Alkyl esters and other indicators for the protection of quality and authenticity of Italian extra virgin oils

Protection of the quality and authenticity of extra-virgin olive oils is provided by EEC Regulation 2568/91 and its subsequent modifications, which have established specific limits for the chemical and chemo-physical parameters, and the sensory evaluation. On this basis, and with the goal of reviewing, and if appropriate, defining, lower limits for some of the parameters adopted by these EEC regulations, the International Olive Council (IOC) has asked its member countries to survey the production of their national extra-virgin olive oils. This move is designed for the better protection of extra-virgin olive oils of good quality, while avoiding the risk of excluding, or even declaring as non-genuine, products that are at the limits of the natural variability of the product characteristics. This request of the IOC relates to the content of ethyl esters, waxes and stigmastadienes. The present study reports on monitoring work carried out by CRA-OLI of Citta Sant'Angelo in collaboration with ASSAM-Marche, on 100 monovarietal virgin olive oils that were produced during the 2011/2012 oil season in the Italian olive-growing regions. Despite the diversity of the soils and the climatic conditions that can result in this product showing considerable variability, the results obtained here show that there is the possibility to applying the new limits proposed by the IOC for the parameters of stigmastadienes and waxes. For ethyl esters, considering that 99 of these samples were below the proposed IOC limit of 30 mg/kg and that the average content was only 6 mg/kg, this confirms that this limit can be set at 30 mg/kg already for the start of the oil season 2013/2014. Principal Component Analysis shows that these oil samples are distributed only in terms of the quality of the olive oil production of individual mills, rather than the region of origin or the cultivars used. There was also good correlation between alkyl esters or ethyl esters and free acidity, while it appears that these parameters are not related at all to the parameters that describe the oxidative status. Furthermore, as might be expected, alkyl esters, fatty acid ethyl and methyl esters, free acidity, waxes, stigmastadienes, spectrophotometric extinction coefficients, and peroxide values are all negatively correlated to the sensory parameters.