Measurement and prediction of the concentration of 1-methylcyclopropene in treatment chambers containing different packaging materials

BACKGROUND: 1-methylcyclopropene (1-MCP) has been shown to suppress ethylene response and extend the post-harvest shelf life and quality of several fruits and vegetables. In the US and Canada, the label treatment dosage for apples is 1.0 and 0.6 mu L L-1, respectively. It has been demonstrated that wood and corrugated fiberboard materials, commonly found in apple storage facilities, absorb 1-MCP. Losses of 1-MCP during the exposure period might compromise the effectiveness of the product. The effects of type of material (corrugated fiberboard and high density polyethylene), relative humidity (50%, 80%, and >95%), ratios of mass of packaging material (kg) per unit volume (m(3)) of airspace in a treatment chamber, and initial concentration of 1-MCP (10 and 20 mu L L-1) on the available concentration of gaseous 1-methylcyclopropene (1-MCP) in an enclosed chamber were studied. RESULTS: The concentration of 1-MCP declined in the presence of the materials tested, but the rate at which 1-MCP gas was removed from the chamber headspace differed markedly. The average percentage loss for HDPE was between 10 and 12% at all conditions tested, while for corrugated fiberboard it ranged from 12 to 94%. CONCLUSIONS: The concentration of 1-MCP at any time, t, follows an exponential decay behavior. For corrugated boxes, the rate at which 1-MCP is removed increased up to 10-fold as the relative humidity increased from 50 to 80%. The 1-MCP depletion rate doubled as the ratio of material was increased from 4 to 8 kg of corrugated fiberboard m(-3) air. An increase of initial concentration from 10 to 20 mu L L-1 reduced the rate by half. This trend was also observed for HDPE boxes. (C) 2009 Society of Chemical Industry