ABSTRACT
Over 50% of Florida citrus is degreened since the fruit has matured to a level above internal grade standards while the peel retains a high chlorophyl level. Degreening is prevalent for all citrus grown in semi-tropical or tropical climates. The driving factor in the chlorophyl breakdown is ethylene. In citrus, as well as banana and tomato, ethylene gas is introduced in a closed room or chamber. Recommended gas concentrations vary dramatically, from 1000 ppm for banana ripening to 5 ppm for citrus degreening. Accurate control and monitoring of ethylene in citrus degreening is essential as levels >10 ppm ethylene have been shown to enhance decay. A novel ethylene sensor, measuring chemical luminescence of an ozone-ethylene reaction, was installed and evaluated at a range of 0 to 30 ppm. The unit was calibrated using gas chromatography equipped with a flame ionization detector. A linear relationship between the standard GC laboratory procedure and the photo-multiplier tube output was found. For fruit quality, it would be advantageous to monitor and control ethylene levels as well as the standard parameters of temperature, humidity and fresh air exchange in the degreening process.
