CA2125952A1

CA2125952A1 - Improved method of combining active ingredients with polyvinyl acetate

Info

Publication number: CA2125952A1
Application number: CA002125952A
Authority: CA
Inventors: Charles M. Copper
Original assignee: Individual
Current assignee: WM Wrigley Jr Co
Priority date: 1991-12-16
Filing date: 1992-12-14
Publication date: 1993-06-24
Also published as: US5229148A; EP0617579A1; EP0617579A4; AU3336693A; WO1993011674A1; AU664729B2

Abstract

An improved method of combining active ingredients with polyvinyl acetate for use in chewing-gum results in significantly less degradation of the active ingredients. After the polyvinyl acetate and one or more active ingredients have been mixed together in an extruder, the mixture is extruded through a die to form a sheet-like extrudate (32). The sheet like extrudate is then cooled using a series of three chilled compression rolls (12, 14 and 16). The extrudate is pinched between adjacent chilled compression rolls and both surfaces of the extrudate maintain contact with at least one of the chilled compression rolls for a period of time. The extrudate is thereby cooled swiftly and thoroughly, resulting in reduced degradation of the active ingredients.

Description

212~9~
93/11674 PCr/US92/10816 IMPROVED METHOD OF COMBTNING
ACTIVE INGREDIENTS WITH POLYVINYL ACETATE

FIELD OF THE INVENTION
This invention relates to an-improved method of combining chewing gum active ingredients such as flavor ingredients, flavor enhancing ingredients, high intensity sweeteners, or the Iike, with polyvinyl acetate; More specifically, the invention is concerned with reducing the time during which the active :ingredients are exposed to high temperature following extrusion, thereby alleviating degradation of the active ingredients.

.
~ACKC,ROUND OF THE_INyENTION
When polyvinyl acetate is combined with active ingredients to form encapsulation mixtures or gradual release structures for use i~ chewing gum, the ::
ingredients are conventionally mixed using an extruder, such as a Leistritz or Werner-Pfleiderer :single screw -or twin screw extruder. :Initially, the granular polyvinyl aceta~e:and active ingredient are added to the~extruder and h~ated to;a temperature of about 90C -.
to about 110Cj causing the polyvinyl acetate to melt and flow ~freely. The~active ingredient may be a flavor ingredient, ,a flavor~enhancing ingredient, a high intenSity sweetener., or otherwise. The active :::
ingredi nt is caused;to mix with the polyvinyl acetate as the screws of the~extruder turn and convey. The mixture is then extruded~through a die, such as a slot ~
die, to form a sheet-like extrudate. The extrudate is .. :
cooled to a solid form before being melt spun (in the case o~ gradual release structures) and/or ground into powder. .~

-'~,.

W093 2 i 2 5 9 PCr/US9~/10816 r The initial cooling of the encapsulation mixture or graduah release structure is conventi~nally accomplished using an air venturi. The air venturi is an apparatus which simply aspires upon the extrudate and uses the force of air to blow it into a cooling trough. Once in the cooling trough, the extrudate is further cooled in air.
The polyvinyl acetate has.a high heat capacity and heat retention, and low thermal conductivity. Accordingly, some of the polyvinyl acetate tends to remain in the molten state long after the encapsulation mixture or yradual release structure leaves the extruder. The air venturi is particularly ineffective in cooling the polyvinyl acetate which is located away from the surface, and near the core, of the extrudate. This prolonged heat history can cause undesira~le degradation of the active ingredient which is being encapsulated in the polyvinyI acetate.
Active ingredients which are particularly susceptible to degradation due to prolonged heat exposure include but are not limited to swee~eners, flavors, flavor enhancers, and high inten.city sweetener~s such as Magnasweet. Degradation of active ingredient results in loss of activity, whether it be ~lavor, flavor enha~cing or sweetening ~ffect.
Degradation is e~ide~ced by an undesirable brown di~color~tion of the extrudate, which is normally white in appearance.
French Pa~ent No. 2,503,989 disclose~ ~
cooling tunnel for cooling a raw extruded product, notably chewing gum. After exiting the extrusion head, the rectilinear material is conveyed in the as-extruded state by a conveyor belt along a ooling tunnel. The cooling is accomplished by evacuating the air from the internal space of the tunnel and feeding air cooled by th~ evaporation system of a cooling circuit~
European Patent Application No. 0,191,980 discloses the cooling of chewing gum slabs-by placing the gum slabs on a metal conveyor belt which is cooled 212~9S2 '. 93/11674 PCT/US92/10816 . .

