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.     

二相离心加工工艺对初榨橄榄油理化指标和氧化稳定性的影响

橄榄油的品质不但与品种有关,还受加工工艺的影响。以‘豆果’‘鄂植8号’‘克罗莱卡’3个品种油橄榄果为原料,研究了二相离心加工工艺对初榨橄榄油脂肪酸组成、色度、酸值、过氧化值、紫外吸光度、微量伴随物、抗氧化能力和氧化稳定性的影响,并与三相离心加工工艺进行对比。结果表明:在融合温度30℃、融合时间45 min条件下,初榨橄榄油的品质较好;‘克罗莱卡’初榨橄榄油中多酚含量最高,氧化稳定性最好,与三相离心加工工艺相比,二相离心加工工艺生产的初榨橄榄油多酚含量显著提高。     

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.     

Influence of the malaxation time and olive ripening stage on oil quality and phenolic compounds of virgin olive oils

The main objective of this study was to evaluate the influence of the malaxation time (Mt) and ripening stage on oil quality and phenolic compounds of Hojiblanca and Picual virgin olive oils. In both varieties of oil, phenolic content and oxidative stability decreased as ripening progressed. The total level of tocopherols diminished by up to 40% as fruit ripened. The compositions of palmitic, stearic, lignoceric, oleic, linoleic and linolenic acids were significantly influenced by the ripening process. The present work shows that an increased Mt promoted the increase of free acidity (up to 13.3%) and tocopherols (up to 11.6%) and negatively affected the oxidative stability and the concentration of phenols. Further research is required to determine ripening stages and malaxation conditions for all olive oil varieties to achieve a satisfactory balance between the improvement of both oil yield and oil quality and composition.     

Changes in quality and phenolic compounds of virgin olive oils during objectively described fruit maturation

The effect of fruit ripening on the quality of the oil extracted and on the changes in the amount of phenolic compounds was determined in two olive varieties (Olea europaea, cvs. Arbequina and Picual) in two crop seasons, characterized by showing the same mean temperature and different rainfalls. Maturation level was evaluated using six methods: Harvest date, ripening index (RI), fruit skin colour, fruit firmness, and amount of chlorophylls and carotenoids in the oil. Oil quality, evaluated using the parameters established to determine the quality level of virgin olive oils (acidity, K₂₃₂, K₂₇₀, peroxide index, and panel test), was not affected by fruit ripening or by the increase in rainfall of the season. However, the changes in oil stability and phenolic compounds in the oils extracted during fruit ripening strongly differed according to the variety, the maturity level of the fruit and the crop season tested. Fruit skin colour and firmness allowed a better discrimination at the initial maturity stages than the other methods tested.     

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.     

Three-year study of fenthion and dimethoate pesticides in olive oil from organic and conventional cultivation

Residues of fenthion and dimethoate pesticides were determined in organic and conventional olive oils by liquid-liquid and solid-phase extractions with subsequent gas chromatography and mass spectrometric analysis. The olive oil samples were collected from Crete during 1997-99. The average concentrations of fenthion in conventional olive oils were 0.1222, 0.145 and 0.1702 mg kg^-1, and for dimethoate were 0.0226, 0.0264 and 0.0271 mg kg^-1 for 1997, 1998 and 1999, respectively. The average concentrations of fenthion in organic olive oils were 0.0215, 0.0099 and 0.0035 mg kg^-1 for 1997, 1998 and 1999, while for dimethoate they were 0.0098, 0.0038 and 0.0010 mg kg^-1, respectively. All the olive oils contained residue levels lower than the maximum resi-due levels according to the FAO/WHO Codex Alimentarius. The organic olive oil contained significantly lower concentrations of the two pesticides. The levels of fenthion and dimethoate in organic olive oils exhibited a decreasing trend following the implementation of the new cultivation method. We propose procedures that should be established in the organic cultivation in order to maximize its effectiveness.     

A comparison between olive oil and extra-virgin olive oil used as covering liquids in canned dried tomatoes: hydrolytic and oxidative degradation during storage

The hydrolytic and oxidative degradation of olive oil and extra‐virgin olive oil, used as covering liquids in canned dried tomatoes, was studied during storage by means of conventional (acidity, peroxide value, p‐anisidine value) and non conventional (polar compounds) analyses. The effects of the addition of spices were also considered. The hydrolysis and oxidation of olive oil increased faster and was higher than that of extra‐virgin olive oil in terms of absolute values but some other indices, such as percentage of oligopolymers and percentage of oxidized triglycerides, increased faster in extra‐virgin olive oil than in olive oil. The antioxidant effect given by a higher concentration of polyphenols in the extra‐virgin olive oil was shown by a reduced amount of secondary oxidation. However, olive oil and extra‐virgin olive oils showed similar behaviour in terms of peroxide formation.     

