Hacked by Security Ghost

Packaging is described as active when it performs some desired role other than to provide an inert barrier between the product and the outside environment, although numerous other definitions also exist (1). Therefore, active packaging differs from conventional passive packaging in that one or more forms of interaction are planned, usually to offset a deficiency in an otherwise suitable package. The active component may be part of the packaging material or may be an insert or attachment to the inside of the pack. Active packaging is largely an innovation dating from the 1980s, although there are examples that have been in use for over a century. The tinplate can, for instance, provides a sacrificial layer of tin that protects the food from accumulation of catalytically active iron salts. Antioxidant release from waxed-paper packs for breakfast cereals has been used, as has been the impregnation of cheese wraps with sorbic acid.    
It was in 1987 that the term ''active packaging'' was introduced by Labuza (2). Prior to that time, terms such as ''smart,'' ''freshness preservative,'' and ''functional'' were used to describe active-packaging materials. Sachets of iron powder have been described as ''deoxidizers,'' ''free oxygen absorbers,'' and ''oxygen scavengers'' (see Oxygen scavengers). Active packaging can enable the properties of the package to more adequately meet the requirements of the product. Therefore, the forms and applications of active packaging are diverse, addressing specific situations in the protection and presentation of foods and other products.

PROBLEMS ADDRESSED BY ACTIVE PACKAGING
Active packaging can be used to minimize the deterioration of the packaged product, which can occur through biological or physicochemical reaction mechanisms. Biological deterioration may result from insect attack as occurs, for instance, in foods, furs, fabrics, and museum specimens. Elevated temperatures and humidities enhance the rate of activity at various stages in the life cycles of insects. Chemical fumigation is possible in some cases but is becoming more tightly controlled with foods such as grains and dried fruits. Accordingly, modified-atmosphere packaging (MAP) is now commonly used in many markets, including Europe and North America. Since low levels of oxygen and/or high carbon dioxide levels are required to suppress growth, packaging systems or adjuncts that assist in achieving such atmospheres can contribute to quality maintenance. Such adjuncts are oxygen scavengers, desiccants, and carbon dioxide emitters.    
The other generically common cause of biological deterioration is microbial growth. This is usually enhanced by the same variables, but there is also danger from anaerobic pathogenic bacteria, such as clostridia, that grow at very low oxygen levels or in the absence of oxygen. Hence, the removal of oxygen is not necessarily a solution to all microbial growth problems. Antimicrobial treatments such as the release of carbon dioxide, ethanol, other preservatives, or fungicides can play a role in reducing microbial growth. Similarly, desiccants can assist in providing the ''hurdle'' of reduced water activity, especially in foods. Where liquid water is formed by condensation on the packages of fresh produce, the use of humidity buffers or condensation control films can be useful. Where tissue fluids from fish or white and red meats is unsightly, the use of drip absorbent pads is commonplace.    
Biological deterioration of fresh produce also occurs naturally as part of the process of senescence. Reduction in the rate of senescence can be achieved in many cases by reduction of the respiration rate by reducing equilibrium oxygen concentrations to B2%. Ethylene synthesis that accelerates ripening and senescence can be suppressed by elevated carbon dioxide concentrations. Existing plastic packaging films seldom allow beneficial equilibrium-modified atmospheres to be developed, so some form of active packaging is needed. Transpiration of water by produce leads to condensation when temperatures fluctuate slightly. Furthermore, ethylene release by one or more damaged or ripe fruit can cause rapid ripening of others. This is akin to the ''one rotten apple in the barrel'' situation. Ethylene removal is therefore a highly desirable property of produce packaging.    
Chemical deterioration vectors act on the widest range of packaged products. These include especially foods and beverages (lipid and nutrient loss, off-flavor generation), but also pharmaceuticals. The protection offered by active packaging is, in many cases, essential to achieving a satisfactory shelf life for pharmacologically active compounds, many of which can lose potency through hydrolysis and, therefore, require the use of a desiccant. With the intense search for new drug candidates, attention is now being directed to compounds that are subject to oxidation, in which case protection from oxygen becomes essential to maintaining efficacy. Similarly, active packaging can be useful for optimizing the shelf life of in vitro diagnostic preparations, which often include chemically and biochemically active compounds that may be subject to hydrolytic or oxidative degradation. The active protection in this case can either be incorporated within the package or be designed into the device itself. Some diagnostic formulas are enzyme-based, with the enzymes in the dry form or a fully hydrated form. The moisture content of dry enzyme preparations must be controlled at an appropriate low level, with sufficient residual moisture to ensure that the protein does not become denatured, thereby inhibiting its activity. Conversely, the moisture content of hydrated enzyme preparations must be maintained at a level that prevents the localized dilution or leaching of formula components caused by moisture evaporation and recondensation as a result of temperature fluctuations during storage and distribution. In this case, active moisture regulation within the package can be useful for maintaining functionality over the required shelf life.    
