Study of the evolution of the ethyl ester content of extra virgin olive oil after one year of storage and its impact on the quality of the oil

This study was carried out on 86 olive oil samples from the 2016 olive growing season, in three Moroccan regions; eastern region, central region and northern region, by analyzing the free acidity by titrimetric test (ISO 660) and the ethyl ester content by gas chromatography method 3 grams (COI / T.20 / DOC N ° 31 November). The samples were stored under special conditions and the study took place over two periods 6 and 12 months of storage. Taking into account the acidity analysis, the results obtained showed no change after 6 months of storage. We conclude that 17.44% of the samples degrade passing from the extra virgin category to a virgin category. For the ethyl ester content, 4.6% of the samples were degraded after 6 months of storage and 29.06% were degraded after one year of storage. In addition, we observed that the growing region of olive trees has an impact on the free acidity and the ethyl ester content of olive oil. For this criterion, we observed that in the central region of Morocco, the olive oil samples are the least degraded compared to other regions. Thus, concerning the content of ethyl esters, 13% of the samples come from the central region, 37% from the eastern region and 39% from the northern region. On the other hand, for the analysis of the acidity, 8% of the samples come from the center, 30% of the samples come from the oriental and 17.39% of the samples come from the north. So we can conclude that for the conservation of extra virgin olive oil, the olive trees of the central region of Morocco can benefit from a good storage while retaining their high nutritional quality proven by the analysis of acidity and the content of ethyl esters