Particulate Materials

Abstract

Novel particulate materials that have been made by a spray process have at least 80% of particles of the same morphology. The particulate materials also have a mono-dispersivity index of not more than 1.2. In preferred particulate materials, the particles have at least two components, a first component being a matrix material and a second component being an active ingredient retained by said first component. Methods of making such particulate materials are also disclosed.

Description

The present invention will now be described by way of example only with reference to the accompanying drawings in which:

FIG. 1 is a schematic view of particle morphology formation;

FIG. 2 is a schematic view of spraying apparatus;

FIG. 3 is a micrograph of the particulate material of sample 1 described in Example 1;

FIG. 4 is a micrograph of the particulate material of sample 2 described in Example 1;

FIG. 5 is a micrograph of the particulate material of sample 4 described in Example 1;

FIG. 6 is a micrograph of the particulate material of sample 5 described in Example 1;

FIG. 7 is a micrograph of the particulate material of sample 6 described in Example 2;

FIG. 8 is a micrograph of the particulate material of sample 6 described in Example 2 taken at a higher magnification;

FIG. 9 is a micrograph of the particulate material of sample 12 described in Example 2;

FIGS. 10 and 11 are micrographs of the particulate material of sample 12 described in Example 2 taken at a higher magnification;

FIGS. 12 and 14 are micrographs similar to FIGS. 9 to 11 but of the particulate material of sample 11 described in Example 2;

FIGS. 15 to 19 are, respectively, micrographs of the particulate materials of samples 21, 23 to 25 and 27 described in Example 4; and

FIGS. 20 and 21 are, respectively, micrographs of the particulate materials of samples 31 and 32 described in Example 7.

As mentioned above, the morphologies are identified as:

• • spherical
  • hollow sphere
  • roughly spherical
  • cenospheres
  • packed porous network.

Referring to FIG. 1, the particulate material of the present invention preferably comprises particles of one of the morphologies shown. As shown, as the droplet is subjected to the gas flow, a crust is formed and each particle is then able to adopt one of the morphologies shown or a spherical morphology (not shown).

In the hollow sphere morphology, the particles generally have a shape close to or actually spherical and are hollow.

The roughly spherical morphology has particles that are generally round, ie sphere-like, in shape but they do not have a smooth surface. The surface appearance can vary from slightly rough, almost scale-like in appearance to very rough, irregular and knobbly or protrusion-covered surfaces. The particles are solid apart from a very small irregular central cavity, which arises as a result of density differences between the precursor formulation and the particle.

In the cenospheres morphology, the particles generally have a shape close to a sphere but are more likely to be slightly elongate or elliptical in appearance as compared to a true sphere and have an opening through the shell into the hollow centre.

As indicated in FIG. 1, the particle density varies across the morphologies as does the release mechanism of the active from the matrix.

In terms of applications, slow dissolution of the particles and/or dispersion of active ingredients therein may be achieved by selecting film-forming materials and morphologies, ie spherical, hollow spheres and cenospheres; medium dissolution of the particles and/or dispersion of active ingredients therein may be achieved by selecting particles having a morphology suited to erosion mechanisms, ie roughly spherical; and fast dissolution of the particles and/or dispersion of active ingredients therein may be achieved by selecting the packed porous network morphology.

A spherical morphology would be similar to the hollow sphere morphology shown in FIG. 1 except that it would be solid apart from a very small irregular central cavity, which arises as a result of density differences between the precursor formulation and the particle. In this instance, the particle would have high density and the release would be erosion controlled.

Referring to FIG. 2, spraying apparatus 10 has a spray tower 12 at the top of which is located a spray head (not shown). A feed line 14 supplies a precursor formulation to the spray head and a gas supply line 16 provides gas via a heater or cooler 18 to the tower 12 for the gas to impinge on droplet streams emitted from the spray head. An exhaust line 20 feeds the particles and exhaust gas to a separator 22 from which products off take 24 and a gas exhaust 26 exit.

As shown, the gas flow is concurrent with the droplet streams. In other arrangements, the gas flow may be counter-current with the gas entering the lower section of the spray tower 12 and being exhausted at its upper end above the spray head.

