Whey protein composition with high heat stability

Abstract

The invention relates to a process for producing a heat stable whey protein composition. Using specific temperatures, shear rates, and holding times and applying re-circulation of at least part of the formed particles results in a whey protein composition with a surprisingly high heat stability and particles that are less prone to sedimentation, which can be advantageous in downstream processing and applications of the material.

Description

[0001] WHEY PROTEIN COMPOSITION WITH HIGH HEAT STABILITY

[0002] Whey proteins are used as protein sources in various nutritional products, such as sports nutrition, medical nutrition, and formula milk; the latter including infant formula, follow-up formula, and growing-up formula.

[0003] Suitable whey protein sources for such nutritional products are whey protein concentrates (WPC) and whey protein isolates (WPI). These products are the result of separating skimmed milk into a casein-rich and a whey protein-rich fraction - either by renneting to form cheese and so-called cheese whey, by acidification to form caseinate and so-called acid whey, or by microfiltration to form a micellar casein fraction and a so-called ideal whey or serum fraction - followed by membrane filtration, precipitation, and / or ion exchange techniques to remove a large part of the water, lactose, and ash from the whey protein-rich fraction.

[0004] WPCs conventionally have a protein content (based on dry solids) of 60 wt% up to about 85 wt%, whereas WPIs are manufactured by removing more of the non-protein components, thereby concentrating the whey protein content to about 90-95 wt%.

[0005] Processes for the production of WPC or WPI may involve concentrating the entire protein fraction in the raw material, but may also include a selective enrichment in particular protein. Examples thereof as WPCs and WPIs selectively enriched in either a-lactalbumin or [3-lactoglobulin.

[0006] The proteins present in WPC and WPI are essentially in 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 possesses all four levels of its biomolecular structure, with the secondary through quaternary structure being formed from weak interactions along the covalently bonded backbone. In a denatured protein, at least part of the weak interactions of the secondary through quaternary structure is disrupted, whereas the primary structure - i.e. the covalently bonded backbone - is still intact. A denatured protein therefore differs from a hydrolysed protein, as in the latter also the primary structure has been disrupted.

[0007] Aqueous compositions of WPC or WPI with concentrations above about 2 wt% can gel and / or aggregate upon heating, thereby affecting the rheology and texture of a food product. This may be desirable for some applications, but undesirable for other. Denatured whey proteins, on the other hand, are less inclined to gel and aggregate upon heating. Denaturation can, amongst others, be achieved by exposure to temperatures above the denaturation temperature. Denaturation, however, makes the proteins more sensitive to pH changes.

[0008] The combination of heat treatment and mechanical forces, in particular high shear, allows for the formation of small micron-size (generally 1 -10 microns) whey protein particles / aggregates with a high degree of denaturation. The so-produced whey protein material is particularly suitable for increasing the protein content of food products and is generally termed microparticulated 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] Microparticulated whey protein was first described in US 4,734,287, which formed the basis for the commercial fat replacer Simplesse®. This fat replacer was offered for use in frozen desserts, cheese, dressings, and mayonnaise, and allowed a creamy texture despite the reduced fat content.

[0010] Equipment used for microparticulation includes pressurized tubular reactors or heat exchangers (WO 2006 / 057968, WO 2010 / 120199) and / or homogenizers (W02008 / 063115).

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

[0012] WO 2007 / 108709 discloses a process for the microparticulation of whey proteins by changing the pH of a WPC or WPI containing 3 g / kg dry solids of a divalent metal ion content, preferably calcium hydroxide, to 6.0-8.5, most preferably 6.9-7.5, followed by heat-treating the obtained solution at more than 70°C, preferably above 85°C. At temperatures of about 120°C only a few minutes were sufficient; at 70°C, 40-60 minutes were required.

[0013] WO 2007 / 108709 theorizes that a high divalent metal ion content affects the proteinprotein interactions, thereby promoting the formation of non-covalently associated aggregates instead of disulphide associated aggregates. The first are more readily broken by mechanical shear than the latter. The median particle size of the resulting whey protein particles was more than 10 microns and less than 70 microns.

[0014] WO 2010 / 120199 discloses a process in which whey protein concentrate or isolate is denatured at a temperature of at least 50°C under turbulent flow conditions and without mechanical shear, after which it is transferred directly to a drier, without any intermediate processing.

