Process for drying milk derivatives

Abstract

A process to obtain from a milk derivative a powder product with a high degree of lactose crystallisation, non-hygroscopic, flowable, non-sticky, highly soluble, non-packing, stable and with a high bulk density.

Description

[0001] PROCESS FOR DRYING MILK DERIVATIVES

[0002] Specification

[0003] The present invention relates, in general, to a process for the industrial drying of milk derivative products. More particularly, the invention relates to a process for drying a milk derivative so as to produce a powder from the milk derivative.

[0004] The milk derivative is chosen, preferably, from whey, whey permeate, milk permeate and scotta.

[0005] As is well known, scotta is a by-product of cottage cheese production and permeates are the products resulting from an ultrafiltration process of whey or milk. In the following description, reference is made to scotta and permeates as obtained as stated above, unless otherwise specified.

[0006] The milk from which the by-product to be treated by the process of the present invention is to be obtained, may be of any origin, thus cow's milk, goat's milk, sheep's milk, etc.

[0007] Whey, the liquid part of the milk that separates from the curd during cheesemaking, is usually used in the food sector, both human and livestock.

[0008] Similar uses, i.e. for the production of products used in both human and animal feed, include milk permeate, whey permeate (obtained by ultrafiltration of milk and whey respectively) and scotta.

[0009] These milk derivatives are particularly used in powder form, which is more practical to market.

[0010] As is well known, in order to obtain powder of these milk derivatives, processes are used that include both drying and grinding.

[0011] In particular, at an industrial level, the drying of said dairy products is carried out by means of a two-stage technology, which first involves spray drying, or ‘spray

[0012] SUBSTITUTE SHEET (RULE 26) dryer’, and then fluid bed drying.

[0013] In spray drying, most of the water present in the milk derivative is quickly removed, then in the fluidised bed the second stage of drying and postcrystallisation of the lactose is carried out.

[0014] According to these processes, this derivative is concentrated to approximately 60 wt.% dry matter and after pre-crystallisation, the product obtained contains a portion of lactose in crystallised form, i.e. approximately 70 wt.% of the total weight of lactose in this product, while the remaining lactose, i.e. approximately 30 wt.%, remains in solution.

[0015] The disadvantages of this procedure relate to several factors.

[0016] On the one hand, the powders obtained using the known technique do not have a high degree of lactose crystallisation, which causes problems of hygroscopicity and packing, which have negative effects, especially during processing and storage.

[0017] In fact, when water is quickly removed, a not inconsiderable amount of the lactose remains in the amorphous state. This quantity of lactose in the amorphous state is sufficient to render the powder obtained with sub-optimal chemical-physical characteristics, i.e. it is a hygroscopic powder, with not high stability due to its tendency to darken during storage (Maillard reaction), and rheological, the powder is sticky and, therefore, not flowable.

[0018] These rheological characteristics as well as the hygroscopicity and stability of the powders obtained depend, in particular, on the post -crystallisation conditions.

[0019] On the other hand, the equipment required in the plant to produce such powder presents certain problems.

[0020] Firstly, drying plants according to the known technique require equipment

[0021] SUBSTITUTE SHEET (RULE 26) with significant volumes, especially in proportion to the quantity of powder obtainable at the end of processing, in particular spray drying towers and fluidised bed dryers.

[0022] Furthermore, such equipment has very high specific gas consumption for their operation.

[0023] The increasing demand for serum proteins from the market is consequently leading to a considerable increase in the volumes of said milk derivatives to be pulverised, and the critical points listed above constitute important limits in the production capacity of the plants and the costs that will determine the final price of the powder obtained at the end of processing.

[0024] The aim of the present invention is to offer a process for drying said dairy products which solves said and other problems of known systems.

[0025] In particular, one purpose of the process according to the present invention is, therefore, to obtain powders whose said chemical-physical and rheological properties are improved. Indeed, the improved rheological behaviour and improved physico-chemical properties enable said powders to be less, or not at all, sticky, so as to be flowable, non-hygroscopic and stable, during storage and transport in big bags and / or in bulk, until their use.

