Depletion of 1-MCP by 'non-target' materials from fruit storage facilities

The sorption of 1-methyicyclopropene(1-MCP) by a number of 'non-target' materials found in apple (Malus x domestica Borkh.) and pear (Pyrus communis L.) fruit storages was measured as a function of time, temperature, and moisture content. Materials included bin construction materials [high density polyethylene (HDPE), polypropylene (PP), extensively- and slightly-weathered oak (Quercus sp.), weathered fir (Abies sp.) plywood, and cardboard] and wall surface materials (polyurethane foam and cellulose-based fire retardant). Bin construction materials test pieces had an external surface area of 180 cm(2). We placed 'non-target' materials in 1-l glass jars and added 1-MCP gas to the headspace at an initial concentration of approximately 30 mu l l(-1). Gas concentrations were measured after 2, 4, 6, 8, 10, and 24 h. The concentration of 1-MCP in empty jars was stable for the 24-h holding period. There was little to no sorption by HDPE, PP, polyurethane foam, or fire retardant. However, plywood, cardboard, slightly-weathered oak, and extensively-weathered oak absorbed 16, 18, 55, and 75% of the 1-MCP after 24 h. Moistening the test material increased the rate of sorption of 1-MCP for cardboard, plywood, weathered oak, and non-weathered oak, resulting in a depletion of approximately 98, 70, 98, and 98%, respectively, in 24 h. For oak bin material, the rate of sorption was not impacted by temperature and increasing the surface area by approximately 100% only marginally increased the rate of sorption. When moistened oak bin material was included with apple fruit in a proportion similar to that found in fruit storage, 90% depletion occurred in 6 h compared to approximately 80% in 24 h for fruit alone. The data suggest that 1-MCP levels can be compromised by wooden and cardboard bin and bin liner materials, but not by plastic bin materials or wall surface materials commonly used in Michigan. (C) 2006 Elsevier B.V. All rights reserved.