**3. Olive oil**

It has been known that climate, soil, variety of tree (cultivar) and time of harvest account for the different organoleptic properties of different *olive oil*s. Two factors are influential: where the olives are grown and which harvesting methods are implemented. Certain locations yield more bountiful harvests; consequently their oil is sold for less. Olive trees planted near the sea can produce up to 20 times more fruit than those planted inland, in hilly areas like Tuscany. It is in these land-locked areas that the olive trees' habitat is pushed to the extreme; if the conditions were just a little more severe, the trees would not survive. Extra-virgin oils produced from these trees have higher organoleptic scores.

It is extremely difficult to establish the origins of *olive oil* using DNA technologies. One approach has been **to target yeasts associated with olives and** *olive oil*. Target for characterization was the LTR retrotransposon (Ty element) (Lenoir et al., 1997, as cited in Popping, 2002) using amplified fragment length polymorphism or similar techniques. This method has been more successful for olives, where different yeast strains are associated with olives and *olive oil*. The yeast strains in *olive oil* appear to be associated with the production site (fattoria) where the *olive oil* was produced. And since the number of production sites is limited, the *olive oil* can be traced back to the fattoria.

But this technique is not yet applicable for routine analysis. For the identification of the origin of *olive oil*, a second, non-DNA-based technology has proven very useful. The technology is called **site-specific natural isotope fractionation nuclear magnetic resonance (SNIF-NMR)** (Gonzalez et al., 1999; Martin et al., 1996).

The basis of this technology is that certain elements have naturally occurring stable isotopes (16O and 18O, 1H and 2H, 12C and 13C). The ratios of the different stable isotopes vary from one geographic location to another. These ratios are maintained in the organic material from that region, e.g. plants, animals etc. The SNIF-NMR technology allows measuring these stable isotope ratios at individual positions in a given molecule.

With an appropriate database listing the location and typical stable-isotope distribution, the origin of *olive oil* can be identified (Popping, 2002).

The large number of cultivars, added to the many cases of synonymous and homonymous name, makes particularly difficult the description and classification of olive varieties (Fabbri et al. 2009). Notice that two varieties are synonymous when they have different names but the same profile of fingerprinting, and two varieties are homonyms when they have the

The size of olive germplasm is controversial: about 1,250 varieties (or in some other references 1,275 cultivars, Sarri et al., 2006), cultivated in 54 countries and conserved in over 100 collections, were included in the FAO olive germplasm database (Bartolini 2008), also if this number is certainly higher because the lack of information on many local cultivars and ecotypes (Cantini et al. 1999). The most part of these cultivars comes from southern European countries such as Italy (538 varieties), Spain (183), France (88) and Greece (52) (Baldoni & Belaj 2009). Due to this richness of the germplasm, olive is an unusual case among horticultural crops and its biodiversity can represent a rich source of variability for

It has been known that climate, soil, variety of tree (cultivar) and time of harvest account for the different organoleptic properties of different *olive oil*s. Two factors are influential: where the olives are grown and which harvesting methods are implemented. Certain locations yield more bountiful harvests; consequently their oil is sold for less. Olive trees planted near the sea can produce up to 20 times more fruit than those planted inland, in hilly areas like Tuscany. It is in these land-locked areas that the olive trees' habitat is pushed to the extreme; if the conditions were just a little more severe, the trees would not survive. Extra-virgin oils

It is extremely difficult to establish the origins of *olive oil* using DNA technologies. One approach has been **to target yeasts associated with olives and** *olive oil*. Target for characterization was the LTR retrotransposon (Ty element) (Lenoir et al., 1997, as cited in Popping, 2002) using amplified fragment length polymorphism or similar techniques. This method has been more successful for olives, where different yeast strains are associated with olives and *olive oil*. The yeast strains in *olive oil* appear to be associated with the production site (fattoria) where the *olive oil* was produced. And since the number of production sites is

But this technique is not yet applicable for routine analysis. For the identification of the origin of *olive oil*, a second, non-DNA-based technology has proven very useful. The technology is called **site-specific natural isotope fractionation nuclear magnetic resonance** 

The basis of this technology is that certain elements have naturally occurring stable isotopes (16O and 18O, 1H and 2H, 12C and 13C). The ratios of the different stable isotopes vary from one geographic location to another. These ratios are maintained in the organic material from that region, e.g. plants, animals etc. The SNIF-NMR technology allows measuring these

With an appropriate database listing the location and typical stable-isotope distribution, the

same name but different fingerprinting profiles.

the genetic improvement of this plant.

produced from these trees have higher organoleptic scores.

limited, the *olive oil* can be traced back to the fattoria.

**(SNIF-NMR)** (Gonzalez et al., 1999; Martin et al., 1996).

origin of *olive oil* can be identified (Popping, 2002).

stable isotope ratios at individual positions in a given molecule.

**3. Olive oil** 

Other techniques such as proton transfer reaction mass spectrometry (PTR-MS), nuclear magnetic resonance spectroscopy (NMR) or high performance liquid chromatography (HPLC) has also been addressed using different methodologies (Luykx & van Ruth, 2008). However, the chemical composition of *olive oil* may differ among seasons and growing areas. Several investigations concerning the origin and authenticity of *olive oil* have shown that chemical analyses per se are not sufficient to assure *olive oil* authenticity or to reveal *olive oil* region (Gimenez et al., 2010). Christopoulou et al., 2004 expressed that no single known parameter could detect the presence of hazelnut and almond oils in *olive oil* which have many chemical characteristics (fatty acid profile, sterol composition, … ) similar to *olive oil*.

Several Protected Denomination of Origin (PDO) *olive oil* regions have been established by legislation to ensure both producer's profits and consumer's rights. In this context, it is mainly the identification of the olive cultivar used for the oil production which is of importance for authentication (Luykx & van Ruth, 2008) since the contribution of cultivars is known for each designation (Gimenez et al., 2010). Different PDO labels such as "Oliva Cilento", "Colline Salernitane", and "Penisola Sorrentina", have been granted for the extravirgin *olive oil* produced in Campania, and some others are in the process of assignment.