. .
from underneath. The reference also discloses the blowing of cool air onto the surface of the gum sla~s u~ing fans.
United States Patent No. 2,224,430 disclo~es passing a chewing gum mass between a pair of cooperating rollers disposed so as to provide a forming space therebetween for forminy the gum into sticks.
The peripheral walls of the rollers are cooled using a refrigerant, in order to prevent the chewing ~um-from sticking to the rollers, and to cause solidification of ;
the chewing gum.
There is a need in the chewing gum industry :~
for a cooling method which significantly increases the ~ates of cooling for encapsulation mixtures and gradual release structures which utilize polyvinyl acetate as :-:
the encapsulant or wall material, thereby reducing the degradation of heat sensitive active ingredients contained therein.
: : :
SU~MARY OF THE INVENTIQN .
The present invention is dire~ted to an -~
improved method of combining a chewing gum active ingredient wi~h-polyvinyl~acetate. The polyvinyl , .
:: :acetate and active ingredient: are mixed together in an : extruder as explained~in the foregoing background :~
~: ~sectinn to produce a mixture. The mixture exits the extruder through a die r preferably a slot die. Then, the extrudate is drawn between and around a series of at least three chilled compression rolls. ~-he compression~rolls are arranged close - . .
enough together so that when the extruded mixture passes between two of the rolls, the mixture is ~
simultaneously pressed against ~he surfaces of both ~-adjacent rolls. The compression rolls are also arranged such that opposite surfaces of the extrudate each remain in contact with one of ~he rolls for a period of time following compression. Initially, the ~'`'' wog3/11~72 ~2S 9~ 2 PCT/US92/10816~ $

extrudate contacts a first chill roll and is pinched between first and second chilled rolls, causing compression. Then, a first surface of the extrudate remains in contact with the second chilled roll for a period of time. Then, the extrudate is pinched.between second and third chilled rolls, again causing compression. Then, a second surface of the extrudate remains in contact with the third chilled roll for a period of time.
With the foregoing in mind, it is a feature and advantage of the invention to provide a method of combining a chewing gum active ingredient using polyvinyl acetate, during which the encapsulation mixture is swiftly and thoroughly cooled immediately followi~g extrusion.
It is also a ~eature and advantage of the ..
invention to provide an improved encapsulation mixkure and gradual release structure of polyvinyl acetate and active ingredient, for use in chewing gum.
T~e foregoin~ and other features and advantages of the in~ention will become further apparent from thP following detailed descripticn of the : presently preferred embodiments, taken in conjunction with the accompanying figures. It is understood hat the detailed description a~d figures are to be .construed as illustrative rather than limitatiYe, the scope of the invention being defined by the appended clai~s and equivalents thereof.

RIEF DESCRIPTION OF THE FIGURES
: Figure l is a front view of a chill roll ass~mbly~which can be used to practice the method of the invention.
Figure 2 is a sectional view taken along the lines 2-2 of Figure l, and also illustrates the path of the extrudate not shown in Figure l.

