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Natural compounds inhibit decay fungi.

At the supermarket, plant physiologist Steven F. Vaughn viewed with dismay the moldy raspberries and strawberries--a sight he had seen many times before. He wondered if maybe there was something he and his ARS colleagues could do to extend the time berries resist the onslaught of fungi. If so, perhaps grocers and consumers could profit from riper and tastier berries than those that are picked early to prolong shelf life.

Vaughn and his coworkers at ARS' National Center for Agricultural Utilization Research, Peoria, Illinois, thought the problem called for afresh approach.

"We thought we'd try surrounding the berries with a little extra amount of a natural antifungal compound they make themselves," he says. The idea was to continuously expose the berries in a closed package to a volatilizing compound--found in their aroma--that would not affect taste but would hold back the growth of three troublesome fungi, Alternaria alternata, Botrytis cinerea, and Colletotrichum gloeosporioides.

Vaughn and chemist Gayland F. Spencer tested 15 major volatile compounds--aldehydes, alcohols, ketones, and esters--that partially make up the aroma of raspberries and strawberries. To do this, they put fungi-inoculated berries into small jars fit into bigger jars containing filter paper soaked with small amounts of the test compounds. Then they sealed the large jars. At 50 [degrees] F, five of the compounds, in concentrations as low as 400 parts per million of air, inhibited all three fungi on both raspberries and strawberries for at least a week in environmental chambers.

Of the compounds tested, 2-nonanone may have the most commercial appeal because it has a fruity floral aroma, does not break down quickly into other compounds, and costs little. Vaughn says that enough 2-nonanone to treat a quart of berries may cost less than a penny.

The researchers have applied for a patent on the use of all these natural compounds. However, commercialization would require further research to obtain U.S. Food and Drug Administration approval.

In other studies at the center, chemist Baruch S. Shasha and Vaughn entrapped 2-nonanone in cornstarch so it could slowly seep out to fungi-inoculated berries held in airtight flasks.

A week later, when the berries were unsealed, they briefly had a slight floral odor, but the fungi had not grown visibly. Fungi did grow when 2-nonanone was no longer around to protect the berries.

Partially ventilated packaging may be more desirable for the berries as they live and breathe in the supermarket, Vaughn says. Such an environment could prevent the fruit from developing off-flavors, while antifungal compounds would remain to prevent premature decay.

Steven F. Vaughn is in the USDA-ARS Bioactive Constituents Research Unit, National Center for Agricultural Utilization Research, 1815 N. University Street, Peoria, IL 61604. Phone (309)-685-4011, fax number (309) 671-7814.
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Author:Hardin, Ben
Publication:Agricultural Research
Date:Sep 1, 1993
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