LACTOSE-CONTAINING PRODUCT IN POWDER FORM AND PRODUCTION PROCESS THEREOF

Abstract

A product in powder form having a dry matter content of at least 90% by weight on its total weight and containing lactose in a quantity of at least 85% by weight on its total weight, as well as having a high bulk density; moreover a process for the production of this product in powder form is disclosed, comprising the steps of vacuum-concentrating a lactose-containing liquid, mixing the so-concentrated liquid with a lactose-containing powder and with a high dry matter content and, finally, drying the so-obtained powdered mixture.

Claims

1. Product in powder form having a dry matter content of at least 90% by weight on its total weight and comprising lactose in a quantity of at least 85% by weight on its total weight, wherein said product has a dispersed bulk density which is greater or equal to 0.65 g/cm3.

2. Product according to claim 1, wherein the dispersed bulk density is greater or equal to 0.69 g/cm3.

3. Product according to claim 1, having a dry matter content between 90% and 99% by weight on its total weight.

4. Product according to claim 1, comprising lactose in a quantity of at least 90% by weight on its total weight.

5. Product according to claim 1, having an average particle size between 30 μm and 400 μm.

6. Product according to claim 1, said product being whey powder.

7. Product according to claim 6, having an hygroscopicity comprised between 0.70% and 1.30%, calculated as a percentage weight increase of absorbed water on the total weight of a product sample which is first lyophilized and then placed in an environment having a relative humidity of 50% at the temperature of 23° C. for a time of 60 minutes.

8. Product according to claim 6, having a specific surface area (BET) between 0.95 and 1.1 m.sup.2/g as calculated in accordance with the method USP 42.

9. Product according to claim 6, having a melting enthalpy between −105 J/g and −125 J/g.

10. Process for the production of a lactose-containing product in powder form according to claim 1, comprising the steps of: a) providing a lactose-containing liquid having a dry matter content between 18% and 65% by weight on its total weight; b) concentrating said lactose-containing liquid at a temperature between 55° C. and 200° C., for a time comprised between 1 minute and 10 minutes and at a pressure which is lower or equal to 20000 Pa, until an over-concentrated fluid product having a dry matter content comprised between 50% and 80% by weight on its total weight is obtained; c) mixing the over-concentrated fluid product obtained by the previous step with a lactose-containing powder having a dry matter content of at least 95% by weight on its total weight, until a powdered mixture having a dry matter content of at least 85% by weight on its total weight is obtained; d) drying said powdered mixture until said product in power form having a dry matter content of at least 90% by weight on its total weight and containing lactose in a quantity of at least 85% by weight on its total weight is obtained; wherein said concentration step b) comprises the following steps: providing a turbo-concentrator comprising a cylindrical tubular body having an inlet opening and a discharge opening, a heating jacket to bring the cylindrical tubular body to a predetermined temperature value, and a rotor, arranged in the cylindrical tubular body and comprising a shaft provided with elements radially projecting therefrom; supplying a continuous flow of said lactose-containing liquid in the turbo-concentrator, so as to form, through the action of the rotor, a turbulent film continuous flow; centrifuging the lactose-containing liquid against the inner wall of the turbo-concentrator, the rotor being driven into rotation at a speed which is higher or equal to 100 rpm, with formation of a highly turbulent, dynamic, thin tubular fluid film, the turbulent film of the lactose-containing liquid advancing in substantial contact with the inner wall of the turbo-concentrator towards the discharge opening so as to obtain said over-concentrated fluid product; and, discharging from the discharge opening a continuous flow of over-concentrated fluid product.

11. Process according to claim 10, wherein the lactose-containing liquid provided during said step a) is a concentrated liquid having a dry matter content comprised between 55% and 65% by weight on its total weight.

12. Process according to claim 10, wherein the lactose-containing liquid provided during step a) is a product or by-product of the milk-diary industry.

13. Process according to claim 10, wherein step b) is carried out at a pressure comprised between 15000 Pa and 11000 Pa.

14. Process according to claim 10, wherein step b) is carried out at a temperature comprised between 55° C. and 120° C.

15. Process according to claim 10, wherein in said mixing step c) the over-concentrated fluid product is mixed with a lactose-containing powder having a dry matter content of at least 97% by weight on its total weight.

