Continuous chewing gum manufacturing process yielding gum with improved flavor perception

Abstract: A method of continuously manufacturing chewing gum with improved flavor perception comprises the steps of adding at least an elastomer and filler into a high-efficiency continuous mixer, and mixing the elastomer and filler together in the continuous mixer; adding a least one ingredient selected from the group consisting of fats, oils, waxes and elastomer plasticizers into the continuous mixer, and mixing said ingredient with the elastomer and filler in the continuous mixer; and adding at least one sweetener and at least one flavor into the continuous mixer, and mixing said sweetener and flavor with the remaining ingredients to form a chewing gum composition. These steps are performed using a single high-efficiency continuous mixer and wherein the flavor is added at a level lower than that used to make the same chewing gum composition in a batch mixer but the flavor intensity in the chewing gum product is comparable to that of said same chewing gum composition made in a batch mixer.

Description: The present invention relates to a process for making chewing gum that produces an improved flavor perception in the gum. More particularly, it relates to a process for making gum in a continuous mixer with short mixing times after the addition of flavor. In a conventional chewing gum manufacturing process, a double arm Sigma blade mixer is used to mix chewing gum ingredients. Gum base, bulking agents such as sugar or sorbitol for sugarless gum, liquids such as syrup or liquid sorbitol, softeners such as glycerin and lecithin, and flavors are mixed for from 5 to 20 minutes to manufacture the gum. This conventional gum making process, using batch mixing, involves an open mixer that allows flavor components to be lost by volatization or degradation, particularly during the relatively long mixing times required to incorporate the flavor into the chewing gum composition. This is true even though flavor is typically added as the last ingredient, and mixed at the minimum temperatures needed for mixing. While most gum flavors, like spearmint, peppermint, cinnamon and wintergreen are subject to volatization, fruit flavors are especially susceptible to this problem. In conventional gum manufacturing, the time at which flavors are added effects the flavor release during chewing. For example, a gum mixed with flavor for extended time periods, longer than 5 minutes, will have a slow flavor release. However, this is not practical in the batch process because a mixing time of 10 or 15 minutes causes much of the flavor to be lost. Thus, optimized flavor perception in the final gum product may have to be sacrificed for the sake of keeping the level of flavor volatization and degradation to a minimum. Conventionally, chewing gum base and chewing gum products have been manufactured using separate mixers, different mixing technologies and, often, at different factories. One reason for this is that the optimum conditions for manufacturing gum base, and for manufacturing chewing gum from gum base and other ingredients such as sweeteners and flavors, are so different that it has been impractical to integrate both tasks. Chewing gum base manufacture, on the one hand, involves the dispersive (often high shear) mixing of difficult-to-blend ingredients such as elastomer, filler, elastomer plasticizer, base softeners/ emulsifiers and, sometimes wax, and typically requires long mixing times. Chewing gum product manufacture, on the other hand, involves combining the gum base with more delicate ingredients such as product softeners, bulk sweeteners, high intensity sweeteners and flavoring agents using distributive (generally lower shear) mixing, for shorter periods. In order to improve the efficiency of gum base and gum product manufacture, there has been a trend toward the continuous manufacture of chewing gum bases and products. U.S. Patent No. 3,995,064, issued to Ehrgott et al., discloses the continuous manufacture of gum base using a sequence of mixers or a single variable mixer. U.S. Patent No. 4,459,311, issued to DeTora et al., also discloses the continuous manufacture of gum base using a sequence of mixers. Other continuous gum base manufacturing processes are disclosed in European Patent Publication No. 0,273,809 (General Foods France) and in French Patent Publication No. 2,635,441 (General Foods France). U.S. Patent No. 5,045,325, issued to Lesko et al., and U.S. Patent No. 4,555,407, issued to Kramer et al., disclose processes for the continuous production of chewing gum products. Haarmann and Reiner report a study of one extrusion process in an article of Food Manufacture, Vol. 62 (1987) Sept. No. 9 pp 47 to 50 entitled "Extrusion : does chewing gum pass the taste test?" . In each case, however, the gum base is initially prepared separately and is simply added into the process. U.S. Patent No. 4,968,511, issued to D'Amelia et al., discloses a chewing gum product containing certain vinyl polymers which can be produced in a direct one-step process not requiring separate manufacture of gum base. However, the disclosure focuses on batch mixing processes not having the efficiency and product consistency achieved with continuous mixing. Also, the single-step processes are limited to chewing gums containing unconventional bases which lack elastomers and other critical ingredients. There is a need for a chewing gum manufacturing process that yields a gum with improved flavor perception and reduces the amount of flavor components volatized and degraded during the mixing process. Even more beneficial would be an integrated continuous manufacturing process having the ability to combine chewing gum base ingredients and other chewing gum ingredients in a single continuous mixer in a way that reduces flavour loss and yields gum with improved flavour perception. According to the present invention there is provided a method of continuously manufacturing chewing gum comprising: a) adding at