Method for producing a milk or whey powder, and use of a germ-removing separator

[0001] Exemplary embodiments of the present invention relate to a method for producing a milk or whey powder, and to a use of a germ-removing separator.

[0002] According to the current prior art, a method is used for the production of powder from whole milk/skimmed milk/whey or similar products, in which the liquid basic product, a previously pasteurized milk or whey, which may be adjusted to a protein content, a protein/fat ratio or similar, is concentrated from the original dry matter content (abbreviated as DM in the following) (approx. 8% DM in the case of skimmed milk) or higher as in the case of whole milk (approx. 12% DM) to a solids content of 40-65% DM via evaporation of the liquid. The base material can be reduced in germ content prior to concentration via a germ-removing separator or germ-removing filtration in order to extend the service life of the evaporator. The resulting concentrate is then dried by a dryer to a powder with 96% DM for skimmed milk powder (SMP) and 97% for whole milk powder (WMP). The common method varies slightly and can be supplemented with pre-concentration and standardization of the protein content.

[0003] With the common evaporation processes, the content of thermoduric spore formers increases with the duration of a production. Particularly for powders with the quality requirement Low Thermo Spore Powder, a point is then reached after a short time at which production must be stopped and cleaning must be carried out in order to maintain the increased requirements for the subsequent powder quality. This makes the production process of Low Thermo Spore powder economically difficult because investments and operating expenses for sufficient plant capacity for continuous production or short production times must be accepted.

[0004] The service life of the evaporator varies depending on the process and product qualities. The following are examples of processes for the evaporation of milk.

[0005] Based on the foregoing, exemplary embodiments of the present invention are directed to making the method for producing a powdered milk product more process-efficient and, in particular, to increase the intervals between two cleaning cycles for cleaning the entire system.

[0006] A method of producing a milk or whey powder according to the invention comprises at least the following steps:

• • [0007] I. Providing milk, especially skimmed milk or whole milk, or whey
    If the quality of the milk or whey is not sufficient with regard to the germs count, an initial sterilization in a germ-removing separator can already take place during preparation.
  • [0008] II. Thickening of the milk or whey by a first evaporation and/or a second evaporation
    Evaporation can take place in a so-called evaporation column. In addition to the DM content (dry substance content) of the milk or whey, the viscosity of the milk or whey also changes.
  • [0009] III. Drying of the thickened milk or whey to produce a milk or whey powder,
    This step can be performed in a spray dryer, roller dryer or similar equipment.

[0010] According to the method of the invention, after the first or the second evaporation process, sterilization of the milk or whey is carried out by means of a centrifugal germ-removing separator. In particular, and especially preferably, sterilization can take place both after the first and after the second evaporation process.

[0011] Sterilization can be performed after the initial evaporation of the milk or whey. Sterilization at this point in the production of a powdered milk product reduces the intensity or frequency of cleaning of subsequent plant components.

[0012] The first and/or second evaporation process can be carried out in an evaporation column.

[0013] The germ-removing separator can be installed directly in the outlet of the evaporator column after the first or second evaporation process. In particular, disinfection by the germ-removing separator can take place both after the first and after the second evaporation process. Two germ-removing separators can also be used.

[0014] Sterilization can be efficiently performed by a single germ-removing separator.

[0015] For more efficient sterilization, sterilization can be carried out by at least two germ-removing separators connected in series. This can achieve a further reduction in the number of germs per gram of milk or whey.

[0016] The sterilization can alternatively be carried out by at least two germ-removing separators that are connected in parallel to each other. Each of the two germ-removing separators, in particular in parallel arrangement, can be designed in such a way that it can be cleaned separately by a clean-in-place (CIP) process.

[0017] Sterilization can advantageously be performed at a temperature between 45-65° C. This temperature range is optimal for setting the sterilization conditions.

[0018] Thickening of the milk or whey by a first evaporation process before sterilization can be carried out to a solids content of 16-26%, preferably between 18-24%. In this range, the germ-removing separator operates particularly efficiently.

[0019] Thickening can be done using a falling film evaporator or plate evaporator.

[0020] The sterilization of pre-concentrated dairy products can be carried out by means of a germ-removing separator with an upstream buffer tank.

[0021] In particular, an upstream buffer tank for buffering the feed volume can be arranged in the feed line of each germ-removing separator.

[0022] Furthermore, a downstream buffer tank for buffering the effluent volume can be arranged in the outlet of each germ-removing separator.

[0023] The buffer tanks decouple the germ-removing separator from the rest of the plant for the production of a powdered milk product with regard to pressure surges.

[0024] Further according to the invention is the use of a germ-removing separator for sterilizing a thickened milk or whey having a solids content of at least 14%, preferably having a solids content between 16-26%.

