Scientists at Washington State University have filed a patent application for a product that could be applied preharvest to pears to extend their storability as an alternative to a postharvest MCP (1-methylcyclopropene) application.
Dr. Amit Dhingra, a molecular biologist based in Pullman, said pears that have been treated with the new product are firm when they come out of controlled-atmosphere storage, but are able to ripen properly afterwards. Since it’s a natural compound, it should be suitable for use in organic production. The substance, which is not related to MCP, was discovered by scientists in his lab.
Dhingra said WSU scientists will test it in various situations in the field during the coming season and hope to do so in collaboration with AgroFresh, which produces and markets MCP. A recent survey of warehouses he conducted showed that between 5 and 10 percent of fresh pears were being treated with MCP, which he said points to the need for a product to enhance storability of pears or control storage disorders.
Experiments he and his colleagues conducted with d’Anjou pears during the past year showed that pears treated with MCP postharvest didn’t ripen properly after controlled-atmosphere storage. The pears were conditioned with ethylene after being stored for six months.
“Nothing happened,” Dhingra reported. “They looked great, but they were rubbery when they came out and that’s how they stayed. They would not wake up.”
The Fresh Pear Committee is funding further research at Dhingra’s lab at Pullman to look at the genomics of pear ripening. A physiological experiment is being conducted to find out why MCP-treated pears don’t respond to ethylene after being stored.
“In apples, after you bring them out of CA, they are able to respond,” he said. “They are still able to go through physiological changes so that they’re edible. In pears, the pressures don’t change. They don’t go down to edible quality.”
Since MCP-treated pears don’t seem to respond to ethylene, Dhingra is exploring whether there might be some other chemical that could be applied to MCP-treated pears to allow them to ripen after storage.