The technical field of the present invention relates to a sweetener tablet of stevia extract prepared by dry granulation method.
Stevia rebaudiana Bertoni is a perennial shrub of the Asteraceae (Compositae) family native to Paraguay and Brazil. Leaves of Stevia rebaudiana are well known for their sweetening properties. The sweet compounds are mainly the diterpene glycosides based on the kaurene skeleton that represent about 14% constituent of dried leaves. The sweet diterpene glycosides include stevioside, steviolbioside, rebaudioside A, B, C, D and E, and dulcoside A and B. Steviol is the aglycone moiety in all these glycosides. Among these, the major sweet components are stevioside that has a molecular weight of 804.9 and a melting point between 196-198° C, and rebaudioside A that has a molecular weight of 967.0 and a melting point between 242-244° C.
Srevia rebaudiana extract is widely accepted as a natural, sweetener world wide, particulary in food and beverages. The major component stevioside is heat and pH stable. It is approximately 300 times sweeter than sucrose, and has zero calorific value. It has been used for more than twenty years in Japan with no adverse effects reported so far. However, the major component stevioside apart from its high level of sweetness has also got inherent properties of unpleasant and undesirable after-taste. The unpleasant taste is also contributed by volatile aromatic or essential oils, tannins, and flavanoids present in Stevia leaf extract (Stevia extract).
Sweetener compositions of stevia extract are disclosed in various publications. For example, Japanese patent 3046763 discloses irregular shaped cubes of stevioside that may be readily mixed in beverages like coffee and tea. Laid open Japanese patent application 4287659, discloses powder composition of stevioside mixed with polydextrose, maltitol, erythritol and thaumatin. Japanese patent 53044666, discloses sweetener composition of stevioside and maltitol for use in low-calorie gelatin jelly.
Stevia extract is fluffy in nature and therefore difficult to compress into tablets as such, using conventional tabletting techniques involving aqueous, non-aqueous granulation.
The tablets develop problems of capping, sticking, and show high disintegration times which is undesirable. Further, direct compression of stevia extract particles lead to excessive sticking.
We have now surprisingly discovered that sweetener tablets of stevia extract having acceptable disintegration properties may be prepared by a process involving dry granulation.
Hence in one general aspect there is provided, a sweetener tablet of stevia extract prepared by dry granulation method.
In another general aspect, there is provided a process of preparing sweetener tablet of stevia extract by dry granulation method wherein the said process comprises the steps of
(i) forming a compact mass of stevia extract or stevia extract and inert excipient,
(ii) milling and/or sieving the compact mass to form granules,
(iii) optionally blending with inert excipient, and
(iv) compressing into tablet.
The compact mass may be prepared in conventionally used compactors such as roller compactor, chilsonator, or by process of slugging in tablet press.
The present invention provides a simple and cost effective method of preparing tablets of the poorly compressible stevia extract. Dry granulation method of preparing stevia extract tablets involves a compaction process. During compaction the air entrapped into stevia extract is released, facilitating compression into tablets of low friability and acceptable disintegration properties.
The term "Stevia extract" as used herein refers to aqueous extract obtained from leaves of Stevia rebaudiana. It is a white, free flowing, fluffy granular powder having
extremely sweet taste, and comprising at least 30% w/w stevioside and at least 10% w/w rebaudioside A, in particular at least 50% w/w stevioside and at least 20% w/w rebaudioside A. The amount of stevia extract may vary from about 5% w/w to about 50% w/w of the sweetener tablet. In particular, it may vary from about 15% w/w to about 25% w/w.
In one of the embodiments, sweetener tablet may comprise stevia extract, and one or more inert excipients.
The term "inert excipient" as used herein includes all physiologically inert excipients used in the art for preparation of sweetener compositions. Examples include flavors, disintegrants/superdisintegrants, binders, fillers, suspending agents, surfactants, , lubricants/glidants, colors, and the like.
