Canadian Plastics

The Complete Package

Today's package designers and manufacturers are confronted with the challenge to make packaging that is functional, appealing, distinctive, user-friendly and, most formidably, "better". Better, here, ...

August 1, 1999   By Michael LeGault, editor



Today’s package designers and manufacturers are confronted with the challenge to make packaging that is functional, appealing, distinctive, user-friendly and, most formidably, “better”. Better, here, refers to packaging that improves shelf life of the product, enhances quality, reduces costs or in some way adds an element of non-traditional value. It is the pursuit of the better package that is making “intelligence”, in the form of new designs, materials or processes, a prominent feature of cutting-edge packaging.

No where is the demand for intelligent packaging stronger than in the food industry. Food is to packaging as a marathon is to running–the ultimate challenge. The food package must not only protect but ideally prolong the shelf life of perishable contents inside it.

BARRIER APPLICATIONS ABOUND

Food packaging applications that use some form of advanced barrier technology have been on the rise for several years. Chantler Packaging’s PEAKfresh film is a low density polyethylene film impregnated with a natural mineral. The impregnated mineral imparts unique absorptive properties to the film, the most significant being the ability to remove ethylene, which is produced by certain fruits and vegetables and can quicken degredation. The film also absorbs moisture and has permeability to gas 4.5 times greater than standard LDPE at room temperature. These properties of the film work to prolong the life of fresh fruit, vegetables and cut flowers, says Beverly Ferguson, special projects coordinator, Chantler Packaging.

Chantler, based in Mississauga, Ont., extrudes PEAKfresh masterbatch into roll stock, carton liners, flat bags, sheets and pallet liners and covers. It is the licensee for the Americas for PEAKfresh film. Ferguson reports that the film is being used in a host of applications, including the shipment of California strawberries to Japan. A large supermarket chain is currently conducting a trial to use the film for shipping broccoli without ice. Shipping broccoli in ice requires waxed cartons which can’t be recycled and adds significant extra weight to the package. Ferguson says the company is planning to launch a retail line of PEAKfresh produce storage bags in the near future.

An exciting new film technology under development at Cryovac, Sealed Air (Canada) Corp. has the potential to extend the shelf life of meat by as much as one-third, says Jennifer Morris, program manager, case-ready packaging. Morris says the film, called LID550P, is essentially two films in one: a gas permeable film, which in turn is laminated to an oxygen-impermeable film. During the meat packing process the meat is placed in a barrier foam tray using a Ross Inpack 3320 tray lidding machine. The trays are indexed forward into a vacuum chamber, a vacuum is drawn and the trays are backflushed with a mixture of approximately 25 percent carbon dioxide and 75 percent nitrogen. The film is then sealed to the tray. When the package reaches the store the outer impermeable layer is peeled away allowing oxygen to enter the package and transform the meat into its consumer-preferred “bloomed” or red state.

“One of the big advantages of this packaging is that you don’t need as much head space as you do in a high oxygen package,” says Morris. “You can have film-to-product contact.”

The film is not yet commercially available in Canada, although it will be once development work is completed, reports Morris. Any meat packager wishing to run the film would have to meet stringent quality control guidelines and have a good partnership with a retailer in order for the program to succeed, says Morris.

The use of oxygen scavengers in PET bottles and bottle closures is becoming more widespread, says Nina Goodrich, Amcor PET Technologies’ director of business development and technology. Oxygen absorbers in closures reduce oxygen amounts in the head space above the level of the juice or soft drink. Goodrich also reports that Amcor is supplying Neilson with a PET milk bottle with a UV barrier and a shrink-wrap label to cut down on visible light entering the bottle.

American National Can has been a leader in barrier

packaging technology since the introduction of its six-layer polypropylene/EVOH process, licensed under Gamma polypropylene. The technology is used to make co-extruded, blow-molded bottles for ketchup and other food products. The company is looking to extend the technology to wide-mouth containers, used for foods such as pickles and pasta suaces, which are presently made of glass, according to Rick Ampleford, manager sales and marketing, American National Can (Canada), Inc.

“We made a 750 ml wide-mouth polypropylene container 10 years ago and the food packaging industry said ‘Oh that’s nice’,” says Ampleford. “The issue with polypropylene is clarity. We’re on our second or third generation of clarified PP resins and we’re closer now than ever in gaining acceptance for it.”

Ampleford says the company’s three-layer Gamma PET barrier technology is being used to manufacture PET beer bottles supplied to Bass Brewers in the Britain. The PET barrier technology keeps oxygen outside and carbon dioxide inside the bottle, says Ampleford. The shelf-life of beer bottled in PET has improved from an intial three-months to the present six months, says Ampleford.

“There are U.S-based food retailers who are saying, ‘get me out of glass’,” says Ampleford. “Glass is breakable, heavier. The challenge in successfully converting to plastic is part technical, such as the high heat required for some food applications, and part perception. The technology is evolving to get there.”