~93tl1674 PCT/US92/10816 DETAILED DESCRIPTION OF THE
PRESENTLY PREFERRED EMBODIMENTS
Referring first to Figure l, a chilled compression roll assembly is shown and is genera;ly designated as l0. The chilled compression roll assembly l0 includes a first compression roll 12, a second compression roll 14/ and a third compression roll l6, all of which are rotatably yet firmly mounted ::
to a stainless steel frame 18 by means of bearing .
assemblies 20, 22, 24, 26, 28 and 30. .
Referring now to Figure 2, the compression rolls 12, 14 and 16 are mounted close enough to each other so that when a typical ex~rudate 32 having a thickness of about 0. 025 to about 0.040 inch passes between the rolls, the extrudate is pinched and compressed between the adjacent rolls. The minimum distance between the adjacent rolls (i . e., the minimum distance between rolls 12 and 14, and the minimum distance between rolls 14 and 16) is typically no ::
greater than about 0.025 inch. Preferably, the minimum : distance between adjacent rolls is no greater than about 0.020 inch, and most prefera~Iy the minimum distance between adjacent rolls is about 0.016 inch. -:~
Preferably, each chilled compression roll has an outer diameter of about five inches. .
Referring again to Figure l, chilling fluid from a source 33 is supplied directly to the interiors of compression rolls l2 and 16 via supply lines 34.and 36, respectively. The chilling fluid can ~e city water which typically has an average temperature of about 40- -70QF, or can be chilled water, or can be a fluid other than water. The chilling fluid passes through the interior of compression rolls 12 and 16 and exits via passages 40 and 42, respectively.
Outlet passages 40 and 42 are in communication with an inlet passage 44 to compression roll 14, allowing chilling fluid which exits chilled :

WO~3/11674 PCT/US92/10816i~ 'F

2~2~95~ - - 6 - ;~

rolls 12 and 16 to enter and pass through the compression roll l~. The chilling fluid exits the compression roll 14 via the passage 36 and enters a recirculating tank 4~. The tank 48 is in communication with the supply lines 34 and 36 via passages 50 and 52, thereby comple~ing the circuit. Some of ~he chilling fluid again passes into the compression rolls 12 and 16 via passages S0 and 52, while the remainder of the ch~lling fluid in the tank 48 is drained.
The chilling fluid should have a sufficiently low temperature and a sufficiently high flow rate that the temperatures in each of the compression rolls 12, 14 and 16 do not exceed about 75F. Preferably, the ~emperatures in the compression rolls should ~e maintained below about 70F, and most preferably below about 65F. The compression rolls themselves should be constructed of a material having a high thermal conductivity such thàt the cooling effects of the chilling fluid are easily transmitted to the outer surf aces in communication with the extrudate 32.
Referring to Figure 2, the walls 13, 15 and 17 o~ the compression }olls 12~, 14 and 16 are prefera~ly constructed of chromium coated steel or another material having similar thermal conductivity.
The thi:ckness of the walls l3t 15 and 17 of the compressiQn rolls also influences the coding effect. The wall thiçkness of a ompression roll constructed of chromium coated steel should not exceed about O . 375 inch, and should preferably be about O r 25 inchO Compression rolls suitable for practicing the invention are availablé from Killion Extruders, Inc. of Ceda Grove, New Jersey. Preferably, the compression rolls 12, 14 and 16 are coated with chromium in order to prevent sticking of the extrudate 32 to the compression rolls. Pre,erably, the first compression roll 12 is positioned about 2 to 3 inches from the slot die end of thei extruder ~not shown). Preferably~ the :~

21259~2 ;~93/11674 ~ PCT/US92/10816 ... ' ~' ' ' . ' compression rolls are mounted vertically with respect .-.
to earh other, as shown in Figures l and 2. .
The compression rolls 12, 14 and 16 eaçh.
rotate in a direction opposite to the direction of rotation.of each adjacent co~pression roll. From the viewpoint of Figure 2, the first compression r~ll 12 and the third compression roll 16 rotate counter- :
clockwise, while the second (center) compression roll :~
14 r~tates in a cl~ckwise direction. Referring to Figure l, all three compression rolls are driven by a :
single motor and gear assembly 54, which transmits .
rotation to the compression rolls via drive shafts 56, .
58, 60, 62 and 6 Referring now to Figure 2, the method of ~he ::~
invention effects a swift and thorough cooling to the i:
extrudate 32 as fol~lows. The extrudate 32 leaves the -~
die~slot ~not shown) and a first surface 29 of the extrudate:immediately contacts the first chilled .
compression roll 1:2. The extrudate 32 win~s about halfway around the compression roIl 12 with its first surface 29 being in constant contact with the chilled ~-~
compression roll. -:
: Then; the extrudate 32 is pinched between the first compression roll 12~and the second compression roll 14.~ This pin~hing enhances the cooling of the extrudate 32 by compressing the extrudake thereby exposin~ greater surface area of the extrudate to the chilIed rolls~ The pinching also enhances the cooling! :
by pulling the trailing portions of the extrudate 3~ :
securely against the first chill ~oll 12, almost ~immediately after the extrudate 32 exit~ the die slot. -~-: ~ After being pinched and compressed hetween ~:
the first and second compression rolls 12 and 14, the extrudate 32 winds about halfway around the second compression roll 14. ~uring this time, the second surface 35 of the extrudate 32 is in constant contact with the chilled compression roll 14. Thus, the .

