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Submitted to: Proceedings of Florida State Horticultural Society
Publication Type: Proceedings Publication Acceptance Date: 1/24/2002 Publication Date: 6/27/2002 Citation: Hagenmaier, R.D. Ethanol content of `Murcott' tangerines harvested at different times and treated with coatings of different oxygen permeability. Proceedings of the Florida State Horticultural Society. 2001. v. 114. p. 170-173. Interpretive Summary: 'Murcott' tangerines were harvested at different times from January through April, coated with different kinds of so-called 'fruit waxes', and stored 7 days at 21 deg C. Fruit with the same coating but harvested at different times had about the same ethanol content, which was used as an indicator of how fast off-flavors develop. The type of coating had a big effect on ethanol content, whose mean value was 800 ppm for fruit with polyethylene coatings, through which oxygen and carbon dioxide gases tend to pass with relative ease, thus permitting the fruit to respire normally. The mean ethanol content was about 1300 ppm for carnauba wax coating, which has somewhat more tendency to block gas exchange. The ethanol content was about 1900 ppm for high-gloss, shellac-resin coatings, similar to those used by many citrus packinghouses. These results suggest that high-gloss, shellac-based coatings are not suitable for 'Murcott' tangerines at any time during the season. On the other extreme, polyethylene-based coatings are suitable, because of little tendency for ethanol to increase. Carnauba wax-based coatings are intermediate. Technical Abstract: 'Murcott' tangerines harvested from January through April were treated with coatings having measured values of O2 permeability, and the coated tangerines were stored 7 days at 21 deg C. The ethanol content of non- coated fruit increased slightly as the season progressed (about 20 ppm/week). The CO2 respiration rate of non-coated fruit was independent of harvest date, as were the ethanol contents of coated fruit. For the season as a whole, the mean ethanol content of juice from non-coated fruit was 320 ppm. Mean ethanol content was 800 ppm for fruit with polyethylene coatings of high O2 permeability (50,000 - 200,000 mL mil m- 2 d-1 atm-1). It was about 1300 ppm for carnauba wax coatings having medium permeability (4,500 - 6,000 mL mil m-2 d-1 atm-1). Ethanol was about 1900 ppm for high-gloss, shellac-resin coatings with low O2 permeability (400 - 700 mL mil m-2 d-1 atm-1). The ethanol content was < 1500 ppm for only 23% of experiments with low permeability coatings, but was always lower than that for fruit with high permeability coatings. |