least elastomer and filler into a continuous mixer, and mixing the elastomer and filler together in the continuous mixer; b) adding at least one ingredient selected from the group consisting of fats, oils, waxes and elastomer plasticisers into the continuous mixer, and mixing said ingredient with the elastomer and filler in the continuous mixer; and c) adding at least one sweetener and at least one flavour into the continuous mixer, and mixing said sweetener and flavour with the remaining ingredients to form a chewing gum composition; d) continuously discharging the chewing gum composition from the mixer; wherein steps a) to d) are performed using a single continuous mixer; and wherein less flavour is added than that used to make the same chewing gum composition in a batch mixer but the flavour intensity of the chewing gum composition discharged from the continuous mixer is substantially the same as or higher than that of said same chewing gum composition made in a batch mixer; and wherein the gum composition has a residence time in the continuous mixer of not more than 30 seconds after the flavour is added. The method continuously manufactures a wide variety of chewing gum products using a continuous mixer and yields gum with improved flavour perception. Preferably the mixer is a single, high-efficiency mixer which does not require the separate manufacture of chewing gum base. According to a further aspect of the present invention there is provided a method of continuously manufacturing chewing gum with improved flavour perception comprising: a) adding at least elastomer and filler into a continuous mixer, and mixing the elastomer and filler together in the continuous mixer; b) adding at least one ingredient selected from the group consisting of fats, oils, waxes and elastomer plasticisers into the continuous mixer, and mixing said ingredient with the elastomer and filler in the continuous mixer; and c) adding at least one sweetener and at least one flavour into the continuous mixer, and mixing said sweetener and flavour with the remaining ingredients to form a chewing gum composition; d) continuously discharging the chewing gum composition from the mixer; wherein steps a) to d) are performed using a single continuous mixer; and wherein less flavour is added than that used to make the same chewing gum composition in a batch mixer but the flavour intensity of the chewing gum composition discharged from the continuous mixer is substantially the same as or higher than that of said same chewing gum composition made in a batch mixer; and wherein the continuous mixer comprises a blade-and-pin mixer. Preferably, at least the elastomer and filler are subjected to dispersive mixing in the continuous mixer. Preferably, at least the sweetener, flavouring agent, elastomer and filler are subjected to distributive mixing in the continuous mixer, to form a chewing gum product. Preferably in the continuous process, flavours are mixed very quickly in a closed system. As a result, flavours have a higher impact in the gum, taste stronger, and make gum taste more flavorful. The high-efficiency mixing allows flavors to be added early or late to a closed system for a short mixing time of 5 seconds or long mixing time of 30 seconds. Another surprising result was noticed when comparing flavor added by conventional batch mixing and flavor added to extruded gum by continuous process. Because of the short mixing time in a closed system, much less flavor is lost and the flavor intensity is perceived to be much higher in the extruded gum. This allows for a reduced overall flavor level in a gum formulation compared to gum made by batch processing. The foregoing and other advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying examples and drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partial exploded perspective view of a preferred Buss high-efficiency mixer used to practice the preferred method of the invention, illustrating a mixing barrel and mixing screw arrangement. Fig. 2A is a perspective view of an on-screw element used on the upstream side of a restriction ring assembly, in a preferred high-efficiency mixer configuration. Fig. 2B is a perspective view of an on-screw element used on the downstream side of the restriction ring assembly in a preferred high-efficiency mixer configuration. Fig. 2C is a perspective view of a restriction ring assembly used in a preferred high-efficiency mixer configuration. Fig. 3 is a perspective view showing the relative positioning of the elements of Figs. 2A, 2B and 2C in a preferred high-efficiency mixer configuration. Fig. 4 is a perspective view of a low-shear mixing screw element used in a preferred high-efficiency mixer configuration. Fig. 5 is a perspective view of a high-shear mixing screw element used in a preferred high-efficiency mixer configuration. Fig. 6 is a perspective view of a barrel pin element used in a preferred high-efficiency mixer configuration. Fig. 7 is a schematic diagram of a preferred arrangement of mixing barrel pins and ingredient feed ports used to practice an embodiment of the invention. Fig. 8 is a schematic diagram of a preferred mixing screw configuration used in conjunction with Fig. 7. Fig. 9 is a schematic diagram of the relative arrangement of the equipment used to practice a presently preferred embodiment of the invention. Fig. 10 is a schematic diagram of the presently preferred mixing screw configuration used in the arrangement of Fig. 9. DETAILED DESCRIPTION OF THE DRAWINGS AND PRESENTLY PREFERRED EMBODIMENTS As used herein, the term "chewing gum" also includes bubble gum and the like. All percentages are weight percentages unless otherwise specified. With preferred embodiments of the invention, it has been found that flavor may be reduced by from 1 to 20% in the gum formulation and obtain a similar flavor intensity as would be produced if the gum were made in a batch process. The level of all flavors, such as spearmint, peppermint, cinnamon, wintergreen, and especially fruit