What’s Active about Intelligent Packaging

Among the appellations attached to a new generation of packaging that does more than we are accustomed to are active, smart, and intelligent. Does this mean that our same-old food packaging is dumb? The overwhelming majority of more than 100,000 participants in American packaging would not agree, since contemporary packaging appears to perform magnificently in protecting our $700 billion worth of food from factory to consumers’ tummies.

In my January 2001 column, I defined active packaging as responding to environmental change, and I threatened to return with what is at this moment described as intelligent packaging—packaging that senses and measures variations in the environment or the package and its contents and communicates to an observer.

It is fuzzy ground bounded on one edge by food and on the other by the new realm of electronics, but I will attempt to summarize the current state of information from a wonderful symposium on Active and Intelligent Packaging organized and conducted last fall by Campden and Chorleywood Food Research in the United Kingdom under the patient direction of Brian Day (who, not incidentally, will summarize all that is European on the topic at the IFT Food Packaging Division symposium at IFT’s Annual Meeting in New Orleans this month).

The two approaches to the concept of active packaging are novel materials which are less expensive and the application of electronics and microelectromechanical (MEMS) systems which are more flexible but too costly today for consumer packages. MEMS reflects a range of sensor and transducer technologies borrowing from semiconductors. MEMS technology can detect pressure, acceleration, humidity, temperature, and other environmental variables. Complementary metal oxide semiconductor technology offers storage devices that allow information to be integrated into packaging. Logging devices are capable of monitoring shock, temperature, and humidity, for example, for chilled fish transport.

There are a variety of applications for these two approaches, with the most important considerations being quality and added value. The dominant applications are time–temperature integrators (TTI). However, there are also other applications such as the occasionally used microwave cooking doneness indicators and reordering-data recording.

Time–Temperature Integrators/Indicators. TTIs are devices that exploit a change in a physical or physicochemical property to produce irreversible evidence of exceeding a predetermined temperature threshold or record the cumulative time–temperature history. Such devices have been proposed for decades, but have hardly been used commercially because of historical unreliability, inconsistency, poor reproducibility, and an inability to accurately correlate the data to actual food deterioration within packages. These devices have been proposed and are being used commercially to track both chilled and frozen foods. They generally function by physical, enzymatic, or chemical reactions following the classical Arrhenius equation that correlates the rate of reaction to temperature. Generally microbiological and biochemical food deterioration follow Arrhenius equations. The reaction in the TTI devices can be observed by color movement, change or development. A key variable is the initiation of the reaction or activation energy required to start the reaction.

The major commercial TTIs in the world are LifeLine™, 3M Monitor Mark®, and Vitsab®, a Swedish product. LifeLine undergoes a chemical polymerization, darkening the center of a bullseye window. LifeLine must be kept frozen prior to use to ensure it is not activated prior to its intended time. The 3M product relies on physical diffusion of a chemical solute, with a colored face migrating on a white wick. Vitsab depends on enzymatic hydrolysis of a lipid that leads to a color change. The 3M and Vitsab devices are activated by breaking seals separating the components.

LifeLine, originated at AlliedSignal some 15 years ago, has been part of an independent organization since 1987. Its Fresh-Check™ has been commercial since 1990 and its HEATmarker™ for monitoring vaccine vials during distribution since 1992. Each integrator is specifically programmed to the time–temperature criteria for each type of product being measured. HEATmarker is required by the United Nations for vaccine distribution packages to ensure that the product has not been exposed to debilitating temperature abuse and therefore are still viable. Fresh-Check is the company’s bullseye-type integrator applied largely for primary or secondary packages to monitor the cold chain for chilled foods. Several European grocery chains, including France’s Monoprix and Netherlands Albert Hiejn, apply Fresh-Check labels on surfaces of packages for products such as fresh meat, fish, salads, dairy products, juices, and fresh pastas. In the United States, Fresh-Check has been used by Campbell’s Soup, Eatzi’s, and Trader Joe’s on their chilled prepared foods packages to signal to consumers if temperature abuse has occurred.

Vitsab has been applied to distribution packages for farmed fish, fresh-cut salad, and ground beef.

Price of the TTIs remains an important variable in decisions to employ them. In the vaccine situation, temperature abuse is a critical efficacy factor, in environments where human life is at stake, so cost is not as important an input. With food products in industrialized distribution situations, cost becomes a much more significant consideration to processors and distributors.

