PT85894B - PROCESS FOR THE PREPARATION OF AN ADOCANT - Google Patents

Abstract

Crystalline sucralose (I) having a mean particle size of at most 10 microns, the maximum particle size being no more than twice the mean, is claimed. An effective method of reducing the particle size to the required dimensions is by jet milling which utilises fluid energy to break the crystals into fine particles.

Description

The present invention relates to a new physical form of high intensity sweetener sucralose (4,1 ', 6'-trichloro-4,1', 6'-trideoxy galactosaccharose) which is more stable to discoloration under heat and drying than the known forms, and a process for producing the same.

Chlorosaccharose sweeteners, that is, with sucrose and galactosaccharose based stations in which one or more of certain hydroxy groups are replaced by chlorine atoms, are described in British Patent I.543.I67. Of particular interest is sucralose, which was first isolated as a syrup (Fairclough, Hough & Richardson, Carbohydrate Research 40, 1975, 285-298), which can be solidified, for example by freeze-drying, to form a hygroscopic glaze powdery. Parents later, a new anhydrous crystalline form of sucralose was prepared, which was much less hygroscopic, as described in British Patent N5. 2,0675,646, of the applicant.

In general, anhydrous crystalline sucralose is relatively stable and inert. However, it has been found that discoloration of crystalline sucralose can occur when the

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mesine is stored under dry conditions at elevated ambient temperatures. For example, if pure dry crystalline sucralose is kept at 100 ° C the color changes from white to pale brown after about 20 minutes. At 50 ° C the same color change is much slower, taking about 9 days. Such relatively minor color changes may have resulted in the product not meeting the specification required for use in food and beverages.

Surprisingly, it has now been found that the thermal stability of dry crystalline sucralose can be considerably increased by reducing the particle size and limiting the size distribution. In practice the average particle size should be half the maximum particle size and it is desirable to have no more than 10 microns. Preferably, the average size is about 5 microns or less and the maximum size is about 10 microns or less, for example an average of about 3 microns. It was unexpected that the reduced particle size would increase stability: a small size with a larger total surface area.

or can often lead to a decrease in stability due to a greater potential for oxidative processes.

It is important that the particles can be relatively uniform in size. Thus, with an average particle size of 5 microns or less, the maximum particle size should not exceed 10 microns, and preferably should not exceed 6 microns. For an average particle size of 2 to 3 microns, the maximum particle size should not exceed 6 microns, and preferably should not exceed ’! microns.

Sucralose crystals are typically in the form of needles, although their size and shape can vary somewhat, depending on the temperature and the solvent from which they are obtained. Thus, crystallization from aqueous solution typically provides crystals with dimensions from 80 microns in length to

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about 8GO microns, and crystallization from organic solvents, such as ethyl acetate, usually gives smaller crystals, for example 15 x 5 microns.

While it is possible to obtain relatively small crystals of sucralose by choosing appropriate crystallization conditions, it is difficult to control the crystallization process to produce small particles of a small size distribution. Likewise, cx'stalisation from organic solvents can leave undesirable solvent residues in the product. Alternatively, the particle size of crystalline material can be reduced by mechanical grinding, but it is difficult to achieve a very small particle size by this means.

It has been found that an effective process for reducing the particle size to the required dimensions is by jet grinding, which uses fluid energy to break the crystals into fine particles. In a jet mill, the material to be sprayed is introduced into streams of elastic fluid, for example compressed air, in which the particles collide with each other. Albus, 1st Annual Powder and Bulk Solids Conference, Rosemont, 1985, p. 867-877). Jet mills are particularly suitable for grinding heat-sensitive materials because they have no moving parts and the light heat generated during grinding is compensated by the cooling effect of the fluid as it expands in the jets through which it is introduced into the crushing chamber.

According to the present invention, therefore, there is provided a process for increasing the thermal stability of sucralose which comprises jet grinding to reduce particle size and size distribution. The average particle size is preferably 5 microns or less for a maximum particle size of no more than 10 microns and most preferably 2 to 3 microns

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for a maximum particle size of up to 5 microns.

The elastic fluid used for the grinding process is conveniently compressed air, typically at a pressure of 2Ο7θθθ Pa to 690G00 Pa.

The following examples better illustrate the invention.

Example 1

Sucralose, which had been crystallized from aqueous solution, having a crystal size of about 100 x 20 micros, was fed to a 30 cm (12 inch) jet mill (micron? Ills Lts., Addlestead Industrial Estate, Tonbridge Road, East Peckham, Kent, UK) at a rate of 15 fcg / hour, using compressed air as a micronizing fluid.

When the jet mill was added at a pressure of 206820 Pa (30 pounds per square inch) the micronized product had a particle size ranging from about 3x3 microns to about 6 x 6 microns, measuring most of the particles around of 5x5 microns. At higher operating pressures of 41364o, 55520 and 689400 Pa (60, 80 and 1CC pounds per square inch), the micronized product had a particle size of about 1 x 1 to 4 x 4 microns, measuring the most particles about 3 x 3 microns. The particle size did not vary appreciably with the operating pressure above this range.

Example 2

Sucralose crystals with a particle size of about 100 x 20 microns, from the same portion used in Example 1, and micronized sucralose from Example 1, were subjected to a constant temperature of 65 ° C in open containers and the time that- 4 58,523

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I am going to reveal a pale brown color. The results were as follows:

Material

Time to develop a pale brown color at 65 ° C

Sucralose crystals

Micronized Sucralose (5 * 5 microns)

Micronized sucralose (3 x 3 niicrons) hours

2.6 hours hours

Example 3

Sucralose crystals (maximum diameter: 100% less than 7OC niicrons; average 5-9 microns) were fed at a rate of 30 kg / hour to a 20 cm (δ inch) Licronizer mill (δ inch) through a vibrating feeder . The mill operated with a chamber pressure of 689400 Pa (100 pounds per square inch) to produce a particle size product; 100 Q less than 4 microns, average size 2 microns. When tested by the process of Example 2, the product had a brown staining time at ø5 ° C of 29 hours, whereas the feed material had a 15 hour time.

In a second phase, a similar material (brown staining time 16 hours) was crushed at 25 kg / hour to provide a product of the same size as in the first phase, with the brown staining time of 31 hours at 65 ° C.

Example 4

Crystals of sucralose, crystallized from ethyl acetate solution, having dimensions of about 15 x 5 microns (average) were tested as in Example 58,523

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>

Sucralose crystallized from;

water crushed ethyl acetate sucralose

Stability

Average size y p O to 05 100 x 50 microns 17 hours 15 x 5 microns 21 hours 3 x 3 microns 31 hours

The numbers in Examples 2 to 4 are shown in Figure 1. The decolorization time at 6-5 ° can be increased from 16 hours to 31 hours or more. The 50 a increase is achieved by an average size of 10 microns.

Claims (5)

- REIVTKDICACC 1 'S 1? · - Process to increase the thermal stability of crystalline sucralose, characterized in that crystalline sucralose is subjected to jet grinding to reduce the size of the oartxcula, and to make the particle size distribution such that the maximum size is not more than twice the average size. 2. The process according to claim 1, characterized in that the particles are reduced to an average size of no more than 10 microns. 3? - recess according to claim 2, characterized in that the particle size is reduced to an average size of up to t microns for a maximum particle size of up to 10 microns, 4? Process according to claim 2, characterized in that the particle size is reduced to an average size of 2 to? microns for a maximum particle size of up to 3 microns. 5 * - · Process according to claim 1, characterized in that the grinding is carried out at a fluid pressure of 2O7COC Pa to ódGvCO Pa.