Dirasat, Agricultural Sciences, Volume 32, No. 3, 2005 - 279 - Effect of Local Storage Conditions on Oil Quality of the Olive Cv. "Nabali Muhassan" Said M. Al-Addasi, Fahmi A. Shatat and Mohammad A. Humeid* ABSTRACT Ripe olives of the Olea europea L. cv. Nabali Muhassan were harvested in 2001 and subjected to five storage treatments; including storage in burlap sacks in an open field and under a shed, storage in plastic crates in an open field and under a shed and spreading the fruits over the ground under a shed. Oil quality was evaluated based on titratable acidity and peroxide value. All storage treatments produced significantly lower oil content after three weeks of storage compared to the control. Among the storage treatments, the highest oil loss 8% and 5.9% was recorded for olives stored in burlap sacks in the open field or under a shed, respectively. Three weeks of storage resulted in about an 8 to 14- fold increase in acidity of oil extracted from olives stored in burlap sacks in an open field or under a shed, respectively compared to the control. Oil extracted from olives spread over the ground under a shed or those stored in plastic crates in an open field had relatively low peroxide values (less than 20mEq/kg) after three weeks storage. Rot incidence increased with storage duration but it was higher in olives stored under the shed compared to those kept in the open field, and in fruits stored in burlap sacks compared to the other treatments. The highest temperature inside the storage containers/fruit layers was recorded for fruits stored in burlap sacks under shed after one, two and three weeks storage and ranged from 19.3°C to 22.9°C. KEYWORDS: Olea europea L, olive fruit storage, olive oil quality. INTRODUCTION The cultivated olive is a long-lived, evergreen tree native to the Mediterranean basin (Castellano et al., 1993), where it is grown in large areas. In Jordan, the olive Tree represents the first major fruit tree due to its adaptability to a wide range of climatic and soil conditions. The total area planted with olive reached about 63.3 thousand ha. in 1999, which represents about 74% of the total area planted with fruit trees (Department of Statistics, 2000). The quality of olive oil can be affected adversely by several factors, including olive variety, environmental conditions, ripening stage at harvest, past infestation, and ex-traction technology. Extra virgin olive oil is obtained from healthy fruits using extraction processes that cause minimal changes in oil composition (Perez-Cammino et al., 2001). The olive oil industry has difficulties in coordinating fruit harvesting with extraction of oil (Castellano et al., 1993), thus fruit storage in "on years" for periods that may range from few days to several weeks is very common. The harvested olives are piled into large heaps, stored in nets, sacks, boxes, or spread over the ground in varying depths. These procedures are mainly done under ambient temperature. The olives may be exposed to unfavorable environmental conditions and mechanical damage resulting in rapid deterioration due to fungal growth. Furthermore, heat production from respiratory activity and fermentation may accelerate the deterioration of the olive fruits (Garcia et al., 1996 a). Storage of olive fruits under proper conditions before oil extraction, is a prerequisite of good quality oil. Therefore, the objective of this study was to investigate the effect of subjecting olive fruits to storage treatments similar to those used by Jordanian olive growers on the * Faculty of Agriculture, University of Jordan. Received on 23/12/2004 and Accepted for Publication on 3/8/2005.