Method for producing serum protein concentrate

Abstract

This invention relates to a method for producing serum protein concentrate, wherein at least one of the microbial reduction steps includes treatment with UV-C radiation, thereby increasing the content of heat-sensitive bioactive components and improving the sustainability of the serum protein concentrate production method.

Description

[0001] This invention relates to a method for producing serum protein concentrate.

[0002] The best nutrition for an infant is generally considered to be the infant's own mother's milk; that is, human milk. However, there may be situations where the infant cannot be fed human milk. In such cases, the infant is usually fed with cow's milk-based formula. These formulas contain a mixture of casein and whey protein to provide an amino acid profile as close as possible to human milk.

[0003] Unfortunately, the protein composition of human milk and cow's milk differs significantly in both quantity and quality. One notable difference is the lower total protein content in human milk: the total protein content of human milk (i.e., total nitrogen content multiplied by 6.25) is typically around 11 g / L; while that of cow's milk is approximately 33-35 g / L.

[0004] A further difference between human milk and cow's milk lies in the different types of proteins they contain.

[0005] The total nitrogenous components in milk can be divided into true protein nitrogen and non-protein nitrogen (NPN), with casein and serum proteins (also known as whey proteins) being the main categories of proteins. Casein is a protein that precipitates at pH 4.6, while whey protein remains soluble at this pH. In human milk, the ratio of whey protein to casein changes from approximately 90:10 on the first day after birth to approximately 60:40 in mature human milk, while in cow's milk the ratio is approximately 20:80.

[0006] The composition of casein and whey protein differs between human and cow's milk. The most abundant whey proteins in human milk are α-lactalbumin, lactoferrin, and immunoglobulins, while the whey protein fraction in cow's milk comprises approximately 50% β-lactoglobulin and approximately 15% α-lactalbumin. The most abundant casein in human milk is β-casein, while cow's milk contains approximately 50% α-casein and approximately 35% β-casein.

[0007] Another important difference is that human milk contains a relatively high amount of essential amino acids. These amino acids cannot be synthesized in the human body and must be obtained from food.

[0008] Formula milk includes infant formula and follow-up formula, which provide complete nutritional support for infants in the first few months after birth until appropriate supplemental feeding is introduced. There are legal regulations governing the required components in such formula milk. One of these requirements is that the minimum levels of essential amino acids and several conditionally essential amino acids must be consistent with the composition of human milk. See, for example, the Codex Alimentarus of 25 September 2015 or European Commission Directive 2016 / 127 / EC.

[0009] To ensure the minimum levels of these (conditional) essential amino acids, conventional dairy-based formula milk has a significantly higher protein content than human milk.

[0010] For example, a common protein source in formula milk is a combination of milk powder or concentrated milk and demineralized whey protein concentrate; typically, it is demineralized casein whey concentrate. The addition of whey protein concentrate brings the whey:casein ratio closer to that found in human milk.

[0011] To ensure the required levels of essential amino acids, the total protein content of infant formula is typically between 1.8 and 3.0 g / 100 kcal. As several studies have shown, the higher end of this range has a drawback: it can lead to rapid weight gain in the first year of life, which may affect later body composition. Therefore, extensive research is underway on infant formulas with lower total protein content without compromising essential amino acid content.

[0012] Examples of methods that can address this problem include adding free amino acids, using casein glycomacropeptide (CMP) depleted whey, adding protein hydrolysates, and / or using whey rich in α-lactalbumin.

[0013] CMP is a cleavage product of κ-casein, formed during cheese production by rennet. High levels of CMP can negatively impact the amino acid pattern of formula milk, particularly the amount of essential amino acids. Furthermore, CMP is rich in threonine, and its oligopeptide form allows for rapid absorption of threonine by the body, potentially leading to overdose and causing hyperthreoninemia in preterm infants.

[0014] A suitable source of CMP-depleted whey is ideal whey. Ideal whey is obtained by separating milk into casein-rich and serum-rich fractions through microfiltration. The serum-rich fraction is called ideal whey. Ideal whey not only contains no CMP, but its protein composition (and consequently its essential amino acid composition) is also directed towards high levels of α-lactalbumin and β-casein, thus making its overall protein and amino acid composition more consistent with that of human breast milk.

