Olive & Oil 03/02/2014

Tunisia wants Italian Coratina olive cultivar for excellent olive oil quality

This variety is known for its goodquality and richness in antioxidants such as polyphenols and tocopherols. The biological activities of olive oil phenolic compounds have prompted several studies on their potential activity in the prevention of cardiovascular diseases and cancer

Tunisia olive groves present several varieties among which Chemlali constitutes the bulk of the Tunisian olive cultivation. Grown in warm coastal and low steppe Chemlali groves occupy nearly 85% of the olive-growing area and contribute over 80% of national production in olive oil. To improve olive oil quality produced in Tunisia, some approaches have been considered among them the introduction of different new cultivars. During the last years, foreign cultivars which showed an excellent olive oil quality and perfect adaptation to modern intensive cultivaion conditions in their original site, have been introduced in Tunisian environment by private Tunisian companies for their easy harvesting and more rapid return on investment. One of the introduced varieties is the Italian Coratina. This variety is known for its goodquality and richness in antioxidants such as polyphenols and tocopherols.

It is well established that olive oil qualityi sinuenced by several factors such as variety, environmental conditions, cultural and harvesting practices and technological processes. Hence, one of the primary causes of loss of olive oil quality is oxidation.The oxidation is an inevitable process that starts after the virgin olive oil has been extracted an dleadstoa deterioration that always becomes more serious during oil storage Initially lipids are radically oxidiz
ed to hydroperoxides, which are odorless and tasteless and do not account for sensory changes.
However, they are susceptible to further oxidation or decomposition into products of secondary reactions, which, conversely, are responsible for typical unpleasant sensory characteristics, identified on their whole as a rancid attribute.
Storage conditions are considered critical variables that influence the quality of olive oil and its shelf life which is attributable to lipid oxidation mechanisms which lead to rancidity. Glass and metal bottles were used for packaging olive oils.
The major function of packaging materials is related to their barrier properties against moisture, oxygen and light. It is known that these reactions are catalyzed by light and heat and are partly slowed down by compounds belonging to the unsaponifiable fraction. Polyphenols and tocopherols are the two main groups of compounds acting as primary antioxidants to inhibit oxidation in virgin olive oils. Many methods for phenol determination from different plants showed a variation of their concentrations which may be due to the exposure to several factors which could explain the significant difference between phenolic profiles from different plants. Regarding the great importance of the protective effect of virgin olive oil against cardiovascular, cancer, and neurodegenerative diseases,
studying functional foods may be of great interest. Virgin olive oil is considered as an exceptional source of polyphenols, equalling all well-known polyphenol-rich plants such as green tea, pomegranate and date Vitis vinifera L. red grape varieties and other plants.
The biological activities of olive oil phenolic compounds have prompted several studies on their potential activity in the prevention of cardiovascular diseases and cancer.
However, a decrease in LDL oxidation was demonstrated with a greater ingestion of virgin olive oil phenolic compounds. In recent years, the anti-inflammatory and vascular protective properties of EVOO polyphenols have been extensively investigated.
This assumption has reinforced the proposed suggestions on phenolic compounds, which are able to interact with biological systems and act as bioactive molecules; in particular, they are important inhibitors of lipid peroxidation lieved to be effective through their f ree radical scavenging and metal-
chelating properties. Despite the numerous studies that have shown the powerful antioxidant properties of olive oil, whether the effects really occur and the mechanisms responsible for these beneficial effects are not presently known. Polyphenols and tocopherols mainly act as chain breakers by donating a radical hydrogen to alkylperoxyl radicals formed during the propagation step of lipid oxidation and subsequently forming a stable radical tocopherols constitute the lipophilic antioxidant group and are noted for their effective inhibition of lipid oxidation in all vegetable oils.
Many studies on oxidation of virgin olive oils were based on accelerated test measurements. In these studies, good correlations between changes in various components and stability were found. However, the extreme conditions in accelerated test high temperatures and with air bubbled into the oils do not simulate actual storage conditions and may lead to qualitative and quantitative changes to the oil that are not related to real-time storage. The main objective of our research is to investigate in depth how the extraction system and storage conditions affect the quality and composition of olive oil quality of two varieties: the Tunisian Chemlali and the Italian Coratina.
To our knowledge, this is the first study of its kind that has applied the graphical modeling for full exploration of factors affecting olive oil physicochemical and sensory characteristics in a real-time shelf life study.

From the present work, we can conclude that the genetic factor, theextraction system and the storage conditions influence significantly the physicochemical and sensorial characteristic sof virgin olive oil.
Coratina oils are characterized by higher amounts of 2-methyl-butanal, cis-3-hexen-1-ol, cis-3-hexenyl acetate, hexyl acetate, cis-2-pentenol, 2-pentanone, and 3-pentanone and it is noteworthy for its higher content of phenolic compounds, while
Chemlali samples were richer in pentanol, trans-3-hexenol, octanal, hexanal and penten-3-ol.
After storage the total phenol content decreases and, consequently, the typical bitter taste and pungent note of fresh EVOO decrease in in-
tensity. Irrespective of the packaging used, all stored VOOs showed a considerable decrease in aromatic compound amounts.
The graphic modeling proved to be a powerful statistical technique for understanding the impact of the various factors under study on the physicochemical characteristics of virgin olive oils and determining the most influencing one. The extraction system was the determining factor for parameters such as free acidity, PV, musty attribute and Δ-tocopherol. The genetic factor was the main factor influencing the γ-tocopherol content. The storage date was the dominant factor influencing K232, β-tocopherol, volatile compounds, fruity and bitter attributes. K270 and α-tocopherol were influenced mainly by the storage date and packaging material type. The packaging material was the dominant factor that influenced pungent, rancid, and fusty attributes.

di R. T.