Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/6/2003
Publication Date: 5/1/2003
Citation: Obenland, D.M., Aung, L.H., Bridges, D.L., Mackey, B.E. Volatile emissions of navel oranges as predictors of freeze damage. Journal of Agricultural and Food Chemistry. 2003. v. 51(11). p. 3367-3371. Interpretive Summary: Prolonged low temperatures in the field can damage navel orange fruit quality and inflict economic loss on the citrus industry. Present means of inspecting freeze-exposed fruit to determine if they have been damaged are labor-intensive and inaccurate and often lead to the shipment of damaged fruit to the marketplace. A number of volatile chemical compounds were found to be released from fruit that had been freeze-damaged. Monitoring of these chemical compounds offers a fast and accurate means to determine if freeze-exposed navel oranges should be marketed.
Technical Abstract: Volative emissions of navel orange fruit were evaluated as a means for predicting and gauging freeze damage. The fruit were subjected to -5C or -7C treatments in a laboratory freezer for various time periods of 2 to 9.5 hours, and stored at 23C for 1, 2, or 7 days, after which the emission of volatiles from the fruit was measured. Following the final day of volatile measurements, the fruit were stored at 5C for an additional 2 to 3 weeks and then evaluated for fruit quality characteristics. Peel injury in the form of brown lesions, drying of the juice vesicles, a decline in acidity and a loss of flavor were observed to occur as a result sof freezing. Corresponding to the loss in fruit quality were large increases in the emission of ethanol, ethyl butanoate, methyl hexanoate and ethyl octanoate. With the exception of methyl hexanoate, for which volatile emissions decreased during storage for 7 days at 23C, all of the other volatiles were relatively unchanged in amount by storage. Treatment at -7C caused greater injury, quality loss, and more volatile emanation than did freezing at -5C. The measurement of volatile emissions appears to be a useful approach to identify freeze-damaged navel oranges.