Volatile compounds from Chétoui olive oil and variations induced by growing area

Fruits from the same variety of Olea europaea L., grown under different environmental conditions in the north of Tunisia, were harvested at the same ripening degree and immediately processed. The volatile profile of virgin olive oils was established using solid phase, micro-extraction (SPME) and gas chromatography-mass spectrometry (GC-MS). Compounds belonging mainly to the following chemical classes characterised the volatile profiles: esters, aldehydes, ketons, aliphatic alcohols and hydrocarbons. Significant differences in the proportions of volatile constituents from oils of different geographical origins were detected and the major volatile in approximately 50% of the oil samples was the aldehyde (E)-2-hexenal. The results suggest that, beside the genetic factor, environmental conditions influence the volatile formation.     

Characterisation of 39 varietal virgin olive oils by their volatile compositions

Thirty-nine single virgin olive oils from eight producer countries, but cultivated in the same orchard under identical agronomic and pedoclimatic conditions, were characterised by 64 volatile compounds quantified by dynamic headspace-gas chromatography. The method was validated by analysing the relative standard deviation in repeatability and intermediate reproducibility of each volatile compound. Data on the total content of volatiles and C6 compounds – responsible for the green odour perception-, and the total content of hydrocarbons, aldehydes, alcohols, ketones and esters are displayed and discussed for each individual virgin olive oil. Fifty volatile compounds were characterised by their sensory attributes, determined by olfactometry. The Student t-test was used to determine the level of significance of each volatile compound characterising the varieties. The odour threshold and the maximum concentration of the most notable volatiles are also displayed. Finally, the Brown-Forsythe test and stepwise linear discriminant analysis were used to check the ability of the volatiles to cluster the varietal virgin olive oils according to their autochthonous geographical origin.     

Effect of the blanching process and olive fruit temperature at milling on the biosynthesis of olive oil aroma

Two sets of experiments were performed in order to study the origin of the modification of olive oil aroma during the industrial heat treatment of olive fruit. Data obtained suggest that both blanching of olive fruit and fruit temperature at milling affect the synthesis of volatile compounds, thus contributing independently to the modification of the aroma volatile profile of olive oil reported for the industrial thermal treatments of olive fruit. Increasing the fruit temperature at milling in the range 20–60 °C produces a decrease in the level of C6 and C5 compounds and a slight modification of the contents of esters. Blanching produced a decrease of the content of C5 compounds independently of the degree of fruit ripening, while esters contents remained unaffected. However, blanching showed to have different effects on the content of C6 compounds in the aroma of olive oil depending on the degree of fruit ripening. Biochemical aspects within the lipoxygenase pathway are discussed in order to explain the results obtained.     

NMR and statistical study of olive oils from Lazio: A geographical,ecological and agronomic characterization

NMR and statistical procedures were used to analyse olive oils obtained from trees grown in different areas of Lazio, an Italian region, under different irrigation conditions. In order to obtain information on “real” commercial olive oils and to study the effects of some agronomical and ecological factors on the olive oil composition, we studied commercial multi-varietal olive oils, all produced in well-characterized areas of Lazio. ¹H and ¹³C NMR techniques, coupled to a suitable multivariate statistical procedure, were used to analyse 72 multi-varietal extra virgin and PDO (Protected Denomination of Origin) olive oils harvested in 2003, from the northern area, the centre and the southern area of Lazio. The intensity of selected ¹H and ¹³C NMR variables were submitted to three different statistical methods, namely, analysis of variance (ANOVA), principal component analysis (PCA) and linear discriminant analysis (LDA). ¹H and ¹³C NMR spectroscopy allowed us to obtain a good chemical characterization of the samples, giving information on major and minor compounds with an experimental error exactly the same and always extremely low for all the analyzed components. As a result of the statistical analysis, olive oils from the same geographical areas were well grouped. Since the amounts of some minor volatile components, such as aldehydes, terpenes and squalene, as well as, the content of β-sitosterol, the most important sterol present in olive oils, are sensitive to the pedoclimatic conditions, the intensity of the corresponding NMR signals turned out to be the most discriminating factors in the geographic classification. Moreover, the NMR and statistical protocol allowed us to investigate the roles of irrigation and altitude on the olive oil composition: the contents of oleic and saturated fatty acids turned out to be strongly influenced by the irrigation practice, whereas the content of volatile compounds was sensitive to the altitude of the olive trees. As a result of our study, olive oils were well grouped according to the irrigation practice as well as to the altitude at which olive trees were grown.     

