Portable PackagingPortable Packaging

Portable Packaging
June 2000 -- New Technologies

By: Kay Cooksey, Ph.D.
Contributing Editor

  There's little doubt that people today are more mobile and busier than ever. We save time by taking meals with us in the car or by eating at our desks while working. Portable packaging helps provide convenience in many ways, and prepared and portion-controlled foods make it easy to pack food for camping trips, weekday lunches and numerous other occasions.

The purpose of packaging

  Ever since nomads used calf stomachs to hold milk, packages have protected foods for people on the go. Today, however, a package must do more than contain and protect. It must also provide convenience, facilitate product use, inform the consumer through Nutrition Facts panels, sell the product through eye-catching graphics, and address environmental concerns such as source-reduction and recycling.

  Packages fulfill these functions through primary, secondary, tertiary and quaternary package components. The primary package is always that which comes directly in contact with the product - an inner pouch used to contain dry cereal, for example. The secondary package contains either one or more primary packages - a folding carton for a cereal pouch perhaps, or one that holds a package of cereal and a fruit-juice box. In addition to bundling, secondary packaging provides space for graphics and structural support for product protection. Tertiary and quaternary package components are used for shipping and distribution. Corrugated boxes are common tertiary packages, while a group of shipping containers bundled on a pallet with stretch wrap represents a quaternary package. Although the portable packages discussed in this article are primary and/or secondary packages, package designers must always consider how the entire system will function when designing each component.

  Portable packages contain everything from single-serve products to entire meals, all promoted for busy people on the go. Portable packages should have the following elements in common: allow one-handed access, provide a single serving size, require minimal assembly, need little or no cooking, and eliminate the need for utensils or a level eating surface. Some products are eaten within minutes of purchase, but others are expected to remain shelf-stable for several months. In some cases, products are likely to be temperature-abused prior to consumption. Thermal processing, aseptic processing/packaging and modified-atmosphere, barrier or selective-permeability materials can help protect such foods.

Combination kits

  Kits are a popular way to combine a grouping of products for a "complete meal." Two basic styles of secondary packages are commonly used to bundle such kits. One is the paperboard folding carton or sleeve, typically made of either cylinder board with a bleached liner for the printed side or solid bleached or unbleached sulfate. Some cartons are die-cut to reveal a component of the kit, which helps provide recognition and consumer appeal. A plastic thermoformed tray or clamshell is the second type of package commonly used to bundle kits. These allow better visibility of the entire contents; some have handles or reclosure features built in for convenience.

  In 1988, Northfield, IL-based Kraft Food's Oscar Mayer Foods division started the trend of portable meal kits with its Lunchables® line. Today there's an expanded lineup of cold cuts, crackers and cheese; pizza; tacos or nachos; hot dogs or hamburgers; and pancakes or waffles. Many of these include condiments, beverages and desserts.

  Convenience can come with a price, though. Consumer groups have complained that these products represent excess packaging. What they fail to recognize is that most companies are not interested in spending money on more packaging than is necessary. Individual packaging is often necessary to preserve product freshness and prevent microbial spoilage and foodborne illness. However, the issues raised by consumers are important to remember when designing packages for kits, and it's always a good idea to reduce the amount of packaging whenever possible.

  Other portable kit-type packages include a tuna-salad mix and a child-oriented snack kit. Newport, KY-based StarKist Food's tuna offering consists of a thermoform tray with a flexible peel lid; inside are a pouch of crackers and a can of premixed tuna salad. The package can be placed on a shelf or hung on a peg or hang-tab display strip. The Snack-a-long snack kit from the foodservice division of Battle Creek, MI-based Kellogg Company is made of a clear, thermoformed clamshell with a handle molded into the tray. The kit, which is available from in-store grocery delis, contains a drink box, fruit-filled snack bar, bag of cereal and a toy.

Packaged to go

  Soups. The "Campbell's Soup to Go" line, marketed by Campbell Soup Company, Camden, NJ, contains 10.75 oz. of soup in a retort cup (foam-covered plastic can) with a plastic snap-fit lid. The paperboard carton also holds a pouch of Goldfish® crackers (1 oz.) and a pouch of cookies (2 oz.). The kit relies on brand-name recognition and familiar graphics to help market the components of the package, which shows the cracker pouch inside through a die cut on the carton.