flavors, may be reduced. Fruit flavors are particularly sensitive to volatile loss and levels may be significantly reduced. Analysis of fruit flavored gum samples made by continuous high-efficiency mixing and conventional mixing have shown that a much lower quantity of volatile components in fruit flavors are lost when made by continuous mixing in a high-efficiency mixer than when made by conventional processing. Because the preferred embodiment of the invention uses a high-efficiency mixer known as a blade-and-pin mixer, and utilizes the manufacture of the gum base as well as the chewing gum composition in one mixer, the total manufacture of chewing gum, using a single continuous high-efficiency mixer, without requiring the separate manufacture of chewing gum base, will first be discussed. This method can be advantageously performed using a continuous mixer whose mixing screw is composed primarily of precisely arranged mixing elements with only a minor fraction of simple conveying elements. A preferred mixer is a blade-and-pin mixer exemplified in Fig. 1. A blade-and-pin mixer uses a combination of selectively configured rotating mixer blades and stationary barrel pins to provide efficient mixing over a relatively short distance. A commercially available blade-and-pin mixer is the Buss kneader, manufactured by Buss AG in Switzerland, and available from Buss America, located in Bloomingdale, Illinois. Referring to Fig. 1, a presently preferred blade-and-pin mixer 100 includes a single mixing screw 120 turning inside a barrel 140 which, during use, is generally closed and completely surrounds the mixing screw 120. The mixing screw 120 includes a generally cylindrical shaft 122 and three rows of mixing blades 124 arranged at evenly spaced locations around the screw shaft 122 (with only two of the rows being visible in Fig. 1). The mixing blades 124 protrude radially outward from the shaft 122, with each one resembling the blade of an axe. The mixing barrel 140 includes an inner barrel housing 142 which is generally cylindrical when the barrel 140 is closed around the screw 120 during operation of the mixer 100. Three rows of stationary pins 144 are arranged at evenly spaced locations around the screw shaft 122, and protrude radially inward from the barrel housing 142. The pins 144 are generally cylindrical in shape, and may have rounded or bevelled ends 146. The mixing screw 120 with blades 124 rotates inside the barrel 140 and is driven by a variable speed motor 201 (Fig. 9). During rotation, the mixing screw 120 also moves back and forth in an axial direction, creating a combination of rotational and axial mixing which is highly efficient. During mixing, the mixing blades 124 continually pass between the stationary pins 144, yet the blades and the pins never touch each other. Also, the radial edges 126 of the blades 124 never touch the barrel inner surface 142, and the ends 146 of the pins 144 never touch the mixing screw shaft 122. Figs. 2-6 illustrate various screw elements which can be used to configure the mixing screw 120 for optimum use. Figs. 2A and 2B illustrate on-screw elements 20 and 21 which are used in conjunction with a restriction ring assembly. The on-screw elements 20 and 21 each include a cylindrical outer surface 22, a plurality of blades 24 projecting outward from the surface 22, and an inner opening 26 with a keyway 28 for receiving and engaging a mixing screw shaft (not shown). The second on-screw element 21 is about twice as long as the first on-screw element 20. Fig. 2C illustrates a restriction ring assembly 30 used to build back pressure at selected locations along the mixing screw 120. The restriction ring assembly 30 includes two halves 37 and 39 mounted to the barrel housing 142, which halves engage during use to form a closed ring. The restriction ring assembly 30 includes a circular outer rim 32, an inner ring 34 angled as shown, and an opening 36 in the inner ring which receives, but does not touch, the on-screw elements 20 and 21 mounted to the screw shaft. Mounting openings 35 in the surface 32 of both halves of the restriction ring assembly 30 are used to mount the halves to the barrel housing 142. Fig. 3 illustrates the relationship between the restriction ring assembly 30 and the on-screw elements 20 and 21 during operation. When the mixing screw 120 is turning inside the barrel 140, and reciprocating axially, the clearances between the on-screw elements 20 and 21 and the inner ring 34 provide the primary means of passage of material from one side of the restriction ring assembly 30 to the other. The on-screw element 20 on the upstream side of the restriction ring assembly includes a modified blade 27 permitting clearance of the inner ring 34. The other on-screw element 21 is placed generally downstream of the restriction ring assembly 30, and has an end blade (not visible) which moves close to and wipes the opposite surface of the inner ring 34. The clearances between outer surfaces 22 of the on-screw elements 20 and 21 and the inner ring 34 of the restriction ring assembly 30, which can vary and preferably are of the order of 1 to 5 mm, determine to a large extent how much pressure build-up will occur in the upstream region of the restriction ring assembly 30 during operation of the mixer 100. It should be noted that the upstream on-screw element 20 has a length to diameter ratio (abbreviated herein as "L/D") of about 1/3, and the downstream on-screw element 21 has an L/D of about 2/3, resulting in a total L/D of about 1.0 for the on-screw elements. The restriction ring assembly 30 has a smaller L/D of about 0.45 which coincides with the L/D of the on-screw elements 20 and 21, which engage each other but do not touch the restriction ring assembly. Figs. 4 and 5 illustrate the mixing or "kneading" elements which perform most of the mixing work. The primary difference between the lower shear mixing element 40 of Fig. 4 and the higher shear mixing element 50 of Fig. 5 is the size of the mixing blades which project outward