Comparative study on volatile compounds from Tunisian and Sicilian monovarietal virgin olive oils

The effects of ripening degree of olives on volatile profile of monovarietal virgin olive oils (VOO) from Tunisian and Sicilian cultivars were investigated. Fruits obtained from Tunisia (Chétoui and Chemlali) and Italy (Nocellara del Belice, Biancolilla and Cerasuola) were picked at three different stages of ripeness and then immediately processed. Moreover, the changes in volatile composition were evaluated in Chétoui variety as a function of the irrigation regime versus the rain-fed control. Using headspace–solid-phase microextraction (HS–SPME) technique coupled to GC–MS and GC–FID, the volatile compounds of the monovarietal virgin olive oils were identified and quantitatively analyzed. The proportions of different classes of volatiles of oils showed significant differences throughout the maturity process. The results suggest that adding to the genetic factor; agronomic conditions affect the volatile formation and therefore the organoleptic properties of VOO.     

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.     

Virgin olive oil aroma: Characterization of some Tunisian cultivars

Fruits from four Tunisian cultivars of Olea europaea L. grown in the North of Tunisia were handpicked at the same ripening degree and processed with a laboratory mill. The oils were submitted to dynamic headspace and their volatile composition was determined.The results showed that the most important contributors to olive oil aroma are C₆ aldehydes, alcohols, and esters. These compounds are biogenerated from polyunsaturated fatty acids through the lipoxygenase (LOX) pathway. Furthermore, they pointed out the predominance of the oxidation of linolenic (LnA) acid over linoleic (LA) acid one.In this predominant part of LOX, the branch A giving rise to trans-2-hexenal, trans-2-hexenol was more important than the branch B giving rise to cis-3-hexenol and cis-3-hexenyl acetate. This pointed out that the isomerization of cis-3-enals forms to trans-2-enal ones is the dominant process of the branch B.The accumulation of the different metabolites in the oils varied according to cultivar indicating a close dependence on the enzymatic store which is genetically determined.     

Volatile compounds and compositional quality of virgin olive oil from Oueslati variety: Influence of geographical origin

Headspace solid-phase microextraction (HS-SPME) was applied to the analysis of volatile compounds of virgin olive oils from Oueslati variety cultivated in different geographical areas. Thus, olives at the same stage of maturation were harvested from seven regions in the Centre and the South of the country for oil extraction and analysis. Twenty-seven compounds were characterised by GC-FID and GC–MS. Compounds belonging mainly to alcohols, esters, aldehydes, ketones and hydrocarbons chemical classes characterised the volatile profiles. Significant differences in the proportion of volatiles from oils of different geographical origins were detected. The results suggest that, besides genetic factors, environmental conditions influence volatile formation.     

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.     

Influence of regulated deficit irrigation strategies applied to olive trees (Arbequina cultivar) on oil yield and oil composition during the fruit ripening period

This study evaluated the effect of regulated deficit irrigation (RDI) strategies applied to olive trees (Arbequina cv) during the fruit ripening and harvest periods on oil yield and oil composition. Fatty acid composition, pigments, colour, polyphenol content and stability of oils were evaluated. The results indicate that regulated deficit irrigation induces fruit ripening; at harvest, oil yield increased when water supply was decreased, probably as a consequence of lower water content in the olive. Acidic composition was not affected by irrigation treatments. Irrigation affected pigment content and oil colour primarily during the early stages of olive ripening. RDI increased polyphenol concentration and stability of oils at all picking dates, especially during the first stages of the ripening period, probably owing to water stress. © 2000 Society of Chemical Industry     