Industrial chemicals such as amines, and particularly some printing inks, are oxidized on storage. Microelectronic components, some metals, and a variety of unrelated items can be subject to attack by oxygen. Often the rate of loss can be reduced adequately by inert-gas flushing and barrier packaging. However, these treatments are not always effective, convenient, or economical, particularly when oxygen levels below 0.5% are desired (3). Nitrogen flushed packs of dry foods often have residual oxygen levels of 0.5–2%. Chemical forms of in-pack oxygen scavenging have been introduced both to reduce these residual levels further and to deoxygenate air headspaces without the use of inert-gas flushing or evacuation. Fried snacks are particularly susceptible to oxidation, depending on their moisture content. Although sliced, processed meats are packaged commercially under vacuum, improved presentation using MAP can be achieved when an oxygen scavenger is present. The pink nitrosomyoglobin is damaged by even low quantities of oxygen in the package. The flavor of alcoholic beverages such as beer and white wines is particularly sensitive to oxygen, so the relatively high oxygen permeability of poly(ethylene terephthalate) (PET) bottles makes them unsuitable for packaging most wines and beers. The presence of oxygen in glass bottles is usually offset by addition of sulfur dioxide to the beverage. However, oxidative loss of this antioxidant still limits the shelf life of beer and white wines and limits their packaging options. A similar sulfur dioxide loss occurs in dried apricots. In these cases the presence of an oxygen scavenger that does not react with this acidic gas is required. Porous adsorbents in current oxygen scavengers may also remove some of the sulfur dioxide.    
The flavor of some foods changes on storage because of effects other than oxidation. Tainting is a recurrent problem. Moldy taints can result from long voyages in shipping containers. Methods of odor interception without the use of expensive barrier packaging are needed for the transportation of low-valued primary products. Besides interception of external taints, there is also a need for removal of food breakdown products that can be formed during storage. These include amines or thiols formed rapidly in fish or rancid odors in oil-containing foods. Such compounds can be present in trace amounts that are significant organoleptically but may not constitute a health hazard. The bitter principle in some orange juices, limonin, is formed on standing, and a method for its removal from juice has been reported (4).    
Two physical properties of a product that can potentially be affected by active packaging are heating and cooling. Thus the microwave heating of packaged multicomponent entrees offers a challenge for uniform heating in spite of varying layer thicknesses and water contents (see Microwave pasteurization and sterilization). Canned drinks, such as sake and coffee, supplied via vending machines in Japan are frequently consumed warm. Other drinks may need to be cooled, and so dispensing from the one machine may necessitate building the temperature changing capacity into the can itself.

GOALS OF ACTIVE PACKAGING
Active packaging is chosen to enhance the ability of conventional packaging to help deliver the product to the user in a desired state. The decision to use some form of active packaging will often be based on one or more of the following considerations (see also Shelf life).
1. Extension of Shelf Life. This extension may exceed the presently accepted limits as with sea shipment of some fresh produce.
2. Less Expensive Packaging Materials. Packaging of limited-shelf-life products may require enhancement of only one property for a fixed period. This can include bakery products, metal components shipped by sea, or chilled meats.
3. Simpler Processing. Introduction of additional microbiological ''hurdles'' can allow MAP to be achieved without use of expensive equipment.
4. Reduction or Removal of Preservatives from Food Formulations. This is done to meet consumer demands for ''fresher'' foods containing fewer additives by transferring preservatives from the food to the packaging.
5. Difficult-to-Handle Products. Oxygen can be removed from tightly packaged products such as cheeses that are subject to mold growth.
6. Allowing Particular Types of Packages to be Used. This could include (a) retortable plastic packages for products with multiyear shelf lives or (b) PET wine bottles.
7. Presentation. Heating by microwave susceptors and other adjuncts has allowed packaging innovation for convenience foods.    
Other goals are developing as the potential is being realized. Indicators of time–temperature and temperature abuse are presently available. The composition of the package headspace can potentially indicate chemical, physiological, or microbiological state or the potency of the packaged product.

