The cultivated strawberry is a popular fruit worldwide with desirable flavor, texture, and visual appeal. In the United States, the value of total strawberry production was $2.2 billion in 2010 [U.S. Department of Agriculture (USDA), 2011]. California accounts for 90% of national production. Fresh fruit are typically transported by refrigerated truck trailers up to 3000 miles from growing areas to markets throughout North America (Mitcham and Mitchell, 2002). Strawberry fruit are a highly perishable commodity, and shipment at low temperature (i.e., 32 °F) is critical for maintaining postharvest quality (Maxie et al., 1959).
The shelf life of strawberry fruit is often limited by their high rates of respiration, softening, and water loss (Kader, 1991). Fruit are also very susceptible to mechanical damage and decay (Sommer et al., 1973). Botrytis cinerea and Rhizopus stolonifer, the causal agents of gray mold and rhizopus rot, respectively, are the main pathogenic fungi to infect strawberry fruit (Maas, 1998; Wells, 1970). With gray mold, infection often begins in the field when the pathogen colonizes senescing flower petals and grows into the fruit (Powelson, 1960). The infection typically remains latent until fruit are exposed to favorable conditions such as physical wounding, high temperature, and high relative humidity (RH) that are sometimes encountered during postharvest handling (Sommer et al., 1973). Symptoms of disease are usually first visualized as light brown lesions on the fruit surface (Maas, 1998). These lesions eventually enlarge and become covered by masses of gray to tan-colored fungal mycelium and spores that render fruit unmarketable.
The application of chemical fungicides and proper cultural practices (e.g., field sanitation) during strawberry production have long been relied on to control fungal pathogens (Maas, 1998). Thereafter, nonchemical treatment strategies are typically used to control fruit decay during postharvest handling. For example, prompt (i.e., within 1 h of harvest) precooling and maintenance of fruit at low temperature during postharvest operations is widely recommended to slow metabolic reactions associated with fruit senescence and pathogen development (Maxie et al., 1959; Sommer et al., 1973). Exposure to a modified atmosphere (MA) of elevated CO2, reduced oxygen (O2), or both can also retard the growth of fungal pathogens (Brooks, 1932; Couey et al., 1966; Couey and Wells, 1970). These fungistatic atmospheres complement proper temperature management in reducing decay, although the additive benefits are reportedly modest below 5 °C because fungal growth is already suppressed at these low temperatures (Harvey et al., 1966; Sommer et al., 1973).
Shipping and storing strawberries in a MA at low temperature is widely practiced by commercial operators in the United States to reduce decay and maintain fruit quality (Kader, 2002). The most commonly used MA system, Tectrol (TransFresh, Corp., Salinas, CA), involves enclosing an entire pallet of strawberries in a plastic cover that is sealed to a plastic sheet on the pallet base. A partial vacuum is established within the pallet and CO2 gas is then injected to establish an atmosphere of 10% to 15% CO2 and 5% to 10% O2 (Harvey et al., 1980; Kader, 1991). An alternative MA system, CO2 West (CO2 West, San Luis Obispo, CA), uses pads containing sodium bicarbonate and citric acid that react with water vapor to liberate CO2 inside the plastic pallet cover (Finnegan and Boldt, 2007), which is open at the pallet base. Two additional pallet cover systems, PEAKfresh (PEAKfresh USA, Lake Forest, CA) and PrimePro (Destiny Packaging, Monterey, CA), simply involve placing a plastic cover over pallets. Both of these MA systems remain open at the pallet base and rely on strawberry fruit respiration to increase CO2 and decrease O2 concentrations.
The pallet cover systems listed above are claimed to extend the postharvest life and enhance the quality of strawberry fruit. However, there is limited publicly available data comparing the efficacy of these systems. In the present study, we evaluated the capacity of the four proprietary pallet cover systems (CO2 West, PEAKfresh, PrimePro, and Tectrol) to reduce decay and maintain quality of strawberry fruit during and after six transcontinental shipments from Watsonville, CA to Atlanta, GA or Jacksonville, FL. Fruit were also evaluated after a 2-d simulated retail display life to determine if there were residual effects of the intransit treatments.
