Method and apparatus for directly heating a protein-rich milk product by introducing water vapor into the milk product

Abstract

The invention relates to a method and a device 1000 for directly heating DE a milk product P enriched with protein by introducing water vapor D into the milk product P, wherein the direct heating DE is designed in the form of an immersion method or a spraying method IFV or UV. The object of the invention is to provide a method of the generic type and a device for carrying out the method which achieves a significant increase in the service life during the method or in the device and which ensures a higher content of undenatured whey proteins in the treated protein-rich milk product compared to the prior art. In terms of process technology, the object is achieved in that, before the direct heating (DE), the preheated and warmed milk product (P) is indirectly cooled (K) by a recuperative cooling step from a preheating temperature (TVE) to a cooling temperature (TK) with a temperature difference (ΔTK) in the range of 5 K (Kelvin) to 10 K (ΔTK<(5 to 10) K); the direct heating is controlled from the cooling temperature (TK) to a high-temperature heating temperature (THE) with direct heating control parameters known per se; and after the measure of feature (d), the milk product (P) is cooled from the high-temperature heating temperature (THE) to the mandatory necessary outlet temperature (TA) by rapid cooling (K).

Description

Technical Field

[0001] The invention relates to a method for directly heating a protein-rich dairy product by introducing water vapor into the dairy product, wherein during direct heating, the water vapor heats the dairy product to a high-temperature heating temperature by direct high-temperature heating in order to produce a sterile state. Prior to direct heating, the dairy product is indirectly preheated to a preheating temperature, and after the preheating, the preheated dairy product is first insulated for a first defined and controlled residence time, as viewed in the flow direction of the dairy product. After direct heating to the high-temperature heating temperature, the high-temperature heated dairy product is second insulated for a second defined and controlled residence time, as viewed in the flow direction of the dairy product. Subsequently, water is extracted from the insulated high-temperature heated dairy product by rapid cooling by expansion to a lower pressure in an amount corresponding to the water vapor supplied previously. The invention also relates to an apparatus for carrying out the method, which, in addition to a direct heating device, has a preheater arranged upstream of the direct heating device with a first insulator arranged downstream of the preheater in the flow direction of the dairy product. A second insulator is arranged downstream of the direct heating device, which opens into a vacuum chamber. Background Art

[0002] In recent years, a consumer trend towards protein-rich milk products has been identified, which necessitates special requirements for the necessary heat treatment in order to extend the storage time and shelf life of the milk products. Protein-rich milk products according to the invention are, for example, raw milk as the starting product of the heat treatment according to the invention, which has a (acid-soluble) beta-lactoglobulin content of 6.85 to 8.35 g / kg of milk, as shown by the measured values ​​of the three tests cited below.

[0003] In contrast, [1] A. Schmid and H. Mayer, Diploma thesis, Best Immunity von Furosin undanderen Erhitzungsindikatoren in Milch mittels HPLC, University of Vienna, May 2009, found that the average value of the native β-lactoglobulin content of the seven raw milk samples tested was 4.02 g / dm 3 Milk (=3.9 g / kg milk), the sample comes directly from agricultural enterprises or from green food specialty stores, with the logo "raw milk".

[0004] Protein-rich dairy products are heat-sensitive and tend to burn at temperatures above 100° C., i.e., under these conditions, a coating forms on the walls of treatment devices for thermal treatment, conveying and conducting the dairy products. This coating formation is also referred to as product “fouling”. This product “fouling” shortens the duration or operating time of the relevant treatment devices between two cleaning cycles. If, in the following, only dairy products are mentioned within the scope of the present invention, this feature always also includes the meaning of “protein-rich”.

[0005] Direct heating of dairy products by means of steam is a known and commonly used method. This direct heating serves to prolong the storage time of the dairy products or of end products derived therefrom. The heat treatment by means of steam (preferably saturated steam, but also superheated) can be carried out in different ways, directly or indirectly ([2], Heinz-Gerhard KESSLER, Lebensmittelverfahrenstechnik, Schwerpunkt Molkereitechnologie, 1st edition, Munich-Weihenstephan, Verlag A. Kessler, 1976, pp. 154 to 159). Indirect methods include, for example, heating using different embodiments of heat exchangers (recuperators: for example tube bundle heat exchangers; plate heat exchangers). Direct methods include two main categories, namely the injection method using steam ([2], pp. 154, 155) and the immersion method using steam ([2], p. 156).

[0006] The milk product is heated directly, quickly and efficiently by direct heat exchange between the steam and the milk product. Due to this rapid method, the processing time can be shortened, which results in a reduced thermal effect on the milk product overall and thus a milk product with a high quality level, especially in terms of taste. This rapid and protected heat treatment in the direct heating method is at the expense of higher energy consumption compared to the indirect heating method.

[0007] In the injection method, the food to be heated is conveyed through an injector. Steam is injected at a relatively high pressure directly into the food to heat it, the food preferably being used as a propulsion jet, and the heat exchange between the mixed material flows is accomplished in a so-called mixing chamber (DE 10 2007 017 704 A1).