The spray head (not shown) may be a nozzle or rotary atomiser in conventional spray drying; alternatively, in accordance with the present invention, it is an accoustic spray head of the type described in WO 94/20204.

The invention will now be illustrated further with reference to the following Examples.

The following tests were performed on the samples:

• • bulk density measurement
  • dispersibility in water
  • SEM micrographies
  • residual moisture
  • retention of active
  • volume mean size.

The tests were carried out as follows:

Bulk Density

The following process was used to measure the bulk density of the spray-dried particulate material. A 100 ml beaker was weighted empty. Particulate material was added to the beaker, which was then tapped and shaken manually to cause the particles to settle and compact. This step was iterated until no further volume change was observed. The now full beaker was weighed. The weight of the empty beaker was subtracted from the weight of the full beaker to obtain the weight of the particulate material in the beaker and the bulk density was then calculated by dividing the weight (in kilograms) by 10⁻⁴ (the volume of the beaker in m³).

Dispersibility in Water

A measured amount of particulate material, approximately 1 g, was poured into a beaker containing a 100 g of demineralised water and its capacity to be completely dissolved or, on the contrary, to remain in particulate form or to aggregate into lumps was observed, together with the time needed to achieve the final condition.

Water Amount Measurement

The water amount in a material can highly influence its physical and chemical properties, causing for example its plasticisation and consequently reducing its glass transition temperature. In the Examples, the test was carried out to measure the residual moisture in the particulate material to enable an appropriate correction to be made to the measured active ingredient retention, which is at least partly dependent on this variable.

The moisture content of the particulate material was measured using a Karl-Fisher water measurement apparatus. To determine the moisture content in a non-aqueous solvent for the particulate material, ie ethanol, 100 μlitres of ethanol was injected into the apparatus and the moisture content of the solvent was measured. Using the same solvent batch, a measured amount, around 1 mg, of particulate material was dissolved in ethanol and 100 μlitres of the solution was injected into the Karl-Fisher apparatus and the moisture content of the solvent was measured. As the amount of water in the pure solvent and in the solution are known and the exact weight of the dissolved and injected particulate material is known, the residual moisture in the sample can be calculated.

Retention of Active Ingredient

In each test, 15 g of particulate material, together with several drops of silicon (as an antifoaming agent) and some boiling chips, were dispersed in 250 ml demineralised water in a distillation apparatus. The mixture was heated until the mixture was boiling. Heat was then applied to the mixture to maintain it at boiling temperature of the mixture for three hours. The apparatus was then allowed to cool to room temperature and the height of oil collected in the distillate collection column was measured using a precision calliper, and the percentage of oil retained was calculated using the formula:

$\%\mathrm{retention}=\frac{\left(X\mathrm{ml}\mathrm{distillate}\right)\left(\mathrm{specific}\mathrm{gravity}\mathrm{distillate}\right)}{\left(\%w\text{/}w\mathrm{load}\right)\left(\mathrm{dry}\mathrm{weight}\mathrm{particulate}\mathrm{material}\right)}\left(100\right)\left(1.04\right)$

The (1.04) in the formula is a correction factor for residual moisture, in this instance 4%.

EXAMPLE 1

In this Example, a modified food starch derived from waxy maize sold under the trade name HI-CAP 100 by National Starch & Chemical Company, USA was used to make particulate materials according to the invention. This particular product has been found to be especially suited for the encapsulation of flavours, clouds, vitamins and spices, at high oil loading.

In this Example, the particulate material was made only using the HI-CAP 100. The HI-CAP 100 is formed into a dispersion which is then subjected to a spray process. The dispersion was prepared following the recommended procedure to prepare a dispersion of HI-CAP 100, namely:

1. disperse HI-CAP 100 in water at ambient temperature with good
   agitation;
2. heat the dispersion preferably with agitation to 82° C. to ensure the
   HI-CAP 100 is completely dispersed;
3. cool the solution to ambient temperature.

Several dispersions were made using HI-CAP 100 at solid concentration of 25%, 35% and 45% by weight, the balance being water; details of the dispersions are shown in Table 1.

