Whey protein composition with high thermal stability

Abstract

The present invention relates to a method for producing a thermally stable whey protein composition. Using specific temperatures, shear rates and holding times and recycling at least a portion of the particles formed results in whey protein compositions having surprisingly high thermal stability and non-settle particles, which may be advantageous in downstream processing and application of materials.

Description

[0001] Whey proteins are used as a protein source in various nutritional products such as sports nutrition products, medical nutrition products, and formula milks; the latter include infant formula milk, follow-on formula milk, and growing-up formula milk.

[0002] Suitable sources of whey proteins for such nutritional products are whey protein concentrate (WPC) and whey protein isolate (WPI). These products are the result of separating skim milk into a casein-rich fraction and a whey protein-rich fraction (by curdling to form cheese and so-called cheese whey, by acidification to form caseinates and so-called acid whey, or by microfiltration to form a micellar casein fraction and so-called ideal whey or serum fraction), followed by removing most of the water, lactose, and ash from the whey protein-rich fraction by membrane filtration, precipitation, and / or ion exchange techniques.

[0003] WPC conventionally has a protein content of 60 wt% to about 85 wt% (based on dry solids), while WPI is manufactured by removing more non-protein components, thus concentrating the whey protein content to about 90 - 95 wt%.

[0004] Methods for producing WPC or WPI can include concentrating all protein fractions in the raw material, but can also include the selective enrichment of specific proteins. Examples thereof are WPC and WPI that selectively enrich α-lactalbumin or β-lactoglobulin.

[0005] The proteins present in WPC and WPI are substantially in the native (i.e., non-denatured) state. A native protein is defined as a protein in its properly folded and / or assembled form, which is operative and functional. It has all four levels of its biomolecular structure, where the secondary to quaternary structures are formed by weak interactions along the covalently bonded backbone. In a denatured protein, at least a part of the weak interactions of the secondary to quaternary structures is disrupted, while the primary structure (i.e., the covalently bonded backbone) remains intact. Thus, a denatured protein is different from a hydrolyzed protein, because in the latter, the primary structure has also been disrupted.

[0006] An aqueous composition of WPC or WPI at a concentration higher than about 2 wt% may gel and / or aggregate upon heating, thus affecting the rheology and texture of food products. This may be desirable for certain applications, but may be undesirable for other applications.

[0007] On the other hand, denatured whey proteins are less prone to gelation and aggregation upon heating. Denaturation can be achieved especially by exposure to a temperature above the denaturation temperature. However, denaturation makes the protein more sensitive to pH changes.

[0008] The combination of heat treatment and mechanical force (especially high shear) allows the formation of small micron-sized (usually 1 - 10 microns) whey protein particles / aggregates with a high degree of denaturation. The whey protein material thus produced is particularly suitable for increasing the protein content of food products and is commonly referred to as micronized whey protein. Other names for these types of particles are heat-denatured whey protein particles, whey protein aggregates or microparticles, and whey protein micelles.

[0009] Micronized whey protein was first described in US 4,734,287, which formed the basis for a commercial fat substitute. This fat substitute was provided for use in frozen desserts, cheeses, dressings, and mayonnaise and had a creamy texture despite a reduced fat content.

[0010] Equipment for micronization includes pressurized tube reactors or heat exchangers (WO 2006 / 057968, WO 2010 / 120199) and / or homogenizers (WO 2008 / 063115).

[0011] An overview of the various applications of micronized whey protein is provided by R. Ipsen, Int. Dairy J. 67 (2017) 73 - 79 and B. Kew, Trends in Food Science & Technology 106 (2020) 457 - 468.

[0012] WO 2007 / 108709 discloses a method for micronizing whey protein by changing the pH of WPC or WPI containing dry solids (preferably calcium hydroxide) with a divalent metal ion content of 3 g / kg to 6.0 - 8.5, most preferably 6.9 - 7.5, and subsequently heat-treating the resulting solution at a temperature above 70 °C, preferably above 85 °C. At a temperature of about 120 °C, only a few minutes are sufficient; at 70 °C, 40 - 60 minutes are required.

