Effect of 1-methylcyclopropene on phenylpropanoid metabolism, the accumulation of phenolic compounds, and browning of whole and fresh-cut ‘iceberg’ lettuce

Abstract

Exposing whole heads or leaves of iceberg lettuce (Lactuca sativa L., iceberg) to 1-methylcyclopropene (1-MCP) significantly decreased the accumulation of phenolic compounds (absorbance of methanol tissue extract at 320 nm) and subsequent tissue discoloration induced by exposure to 1.0 μL L−1 ethylene in air at 5 °C. The 0.5 μL L−1 concentration of 1-MCP was just as effective as 1.0 μL L−1, and a 3-h exposure was just as effective as a 24-h exposure at 5 °C. In contrast, exposure to 1-MCP either before or after excision of mid-rib tissue did not interfere with the wound-induced increase in phenolic content of the tissue. It appears that wounding and ethylene act independently in the induction of phenylpropanoid metabolism and the accumulation of those phenolic compounds that contribute to browning of mechanically injured (e.g., fresh-cut) iceberg lettuce.