The dispersions were then each subjected to a spray process using apparatus shown schematically in FIG. 2 and more specifically described in WO 94/20204. The process conditions of inlet and outlet temperature, as well as jets number and size for each sample are described in Table 2.

The resultant particulate samples were free flowing and non-dusty.

The bulk density of the resultant particulate samples were measured as described above and the results are shown in Table 3.

TABLE 1
		Density	Viscosity	Surface Tension
Sample	Cs %	[kg/m3]	(Pa · s)	(N/m)
1	25%	1100	0.07	0.03
2	35%	1200	0.1	0.03
3	45%	1300	0.15	0.03
4	35%	1200	0.1	0.03
5	35%	1200	0.1	0.03

TABLE 2
		Jet
		Reynolds	Frequency	Weber	Inlet T	Outlet	Jets no × diameter
Sample	Ohn	No	fw [kHz]	No	° C.	T ° C.	[μm]
1	0.8	Approx 25	11	600	250	130	25 × 120
2	1	Approx 18	7	600	210	120	15 × 150
3	2	Approx 13	6	600	210	110	20 × 150
4	1	Approx 20	10	900	210	110	30 × 120
5	1	Approx 20	10	900	230	126	30 × 120

TABLE 3
Sample Density [kg/m3]
1      340
2      460
3      340
4      450
5      400

All of the samples were tested for dispersibility as described above. All of the particulate material dispersed well in the water within a few minutes, there being no discernible amounts of particulate material present whether as added or aggregating in clumps.

Reference is now made to FIGS. 3 to 6.

The particles sizes are in the range from 250 to 500 microns depending on the nozzles used.

In FIGS. 3 and 4 (Samples 1and 2, respectively), roughly spherical morphologies are exhibited by the particulate material, each morphology being at the extreme of roughly spherical.

In FIG. 5, roughly spherical morphology is exhibited and in FIG. 6 cenospherical morphology is exhibited.

EXAMPLE 2

Further samples of particulate materials according to the invention were made in accordance with the procedure described in Example 1, with the exception that an active ingredient was added to the process. The active ingredient was orange oil—Givaudan orange oil: code 705820, Single Fold, Citrus Valley Blend available from Givaudan, USA. In making the emulsion, the orange oil was added after step 3 with suitable agitation to disperse it in the water/starch dispersion, which dispersion was then subjected to an emulsification process using a Silverson mixer to create an emulsion in which the oil particles were of the order of 1 to 2 μm. The parts by weight of the components in the emulsion were as shown in Table 4.

TABLE 4
Ingredient Parts by Weight
HI-CAP 100 24
Orange Oil 16
Water      60

The emulsion had a density of 1300 kg/m3, a viscosity of 0.15 Pa·s and a surface tension of 0.03 N/m.

These samples were used to generate particulate under the conditions recorded in Table 5.

The resultant particulate samples were free flowing and non-dusty.

The bulk density, orange oil retention and residual moisture content were determined as described above and the results are shown in Table 6.

TABLE 5
		Jet
		Reynolds	Frequency	Weber	Inlet T	Outlet	Jet no × diameter
Sample	Ohn	No	fw [kHz]	No	° C.	T ° C.	[μm]
6	1	17.5	5.4	600	190	108	16 × 200
7	1	17.5	5.4	600	215	102	16 × 200
8	2	12	6	600	190	98	30 × 150
9	2	13	6	600	200	108	25 × 150
10	2	13	6	600	250	120	25 × 150
11	2	13	6	600	215	110	25 × 150
12	2	20	9	1500	210	115	15 × 150
13	1	17.5	5.4	600	210	120	15 × 200
14	1	17.5	5.4	600	220	115	15 × 200
15	2	14	9	900	190	112	15 × 120
16	2	13	9	900	200	107	20 × 120
17	1	17.5	5.4	600	180	89	15 × 200

	TABLE 6
		Density	Orange Oil
	Sample	[g/cm3]	Retention %	Residual moisture %
	6	480	93.40	3.6
	7	510	89.80	4.48
	8	470	96.40	2.7
	9	430	93.50	3.0
	10	450	95.80	2.9
	11	270	97.50	2.57
	12	500	94.40	2.83
	13	500	94.36	3.1
	14	450	95.60	3.3
	15	440	96.60	2.60
	16	470	98.20	2.58
	17	295	94.80	2.63
	18	530	89.20	4.70

All of the samples were tested for dispersibility as described above. All of the particulate material dispersed well in the water within a few minutes, there being no discernible amounts of particulate material present whether as added or aggregating in clumps.

