Chemical composition of virgin olive oils from Koroneiki cultivar grown in Tunisia with regard to fruit ripening and irrigation regimes

The impact of different irrigation regimes based on two ripeness index, on the quantity and quality of virgin olive oil from the introduced olive cultivar Olea europaea L. Koroneiki grown at a high‐density olive orchard in northern Tunisia, was assessed. Olive trees were subjected to three treatments (T1, T2 and T3) that received a seasonal water amount equivalent to 50%, 75% and 100% of the estimated local evaporative demand by a drip irrigation system and olives were collected in two different ripeness index. The olive oil content decreased when the water applied was increased but rose during ripening. The quality indexes and fatty acid composition were less affected by the irrigation schedule but most significantly by the maturity of olives. Moreover, phenol contents increased according to fruit ripening whereas no clear cut differences or consistent effects were observed by irrigation. α‐tocopherol decreased slightly in the oils as ripening progressed while insignificant differences between the irrigation treatments studied were obtained. Consequently, a restitution of 75% of crop evapotranspiration (ET_c.) was sufficient to achieve good minor compounds; however, higher water volumes (100% ET_c.) gave little additional α‐tocopherol and phenols increases.     

Using Lipid Profiles for the Characterization of Turkish Monocultivar Olive Oils Produced by Different Systems

The aim of this study was to characterize the biochemical profiles of the virgin olive oils produced in various districts of Aegean and South East Anatolia regions of Turkey over two growing seasons (2001–2002). The olive oils were extracted by classic hydraulic pressing, three phase continuous system, Abencor oil method at laboratory scale, and foot oil process from monocultivar Turkish olives, including Ayvalik, Memecik, Nizip Yaglik, Gemlik, Domat, and Uslu. Total phenolics, ortho-diphenols, oxidative stability, and total chlorophylls of the oils differed by location. The cis-trans fatty acids, triacylglycerols, and the actual versus theoretical equivalent carbon number of 42 (ECN 42) triglycerol content (ΔECN42) were within national and international averages. Oil samples from the three phase continuous system had higher total phenolic contents than those of the hydraulic pressure system. Turkish monocultivar virgin olive oil samples were classified by biochemical profiles using the principal component and hierarchical cluster analyses multivariate statistical methods. Clustering analysis defined groups according to growing location. Triacylglycerols and fatty acid profiles can be used for identification of monocultivar olive oils with regard to authenticity and classification.     

Comparative Study of Bioactive Constituents in Turkish Olive Oils by LC-ESI/MS/MS

The purpose of this research was to evaluate and compare the differences in the phenolic composition, antioxidant properties, and fatty acids of virgin olive oils from the Ayvalik, Gemlik, and Memecik olive varieties cultivated in their respective growing areas over two harvest years. The phenolic composition of olive oils was carried out by liquid chromatography coupled with diode array detection and electrospray ionization mass spectrometry analysis and the fatty acid composition was determined by gas chromatography analysis. Fourteen phenolic compounds were identified and, among these, the most dominant were elenolic acid, tyrosol, and hydroxytyrosol. For olives from both years, the highest total phenolic content was determined in Memecik followed by Ayvalik and Gemlik. 2,2-diphenyl-1-picryl hydrazyl and 2,2′-azino-bis- (3-ethyl-benzothiazoline-6-sulphonic acid) methods were used to determine the antioxidant capacity of the olive oil extracts. In both methods, the antioxidant capacity values were higher for oil from cv. Ayvalik. Thirteen fatty acids were identified and quantified in all samples. Oleic acid was the highest concentration and this acid was more dominant in Gemlik oils.     