WO93/11674 PCT/US~2/10816(. ) 9~ ~ - 8 -extrudate 32 is thorouqhly cooled from both sides - :
first, with surface 29 in contact with the chilled compression roll 12, and second, with surface 35 in contact with the chilled compression roll 14.
After traveling halfway around the second compression roll 14, the extrudate 32 is again pinched, this time between the second and third compression rolls 14 and 16. The extrudate 32 then travels about halfway around the third compression roll 16, with the first surface 29 in contact with the third compression roll 16. After leaving the third compression roll 16, the extrudate 32 passes through another roller assembly, not shown, which consists of two rolls covered with rubber or plastic which are not chilled.
The last two rolls pinch and pull the extrudate to help - maintain tension in the extrudate, and direct ~he extrudate to a collection bin.
The method of the invention is useful for man~facturi~g any polyvinyl acetate encapsulated active ingredient, and is particularly useful when the active ingredient is sensitive to prolonged exposure to high temperature. .
The m~thod of the invention is contemplated for use in the produc~i~on of any encapsulation matrix or gradual~release struature which utilizes polyvinyl acetate as the wall material and whi~h contains more than zero but less than about 55 weight percent active .ingredient, prefera~ly about lO to about 55 weight per cent active ingredient. The method contemplates that ~-the active agent and~polyvinyl acetate will be mixed together when the polyvinyl acetate is in the molten state. Preferably,:the components will be mixed using an extruder, and the encapsulation mixture will be extruded through a slot die, so that the extrudate is in the form of a sheet. An example of a slot die . `~
useful with the method of the invention is a die wh.ich :.

~o 93/11674 212 5 9 5 2 Pcr/usg2!1flg16 :~ :
.,. , 9 '~ :, has a 1 inch by 1/8 inch, substantially rectangular opening. .
The active ingredient can be any material such as artificial sweeteners, flavoring agents, flavor enhancing agents, or drugs, of which the slow or delayed release may be desired. ~he active ingredient should be solid or in the form of powders, including :
liguids encapsulated by spray drying techniques or liquids adsorbed or absorbed into or onto a supporting material such as silica, zeolite, carbon black, or p~rous matrices. Combinations of different active agents in the same structure may al50 be employed.
For purposes of illustration, possible active ingredients may be: high intensity sweeteners, such as Aspartame, Alitame, Acesulfame-k and its salts, saccharin and its salts, Thaumatin, Sucralose, Cyclamic acid and its salts, Monèllin, and Dihydrochalcones;
acidulants, such as malic acid, citric acid, tar~aric acid, and fumaric acid; Balt, such as sodium chloride and potassium chloride; bases, such as, magnesium hydroxide and urea; flavors, such as spray dried natural or synthetic adsorbed onto silica, and absorbed into maltodextrin; flavor modifiers, such ~s Thaumatin;
breath ~resheners, such as zinc chloride, encap~ul~ted :menthol, encapsula~ed anise, zinc glucinate, and en apsulated chlorophyll; glycyrrhizins, including glycyrrhizic acid or salts (food grade) thereof, one such commercially available compound called Magnasweet 135 is manufactured by MacAndrew and Forbes, Camden, New Jersey, these compounds may be combined with a ugar; and medicaments.
Of the various types of high intensity sweeteners, glycyrrhizins, surh as Magnasweet 135, show :-~urprisingly good results when combined wi~h wall such ;
as PVAc. When using Magnasweet 135, the occurrence of "off notes" (a residual taste of licorice) can be avoided by combining the product with a sugar.

.

WO93/1~6~ 9S ~ PCT/US92/10B16~.