[0015] Although the heat stability of whey protein particle compositions is high compared to non-denatured whey protein, its application in heat treated products (e.g. sterilized high protein drinks) still encounters limitations in terms of gelation, sedimentation, heat stability, viscosity, and / or sandy / gritty mouth feel.

[0016] It has now been found that the heat stability of such whey protein compositions can be further improved by the process as defined below. This process involves the application of specific temperatures, shear rates, and holding times and re-circulation of at least part of the formed particles. It is theorized that recirculation provides a high temperature flow of aggregates that allows fast temperature rise of the nonaggregated whey protein flow. This increases the reactivity and reduces the time required in the heater. Furthermore, deposition of unfolding proteins on the outer surface of already formed aggregates stabilizes the aggregates during high temperature transportation and application in final recipes.

[0017] In addition, recirculation allows decoupling of the microparticulation process from any downstream processing steps, thereby enabling alignment of capacities without affecting or changing the tube dimensions that control the shear rate in heater and holding sections.

[0018] This process results in a whey protein composition with a surprisingly high heat stability; defined by the heat coagulation time (HCT). In addition, it is observed that the particles are less prone to sedimentation, which can be advantageous in downstream processing and applications of the material. The invention therefore relates to a heat stable whey protein composition with a heat coagulation time - defined as the time required for a 10 wt% aqueous protein solution with pH 6.6 at 121 °C to form the first visible stagnation - of at least 200 seconds, preferably at least 400 seconds, even more preferably at least 600 seconds, and most preferably at least 800 seconds.

[0019] The HCT can be determined with the oil bath method described by J.B. Magan et al., in: Encyclopedia of Dairy Sciences (third edition), Elsevier, 2022, pages 391 -399. Glass tubes with an inner diameter of 8 mm are filled with 2 mL of a 10 wt% protein solution with a pH of 6.6. The glass tubes are placed in an oil bath at 121 °C under continuous motion of an oscillating rack with a speed of 7.5 oscillations per minute.

[0020] The change in visible appearance is monitored by a camera and the time lapsed until the liquid stagnates in the tube and stops flowing freely is the heat coagulation time.

[0021] The heat stable whey protein composition of the present invention has a protein content, based on dry matter, of 60-95 wt%, preferably 75-95 wt%, most preferably 80 - 85 wt%.

[0022] The total concentration of a-lactalbumin and [3-lactoglobulin, based on total protein, is at least 50 wt%, preferably at least 60 wt%, more preferably at least 70 wt%, most preferably at least 80 wt%. This total concentration includes both native and denatured alpha-lactalbumin and beta-lactoglobulin.

[0023] The total concentration of native a-lactalbumin and native [3-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%, based on total protein. The remaining part of the total a-lactalbumin and [3-lactoglobulin content being in denatured form.

[0024] The extent of a-lactalbumin denaturation 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 extent of [3-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%.

[0025] The native a-lactalbumin and [3-lactoglobulin content can be determined by means of high pressure gel permeation liquid chromatography, as described by C. Holt et al., Int. J. Food Sci. Techn. 34 (1999) 543-556, method 1 of BDI laboratory 1 . To this end, 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 HCI. After 0.5 hour standing at ambient temperature, the sample is filtered using a 0.45 pm membrane and subsequently separated using a size exclusion (TSK G2000 SEXL) column, a pH 6.0 phosphate buffer, and detection at 280 nm. The concentration of native [3-lactoglobulin and a- lactalbumin is determined by integration of the peak area. By comparing these concentrations with those of the starting whey protein material, the degree of denaturation can be calculated.

[0026] In one embodiment, the heat stable whey protein composition has 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%.

[0027] In another embodiment, the heat stable whey protein composition is in dried, e.g. spray-dried, form.

[0028] The process according to the present invention involves the following steps: a) providing a whey protein composition with a protein content of 60-95 wt%, based on dry matter, and a total concentration of native a-lactalbumin and native [3- lactoglobulin, based on total protein, of at least 50 wt%, b) providing an aqueous whey protein solution comprising said whey protein composition in a dry matter concentration of 15-50 wt%, said solution having a pH in the range 6.0-7.5 c) optionally pre-heating said aqueous whey protein solution to a temperature up to 70°C using a heat exchanger, d) transporting the optionally pre-heated aqueous whey protein solution through a tubular heat exchanger and with a shear rate of at least 1500 s-1, thereby heating the aqueous whey protein solution to a temperature in the range 70-140°C, preferably 75-95°C, e) holding the aqueous whey protein product resulting from step d) at 70-140°C, preferably 75-95°C, in a holding tube with a residence time of 1 second to 10 minutes and a shear rate of at least 1000 s-1in order to denature at least 50% of the initial concentration of a-lactalbumin and [3-lactoglobulin, based on total protein, and f) re-circulating at least one part of the aqueous dispersion of whey protein particles to the heat exchanger of step d) and transporting the other part to a cooling device or a dryer.

