Time of harvest may have a profound influenceontheyield,qualityandstabilityofoliveoil.However,thereare few clear guidelines that producers can use to determine the optimum harvesting time. Therefore, the aim of the present study was to investigate the effect of harvesting date on the compositional quality of extracted oils from Maraky and Wettagen cultivars grown in Siwa's Oasis. Some physical properties and oil quality were determined during ripening period of fruits from August up to January during the season of 2005/2006. Quality parameters included FFA, PV, UV absorption, fatty acid profile,pigments(chlorophyllsandcarotenoids),tocopherols,phenoliccompounds,sterols and squalene.
The results indicated that, the amount of oil recovered from each cultivar in the early/ unripe (August and September) and overripe (December and January) stages of maturity were very low. The highest amount of oil extracted was achieved in November in both two cultivars. The FFA content was in the lowest level in the immature fruits and was the highest level in the overripe fruits. Oleic and palmitic acids were found to decrease while linoleic acid increased during ripening. The percentage of oleic acid in olive oil from the two cultivars was obviously lower than that reported in literature from other areas and higher for linoleic and palmitic acids. Chlorophyll and β-carotene, tocopherol, phenolic compounds, sterol and squalene contents were in the highest levels in September and were in the lowest levels in January. Data obtained may advance our knowledge on the physical and chemical changes that take place during fruit ripening and from this we can definemonitoringparametersthatwillassistoliveproducerstodetermine optimum harvest time for optimal olive oil quality. These parameters include International Olive Oil Council standards as well as the minor components in olive oil as pigments, polyphenols and sterols which play an important role in olive oil quality.