The bitter after taste of stevioside may be masked by inclusion of one or more flavors in the sweetener tablet composition. Examples of flavors include any FEMA/GRAS approved flavor for oral use. In particular, flavors comprising maltol may be used. Maltol (Larixinic acid) is a white, crystalline compound obtained from larch bark, pine needles, chicory, or roasted malt. Maltol is soluble in water and glycerine, slightly soluble in alcohols, chloroform; and has a melting point of 161° C. Maltol and its derivatives have a caramel like odor and is used as versatile flavor enhancer and modifier (sweet, caramel, fruity, strawberry) in foods, wines, and perfumes. Commercially maltol is available under various trade names such as Veltol and Pyromaltol. Maltol is also an important constituent of many flavors approved for oral use, for example Contramarum Forte (Flavour 225023) obtained from Symrise. Besides maltol, Contramarum Forte Flavour comprises maltodextrin, gum arabic, and artificial and natural identical ingredients like menthyl esters and food esters. On combining maltol with stevia extract in sweetener tablet compositons, the bitter after taste is masked to acceptable limits. Further, maltol is required in very low quantity.
Specific examples of disintegrants/superdisintegrants include starch, cellulose derivatives, natural and synthetic gums, sodium starch glycolate, croscarmellose sodium, crospovidone, and low-substituted hydroxypropylcellulose. Superdisntegrants aids in quick disintegration of the sweetener tablet.
Specific examples of binders include starch; gelatin; sugars such as molasses, lactose, glucose, dextrose and sucrose; natural and synthetic gums such as acacia, sodium alginate, carboxymethyl cellulose, methylcellulose, polyvinyl pyrrolidone and veegum.
Specific examples of fillers include calcium carbonate, calcium phosphate-dibasic, calcium phosphate-tribasic, calcium sulfate, microcrystalline cellulose, powdered cellulose, dextrates, dextrins, fructose, kaolin, lactitol, lactose, mannitol, sorbitol, starch, sucrose, sugar compressible, and sugar confectioners. In particular, microcrystalline cellulose may be used.
Specific examples of suspending agents include microcrystalline cellulose, sodium carboxy methylcellulose, colloidal anhydrous silica, mannitol, povidone, sodium starch glycolate, and veegum.
Examples of surfactants include both non-ionic and ionic (cationic, anionic and zwitterionic) surfactants suitable for use in sweetener compositions. These include polyethoxylated fatty acids and its derivatives, for example polyethylene glycol 400 distearate, polyethylene glycol - 20 dioleate, polyethylene glycol 4 -150 mono dilaurate, polyethylene glycol -20 glyceryl stearate; alcohol - oil transesterification products, for example polyethylene glycol - 6 corn oil; polyglycerized fatty acids, for example polyglyceryl - 6 pentaoleate; propylene glycol fatty acid esters, for example propylene glycol monocaprylate; mono and diglycerides for example glyceryl ricinoleate; sterol and sterol derivatives; sorbitan fatty acid esters and its derivatives, for example polyethylene glycol - 20 sorbitan monooleate, sorbitan monolaurate; polyethylene glycol alkyl ether or phenols, for example polyethylene glycol - 20 cetyl ether, polyethylene glycol - 10 -100 nonyl phenol; sugar esters, for example sucrose monopalmitate; polyoxyethylene -
polyoxypropylene block copolymers known as "poloxamer"; ionic surfactants, for example sodium caproate, sodium glycocholate, soy lecithin, sodium stearyl fumarate, propylene glycol alginate, octyl sulfosuccinate disodium, and palmitoyl carnitine.
Specific examples of lubricants/glidants include colloidal anhydrous silica, stearic acid, magnesium stearate, calcium stearate, zinc stearate, sodium stearyl fumarate, talc, hydrogenated castor oil, sucrose esters of fatty acid, microcrystalline wax, yellow beeswax, and white beeswax.
Examples of colors include any approved color for oral use.
Sweetener tablets prepared in any of the embodiments above, showed a hardness of about 1.5-2.0 kg and a disintegration time of less than about 3 minutes, in particular less than about 1 minute.