Freshness Indicators. Freshness indicators differ from time–temperature integrators in that they signal product quality directly rather than depending on inference from temperature history. Among the methods suggested today are visible indicator tags in contact with the package headspace, labels, electronic detectors, and optical detectors. Generally, freshness indicators function by detecting the presence of microbiological metabolites such as carbon dioxide, sulfur dioxide, ammonia, amines, hydrogen sulfide, organic acids, ethanol, toxins, or enzymes. The indicator systems for metabolites include color change of a dye or liquid crystals, formation of color compounds, changes in optical properties, or miniaturized electronic nose or headspace gas detector suggested by Aromascan.

Thus, freshness indicators may detect volatile or nonvolatile compounds or changes in the product itself. Volatile compounds such as hydrogen sulfide may be detected by myoglobin-based or chemical indicators. Nonvolatile compounds such as biogenic amines or ATP degradation products may be detected by enzymatic indicators. Product changes may be detected by immunochemical methods.

Myoglobin-based freshness indicators are based on the visible absorption spectrum of myoglobin. This spectrum is altered by hydrogen sulfide, with the change correlated with the hydrogen sulfide concentration. In commercial metmyoglobin-based freshness indicator sachets, the color changes from brown to red in the presence of hydrogen sulfide volatiles resulting from spoilage. Such indicators have been employed commercially to track microbiological quality of modified-atmosphere-packaged poultry and have been demonstrated to correlate well with sensory results.

Ethanol indicators are based on the correlations that have been determined between ethanol concentration and microbiological spoilage of poultry and fresh fish.

The only known commercial freshness indicator is the Fresh Tag® label produced by Cox Recorders. Fresh Tag reacts to volatile amines with a color change. The label consists of a plastic chip in which is incorporated a reagent-containing wick. Attaching the label to the package exposes a barb that penetrates the package and thus establishes contact between the interior headspace gases and the reagent. Color develops as the amines pass through the wick.

Toxin Guard™ from Toxin Alert is claimed to detect the presence of pathogenic bacteria using immobilized antibodies. As a toxin or microorganism contacts the material, it is bound first to a specific labeled antibody printed as a certain pattern.

Food Sentinel™ from Sira Technologies is based on an immunochemical reaction taking place within a bar code. In the presence of a particular microorganism, the bar code is no longer readable.

Lawrence Berkeley Laboratories have developed a sensor material specific to the detection of Escherichia coli O157:H7 enterotoxin. Cross-linked polymerized polydiacetylene incorporated into plastic exhibits a deep blue color. In the presence of the enterotoxin, the plastic color turns to red.

Although the sensors are based on chemical reactions, their outputs may be converted into electronic signals that may be readable through a wireless radiofrequency (RF) interface. Printed circuits containing conducting polymers become electronic tags capable of detecting freshness or its absence.

Other Applications. Other active packaging applications have been developed.

Counterfeiting is a major problem in many geographies for pharmaceuticals, distilled beverages and nonfood items. Holograms, microtaggants, diffraction devices, and electronic data tags are now used widely to deter counterfeiting. Holograms cannot be duplicated by copiers, scanners, or printers. Furthermore, their visual effects cannot be readily reconstructed or simulated. Holograms may now be incorporated into films, transfer foils, tear tapes, and labels in all manner of two- and three-dimensional designs intended to thwart thieves and, incidentally, to decorate the packages.

Theft Protection is another area in which active packaging may be used. Electronic Article Surveillance (EAS) is used commonly to deter theft for higher-priced goods, and is leading into acousto-magnetic, electronic, and RF tagging.

Supply Chain Management and Traceability is aided by automatic data capture and distributed data technologies, which can trace the product anywhere in the supply channel. The technologies employed include linear and two-dimensional bar codes, memory tags, and RF-emitting tags. These devices are used in distribution channels to keep track of pallet loads of food products, and are increasingly essential to the notion of reusable containers, such as pallets or produce totes. Traceability devices are being applied to track chilled foods from kitchen to store; to track fresh produce by weight, size, and grade from the harvest venue through the packing house, enabling the labeling of pallets and even cases with key data for movement to the retailer; and to follow distilled or even brewed beverages through distribution.

