Future Trends and Innovations in Controlled ...

Future Trends and Innovations in Controlled Atmosphere Storage and Modified Atmosphere Packaging Technologies R.M. Beaudry Department of Horticulture, Michigan State University East Lansing, MI 48824 USA Keywords: CA, MA, quality, storage, storage technology Abstract Modern technologies in controlled atmosphere (CA) storage and modified atmosphere packaging (MAP) can be traced back to the early- to mid-twentieth century and coincide with the realization that important components of developmental physiology are regulated by oxygen and carbon dioxide. CA and MAP are relatively mature technologies today, comprising important storage strategies for a number of commodities. Primary metabolic targets for CA and MAP include inhibition of: ethylene action, cut surface browning, chlorophyll degradation, decay, and human pathogen proliferation. These processes are targeted by recently developed technologies such as solid-state ethylene monitoring, breathable patches on packages, ethylene action inhibition by 1-MCP, and dynamic controlled atmosphere storage. Regarding future innovation, promising research suggests that additional advancement could come soon in the areas of sense-andrespond systems for packages and CA environments, packaging films with new properties, miniature active and passive control devices for packages, and, finally, in the very fruit itself. Postharvest innovation, begun over 5000 years ago with the first modified atmosphere environments, continues and promises improved capabilities and better food for the consumer in the years to come. INTRODUCTION The purpose of controlled atmosphere (CA) storage and modified atmosphere packaging (MAP) technologies is to maintain the quality and, thereby, the value of the produce contained within the MA environment to meet the needs of value chain participants from the producer to the retailer. These technologies act to take advantage of particular features of the biology of the confined plant material that enable the retention of a greater proportion of the initial value of the product than if no atmosphere modification were imposed. Ultimately, the concept is to retain sufficient value that the consumer will pay a sufficiently high price to cover the cost imposed by the storage technologies and the many handling steps required for delivery (Fig. 1). Depending on the particular value chain, the emphasis may be on enhancing particular components of quality to maximize value, to maximize storability, or to place a premium on convenience. Generally speaking, suitable appearance can be maintained somewhat longer than optimal textural or taste quality. ABBREVIATED HISTORY OF CA AND MAP Historically, the use of modified atmospheres (hereafter an umbrella term for both CA and MAP technologies) can be said to date back over 2000 years (Table 1). Perhaps the earliest written documentation of a form of modified atmosphere storage can be found in the translation by Rev. T. Owen (1800) of the Roman Terentius Varro’s account of agricultural practices, which included pit or silo storage of grain. Varro wrote “getting into [the silos] is attended with danger, when they are first opened, on account of the confined air”, thereby recording the impact of respiration on the depletion of oxygen and accumulation of CO2 in a confined space. While the alteration of the atmosphere was likely inadvertent, the fact that the confined air posed risk upon entry can be taken to mean that the atmosphere would have prevented infestation by rodents and possible Proc. 10th Intern. Controlled and Modified Atmosphere Research Conference Eds.: M. Erkan and U. Aksoy Acta Hort. 876, ISHS 2010