Furthermore, Magnasweet 135 can be used to form a gradual release structure, by combining it with a wall material such as PVAc and a sugar and heating the mixture in the temperature range of 140-160~C. The resulting material can then be ground and exhibits gradual release charact~ristics.
While any commercially available polyvinyl acetate may be used as the wa~l material, it is preferred that the polyvinyl acetate have an average molecular weight of about 40,000 to about 100,000, mos~
preferably about 52,000. It is believed that polyvinyl acetate having a molecular wei~ht greater than about 100,000 will have less tendenc~ to exhibit gradual release by deformation during chewing.
By way of example, combinations of polyvinyl acetate and active ingredients ha~ing the following .compo~itions can be:produced according to the method of the invention. Percentages are given by weight~
(1) 75% PVAc having a molecular weight of about 50,000 - 80,000 as the wall material ~nd 2S%
Acesulfame-k as the active agent, extruded at a temperature of about 90-100C;
(2)~ 47.26% PVAc having a molecular weight of a~bout 30,000 and 37.81~ PVAc having a molecular weight of about 15,000 as the wall materiaI and 37081%
sucrose, 9.45~ Magnasweet 135, and 0.50% Magnesium StearatQ as the:active agent, extruded at a temperature of about 90-95C;
- . .

(3). 75% PVAc having a molecular weight of about 50,000 - 80,000 as the wall material and 25%
finely ground salt as the active agent, extruded at a temperature of about 100-110C;

(4) 75% PVAc having a molecular weight of about 30,000 as the wall material and 25% Acesulfame-k as the active agent, extruded at a temperature of about 90-100C;
~ .

~93/11674 2 I 2 ~ 9 S 2 PCT/US92/10816 (5) 74.6% PYAc having a molecular weight of about 50,000 - 80,000 as the wall material and 13.8%
~agnasweet 135, 11.1% finely ground salt, and 0.5%
Magnesium Stearate as the active agent, extruded a~ a temperature of about 95-100C;

(6) 75% PVAc having a molecular weight of about 50,000 - 80,000 as the wall material and 15%
Magnasweet 135 and 10% sugar as the active agent, extruded at a temperature of about 109C;

(7) 99.5% (a mixture of 74.6% PVAc having a molecular weight of about 50,000 - 80,000 as the wall material and 13.8% Magnasweet 135, 11.1% finely ground salt, and 0.5% Magnesium Stearate as the active agent) and 0.5% fumed silica, extruded at a temperature of about 100C;

(8) 99.5% (~ mixture of 75% PVAc having a molecular weiyht of about 50,000 - ~o,000 as the wall material and 15% Magnasweet 135 and 10% sugar as the activ~ agent) and 0,5% fumed silica, extruded at a temperature of about 100C;
~ 9) 83% PVAc having a molecular weight at about 50,000 - 80,000:as the wall material and 17% L-aspartyl-L-phenylanaline methyl ester (Aspartame) as the active agent, extruded at a temperature of about 100C;
~ (10) 7~1%~PVAc having a molecular weight of about 50,000 - 80,000 as the wall material and 29%
Aspartame as the active agent, extruded at a temperature of about 100C; ~ `
(11) 65%:PVAc having a molecular weight of about 50,000 - 80,000 as the wall material and 35%
Aspartame as the active agent, extruded at a temperature of about 100C;
) 90% PVAc having a molecular- weight of about 50,000 - 80,000 as the wall material and 10%
Acesulfame~k as khe active agent, extruded at a temperature of about 110-115C;

