Those who cannot remember the past are condemned to repeat it. So said philosopher and author George Santayana, and these words of wisdom bear repeating. It seems astonishing to many that the real future of food packaging is built on a foundation of our past that lies in the marriage of processing and packaging—déjà vu Nicolas Appert!
Headlines in packaging and trade journals—and too many media relations proclamations—shout of what will assuredly disrupt current food packaging and drive major innovation. In no special order, they include nano technologies; BPA-free can coatings; polymers derived by fermenting vegetable materials to produce alcohol, which is then converted at no small cost into ethylene for polymerization; compostable polylactic acid (natureworksllc.com); beta radiation, and—the silver bullet of all—perfect barrier plastics to replace metal and glass.
Archivists, however, have reviewed our history of the wildly heralded “disrupters from yesteryear”—polyethylene naphthalate (www.dupont.com), Tetra Pak’s Rigello plastic beer containers, selfheating cans, Merolite flexible beer tubes, liquid crystal barrier plastic, case-ready red meat from companies such as Excel (www.cargillmeatsolutions.com), polyacrylonitrile copolymers (www.dupont.com), oriented polyethylene film, and many more. And, they note, the actual “revolutions” of today required years of resource investment to generate the food packaging that 2011’s consumers accept routinely without even being able to cite them: recloseable zippers (www.ziploc.com), stand-up flexible pouches, modified atmosphere packaged fresh-cut produce (www.amcor.com), retort pouches and trays, aseptic cartons and cups, plastic cans, microwave susceptors (www.inlinepkg.com), and barrier polyester bottles (www.constar.net). Most of these successes were developed over prolonged periods by dedicated scientists and technologists and introduced as comprehensive product/machine/ package/distribution systems.
Drivers for the Future
With those records imbedded in our minds, let us dig deeply into the science, technology, and marketing that will drive today’s food packaging landscape. Contemporary psychographic studies of consumers present us with greater convenience to accompany the axiomatic safety and expected quality. The obvious response to this consumer desire is extended (refrigerated) shelf life (ESL) applying the principles of holistic hurdle technologies. The chilled circumferences of our retail groceries are filled with packaged ESL chocolate milk, prepared entrees and side dishes, sauces, soups, desserts, salads, sandwiches, etc. Safe shelf lives of months are achieved by linking the processing and reducing oxygen within the barrier package. Temperature abuse is minimized through oversight by processors, distributors, and marketers. And the rigid application of chilling and oxygen reduction together offer consumers food that matches the appearance, flavor, and mouthfeel of freshly prepared dishes.
ESL applies minimal process technologies. As one result, the package structure can be relatively lightweight plastic, which means that it is more sustainable. ESL products are usually very easy to prepare—with the packaging also functioning as a heating and serving dish.
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Oxygen is a key participant in aerobic microbiological growth, oxidative rancidity, and browning. Mechanical, steam or inert gas flush, or liquid nitrogen can reduce the oxygen to hundreds of parts per million. But packaging methods only remove the oxygen from the headspace, leaving dissolved and entrained—and entering—oxygen to react with the contents. And, unfortunately, none of the commercial oxygen scavengers can yet reach our targeted significantly reduced oxygen. Studies on oxygen-sensitive food products such as juices and beer have demonstrated that reducing oxygen present to parts per billion significantly reduces undesirable biochemical changes in the food. Shelf life can be extended to months, which translates into “fresh-like” quality retention for commercial distribution periods.
Micro-oxygen Processing and Packaging
As recited in a previous issue, reducing oxygen to micro-oxygen concentration requires integration of processing and packaging such as is performed with beer. Micro-oxygen will soon be applied commercially to high acid oxygen-sensitive foods and beverages. And soon after, when the research on low acid foods such as entrees and side dishes is completed, they will appear. In the beginning, watch for micro-oxygen packaged foods in ESL format, which will eventually evolve to shelf-stable packaged foods that may be kept at ambient temperature.
Although micro-oxygen is one component of this evolution, it is hardly the only active agent. Elements such as ultra high pressure processing, aseptic processing and packaging, and thermal processing also contribute to combination technologies. The application of pasteurizing heat after packaging provides extended chilled shelf life to soups, main courses, and side dishes.