[0015] Ideal whey is preferably added to infant formula in the form of a powdered concentrate. In this specification, the ideal whey concentrate is referred to as serum protein concentrate (SPC). The preparation of SPC involves microfiltration of skim milk to obtain a concentrated (micelle) casein-retained fraction and a serum fraction (ideal whey) containing most of the whey protein as a permeate. The permeate fraction is then concentrated by ultrafiltration to remove lactose, ash, and water. The concentrate can then be spray-dried to obtain SPC powder.

[0016] The use of SPC allows for the preparation of formula milk with low protein content and relatively high essential amino acid content. Furthermore, its preparation involves only a few processing steps that can denature bioactive components such as heat-sensitive vitamins and proteins. Examples of the latter are lactoferrin and immunoglobulins.

[0017] However, conventional SPC production still includes heat treatment steps that can cause denaturation of bioactive components. These process steps are microbial reduction steps performed to ensure microbiological quality. One example of such sterilization heat treatment steps is heat pasteurization (at least 72°C for at least 15 seconds). Denaturation of most bioactive proteins begins above 65°C, meaning that the nutritional value of SPC will be adversely affected by such heat treatment. Furthermore, such heat treatment requires a significant amount of energy.

[0018] Skimmed raw milk is typically heat-pasteurized before the microfiltration step. Removing microorganisms at this early stage is important to prevent bacterial load from increasing during processing and to prevent microbial clogging of the microfiltration membrane.

[0019] Another type of heat treatment is routinely applied just before spray drying. The SPC is conveyed via the tower feed line to the top of the spray drying tower while being heated under heat pasteurization conditions in a pasteurizer, and then atomized in the spray dryer. During this conveyance to the top of the spray dryer, the product is not actively cooled and is therefore maintained at approximately 72°C, as cooling would adversely affect the throughput and energy input of the spray drying method, and would also negatively impact the size of the spray-dried particles. In practice, this means that the SPC remains at a temperature of at least 72°C for several minutes.

[0020] Another microbial reduction step frequently used in milk (also in SPC production) is ceramic microfiltration (CMF). This step involves using microfiltration membranes with pore sizes ranging from 0.1 to 10 µm, thus removing bacteria and spores, but not casein and whey proteins. Compared to pasteurization, CMF avoids high-temperature (>65°C) treatment, therefore not affecting heat-sensitive components such as proteins, flavor, and viscosity. Additionally, CMF can remove heat-resistant microorganisms that are more resistant to conventional heat pasteurization conditions.

[0021] However, ceramic microfiltration requires significant amounts of water and energy. Therefore, removing this step without adversely affecting microbiological quality and the naturalness of heat-sensitive components would significantly improve the sustainability of SPC production methods.

[0022] The object of this invention is to provide a more sustainable and energy-efficient method for producing microbiologically safe SPCs. Another object is to provide a method for minimizing the denaturation of heat-sensitive bioactive components in the concentrate.

[0023] It has been found that these objectives can be achieved by applying UV-C radiation treatment during at least one microbial reduction step in the production of serum protein concentrate. In a preferred embodiment, at least one heat pasteurization and / or CMF step is replaced by UV-C treatment, thereby increasing the content of heat-sensitive bioactive components and / or improving the sustainability of the SPC production method.

[0024] In addition, UV-C has been found to destroy heat-resistant bacteria resistant to heat pasteurization conditions, such as Streptococcus thermophilus and Microbacterium species.

[0025] Ultraviolet (UV) irradiation is subdivided by wavelength into UV-A (320-400 nm), UV-B (280-320 nm), UV-C (200-280 nm), and vacuum ultraviolet (100-200 nm). UV-C has the highest bactericidal effect, especially between 250 and 270 nm, and can kill bacteria, viruses, protozoa, yeast, mold, and algae. The penetration depth of UV-C depends on the absorbance and scattering of UV light by the liquid.