FORMS OF ACTIVE PACKAGING
The active components in packaging can exist either as part of an otherwise unmodified package or as an elaborate adjunct or design modification. The major form in use at present is the insertion of sachets of various scavengers or emitters. These have been followed more recently by plastics blends or compounds and, to a lesser extent, by composite packages of various forms.

Sachets and Other Inserts
Desiccants. Silica gel has been supplied for protection of packaged goods from water for many years. A range of sachets and porous canisters as well as saddles are manufactured in sizes from grams to kilograms by companies such as Multisorb Technologies, Inc. (Buffalo, NY) and Süd-Chemie. Silica gel has a capacity when dried for taking up 40% of its own weight of water vapor. An alternative is lime (calcium oxide), which takes up 28%. Both are used largely in the shipment of goods through humid atmospheres to protect against corrosion (steel, aluminum computers), caking (pharmaceuticals), or mold growth (foods). In Japan these are used with some snacks such as rice crackers to give a high level of crunchiness, as well as a sticky, dehydrating sensation on the tongue. Many variants in form have facilitated new uses for these well-known materials. Sachets are marked ''Do not eat'' and are often between the primary and secondary package. Less severe desiccants can be also used for condensation control in the wholesale distribution of produce, particularly where the carton liner bag is heat-sealed to generate a modified atmosphere. A few products such as tomatoes are packed with large microporous sachets of salts, like sodium chloride, which absorb excess water at the high relative humidities experienced in such closed packages. The relative humidity can be lowered from B95% to 80%. This was a first-generation approach to humidity buffering.

Oxygen Scavengers. Oxygen scavenging sachets were introduced in Japan in 1969 initially containing sodium dithionite and lime. This followed early work by Tallgren in Finland in 1938 using iron and other metals (5). Mitsubishi Gas Chemical Co. introduced Ageless® sachets in 1977 containing reduced iron powder, salt, and trace ingredients. This technology has developed with a wide variety of formulations being provided by Mitsubishi and other companies in Japan. Multisorb Technologies, Inc. manufactures the FreshPaxt series of iron-based oxygen absorbers, which are also marketed in the United Kingdom, and Standa Industrie of Caen manufactures a range of sachets under the name ATCO in France. It was estimated that around 12 billion such sachets were manufactured in Japan in 2001, and it is predicted that sales for 2007 will be on the order of 14.4 billion in Japan, 4.5 billion in the United States, and 5.7 billion in Europe (6). The global value of this market is predicted to grow from $588 million in 2005 to around $924 million in 2010 (7). The oxygen scavenging materials can also be bonded to the inside of the package, resulting in even less chance of accidental ingestion or incorporation into food preparations. Mitsubishi Gas Chemical Co. introduced a hot-melt adhesive system for sachets, and Multisorb Technologies, Inc. market an adhesive label (FreshMaxs), which is sufficiently thin that it can be applied with conventional labeling machinery (see Figure 1). The contents of oxygenscavenging sachets differ, depending on the relative humidity of the product, usually food. Some are designed to operate at refrigerator or even freezer temperatures.

Figure 1. FreshMax® oxygen-absorbing label attached to the inside of processed meat package. (Courtesy of Multisorb Technologies, Inc.)

