula is high and the proportion of whey protein is high, thermal treatment processes such as sterilization cannot be achieved. Although dry production can avoid the above problems, the microbial indicators of the product are difficult to control, and the risk of containing Cronobacter (Enterobacter sakazakii) is high. Enterobacter sakazakii is a "conditional pathogen" and has been identified by the World Health Organization and many countries as an important conditional pathogen that causes infant mortality. It can cause diseases in people of any age group, especially for premature / low birth weight infants or immunocompromised infants. The threat is greatest. In severe cases, it can lead to sepsis, meningitis or necrotizing enterocolitis. Microfiltration (MF) is a non-thermal processing technology that achieves separation based on the size difference of components. It can be used to selectively remove bacteria and somatic cells in skim milk while maintaining the nutritional and bioactive components of milk. Studies have shown that when skim milk is treated with microfiltration using a 1.4μm pore size ceramic membrane at 50°C, the total colony count was reduced by 3.8lg CFU / mL, which is higher than the 1.7lg CFU / mL reduced by high temperature short time sterilization (HTST) treatment. The combination of pasteurization and microfiltration to produce pasteurized milk has been industrialized, but current technologies require fat separation before microfiltration, filtering and sterilizing the skim milk, and heat treatment and sterilization of the separated cream separately before mixing it with the sterilized skim milk. This feature restricts the application of microfiltration technology in milk powder production. In summary, it is of great significance to develop a powdered nutritional composition suitable for premature infants with high protein and high whey protein ratio and provide a preparation method thereof to ensure compliance with microbial indicators. References: Reference 1: CN105941632A. Summary of the invention Problem that the invention aims to solve In order to achieve the development of high-protein premature infant formula, existing technologies have been studied at multiple levels. However, as of June 2023, the State Administration for Market Regulation has approved 13 special medical purpose premature / low birth weight infant formulas. The protein content of all products does not exceed 3.2g / 100kcal, and most are designed at 2.6-3.0g / 100kcal. It can be seen that the existing technology for the research of premature infant formula is still not sufficient, and it is still not completely sufficient to make the weight gain of extremely premature infants / extremely low birth weight infants reach the level of normal fetuses of the same gestational age. Furthermore, the key points of the current common wet and dry production process of infant formula powder include: ① Mixing: Use raw milk to fully dissolve whey powder, lactose and other raw materials, as well as vitamins and minerals in the batching equipment, and then mix the oil ingredients evenly in the batching equipment. ② Homogenization: Preheat the material to 50-55℃ for homogenization, and the homogenization pressure is 18-20MPa. ③ Sterilization: The material is sterilized by heat treatment at 75-85℃ for 16-30s. ④ Concentration: The material is concentrated to a concentrated milk density of 1000-1200kg / m 3 ⑤ Spray drying: spray drying the liquid feed, with an inlet air temperature of 165-190°C and an exhaust air temperature of 68-85°C. ⑥ Dry mixing: dry mixing unstable or heat-sensitive raw materials. When the above preparation method is used to produce high-protein and high-whey protein formulas, the whey protein in the liquid feed will flocculate and denature after heat treatment, making it impossible to produce products that meet the standard requirements; while reducing the intensity of heat treatment may bring microbial risks. However, in industrial practice, the present inventors have found that, although it is hoped to further increase the protein content on the basis of existing products ("the protein content does not exceed 3.2g / 100kcal, and most are designed to be 2.6-3.0g / 100kcal"), more macromolecular substances will bring difficulties to the preparation process. For example, after thermal experience (homogenization, sterilization, drying, etc.), it may lead to problems with the uniformity of material mixing and increased gelation, resulting in the existing process and equipment being unable to work normally and stably. In this regard, the present invention provides a powdered nutritional composition suitable for premature infants with high protein and high whey protein ratio suitable for wet mixing process and a preparation method thereof, which can allow a higher amount of protein to be added without affecting stable production. Specifically, raw materials with higher microbial risks are sterilized by microfiltration technology, oil is added online during the homogenization process, and then pasteurized or directly concentrated and spray-dried, and finally dry-mixed and added with other trace nutrients, so as to prepare a fortified formula powder with a protein content that meets the nutritional needs of extremely premature infants / very low birth weight infants. Solutions for solving problems In order to solve the above technical problems, the present invention provides the following technical solutions: [1]. A nutritional composition suitable for premature infants, wherein the nutritional composition contains: carbohydrates, proteins, fats, minerals and vitamins; And in the nutritional composition, based on the total mass of the nutritional composition: the protein content is 3.5 g / 100 kcal or more, and the whey protein accounts for 60 to 75 mass % of the total protein; Furthermore, the nutritional composition is a powdered solid. [2] The nutritional composition according to [1], wherein the raw materials of the nutritional composition include one or more of maltodextrin, skim milk powder, whey protein powder, desalted whey powder, edible oils and fats, lactose, mineral supplements and vitamin supplements. [3] The nutritional composition according to [2], wherein the edible oil comprises one or more of vegetable oil, medium chain triglycerides, arachidonic acid oil and docosahexaenoic acid oil. [4] The nutritional composition according to any one of [1] to [3], wherein the tap density of the nutritional composition is in the range of 180-220 mL / 100 g. [5] The method for preparing a nutritional composition according to any one of [1] to [4], wherein the method comprises the following steps: step: The step of mixing a raw material component I including carbohydrates and proteins with water to obtain a premix liquid; The step of microfiltration sterilization of the premix liquid; The step of mixing the premix liquid after microfiltration and sterilization with the raw material component II including fat, concentrating after homogenization, and spray drying to obtain a semi-finished product powder; The semi-finished product powder is dry-mixed with raw material component III including minerals, vitamins and fat. [6] The preparation method according to [5], wherein, in the preparation method, between the homogenization and concentration steps, a step of pasteurizing the homogenized liquid is also included. [7]. The preparation method according to [5] or [6], wherein the temperature of the microfiltration is 40-50°C and the pore size of the microfiltration membrane is 0.8-1.6 μm. [8] The preparation method according to any one of [5] to [7], wherein the raw material component I comprises one or more of maltodextrin, skim milk powder, whey protein powder, desalted whey powder and lactose. [9]. The preparation method according to any one of [5] to [8], wherein the raw material component II includes edible oils and fats, and the edible oils and fats include vegetable oils and medium-chain triglycerides.

