System and method for industrial encapsulation of thermolabile substances

Abstract

A facility for industrial drying and/or encapsulation of thermolabile substances comprising at least one injection unit (1) wherein the thermolabile substance is introduced, an encapsulating material when the facility is used to encapsulate, a solvent, additives and an injection gas flow for obtaining droplets from the thermolabile substance. It further comprises a drying unit (2) through which the droplets and a drying gas are introduced for evaporating the solvent and comprises a collection unit (3) configured to separate the microcapsules generated from the drying gas and which is selected from a cartridge filter collector, a cyclone collector or a combination of the two. It also describes a method for the industrial encapsulation of thermolabile substances which is carried out at the proposed facility.

Claims

1. A method for the industrial encapsulation of thermolabile substances characterised in that it is carried out in a facility for industrial drying and/or encapsulation of thermolabile substances comprising at least: one injection unit comprising at least: one inlet for a solution; one inlet for injection gas; and one outlet for droplets through which sprayed droplets of solution are released, one drying unit arranged after the injection unit and comprising at least: one inlet for drying gas; one inlet for droplets; one longitudinal receptacle through which the droplets with the drying gas move until the solvent of the droplets evaporates, forming microcapsules; and one outlet for microcapsules and drying gas through which the microcapsules and drying gas that drags the evaporated solvent with it are released from the receptacle; one collection unit arranged after the drying unit, which is configured to separate the microcapsules generated from the drying gas; wherein the method comprises the following stages: a) preparing a polymer solution comprising: a thermolabile substance to be encapsulated, an encapsulating precursor; an organic or aqueous solvent selected from ethanol, water and a combination thereof; and b) forming droplets from a polymer solution obtained in stage (a) in the presence of an injection gas flow; c) drying the droplets obtained in stage (b) in the drying unit at a controlled temperature to obtain microcapsules; and d) collecting the microcapsules obtained in stage (c) by means of the collection unit; and wherein the stage b) of forming droplets is carried out by applying a voltage of between 0.1 kV and 500 kV to the solution and injection gas flow at the outlet of the injection unit.

2. The method of claim 1, wherein the stage c) is carried out at ambient or sub-ambient temperature.

3. The method of claim 1, wherein the encapsulating precursor of stage (a) is selected from animal, vegetable and microbial proteins.

4. The method of claim 3, wherein the encapsulating precursor of stage (a) is selected from milk serum, caseins, natural polypeptides or obtained from the genetic modification of microorganisms, collagen, soy protein and zein.

5. The method of claim 1, wherein the encapsulating precursor of stage (a) are oligosaccharides selected from lactose, sucrose, maltose and fructo-oligosaccharides.

6. The method of claim 1 wherein an additive is used in stage a).

7. The method of claim 6, wherein the additive is a surfactant.

8. The method of claim 1, wherein the stage b) of forming droplets is carried out by applying a voltage of between 5 kV and 15 kV to the solution and injection gas flow at the outlet of the injection unit.

9. The method of claim 1, wherein the stage b) of forming droplets is carried out by applying a voltage in alternating current.

Description

DESCRIPTION OF THE FIGURES

(1) As a complement to the description being made, and for the purpose of helping to make the characteristics of the invention more readily understandable, in accordance with a preferred example of a practical embodiment thereof, said description is accompanied by a set of drawings constituting an integral part thereof which, by way of illustration and not limitation, represent the following.

(2) FIG. 1a. Shows an exemplary embodiment of the facility for industrial drying and/or encapsulation of thermolabile substances wherein the injection unit (1), drying unit (2) and collection unit (3) can be seen.

(3) FIG. 1b. Shows another exemplary embodiment of the facility for industrial drying and/or encapsulation of thermolabile substances comprising an electric circuit (9) arranged at the droplet outlet (14) of the injection unit (1);

(4) FIGS. 2a-2d. Show SEM micrographs and particle size graphs obtained for an exemplary embodiment wherein Omega-3 is encapsulated in a facility whose injection unit is a nebuliser and wherein zein and pullulan have been used as an encapsulating precursor;

(5) FIG. 3. Shows a comparative viability study normalised at 1 obtained by infrared transmittance spectroscopy on KBr pellets of the microcapsules and of the non-encapsulated omega-3 obtained in accordance with the examples represented in FIGS. 2a-2d;

