SOLID PHASE MICROEXTRACTION-GAS CHROMATOGRAPHY APPLIED TO THE ANALYSIS OF VOLATILE COMPOUNDS DURING THE STORAGE OF EXTRA-VIRGIN OLIVE OIL CV ARBEQUINA.

BIOLATTO, A; G. GRIGIONI; MARÍA SOL MOLINA; CESAR MATÍAS

Florianópolis (SC), Brasil

Congreso; Congresso Latino-Americano de Cromatografia e Técnicas Relacionadas.; 2008

Virgin olive oil flavour is usually characterized by pleasant sensory notes that are much appreciated by consumers. The flavour of a product is mainly perceived by the interactions of volatile compounds with the olfactory epithelium in the nasal cavity. High quality olive oils have a profile of volatile compounds-mainly constituted of aldehydes, esters, alcohols and ketones – that generates a balanced flavour of green and fruity sensory characteristics. These compounds are generated by lipoxygenase (LOX) pathway  and during both the processing and storage of the fruit and the oil, so contributing greatly to the flavour and overall quality of olive oil. Several processes can alter the initial pleasant flavour of olive oil producing off-flavour. Oxidation of the triglycerides and their derivatives in virgin olive oil causes changes sensory properties of the oil that affect the quality of the oil. Oxidative rancidity development has been recognised as the predominant cause of oil deterioration during storage. Many analytical procedures have been used to isolate, identify and quantify the volatile components resulting from fatty acid oxidation. Among them, solid phase microextraction (SPME) is a solvent-free extraction technique that has already proved to be an effective tool for detecting low levels of fat derived flavour compounds, and is also a simple and fast technique to implement. The goal of this work was the application of SPME method to determine the evolution of volatile aldehydes of Arbequina extra-virgin olive oil, during 9 months of storage at room temperature and in the darkness. Arbequina extra-virgin olive oil samples were collected from oil mill located in the area of Valle Central de Catamarca-Argentina during crop season 2007. Samples were subjected to storage during ninth months at room temperature in darkness using amber glass bottles. Divinylbenzene/Carboxen/Polydimethylsiloxane (CAR/PDMS/DVB) 50/30mm fiber was used to extract/concentrate volatile aldehydes from Arbequina extra-virgin olive oil. The sample (5 ±0.01 g) was placed in a 10 mL ambar glass vial equipped with screw cap and silicon septum. SPME fiber was exposed to the headspace (HS) of the sample for 40 min at 25 ±0.5 C. The extra-virgin olive oil was sampled at intervals of 45 days. Analysis were carried out by triplicates. The results showed a reduction in the levels of trans-2-hexenal, trans-2-heptenal and trans-2-nonenal at the end of the storage. Others authors reported a decreasing of trans-2-hexenal in olive oil stored at room temperature in darkness. trans-2-hexenal derive from the enzymatic transformation (LOX) and it was the principal component extracted by HS-SPME. Several authors have been reported that  trans-2-hexenal is an important constituent of olive oil aroma. On the other hand, an increase of hexanal, heptanal, octanal, and nonanal levels was noted during the storage of Arbequina extra virgin olive oil. These compounds have been detected by others authors during oxidation. These aldehydes are characterized by sensory notes related to the perceptions rancid, oily and fatty, so justifying their importance in the development of the rancidity in olive oils. Some proposed markers of oxidation include nonanal, hexanal, the ratio of hexanal/nonanal. The majority of the studies have used nonanal as a primary indicator of rancidity.  In contrast, hexanal can not be considered as marker of oxidation  because it does not distinguish oxidised oils from virgin olive oil as this compounds originates from both the enzymatic and chemical oxidation pathways. It is important to note that in the literature is documented that the stability of virgin olive oil usually ranges from 9 to more than 18 months. In conclusion this study showed that HS-SPME-GC technique was suitable to determine the evolution of aldehydes associated to oxidative stability during storage of  in Arbequina extra virgin olive oil.