[0013] WO 2007 / 108709 theorizes that the high divalent metal ion content affects protein-protein interactions, thus promoting the formation of non-covalently associated aggregates rather than disulfide-bonded aggregates. The former are more easily disrupted by mechanical shear than the latter.

[0014] The median particle size of the resulting whey protein particles is greater than 10 microns and less than 70 microns.

[0015] WO 2010 / 120199 discloses a method in which a whey protein concentrate or isolate is denatured at a temperature of at least 50 °C under turbulent conditions and without mechanical shear, and is then transferred directly to a dryer without any intermediate processing.

[0016] Although the whey protein particle composition has a higher thermal stability compared to native whey protein, its application in heat-treated products (such as sterilized high-protein beverages) still has limitations in terms of gelation, sedimentation, thermal stability, viscosity, and / or sandy / gritty mouthfeel.

[0017] It has now been found that the thermal stability of such whey protein compositions can be further improved by a method defined as follows. The method includes applying specific temperature, shear rate, and holding time, and recycling at least a portion of the formed particles. It is theoretically believed that recycling provides a high-temperature flow of aggregates, which allows for a rapid temperature increase of the non-aggregated whey protein stream. This increases the reactivity and reduces the time required in the heater. In addition, the deposition of unfolded proteins on the outer surface of the already formed aggregates stabilizes the aggregates during high-temperature transportation and application to the final formulation.

[0018] In addition, recycling allows the atomization process to be separated from any downstream processing steps, thus enabling the adjustment of capacity without affecting or changing the tube size that controls the shear rate in the heater section and the holding section.

[0019] The method produces a whey protein composition with unexpectedly high thermal stability; this thermal stability is defined by the heat coagulation time (HCT). In addition, it is observed that the particles are not prone to sedimentation, which may be advantageous in the downstream processing and application of the material.

[0020] Accordingly, the present invention relates to a thermally stable whey protein composition having a heat coagulation time of at least 200 seconds, preferably at least 400 seconds, even more preferably at least 600 seconds, and most preferably at least 800 seconds - defined as the time required for a 10 wt% aqueous protein solution at pH 6.6 to form the first visible stagnation at 121°C.

[0021] The HCT can be determined by the oil bath method described by J.B. Magan et al. in Encyclopedia of Dairy Sciences (Third Edition), Elsevier, 2022, pages 391 - 399. A 2 mL 10 wt% protein solution with a pH of 6.6 is loaded into a glass tube with an inner diameter of 8 mm. The glass tube is placed in an oil bath at 121°C and continuously moved on a shaker at a speed of 7.5 oscillations per minute.

[0022] The change in visible appearance is monitored by a camera, and the time elapsed until the liquid stagnates in the tube and stops flowing freely is the heat coagulation time.

[0023] The heat-stable whey protein composition of the present invention has a protein content of 60 - 95 wt%, preferably 75 - 95 wt%, and most preferably 80 - 85 wt% based on dry matter.

[0024] Based on the total protein, the total concentration of α-lactalbumin and β-lactoglobulin is at least 50 wt%, preferably at least 60 wt%, more preferably at least 70 wt%, and most preferably at least 80 wt%. This total concentration includes native and denatured α-lactalbumin and β-lactoglobulin.

[0025] Based on the total protein, the total concentration of native α-lactalbumin and native β-lactoglobulin in the heat-stable whey protein composition of the present invention is not higher than 40 wt%, preferably not higher than 30 wt%, more preferably not higher than 20 wt%, even more preferably not higher than 15 wt%, even more preferably not higher than 10 wt%, and most preferably not higher than 5 wt%. The remaining part of the total α-lactalbumin and β-lactoglobulin content is in denatured form.

[0026] The degree of denaturation of α-lactalbumin is preferably at least 30%, preferably at least 40, more preferably at least 50%, even more preferably at least 60%, and most preferably at least 70%. The degree of denaturation of β-lactoglobulin is preferably at least 60%, preferably at least 70%, more preferably at least 75%, even more preferably at least 80%, and most preferably at least 85%.

