Composition Of Virgin Olive Oil Research Articles

Oxidative stability of virgin olive oil

Virgin olive oil has a high resistance to oxidative deterioration due to both a triacylglycerol composition low in polyunsaturated fatty acids and a group of phenolic antioxidants composed mainly of polyphenols and tocopherols. Polyphenols are of greater importance to virgin olive oil stability as compared with other refined oils which are eliminated or drastically reduced during the refining process. This paper covers the main aspects related to the oxidative stability of virgin olive oil during storage as well as at the high temperatures of the main processes of food preparation, i.e., frying and baking. Differences between oxidation pathways at low and high temperature are explained and the general methods for the measurement of stability are commented on. The compounds contributing to the oxidative stability of virgin olive oils are defined with special emphasis on the antioxidative activity of phenolic compounds. Finally, the variables and parameters influencing the composition of virgin olive oils before, during and after extraction are discussed.

Acid hydrolysis of secoiridoid aglycons during storage of virgin olive oil.

The main change found in the phenolic composition of virgin olive oils of Arbequina, Hojiblanca, and Picual varieties during storage in darkness at 30 degrees C was the hydrolysis of the secoiridoid aglycons. This reaction gave rise to an increase in the free phenolics hydroxytyrosol and tyrosol in the oil. Filtration of oil and acidity influenced the hydrolysis to a large extent. Thus, the addition of commercial oleic acid to Hojiblanca and Picual oils increased the hydrolysis rate of the secoiridoid aglycons. In contrast, the concentration of lignans 1-acetoxypinoresinol and pinoresinol remained constant during storage. It must also be stressed that the total molar concentration of the phenolic compounds analyzed in the oils changed slightly (<20% reduction) after one year of storage, which is important from a nutritional point of view. However, the transformation of the secoiridoid aglycons into free phenolics may have consequences on oil taste and antioxidant capacity.

Composición química de distintas calidades de aceites de oliva virgen de la variedad “Empeltre” en el bajo Aragón

The variability of the parameters of chemical composition of virgin olive oil, “Empeltre” variety, in 472 samples coming from the Bajo Aragon region, in three seasons 1996/97, 1997/98 y 1998/99 was studied in this work. The free acidity, peroxide values, ultraviolet absorbances, fatty acid composition, sterolic composition and the level of waxes and polyphenols were analized. Considering their chemical composition, the majority of the analysed oils are of great quality. The oils of the 1997/98 season differ more from those of other seasons, having been affected by the attack of the Dacus oleae, which gave a higger acidity level, raising the peroxides and the waxes as well. The sterolic composition was also affected. The “Empeltre” variety from the Bajo Aragon region shows high values of Delta7 stigmastenol, which in many cases exceed the maximum value of the European Union Commission Regulation.

Improvement of phenolic compound content in virgin olive oils by using enzymes during malaxation

The effect of enzyme addition to the olive paste on the phenolic composition of virgin olive oil has been studied. The experiments were carried out with both Picual and Arbequina cultivars, using the continuous two-phase extraction system at industrial scale and for three consecutive seasons. Phenolic compounds, in particular orthodiphenols, increased their concentration in oils when enzymes were added to the olive paste before the malaxation stage. Among non-orthodiphenols, the lignans 1-acetoxypinoresinol and pinoresinol slightly increased their concentration. In general, the positive effect of enzymes was more marked for Arbequina than for the Picual cultivar. The peroxide index and “Rancimat” stability of oils were also positively affected when using enzymes. Besides, wash waters from the vertical centrifuge showed a higher concentration of phenolics when the pastes were treated with enzymes. Therefore, the use of enzymatic formulations during the extraction process of olive oil may not only increase the oil yield but also the nutritional quality of the oil.

Effect of extraction system, stage of ripeness, and kneading temperature on the sterol composition of virgin olive oils

AbstractComparative extraction trials were carried out among a classical pressing, a dual‐, and a three‐phase centrifugation system using olive crops of Koroneiki variety. Two different kneading temperatures, 30 and 45°C, were tested at three stages of ripeness for two consecutive years of harvest, 1995–1996 and 1996–1997. Composition of the sterol fraction was determined in the resulting olive oil samples (n=72). Stigmasterol was found to be affected by the extraction system; it was obtained in the highest amount in the pressing system. The ratio campesterol/stigmasterol was significantly higher in oils extracted by dual‐ and three‐phase centrifugation. Sterols were significantly affected by the ripening stage of the fruit. During December, the ratio campesterol/stigmasterol reached the maximal and β‐sitosterol the minimal values; this appears to be the optimal period for harvesting the olives. Comparison of the different kneading temperatures showed that at 30°C, Δ5‐avenasterol and campesterol/stigmasterol ratio reached higher values than at 45°C.