(6) FIGS. 4a-4h. Show SEM micrographs and particle size graphs obtained for one exemplary embodiment wherein omega-3 is encapsulated in a facility whose injection unit is an electronebuliser and wherein ethanol 70% has been used as a solvent and zein as an encapsulating precursor;

(7) FIGS. 5a-5h. Show SEM micrographs and particle size graphs obtained for one exemplary embodiment wherein omega-3 is encapsulated in a facility whose injection unit is an electronebuliser and wherein water has been used as a solvent and pullulan as an encapsulating material and Tego® as a surfactant;

(8) FIGS. 6a-6f. Show SEM micrographs and particle size graphs obtained by means of different existing commercial omega-3 encapsulation methods;

(9) FIGS. 7a-7b. Show a SEM micrograph and a particle size graph obtained for encapsulating Lactobacillus rhamnosus in a facility whose injection unit is a nebuliser;

(10) FIGS. 8a-8h. Show SEM micrograph and particle size graphs obtained for one exemplary embodiment wherein Lactobacillus rhamnosus is encapsulated in a facility whose injection unit is an electronebuliser and wherein milk serum protein has been used as an encapsulating precursor, Tego® as a surfactant and whole milk as a liquid matrix.

(11) FIG. 9. Shows a viability study presenting a comparison between Lactobacillus rhamnosus microparticles obtained by freeze-drying according to a standard method using maltodextrin as a cryoprotector and microparticles obtained using the described method and facility when the injection unit is a nebuliser and when it is an electronebuliser.

PREFERRED EMBODIMENT OF THE INVENTION

(12) What follows is a description of exemplary embodiments of the facility for industrial drying and/or encapsulation of thermolabile substances that refer to a manufacturing scale of 1 kg/h of dry or encapsulated product. It is expected that facilities that generate a higher production volume may require greater, scalable facility and processing parameters to those described and therefore the proposed parameters must not be considered limiting in nature. Likewise, exemplary embodiments of methods for the industrial encapsulation of thermolabile substances in the proposed facility are also described.

(13) As shown in FIG. 1, the facility comprises at least: one injection unit (1) comprising at least one injector with at least one inlet for a solution (6) (which already includes the thermolabile substance to be encapsulated, the encapsulating material in the case that it is used for an encapsulation process, a solvent and necessary additives), an inlet for the injection gas (8) and an outlet for droplets (14) for the solution that exits sprayed in droplets; one drying unit (2) arranged after the injection unit (1) and comprising at least one drying gas inlet (7) and an inlet for the droplets (11) that exit the injection unit (1); and comprising a longitudinal receptacle (12) which preferably has a cylindrical configuration, and which is arranged with its longitudinal direction horizontal and which has sufficient length to allow the evaporation of all the solvent of the droplets; and has a microcapsule and drying gas outlet (13) through which microcapsules pass (which are the droplets without the solvent, which has evaporated during its circulation through the drying unit); one collection unit (3) arranged after the drying unit, which is configured to separate the microcapsules generated from the drying gas (it drags the solvent which has evaporated in the drying unit) and comprises an outlet for said generated microcapsules (4) and an outlet for the drying gas (5).

(14) In one exemplary embodiment of the invention, the collection unit further comprises a solvent condensing device (10), arranged at the drying gas outlet (5), downstream from the collection unit (3). In another exemplary embodiment, the facility may comprise a drying gas recirculation device that makes it possible to redirect the drying gas towards the injection unit (1) and/or the drying unit (2).

(15) In one exemplary embodiment, the injector of the injection unit is a nebuliser consisting of a sprayer such as that described above. The injection gas flow rate, in one exemplary embodiment, is between 1 and 500 LPM. The flow rate of the injected liquid, which can be found in the form of solution, emulsion or suspension, ranges preferably between 1 ml/h and 50 L/h.

(16) In one exemplary embodiment, the facility additionally comprises a high-voltage electric circuit (9) at the outlet of the injection unit (1). The voltage used in the circuit depends on the flow rate of the injected solution and ranges between 100 kV and 500 kV. The effect achieved is that of charging the solution, focusing the droplet beam and collaborating in the formation of the droplets, improving control over the size thereof. It also influences the monodispersity of the droplets, since it generates a more homogeneous size distribution. A high monodispersity may be essential to the final product, since it enables greater homogeneity in the protection or release of the thermolabile material that has been encapsulated and, therefore, greater control over the encapsulation process.

