Rimming the perimeter of every retail grocery in the United States is that arena of nearer-to-fresh foods seemingly favored by most consumers: the refrigerated foods departments. Generating the highest margins and greatest growth rates among all foods gracing the interiors of retail food establishments, chilled foods represent the niche which food processor/marketers have been attempting to capture for the past 20 years. They represent the fastest-growing segment of food science and technology.

Modified-atmosphere packaging is being used for a variety of products distributed under refrigeration. From left, Jimmy Dean processed meat sandwiches; home-meal replacement kits consisting of sauce plus individual packets of modified-atmosphere-packaged pasta and modified-atmosphere-packaged fresh-cut vegetables; and DiGiorno high-acid pasta sauce.Ranging from fresh ingredients such as backroom-cut red meat through minimally processed such as fresh-cut vegetables and to ready-to-heat-and-eat prepared foods, chilled foods have surged into a large share of stomach leadership. With better flavor/mouthfeel quality and perceived nutritional value, refrigerated foods are now at the core of debate regarding their safety. 

Long ago, refrigerated foods were milk, cheese, sour cream, barely washed vegetables, whole fish, and red meat cut from carcass with the consumer as witness. The belief was that refrigeration changed the product the least but afforded the least shelf life. Times to retain microbiological safety ranged from hours for meat to days for dairy products if enough ice were available. Visible mold on processed meat and cheese, sour odor from fluid milk, decaying lettuce, and stinky seafood were the norm, all accompanied by the potential and reality of adverse public health problems. 

Concepts such as thermal pasteurization of milk and vacuum packaging of processed meats were resisted—in many instances, vigorously. Packaging in those “good old days” was primitive, if it existed at all: returnable glass bottles for fluid milk, waxed paperboard tubs with metal closures for cheese, no packaging for frankfurters or lettuce. Packaging did not contribute to food preservation for refrigerated foods back then, and the foods suffered as a consequence. 

During the 1950s–60s period of emergence of food packaging technology, professionals dared to marry reduced oxygen to the newly developed oxygen-barrier-plastic packaging structures to generate vacuum packaging of processed meats and primal cuts of fresh red meats. Organizations such as Pure Pak, Mahaffay and Harder, Multivac, Hayssen, Standard Packaging, American Can, Cryovac, Whirlpool, and others, mostly from the realm of packaging, reached out to pioneer the dramatic changes in delivery of refrigerated foods. The most important element that all learned and conveyed was that packaging alone could accomplish relatively little. They mirrored those few seers in food science and technology who conceded that their discipline in isolation from packaging and distribution could not deliver the requisite safe quality food. Packaging could not compensate for mediocre-initial quality; and food science could not deliver fresh food even under the best commercial refrigeration. 

Here are some areas where progress has been made:
Processed Meats. And so, during the 1950s, vacuum packaging of hot dogs, luncheon meats, and sliced bacon offered the means for a wide variety of cured meats that sated consumers who had been confined to Saturday night visits to the neighborhood delicatessen. Processed meats in flexible transparent plastic packaging were the harbinger of families of foods capable of weeks of shelf life in what was then a very crude refrigerated-distribution infrastructure. 

Reduction and retention of oxygen were just two components of a total system that, in retrospective, were among the earlier holistic packaging. New concepts in sanitation, cooling of the product during processing and later distribution, reduced contaminants in seasonings, optimization of salt and nitrite, cooking and smoking when applicable to reduce microbiological loading, and moisture control all contributed to the total effect. 

The laminations may be thinner and the packaging equipment may be computerized,but the principles are the same today, with one result a massive industry serving consumers throughout the country and the world.

Block and Sliced Cheese. It was evident to many that the same principles could aid in preserving cured cheese, so new oxygen/moisture-barrier laminations were wrapped around blocks and slices of Cheddar, Swiss, and all varieties of other cheeses. The classical Hayssen horizontal RT wrapping machines, with counterflow carbon dioxide to reduce oxygen and function as an antimicrobial, were coupled with a new cellophane/polyvinylidene chloride lamination to extend mold-free shelf life to months—under refrigeration. Some cheese makers continue to use the horizontal flow wrappers, but with contemporary laminations containing oriented polypropylene in place of the now archaic cellophane. But many cheese makers have converted to horizontal thermoform/vacuum/seal machine such as used for processed meats.