on the mixing elements. In Fig. 5, the higher shear mixing blades 54 which project outward from the surface 52 are larger and thicker than the lower shear mixing blades 44 projecting outward from the surface 42 in Fig. 4. For each of the mixing elements 40 and 50, the mixing blades are arranged in three circumferentially-spaced rows, as explained above with respect to Fig. 1. The use of thicker mixing blades 54 in Fig. 5 means that there is less axial distance between the blades and also less clearance between the blades 54 and the stationary pins 144 as the screw 120 rotates and reciprocates axially (Fig. 1). This reduction in clearance causes inherently higher shear in the vicinity of the mixing elements 50. Fig. 6 illustrates a single stationary pin 144 detached from the barrel 140. The pin 144 includes a threaded base 145 which permits attachment at selected locations along the inner barrel shaft 142. It is also possible to configure some of the pins 144 as liquid injection ports by providing them with hollow center openings. Fig. 7 is a schematic view showing a preferred barrel configuration, including a preferred arrangement of barrel pins 144. Fig. 8 is a corresponding schematic view illustrating a preferred mixing screw configuration. The mixer 200 whose preferred configuration is illustrated in Figs. 7 and 8 has an overall active mixing L/D of about 19. The mixer 200 includes an initial feed zone 210 and five mixing zones 220, 230, 240, 250 and 260. The zones 210, 230, 240, 250 and 260 include five possible large feed ports 212, 232, 242, 252 and 262, respectively, which can be used to add major (e.g. solid) ingredients to the mixer 200. The zones 240 and 260 are also configured with smaller liquid injection ports 241, 243, 253, 261, 263, 264, 265, 266, 267 and 268 which are used to add liquid ingredients. The liquid injection ports 241, 243, 253, 261, 263, 264, 265, 266, 267, and 268 include special barrel pins 144 formed with hollow centers, as explained above. As such, the positions of the smaller liquid injection ports can readily be changed. Also, not all of the injection ports need be used during a particular gum manufacturing operation. In that case, normal barrel pins will be used at the locations marked in Fig. 7 as a liquid injection port. Temperature sensors may also be used on some barrel pins 144 to measure product temperatures within the mixer. Referring to Fig. 7, barrel pins 144 are preferably present in most or all of the available locations, in all three rows as shown. Referring to Fig. 8, one preferred configuration of the mixing screw 120 for some chewing gum products is schematically illustrated as follows. Zone 210, which is the initial feed zone, is configured with about 1-1/3 L/D of low shear elements, such as the element 40 shown in Fig. 4. The L/D of the initial feed zone 210 is not counted as part of the overall active mixing L/D of 19, discussed above, because its purpose is merely to convey ingredients into the mixing zones. The first mixing zone 220 is configured, from left to right (Fig. 8), with two low shear mixing elements 40 (Fig. 4) followed by two high shear elements 50 (Fig. 5). The two low shear mixing elements contribute about 1-1/3 L/D of mixing, and the two high shear mixing elements contribute about 1-1/3 L/D of mixing. Zone 220 has a total mixing L/D of about 3.0, including the end part covered by a 57mm restriction ring assembly 30 with cooperating on-screw elements 20 and 21 (not separately designated in Fig. 8). The restriction ring assembly 30 with cooperating on-screw elements 20 and 21, straddling the end of the first mixing zone 220 and the start of the second mixing zone 230, have a combined L/D of about 1.0, part of which is in the second mixing zone 230. Then, zone 230 is configured, from left to right, with three low shear mixing elements 40 and 1.5 high shear mixing elements 50. The three low shear mixing elements contribute about 2.0 L/D of mixing, and the 1.5 high shear mixing elements contribute about 1.0 L/D of mixing. Zone 230 has a total mixing L/D of about 4.0. Straddling the end of the second mixing zone 230 and the start of the third mixing zone 240 is a 60mm restriction ring assembly 30 with cooperating on-screw elements 20 and 21 having an L/D of about 1.0. Then, zone 240 is configured, from left to right, with 4.5 high shear mixing elements 50 contributing a mixing L/D of about 3.0. Zone 240 also has a total mixing L/D of about 4.0. Straddling the end of the third mixing zone 240 and the start of the fourth mixing zone 250 is another 60mm restriction ring assembly 30 with cooperating on-screw elements having an L/D of about 1.0. Then, the remainder of the fourth mixing zone 250 and the fifth mixing zone 260 are configured with eleven low shear mixing elements 40 contributing a mixing L/D of about 7 1 3 . Zone 250 has a total mixing L/D of about 4.0, and zone 260 has a total mixing L/D of about 4.0. Before explaining where the various chewing gum ingredients are added to the continuous mixer 200, and how they are mixed, it is helpful to discuss the composition of typical chewing gums that can be made using the method of the invention. A chewing gum generally includes a water soluble bulk portion, 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 process. The insoluble gum base generally includes elastomers, elastomer plasticizers (resins), fats, oils, waxes, softeners and inorganic fillers. The elastomers may include polyisobutylene, isobutylene-isoprene copolymer, styrene butadiene copolymer and natural latexes such as chicle. The resins may include polyvinyl acetate and terpene resins. Low molecular weight polyvinyl acetate is a preferred resin. Fats and oils may include animal fats such as lard 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, candellia, carnauba and polyethylene wax. 