[0026] The use of UV-C irradiation for microbial reduction or sterilization of transparent liquids is well-known. However, milk and dairy products are not transparent. MMDelorme, Trends in Food Science 102 (2020) 146-154 reviews the treatment of milk and dairy products with UV-C radiation. The advantages of UV-C treatment of dairy products are effective inactivation of microorganisms, minimal loss of nutritional and sensory quality, and no toxicity or waste generation. Compared to conventional heat pasteurization, UV-C treatment may require only one-thousandth of its energy. However, a major disadvantage involves the fact that milk and dairy products are opaque and have a high absorption coefficient at UV-C wavelengths. In other words, the penetrating power of UV-C light is limited, making it difficult to ensure that all microorganisms are directly exposed to UV-C light.

[0027] In other words, UV-C treatment of milk or whey—such as WO 2017 / 027091, WO 2019 / 057257, WO2021 / 063462, WO 2019 / 076413, US 2022 / 0305155, C. Schubert et al., Int. Dairy J. 147 (2023) 105785, L. Christen et al., PLOS ONE (8) 2013 e68120, W. Zhang et al., LWT – Food Sci. Techn. 141 (2021) 110945, P. Padademas et al., Animals 11 (2021) 42, C. Michel et al., Int. Dairy J. As disclosed in 122 (2021) 105149 and JA Ansari et al., Innovative Food Science and Emerging Technologies 52 (2019) 387-393—this is already a challenge; successfully reducing microbes in more concentrated dairy streams, such as whey protein concentrate, is considered an even greater challenge.

[0028] Despite these anticipated problems, the inventors have discovered that UV-C treatment can reduce the bacterial load in more concentrated dairy streams to such an extent that it can replace at least one conventionally used microbial reduction step in the production of serum protein concentrates.

[0029] Therefore, the present invention relates to a method for producing serum protein concentrate, the method comprising the following steps:

[0030] a) Demulsify the raw milk to provide skim milk.

[0031] b) subject the skim milk to at least one microbial reduction step to provide decontaminated skim milk.

[0032] c) The decontaminated skim milk is microfiltered to obtain a casein-rich retentate and a serum-rich permeate.

[0033] d) The serum-rich permeate is concentrated by ultrafiltration to obtain a serum protein concentrate as a retentate.

[0034] e) subjecting the serum protein concentrate to at least one microbial reduction step, and

[0035] f) Spray-dry the serum protein concentrate.

[0036] At least one of these microbial reduction steps includes treatment with UV-C radiation.

[0037] The method of the present invention can produce SPCs in which the plate count is at least equivalent to that obtained by heat pasteurization alone, while significantly reducing the denaturation of bioactive compounds. It also produces SPCs in which thermostable bacteria, such as Streptococcus thermophilus and Microbacterium species, are inactivated; these bacteria cannot be inactivated by heat pasteurization.

[0038] In one embodiment, UV-C radiation is used in step e). The advantage of performing UV-C treatment just before spray drying is that it allows for assurance of the microbiological quality of the final product.

[0039] In another embodiment, a UV-C irradiation treatment is performed in step b), optionally combined with a CMF or heat pasteurization step. The advantage of performing UV-C irradiation early in the process is that it ensures the cleanliness of the process.

[0040] Step b) may involve treatment with UV-C radiation followed by heat pasteurization, or vice versa.

[0041] Alternatively, step b) can involve ceramic microfiltration followed by treatment with UV-C radiation, or vice versa. The advantage of performing UV-C treatment after ceramic microfiltration is that the reduction in microorganisms achieved through ceramic microfiltration enhances the effectiveness of the UV-C treatment.

[0042] The advantage of UV-C treatment before ceramic microfiltration is that the liquid before ceramic microfiltration may have a lower dry matter content, and therefore lower absorbance and scattering, as well as deeper penetration of UV-C radiation.

[0043] In a preferred embodiment, neither CMF nor heat pasteurization is performed prior to microfiltration step c), and the treatment with UV-C radiation is the only microbial reduction step prior to microfiltration step c).

[0044] In another embodiment, no heat pasteurization is applied throughout the process. An even more preferred method is where the sole microbial reduction step is UV-C treatment, without any heat pasteurization or CMF steps. This allows for the highest possible retention of bioactive compounds in the most sustainable manner.

[0045] The bactericidal properties of UV radiation are mainly attributed to the inactivation of bacteria and viruses by inducing DNA mutations in DNA molecules through the absorption of UV light at very specific bactericidal wavelengths, typically between 253.7 nm and 254.1 nm.