[0029] The starting material is a whey protein composition with a protein content, based on dry matter, in the range 60-95 wt%, and a total concentration of native a-lactalbumin and [3-lactoglobulin, based on total protein, 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%.

[0030] The proteins in the starting material are mostly native, i.e. non-denatured. The denaturation degree of the a-lactalbumin and [3-lactoglobulin in said starting material is less than 20%, preferably less than 15%, more preferably less than 10%, and most preferably less than 5%.

[0031] The protein content can be determined using the well-known Kjeldahl nitrogen analysis method and the application of a Kjeldahl factor of 6.38.

[0032] Examples of suitable whey protein compositions are whey protein concentrate, whey protein isolate, a-lactalbumin enriched WPC or WPI, and [3-lactoglobulin enriched WPC or WPI.

[0033] The starting material may be a dried / powdered whey protein composition or a liquid whey protein composition. An example of such a liquid whey protein composition is a whey product obtained when removing part of the water, lactose and minerals from acid whey (i.e. whey resulting from caseinate production), cheese whey, or ideal whey. More in particular, the liquid whey protein composition is the ultrafiltration retentate of whey, which may have been subjected to further concentration, filtration and / or purification steps.

[0034] The whey protein composition has a calcium content preferably below 1900 mg / 100 g protein, more preferably below 1250 mg / 100 g protein, even more preferably below 950 mg / 100 g protein, and most preferably below 750 mg / 100g protein. Lower calcium contents improve the heat stability. In one embodiment, the whey protein composition has been obtained by concentrating whey, preferably cheese whey. In contrast to acid whey or ideal whey, cheese whey contains caseinomacropeptide (CMP). CMP helps to prevent the formation of strong continuous gel structures and might assist in preventing the aggregation of microparticles during heating.

[0035] In another embodiment, the whey protein concentrate or isolate has been obtained by concentrating acid whey.

[0036] Concentration of the whey proteins may have been performed by standard methods, such as ultrafiltration.

[0037] The whey protein composition is either dissolved in water (in case the whey protein concentrate or isolate is in dried or powdered form), or used as is or be diluted with water (in case a liquid whey protein composition is used as the whey protein composition) in amounts that result in a solution with a dry matter content of 15-50 wt%, preferably 15-45 wt%, most preferably 25-35 wt%. Lower dry matter contents negatively affect the heat stability; higher dry matter contents result in too high viscosity and would require very high shear rates.

[0038] The pH of the resulting solution should be in the range 6.0-7.5. Outside these ranges, aggregation occurs too quickly upon heating.

[0039] If the pH of the whey protein solution is not already in this range, it may be adjusted to this range by the addition of an acid or base. Suitable acids and bases are KOH, NaOH, Ca(OH)2, Mg(OH)2, NH4OH, carbonates and bicarbonates, trisodium citrate, tripotassium citrate, phosphates, HCI, phosphoric acid, citric acid, lactic acid, tartaric acid, acetic acid, sulphuric acid, hydrochloric acid, malic acid, maleic acid, fumaric acid, and succinic acid.

[0040] In order to denature at least part of the whey protein and form particles, the aqueous whey protein solution is first heated under shear in a tubular heat exchanger to a temperature in the range 70-140°C, preferably 70-110°C, more preferably 75-95°C, even more preferably 75-90°C, and most preferably 75-85°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. The shear rate is controlled by the internal diameter of the tubular heat exchanger and by the flow rate of the aqueous solution.

[0041] The residence time of the solution in the tubular heat exchanger is depending on the temperature used and is preferably in the range 1-600 s, more preferably 1 -180 s, most preferably 1 -60 s when using the temperature range of 70-140°C.

[0042] In one embodiment, the tubular heat exchanger can be used to heat the whey protein solution starting from room temperature or below.

[0043] In another embodiment, the whey protein solution is first pre-heated before entering the tubular heat exchanger. It may be pre-heated up to any temperature, provided the temperature stays below the denaturation temperature of a-lactalbumin and [3- lactoglobulin. In practice, this means a temperature not higher than 70°C, preferably not higher than 65°C. Said pre-heating can be performed 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.