16. Process according to claim 10, wherein in mixing step c) the over-concentrated fluid product is mixed with a lactose-containing powder produced during the drying step d) of a previous cycle for carrying out the process according to claim 10.

17. Process according to claim 10, wherein in said drying step d) the lactose-containing product in powder form has a dry matter content between 90% and 99% by weight on its total weight.

18. Process according to claim 10, wherein the drying step d) comprises the following steps: providing a turbo-dryer comprising a cylindrical tubular body having an inlet opening and a discharge opening, a heating jacket to bring the cylindrical tubular body to a predetermined temperature value, and a rotor, arranged in the cylindrical tubular body and comprising a shaft provided with elements radially projecting therefrom; supplying a continuous flow of said powdered mixture in this turbo-dryer; centrifuging the powdered mixture against the inner wall of the turbo-dryer, the rotor being driven into rotation at a speed which is higher or equal to 100 rpm, the particles of the powdered mixture advancing in substantial contact with the inner wall of the turbo-dryer towards the discharge opening, so as to form said product in powder form; and, discharging from the discharge opening the product in powder form.

19. Process according to claim 18, wherein drying step d) is carried out bringing the cylindrical tubular body the turbo-dryer to a temperature between 40° C. and 200° C. by heating its inner wall by means of said heating jacket.

20. Process according to claim 10, wherein drying step d) is performed at the atmospheric pressure.

21. Process according to claim 10, wherein said process is carried out continuously.

22. (canceled)

23. Process according to claim 12, wherein the lactose-containing liquid provided during step a) is a product or by-product of the milk-diary industry selected from skimmed milk, semi-skimmed milk, whole milk, whey, permeated obtained by membrane filtration of milk or permeated obtained by membrane filtration of whey.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0126] FIG. 1 shows a schematic view of a plant where the process according to the present invention can be carried out according to a preferred embodiment thereof.

[0127] FIG. 2 shows SEM images of a powder sample according to the present invention (FIG. 2, A) and of a powder sample not according to the present invention (FIG. 2, B).

[0128] FIG. 3 shows a water absorption profile, assessed for a powder sample according to the present invention (points defining a lower curve) and, at the same time, a water absorption profile for a powder sample not according to the present invention (points defining an upper curve).

[0129] FIG. 4 shows a pair of thermograms for a powder sample according to the present invention (curve at the top) and for a powder sample not according to the present invention (curve at the bottom).

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0130] A preferred embodiment of the process according to the present invention is described hereafter, which can be carried out in a plant illustrated in FIG. 1.

[0131] A falling film tubular evaporator 10 is first represented in a completely schematic manner. The evaporator 10 can be for example a multiple-effect evaporator, in which in a completely optional manner the above-mentioned preliminary vacuum concentration step can be performed.

[0132] The evaporator 10 comprises an outlet 17 for discharging a lactose-containing liquid preliminarily concentrated and having a dry matter content comprised between 55% and 65% by weight on its total weight.

[0133] Downstream of the evaporator 10 a turbo-concentrator 100 is positioned in fluid communication with the former through a pipe 12.

[0134] The turbo-concentrator 100 comprises a cylindrical tubular body 101, closed at opposite ends by bottom plates 102 and 103, and coaxially provided with a heating jacket 104, intended to be crossed by a thermal exchange fluid, for example diathermic oil, for keeping the inner wall of the cylindrical tubular body 101 at a pre-set temperature.

[0135] This heating jacket 104 has an inlet opening 104a and a discharge opening 104b, generally arranged for the inlet of the heated thermal exchange fluid and for the outlet of the cooled thermal exchange fluid, respectively.

[0136] The direction of the arrows drawn at the openings 104a and 104b exemplifies the direction of this incoming thermal exchange flow and this outgoing flow of the thermal exchange fluid, respectively.

[0137] The tubular body 101 is provided with inlet openings 105 and 106 for a continuous flow of a lactose-containing liquid.

[0138] In an entirely preferred manner, the opening 105 is in fluid communication with the outlet 17 of the evaporator 10 so as to be able to supply in the tubular body 101 of the turbo-concentrator 100 a lactose-containing fluid preliminarily concentrated for the following concentration step.

