Fresh Fruit Gets a New Protective Coat

By Rosalie Marion Bliss
August 21, 2002

Apples and citrus are about to get a uniform new coat. But it's not to keep the fruit warm on cold orchard nights. Instead, these coatings act as biofungicides that keep fruit fresh longer during storage.

Agricultural Research Service scientists have been working to improve earlier biofungicides aimed at controlling decay of fruits and vegetables after harvest. Such fungal decay can destroy more than 25 percent of the world's harvested fruit.

Biological products, such as friendly yeasts, are used for environmentally safe pest control and to reduce dependence on synthetic chemicals. They work by consuming nutrients on fruit and vegetable skins that otherwise would allow rot-causing fungi to grow.

Charles L. Wilson, a plant pathologist with the ARS Appalachian Fruit Research Station, Kearneysville, W.Va., and Ahmed El Ghaouth, a postharvest plant pathologist employed by Micro Flo Co. of Memphis, Tenn., conducted research leading to two patents issued this year.

One of the two new patents discloses how chitosan, a natural fungicide, can be compatibly combined with an antagonistic yeast named Candida saitoana by adding a softener. Antagonistic yeast organisms are normally found on fruit and vegetable skins, but are benign to people. The other patent approved this year discloses a mixture of C. saitoana with lysozyme, an antifungal enzyme.

Development of postharvest biological products based on technology described in the patents is being furthered by Micro Flo, a subsidiary of the international chemical company BASF, through a cooperative research and development agreement. Micro Flo is pursuing the lysozyme and C. saitoana mixture to create a product named Biocure.

The annual worldwide market for postharvest treatments is currently more than $18 million for citrus and more than $8 million for apples, according to El Ghaouth.

ARS is the U.S. Department of Agriculture's chief scientific research agency.