Modified Atmosphere Packaging— Toward 2000 and Beyond Adel A. Kader1 and Christopher B. Watkins2 ADDITIONAL INDEX WORDS. postharvest, storage, plastics, minimal processing, carbon dioxide, oxygen SUMMARY. Rapid expansion of modified atmosphere packaging (MAP) for horticultural produce has occurred during the last 10 years, especially for fresh cut (minimally processed) products, but limitations to further expansion reside in both responses of products and available technology. We introduce the workshop on Modified Atmosphere Packaging— Toward 2000 and Beyond by reviewing the current status of MAP technology for fresh and minimally processed products, highlighting research needs and future advances, and providing a list of selected references on MAP published since 1989. odified atmosphere packaging (MAP) requires little intro- duction to any reader of the postharvest literature. The Mconcept of using polymeric films that will allow develop- ment, and/or maintenance of atmospheres other than air, dates from the first availability of plastics. However, commercial utilization of MAP for storage and transportation of horticultural products has been limited to a few commodities for reasons that are described below. However, in recent years, a rapid growth of MAP for preservation of fresh cut (minimally processed) products has occurred (Lange, 2000). MAP is especially important for these products because of their greater susceptibility to water loss, cut surface browning, higher respiration rates, enhanced ethylene biosynthesis and action, and microbial growth (Gorny, 1997). MAP, for example, has allowed marketing of value added produce such as broccoli florets (Brassica oleracea L. Italica Group) and asparagus tips (Asparagus officinalis L.) (Lange, 2000). The use of MAP for both whole and fresh cut products can be restricted for a number of reasons. • The unavailability of appropriate films that provide safe modified atmospheres (MAs), especially under abusive temperature conditions that can occur in the handling chain. Packages that provide safe atmo- spheres at one temperature may result in anaerobic conditions at higher temperature (Clarke and DeMoor, 1997). The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact. 1Department of Pomology, University of California, Davis CA 95616. 2Department of Horticulture, Cornell University, Ithaca NY 14853. ● July–September 2000 10(3) 483 • The expense of using MAP technol- processed fruit and vegetables , but his placement for N2 in MAP of fresh pro- ogy, both on the basis of film cost and paper is not reported in these proceed- duce. on the need for modifications to pack- ings. Many types of plastic films are ing line systems. These expenses nor- available for packaging, but relatively mally fall on the producer/processor Current applications of few have been used to wrap fresh pro- and unless costs are recovered, or appli- MAP technology for fresh duce. Low-density polyethylene, poly- cation of MAP provides penetrations of and minimally processed vinyl chloride, and polypropylene are markets that were previously unavail- products the main films used to package fruit able, the use of MAP will result in and vegetables. Polystyrene has been reduced profit margins. For example, MA can be created inside a pack- used, but polyvinylidene, and polyes- use of MAP permits sea freight of per- age either passively through product ter have such low gas permeabilities simmons (Diospyros kaki L) from New respiration or by actively by replacing that they would be suitable only for Zealand to Japan (MacRae, 1987), but the atmosphere in the package with a commodities with very low respiration can rarely be justified on fruit condition desired gas mixture. With commod- rates. However, perforating these films alone for export of apples (Malus domes- ity-generated or passive MA, if prod- can expand their use to many com- tica Borkh.) with lower profit margins uct and film permeability characteris- modities. Recent advances in the tech- in the marketplace (Watkins et al., 1998). tics are properly matched, the desired nology of manufacturing polymeric • Problems associated with maintain- MA can passively evolve within a sealed films have permitted tailoring films for ing package integrity during storage package through consumption of O2 specific gas diffusion needs of some and transport operations. The plastic and production of CO2 by respiration. fruit, vegetables, and their products. must be flexible and easy to use, but The gas permeability of the selected MAP is most commonly used for fresh- strong enough to survive normal han- film must allow O2 to enter the pack- cut (minimally processed) fruit and dling operations. age at a rate offset by the consumption vegetables and for highly perishable, However, the time periods for stor- of O2 by the commodity. Similarly, high value commodities, such as cherry age required for cut produce are gener- CO2 must be vented from the package (Prunus avium L.), fig (Ficus carica ally shorter than for whole products, to offset