WO93/11674 . PCTJUS~2/10~16~"
~259~ 12 -(13) 75~ PVAc having a molecular weight of about 50,000 - 80,000 as the wall material and 25%
Acesulfame-k as the active agent, extruded at a temperature of about 110-115C;
(14) 65% PVAc having a molecular weight of about 50,000 - 80,000 as the wall material and 35%
sodium saccharin as the active agent, extruded at a temperature of about 100C;
(15) 90% PVAc having a molecular weight of about 30,000 as the wall materiaI, and 6.13% sodium chloride and 3.87~ potassium chloride as active agents, extruded at a temperature ~f about 110-115C;
(16) 90% PVAc having a molecular weight of about 15,000 as the wall material, and 6.13% sodium chloride and 3.87% potassium chloride as active agents, extruded at a temperature of about 90C;
(17) 75% PVAc having a molecular weight of about 50,000 - 8:0,000 as the wall material and 25%
diammonium phosphate as ~he active agent, extruded at a temperature of about::100C;
(18) 75% PVAc having a molecular weight of about 50,000 - 80,G00 as ~he wall material and 25%
sodium fluoride as~the active agent, extruded at a temperature of about 90=100C;
: ~(19) 75~ PVAc having~a molecular weight of ;about 50,000 - 80:,000 as the wall material and 25% by weight magnesium hydroxide as the active agent, extruded at a temperature of about 90-100C;
(20) 50~ PVAc having a molecular w`eight of about 30,000 as the wall material, and 10% Magnasweet .
135 and 40% sugar as active agents, extruded at a temperature of about 80-100C;
(21) 45% PVAc with a molecular weight of about 30,000 and 10% PVAc with a molecular weight of about 50,000 - 80,000 as the wall material/ and 9%
Magnasweet 135 and 36% sugar as.active agents, extruded at a temperature of about 90-100C;

93/11674 21 PCT/US92t1-16 (22) 60% PVAc with a molecular weight of about 30,000 as the wall material, and 10% Magnasweet 135 and 30% sugar as active agents, extruded at a temperature of about 90-lO0C;
(23) 70~ PVAc with a molecular weight of about 50,000 - 80,000 as the wall material, and 10%
Magnasweet 135 and 20% sugar as active agents, extruded at a temperature of about 90-100C; and (24) 47.5~ PVAc with a molecular weight of about 30,000 and 5% PVAc wi~h a molecular weight o~
a~out 50,000 - 80,000 as the wall material, and 9.5%
Magnasweet 135 and 38% sugar as active agents, extruded at a temperature of about 80-100C.
The gradual release structures and encapsulation mixtures produced according to the in~ention can be used in chewing gum. A chewing gum : composition generally includes a water soIuble bulk portlon, a water insoluble chewing gum base portion and one or more flavoring agents. The water soluble portion dissipates over a period of time~during chewing. The gum base portion is retained in the mouth throughout the chewing phase.
.

. The insoluble gum base ~enPrally includes ; ~ e-1astomers, resins, fats, oils, waxes, softeners and inorganic fi~lers. ~The elastomers may include .
polyi~obutylene/~isobuty1ene-isop~ene copolymPr, styrene butadiene rubber and natural latexes ~uch as chicle. The:resins may include polyvinyl acetate and terpene resins.i Low molecular weight polyvinyl acetate is a preferred resin. Fats and oils may include animal fats such as Iard ~and tallow, vegetable oils such as soybean and cottonseed oils, hydrogenated and partially hydrogenated vegetable oils, and cocoa butter.
Commonly used waxes include petroleum waxes such as paraffin and microcrystalline wax, natural waxes such as beeswax, candell1a, carnau~a and polyethylene wax~

.