Shredded Cheese. Shredded cheeses suffer from high surface area that fosters growth of visible mold. These toppings for pizza and casseroles can experience prolonged shelf life under carbon dioxide in gas-barrier packaging, especially when the interior of the package material is powdered with sorbic acid, one of the earlier manifestations of antimicrobial active packaging. But the early vertical form/fill/seal machines had to be modified before shredded cheese entered the mainstream. Zipper, and now slide, reclosures permitted consumers to open, retrieve part of the contents, and then reclose snugly, a major benefit immediately perceived by consumers.

Red Meat. Engineering the conversion of red meat from the traditional and hazardous hanging carcass were those who proposed reducing the meat to primal cuts and placing them in (oxygen) barrier bags which, under refrigeration, could offer six weeks of shelf life, while simultaneously tenderizing the contents through natural enzymatic action. Much bone and fat were eliminated, thus reducing the distribution costs despite the packaging costs. Microbiological spoilage was markedly reduced by the combination of better sanitation, temperature control, separation from the air, and reduced oxygen. Eventually, virtually all beef and pork was being distributed in barrier bags, now improved with integral bone protection and better gas barrier. 

But hanging over the barrier bag as a mechanism for fresh-meat delivery is case-ready red meat, about which much has been written in this column and elsewhere. With one major driver being reduction of the potential for Escherichia coli O157:H7, the many different packaging options implemented and proposed to date suggest greater microbiological safety—attributable to the better controls required to support the packaging systems. Again, packaging, processing, and distribution are inextricably linked—sanitation and temperature control are indispensable for high or low oxygen or air packaging, barrier or non-barrier, individual or master packaging. And none of the identified developing technologies appears to offer more from a microbiological safety perspective. Each case-ready packaging technology addresses the issues of microbiological spoilage and red color differently, with some suggestions of longer refrigerated shelf lives possible. 

One disturbing aspect to all of the rhetoric surrounding the case-ready red meat situation is the misinformation, disinformation, and ignorance being communicated. Objectivity stemming from independent and detached professionals is not a hallmark of the march into case-ready red meat. Too few universities are fulfilling their charter of providing sound scientific support for this incredibly complex emergent and important sector of chilled foods. Too much of the field appears to belong to hucksters and opportunists, a situation that might become hazardous to consumers’ health.

Fresh-Cut Produce. By definition, controlled-atmosphere packaging (CAP) includes temperature control, and modified-atmosphere packaging (MAP) includes the essential temperature control. CAP and MAP are not effective except at reduced temperatures. Although applied to a myriad of food products, including red meat, poultry, sandwiches, cured meats, cheese, pizza, and prepared foods, MAP is most highly publicized for fresh-cut produce. Born nearly 20 years ago as a safer and better method to provide salads for hotel/restaurant/institutional (HRI) operations, fresh-cut produce graduated to retail during the 1990s, when it exploded into the top-volume-growth product of that era. 

By employing freshly harvested produce that is processed in clean and cold plants, thoroughly cleaned in flowing chlorinated water, distributed under ensured controlled refrigeration, fresh-cut produce has demonstrated its microbiological safety in literally billions of commercial packages and thousands of laboratory tests. Fresh-cut produce is cleaner and safer than whole head lettuce, cabbage, carrots, or any other analogous vegetable. Consumers of the convenient fresh-cut vegetables do not have to try to remove the dirt, debris, and spoiled outer leaves in their always-less-than-ideal kitchens, and certainly are not urged to cook their lettuce or spinach before mixing it into salads. 

The major issue with fresh-cut produce is that it continues to respire and consume oxygen. In packages sealed to block microbiological contamination, reduction of oxygen to near zero leads to respiratory anaerobiosis and its attendant adverse flavor consequences. Overcoming this problem has required the development of package structures capable of admitting air—by actual openings, high-gas-permeability polymers, and doped plastics. While passing oxygen, these structures must maintain their internal moisture and, not incidentally, foster transparency through the use of anti-fog agents on the package material. 

