Methods for processing a permeate from a milk protein concentrate process and permeate-containing powder obtained thereby

Abstract

The present invention relates to milk powder production and in particular to the processing of permeates arising from production of milk protein concentrate powder. It also relates to efficient utilization of permeate produced in milk processing systems comprising both milk protein concentrate production and (whole / skim) milk powder production.

Description

[0001] Methods for processing a permeate from a milk protein concentrate process and permeate-containing powder obtained thereby

[0002] Technical Field

[0003] The present invention relates to production of milk powders, in particular to the utilization of the permeate arising from production of milk protein concentrate using membrane filtration.

[0004] Background Art

[0005] Milk can be dried to form milk powder which serves to increase the shelf life among other advantages. The milk powder can be reconstituted in water to once again form a milk liquid or it can be used directly as ingredient in various food products. Milk powder is mainly available as whole milk powder or skim milk powder where the difference is the fat content due to cream being skimmed off the cream in skim milk powder. Such milk powders are typically standardized to meet set criteria for protein and fat content. Whole or skim milk powders can be effectively produced by spray drying, using for example the applicant's MSD® spray dryer.

[0006] Other types of milk powder products exist, such as milk protein concentrate, abbreviated MPC, which has a high protein content (casein and whey proteins). MPC is produced by concentration using membrane filtration of typically skim milk and typically involves an ultrafiltration and / or microfiltration steps, prior to drying of the re- tentate portion to MPC. The membrane filtration steps of the MPC process results in permeate(s) which is a liquid rich in lactose and comprising minerals.

[0007] The solid content of permeates from MPC processes is mainly lactose, which is not a high value product. Hence, the permeates are sometimes considered a waste and not further processed. One way to make use of the permeate for standardization of milk products, such as milk powders, e.g. by adding the permeate to the milk which is to be dried. However, it may not be possible to utilize all the permeate produced in the MPC process for standardization of other milk products, especially as the shelf life of the liquid permeate is short, which limits the applicable geographical area, even if this use can offset the costs of handling and transporting, which may not be the case. EP3656220A1 is an example of this and describes a process where a permeate from MPC production is concentrated using reverse osmosis and the resulting lactose-rich fraction is used to standardize the protein content of normal milk.

[0008] Another way to utilize the permeate is to process it into a dry powder form which is typically referred to as "permeate powder" or "lactose powder". This increases the shelf life and allows the permeate powder to be stored, transported and used for products where lactose enrichment is desired. However, the value of lactose in itself is low and processing the permeate to powder may not be viable, especially considering that dedicated equipment is needed to dry permeate. The permeate cannot be spray dried as the lactose will become sticky and foul the spray drying equipment. Instead permeate powders are produced by concentrating the permeate in a concentrator and the crystallizing the lactose in a crystallization unit and then drying the concentrated, crystallized liquid to provide the permeate powder. EP3253222A1 is an example of such a process. EP1809117A1 proposes a similar use of permeate, where the permeate is mixed with milk and then subjected to concentration, crystallization and spray drying in order to provide a powder product. Similarly, Hogan and O'Callaghan, International Dairy Journal, Volume 20, Issue 3, March 2010, Pages 212- 221, describes making a powder which contains 15.5 g / 100 g protein and 0.85 g / 100 g of fat from a mixture of skim milk and permeate, by evaporating to a total solids content of 60 % and then crystallizing the mixture to achieve a crystallisation degree of 68 % before spray drying.

[0009] These processes may provide increases shelf life of the permeate, but require dedicated equipment for producing low value product, which may not be viable.

[0010] In view the above, it is an object of the invention to provide a method for utilization of permeate from MPC processes, and especially to provide such a method which is efficient in terms of operational cost and / or equipment requirement.

[0011] Summary of the Invention

[0012] These and further objects are obtained by a method for processing a permeate from a milk protein concentrate, abbreviated MPC, process, comprising the steps of - providing a milk to the MPC process and obtaining an MPC powder and a permeate using membrane filtration, which permeate comprises lactose,

[0013] - mixing the permeate with a whole milk, a skim milk or combination thereof to obtain a liquid mixture, which liquid mixture has a protein content of 9 to 29 w / w% on a total solids basis,

[0014] - spray drying said liquid mixture to obtain a permeate-containing powder, wherein 95 % or more of the lactose in the liquid mixture being spray dried is dissolved in the liquid mixture.