(17) In one exemplary embodiment, the drying gas flow rate ranges between 10 and 100,000 m.sup.3/h. In the case of working with aqueous solutions, the drying is more complex because the drying gas is humidified and, therefore, it takes longer to remove the water from the solution in the drying unit.

(18) To this end, in these cases the facility may additionally comprise a device for pre-drying the drying gas in order for said drying gas introduced in said unit to be drier, thereby increasing the yield of the facility. In those cases where ethanol, isopropanol and other non-aqueous solutions are used drying is easier because the drying gas, typically air, does not include a solvent. Therefore, the drying gas is free from ethanol and, therefore, does not affect the speed of evaporation of the ethanol in the drying unit.

(19) In order to control the evaporation of the solvent in the facility more efficiently, the drying unit further comprises, in one exemplary embodiment, a pressure control device that makes it possible to work at different pressures, even in a vacuum.

(20) Preferably, the facility is designed to obtain a microcapsule size ranging between 1 and 50 micrometres in diameter. For typical drying flow rates between 10 and 100,000 m.sup.3/h, the optimum diameters and lengths of the drying unit range between 20 and 200 cm in diameter and between 20 cm and 20 metres in length. In an exemplary embodiment detailed below, the drying unit comprises a cylindrical receptacle 60 centimetres in diameter and 2 metres in length with cone-shaped inlets and outlets.

(21) Another object of the present invention is a method for the industrial encapsulation of thermolabile substances carried out in the previously described facility. This method comprises the following stages:

(22) a) preparing a polymer solution comprising:

(23) a thermolabile substance to be encapsulated, an encapsulating precursor, an aqueous or organic solvent and that will preferably be selected from ethanol, isopropanol, water and a combination thereof, and
b) forming droplets from the polymer solution obtained in stage (a) in the presence of an injection gas flow;
c) drying the droplets obtained in stage (b) in the drying unit at ambient temperature and using an air flow rate ranging between 10 m.sup.3/h and 100,000 m.sup.3/h to obtain microcapsules; and
d) collecting the microcapsules obtained in stage (c) by means of the collection unit.

(24) Throughout the specification, it is understood that the polymer solution of stage (a) may be a solution as such, i.e. a mixture of liquids or a mixture of miscible liquid-solid solids; an emulsion, i.e. a mixture of immiscible liquids; or a suspension, i.e. a mixture of insoluble solids in a liquid.

(25) Preferably, the encapsulating precursor of stage (a) is selected from animal, vegetable and microbial proteins. More preferably, the encapsulating precursor of stage (a) is selected form milk serum, caseins, natural polypeptides or obtained from the genetic modification of microorganisms, collagen, soy protein and zein. Even more preferably, the encapsulating precursor of stage (a) is selected between zein and milk serum protein.

(26) In another exemplary embodiment, the encapsulating precursor of stage (a) are oligosaccharides selected from lactose, sucrose, maltose and fructo-oligosaccharides. More preferably, the encapsulating precursor of stage (a) is a fructo-oligosaccharide.

(27) In another exemplary embodiment, the encapsulating precursor of stage (a) are polysaccharides selected from alginate, galactomanan, pectins, chitosan, rubbers, carragenates, pullulan, FucoPol, starch, dextran, maltodextrin, cellulose, glycogen and chitin. More preferably, the encapsulating precursor of stage (a) is selected from pullulan, dextran, maltodextrin, starch and any combination thereof.

(28) Optionally, in stage (a) additives are used to optimise the properties of the solution. In the present invention, additive is understood to be a substance selected from a plasticiser, tensioactive agent, emulsifier, surfactant, antioxidants or any combination thereof. Examples of additives in the present invention would be the surfactants commercially named Tween®, Span® and Tego®, more preferably Tego®, since their use in food is allowed.

(29) Preferably, stage b) of forming droplets is carried out by applying a voltage between 0.1 kV and 500 kV to the solution and drying gas flow at the outlet of the injection unit. More preferably, stage b) of forming droplets is carried out by applying a voltage between 5 kV and 60 kV to the solution and drying gas flow at the outlet of the injection unit. Preferably, the voltage applied ranges between 5 kV and 15 kV.