[0046] The main commercial UV light sources that emit sufficient energy within the germicidal wavelength range are mercury lamps and deuterium lamps. Mercury lamps emit more intense radiation, while deuterium lamps have a wider emission spectrum.

[0047] For opaque liquids, UV treatment requires sufficient turbulence.

[0048] Turbulence can be represented by the Reynolds number (Re) and is affected by the diameter of the pipe through which the liquid is transported, the flow rate through the pipe, and the viscosity of the liquid. The viscosity, in turn, depends on the properties of the liquid, its dry matter content, and its temperature.

[0049] The UV-C treatment in the method of the present invention is preferably carried out on a liquid stream with a Reynolds number (Re) of at least 700, preferably at least 1,000, more preferably at least 1,500, even more preferably at least 2,300, more preferably at least 3,000, even more preferably at least 4,000, more preferably at least 6,000, and most preferably at least 10,000.

[0050] To prevent protein denaturation, UV-C treatment is preferably carried out at a temperature below 70°C, more preferably below 60°C.

[0051] On the other hand, in order to reduce viscosity, it is desirable to carry out the UV-C treatment at a temperature higher than the standard processing temperature (5°C) of the dairy product flow. Therefore, the UV-C treatment is preferably carried out at a temperature in the range of 10°C-70°C, more preferably 10°C-60°C, even more preferably 20°C-60°C, and most preferably 30°C-60°C.

[0052] The oxidation of any compound can be minimized by using additional optical filters to narrow the spectral bandwidth (as disclosed in WO 2021 / 063462) or by degassing the feed stream prior to UV-C treatment to remove oxygen / air.

[0053] In this specification, the term "milk" refers to milk obtained from livestock (e.g., cows, buffalo, sheep, goats, horses, and camels), but also refers to human milk. The preferred milk used in the methods of this invention is cow's milk.

[0054] Cream and skimmed milk can be obtained by defatting / stripping milk using conventional techniques such as centrifugal cream separation.

[0055] According to the method of the invention, skim milk is subjected to a microbial reduction step to provide decontaminated skim milk. If the total plate count has been reduced to a low value, the skim milk is considered decontaminated. The total plate count can be determined according to ISO 4833-1:2013 Part 1 (pour plate method). The total plate count is preferably reduced to less than 1000 CFU / ml, more preferably less than 100 CFU / ml, and most preferably less than 10 CFU / ml.

[0056] Microbial reduction can involve heat pasteurization (preferably in combination with the aforementioned ceramic microfiltration (CMF) step) or treatment with UV-C radiation (optionally in combination with heat pasteurization or CMF).

[0057] For heat pasteurization, various suitable combinations of time and temperature can be used. Examples of suitable combinations are: 72°C-75°C for 15-20 seconds, 63°C-65°C for 30-40 minutes, and 80°C-85°C for 1-5 seconds.

[0058] The legal requirement for pasteurization is to keep each part of the product composition at ≥ 72°C for at least 15 seconds, or under the equivalent conditions specified in the FDA Pasteurized Milk Regulation.

[0059] Ceramic microfiltration (CMF) is a well-known technique for removing particles such as bacteria and spores. Membranes with pore sizes in the range of 0.1-10 μm, preferably 0.5-2 μm, even more preferably 0.5-1.8 μm, and most preferably about 0.7-1.5 μm are used. Low bacterial content is achieved in the CMF permeate. CMF can be carried out at temperatures in the range of 45°C-60°C or 5°C-20°C. From a microbiological perspective, lower temperatures are preferred; on the other hand, higher temperature processing results in more efficient separation and allows for the use of smaller membrane areas. The temperature is preferably in the range of 40°C-60°C, more preferably 45°C-55°C.

[0060] UV-C treatment can replace CMF and / or heat pasteurization. The advantage of applying UV-C treatment at this stage of the process is that the absorbance and scattering in the milk are quite limited compared to the absorbance and scattering in the more concentrated stream further downstream of the process, thus improving the effectiveness of UV-C.