[0015] By mixing the permeate with milk to provide said liquid mixture it is possible to spray dry the liquid mixture without the need for equipment dedicated to drying the liquid permeate as such, using instead a similar spray dryer as is used for whole or skim milk powder production, without the lactose becoming sticky and fouling / clog- ging the spray dryer. This can be done without lactose crystallisation and with the lactose dissolved in the liquid mixture, thus avoiding the dedicated crystallization equipment needed in known processes to crystallize the lactose before spray drying. Hence, there is provided an efficient manner in which to process MPC permeates. The process provides a permeate-containing powder which has an improved shelf life and less bulk volume compared to the liquid permeate, whereby it is more easily stored and / or transported for further use. The permeate-containing powder does not fulfil the requirements of milk powder in terms of composition itself but can for example be used for standardization of skim or whole milk powder production as will be described in greater detail below. As specified, at least 95 % of the lactose in the permeate remains in solution in the liquid mixture, and not in crystallized form. Hence, equivalently, at most 5 % of the lactose is in crystal form in the liquid mixture. The amount of lactose in crystal form may be determined as the Degree of Crystallization (DoC) of the lactose in the liquid mixture, which is at most 5 % when spray dried according to the invention. It is understood that the process is performed without a controlled lactose crystallization step, but that lactose may inadvertently crystalize to a small degree as part of other process steps, such as cooling in between mixing and drying. A controlled lactose crystallization step could be in a crystallization belt unit or jacketed crystallizer, but such a unit is not used in the method according to the invention. The milk with which the permeate is mixed contains dairy protein (casein and whey) and milk fat and can comprise a skim milk, a whole milk or a combination thereof providing a milk having a composition falling between skim and whole milk. Addition of further ingredients, such as a cream part is also possible. The milk part of the liquid mixture will generally be a bovine milk. Skim milk as used herein refers to milk having a fat content of 1.5 or less w / w% on liquid basis. Whole milk as used herein refers to a milk having a fat content of 3.5 w / w% or above on liquid basis, typically 3.5 to 6 w / w%. The permeate obtained from the membrane filtration of the MPC process is rich in lactose and minerals, typically containing 85 w / w% (total solids) lactose or more, 87 w / w% (total solids) being a typical lactose content. The membrane filtration retains dairy protein and milkfat in retentate, but the permeate may still contain small amounts of e.g. dairy protein, such as less than 4 or less than 3 w / w% total solids. The membrane filtration in MPC production is typically ultrafiltration possibly combined with a diafiltration step, and the term "permeate" as used herein includes permeates from both the ultrafiltration and possible diafiltration steps, alone or in combination. Spray drying the liquid mixture is done at conditions corresponding to those used for milk powders, hence, the liquid mixture may be spray dried at a pressure ranging from a few bar to 250 bar(a) depending on the type of atomizing means, and a temperature of 180 to 220 °C.

[0016] In preferred embodiments, all of the lactose of the liquid mixture being spray dried is dissolved in the liquid mixture.

[0017] It is presently considered preferable to maximize the amount of permeate and minimize the amount of milk in the liquid mixture. Accordingly, the liquid mixture preferably has a protein content of 10 to 22 w / w% on total solids basis, and even more preferably 11 to 20 w / w % on total solids basis.

[0018] In some embodiments, the liquid mixture has a fat content of 0.1 to 1.5 w / w% on total solids basis, preferably 0.3 to 1.2 w / w% on total solids basis, and a protein content of 15 to 29 w / w% on total solids basis, suitably a protein content of 15 to 22 w / w %. The low fat content of these embodiments, which are denoted low- fat permeate-containing powders, are suitably made by mixing primarily, or even only, skim milk with the permeate to obtain the liquid mixture. The low fat content in the skim milk makes it advantageous to formulate a liquid mixture with the above protein content in order to spray dry the liquid mixture without a preceding crystallisation step.

[0019] In some embodiments, the liquid mixture has a fat content of 1.5 to 18 w / w% on total solids basis, preferably 2 to 15 w / w%, more preferably 4 to 12 w / w% on total solids basis, and a protein content of 9.5 to 23.5 w / w%, more preferably 10 to 20 w / w% on total solids basis. The high fat content of these embodiments, which are denoted high-fat permeate-containing powders, are suitably made by mixing primarily, or even only, whole milk with the permeate to obtain the liquid mixture. The high fat content in the whole milk makes it advantageous to formulate a liquid mixture with the above protein content, as the fat content may contribute to keeping the mixture spray-dryable even at lower protein content.

[0020] In some embodiments, a total of protein and fat constitutes at least 15 w / w% of the liquid mixture on total solids basis. This may also apply the low-fat and high-fat permeate containing powders above, where the liquid mixture may be blended to reach at least 15 w / w% of fat and protein combined on total solids basis.

[0021] In some embodiments, the lactose content of the liquid mixture is up to 75 w / w% on total solids basis, such as in the range to 45 to 75 w / w%. High lactose contents close to 75 w / w% may be achieved with protein and / or fat at the lower end of the ranges described above, and exemplified in the examples below.

[0022] As described, the liquid mixture is spray dried without a controlled crystallization step before spray drying. Hence, the step of spray drying the liquid mixture may follow directly from the step of mixing the permeate with the whole and / or skim milk to form the liquid mixture. In this context, "follows directly" is understood to included optional steps of concentrating the liquid mixture, transporting the liquid mixture, homogenizing the liquid mixture or holding the liquid mixture before spray drying the liquid mixture. Holding the liquid mixture includes cooling and holding the liquid mixture in a suitable vessel.

[0023] In some embodiments, the permeate-containing powder is used to standardize a milk product. Preferably the permeate-containing powder is used in standardization of a milk powder. The milk powder may for example be a whole milk powder or a skim milk powder. Standardization refers to blending a milk product with an additional component in order to reach a target composition. The target composition may be a target fat content and / or protein content. For milk powders standardizing to reach a target protein content is typical. The permeate-containing powder can be reconstituted in water and then used for standardization. The permeate containing powder may also be used in dry form standardization.

[0024] In preferred embodiments, the standardization comprises dry mixing of the permeate-containing powder and the milk powderto obtain a standardized milk powder. Preferably the milk powder is a whole milk powder and the dry mixing provides a standardized whole milk powder. Dry mixing refers to mixing the permeate-containing powder in dry form into milk product also in dry form to standardize the milk product. By dry mixing, as opposed to wet mixing with reconstituted permeate containing powder, saves energy as there is less water to evaporate.