[0010] . The preparation method according to any one of [5] to [9], wherein the raw material component III includes a mineral supplement, a vitamin supplement, arachidonic acid oil powder and docosahexaenoic acid oil powder. Effects of the Invention Through the implementation of the above technical solution, the present invention achieves the following technical effects: The present invention first provides a powdered nutritional composition suitable for premature infants, wherein the protein content is above 3.5 g / 100 kcal, and can even reach 3.6 g / 100 kcal, based on the total mass, and the whey protein accounts for 60-75% by mass of the total protein, preferably 60-70% by mass, which can meet the clinical nutritional needs of extremely premature infants / extremely low birth weight infants. At the same time, the present invention also provides a method for preparing the above-mentioned powdered nutritional composition suitable for premature infants, which uses microfiltration technology combined with online addition of oil to overcome the problems of denaturation and flocculation of high-protein and high-whey protein formulas after heat treatment, so that it can be prepared in large quantities by spray drying, and pasteurization can be added in time for secondary sterilization according to the microbial level of the material to further reduce the microbial risk. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1: A flow chart of the preparation process of the powdered nutritional composition provided in the present application. Figure 2: Flow chart of the existing commonly used milk powder preparation process. Figure 3: The state of protein in the concentrated feed solution during the preparation process of Example 4 (no denaturation, no flocculation). Figure 4: Protein status (denaturation, flocculation) in the concentrated feed solution during the preparation process of Comparative Example 1. DETAILED DESCRIPTION The following describes the embodiments of the present invention, but the present invention is not limited thereto. The present invention is not limited to the various structures described below, and various changes can be made within the scope of the invention claim, and the embodiments and examples obtained by appropriately combining the technical means disclosed in different embodiments and examples are also included in the technical scope of the present invention. In the present invention, a numerical range expressed using "a numerical value A to a numerical value B" means a range including the numerical values ​​A and B at the end points. In the present invention, a numerical range expressed using "above" or "below" means a numerical range including the number. In the present invention, the word "may" includes both performing a certain process and not performing a certain process. In the present invention, the use of "optional" or "optionally" indicates that certain substances, components, execution steps, applied conditions and other factors are used or not used. In the present invention, the unit names used are all international standard unit names, and if there is no special statement, the "%" used represents weight or mass percentage. In the present invention, the term "about" or "substantially" or "essentially" may mean that a value includes the standard deviation of the error of the device or method used to determine the value. The numerical ranges and parameters used to define the present invention are all approximate values, and the relevant numerical values ​​in the specific embodiments have been presented as accurately as possible. However, any numerical value essentially inevitably contains the standard deviation caused by the aforementioned testing device or method. Therefore, unless otherwise explicitly stated, it should be understood that all ranges, quantities, numerical values ​​and percentages used in the present invention are modified by "about". Here, "about" generally means that the standard deviation of the actual value and the theoretical model or theoretical data is within 2%, preferably 1%, and more preferably 0.5%. In the present invention, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc., mean that the specific elements (e.g., features, structures, properties and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner. In the present invention, the unit of "parts by mass" or "parts by weight" may be any weight unit such as g, mg, kg or t. In the present invention, the "infant formula for special medical purposes" refers to a powdered or liquid formula food designed to meet the nutritional needs of infants with special medical conditions such as special disorders, diseases or medical conditions, including formula food suitable for premature / low birth weight infants. In the present invention, for the convenience of describing fatty acid glycerides, the following characters are used to refer to different types of fatty acids: ARA: eicosatetraenoic acid (C20:4); DHA: docosahexaenoic acid (C22:6). In the present invention, when fatty acid esters, oils, mixed structure esters, etc. are mentioned as "mainly comprising" or "main components", it means that the content of the corresponding component is higher than the content of other components in the system. In the present invention, "medium-chain fatty acids" named for the chain length of fatty acids refer to fatty acids with a main chain length of 6 to 12 carbon atoms, and "long-chain fatty acids" refer to fatty acids with a main chain length of more than 12 carbon atoms. In addition, unless otherwise defined, other technical and scientific terms used in the present invention have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. The technical solution of the present invention is mainly completed based on the following insights: According to the nutritional needs of premature infants with a birth weight of less than 1kg, the protein content in the fortified formula powder for them needs to reach 3.6g / 100kcal, and at least half of it comes from whey protein. Although the prior art has made many attempts to this end, it is still impossible to prepare a fortified formula powder for premature infants that meets the corresponding market demand. The inventors of the present invention have found through a large number of studies that the main reason for this phenomenon is that the existing dry and wet production process of infant formula powder mainly includes the steps of mixing, homogenization, sterilization, concentration, spray drying and dry mixing. However, when such a preparation method produces a high-protein, high-whey protein formula, the whey protein in the feed liquid will flocculate and denature after heat treatment, which makes it impossible to mass-produce it by spray drying, or even if a solid product is produced, such a product is prone to lumps, resulting in poor dissolution usability; and reducing the intensity of heat treatment may bring microbial risks. In this regard, the present invention, while paying attention to the total protein and whey protein content