Differential sorption of 1-methylcyclopropene to fruit and vegetable tissues, storage and cell wall polysaccharides, oils, and lignins

This study was designed to determine the nature and multiplicity of non-specific 1-methylcyclopropene (1-MCP) sorption sites in fruit and vegetable tissues. 1-MCP sorption rates and capacities were measured for plant tissues, cell wall polysaccharides, starch, oils, and lignins sealed in 130 mL jars and provided with 18.6 mu LL L-1 gaseous 1-MCP (SmartFresh (TM) Technology). Significant variation was noted in the sorption properties of the different plant tissues, with both sorption rates and capacities being notably higher for external/exocarp tissues compared with internal tissues. Among the tissues examined, avocado exocarp, mesocarp and seed coat, plantain exocarp, and asparagus stem tissues exhibited the highest sorption rates and capacities. Sorption was markedly reduced in response to tissue drying but recovered to different extents in response to rehydration. Avocado mesocarp treated to deplete oil content showed reduced 1-MCP sorption rate and capacity whereas the exocarp was negligibly affected, indicating that multiple cellular components contribute to non-specific sorption. Starch and the cell wall polysaccharides cellulose, polygalacturonic acid and xyloglucan showed low sorption properties and were unaffected by polymer hydration. In contrast, high methoxy pectic polymers and lignins were strong molecular sinks for 1-MCP sorption. Sorption to pectin was dependent on the esterified methyl moiety, as de-esterification reduced sorption rate and capacity to levels comparable with polygalacturonic acid. Plantain-exocarp and spruce lignins, and avocado and safflower oils exhibited the highest initial sorption rates. For oils, rapid initial sorption was followed by establishment of stable equilibrium between gaseous and partitioned 1-MCR Compared with oils, the binding capacity of lignins was markedly higher and irreversible. The data collectively demonstrate that 1-MCP sorbs to several cellular targets and that hydrophobic components are preferred sorption sinks. The highly disparate 1-MCP sorption rates and capacities of the different fruit and vegetable tissues examined are consistent with compositional differences in lignin, methylated pectin, and oil levels. (C) 2008 Elsevier B.V. All rights reserved.