[0026] A further scope of the present invention is to provide a process for drying said milk derivatives, which can be conducted in small-scale plants in proportion to the quantity of powdered product obtainable.

[0027] A further object of the present invention is to provide a process for drying said dairy products, which can be carried out using equipment with low energy consumption, i.e. by significantly reducing the consumption, generally, of natural gas. This is achieved by a considerable reduction in heat loss due to the small size

[0028] SUBSTITUTE SHEET (RULE 26) of the plant.

[0029] These and other purposes are achieved, according to the invention, by a process for obtaining a powdered product P from a mixture M1 of crystallised particulate matter in the form of a moist powder obtained from a milk derivative chosen from whey, whey permeate, milk permeate and scotch, characterised by the fact that it comprises at least one drying step of the mixture M1 , said drying step being carried out by means of a thermopneumatic drying plant.

[0030] The use of a thermo-pneumatic drying plant makes it possible to significantly reduce energy consumption.

[0031] The drying of the mixture by means of a thermo-pneumatic drying plant preferably comprises the following stages:

[0032] (a) dispersion of the moist M1 mixture in a stream of hot air;

[0033] (b) pneumatic transport of the M1 mixture through a suitably sized drying duct, in which the dehydration of the suspended particulate matter takes place

[0034] (c) maintenance of the temperature of the M1 mixture always below the glass transition temperature of the lactose in the M1 mixture, in each section of the duct; and

[0035] (d) stabilisation, and eventual cooling, of the M1 mixture in a fluidised bed.

[0036] At the end of this drying stage, the dried mixture has a final residual moisture content of about 1 -4% by weight.

[0037] Prior to stage a), the ambient air, suitably filtered and dehumidified, can be conveyed by a fan (fan 1 ) to a heat exchanger where it is heated to the desired temperature.

[0038] The hot air passes through a Venturi system where it creates a vacuum suitable for sucking in the humid M1 mixture. Preferably, this mixture is passed

[0039] SUBSTITUTE SHEET (RULE 26) through a smoke breaker to reduce the size of the agglomerated granules present.

[0040] The M1 mixture is suspended in hot air, which transports it along the thermopneumatic drying duct where dehydration takes place.

[0041] The product temperature is maintained below that of said glass transition in each section of the duct to prevent plasticisation of the powder.

[0042] Control of the powder temperature of the M1 mixture in stage c) is achieved by adjusting the air flow in the drying duct so as to have a low residence time (approximately a few seconds) of the M1 mixture in the duct. This arrangement does not allow the dust particles in the M1 mixture to reach thermal equilibrium with the air that carries them, but allows dehydration to the desired degree.

[0043] The drying duct is preferably insulated.

[0044] In addition, the exhausted air is filtered through bag filters before it is expelled.

[0045] These and other purposes are also achieved, according to the invention, by a process for producing a powdered P product of a milk derivative in which the process comprises several steps including subjecting the milk derivative to concentration of the milk derivative, crystallisation of the lactose, post-crystallisation of the lactose and drying of the product containing the crystallised lactose, wherein the post-crystallisation of the lactose, present in said concentrated milk derivative having up to 85% by weight of dry matter, takes place in the presence of a product with a minimum amount of water and a high amount of crystallised a-lactose, such as the powdered product P obtained by the process according to the present invention.

[0046] In particular, the process according to the present invention comprises the following steps in which

[0047] SUBSTITUTE SHEET (RULE 26) A) said milk derivative to a first concentration treatment, obtaining a product

[0048] A concentrated to 60% by weight of dry matter;

[0049] B) product A obtained in step (A) to a first crystallisation (called precrystallisation), obtaining a product B

[0050] C) product B to a second concentration treatment, carried out until obtaining a product C containing 75-82% by weight of dry matter;

[0051] D) the product C obtained in step (C) and the powdered milk derivative product P according to the present invention to mixing, resulting in a mixture M

[0052] E) the mixture M to a second crystallisation (called post-crystallisation), obtaining a mixture M1

[0053] F) the M1 mixture to drying as defined above, the drying taking place along the thermo-pneumatic drying duct; and

[0054] G) the M1 mixture to stabilisation in a fluidised bed and, usually, subsequent grinding, to obtain a powder product P with a controlled particle size.

