Profiles of volatile compounds from some monovarietal Tunisian virgin olive oils. Comparison with French PDO

The volatile profiles of seven Tunisian and four French virgin olive oils were established by solid phase micro-extraction (SPME) and gas chromatography (GC), using flame ionisation and mass spectrometer detectors. Eighty-six compounds were identified and characterized, representing 97.4–99.9% of the total GC area. (E)-2-hexenal, the main compound extracted by SPME, characterized the olive oil headspace for approximately 90% of the oils examined. Significant differences in the proportions of volatile constituents from oils of different varieties were detected. The results demonstrated that the accumulation of the different metabolites in the oils obtained from the various cultivars was strictly connected with the varietal parameters on the basis of the enzyme differences genetically determined. This feature made possible the differentiation of the examined cultivars on the basis of the percent of each metabolite.     

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 filtration on volatile compounds and sensory profile of virgin olive oils

The influence of filtration through a hydrophilic cotton layer on volatile compounds, sensory characteristics and colour of two monovarietal oils was investigated in this study. Volatiles were evaluated using headspace solid-phase microextraction-gas chromatography. After the filtration of Bu?a oils only a slight increase in total alcohols was noticed. In filtered ?rna oils a significant decrease of total alcohols and slight changes in total aldehydes, total ketones and total C5 volatile compounds concentration were detected. No significant influence on the sensory scores of oils, but some slight changes in sensorial profiles were noted (slightly higher intensities of sensory characteristics apple and grass, and higher values of the lightness L^∗ in filtered samples). The results point to unequal filtration impact on different monovarietal oils and could be useful in developing targeted technologies for specific monovarietal oils quality improvement.     

Pigments profile in monovarietal virgin olive oils from various Italian olive varieties

This paper presents the investigation of the chlorophyll and carotenoid pigments composition in monovarietal virgin olive oils produced from the five main olive varieties (Minuta, Ottobratica, Calabrese, Ogliarola, Baddarica) cultivated in Sicily (southern Italy), from four main olive varieties (DolceAgogia, Moraiolo, Leccino, Frantoio) cultivated in Umbria (central Italy), and from three main olive varieties (Leccino, Oliva Nera di Collecorto, Noccioluta) cultivated in Molise (central Italy). Reversed-phase high performance liquid chromatography using a C-30 column with photodiode array detection was used for pigments analyses. In all, 19 compounds were identified and quantified in 60 olive oils samples. The qualitative pigments pattern was similar among the varieties investigated, whereas quantitative differences were found among the different cultivars; among the varieties investigated in this work, the oils from Umbria showed the highest pigment content (34.19 ppm in average), followed by the oils from Molise (18.61 ppm in average) and the oils from Sicily which showed the lowest pigment contents (13.38 ppm in average). In general, pheophytin a was the major component (range 0.49–19.42 ppm), followed by β-carotene (range 1.27–9.30 ppm) and lutein (range 0.44–5.12 ppm). Those differences may be due to genetic factors and/or geographical differences. Moreover, auroxanthin was detected for the first time in olive oils and was detected only in olive oils from Umbria and Molise regions. The ratio between the two isochromic pigment fractions, namely the ratio between the chlorophyll and carotenoid fractions showed an average value close to unity. The lutein/β-carotene ratio was less than one in the majority of the cases. These parameters, along with other analytical parameters, could be used as indicators of typicality in olive oils. The presence of a specific pigment profile in olive oils could infact be used to guarantee the genuineness of the product, since the quality control of food requires a precise knowledge of the pigments composition of the original products.     

Monitoring of virgin olive oil volatile compounds evolution during olive malaxation by an array of metal oxide sensors

In addition to the sanitary aspects of production and the genetic and/or geographic origin of the drupes olive malaxation is a critical control point of virgin olive oil (VOO) production from a qualitative point of view. In particular the sensory peculiarities of malaxation are determined by the presence of C₆ and C₅ aldehydes and alcohols in the VOO head space due to lipoxygenase activity. On-line monitoring of the evolution of these substances during VOO processing could be very useful for defining the operative conditions of malaxation (i.e. time and temperature) in order to improve the VOO sensory quality according to product type.     

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.     

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.     

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.     