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, color and emulsifiers. The gum base constitutes from 5 to 95% by weight of the chewing gum composition, more typically from 10 to 50% by weight of the chewing gum, and most comnonly from 20 to 30% by weight of the chewing gum. The water soluble portion of the chewing gum may 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 from 0.5 to 15% by weight of the chewing gum. The softeners may include glycerin, lecithin, and combinations thereof. Aqueous sweetener solutions such as those containing sorbitol, hydrogenated starch hydrolysates, corn syrup and combinations thereof, may also be used as softeners and binding agents in chewing gum. Bulk sweeteners constitute from 5 to 95% by weight of the chewing gum, more typically from 20 to 80% by weight of the chewing gum and most comnonly from 30 to 60% by weight of the chewing gum. Bulk sweeteners may include both sugar and sugarless sweeteners and components. Sugar sweeteners may include saccharide containing components including but not limited to sucrose, dextrose, maltose, dextrin, dried invert sugar, fructose, levulose, galactose, corn syrup solids, and the like, alone or in combination. Sugarless sweeteners include components with sweetening characteristics but are devoid of the commonly known 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 use high intensity sweeteners typically constitute from 0.001 to 5% by weight of the chewing gum, preferably from 0.01 to 1% by weight of the chewing gum. Typically, high intensity 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 acid and its salts, glycyrrhizin, dihydrochalcones, thaumatin, monellin, and the like, alone or in combination. Combinations of sugar and/or sugarless sweeteners may be used in chewing gum. The sweetener may also function in the chewing gum in whole or in part as a water soluble bulking agent. Additionally, the softener may provide additional sweetness such as with aqueous sugar or alditol solutions. Flavor should generally be present in the chewing gum in an amount within the range of from 0.1 to 15% by weight of the chewing gum, preferably from 0.2 to 5% by weight of the chewing gum, most preferably from 0.5 to 3% by weight of the chewing gum. Flavoring agents may include essential oils, synthetic flavors or mixtures thereof including but not limited to oils derived from plants and fruits such as citrus oils, fruit essences, peppermint oil, spearmint oil, other mint oils, clove oil, oil of wintergreen, anise and the like. Artificial flavoring agents and components may also be used in the flavor ingredient of the invention. Natural and artificial flavoring agents may be combined in any sensorially acceptable fashion. Optional ingredients such as colors, emulsifiers, pharmaceutical agents and additional flavoring agents may also be included in chewing gum. In the preferred embodiments of the invention, the gum base and ultimate chewing gum product are made continuously in the same mixer. Generally, the gum base portion is made using a mixing L/D of about 25 or less, preferably about 20 or less, most preferably about 15 or less. Then, the remaining chewing gum ingredients, including the rework, are combined with the gum base to make a chewing gum product using a mixing L/D of about 15 or less, preferably about 10 or less, most preferably about 5 or less. The mixing of the gum base ingredients and the remaining chewing gum ingredients may occur in different parts of the same mixer or may overlap. When the preferred blade-and-pin mixer is used, having the configuration described above, the total chewing gum can be made using a mixing L/D of about 19. The gum base can be made using an L/D of about 15 or less, and the remaining gum ingredients can be combined with the gum base using a further L/D of about 5 or less. In order to accomplish the total chewing gum manufacture using the preferred blade-and-pin mixer 200 (Fig. 1), it is advantageous to maintain the rpm of the mixing screw 120 at less than about 150, preferably less than about 100. Also, the mixer temperature is preferably optimized so that the gum base is at about 54°C (130°F) or lower when it initially meets the other chewing gum ingredients, and the chewing gum product is at about 54°C (130°F) or lower (preferably 52°C (125°F) or lower) when it exits the mixer. This temperature optimization can be accomplished, in part, by selectively heating and/or water cooling the barrel sections surrounding the mixing zones 220, 230, 240, 250 and 260 (Fig. 7). In order to manufacture the gum base, the following procedure can be followed. The elastomer, filler, and at least some of the elastomer solvent are added to the first large feed port 212 in the feed zone 210 of the mixer 200, and are subjected to highly dispersive mixing in the first mixing zone 220 while being conveyed in the direction of the arrow 122. The remaining elastomer solvent (if any) and polyvinyl acetate are added to the second large feed port 232 in the second mixing zone 230, and the ingredients are subjected to a more distributive mixing in the remainder of the mixing zone 230. Fats, oils, waxes (if used), emulsifiers and, optionally, colors and antioxidants, are added to the liquid injection ports 241 and 243 in the third mixing zone 240, and the ingredients are subjected to distributive mixing in the mixing zone 240 while being conveyed in the direction of the arrow 122. At this point, the gum base manufacture should be complete, and the gum base should leave the third mixing zone 240 as a substantially homogeneous, lump-free compound with a uniform color. The fourth mixing zone 250 is used primarily to cool the gum base, although minor ingredient addition may be accomplished. Then, to manufacture the final chewing gum product, glycerin, corn syrup, other bulk sugar sweeteners, rework gum, high intensity sweeteners, and flavors can be added to the fifth mixing zone 260, and the ingredients are subjected to distributive mixing. If the gum product is to be sugarless, hydrogenated starch hydrolyzate or sorbitol solution can be substituted for the corn syrup and powdered alditols can be substituted for the sugars. Glycerin may be