[0061] Separating the milk into a casein-rich retentate and a whey-rich permeate (step c) can be performed in a conventional manner well known to those skilled in the art. For example, skim milk (optionally diluted with water at a water / milk volume ratio of 0.5-1.5) can be subjected to cross-flow filtration using a microfiltration membrane at a temperature in the range of 10°C-20°C or 50°C-55°C. The temperature is preferably in the range of 10°C-20°C, more preferably 10°C-15°C. This temperature allows β-casein to pass through the membrane.

[0062] All conventional types of microfiltration membranes (spiral wound membranes, ceramic membranes, hollow fiber membranes, etc.) can be used. The membranes can be constructed from various polymer types, such as polysulfone (PS), (modified) polyethersulfone (PES), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), cellulose acetate (CA), and polypropylene (PP), as well as several ceramic materials, such as alumina, zinc oxide, and titanium oxide.

[0063] The molecular weight cutoff (MWCO) and pore size of the membrane are preferably in the range of 50-1000 kDa and / or 0.01-1.0 micrometers, more preferably in the range of 100-800 and / or 0.02-0.5 micrometers, and most preferably in the range of 100-500 kDa and / or 0.05-0.2 micrometers.

[0064] Microfiltration is preferably operated at a transmembrane pressure of 0.1-5 bar, more preferably 0.2-3 bar, and most preferably 0.2-1 bar.

[0065] Microfiltration can be implemented as a single-pass filtration or by using a series of membranes arranged in series. Preferably, the microfiltration is configured as a cross-flow filtration.

[0066] The feed flow rate is preferably 15 to 20 m. 3 Within the range of / hr.

[0067] The flux across the membrane (i.e., the ratio between product flow rate and membrane surface area) is preferably relatively low, more preferably 2-30, and most preferably 2-10 l / m 2 Within a range of / hr. This allows only the smallest casein molecules to pass through the membrane, resulting in a high whey protein to casein ratio.

[0068] Preferably, microfiltration and percolation are combined, and more preferably, the concentration is 2-30, preferably 2-10 l / m 2 The ratio between percolation flow rate and membrane surface area within the range of / hr.

[0069] The crossflow over the membrane is preferably at 50-300 m. 3 Within the range of / hr.

[0070] The serum-rich permeate produced by the microfiltration step—i.e., the microfiltration permeate—is concentrated by ultrafiltration (UF), optionally prior to the reverse osmosis step to increase the dry matter content. Ultrafiltration results in the removal of water, lactose, and minerals. The resulting UF retentate is serum protein concentrate (SPC).

[0071] Ultrafiltration is preferably performed using a 1-20 kDa membrane, more preferably a 5-10 kDa membrane.

[0072] The ultrafiltration temperature is preferably in the range of 10°C-20°C, more preferably 10°C-15°C, and most preferably 10°C-12°C.

[0073] All conventional types of ultrafiltration membranes (spiral wound membranes, ceramic membranes, hollow fiber membranes, etc.) can be used. Membranes can be constructed from various polymer types, such as polysulfone (PS), (modified) polyethersulfone (PES), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), cellulose acetate (CA), and polypropylene (PP), as well as several ceramic materials, such as alumina, zinc oxide, and titanium oxide. Spiral wound membranes are preferred ultrafiltration membranes. Hydrophilic polyethersulfone (PES) membranes are even more preferred.

[0074] The transmembrane pressure during ultrafiltration is preferably in the range of 0-6.0 bar, more preferably 3.5-5.0 bar, and most preferably 3.5-4.0 bar.

[0075] Ultrafiltration is preferably combined with percolation.

[0076] If necessary, the SPC can be further concentrated, demineralized, and / or dried, for example by nanofiltration, ion exchange, electrodialysis, reverse osmosis, desalination, and / or evaporation.

[0077] According to the method of the invention, the SPC undergoes a microbial reduction step before the subsequent spray drying step. This step may involve heat pasteurization or treatment with UV-C radiation.

[0078] To achieve the turbulence required for UV-C treatment, SPC may need to be diluted with water to reduce its dry matter content. The degree of dilution will depend on factors such as the viscosity of the SPC at the applied temperature, the pipe diameter through which the SPC flows during UV-C treatment, and the flow rate through the pipe. A suitable dry matter content is typically in the range of 5-15 wt%, preferably 6-12 wt%.