  There are a variety of portable packaging options for soups depending on whether the soup is thermal-stabilized or dried. Most thermal-stabilized soups are packaged in steel or plastic cans (polyacrylonitrile or nylon coextruded) with an easy-open metal top. The plastic cans have a foam insulation sleeve and a plastic snap-fit lid with vent holes in the top, which makes it possible to microwave and eat from the same package. Dry soups are often packaged in a cup made of solid bleached-sulfate paperboard with a moisture-resistant coating or a polystyrene cup. Both types of cups typically have paper-based, foil-laminated peelable lidding.

  Another option is to use a pouch. Sahara Natural Foods, Irwindale, CA packages its organic soups in pouches, which the company says use up to 84% less packaging than cups of the same serving size. The company also says that foil-based laminate provides a better-quality product with a longer shelf life than with a paper-based cup. This is not surprising, since foil is an absolute barrier and can provide better protection than most polymer coatings used on paper and paperboard.

  Cereal. Breakfast is usually the first thing eliminated at the start of a busy day. Nevertheless, a number of portable packaging systems have been designed for that long-time breakfast favorite, cereal.

  For many years, small portion-controlled cereal pouches were packaged in paperboard cartons perforated on the principal display panel to create a "bowl." Once the carton was opened, the pouch could be ripped open and milk poured inside. This design has been popular for many years.

  More recently, polystyrene foam or polypropylene thermoformed bowls prefilled with cereal and a peelable lidding have been commonly found in restaurants, institutions and hotels with self-serve breakfast bars. These packages, however, require the addition of milk before leaving the serving location. One solution to this dilemma came in the form of Breakfast Mates, introduced by Kellogg's. This kit contained a single serving of 2% milk along with a 3/4-oz. carton of cereal, all bundled in a paperboard secondary carton. Consumers were dubious about the aseptic milk, however, and there was difficulty identifying the best retail display location. Although the aseptic milk didn't require refrigeration, the kit was sold from the refrigerated case, which may have also helped bring about the demise of this package/product combination.

  Beverages. Beverages have always been considered an on-the-go product, but package designs continue to drive new sales. For example, Franklin Park, IL-based Dean Foods' Milk Chugs®, which have won a variety of package design awards, combine bottle size and shape with eye-catching graphics, all of which have helped increase milk sales. The easy-to-hold product's bottle and cap are made of high-density polyethylene (HDPE), and have the look of an old-fashioned glass milk bottle. The label is made of polyvinyl chloride (PVC) that shrinks to the shape of the bottle.

  Land O'Lakes, Minneapolis, is also using a shaped HDPE bottle with a PVC shrink label to sell its Grip'n Go™ milk. The company is selling milk in 12-oz. bottles, intended to compete with canned and bottled soft drinks of a similar size.

  One of the most portable of all packages, aseptically packaged drink boxes are popular because they're easy for a child to hold, fit well in lunchboxes or gym bags, allow product to remain fresh at room temperature, and can be frozen. This packaging has even been used for military MRE (Meal Ready to Eat) field rations. The boxes are constructed of paperboard (for stiffness), polymer (adhesive and moisture resistance), and foil (barrier) layers. An individually wrapped straw is generally adhered to each box.

  Variations of this type of package are straight-sided and contour stand-up pouches. These are form/fill/seal pouches made of polyester laminated to foil and ionomer for a sealing layer. Like the boxes, they also have a straw spot-adhered to the pouch, although some converters can provide a pouch with a straw inside that can be punched from the inside-out.

  SaddleSprings Beverage Company, Torrance, CA, markets a 200-ml shaped stand-up pouch of water for lunch boxes or for campers and hikers. The pouches can be displayed in a variety of ways. In club stores, the tertiary package serves as a display, while in convenience stores, the pouches can hang on a strip or sit in a tray adhered with suction cups to the doors of refrigerated cases.

  Yogurt. Yogurt has been aseptically processed and packaged in individual-serving thermoformed cups for many years. Recently, a couple of new designs specially targeted for portability have helped boost yogurt sales. Yoplait Go-Gurt™, produced by Minneapolis-based General Mills, is packaged in a three-sided tube-shaped pouch; no spoon is required to eat the yogurt. The pouch is made of polyester/LDPE/LDPE-based sealant layer and produced on a form/fill/seal machine. The tubes are packaged in solid bleached-sulfate cartons in multiples of eight.

  Colombo yogurt, another General Mills brand, caters to the on-the-go market by selling yogurt in containers that have a snap-out spoon molded into the lid.

  Snack foods. Dean Foods is introducing a line of single-serve dips for chips or fresh vegetables. The HV Food Products Company, Oakland, CA, has a similar line of Hidden Valley® products. Such dips are sold in thermoformed cups with a foil-based peel lid, and are bundled in paperboard sleeves in packs of four or six. The size and shape of the cup must facilitate dipping.