Reference is now made to FIGS. 7 to 11.

In FIGS. 7 and 8 (Sample 6), the particulate material exhibits hollow spherical morphology, the voids left by the evaporation of encapsulated oil particles clearly being visible in the wall structure of the hollow spherical particle. In FIGS. 9 to 11 (Sample 12), the particulate material exhibits roughly spherical morphology, the encapsulated oil particles clearly being visible in the wall structure of the roughly spherical particle. In FIGS. 12 to 14 (Sample 11), the particulate material exhibits cenospherical morphology, the encapsulated oil particles clearly being visible in the wall structure of the cenospherical particle.

EXAMPLE 3

Example 1 was repeated but using a modified starch sold under the trade name Tuk 2001 by National Starch & Chemical Co, USA was used to make particulate materials according to the invention. The details of the dispersion samples made using Tuk 2001 starch material are given in Table 7 below.

A comparative sample 20 was also prepared.

TABLE 7
		Density	Viscosity	Surface Tension
Sample	Cs %	[kg/m3]	(Pa · s)	(N/m)
18	34%	1200	0.1	0.03
19	34%	1200	0.1	0.03
20*	34%	1200	0.1	0.03
*Comparative

The dispersion samples 18 and 19 were each then subjected to a spray process in accordance with the invention using the conditions shown in Table 8.

Sample 20 was subjected to a rotary spray process using a rotary wheel atomiser from Niro in which the inlet temperature was 230° C., the outlet temperature was 111° C. and the rotary wheel speed was 2000 rpm.

The resultant particulate samples 18 and 19 were free flowing and non-dusty. In contrast, sample 20 was extremely dusty and not free flowing.

TABLE 8
		Jet
		Reynolds	Frequency		Inlet T	Outlet	Jets no × diameter
Sample	Ohn	No	[kHz]	fw	° C.	T ° C.	[μm]
18	2	10	9	600	250	110	21 × 120
19	1	18	6	600	250	120	10 × 200

The bulk density of the resultant particulate samples were measured as described above together with the volume mean size (VMS) and the mono-dispersivity index (MDI) and the results are shown in Table 9.

	TABLE 9
	Sample	VMS [μm]	MDI	Density [kg/m3]
	18	275	0.4	370
	19	433	0.6	270
	20*	150	1.4	260
	*Comparative

The samples were tested for dispersibility as described above. In respect of samples 18 and 19, all of the particulate material dispersed well in the water within a few minutes, there being no discernible amounts of particulate material present whether as added or aggregating in clumps. In contrast, sample 20 took a relatively long time, ie of the order of 45 minutes, to disperse, forming aggregates in the process.

The particulate material of sample 18 was essentially completely of cenospherical morphology whereas the particulate material of sample 19 was essentially completely of a denser, roughly spherical morphology. The particulate material of sample 20 exhibited mixed morphologies.

EXAMPLE 4

Example 2 was repeated using the Tuk 2001 starch material identified in Example 3 and an acord fragrance available from Quest Fragrances, Ashford, Kent, GB. Emulsion samples were made as shown in Table 10. In contrast to the emulsions in Example 2, these emulsions were prepared by weighing the ingredients into a tank, recirculating the ingredients through an inline mixer to form a premix and then passing the premix through an APV Rannie 2-stage high pressure homogeniser.

TABLE 10
		Density	Viscosity	Surface Tension
Sample	Cs %	[kg/m3]	(Pa · s)	(N/m)
21	40	1250	0.17	0.03
22	50	1300	0.2	0.03
23	50	1300	0.2	0.03
24	50	1300	0.2	0.03
25*	40	1250	0.17	0.03
26*	50	1300	0.2	0.03
27*	50	1300	0.2	0.03
*Comparative

The emulsion samples 21 to 24 were each then subjected to a spray process in accordance with the invention using the conditions shown in Table 11.