(30) In another exemplary embodiment, stage b) of forming droplets is carried out applying a voltage in alternating current.

(31) In one exemplary embodiment, the injection gas flow rate of stage (b) ranges between 1 and 500 LPM.

(32) Preferably, in stage (c) drying gas flow rates ranging between 10 m.sup.3/h and 100,000 m.sup.3/h are used to obtain microcapsules between 1 and 20 micrometres in diameter.

(33) The thermolabile compounds to be protected are preferably microorganisms, antioxidants, viruses, enzymes, polyunsaturated fatty acids, essential elements or any derived molecule or compound derived.

(34) According to another preferred embodiment, the thermolabile compounds are selected from the group formed by antioxidants (vitamin C, vitamin E, carotenoids, phenolic compounds such as flavonoids and resveratrol) and natural or synthetic antioxidant concentrates or isolates, biological organisms such as cells of value to biomedicine and probiotics (such as Lactobacillus and Bifidobacterium), other microorganisms such as Cyanobacterium, Rhodobacterals and Saccharomyces, prebiotics (lactulose, galacto-oligosaccharides, fructo-oligosaccharides, malto-oligosaccharides, xylo-oligosaccharides and soy oligosaccharides), symbiotics, functional fibres, oleic acid, polyunsaturated fatty acids (omega-3 and omega-6) and other marine oils, phytosterols, phytoestrogens, protein ingredients (AON and its derivatives, lactoferrin, ovotransferrin, lactoperoxidase, lysozyme, soy protein, immunoglobulins, bioactive peptides) and pharmaceutical products such as nutraceutics and other value-added preparations and substances for the pharmaceutical, biomedical, cosmetics, food and chemical industries which may be destabilised by ambient, processing or storage conditions in its commercial presentation or any combination thereof.

(35) More preferably, the thermolabile compounds are selected from the group formed by: carotenoids and polyphenols probiotics (Lactobacillus and Bifidobacterium) cells of biomedical interest for bone and tissue regeneration polyunsaturated fatty acids (omega-3 and omega-6) enzymes and other proteins of technological value selected from lactoferrin, ovotransferrin, lactoperoxidase, lysozyme, soy protein and immunoglobulins bioactive peptides selected from antihypertensive and antimicrobial peptides.

(36) Below, various exemplary methods are shown wherein the thermolabile substances to be encapsulated are omega-3 and probiotics. In a specific exemplary embodiment, the selected probiotic was Lactobacillus rhamnosus.

(37) In examples 1.1 and 1.2, non-limiting methods for encapsulating omega-3 fatty acid are described and corresponding viability studies are described.

Example 1.1 Encapsulation of Omega-3 Using a Nebuliser as an Injector

(38) In this example, a conventional nebuliser was used as an injection unit. Additionally, different natural polymer candidates are used to encapsulate omega-3 fatty acid and thus prevent its oxidation and the transmission of odours and flavours to food in direct contact, such as for example zein, pullulan, milk serum protein and modified maltodextrins (Pineflow® and Nutriose®). The capsules generated using the materials with the greatest potential, zein and pullulan, can be seen in the SEM micrographs of FIGS. 2a and 2b, respectively. The optimum sizes can be observed in FIGS. 2c and 2d, within the range of 2-10 microns, in size distribution graphs, corresponding respectively to the micrographs of FIGS. 2a and 2b. The experimental parameters and ranges of use are shown in tables 1 and 2, respectively.

(39) TABLE-US-00001 TABLE 1 Experimental parameters and operating ranges of the method of example 1.1 using zein. Minimum value Maximum value Parameters Solution flow rate 1 mL/h 50 L/h Injection gas flow rate 1 LPM 500 LPM Solution Omega-3 fatty acid 0.05% w/w 50% w/w Ethanol 70% solvent solvent Zein 0.05% w/w 50% w/w

(40) TABLE-US-00002 TABLE 2 Experimental parameters and operating ranges of the processing of example 1.1 using pullulan. Minimum value Maximum value Parameters Solution flow rate 1 mL/h 50 L/h Air flow rate 1 LPM 500 LPM Solution Omega-3 0.05% w/w 50% w/w Water solvent solvent Pullulan 0.05% w/w 50% w/w Tego 0.01% w/w 10% w/w

(41) FIG. 3 shows a viability study where it can be observed how encapsulation by means of the facility of the invention visibly improves the viability of the product (Omega-3) under all the temperature and relative humidity conditions studied. The viability curves indicate that the described facility and method enable microcapsules with viabilities substantially higher than those of the free product to be obtained.