[0025] The dry mixing may advantageously be implemented by dosing the permeate containing powder into a fines recovery system of the spray drying units. The exhaust gas of a spray drying unit typically has small milk powder particles entrained therein, which are referred to as fines. These fines can be recovered by having a fines recovery system downstream of the spray drying unit. The fines recovery system may for example use sedimentation, e.g. in a cyclone, or filtration, e.g. a bag filter unit, or a combination thereof to recover the fines. The recovered fines is then recycled into the spray drying unit and / or into the milk powder downstream from spray drying unit, e.g. in a fluidized bed provided to transport, dry and / or cool the milk powder after spray drying.

[0026] The liquid mixture obtained by mixing permeate with whole or skim milk can be spray dried in the spray dryer used to produce whole or skim milk powder in the milk powder section, whereby the method allows for processing of the permeate without additional equipment. Typically the milk powder section will comprise plurality of the spray dryers, a subset of which can be isolated and used for drying the liquid mixture or permeate-containing powder when needed.

[0027] The invention may advantageously be used in dairy powder plants which has both MPC production and whole and / or skim milk powder production. In some embodiments, the MPC process is performed in an MPC section of a milk processing system, which milk processing system further comprises a milk powder section configured for receiving milk and spray drying the milk in at least one spray dryer to provide a milk powder, and the step of spray drying the liquid mixture to obtain the permeate-containing powder is performed in a spray dryer of the milk powder section or of the MPC section. Preferably the liquid mixture is spray dried in a spray dryer of the milk powder section, as there may be a surplus of spray drying capacity in the milk powder section as described below and by not switching between different products in particular spray drying unit, the cleaning requirements are reduced. The milk processing system can be a single dairy plant which has both milk powder production line(s) and MPC production line(s) at the same location. "The same location" is understood to be a site where there is no significant transport of milk, intermediates or products between unit operations, transport referring to transport by truck or rail.

[0028] The term milk powder section is used to refer to the unit operations in the milk powder production line(s) and the term MPC section is used to refer to the unit operations in the MPC production line(s).

[0029] The invention may advantageously be used to handle a varying milk input volume to a dairy plant which has both MPC production and milk powder production. Variations in milk input volume to a dairy powder plant may arise for example in regions where milk production is seasonal with a high volume season and a low volume season. The capacity of the dairy plant will be sized to handle the high volume season input, through an MPC production capacity and a whole and / or skim milk powder production capacity. In this situation with high volume, all of the permeate produced by the MPC production can typically be utilized for standardization of the whole or skim milk powder production. In the low volume season it will generally be desirable to utilize all of the MPC production capacity, while the milk powder production is at less than full capacity. This may lead to a situation in which the permeate produced by the MPC production will be in excess of what can be utilized for standardization of milk powder at the dairy plant.

[0030] By producing the permeate-containing powder in this first time period where permeate is in excess of what can be utilized in the milk powder section, the permeate can be stored for later use. This first time period may be the low volume season described above. A possible further advantage is the utilization of spray dryer capacity in the milk powder section which is in excess during the first period. The standardization requirement of the milk powder section is understood to be the volume of permeate which can be utilized for standardization of the product in the milk powder section at a given time. As the skilled practitioner will appreciate, this standardization requirement will depend on the capacity and input to the dairy plant in question, as well as the composition of the milk input, which can vary.

[0031] Hence, in some embodiments the permeate-containing powder is produced in a first time period where a production of permeate from the MPC section exceeds a standardization requirement of the milk powder section, which standardization requirement is the amount of permeate which the milk powder section can utilize for standardizing the milk powder produced in the milk powder section. MPC and milk powder production is typically continuous processes. Hence, the permeate production and standardization requirement are expressed as rates (mass or volume). The safe storage time of the permeate is short, in the order of days, typically around 2 to 3 days, while the standardization requirements may change on a timescale of weeks and months, hence there is limited options for buffering the permeate for later use. Accordingly, determining whether the production of permeate exceeds the standardization requirement, may be done by comparing the hourly or daily permeate production, with the standardization requirement calculated from the hourly or daily milk powder production. As noted above the MPC section can comprise multiple MPC production lines and the milk powder section can comprise multiple milk powder production lines, and even both skim milk powder production lines and whole milk powder production lines, in which case the standardization requirement is determined by the standardization requirement of all milk powder production lines in the milk processing system. A surplus of permeate in a given milk processing system may in practice be indicated by permeate being discarded. The standardization requirement may be determined by the permeate volume needed to reach any recognized market standard for milk powder, such as defined in US FDA Codex Alimentarius or other regional or country specific guidelines. Whole milk powders may for example be standardized to a milkfat content of >26.2% w / w% and protein content of >24.2% w / w% with a protein to solids non-fat content of >34% and while skim milk powders may for example be standardized to a milkfat content of <1.5% w / w% and protein content of 32.2% w / w% with a protein to solids non-fat content of >34%.

[0032] In some embodiments, the permeate-containing powder is used in standardization of the milk powder produced in the milk powder section in a second time period where the production of permeate from the MPC section is less than a standardization requirement of the milk powder section. In this way, permeate-containing powder previously produced can be used to balance a shortage of permeate in the second time period.

[0033] In some embodiments, the liquid mixture is concentrated prior to spray drying providing a concentrated liquid mixture. As is well known by the skilled practitioner, concentration is achieved by evaporating water in a concentrator suitable for dairy products, e.g. a falling film evaporator. Preferably the concentrated liquid mixture has a total solids content of 40 to 65 w / w%. The concentration be by concentrating the liquid mixture as such or by concentrating the permeate and / or the milk with which the permeate is mixed, prior to the step mixing to form the liquid mixture.