[0008] The immersion method uses steam immersion heating, in which the finely divided dairy product is heated in a steam chamber. The steam pressure and product system pressure are nearly identical in this method. As a result, the temperature difference between heating medium and dairy product is significantly smaller than in the spray method, resulting in a protected product treatment. Disadvantages of the immersion method compared to the spray method are the complex product technology and the higher investment costs. [3] Saskia SCHWERMANN, Uwe SCHWENZOW in "Verfahrenskonzepte zur Herstellung von ESL-Milch", Deutsche Milchwirtschaft, Vol. 3, 11 / 2008 to 13 / 2008 (Vol. 59) provide an overview of the design of methods for sterilizing foods, in particular also taking into account different types of direct heating methods.

[0009] EP 0 958 745 A2 discloses a UHT method for milk-based products, wherein the milk is preheated to 65-85° C., the temperature is raised to 85-105° C. by steam injection, thereafter held and stabilized at this temperature, and subsequently heated in an immersion heater to a temperature of 140-145° C. After a holding time in the range of 3-90 seconds, the product is introduced into a vacuum chamber, where expansion occurs, cooling occurs and thus an amount of water corresponding to the amount of steam supplied in the preceding sterilization process is extracted from the product. In the further course of the process, the product is homogenized and further cooled.

[0010] WO 2018 / 115 131 A1 describes a device and a method for heating liquid concentrated milk, wherein the product is preheated to a temperature of 5-75° C., then directly heat-treated with steam in an immersion heater and from there kept warm on the way to a vacuum chamber. In the vacuum chamber, water is extracted from the product in a manner known per se by expansion and cooling, and then it is cooled further.

[0011] EP 0 617 897 A1, which is considered to be the closest prior art, describes a method and a system of the type described. This document discloses a method and a system for directly heating a milk-based product. Here, the product is first preheated with steam before direct heating. After direct heating, the product is first indirectly cooled before finally cooling to the final temperature by flash cooling.

[0012] Other related prior arts include: [4] KELLEHER, CM et al., A comparison of pilot-scale supersonic direct steam injection to conventional steam infusion and tubular heating Systems for the heat treatment of protein-enriched skimmilk-based beverages; Innovative Food Science and emerging Technologies, 2019, Vol. 52, pp. 282-290, - ISSN 1466-8564 and [5] LEE, AP et al., The influence of ultra-pasteurization by indirect heating versus direct steam injection on skimand 2% fat milks; Journal of Dairy Science, 2017, Vol. 100, pp. 1688-1701, - ISSN 0022-0302.

[0013] Reference [4] discloses in FIG1 a flow chart for treating a protein-rich milk beverage by steam immersion and steam injection (see the last paragraph of the right column on page 283; FIG1 on page 284; Table 1 on page 285; the left column on page 285 to the first paragraph of the left column on page 286; paragraph 286 Figure 2 ). Document [5] also discloses a method for heating milk by direct heating using steam (see FIG. 1 ).

[0014] Document [5] also discloses a method for heating milk by direct heating with steam; see Figure 1, right. The preheating step is followed by direct heating with steam and then vacuum cooling.

[0015] Denaturation of some whey proteins present in milk already begins at temperatures of 65° C., the main source of the released sulfhydryl (SH) groups being β-lactoglobulin, which is completely denatured at 130° C. and reaches its maximum extent in terms of the formation of toasty flavors. For the heating process, this has a significant impact on the operating or production time, since the denaturation of whey proteins increases from a temperature range of more than 75° C. (≥75° C.) and whey proteins are deposited on the walls of the heater. This aforementioned product “fouling” leads to the growth of a gradually thickening “fouling” layer over a longer operating time, as a result of which the heat transfer in the heater becomes increasingly poor.

[0016] In order to prevent this effect, the milk product is kept warm at 80°C to 90°C. A common temperature-time combination here is 120 seconds at 90°C. This measure or similar measures are not disclosed in [3]; however, such measures can be regarded as prior art (EP 0 958745A2). In this temperature range, a targeted denaturation of the whey proteins is forced, which are now bound to a specific part of the casein (k-casein). Casein constitutes about 80% of the total protein content in milk and is heat-stable compared to whey proteins.

[0017] In the case of protein-enriched milk or milk products, the subject matter of the present invention is to increase the protein content and thereby also the content of heat-stable whey proteins.

[0018] If we look at the proportion of denatured β-lactoglobulin, a comparison between indirectly and directly heated milk shows that this proportion is significantly higher at 83% when the milk is indirectly heated compared to 66% when the milk is directly heated (see [2], pages 132 and 133).