Determination of apolar and minor polar compounds and other chemical parameters for the discrimination of six different varieties of Tunisian extra-virgin olive oil cultivated in their traditional growing area

A study on the characterization of Tunisian extra-virgin olive oil varieties produced in their place of origin has been carried out. Due to the influence of the genotype and environmental, agronomic and technological factors on the chemical composition of olive oil and its quality, all the olives studied were collected on the same season, and the oil was obtained under the same processing technique. Several analyses were performed to characterize the different olive oils: free acidity, peroxide value, fatty acid composition, radical scavenging activity, Rancimat assay, pigments content and phenolic compounds by HPLC–MS. In order to evaluate all the results obtained (36 parameters for each variety), different statistical analyses were used to discriminate the extra-virgin olive oil varieties: one-way analysis of variance was performed to check significant differences among cultivars (p ≤ 0.05); PCA was applied to the data showing that variables such as oleic, linoleic, quinic and vanillic acids, apigenin, luteolin, taxifolin, oleuropein aglycon, pinoresinol acetate, elenolic acid and oxidative stability allowed discriminating among the different varieties of extra-virgin olive oil studied. Besides, LDA model was able to classify the samples depending on their geographical origin in Tunisia (North, Centre and South).     

Classification of Turkish olive oils with respect to cultivar,geographic origin and harvest year,using fatty acid profile and mid-IR spectroscopy

Fatty acid composition and mid-infrared spectra of olive oils in combination with chemometric techniques were used in the classification of Turkish olive oils with respect to their varieties, growing location and harvest year. In particular, olive oil samples belonging to five different cultivars were obtained from the same orchard in the middle part of Aegean region and two of these varieties were also received from another orchard in northern part of the same region of Turkey in two consecutive harvest years. Evaluation of nine different fatty acid compositions with principal component analysis revealed clear differentiation with respect to variety, geographical origin and harvest year. On the other hand, mid-infrared spectra also achieved varietal and seasonal discrimination to some extent, but differentiation is not as clear as that obtained using fatty acid compositions.     

The Historical Development and Nutritional Importance of Olive and Olive Oil Constituted an Important Part of the Mediterranean Diet

The olive tree (Olea europaea) is widely cultivated for the production of both oil and table olives and very significant because of its economic value. Olive and olive oil, a traditional food product with thousands of years of history, are the essential components of the Mediterranean diet and are largely consumed in the world. Beside of their economical contribution to national economy, these are an important food in terms of their nutritional value. Olive and olive oil may have a role in the prevention of coronary heart disease and certain cancers because of their high levels of monosaturated fatty acids and phenolic compounds. In addition, olives (Olea europaea L.) and olive oils provide a rich source of natural antioxidants. These make them both fairly stable against auto-oxidation and suitable for human health. The aim of this paper is to define the historical development and nutritional importance of olive and olive oil constituted an important part of the Mediterranean diet.     

Comparative study of extra virgin olive oil flavor profile of Koroneiki variety (Olea europaea var. Microcarpa alba) cultivated in Greece and Tunisia during one period of harvesting

The effects of geographical region, irrigation and ripening degree of olives on the profile of volatile compounds isolated by monovarietal virgin olive oils from Crete and Tunisia of Koroneiki variety (Olea europaea var. Microcarpa alba) using the SPME GC/MS technique were investigated. Fruits obtained from Greece (island of Crete) and Tunisia (Sfax region) were picked at three and two different growth stages respectively and then immediately processed. The most important compounds identified were esters, alcohols, carbonyl compounds and hydrocarbons. The main volatile compounds present in the oil samples were C6 derivatives, such as [E]-2-hexenal, [E]-2-hex-1-enol, [Z]-3-hexen-1-ol and 1-hexanol. In addition to C6 compounds, the aroma of the studied samples contained reasonable amounts of various classes of C5 components. The tested oil samples showed different volatile profiles. Specifically, the concentration of total esters, carbonyl, C6 and C5 compounds increased significantly with the ripening degree in Cretan, but not in Tunisian olive oils. Principal component analysis of the results indicated that primary maturity and geographical region rather than irrigation affected significantly the volatile’s profile of olive oil.     

Chemometric characterization of three varietal olive oils (Cvs. Cobrançosa,Madural and Verdeal Transmontana) extracted from olives with different maturation indices

This paper evaluates the usefulness of three chemical parameters (compositions on tocopherols, sterols and fatty acids) as a tool to discriminate three varietal olive oils (Cvs. Cobrançosa, Madural and Verdeal Transmontana), which are permitted cultivars for the production of “Trás-os-Montes olive oil”, a Portuguese protected designation of origin (PDO) product. The olives were collected during the year crop 2000/2001 from the same orchard, in order to eliminate the geographical and climatic influences. Lots with different maturation indices were prepared to allow the evaluation of the ripening stage on the characteristics of varietal olive oils produced from each cultivar. Statistical methods such as multivariate analysis of variance (MANOVA), principal components analysis (PCA) and cluster analysis were used to evaluate significant differences on the studied parameters. Regarding the results, the three cultivars were clearly discriminated.     