[0027] The content of native α-lactalbumin and β-lactoglobulin can be determined by high-pressure gel permeation liquid chromatography as described in Method 1 of C. Holt et al., Int. J. Food Sci. Technol. [International Journal of Food Science and Technology] 34 (1999) 543 - 556, BDI Laboratories 1. For this purpose, the protein sample is dissolved in distilled water at approximately 2 g / l and the pH of the solution is adjusted to pH 4.6 with 0.5 M HCl. After standing for 0.5 hours at ambient temperature, the sample is filtered using a 0.45 μm membrane and then separated using a size exclusion (TSKG2000 SEXL) column and a pH 6.0 phosphate buffer, and detected at 280 nm. The concentrations of native β-lactoglobulin and α-lactalbumin are determined by integration of the peak areas. By comparing these concentrations with the concentration of the starting whey protein material, the degree of denaturation can be calculated.

[0028] In one embodiment, the heat-stable whey protein composition is in the form of an aqueous dispersion with a dry matter of 15 - 50 wt%, more preferably 18 - 45 wt%, and most preferably 25 - 35 wt%.

[0029] In another embodiment, the heat-stable whey protein composition is in a dry form, such as spray-dried form.

[0030] The method according to the invention comprises the following steps:

[0031] a) providing a whey protein composition having a protein content of 60 - 95 wt% based on dry matter and a total concentration of native α-lactalbumin and native β-lactoglobulin of at least 50 wt% based on total protein,

[0032] b) providing an aqueous whey protein solution comprising said whey protein composition at a dry matter concentration of 15 - 50 wt%, the pH of said solution being in the range of 6.0 - 7.5

[0033] c) optionally preheating said aqueous whey protein solution to a temperature of up to 70 °C using a heat exchanger,

[0034] d) passing the optionally preheated aqueous whey protein solution through a tubular heat exchanger at a shear rate of at least 1500 s -1 so as to heat said aqueous whey protein solution to a temperature in the range of 70 °C - 140 °C, preferably 75 °C - 95 °C,

[0035] e) holding the aqueous whey protein product obtained in step d) in a holding tube at 70 °C - 140 °C, preferably 75 °C - 95 °C, with a residence time of 1 second to 10 minutes and a shear rate of at least 1000 s -1 so as to denature at least 50% of the initial concentration of α-lactalbumin and β-lactoglobulin based on total protein, and

[0036] f) recycling at least a portion of the aqueous dispersion of whey protein particles to the heat exchanger of step d) and conveying another portion to a cooling device or a dryer.

[0037] The starting material is a whey protein composition having a protein content in the range of 60 - 95 wt% based on dry matter and a total concentration of native α-lactalbumin and β-lactoglobulin of at least 50 wt%, preferably at least 60 wt%, more preferably at least 70 wt%, more preferably at least 80 wt%, even more preferably at least 85 wt%, more preferably at least 90 wt%, more preferably at least 95 wt%, most preferably at least 99 wt% based on total protein.

[0038] Most of the proteins in the starting material are native, i.e., non-denatured. The degree of denaturation of α-lactalbumin and β-lactoglobulin in said starting material is less than 20%, preferably less than 15%, more preferably less than 10%, and most preferably less than 5%.

[0039] The protein content can be determined using the well-known Kjeldahl nitrogen analysis method and applying a Kjeldahl factor of 6.38.

[0040] Examples of suitable whey protein compositions are whey protein concentrates, whey protein isolates, WPC or WPI rich in α-lactalbumin, and WPC or WPI rich in β-lactoglobulin.

[0041] The starting material can be a dry / powdered whey protein composition or a liquid whey protein composition. Examples of such liquid whey protein compositions are whey products obtained when removing the water, lactose, and mineral fractions from acid whey (i.e., whey produced from caseinate), cheese whey, or ideal whey. More particularly, the liquid whey protein composition is the ultrafiltration retentate of whey, which may have undergone further concentration, filtration, and / or purification steps.