added to the first liquid injection port 261 in the fifth mixing zone 260. Solid ingredients (bulk sweeteners, encapsulated high intensity sweeteners, etc.) are added to the large feed port 262. Syrups (corn syrup, hydrogenated starch hydrolyzate, sorbitol solution, etc.) are added to the next liquid injection port 263, and flavors are added to the final liquid injection port 264. Flavors can alternatively be added at ports 261 and 263 in order to help plasticize the gum base, thereby reducing the temperature and torque on the screw. This may permit running of the mixer at higher rpm and throughput. The effect of adding flavor very late in the continuous process, such as at injection port 264, is to obtain a gum product having a very fast flavor release, short duration, and high initial impact. The flavor is preferably mixed only from 5 to 10 seconds in the gum, compared to conventional gum manufacturing where flavor is mixed about 5 minutes. The effect of adding flavor a little earlier in the continuous process, such as at injection port 263, is to obtain a gum product having a slower flavor release, longer duration and mild flavor impact. The gum ingredients are compounded to a homogeneous mass which is discharged from the mixer as a continuous stream or "rope". The continuous stream or rope can be deposited onto a moving conveyor and carried to a forming station, where the gum is shaped into the desired form such as by pressing it into sheets, scoring, and cutting into sticks. Because the entire gum manufacturing process is integrated into a single continuous mixer, there is less variation in the product, and the product is cleaner and more stable due to its simplified mechanical and thermal histories. Testing The Suitability Of A Continuous Mixer The following preliminary test can be employed to determine whether a particular continuous mixer with a particular configuration meets the requirements of a high-efficiency mixer suitable for practicing the preferred method of the invention. A dry blend of 35.7% butyl rubber (98.5% isobutylene - 1.5% isoprene copolymer, with a molecular weight of 120,000-150,000, manufactured by Polysar, Ltd. of Sarnia, Ontario, Canada as POLYSAR Butyl 101-3); 35.7% calcium carbonate (VICRON 15-15 from Pfizer, Inc., New York, New York); 14.3% polyterpene resin (ZONAREZ 90 from Arizona Chemical Company of Panama City, Florida) and 14.3% of a second polyterpene resin (ZONAREZ 7125 from Arizona Chemical Company) is fed into the continuous mixer in question equipped with the mixer configuration to be tested. The temperature profile is optimized for the best mixing, subject to the restriction that the exit temperature of the mixture does not exceed 170°C (and preferably remains below 160°C) to prevent thermal degradation. In order to qualify as a suitable high-efficiency mixer, the mixer should produce a substantially homogeneous, lump-free compound with a uniform milky color in not more than about 10 L/D, preferably not more than about 7 L/D, most preferably not more than about 5 L/D. To thoroughly check for lumps, the finished rubber compound may be stretched and observed visually, or compressed in a hydraulic press and observed, or melted on a hot plate, or made into a finished gum base which is then tested for lumps using conventional methods. Also, the mixer must preferably have sufficient length to complete the manufacture of the gum base, and of the chewing gum product, in a single mixer, using a total mixing L/D of not more than about 40. Any mixer which meets these requirements falls within the definition of a high-efficiency mixer suitable for practicing the preferred method of the invention. Examples All of the examples were made using the following gum formula: % Base 19.46 Sugar 62.24 45.5° Baume Corn Syrup 15.57 Glycerin 1.05 Color 0.29 Flavor 1.39 100.00 Comparative Example A The foregoing formula was made by a conventional batch mixing process in a 568 liter (150 gallon) double arm sigma blade mixer with a batch weight of 713.7 kg (1573 pounds). The gum base was compounded and added to the mixer as a premixed base formulation. The chewing gum when discharged had a temperature of 45°C (113°F). Example 1-4 For the Examples below, various heated tanks, feeders and a BUSS blade and pin mixer with a 100mm mixer screw diameter were set up as shown in Figs. 7 and 9. The mixer 200 was set up with five mixing zones having a total mixing L/D of 19, and an initial conveying zone having an L/D of 1-1/3. No die was used at the end of the mixer, unless indicated otherwise, and the product mixture exited as a continuous rope. Liquid ingredients were fed using volumetric pumps from tanks 272, 276, 277 and 278 into the large feed ports 212 and smaller liquid injection ports. The pumps were appropriately sized and adjusted to achieve the desired feed rates. Dry ingredients were added using gravimetric screw feeders 271, 273, 274 and 275 into the large addition ports 212, 232 and 262. Again, the feeders were appropriately sized and adjusted to achieve the desired feed rates. Temperature control was accomplished by circulating fluids through jackets surrounding each mixing barrel zone and inside the mixing screw. Water cooling was used where temperatures did not exceed 93°C (200°F), and oil cooling was used at higher temperatures. Where water cooling was desired, tap water (typically at about 14°C (57°F)) was used without additional chilling. Temperatures were recorded for both the fluid and the ingredient mixture. Fluid temperatures were set for each barrel mixing zone (corresponding to zones 220, 230, 240, 250 and 260 in Figs. 7 and 8), and are reported below as Z1, Z2, Z3, Z4 and Z5, respectively. Fluid temperatures were also set for the mixing screw 120. Actual mixture temperatures were recorded by temperature sensors 281, 282, 283, 284, 285 and 286 (Fig. 7). These sensors were located near the downstream end of mixing zones 220, 230, 240 and 250 and at two places in mixing zone 260. Actual mixture temperatures are influenced