New Fruit Coatings Help Abate Post-Harvest Fruit Decay

The shine that helps fruits glisten at the local produce stand may soon be only the most visible manifestation of a more natural way to preserve fruit—34 million tons harvested in the U.S. in 1998—while on its way to market.

Agricultural Research Service scientists and cooperators have developed fruit coatings made from reformulated shellac and sucrose ester, a compound derived from combining sugar with a fatty acid. These biocontrol coatings help maintain quality by promoting the growth of beneficial bacterial and yeast populations naturally on the fruit. The research is part of a continuing effort to decrease fruit producers’ reliance on chemicals to delay post-harvest decay.

The chemicals traditionally used to preserve harvested fruit—imazalil, which costs $1,000 per liter, and thiabendazol for Florida grapefruit—have been found to kill beneficial bacterial and yeast populations. These populations help maintain fruit quality by competing more efficiently than pathogens for nutrients, such as sugars and proteins, at a critical early stage in the pathogen’s development. In essence, these beneficial bacteria and yeasts starve the pathogens that would otherwise feast on the fruit nutrients and cause decay.

Raymond McGuire at ARS’ Subtropical Horticulture Research Station in Miami, Fla., and cooperators from Mantrose Haeuser Co Inc. of Westport, Conn., have also tested both reformulated shellac and sucrose ester coatings for their ability to reduce the development of off-flavors caused by the buildup of ethanol. Preliminary test results on grapefruit indicate that both the reformulated shellac and, to a larger extent, sucrose ester coatings prevented off-flavors by allowing for a better exchange of oxygen and carbon dioxide than commercial chemicals permit.

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

Scientific contact: Raymond G. McGuire, ARS Subtropical Horticulture Research Station, Miami, Fla.; phone (305) 254-3641, fax (305) 238-9330, miarm@ars-grin.gov.