Analytical evaluation of two monovarietal virgin olive oils cultivated in the south of Tunisia: Jemri‐Bouchouka and Chemlali‐Tataouin cultivars

BACKGROUND: The characterisation of virgin olive oils from two Tunisian cultivars, growing in the Tataouin zone, namely Jemri‐Bouchouka, a rare olive cultivar, and Chemlali‐Tataouin, was carried out. Several analytical parameters were evaluated; these include quality index, fatty acids, phenolic, chlorophyll, carotenoid, squalene, α‐tocopherol compositions and oxidative stability. RESULTS: Jemri‐Bouchouka olive oil had the highest value of oleic acid (74.50%) while Chemlali‐Tataouin was characterised by a high percentage of palmitic acid (14.75%), which makes this oil freeze at a low temperature. On the other hand, Jemri‐Bouchouka oil was characterised by a low phenolic and α‐tocopherol content (267.72 mg GAE kg^?1 and 278.34 mg kg^?1, respectively). Ten phenolic compounds were identified. The main phenols found in the two olive oils were oleuropein aglycon and pinoresinol. All phenolic compounds showed significant correlations with oxidative stability. CONCLUSION: The analytical parameters of virgin olive oil that were determined in this study were greatly influenced by cultivar. © 2012 Society of Chemical Industry     

Influence of fruit ripening process on the natural antioxidant content of Hojiblanca virgin olive oils

The effect of fruit ripeness on the antioxidant content of `Hojiblanca' virgin olive oils was studied. Seasonal changes were monitored at bi-weekly intervals for three consecutive crop years. Phenolic content, tocopherol composition, bitterness index, carotenoid and chlorophyllic pigments and oxidative stability were analysed. In general, the antioxidants and the related parameters decreased as olive fruit ripened. The phenolics and bitterness, closely related parameters, did not present significant differences among years. Although in general, the tocopherols decreased during olive ripening γ-tocopherol increased. Differences between crop years were found only for total tocopherols and α-tocopherol, which showed higher content in low rainfall year oils. The pigment content decreased during ripening, chlorophyll changing faster. For low rainfall years, the level of pigments was higher, reaching significant differences between yields. Significant differences among years were found for oil oxidative stability; higher values were obtained for drought years. A highly significant prediction model for oxidative stability has been obtained.     

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.     

Effect of cultivar and ripening on minor components in Spanish olive fruits and their corresponding virgin olive oils

Phenolics and volatiles are the compounds mainly responsible for the desirable flavour of extra virgin olive oils and therefore to a large extent determine the degree of consumer preference for this highly regarded product. The effect of both (i) the nature of the cultivar and (ii) the degree of ripening of the olive fruit on the biophenolic and volatile profiles of six different Spanish varieties (Arbequina, Cornicabra, Morisca, Picolimón, Picudo and Picual) and their corresponding virgin olive oils was determined in this study. A clear and statistically significant difference was observed for the oleuropein content, the main phenolic component found in the olive varieties studied. Demethyloleuropein was only found in the Arbequina variety and its content doubled during the ripening process. Verbascoside steadily increased throughout fruit maturation and cyanidin 3-O-rutinoside was the most abundant anthocyanin in all the varieties studied. Within the same cultivar a relationship between the oleosides content in the fruit and the presence of secoiridoids in the virgin olive oils was observed; however, the ratio between biophenols content in the olive fruit and in the virgin olive oil varied significantly for each of the cultivars studied (ranging from 2.3 for Picudo and 28 for Picolimon). The major volatile component was the C6 aldehyde fraction whose content varied greatly between the different varieties studied: E-2-hexenal content ranged from 20.5 mg of internal standard (4-methyl-2-pentanol) per kg of oil in the Arbequina variety to 3.1 mg/kg for Cornicabra; the amount of hexanal ranged from 1.75 mg/kg in Morisca to 0.70 mg/kg for Picual samples.     