in the fortified formula powder for premature infants, makes reasonable improvements to its production process, thereby making it possible to prepare a large amount of fortified formula powder for premature infants with high protein, high whey protein ratio and microbial compliance by spray drying. The technical solution of the present invention is further described below: Nutritional composition suitable for premature infants The present invention provides a powdered nutritional composition for meeting the clinical nutritional needs of mid- to late-stage premature infants / low birth weight infants, or extremely premature infants / extremely low birth weight infants, preferably extremely premature infants / extremely low birth weight infants. In order to meet the clinical nutritional needs of premature infants at all stages, especially extremely premature infants / extremely low birth weight infants, the powdered nutritional composition provided by the present invention contains: carbohydrates, proteins, fats, minerals and vitamins; and in the nutritional composition, based on the total mass of the nutritional composition: the protein content is 3.5g / 100kcal or more, and whey protein accounts for 60-75% of the total protein by mass. At the same time, the preparation method of the nutritional composition provided by the present invention at least includes the step of spray drying. Moreover, the tap density of the finished powdered nutritional composition provided by the present invention is in the range of 180-220mL / 100g, preferably 180-200mL / 100g. At the same time, the powdered nutritional composition provided by the present invention Based on the total mass, the cystine content is greater than or equal to 0.3g / 100g. In some specific embodiments, the nutritional composition contains: carbohydrates, proteins, fats, minerals, vitamins and nucleotides. In some specific embodiments, based on the total mass of the nutritional composition, the protein content is 3.6 g / 100 kcal, that is, the protein content is 17.5 g / 100 g. In some specific embodiments, based on the total mass of the nutritional composition, whey protein accounts for 60 mass%, 61 mass%, 62 mass%, 63 mass%, 64 mass%, 65 mass%, 66 mass%, 67 mass%, 68 mass%, 69 mass%, 70 mass%, 71 mass%, 72 mass%, 73 mass%, 74 mass% or 75 mass% of the total protein; preferably, it accounts for 60-70%, that is, the content of whey protein is 10.5g / 100g to 12.3g / 100g. Further, in order to provide more adequate nutrition and facilitate the preparation of the nutritional composition, the present invention uses one or more of raw materials selected from maltodextrin, skim milk powder, whey protein powder, desalted whey powder, edible oils and fats, lactose, mineral supplements and vitamin supplements to prepare the nutritional composition. The present invention does not specifically limit the specific sources of the above raw materials, for example, the finished raw materials can be purchased through commercial channels, or prepared by methods such as biological fermentation and physical purification. In some specific embodiments, the raw materials of the nutritional composition include maltodextrin, skim milk powder, whey protein powder, desalted whey powder, edible oils and fats, mineral supplements, vitamin supplements and optional lactose. In some more specific embodiments, the raw materials of the nutritional composition include maltodextrin, skim milk powder, whey protein powder, desalted whey powder, edible oils and fats, mineral supplements, vitamin supplements, nucleotide supplements, choline chloride and optional lactose. Maltodextrin is a glucose polymer that does not contain free starch and is made from starch or starchy substances through low-grade enzymatic hydrolysis, refining, and spray drying. Lactose is the main carbohydrate in breast milk and the preferred carbohydrate source for infants. However, compared with full-term infants, premature infants have insufficient lactase secretion and limited ability to digest lactose. Therefore, maltodextrin is used to replace part of the lactose because premature infants have stronger glycosidase activity, which can promote the decomposition of maltodextrin. In addition, maltodextrin has less effect on the osmotic pressure of the product when providing the same energy. In order to better adjust the proportion of each nutrient component in the nutritional composition of the present invention, in some specific embodiments, based on the total mass of the raw materials of the nutritional composition as 1000 parts by weight, the amount of maltodextrin is 220-260 parts; illustratively, it can be about 220 parts, 222 parts, 224 parts, 226 parts, 228 parts, 230 parts, 232 parts, 234 parts, 236 parts, 238 parts, 240 parts, 242 parts, 244 parts, 246 parts, 248 parts, 250 parts, 255 parts or 260 parts, etc.; the preferred amount is 230-250 parts; the more preferred amount is 235-245 parts; and the even more preferred amount is 238-242 parts. Skim milk powder is made from raw milk, after the fat is removed and dried. Milk powder. The present invention does not particularly limit the milk source of the milk powder, for example, it can be cow's milk, goat's milk, etc., and skimmed milk powder is preferably used. In order to better provide the nutrition of the nutritional composition, in some specific embodiments, the amount of the skimmed milk powder is 200-270 parts based on the total mass of the raw materials of the nutritional composition as 1000 parts by weight; illustratively, it can be about 200 parts, 210 parts, 215 parts, 220 parts, 225 parts, 230 parts, 235 parts, 240 parts, 245 parts, 250 parts, 255 parts, 260 parts, 265 parts or 270 parts, etc.; the preferred amount is 201-266 parts; the more preferred amount is 201-255 parts; and the even more preferred amount is 201-245 parts. Whey protein powder is a powdered product with a protein content of not less than 25% by mass, which is made from whey as raw material through separation, concentration, drying and other processes. In order to make the protein of the nutritional composition closer to breast milk and balance the ratio of whey protein to casein, in some embodiments, the amount of the whey protein powder is 90 to 130 parts based on the total mass of the raw materials of the nutritional composition as 1000 parts by weight; exemplary, it can be about 90 parts, 92 parts, 94 parts, 96 parts, 98 parts, 100 parts, 102 parts, 104 parts, 106 parts, 108 parts, 110 parts, 112 parts, 114 parts, 116 parts, 118 parts, 120 parts, 125 parts or 130 parts, etc.; preferably, the amount is 90 to 125 parts; more preferably, the amount is 90 to 120 parts; even more preferably, the amount is 96 to 118 parts. Desalted whey powder is a powdered product made of whey as raw material, desalted and dried, and its protein content is not less than 10% by mass. In order to make the protein of the nutritional composition closer to breast milk, balance the ratio of whey protein to casein, increase the lactose content and reduce the ash content, in some