Several months ago in this publication, we described microwave pasteurization technologies that integrate several technologies to extend chilled shelf life to 45+ days. Hermetically sealed, microwave-transparent heat seal, lidded barrier trays are fitted with steam vents and exposed to 2,450 MHz microwave energy. The microwave energy heats the food and generates steam within the package to compensate for the nonuniformity of the microwave energy within the food. The steam vent releases excess pressure during a heating cycle of less than 10 minutes.
With the driver of European success plus the debut of microwave assisted thermal sterilization (MATS), a revolution in thermal preservation of foods is arriving.
Microwave Assisted Sterilization
MATS will be commercially introduced in the United States next year. Food is packaged in hermetically sealed microwaveable barrier trays conveyed through a pressurized hot water tunnel (www.matspack.com). Combination of the elevated-temperature hot water with incident 915 MHz microwave energy and steam generated within the package can sterilize the product in less than 10 minutes. Heating is followed by pressure cooling to arrest the cook process. Product quality is like fresh for salmon, macaroni and cheese, and cooked potatoes—even after ambient temperature storage.
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Might the MATS systems at Washington State University also be applied for lower-heat pasteurization? Combining microwave pasteurization in hurdle technologies are we gazing at the master food packaging innovation for tomorrow? Couple MATS with more recent developments in line-continuous microwave sterilization of pumpable foods in a tube: now, commercially aseptically packaged sweet potato puree from Yamco LLC (www.yamco.net) and tomorrow, such foods as sauces, soups, baby foods, initially in institutional sizes but eventually to enter the realm of consumer-sized packages.
Aseptic Processing and Packaging of Particulate Foods
The realm of microwave heat preservation leads us into aseptic packaging of food particulates now being used by SIG Combibloc (www.sig.biz). So far only a limited number of particulate- containing soups have reached our shelves, suggesting that Industrial Microwave’s system for in-line microwave plus aseptic packaging is applicable to consumer sizes.
Hurdle Microwave Preservation and Other Preservation Technologies
We could link microwave thermal treatment with ultra high pressure assisted thermal sterilization (PATS) and to reduce the heat damage even more, couple micro-oxygen and integrate with aseptic packaging. Dare we not enter this universe to offer the consumer safe packaged food that is even better than the locavore’s demand and the misguided howls for unprocessed foods without protective packaging?
Today even more dramatic technologies can reduce thermal inputs to sterilize. Still, hydrostatic and even rotary retorts suffer from relatively long cook times under high temperatures to reach sterility in metal cans, glass jars, and barrier plastic cans. By engineering pressure cookers to agitate the packages by reciprocating or rocking actions, sterilization and cooling times may be reduced by 30% to 80% (www.allpax.com). Less heat enables canners, bottlers, retort pouch packers, and barrier plastic can processors to reach their goal of better quality. At the outset for retort pouches and trays, the belief was that the higher product surface-to-volume ratio would foster much faster heat penetration with consequent better quality. Might the new retorts be able to deliver on the original promise?
Could we close without comment on another of the hurdle technologies—active packaging? So long in development—oxygen scavengers to remove oxygen, odor scavengers to eliminate transient odors, and that favorite, antimicrobials, have not yet arrived. But oxygen scavengers can now be incorporated into the plastic material of the primary package instead of by inserting sachets by Multisorb (www.multisorb.com) and Cryovac (www.cryovac.com) and by multiphase plastics from CSP Technologies (www.csptechnologies.com). The world of antimicrobials is now being revisited with chlorine dioxide precursors that minimize adverse secondary discoloration and with allyl isothiocyanate (AIT) that destroys pathogenic microorganisms on meat surfaces. Silver salts that have been sprinkled into paper for fresh meat handling represent yet another option.
Our Future Rests on Courageous Hurdling
Active packaging, the one publicized technology that has not been commercialized effectively, will come down from its attic and impact us within this decade. The same is true for the less visible hurdle technologies, with their reduced oxygen and reduced heat and microwave assists and aseptic packaging of more solids. This will serve to buttress our notion that the future lies in ESL technology, with all of its product, process, and package benefits.
Aaron L. Brody, Ph.D.,
President and CEO, Packaging/Brody Inc., Duluth, Ga., and Adjunct Professor, University of Georgia