[0055] In the process of the present invention, the listed steps are to be performed in the order indicated.

[0056] The process according to the present invention is a continuous process.

[0057] At the end of this process, a powder product P having the following characteristics is obtained:

[0058] - containing at least 96.5%, preferably 97%, more preferably 98%, typically 98 to 98.5%, by weight of dry mass;

[0059] - residual moisture content of 1 .2 to 2.5 %;

[0060] - bulk density not less than 850kg / m3, preferably 880kg / m3.

[0061] In addition, the powdered product P is in the form of particles in the form of square, compact, i.e. non-porous granules. Indicatively, said granules are 65%,

[0062] SUBSTITUTE SHEET (RULE 26) preferably 75%, by weight smaller than 300 pm.

[0063] Typically, the powdered product P has a solubility of at least 99% by weight.

[0064] The milk derivative to be subjected to the process according to the present invention is a product having an amount of dry matter of, typically, at least 20%, typically 24%, by weight.

[0065] The process according to the present invention comprises various treatments of said milk derivative as well as of its processing products, said treatments being well known to a person skilled in the art, therefore they will not be described in detail.

[0066] Generally, the milk derivative used in the process according to the present invention is a product which has previously undergone pasteurisation, according to the applicable law, i.e. typically under temperature conditions of between 70-75°C, preferably 72°C, and for a time lapse of 12-20 seconds, preferably 15 seconds.

[0067] In this phase (A), an initial concentration treatment is carried out on the milk derivative. This treatment can be carried out, for example, by the water evaporation method. Usually, the milk derivative is treated in conventional evaporators.

[0068] At the end of this A phase, a concentrated A product is obtained, comprising a mass with a dry matter of typically 55 to 62% by weight of the total weight of the A product. This product still includes some lactose in solution.

[0069] In the next step (B), the concentrated product A from the previous step (A) is treated in order to obtain crystallisation of the lactose present (first crystallisation of lactose or pre-crystallisation). For this purpose, for example, product A undergoes a cooling treatment, bringing it to a temperature of 20-32 °C. The lowering of the temperature takes place in temperature-controlled refrigerated crystallisers, following a conventional procedure.

[0070] At the end of this initial crystallisation, a product B is obtained which has

[0071] SUBSTITUTE SHEET (RULE 26) crystallised lactose monohydrate, generally in an amount of 65 to 75 % by weight in relation to the weight of the entire amount of lactose in solution present in product A.

[0072] The product B thus obtained, which is at said temperature, is preferably subjected to a heating treatment (intermediate step I), up to a temperature, indicatively, of 55-63°C,

[0073] In the next step (C), the possibly heated product B is subjected to a second concentration treatment, so as to obtain a product with a dry matter mass of between 70 and 85%, preferably 72-83% more preferably 75-82%, by weight with respect to the weight of the entire concentrated product C, having a temperature of more than 50°C, typically between 60 and 62°C.

[0074] In particular, the product C has an amount of dry matter which also depends on the type of milk derivative used in the process; thus, if the starting milk derivative is permeate, the dry matter may be present up to 82% by weight of the weight of the product C obtained, while if the starting milk derivative is whey, the dry matter may be present up to 75% by weight of the weight of the product C obtained.

[0075] Said second concentration treatment is preferably carried out under vacuum, for example by using a horizontal axis concentrator.

[0076] The product C thus obtained is possibly subjected to one or more further treatments before being subjected to step D.

[0077] The product C may be subjected to a cooling treatment (intermediate step II), until a product C having a temperature, indicatively, of 30-35°C is obtained.