embodiments, the total mass of the raw materials of the nutritional composition is 1000 parts by weight, and the amount of the desalted whey powder is 100-150 parts; exemplary, it can be about 100 parts, 101 parts, 103 parts, 105 parts, 109 parts, 110 parts, 111 parts, 113 parts, 115 parts, 119 parts, 120 parts, 125 parts, 130 parts, 135 parts, 140 parts, 145 parts or 150 parts, etc.; preferably, the amount is 100-145 parts; more preferably, the amount is 101-142 parts. Furthermore, in order to better adjust the content of whey protein and total protein, in some embodiments, the total content of the skimmed milk powder, whey protein powder and desalted whey powder can be controlled. For example, based on the total mass of the raw materials of the nutritional composition as 1000 parts by weight, the total amount of the above three raw materials added is not less than 400 parts by weight and not more than 500 parts by weight, preferably not less than 420 parts by weight and not more than 485 parts by weight, more preferably not less than 440 parts by weight and not more than 475 parts by weight, and even more preferably not less than 450 parts by weight and not more than 465 parts by weight. In order to provide comprehensive nutrition, the fatty acid structure in the final nutritional composition is more reasonable to meet the nutritional needs of premature infants, and the present invention uses a variety of edible oils and fats to supply fat components. In some embodiments, the edible oils and fats include vegetable oils, medium-chain triglycerides, arachidonic acid oils and fats, and one or more of docosahexaenoic acid oils and fats. In some specific embodiments, the edible oils and fats include vegetable oils, medium-chain triglycerides, arachidonic acid oils and fats, and docosahexaenoic acid oils and fats. In order to increase and balance the monounsaturated fatty acids, polyunsaturated fatty acids, medium-chain fatty acids, long-chain fatty acids, etc. in the nutritional composition, in some embodiments, the present invention utilizes mixed vegetable oils, arachidonic acid oil powder and docosahexaenoic acid oil powder as fat sources. Mixed vegetable oil refers to edible oils and fats prepared by blending two or more edible vegetable oils made from edible vegetable oils or crude vegetable oils. In addition, in order to increase the medium-chain fatty acids, medium-chain triglycerides are added to the mixed vegetable oil, and the fat content of the medium-chain triglyceride product is not less than 65% by mass. In some specific embodiments, the mixed vegetable oil is composed of the following components: 70-80 parts of medium-chain triglycerides, 55-65 parts of high oleic sunflower oil, 50-60 parts of sunflower oil, and 45-55 parts of low-erucic rapeseed oil, of which medium-chain fats account for 27% to 36% of the total fat. Arachidonic acid oil powder refers to a powder product made by adding other food raw materials and food additives, such as whey protein powder, whey powder, modified starch, maltodextrin, lactose, white sugar, gum arabic, sodium octenyl succinate starch, sodium caseinate, vitamin E, ascorbyl palmitate, etc., to arachidonic acid oil powder (which can be derived from Mortierella alpina, etc., and can be obtained by biological fermentation) as raw materials, and processing. Among them, the fat content in arachidonic acid oil powder is not less than 20% by mass, and the content of arachidonic acid is not less than 10% by mass. Docosahexaenoic acid oil powder refers to a powder product made by using docosahexaenoic acid oil (which can be derived from Schizochytrium, Oken's Chytrium, Cryptodinium cohnii, tuna oil, etc., and can be obtained by biological fermentation) as raw materials, adding other food raw materials and food additives and other auxiliary materials, such as whey protein powder, whey powder, modified starch, maltodextrin, lactose, white sugar, gum arabic, sodium octenyl succinate starch, 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 content of docosahexaenoic acid is not less than 7% by mass. In some embodiments, based on the total mass of the raw materials of the nutritional composition as 1000 parts by weight, the amount of the mixed vegetable oil is 220-260 parts; illustratively, it can be about 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, 240, 242, 244, 246, 248, 250, 255 or 260 parts, etc.; the preferred amount is 230-255 parts; the more preferred amount is 230-250 parts; and the even more preferred amount is 230-240 parts. In some embodiments, based on 1000 parts by weight of the total mass of the raw materials of the nutritional composition, the amount of the arachidonic acid oil powder is 11 to 15 parts; illustratively, it can be about 11 parts, 12 parts, 13 parts, 14 parts or 15 parts, etc.; the preferred amount is 12 to 14 parts. In some embodiments, based on 1000 parts by weight of the total mass of the raw materials of the nutritional composition, the amount of the docosahexaenoic acid oil powder is 9 to 13 parts; illustratively, it can be about 9 parts, 10 parts, 11 parts, 12 parts or 13 parts, etc.; the preferred amount is 10 to 12 parts. In addition, the addition of lactose is not necessary in the nutritional composition, in order to better provide energy and promote the absorption of calcium by premature infants. In some embodiments, the amount of lactose is 0-15 parts; exemplary, it can be about 0 parts, 1 parts, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts or 15 parts, etc.; preferably, the amount is 0-10 parts; more preferably, the amount is 0-8 parts; even more preferably, the amount is 0-5 parts. In order to provide a variety of minerals, vitamins and nucleotides, the present invention uses complex minerals, complex vitamins, complex nucleotides and choline chloride as supplements. In order to facilitate the subsequent preparation of the nutritional composition, the compound minerals are divided into compound minerals-1 and compound minerals-2. In some embodiments, the compound mineral-1 is composed of the following ingredients: 9-11 parts of tricalcium phosphate, 4-5 parts of sodium chloride, 3-4 parts of calcium carbonate, 2-2.5 parts of magnesium sulfate, 1.5-2.5 parts of dipotassium hydrogen phosphate, 1.5-2 parts of sodium citrate, 0.4-0.7 parts of potassium citrate, 0.3-0.6 parts of potassium chloride, and 0.5-2 parts of maltodextrin. In some embodiments, the compound mineral-2 is composed of the following ingredients: 0.4-0.7 parts of ferric pyrophosphate, 0.1-0.3 parts of zinc sulfate, 0.1-0.3 parts of potassium iodate, 0.05-0.15 parts of copper sulfate, 0.02-0.08 parts of sodium selenite, 0.01-0.02 parts of manganese sulfate, and 0.5-1.5 parts of maltodextrin. In some embodiments, the compound vitamin is composed of the following ingredients: 2-3 parts of L-sodium ascorbate, 0.8-1.5 parts of inositol, 0.4-1.4 parts of dl-α-tocopherol acetate, 0.3-0.6 parts of taurine, 0.1-0.4 parts of L-carnitine, 0.1-0.3 parts of retinyl acetate, 0.1-0.2 parts of niacinamide, 0.1-0.15 parts of cholecalciferol, and 