effect of fruit harvest time on oil yield and quality of some olive olea europaea l.) cultivars in roudbar region

Fruit ripening stage at harvesting time is potentially a major contributor to olive oil yield and quality. Therefore, one of the main causes for low olive oil quality, at least in northern Iran, is harvesting fruits at improper time. In this study, effect of fruit harvest time on oil yield and quality of four olive cultivars, Zard, Rowghany, Arbequina and Coratina was investigated at Roudbar region, Guilan Province, northern Iran. The fruits of all studied cultivars were harvested at four different times and the characteristics such as fruit maturity index, oil percent, free fatty acid, peroxide value, K232, K270, and sensory quality of oil were evaluated. The results showed that in contrast to free fatty acid and peroxide values which increased with progressing fruit ripening, oil sensory quality for all studied cultivars were decreased. In addition, while a delay in fruit harvesting time resulted in an increased K270 value, no such changes were observed for K322. Overall, delay in fruit harvesting was concomitant to increase in oil percent and decrease in oil quality.  According to the results of this study, the optimum harvest time for olive cultivars Zard, Rowghany, Arbequina and Coratina at Rodbar under the conditions of this experiment seemed to be at fruit maturity indices of 3.47-4.21, 4.42-5.2, 3.9-5 and 3.9-4.25, respectively.