In conventional chewing gum processes, a gum base and plasticizer are initially kneaded in baker type kneaders. Once the gum base has become a viscous melt, additional ingredients, such as sugar, rework, artificial colorings and the like are mixed into the melt. The mixing step usually involves first adding about one tenth of the total sugar and a starch hydrolyzate such as corn syrup and thoroughly mixing in those ingredients. Then, the remaining sugar is added and thoroughly mixed in. The flavoring is typically added last so that the flavoring is only mixed into the chewing gum paste for about one to three minutes. A typical processing rate is 2.5 metric tons per hour, requiring two one-ton capacity kneaders each operating on a 20 minute cycle.
Difficulties with this kneading and mixing operation are that it requires a complex intermitent timing control for ingredient addition, does not lend itself to feedback loop control, and tends to be labor intensive.
After the chewing gum paste has been thoroughly kneaded and mixed, the paste is held for about 30 minutes and then formed into a loaf by using either a chewing gum extruder pump and guillotine or a loaf forming machine which forms loaves by calendering and cutting. The loaves are typically 1/2" to 11/2" thick, 1 to 11/2 ft. wide and about 18 inches long. The temperature of the loaves after forming is about 55.degree. C. The loaves are then cooled to about 48.degree. C. to 52.degree. C. If the temperature of the formed loaves is much above 55.degree. C., the loaves, due to their thickness, cannot be cooled quickly enough which results in a detrimental change in the gum paste texture, and if kept at high temperatures too long affects crystal structure. Improper gum paste texture results in difficulty with further processing, and improper crystal structure results in a hard and brittle gum product.
After the loaves are cooled, they are transported to a forming extruder which consists of a nonintermeshing counter rotating twin screw pump with a rectangular orifice. The loaves are formed into slabs 13 to 25 mm thick and 16 to 18 inches wide. These thick gum paste slabs must be thinned into slabs the thickness of a stick of gum, typically 1.6 to 1.8 mm. Such thinning is accomplished by passing the slabs through a series of calender rolls. The speed of the slabs increase upon exiting each set of calender rolls, and the thinned slabs gain considerable speed (40 to 55 meters per minute) by the time they exit five sets of rolls. Typically, five sets of such calender rolls are used for an industrial unit operating at 21/2 tons per hour. Maintaining precise dimensional control by using a number of calender rolls such as five sets of calender rolls has been found difficult and the multiple calendering is very sensitive to viscosity variations. Furthermore, coating material such as sugar must be applied to the slabs to prevent sticking. When multiple calender rolls are used, very large amounts of coating material are applied to the slabs before the first roller to carry through the remaining rollers. Since large amounts of coating material are used (12 to 15 weight percent based on the finished product), the excess coating material must be collected after calendering and recirculated requiring complex material handling equipment to minimize dust problems. Furthermore, the use of large amounts of coating material often results in excess coating materials on the gum pieces which affects the efficiency of subsequent packaging.
The speeding thinned gum paste slabs are then sliced into separate sheets containing scored bands which are suitable for feeding to an automatic wrapping machine. Because of the rapid speed of the thinned slabs, precise slicing is difficult resulting in varying dimensions and a significant amount of material (7 to 15 weight percent based on the final product) which must be refed to the system as rework. Each sheet is dimensioned to be as long as the width of about twenty-three to twenty-four sticks of gum and as wide as the length of about five or six sticks of gum. The individual sheets are scored into about five or six bands, each about as wide as twenty-three to twenty-four sticks of gum and as long as one stick of gum. The bands are removed by a takeaway conveyor and are stacked for feeding to the wrapping machine. The stacked bands are usually cured for about 16 to 24 hours at a temperature of about 20.degree. C. One of the more widely used wrapping machines is the ACX-5 supplied by the Packaging Machinery Company of Springfield, Mass.
While the present system has performed satisfactorily, it has been desired to produce chewing gum which is less sensitive to product viscosity; has minimum material in the mixing operation resulting in better process response time, shorter flavor turnover time, and wider capacity operating range; lends itself to simplified process control; is compact; produces properly dimensioned product with textural consistency; reduces rework; and reduces the need for a complex sugar recirculation and dust collection system.
There have been attempts to address the desires of the industry. For example, U.S. Pat. No. 2,256,190 discloses an apparatus and method of handling chewing gum which utilizes a twin screw extruder for mixing a gum base material and extruding an elongated strand of material that is then rolled, calendered and cut. U.S. Pat. Nos. 1,852,005 and 1,953,295 disclose a twin auger mixing device wherein the ingredients are centered through a single opening and mixed by the twin screw auger in a steam jacket. The gum is extruded through a strip forming orifice. U.S. Pat. Nos. 3,455,755 and 3,644,169 disclose a method and apparatus for producing laminated slabs of chewing gum paste wherein a hot viscous melt is transferred from a holding pot to a sheeting nozzle which forms ribbons preferably 1/8" to 3/8" thick. The ribbon is then calendered and folded to form the laminated gum.
These efforts, however, have not been entirely satisfactory.