Characteristics of some commonly used sachets are shown in Table 1. The form of triggering is one of the key aspects of oxygen scavengers of any type. It is preferable that the scavenging composition can be activated when required, because premature reaction with atmospheric air leads to loss of scavenging capacity and potential failure in the sealed package.    
Combination sachets are also available from Mitsubishi Gas Chemical Co. and EMCO Packaging Systems (UK). Some of these release carbon dioxide while taking up oxygen. These are normally based on ascorbic acid and sodium bicarbonate. Ageless® E sachets contain lime as well as iron to absorb CO2 and oxygen and are used in roasted-coffee packs.

Table 1. Properties of Some Oxygen Scavenging Sachets^a

^aData from technical information from manufacturers and references 5 and 22.

Ethanol and Sulfur Dioxide Emitters. Low concentrations of ethanol, 1–2% in bakery products, have been shown to suppress the growth of a range of common molds. Higher levels are necessary to suppress bacteria and yeasts, and the effectiveness is dependent on the water activity of the product. Freund Corp. (Japan) has developed two ethanolemitting sachets which release ethanol vapor in response to the absorption of water vapor from the food headspace. Antimold-milds (also known as Ethicap) sachets contain food-grade ethanol (55%) adsorbed in silica powder (35%). The sachets consist of films of varying permeabilities to provide some control of the rate of ethanol release. Sachets are available from Freund in sizes of 0.6–6G containing 0.33–3.3 g of ethanol. The size of the sachet required can be calculated from knowledge of the water activity and weight of the product and the shelf life desired. Food packages containing ethanol-releasing sachets should have an ethanol vapor permeability of o2 g/m2 per day at 301C (Freund Corp.). Packaging films used with ethanol generators can be as simple as oriented polypropylene/ polypropylene, but polyethylenes are too permeable for use. Ethicap has been investigated with pita bread, apple turnovers, strawberry layer cakes, and madeira and cherry cream cake. It is used widely in Japan with semimoist or dry fish products.    
The second type of ethanol emitting sachet marketed by Freund Corp., under the name Negamolds, is a combined oxygen scavenger and ethanol emitter. This type of sachet is not widely used. Ethanol-emitting sachets are manufactured by other companies in Japan, including Ohe Chemicals Inc. (Oytech L). Pira International Ltd. estimated that the total global market (predominantly in Japan) in 2005 for these types of sachets was $37 million, and it forecasts growth to $65 million by 2010 (8). Sulfur-dioxide-releasing pads are available for use in the transportation of cartons of table grapes. Grapes are readily separated from their stalks by the action of fungi in the moist atmosphere of polyethylene-lined cartons. Microporous pads containing sodium metalbisulfite (B7 g) placed on top of the fruit release sulfur dioxide as water vapor is absorbed. If the uptake of water vapor is too rapid, as is often the case, the rapid premature hydrolysis results in excessive levels of sulfur dioxide, resulting further in bleaching of the grapes, commencing at the bottom of the berries. Such pads are largely manufactured in Chile by companies such as Productions Quimicos & Alimenticos Osku SA, of Santiago (e.g., OSKU-VIDs Grape Guard), and are widely distributed internationally.

Ethylene Absorbers. Ethylene-absorbing sachets, sometimes made of steel mesh, are available and follow from the variety of porous slabs and blankets developed for ethylene removal in cool stores and shipping containers. Several minerals are used to contain potassium permanganate in the form of purple beads or in other shapes. Typical inert substrates include perlite, alumina, silica gel, and vermiculite containing 4–6% potassium permanganate. The manner in which these might be used should be checked because potassium permanganate is toxic. There are many manufacturers such as Ethylene Control, Inc. of Salinas, CA and Purafil Co. of Chalamblee, GA. The efficiency of such absorbers will depend on the product, the surface area of the substrate, and possibly any water condensation.    
Ethylene-absorbing sachets based on other principles for destruction of the ethylene, such as the use of carbon activated with a palladium catalyst, have also been reported (8). Nonspecific absorbents have also been marketed in sachet form in Japan for removal of gases such as ethylene, carbon dioxide, and unwanted odors from food packs. A product based on activated carbon is marketed by Mitsubishi Gas Chemical Co. (Ageless® C-P, which includes slaked lime). The capacity of such absorbents for ethylene at physiological concentrations (e.g., o1 ppm, 95% RH) and at the typically low temeprartures used for storage needs to be defined.