Evaluation of a numerical method to predict the polyphenols content in monovarietal olive oils

Three monovarietal virgin olive oils obtained from olives grown under biological agricultural system, in Portugal, with different ripening stages, were studied in what concerns the parameters usually related with oxidation status (total polyphenols, tocopherols, chlorophylls and carotenoids, peroxide values, oxidative stability, specific extinction coefficients K₂₃₂ and K₂₇₀ and titratable acidity). A total of 18 samples were analyzed: seven from Cv. Cobrançosa (maturation indices 1–7), five from Cv. Madural (maturation indices 3–7) and six from Cv. Verdeal Transmontana (maturation indices 1–6). Oxidative stability and polyphenols profile presented high correlation coefficients. Given this high correlation, a numerical method was developed and evaluated to predict total polyphenols contents in olive oil. The method is based on the kinetic equation of the oxidation process in the presence of antioxidants and on Rancimat profiles. Total polyphenols contents obtained with this method were similar to those obtained by the Folin-Ciocalteau method.     

Volatile phenols in virgin olive oils: Influence of olive variety on their formation during fruits storage

The potential significance as odorants and markers of olive fruits degradation has been recently pointed out for volatile phenols in virgin olive oil (VOO) and related to the appearance of VOO sensory defects. The few studies carried out in order to elucidate the factors affecting their formation in olive fruits or VOOs, indicated that they could be considered as analytical indices of olive fruits degradation during storage, likely reflecting the microbiological activity. In the present study, the effect of the olive variety (‘Arbequina’, ‘Arbosana’ and ‘Leccino’) on the production of volatile phenols during twelve days of storage in closed plastic bags was evaluated. The different resistance of each variety to the microbiological attach was observed during olive fruit storage, and it was reflected by the evolution of guaiacol, 4-ethylphenol and 4-ethylguaiacol, and related to free acidity values. On the contrary, a scarce dependence on the microbial growth or varietal factors was observed for 4-vinyl derivatives, which appeared more directly related to the time of olives storage. The evolution of volatile phenols found certain correspondence in the sensory characteristics of the resulting VOOs, while the rest of VOO chemical quality indices did not show major variations during fruits storage.     

Volatile compounds characterising Tunisian virgin olive oils: the influence of cultivar

In this work, the volatile profiles of four Tunisian virgin olive oils were established by headspace‐solid phase microextraction and gas chromatography, using flame ionisation and mass spectrometer detectors. More than eighty compounds were isolated and characterised, representing 97–99% of the total GC area. The main volatile compounds present in the oil samples were determined quantitatively, the major constituents were often aldehydes, particularly (E)‐2‐hexenal (48–90%). Significant differences in the content of volatile constituents were observed. These quantitative differences were used to distinguish between virgin olive oils from different varieties.     

Pigments composition in monovarietal virgin olive oils from various sicilian olive varieties

This paper presents the first investigation of the chlorophyll and carotenoid pigments composition in sicilian monovarietal virgin olive oils from the three (Cerasuola, Nocellara, Biancolilla) main olive varieties cultivated in Sicily (Italy). In all, 19 compounds were identified and quantified in 24 olive oil samples. The application of reversed-phase liquid chromatography with photodiode array detection using a C-30 column in the simultaneous qualitative–quantitative analysis of virgin olive oils pigments, has been shown. The qualitative pigment pattern was similar among the varieties investigated, whereas quantitative differences were found among the different cultivars, which can all be considered as having an high pigment content. Pheophytin a, was the major component (19.36–25.04 ppm), followed by β-carotene (8.06–16.27 ppm). Pheophytin a′ (2.92–4.17 ppm), lutein (2.28–4.49 ppm) and neoxanthin (1.54–2.11 ppm) were also well represented. The presence of carotenoid esters was also detected. The neoxanthin and β-carotene contents were higher compared to reports present in the literature for other olive oil varieties. This may be due to genetic factors and/or geographical differences. The ratio between the two isochromic pigment fractions, namely the chlorophyll and the carotenoid fractions, was around one in all varieties, showing that they were in balance. The lutein/β-carotene ratio was less than one in all cases. These parameters, along with other analytical parameters, could be used as indicators of typicality in olive oils. The presence of a specific pigment profile in olive oils could in fact be used to guarantee the genuineness of the product, since the quality control of food requires a precise knowledge of the pigments composition of the original products.     