[0019] The degree of denaturation of dairy products is dependent on the degree and intensity of the heat treatment, that is to say the heat treatment used in each case, and the degree of denaturation is currently also qualitatively determined by so-called heat indicators. Such heat indicators are, in particular, acid-soluble β-lactoglobulin (undenatured β-lactoglobulin) and furosine. The heat indicators serve as indicators for estimating and checking the actual heat load of dairy products over an extended shelf life. It is well established that the degree of denaturation decisively determines the nutritional-physiological and sensory quality of dairy products. There is a known relationship between the furosine content and undenatured β-lactoglobulin, which can be determined in identical and identically treated dairy products. An increase in the furosine content is associated with a decrease in the β-lactoglobulin content. The greater the heat load (temperature and exposure time), the higher the furosine content and the lower the β-lactoglobulin content [1]. Summary of the invention

[0020] The object of the present invention is to provide a method of the generic type and a device for carrying out the method which achieve a significant increase in the service life during the method or in the device and which ensure a higher undenatured whey protein content in the processed protein-rich milk product compared to the prior art.

[0021] This object is achieved by a method having advantageous features. A device for carrying out this method is the subject of the invention.

[0022] The invention is based on EP 0 617 897 or a known method for direct heating of liquid foods by steam, such as disclosed in EP 0 794 706 B1 (immersion method) or in WO 2011 / 101077 A1 (immersion method; spray method), which claims priority from DE 10 2010 008448 A1. According to these two documents, liquid foods, such as whey protein concentrate, baby food, liquid concentrated baby food, nutritional drinks or cheese milk, are directly heated by steam to produce a sterile state, wherein water is extracted by expansion to a lower pressure in an amount corresponding to the amount of steam supplied previously. On the other hand, in the subject matter of the invention, in contrast to the prior art given by the literature cited above, a preheating known per se is provided before the direct heating and in particular an additional, preferably defined and controlled first insulation following the preheating is also provided in the flow direction of the milk product.

[0023] The object underlying the invention is achieved in that, in a method of the generic type:

[0024] Prior to direct heating, the preheated and warmed milk product is indirectly cooled by a recuperative cooling step from the preheating temperature to the cooling temperature with a temperature difference in the range of 5 K (Kelvin) to 10 K (ΔTK≤(5 to 10) K),

[0025] controlling said direct heating from the cooling temperature to the high temperature heating temperature with direct heating adjustment parameters known per se, and

[0026] After the measure of feature (d), the milk product (P) is cooled from the high temperature heating temperature to the mandatory necessary output temperature by rapid cooling.

[0027] The basic inventive concept is therefore to provide a recuperative cooling step by indirect cooling after the first incubation and before the high-temperature heating in order to obtain the highest possible nutritional-physiological and sensory quality of the treated milk product in the form of undenatured whey proteins. This cooling step with a temperature difference from the preheating temperature to the cooling temperature in the range of 5 to 10 K (Kelvin) leads to unforeseeable and surprisingly advantageous results, since this cooling step reduces the residence time of the milk product at the high-temperature heating temperature on the one hand and thereby reduces further denaturation of the whey proteins on the other hand.

[0028] The subsequent direct heating starts at the level of the cooling temperature and heats the milk product to the high-temperature heating temperature using variable direct heating control parameters known per se. According to one embodiment of the method, the direct heating control parameters are the pressure, temperature and duration of action of the water vapor.

[0029] During rapid cooling, the milk product treated in this way must be cooled to the absolutely necessary outlet temperature, depending on the additional steam supply required due to indirect cooling. This outlet temperature ensures that the treated milk product regains its water content in the state it was in before direct heating, that is, before the steam supply for high-temperature heating.

[0030] At high temperature heating temperatures in the range of up to 140° C., the cooling of the preheated and insulated milk product according to the invention from the preheating temperature to the cooling temperature comprises a temperature difference in the range of 5 K (Kelvin) to 10 K. The length of the first residence time of the milk product in the first insulation before the high temperature heating is set can also influence the size of the specific temperature difference.

[0031] A person skilled in the art responsible for realizing the subject matter of the present invention can, under specific process conditions and production requirements, optimize all of the above-mentioned influencing variables on the one hand while taking into account the service life, and on the other hand achieve a high nutritional, physiological and sensory quality of such a heat-treated, protein-rich dairy product without having to engage in creative work.

[0032] In the embodiment described in detail below according to the present invention, high-temperature heating from 85°C to 137.5°C is set for current production requirements without a cooling step according to the present invention. In this embodiment, optimization in the sense described above is achieved by cooling or utilizing a cooling step with a temperature difference of 10K. The first residence time of the first insulation is 30 seconds and the high-temperature heating is thereby performed from 75°C to 137.5°C.

[0033] The specific, targeted cooling temperature is dependent on the specific process data of the direct heating. The cooling temperature is designed so that, with the direct heating control parameters provided and variable within a limited range, such as the pressure, temperature, and duration of action of the water vapor, high-temperature heating from the achieved cooling temperature to the high-temperature heating temperature still required by the cooling step according to the invention is energetically ensured.

