Cultivar Differences in Gaseous 1-Methylcyclopropene Accumulation in Whole and Fresh-cut Apple Fruit

Wednesday, July 24, 2013
Desert Ballroom: Salons 7-8 (Desert Springs J.W Marriott Resort )
Xiaoqing Dong , Horticultural Sciences Department, IFAS, University of Florida, Gainesville, FL
Donald J. Huber , Horticultural Sciences Department, Horticultural Sciences Department, IFAS, University of Florida, Gainesville, FL
Maricruz Ramirez-Sanchez , Horticultural Sciences Department, IFAS, Horticultural Sciences Department, IFAS, University of Florida, Gainesville, FL
Jing-Ping Rao , College of Horticulture, College of Horticulture, Northwest A&F University, Yangling, China
Jinsu Lee , Horticultural Sciences Department, Horticultural Sciences Department, IFAS, University of Florida, Gainesville, FL
Christopher B. Watkins , Department of Horticulture, Cornell University, Ithaca, NY
A number of studies have shown that responsiveness of apple fruit to 1-methylcyclopropene (1-MCP) can vary considerably among cultivars, with some requiring higher concentrations to control ripening. The present study was designed to determine if different cultivars show differences in accumulation of gaseous 1-MCP.  Freshly harvested apple fruit were immersed in water or a  wax/water (50:50; v/v,) suspension (Sta-Fresh 8711). After drying, fruit were placed individually in 1.76 L jars that were sealed and injected with 20 µL·L-1 1-MCP. After 12 h, fruit were removed, immersed in diH2O and 1 mL samples removed using a syringe.  Accumulation of internal gaseous 1-MCP varied markedly among cultivars, ranging from 0.14 ± 0.06., 0.22 ±  0.03, , and 0.77 ± 0.30 in unwaxed ‘Redcort’, ‘McIntosh’, and ‘Empire’, respectively, to 2.10 ± 0.28, 3.33 ± 0.13, and 6.93 ± 0.35 µL·L-1 in unwaxed ‘Gala’, ‘Cameo’, and ‘Honeycrisp’, respectively.  Cultivars accumulating higher internal gaseous 1-MCP showed greater post-exposure off-gassing. Accumulation of gaseous 1-MCP was reduced from 17%  to 78% in waxed fruit. The role of the epidermis at influencing 1-MCP ingress was determined by measuring gaseous 1-MCP accumulation in fresh-cut tissue.  Apple slices from the different cultivars were placed in 244 mL jars and treated with 20 µL·L-1  1-MCP for 1 h. Fresh-cut tissue of all cultivars rapidly depleted headspace 1-MCP (> 95%) over the 1 h exposure yet showed negligible accumulation of internal gaseous 1-MCP (≤ 0.07 µL·L-1). By contrast, fresh-cut tissue treated with L-ascorbic acid or aged for several hours prior to exposure showed markedly reduced consumption of headspace 1-MCP (≈25%) and high accumulation of gaseous 1-MCP. Internal [1-MCP] in apple slices ranged from 0.23 ± 0.07, 0.37 ± 0.18, and 1.09 ± 0.14 µL·L-1 in ‘Empire’ ‘McIntosh’ and ‘Redcort’, respectively, to 2.40 ± 0.71, 4.55 ± 0.15, and 6.24 ± 0.85 in Gala’, ‘Cameo’, and ‘Honeycrisp’, respectively.  Maximum ingress in fresh-cut tissue is dependent on measures (antioxidants, tissue aging) that minimize wound-related metabolism. Although commercial wax clearly influences gaseous 1-MCP accumulation, the comparable accumulation capacities in unwaxed whole and ascorbate-treated fresh-cut apple fruit suggest that epidermal tissue/native waxes do not strongly influence 1-MCP ingress.  The physical and biochemical bases for cultivar differences in gaseous 1-MCP accumulation could reflect differences in intercellular diffusivity as well as capacities for physical sorption and/or metabolism.
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