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.     

Volatile compounds of Algerian extra-virgin olive oils: Effects of cultivar and ripening stage

The distinctive extra-virgin olive oil aroma consists of a complex mixture of volatile compounds. We comparatively studied the volatiles of eight autochthonous monovarietal extra-virgin olive oils from the north-east part of Algeria via headspace solid-phase microextraction GC-MS. We determined the effect of ripening of Chemlal olive fruit on aroma compounds. Twenty volatile analytes belonging to different chemical classes were identified and quantified. Both quantitative and qualitative differences were found among cultivars, indicating a close dependence of the composition of the volatile profile on the enzymatic pool, directly related to genetic characteristics. Moreover, differences in volatiles composition were observed for Chemlal oils during maturation.

Abbreviations: AAT, alcohol acetyl transferase; E, east; EVOO, extra-virgin olive oil; GC, gas chromatography; HS, headspace; LOX, lipoxygenase; MI, maturity index; MS, mass spectrometry; N, north; PCA, principal component analysis; SD, standard deviation; SPME, solid-phase microextraction technique; VOO, virgin olive oil.     

Advance technology in virgin olive oil production from traditional and de-stoned pastes: Influence of the introduction of a heat exchanger on oil quality

An experimental investigation was carried out to evaluate the quality of virgin olive oils obtained when a de-stoner were used for the olive paste preparation in comparison to the use of a traditional stone mill. In order to improve the slightly differences of oil yields due to the use of the de-stoner also a heat exchanger has been introduced in the processing line. The experimental data showed that resistance to the oxidation, total phenols and pleasant volatile compounds were higher in the de-stoned olive oils than in the oils obtained from the whole paste. Resistance to oxidation was assessed by Rancimat method and showed a positive correlation with the amount of total phenols.     

陇南两种单品种初榨橄榄油的化学性质和脂肪酸组成随成熟度的变化

分析了陇南2个品种初榨橄榄油的化学性质和脂肪酸组成随成熟度增加的变化规律。结果表明：随着成熟度的增加2个品种的鲜果出油率增加且存在显著性差异。初榨橄榄油风味成分中氮氧化合物、含硫以及烷烃类化合物变化幅度较大,通过电子鼻可以区分不同品种不同成熟度的橄榄油。恩帕特雷和科拉蒂的k232、270值最高分别为1.85和1.91、0.18和0.14,多酚、黄酮含量变化范围分别为2.39～4.53和7.47～10.39、0.07～0.40和0.75～2.84 mg/g。氧化稳定时间在第6（6.28 h）和第5(16.71 h)成熟度为最高。酸价的变化范围分别为0.37～1.02和0.19～0.38 mg/g,过氧化值的变化范围分别为2.92～8.32和2.38～5.19 mmol /kg,油酸含量分别为72.36%～77.76%和59.23%～65.73%,亚油酸含量分别为7.70%～11.81%和9.74%～15.86%,SFA含量分别为11.81%～13.15%和14.25%～20.99%,PUFA含量分别为8.34%～12.36%和10.92%～16.84%,MUFA含量为72.69%～78.50%和62.36%～68.20 %。同一品种的MUFA/PUFA、C18:1/C18:2和MUFA含量变化趋势一致,与PUFA呈相反的变化趋势,2个品种之间各种脂肪酸含量差异明显,上述测定指标完全符合GB 23347—2009中特级初榨橄榄油的标准。科拉蒂的出油率、多酚、黄酮、油酸含量和氧化稳定时间明显大于恩帕特雷,而酸价、过氧化值低于后者。综合考虑认为科拉蒂的初榨橄榄油品质优于恩帕特雷,恩帕特雷和科拉蒂分别在第6和第5成熟度的初榨橄榄油品质最好。     

Composition,volatile profiles and functional properties of virgin olive oils produced by two-phase vs three-phase centrifugal decanters