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insects and decay organisms. Another likely instance of the use of modified atmospheres to preserve produce, in this case litchi fruit, is recorded in an 8th century Chinese poem (Wang, 2008). The poem describes how Tang Min-hung, an emperor of the Tang Dynasty, secretly ordered an early ‘Pony Express Service’ to fetch fresh litchi from distant growing areas in order to please his favorite princess using sealed bamboo stems lined with litchi leaves and stuffed with the delicate litchi fruit. The first scientific publication of the utility of modified atmospheres can probably be attributed to the work of Jacques Etienne Berard (1821), who determined that harvested fruits utilize oxygen and produce CO2. He noted that fruits placed in an atmosphere deprived of oxygen do not ripen and further determined that the ripening process can be reactivated by return of the fruit to regular air as long as the fruit are not held without oxygen for too long. Importantly, Berard grasped several fundamental aspects of modified atmosphere storage important to its successful application, including the identity of and distinction in effects of oxygen and carbon dioxide in the storage environment. He also recognized the fact that although storage could be lengthened, there were still limits to storability and that the biology of the product was fundamental to the success of the procedure. It is important to note that the crops with which he was successful are all considered to be climacteric in nature and include peaches, prunes, apricots, pears and apples. While the first CA storage was built by Benjamin Nyce in the US in the 1860’s, the ‘experiment’ in technology was short-lived, despite his financial success (Dalrymple, 1967). Successful CA storage followed the work of Franklin Kidd and Cyril West in the 1910’s and 1920’s. Kidd and West (1914, 1927) conducted the first truly systematic and comprehensive studies on controlled atmosphere storage. They based their initial hypothesis on the manner in which oxygen and carbon dioxide influence fruit storability on the involvement of these vital gases in respiration and their impact on the respiratory process. The work of Kidd and West on “gas storage” quickly translated into a successful controlled atmosphere industry by the early 1930’s (Dalrymple, 1967; Dilley, 1990). The success of CA storage inspired work using polymeric packages to limit gas exchange by the late 1940’s and early 1950’s, although the first use of polymer packages was primarily to suppress moisture loss (Beaudry, 2006). Platenius (1946) determined that package ‘failure’ was due to instances of tightly sealed packages, which resulted in the spoilage of contained produce. He understood that both oxygen and CO2 permeated through the polymer, but that the rate was insufficient to keep pace with respiratory demand. This work was the first to relate gas transmission characteristics and respiratory activity and set the stage for future modeling efforts. Also about this time, Allen and Allen (1950) determined that packaging could suppress ripening. The potential for using packages to modify the atmosphere to improve storability was boosted by the discovery of low density polyethylene (LDPE) by ICI in Britain. Its use in research evaluating its utility was reported early on by Ryall and Uota (1955) and Workman (1957, 1959), who evaluated its potential for suppressing apple ripening. An early and important observation was that control of the package atmosphere was variable, which limited MAP applicability (Tomkins, 1962; Workman, 1959). For this reason, mathematical models were constructed to try to understand how various package, product, and environmental factors affected the atmosphere in MA packages. One of the first relatively complete models was developed by Jurin and Karel (1963), who recognized the essential packaging elements of film permeability, film thickness and area, product respiration, and product type and quantity. A dynamic model including package volume was found to be useful in predicting the O2 partial pressure in the package over time (Henig and Gilbert, 1975). This was probably the first study employing computers for modeling in MAP. TECHNOLOGY MEETS BIOLOGY Technological advances in postharvest storage were often paralleled by inquiry into the nature of the biological response of the plant material to the applied atmosphere. It was likely obvious at a nearly stage that the extent to which oxygen and/or carbon 22

dioxide modification is appropriate is dependent on the biology of the harvested plant organ and those components of physiology and pathology comprising limiting factors for quality. Beaudry (2006) proposed that “as we attempt to improve quality retention using tools like MAP, it should be with a strategy that takes advantage of our fullest knowledge of the biology of the commodity.” He attempted to categorize modified atmosphere applications based on the biology of the response (Table 2). Oxygen responses of commercial utility were identified as: reduced ethylene perception, reduced oxidative browning of cut surfaces, suppressed respiratory and associated metabolic activity, and suppressed meristematic activity. Commercially viable responses to carbon dioxide were recognized as: reduced ethylene perception, reduced chlorophyll degradation, and suppressed decay (via inhibition of fungal sporulation and/or growth). Of the responses to oxygen, the most commercially important are the suppression of ethylene action and the inhibition of cut surface browning. The former is critical in the prevention of the onset of ripening for pear, apple, and banana fruit. The latter is critical in the success of MAP of cut lettuce (primarily iceberg type) sold to consumers and to institutions for salad preparation. The use of low oxygen for suppression of respiration and global metabolic activity is likely not of major commercial potential. If it were, then commodities other than typical climacteric fruits and ethylene-responsive Brassicas would be commonly stored in CA. Perhaps the only situation in which respiratory suppression provides sufficient advantage to improve storability is in hypobaric storage (Ben-Yehoshua et al., 2005; Burg, 2004), which has not yet realized its full potential commercially. It is interesting and perhaps a little ironic to observe that the works of Kidd and West were founded on the notion that inhibition of respiration had value. However, it is apparent that this hypothesis is not true, but that it is the suppression of ethylene action by low oxygen (and elevated CO2) on which the success of the CA industries that they inspired depend (Burg and Burg, 1965, 1967). Of the responses to CO2, perhaps the most valuable are the inhibition of ethylene action (a response not yet fully understood) and the inhibition of decay by fungi. Although Nyce believed that carbon dioxide was inert in his early CA storages (Dalrymple, 1967), it has been shown to be otherwise. Even so, the relative value conferred by CO2 in CA storages seems to be diminishing as ever lower oxygen levels and the use of 1-methylcyclopropene render apple fruit increasingly sensitive to the sometimes damaging effects of CO2. It is precisely this potential toxicity that makes carbon dioxide valuable in the storage of berry crops, which are notably resistant to the effects of this respiratory gas. One of the primary limiting factors of berry storage is their susceptibility to decay and while they do respond to decay via increased fermentation in some cases (Beaudry, 1993; Zhang and Watkins, 2005) fungal activity is suppressed (Brown, 1922). Decay suppression is central to the success of trans-continental and international MA pallet and CA container shipments of strawberry, blackberry, raspberry, blueberry, and, to a more limited extent, cherry fruit. Low oxygen is not considered to provide benefits in the storage of these fruit, as one might anticipate given the previous discussion, since none of these have an ethylene-dependent postharvest development. FUTURE TRENDS AND INNOVATIONS If one reduced the CA and MAP systems to their simplest conceptual form, it can be represented as a two-component system comprised of a ‘box’ and a product contained within. Advancements, therefore, will likely come from improving either the ‘box’ or the product - i.e., making one or the other ‘smarter’. The potential for technologies to make the MA package or the CA system smarter and more effective at sensing and controlling the environment around the product is quite good. However, improving the product or product responses is significantly more challenging. The potential for future development and technological advancement is constrained by biology in the manner previously described - there are only so many plant responses to oxygen and carbon dioxide that might be exploited. Further, the number of potential new crops that are amenable to CA or MAP systems is relatively small. The easy crops have already been evaluated and 23