[0034] In a further aspect of the invention, there is provided the permeate containing powder obtained by method according to the invention described above. In a still further aspect of the invention, there is provided a milk powder, whole or skim milk powder, containing the permeate-containing powder, which milk powder is obtained by any of the embodiments of the method which includes a standardization step.

[0035] The composition of various products and intermediates are described herein by referring to the content of various components and other parameters. Any method suitable for determining these contents and parameters may be used.

[0036] In particular, the protein content of a milk or product derived from milk (incl. the liquid mixture of the invention), may be determined by the Kjeldahl method e.g. according to IS 8968-4:2016 or IDF20-4:2016.

[0037] The fat content of a milk or product derived from milk (incl. the liquid mixture of the invention), may be determined gravimetrically, e.g. by according to IDF

[0038] 1:2010. The lactose content of a milk or product derived from milk (incl. the liquid mixture of the invention), may be determined according to ISO 26242:2010 or IDF 214:2010.

[0039] The degree to which lactose in a milk or product derived from milk (incl. the liquid mixture of the invention) is in solution can be determined by the degree of lactose crystallization as described in the applicant's published method "A l e - Water of Crystallization" or by the methods described in L. Nprgaard et al. / International Dairy Journal 15 (2005) 1261-1270, where the former is also described in Example III below.

[0040] The total solids content in a milk in a milk or product derived from milk (incl. the liquid mixture of the invention) can be determined by drying a sample to remove water and comparing the mass before and after. Suitable methods are provided in IS 6731:201 or ID 21:2010 for liquid milk and ISO 5537 or IDF 26: 2023 for milk powders.

[0041] A "powder" as used herein may refer to a granular material with a low moisture content, e.g. 5 % by weight or lower.

[0042] Unless otherwise specified weight percentages specified herein refers to the total solids content, i.e. the dry weight.

[0043] Brief Description of Drawings

[0044] In the following the invention will be described with reference to the exemplary embodiment shown in the enclosed drawings, in which

[0045] Fig. 1 shows a schematic process diagram of a milk processing system having a milk powder section and an MPC section, where a permeate of the MPC section is processed into a permeate-containing powder,

[0046] Fig. 2 shows a schematic process diagram of a milk powder process with three different options for adding permeate-containing powder to standardize a milk powder,

[0047] Fig. 3 shows a preferred method for standardizing a milk powder with the permeate-containing by dry-mixing into a fines recovery section of a spray-drying system, and

[0048] Fig. 4 shows a schematic timeline of production in a dairy powder system with a first time period with excess permeate and a second time period with shortage of permeate.

[0049] Detailed description

[0050] Referring initially to Fig. 1 which shows a milk processing system 4 having a milk powder section 10 which receives a first milk stream 1 and produces a milk powder 12 and an MPC section 30 which receives a third milk stream 3 and produces an MPC powder 33. The term MPC will be used throughout as an abbreviation of milk protein concentrate. The method according to invention can be particularly advantageous in systems such as the one shown in Fig. 1, but some embodiments of the invention may be employed for systems having just the MPC section 30. Milk processing systems 4 may comprise a number of processing steps which may be done in common for several production processes of the system. Fig. 1 includes common operations 40 which including such common processing steps, such as one or more of clarification, pasteurization, standardization, and evaporation.

[0051] The milk powder section 10 may be the process which receives the first milk stream 1 and produces milk powder 12 by spray drying. In the embodiment shown, the milk powder section 10 receives first milk stream 1 from common operations 40, which first milk stream 1 is then concentrated in concentrator 100 to produced milk concentrate 11 which can be spray dried. The milk concentrate 11 will typically have a solids content of 40 to 65 w / w%. The milk concentrate 11 is then sent to spray drying section 110 which comprises a plurality of spray drying units 111, 112, 113 which produces milk powder 12. The milk powder 12 can be a skim milk powder or whole milk powder. In the operational situation shown in Fig. 1, one of the spray drying units 113 of the spray drying section 110 in the milk powder section 10, is used to produce permeate-containing powder 23, which will be described below, while two of the spray drying units 112 produce milk powder 12. Spray dying of milk powder is typically done at a temperature range of 180 to 220 °C and pressure range ranging from a few bar to 250 bar(a) depending on the type of atomizing means. The concentrator 100 may be any concentration unit(s) suitable for concentrating milk, e.g. a falling-film evaporator. Concentrators are commercially available and are sometimes referred to as evaporators. Suitable spray drying units 111-113 for milk powder are also commercially available, such as the applicant's MSD® Spray dryer. The spray drying section 110 may comprises further units (not shown) such as fines recovery system for recovering milk powder fines from the exhaust drying air (cyclones, bag filters, etc.) and fluidized beds for conveying, drying and / or cooling the powder produced by the spray drying units 111-113. The milk powder section 10 may also comprise further unit operations between first milk stream 1 and milk powder 12, examples are units for standardization or homogenization.

