RESPONSE OF CITRUS-FRUIT TO HIGH-PRESSURE WASHING

The effect of high-pressure mashing (HPW) on the surface morphology an d physiology of citrus fruit was examined. Mature white (Citrus paradi si Macf. 'Marsh') and red (Citrus paradisi Macf. 'Ruby Red') grapefrui t, oranges (Citrus sinensis L, 'Hamlin'), and tangelos (Citrus reticul ata Blanco x Citrus paradisi Macf. 'Orlando') were washed on a roller brush bed and under a water spraying system for which water pressure w as varied. Washing white grapefruit and oranges for 10 seconds under c onventional low water pressure (345 kPa at cone nozzle) had little eff ect on peel was fine structure. Washing fruit for 10 seconds under hig h water pressure (1380 or 2760 kPa at veejet nozzle) removed most epic uticular wax platelets from the surface as well as other surface debri s such as sand grains. Despite the removal of epicuticular was, HPW di d not affect whole fruit mass loss or exchange of water, O-2, or CO2 a t the midsection of the fruit. Analysis of the effect of nozzle pressu re (345, 1380, or 2760 kPa), period of exposure (10 or 60 seconds), an d wax application on internal gas concentrations 18 hours after washin g showed that increasing nozzle pressure increased internal CO2 concen trations while waxing increased internal ethylene and CO2 concentratio ns and decreased O-2 concentrations. An apparent wound ethylene respon se was often elicited from fruit washed under high pressures (greater than or equal to 2070 kPa) or for long exposure times (greater than or equal to 30 seconds).