[0044] The aqueous whey protein product leaving the tubular heat exchanger is subsequently held in a holding tube at a temperature in this same range 70-140°C, preferably 70- 110°C, more preferably 75-95°C, even more preferably 75-90°C, most preferably 75- 85°C, a shear rate of at least 1000 s-1, preferably at least 1300 s-1, most preferably at least 1500 s-1, and with a residence time of 1 -600 seconds in order to denature the a- lactalbumin and [3-lactoglobulin to a sufficient extent.

[0045] The higher the temperature, the shorter the holding time period required.

[0046] 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.

[0047] After leaving the holding tube, part - 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 re-circulated to the tubular heat exchanger of step d). This can be performed with a high pressure pump.

[0048] The other part of the aqueous dispersion is either collected as liquid (optionally after a cooling step), cooled down and stored till further processing (e.g. drying) or use, and / or directly sent to drying or other further processing equipment. Drying can be performed in various ways, including evaporation, spray-drying, freeze-drying. Spraydrying is a preferred form of drying.

[0049] The process of the present invention preferably results in (i) 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% of the native a-lactalbumin present in the whey protein composition of step a) and (ii) 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% of the native [3-lactoglobulin present in the whey protein composition of step a).

[0050] Since these proteins in the starting whey protein composition are mainly in native state, this means that the heat stable whey protein composition resulting from the process of the present invention preferably contains (ii) a-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) [3- 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%.

[0051] The whey protein particles in the heat stable whey protein composition according to the present invention preferably have a D50 volume average particle diameter in the range 0.05 -20 microns, more preferably 0.05 -10 microns, most preferably 0.05 - 1 .0 microns. Preferably, 90 vol% of the particles (D90) has a diameter of less than 60 microns, more preferably less than 10 microns, most preferably less than 5.0 microns. The span (=(D90-D10) / D50) is preferably in the range 5.0-40, more preferably 5.0-30, most preferably 5.0-20.

[0052] This particle diameter and size distribution are determined using laser diffraction (Malvern Matersizer 2000), with a refractive index of 1 .47, and assuming non-spherical particles with an adsorption of 0.

[0053] The heat stable whey protein composition of the present invention has a wide range of utilities, in particular for raising the protein content of food products without significant change in the texture. Examples of such food products are processed cheese, yoghurt, ice cream, fermented milk products, whey crisps, bakery applications, (high protein) beverages, high protein medical nutrition, and convenience food.

[0054] In one embodiment, the heat stable whey protein composition is used for preparing high protein medical nutrition, such as enteral compositions.

[0055] There are instances where individuals have to rely on liquid nutritional compositions as their sole source of nutrition, for example surgical patients, patients suffering from a trauma or receive cancer therapy, or individuals whose general health status makes them too weak or unwilling to eat or drink at all or in sufficient amounts. Often such individuals have to rely on sip feeding or tube feeding. Medical compositions for enteral use may comprise, in addition to a relatively high concentration of protein, sources of fat and carbohydrate that together bring the total energy density to values in the range of e.g. 1.5-2.5 kcal / ml, especially when the compositions are concentrated compositions intended for patients with a fluid restriction. Compositions intended to provide a complete diet, such as enteral compositions intended for sip feeding and / or tube feeding, may also contain the required amounts of vitamins, minerals and / or fibers (complete nutritional products).

[0056] A known problem with concentrated compositions is that the high concentration of protein may lead to a high viscosity of the composition, especially after heat-treatment of the compositions (e.g. to sterilize them). This is particularly problematic in compositions intended for use as a sip feed or a tube feed in medical nutrition, which may also contain fat, carbohydrates, and vitamins, and minerals. Also for patients who have problems swallowing, viscosity of the composition is important. In compositions intended for sip or tube feeding, particularly in compositions intended for sip feeding, it is important that a relatively small serving of the composition comprises a high amount of protein, and preferably also carbohydrate and / or fat. In these compositions it is further preferred that the energy density is relatively high, e.g. in the range of 1 .5- 2.5 kcal / ml.

[0057] The use of the heat stable whey protein composition according to the present invention as the or at least one of the protein sources of such high protein liquid medical nutritional composition allows to keep the viscosity of such compositions relatively low. Such liquid compositions may contain 10-25 wt%, preferably 10-20 wt% protein, 25- 100 wt%, preferably 40-60 wt% thereof being the heat stable whey protein composition according to the present invention. Examples of additional protein sources are micellar casein isolate, milk protein isolate, milk protein concentrate, caseinate, and combinations thereof.

