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Berry scent defends fruit from fungus.

"I got sick of going to the supermarket and buying moldy raspberries," says Steven F. Vaughn. So the plant physiologist decided to see if he couldn't sniff out -- literally -- a means of extending the shelf life of this very perishable product. The fruits of his labors now include five odor compounds emitted by ripening strawberries and raspberries.

Bringing soft fruit to market decay-free remains a challenge. Raspberries, harvested ripe, can sport heavy growths of mold within three to five days. To limit the problem in strawberries, growers often harvest the fruit green -- a technique that can compromise flavor. And while the industry can irradiate citrus and other thick-skinned crops to kill or sterilize pests, radiation sufficient to kill fungi would destroy the structure of soft berries, Vaughn notes.

All of which explains his excitement over the berry scents. When slowly released into closed containers of strawberries or raspberries, the least toxic of these volatile compounds totally suppressed fungal decay for at least seven days.

"We weren't expecting miracles," acknowledges Vaughn, at the Agriculture Department's Bioactive Constituents Research lab in Peoria, Ill. But his data on one of the odorants -- a straight-chained hydrocarbon known as 2-nonanone--have already sparked commercial interest. The USDA has taken steps to patent nonanone as a fungicide for soft fruit.

Vaughn happened onto the idea for fumigating berries with a slowly released derivative of their own fragrance while scanning published lists of compounds that contribute to a ripe berry's characteristic smell. Though many of the chemicals were known antifungal agents, he observed that "they aren't normally present in fruit at high enough levels to do anything but smell."

In a series of tests, he investigated the concentrations at which 15 of these compounds inhibited cultures of the fungi primarily responsible for berry decay. Then he tested the five best inhibitors on the fruit.

Though nonanone was not the most inhibitory of the chemicals, it won out on the basis of its overall attributes, which include low toxicity, low potential for damaging the fruit, low cost, stability, a scent that blends well with that of the treated fruit, and its status as a federally approved flavoring. A report of the findings will appear this fall in the JOURNAL OF FOOD SCIENCE.

Vaughn suspects growers may ultimately want to incorporate some slow-release form of nonanone into the packaging of field-boxed berries.
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Title Annotation:fungicides derived from berry odors used to preserve fruit
Author:Raloff, Janet
Publication:Science News
Article Type:Brief Article
Date:Aug 7, 1993
Words:392
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