[0052] Milk protein concentrate, MPC, is complete in dairy protein, i.e. it contains both casein and whey protein and is produced by membrane filtration which retains the dairy protein in the retentate. Producers and official governing bodies apply different definitions, but in general an MPC product should have at least 40 w / w% of protein, but the protein content of MPC may be as high as 85 w / w% or even 90 w / w%. The milk processing system 4 in Fig. 1 has MPC section 30 which receives third milk stream 3 and produces MPC powder 33. The third milk stream 3 is a skim milk which is sent to membrane filtration in membrane filtration system 300, producing a retentate 31 and permeate 32. The membrane(s) of the membrane system has a pore size which retains dairy protein in the retentate 31 while allowing lactose and minerals to pass through the membrane into the permeate 31. Ultrafiltration membranes are suitable. The membrane filtration step may also comprise diafiltration step for further concentrate dairy protein in the retentate 31. The retentate 31 is then dried 310 to provide the MPC powder 33. The drying may include a concentration step where water is removed but the retentate remains liquid, before the final drying to powder form. The final drying may be done by spray drying, for which suitable units are commercially available, such as the applicant's MSD® spray dryer. The permeate 32 is rich in lactose and minerals, but contains substantially no dairy protein. The permeate will typically have a lactose content of at least 85 w / w % on total solids basis. Permeate as used herein refers both to the permeate from ultrafiltration and diafiltration steps of the membrane filtration. This permeate 32 cannot be spray dried as the high lactose content would form a sticky mass and clog the nozzles of the spray dryer.

[0053] According to the invention the permeate 32 from the MPC section is mixed with a second milk stream 2, which in Fig. 1 is shown as mixer 200, to form liquid mixture 21. Second milk stream 2 and permeate 32 is mixed in a proportion allowing the liquid mixture to be spray dried. The second milk stream 2 may be a skim milk, a whole milk, or a milk composition falling between a skim and a whole milk. In the embodiment of Fig. 1, the liquid mixture 21 is then concentrated in concentrator 210, to provide concentrated liquid mixture 22. This concentrated liquid mixture 22 is then spray dried, while the lactose therein remains substantially in solution, i.e. non-crys- tallized. "Remains substantially in solution" as used herein refers to at least 95 % by weight of the lactose is in solution in the liquid mixture 21 and in concentrated liquid mixture 22, as some lactose may precipitate / crystallize inadvertently due to for example cooling of the mixture or other process steps or handling which are not provided to crystallize lactose. In the embodiment show in Fig. 1, one spray drying unit 113 of the spray drying section 110 of the milk powder section 10 is used to spray-dry the concentrated liquid mixture 22 to yield the permeate-containing powder 23. In this way, spare spray drying capacity of the milk powder section can be utilized, as will be described in greater detail below in relation to Fig. 4. The concentration 210 may be a concentration unit of the milk powder section and not a separate concentrator dedicated to the liquid mixture.

[0054] In Fig. 1 the permeate 32 is mixed with a second milk stream 2 from the common operations 40, but in alternative embodiments the permeate could be mixed with a milk in concentrated form, such as part of milk concentrate 11.

[0055] The permeate-containing powder 23 does not have a composition which matches commercial dairy powders, as it is rich in lactose, but low in fat and low in protein content. However, the permeate-containing powder 23 provides a means for storing permeate without requiring a specific production line for crystallizing and drying permeate.

[0056] Currently, the main application envisioned for of the permeate-containing powder 23 is standardization of milk products. Fig. 2 and 3 shows embodiments of processes where the permeate-containing powder is used to standardize milk powder. Standardization refers to the adjustment of the composition of a milk to meet specified levels. Typically fat and / or protein content is standardized, but it depends on the milk product. For milk powders, at least protein content may be standardized. The standardization is achieved by mixing milk and products derived from milk to reach the specified levels. Fig. 2 shows part of a milk powder production process where the first milk stream 1, which can be skim or whole for exam pie, is concentrated 100 to concentrated milk 11 which is then dried 110 to milk powder 12. Permeatecontaining powder 23 can be added to the process to standardize the milk powder 12 at various points in the process and Fig. 2 shows three alternatives indicated by the dashed lines. The permeate-containing powder 23 can be mixed with the first milk stream 1 prior to concentration 100 or to the concentrated milk 11 prior to drying 110, which may be referred to as wet mixing as the milk is liquid when standardizing. The permeate-containing powder 23 can be reconstituted in water prior to wet mixing. In the third alternative, the permeate-containing powder is added to the milk powder 12 after or during drying, which may be referred to as dry mixing. By drymixing the reconstitution step can be omitted, reducing energy consumption as there is no reconstitution water to remove in the concentration and / or drying step.

[0057] Fig. 3 shows further details of the dry mixing of permeate-containing powder 23 into milk powder 12. The spray drying section 110 comprises spray drying unit 111 which receives the concentrated milk 11 and produces milk powder 12 by removing water which is carried away in exhaust gas 1110. Small milk powder particles not settled in the spray drying unit 111 are entrained in the exhaust gas 1110 and are referred to as "fines". A fines recovery system 1111 is provided to recover fines 1112 from the exhaust gas and return them to the milk powder 12, leaving gas stream 1113 to be discharged or recycled into the drying process. The permeate-containing powder 23 is dry-mixed into the recovered fines 1112 and thus also into the milk powder 12. Fines recovery systems are known to the skilled practitioner and examples are disclosed in W02017 / 076411A1 and WO2017 / 221048A1 to the same applicant. The fines recovery system 1111 typically involves a cyclone to settle fines and / or a filter unit, such as a bag filter unit. The permeate-containing powder 23 may be added to such units or the fines stream recovered by such units. In Fig. 3 the fines 1112 are shown as being returned to the spray drying unit 111, which is preferred as it may lead to a more uniform powder as the permeate containing powder takes part in the agglomeration process of the spray drying step, but it also possible to add the fines 1112 with permeate-containing powder 23 to the milk powder 12 recovered from the spray drying unit 111, especially if the two are similar in terms of powder particle size distribution. As previously mentioned, some spray drying sections 100 have a fluidized bed system downstream of the spray drying unit 111 to convey, dry and / or cool the milk powder 12, and the fines 1112 with permeate-containing powder 23, can be added to such fluidized beds.