[0078] Subsequently, product C, possibly cooled, is subjected to pH adjustment (intermediate phase III) to obtain the desired pH.

[0079] Product C at the end of phase (C) has a pH value between 6 and 6.5.

[0080] SUBSTITUTE SHEET (RULE 26) If necessary, the product C is brought to the desired pH with the above- mentioned values by addition of a basic agent, for example, chosen from dibasic sodium phosphate, potassium hydroxide, sodium hydroxide and, preferably, calcium hydroxide.

[0081] Preferably, the product C is subjected to a cooling treatment (intermediate step IV), to cool the product C down to a temperature of 16-20 °C.

[0082] The above-mentioned cooling treatments in intermediate phases II and IV can be carried out, for example, in water-cooled shell and tube heat exchangers. In the second cooling phase, ice-cold water is used, i.e. at a temperature of approximately 2 to 5 °C.

[0083] Product C, which is ready for the subsequent phase D, has a dry mass typically between 75 and 82 per cent by weight of the entire product C.

[0084] In the subsequent step D, a mixture M is prepared. The starting components for preparing said mixture are the product C from the previous step C and the powder product P obtained according to the process of the present invention.

[0085] The product C and the powdered product P are mixed according to a weight ratio such as to obtain a mixture M having a moisture content between 4 and 10% w / w. Said moisture content is determined according to the analytical method described below.

[0086] The resulting mixture M preferably has a temperature of 5-22 °C, more preferably 18-22 °C.

[0087] The resulting powdered mixture M then has a pH of between 6 and 6.5 and a moisture content of between 4 and 10%, preferably 5-10%, w / w.

[0088] The mixing can be carried out, for example, in a vertical-axis or horizontalaxis type mixer.

[0089] SUBSTITUTE SHEET (RULE 26) In the following step E, the mixture M is subjected to a crystallisation treatment (hereinafter referred to as post-crystallisation).

[0090] A post-crystallisation method consists of passing the M-mixture under a flow of dehumidified air (relative humidity 55-65%) and a temperature, indicatively, of 18- 22 °C, preferably 20°C. For this purpose, a conveyor belt on which the M mixture to be treated is distributed is used, for example.

[0091] The post-crystallisation time is approximately 30-60 minutes, typically 45 minutes.

[0092] A crystallised M1 mixture is obtained, in which at least 90%, preferably at least 95%, by weight of the total lactose is in the form of crystallised a-lactose monohydrate.

[0093] The crystallised M1 mixture is then subjected to drying, conducted with hot air at a temperature, indicatively, of 90-150° C.

[0094] The M1 mixture appears as crystallised particulate in the form of a moist powder. This M1 mixture is subjected to a thermopneumatic drying phase as defined above.

[0095] The obtained dried mixture M2 is then, preferably, first subjected to an air separation treatment and then to a stabilisation and cooling treatment in a fluidised bed, so as to obtain a mixture (mixture M4) having a temperature of 30-43°C, more preferably 33-42°C, more preferably 35-40°C.

[0096] The resulting mixture, mixture M4, is a powder whose particles are generally larger in size than the standard ones. Therefore, it is preferable to subject the M4 mixture to a process of standardising the particle size of its particles.

[0097] Typically, this process is carried out by continuous grinding of the powder constituting the M4 mix. The grinding can be conducted, for example, with knife or

[0098] SUBSTITUTE SHEET (RULE 26) hammer mills.

[0099] After grinding, the M5 mixture is again cooled down to 15-25 °C, preferably 18-20 °C.

[0100] Cooling is performed, for example, by treating the powder with dehumidified air (relative humidity between 35 and 50%) having a temperature of 3-10 °C, preferably 5-7 °C.

[0101] The cooled M6 mixture obtained from this cooling treatment is again separated from the air by, for example, a third cyclone.

[0102] The powdered product P thus obtained will be partly marketed and partly reused in the process of the present invention as previously described.