初榨橄榄油挥发性风味成分的鉴定

采用顶空固相微萃取-气质联用(HS-SPME-GC/MS)分离鉴定了陇南市武都初榨橄榄油和西班牙特级初榨橄榄油中的挥发性风味成分。结果表明,在7个不同品种油橄榄的国产初榨橄榄油中共鉴定出86种化合物,主要是C6的醛和醇,以及它们相应的酯,还有一些烯烃和萜烯类化合物。其中(E)-2-己烯醛相对质量分数为7.14%~46.22%;在6个西班牙特级初榨橄榄油中共鉴定出101种化合物,其中(E)-2-己烯醛质量分数(1.76%~5.25%)低于国产初榨橄榄油,而(Z)-乙酸-3己烯酯(7.53%~13.76%)和(E)-2-十二碳烯(5.47%~34.75%)相对质量分数较高。试验结果还表明,初榨橄榄油挥发性风味成分很大程度上取决于油橄榄品种和产地。     

Volatile compounds of olive oils from different geographic regions in Turkey

In this research, changes in volatile compounds of olive oil were investigated in terms of cultivar, harvest year, and geographic regions (Mediterranean, Aegean, Southeastern Anatolia, Marmara, and Black Sea) were investigated. Volatile compounds of olive oils were extracted by using solid-phase microextraction (SPME) method and were identified with gas chromatography–mass spectrometry. A total of 59 volatile compounds from seven different chemical groups including aldehydes, ketones, hydrocarbons, alcohols, esters, terpenes, and furans were identified. Aldehydes were detected as the major group in all geographic regions. Among aldehydes, trans-2-hexenal was found to be relatively higher. Alcohols and esters were determined as other important compounds. While many volatile compounds were affected by olive cultivar factor, this factor had no significant effect on esters. Principal component analysis showed that volatile compounds could play an important role in the separation of regions.     

Volatile profile of Arbutus unedo L. fruits through ripening stage

Arbutus unedo L. is a Mediterranean shrub used in the production of jams, marmalades and beverages, as well as in traditional medicine. In this work, the effect of ripening on the volatile compounds of the fruits of A. unedo was evaluated, using headspace-solid phase microextraction combined with gas chromatography/ion trap-mass spectrometry. Alcohols are the main component of the volatile fraction of A. unedo fruits, followed by aldehydes and esters. The main volatile compounds identified were (Z)-3-hexen-1-ol, 1-hexanol, hexanal, (E)-2-hexenal and hexyl acetate, all formed through the lipoxygenase pathway (LOX). The green odours are progressively replaced during ripening by floral and sweet sensations, due to the decrease in alcohols, aldehydes and esters, resulting in the unmasking of the aromas associated with the minor compounds (mainly monoterpenes and norisoprenoid compounds) that compose A. unedo fruits.     

Dynamic accumulation of 4-desmethylsterols and phytostanols during ripening of Tunisian Meski olives (Olea europea L.)

Eleven 4-desmethylsterols and two phytostanols were identified by GC–MS during the ripening of Meski olive. The maximum levels of 4-desmethylsterols (1300 mg/100 g oil) and phytostanols (7.5 mg/100 g oil) were reached at the 26th week after the flowering date (WAFD) of fruit. β-Sitosterol (72–86% of total 4-desmethylsterols) was the major 4-desmethylsterols during the maturity of fruit, while sitostanol was the predominant phytostanols (75–85% of total phytostanols). Δ5-Avenasterol (2–18%) and campesterol (1.6–4%) were the second and the third 4-desmethylsterol levels detected, respectively, during the ripening of Meski olive. The levels of campestanol varied from 15% to 25% of phytostanols. The rate of accumulation of those compounds occurred before 30th WAFD. Some of these compounds (4-desmethylsterols and phytostanols) showed nearly the same profile during the ripening of Meski olive which could be linked to the relation between these compounds during their biosynthetic pathway.     