Samples 25 and 26 were subjected to a rotary spray process as described in Example 3. Sample 27 was subjected to a two-fluid nozzle spray process in which pressurised air is used to atomise the emulsion. The run conditions for sample 27 were inlet temperature=230° C., outlet temperature=120° C. and air pressure=2 bar.

TABLE 11
		Jet
		Reynolds	Frequency	Weber	Inlet T	Outlet	Jets no × diameter
Sample	Ohn	No	fw [kHz]	No	° C.	T ° C.	[μm]
21	2	9	7	600	190	108	21 × 120
22	2	13	4	900	190	120	10 × 200
23	2.4	15	8	1500	190	110	13 × 150
24	1.6	12	5	800	190	115	15 × 170

The resultant particulate samples 21 to 24 were free flowing and non-dusty. In contrast, samples 25 to 27 were extremely dusty and not free flowing.

The bulk density of the resultant particulate samples were measured as described above and the mono-dispersivity index (MDI) and the results are shown in Table 12. The weight mean size (WMS) was also determined and is also shown in Table 12. The WMS was determined by sieving 100 g of particulate material using 6 sieves having mesh sizes in the range 710 to 125 μm for 30 minutes and plotting the resultant weight distribution of particles at each size to enable the weight mean size to be interpolated.

	TABLE 12
	Sample	WMS [μm]	MDI	Density [kg/m3]
	21	230	0.4	610
	22	360	0.6	510
	23	320	0.8	530
	24	330	0.9	410
	25*	380	1.3	420
	36*	375	1.4	460
	27*	290	1.6	380
	*Comparative

The samples were tested for dispersibility as described above. In respect of samples 21 to 24, all of the particulate material dispersed well in the water within a few minutes, there being no discernible amounts of particulate material present whether as added or aggregating in clumps. In contrast, samples 25 to 27 took a relatively long time, ie of the order of 35 minutes, to disperse, forming aggregates in the process.

The morphologies of the samples in this Example 4 are shown in FIGS. 15 to 19. As can be seen, the particles in FIGS. 15 (sample 21) and 16 (sample 23), exhibit essentially completely roughly spherical morphology having a very narrow size distribution; the particles of sample 21 having a more shrivelled appearance than the particles of sample 23. Sample 22 was very similar to sample 21.

Sample 24 (FIG. 17) exhibited essentially completely cenospherical morphology having a very narrow size distribution.

In contrast, FIGS. 18 (sample 25) and 19 (sample 27) show mixed morphologies and wide size distributions. Sample 26 was very similar to sample 25.

EXAMPLE 5

Example 2 was repeated but using Capsul, an encapsulant obtained from Quest Foods, Naarden, Holland, maltodextrin, sugar and lemon oil obtained from Quest Foods. The emulsion compositions are shown in Table 13; the proportions are in parts by weight. The resultant emulsions had a 50% solids concentration and a viscosity of 0.15 PA·s.

TABLE 13
Sample	Capsul	Maltodextrin	Sugar	Water	Lemon Oil
28	500	250	250	1000	332
29	500	250	250	1000	332

The emulsion samples 28 and 29 were each then subjected to a spray process in accordance with the invention using the conditions shown in Table 14.

TABLE 14
		Jet
		Reynolds	Frequency	Weber	Inlet T	Outlet	Jets no × diameter
Sample	Ohn	No	fw [kHz]	No	° C.	T ° C.	[μm]
28	1	12	6.4	600	180	100	25 × 150
29	1	12	6.4	600	200	108	25 × 150

The resultant particulate samples 28 and 29 were free flowing and non-dusty

The particulate samples 28 and 29 were tested for dispersibility as described above. All of the particulate material dispersed well in the water within a few minutes, there being no discernible amounts of particulate material present whether as added or aggregating in clumps.

Sample 28 exhibited essentially complete cenospherical morphology whereas sample 9 exhibited essentially complete roughly spherical morphology, the particles having a shrivelled appearance; both samples exhibited a narrow size distribution.

