1-MCP Inhibition of Ripening in ‘D’Anjou’ Pears: Biochemical Characterization and Ripening Solutions

Evan C. Stowe

doi:10.7273/000006389

Changes in global climate patterns will continue to stress food production and distribution far into the future. In fruits, early ripening, and associated processes such as flesh softening, and starch-to-sugar conversion are major causes of food wastage post-harvest. One means of combatting food wastage, especially in vulnerable crops such as climacteric fruit, is to delay the onset of ripening. Perhaps the most powerful tool for this effort is the 4-carbon gaseous molecule 1-methylcyclopropene (1-MCP), which inhibits perception of the “ripening phytohormone” ethylene. Delaying ripening by 1-MCP treatment allows distributors to extend storage and transportation times and researchers to investigate the molecular physiology of climacteric fruit ripening at increasingly granular levels. However, 1-MCP effects in European pears (Pyrus communis) yield perplexing results, with fruit often failing to ever ripen after treatment. To preserve this valuable chemical treatment tool, research has identified a putative ‘ripening compound’ glyoxylic acid (GLA) as a chemical means of restoring ripening competency in 1-MCP treated winter pear varieties such as ‘D’Anjou’. Physiological investigations reveal that peak ethylene evolution is up to two-fold higher and terminal flesh firmness is lower, on average 1 lbs-force in 1-MCP + 3% (w/v) GLA treated fruit over 1-MCP only fruit. GLA-treated fruit also respire on average 450 µg CO2 kg -1 hr -1 more than their 1-MCP only counterparts in 4oC cold storage though there are no discernable differences in endogenous organic acid pools between the two treatments. Brown necrotic spots visible on GLA-treated fruits are likely due to lipid peroxidation, as the occurance of lipid hydroperoxides is up to 30% higher in GLA-treated fruits. Previous research using 1-MCP treated fruit obtained from packing houses and stored in different stroage conditions than this study has proposed that GLA is metabolized via malate synthase in the glyoxylate pathway. In this study, where precise quantifiable application of 1-MCP was used without prolonged storage, no increase in enzyme activity could be observed in vitro after GLA treatment. Furthermore a novel cost effective method of 1-MCP application is documented allowing for accurate application of the ripening inhibitor for small scale research down to 50 parts per billion.

1-MCP Inhibition of Ripening in ‘D’Anjou’ Pears: Biochemical Characterization and Ripening Solutions

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