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Submitted to: Subtropical Technology Conference Proceedings
Publication Type: Abstract Only Publication Acceptance Date: 9/16/2003 Publication Date: 10/16/2003 Citation: Hagenmaier, R.D. 2003. Further quality evaluations of fresh citrus as affected by coatings: 1) changes during cold storage of late-season marsh; and 2) relations between internal gas concentrations and peel resistance. Subtropical Technology Conference Proceedings. 54:31. Interpretive Summary: Technical Abstract: 1. The goal was to determine how quality of late-season white 'Marsh' grapefruit depended on harvest date and selection of coatings. Grapefruit was harvested five times from March 27 to June 2, and the fruit from each harvest treated with six different coatings, each made up of 0 to 100% polyethylene formulation, with the balance (100-0%) being a high-gloss resin wax. The coated fruit were stored at 6 °C. Chilling injury and weight loss were measured to determine changes in external quality during storage. Internal gas concentrations and ethanol content were monitored as indicators of internal quality. Coatings with high percentages of polyethylene suffered more chilling injury, but had lowest weight loss. Coatings with high polyethylene content also tended to present a low barrier to gas exchange, resulting in lower internal CO2, higher internal O2, and slower increase in ethanol content. The disadvantages and advantages of polyethylene coatings relative to resin coatings were known beforehand, and these confirmed by the results of these experiments. What was not already known was what ratio of polyethylene to resin might result in optimum quality, and the results of this work suggest that 20-40% polyethylene may be optimum for Marsh grapefruit. There was no evidence that later harvest date detracted from fruit quality. 2. A new and simplified method was devised to test the barrier properties of citrus fruit peel. Valencia oranges with different coating treatments were exposed to ethane for about 30 minutes, followed by measurement of internal gas concentration for levels of ethane. Measurements were also made of interior CO2 content and CO2 respiration rates in order to compare the barrier properties of peel to ethane and CO2. The results were comparable, showing that the ethane method can serve as an alternate measurement of barrier properties. |