The Influence of Debaryomyces hansenii, Candida deformans and Candida zeylanoides on the aroma formation of dry-cured “lacón”

The volatile profile of dry-cured “lacón” that has been inoculated with three different yeasts were determined and compared with a non-inoculated dry-cured “lacón”. Yeasts (Debaryomyces hansenii, Candida deformans and Candida zeylanoides) that were used as starter cultures in the present study were selected among yeasts that were isolated from native dry-cured “lacón” at different stages of ripening process. These starters were spread on dry-cured “lacón” surface in order to test their capacity to contribute on the generation of volatile compounds. A total of forty two volatile compounds were detected by dynamic headspace sampling followed by gas chromatography–mass spectrometry analysis. Significant differences (P < 0.001) on the volatile profiles of different batches were found in comparison with non-inoculated samples, showing the highest total area values for the inoculated ones. Esters were the most abundant chemical family in all batches studied except for C. zeylanoides batch, which showed greater amount of hydrocarbons than esters. The second more abundant family was hydrocarbons for control and C. deformans batches (147.6 and 445.24 × 10⁶ area units, respectively), alcohols for D. hansenii (363.77 × 10⁶ area units) and esters for C. zeylanoides (248.33 × 10⁶ area units). However, the aldehyde compound group in control batch samples was found to be significantly higher than in the inoculated ones (P < 0.001). Among inoculated batches, D. hansenii batch showed the lowest hexanal content (14.42 × 10⁶ area units) in comparison with non-inoculated batch (105.99 × 10⁶ area units). Among all batches studied, D. hansenii batch presented the highest area values for esters, alcohols, linear hydrocarbons, ketones, acids and furans; control batch for aldehydes and C. zeylanoides batch for branched hydrocarbons. Therefore, the study showed that every yeast strain produced a specific volatile profile which was also different from that of the control dry-cured “lacón”.     

Comparative study of the effect of the maturation process of the olive fruit on the chlorophyll and carotenoid fractions of drupes and virgin oils from Arbequina and Farga cultivars

Two varieties of olive fruit (Arbequina and Farga) have been characterized by their contents and types of chlorophyll and carotenoid pigments during the olive ripening. Independently of the initial content, the pigment concentrations decreased with fruit maturity. Chlorophyllides a and b, esterified xanthophylls and α-carotene were only detected in Arbequina fruits. Moreover, the synthesis of esterified xanthophylls, when the skin fruit colour changed from green to turning-colour only, was observed in this variety. The pigments transferred from fruit to the oil were also studied. All the pigments that were found in the fruit were transferred to the oils, in addition to derivative pigments associated with acidic medium in the oil extraction process. The destruction of the chlorophyll fraction was greater than of the yellow pigments during the olive oil extraction process.     

GC-O结合OAV鉴定陇南初榨橄榄油关键香气成分

选取甘肃陇南代表性品种莱星和鄂植8号初榨橄榄油及消费口碑良好的特级混合初榨橄榄油为研究对象,通过气相色谱-质谱（gas chromatography-mass spectrometry,GC-MS）检测比较3 种初榨橄榄油的挥发性物质组成,同时采用气相色谱-嗅闻（gas chromatography-olfactometry,GC-O）技术筛选其香气活性物质,最后结合香气活性值（odor activity value,OAV）分析各呈香组成对橄榄油香气轮廓呈现的贡献性,从而鉴定出3 种橄榄油各自的关键香气成分。结果表明：采用GC-MS在莱星、特级混合及鄂植8号初榨橄榄油中各检测出35、30 种及25 种挥发性成分,其中己醇、3-己烯-1-醇、(E)-2-己烯-1-醇和(E)-2-己烯醛的含量丰富。采用GC-O在3 种初榨橄榄油中各筛选出13、15 种和12 种香气活性成分,包含具有青草特征的C6化合物、呈现油脂香气的庚醛和(E,E)-2,4-癸二烯醛以及表现其他气味信息的香气物质。OAV分析发现3 个样品各有12、13 种及11 种关键香气成分（OAV≥1）,以1-辛烯-3-醇、芳樟醇、(E)-2-己烯醛和(E,E)-2,4-癸二烯醛为代表的OAV较高,对初榨橄榄油呈香品质具有重要作用。本研究筛选出3 种初榨橄榄油的关键香气成分,结果可为提升初榨橄榄油风味品质提供理论基础。     

Single-laboratory validation of a GC/MS method for the determination of 27 polycyclic aromatic hydrocarbons (PAHs) in oils and fats.