Plastic-Based Active Packaging Materials
Moisture Control. Moisture in packages may be in the form of liquid (condensate or drip/weep) or as the vapor. Desiccants remove both forms of water, although they are designed to remove the vapor. The simple form of liquid moisture sorption has been provided by drip-absorbent sheets consisting of two layers of nonwoven polyolefin, divided by heat seals into pouches containing polyacrylate superabsorbent polymers. These sheets are used under chicken or turkey pieces and sometimes under red meats to absorb drip during display. Other uses are to absorb drip from seafood, especially when air-freighted to avoid corrosion of airframes caused by spilling. These sheets are widely available from companies such as Maxwell Chase Inc. (Douglasville, USA) (Fresh-R-Paxt).    
Although superabsorbent polymers can absorb up to 500 times their own weight of water, they do not function as such rapid absorbents for water vapor. Condensation can be prevented by use of multilayer plastic sheets containing a humectant or moisture absorbent material between the layers, such as those developed by Showa Denko K.K. (Japan) (9) and CSIRO (Australia) (10). At least one water vapor absorbent sheet has been produced for domestic use, known as Pichit. This consisted of an envelope of polyvinyl alcohol film sandwiching a glycol and carbohydrate in a strong water vapor absorber (see Figure 2). It is manufactured by Shoko Co. Ltd. (a subsidiary of Showa Denko K.K) and sold as a perforated role and as packs of single sheets for wrapping food portions in domestic refrigerators. Su¨d Chemie produce a desiccant polymer (2APs) for use in a wide range of package formats including tubes and caps, and have patented approaches for producing such materials by inclusion of microchannels and humectants or desiccants.

Figure 2. Pichit bilayer sheet for absorbing water from food portions. (Courtesy of Showa Denko K. K.)

Oxygen Scavenging. Oxygen scavenger films have been a goal of packaging industry researchers since the work of the American Can Co. in 1976 with the palladium-catalyzed reaction of oxygen with hydrogen. That package, marketed by American Can Co. as Maraflex, was not widely used commercially because of its complexity and its requirement for flushing with a nitrogen/hydrogen mixture. Oxygen-scavenging films or other plastic materials offer the opportunity to prevent oxygen ingress to the package by permeation as well as removing that originally present inside the package. They also offer the potential for package fabrication, filling, and sealing without the need for insertion or attachment of a sachet. Despite the substantial international R&D effort over the last two decades (11), only a few oxygen-scavenging film technologies have been commercialized, such as Sealed Air's lightactivated Cryovac® OS System, which is based on the transition metal-catalyzed oxidation of rubber-like unsaturated polymeric components.    
Oxygen-scavenging closure products are marketed by a number of companies, including Silgan White Cap (Stamford, Connecticut) (Plasti-Twist®), Grace Darex® Packaging Technologies (a business unit of W. R. Grace Company), and Bericap (O2S®). The Grace Darex® compositions, exemplified by Daraforms 6490, include up to 7% sodium sulfite and 4% sodium ascorbate in a polyolefin base (12), and they have been used by Heineken and Anheuser-Busch beer produced under license in the United Kingdom. More recently, Grace Darex® launched Celox™, a closure liner that is claimed by the manufacturer to provide a substantially faster scavenging rate. Toyo Seikan Kaisha Ltd. (Yokohama, Japan) has taken a different approach using a reduced iron base for reaction with oxygen. The crown closure consists of three layers with the middle, reactive layer separated from the beer by a microporous polymer layer. The scavenging reaction involves water vapor from the beer, especially during pasteurization, and premature reaction is presented by keeping the composition dry prior to use. The closure sealant designs can be compared by reference to Figure 3, which represents the Grace approach (top) and the Toyo Seikan Kaisha approach (bottom).

Figure 3. Oxygen absorbing closure liners for bottles. Top: W. R. Grace type. Bottom: Toyo Seikan Kaisha Ltd. type.    