DISCRIMINATION OF SOME TUNISIAN OLIVE OIL VARIETIES ACCORDING TO THEIR OXIDATIVE STABILITY, VOLATILES COMPOUNDS AND CHEMOMETRIC ANALYSIS

Oxidation stability is a key property of olive oil quality and is affected by different antioxidant compounds whose levels may be influenced by several factors such as cultivar and place of production. Polyphenols, carotenoids, chlorophylls, fatty acids levels and some volatiles were correlated to oxidative stability in olive oils in five samples studied. Total polyphenols and saturated to polyunsaturated fatty acids (and/or oleic to linoleic acid ratio) ratio were shown to be the major parameters in oil antioxidant stability, according to analysis of variance and principal component analysis. The hexanal/E-2-hexenal ratio is a very important indicator of the freshness of the oils and can estimate their oxidation degree.

PRACTICAL APPLICATIONS

The present study gives information about the importance and the variability of some Tunisian olive oil varieties in both their quality (high oxidative stability) and good organoleptic properties which could be appreciated by consumers.     

Oxidative and Antiradical Stabilities of Two Important Virgin Olive Oils from Ayvalik and Memecik Olive Cultivars in Turkey

Memecik and Ayvalik olive cultivars were harvested from Mugla province of Turkey and processed into oil using a three phase decanter. The oils of these cultivars were subjected to free fatty acid, peroxide value, ultra violet absorption, and fatty acid composition analysis. The results showed that all obtained values were very similar and within the limits of the International Olive Oil Council regulation for virgin olive oil. The oxidative stability in samples was assessed in terms of primary and secondary oxidation products using peroxide values and induction times, respectively. Total phenol and o-diphenol contents were determined by spectrophotometric assays. The antiradical capacity of phenolic fraction was determined by 1,1-diphenyl-2picrylhydrazyl method. These analyses showed that oxidative resistance, antiradical capacity, and the content of phenols and o-diphenols were higher for Memecik oil than Ayvalik oil.     

Application of solid-phase microextraction to the analysis of volatile compounds in virgin olive oils from five new cultivars

Evaluation and identification of wild olive genetic resources allowed us to select new olive varieties and to recognize Tunisian grove richness and diversity. Five new olive cultivars were previously selected among populations of wild olive plants on the basis of agronomic and chemical evaluations. Their virgin olive oils were analysed for their fatty acid composition, quality indices (Free acidity, PV and UV characteristics) and oxidative stability. They were then submitted to solid phase microextraction (SPME) and their volatile compositions were determined.     

CHEMOMETRIC CHARACTERIZATION OF FIVE TUNISIAN VARIETALS OF OLEA EUROPAEA L. OLIVE FRUIT ACCORDING TO DIFFERENT MATURATION INDICES

The usefulness of some chemical parameters as a tool to discriminate five varietals of olives was evaluated. Fruits were collected from the same orchard in order to eliminate geographical and climatic effects. Biochemical and quality characteristics in the fruits at complete ripeness were also investigated. Results showed that pomological characteristics and fatty acid composition may differ, depending on the variety and ripeness state, which is confirmed by an analysis of variance. A linear trend between mannitol and oil content was observed ( r =  0.665; P <  0.001). Jeddaria Chaal olive oil had both the highest triolein (39.33%) and oleic acid value (74.43%). However, Chemlali Chouamekh olive oil showed the highest pigment (59.29 and 26.37 mg/kg of chlorophylls and carotenes, respectively) and α-tocopherol content (201.40 mg/kg). Thus, the cultivars were clearly differentiated in their metabolic behavior and the biochemical characteristics of their oils. Ripening state is used mainly as a guideline to establish the olive harvest time. The present data provide information about the maturation patterns of different cultivars and how it can influence the quality of the final product.