[0139] In contrast, the opening 106 is arranged for the introduction into the cylindrical body 101 of a fluid containing lactose and having a dry matter content comprised between 18% and 65% by weight on its total weight, which could not be subjected to a preliminary concentration step.

[0140] It is clear that, in the event that the plant does not envisage the presence of a preliminary concentrator 10 upstream of the turbo-concentrator 100, the latter can comprise a single inlet opening for the introduction of an above lactose-containing fluid.

[0141] The tubular body 101 pivotally supports therein a rotor comprising a shaft 108 equipped with radially projecting blade-shaped elements 109, these blades 109 being helicoidally oriented for centrifuging and simultaneously conveying towards a discharge opening 107 a flow of over-concentrated fluid product having a dry matter content comprised between 50% and 80% by weight on its total weight.

[0142] The direction of the arrows drawn at the openings 105, 106 and 107 exemplifies the direction of these incoming fluid flows and the outgoing flow of the so-concentrated fluid product, respectively.

[0143] In particular, when it enters the tubular body 101 of the turbo-concentrator 100, placed under vacuum, this continuous flow of lactose-containing liquid is centrifuged by the blades 109 of the rotor shaft against the inner wall of the cylindrical tubular body 101, which is heated by means of the heating jacket 104.

[0144] This turbo-concentrator 100 is therefore suitably arranged for performing the concentration step b).

[0145] A motor not being shown is suitably provided for the operation of the rotor of the turbo-concentrator 100 at variable speeds, which can be equal or higher than 100 rpm.

[0146] The discharge opening 107 is in fluid communication with a discharge pipe 112 in which a continuous flow of the over-concentrated lactose-containing fluid product is conveyed exiting the tubular body 101.

[0147] Once it has exited this turbo-concentrator 100, the flow of over-concentrated lactose-containing fluid product is continuously supplied to the mixer 200 through the inlet opening 205 for performing the mixing step c).

[0148] The mixer 200 is provided with a heating jacket 204 intended to be crossed by a thermal exchange fluid for keeping the over-concentrated fluid product therein at a pre-set temperature.

[0149] The mixer 200 is provided with inlet openings 205 and 206 for a continuous flow of this over-concentrated lactose-containing fluid product and for a continuous flow of lactose-containing powder having a dry matter content of at least 95% by weight on the total weight of this powder, respectively, as well as with a discharge opening 207.

[0150] A bladed shaft is installed inside the mixer 200, which is capable of centrifuging and simultaneously conveying towards the discharge opening 207 a flow of powdered mixture resulting from mixing the above two flows.

[0151] The discharge opening 207 is in fluid communication with a discharge pipe 212 in which a continuous flow of powdered mixture exiting the mixer 200 is conveyed.

[0152] The flow of powdered mixture can be finally supplied to a turbo-dryer 300 through an inlet opening 305 for performing the drying step d).

[0153] The turbo-dryer 300 comprises a cylindrical tubular body 301, closed at opposite ends by bottom plates 302, 303 and coaxially provided with a heating jacket 304 intended to be crossed by a fluid, for example a diathermic oil, for keeping the inner wall of the tubular body 301 at a pre-set temperature.

[0154] This heating jacket 304 has an inlet opening 304a and a discharge opening 304b, generally arranged for the inlet of the heated thermal exchange fluid and for the outlet of the cooled thermal exchange fluid, respectively.

[0155] The direction of the arrows drawn at the openings 304a and 304b exemplifies the direction of this incoming thermal exchange flow and this outgoing flow of the thermal exchange fluid, respectively.

[0156] The tubular body 301 is equipped with openings 305 and 306 for the inlet of the powdered mixture discharged from the discharge opening and of pre-heated hot air, respectively, as well as with a discharge opening 307.

[0157] The tubular body 301 pivotally supports therein a rotor comprising a shaft 308 equipped with blade-shaped elements 309 radially projecting therefrom, these blades 309 being helicoidally arranged and oriented for centrifuging and simultaneously conveying towards the discharge opening 307 the hot air flow and the so-dried powdered mixture, leading to the formation of a product in powder form containing lactose and having a dry matter content of at least 90% by weight on its total weight.

[0158] The turbo-dryer 300 is therefore suitably arranged for performing the drying step d).