Amazing how what was not even dreamed of ten years ago is now being seriously considered and even offered commercially. Like their time–temperature integrator cousins, freshness indicators are suspect—for their ability to accurately and precisely reflect the product content deterioration situation. But study is underway because market and regulatory drivers are becoming stronger. We have always had difficulty in defining food quality through consumers, and now we have embarked on a trek to have our computers perform the task for us. If computers are correcting our spelling, grammar, syntax, global positioning, and presidential elections, and answering our telephone inquiries, why can’t they tell us the quality of our food before we eat it?

As I asserted when I began this journey into active and intelligent packaging, the boundary is semantic today. Many would and do argue that active and intelligent packaging are different. But, the differences are blurred: when do we react to a signal such as temperature abuse—after the food spoilage occurs, during the adverse action, or in anticipation as we predict from the incoming data that problems are about to arise? Already, instrumentation companies are installing temperature controllers linked to the food packages in retail display cases, as contrasted to being in the air discharge of a refrigeration evaporator. And we are reading of indicators that can convert a signal into an overt action.

We might have doubts about the reliability of the current intelligent packaging, but soon, probably sooner than you think, their outputs will reflect the real situation—and our next step will be to control from the signal.

What an exciting prospect for the next decade: the ability to not only know what is happening to our packaged food in distribution, but also to speed, slow, stop, or otherwise change the course to better retain quality. The main challenge then will be to better define quality, but then, we have been pondering this problem for years, haven’t we?

PRODUCTS & LITERATURE
Co-Extruded Plastic Container may be used to protect contents in varying environmental conditions. The container includes an inflatable dunnage protection device. The 55-gal plastic drum was specifically designed for the processed tomato industry to protect its perishable products, reduce storage space, and lower total packaging costs. It uses a multi-layer, co-extruded plastic technology to produce drums that can withstand a wide range of temperatures and weather conditions common in tomato-growing regions. The tomato drum also features an inflatable dunnage system that completely fills the headspace between the lid and tomato products packed in an  septic bag. This airbag replaces corrugated or foam disks, and more effectively protects aseptic bags during transit from flex cracking, which can permit oxygen penetration and product spoilage. The co-extrusion design is said to have durability characteristics that allow the container to withstand the pressure of its contents and also the weight of at least three drums stacked on top of it. The drums may be reused and are tapered to allow empty drums to be nested within each other. For more information, contact Greif Bros. Corp., 425 Winter Rd., Delaware, OH 43015 (phone 740-549-6000)—or circle 318.

Barrel-Shaped Retort Can comes with a peelable foil membrane can end that allows for easy opening for access. The rolled under edges around the can top are said to provide safe reaching inside the can. The peelable aluminum foil membrane is lacquered for protection of the product, embossed for strength, and imprinted for product promotion. The container may be sealed immediately after hot filling, creating a vacuum in the can. Applications include powders, liquids, or food for hot fill or retort. For more information, contact Packaging Technologies & Inspection, LLC., 145 Main St., Tuchahoe, NY 10707 (phone 800-784-3899 or 914-337-2005)—or circle 319.

Potato Packaging may be produced with a variety of vertical/form/fill/seal machines from Sandiacre Packaging Machinery. The V/F/F/S machines can produce block-bottom/gable-top clear poly bags which are said to increase production rates. The machines can fill up to 40 to 45 bags/min depending on bag size and quantity of product being packaged. The machines are said to offer a wide range of bag styles to suit almost any product application. For more information, contact Sandiacre Packaging Machinery, 1175 Manheim Pike, Suite 200, Lancaster, PA 17601 (phone 717-239-5081; fax 717-239-5084)—or circle 320.

Bottle Uncaser, the Model 156, is said to offer processors who buy bottles or containers in reshipper cases the ability to unload a full range of glass or plastic containers, round or non-round. The three-in-one machine functions as a flap opener/positioner, unpacker, and bottle single filer. In continuous, high-speed motion, the unit opens the case flaps, unloads and single-files containers, and uprights the empty cases for conveying to case packaging—at speeds to 50 cases/min. The unit is said to be a good choice for processors who run a variety of bottle or container styles, as changeover is a relatively simple task and requires no change parts, unlike lift-out-style decasers. It is designed to single file bottles with minimum bottle-to-bottle contact, which offers advantages whether running glass bottles or plastic. For more information, contact A-B-C Packaging Machine Corp., 811 Live Oak St., Tarpon Springs, FL 34689 (phone 800-237-5975; fax 727-938-1239)—or circle 321.

by AARON L. BRODY
Contributing Editor