[0025] The germ-removing separator may have a disk pack with separator disks.

[0031] The starting materials in the various embodiments of the present invention are liquid dairy products. In the embodiment variants described below, the liquid dairy products are skimmed milk 100, whole milk 101 or whey 102, in particular sweet whey.

[0032] In the production of milk powder, certain preconditions must be met for the starting materials.

[0033] FIG. 1 shows the processing of the starting product skimmed milk 100, which should preferably be further processed to skimmed milk powder in less than 48 h after milking. Storage between milking and processing according to the method of the invention can advantageously take place at a maximum of 5° C. The milk can be pretreated. This concerns centrifugal skimming or clarification and/or pasteurization.

[0034] The number of microorganisms per gram of milk should preferably be less than 50,000 colony forming units (CFU), particularly preferably less than 30,000 CFU. If the number of microorganisms is too high, the milk or skimmed milk can be sterilized before being used for the method according to the invention. This can be carried out by microfiltration or by a centrifugal germ-removing separator. Preferably, the milk used should be of Class A quality. The dry matter content of skimmed milk 100 is about 9% (+/−1%).

[0035] In a first optional step 200 of the method according to the invention, a protein standardization 200 may be performed. This can be carried out, for example, by ultrafiltration of skimmed milk, wherein either the retentate obtained or the permeate is mixed with further skimmed milk, depending on whether a skimmed milk with a higher or lower protein content is desired. This protein standardization serves, among other things, to set a homogeneous milk quality for further processing.

[0036] In a second, also optional step 300, pretreatment can be carried out, e.g., stabilization of skimmed milk. In this step, the skimmed milk 100 is heated. Depending on the composition of the skimmed milk, an optimum of a temperature/time combination can be determined by tests. For example, a temperature treatment in the range between 100 to 120° C. for 1-4 min has been found to be favorable. Subsequently, the milk can be cooled to a temperature higher than 50° C., preferably 65-75° C., and fed to the evaporator. This second step serves to improve the heat stability of the proteins contained in the skimmed milk, especially casein. Furthermore, some types of germs can be killed and a presetting of the temperature for the subsequent evaporator can be made.

[0037] In a third step 400, the milk is evaporated or thickened in an evaporator. This increases the viscosity and density of the skimmed milk. Preferably, circulation, falling film or plate evaporators can be used as evaporators. Evaporation takes place in two stages, with the third step 400 representing the first stage of evaporation. In this process, a concentrated skimmed milk with a dry matter of about 16-26% is obtained. Preferably, so-called evaporator columns can be used as evaporators.

[0038] This can then be fed in a fourth step 501 to a germ-removing separator for centrifugal sterilization. The germ-removing separator or separators are designed as centrifugal disk separators, which are operated as clarifiers. Impurities in the milk/whey, such as undesirable spores, germs and/or bacteria, are reliably separated.

[0039] The milk temperature of the concentrated skimmed milk may be more than 40° C., preferably 50 to 60° C.

[0040] The drum must be provided with the maximum possible clarifying area. The recirculation line used on the germ-removing separators returns a certain amount of concentrate (entrained liquid) to the skimmed milk flowing to the separator. This entrained liquid consists of an intermediate phase between the light, clarified milk phase and the heavy solids phase. The continuous flow of the entrained liquid in the disk pack promotes the sterilization effect.

[0041] Preferably, the drum solids space can be emptied discontinuously so that impurities together with the bacteria can be removed from the drum.

[0042] The germ-removing separator is adapted for sterilization of highly viscous and denser dairy products.

[0043] Compared to a degerminator for milk, which is known per se, the feed capacity is reduced for highly viscous and denser milk products.

[0044] It is also possible and preferred to arrange two or more germ-removing separators in parallel after the evaporator.

[0045] FIG. 4 shows a section of a plant 1 for the production of milk or whey powder. This plant 1 is merely an example and can be supplemented in particular by further evaporation columns and/or germ-removing separators.

[0046] A germ-removing separator 2 is thereby arranged in an evaporator 4 with several evaporator columns 5. The separator 2 can preferably be installed in the inlet of the next evaporator column or the outlet of the previous evaporator column 5 of step 400 for further processing. In the germ-removing separator 2, centrifugal forces are then used to separate the microorganisms present, including the thermoduric spore formers.

[0047] For more efficient bacteria removal, an additional germ-removing separator can optionally be connected in series with germ-removing separator 2. This can achieve a further reduction in the number of germs per gram of milk or whey.

[0048] In order to ensure sterilization over the entire period, a second germ-removing separator can be installed as an option, which can be integrated into the process as an alternative to the first separator if required (parallel). In parallel operation, the first separator can be cleaned during this time via a separately installed CIP supply.

