Kraft's clamshell says 'Manchego'

Last May, Kraft Foods de Mexico introduced its Manchego-style sliced pro-cessed cheeses in two hinged clamshells that stand out from the flexible film packs that dominate cheese packaging in Mexico. The unique Barex® CAM resin used to make the clamshell is supplied by BP Chemicals (Cleveland, OH). BP makes the resin exclusively for American Mirrex (New Castle, DE). AM uses calendering equipment to produce its Mirran(TM) sheet stock. Blistertec (Anahuac, Mexico) thermoforms that sheet into individual clamshells. Jorge Saucedo Varela, Kraft's packaging engineer for the Manchego cheese project, says Mexican consumers typically use the processed cheese for dishes such as quesadillas, or melt it over tortillas. Saucedo admits that clamshells are a costlier alternative than flexible film packs. In this instance, however, package differentiation was more important than economics. The decision has proven to be a smart one. "We are now packaging up to 12 tons of the product per week, compared to 10 tons in the first month of production," he says. "It's proving to be very successful." Mexico City-based Kraft Foods de Mexico manually packs the clamshells with slices that are individually wrapped in a polyethylene/ polypropylene film lamination. For the 10-slice version, five slices are placed into each of the clamshell's two compartments. The larger package holds 10 slices per side. Economics weren't completely forgotten. For example, both clamshell sizes are thermoformed using a single mold. The difference is the draw; the larger size is about 1/2" deeper than the 10-slice version. For the smaller clamshell, Blistertec adds an insert to the mold to reduce the depth. The resin's rigidity and thermoforming characteristics allow production of a 20-g clamshell for the larger version. It performs comparably to 35-g clamshells made from alternate resins, Saucedo says. One competitor in Mexico markets sliced cheese in a polyvinyl chloride blister. However, Saucedo believes that clamshell has weaknesses. "That package, we feel, doesn't have as good an appearance as ours, and there's some damage to those clamshells. It has structural problems because it is made from a thin layer of PVC so it gets compressed in transport, and the borders and bottoms get bent. "We selected the Mirran sheet," he continues, "because we wanted a higher oxygen barrier for ensuring product freshness and [to give] us a longer shelf than other resins could provide. The clamshell for the cheese provides excellent oxygen and aroma barriers that prevent the cheese from picking up the scent of other products in the refrigerator. "Its ergonomic shape makes it easy to handle and its snap closing top makes it easy for the consumer to open," he adds. Corrugated shippers containing the clamshell-packed cheeses have been distributed as far as 3ꯠ km (1꽀 miles) without damage. Product testing indicates that the product is good for one year, although Kraft codes it for five months. That makes it comparable to the company's sliced cheeses packed in flexible film. Unique resin Production of the CAM resin began within the past year, according to Joe McCaul, export manager, Barex. Like earlier Barex versions, CAM is a high-barrier, impact-modified acrylonitrile methylacrylate copolymer. The difference, McCaul says, is that CAM is manufactured specifically for the calendering process at American Mirrex. "We are moving into the area of calendering," he explains, "where it makes sense with large customers that have specific machinery, like American Mirrex. Barex has run on small calendering machines in Europe for years, but only recently has American Mirrex begun to use this process with Barex in the U.S. Kraft Foods de Mexico represents one of the first end users of the resin." At American Mirrex, the resin is heated and mixed by a "fluxing" device. This machine heats the resin to a near-molten state, similar to an extruder, but instead of going through an extrusion sheet die, the material proceeds through a calender that consists of four large rolls that flatten the material into a continuous sheet. In the case of the material used by Blistertec, the sheet measures approximately 21" wide, and is 15 mils thick. During calendering, temperature, tension, shrink characteristics, and cooling are precisely controlled by American Mirrex to produce the Mirran rollstock for Blistertec. Once the sheet goes through the calender, it winds through additional cooling rolls. According to American Mirrex, calendering improves thickness control, and esthetics, when compared to extruded sheet. American Mirrex sends the calendered material to Blistertec. Miguel Batista of Blistertec says an existing Spanish-built, six-cavity thermoforming machine automatically produces 48 clamshells/min. Clamshells are then die-cut. The thermoformer recently manufactured a semi-automatic machine that places a four-color, pressure-sensitive label on the inner side of the hinged portion of the clamshell. Labeled clamshells are shipped to Kraft Foods de Mexico. "Our marketing department wanted a package that would give us a different presentation on the store shelf," recalls Kraft's Saucedo. "We sell American cheese slices in flexible film packs, like most sliced cheese in Mexico. But this clamshell gives this product a difference, and it also presents a difference in the consumer's refrigerator."