HOW DID THEY DO THAT? SHELF STABLE PACKING
A SYNERGISTIC COMBINATION OF INNOVATIONS IN PACKAGING EQUIPMENT, CONTROLS, BARRIER MATERIALS AND PROCESS TECHNOLOGY IS BRINGING A GROWING NUMBER OF SHELF-STABLE PRODUCTS TO STORE SHELVES IN RESTORABLE PLASTIC PACKAGING.
By Hallie Forcinio
There was a time—not that long ago—when retort and plastic would never be used in the same sentence. Today retorted products in plastic pouches, trays, cups and bottles are proliferating. In fact, three out of the 15 finalists in the 2006 PACK EXPO Selects™ competition were retorted products in plastic packaging, and one, Beneful® Prepared Meals™ dog food from Nestlé Purina Petcare Co. of St. Louis, Mo., was voted Best of Show by attendees at PACK EXPO International.
The Beneful Prepared Meals dog food package consists of a lidded multilayer tray with a windowed shrink sleeve label that provides product visibility. An overcap not only protects the tabbed, peelable lidstock during distribution and storage, but also provides a means of easy reclosure if the contents are not consumed in one meal.
The other two retorted products among the 2006 PACK EXPO Selects finalists helped round out the competition’s top five vote-getters: Ready-to-drink Cool Java iced cappuccino from Kan-Pak, LLC of Arkansas City, Kan., in a retorted, rib-less, multilayer plastic bottle from Sonoco of Hartsville, S.C., and Meow Mix Market Select wet cat food from Del Monte Foods of San Francisco, Calif., in an embossed, multilayer plastic cup from Printpack of Atlanta, Ga., with printed foil laminate lidstock.
Another retorted plastic packaging success story is the switch from a can to a reclosable, shrink-sleeve-labeled, multilayer bottle for Ensure liquid meal replacement from Abbott Laboratories’ Ross Products Division of Columbus, Ohio. The design, which won a Gold Award in the DuPont Awards competition in 2004, is widely viewed as a game-changing innovation that boosted sales for the brand and has competitors scrambling to follow.
Hormel Foods Corp. of Austin, Minn., which is perhaps best known as the maker of Spam in rectangular cans, has introduced a number of shelf-stable products in innovative plastic containers in recent years including Hormel Compleats and Kid’s Kitchen microwaveable meals in lidded trays and easy-open cups, respectively. Indicative of how important next generation retorted products are to Hormel is the recent appointment of Michael L. Devine, a 31-year company veteran, as director of operations strategy. In the newly created position, Devine will make sure the company’s shelf-stable product initiatives are supported with the right resources.
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PACK EXPO Selects The PACK EXPO Selects™ competition debuted in 2006 as part of The Showcase of Packaging Innovations™, a special pavilion sponsored by The Dow Chemical Co. of Midland, Mich., at PACK EXPO. It consisted of a special display and electronic voting system that allowed attendees to recognize the year’s most innovative packaging designs by voting for their two favorites. Each of the finalist packages were developed, designed, converted or produced by one or more PACK EXPO International 2006 exhibitors. Attendees at this year’s PACK EXPO Las Vegas will have an opportunity to vote for their favorite 2007 PACK EXPO Selects finalists. Remember to visit The Showcase of Packaging Innovations and vote at the show! |
Retorted products in plastic pouches, trays, cups or bottles require a combination of innovative material, machinery and control technology if the packaging is to withstand the rigors of the retort process and provide a reasonably long shelf life. This may necessitate changes in the retort process itself to provide air overpressure that prevents plastic packages from exploding or imploding as well as more precise control of the retort cycle.
Seals also must be strong enough to withstand the hydraulic forces of product sloshing around in the container, yet may also need to be peelable for easy opening. As a result, sealing must be consistently flawless, and quality control requirements are stringent to confirm seal integrity and identify any damaged containers.
Filling precision may need to be increased to prevent spills and splashes that could contaminate the seal area and cause voids. “People are still trying to come up with foolproof technology to prevent particulates in the seal area of pouches,” says Tyler Hudson, business development manager at Allpax Products, Inc. of Covington, La., a maker of retorts and related material handling systems, which became part of Pro Mach of Cincinnati, Ohio, in 2006 and now operates as part of its Primary Packaging Business Unit. Even today, “many companies do 100 percent [manual] seal inspection after the retort,” reports Hudson.
