|Obenland, David - Dave|
|ARPAIA, MARY LU|
Submitted to: American Society of Horticulture Science Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2007
Publication Date: 7/1/2008
Citation: Obenland, D.M., Arpaia, M., Margosan, D.A., Slaughter, D., Thompson, J., Collin, S., Sievert, J., Field, K. 2008. Exposure to ultraviolet light as a means of predicting damage in oranges exposed to freezing conditions. American Society of Horticulture Science Meeting. 42(4):980.
Technical Abstract: Current methods of evaluating whether an orange has been damaged by a period of freezing temperatures require fruit to be cut and physically examined for signs of freeze damage. This method is destructive, slow, and inaccurate and relies on visual evaluation. Visual symptoms of freeze damage may take several days to weeks to appear, thus sometimes allowing damaged, inedible fruit to reach the marketplace. It was found that freeze-damaged fruit had small fluorescent orange-yellow dots on the flavedo when exposed to long-wave UV radiation. These dots appear within 1 to 2 h after thawing of the peel and they are likely due to the migration of fluorescing component(s) present in oils found in the flavedo cells into the epidermal layer of the flavedo. In January 2007, following a major freeze event in California, five lots (105 to 141 fruit per lot) of oranges that were thought to differ in amounts of freeze damage were harvested from commercial groves, rated for the occurrence and amount of UV fluorescence, and cut using the California Department of Food and Agriculture (CDFA) method to rate freeze damage. The agreement between the two rating methods was 46 to 95%, with the closest agreement occurring in a lot that suffered no apparent freeze damage. It was apparent, however, that internal freeze damage in the form of hesperidin crystals and soaking of the segments was present in some of the fruit that had UV fluorescence but did not rate as damaged by the CDFA method. Exposure to UV light may offer a rapid, non-destructive means to detect freeze damaged oranges soon after a freeze event in both the field and in the packinghouse.