either used or rejected. One of the most promising of the smarter box concepts is that of dynamic controlled atmosphere (DAC), which employs a sensor system of some sort to assess the condition of the stored product and adjust the room environment accordingly (Yearsley et al., 2002). Literature Cited Allen, A.S. and Allen, N. 1950. Tomato-film findings. Modern Packaging 23:123126,180. Anon. 2003. Fresh-cut sales of retail produce approaching $4 billion a year. Fresh Cut, Nov. 2003, Columbia Pub. and Design, Yakima, Wash. (http://www.freshcut.com). Bai, J.-H., Saftner, R.A., Watada, A.E. and Lee, Y.S. 2001. Modified atmosphere maintains quality of fresh-cut cantaloupe (Cucumis melo L.). J. Food Sci. 66:12071211. Beaudry, R.M. 1993. Effect of carbon dioxide partial pressure on blueberry fruit respiration and respiratory quotient. Postharvest Biol. Technol. 3:249-258. Beaudry, R.M. 2000. Responses of horticultural commodities to low oxygen: limits to the expanded use of modified atmosphere packaging. HortTechnology 10:491-500. Beaudry, R.M., Cameron, A.C., Shirazi, A. and Dostal-Lange, D.L. 1992. Modifiedatmosphere packaging of blueberry fruit: Effect of temperature on package O2 and CO2. J. Amer. Soc. Hort. Sci. 117:436-441. Beaudry, R., Luckanatinvong, V. and Solomos, T. 2006. Maintaining quality with CA and MAP. Acta Hort. 712:245-252. Ben-Yehoshua, S., Beaudry, R.M., Fishman, S., Jayanty, S. and Mir, N. 2005. Modified atmosphere packaging and controlled atmosphere storage. p.534. In: S. Ben-Yehoshua (ed.), Environmentally Friendly Technologies for Agricultural Produce Quality. CRC Press, Boca Raton, FL. Berard, J.E. 1821. Memoire sur la maturation des fruits. Ann. Chim. Phys. 16:152-183, 225-251. Brown, W. 1922. On the germination and growth of fungi at various temperatures and in various concentrations of oxygen and carbon dioxide. Ann. Bot. 36:257-283. Burg, S.P. 2004. Postharvest physiology and hypobaric storage of fresh produce. CAB International, Wallingford, UK. Burg, S.P. and Burg, E.A. 1965. Ethylene action and the ripening of fruits. Science. 148:1190-1196. Burg, S.P. and Burg, E.A. 1967. Molecular requirements for the biological activity of ethylene. Plant Physiol. 42:114-152. Cameron, A.C., Talasila, P.C. and Joles, D.J. 1995. Predicting the film permeability needs for modified-atmosphere packaging of lightly processed fruits and vegetables. HortScience 30:25-34. Cameron, A.C., Beaudry, R.M., Banks, N.H. and Yelanich, M.V. 1994. Modifiedatmosphere packaging of blueberry fruit: modeling respiration and package oxygen partial pressures as a function of temperature. J. Amer. Soc. Hort. Sci. 119(3):534539. Cameron, A.C., Boylan-Pett, W. and Lee, J. 1989. Design of modified atmosphere packaging systems: modelling oxygen concentrations within sealed packages of tomato fruits. J. Food Sci. 54:1413-1416, 1421. Dalrymple, D.G. 1967. The development of controlled atmosphere storage of fruit. Div. of Marketing and Utilization Sciences, Fed. Extension Service, USDA Bulletin. 56p. Dilley, D.R. 1990. Historical aspects and perspectives of controlled atmosphere storage, p.187-196. In: M. Calderon and R. Barkai-Golan (eds.), Food preservation by modified atmospheres. CRC Press, Boca Raton, Fla. Ekman, J.H., Clayton, M., Biasi, W.V. and Mitcham, E.J. 2004. Interactions between 1MCP concentration, treatment interval and storage time for ‘Bartlett’ pears. Postharvest Biol. Technol. 31:127-136. 24