W09~ PCT/US92/1~81 The present invention contemplates the use of any commercially acceptable chewing gum base.
The gum base typically also includes a filler component such as calcium carbonate, magnesium carbonate, talc, dicalcium phosphate and the like;
softeners, including glycerol monostearate and glycerol triacetate; and optional ingredients such as antioxidants, colors and emulsifiers. The gum base constitutes between 5-95% by weight of the chewing gum composition, more typically 10-50% by weight of the chewing gum, and most commonly 20-30% by weight of the chewing gum.
The water soluble portion of the chewing gum r.~ay include softeners, bulk sweeteners, high intensity sweeteners, flavoring agents and combinations thereof.
Softeners are added to the chewing gum in order to optimize the chewability and mouth feel of the gum.
The softeners, which are also known as plasticizers or plasticizing agents, generally constitute ~etween a~out 0.5-15% by weight of the chewing gum. The softeners may include glycerin, lecithin, and combina~ions thereof.
Aqueous sweetener solutions such as those containing sorbitol, hydrogenated starch hydrslysa~es, corn syrup and combinations thereof~ may also be used as softeners ~ and binding agents in chewing gum.
- ~ Bulk: sweeteners constitute between 5-95% by weight of the chewing gum, more typically 20-80% by weight of the chewing gum and most commonly 30-60% by weight of the chewing gum. ~ulk sweeteners may include both sugar and sugarless sweeteners and componentsO
Sugar sweeteners may include saccharide containing components including but not limited to sucrose, dextrose, maltose, dextrin, dried invert sugar, fructose, levulose, ~alactose, corn syrup solids, and the like, alone or in combina~ion. Sugarless ~weeteners include components with sweetening : characteristics but are devoid of the commonly known -~093/11674 2~ 2 59 S2 PCT/US92/10816 sugars. Sugarless sweeteners include but are not limited to sugar alcohols such as sorbitol, mannitol, xylitol, hydrogenated starch hydrolysates, maltitol, and the like, alone or in combination.
High intensity sweeteners may also be present and are commonly used with sugarless sweeteners. When used, high intensity sweeteners typically constitute between 0.00l-5% by weight of the chewing gum, preferably between 0.0l-l% by weight of the chewing gum. Typically~ high intensi~y sweeteners are at least 20 times sweeter than sucrose. These may include but are not limited to sucralose, aspartame, salts of acesulfame, alitame~ saccharin and its salts, cyclamic ac~d and its salts, glycyrrhizin, dihydrochalcones, thaumatin, monellin, and the like, alone or in combination.
: Combinations of sugar and/or sugarless swee~eners may be used in chewing gum. The swe~tener may also function in the chewing gum in whole or in part as a water:soluble bulking agent. Additionally, : the softener may al~o provide additional sweetness such as with aqueous su~ar or alditol solutions.
Flavoring agents should generally be~present :~ in the chewing gum in an amount:within the range of ~:: about 0.1-15% by weight of the chewing gum, preferably between about 0.2~-5% by weight of :the chewing gum, most preferably between~about 0.5-3~ by weight of the chewing gum.~ As previously indicated, flavoring agen~s may include essential oils, synthetic flavors or mixtures thereof including but not limited to oils derived from~plants and fruits such as citrus oils, ~ruit essences:, peppermint oil, spearmint oil, other ~mint oils, clove oil, oil of wintergreen, anise and the like. Artificial flavoring ayen~s and componen s may also bP used in the flavor-ingr~dient of the in~entivn.
Natural and artificial flavoring agents may be combined in any sensorialIy acceptable fashion.

2 ~ 9~ 2 - 16 -Optional ingredients such a.s colors, emulsifiers, pharmaceutical agents and additional flavoring agents may also be included in chewing gum.
Chewing gum is generally man~factured by sequentially adding the various chewing gum.ingredients to any commercially available mixer known in the art.
After the ingredients have been thoroughly mixed, the ~:
gum mass is discharged from the mixer and shaped into the desired form such as by rolling into sheets and cuttin~ into sticks, extruding into chunks, or casting into pellets. Generally, the ingredients are mixed by first melting the gum base and adding it to the running mixer.. The gum base may alternatively be melted in the mixer. Color and emulsifiers can be added at this time.
A softener such as ~lycerin can be added next along with syrup and part of the bulk portion. Further parts of the bulk port:ion may then be added to the mixer. Fla~oring agents and optional flavor enhancing agents are typically added with the ~inal part of the bulk portion. The entire mixing pro~ess typically takes about fifteen minutes, although longer mixing : times are.sometimes required. Those skilled in the art will recognize that variations of this mixing procedure, or other mixing procedures, may be foll~wed.
While the embodiments of the invention dis~losed herein are at prese~t considered to be preferred, various modifications and improvements can ~e made without departing from the spirit and scope of the invention. The scope of the invention is indicated in the appended claims, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.