[0103] In the process according to the present invention at least some of the equipment used has a much lower specific volume than that used in processes of known art. Therefore, the specific consumption of natural gas for operating the equipment according to the invention is much lower than that required for operating the equipment in the case of the conventional process.

[0104] The process according to the present invention leads to the crystallisation of lactose in the form of a-lactose monohydrate with a high degree of crystallisation, indicatively equal to or greater than 90%, preferably 95%, by weight before entering the dryer. The high degree of crystallisation ensures a powder with said physicochemical and rheological properties, i.e. non-hygroscopic, stable over time and flowable.

[0105] Although the present invention is not limited by any particular theory of operation, it is believed, that with this process, the kinetics of lactose crystallisation increases, which leads to the achievement of a high degree of lactose crystallisation and to a crystallised lactose with a different morphology than with spray dryer

[0106] SUBSTITUTE SHEET (RULE 26) processes.

[0107] It is believed that this effect on crystallisation kinetics is due, on the one hand, to the lower water activity obtained by mixing the powder with the concentrate, as opposed to the known technique procedures where this lower water activity is caused by its evaporation, and, on the other hand, to the crystalline a-lactose monohydrate present in the M-mixture, which is subject to the post-crystallisation phase: a-lactose monohydrate has the trigger function on the post-crystallisation process of lactose, which is present in the aqueous phase of the concentrated product.

[0108] The low water activity and the presence of a-lactose monohydrate have a positive effect on crystallisation kinetics that is evident in the achievement of the said high degree of lactose crystallisation.

[0109] It is also believed that mixing the concentrated C product with the powdered P product results in a re-agglomeration of the particles and that the subsequent post-crystallisation of lactose leads to a natural increase in particle size with each recycling. Consequently, standardisation of the particle size of the powder product obtained is preferable.

[0110] A constant particle size distribution in the powder of the mixture M5 and, in general, in the powder product P of the process according to the present invention is preferable. The powder, for example the powder fed into the mixer, having a constant particle size allows optimal mixing and has good flowability.

[0111] As a result of the process according to the present invention, drying of the mixture M1 can be carried out in a plant with a low specific volume, up to at least 20 times less than plants of known technique. The equipment of the drying process of the present invention has a total specific volume of 30m3per ton / h of dried powder

[0112] SUBSTITUTE SHEET (RULE 26) produced, whereas a spray dryer type plant has a specific volume of about 690m3per ton / h.

[0113] The low specific volume of the equipment limits heat dispersion, resulting in lower methane gas consumption, at least indicatively about 60% less, e.g. 53Sm3 / ton of dried powder versus 129Sm3 / ton of dried powder for a spray dryer.

[0114] In each step of the process according to the present invention the product is maintained at a temperature below said glass transition temperature corresponding to the value of the water content in the product at that step of the process, so as to avoid the known phenomena of plasticisation.

[0115] In the process according to the present invention, the concentrated product C is brought to pH with the above-mentioned desired values in order to neutralise the lactic acid present in the concentrated product C. It is known, in fact, that lactic acid hinders the crystallisation of lactose and the evaporation of residual water. The basic agent, added within the limits of the regulations in force, neutralises the lactic acid (hygroscopic) by forming calcium lactate (non-hygroscopic), a salt already normally present in said milk derivatives.

[0116] Further features and details may be better understood from the following example, provided for illustrative, but not limiting purposes, of the process according to the present invention.

[0117] According to a form of embodiment of the process according to the present invention, the process comprises the following steps illustrated in the Table A.