0.2-0.3 parts of d-hydroxy-1 ... - 0.04-0.08 parts of calcium pantothenate, 0.01-0.03 parts of riboflavin, 0.01-0.02 parts of thiamine nitrate, 0.01-0.02 parts of pyridoxine hydrochloride, 0.02-0.04 parts of folic acid, 0.02-0.04 parts of D-biotin, 0.02-0.04 parts of cyanocobalamin, 0.01-0.02 parts of phytonadione, and 0.5-1.5 parts of maltodextrin. In some embodiments, the composite nucleotide contains 0.17-0.27 parts of 5'-cytidylic acid disodium, 0.07-0.12 parts of 5'-uridylic acid disodium, 0.7-0.11 parts of 5' adenosine monophosphate, 0.05-0.09 parts of 5'-guanylic acid disodium, and 0.02-0.04 parts of 5'-inosinic acid disodium. In some embodiments, based on 1000 parts by weight of the total mass of the raw materials of the nutritional composition, the amount of the complex mineral-1 is 25 to 28 parts; illustratively, it can be about 25 parts, 25.5 parts, 26 parts, 26.5 parts, 27 parts, 27.5 parts or 28 parts, etc.; the preferred amount is 25 to 27 parts; and the more preferred amount is 25.5 to 27 parts. In some embodiments, based on 1000 parts by weight of the total mass of the raw materials of the nutritional composition, the amount of the complex mineral-2 is 1.5 to 2 parts; illustratively, it can be about 1.5 parts, 1.75 parts or 2 parts. In some embodiments, based on 1000 parts by weight of the total mass of the raw materials of the nutritional composition, the amount of the complex vitamins is 5 to 7 parts; illustratively, it can be about 5 parts, 6 parts or 7 parts, etc. In some embodiments, based on 1000 parts by weight of the total mass of the raw materials of the nutritional composition, the amount of the complex nucleotide is 0.4 to 0.6 parts; illustratively, it can be about 0.4 parts, 0.5 parts or 0.6 parts, etc. In addition, the present invention utilizes choline chloride to increase the choline content in the nutritional composition. In some embodiments, Based on 1000 parts by weight of the total mass of the raw materials of the nutritional composition, the amount of choline chloride used is 1.0 to 1.5 parts; illustratively, it can be about 1.0 parts, 1.25 parts or 1.5 parts. Further, in some specific embodiments, based on the total mass of the raw materials of the nutritional composition as 1000 parts by weight, the nutritional composition comprises the following raw materials in parts by weight: 220-260 parts of maltodextrin, 220-260 parts of mixed vegetable oil, 200-270 parts of skimmed milk powder, 100-150 parts of desalted whey powder, 90-130 parts of whey protein powder, 0-15 parts of lactose, 25-28 parts of complex mineral-1, 11-15 parts of arachidonic acid oil powder, 9-13 parts of docosahexaenoic acid oil powder, 5-7 parts of complex vitamins, 1.5-2 parts of complex mineral-2, 1.0-1.5 parts of choline chloride, and 0.4-0.6 parts of complex nucleotides. Preparation method of nutritional composition suitable for premature infants The present invention also provides a method for preparing the above-mentioned powdered nutritional composition suitable for premature infants, which comprises the following steps: a step of mixing a raw material component I including carbohydrates and proteins with water to obtain a premix liquid; a step of microfiltration sterilizing the premix liquid; a step of mixing the microfiltration sterilized premix liquid with a raw material component II including fat, homogenizing, concentrating, and spray drying to obtain a semi-finished product powder; and a step of dry mixing the semi-finished product powder with a raw material component III including minerals, vitamins and fats. In some embodiments, the raw material component I includes one or more of maltodextrin, skim milk powder, whey protein powder, desalted whey powder and lactose. In addition, in order to facilitate the subsequent sterilization by microfiltration, fat is not included in the raw material component I. In some specific embodiments, the specific operation of the step of mixing the raw material component I including carbohydrates and proteins with water to obtain a premix liquid can be: adding production water to a vacuum mixing tank, heating to 40-50°C, adding maltodextrin, optional lactose, whey protein powder, skim milk powder, desalted whey powder, and maintaining vacuum stirring to obtain a premix liquid. In some specific embodiments, the specific operation of the step of microfiltration sterilization of the premix liquid can be: sterilizing the premix liquid through ceramic membrane microfiltration, the microfiltration temperature is 40-50°C, preferably 42-48°C, and the microfiltration membrane pore size is 0.8-1.6μm, preferably 1.2-1.4μm. In some embodiments, the raw material component II includes edible oils and fats, and the edible oils and fats include vegetable oils and medium-chain triglycerides. In some specific embodiments, the raw material component II is a mixed vegetable oil. In some specific embodiments, the specific operation of the step of mixing the premix liquid after microfiltration and sterilization with the raw material component II including fat, homogenizing, and then concentrating and drying to obtain a semi-finished powder can be: preheating the sterilized premix liquid to 45-55°C, mixing it with the online metered vegetable oil, and then homogenizing it, and the homogenization pressure is 20-30MPa; the homogenized liquid is concentrated by a triple-effect evaporator to a liquid concentration of 35% to 45%, preferably concentrated to 35% to 40%; the concentrated liquid is spray-dried, and the drying tower inlet air temperature is 160-200°C, and the exhaust air temperature is 75-95°C. In some embodiments, between the steps of homogenization and concentration and drying, the homogenized liquid is further subjected to In some specific embodiments, the pasteurization temperature is 72-76°C and the sterilization time is 15-20 seconds. Before concentration, adding a secondary sterilization at a lower temperature can further reduce the microbial risk of the finished product. In some embodiments, the raw material component III includes compound minerals, compound vitamins, compound nucleotides, choline chloride, arachidonic acid oil powder and docosahexaenoic acid oil powder. In some specific embodiments, the specific operation of the step of dry mixing the semi-finished product powder with the raw material component III including minerals, vitamins, nucleotides and fats can be: dry mixing the semi-finished product powder with compound minerals-1, compound minerals-2, compound vitamins, compound nucleotides, arachidonic acid oil powder, docosahexaenoic acid oil powder and choline chloride, the dry mixing speed is 50rpm, and the dry mixing time is 2 to 4min. In addition, in order to improve the uniformity of the dry mixing step, in some embodiments, the compound mineral-2, compound vitamins, choline chloride, and compound nucleotides can be premixed and amplified with the semi-finished product powder respectively, and the premixing ratio is independently 1:1 to 1:10 by mass, and the premixing time is 1 to 3 minutes, and then mixed