Claims

WE CLAIM:

1. An improved method of preparing encapsulation mixtures and gradual release structures for use in chewing gum, comprising the steps of:
feeding polyvinyl acetate to an extruder, at a first rate;
feeding one or more active ingredients to the extruder, at a second rate;
heating the polyvinyl acetate and active ingredient in the extruder to a temperature of about 90°C to about 110°C;
mixing the polyvinyl acetate and active ingredient in the extruder to form a mixture;
the first and second rates being selected such that the mixture contains more than zero but less than about 55 weight per cent active ingredient;
extruding the mixture through a die, to form a sheet-like extrudate;
contacting a first surface of the extrudate with a first chilled compression roll;
pinching the extrudate between the first and a second chilled compression roll;
contacting a second surface of the extrudate with a second chilled compression roll;
pinching the extrudate between the second and a third chilled compression roll; and contacting the first surface of the extrudate with the third chilled compression roll.

2. The method of claim 1, wherein the first chilled compression roll rotates continuously, and the first surface of the extrudate maintains contact with the first chilled compression roll during rotation for about half of one revolution.

3. The method of claim 2, wherein the second chilled compression roll rotates continuously, and the second surface of the extrudate maintains contact with the second chilled compression roll during rotation for about half of one revolution.

4. The method of claim 3, wherein the third chilled compression roll rotates continuously, and the first surface of the extrudate maintains contact with the third chilled compression roll during rotation for about half of one revolution.

5. The method of claim 1, wherein the minimum distance between the first and second compression rolls and the minimum distance between the second and third compression rolls are each no greater than about 0.025 inch.

6. The method of claim 1, wherein the minimum distance between the first and second chilled compression rolls and the minimum distance between the second and third chilled compression rolls are each no greater than about 0.020 inch.

7. The method of claim 1, wherein the minimum distance between the first and second chilled compression rolls and the minimum distance between the second and third chilled compression rolls are each about 0.16 inch.

8. The method of claim 1, wherein the chilled compression rolls are constructed of a material comprising chromium coated steel.

9. The method of claim 1, wherein the first, second and third chilled compression rolls are cooled by providing chilling fluid to the respective interiors of the first, second and third compression rolls.

10. The method of claim 9, wherein the chilling fluid comprises water having an average temperature of about 40°F to about 70°F.

11. The method of claim 9, wherein the interiors of the first, second and third chilled compression rolls have a temperature which does not exceed about 75°F.

12. The method of claim 9, wherein the interiors of the first, second and third chilled compression rolls have a temperature which does not exceed about 70°F.

13. The method of claim 9, wherein the interiors of the first, second and third chilled compression rolls have a temperature which does not exceed about 65°F.

14. The method of claim 8, wherein each of the first, second and third compression rolls has a wall thickness of about 0.25 inch.

15. An encapsulation mixture prepared according to the method of claim 1.

16. The encapsulation mixture of claim 15 in a chewing gum.

17. A gradual release structure prepared according to the method of claim 1.

18. The gradual release structure of claim 17 in a chewing gum.

19. An improved method of preparing encapsulation mixtures and gradual release structures for use in chewing gum, comprising the steps of:
heating and mixing polyvinyl acetate and an active ingredient in an extruder in such quantities that the resulting mixture includes bout 10 to about 55 weight per cent active ingredient;
extruding the mixture through a slot die, to form a sheet-like extrudate;
providing a series of three chilled compression rolls in the vicinity of the slot die, each compression roll being rotatably mounted and spaced apart from an adjacent compression roll at a minimum distance not greater than about 0.025 inch;
chilling the compression rolls to a temperature below about 75°F; and cooling the extrudate by placing the extrudate in contact, sequentially, with all three of the chilled compression rolls.

20. The method of claim 19, wherein the chilled compression rolls are vertically mounted with respect to each other.

21. The method of claim 19, wherein the chilled compression rolls are constructed from a material comprising chromium coated steel.

22. The method of claim 19, herein the slot die has a substantially rectangular opening with dimensions of about one inch by about .125 inch.

23. The method of claim 19, further comprising the step of pinching the extrudate between two of the chilled compression rolls.

24. The method of claim 19, wherein each chilled compression roll has an outer diameter of about five inches.

25. The method of claim 19, wherein each chilled compression roll has a chromium coating.

26. An encapsulation mixture prepared according to the method of claim 19.

27. The encapsulation mixture of claim 26 in a chewing gum.

28. A gradual release structure prepared according to the method of claim 19.

29. The gradual release structure of claim 28 in a chewing gum.