The first thermoformable oxygen-scavenging sheet (Oxyguard™) was commercialized in 1994 by Toyo Seikan Kaisha Ltd. for use in retortable plastics trays. The oxygen scavenging layer is between the EVOH (ethylene vinyl alcohol) oxygen-barrier layer and the inner, permeable polypropylene layer. Figure 4 shows this structure diagramatically. The scavenging process involves moisture- activated reaction of oxygen with iron particles embeded in the polypropylene layer. Similar thermoformable oxygen-scavenging polymeric materials are also produced by Ciba Speciality Chemicals (SHELFPLUS® O2).    

Figure 4. Oxygen-absorbing thermoformed multilayer tray for semiaseptic rice (PP, polypropylene; EVOH, ethylene vinyl alcohol copolymer). (Courtesy of Toyo Seikan Kaisha Ltd.)   

Active Oxygen Barriers. More recently, oxygen-scavenging has been used to improve the barrier performance of PET containers. The Oxbar™ technology involves the transition- metal-catalyzed oxidation of polymeric materials such as MXD6 Nylon, and it was originally developed by CMB Technologies plc UK for making PET bottles oxygenimpermeable while scavenging oxygen from the packaged beverage. This technology is now the basis of PET bottles manufactured by Constar International Inc. (Philadelphia, Penn.), as well as by other packaging companies, such as Amcor Ltd. (Melbourne, Australia), under license. Other approaches based on the use of transition-metal-catalyzed oxidation to produce PET bottles having enhanced oxygenbarrier properties include those of BP Amoco (Amosorb®), Valspar (ValOR™), and Toyo Seikan Kaisha Ltd. (Oxyblock, also referred to as SIRIUS101). M&G has developed a technology involving incorporation of iron particles into the PET, and it produces actively enhanced oxygen barrier PET bottles (ActiTUF®).

Antimicrobial Films. Antimicrobial agents, fungicides, and natural antagonists are applied to harvested produce in the form of aqueous dips or as waxes or other edible coatings. Their roles and their U.S. regulatory status have been tabulated (13). Besides produce, foods with cut surfaces are subject to largely superficial microbial attack and some cheeses are packaged with wrappings or separating films (sliced cheese) containing sorbic acid. Although many foods are subject to rapid attack at the cut surfaces, potentially useful antimicrobial packaging films are still largely a subject of research (14–16).    
Sinanen Zeomic Co. Ltd. in Japan produces a synthetic zeolite, Zeomic, which has silver ions bonded into the surface layers of the pores. The zeolite is dispersed in, for instance, a polypropylene or polyethylene 3- to 6-mm-thick layer and protrudes into the package from this layer as indicated in Figure 5. Other layers provide package strength and permeation barrier as required. Liquid in the food is meant to have access to the zeolite, and it appears that the mode of action is uptake of silver ion that dissolves in the aqueous phase (17). The zeolite has been found to be highly effective against several vegetative bacteria, especially dispersed in water, saline solution, or oolong tea. The effect of amino acids in food proteins is the subject of research (18). Zeomic is approved as a Food Contact Substance by the U.S. FDA and can be used in any type of food packaging resin product. The Zeomic product is distributed outside Japan and in parts of Southeast Asia by AgION Technologies Ltd. (Wakefield, MA).

Figure 5. Antimicrobial thermoformed tray containing Zeomic silver zeolite heat-seal layer. (CPP, cast polypropylene; HIPS; high-impact polystyrene). (Courtesy of Sinanen Zeomic Co. Ltd.)   

Odor Absorption. Since odors can be sensed at very low levels, there is the opportunity to use packaging materials to reduce the concentrations of these components in otherwise acceptable foods (see Aroma barrier testing). The inclusion of molecular sieves and other agents capable of adsorbing odorous volatile compounds has been explored. Packaging technologies capable of removing specific classes of odorous compounds through chemical reaction have also been investigated with several patents in this area relating to elimination of aldehydes having been granted to Dupont and Cellresin Technologies LLC. A different approach has been patented by Minato Sangyo Co. Ltd., based on ascorbic acid and an iron salt dispersed in the plastic, and is aimed at removing amine or sulfur compounds from fish in domestic refrigerators.