Effect of extraction systems on the phenolic composition of virgin olive oils

The effect of extraction systems on the phenolic composition of virgin olive oils obtained from two different Italian cultivars (Coratina and Oliarola) was determined. The oils extracted using two-phase centrifugation showed in all cases higher phenolic concentration in comparison to oils obtained from three-phase centrifugation. In particular, the highest differences were observed for aglykone derivatives of oleuropein (3,4-DHPEA-EDA and 3,4-DHPEA-EA) that are the most concentrated antioxidant phenolic compounds of virgin olive oil. These results were confirmed by the autoxidation stability of the oils examined. Über die Auswirkung von Gewinnungsverfahren auf die Phenolzusammensetzung in unbehandeltem Olivenöl.Die Auswirkung von unterschiedlichen Extraktionssystemen auf die Phenolzusammensetzung in unbehandelten Olivenölen aus zwei verschiedenen italienischen Olivensorten (Coratina und Oliarola) wurde bestimmt. Öle, die mit dem Zweiphasen-Dekanter erzeugt wurden, zeigten in jedem Falle eine höhere Phenolkonzentration als Öle, die mit dem Dreiphasen-Dekanter gewonnen wurden. Insbesondere wurden höchste Unterschiede bei den Aglykonderivaten von Oleuropein (3,4-DHPEA-EDA und 3,4-DHPEA-EA) festgestellt, den am stärksten konzentrierten antioxidierenden Phenolverbindungen im unbehandelten Olivenöl. Diese Ergebnisse wurden durch die Stabilität der geprüften Öle gegen Autoxidation bestätigt.

Characterization of Italian Extra Virgin Olive Oils Using 1H-NMR Spectroscopy

High-field (600-MHz) proton nuclear magnetic resonance (1H-NMR) spectroscopy was applied to the analysis of 55 extra virgin olive oil samples from four Italian regions (Campania, Lazio, Sicily, and Umbria) and obtained from diffrent olive varieties. The multivariate statistical analysis (PCA, hierarchical clustering) performed on the normalized intensities of 1H- NMR resonances due to minor components (β-sitosterol, n-alkenals, trans-2-alkenals, and other volatile compounds) allows a good classification of oil samples obtained from traditional varieties with respect to the region of origin (96% of oils correctly classified). Samples obtained from one new experimental cultivar (FS-17) were not correctly classified, indicating a strong contribution of olive variety on the chemical composition of virgin olive oils. The potential contribution and limits of NMR in the authentication of virgin olive oil geographical origin and variety are discussed. Keywords: Proton NMR spectroscopy; virgin olive oil; hierarchi...

Biogeneration of Volatile Compounds in Virgin Olive Oil: Their Evolution in Relation to Malaxation Time

The volatile composition of oils obtained from fruits of two Italian varieties, Coratina and Frantoio, using different malaxation times of pastes was determined. The results show that the biogeneration of aroma components was very fast and took place just after cell disruption, owing to the activation of enzymes contained in the fruit. The cleavage by heterolytic hydroperoxide lyase is the most important process in both varieties considered and gives rise to C6 compounds which represent the major compounds of the olive oil aroma. C6 aldehydes and alcohols increase with the prolonging of malaxation, whereas esters considerably decrease after 30 min. In addition, C5 alcohols, C5 carbonyl compounds, and pentene dimers have been detected in the volatile composition of virgin olive oils.

Evolution of phenolic compounds in virgin olive oil during storage

AbstractPhenolic compounds are of fundamental importance to the shelf life of virgin olive oils because of their antioxidative properties. In this paper, the evolution of simple and complex olive oil phenols during 18 mon of storage is studied by high‐performance liquid chromatography (HPLC) analysis. The olive oils under examination were from various olive cultivars, harvested in two sectors in the same region at different stages of ripeness. The findings indicate that it is not the variety but rather the ripeness of the olives and the soil and climate that influence the phenol composition of virgin olive oil. In addition, a positive correlation was found between the age of the oils and the tyrosol to total phenols ratio. Lastly, gas chromatography‐mass spectrometry analysis confirmed that the unidentified peaks detected by HPLC were of a phenolic nature.

Changes in the Volatile Composition of Virgin Olive Oil during Oxidation: Flavors and Off-Flavors

A thermoxidation process has been applied to extra-virgin olive oil to develop new knowledge on the evolution of the volatile compounds responsible for virgin olive oil flavor during oxidative deterioration. The initial volatiles (a total of 60), many of them responsible for the pleasant sensory characteristics of the oil and produced mainly through biochemical pathways, disappeared in the first hours, and the formation of off-flavors, produced through oxidative pathways, gradually increased. The main volatile compounds possibly responsible for off-flavors (51) were identified, and their evolution during the oxidative process was studied. The fatty acids content was determined during the process. Unsaturated fatty acids were found to be the main precursors of the volatile compounds found in oxidized samples. The early measurement of nonanal (which was not detected at all, or only at trace levels, in extra-virgin olive oil samples) could be an appropriate method to detect the beginning of the oxidation. Th...

Effect of climate on the chemical composition of virgin olive oil

The effect of climate on the chemical composition of virgin olive oil has received scant attention. In this work, the relationship between chemical composition and altitude, the latter being an indirect parameter related to climate and soil, was studied. Two altitudes, valley (< 400 m) and mountains (700 m) were studied; 126 samples of virgin olive oil were characterized by 53 compounds and it was found that sterols and some triterpenic alcohols and hydrocarbons changed systematically with altitude. Two linear discriminant equations, with correct classifications greater than 90%, were obtained and verified with samples of another crop. Similar results were obtained.

Definite influence of the extraction methods on the chemical composition of virgin olive oil

The extraction methods of virgin olive oil affect the quantification values of some chemical compounds. Statistical tests and procedures have been applied to a set of 142 samples collected from all over Andalusia and characterized by 55 chemical compounds. It has been estimated that two aliphatic alcohols, one sterol and one fatty acid have the best significance levels identifying the extraction methodology (pressure, centrifugation). Stepwise Lineal Discriminant procedure has been used to characterize olive oils by the extraction systems. 205 samples from other provinces, varieties or harvests were used to verify these decision equations.