[0034] As proposed, the method steps according to the invention are advantageously used for direct heating by means of an immersion method known per se or a spraying method known per se.

[0035] In summary, the following advantages are obtained by the cooling step according to the invention:

[0036] Reduced denaturation of whey protein (reduced toasty taste due to released sulfhydryl groups);

[0037] Reduced Maillard reaction (browning reaction);

[0038] Reduces the formation of furosine;

[0039] The use time is significantly extended, with little to no product "fouling" being confirmed after 5 hours of production time, and the maximum use time being extended by two to three times relative to the use time of the prior art methods or apparatuses.

[0040] Cooling energy is required for the above-described process and production improvements. The hot coolant (preferably cooling water) that is fed back is used for the mixing process or regeneratively for heating in order to achieve an energetic improvement of the overall process.

[0041] The device according to the invention for carrying out the method according to the invention is based on EP 0 617 897 A1 or on the following combination of features known per se, which are mostly disclosed in the above-mentioned EP 0 794 706 B1 (immersion device) or in WO 2011 / 101077 A (immersion device; direct heating device with injection device), the first incubator known per se between the preheater and the direct heating device (EP 0 958 745 A2) likewise being known from the prior art mentioned in the literature:

[0042] Direct heating device for dairy products, used for direct heating to high temperature by water vapor,

[0043] a preheater arranged upstream of the direct heating device, viewed in the flow direction of the dairy product, and designed as a recuperator, for preheating the dairy product to a preheating temperature,

[0044] A first insulator, used for first insulating the preheated milk product, wherein the first insulator is arranged between the direct heating device and the preheater,

[0045] A first conveying device arranged downstream of the direct heating device, used for conveying high-temperature heated dairy products,

[0046] A second insulator arranged downstream of the first conveying device is used to perform a second insulator for heating the high-temperature heated dairy product.

[0047] A vacuum device arranged downstream of the second insulator, in which water is subsequently extracted from the insulated high-temperature heated milk product in an amount corresponding to the amount of water vapor supplied previously by rapid cooling by expansion to a lower pressure.

[0048] Based on a device of the type described, the object underlying the invention is achieved in terms of device technology in the following way:

[0049] A cooler configured as a recuperator is arranged between the direct heating device and the first insulator, and cools the preheated and insulated dairy product from a preheating temperature to a cooling temperature by indirect cooling.

[0050] As already mentioned, the arrangement of the cooler according to the invention is advantageously equally applicable to direct heating devices in the form of immersion devices known per se or in the form of injection devices known per se. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The following description and the accompanying drawings provide a more in-depth description of the invention. The invention is implemented in different embodiments of the method of the type described and in different embodiments of the device of the type described for implementing the method, and a preferred embodiment of the method according to the invention and the device according to the invention is described below with reference to the accompanying drawings. Among them:

[0052] FIG1 schematically shows an apparatus according to the prior art for directly heating a protein-rich milk product by introducing water vapor into the milk product;

[0053] Figure 2 The device according to the invention with a cooler arranged according to the invention is shown schematically and based on the known device according to FIG. 1 ;

[0054] FIG3 shows a block diagram of a method according to the prior art (experiment I);

[0055] Figure 3a Block diagram showing a method according to the invention with cooling at ΔT=5 K (Test II);

[0056] Figure 3bBlock diagram showing a method according to the invention with cooling at ΔT=10 K (Test III);

[0057] Figure 4 Show according to Figure 2 a portion in the upstream region of a direct heating device without cooling or cooling the preheated and warmed milk product, for carrying out the method according to the prior art;

[0058] Figure 5 Show according to Figure 2 a part of a device with cooling according to the invention of a preheated and warmed milk product by means of a cooler provided according to the invention for carrying out the method according to the invention;

[0059] Figure 6 The results of the tests I to III show the Figure 2 , 4 and 5 ;

[0060] Figure 7 The results of tests I to III show the Figure 2 , 4 and 5 ;

[0061] Figure 8a , 8b , 9a, 9b, 10a, 10b show photographs of a product "dirt" or "dirt" layer at the inlet of a second conveying device arranged downstream of a direct heating device after a production time of 5 hours, each two photographs arranged vertically relative to each other (8a, 8b; 9a, 9b; 10a, 10b) being assigned to and showing tests I to III in the order described. DETAILED DESCRIPTION