the production of CO2 by the L.), raspberry (Rubus idaeus L.), and leading to shorter exposure times to commodity. Furthermore, the desired strawberry (Fragaria ×ananassa atmospheres that might injure products MA must be established within 1 to 2 Duch.). over longer time periods. Also, quality d without creating anoxic conditions Benefits of film packaging, other control factors, such as temperature, are or injuriously high levels of CO2 that than creation of MA conditions can more consistently applied because the may induce fermentative metabolism. include maintenance of high relative products tend to be high value, and Because of the limited ability to humidity and reduction of water loss; because of heightened concern about regulate a passively established atmo- improved sanitation by reducing con- food safety. Therefore, the growth of sphere, actively establishing the atmo- tamination of the products during han- MAP usage for cut produce is expand- sphere is becoming more preferred. dling; minimized surface abrasions by ing rapidly. Advances in film technol- This can be done by pulling a slight avoiding contact between the com- ogy are occurring, but it is also the vacuum and replacing the package at- modity and the material of the ship- responses of the commodities that are mosphere with the desired gas mix- ping container; reduced spread of de- critical. It can be argued that in some ture. This mixture can be further ad- cay from one produce item to another; cases it is less the limitation of technol- justed through the use of absorbing or use of the film as carrier of fungicides, ogy than the ability of the commodities adsorbing substances inside the pack- scald inhibitors, ethylene absorbers, or to withstand the technology that is lim- age with the respiring commodity that other chemicals; facilitation of brand iting. Therefore, the Postharvest Work- scavenge O2, CO2, and/or ethylene identification and providing relevant ing Group sponsored a workshop at (C2H4). Although active establishment information to the consumers. ASHS-99 to consider the future of MAP. implies some additional costs, its main In many cases the benefits of us- We have taken two approaches. First, in advantage is that it ensures the rapid ing MAP relate more to one or more of this paper, we briefly review the current establishment of the desired atmo- these positive effects than to the sphere. Ethylene absorbers can help applications of MAP technology for changes in O2 and CO2 concentrations fresh and minimally processed com- delay the climacteric rise in respiration within the package. In contrast, the modities, and then Diana Lange out- and associated ripening for some fruit. negative effects include slowing down lines new film technologies for horticul- Carbon dioxide absorbers can prevent cooling of the packaged products and tural commodities. Second, Randolph a buildup of CO2 to injurious levels, increased potential for water conden- Beaudry and Chris Watkins review the which can occur for some commodi- sation within the package, which may responses of horticultural commodities ties during passive modification of the encourage fungal growth. to oxygen (O ) and carbon dioxide package atmosphere. Superat- The design of modified atmo- 2 mospheric O levels (>21%) may be (CO2), respectively, and then Jim 2 sphere packages requires knowledge Mattheis and John Fellman review the used in combination with fungistatic of mass transport properties of poly- effects of MAP on aroma and other CO2 levels (>15%) for a few commodi- meric films and the respiration rates of quality attributes of horticultural com- ties that do not tolerate these elevated fresh produce placed inside the pack- modities. At the workshop, Tom CO2 atmospheres when combined with ages. Mathematical models are useful Hankinson of Pure Produces (Worces- air or low O2 atmospheres. There is no in determining the changes in gas con- ter, Mass.) outlined interactions between evidence supporting the use of argon, centrations in a package caused by the MAP and microbiology of minimally helium, or other noble gases as a re- respiring products inside the package 484 ● July–September 2000 10(3) Table 1. Selected references published since 1989 on modified atmosphere packaging. Brody, A.L. (ed.). 1989. Controlled/modified atmosphere/vacuum packaging of foods. Food & Nutr. Press, Trumbully, Conn. Calderon, M. and R. Barkai-Golan (eds.). 1990. Food preservation by modified atmospheres. CRC Press, Boca Raton, Fla. Cameron, A.C., P.C. Talasila, and D.W. Joles. 1995. Predicting film permeability needs for modified-atmosphere packaging of lightly processed fruits and vegetables. HortScience 30:25-34. Christie, G.B.Y., J.I. Macdiarmid, K. Schliephake, and R.B. Tomkins. 1995. Determination of film requirements and respiratory behavior of fresh produce in modified atmosphere packaging. Postharvest Biol. Technol. 6:41-54. Church, I.J. and A.L. Parsons. 1995. Modified atmosphere packaging technology: A review. J. Sci. Food Agr. 67:143-152. Emond, J.P., F. Castaigne, C.J.