High-gas-transmission structures are diametrically opposite of the barrier structures that packaging material suppliers have been targeting for the past half century. Amazing how packaging technologists had to turn completely to provide the needs of a new sector of the chilled foods industry—and thus help to spark this industry to its mainstream position.

Prepared Foods. A product category officially designated home-meal replacements (HMRs) dawned about ten years ago, despite the fact that convenience foods have been a major food product segment since Mr. Heinz invented ketchup and Mr. Campbell offered canned condensed soups. HMRs are even more convenient, since they are neither canned nor frozen, but rather are fully or nearly fully prepared and ready for the microwave oven or for direct eating, often right from the package. 

Because quality was equal to convenience in importance, the category has been generally centered around foods that are prepared and chilled for distribution or even acquired hot: soups, meat salads, sandwiches, sauced pastas, mixed component entrees, barbecue chicken, pizza, and pudding-type desserts. Retail grocers had sensed a loss of business to nearby restaurants and reacted with their own version of take-away. Because of the very short shelf lives, retailers often elected to prepare the products in backroom kitchens and package them in the most rudimentary structures, such as black (to suggest quality) polystyrene trays with polyvinyl chloride film overwraps for short shelf life. These products might not be readily differentiated from restaurant take home, or even leftovers. 

Food processors responded in kind by launching convenience foods with longer shelf lives, applying holistic technologies combining formulation with sanitation in processing and rapid chilling plus MAP. The chilly perimeter of supermarkets proliferated with plastic-packaged lunch and pizza “kits,” soups, cooked chicken, and heat-pasteurized entrees. Food microbiologists soon perceived these foods to be potentially hazardous, since many were packaged under reduced oxygen that suppresses spoilage microorganisms and thus removes competition against pathogenic anaerobic spores. Indeed, when the distribution temperature is abused, as is hardly uncommon in commerce today, the issue is real. But extensive testing has demonstrated that sensory quality deteriorates long before microbiological problems arise—not the most perfect of barriers. By truncating the expiration times and controlling carefully, most of the susceptible HMR products have proven to be safe in commercial distribution channels. And the quality, while not yet gourmet, is good to excellent—a definite stimulus to rapid turnover and consumption. 

Microbiological safety remains a concern, as it always has and always will in an environment in which, after all, refrigeration is the final sole barrier to adverse microbiological consequences. MAP, even with excess oxygen in the hermetically sealed barrier package most pathogens, so other hurdles such as pH and water activity control and mild post-fill thermal processing are integrated. But temperature control throughout distribution channels remains the most effective technology. Our commercial channel members must address this issue—as they have for many years, but now with added incentives. 

Several textbooks have been written recently about chilled foods. In addition, the University of Georgia Dept. of Food Science and Technology has instituted a graduate course in chilled foods that at the very least raises all the questions posed here and more, and alerts those students who are about to enter our industry that a host of technical problems await them when they step into the growth arena of chilled foods. The real issue is that chilled foods do not follow the relatively simple single-technology model of our past but rather represent a complex of interacting science that must be studied and implemented as a whole—the concept of holistics. 

Chilly is a hot topic today and will be for as far into the future as we can envision. 

Plastic Mesh Netting for use as shrinkable overwraps for turkey, hams, and other packaged meat products is made of specially blended resins. The net shrinks tightly over products packaged in Cryovac® bags when processed through a standard hot-water shrink tunnel. The tight-fitting overwrap is said to be less likely to catch or tear, making handling easier and safer. For more information, contact NSW, LLC, 530 Gregory Ave., Roanoke, VA 24016 (phone 800-368-3610 or 540-981-0362, fax 540-345-8421).

Reusable Bulk Container, the Exotainer, is suitable for storage of such food-grade liquids as tomato paste, juices, or purees. The wide, full-open top of the steel-and-plastic container accepts all aseptic fillers in the market and adapts to existing aseptic bag liners. The water-proof container can be stacked six high outdoors and allows compact storage on return freight. For more information, contact Paper Systems, Inc., 321 S.W. 4th St., Des Moines, IA 50309 (phone 800-342-2855, fax 515-280-9219).

Contributing Editor
President and CEO, Packaging/Brody, Inc.
Duluth, Ga.