with other ingredients. The preparation method provided by the present invention adopts microfiltration technology combined with online addition of oil to overcome the problems of denaturation and flocculation of high-protein and high-whey protein formulas after heat treatment, and timely adds pasteurization for secondary sterilization according to the microbial level of the material to further reduce the microbial risk. The differences from the existing preparation process are shown in the preparation process flow charts shown in Figures 1 and 2. Example In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with embodiment.It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art. Example 1 A high-protein, high-whey protein ratio fortified formula powder for premature infants, comprising the following ingredients in parts by weight: 238 parts of maltodextrin, 237 parts of mixed vegetable oil, 235 parts of skimmed milk powder, 108 parts of whey protein powder, 119 parts of desalted whey powder, 26.5 parts of compound mineral-1, 13 parts of arachidonic acid oil powder, 11 parts of docosahexaenoic acid oil powder, 6 parts of compound vitamins, 3 parts of lactose, 1.75 parts of compound mineral-2, 1.25 parts of choline chloride, and 0.5 parts of compound nucleotides. The mixed vegetable oil consists of the following components: 76 parts of medium-chain triglycerides, 59 parts of high-oleic sunflower oil, 55 parts of sunflower oil, and 47 parts of low-erucic acid rapeseed oil, wherein the medium-chain fat accounts for 32% of the total fat. The composite mineral-1 is composed of the following ingredients: 9.9 parts of tricalcium phosphate, 4.5 parts of sodium chloride, 3.3 parts of calcium carbonate, 2.2 parts of magnesium sulfate, 1.9 parts of dipotassium hydrogen phosphate, 1.8 parts of sodium citrate, 0.54 parts of potassium citrate, 0.45 parts of potassium chloride, malt paste 1.91 parts of essence. The compound vitamin consists of the following ingredients: 2.51 parts of L-sodium ascorbate, 1.13 parts of inositol, 0.87 parts of dl-α-tocopherol acetate, 0.43 parts of taurine, 0.24 parts of L-carnitine, 0.22 parts of retinyl acetate, 0.15 parts of niacinamide, 0.12 parts of cholecalciferol, 0.06 parts of D-calcium pantothenate, 0.02 parts of riboflavin, 0.01 parts of thiamine nitrate, 0.01 parts of pyridoxine hydrochloride, 0.03 parts of folic acid, 0.03 parts of D-biotin, 0.03 parts of cyanocobalamin, 0.01 parts of phytonadione, and 0.13 parts of maltodextrin. The composite mineral-2 is composed of the following ingredients: 0.54 parts of ferric pyrophosphate, 0.18 parts of zinc sulfate, 0.18 parts of potassium iodate, 0.09 parts of copper sulfate, 0.05 parts of sodium selenite, 0.01 parts of manganese sulfate, and 0.7 parts of maltodextrin. The complex nucleotides were purchased from Nanjing Tongkai Zhaoye Biotechnology Co., Ltd., the arachidonic acid oil powder and docosahexaenoic acid oil powder were purchased from Roquette Bio-Nutrients (Wuhan) Co., Ltd., the skim milk powder was purchased from Kerry Ingredients (Ireland) Ltd, the whey protein powder was purchased from Wheyco, Germany, the desalted whey powder was purchased from DOMO, the Netherlands, the maltodextrin was purchased from Shandong Baolingbao, the lactose was purchased from ARLA, Germany, and the choline chloride was purchased from Beijing Jinkangpu. A method for preparing a high-protein, high-whey protein ratio fortified formula powder for premature infants, comprising the following steps: S01, carbohydrate and protein mixing: add production water into a vacuum mixing tank, heat to 45°C, add maltodextrin, lactose, whey protein powder, skim milk powder, desalted whey powder, keep vacuum stirring for 5 minutes, and obtain a premix liquid. S02, microfiltration: The premix liquid is sterilized by microfiltration through a ceramic membrane, the microfiltration temperature is 45°C, and the pore size of the microfiltration membrane is 1.4 μm. S03, oil addition and homogenization: preheat the sterilized premix liquid to 50°C, mix it with the online metered vegetable oil, and then homogenize it at a homogenization pressure of 25MPa. S04, concentration and drying: The homogenized liquid is concentrated by a triple-effect evaporator to a dry matter mass percentage of 38%. The concentrated liquid is spray dried, and the inlet air temperature of the drying tower is 175°C and the exhaust air temperature is 90°C. S05, fluidized bed cooling: The semi-finished product powder temperature is controlled to be ≤35°C through four-stage cooling of the fluidized bed. S06, dry mixing: dry mix the semi-finished product powder with compound mineral-1, compound mineral-2, compound vitamins, compound nucleotides, choline chloride, arachidonic acid oil powder, and docosahexaenoic acid oil powder at a dry mixing speed of 50 rpm and a dry mixing time of 3 min. S07, packaging and testing. The protein content of the finished product prepared in this embodiment is 3.6g / 100kcal (17.5g / 100g), whey protein accounts for 65% (11.3g / 100g) of the total protein, the tap density of the finished powder is 190mL / 100g, the cystine content is 0.33g / 100g, and the total bacterial count test results in the preparation process and the finished product are as follows: Table 1 Results of total colony count in the preparation process and finished products Example 2 The difference between this embodiment and embodiment 1 is that: a high-protein, high-whey protein ratio fortified formula powder for premature infants comprises the following ingredients in parts by weight: 240 parts of maltodextrin, 237 parts of mixed vegetable oil, 266 parts of skim milk powder, 96 parts of whey protein powder, 101 parts of desalted whey powder, 26.5 parts of compound mineral-1, 13 parts of arachidonic acid oil powder, 11 parts of docosahexaenoic acid oil powder, 6 parts of compound vitamins, 1.75 parts of compound mineral-2, 1.25 parts of choline chloride, and 0.5 parts of compound nucleotides. The specific components and sources of each raw material are the same as those in Example 1. The preparation method of the fortified formula powder for premature infants in this example is the same as the preparation method of the fortified formula powder for premature infants in Example 1. The protein content of the finished product prepared in this embodiment is 3.6g / 100kcal (17.5g / 100g), whey protein accounts for 60% (10.5g / 100g) of the total protein, the tap density of the finished powder is 184mL / 100g, and the cystine content is 0.31g / 100g. Example 3 The difference between this embodiment and embodiment 1 is that: a high-protein, high-whey protein ratio fortified formula powder for premature infants comprises the following ingredients in parts by weight: 242 parts of maltodextrin, 237 parts of mixed vegetable oil, 201 parts of skim milk powder, 118 parts of whey protein powder, 142 parts of desalted whey powder, 26.5 parts of compound mineral-1, 13 parts of arachidonic acid oil powder, 11 parts of docosahexaenoic acid oil powder, 6 parts of compound vitamins, 1.75 parts