[0062] The device 100 known from the prior art document according to FIG. 1 (as far as the immersion device and other devices arranged downstream of the immersion device) is disclosed, for example, in EP 794 706 B1 or WO 2011 / 101077 A1. The device 100 comprises a direct heating device 8 in the form of an immersion device 80 for carrying out a high-temperature heating HE in the form of direct heating DE for carrying out the immersion method IFV. The immersion device 80 can have a product inlet 28 in its head space (WO 2010 / 086082 A1), through which the protein-rich milk product P to be heat treated is supplied to the immersion device 80, for example, preferably centrally and in an annular manner. For direct heating, water vapor D is supplied to the supplied milk product P, for example and preferably radially on the outside and at the same time radially from the inside, through external and internal water vapor inlets 26, thereby achieving high-temperature heating HE from a preheating temperature T2=TVE to a high-temperature heating temperature T4=THE. Numerous other possibilities are known in the prior art for designing the supply of milk product P and water vapor D, which can also be used within the scope of the present invention. The immersion device 80 is supplied with a first coolant K1 to the coolant space on the bottom side of the container via a first coolant inlet 40 for cooling the bottom of the immersion device 80. The first coolant K1 is discharged via a first coolant outlet 42. The outlet opening at the lower end of the immersion device 80 is connected to a first conveying device 10, such as a rotary positive displacement pump or a centrifugal pump, via an outlet pipe 30, which is connected to a second insulator 12 for achieving a second insulation HH2 via a third product line section 32, the purpose of the second insulation being to maintain a high temperature heating temperature T5=THE over a second residence time Δt2. The second insulator 12 leads to the vacuum chamber 14 via a fourth product line section 34. The second conveying device 10 conveys the milk product P that has been heated at a high temperature and is insulated at the high temperature heating temperature THE from the immersion device 80 to the vacuum chamber 14. The vacuum chamber 14 is designed to extract, by so-called flash cooling FK, a quantity of water corresponding to the quantity supplied to the immersion device 80 in the form of water vapor D from the milk product P cooled by the pressure reduction as so-called evaporated liquid or steam, and to discharge the steam via a steam outlet 38, preferably arranged in the upper region. The milk product P treated in this way leaves the vacuum chamber 14 at a discharge temperature T6=TA via a discharge line 36 arranged on the tapering bottom in the lower region of the vacuum chamber and passing through the second conveying device 16 on the way.

[0063] The milk product P to be heat treated enters the preheater 2 via the milk product inlet 18 in order to preheat VE to a preheating temperature T1 = TVE. The preheater 2 leads via a first product line section 20 to a first insulator 4 for a first heat preservation HH1, which is used to maintain the preheating temperature T2 = TVE over a first residence time Δt1. The first insulator 4 leads via a second product line section 22 and a subsequent product inlet 28 into the head space of the immersion device 80. On the way, the preheater 2 is charged with a preferably regenerative heat medium M via a heat medium inlet 2a and a reheater outlet 2b.

[0064] Alternatively to the immersion device 80 described above, the direct heating device 8 of the apparatus 100 ( FIG. 1 ) can be designed as a spraying device 800 for carrying out the spraying method IJV. In this known design, the milk product P enters the spraying device 800 for high-temperature heating through the product inlet 28 and preferably forms a propulsion jet here. The propulsion jet flows through the mixing chamber of the spraying device 800, where the flow of the heating medium water vapor D for introduction into the milk product P is caused by the pressure drop, which is formed by the milk product P designed as a propulsion jet. The water vapor inlet 26 also opens into the mixing chamber and here preferably acts on the water vapor D in the transverse direction with the propulsion jet.

[0065] According to the invention, a device 1000 ( Figure 2 ) is derived in the same way from the known device 100 according to Figure 1, and the reference numerals are used unchanged here. In order to avoid repetition, only the differences are explained below, by which the device 1000 according to the invention is distinguished from the known device 100.

[0066] A cooler 6 designed as a recuperator is provided between the direct heating device 8, 80, 800 and the first insulator 4, the product side of which is conducted via a second product line section 22. The cooler 6 is supplied with a second coolant K2, preferably cooling water, via a second coolant inlet 6a and a second coolant outlet 6b, and has the task of cooling the preheated and insulated milk product P from a preheating temperature T2=TVE to a cooling temperature T3=TK by indirect cooling K with a temperature difference ΔTK.

[0067] Several tests were carried out with the device 1000 according to the invention to demonstrate that the objectives described in the task according to the invention have been achieved. Of these tests, three tests carried out over several days, designated as tests I, II and III, are described below with regard to the corresponding results and the selection of measured values.

[0068] Trials I, II and III - Overview

[0069] I. First test (without cooling K), according to the process of Figures 3 and 4

[0070] II Second test (with cooling K), according to Figure 3a , 5 Process

[0071] III The third test (with cooling K), according to Figure 3b , 5 Process

[0072] In Experiment I ( Figure 4 and 3), the milk product P preheated to the preheating temperature T2 = TVE and kept warm is conducted through the "unactivated" cooler 6 via the second product line section 22 without cooling K and supplied to the direct heating device 8 configured as an immersion device 80 at the preheating temperature T2 = TVE.

[0073] In Experiments II and III ( Figure 5 and 3a or Figure 5 and 3b ), the milk product P preheated to the preheating temperature T2 = TVE and kept warm is guided through the "validation" cooler 6 via the second product pipe section 22, where it is directly cooled K to a cooling temperature T3 = TK with a temperature difference ΔTK, where the temperature difference ΔTK of test II is different from the temperature difference of test III. The milk product P enters the direct heating device 8 configured as an immersion device 80 with the corresponding cooling temperature T3 = TK.

