Potential MCP Revolution
Potential MCP Revolution
Ethylene is a naturally occurring plant hormone that causes some fruits to ripen. Unlike other plant hormones, it is a gas. In normal fruit ripening, ethylene is produced in the fruit, and it then attaches to a receptor molecule. Ethylene attaching to the receptor is much like a key fitting in a lock, with ethylene as the key, and the receptor as the lock. When ethylene attaches to the receptor, it is like the lock turns and a door opens. A cascade of events then takes place, such as the fruit begins to soften, produce volatiles, and changes color. Another gas, 1-methylcyclopropene (1-MCP), is able to attach to the ethylene receptor. It also can act as a key that goes into the lock, but it is unable to turn the lock and open the door. When the 1-MCP key is in the lock, it is not possible for the ethylene key to go in the lock. It is in this way that 1-MCP can act as an ethylene inhibitor for fruit ripening.
Because gases are often difficult to handle, 1-MCP was put into a solid formulation. It is a white powder, which has the trade name EthylBloc and is a Rohm and Haas product. This white powder, when mixed with a dilute base, will release 1-MCP. The 1-MCP will evolve off as a gas.
EthylBloc (1-MCP) can be used to inhibit ethylene responses in plants. A typical postharvest scenario might be to enclose a plant product, such as apples, in an airtight container/room. 1-MCP gas would be released into the air and penetrate the product. After a short period of time (hours), the product would be returned to air. The product would then continue on the postharvest route to the buyer. In apples, it appears that treatment with EthylBloc permanently blocks the ethylene receptors.
The success of the EthylBloc treatment depends on a number of things. The concentration of the 1-MCP gas must be high enough to saturate the receptors and compete with any ethylene present. The treatment time must be long enough for the gas to penetrate the tissue. The temperatures at which the treatment takes place will influence the length of time needed for treatment. The gas must be able to penetrate through packaging and into the plant tissue.
In apples, some of the benefits are maintenance of fruit firmness and titratable acidity, sweet fruit with starch loss, and inhibition of scald.
North Carolina State University
Horticultural Science Department
Raleigh, NC 27695
16th Annual Postharvest Conference, Yakima, WA
March 14-15, 2000