[0058] The pH of such nutritional compositions is preferably about neutral, e.g. 6.0-7.5. The nutritional composition may furthermore contain carbohydrates, fats, vitamins, and minerals.

[0059] Carbohydrates preferably provide 20 to 60% of the total energy content of such nutritional compositions. Examples of suitable carbohydrates include maltodextrin, hydrolyzed, intact, naturally and / or chemically modified starch or cornstarch, malt, maltose, isomaltose, isomaltulose, glucose polymers, corn syrup, corn syrup solids, rice or potato derived carbohydrate, glucose, fructose, sucrose, lactose, trehalose, palatinose, high fructose corn syrup, and combinations thereof.

[0060] Fats preferably provide 20 to 50% of the total energy content of the composition. Nonlimiting examples of sources of fat that are suitable for use in the nutritional composition include milk fat or milk fat fractions, food grade coconut oil, fractionated coconut oil, soy 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 and palm kernel oils, palm olein, canola oil, marine oils (e.g. fish oil), cottonseed oils, 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 comprise one or more structured lipids. Structured lipids are predominantly triacylglycerols containing mixtures of medium and long chain fatty acids on the same glycerol backbone.

[0061] In another embodiment, the invention relates to liquid high protein compositions, e.g. protein shots or yoghurt drinks, suitable for athletes, elderly, patients, and anybody else desiring to improve protein intake, recovery and / or muscle synthesis.

[0062] 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% thereof being the heat stable whey protein composition according to the present invention. Examples of additional protein sources are micellar casein isolate, milk protein isolate, milk protein concentrate, caseinate, and combinations thereof, wherein micellar casein isolate is the most preferred additional protein source. Such compositions preferably do not contain significant amounts fats and carbohydrates.

[0063] EXAMPLES

[0064] HCT determination

[0065] The HCT was be determined as follows. Glass tubes with an inner diameter of 8 mm were filled with 2 mL of a 10 wt% protein solution. The pH of the solutions was 6.6. The glass tubes were placed in an oil bath at 121 °C under continued motion of an oscillating rack with a speed of 7.5 oscillations per minute, using dedicated Hettich Benelux test equipment.

[0066] The change in visible appearance was monitored by a camera. The time lapsed until the liquid stagnates in the tube and stops flowing freely is the heat coagulation time.

[0067] Example 1

[0068] An aqueous whey protein concentrate (WPC) with 23 wt% protein, pH 6.6, and a whey protein content of 80 wt% on dry matter (20 wt% a-lactalbumin, 77 wt% [3-lactoglobulin based on total protein; 10% denatured a-lactalbumin + [3-lactoglobulin, based on total on total protein) was preheated to 65°C in a tubular heater (internal diameter 7 mm) at 270 L / h. Subsequently, the preheated solution was displaced into the main tubular heater (internal diameter 7 mm, shear rate: 2400 s-1) by means of a positive displacement pump, in which the solution was heated to 80°C. The concentrate subsequently entered a tubular holder (internal diameter 7 mm) without any heating and with a shear rate of 2400 s-1, in which the fluid was held for 30 seconds.

[0069] Of the liquid leaving the holder, 10 vol% was recirculated to the suction side of the positive displacement pump (30 L / h). The remaining 90 vol% was displaced towards a spiral cooler to reach a temperature of 5°C.

[0070] All flows in this setup were monitored and controlled with flowmeters.

[0071] As shown in Table 1 , the HCT of the resulting product was more than 989 seconds. The D50 of the resulting particles was 0.13 pm, the D90 was 2.00 pm, the span was 15.8. Of the whey proteins, 75% was denatured a-lactalbumin and [3-lactoglobulin. Example 2

[0072] Example 1 was repeated, except that a drain valve was placed between the main tubular heater and the tubular holder. By opening this valve, 100 L / h of the heated concentrate was drained, effectively lowering the velocity and shear rate in the holder. The results are summarized in Table 1 .

[0073] Example 3

[0074] Example 1 was repeated except that the main tubular heater and the tubular holder had an internal diameter of 12 mm. This increase in internal diameter directly affected the velocity and shear rate. The properties of the resulting product are presented in Table 1 .

[0075] Table 1

[0076] Example 4

[0077] The HCT of several commercially available microparticulated whey protein products was determined and compared with that of the product of Example 1 . The results are displayed in Table 2.