PRACTICAL APPLICATIONS

This research is strongly oriented to the agronomic application. The obtained results can orient an agronomist to the optimum ripening date of olive fruits with a good amount of oil and a balanced fatty acid composition.     

Characterization of several hazelnut (Corylus avellana L.) cultivars based in chemical, fatty acid and sterol composition

Nineteen cultivars of hazelnuts (Corylus avellana L.) collected during the 2001 crop, from Vila Real, Portugal, were analysed for chemical composition, including moisture, total oil content, crude protein, ash, carbohydrates and nutritional value. Fat was the predominant component, ranging from 59.3 to 69.0%. Total oil was extracted and analysed for fatty acid and sterol compositions and oxidative stability. Fatty acid and sterol compositions were determined by Gas–Liquid Chromatography coupled to a Flame Ionisation Detector (GLC/FID). Monounsaturated fatty acids, particularly oleic acid, were predominant (78.7–84.6%). Total phytosterol content ranged from 133.8 to 263.0 mg/100 g of oil. Among the nine sterols identified and quantified, β-sitosterol was the major one with a mean percentage of 83.6%, while Δ⁵-avenasterol and campesterol were the second and the third components of the group with mean values of 6.1 and 5.8%, respectively. Since hazelnut oil can be used in olive oil adulteration, the values obtained were compared with published mean values of olive oils from different geographical origins.     

Effect of the growing area conditions on differentiation between Chemlali and Chétoui olive oils

This paper reports a discrimination study based on the antioxidant compounds, oxidative stability, aroma and sensory profiles of virgin olive oils from the main Tunisian cultivars, Chemlali and Chétoui, grown in two different locations, north and south Tunisia, with important differences in altitude, latitude and climatic conditions. There were significant differences between the oils from both cultivars when grown in the different environments. At higher altitude, the oils showed a greater amount of oleic acid, phenols and a higher stability, whilst in the open the oils had higher saturated and linoleic acid content. Aroma profiles were also influenced by the pedoclimatic conditions; hence, oils from the South had the highest level of (E)-2-hexenal and 1-hexanol, whereas varieties from the North were higher in (E)-3-hexenyl acetate and hexyl acetate. In general, and independently of the growing area conditions, oils from Chétoui olives had higher levels of antioxidants, greater oxidative stability, higher antiradical activities and more marked intensity of bitterness. These results can be used to discriminate and to characterise the Chemlali and Chétoui olive oils from each region.     

云南省不同引种地油橄榄果制取的油脂脂肪酸组成和角鲨烯含量分析

为了对云南省引种油橄榄优异种质资源提供理论依据,收集云南省不同引种地不同品种的油橄榄果,用索氏法提取橄榄油,通过气相色谱法测定其脂肪酸组成及角鲨烯含量。结果表明：不同引种地同一品种的橄榄油脂肪酸组成具有一定的相似性,大多聚于一类;不同品种橄榄油具有不同的脂肪酸组成,同一品种不同成熟度油橄榄果制取的橄榄油脂肪酸组成差异不大;不同品种橄榄油中角鲨烯含量变化幅度较大,最低值与最高值之间相差8.2 mg/g。综上,同一品种橄榄油的脂肪酸组成总体上具有一定的遗传稳定性,不同品种橄榄油具有不同的脂肪酸组成,且角鲨烯含量差异显著。     

Chemical composition and oxidative stability of Tunisian monovarietal virgin olive oils with regard to fruit ripening

The chemical composition of virgin olive oil may be influenced by genotype and different agronomic (i.e. fruit ripeness degree, water supply) and technological factors. This article reports the evaluation of the influence of the olive ripening stage on the quality indices, the major and the minor components and the oxidative stability of the two main monovarietal Tunisian cultivars (cvv. Chétoui and Chemlali) virgin olive oils. Moreover, the olives cv. Chétoui were tested in a rain-fed control and an irrigation regime. The oils sampled at five different ripeness stages were submitted to liquid chromatographic determination (HPLC-DAD/MSD) of their quali-quantitative phenolic and tocopherolic profiles. Moreover, the triacylglycerol and fatty acid compositions, and minor components such as squalene, pigments and their relation with the oil oxidative stability were evaluated. The tested oils showed very good correlation between the oxidative stability and the concentrations of total phenols, practically secoiridoids and α-tocopherol.     

