Using peel fluorescence in black light rooms to identify navel oranges with shorter storage life and poor rind quality

Authors: Smilanick, Joseph; Obenland, David - Dave; Margosan, Dennis; Mackey, Bruce

Submitted to: Citrograph
Publication Type: Popular Publication
Publication Acceptance Date: 3/1/2011
Publication Date: 4/1/2011
Citation: Smilanick, J.L., Obenland, D.M., Margosan, D.A., Mackey, B.E. 2011. Using peel fluorescence in black light rooms to identify navel oranges with shorter storage life and poor rind quality. Citrograph. 2(2):27-31.

Interpretive Summary: A large portion of citrus fruit will rot after harvest unless actions are taken to reduce this process, such as the application of fungicides to the fruit after harvest. We examined the use of peel fluorescence under ultraviolet light to identify and remove fruit with rind injuries, because these injuries provide opportunities for rot organisms to enter and destroy the fruit. We found fruit with moderate levels of fluorescence had poorer peel quality and developed a higher percentage of decay during subsequent storage. The practical messages of this study are that fruit lots with very low peel fluorescence are the highest in initial peel quality and are also those most likely to retain their quality during prolonged transport or extended storage, and that sorter technology that identifies fruit with moderate levels of peel fluorescence for removal may be a promising non-chemical approach to maximize citrus fruit shelf-life.

Technical Abstract: The objective of this project is to minimize postharvest decay losses of fresh citrus fruits. Among the approaches recently examined was peel fluorescence under ultraviolet light. In addition to its usual application to identify fruit with developing decay lesions (“blister” or “clear” rot) in black light rooms, it can also provide useful information about overall peel quality and storability of fruit. We found fruit with moderate levels of fluorescence had poorer peel quality and developed a higher percentage of decay during subsequent storage. In tests done as fruit matured through the season, the fruit with moderate levels of fluorescence had poorer rind quality than those with little or no fluorescence. In tests done late in the navel orange season, we found moderate levels of initial fluorescence also predicted a much higher incidence of decay during subsequent storage. The practical message of this study to a packinghouse manager is that fruit lots with very low peel fluorescence are the highest in initial peel quality and are also those most likely to retain their quality during prolonged transport or extended storage.