Kanner, J., Division of Food Technology, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel
Elmaleh, H., Division of Food Technology, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel
Reuveni, O., Department of Horticulture, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel
Ben-Gera, I., Division of Food Technology, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel

Invertase activity during the last stages of fruit development was determined in three date cultivars. The development of invertase activity occurs in all three cultivars at the beginning of the "Rutab" stage. It was found that maximum invertase activity and its gradual development were different in the three cultivars studied and invertase activity was almost 250 times higher in Khadrawi fruits than in Deglet Noor. These enormous differences in invertase activity between cultivars affect the water activity in the fruits. As a result of this, the rate of water evaporation was lower in fruits of high invertase activity than those with low invertase activity. A significant decrease in the enzyme activity was found at all cultivars during the natural drying of the fruits on the palm or after artificial ripening of "Rutab" fruits. The presence of so many types, of dates which differ in texture, color, and taste are discussed in respect to our results. © 1978 American Chemical Society.