[0042] The whey protein composition has a calcium content of preferably less than 1900 mg / 100 g protein, more preferably less than 1250 mg / 100 g protein, even more preferably less than 950 mg / 100 g protein, and most preferably less than 750 mg / 100 g protein. The lower calcium content improves the thermal stability.

[0043] In one embodiment, the whey protein composition is obtained by concentrating whey, preferably cheese whey. Compared to acid whey or ideal whey, cheese whey contains caseinomacropeptide (CMP). CMP helps prevent the formation of a strong continuous gel structure and can help prevent the aggregation of particles during heating.

[0044] In another embodiment, a whey protein concentrate or isolate is obtained by concentrating acid whey.

[0045] The concentration of whey protein can be carried out by standard methods such as ultrafiltration.

[0046] The whey protein composition is dissolved in water (in the case where the whey protein concentrate or isolate is in dry or powdered form), or used as it is or diluted with a certain amount of water (in the case where a liquid whey protein composition is used as the whey protein composition), and the amount of water is such that a solution with a dry matter content of 15 - 50 wt%, preferably 15 - 45 wt%, and most preferably 25 - 35 wt% is produced. A lower dry matter content will have a negative impact on thermal stability; a higher dry matter content results in too high viscosity and will require a very high shear rate.

[0047] The pH of the resulting solution should be in the range of 6.0 - 7.5. Outside these ranges, aggregation occurs too quickly upon heating.

[0048] If the pH of the whey protein solution is already outside this range, it can be adjusted to this range by adding an acid or a base. Suitable acids and bases are KOH, NaOH, Ca(OH)2, Mg(OH)2, NH4OH, carbonates and bicarbonates, trisodium citrate, tripotassium citrate, phosphates, HCl, phosphoric acid, citric acid, lactic acid, tartaric acid, acetic acid, sulfuric acid, hydrochloric acid, malic acid, maleic acid, fumaric acid, and succinic acid.

[0049] To denature at least a portion of the whey protein and form particles, an aqueous whey protein solution is first heated in a tubular heat exchanger under shear to a temperature in the range of 70°C - 140°C, preferably 70°C - 110°C, more preferably 75°C - 95°C, even more preferably 75°C - 90°C, and most preferably 75°C - 85°C. The shear rate during this heating step is at least 1500 s -1 , preferably at least 2000 s -1 , and most preferably at least 2300 s -1 .

[0050] The shear rate is controlled by the inner diameter of the tubular heat exchanger and the flow rate of the aqueous solution.

[0051] The residence time of the solution in the tubular heat exchanger depends on the temperature used and, when using a temperature range of 70°C - 140°C, is preferably in the range of 1 - 600 s, more preferably 1 - 180 s, and most preferably 1 - 60 s.

[0052] In one embodiment, the tubular heat exchanger can be used to heat the whey protein solution starting from room temperature or below room temperature.

[0053] In another embodiment, the whey protein solution is preheated before entering the tubular heat exchanger. It can be preheated to any temperature provided that the temperature remains below the denaturation temperature of α-lactalbumin and β-lactoglobulin. In practice, this means a temperature not higher than 70°C, preferably not higher than 65°C. The preheating can be carried out with any suitable equipment, including plate heat exchangers, tubular heat exchangers, and scraped surface heat exchangers. In a preferred embodiment, a tubular heat exchanger is used.

[0054] Subsequently, the aqueous whey protein product exiting the tubular heat exchanger is held in a holding tube at the same temperature range of 70°C - 140°C, preferably 70°C - 110°C, more preferably 75°C - 95°C, even more preferably 75°C - 90°C, most preferably 75°C - 85°C, for at least 1000 s -1 , preferably at least 1300 s -1 , most preferably at least 1500 s -1held at a shear rate and with a residence time of from 1 to 600 seconds in order to denature the α-lactalbumin and β-lactoglobulin to a sufficient extent.

[0055] The higher the temperature, the shorter the holding period required.

[0056] Examples of suitable combinations of temperature and residence time are 70 °C for 120 seconds, 80 °C for 30 seconds, and 90 °C for 10 seconds.