  Frito-Lay, Plano, TX, has taken this concept a little further by providing chips with the dip. A segmented thermoformed tray contains chips on one side and a cup of salsa or nacho cheese dip on the other. The entire package is flushed with nitrogen to maintain the low-oxygen atmosphere. An excellent seal is also necessary to prevent leaks.

  Another of the company's products combines chips with chili; a retortable double-seamed "bowl" with a metal lid and plastic reclosable overcap is used for chili. The entire package is capable of withstanding microwave heating for 60 seconds, as long and the tray lidding and the chili-bowl lid are removed prior to heating.

  Packages that can stand up on their own are important for foods eaten while driving or working at a desk. Paperboard-based composite cans economically provide this function. Kellogg's Snack'Ums™, for example, is a line of cereal snacks packaged in a composite can with a plastic snap-fit top. The resealable package stands on its own and has a shape and form associated with other snack foods such as Pringles® potato chips, which helps convey the idea that this product is indeed a snack.

  Shelf-stable, ready-to-eat fruits in steel cans with an easy-open pop-top have been available for many years. But now Del Monte Foods, San Francisco, is marketing a product called Fruit To-Go in a clear, 4-oz. plastic cup that is flushed with a mixture of gases to provide up to an 18-month shelf life when stored at room temperature. The fruit is cold-filled and then retorted in the package. Polypropylene provides heat resistance during retorting and ethylene vinyl alcohol acts as an oxygen-barrier layer to help maintain product quality and safety.

  One of the most unusual products/packages to be introduced recently is IncrEdibles™, from Breakaway Foods LLC, Columbus, OH. These egg- or pasta-based products are packed in a paperboard tube with a stick that pushes the product up from the bottom. The product is microwave heated, which means the paperboard tube must withstand temperatures of up to 160°F. Therefore, the paperboard requires a heat-resistant coating such as polyester. The packages can be frozen for shipping and retail storage, then thawed at refrigeration temperature and microwave-heated in about 2 minutes. The tubular shape also facilitates heating on hotdog-roller machines, without ever removing the product from the package. In addition to using existing equipment, the company promotes this feature as a way to prevent product contamination from handling.

Out and about food

  For years, fast-food drive-up windows have catered to people who want to eat in their cars or somewhere other than a dining room. Grocery stores and take-out delis now also help fill this niche. Some newer developments include pocket-shaped sandwich wraps that trap drippings, french fries in self-standing cups, and wax- or polymer-coated take-out bags that can serve as placemats.

  Shelf life is an important concern for take-out foods, especially when foods are prepared in a central location and then shipped for sale at another location, such as a convenience mart or gas station. One company, Made-Rite, Ooltewah, TN, found that the shelf life of their prepared sandwiches could be extended from 14 days to 30 to 60 days (depending upon the variety of sandwich) just by switching to a material that maintained a 0.5% residual oxygen level and a mixture of carbon dioxide and nitrogen. The company says the previous polystyrene-based packaging allowed too much oxygen inside the package, causing a 13% to 20% stale rate for sandwiches, while with the new material, stale rates have dropped to 5% to 6%.

  Modified-atmosphere pouches and trays require a strong seal. Any leaks could cause a change in the atmosphere that would reduce product quality and permit growth of foodborne-illness-causing bacteria. Materials such as linear low-density polyethylene (LLDPE), ionomer and ethylvinyl acetate (EVA) have been used for heat sealing. However, metallocene polyethylene resins are now becoming the choice for strong heat seals as well as for improving package strength. Made-Rite uses this material for their new sandwich packages, and it's also used by Salinas, CA-based Tanimura & Antle's SaladTime® line of modified-atmosphere precut salads. One of the advantages of metallocene resins is a strong melt strength during blown-film production and an ability to achieve precise oxygen transmission rates by adjusting the material's density.

  Portability is clearly a major marketing trend for many new products entering the market. It has also proven effective for boosting sales of standard products such as milk and yogurt. Innovative use of materials, structural design and graphics will continue to make portable packages popular for many years to come.

  Kay Cooksey is an associate professor in the department of packaging science at Clemson University, Clemson, SC. She received a B.S. in food science from Purdue University, an M.S. in industrial mechanical technology from Indiana State University, and a Ph.D. in foods and nutrition from the University of Illinois at Urbana-Champaign. She is currently chair-elect of the Institute of Food Technologist's food packaging division.

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