[0049] In order to be able to decouple the evaporators, or the concentration equipment if necessary, from the separators in the event of pressure surges and the like, and to keep the flow constant if required, a buffer vessel 3 can be installed in the inlet and/or outlet of the separator 2 or separators, as shown in FIG. 4.

[0050] In a modification of FIG. 4, one buffer vessel in the inlet and one in the outlet for each separator and/or one buffer vessel each in the inlet and outlet for both separators can be planned.

[0051] Furthermore, a buffer tank 6 can be arranged on the inlet side of the arrangement 4 consisting of several evaporator columns 5.

[0052] After a first sterilization 501, a further evaporation 600 can be performed. For this purpose, the thickened milk can be fed to a second evaporator column or returned to the evaporator from step 400. A thickened skimmed milk with a dry matter content of up to 50% can be obtained by the second evaporation.

[0053] After the second evaporation 600, a second sterilization 502 can follow. This second sterilization 502 can be performed in the same way as the first sterilization 501. The second sterilization 502 can further reduce the bacterial count.

[0054] Within the scope of the present invention, it is also possible to carry out the first and second evaporations first and only then to carry out sterilization.

[0055] Finally, in a further step 700, drying is carried out. This drying can be carried out, for example, by spray drying. In this process, milk may be fed from a product feed tank or directly from the evaporator or degerminator to an atomizing device. This atomizing device may be part of an air distributor in the upper part of a drying tower. Finely atomized droplets then meet hot air in the drying tower and evaporation takes place with simultaneous air cooling. Most of the dried milk powder falls into the lower part of the drying tower and can already be cooled at this point by an appropriate cooling system.

[0056] The product is skimmed milk powder. The residual moisture of this skimmed milk powder is about 4% (+/− 0.2%). Preferably, the product is a skimmed milk powder having a plate count of thermophilic spores (113 F to 158 F) of less than 100 cfu/g, more preferably less than 50 cfu/g. The aforementioned skimmed milk powder may be referred to as a “low thermospore” powder. Normal skimmed milk powder may have a plate count of thermophilic spores of up to 1000 cfu/g.

[0057] Typically, the production of a skimmed milk powder with the aforementioned plate count, for example according to a method sequence as described in US 20160113302 A1, requires cleaning of the evaporator at short intervals. Due to the sterilization in the evaporator process, a plant for the production of milk powder can be operated in the production mode for a considerably longer time and the cleaning mode only needs to be activated at longer intervals.

[0058] By using the germ-removing separators in the evaporation process, the quality of the final products (e.g., skimmed milk powder) can be guaranteed with a significant increase in production time.

[0059] FIG. 2 shows the processing of the starting product whole milk 101, which should also preferably be further processed into whole milk powder 801 less than 48 h after milking. Storage between milking and processing according to the method of the invention can advantageously take place at a maximum of 5° C. The milk can be pretreated. This concerns centrifugal skimming or clarification, standardization of the fat content by separation of fat or addition of skimmed milk and/or pasteurization.

[0060] The number of bacteria per gram should preferably be less than 50,000, particularly preferably less than 30,000. If the number of bacteria is too high, the whole milk can be sterilized before being used for the method according to the invention. This can be done by microfiltration or by a centrifugal germ-removing separator. Preferably, the milk used should be of Class A quality. The dry matter content of whole milk is about 12% (+/−1%).

[0061] The whole milk 101 can be subjected directly to an evaporation 401 for the purpose of thickening. In this process, the whole milk 101 can be fed to an evaporation column in a manner analogous to the treatment of skimmed milk 100. Thereby, a concentrated whole milk with a dry matter of up to 28% is obtained.

[0062] Following the first evaporation 401, a homogenization 900 of the milk may take place.

[0063] After homogenization 900, sterilization 501 can be performed. The sterilization can be carried out analogously to the aforementioned embodiment. Thus, sterilization with a single germ-removing separator is advantageous as single sterilization, but double sterilization with two germ-removing separators connected in series can also be carried out.

[0064] After a first sterilization 501, a second evaporation process 601 can be performed. For this purpose, the thickened and sterilized whole milk can be fed to a second evaporation column or returned to the evaporation column from step 401. Through the second evaporation process, a thickened whole milk with a dry matter content of up to 50% can be achieved.

[0065] Optionally, after this second evaporation, a repeated sterilization 502 can be performed.

[0066] Finally, the thickened and sterilized whole milk can be fed to a drying unit, e.g., a spray dryer, for drying 701. In this process, the thickened whole milk is converted into whole milk powder. The residual moisture of whole milk powder is about 2.5% (+/−0.2%).