[0057] After leaving the holding tube, a portion (preferably 5 - 60 wt%, more preferably 5 - 40 wt%, even more preferably 5 - 25 wt%, and most preferably 10 - 25 wt%) of the resulting aqueous dispersion is recycled to the tubular heat exchanger of step d). This can be done with a high-pressure pump.

[0058] Another portion of the aqueous dispersion is collected as a liquid (optionally after a cooling step), cooled and stored until further processing (such as drying) or use, and / or sent directly to a drying or other further processing device. Drying can be carried out in various ways, including evaporation, spray drying, freeze drying. Spray drying is the preferred form of drying.

[0059] The process of the present invention preferably results in (i) at least 30%, preferably at least 40%, more preferably at least 50%, even more preferably at least 60%, and most preferably at least 70% denaturation of the native α-lactalbumin present in the whey protein composition of step a) and (ii) at least 60%, preferably at least 70%, more preferably at least 75%, even more preferably at least 80%, and most preferably at least 85% denaturation of the native β-lactoglobulin present in the whey protein composition of step a).

[0060] Since these proteins in the starting whey protein composition are mainly in the native state, this means that the heat-stable whey protein composition obtained by the process of the present invention preferably contains (ii) α-lactalbumin with a degree of denaturation of at least 30%, preferably at least 40%, more preferably at least 50%, even more preferably at least 60%, and most preferably at least 70% and (ii) β-lactoglobulin with a degree of denaturation of at least 60%, preferably at least 70%, more preferably at least 75%, even more preferably at least 80%, and most preferably at least 85%.

[0061] The whey protein particles in the heat-stable whey protein composition according to the invention preferably have a D50 volume average particle size in the range of 0.05 - 20 microns, more preferably 0.05 - 10 microns, and most preferably 0.05 - 1.0 micron. Preferably, 90 vol% of the particles (D90) have a diameter of less than 60 microns, more preferably less than 10 microns, and most preferably less than 5.0 microns. The span (= (D90 - D10) / D50) is in the range of preferably 5.0 - 40, more preferably 5.0 - 30, and most preferably 5.0 - 20.

[0062] The particle size and particle size distribution are determined using laser diffraction (Malvern Mastersizer 2000) with a refractive index of 1.47 and assuming an adsorption of 0 for non-spherical particles.

[0063] The heat-stable whey protein composition of the invention has a wide range of uses, particularly for increasing the protein content of food products without significant texture changes. Examples of such food products are processed cheese, yogurt, ice cream, fermented dairy products, whey crisps, bakery applications, (high-protein) beverages, high-protein medical nutriments, and convenience foods.

[0064] In one embodiment, the heat-stable whey protein composition is used for the preparation of high-protein medical nutriments, such as enteral compositions.

[0065] There are instances where individuals must rely on liquid nutritional compositions as their sole source of nutrition, such as surgical patients, patients suffering from trauma or undergoing cancer treatment, or individuals whose overall health condition renders them too weak or unwilling to eat or drink completely or in sufficient amounts. Typically, such individuals must rely on sipping or tube feeding. In addition to a relatively high protein concentration, medical compositions for enteral use may also contain sources of fat and carbohydrates that together bring the total energy density to a value in the range of, for example, 1.5 - 2.5 kcal / ml, especially when the composition is a concentrated composition intended for patients with fluid restrictions. Compositions intended to provide a complete diet, such as enteral compositions intended for sipping and / or tube feeding, may also contain the required amounts of vitamins, minerals, and / or fiber (complete nutriments).

[0066] Known problems with concentrated compositions are that high concentrations of protein can lead to high viscosities of the compositions, especially after heat treatment of the compositions (such as sterilization thereof). This is particularly problematic in compositions intended for sipping or tube feeding in medical nutrition, which may also contain fats, carbohydrates, vitamins and minerals. Also for patients with swallowing problems, the viscosity of the composition is important. In compositions intended for sipping or tube feeding, especially in compositions intended for sipping, it is important that a relatively small portion of the composition contains a large amount of protein and preferably also contains carbohydrates and / or fats. In these compositions, it is further preferred that the energy density is relatively high, for example in the range of 1.5 - 2.5 kcal / ml.