A protocol for the measurement of 27 polycyclic aromatic hydrocarbons (PAHs) in vegetable oils by GC/MS has undergone single-laboratory validation. PAHs were measured in three oils (olive pomace, sunflower and coconut oil). Five samples of each oil (one unfortified, and four fortified at concentrations between 2 and 50 microg kg(-1)) were analysed in replicate (four times in separate runs). Two samples (one unfortified and one fortified at 2 microg kg(-1)) of five oils (virgin olive oil, grapeseed oil, toasted sesame oil, olive margarine and palm oil) were also analysed. The validation included an assessment of measurement bias from the results of 120 measurements of a certified reference material (coconut oil BCR CRM458 certified for six PAHs). The method is capable of reliably detecting 26 out of 27 PAHs, at concentration <2 microg kg(-1) which is the European Union maximum limit for benzo[a]pyrene, in vegetable oils, olive pomace oil, sunflower oil and coconut oil. Quantitative results were obtained that are fit for purpose for concentrations from <2 to 50 microg kg(-1) for 24 out of 27 PAHs in olive pomace oil, sunflower oil and coconut oil. The reliable detection of 2 microg kg(-1) of PAHs in five additional oils (virgin olive oil, grapeseed oil, toasted sesame oil, olive margarine and palm oil) has been demonstrated. The method failed to produce fit-for-purpose results for the measurement of dibenzo[a,h]pyrene, anthanthrene and cyclopenta[c,d]pyrene. The reason for the failure was the large variation in results. The likely cause was the lack of availability of (13)C isotope internal standards for these PAHs at the time of the study. The protocol has been shown to be fit-for-purpose and is suitable for formal validation by inter-laboratory collaborative study.     

基于电子鼻和气相色谱-质谱法结合相对气味活度值分析植物油对红油辣椒气味的影响

目的 为探究植物油对红油辣椒气味的影响。方法 采用电子鼻、气质联用技术(gas chromatography-mass spectrometry,GC-MS)结合正交偏最小二乘判别分析(orthogonal partial least squares discriminant analysis,OPLS-DA)和相对气味活度值(Relative Odor Activity Value,ROAV)等分析方法探究不同品种的植物油对红油辣椒气味物质的影响。结果 电子鼻检测结果结合OPLS-DA分析表明不同品种的植物油制备的红油辣椒其整体气味轮廓差异明显。GC-MS检测结果表明5种植物油制备的红油辣椒共检测到101种挥发性物质,其中醇类29种、醛类30种、烃类12种、硫醚类3种、酯类6种、酸类2种以及其他化合物19种；醇类、醛类、硫醚类是红油辣椒的主要挥发性物质。ROAV分析表明A样品(精炼菜籽油)的关键性化合物是：苯乙醛、反-2-壬醛、二甲基硫醚；B样品(大豆油)的关键性化合物是：1-庚烯-3-酮、二甲基硫醚；C(花生油)、E(菜籽油)样品的关键性化合物是：二甲基硫醚; D(玉米油)样品的关键性化合物是：二甲基硫醚、(Z)-2-壬烯醛、1-辛烯-3-酮。结论 不同品种的植物油制备的红油辣椒的主要挥发性物质有一定差,二甲基硫醚是红油辣椒的共有关键性化合物。     

Phenolic characterization and geographical classification of commercial Arbequina extra-virgin olive oils produced in southern Catalonia

The aim of this work was to characterize Arbequina extra-virgin olive oils (EVOOs) from different locations in southern Catalonia (Spain) in terms of their phenolic profile, to show the classification of oil samples with respect to geographical area. The phenolic compounds present in 32 olive-oil samples were analyzed by a rapid and effective HPLC–ESI-TOF/MS method, and 18 phenolic compounds belonging to different phenolic types were identified. The results showed no qualitative differences in the phenolic fractions among EVOO from different geographical region. However, quantitative differences were observed in a wide number of phenolic compounds. In all olive-oil samples studied, secoiridoids were the most abundant, followed by lignans, phenolic alcohols, and flavonoids, respectively. Multivariate data were analysed by canonical discriminant analyses. Seventeen variables were used without a variable reduction step. Phenolic content of extra-virgin olive oils was found to depend highly on geographical area.