The effects of temperature and gas atmosphere on fresh produce physiology and quality have been extensively studied to the point where optimal storage conditions for most products are widely available (Anon., 2006; Gross et al., 2004). However, in the commercial environment, temperature variations occur as a result of logistic constraints (e.g., limited access to power at the location of the container storage unit), mechanical refrigeration breakdown, or management decisions (e.g., choice of nonrefrigerated vehicles over refrigerated vehicles). Another common temperature break scenario arises through the refrigerated storage of fruit in bins immediately after harvest. At a later time, the fruit are removed from the cool store, graded, and packed before shipping in a refrigerated environment to markets. Because the packing facility is often not refrigerated, the fruit is warmed and then recooled.
The use of controlled breaks in cool storage, either before (DeLong et al., 2004) or during storage (Watkins et al., 2000), has previously been investigated primarily as a means to minimize chilling injury development and hence extend the product storage life. This body of work provides evidence of increased ethylene production (Liu, 1986; Zhou et al., 2001) as a result of exposure to ambient temperatures (10 to 25 °C) for short time periods. Unintentional breaks in refrigeration differ from the application of intentionally applied cool storage breaks, because they tend to be sporadic and unpredictable in terms of magnitude (time and temperature). How these uncontrolled breaks in storage conditions affect product physiology and quality on return to refrigerated storage conditions has rarely been investigated.
The postharvest behavior of apples is well documented. Apples ripen with a typical climacteric ethylene and respiratory pattern during postharvest storage (Jobling and McGlasson, 1995; Larrigaudiere et al., 1997), whereas fruit quality changes progress for some time during the postclimacteric phase (Johnston et al., 2001a). Key quality changes for apples are changes in firmness (from hard to soft) and background color (from green to yellow). There is significant experimental evidence that both of these quality attributes are ethylene-sensitive (Golding et al., 2005; Saftner et al., 2003).
This study aimed to assess the effects of exposing apples stored at 0 °C in air to short-term periods at 20 °C on subsequent fruit physiology and quality both during the time of the exposure and on return to cool storage at 0 °C. This investigation was based around assessing fruit response to what would be considered the most extreme (yet still likely) breaks in the cool chain (3 d at 20 °C). This approach was taken to detect changes in the extreme situation with the assumption that if no significant changes occur in this scenario, then breaks of a lesser magnitude (in time or temperature) could also be assumed to have no effect. The influence of harvest maturity, time in storage before exposure, length of exposure to 20 °C, and multiple exposures to 20 °C on the responses of the fruit were also studied. ‘Cripps Pink’ (‘Pink Lady™’) apples were chosen as the cultivar in which to investigate these effects.
Alwan, T.F. & Watkins, C.B. 1999 Intermittent warming effects on superficial scald development of ‘Cortland’, ‘Delicious’ and ‘Law Rome’ apple fruit Postharv. Biol. Technol. 16 203 212
Anon 2006 Postharvest Technology Research and Information Centre, University of Califormia, Davis home page 10 July 2006 <http://postharvest.ucdavis.edu>.
Artés, F., García, F., Marquina, J., Cano, A. & Fernández-Trujillo, J.P. 1998 Physiological responses of tomato fruit to cyclic intermittent temperature regimes Postharv. Biol. Technol. 14 283 296
Banks, N.H., Cleland, D.J., Cameron, A.C., Beaudry, R.M. & Kader, A.A. 1995 Proposal for a rationalized system of units for postharvest research in gas exchange HortScience 30 1129 1131
Bartley, I.M. 1986 Changes in sterol and phospholipids composition of apples during storage at low temperature and low oxygen concentration J. Sci. Food Agr. 37 31 36
Cabrera, R.M. & Salveit, M.E. 1990 Physiological response to chilling temperatures of intermittently warmed cucumber fruit J. Amer. Soc. Hort. Sci. 115 256 261
DeLong, J.M., Prange, R.K. & Harrison, P.A. 2004 The influence of delayed cooling on quality and disorder incidence in ‘Honeycrisp’ apple fruit Postharv. Biol. Technol. 33 175 180
East, A.R. 2006 The influence of breaks in optimal storage conditions on ‘Cripps Pink’ apple physiology and quality Massey University Palmerston North, New Zealand PhD Diss.
Golding, J., Satyan, S., Rath, A.C., Jobling, J. & James, H. 2005 Retain® maintains Pink Lady™ fruit quality during long term storage Acta Hort. 682 119 125
Gross, K.C., Wang, C.Y. & Saltveit, M.E. 2004 The commercial storage of fruits, vegetables and florist and nursery stocks. 3rd Ed. Agri. Hndbk. No. 66 U.S. Dept. Agr., Agr. Res. Serv Washington, DC
Hertog, M.L.A.T.M., Ben-Arie, R., Roth, E. & Nicolai, B.M. 2004 Humidity and temperature effects on invasive and non-invasive firmness measurements Postharvest Biol. Technol. 33 79 91
Jobling, J.J. & McGlasson, W.B. 1995 A comparison of ethylene production, maturity and controlled atmosphere storage life of Gala, Fuji and Lady Williams apples Postharv. Biol. Technol. 6 209 218
Johnston, J.W. 2001 Postharvest apple softening: Effects of at-harvest and post-harvest factors Massey University Palmerston North, New Zealand PhD Diss.
Johnston, J.W., Hewett, E.W., Hertog, M.L.A.T.M. & Harker, F.R. 2001a Temperature induces differential softening responses in apple cultivars Postharv. Biol. Technol. 23 185 196
Johnston, J.W., Hewett, E.W. & Hertog, M.L.A.T.M. 2005 Apple (Malus domestica) softening in the postharvest coolchain: Effects of delayed cooling and shelf-life temperatures New Zeal. J. Crop Hort. 33 283 292
Larrigaudiere, C., Graell, J., Salas, J. & Vendrell, M. 1997 Cultivar differences in the influence of a short period of cold storage on ethylene biosynthesis in apples Postharv. Biol. Technol. 10 21 27
Liu, F.W. 1986 Effects of delayed cooling and delayed low-ethylene CA storage on keeping quality of ‘McIntosh’ apples J. Amer. Soc. Hort. Sci. 111 719 723
Saftner, R.A., Abbott, J.A., Conway, W.S. & Barden, C.L. 2003 Effects of 1-methylcyclopropene and heat treatments on ripening and postharvest decay in ‘Golden Delicious’ apples J. Amer. Soc. Hort. Sci. 128 120 127
Tan, T. & Bangerth, F. 2000 Regulation of ethylene, ACC, MACC production, and ACC-oxidase activity at various stages of maturity of apple fruit and the effect of exogenous ethylene treatment Gartenbauwissenschaft 65 121 128
Watkins, C.B., Bramlage, W.J., Brookfield, P.L., Reid, S.J., Weis, S.A. & Alwan, T.F. 2000 Cultivar and growing region influence efficacy of warming treatments for amelioration of superficial scald development on apples after storage Postharv. Biol. Technol. 19 33 45
Zhou, H.-W., Lurie, S., Ben-Arie, R., Dong, L., Burd, S., Weksler, A. & Lers, A. 2001 Intermittent warming of peaches reduces chilling injury by enhancing ethylene production and enzymes mediated by ethylene J. Hortic. Sci. Biotechnol. 76 620 628