[0058] Turning now to Fig. 4 which shows an illustrative chart with time on the abscissa and volume rates of a several flows in a milk processing system on the ordinate. The milk processing system receives a milk input 41 shown as a solid line and has a milk powder section producing milk powder and an MPC section producing MPC. For a milk processing system 4 as in Fig. 1, the milk input 41 corresponds to the sum of milk flows 1, 2, and 3. As can be seen, the milk input 41 to the milk processing system varies and is lower in a first time period T1 than in a subsequent time period T2. Such a situation can arise in regions with seasonal variation in milk production, leading to lower milk input to the milk processing system in the low volume season than in high volume season. This will the common situation, but variation in milk input 41 can arise for other reasons, such as temporary supply issues. Part of the milk input 41 is used to produce MPC in the MPC section which produces permeate 32, which is shown as dotted line in Fig. 4. The permeate 32 production is substantially constant across the first and second time period as it is generally desirable to operate the MPC section at full capacity. Another part of the milk input 41 is used to produce milk powder in the milk powder section, and the varying milk input 41 carries into the milk powder section which produces less milk powder in the first time period T1 than in the second time period T2. In the second time period, the milk powder section will typically operate at full capacity. At a given production rate of milk powder the need to standardize the milk powder gives rise to a standardization requirement 12' of the milk powder section depicted by the dashed line in Fig. 4. The standardization requirement 12' is the volume rate of permeate 32 needed to standardize the milk powder at a given. The requirement will depend on the composition of the milk input 41 and the volume of milk powder produced, but is shown as constant during each of the two time periods Tl, T2 for illustrative purposes. In the first time period Tl, the lower production of milk powder leads to a lower standardization requirement 12' and as can be seen the rate of permeate 32 exceeds the standardization requirement 12'. This surplus of permeate in the first timer period T1 is advantageously processed into permeate-containing powder according to the invention, as its shelf-life is short. An amount of permeate corresponding to the standardization requirement 12' can be used to standardize the milk powder during the first time period Tl, while only the surplus is processed into permeate containing powder. It is also possible that all of the permeate 32 is processed into permeate powder. As the milk powder section is not operating at full capacity in the first time period Tl, one or more spray drying units of the milk powder section can be used to spray dry the permeate-containing powder as shown in Fig. 1. In the second time period T2, the milk input 41 is higher and the standardization requirement 12' increases. In Fig. 4 the standardization requirement even exceeds that permeate production 23, but this will of course depend on the respective capacities of the milk powder section and MPC section in a particular milk processing system, and need not be the case. In the second time period T2, permeate-containing powder previously produced can be used to standardize the milk powder, thereby contributing to remedying the shortage of permeate compared to the standardization requirement 12'. Fig. 4 is provided to illustrate how the method according to the invention may be used to advantageously balance production in a system across periods with varying milk volume input, but it will be appreciated that the method also finds application in other situations. For example, permeate can be stored in the permeatecontaining powder which can then be transported to other milk processing plants and used for production therein, e.g. for standardization. In this way, the geographical range in which the permeate can be used is extended beyond the range reachable within the safe storage time of the liquid permeate.

[0059] Example I

[0060] This example shows two different permeate containing powders blended from a UF permeate and skim milk. The compositions are shown in Table I where "N / A" in the water row indicates that the column refer to the composition on total solids basis. The skim milk is ultra-filtrated (UF) to provide UF permeate and the retentate is concentrated and spray dried to MPC powder. The UF permeate is blended with skim milk at a ratio of 1.91:1 and 0.36:1 (Permeate:milk) to form respective liquid mixtures which is then concentrated and spray dried to Permeate Powder 1 and Permeate Powder 2, which is used at shorthand for permeate containing powders according to the invention.

[0061] Table I

[0062] The Permeate Powders 1 and 2 can be used to standardize a skim milk powder. For example, skim milk having the composition in Table I, or a skim milk powder made therefrom, can be protein standardized to 34 % protein non-fat solids by blending with Permeate Powder 1 at a ratio of 1:4.17 (Permeate:milk) or with Permeate Powder 2 at a ratio of 1:1.1 (Permeate:milk).

[0063] Example II

[0064] This example shows three different permeate containing powders blended from a UF permeate and modified whole milk. The UF permeate is the same as the one in Table I. The composition (total solids) of the three modified whole milks 3-5 blended with the UF permeate and the resulting three Permeate Powders 3-5 are shown in Table II.

[0065] The permeate:milk ratio is 2.76:1, 1.16:1, and 0.3:1 in Permeate Powder 3, 4, 5 respectively.

[0066] Table II

[0067] The Permeate Powders 3-5 can be used in standardization a whole milk powder. Table III shows the composition (total solids) of a whole milk and composition of the target protein standardized milk powder having a 34 % protein on non-fat solids basis. In addition, Table III shows the composition of a skim milk which can be used alongside the Permeate Powders to standardize the whole milk.

