Courtesy Agricultural Research ServiceOrange peel blemishes glow under ultraviolet light.Using ultraviolet light to detect blemishes on oranges is nothing new, with the practice having been used in California more than 50 years ago.
But a group of U.S. Department of Agriculture researchers believe the technology could be used to find other, less-noticeable, blemishes on oranges, according to a news release.
Among them were David Obenland and Joseph Smilanick, both stationed at the USDA Agricultural Research Service's Parlier, Calif., facility.
In the early days, oranges with spots the size of quarters or larger when viewed under UV light were culled.
The researchers believe that other patterns of fluorescenes, such as specks, smears, smudges or blotches, also indicate cuts, punctures or other peel wounds that provide openings for decay pathogens.
The researchers sampled 5,000 navel oranges during a two-year period and sorted them based on fluorescenes levels.
In addition, the oranges were evaluated under normal light within 24 hours of UV screening and after the fruit had been stored at 59 degrees Fahrenheit for three weeks.
Although fruit with high fluorescence developed further decay and peel quality problems, so di many of the oranges that only had moderate fluorescence.