Application of 1-MCP At Different Ripeness Stages Affects Physiology and Final Tomato Fruit Quality

It is well known that tomato fruit ripening can be regulated by the application of 1-MCP (1- methylcyclopropene or SmartFresh™), but the effects depend on fruit ripening stage at treatment and 1-MCP concentrations.  The objectives of this study were to 1) assess retardation of tomato ripening in relation to 1-MCP concentrations and fruit color stage and 2) determine if color stage is a sufficiently accurate indicator of the physiological state of the fruit to achieve consistent 1-MCP effects.   Field grown tomatoes (cv 901 from Syngenta) were harvested as vine-ripe fruit and held at 12.5 °C until used.  Fruit at 20 °C were selected for color stage (2, 3, or 4 on USDA color chart), fruit respiration and ethylene production rates were measured on individual fruit before treatment, fruit were treated for 8–12 h with 1-MCP (0, 300, 400, or 500 nL/L), and then placed in individual containers to follow respiration and ethylene production rates at 20 °C until the fruit reached the table ripe stage (color stage 6).  The treated fruit had suppressed respiration rates, with greater suppression observed in fruit treated with higher 1-MCP concentrations or with application of 1-MCP at earlier color stages.  After the 1-MCP treatment, there was a peak in ethylene production rates followed by decreasing rates to below those of untreated fruit.  Red color development (to table-ripe or color stage 6) of fruit treated with a single application of 300, 400, or 500 nL/L 1-MCP was delayed by 2 to 3, 4 to 7, and 8 to 13 days, respectively. Firmness, hue, and lycopene concentrations of fruit treated with 300 nL/L 1-MCP were the same or slightly higher than values for untreated fruit after 10 days. However, after treating fruit with 500 nL/L 1-MCP, the same parameters were significantly different from those of untreated fruit, indicating that 1-MCP clearly retarded the ripening process too much.   Treatment with 400 nL/L 1-MCP resulted in an intermediate delay of ripening. Treating with 1-MCP at too early a ripeness stage (color stage 2), too high 1-MCP concentration (500 nL/L), or too long exposure (12h), affected the recovery of the ripening process, the uniformity of ripening and final fruit quality.  The color stage of the fruit did indicate similar physiological behavior (respiration and ethylene production rates) and was sufficiently accurate to ensure a uniform 1-MCP response.