[0078] Table 2 Example 5

[0079] Liquid enteral high protein formulations (A-H) were prepared using the whey protein product of Example 1 and the viscosity of these formulations was determined with a rotational viscometer using a cup and bob geometry (Anton Paar MCR302 Rheometer with a CC-27) at 20°C, after storage for six days at room temperature, and at a shear rate of 100 s-1.

[0080] The composition of the nutritional compositions was as in Table 3.

[0081] Table 3 n.d. = not determined

Claims

CLAIMS1. Process for producing a heat stable whey protein composition, the process comprising the steps of: a) providing a whey protein composition with a protein content of 60-95 wt%, based on dry matter, a total concentration of native a-lactalbumin and native [3-lactoglobu lin , based on total protein, of at least 50 wt%, b) providing an aqueous whey protein solution comprising the whey protein composition of step a) in a dry matter concentration of 15-50 wt%, said solution having a pH in the range 6.0-7.5, c) optionally pre-heating said aqueous whey protein solution to a temperature up to 70°C using a heat exchanger, d) transporting the optionally pre-heated aqueous whey protein solution through a tubular heat exchanger and with a shear rate of at least 1500 s-1, thereby heating the aqueous whey protein solution to a temperature in the range 70-140°C, e) holding the aqueous whey protein product resulting from step d) at 70- 140°C in a holding tube with a residence time of 1 second to 10 minutes and a shear rate of at least 1000 s-1in order to denature at least 50% of the initial concentration of a-lactalbumin and [3-lactoglobulin, based on total protein, and f) re-circulating at least one part of the aqueous dispersion of whey protein particles to the heat exchanger of step d) and transporting the other part to a cooling device or a dryer.

2. Process according to claim 1 wherein the optionally pre-heated aqueous whey protein solution is transported through the tubular heat exchanger at a temperature in the range 70-110°C, preferably 75-95°C, even more preferably 75-90°C, and most preferably 75-85°C.

3. Process according to claim 1 or 2 wherein the optionally pre-heated aqueous whey protein solution is transported through the tubular heat exchanger at a shear rate of at least 2000 s-1, preferably at least 2300 s-1.

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

5. Process according to any one of the preceding claims wherein the aqueous whey protein product resulting from step d) is held in the holding tube at a shear rate of at least 1300 s-1, most preferably at least 1500 s-1.

6. Process according to any one of the preceding claims wherein the aqueous whey protein product resulting from step d) is held in the holding tube with a residence time of 1 -600 seconds, preferably 1 -400 seconds, most preferably 1 -120 seconds.

7. Process according to any one of the preceding claims wherein the process results in (i) 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% of the native a-lactalbumin present in the whey protein composition of step a) and (i) 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% of the native [3-lactoglobu I in present in the whey protein composition of step a).

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

9. Heat stable whey protein composition comprising:- a protein content, based on dry matter, of 60-95 wt%, preferably 70-95 wt%, most preferably 80-85 wt%,- a total concentration of native and denatured a-lactalbumin and [3-lactoglobulin, based on total protein, of at least 50 wt%, preferably at least 60 wt%, more preferably at least 70 wt%, most at least 80 wt%, and- a total concentration of native a-lactalbumin and native [3-lactoglobulin 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%, and most preferably not higher than 10 wt%, the heat stable whey protein composition having a heat coagulation time - defined as the time required for a 10 wt% aqueous protein solution of 6.6 at 121 °C to form the first visible stagnation - of at least 200 seconds.

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

11. Heat stable whey protein composition according to claim 9 or 10 wherein the extent of a-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 extent of [3-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. Heat stable whey protein composition according to any one of claims 9-11 having the form of an aqueous dispersion, said dispersion preferably having a dry matter content of 15-50 wt%, more preferably 18-45 wt%, and most preferably 25-35 wt%.

13. Food product comprising the heat stable whey protein composition of any one of claims 9-12 or the heat stable whey protein composition obtainable by the process of any one of claims 1-8, said food product being preferably selected from the group consisting of cheese, yoghurt, ice cream, fermented milk products, whey crisps, bakery applications, food bars, protein beverages, high protein medical nutrition, and convenience food.

14. Liquid nutritional composition with an energy density of 1 .5-2.5 kcal / ml having 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 proteincomposition of any of claims 9-12 or a heat stable whey protein composition obtainable by the process of any of claim 1-8.

15. 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 of any of claims 9-12 or a heat stable whey protein composition obtainable by the process of any of claim 1-8.

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