In one of the embodiments, sweetener tablet of stevia extract may be prepared by a process comprising the steps of
(i) preparing a compact mass of stevia extract in conventionally used compactors such as roller compactor, chilsonator, and tablet press;
(ii) milling, and sieving through suitable sieves to form granules,
(iii) blending the granules of step (ii) with one or more of filler, superdisintegrant, and lubricant/glidant; and
(iv) compressing into tablet using appropriate toolings.
In another embodiment, the sweetener tablets prepared above may comprise a flavoring agent, particularly maltol.
The invention is further illustrated by the following examples, which is for illustrative purpose and should not be construed as limiting the scope of the invention in any way.
Examples
Compact mass composition of stevia extract
(Table Removed)
*AII stevia extract particles pass through # 100 sieve
Procedure
1. Stevia extract was dried in an hot air oven at 70° C for 3 hours, and blended with lactose (only compact mass 2).
2. Dried stevia extract or blend with lactose was feeded in roller compactor to form compact mass. The compactor parameters were as follows – Screw feeder speed: 40 rpm, Roller speed: 4 rpm, and Hydraulic pressure: 20 bars (for compact mass 1) and 90 bars (for compact mass 2)
3. The compact masses of step 2 were passed through # 30 sieve using oscillating granulator.
Stevia extract tablet composition
(Table Removed)
Procedure
1. Croscarmellose sodium, silicon dioxide and stearic acid were individually sieved through # 60 sieve.
2. Sieved croscarmellose sodium, silicon dioxide and stearic acid of step 1 were blended in a suitable mixer followed by blending with a part of lactose.
3. Stevia extract granules prepared above were then added to the blend of step 2 and mixed for about 5-10 minutes, followed by blending with the remaining part of lactose for about 10-15 minutes.
4. The blend of step 3 was compressed into 100 mg tablets using appropriate toolings.
The tablets prepared as per Examples 1 and 2 were tested for hardness using Monsanto hardness tester, and in vitro disintegration using Electrolab® instrument. The parameters are listed below.
(Table Removed)

WE CLAIM:
1. A sweetener tablet of stevia extract prepared by dry granulation method wherein in addition to stevia extract the tablet further comprises inert excipients selected from the group consisting of flavors, disintegrants/superdisintegrants, binders, fillers, suspending agents, surfactants, colors, and lubricants/glidants
2. The sweetener tablet of claim 1 comprising stevia extract from about 5% w/w to about 50% w/w.
3. The sweetener tablet of claim 1 wherein stevia extract comprises stevioside.
4. The sweetener tablet of claim 3 wherein stevia extract comprises at least 30% w/w stevioside.
5. The sweetener tablet of claim 1 wherein stevia extract further comprises rebaudioside A.
6. The sweetener tablet of claim 5 wherein stevia extract comprises at least 10% w/w rebaudioside A.
7. The sweetener tablet of claim 1 wherein flavor is selected from any FEMA/GRAS approved flavor for oral use.
8. The sweetener tablet of claim 7 wherein flavor is maltol.
9. The sweetener tablet of claim 1 wherein tablet disintegrates in water in less than about 60 seconds.
10. The sweetener tablet of claim 1 wherein tablet has a hardness of at least 1 kg.
11.A process of preparing sweetener tablet of stevia extract by dry granulation method wherein the said process comprises the steps of (i) forming a compact mass of stevia extract or stevia extract and inert excipients selected from the group consisting of flavors, disintegrants/superdisintegrants, binders, fillers, suspending agents, surfactants, colors, and lubricants/glidants; (ii) milling and/or sieving the compact mass to form granules; (iii) optionally blending with inert excipient; and (iv) compressing into tablet. 12. The process of preparing sweetener tablet of claim 11 wherein compact mass is
prepared in a tablet press, roller compactor or chilsonator. 13.A sweetener tablet of stevia extract prepared by dry granulation method as described and illustrated by the examples herein.