of compound mineral-2, 1.25 parts of choline chloride, and 0.5 parts of compound nucleotides. The specific components and sources of each raw material are the same as those in Example 1. The preparation method of the fortified formula powder for premature infants in this example is the same as the preparation method of the fortified formula powder for premature infants in Example 1. The protein content of the finished product prepared in this embodiment is 3.6g / 100kcal (17.5g / 100g), and the whey content of the total protein is The protein content is 70% (12.3g / 100g), the tap density of the finished powder is 198mL / 100g, and the cystine content is 0.36g / 100g. Example 4 The ingredients of the high-protein, high-whey protein fortified formula powder for premature infants in this embodiment are the same as those of the fortified formula powder for premature infants in Example 1. The difference between this embodiment and embodiment 1 is: a method for preparing a high-protein, high-whey protein ratio fortified formula powder for premature infants: S01, carbohydrate and protein mixing: add production water into a vacuum mixing tank, heat to 45°C, add maltodextrin, lactose, whey protein powder, skim milk powder, desalted whey powder, keep vacuum stirring for 5 minutes to obtain a premix liquid. S02, microfiltration: The premix liquid is sterilized by microfiltration through a ceramic membrane, the microfiltration temperature is 45°C, and the pore size of the microfiltration membrane is 1.4 μm. S03, oil addition and homogenization: preheat the sterilized premix liquid to 50°C, mix it with the online metered vegetable oil, and then homogenize it at a homogenization pressure of 25MPa. S04, pasteurization: the homogenized liquid is pasteurized at a temperature of 75°C and a sterilization time of 15s. S05, concentration and drying: The feed liquid is concentrated by a triple-effect evaporator until the dry matter mass percentage of the feed liquid is 38%. After concentration, the feed liquid is spray dried, and the air inlet temperature of the drying tower is 175°C and the exhaust air temperature is 90°C. S06, fluidized bed cooling: through the four-stage cooling of the fluidized bed, the temperature of the semi-finished powder is controlled to be ≤35℃. S07, dry mixing: dry mix the semi-finished product powder with compound mineral-1, compound mineral-2, compound vitamins, choline chloride, compound nucleotides, arachidonic acid oil powder, and docosahexaenoic acid oil powder at a dry mixing speed of 50 rpm and a dry mixing time of 3 min. S08, packaging and testing. In the preparation process S05 of this embodiment, the protein in the feed liquid has no obvious denaturation or flocculation after concentration, as shown in Figure 3. The tap density of the finished powder is 188 mL / 100 g. Example 5 The ingredients of the high-protein, high-whey protein fortified formula powder for premature infants in this embodiment are the same as those of the fortified formula powder for premature infants in Example 1. The difference between this embodiment and embodiment 1 is: a method for preparing a high-protein, high-whey protein ratio fortified formula powder for premature infants: S01, carbohydrate and protein mixing: add production water into a vacuum mixing tank, heat to 45°C, add maltodextrin, lactose, whey protein powder, skim milk powder, desalted whey powder, keep vacuum stirring for 5 minutes, and obtain a premix liquid. S02, microfiltration: The premix liquid is sterilized by microfiltration through a ceramic membrane, the microfiltration temperature is 45°C, and the pore size of the microfiltration membrane is 1.4 μm. S03, oil addition and homogenization: preheat the sterilized premix liquid to 50°C, mix it with the online metered vegetable oil, and then homogenize it at a homogenization pressure of 25MPa. S04, concentration and drying: The feed liquid is concentrated by a triple-effect evaporator to a feed liquid concentration of 38%. After concentration, the feed liquid is spray dried, and the inlet air temperature of the drying tower is 175°C and the exhaust air temperature is 90°C. S05, fluidized bed cooling: The semi-finished product powder temperature is controlled to be ≤35°C through four-stage cooling of the fluidized bed. S06, premixing: premix the compound mineral-2, compound vitamins, and choline chloride with the semi-finished product powder at a mass ratio of 1:5, and premix the compound nucleotide with the semi-finished product powder at a mass ratio of 1:10. The premixing time is 2 minutes. S07, dry mixing: dry mix the semi-finished product powder with the premixed raw materials, compound mineral-1, arachidonic acid oil powder, and docosahexaenoic acid oil powder at a dry mixing speed of 50 rpm and a dry mixing time of 3 minutes. S08, packaging and testing. In this embodiment, the preparation process is smooth and has no abnormalities, and the tap density of the finished powder is 184 mL / 100 g. Comparative Example 1 The ingredients of the fortified formula powder for premature infants in this comparative example are the same as those of the fortified formula powder for premature infants in Example 1. The difference between this comparative example and Example 1 is that a high-protein, high-whey protein ratio fortified product for premature infants is prepared by a general preparation method of the prior art: S01, ingredients: add purified water to a vacuum mixing tank, heat to 50°C, first add whey protein powder, skim milk powder, desalted whey powder, maltodextrin, lactose, then add mixed vegetable oil, keep vacuum stirring, then add pre-dissolved complex mineral-1, choline chloride, complex nucleotides, complex mineral-2 and complex vitamins in sequence, after all raw materials are added, stir for 5 minutes to obtain a premix liquid; S02, homogenization: the premix liquid is homogenized at 50°C, and the total homogenization pressure is 25 MPa. S03, sterilization: the homogenized liquid is sterilized by DSI, the sterilization temperature is 85°C, and the sterilization time is 20s. S04, concentration: The sterilized liquid is concentrated by a triple-effect evaporator until the dry matter mass percentage of the liquid is 45%. In this comparative example, the feed liquid undergoes gel-like flocculation during the concentration process after sterilization, as shown in FIG4 , and a solid product is finally obtained. Although Comparative Example 1 obtained a product with good nutritional value, its solid product had poor reconstitution properties. Comparative Example 2 The difference between this comparative example and Example 1 is that: a high-protein, high-whey protein ratio fortified formula powder for premature infants comprises the following ingredients in parts by weight: 345 parts of skim milk powder, 237 parts of mixed vegetable oil, 230 parts of maltodextrin, 78 parts of whey protein powder, desalted whey powder 50 parts, compound mineral-1 26.5 parts, arachidonic acid oil powder 13 parts, docosahexaenoic acid oil powder 11 parts, compound vitamins 6 parts, compound