Brooks, C. 1932 Effect of solid and gaseous carbon dioxide upon transit diseases of certain fruits and vegetables. U.S. Dept. Agr. Tech. Bul. 318
California Strawberry Commission 2012 Varieties and season information. 21 May 2012. <http://www.calstrawberry.com/commission/varieties.asp>
Couey, H.M., Follstad, M.N. & Uota, M. 1966 Low oxygen atmospheres for control of postharvest decay of fresh strawberries Phytopathology 56 1339 1341
Couey, H.M. & Wells, J.M. 1970 Low oxygen or high carbon dioxide atmospheres to control postharvest decay of fresh strawberries Phytopathology 60 47 49
El-Kazzaz, M.K., Sommer, N.F. & Fortlage, R.J. 1983 Effect of different atmospheres on postharvest decay and quality of fresh strawberries Phytopathology 73 282 285
Finnegan, M.J. & Boldt, W.L. 2007 CO2 generating absorbent pads. U.S. Patent 7189666. U.S. Patent and Trademark Office, Washington, DC
Gil, M.I., Holcroft, D.M. & Kader, A.A. 1997 Changes in strawberry anthocyanins and other polyphenols in response to carbon dioxide treatments J. Agr. Food Chem. 45 1662 1667
Harker, F.R., Elgar, H.J., Watkins, C.B., Jackson, P.J. & Hallett, I.C. 2000 Physical and mechanical changes in strawberry fruit after high carbon dioxide treatments Postharvest Biol. Technol. 19 139 146
Harvey, J.M. 1982 CO2 atmospheres for truck shipments of strawberries, p. 359–365. In: D.G. Richardson and M. Meheriuk (eds.). Controlled atmospheres for storage and transport of perishable agricultural commodities. Timber Press, Portland, OR
Harvey, J.M., Couey, H.M., Harris, C.M. & Porter, F.M. 1966 Air transport of California strawberries: Factors affecting market quality in summer shipments - 1965. U.S. Dept. Agr. Mktg. Res. Rpt. 751
Harvey, J.M., Harris, C.M. & Porter, F.M. 1971 Air transport of California strawberries: Pallet covers to maintain modified atmospheres and reduce market losses. U.S. Dept. Agr. Mktg. Res. Rpt. 920
Harvey, J.M., Harris, C.M., Tietjen, W.J. & Seriol, T. 1980 Quality maintenance in truck shipments of Californian strawberries. Adv. Agr. Technol. AAT-W-12. U.S. Dept. Agr., Sci. Educ. Admin., Washington, DC
Holcroft, D.M. & Kader, A.A. 1999 Carbon dioxide-induced changes in color and anthocyanin synthesis of stored strawberry fruit HortScience 34 1244 1248
Kader, A.A. 1991 Quality and its maintenance in relation to the postharvest physiology of strawberry, p. 145–152. In: A. Dale and J.J. Luby (eds.) The strawberry into the 21st century. Timber Press, Portland, OR
Kader, A.A. 2002 Modified atmospheres during transport and storage, p. 135–144. In: A.A. Kader (ed.). Postharvest technology of horticultural crops. 3rd ed. Univ. of Calif. Div. Agr. Natural Resources Publ. 3311
Larsen, M. & Watkins, C.B. 1995 Firmness and concentrations of acetaldehyde, ethyl acetate and ethanol in strawberries stored in controlled and modified atmospheres Postharvest Biol. Technol. 5 39 50
Li, C. & Kader, A.A. 1989 Residual effects of controlled atmospheres on postharvest physiology and quality of strawberries J. Amer. Soc. Hort. Sci. 114 629 634
Maas, J.L. 1998 Compendium of strawberry diseases. 2nd ed. Amer. Phytopathol. Soc., St. Paul, MN
Maxie, E.C., Mitchell, F.G. & Greathead, A. 1959 Studies on strawberry quality: High temperatures that may occur in harvesting and handling of strawberries influence the rate of fruit deterioration. California Agr. 13(2):11,16
Meyer, U.M. & Dewey, F.M. 2000 Efficacy of different immunogens for raising monoclonal antibodies to Botrytis cinerea Mycol. Res. 104 979 987
Mitcham, E.J. & Mitchell, F.G. 2002 Postharvest handling systems: Small fruits, strawberries and cane berries, p. 364–370. In: A.A. Kader (ed.). Postharvest technology of horticultural crops. 3rd ed. Univ. Calif. Div. Agr. Natural Resources Publ. 3311
Nunes, M.C.N., Brecht, J.K., Sargent, S.A. & Morais, A.M.M.B. 1995a Effects of delays to cooling and wrapping on strawberry quality (cv. Sweet Charlie) Food Contr. 6 323 328
Nunes, M.C.N., Emond, J.-P., Rauth, M., Dea, S. & Chau, K.V. 2009 Environmental conditions encountered during typical consumer retail display affect fruit and vegetable quality and waste Postharvest Biol. Technol. 51 232 241
Nunes, M.C.N., Morais, A.M.M.B., Brecht, J.K. & Sargent, S.A. 1995b Quality of strawberries after storage in controlled atmospheres at above optimum storage temperatures Proc. Florida State Hort. Soc. 108 273 278
Pelletier, W., Brecht, J.K., Nunes, M.C.N. & Emond, J.-P. 2011 Quality of strawberries shipped by truck from California to Florida as influenced by postharvest temperature management practices HortTechnology 21 482 493
Sommer, N.F., Fortlage, R.F., Mitchell, F.G. & Maxie, E.C. 1973 Reduction of postharvest losses of strawberry fruits from gray mold J. Amer. Soc. Hort. Sci. 98 285 288
U.S. Department of Agriculture 1975 Strawberries and other berries: Shipping point and market inspection instructions. U.S. Dept. Agr., Agr. Mktg. Serv., Fruit Veg. Div., Fresh Products, Washington, DC
U.S. Department of Agriculture 2011 Non citrus fruits and nuts: 2010 Summary. 24 June 2012. <http://usda01.library.cornell.edu/usda/nass/NoncFruiNu//2010s/2011/NoncFruiNu-07-07-2011.pdf>
Watkins, C.B., Manzano-Mendez, J.E., Nock, J.F., Zhang, J. & Maloney, K.E. 1999 Cultivar variation in response of strawberry fruit to high carbon dioxide treatments J. Sci. Food Agr. 79 886 890
Wells, J.M. 1970 Modified atmosphere, chemical, and heat treatments to control postharvest decay of California strawberries Plant Dis. Rptr. 54 431 434