[0068] Using Permeate powder 3, the whole milk can be standardized by blending at Permeate:Whole milk:Skim milk ratio of 1:7.07:0.89.

[0069] Using Permeate powder 4, the whole milk can be standardized by blending at Permeate:Whole milk:Skim milk ratio of 1:4.85:0.53.

[0070] Using Permeate powder 5, the whole milk can be standardized by blending at Permeate:Whole milk ratio of 1:1.47.

[0071] Example III - Measuring lactose in solution

[0072] The pertinent contents of the applicant's published method "A l e - Water of Crystallization", Revised September 2006, is reproduced below, which may be used determine the amount of lactose in solution in the liquid mixture of the invention.

[0073] The amount of lactose which is not solution in the liquid mixture can be determined as the Degree of Crystallization of the lactose in the liquid mixture. The degree of crystallization (DoC) is calculated by:

[0074] — % water of crystallization X 19

[0075] DoC = - - - - x 100%

[0076] %L

[0077] The percentage of lactose in solution = 100 % - DoC.

[0078] The constant 19 is the relation between the molecular weight of water (MW:18 g / mol) to lactose anhydride (MW:342.3 g / mol). % water of crystallization is the difference between total moisture and free moisture in the liquid mixture, expressed as a percentage:

[0079] %water of crystallization = % total moisture — % free moisture

[0080] And %L is the lactose content of the liquid mixture expressed as anhydride, which can be determined 26242:2010 or IDF 214:2010.

[0081] The free water can be determined by drying the liquid mixture at 87 °C for 6 hours as described in the Applicant's published method "A l e - Free moisture", Revised September 2006. The total moisture can be determined by Karl Fisher Titration of the liquid mixture as described in the Applicant's published method "A 1 d - Total moisture (KF Titration)", Revised September 2006. Method A i d was originally published in 1978. The pertinent details of these methods are described below.

[0082] Free moisture procedure:

[0083] FM1. Dry a weighing dish with open lid in an oven, and cool it in a desiccator.

[0084] FM2. Weigh the empty dish (a), add approx. 3 g of sample and weigh again (b).

[0085] FM3. Place the loaded dish with open lid in the oven at 87°C ± 2°C for 6 hours.

[0086] FM4. Cool the closed dish to room temperature in desiccator, and weigh (c). b — c

[0087] FM5. Calculate % Free moisture = — x 100% b—a

[0088] Total Moisture procedure:

[0089] Apparatus and Reagents

[0090] - Karl Fisher titrator.

[0091] - Analytical balance, sensibility 0.1 mg.

[0092] - Closed glass weighing spoon.

[0093] - Karl Fisher reagent.

[0094] - Methanol, moisture free

[0095] - Sodium sulphate (Na2SO4), moisture free

[0096] - Sodium tartrate dihydrate (Na2C4H40e • 2 H2O)

[0097] Standardization

[0098] TM1. New bottles containing 'Composite 5' or 'Titrant 5' must be standardized against sodium tartrate dihydrate. 230.10 g sodium tartrate dehydrate corresponds to 36.04 g H2O.

[0099] TM2. Use procedure TM6. to TM13. using approx. 0.1 g sodium tartrate dihydrate as sample.

[0100] TM3. Fresh solvent is used between each standardization.

[0101] TM4. The standardization is accepted when two determinations agree within 0.5% relative.

[0102] TM5. The factor F (mg FhO / ml KF reagent') is calculated as: F = ax36.04x1000 > axl56.8 mlx230.10 ml ' where a = g sodium tartrate dihydrate, ml = ml KF reagent.

[0103] TM6. Choose titrant and solvent based on the standardization. Check standardization each day by doing step TM6. to TM13., using two drops of water as sample. Results must be between 99.0 and 101.0 % water. If that is not obtained, re-standardize the titrant using the procedure in TM1 to TM4.

[0104] TM7. Add fresh solvent (see remark below) into the titration vessel.

[0105] TM8. The solvent is titrated till dryness (drift < 20 pml / min. is used as stop criteria).

[0106] TM9. The sample is transferred to a closed glass weighing spoon. The amount of sample depends on the water content; an expected amount of 10-50 mg water is suitable.

[0107] TM10. The weighing spoon with a sample is placed on the balance. Zero the balance.

[0108] TM11. Dose the sample into the titration vessel. Keep the time the titration vessel is open as short as possible.

[0109] TM12. The weighing spoon with remaining powder is placed on the balance. Read the sample weight (w).

[0110] TM13. Execute the titration. When the end-point is reached (drift < 20 pml / min.) the amount of titrant is read (ml). If the amount of KF reagent added is less than 0.5 ml, increase the amount of sample to be analysed.

[0111] TM14. All measurements are to be made in duplicate.

[0112] Z? xf x 100

[0113] Calculate % total moisture = - , where b =ml KF reagent used lOOOxw ° for sample, F = factor mg H2O / ml KF reagent, and w = weight in g. Remarks:

[0114] Choosing the working media: a) Methanol is the preferred choice. b) Mixtures of methanol and chloroform are suitable for products containing fat. Methanol content should not be less than 25%. c) Mixtures of methanol and formamide improve the solubility of polar substances. The methanol content should not be less than 50%. d) KF titration has an optimum pH range of 5-7. At higher pH a side reaction occurs, which consumes iodine slowly. In a strongly acid solution, the reaction decreases proportionally to the pH value. Strong acid or bases have to be neutralized before titration.