[0067] Using the heat - stable whey protein composition according to the invention as the protein source or at least one of the protein sources in such a high - protein liquid medical nutrition composition allows the viscosity of such compositions to be kept relatively low.

[0068] Such liquid compositions can contain 10 - 25 wt%, preferably 10 - 20 wt% of protein, 25 - 100 wt%, preferably 40 - 60 wt% of which is the heat - stable whey protein composition according to the invention. Examples of additional protein sources are micellar casein isolates, milk protein isolates, milk protein concentrates, caseinates and combinations thereof.

[0069] The pH of such nutritional compositions is preferably approximately neutral, for example 6.0 - 7.5. In addition, the nutritional compositions can also contain carbohydrates, fats, vitamins and minerals.

[0070] Carbohydrates preferably provide 20% to 60% of the total energy content of such nutritional compositions. Examples of suitable carbohydrates include maltodextrin, hydrolyzed, intact, natural and / or chemically modified starch or corn starch, malt, maltose, isomaltose, isomaltulose, glucose polymers, corn syrup, corn syrup solids, rice - or potato - derived carbohydrates, glucose, fructose, sucrose, lactose, trehalose, palatinose, high - fructose corn syrup and combinations thereof.

[0071] Fats preferably provide 20% to 50% of the total energy content of the composition. Non-limiting examples of fat sources suitable for use in nutritional compositions include milk fat or milk fat fractions, food grade coconut oil, fractionated coconut oil, soybean oil, corn oil, olive oil, rapeseed oil, safflower oil, high oleic safflower oil, MCT oil (medium chain triglycerides), sunflower oil, high oleic sunflower oil, palm oil and palm kernel oil, palm olein, canola oil, marine oils (such as fish oil), cottonseed oil, long chain polyunsaturated fatty acids such as arachidonic acid (ARA), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), and combinations thereof. The nutritional composition may also contain one or more structured lipids. Structured lipids are mainly triacylglycerols that contain a mixture of medium chain and long chain fatty acids on the same glycerol backbone.

[0072] In another embodiment, the present invention relates to liquid high protein compositions, such as protein shots or yogurt drinks, which are suitable for athletes, the elderly, patients and anyone else who wishes to improve protein intake, recovery and / or muscle synthesis.

[0073] Such compositions may contain 10 - 25 wt%, preferably 10 - 20 wt%, more preferably 15 - 20 wt% protein, 30 - 60 wt%, preferably 30 - 50 wt%, most preferably 35 - 45 wt% of which is a heat-stable whey protein composition according to the present invention. Examples of additional protein sources are micellar casein isolates, milk protein isolates, milk protein concentrates, caseinates and combinations thereof, with micellar casein isolates being the most preferred additional protein source.

[0074] Such compositions preferably do not contain large amounts of fat and carbohydrates.

[0075] Examples

[0076] HCT determination

[0077] HCT is determined as follows. A 2 mL 10 wt% protein solution is loaded into a glass tube with an inner diameter of 8 mm. The pH of the solution is 6.6. The glass tube is placed in an oil bath at 121 °C and continuously moved on a shaker using a dedicated Hettich Benelux test device at a speed of 7.5 oscillations per minute.

[0078] The change in visible appearance is monitored by a camera. The time elapsed until the liquid stagnates in the tube and stops flowing freely is the heat coagulation time.

[0079] Example 1

[0080] An aqueous whey protein concentrate (WPC) having 23 wt% protein, pH 6.6, and a whey protein content of 80 wt% based on dry matter (20 wt% α-lactalbumin and 77 wt% β-lactoglobulin based on total protein; 10% of the total protein being denatured α-lactalbumin + β-lactoglobulin) was preheated to 65 °C at 270 L / h in a tubular heater (inner diameter 7 mm). Subsequently, the preheated solution was transferred into the main tubular heater (inner diameter 7 mm, shear rate: 2400 s -1 ) by a positive displacement pump, where the solution was heated to 80 °C. The concentrate then entered a tubular holding heater (inner diameter 7 mm) without any heating and with a shear rate of 2400 s -1 , where the fluid was held for 30 seconds.