Thermal Control. Microwavable packages containing foods with differing reheating requirements can be made to crisp or brown some components by use of susceptors and reduce the heating of other components by use of foil shields. Susceptors normally consist of a vacuum-deposited layer of aluminum, typically with a light transmission of 50–60%, or a 12-mm-thick film of biaxially oriented PET. The film is laminated to paper or paperboard by means of an adhesive. In a microwave field, susceptors have reached a temperature of 3161C in the absence of food, or 2231C in pizza packs (19). These temperatures have caused regulatory authorities to investigate the stability of all components of susceptor films, particularly the adhesives. The microwave field strength can be intensified by specific distributions of foil patches in the dome lids of microwaveable packs.    
Beverage cans can be made either ''self-heating'' or ''self-cooling'' by means of chemical reactions in compartments separated from the beverage (20). Sake is heated by the exothermic reaction of lime with water in aluminum cans. This process is potentially valuable in the vending machine market. Cooling is achieved by the endothermic dissolution of ammonium nitrate and ammonium chloride with water. Both of these thermal effects are brought about by shaking and thus are unsuitable for use with carbonated beverages.

RESEARCH AND DEVELOPMENT
Active packaging materials have been evolving through a series of innovations dating from the late 1980s, with many hundreds of primary patent applications having been filed for both chemical principles and package designs relating to oxygen scavenging alone. Despite considerable industry interest, so far very few of these innovations have led to commercial products. There is a substantial amount of innovation in progress, especially in the area of active plastic-based packaging incorporating in-polymer chemistry. Methods of activating chemical systems that are stable during thermal processing are particularly interesting. The benefits of using active packaging need to be established clearly, and performance claims for these technologies need to be supported by unambiguous, independent research results demonstrating their effectiveness.

SUMMARY
The emergence of active packaging has required reappraisal of the normal requirement that the package should not interact with the packaged product. For example, the introduction of a new EU Regulation (1934/2004) repealing the earlier relevant EU Directives for food contact materials (89/109/EEC and 80/590/EEC) attempts to reconcile the EU's philosophy that food contact materials should not give rise to chemical reactions that alter the initial composition or organoleptic properties of the food, while recognizing the potential benefits of active packaging technologies to enhance the preservation of packaged food. The introduction of this new EU Regulation paves the way for more rapid uptake of these new packaging materials (21). Active packaging introduced so far represents substantial fine-tuning in the matching of packaging properties to the requirements of the product. Accordingly, it will be seen increasingly in niche markets and in wider applications in which specific problems are inhibiting the marketing of the product. Indeed, the specific examples being introduced are too numerous to describe here, and the reader is referred to the Bibliography and the Further Reading sections.

Andrew Scully
CSIRO Materials Science and Engineering, Melbourne, Victoria 3169, Australia
This is a revised and updated version of the article written by Michael Rooney