Evaluation of Functional Phytochemicals in Destoned Virgin Olive Oil

Processing destoned olives by means of extracting adjuvants micronised food talc and depolymerising Cytolase 0 enzyme complex have been studied in the present work. This innovative processing technology increased the plant efficiency (amounts of olives processed per hour) by 20%, as well as the nutritional quality of the end product with respect to functional compounds. The oils showed higher contents of biophenols, aromas, and tocopherols. An intense and balanced flavor and a potentially higher stability and endurance to oxidation (shelf-life) was found. Contents of chloroplast pigments (chlorophylls, pheophytins, carotenes, and xanthophylls) appeared to be lower in comparison to conventional processing. The processing aids allowed to increase significantly the oil yields and to reduce the oil percentage in the byproducts. Traceability of the new products was still possible applying chemometric data analysis for discriminating between cultivars.     

Compositional quality of virgin olive oil from two new Tunisian cultivars obtained through controlled crossings

This work was carried out on the study of virgin olive oil from two olive descendants obtained through controlled crossings on Chemlali, the dominant Tunisian olive oil variety. These crossings on Chemlali were undertaken to improve its oil quality. Preliminary work evaluating the oil fatty acid composition of the oil of 40 descendants showed the performance of two cultivars among the studied hybrids. These two new cultivars (Hd 034 and Hd 039) have an improved oil composition compared to that of Chemlali. A further study was therefore required for their complete characterization. The analytical parameters (fatty acid composition, total phenolic compounds, chlorophylls and carotenoids contents, oxidative stability, free acidity, peroxide value and ultraviolet characteristics) showed significant differences between oils from both cultivars. Copyright © 2007 Society of Chemical Industry     

Phenolic compounds in virgin olive oils: influence of the degree of olive ripeness on organoleptic characteristics and shelf-life

 An experimental investigation was performed on virgin olive oils from Coratina and Ogliarola salentina cultivars extracted from green, partially blackened and totally blackened olives in order to evaluate changes in the organoleptic properties and in the shelf-life of the oil. The aim of the investigation was to identify the optimal stage of olive maturation for each cultivar to produce higher quality oils. Routine analyses in accordance with EC regulation no. 2568/91, the determination of phenols by HPLC and induction times were carried out. On the whole, the simple phenolic compounds increased as darker olives were used whereas the hydrolysable phenolic compounds decreased. In both the cultivars, total phenols and induction times were significantly higher in the oils obtained from green olives than in oils from totally blackened olives. Hence, it seems advisable to delay olive harvesting for cultivars usually yielding bitter to pungent oils (e.g. Coratina), but to anticipate harvesting for olives producing sweet tasting oils (e.g. O. Salentina). This would produce less bitter Coratina oils, with organoleptic features which may better fulfil consumers' expectations, and O. Salentina oils more resistant to oxidation. Received: 5 June 2000     

Preliminary characterisation of virgin olive oils obtained from different cultivars in Sardinia

Chemical characterisation was carried out on 12 virgin olive oil samples obtained from seven olive cultivars (Bosana, Carolea, Nocellara del Belice, Pizz'e Carroga, Semidana, Tonda and Zinzala cvs.). The olives came from different groves in Sardinia (Italy) and Corsica (France) that were processed by different types of continuous mills. Several qualitative parameters were evaluated (free acidity, peroxide value, and UV spectrophotometric indices) and analyses of major (fatty acids and triacylglycerol compositions) and minor components (chlorophylls, carotenoids, tocopherols and phenolic compounds) was also carried out. The oxidative stability index (OSI) and ABTS^•− test values were determined to evaluate the oxidative stability and antioxidant activity of the phenolic fraction, respectively. The results were subjected to a discriminative study by principal component analysis (PCA) to characterise the different oils. A first PCA using only the triglyceride compounds and a second using the minor polar compounds and their antioxidant activity was performed. The triglyceride composition was found to be particularly useful in discriminating the oil samples.