[0115] If the drift in ml / min is not stable or the titration is very slow (more than 2-4 min.) it is an indication of troubles with side reactions or very slow liberation of the water.

[0116] List of Reference Numerals

[0117] 1 First milk stream 10 Milk powder section 11 Concentrated milk 12 Milk powder 12' Standardization requirement of milk powder section 100 Concentrator / concentration step 110 Spray drying section 111 Spray drying unit 112 Spray drying unit 113 Spray drying unit 1110 Exhaust gas with fines 1111 Fines recovery system 1112 Fines 1113 Exhaust gas stream

[0118] 2 Second milk stream 21 Liquid mixture

[0119] 22 Concentrated liquid mixture 23 Permeate-containing powder 200 Mixer / mixing step 210 Concentrator / concentration step 3 Third milk stream 30 MPC section 31 Retentate 32 Permeate 33 MPC powder 300 Membrane filtration system 310 Dryer / drying step

[0120] 4 Milk processing system 40 Common operations 41 Milk input T1 First time period T2 Second time period

Claims

Claims1. A method for processing a permeate (32) from a milk protein concentrate, abbreviated MPC, process (30), comprising the steps of- providing a milk (3) to the MPC process (30) and obtaining an MPC powder (33) and a permeate (32) using membrane filtration, which permeate (32) comprises lactose,- mixing the permeate (32) with a whole milk, a skim milk or combination thereof, (2) to obtain a liquid mixture (21), which liquid mixture has a protein content of 10 to 22 w / w% on total solids basis,- spray drying said liquid mixture (21, 22) to obtain a permeate-containing powder (23), wherein 95 % or more of the lactose in the liquid mixture (21, 22) being spray dried is dissolved in the liquid mixture (21, 22).

2. The method according to claim 1, wherein all of the lactose of the liquid mixture (21, 22) being spray dried is dissolved in the liquid mixture (21, 22).

3. The method according to any one of the preceding claims, wherein the liquid mixture (21, 22) has a protein content of 11 to 20 w / w% on total solids basis .

4. The method according to any one of the preceding claims, wherein the liquid mixture has a fat content 0.1 to 1.5 w / w% on total solids basis, preferably 0.3 to 1.2 w / w% on total solids basis, and a protein content of 15 to 22 w / w% on total solids basis.

5. The method according to any one claims 1 to 3, wherein the liquid mixture has a fat content of 1.5 to 18 w / w% on total solids basis, preferably 2 to 15 w / w% on total solids basis, and a protein content of 10 to 22 w / w% on total solids basis.

6. The method according to any one of the preceding claims, wherein a total of protein and fat constitutes at least 15 w / w% of the liquid mixture on total solids basis.

7. The method according to any one of the preceding claims, the lactose content of the liquid mixture is up to 75 w / w% on total solids basis, such as in the range to 45 to 75 w / w%.

8. The method according to any one of the preceding claims, wherein the step of spray drying the liquid mixture follows directly from the step of mixing (200) the permeate (22) with a whole and / or skim milk (2), with the proviso that optional steps of holding, transporting, homogenizing and / or concentrating (210) the liquid mixture (21) before spray drying the liquid mixture (21, 22) are possible.

9. The method according to any one of the proceeding claims, wherein the permeate-containing powder (23) is used in standardization of a milk powder (12), such as a whole milk powder.

10. The method according to claim 7, wherein the standardization comprises dry mixing of the permeate-containing powder (23) and the milk powder (12) to obtain a standardized milk powder, preferably wherein the milk powder is a whole milk powder and the dry mixing provides a standardized whole milk powder.

11. The method according to any one of the preceding claims, wherein the MPC process is performed in an MPC section (30) of a milk processing system (4), which milk processing system (4) further comprises a milk powder section (10) configured for receiving milk (1) and spray drying the milk (1) in at least one spray dryer (111-113) to provide a milk powder (12), and the step of spray drying the liquid mixture (21, 22) to obtain the permeate-containing powder (23) is performed in the spray dryer (113) of the milk powder section (10) or of the MPC section (30), preferably a spray dryer (113) of the milk powder section (10).

12. The method according to claim 9, wherein the permeate-containingpowder (23) is produced in a first time period (Tl) where a production of permeate (32) from the MPC section (30) exceeds a standardization requirement (12') of the milk powder section (10), which standardization requirement (12') is the amount of permeate (32) which the milk powder section (10) can utilize for standardizing the milk powder (12) produced in the milk powder section (10).

13. The method according to claim 9 or 10, wherein the permeate-containing powder (23) is used in standardization of the milk powder (12) produced in the milk powder section (10) in a second time period (T2) where the production of permeate (32) from the MPC section (30) is less than a standardization requirement (12') of the milk powder section (10).

14. The method according to any one of claims 8 to 10, wherein the milk processing system (4) is a single dairy powder plant.

15. The method according to any one of the preceding claims, wherein protein and fat constitutes at least 15 w / w% of the liquid mixture on total solids basis.

16. The method according to any one of the preceding claims, wherein the liquid mixture (21) is concentrated prior to spray drying providing a concentrated liquid mixture (22), preferably to a total solids content of 40 to 65 w / w%.

17. The method according to any one of the preceding claims, wherein the liquid mixture is spray dried at a temperature of 180 to 220 °C.

18. A permeate-containing powder (23) or a milk powder (12) containing the permeate-containing powder (23), obtained by any one of the preceding claims.

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