Carica papaya L. cv. Solo fruit were taken off different points in a commercial postharvest handling system to determine where in the handling chain mechanical injury occurred and what caused it. "Green islands" (GI) apparently induced by mechanical injury were seen in all fruit and the occurrence increased as fruit moved through the handling system. This type of injury was only seen in fruit taken from the sides but not in fruit taken from the center of the field bins. To duplicate the GI seen in fruit from the handling system, fruit at different stages of ripeness (5 to 50% yellow) were dropped from different heights (0 to 100 cm) onto a smooth steel plate. Injury seen did not resemble the GI seen in fruit from the handling system. Fruit (10 to 15% yellow) were then dropped on different grades of sandpaper (220 mesh to 36 mesh) from a height of 10 cm. GI similar to those seen on fruit from the handling system were observed in fruit dropped on all grades of sandpaper. Fruit dropped on fine sandpaper had a higher severity of GI than those dropped on coarse sandpaper. A lesser severity of GI was seen in 40 to 50% yellow fruit dropped onto 150 mesh sandpaper from a height of 10 cm compared to greener fruit. These results suggest that abrasion damage was more important than impact damage in Solo papaya fruit.
Respiration rate and ethylene production did not significantly increase when fruit were dropped onto a smooth steel plate or sandpaper from a height of 10 cm. Similar results were seen even when the number of drops were increased to eight.
Washing off the latex did not affect the severity of GI. Heating fruit at 48°C for ~ 6 hours or until fruit core temperature (FCT) reached 47.5°C aggravated the severity of GI. Delaying the time of heating from the time of dropping did not significantly lower the severity of GI, except for fruit heated 24 hours after dropping. Heating also resulted in fruit that had a rubbery texture. Waxing fruit alleviated the severity of GI and it did not matter whether waxing was done before or after the heat treatment