BIBLIOGRAPHY
1. G. L. Robertson, Food Packaging: Principles and Practice, Taylor & Francis, Boca Raton, FL, 2006, pp. 286–289.
2. T. P. Labuza and W. M. Breene, J. Food Proc. Preservat. 13, 1–69 (1989).
3. Y. Abe and Y. Kondoh, ''Oxygen Absorbers'' in A. L. Brody, ed., Controlled/Modified Atmosphere/Vacuum Packaging of Foods, Food and Nutrition Press, Trumbull, CT, 1989, pp. 149–174.
4. B. V. Chandler and R. L. Johnson, J. Sci. Food Agric. 30, 825–832 (1979).
5. Y. Abe, ''Active Packaging—A Japanese Perspective'' in Proceedings International Conference Modified on Atmosphere Packaging, Camden Food and Drink Research Association, Chipping Camden, U.K., 1990, Part 1.
6. Pira International Ltd., Active & Intelligent Pack News 2(11), 5 (2004).
7. Pira International Ltd., Active & Intelligent Pack News 3(25), 5 (2005).
8. N. Takahashi and K. Yoshie, U.S. Patent No. 5015282, 1991.
9. M. Takuno, U.S. Patent No. 5143773, 1992.
10. M. R. Gibberd and P. J. Symons, International Patent Application, WO 05/053955, 2005.
11. M. L. Rooney, ''Overview of Active Packaging'' in M. L. Rooney, ed., Active Food Packaging, Blackie Academic and Professional, Glasgow, UK, 1995, pp. 1–37.
12. F. N. Teumac, The History of Oxygen Scavenger Bottle Closures in M. L. Rooney, ed., Active Food Packaging, Blackie Academic and Professional, Glasgow, 1995, pp. 193–202.
13. S. L. Cuppett, ''Edible Coatings as Carriers of Food Additives, Fungicides and Natural Antagonists'' in J. M. Krochta, E. A. Baldwin, and M. Nisperos-Carriedo, eds., Edible Coatings and Films to Improve Food Quality, Technomic Publishing, Lancaster, PA, 1994, pp. 123–124.
14. R. D. Joerger, Packag. Technol. Sci. 20, 231–274 (2007).
15. P. Suppakul, J. Miltz, K. Sonneveld, and S. W. Bigger, J. Food Sci. 68, 408–420 (2003).
16. J.W. Rhim and P. K. Ng, Crit. Rev. Food Sci. Nutr. 47, 411–433 (2007).
17. J. H. Hotchkiss, ''Safety Considerations in Active Packaging'' in M. L. Rooney, ed., Active Food Packaging, Blackie Academic and Professional, Glasgow, 1995, pp. 238–255.
18. T. Ishitani, ''Active Packaging for Foods in Japan'' in P. Ackermann, M. Ja¨gerstad, and T. Ohlsson, eds., Food and Packaging Materials—Chemical Interactions, Royal Society of Chemistry, Cambridge, UK, 1995, pp. 177–188.
19. G. L. Robertson, Food Packaging: Principles and Practice, Taylor & Francis, Boca Raton, FL, 2006, pp. 280–282.
20. G. L. Robertson, Food Packaging: Principles and Practice, Taylor & Francis, Boca Raton, FL, 2006, pp. 297–298.
21. J. Heckman, Active and Intelligent Packaging—A European Anomaly, November 2005. http://www.packaginglaw.com/index_fcn.cfm?id=38&pf=yes(2005) (accessed March 4, 2008).
22. J. P. Smith, H. S. Ramaswamy, and B. K. Simpson, Trends in Food Sci. Technol. 111–118 (Nov. 1990).

Further Reading
G. L. Robertson, ''Active and Intelligent Packaging,'' Chapter 14 in Food Packaging: Principles and Practice, Taylor & Francis, Boca Raton, FL, 2006, pp. 286–309.
W. D. van Dongen, A. R. de Jong, and M. A. H. Rijk, ''European Standpoint to Active Packaging—Legislation, Authorization and Compliance Testing,'' Chapter 9 in Packaging for Nonthermal Processing of Food, J. H. Han, ed., Blackwell Publishing Professional, Ames, IA, 2007.
A. Scully and M. Horsham, ''Emerging Packaging Technologies for Enhanced Food Preservation,'' Food Sci. Technol. 20, 16–19 (2006).
J. H. Han, ed., Innovations in Food Packaging, Elsevier Academic Press, San Diego, CA, 2005.
C. L. Wilson, ed., Intelligent and Active Packaging for Fruits and Vegetables, CRC Press, Boca Raton, FL, 2007.
A. L. Brody, E. R. Strupinsky, and L. R. Kline, Active Packaging for Food Applications, Technomic, Lancaster, PA, 2001.
M. L. Rooney, ed., Active Food Packaging, Blackie Academic and Professional, Glasgow, 1995.
T. P. Labuza and W. M. Breene, ''Applications of Active Packaging for Improvement of Shelf-life and Nutritional Quality of Fresh and Extended Shelf-Life Foods,'' J. of Food Process. Preserv., 13, 1–69 (1989).
A. López-Rubio, E. Almena, P. Hernandez-Muñoz, J. M. Lagarón, R. Catalá , and R. Gavara, ''Overview of Active Polymer-Based Packaging Technologies for Food Applications,'' Food Rev. Int. 20(4), 357–387, 2004.