Fonseca, S.C., Oliveira, F.A.R., Lino, I.B.M., Brecht, J.K. and Chau, K.V. 2002. Modelling O2 and CO2 exchange for development of perforation-mediated modified atmosphere packaging. J. Food Eng. 52:99-119. Hardenburg, R.E., Watada, A.E. and Wang, C.Y. 1986. The commercial storage of fruits, vegetables, and florist and nursery stocks. U.S. Dept. Agr., Agr. Handbook 66 (revised). 136p. Henig, Y.S. and Gilbert, S.G. 1975. Computer analysis of the variables affecting respiration and quality of produce package in polymeric films. J. Food Sci. 40:10331035. Hertog, M.L.A.T.M., Peppelenbos, H.W., Evelo, R.G. and Tijskens, L.M.M. 1998. A dynamic and generic model of gas exchange of respiring produce: the effects of oxygen, carbon dioxide and temperature. Postharvest Biol. Technol. 14:335-349. Jurin, V. and Karel, M. 1963. Studies on control of respiration of McIntosh apples by packaging methods. Food Tech. 17:104-108. Kader, A.A., Zagory, D. and Kerbel, E.L. 1989. Modified atmosphere packaging of fruits and vegetables. CRC Crit. Rev. Food Sci. Nutr. 28(1):1-30. Kidd, F. and West, C. 1914. The controlling influence of carbon dioxide in the maturation, dormancy, and germination of seeds. Proc. Royal Soc. Lond. B 87:408421. Kidd, F. and West, C. 1927. A relation between the concentration of oxygen and carbon dioxide in the atmosphere, rate of respiration, and length of storage of apples. Food Investigation Bd. Rpt. London 1925, p.41-42. Kubo, Y., Inaba, A. and Nakamura, R. 1990. Respiration and C2H4 production in various harvested crops held in CO2-enriched atmospheres. J. Amer. Soc. Hort. Sci. 115:975978. Legnani, G., Watkins, C.B. and Miller, W.B. 2002. Use of low-oxygen atmospheres to inhibit sprout elongation of dry-sale Asiatic lily bulbs. Acta Hort. 570:183-189. Mangin, L. 1896. Sur la végétation dan une atmosphère viciée par la respiration. Compt. Rend. Acad. Sci.[Paris] 122:747-749. Mir, N., Cañoles, M., Beaudry, R., Baldwin, E. and Mehla, C. 2004. Inhibition of tomato ripening by 1-methylcyclopropene. J. Amer. Soc. Hort. Sci. 129:112-120. Nobel, P.S. 1983. Biophysical Plant Physiology and Ecology. W/H. Freeman and Co., N.Y. Owen, T. 1800. The Three Books of M. Terentius Varro Concerning Agriculture (trans.) Oxford, 257p. Platenius, H. 1946. Films for produce: Their physical characteristics and requirements. Modern Packaging 20(2):139-143,170. Ryall, A.L. and Uota, M. 1955. Effect of sealed polyethylene liners on the storage life of Watsonville Yellow Newtown apples. Proc. Amer. Soc. Hort. Sci. 65:203-210. Sfakiotakis, E.M. and Dilley, D.R. 1973. Induction of autocatalytic ethylene production in apple fruits by propylene in relation to maturity and oxygen. J. Amer. Soc. Hort. Sci. 98:504-508. Smittle, D.A. 1989. Controlled atmosphere storage of Vidalia onions. In: Proc. 5th Intl. Cont. Atm. Res. Conf., Wenatchee, WA, vol. 2, p.171-177. Smyth, A.B., Song, J. and Cameron, A.C. 1998. Modified-atmosphere packaged cut iceberg lettuce: effect of temperature and O2 partial pressure on respiration and quality. J. Ag. Food Chem. 46:4556-4562. Song, J., Leepipattanawit, R., Deng, W. and Beaudry, R.M. 1996. Hexanal vapor is a natural, metabolizable fungicide: Inhibition of fungal activity and enhancement of aroma in apple slices. J. Amer. Soc. Hort. Sci. 121:937-942. Suppakul, P., Miltz, J., Sonneveld, K. and Bigger, S.W. 2003. Active packaging technologies with an emphasis on antimicrobial packaging and applications. J. Food Sci. 68:408-420. Tomkins, R.G. 1962. Film packaging of fresh fruit and vegetables - the influence of permeability. p.64-69. Inst. Packaging Conf. Guide 1961, Larkfield, Maidstone, Kent, 25