[0081] 10 vol% of the liquid leaving the holding heater was recycled to the suction side of the positive displacement pump (30 L / h). The remaining 90 vol% was transferred to a spiral cooler to reach a temperature of 5 °C.

[0082] All flows in the device were monitored and controlled with flow meters.

[0083] As shown in Table 1, the HCT of the resulting product exceeded 989 seconds. The D 50 of the resulting particles was 0.13 μm, the D 90 was 2.00 μm, and the span was 15.8. 75% of the whey protein was denatured α-lactalbumin and β-lactoglobulin.

[0084] Example 2

[0085] Example 1 was repeated, except that a drain valve was placed between the main tubular heater and the tubular holding heater. By opening the valve, 100 L / h of the heated concentrate was drained, effectively reducing the velocity and shear rate in the holding heater. The results are summarized in Table 1.

[0086] Example 3

[0087] Example 1 was repeated, except that the main tubular heater and the tubular holding heater had an inner diameter of 12 mm. The increase in this inner diameter directly affected the velocity and shear rate. The characteristics of the resulting product are presented in Table 1.

[0088] Table 1

[0089]

[0090]

[0091] Example 4

[0092] Determine the HCT of several commercially available microparticulated whey protein products and compare it with the HCT of the product of Example 1. The results are shown in Table 2.

[0093] Table 2

[0094] Product HCT [seconds] Example 1 ＞989 Market reference A 62 Market reference B 48

[0095] Example 5

[0096] Prepare liquid enteral high-protein formulations (A-H) using the whey protein product of Example 1 and, after storage at room temperature for six days, determine the viscosities of these formulations at 20 °C and at a shear rate of 100 s -1 using a rotational viscometer with a cup-and-bob geometry (MCR302 rheometer from Anton Paar with CC-27) from Anton Paar GmbH.

[0097] The composition of the nutritional composition is shown in Table 3.

[0098] Table 3

[0099]

[0100]

[0101] n.d. = not determined

Claims

1. A method for producing a heat-stable whey protein composition, the method comprising the following steps: a) providing a whey protein composition having a protein content of 60-95 wt% based on dry matter, and a total concentration of native α-lactalbumin and native β-lactoglobulin of at least 50 wt% based on the total protein, b) providing an aqueous whey protein solution comprising the whey protein composition of step a) with a dry matter concentration of 15-50 wt%, the pH of the solution being in the range of 6.0-7.5, c) optionally preheating the aqueous whey protein solution to a temperature of up to 70 °C using a heat exchanger, d) Feed the optionally pre-heated aqueous whey protein solution through a tubular heat exchanger at a shear rate of at least 1500 s -1 to heat the aqueous whey protein solution to a temperature in the range of 70 °C to 140 °C e) Hold the aqueous whey protein product obtained in step d) in a holding tube at 70 °C - 140 °C, with a residence time of 1 second to 10 minutes and a shear rate of at least 1000 s -1 , in order to denature at least 50% of the initial concentration based on the total proteins α-lactalbumin and β-lactoglobulin, and f) recycling at least a portion of the aqueous dispersion of whey protein particles to the heat exchanger of step d), and conveying another portion to a cooling device or a dryer.

2. The method according to claim 1, wherein, Convey the optionally preheated aqueous whey protein solution through the tubular heat exchanger at a temperature in the range of 70 °C - 110 °C, preferably 75 °C - 95 °C, even more preferably 75 °C - 90 °C, and most preferably 75 °C - 85 °C.

3. The method according to claim 1 or 2, wherein The optionally preheated aqueous whey protein solution is pumped through the tubular heat exchanger at a shear rate of at least 2000 s -1 and preferably at least 2300 s -1 .

4. The method according to any one of the preceding claims, wherein, Keep the aqueous whey protein product obtained from step d) in the holding tube at 70 °C - 110 °C, preferably 75 °C - 95 °C, more preferably 75 °C - 90 °C, and most preferably 75 °C - 85 °C.