[0079] Furthermore, the temperature during UV-C treatment of whey protein phospholipid concentrate is preferably in the range of 10°C-70°C, more preferably 10°C-60°C, more preferably 20°C-60°C, and most preferably 30°C-60°C.

[0080] Before or after such UV-C treatment, serum protein concentrate can be preheated to a temperature within the range of 40°C-65°C, preferably 50°C-65°C, and most preferably 55°C-65°C, which is below the denaturation temperature of most (health-promoting) bioactive molecules. Preheating should not result in temperatures exceeding 65°C. Preheating is used to reduce the electrical energy input during subsequent spray drying steps, thereby making the method more energy-efficient. Preheating can be performed in batches or continuously in any suitable equipment. Batch preheating can be carried out in a container; continuous preheating can be carried out using a heat exchanger (e.g., a plate heat exchanger). Preheating is preferably performed continuously.

[0081] After reaching the desired preheating temperature, the preheated liquid composition is conveyed to the top of the spray drying tower. It is not necessary to maintain the composition at the desired temperature for a specific period of time before this conveying. Therefore, the entire process can be carried out continuously.

[0082] If not preheated, the serum protein concentrate is preferably kept below 20°C, more preferably below 15°C, and most preferably below 10°C in step e) until it reaches the top of the spray drying tower.

[0083] The resulting SPC is spray-dried. Spray drying is preferably carried out using hot air in the temperature range of 140°C-300°C, preferably 150°C-260°C, and most preferably 170°C-210°C.

[0084] Any type of spray dryer can be used, such as single-stage, two-stage, multi-stage, and Filtermat® spray dryers.

[0085] The SPC prepared according to the method of the present invention can be used to prepare formula milk by combining the SPC with at least one lipid source, carbohydrate source, vitamin and mineral.

[0086] The lipid source can be any lipid or fat suitable for use in formulated milk. Preferred fat sources include milk fat, safflower oil, egg yolk lipids, rapeseed oil, olive oil, coconut oil, palm kernel oil, soybean oil, fish oil, palmitoleic acid, high-oleic sunflower oil and high-oleic safflower oil, and microbially fermented oils containing long-chain polyunsaturated fatty acids. In one embodiment, anhydrous milk fat is used. The lipid source can also be a fraction derived from these oils (such as palmitolein, medium-chain triglycerides, and esters of fatty acids such as arachidonic acid, linoleic acid, palmitic acid, stearic acid, docosahexaenoic acid, linolenic acid, oleic acid, lauric acid, capric acid, caproic acid, etc.). Small amounts of oils containing large amounts of pre-formed arachidonic acid and docosahexaenoic acid, such as fish oil or microbial oils, can also be added. The fat source preferably has an n-6 to n-3 fatty acid ratio of about 5:1 to about 15:1; for example, about 8:1 to about 10:1. In one particular aspect, infant formula milk powder contains an oil mixture containing palmitic acid esterified to triacylglycerol, for example, wherein the amount of palmitic acid esterified at the sn-2 position of the triacylglycerol is 20% to 60% by weight of the total palmitic acid and the amount of palmitic acid esterified at the sn-1 / sn-3 position of the triacylglycerol is 40% to 80% by weight of the total palmitic acid.

[0087] Examples of vitamins and minerals preferably found in formula milk include vitamin A, vitamin B1, vitamin B2, vitamin B6, vitamin B12, vitamin E, vitamin K, vitamin C, vitamin D, folic acid, inositol, niacin, biotin, pantothenic acid, choline, calcium, phosphorus, iodine, iron, magnesium, copper, zinc, manganese, chloride, potassium, sodium, selenium, chromium, molybdenum, taurine, and L-carnitine. Minerals are usually added in the form of salts.

[0088] Examples of carbohydrates preferably present in formula milk are lactose, indigestible oligosaccharides such as galacto-oligosaccharides (GOS), fructooligosaccharides (FOS), inulin, xylooligosaccharides, and human milk oligosaccharides (HMOs). Suitable HMOs include 2'-FL, 3-FL, 3'-GL, 3'-SL, 6'-SL, LNT, LNnT, and combinations thereof. HMOs are commercially available or can be isolated from milk, particularly human breast milk.