[0074] All relevant temperatures and residence times for the heat treatment of the protein-rich dairy product P from preheating VE in the preheating 2 at a preheating temperature T1=TVE to the treated dairy product P (FIGS. 1, 2) with a discharge temperature T6=TA in the discharge line 36 for tests I to III are summarized in the following Table 1. For the heat treatment, the following applies in principle: Test I: TVE-TA=2K; Test II: TK-TA=1.5K; Test III: TK-TA=2K.

[0075] test TVE℃ Δt1 sec TK℃ THE℃ Δt2 seconds TA℃ I 85 30 - 137.5 1 83 II 85 30 80 137.5 1 78.5 III 85 30 75 137.5 1 73

[0076] Table 1

[0077] Test results

[0078] A selection of the measured values ​​determined in experiments I to III is summarized in the preceding Table 2. The subject of the preceding text is the relevant heating parameters for estimating and checking the actual thermal load of the dairy product, namely undenatured β-lactoglobulin and furosine and their significance for the nutritional physiology and sensory quality of such dairy products. The relevant measured values ​​obtained from experiments I to III are highlighted in Table 2 by grey markings.

[0079] exist Figure 6 In the figures for tests I to III the normalized content L / Lo of undenatured β-lactoglobulin in the treated milk product P is shown [1]. Here L in g / kg protein (*) represents the corresponding measured value (β-Lg) of undenatured β-lactoglobulin in the treated milk product P, which is related to Lo, which here represents the corresponding measured value of undenatured β-lactoglobulin in the untreated milk product P (raw milk) as a reference quantity for normalization.

[0080]

[0081] Table 2 Results

[0082] The tests (Table 2) show that, relative to test I (without cooling: ΔTK=0K→L / Lo=0.25), test II (ΔTK=5K→L / Lo=0.34) and test III (ΔTK=10K→L / Lo=0.42) demonstrate that the indirect cooling K according to the invention achieves a desired, unexpected and surprising increase in the content of undenatured β-lactoglobulin, where, given the other process conditions in the apparatus 1000, cooling with ΔTK=10K in test III provides the best results ( Figure 6 ).

[0083] exist Figure 7 The normalized furosine content F / Fo in the treated milk products P for tests I to III is shown in the figure [1]. Here F in mg / 100 g protein (*) represents the corresponding measured value of furosine in the treated milk product P, which is related to Fo, which represents the corresponding measured value of furosine in the untreated milk product P (raw milk) as a reference quantity for normalization.

[0084] result

[0085] The test results (Table 2) show that, relative to test I (without cooling: ΔTK=0K→F / Fo=3.55), test II (ΔTK=5K→>F / Fo=3.38) and test III (ΔTK=10K→F / Fo=3.14) demonstrate that the indirect cooling K according to the present invention achieves the desired, unexpected and surprising reduction in the furosine content, where, given the other process conditions in the given device 1000, cooling with ΔTK=10K in test III provides the best results.

[0086] However, whether the increase in the β-lactoglobulin content and the reduction in the furosine content are attributable only to the indirect cooling according to the invention before the direct heating DE cannot necessarily be confirmed by tests I to III. It cannot be excluded that a major part of the desired, unexpected and surprising differences determined are attributable to the indirect cooling K according to the invention and, if any, also to a small part to the necessary stronger cooling of the protein-rich milk product P during the rapid cooling FK (different output temperatures for test II or test III, 78.5° C. and 73° C., respectively, compared to TA=83° C. for test I).

[0087] However, this unknown is not important for the present invention, since tests II and III must necessarily end with different outlet temperatures TA relative to one another and respectively relative to test I. The latter situation necessarily results from the conditions set forth in feature (d) of the present invention, and ultimately the indirect cooling according to the present invention is also causally responsible for this fact and its possible effect.

[0088] The fulfillment of feature (d) is only achieved in relation to the amount of water vapor (preferably saturated steam) supplied during the indirect heating DE in the tests I to III, and thus necessarily with correspondingly matched outlet temperatures TA that differ from one another. The rapid cooling TK also includes the withdrawal of such an amount of water, which the corresponding indirect cooling K from the preheating temperature TVE to the cooling temperature TK (enthalpy reduction) in turn compensatingly requires in the form of an amount of water vapor D equal to that in the direct heating DE from the cooling temperature TK to the high-temperature heating temperature THE (enthalpy increase).

[0089] In order to satisfy the conditions set forth in feature (d), the output temperatures TA (see Table 1) corresponding to Tests I to III must be different for the following reasons.

[0090] Test I (no cooling)

[0091] In order to extract the amount of water corresponding to the amount of water vapor D previously supplied for heating from the preheating temperature TVE=85°C to the high temperature heating temperature THE=137.5°C during the rapid cooling FK, a vacuum device 14 (see Figure 2) sets a saturation pressure ps or a corresponding absolute pressure (negative pressure relative to the ambient pressure) which causes the dairy product P to boil at a saturation temperature Ts(ps) = 83° C. which also corresponds to the output pressure TA.