[0067] FIG. 3 shows the processing of sweet whey 102 into sweet whey powder 802.

[0068] In the case of sweet whey 102, it should preferably come from the production of cheese, which was made from fresh cow's milk and without additives.

[0069] A short storage time of less than 1 h is preferred, provided that the whey is stored at a temperature of more than 10° C. between cheese production and further processing into whey powder. At temperatures below this, the maximum storage time is 10 h. The dry matter content of sweet whey is approx. 6% (+/−1%).

[0070] In a first step, the sweet whey can be thickened by an evaporation process 402. This thickening can be carried out analogously to the embodiment variant of FIG. 1. The dry matter content of the thickened sweet whey is up to 26%.

[0071] Then a sterilization 501 is carried out in a germ-removing separator. This sterilization can be performed as single sterilization or double sterilization.

[0072] A further evaporation process 602 then takes place so that the thickened sweet whey has a dry matter content of up to 50%.

[0073] Optionally, after this second evaporation process, a repeated sterilization 502 can be performed.

[0074] Finally, the thickened sweet whey is dried 702 to a sweet whey powder with a residual moisture content of about 4% (+/−0.2%) based on the weight of the powder.

[0075] In the methods shown in FIGS. 1-3, the production lines are supplemented by at least one germ-removing separator, preferably two germ-removing separators connected in parallel or in series, which are designed for the sterilization of highly viscous and denser dairy products.

[0076] In this case, the sterilization takes place after a step of evaporation. Preferably, one or more germ-removing separators can take place after an evaporation column of a first evaporation step or thickening step 400, 401, 402. For example, at least one germ-removing separator may be installed in the feed of an evaporation column of a second evaporation step 600, 601, 602 or in the outlet of the evaporation column of the second evaporation step 600, 601, 602.

[0077] The installation of a germ-removing separator after the evaporator column of the first evaporation step 400, 401, 402 is considered to be particularly advantageous in this respect, in which the product with a dry matter of about 16-26%, preferably 18-24% DM is pumped from the evaporator into the germ-removing separator.

[0078] In the germ-removing separator, centrifugal forces are then used to separate the microorganisms present, including the thermoduric spore formers.

[0079] In order to achieve a further reduction in the number of germs per gram of milk or whey, another germ-removing separator can optionally be connected in series with germ-removing separator 2.

[0080] In order to ensure sterilization over the entire period, a second germ-removing separator is installed, which can be integrated into the process as an alternative to the first separator (parallel connection) if required. In the case of a parallel connection, the first separator can be cleaned during this time via a separately installed CIP supply.

[0081] In order to decouple the evaporators or the concentration equipment from the germ-removing separators for pressure surges and the like, and to keep the flow constant as far as required, buffer tanks 3 can be installed in the inlet and outlet of the separators. For each separator, one buffer tank can be installed in the inlet and one in the outlet, as well as one buffer tank each in the inlet and outlet for both separators.

[0082] Although the invention has been illustrated and described in detail by way of preferred embodiments, the invention is not limited by the examples disclosed, and other variations can be derived from these by the person skilled in the art without leaving the scope of the invention. It is therefore clear that there is a plurality of possible variations. It is also clear that embodiments stated by way of example are only really examples that are not to be seen as limiting the scope, application possibilities or configuration of the invention in any way. In fact, the preceding description and the description of the figures enable the person skilled in the art to implement the exemplary embodiments in concrete manner, wherein, with the knowledge of the disclosed inventive concept, the person skilled in the art is able to undertake various changes, for example, with regard to the functioning or arrangement of individual elements stated in an exemplary embodiment without leaving the scope of the invention, which is defined by the claims and their legal equivalents, such as further explanations in the description.

• • [0083] 100 Skimmed milk
  • [0084] 101 Whole milk
  • [0085] 102 Whey
  • [0086] 200 Protein standardization
  • [0087] 300 Pretreatment
  • [0088] 400 Evaporation process
  • [0089] 401 Evaporation process
  • [0090] 402 Pretreatment
  • [0091] 501 Sterilization
  • [0092] 502 Sterilization
  • [0093] 600 Evaporation process
  • [0094] 601 Evaporation process
  • [0095] 602 Evaporation process
  • [0096] 700 Drying
  • [0097] 701 Drying
  • [0098] 702 Drying
  • [0099] 800 Skimmed milk powder
  • [0100] 801 Whole milk powder
  • [0101] 802 Whey powder
  • [0102] 900 Homogenization
    • [0103] 1 Plant
    • [0104] 2 Germ-removing separator
    • [0105] 3 Buffer tank
    • [0106] 4 Evaporator
    • [0107] 5 Evaporation column
    • [0108] 6 Buffer tank