[0089] If necessary, the nutritional composition may contain emulsifiers and stabilizers, such as citrates of soy lecithin, monoglycerides, and diglycerides. The nutritional composition may also contain other substances that may have beneficial effects, such as lactoferrin, nucleotides, nucleosides, and probiotics.

[0090] Suitable probiotics include lactobacilli, Bifidobacterium lactis such as Bifidobacterium lactis Bb12, Streptococcus thermophilus, Lactobacillus johnsonii La1, Bifidobacterium longum BL999, Lactobacillus rhamnosus LPR, Lactobacillus rhamnosus GG, Lactobacillus reuteri, and Lactobacillus salivarius. These prebiotics are commercially available.

[0091] Formula milk is typically made from milk powder (mixed with water) or liquid (with or without added water) and is intended for bottle or cup feeding.

[0092] Formula milk is typically supplied in the form of spray-dried powder. Spray drying involves an additional heating step. To retain as much of the natural protein as possible, it is desirable to maintain the gentlest possible heating conditions during spray drying.

[0093] To reduce the number of processing steps that may denature any proteins, it is preferable to dry-mix SPC with other ingredients in the formula milk or to mix liquid SPC with other liquid ingredients.

[0094] The formulated milk according to the invention can be in the form of a dry, semi-dry, or liquid composition. For example, it is a powdered composition suitable for use in aqueous solutions, preferably reconstituted with water to produce a liquid composition.

[0095] In another embodiment, it is a liquid composition, such as a consumable, drinkable, or spoonable composition. Example

[0096] Comparative Example 1

[0097] Serum protein concentrate is prepared by microfiltration of legally pasteurized skim milk. The microfiltration permeate is then subjected to ultrafiltration. The ultrafiltration residue—i.e., serum protein concentrate (SPC)—has a dry matter content of 26 wt% and a protein content of 60 wt% on a dry matter basis.

[0098] The SPC was then pasteurized at different temperatures ranging from 68°C to 76°C using a continuous-flow micro pasteurizer equipped with a tubular heat exchanger and a holder to simulate industrial pasteurization. The holding time in all experiments was 180 seconds, representing 18 seconds of industrial pasteurization, followed by 162 seconds of transfer to a spray drying tower.

[0099] Total plate count (also known as aerobic mesophilic count) was determined according to ISO 4833-1:2013. 1 ml of product was poured into plate counting milk agar and the plates were aerobically incubated at 30°C for 72 hours. The plates were then counted, and the number of colonies observed on the plates was reported as the number of colony-forming units (CFU) per ml of product at dilutions between 10 and 300.

[0100] For low heat-resistant plate counting, the sample is treated at 63.5°C for 30 minutes before plate laying. This method is equivalent to NEN6807.

[0101] For high heat-resistant plate counting, treat the sample at 80°C for 5 minutes before plate laying.

[0102] The total plate count remained at an initial low level of 800 cfu / ml in all experiments. Therefore, the microbiology in the resulting SPCs was independent of the pasteurization temperature and consisted of both highly and less heat-resistant bacteria and spores.

[0103] As a measure of protein bioactivity, the content of natural IgG was determined using a bovine IgG ELISA quantification device, as described in RLValk-Weeber, T. Eshuis-de Ruiter, L. Dijkhuizen and SS van Leeuwen, International Dairy Journal, Vol. 110, November 2020, 104814.

[0104] The reduction in bioactive (i.e., natural) IgG levels was largely temperature-dependent and decreased to 44% of its initial value after pasteurization at 76°C. Natural lactoferrin concentration was reduced to 10% of its initial value.

[0105] The resulting SPC was spray-dried on a small-scale pilot dryer.

[0106] Example 2

[0107] Comparative Example 1 was repeated, except that instead of pasteurization, the SPC was treated with UV-C using a Lyras® pilot-scale UV-C device with a capacity of 100-800 L / h. Given the high turbidity of the 26 wt% dry matter SPC suspension, the SPC was first diluted to a dry matter content of 9 wt%.

[0108] The cooled (10°C) diluted SPC is pumped through a spirally wound transparent tube (7 mm diameter) at the maximum possible flow rate (417 L / h) and a Reynolds number of 9270. This flow rate is limited by the pump capacity and the pressure drop allowed by the UV-C equipment.

