1 Influence of Metrological Factors Variations Between Eastern and Western Foothills on Olive Oil Quality: A Case study in Northern West Bank Mahmoud Amarna*, Amer Marei and Fuad Al-Rimawi Water and Environmental research lab, Alquds University, Jerusalem - Palestine. Abstract: This Study investigated the effect of metrological factors variations between eastern and western foothills on olive oil quality in northern West Bank. Samples were collected from two villages: Assera Al Shamalia (locates on Western foothills) and Bet Dagan (Locates on Eastern foothills). Differences in metrological factors and harvesting times between the two villages cause differences in olive oil quality and higher content of stigmastadiene in Bet Dagan than Assera olive oil. The higher monthly averages of minimum and maximum temperatures of Bet Dagan cause the increase of Stigmastadiene content of olive oil. While the higher amount of precipitation In Assera; cause higher quality and quantity of produced olive oil in Assera compared to Bet Dagan. The lower relative humidity and longer day hours; in Assera village enhances higher amounts of olive oil accumulation and better quality as this is the favorable conditions for olive oil formation. The compression between Cuba, Crete, Spain and Italy olive oil quality with Palestinian olive oil quality, we found that Palestinian olive oil shows good competition quality parameters for Acidity and Peroxide values according to the International olive oil council limits compared with these countries olive oil acidity and peroxide values. Key words: Sterenes, metrological factors, stigmastadiene & foothills. 1. Introduction Olive oil is composed from major component (fatty acids and triacylglycerol) and other minor component (include sterols, phenolics, vitamins …etc). Fatty acid is composed from long chain of carbon (in olive oil from 16 to 18 carbon atom) with carboxyl group. Fatty acids could be saturated or unsaturated, the fatty acids in oil is attached in group of three fatty acids with a glycerol molecule forming triacylglycerol (TAG). The TAG may lose one Corresponding author: Mahmoud Amarna, Master degree in Environmental sciences, E- mail: mahmoudnasr1984@gmail.com. or two of its fatty acids that will be found in oil as free fatty acid. Sterols are minor component of olive oil, they play nutritional role for consumer, and also they reduce the cholesterol absorption into the body. They include stigmasterol and campesterol. Sterols are very good test for olive oil adulteration as sterols are specific for each species. Olive oil classified according to its quality; table (1) illustrates this classification, [1]. The European committee has introduced quality standards by the International Olive Oil Council (IOOC) for olive oil for being accepted to export to their markets. These standards include; among others; free acidity,