FORM-FILL-SEAL GROWING UP

It is hardly surprising that a process that increases packaging line speed, uses less packaging material and reduces waste is gaining wider acceptance among packaging end-users. As the name suggests, form-fill-seal is a process which, starting with a roll of printed film, converts the film into a bag, fills the bag and seals it in one continuous operation.

“There is a shift away from bag-inside-a-box applications, for instance cereals and crackers, to stand up pouches and flexible packaging,” says Jeffery Wooster, value chain manager at Dow Plastics. “Vertical form-fill-seal is very efficient and we’re seeing some markets which have traditionally preferred pre-formed bags moving to this newer technology.”

Wooster says form-fill-seal has been given a boost by advances in decorative film technology, so that in some cases a package actually gains aesthetic appeal by switching from a box to a form-fill-seal bag or pouch.

Another factor pushing form-fill-seal applications is advances in packaging machinery, notes Paul Zeff, director of engineering at Zarpak Inc., an engineering services company that designs, integrates and installs packaging lines for end-users.

“A single vertical form-fill-seal machine is like a work cell in that it integrates the functions of a number of different machines,” says Zeff. “There’s a higher up-front cost but the payback is in the tremendous efficiency and space savings.”

Zeff says the company has helped design a number of proprietary form-fill-seal lines and that the technology is just coming into its own. “At the higher end, you’re seeing a switch to multi-lane machines that can do six, eight or 10 bags at every draw. Some of these machines can make 70 draws a minute, so in a multi-lane configuration, that’s dropping a lot of bags.”

Using the form-fill-seal process, Arkmount Systems Inc. created the A-Pak stand-up pouch system, from machine to film, as an alternative to other single-serve packages, such as Tetra packs, glass bottles and gable top cartons (Canadian Plastics, Jan. 1998). The A-Pak pouch system is used to produce stand-up milk pouches for Neilson Dairy. The pouch is made of a co-extruded polyethylene film laminated to PET. The pouches are printed and formed in an interlocking pattern, so that the base of one is next to the neck of another, so little film is wasted.

ATMOSPHERE IS EVERYTHING

Modified atmosphere packaging (MAP) is the replacement of the air in
a package headspace with a specific gas or gas mixture in order to preserve the appearance of fresh foods and extend the shelf life. In general, use of MAP has been shown to extend shelf life of food by 50 to 90 percent, says Caroline Moziar, food market manager for Air Liquide Canada Inc.

The three gases used in MAP are nitrogen, carbon dioxide and oxygen, either singly or in combination, says Moziar. Nitrogen is used to displace oxygen, reduce oxidative reactions and inhibit growth of aerobic microorganisms. It is also used as a filler gas to prevent package collapse. Carbon dioxide inhibits microbial and mold growth. Oxygen is needed to sustain respiration of fresh produce and preserve color “bloom” of red meat.

Air Liquide supplies MAP gases under the brand name of Aligal food shielding atmospheres. Aligal gas is approved for food contact and is supplied as single, bi-mixtures or tri-mixtures of gases. Use of a particular gas or combination of gases is dependent on food moisture content. As a rule, Moziar notes, 100 percent nitrogen is used in dry product such as chips, a combination of nitrogen and oxygen is best for food of intermediate moisture, such as cheese, pasta entrees, prepared sandwiches and sliced deli meats, and 100 percent carbon dioxide for high moisture meats such as chicken.

Film technology is evolving to meet new performance requirements brought by modified atmosphere packaging. Mobil Chemical Company has developed a high barrier metallized film, 70 Met-HB, to meet the barrier properties required for snack and other food packaging flushed with nitrogen. ClearFoil SiOX-F laminate developed by Rollprint Packaging Products provides oxygen permeability of only 0.003 cc per 100 sq. in. per day at ambient temperatures, as well as low water vapor permeability.

In a recent paper, Dow Plastics’ Jeffery Wooster discusses some of the factors for designing or finding the right film for modified atmosphere packaging used for keeping fresh-cut produce. Fresh-cut produce continues to breathe, consuming oxygen and giving off carbon dioxide. Wooster argues that a properly designed MAP system should reduce produce respiration but not completely stop it. Enough oxygen must be present in the package to allow limited aerobic respiration, otherwise spoilage can result. Each type of produce respires at a different rate, so matching the selective barrier properties of the package with the respiration rate under the expected conditions is the key to successful MAP applications, writes Wooster.

Factors to consider when designing a proper film structure include resin selection, film construction (monolayer, co-extruded, laminated), film thickness, additives and processing conditions.

Says Wooster: “As packaging systems advance there really seems to be an emphasis on packaging integrity as it relates to food safety and quality. New packaging designs have created a new standard for package performance.” CPL


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