Changes in phenolic compounds and Rancimat stability of olive oils from varieties of olives at different stages of ripeness

BACKGROUND: Recently, diets rich in natural foods and food‐derived components, such as phenolic compounds, have received a great deal of attention because they are perceived as ‘safe’ and ‘non‐medicinal’. In fact, some are known to function as chemopreventive agents against oxidative damage, cerebrovascular disease, and aging. RESULTS: Phenolic compounds, natural antioxidants present in virgin olive oil, play an important role in oil quality by contributing significantly to protecting oil stability against oxidation. In addition, polyphenols are the main contributors to olive oil bitterness, astringency and pungency. The data were fit by linear regression, giving Rancimat stability (h) = 0.18× Total polyphenols (mg L^?1) in the virgin olive oil. CONCLUSIONS: The practice of harvesting ripe olives as soon as possible to produce oils of high phenolic contents and thus high oxidative stability implies bitter and piquant oils, this being admissible for oils of some varieties but detrimental to others appreciated in the market for being more fruity and sweeter. Copyright © 2010 Society of Chemical Industry     

Extra‐virgin and refined olive oils decrease plasma triglyceride,moderately affect lipoprotein oxidation susceptibility and increase bone density in growing pigs

The objective of this study was to determine the health benefits of extra‐virgin and refined olive oils, which are high in mono‐unsaturated fatty acids (MUFAs) and polyphenolic compounds using the pig as a model. Thirty‐two cross‐bred pigs were individually penned, allocated to one of four dietary treatments and fed ad libitum for 28 days. Two of the experimental diets consisted of a basal diet containing 12% tallow and either 7% sunflower oil (TSO) or 7% extra‐virgin olive oil (TEVO) on a w/w basis. The remaining diets contained 19% extra‐virgin olive oil (EVO) or 19% of refined olive oil (RO). On days 7, 14 and 28 fasted and 3‐h post‐prandial blood samples were taken. Body composition was measured at the beginning and end of the study using dual energy X‐ray absorptiometry. Daily gain, feed intake and lean and fat deposition were not significantly different between the treatments. However, the daily increase in bone mineral density was higher in pigs fed diets containing olive oil (1.23 vs 2.54, 6.28, 5.20 mg cm^?2 per day for TSO, TEVO, EVO and RO, respectively, P = 0.050). Both fasting and non‐fasting plasma triglycerides were lower (P = 0.003) in pigs fed MUFA‐rich diets, while the cholesterol profile was not significantly different between the treatments. The results from in vitro copper‐induced lipid peroxidation, expressed in terms of conjugated dienes, showed that low density lipoprotein (LDL) particles in postprandial serum from pigs fed olive oil were moderately more resistant to oxidative modification. In conclusion, these data demonstrate that both extra‐virgin and refined olive oils attenuate postprandial hypertriglyceridaemia, moderately affect oxidation susceptibility and increase bone mineral density in growing pigs. Copyright © 2006 Society of Chemical Industry     

Sensory and chemical profiles of three European olive varieties (Olea europea L); an approach for the characterisation and authentication of the extracted oils

Sensory data (1–16) as described by a trained panel, several characteristics (acidity, peroxide value, extinction coefficients at 232 and 270 nm, stability and phenolic compounds) (17–30) and chemical compositional data (fatty acids, sterols and triterpene diols, aliphatic and triterpene alcohols, and triglycerides) (31–67) were obtained for virgin olive oils of three European olive varieties, Coratina (Italy), Picual (Spain) and Koroneiki (Greece), at a certain stage of maturity—when half of the olives displayed partial or total purple colour—for two consecutive years of harvest, 1995–96 and 1996–97. The most remarkable characteristics for the classification of the oils were extracted using multivariate statistical analysis (correlation, hierarchical clustering and canonical discriminant analysis). Both sensory and/or chemical and quality characteristics were found to have significant potential for the authentication of the virgin olive oil varieties under investigation. © 2000 Society of Chemical Industry     

Influence of genetic matrix and crop year on chemical and sensory profiles of Italian monovarietal extra‐virgin olive oils

BACKGROUND: Commercial virgin olive oils belonging to the cultivars (Bosana, Carolea, Coratina, Frantoio, Itrana, Leccino, Moraiolo, Peranzana, Piantone di Mogliano and Ravece) most represented at the Italian National Review of Monovarietal olive oils (Rassegna Nazionale Italiana degli oli Monovarietali) were considered. The evaluation of the influence of the cultivar and of the crop year as well as their interaction on oil composition were statistically analysed by a complete factorial design by principal components analysis and by linear discriminant analysis. RESULTS: In fatty acids composition, the effect of the cultivar and crop year and their interaction were highly significant. The statistical analysis showed that the sensory attributes (olive fruity, grassy, fresh almond, artichoke, tomato, aromatic herbs, bitter and pungent) were strongly influenced by the cultivar. The prevalent effect of the cultivar on the sensory profile was also demonstrated by the low or absent level of significance observed in the crop year. CONCLUSION: The construction of a databank based on a large number of samples, which is available at URL http://www.olimonovarietali.it , has contributed to the reduction of the variable effects involved in the oil production process. Knowledge of the chemical and sensory profiles of the Italian monovarietal olive oils could start a certification process of these oils, thus giving greater guarantees about their origin. Copyright © 2010 Society of Chemical Industry     