[0118] SUBSTITUTE SHEET (RULE 26) Properties and Methods

[0119] The product samples were subjected to analyses to assess their physical and chemical characteristics and chemical composition. The methods adopted to carry out these analyses are described below:

[0120] - moisture content: the value is determined by thermogravimetric analysis measuring loss in weight using the METTLER TOLEDO HX204 Moisture Analyzer thermobalance at a temperature of 105°C;

[0121] - bulk density: determined with Tap Density Tester Mod. 7700 FUNKE GERBER;

[0122] - solubility: determined according to method ISO 8156:2005;

[0123] - blanched particles: determined according to ADPI (American Dairy Products Institute), Bulletin 916, method no. A 4a;

[0124] - particle size distribution measured with a HOSOKAWA automatic sieve shaker, model ALPINE 200 LS;

[0125] - chemical composition: by means of a Broker near-infrared (NIR) spectrometer, model MPA II;

[0126] - scanning electron microscope (SEM) analysis: performed in high vacuum after surface metallisation.

[0127] Example

[0128] Whey permeate with 24% dry matter by weight, collected in suitable tanks, is pasteurised at 72°C for 15 seconds.

[0129] The whey permeate, once pasteurised, undergoes a pulverisation process starting with a concentration step by evaporation of the water leading to an A product with a dry matter concentration of 58% by weight.

[0130] By cooling to a temperature of 30°C, pre-crystallisation of the lactose in the

[0131] SUBSTITUTE SHEET (RULE 26) permeate is achieved.

[0132] This yields a crystallisation yield in a-lactose monohydrate of approx. 70 % (product B).

[0133] The product B obtained is preheated to 60°C, and then concentrated in a horizontal-axis concentrator (capacity of 3.6 tons / h); in this way, at a temperature of between 60°C and 62°C, part of the water evaporates, bringing the dry matter to a value of between 80% and 83% w / w, resulting in product C.

[0134] Subsequently, the concentrated product C in a quantity of approx. 2.4 tons / h is cooled to a temperature of between 30°C and 35°C by means of a shell and tube heat exchanger, which is fed with water.

[0135] Subsequently, calcium hydroxide is added to the concentrated C product in order to adjust the pH value to between 6 and 6.5.

[0136] The concentrated product C is then further cooled to a temperature of between 16°C and 20°C by means of a second shell and tube heat exchanger, supplied with ice water.

[0137] The concentrated and cooled product C, in an amount of 2.4 tons / h, is then fed into a mixer in which it is mixed with powdered product P obtained at the end of the process according to the present invention, in an amount of 8.6 tons / h, at a temperature of 20°C, resulting in a mixture M.

[0138] The obtained mixture M has a temperature of between 20°C and 22°C and a humidity of about 5%. The mixer used is a vertical axis mixer.

[0139] The M mixture is then fed and transported on a conveyor belt on which it remains for a period of 30 minutes, where post-crystallisation of the lactose takes place. At the end, a powder (M1 mixture) with a moisture content of 5 wt% with a high degree of lactose crystallisation (above 90 %) is obtained.

[0140] SUBSTITUTE SHEET (RULE 26) Subsequently, the M1 mixture is dried by means of a thermopneumatic drying plant, which essentially consists of a one- or two-loop duct with one or more risers. The air flow is provided by two fans: fan 1 on the supply side; fan 2 on the suction side.

[0141] The characteristics of the thermopneumatic drying duct used in the example are shown in Table B below.

[0142] Table B

[0143] The ambient air is filtered and then conveyed by fan 1 into a heat exchanger in which the air is heated to a temperature of 130°C.

[0144] The hot air passes through a Venturi system in which it creates a vacuum suitable for sucking in the moist M1 mixture with crystallised particles (11 tons / h; 5% moisture by weight), this mixture passes through a smoke breaker to reduce the size of the agglomerated granules present.

[0145] The moist M1 mixture is thus suspended in hot air and transported along the thermopneumatic drying duct where dehydration takes place. The product temperature is kept below the glass transition temperature of the lactose in the M1 mixture in each section of the duct to prevent plasticisation of the powder.

[0146] The dried particulate is separated from the air by a cyclone.

[0147] The exhausted air, after filtration with a bag filter, is expelled by fan 2.

[0148] Table C below shows the dust temperatures and humidity in the different sections of the drying duct. The dust temperatures are compared with the glass transition temperatures corresponding to the humidity.