mineral-2 1.75 parts, choline chloride 1.25 parts, compound nucleotides 0.5 parts. The specific components and sources of each raw material are the same as those in Example 1. The preparation method of the fortified formula powder for premature infants in this comparative example is the same as the preparation method of the fortified formula powder for premature infants in Example 1. The protein content of the finished product prepared in this embodiment is 3.6 g / 100 kcal (17.6 g / 100 g), whey protein accounts for 50% (8.8 g / 100 g) of the total protein, and the cystine content is 0.28 g / 100 g. It can be seen that under the raw material composition of high protein and low whey protein ratio, the preparation process provided in this application can still successfully prepare a powder product by spray drying, but such a product has too low whey protein content and the cysteine ​​(cystine) content in the formula cannot meet the nutritional needs of premature infants. Comparative Example 3: The difference between this comparative example and Example 1 is that: a high-protein, high-whey protein ratio fortified formula powder for premature infants comprises the following ingredients in parts by weight: 243 parts of maltodextrin, 236 parts of mixed vegetable oil, 178 parts of desalted whey powder, 145 parts of whey protein powder, 138 parts of skim milk powder, 26.5 parts of compound mineral-1, 13 parts of arachidonic acid oil powder, 11 parts of docosahexaenoic acid oil powder, 6 parts of compound vitamins, 1.75 parts of compound mineral-2, 1.25 parts of choline chloride, and 0.5 parts of compound nucleotides. The specific components and sources of each raw material are the same as those in Example 1. The preparation method of the fortified formula powder for premature infants in this comparative example is the same as the preparation method of the fortified formula powder for premature infants in Example 1. The protein content of the finished product prepared in this comparative example is 3.6g / 100kcal (17.6g / 100g), and whey protein accounts for 80% (14.1g / 100g) of the total protein. However, the particles of the prepared formula powder are relatively fine, which is easy to cause blockage during subsequent pipeline transportation, causing inconvenience to process steps such as filling, and the formula powder obtained in this comparative example has poor solubility and poor usability. Comparative Example 4: The difference between this comparative example and Example 1 is that: a high-protein, high-whey protein ratio fortified formula powder for premature infants comprises the following ingredients in parts by weight: 245 parts of mixed vegetable oil, 223 parts of maltodextrin, 196 parts of desalted whey powder, 195 parts of skim milk powder, 81 parts of whey protein powder, 26.5 parts of compound mineral-1, 13 parts of arachidonic acid oil powder, 11 parts of docosahexaenoic acid oil powder, 6 parts of compound vitamins, 1.75 parts of compound mineral-2, 1.25 parts of choline chloride, and 0.5 parts of compound nucleotides. The specific components and sources of each raw material are the same as those in Example 1. The preparation method of the fortified formula powder for premature infants in this comparative example is different from the preparation method of the fortified formula powder for premature infants in comparative example 1. The preparation method is the same. The protein content of the finished product prepared in this comparative example is 3.0 g / 100 kcal (15 g / 100 g), and whey protein accounts for 65% (9.75 g / 100 g) of the total protein. It can be seen that under the raw material composition of low protein and high whey protein ratio, although the traditional preparation process can prepare powder products through spray drying, it cannot meet the nutritional needs of premature infants at all stages, especially extremely premature infants / extremely low birth weight infants. Industrial Applicability The powdered nutritional composition suitable for premature infants and the preparation method thereof provided by the present invention can be implemented in industry.

Claims

1. A nutritional composition suitable for premature infants, characterized in that: The nutritional composition contains: carbohydrates, proteins, fats, minerals and vitamins; And in the nutritional composition, based on the total mass of the nutritional composition: the protein content is 3.5 g / 100 kcal or more, and the whey protein accounts for 60 to 75 mass% of the total protein; Furthermore, the nutritional composition is a powdered solid.

2. The nutritional composition according to claim 1, characterized in that The raw materials of the nutritional composition include one or more of maltodextrin, skim milk powder, whey protein powder, desalted whey powder, edible oil, lactose, mineral supplement and vitamin supplement.

3. The nutritional composition according to claim 2, characterized in that The edible oil comprises one or more of vegetable oil, medium chain triglyceride, arachidonic acid oil and docosahexaenoic acid oil.

4. The nutritional composition according to any one of claims 1 to 3, characterized in that The tap density of the nutritional composition is in the range of 180-220 mL / 100 g.

5. The method for preparing the nutritional composition according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: The step of mixing a raw material component I including carbohydrates and proteins with water to obtain a premix liquid; The step of microfiltration sterilization of the premix liquid; The step of mixing the premix liquid after microfiltration and sterilization with the raw material component II including fat, concentrating after homogenization, and spray drying to obtain a semi-finished product powder; The semi-finished product powder is dry-mixed with raw material component III including minerals, vitamins and fat.

6. The preparation method according to claim 5, characterized in that: In the preparation method, between the homogenizing and concentrating steps, a step of pasteurizing the homogenized liquid is also included.

7. The preparation method according to claim 5 or 6, characterized in that: The temperature of the microfiltration is 40-50° C., and the pore size of the microfiltration membrane is 0.8-1.6 μm.

8. The preparation method according to any one of claims 5 to 7, characterized in that: The raw material component I includes one or more of maltodextrin, skim milk powder, whey protein powder, desalted whey powder and lactose.

9. The preparation method according to any one of claims 5 to 8, characterized in that: The raw material component II includes edible oils and fats, and the edible oils and fats include vegetable oils and medium-chain triglycerides.

10. The preparation method according to any one of claims 5 to 9, characterized in that: The raw material component III includes mineral supplements, vitamin supplements, arachidonic acid oil powder and docosahexaenoic acid oil powder.

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