[0159] Once it has exited the turbo-dryer 300, the flow of product in powder form containing lactose and having a high dry matter content can be continuously supplied to a separation unit not being represented, for example a screen, for the separation of a finer fraction of the product from a coarser fraction.

[0160] The fine fraction discharged from the screen advances towards a storage silo, not represented, while the coarser fraction is sent to a mill, not represented too, for the reduction of the particle size up to the desired values. The powder exiting the mill is then sent to the storage silo.

[0161] A mode for carrying out the process according to the invention is reported hereafter, carried out by the above-mentioned apparatus starting from a lactose-containing liquid available on the market.

Example 1

[0162] First of all, a preliminary concentration step is performed, supplying a whey flow with a quantity of dry matter of about 20% by weight on its total weight to a multiple-effect falling film tubular evaporator 10 (the total number of stages being equal to 3), provided by the company FARCK Spa.

[0163] The residence time inside the tubular evaporator 10 was of about 15 minutes with an advance speed of about 1000 L/h and with the following temperature profile, from the first to the third stage: 82° C./70° C./64° C.

[0164] The vacuum partial pressure was of 25000 Pa.

[0165] The liquid concentrate obtained at the outlet of the evaporator 10 contained a dry matter content of about 60% by weight on its total weight.

[0166] The liquid concentrate was then supplied, with a flow rate of 100 Kg/h to a turbo-concentrator 100 of the company Vomm, driving the rotor of the turbo-concentrator 100 at a speed of about 500 rpm and letting hot diathermic oil flow in the heating jacket 104, so as to bring the temperature inside the cylindrical tubular body 101 of the turbo-concentrator 100 to about 60° C.

[0167] The pressure inside the cylindrical tubular body 101 of the turbo-concentrator 100 was of about 15000 Pa.

[0168] The liquid concentrate was kept inside the turbo-concentrator 100 for a time of about 6 minutes.

[0169] An over-concentrated product having a dry matter content of about 75% by weight on its total weight was thereby obtained.

[0170] The over-concentrated product was discharged from the outlet 107 and then supplied to the mixer 200; the over-overconcentrated product was in form of the highly viscous fluid.

[0171] The over-overconcentrated fluid product was then subjected to a mixing step with a standard lactose-containing powder having a dry matter content of about 98% by weight, until a powdered mixture is obtained having a dry matter content of about 89% by weight on its total weight.

[0172] The mixing step was carried out for 10 minutes, at a temperature of 20° C. at the atmospheric pressure.

[0173] The bladed shaft of the mixer 200 is driven at a speed of 75 rpm for all the time of execution of the mixing step.

[0174] The powdered mixture was homogeneous and with a grainy appearance;

[0175] afterwards, it was discharged from the mixer 200 from the outlet 207, before being supplied (with the same flow rate) to a turbo-dryer 300 of the company Vomm.

[0176] A drying step was then performed inside the turbo-dryer 300: the powdered mixture was supplied through the inlet opening 305 and immediately centrifuged from the shaft 308 of the rotor driven into rotation at a speed of about 550 rpm, letting hot diathermic oil flow in the heating jacket 304, so as to bring the temperature inside the cylindrical tubular body 301 of the turbo-dryer 300 to about 150° C.

[0177] At the same time, an air flow (with a flow rate of about 1000 m.sup.3/h) pre-heated at the temperature of about 150° C. was supplied inside the cylindrical tubular body 301 of the turbo-dryer 300, through the inlet opening 306, in equicurrent with the flow of powdered mixture advancing inside the cylindrical tubular body 301 itself.

[0178] The drying step was carried out at the atmospheric pressure.

[0179] The powdered mixture was kept inside the turbo-dryer 300 for a time of about 8 minutes.

[0180] A product in powder form having a dry matter content of about 98% by weight on its total weight was thereby obtained.

[0181] The dry matter content of the above-mentioned product in powder form is calculated by using a thermo-balance at 80° C. for 180 minutes.

[0182] The lactose content inside the so-obtained product was of about 95% by weight on its total weight.

Example 2

[0183] The process according to the present invention in accordance with a different embodiment was then carried out.