by the temperatures of the circulating fluid, the heat exchange properties of the mixture and surrounding barrel, and the mechanical heating from the mixing process, and often differ from the set temperatures due to the additional factors. All ingredients were added to the continuous mixer at ambient temperature (about 25°C (77°F)) unless otherwise noted. The screw was configured as follows (Fig. 10): In the first barrel section, four low shear then two high shear elements having a total L/D of 4 were fitted to the screw shaft. Straddling the end of the first section and the beginning of the second was a 57mm restriction ring which, along with its on-screw hardware, had a L/D of 1. In the second section, three low shear elements then 1½ high shear elements having a total L/D of 3 were fitted. Straddling the end of the second section and beginning of the third was a 60mm restriction ring (1 L/D). In the third section was fitted 4½ high shear elements (3 L/D). A 60mm restriction ring (1 L/D) straddled the third and fourth sections. The fourth section was fitted with 5 low shear elements (3 1 / 3 L/D). The fifth section was fitted with two conveyor elements, one adjacent to the ingredient addition port 262, each having an L/D of 1. This was followed by 3 low shear elements having a total L/D of 2. The total screw length was 20 1 / 3 L/D. The zone temperatures (Z 1 - Z 5 in) were set to 177°C (350°F), 177°C (350°F), 66°C (150°F), 13°C (55°F) and 13°C (55°F). The screw was heated to 66°C (150°F). Several premix compositions were prepared to simplify the mixing process. Rubber Blend Three parts butyl rubber were ground with one part calcium carbonate. 32.785% of the ground mixture was dry blended with 51.322% calcium carbonate and 15.893% glycerol ester of hydrogenated rosin. Polyvinyl Acetate Blend 48.421% low molecular weight PVAc was dry blended with 11.849% glycerol ester of polymerized rosin and 39.730% glycerol ester of hydrogenated rosin. Fat Blend The following ingredients were melted and blended: 7.992% Hydrogenated Soybean Oil 13.712% Hydrogenated Cottonseed Oil 12.199% Glycerol Monostearate 37.070% Paraffin Wax 28.851% Microcrystalline Wax 0.176% BHT Corn Syrup/Glycerin Blend 93.710% 45.5° Baume corn syrup was heated and blended with 6.290% glycerin. Sugar/Color Blend 10% of a glycerin slurry of red lake was mixed with 90% sugar in a Hobart mixer. The resulting product was a damp powder which could be fed into the extruder with a twin screw volumetric feeder. The feed ports for the mixer are depicted in Figs. 7 and 9. To the first port 212 were added the rubber blend (15.7kg (34.67lbs)/hr) from feeder 271 and molten polyisobutylene (2.63 kg (5.80 lbs)/hr) from tank 272. Into the second port 232 was added the polyvinyl acetate blend at 11.34 kg (24.98 lbs)/hr from feeder 273. The molten fat blend was injected in equal portions from tank 276 through two injection pins 241 and 243 in section 240 at a total rate of 12.24 kg (26.98 lbs)/hr. The heated corn syrup/glycerin blend was injected from tank 277 through pin 267 located at the beginning of section 260 at a rate of 35.8 kg (78.92 lbs)/hr. Sugar was added from feeder 275 into port 262 at a rate of 128.47 kg (283.15 lbs)/hr along with the sugar/color blend from feeder 274 at 6.29 kg (13.87 lbs)/hr. Example 1 Cinnamon flavor was injected through pin 264 near the end of section 260 at a rate of 3 kg (6.62 lbs)/hr. This produced a total output of approximately 216 kg (475 lbs)/hr from the extruder. With this configuration, it was necessary to operate the screw at 109 rpm in order to prevent a backup of sugar in the fifth intake port 262. The finished gum exited at 53°C (127°F). Example 2 Another example was made using the same procedures as Example 1, but with 5% less flavor. The formulation flavor level was 1.32% cinnamon flavor, compared to 1.39% flavor in Example 1. The final discharge temperature of the product was 52°C (126°F). Example 3 Another example was made using the same procedures as Example 1, but with 10% less flavor. The formulation flavor level was 1.25% cinnamon flavor, compared to 1.39% flavor in Example 1. The final discharge temperature of the product was 52°C (125°F). Example 4 Another example was made using the same procedures as Example 1, but with 15% less flavor. The formulation flavor level was 1.18% cinnamon flavor, compared to 1.39% flavor in Example 1. The final discharge temperature of the product was 52°C (125°F). Sensory evaluation of the gums of Examples 1 and 2 vs. the gum of Comparative Example A shows that the gum of Example 1 had a higher flavor impact and hot spicy cinnamon character that was stronger than the flavor of the gum of Comparative Example A. Sensory evaluation of the gum of Example 2 vs. the gum of Comparative Example A showed that the gum of Example 2 had a cleaner, milder cinnamon flavor that was more like that of the gum of Comparative Example A. This shows that flavor levels may be reduced using high-efficiency mixing extruders compared to conventional mixers. A further reduction in the flavor may be possible, but a lower flavor level reduces plasticization of the gum base, causing it to be more rubbery and cohesive. Any lower flavor levels used would require some additional base reformulation work. It should be appreciated that the methods of the present invention are capable of being incorporated in the form of a variety of embodiments only a few of which have been illustrated and described above. It will be appreciated that the addition of some other ingredients, process steps, materials or components not specifically included will have an adverse impact on the present invention. The best mode of the invention may therefore exclude ingredients, process steps, materials or components other than those listed above for inclusion or use in the invention. However, the described embodiments are to be considered in all respects only as illustrative and not restrictive, and the scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description.