Example 1.2 Encapsulation of Omega-3 Using an Electronebuliser as an Injector

(42) In this exemplary embodiment, an electronebuliser was used as an injection unit and the same natural polymers of example 1.2 were used. In FIGS. 4a-4d the effect of the technical field on microcapsule geometry can be observed. More specifically, said figures show the microcapsules when an electric field is not applied (FIG. 4a), when the electric field is 1 kV (FIG. 4b), when the electric field is 5 kV (FIG. 4c) and when the electric field is 10 kV (FIG. 4d). Therefore, it can be observed how an optimised electric field enables greater control over microcapsule geometry, allowing highly spherical geometries, high monodispersity and size control. In the case of zein, wherein in example 1.1 it can be observed that the capsules collapse, it can now be observed how they maintain their spherical structure due to the charge provided by the electric field, which prevents the droplets from collapsing during the evaporation of the solvent. FIGS. 4e-4h show the distribution of particle size for each of the micrographs of FIGS. 4a-4d, respectively. The experimental parameters and ranges of use are shown in table 3.

(43) TABLE-US-00003 TABLE 3 Experimental parameters and operating ranges of the method of example 1.2 using a solution comprising ethanol 70% and zein. Minimum value Maximum value Parameters Solution flow rate 1 mL/h 50 L/h Injection gas flow rate 1 LPM 500 LPM Drying gas flow rate 10 m.sup.3/h 100,000 m.sup.3/h Voltage 0 500 kV Solution Omega-3 fatty acid 0.05% w/w 50% w/w Ethanol 70% solvent solvent Zein 0.05% w/w 50% w/w

(44) In the event of using a solution which, in addition to the thermolabile substance omega-3, comprises water, pullulan and Tego®, results are obtained such as those shown in FIGS. 5a-5d, where the results have been represented in accordance with the electric field (the values of said electric field have been made to vary as described earlier: without electric field, with a 1 kV electric field, with a 5 kV electric field and with a 10 kV electric field). FIGS. 5e-5h show particle size distribution for each of the micrographs of FIGS. 5a-5d, respectively. The experimental parameters and ranges of use for obtaining the described results are shown in table 4.

(45) TABLE-US-00004 TABLE 4 Experimental parameters and operating ranges of the processing of example 1.2 using a solution comprising water, pullulan and Tego ®. Minimum value Maximum value Parameters Solution flow rate 1 mL/h 50 L/h Injection gas flow 1 LPM 500 LPM Drying gas flow rate 10 m.sup.3/h 100,000 m.sup.3/h Voltage 0 kV 500 kV Solution Omega-3 fatty acid 0.05% w/w 50% w/w Water solvent solvent Pullulan 0.05% w/w 50% w/w Tego 0.01% w/w 10% w/w

(46) FIGS. 6a-6f show SEM micrographs and particle size distribution corresponding to different methods for obtaining existing commercial microcapsules. FIGS. 6a-6d show results obtained using methods known in the state of the art. More specifically, FIG. 6a shows the results obtained using BASF (spray-drying in a nitrogen atmosphere), FIG. 6b shows the results obtained using LIFE (spray-drying in air), FIG. 6c shows the results obtained using MEG (spray-drying in air) and FIG. 6d shows the results obtained using STEPAN (spray-drying in a nitrogen atmosphere).

(47) FIGS. 6e and 6f show the results obtained using the method of the present invention (FIG. 6e shows the results obtained when the method is carried out in a facility wherein the injection unit is a nebuliser and FIG. 6f shows the results obtained when the method is carried out in a facility wherein the injection unit is an electronebuliser). As shown in said figures, a significant reduction in the size of the microcapsules and an improvement in their monodispersity is observed upon using the method and facility of the present invention.