[0092] Test II (with cooling: cooling from TVE = 85 ° C to TK = 80 ° C; ΔTK = 5K)

[0093] Cooling the milk product P with a temperature difference ΔTK=5 K requires a corresponding removal of heat from the milk product P or a reduction in enthalpy in the milk product P. The reduction in enthalpy in test II must be compensated during direct heating DE by additional supply of water vapor, preferably saturated steam, compared to test I, in order to reach the same high temperature heating temperature THE as in test I (THE=137.5° C.).

[0094] In order that the milk product P is not "diluted" by the additional steam supply in test II, an amount of water corresponding to the additional amount of water vapor must be extracted in the form of steam in the vacuum chamber 14 by so-called flash cooling FK. This process takes place when the milk product P is in a saturated state.

[0095] Test III (with cooling; cooling from TVE = 85 ° C to TK = 75 ° C; ΔTK = 10K)

[0096] Cooling the dairy product P with a temperature difference ΔTK=10 K requires a corresponding removal of heat from the dairy product P or a reduction in enthalpy in the dairy product P. The reduction in enthalpy in test III had to be compensated during the direct heating DE by additionally supplying water vapor, preferably saturated steam, to a greater extent than in test I and correspondingly also to a greater extent than in test II, in order to reach the same high temperature heating temperature THE as in test I or in test II (THE=137.5° C., respectively).

[0097] In order to prevent the milk product P from being "diluted" by the additional supply of steam in test III to a greater extent than in test II, an amount of water corresponding to the additional amount of water vapor must be extracted in the form of steam in the vacuum chamber 14 by so-called flash cooling FK. This process takes place when the milk product P is in a saturated state.

[0098] Figure 8a , 8b , 9a, 9b and 10a, 10b qualitatively show that after 5 hours of production time, for tests I to III, in the usually critical area of ​​the device 1000, namely downstream of the outlet from the direct heating device 8, 80 and here at the second conveying device 10 ( Figure 2 ) in the area of ​​the easily accessible suction pipe of the product, the extent of the product "dirt" or "fouling" layer. Figure 8a , 8b The photos correspond to Experiment I, Figure 9a , 9b The photographs correspond to Experiment II, and Fig.10a , 10b The photographs correspond to Experiment III.

[0099] Figure 8a , 8b (Test I, without cooling K) shows a complete "fouling" layer PF with a relatively large thickness after 5 hours of production time, which can affect the heat transfer in the relevant high-temperature heating area and generally the functionality of the system components. After about 10 hours of production time, it is necessary to interrupt production and clean the system 1000.

[0100] Figure 9a , 9b (Test II, with cooling; ΔTK=5K) Deposits on the periphery of the wall of the area with multiple island-shaped interruptions are caused by a "fouling" layer PF of significantly more moderate thickness, which has almost no effect on the heat transfer in the relevant high-temperature heating area and on the functionality of the equipment components in general, so that it is not necessary to interrupt production and clean the equipment 1000 until about 20 hours (production time is about 2 to 3 times that in Test I).

[0101] exist Fig.10a , 10b (Test III, with cooling; ΔTK=10K) The island-like, surface-like and very limited deposits on the wall are formed by a "fouling" layer PF of moderate thickness, which has almost no effect on the heat transfer in the relevant high-temperature heating area and on the functionality of the equipment components in general, so that it is necessary to interrupt production and clean the equipment 1000 only after about 20 hours (production time is about 2 to 3 times that in Test I).

[0102] Figures 9a to 10b The dark areas visible on the end side of the suction pipe in the black and white image are small deposits of the high-temperature heated milk product P, which have a brown or reddish-brown discoloration, which may be caused by small leaks at the flange connection and indicate that the milk product has undergone a Maillard reaction MR.

[0103] The facts and results shown above with reference to the direct heating device 8 configured as an immersion device 80 can be reasonably transferred to the direct heating device 8 configured as an injection device 800 (Figures 1 and 2). A person skilled in the art, a process engineer, or a technician in the dairy discipline or food method technology field who is familiar with the solution of the purpose of the present invention can also apply the teachings of the present invention to injection methods not specifically described in the present application and optimize the present invention in terms of process parameters that still need to be determined without the need for creative work.