Possibility of improving the quality characteristics of olive‐pomace oil and enhancing its differentiation from refined olive‐pomace oil

An investigation was carried out to evaluate the oxidative and hydrolytic degradation of 37 olive‐pomace oils marketed in southern Italy and to compare the results with those obtained from 10 deodorised olive‐pomace oils representative of large stocks of oil obtained after the final step of refining. One aim of the research was to ascertain the quality characteristics of commercial olive‐pomace oils; another was to verify whether the legally prescribed addition of virgin olive oil to refined pomace oil, so that the final product may be classified commercially as olive‐pomace oil, was actually sufficient to justify upgrading. The analytical methods used were silica gel column chromatography and high‐performance size exclusion chromatography. The data obtained showed that the final retail olive‐pomace oils had a lower degree of oxidative degradation than the refined oils, as indicated by the lower values obtained when summing the proportions of triglyceride oligopolymers and oxidised triglycerides. Conversely, hydrolytic degradation, which was evaluated by determining diglycerides, proved to be the same in the two categories of oil. The proportions of virgin olive oil added are small, as indicated by the statistically indistinguishable values of triglyceride oligopolymers and free fatty acids obtained. The possibility of setting a limit to the amount of triglyceride oligopolymers present in the commercial category of olive‐pomace oil has been considered. This limit would ensure standardisation of the level of oxidation and, consequently, of the quality of marketed oils and would enhance differentiation between olive‐pomace oil and refined olive‐pomace oil. © 2000 Society of Chemical Industry     

Performance of virgin olive oil and vegetable shortening during domestic deep-frying and pan-frying of potatoes

The performance of virgin olive oil and a commercial vegetable shortening was investigated during 10 successive pan-fryings of potatoes at 180 °C for a total period of 60 min and during 10 successive deep-fryings at 170 °C for a total period of 120 min. These are typical conditions of Greek domestic cooking. For both the oils tested the effect of pan-frying on K232, K268, K316, α-tocopherol, total polar artefacts, Rancimat induction times, octanoic acid formation and linoleic acid decomposition was worse than the effect of deep-frying on the same variables. The same was true for visible spectrum and total phenols in virgin olive oil. No systematic variations of oleic acid, refractive index and trans -isomers of fatty acids were detected. None of the oils reached the limit of 25–27% total polar artefacts. Both oils performed similarly during pan-frying, while virgin olive oil performed better during deep-frying. A very strong correlation between octanoic acid formation and total polar artefacts in the whole data set was observed.     

Oxidative changes in hazelnut,olive, soybean,and sunflower oils during microwave heating

The effects of microwave heating for 3, 6, and 9 min at a frequency of 2450 MHz on fatty acid composition, tocopherols, iodine value, free fatty acids (%), peroxide value, conjugated dienes and trienes, and hexanal contents of refined hazelnut, soybean, sunflower, and virgin olive oils were investigated. A significant (p < 0.05) decrease was observed in linoleic and linolenic acids contents of soybean oil during exposure to microwave heating. Tocopherol contents of oil samples significantly decreased (p < 0.05) during microwave heating. Free fatty acids of the samples slightly increased and iodine value showed reduction throughout the process. Conjugated dienes contents of samples showed an increasing trend up to the 6 min, followed by a reduction at 9 min. Conjugated triene fatty acids of all the samples significantly increased (p < 0.05) throughout the application. While peroxide value showed increasing trend up to the 3 min and sharply decreased at 9 min, hexanal contents of refined hazelnut, virgin olive, soybean, and sunflower oils increased 63, 28, 55, and 389 fold, respectively, after 9 min exposure to microwave heating. Kinetic analysis of data showed that the reaction orders for peroxide and hexanal formation were zero and first order, respectively, and in the tested oils the reaction rate followed the order: soybean oil ? sunflower oil ? hazelnut oil ? virgin olive oil for peroxide, and sunflower oil ? soybean oil ? hazelnut oil ? virgin olive oil for hexanal formation. It was concluded that hexanal could be considered as a parameter for evaluation of the quality of oils exposed to microwave heating.