[0184] A whey flow having a lactose content of about 56% by weight on its total weight and a dry matter content of 60% by weight on its total weight was continuously supplied (with a flow rate of 150 kg/h) through the opening 105 in the turbo-concentrator 100, inside which the rotor, comprising the bladed shaft 108, was driven into rotation at a speed of 900 rpm.

[0185] Immediately at the inlet of the turbo-concentrator 100, through the action of the bladed shaft 108, provided with the radially projecting elements 109, the whey flow was mechanically dispersed in particles which were immediately centrifuged.

[0186] Simultaneously, diathermic oil was flowed inside the heating jacket 104 at the temperature of 115° C., while the pressure inside the cylindrical tubular body 101 was kept at about 15000 Pa for the whole duration of the concentration step.

[0187] After a residence time of about 7 minutes inside the turbo-concentrator, an over-concentrated product with a dry matter content of 80% by weight on its total weight was continuously discharged from the opening 107.

[0188] The over-overconcentrated product was in the form of a highly viscous fluid.

[0189] The over-concentrated fluid product was then supplied in the mixer 200, through the inlet opening 205 with a flow rate of about 115 kg/h.

[0190] Simultaneously, a lactose-containing powder having a dry matter content of about 97% by weight, as well as a lactose content of 94% on its total weight, was added to the over-concentrated fluid product supplied in the mixer 200, which was mixed therewith.

[0191] In the mixer 200 the rotation speed of the bladed shaft was steadily kept at 100 rpm.

[0192] The pressure inside the mixer 200 was kept almost at the atmospheric pressure for the whole duration of the mixing step.

[0193] Afterwards, a flow of powdered mixture with a dry matter content of 90% was continuously discharged from the mixer 200.

[0194] Finally, the so-obtained powdered mixture was continuously supplied in the turbo-dryer 300, through the inlet opening 305 with a flow rate of about 345 kg/h, in equicurrent with an air flow pre-heated at a temperature of about 110° C., supplied through the inlet opening 306.

[0195] In the turbo-dryer 300, the wall temperature was kept at a value of 110° C., while the rotation speed of the rotor comprising the bladed shaft 308 was steadily kept a 900 rpm.

[0196] After a residence period of 2 minutes in the turbo-dryer 300, a flow of so-dried product in powder form was continuously discharged from the turbo-dryer 300, through the discharge opening 307.

[0197] The so-obtained product in powder form has a dry matter content of 97% by weight on its total weight, as well as a lactose content of 94% on its total weight, and it was a finely divided powder, featuring a high flowability and the crystalline appearance.

[0198] The experimental analyses conducted on the so-obtained product in powder form are shown hereafter; the product being concerned was characterized and compared with regard to its chemical-physical properties with those of a standard powder obtained by whey concentration and drying, specifically a product in powder form available on the market having a dry matter content of 97% by weight on its total weight and containing lactose in a quantity of about 95% by weight on its total weight.

[0199] Scanning Electron Microscope Analysis

[0200] With reference to FIG. 2, a photograph (FIG. 2a) taken with a scanning electron microscope (SEM) of the above powder (magnification 250×) is first shown, obtained by carrying out the process according to the present invention (Example 2).

[0201] A photograph (FIG. 2b) (SEM, magnification 250×) of the above product in powder form available on the market (hereafter “standard powder”) is shown alongside.

[0202] This standard powder was obtained by a spray-drying process.

[0203] As it is evident, the powder according to the present invention has particles with a particle size which is lower than 100 μm; the particles with a diameter which is lower than 10 μm are not many. In general, the particles have a quite compact shape, with a porous and ragged surface area.

[0204] In contrast, the particles of the above standard powder are split in two well differentiated categories: coarser globular-shaped particles with a size of about 50 μm, partially covered by particles having a size which is much lower than 20 μm.

[0205] As a whole, the particle size of the powder according to the present invention is higher than the globular-shaped particles of the above standard powder.

[0206] Specific Surface Area Assessment

[0207] The specific surface area values obtained by a BET analysis (Brunauer-Emmett-Teller) of a first and a second sample of the powder obtained in the example 2 are shown in the following Table 1; at the same time the specific surface area values obtained by a BET analysis of a first and a second sample of the above standard powder are shown.

