| المستخلص: |
The olive tree (Olea europaea L.) and olive oil play important roles in the heritage of Palestinians. As an agriculture country, Palestine and its economy are dependent on olive harvesting and the production of olive oil. The quality of Palestinian extra virgin olive oil (EVOO) is excellent as it contains a plethora of nutritious molecules that contribute to its remarkable health benefits. However, olive oil can be considered labile to some extent, since its distinctive chemicals start to deteriorate from the moment of production if the environment is not feasible for storage. It is a Palestinian societal habit to purchase (or produce) excessive amounts of olive oil at the beginning of the harvest season in October, and store it for long periods (at least one year) in various types of storage containers. It is therefore paramount to correctly characterize the best type of container to use for the long-term storage of olive oil that may significantly contribute to maintaining its EVOO designation. Hence, the overarching goal of this research was to study the effects of storing freshly-produced EVOO from Palestine (Deir Dibwan, Ramallah) in different storage containers on its characteristics. Storage methods similar to the way many Palestinians store their oil were followed, in terms of duration and containers type. We systematically studied some selected key values that measure the quality of olive oil according to international and local standards. To complete this study, EVOO was continuously checked from the moment of production, and every four months for one year, at room temperature (RT) in the dark in three different types of containers: high density polyethylene (HDPE), dark glass (DG) and Palestinian pottery (PP). A commonly-used container in the households of most Palestinians’ to store EVOO is HDPE. DG is also a common container found in major supermarkets and points of sale. The use of PP, albeit not commonly-used, is an ancient method (that has been used for thousands of years) for storage of Palestinians olive oil. After careful analysis, we show that storing EVOO in DG maintained its current established designation for 8 months while failing at 12 months, whereas EVOO stored in the other containers failed the established EVOO designation at 8 months. Therefore, we conclude that DG is the best packaging material for the long-term storage of EVOO. We can also suggest that storage of EVOO in PP is more favored to storage in HDPE due to its advantages in quality testing results and its environmental superiority. In addition, the effects of freezing freshly-produced EVOO for 12 months were compared to RT storage. Indeed, freezing Palestinian EVOO at -20˚C in DG maintained current EVOO established designation while oil stored for 12 months at RT failed such designation. Moreover, for the first time, we show that storing EVOO at -80˚C maintained its designation and slightly preserved its vitamin E content better with a 40% decrease in content after 12 months of storage. In contrast, vitamin E content decreased by 45% and 48% when stored at -20˚C and RT, respectively. Therefore, freezing olive oil could be a method of extending EVOO designation to 12 months and beyond, while keeping its nutritional advantage.
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