Extend fruit post-storage quality.

A mushy apple makes a disappointing snack. Despite extensive precautions taken to properly store freshly picked fruit and market it to consumers in a timely fashion, mushy apples cannot be completely avoided.

Now, thanks in part to USDA-ARS scientists, a gaseous compound, 1-methylcyclopropene (1-MCP), is helping prolong the fruit's quality and crispness. 1-MCP works by blocking ethylene, which naturally regulates ripening and aging. Studies have shown that 1-MCP prevents superficial apple scald, a peel-discoloring disorder that's a major storage problem. That finding, in turn, has led to 1-MCP's use as an alternative to preventing apple scald with diphenylamine, a chemical antioxidant that requires close monitoring.

Research also showed that 1-MCP can inhibit fungal rots in apples stored under a controlled-atmosphere (CA) environment, which can slow ethylene production. Apples not intended for fresh market are stored at low temperatures, with low levels of oxygen and high levels of carbon dioxide. While this slows the apples' natural production of ethylene and its effects, fungicides must often be applied to prevent fungal rots from taking hold.

Commercial use of 1-MCP, marketed as the product SmartFresh(tm), has helped reduce fungicide use in apples. Maine's 2004 apple crop, for example, experienced a 43% decrease in fungicide use. And on CA-stored Red Delicious and Granny Smith apples, 1-MCP treatments effectively prevented scald without diphenylamine.

Under a trust fund agreement with the Washington Tree Fruit Research Commission, ARS scientists evaluated the gas on Gala, Red Delicious, Golden Delicious, Braeburn, Granny Smith, Fuji and Pink Lady apples. These studies identified the best application methods and dosages of the gas to use for each variety, and also showed their physiological responses to the regimens. Apples treated with 1-MCP generally remained firm for three to six months longer than the untreated controls under CA-storage conditions. Red Delicious apples, for example, stayed crunchier for two to three weeks longer than untreated controls when removed from storage, we're told.

Under an agreement with AgroFresh, a Rohm and Haas Company, investigators also worked with the firm to evaluate the gas's use, first on pears and then on apples. Researchers also found that 1-MCP decreased the degreening of broccoli, browning of lettuce and bitterness in carrots.

Further information. James Mattheis, USDA-ARS Tree Fruit Research Laboratory, 1104 N. Western Ave., Wenatchee, WA 98801; phone: 509-664-2280; fax: 509-664-2287; email: mattheis@tfrl.ars.usda.gov.