In fact, most seal integrity and leak testing is done off-line on samples pulled from the line at specified intervals. However, the classic leak tests, the blue dye water bath, drop and burst tests that destroy the samples, are frequently being replaced by nondestructive tests based on pressure or vacuum decay. In addition, inspections are no longer limited to off-line, periodic testing.
Online seal integrity testing of flexible packaging is possible with noncontact, ultrasonic Seal-Scan technology from Packaging Technologies and Inspection, LLC of Tuckahoe, N.Y. Available in two online models capable of 100 percent seal inspection, the Seal-Scan systems locate a wide array of defects by studying how the seal passes an ultrasonic signal. The Seal-Scan systems can locate wrinkles, contamination/inclusions, channel defects, misaligned seals or delamination/blister flaws in seal widths measuring up to 6 millimeters (mm). The Seal-Scan 550 and Seal-Scan 540 can check seal widths from 3-6mm at speeds up to 150 and 100 pouches per minute, respectively.
Another concern related to retortable plastic packaging is handling of empty and full containers to prevent damage that could compromise product safety. In many cases, especially with trays and pouches, conveyor back pressure needs to be eliminated so packs don’t shingle and jam. Finally, retortable plastic packaging may require more robust distribution packaging than a comparably sized three-piece steel can or glass jar.
A successful transition to retortable plastic packaging also depends on the availability of appropriate line speeds for filling, sealing and end-of-line operations. For example, on the line filling Beneful Prepared Meals dog food, multilayer trays thermoformed by Printpack Inc. of Atlanta, Ga., from a proprietary, clear, seven-layer polypropylene/ethylene vinyl alcohol coextrusion are filled, vacuumed, gas-flushed and sealed at 250/minute on a seven-lane machine from Rychiger AG, of Steffisburg, Switzerland. Designed for ultra-precise sealing, the fill-seal machine continuously monitors the temperature of each seal head while combining a mechanical seal stroke with preloaded individual air-springs on every lane to deliver high seal forces in a short dwell time. The combination of short dwell time, high pressure and low temperature makes it possible to form seals that are secure, yet peelable.
Sealed trays are discharged to a conveyor for transport into a retort basket. After leaving the retort, trays are dried and flipped upside down so a shrink label applicator from PDC Corp. of South Norwalk, Conn., can apply a windowed shrink label. After passing through a steam tunnel to shrink the label, trays are turned base down. A worm screw then orients the trays and spaces them at a fixed distance for the trip through the overcapping equipment from Orics Industries. Moving grippers grab each tray from both sides. As the tray moves under a chute that feeds lids from Alcoa Closure Systems International of Indianapolis, Ind., the leading lip of the tray contacts the lid and pulls it on. Once the lid is snapped in place, the grippers release the tray, and it’s conveyed to the case packer.
Should a back-up occur, free rollers in the conveyor eliminate friction between the moving belt and the bottom of the containers.
Speed is also an issue on the processing side, where reduced heat exposure can improve product freshness, color and texture. Performance testing indicates a new retort design from Allpax reduces cycle time up to 95 percent compared to static retorts. A back-and-forth agitation of the containers accelerates heat transfer through the product, potentially cutting a processing time of 80 minutes to as little as eight minutes. Briefer heat exposure means a finished product with significantly improved organoleptic qualities such as flavor, mouth feel, texture, color, as well as nutrient retention. A lab-size 2402SK Shaka retort with a patent-pend-
ing, spring-based vibration-dampening design was introduced in the fall of 2006 at PACK EXPO International and will soon be joined by full-size models.
Retorts used to process product in plastic pouches, cups, trays or bottles also benefit from today’s more advanced programmable logic control systems. “Because [these types of] containers are far more fragile and delicate than a can or jar, precision control especially of pressure and steam, becomes critical,” concludes Hudson.
Hallie Forcinio has been covering trends in the packaging industry for more than 20 years.