EXAMPLE 6

Example 1 was repeated but using magnesium sulphate obtained from British Drug Houses (BDH). The solution is shown in Table 15; the proportions are in parts by weight.

The emulsion sample 30 was then subjected to a spray process in accordance with the invention using the conditions shown in Table 16.

TABLE 15
	Magnesium		Density	Viscosity	Surface Tension
Sample	sulphate	Water	[kg/m3]	(Pa · s)	(N/m)
30	400	1000	1100	0.008	0.04

TABLE 16
		Jet
		Reynolds	Frequency	Weber	Inlet T	Outlet	Jets no × diameter
Sample	Ohn	No	fw [kHz]	No	° C.	T ° C.	[μm]
30	0.1	280	11	600	280	167	8 × 200

The resultant particulate sample 30 was free flowing and non-dusty

The bulk density of the resultant particulate samples were measured as described above together with the weight mean size (WMS) and the mono-dispersivity index (MDI) and the results are shown in Table 17.

	TABLE 17
	Sample	WMS [μm]	MDI	Density [kg/m3]
	30	387	0.6	300

The particulate sample 30 was tested for dispersibility as described above. All of the particulate material dispersed well in the water within a few minutes, there being no discernible amounts of particulate material present whether as added or aggregating in clumps.

Sample 30 exhibited essentially completely a roughly spherical morphology and had a narrow size distribution.

EXAMPLE 7

Example 1 was repeated but using a polyvinylacetate (PVA) available under the trade name Elotex WRRP by Elotex, a division of National Starch & Chemical Co, USA. The emulsion compositions were made up using the PVA and water and are shown in Table 18; the proportions are in parts by weight.

TABLE 18
		Density	Viscosity	Surface Tension
Sample	Cs %	[kg/m3]	(Pa · s)	(N/m)
31	42.65	1070	0.025	0.02
32*	42.65	1070	0.025	0.02
*Comparative

The emulsion sample 31 was then subjected to a spray process in accordance with the invention using the conditions shown in Table 19. Emulsion sample 32 was subjected to a rotary spray process as described in Example 3.

TABLE 19
		Jet
		Reynolds	Frequency	Weber	Inlet T	Outlet	Jets no × diameter
Sample	Ohn	No	fw [kHz]	No	° C.	T ° C.	[μm]
31	0.4	64	8	800	174	100	48 × 150

The resultant particulate sample 31 was free flowing and non-dusty in contrast to the resultant particulate sample 32 which was dusty and not free flowing.

The bulk density of the resultant particulate samples were measured as described above together with the weight mean size (WMS) and the mono-dispersivity index (MDI) and the results are shown in Table 20.

TABLE 20
Sample	WMS [μm]	MDI	Density [kg/m3]	Residual moisture %
31	250	1.1	400	0.99
32	80	1.4	400	1.4

The morphologies of these samples are shown in FIGS. 20 and 21 respectively. As can be seen from FIG. 20, sample 31 is shown to have essentially a completely cenospherical morphology and a narrow size distribution in contrast to the mixed morphologies and sizes exhibited by comparative sample 32 as shown in FIG. 21.

Claims

1. A particulate material made by a spray process has at least 80%, preferably at least 90% and more especially at least 95% of the particles of the same morphology, said particulate material having a mono-dispersivity index of not more than 1.2, preferably not more than 1.0 and more especially not more than 0.6.

2. A particulate material made by a spray process has at least 80%, preferably at least 90% and more especially at least 95% of the particles of the same morphology, said particles having at least two components, a first component being at least one matrix material and a second component being at least one active ingredient retained by said first component, and said particulate material having a mono-dispersivity index of not more than 1.2, preferably not more than 1.0 and more especially not more than 0.6.

3. A particulate material according to claim 1 in which the particles have a morphology selected from hollow sphere, roughly spherical, cenospheres and packed porous network morphologies.

4. A particulate material according to claim 1 in which the particles have a mono-dispersivity index of greater than 0.05 and is more typically greater than 0.1, and is usually greater than 0.2.