[0109] Expose the SPC in the tube to light using a lamp placed on the outside of the spiral. Place a filter between the lamp and the tube to ensure a small wavelength peak at approximately 254 nm, thereby minimizing chemical side reactions such as oxidation.

[0110] The UV-C power used—that is, the percentage of the device's maximum power—is 80%.

[0111] As a result of this UV-C treatment, the total plate count decreased from 800 to 10 cfu / ml; and the number of heat-resistant microorganisms that could not be inactivated by pasteurization (LTR and HTR) was reduced to 10 and 0 cfu / ml, respectively.

[0112] Further investigation revealed that the contents of natural IgG and lactoferrin were not affected by UV-C treatment. They remained stable at 1.54 wt% and 0.13 wt%, respectively.

[0113] Example 3

[0114] Repeat Example 2, except that the suspension was first diluted to a dry matter content of 12.5 wt% and heated to 30°C, then pumped through a spirally wound transparent tube and exposed to UV-C light.

[0115] The total plate count, thermostable microbial content, and degree of denaturation of bioactive compounds were similar to those obtained in Example 2.

[0116] Example 4

[0117] Repeat Example 2, except that the suspension was first diluted to a dry matter content of 14.7 wt% and heated to 52°C, then pumped through a spirally wound transparent tube and exposed to UV-C light.

[0118] Different flow rates were used in the range of 57–448 L / h. With increasing flow rate, not only did the Reynolds number increase, but also the residence time and consequently, the UV-C energy input. When the differences in energy input were corrected for, a significant increase in the inactivation of microorganisms (total plate count) (including thermostable microorganisms) was observed at Reynolds numbers of 1500 and above.

Claims

1. A method for producing serum protein concentrate, the method comprising the following steps: a) Demulsify the raw milk to provide skim milk. b) subject the skim milk to at least one microbial reduction step to provide decontaminated skim milk. c) The decontaminated skim milk is microfiltered to obtain a casein-rich retentate and a serum-rich permeate. d) The serum-rich permeate is concentrated by ultrafiltration to obtain a serum protein concentrate as a retentate. e) subjecting the serum protein concentrate to at least one microbial reduction step, and f) Spray-dry the serum protein concentrate. At least one of these microbial reduction steps includes treatment with UV-C radiation.

2. The method of claim 1, wherein the treatment with UV-C radiation is carried out on a liquid stream having a Reynolds number (Re) of at least 700, preferably at least 1,000, more preferably at least 1,500, even more preferably at least 2,300, more preferably at least 3,000, even more preferably at least 4,000, more preferably at least 6,000, and most preferably at least 10,000.

3. The method according to claim 1 or 2, wherein the treatment with UV-C radiation is performed at a temperature in the range of 10°C-70°C, preferably 10°C-60°C, more preferably 20°C-60°C, and most preferably 30°C-60°C.

4. The method according to any one of the preceding claims, wherein step e) comprises a treatment with UV-C radiation.

5. The method according to claim 4, wherein the serum protein concentrate subjected to UV-C radiation has a dry matter content in the range of 5-15 wt%, preferably 6-12 wt%.

6. The method according to any one of claims 4-7, wherein the serum protein concentrate subjected to UV-C radiation has a temperature in the range of 10°C-70°C, preferably 10°C-60°C, more preferably 20°C-60°C, and most preferably 30°C-60°C.

7. The method according to any one of claims 4-6, wherein step b) comprises ceramic microfiltration and / or heat pasteurization.

8. The method according to any one of claims 4-7, wherein step e) comprises preheating the serum protein concentrate to a temperature of up to 65°C, followed by UV-C irradiation treatment.

9. The method according to any one of claims 4-8, wherein step e) comprises UV-C radiation treatment without heat treatment.

10. The method according to any one of claims 1-6 and 8-9, wherein step b) comprises a treatment with UV-C radiation.

11. The method of claim 10, wherein step b) comprises a treatment with UV-C radiation followed by heat pasteurization.

12. The method of claim 10, wherein step b) comprises ceramic microfiltration followed by treatment with UV-C radiation.

13. The method of claim 10, wherein step b) comprises a treatment with UV-C radiation as the only microbial reduction step prior to microfiltration step c).