[0104] List of reference numerals for the abbreviations used

[0105] Figure 1 (Prior Art)

[0106] 100 Equipment according to the prior art

[0107] 8 Direct heating device

[0108] 80 Immersion device

[0109] 800 Injection Device

[0110] 2 Preheater

[0111] 2a Heat transfer medium inlet

[0112] 2b Heat transfer medium outlet

[0113] 4. First Heater

[0114] 10 First conveying device

[0115] 12 Second Insulator

[0116] 14 Vacuum device

[0117] 16 Second conveying device

[0118] 18 Dairy product import (for processed dairy products P)

[0119] 20 First product pipeline section

[0120] 22 Second product pipeline section

[0121] 26 Steam inlet

[0122] 28 Product Entry

[0123] 30 outlet pipe

[0124] 32 Third product pipeline section

[0125] 34 Fourth product pipeline section

[0126] 36 Discharge pipe (for processed milk products P)

[0127] 38 Steam outlet

[0128] 40 First coolant inlet

[0129] 42 First coolant outlet

[0130] D. Water vapor

[0131] DE Direct Heating

[0132] FK Rapid Cooling

[0133] HE High Temperature Heating

[0134] HH1 First Insulation

[0135] HH2 Second insulation

[0136] IFV immersion method

[0137] IJV injection method

[0138] K1 First coolant M Heat transfer medium

[0139] P Dairy products (rich in protein) TA output temperature (=T6)

[0140] TVE preheating temperature (= T1, T2) THE High temperature heating temperature (=T4, T5) VE preheating

[0141] W Water

[0142] Δt1 First residence time Δt2 Second dwell time

[0143] Figures 2 to 4

[0144] 1000 devices

[0145] 6 Cooler

[0146] 6a Second coolant inlet 6b Second coolant outlet K Cooling

[0147] K2 Second coolant TK Cooling temperature (= T3)

[0148] ΔTK Temperature difference

[0149] ps saturation pressure

[0150] Ts saturation temperature

[0151] Figures 6 to 10b I First test (without cooling K) II Second test (with cooling K) III The third test (with cooling K)

[0152] test TVE℃ Δt1 sec TK℃ THE℃ Δt2 seconds TA℃ I 85 30 - 137.5 1 83 II 85 30 80 137.5 1 78.5 III 85 30 75 137.5 1 73

[0153] Table 1

[0154]

Claims

1. A method for directly heating a protein-rich milk product by introducing water vapor into the milk product, (a) wherein, during direct heating, the water vapor heats the milk product to a high temperature heating temperature by direct high temperature heating so as to form a sterile state, (b) where: Prior to the direct heating, the milk product is indirectly preheated to a preheating temperature and, viewed in the flow direction of the milk product, after the preheating, a first holding of the preheated milk product is performed for a first determined and controlled residence time, (c) wherein, viewed along the flow direction of the milk product, after being directly heated to the high-temperature heating temperature, a second insulation is performed on the high-temperature heated milk product for a determined and controlled second residence time, and (d) wherein water is subsequently extracted from the insulated high temperature heated milk product in an amount corresponding to the water vapor supplied previously by rapid cooling by expansion to a lower pressure, It is characterized in that Prior to direct heating, the preheated and warmed milk product is indirectly cooled by a recuperative cooling step with a temperature difference in the range of 5 K to 10 K from the preheating temperature to the cooling temperature, controlling said direct heating from the cooling temperature to the high temperature heating temperature with direct heating adjustment parameters known per se, and After the measure of feature (d), the milk product is cooled from the high temperature heating temperature to the mandatory necessary output temperature by rapid cooling.

2. The method according to claim 1, characterized in that The temperature difference is 10K.

3. The method according to claim 1 or 2, characterized in that: The direct heating adjustment parameters are the pressure, temperature and action time of the water vapor.

4. The method according to claim 1 or 2, characterized in that: The direct heating is achieved by an immersion method known per se.

5. The method according to claim 1 or 2, characterized in that: The direct heating is achieved by a spraying method known per se.

6. A device (1000) for directly heating a protein-rich milk product by introducing water vapor into the milk product, the device comprising, in a manner known per se: A direct heating device (8) for the dairy product, the direct heating device is used for directly heating the dairy product to a high temperature by means of water vapor, A preheater (2) arranged upstream of the direct heating device (8) and configured as a recuperator, viewed in the flow direction of the dairy product, is used to indirectly preheat the dairy product to a preheating temperature. a first insulator (4) for performing a first insulation on the preheated dairy product, wherein the first insulator is arranged between the direct heating device (8) and the preheater (2). A first conveying device (10) disposed downstream of the direct heating device (8) is used to convey the high-temperature heated dairy product. The second insulator (12) is arranged downstream of the first conveying device (10) and is used to perform a second insulation on the high-temperature heated dairy product. a vacuum device (14) arranged downstream of the second insulator (12), in which water is subsequently extracted from the insulated high-temperature heated milk product in an amount corresponding to the water vapor previously supplied by rapid cooling by expansion to a lower pressure, It is characterized in that A cooler (6) configured as a recuperator is arranged between the direct heating device (8) and the first insulator (4), and cools the preheated and insulated dairy product from a preheating temperature to a cooling temperature by indirect cooling.

7. The device according to claim 6, characterized in that The direct heating device is designed in the form of an immersion device known per se.

8. The device according to claim 6, characterized in that The direct heating device is designed in the form of an injection device known per se.

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