Proper mix of ethylene, temperature brings out best in long-stored fruit
By MITCH LIES
MEDFORD, Ore. -- Oregon State University professor David Sugar is working with University of California-Davis scientists on enhancing the flavors of pears by stimulating ripening.
The result could be better-tasting pears earlier in the season.
Sugar has found that subjecting pears to ethylene treatment and then storing them at 50 degrees Fahrenheit for three or four days "really brings out the aromas," he said.
"The eating experience seems to be enhanced," he said.
Ethylene is a ripening hormone that naturally occurs in fruit. Depending on the variety, it takes pears one to two months in cold storage before they will naturally produce enough ethylene to ripen when exposed to room temperature.
Sugar has been working on stimulating ripening for several years with the idea it could provide growers access to early-season markets.
"For producers, this would extend their marketing season and, hopefully, allow them to bring in more revenue," Sugar said.
Growers and packers use temperature-control storage to ripen pears because of the fruit's propensity to get gritty and ripen unevenly when it ripens on trees, Sugar said.
The use of ethylene to coax ripening has become common in recent years, Sugar said. Packers will dose pears with ethylene for 24 to 72 hours to reduce the time it takes the fruit to produce its own ethylene.
Ethylene treatments also are widely used to ripen avocados, tomatoes, bananas and citrus, Sugar said. Little is known, however, about how stimulating ripening affects flavors.
Sugar's experiment evolved when the Southern Oregon extension horticulturist noticed pears exhibited enhanced aromas under certain ripening stimulation techniques.
At about the same time, UC-Davis scientist Elizabeth Mitcham and a graduate student started comparing how different methods of stimulating ripening affected aroma production.
The scientists found that pears dosed with ethylene for 48 hours then exposed to 50-degree temperatures for three or four days exhibit the buttery, juicy texture and high fruity aromas that are the fruit's signature.
To date, Sugar and the UC-Davis researchers have two years of data with Comice and Anjou varieties. They are wrapping up their second year of studying how the different treatments affect the flavor characteristics of Red Anjou and Packham's Triumph, a southern hemisphere variety similar in appearance to Bartlett pears that is growing in popularity here.
Sugar will provide the industry a progress report on his studies at the 2013 Northwest Pear Research Review, Feb. 19 at the Best Western Inn in Hood River, Ore. The review begins at 8 a.m.
The project is partially funded by Pear Bureau Northwest.