England. Watkins, C.B. 2002. Ethylene synthesis, mode of action, consequences and control. In: M. Knee (ed.), Fruit quality and its biological basis. CRC Press, Boca Raton, FL. 279p. Workman, M. 1957. A progress report on the use of polyethylene film box liners for apple storage. Purdue University Agriculture Extension Service, HO-50-4, August, 1957, 8p. Workman, M. 1959. The status of polyethylene film liners to provide modified atmosphere for the storage of apples. Eastern Fruit Grower 23:6, 10-14. Yearsley, C.W., Lallu, N., Burmeister, D., Burdon, J. and Billing, D. 2003. Can dynamic controlled atmosphere storage be used for ‘Hass’ avocados? New Zealand Avocado Growers’ Association Annual Report. p.83-92. Zhang, J. and Watkins, C.B. 2005. Fruit quality, fermentation products, and activities of associated enzymes during elevated CO2 treatment of strawberry fruit at high and low temperatures. J. Amer. Soc. Hort. Sci. 130:124-130.

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Tables Table 1. Important conceptual and technological advances in CA and MAP storage. 100 BC 1821 1869 1914 1927 1929 1930’s 1940’s 1963

Romans use sealed underground pits Jacques Berard links respiratory gasses with the biology of harvested plant material Benjamine Nyce builds first CA storage in Cleveland, Ohio, USA Kidd and West observe impact of elevated CO2 and reduced O2 on plant metabolism using seeds Kidd and West detail the influence of elevated CO2 and reduced O2 on fruit ripening CA storage becomes a commercial success in England Low density polyethylene (LDPA) is developed in England by ICI Platenius, Allen and Allen, Workman and others conduct early MAP studies Jurin and Karel start modern modeling efforts for packaging

Table 2. Responses of plant organs to ranges of O2 and CO2 and examples of commodities benefiting from modification of these responses (Ben-Yehoshua et al., 2005; Hardenburg et al., 1986; Smittle, 1989; Smyth et al., 1998). Gas

Range (kPa)

Response

0.5-5

1-5

Reduced ethylene perception Reduced oxidative browning of cut surfaces Suppressed respiratory and associated metabolic activity Suppressed meristematic activity Reduced ethylene perception

3-5

Reduced chlorophyll degradation

5-20

Suppressed decay (fungal sporulation and/or growth)

0.0-1.0 O2

0.5-5 3

CO2

Examples of benefited commodities Apple, pear, banana, kiwifruit, cabbage Fresh-cut lettuce Apple, pear, banana, kiwifruit, cabbage Onion Apple, banana, kiwifruit, cabbage Apple, banana, kiwifruit, asparagus, cabbage, broccoli, spinach Blueberry, blackberry, cherry, raspberry, strawberry, onion

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Figures

Fig. 1. Schematic example of a simplified value chain for produce. For this value chain, inadequate storage technologies (lower dashed line) will not allow the retention of sufficient quality for the consumer to value the product enough to pay a price that will cover incident costs. Intervention with appropriate postharvest technologies such as CA storage or MAP (upper dashed line) can ensure maintenance of sufficient quality over the time or duration of the handling period such that consumer value meets or exceeds production and distribution costs, realized as product price (solid line).

Fig. 2. A conceptually simple diagram of the CA or MAP system in its simplest form - a two component system comprised of a containing ‘box’ and a contained ‘product’. Future opportunities in CA will likely result from improvements in the capabilities of one or the other component, although the potential for more rapid advancement is more likely for engineering a better box, rather than engineering (or discovering) better products.

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