5. The method according to any one of the preceding claims, wherein, The aqueous whey protein product obtained in step d) is incubated in this holding tube at a shear rate of at least 1300 s -1 , most preferably at least 1500 s -1 .

6. The method according to any one of the preceding claims, wherein, Keep the aqueous whey protein product obtained from step d) in the holding tube, wherein the residence time is 1-600 seconds, preferably 1-400 seconds, and most preferably 1-120 seconds.

7. The method according to any one of the preceding claims, wherein, The method results in (i) at least 30%, preferably at least 40%, more preferably at least 50%, even more preferably at least 60%, and most preferably at least 70% of the native α-lactalbumin present in the whey protein composition of step a) being denatured and (i) at least 60%, preferably at least 70%, more preferably at least 75%, even more preferably at least 80%, and most preferably at least 85% of the native β-lactoglobulin present in the whey protein composition of step a) being denatured.

8. The method according to any one of the preceding claims, wherein, The whey protein composition of step a) has a calcium content of less than 1900 mg / 100 g protein, preferably less than 1250 mg / 100 g protein, more preferably less than 950 mg / 100 g protein, and most preferably less than 750 mg / 100 g protein.

9. A heat-stable whey protein composition, comprising: - a protein content of 60-95 wt% based on dry matter, preferably 70-95 wt%, most preferably 80-85 wt%, - a total concentration of native and denatured α-lactalbumin and β-lactoglobulin of at least 50 wt% based on the total protein, preferably at least 60 wt%, more preferably at least 70 wt%, most preferably at least 80 wt%, and - a total concentration of native α-lactalbumin and native β-lactoglobulin of not more than 40 wt%, preferably not more than 30 wt%, more preferably not more than 20 wt%, even more preferably not more than 15 wt%, and most preferably not more than 10 wt%, The heat-stable whey protein composition has a heat coagulation time of at least 200 seconds -- defined as the time required for a 10 wt% aqueous protein solution at 6.6 to form a first visible stasis at 121 °C.

10. The heat-stable whey protein composition according to claim 9, wherein, The heat coagulation time is at least 400 seconds, even more preferably at least 600 seconds, and most preferably at least 800 seconds.

11. The heat-stable whey protein composition according to claim 9 or 10, wherein, The degree of α-lactalbumin denaturation is at least 30%, preferably at least 40%, more preferably at least 50%, even more preferably at least 60%, and most preferably at least 70%, and the degree of β-lactoglobulin denaturation is preferably at least 60%, preferably at least 70%, more preferably at least 75%, even more preferably at least 80%, and most preferably at least 85%.

12. The heat-stable whey protein composition according to any one of claims 9-11, which is in the form of an aqueous dispersion, the dispersion preferably having a dry matter content of 15-50 wt%, more preferably 18-45 wt%, and most preferably 25-35 wt%.

13. A food product comprising the heat-stable whey protein composition according to any one of claims 9-12 or a heat-stable whey protein composition obtainable by the method according to any one of claims 1-8, the food product preferably being selected from the group consisting of: cheese, yogurt, ice cream, fermented dairy products, whey crisps, baking applications, food bars, protein beverages, high-protein medical nutriments, and convenience foods.

14. A liquid nutritional composition having an energy density of 1.5-2.5 kcal / ml and a protein content of 10-25 wt%, preferably 10-20 wt%, wherein 25-100 wt%, preferably 40-60 wt% of the protein content is the heat-stable whey protein composition according to any one of claims 9-12 or a heat-stable whey protein composition obtainable by the method according to any one of claims 1-8.

15. A liquid nutritional composition having a protein content of 10-25 wt%, preferably 10-20 wt%, more preferably 15-20 wt%, wherein 30-60 wt%, preferably 30-50 wt%, most preferably 35-45 wt% of the protein content is the heat-stable whey protein composition according to any one of claims 9-12 or a heat-stable whey protein composition obtainable by the method according to any one of claims 1-8.

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