5. A particulate material according to claim 1 in comprising particles that are substantially all of the same morphology.

6. A particulate material according to claim 1 comprising particles having a volume mean size in the range to 3000 μm.

7. A particulate material according to claim 6 comprising particles having a mean size in the range to 2000 and more especially in the range 100 μm to 2000 μm and more especially in the range 100 μm to 1000 μm.

8. A particulate material according to claim 6 comprising particles having a mean size in the range 100 μm to 600 μm, more especially 200 μm to 500 μm.

9. A particulate material according to claim 1 which is essentially dust free.

10. A particulate material according to claim 1 which essentially does not contain any particles having a volume mean size less than 20 μm; more preferably essentially does not contain any particles having sizes less than 50 μm and especially essentially does not contain any particles having a volume mean size less than 80 μm.

11. A particulate material according to claim 1 in which the particles are biocompatible.

12. A particulate material according to claim 11 in which the particles or the first component thereof are selected from sugars, polysaccharides, starches and glycerides, especially di- and tri-glycerides.

13. A particulate material according to claim 1 in which the material from which the particles or the first component thereof is made is film forming.

14. A particulate material according to claim 13 in which the first component is selected from polyvinyl acetate and ethylene vinyl acetate copolymers including mixture thereof with each other or with other materials.

15. A particulate material according to claim 2 in which the first component forms a material network that has interstices in which the second component is held.

16. A particulate material according to claim 2 in which the second component is selected from materials that are compatible with the first component.

17. A particulate material according to claim 2 in which the second component of the particles is a binary or higher order particle.

18. A particulate material according to claim 2 in which the second component comprises between 25 wt % to 55 wt %, more preferably between 30 wt % to 50 wt % of the particles.

19. A particulate material according to claim 2 which comprises the first component being at least one matrix material selected from sugars, polysaccharides, starches and glycerides, especially di- and tri-glycerides, and the second component being at least one active ingredient retained by said first component and being an organoleptic.

20. A particulate material according to claim 2 which comprises the first component being at least one film-forming polymeric matrix material.

21. A method of making a particulate material according to claim 1 comprising projecting from a body of liquid comprising a precursor formulation for said particulate material an array of mutually divergent jets, disturbing the jets to cause break up thereof into streams of droplets of narrow size distribution, contacting the array of resulting droplet streams with a gas flow to reduce coalescence of the droplets in each stream and causing or allowing the droplets to solidify at least partially in flight, wherein said precursor formulation has a density in the range 800 kg/m3 to 1700 kg/m3, more preferably 1000 kg/m3 to 1700 kg/m3 a viscosity in the range 0.01 Pa·s to 1 Pa·s, more preferably in the range 0.06 Pa·s to 1 Pa·s and a surface tension in the range 0.01 N/m to 0.72 N/m, more preferably 0.02 N/m to 0.72 N/m and an Ohnesorge Number in the range 0.005 to 2.5, more especially in the range 0.008 to 1 and wherein the liquid jets have a Reynolds Number (Rej) in the range 10 to 5000, more especially in the range 10 to 2000.

22. A method according to claim 21 in which the divergent jets are disturbed to cause break up thereof by acoustic vibration.

23. A method according to claim 22 in which the Weber frequency (fw) used for droplet generation is in the range 0.5 kHz to 100 kHz.

24. A method according to claim 21 in which the flow in the jets is laminar.

25. A method according to claim 21 in which, when the particles comprise first and second components, the first component is at least one matrix material selected from sugars, polysaccharides, starches and especially di- and tri-glycerides and the method comprises the liquid jets having a Rej in the range 10 to 5000 and the drops are generated using an fw in the range 2 kHz to 15 kHz.

26. A method according to claim 21 in which, when the particles comprise first and second components, the first component is at least one film-forming polymeric matrix material and the method comprises the liquid jets having a Rej in the range 10 to 100 and the drops are generated using an fw in the range 10 kHz to 100 kHz.

27. A method according to claim 21 wherein a material network is formed comprises the liquid jets having a Rej in the range 10 to 1000 and the drops are generated using an fw in the range 2 kHz to 50 kHz.