[0149] SUBSTITUTE SHEET (RULE 26) Table C

[0150] The resulting powder (M4 mixture) is processed in mills to standardise its particle size, resulting in an M5 mixture with a substantially constant particle size.

[0151] The M5 mixture is then transported and simultaneously cooled to a temperature of about 20°C by dehumidified cold air having a temperature of 5°C and a relative humidity (RH) of 50%, resulting in a powder mixture 6.

[0152] Said mixture 6 is sent to a third cyclone so as to separate the same powder from the air, thus obtaining a powder product P.

[0153] The powder product P obtained is divided into two parts: a first part, 8.6 tons / h, is reused in the process by feeding it into the mixer for re-agglomeration with the concentrate and post-crystallisation; the second part, in a quantity of about 2 tons / h, is sent to the silos by pneumatic transport and constitutes the finished product.

[0154] The process which is the subject of the invention has been described as being carried out following the processing of a milk derivative, specifically a specific concentration and crystallisation process. But it is understood that the protection is to be referred to the process of drying a mixture of crystallised particulate matter in the form of a moist powder always obtained from a milk derivative chosen from whey, whey permeate, milk permeate and scotch, but independently of the process by which said mixture is obtained.

[0155] SUBSTITUTE SHEET (RULE 26)

Claims

CLAIMS1. A process to obtain a powdered product P from a mixture M1 of crystallized particulate matter in the form of a wet powder obtained from a milk derivative chosen from whey, whey permeate, milk permeate, and scotte, characterized by including at least one drying step of the M1 mixture, said drying step being carried out by means of a thermopneumatic drying plant.

2. The process according to the previous claim, wherein the steps of: a. Dispersion of the moist M1 mixture in a stream of warm air; b. pneumatic transport of the M1 mixture through a drying duct, wherein dehydration of suspended particulate matter takes place; c. Maintaining the temperature of the M1 mixture always below the glass transition temperature of lactose in the M1 mixture, in each section of the conduit; and d. Stabilization and cooling in a fluidized bed of the M1 mixture.

3. The process according to the previous claim, wherein, prior to the dispersion of the humid M1 mixture in a stream of warm air, the ambient air is conveyed by a first fan into a heat exchanger so that it is heated to a specified temperature.

4. The process according to the previous claim, wherein hot air passes through a Venturi system wherein it creates a suitable vacuum to draw in the moist M1 mixture.

5. The process according to one of claims 2 to 4, wherein the M1 mixture is passed through a granule breaker to reduce the size of the agglomerated granules present.

6. The process according to one of claims 2 to 5, wherein the temperature control of the M1 mixture powder in step (c) is achieved by adjusting the air flow rate inthe drying duct so as to have a low residence time of the M1 mixture in the duct.

7. The process according to one of claims 2 to 6, wherein the duct is insulated.

8. The process according to one of claims 2 to 7, wherein the hot air has a temperature between 90°C and 150°C.

9. The process according to one of claims 2 to 8, wherein the spent air obtained from step (c) is filtered through bag filters before it is expelled.

10. Process to obtain a powdered P product from a milk derivative chosen from whey, whey permeate, whey permeate, and scald, said process includes the following steps wherein it undergoes:A) said milk derivative to an initial concentration treatment (step A), resulting in a product A concentrated to 60 percent dry matter by weight;B) product A, obtained in stage (A), to a stage of first crystallization or precrystallization (stage B), resulting in product B; said procedure being characterized by the fact that:C) said product B is subjected to a second concentration treatment (step C) to obtain a product C having 75 to 82 percent dry matter by weight;D) product C obtained in step C and powdered product P of milk derivative according to the present invention are subjected to mixing (step D) resulting in a mixture M;E) the M mixture obtained in the previous step is subjected to a postcrystallization step (step E), resulting in an M1 mixture;F) M1 mixture is subject to a drying step according to one of the previous claims;G) the M1 mixture is subjected to a stabilization and cooling stage in a fluidized bed and subsequent, grinding to obtain a powder product P.

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