Apple Browning Significantly Delayed In USDA Tests

Writing in the January 18 print issue of the Journal of Agricultural and Food Chemistry, researchers at the U.S. Department of Agriculture in Beltsville, Md., claim they have been able to prevent the browning of cut apples for five weeks under "normal atmospheric conditions," a significant jump over the current five to seven day shelf life for most cut fruit that has been treated against browning. The monthly journal is a peer-reviewed publication of the American Chemical Society, the world's largest scientific society. The article initially appeared in the journal's online edition Dec. 8.

Most apples, once cut, begin to turn brown in a matter of minutes. This browning, known as enzymatic oxidation, has been a major impediment to expanding the "shelf life" and marketability of fresh-cut fruit. At best, in the case of apples, browning generally can only be delayed for a few days by dipping slices in ascorbic acid found in such citrus fruits as lemons, limes, oranges and grapefruit and storing the slices at low temperatures. The new USDA treatment dramatically extends that time.

"We have devised an anti-browning treatment that is a combination of compounds, either natural products or their derivatives that are food additives," says USDA researcher George Buta, Ph.D., lead author of the report. Various combinations of enzymatic inhibitors, reducing agents and anti-microbial compounds containing calcium were tested, according to the report. The treatment also "slowed down microbial decay and changes in organic acids and sugars during storage," claims Buta.

Treated slices of Red Delicious apples, the variety used for the study, were stored during testing at temperatures of 5 and 10 C (41 and 50 F). The success with apples has prompted the researchers to begin investigating natural product combinations to prevent browning in other fresh-cut fruit, including bananas, peaches and pears.