Inhibiting Tomato Ripening with 1-Methylcyclopropene

The capacity for 1-methylcyclopropene (1-MCP) to inhibit color change and firmness loss and alter aroma profi les for tomato (Lycopersicon esculentum Mill.) fruit was evaluated as a function of 1-MCP concentration, multiple and continuous applications, and stage of ripeness. In addition, the relationship between external and internal fruit color and fi rmness was determined. 1-MCP reduced the rate of red color development in fruit of all stages of ripeness. A single application of 1-MCP delayed color development by ≈6 days. A second application of 1-MCP 10 days after fi rst treatment additionally delayed color development of mature green fruit by another 8 to 10 days. Continuous 1-MCP application completely inhibited color development of breaker and half-ripe fruit for the duration (34 days) of application, but only partially inhibited fi rmness loss. When fruit at 50% color development were treated with 1MCP, gel color development tended to lag behind the external fruit color change compared to nontreated fruit. Some aroma volatiles were affected by 1-MCP applied at the mature green and breaker stages, but the effect was relatively minor; 1-MCP did not affect sugar or titratable acid levels in these fruit. Collectively, the data indicate 1-MCP caused minor shifts in the quality attributes of locule color, aroma, and fi rmness relative to external color, which may reduce the value of this treatment, but benefi ts accrued by slowed fi rmness loss and color development may afford suffi cient compensation to make 1-MCP application commercially feasible. Controlling tomato (Lycopersicon esculentum Mill.) fruit ripeness and quality throughout the distribution chain is a priority for the United States commercial fresh tomato industry. Typically, mature green fruit are harvested and the fruit are then ripened for 2 to 3 d using a controlled ethylene application to initiate and synchronize fruit ripening. Elimination of immature green tomatoes from the market by harvesting fruit after the onset of external red color formation would boost overall tomato fl avor quality (Maul et al., 1998a, 1998b). Mature green tomatoes comprise four stages of ripening based on locular gel development (Kader and Morris, 1976). Stages 1 and 2 have solid locular tissue that can only be determined by cutting the fruit open. These fruit will eventually ripen, albeit with poor quality (Kader et al., 1978; Maul et al., 1997, 1998a, 1998b). Unfortunately, immature green fruit can comprise an average of 31% to 49% of fruit intended to be harvested at the mature green stage because of the diffi culty in distinguishing them from the mature green fruit based on surface color (Maul et al., 1998b). Mature green tomatoes at stages 3 and 4 contain gelatinous locular tissue, some internal red pigment in green stage 4, and ripen with good quality. Ethylene plays a central role in initiating and accelerating ripening-related processes that we perceive as changes in qualReceived for publication 24 July 2002. Accepted for publication 10 July 2003. We thank Charles Vavrina for providing plant material in the off-season. Research supported by the Project for Generating Research and Extension to meet Economic and Environmental Needs (GREEEN). Use of trade names does not imply endorsement of the products named or criticism of similar ones not named. 1Currently vice president of product development, Mid-Atlantic Perishable Commodities Services, 201 Falem Rd. Moorestown, NJ 08057.