Introduction Maintaining low temperatures during the storage, transit and handling of many fruit and vegetables is a core strategy for maximising postharvest quality and extending storage and transit time (Wang 1990; Paull 1999). Optimal postharvest storage temperatures vary among species, varieties and plant parts, and temperatures below optimum can result in chilling injury. Chilling injury occurs as a result of physiological damage due to exposure to low, non- freezing temperatures applied for extended periods of time (Wang 1990). Navel oranges (Citrus sinensis), like many tropical and subtropical fruit, are susceptible to developing chilling injury. Visual symptoms typically develop after storage and are apparent as pitting of the rind and discoloration (Rodriguez et al. 1981; Wang 1990). Erkan and Pekmezci (2000) found that the incidence of chilling injury in Washington Navel was a function of both temperature and storage time. In their study, the development of pitting and browning-like symptoms increased with storage time, and was increased 8-fold (up to 50% of fruit) as storage temperatures were decreased from 7 or 5°C to 3°C. Other studies of chilling injury in citrus have also implicated low temperature and long exposure time. For example, chilling injury has been studied in Tarocco (blood) (Schirra et al. 1997) and Washington Navel (Edwards et al. 1994) oranges, and closely related species such as grapefruit (C. paradisi) (Schiffmann-Nadel et al. 1971; Purvis 1985) and lemon (C. limon) (Underhill et al. 1999). From these studies, the recommended minimum storage temperatures to minimise the risk of chilling injury are 13, 12 and 6°C for lemon, grapefruit and orange, respectively. Importantly, these studies also indicate that there is significant variation in temperature sensitivity among a comparatively narrow range of genetic material for citrus, and imply that it may not be possible to apply the results from one genotype directly to another. Over the past decade, the Australian export citrus industry has been adopting the use of prolonged cold storage (1°C for about 16 days) for disinfestation against fruit fly instead of chemical fumigation methods (Wild 1993; Taverner and Cunningham 1998). The optimum temperature for Australian Journal of Experimental Agriculture, 2005, 45, 453–458 0816-1089/05/040453 10.1071/EA03260 © CSIRO 2005 R. E. Henriod A,C , M. R. Gibberd A,B and M. T. Treeby A A CSIRO Plant Industry, PMB, Merbein, Vic. 3505, Australia. B Present address: Centre for Wine Excellence, Muresk Institute, Curtin University of Technology, Margaret River Education Campus, PMB1, Margaret River, WA 6285, Australia. C Corresponding author. Email: robert.henriod@csiro.au Abstract. The navel orange cultivar Lanes Late is an important export commodity for the Australian citrus industry with key markets in Asia and the United States of America. Low temperatures during storage and transport are used to extend postharvest life and for the purpose of insect disinfestation, making fruit more prone to chilling injury. The effects of low temperature and storage duration on the development of chilling injury were therefore examined. Cartons of about 100 fruit were stored at 3, 1 or –1°C for 0, 10, 20 or 30 days before transfer to a 22°C post-storage observation room. Fruit were assessed for chilling injury at transfer and every 10 days post-storage for 30 days. At all observation times the main effects of temperature and storage duration on the incidence of chilling injury and chilling injury index were significant with no interaction. The highest incidences of chilling injury were observed for fruit stored at –1°C (21%) and for 30 days (28%). Similarly, the chilling injury index was greatest for fruit stored at –1°C (0.47) for 30 days compared with fruit stored at 3 and 1°C (0.34 and 0.27, respectively). The incidence of chilling injury and the chilling injury index increased 2.1- and 3.0-fold, respectively, between the 10 and 30 day post-storage observations. Moisture loss was positively correlated with the chilling injury index (R 2 = 0.53; P<0.001), supporting the hypothesis that moisture loss and time are important determinants of the expression of chilling injury. Based on this study, it is recommended that fruit storage and transit time be kept to ≤20 days and transport temperatures are maintained at ≥1°C. The expression of chilling injury could be minimised by reducing the post-storage handling time when moisture loss is expected to be highest. Additional keywords: postharvest, rind, breakdown, flavedo, Citrus sinensis. Storage temperature effects on moisture loss and the development of chilling injury in Lanes Late navel orange www.publish.csiro.au/journals/ajea CSIRO PUBLISHING