Natural chemical armor for fruit.

Applying an extra dose of some natural flavor compounds found in fruit can protect it from going moldy and generate further flavor chemicals, according to scientists at the University of Kentucky (College of Agriculture, Department of Horticulture and Landscape Architecture, Lexington, KY 40546). Investigators are taking natural chemicals, produced in plants and normally in our diets, and trying to see if they can be used in place of synthetic pesticides for preserving fruits and vegetables.

When investigators fumigate fruit with these natural chemicals, the fruit metabolizes about two-thirds of the chemicals into new products. It turns out that many of the new products are also natural chemicals that are in the aroma of fruits and vegetables. Fruits and vegetables that could potentially be treated include grapes, apples, blackberries and raspberries, as well as strawberries, which are vulnerable to attack in the field by the gray mold Botrytis.

The number of synthetic pesticides available to strawberry growers is dwindling, and none are currently available commercially to treat the ripe fruit. There's more. The technique that is under development could be used to kill the mold in refrigerated trucks that transport strawberries to market.

But researchers have yet to determine the optimum concentrations of natural flavor compounds needed to impede mold growth. Low concentrations of the compounds may actually stimulate the growth of mold.

Because strawberries metabolize the applied chemicals into other flavor compounds, the technique also could be used to improve the taste of flavor-challenged fruit. But this application could backfire if it upsets the delicate balance among the myriad different compounds that comprise the flavor of a berry.

In the past we told you how a fungus, which makes a compound found in natural peach essence, kept kiwifruit safe from mold for a year in refrigerated storage. Trichoderma harzanium or its extract protected more than 99% of 6000 kiwifruit from Botrytis mold in a New Zealand test. Peaches make this compound. It's found in natural peach essence, and the synthetic version is used in some foods and perfumes. A taste panel found no loss of flavor or quality in the treated fruit. Half the untreated fruit were damaged with mold. In this project, USDA researchers worked jointly with New Zealand researchers and are seeking joint patent protection.

Further information. Thomas Hamilton-Kemp; phone: [phone]; fax: [phone].