Claims: A method of continuously manufacturing chewing gum comprising: a) adding at least elastomer and filler into a continuous mixer, and mixing the elastomer and filler together in the continuous mixer; b) adding at least one ingredient selected from the group consisting of fats, oils, waxes and elastomer plasticisers into the continuous mixer, and mixing said ingredient with the elastomer and filler in the continuous mixer; and c) adding at least one sweetener and at least one flavour into the continuous mixer, and mixing said sweetener and flavour with the remaining ingredients to form a chewing gum composition; d) continuously discharging the chewing gum composition from the mixer; wherein steps a) to d) are performed using a single continuous mixer; and wherein less flavour is added than that used to make the same chewing gum composition in a batch mixer but the flavour intensity of the chewing gum composition discharged from the continuous mixer is substantially the same as or higher than that of said same chewing gum composition made in a batch mixer; and wherein the gum composition has a residence time in the continuous mixer of not more than 30 seconds after the flavour is added. A method as claimed in claim 1 wherein the continuous mixer comprises a blade-and-pin mixer. A method of continuously manufacturing chewing gum with improved flavour perception comprising: a) adding at least elastomer and filler into a continuous mixer, and mixing the elastomer and filler together in the continuous mixer; b) adding at least one ingredient selected from the group consisting of fats, oils, waxes and elastomer plasticisers into the continuous mixer, and mixing said ingredient with the elastomer and filler in the continuous mixer; and c) adding at least one sweetener and at least one flavour into the continuous mixer, and mixing said sweetener and flavour with the remaining ingredients to form a chewing gum composition; d) continuously discharging the chewing gum composition from the mixer; wherein steps a) to d) are performed using a single continuous mixer; and wherein less flavour is added than that used to make the same chewing gum composition in a batch mixer but the flavour intensity of the chewing gum composition discharged from the continuous mixer is substantially the same as or higher than that of said same chewing gum composition made in a batch mixer; and wherein the continuous mixer comprises a blade-and-pin mixer. A method as claimed in claim 3 wherein the gum composition has a residence time in the mixer of not more than 30 seconds after the flavour is added. A method as claimed in any one of claims 1 to 4 wherein the mixer is a high-efficiency mixer. A method as claimed in any one of claims 1 to 5 wherein: at least the elastomer and filler are subjected to dispersive mixing in the continuous mixer; and in step c)at least the sweetener, flavouring agent, elastomer and filler are subjected to distributive mixing in the continuous mixer, to form a chewing gum product. A method as claimed in any one of claims 1 to 6 wherein the amount of flavour is from 1% to 20% less than that used in said same chewing gum composition made in a batch mixer. A method as claimed in any one of claims 1 to 6 wherein the amount of flavour is from 5% to 15% less than that used in said same chewing gum composition made in a batch mixer. A method as claimed in any one of claims to 1 to 6 wherein the amount of flavour is from 10% less than that used in said same chewing gum composition made in a batch mixer. A method as claimed in any one of claims 1 to 9 wherein the gum composition has a residence time in the mixer of not more than 15 seconds after the flavour is added. A method as claimed in any one of claims 1 to 10 wherein the gum composition has a residence time in the mixer of from 5 to 10 seconds after the flavour is added. A method as claimed in any one of claims 1 to 8 wherein steps a)to c) are performed using a mixing length to diameter ratio of not more than 40. A method as claimed in any one of claims 1 to 12 wherein steps a) and b) are performed using a mixing length to diameter ratio of not more than 25. A method as claimed in any one of claims 1 to 13 wherein step c) is performed using a mixing length to diameter ratio of not more than 15. A method as claimed in any one of claims 1 to 14 wherein an elastomer plasticizer selected from the group consisting of polyvinyl acetates, terpene resins and mixtures thereof is added in step a). A method as claimed in any one of claims 1 to 15 wherein said at least one ingredient added in step b) is subjected to distributive mixing with the elastomer and filler. A method as claimed in any one of claims 1 to 16 wherein at least one flavouring agent is selected from the group comprising citrus oil, fruit essences, peppermint oil, spearmint oil, other mint oils, clove oil, oil of wintergreen, anise, cinnamon and mixtures thereof. A method as claimed in any one of claims 1 to 17 wherein the mixer comprises a mixing screw which rotates at less than 150 rpm. A method as claimed in claim 18 wherein the mixing screw rotates at less than 100 rpm. A method as claimed in any one of claims 1 to 19 wherein the mixer comprises first, second, third, fourth and fifth mixing zones. A method as claimed in claim 20 wherein steps a) and b) are substantially performed before the fifth mixing zone. A method as claimed in claim 20 or claim 21 wherein step a) is substantially performed before the third mixing zone. A method as claimed in any one of claims 20 to 22 wherein step c) is substantially performed after the third mixing zone. A method as claimed in any one of claims 1 to 23 wherein the mixer includes one or more points of restriction before step c). A method as claimed in claim 24 wherein the one or more points of restriction are created by one or more restriction rings.

Inventors: BRODERICK KEVIN B, RECORD DAVID W, SCHNELL PHILIP G, SONG JOO H, SUNDSTROM CHRISTAFOR E, TOWNSEND DONALD J, BRODERICK, KEVIN B., RECORD, DAVID W., SCHNELL, PHILIP G., SONG, JOO.H, SUNDSTROM, CHRISTAFOR E., TOWNSEND, DONALD J, SUNDSTROM, CHRISTAFOR E.,
Applicants: WRIGLEY W M JUN CO, WM. WRIGLEY JR. COMPANY
Application year: 1995
Main classification: A23G3
IPC codes: A23G4