[0208] BET analyses were performed according to the method USP 42 (United States Pharmacopeia, Physical Tests, Specific Surface Area, Volumetric Method), by weighting about 1 g of product in powder form, by introducing it in a sample tube, then placed under vacuum for 15 hours at 30° C. and, finally, by performing the BET analysis by means of the instrument SA3100 Surface Area Analyzer. The measurements were performed in duplicate.

TABLE-US-00001 TABLE 1 Average Initial Net weight BET specific BET specific weight after vacuum surface area surface area Sample (g) (g) (m.sup.2/g) (m.sup.2/g) Powder example 2 - 1.14053 1.11657 0.976 1.061 first sample Powder example 2 - 1.04053 1.01751 1.146 second sample Standard powder - 0.72035 0.69078 1.649 1.7075 first sample Standard powder - 0.85113 0.83223 1.766 second sample

[0209] As it is evident, the standard powder has a specific surface area which is significantly greater than the powder according to the present invention; specifically, the former has a specific surface area which is 60% higher than the specific surface area of the latter.

[0210] Bulk Density Assessment

[0211] The dispersed bulk density value of a sample of the powder according to the example 2 was calculated; at the same time the dispersed bulk density value of a sample of the above standard powder is reported herebelow.

[0212] The dispersed bulk density values were calculated by pouring into a hopper a quantity of material being enough to fill a cylinder with a volume of 100 cm.sup.3 placed therebelow.

[0213] A static sieve with a mesh size complying with the particle average size of the so-manipulated powder, that is a mesh which is large enough to prevent the sieve pores from being obstructed, was positioned 1.5-2 cm below the hopper discharge hole.

[0214] The cylinder filling operation was carried out at a temperature of 23° C. and under relative humidity conditions of 50%.

[0215] Advantageously, the dispersed bulk density calculated for the powder according to the example 2 was of 0.699 g/cm.sup.3, while the dispersed bulk density of the above standard powder was of 0.521 g/cm.sup.3.

[0216] Hygroscopicity Assessment

[0217] The hygroscopicity value of a sample of the powder according to the example 2 was determined; at the same time the hygroscopicity value of a sample of the above standard powder is reported hereafter.

[0218] The kinetic of water absorption was monitored over time after lyophilizing the samples for 48 hours, keeping the samples at 23° C. and 50% of relative humidity for a determined period of time.

[0219] Specifically, the weight was assessed immediately after removing the sample from the lyophilizer (0.1 min) and after 15 minutes, 30 minutes, 45 minutes, 60 minutes, 120 minutes and 150 minutes. A last measurement was performed after 3030 minutes (i.e. about 2 days) to check if the moisture absorption had reached a plateau, indicating the equilibrium water content of the sample. The results are shown in FIG. 3 and in the following Table 2.

TABLE-US-00002 TABLE 2 Time Water absorption (%) (minutes) Standard powder Powder according to the example 2 0.1 0.00 0.00 15 0.84 0.02 30 1.14 0.23 45 1.44 0.60 60 1.99 1.08 120 3.65 1.76 150 3.96 2.06 3030 3.99 2.79

[0220] As shown, the powder according to the invention has a water absorption profile which is much slower than that of the standard powder. Advantageously, the water absorption of the powder according to the invention after 60 minutes and, in general, the overall one is lower than that of the standard powder.

[0221] Melting Enthalpy Assessment

[0222] The melting enthalpy of a sample of the powder according to the example 2 was calculated by the DSC (Differential Scanning calorimetry) technique under nitrogen atmosphere; moreover the melting enthalpy value of a sample of the above standard powder was calculated by DSC.

[0223] The instrument used was the calorimeter Mettler Toledo DSC1 according to the following temperature program: from 25° C. to 250° C. with a gradient of 10° C./minute.

[0224] The melting enthalpy value calculated for the powder according to the example 2 was of −112.78 J/g, while the melting enthalpy value calculated for the above standard powder was of −75.36 J/g.

[0225] In particular, the thermograms calculated for the above two samples are shown in FIG. 4.

[0226] From FIG. 4, it can be derived that the powder as obtained from Example 2 mainly comprises a-Lactose monohydrate.

[0227] In conclusion, in view of the markedly higher melting enthalpy value for the powder according to the present invention compared to the standard powder, it can be stated that the powder according to the present invention has a substantially higher level of crystallinity compared to the standard powder.