(48) Likewise, table 5 shows a sampling study carried out by mixing a fixed amount of omega-3 microcapsules with powdered milk and water. A mixture of powdered milk and water was used as a sampling reference and the nomenclature followed to rate the samples was the following:

(49) 0: No differences with respect to the reference.

(50) 1: Small differences with respect to the reference.

(51) 3: Clear differences with respect to the reference.

(52) 5: Major differences with respect to the reference.

(53) TABLE-US-00005 TABLE 5 Omega-3 microcapsule sampling results. FISH FISH FISH FISH SAMPLE SAMPLE OIL OIL OIL OIL SAMPLE SAMPLE COLOUR COLOUR SMELL SMELL FLAVOUR FLAVOUR DISPERSION DISPERSION (T = 0 (T = 100 (T = 0 (T = 100 (T = 0 (T = 100 (T = 0 (T = 100 SAMPLE DAYS) DAYS) DAYS) DAYS) DAYS) DAYS) DAYS) DAYS) BASF 0 0 0 1 0 1 0 0 LIFE 0 0 0 1 0 1 0 0 MEG 0 0 0 1 1 3 0 0 STEPAN 0 0 0 1 0 1 0 0 Example 0 0 0 0 0 0 0 0 1.1 Example 0 0 0 0 0 0 0 0 1.2

(54) Examples 2.1 and 2.2 describe non-limiting methods for encapsulating Lactobacillus rhamnosus probiotics and describe the corresponding viability studies.

Example 2.1 Encapsulation of a Probiotic Using a Nebuliser as an Injector

(55) In this exemplary embodiment, a nebuliser was used as an injection unit and milk serum protein as a polymer to encapsulate the probiotic. FIG. 7a shows a SEM micrograph showing the microcapsules obtained and FIG. 7b shows a graph with the size distribution obtained. Table 6 shows the experimental parameters and ranges of use of this example.

(56) TABLE-US-00006 TABLE 6 Experimental parameters and operating ranges of the processing of example 2.1 using a solution comprising milk serum protein, Tego ® and whole milk. Minimum value Maximum value Parameters Solution flow rate 1 mL/h 50 L/h Air flow rate 1 LPM 500 LPM Drying gas flow rate 10 m.sup.3/h 100,000 m.sup.3/h Solution LR 0.05% w/w 50% w/w WHS 0.05% w/w 50% w/w Tego 0.01% w/w 10% w/w Whole milk solvent Solvent

Example 2.2 Encapsulation of a Probiotic Using an Electronebuliser as an Injector

(57) In this case, an electronebuliser as an injection unit was used and the same natural polymer (milk serum protein) as in example 2.1 was used. FIGS. 8a-8d show SEM micrographs of the microcapsules obtained by applying different electric current values (more specifically, without applying electric current, applying 1 kV, 5 kV and 10 kV, respectively). Additionally, FIGS. 8e-8h show the value of the size of the microcapsules obtained in said cases. Table 7 shows the experimental parameters and ranges of use of this example.

(58) FIG. 8 shows the effect of adding the bacterium on microcapsule size.

(59) TABLE-US-00007 TABLE 7 Experimental parameters and operating ranges of the processing of example 2.2 using a solution comprising milk serum protein, Tego ® and whole milk, without using electric current and using a 10 kV electric current. Minimum value Maximum value Parameters Solution flow rate 1 mL/h 50 L/h Air flow rate 1 LPM 500 LPM Drying gas flow rate 10 m.sup.3/h 100,000 m.sup.3/h Voltage 0 kV 500 kV Solution LR 0.05% w/w 50% w/w WHS 0.05% w/w 50% w/w Tego 0.01% w/w 10% w/w Whole milk solvent solvent

(60) Likewise, FIG. 9 presents a viability study showing how encapsulation by means of the facility of the present invention, in examples 2.1 and 2.2 using an electronebuliser, has better viability than encapsulation using a nebuliser.

(61) Additionally, as can be observed in the figure, both encapsulation using an electronebuliser and encapsulation using a nebuliser show better results than those obtained using the technique known as freeze-drying, which is that represented as the reference technique.

(62) The results shown are for the encapsulation of a Lactobacillus rhamnosus probiotic, taking a freeze-dried model sample of this type of probiotic (1%) and maltodextrin (10%) in a phosphate-buffered saline solution as a reference.