Postharvest Biology and Technology 35 (2005) 43–60 1-MCP reduces physiological storage disorders of ‘Hass’ avocados Allan. B. Woolf a,∗ , Cecilia Requejo-Tapia a , Katy A. Cox a , Richard C. Jackman a , Anne Gunson a , Mary Lu Arpaia b , Anne White a a The Horticulture and Food Research Institute of New Zealand, Private Bag 92 169, Auckland, New Zealand b Kearney Agricultural Centre, University of California, 9240 S. Riverbend Ave., Kearney, CA, USA Received 14 March 2004; accepted 10 July 2004 Abstract Physiological disorders occur when ‘Hass’ avocados are stored for more than approximately 4–6 weeks. The major disorder is diffuse flesh discolouration (“flesh greying”, or “internal chilling injury”), but others include vascular browning, vascular leaching (browning of flesh around the vascular bundles), stringy vascular tissue (thickening and separation of the vascular strands), and outer flesh blackening (blackening of the outmost layer of the mesocarp). We have examined 1-MCP effects on ‘Hass’ avocados stored for 4 or 7 weeks at 5.5 ◦ C following treatment with 50–1000 nl l -1 1-MCP for 6–24 h, at 6 or 15 ◦ C. The effect of harvest date (fruit maturity) on responsiveness to 100 and 500 nl l -1 1-MCP was examined. 1-MCP treated fruit were firmer following storage, had reduced skin colouration (purpling) at removal from storage (4 or 7 weeks), increased time to softening, and reduced physiological disorders associated with long-term storage. Relatively little difference was observed between fruit treated at 15 and 6 ◦ C, and thus a treatment temperature of 6 ◦ C was used in the remaining experiments. For lower 1-MCP concentrations, short treatment durations influenced time to ripen, but not fruit quality. Treatment times of 12 and 24h produced similar results. Harvest date (fruit maturity) influenced the levels of disorders in non-1-MCP treated fruit, but had little overall effect on 1-MCP efficacy. 1-MCP treatment was of little benefit for fruit stored for 4 weeks but, particularly if the 1-MCP concentration was high (250 nl l -1 ), excessively delayed the time to ripen. After 7 weeks storage 100 nl l -1 1-MCP almost completely eliminated some long-term storage disorders. A small trial showed that 500 nl l -1 1-MCP did not reduce external chilling injury (skin blackening) of ‘Hass’ avocados induced by 0 ◦ C storage. Overall, 1-MCP shows promise as a tool for reducing internal physiological disorders due to long-term storage of ‘Hass’ avocados. © 2004 Elsevier B.V. All rights reserved. Keywords: Persea americana (Mill.); 1-Methylcyclopropene; Quality; Maturity; Softening; Chilling injury; Fruit firmness ∗ Corresponding author. Tel.: +64 9 815 4200; fax: +64 9 815 4202. E-mail address: awoolf@hortresearch.co.nz (Allan.B. Woolf). 1. Introduction The main limitation to storing ‘Hass’ avocados for longer than about 4 weeks is the occurrence of internal diffuse flesh discoloration (“flesh greying”, or “inter- nal chilling injury”; Fig. 1A), which can also occur 0925-5214/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.postharvbio.2004.07.009