The present study was designed to compare the impact of a two- vs a three-phase decanter on the quality parameters, sterols, fatty acids, terpenes, phenolic compounds and volatile compounds, as well as antiradical activity of the obtained oils. Moreover, serum lipid antioxidant capacity and anti-inflammatory potential in human mononuclear cells were tested as more biologically relevant assays than the chemical radical scavenging assays. Results show that the cold pressed olive oils obtained from both technologies were of the extra virgin quality. Peroxide values were significantly lower in two-phase decanter samples, while ω6 polyunsaturated fatty acids were higher in two- vs three-phase samples. The significantly higher phenolics content in oil produced by two- vs three-phase centrifuge was attributed to higher hydroxytyrosol, as well as to higher tyrosol, vanillin and homovanillic alcohol levels. Evaluation of the effect of centrifuge system on oils' functional properties showed a clear superiority of two-phase decanter samples as to health maintenance, as these exerted higher ferric reducing capacity, elongation of serum lipid lag time and decrease in cytokine response of stimulated human mononuclear cells, compared to those from three-phase decanter. The two-phase oil samples contained more volatile aroma compounds and more C5–C6 alcohols and aldehydes.     

Microsatellite markers to identify specific alleles in DNA extracted from monovarietal virgin olive oils

The suitability of DNA present in olive oil for PCR analysis has been reported by several authors. However, low concentration, degradation, and the possible presence of additional alleles due to paternal contribution in oils extracted from entire drupes, should be taken into consideration when comparing the amplification profiles of leaves with the corresponding oils for varietal traceability purposes. The aim of this work was to assess, by capillary electrophoresis of microsatellite markers, the phenetic relationships among seven certified Olea europaea L. cultivars, and to verify the genomic equality between leaf DNA and the corresponding monovarietal oil DNA. Moreover, the aim was to establish an identification key to distinguish all the types of oil among them with the minimum number of markers. The results referred to oil DNA, obtained in 70 PCR experiments, confirmed the possibility, in 85.7% of cases, of extracting DNA suitable for the analysis of microsatellites. Ninety percent of the successful amplifications led to identical patterns for leaves and oil DNA. Cima di Melfi shared only 20% of the alleles with the other cultivars. Toscanina and Leccino, showed the highest similarity (about 60%). A single microsatellite was able to distinguish the seven types of oil.     

Pigment profile and colour of monovarietal virgin olive oils from Arbequina cultivar obtained during two consecutive crop seasons

Monovarietal virgin olive oils are labelled with the olive varieties giving them their distinctive character. There are numerous studies focussed on the characterisation and quantification of the minor fractions of virgin olive oils that have generated databases on varietal olive oils. However, few studies have focussed on the components of the pigment fraction of virgin olive oils. The aim of this work was to quantify the components of the chlorophyll and carotenoid fractions of the monovarietal virgin olive oils from the Arbequina cultivar, growing in the Spanish area of Catalonia, during two consecutive crop seasons. Additionally the pigment changes occurring during 24 months of oil storage were evaluated. The results of this study showed minor qualitative differences between monovarietal virgin olive oils from two consecutive seasons. The quantitative differences could be attributed to the harvest period in each season rather than to the year’s weather conditions. Storage of the monovarietal virgin olive oils probably caused an important loss of the chlorophyll fraction, mainly chlorophyll a, during the first 6 months of storage. On the other hand, the carotenoid fraction was very stable and the retention of provitamin A was close to 80%, even after 24 months of storage.     

Pigment profile and chromatic parameters of monovarietal virgin olive oils from different Italian cultivars

The aim of this study was to characterise the pigment profile (chlorophylls and carotenoids) of monovarietal virgin olive oils from six Italian olive cultivars (Ghiacciolo, Giarraffa, Sant’Agatese, Biancolilla, Nocellara del Belice and Gentile di Larino), from three Italian olive-growing regions (Emilia-Romagna, Sicily and Molise). The results show that the qualitative study of the pigment chlorophyll and carotenoid fractions of virgin olive oils demonstrated a common pattern that did not depend on the olive cultivar or growing region. Besides these, mutatoxanthin was only detected in oils from the Nocellara del Belice and Gentile di Larino cultivars, and pheophorbide a was only detected in oils from the Ghiacciolo and Sant’Agatese cultivars. However, significant quantitative differences were observed in the composition of the pigment fractions. The principal component discriminate analysis showed that the first two discriminate functions of the statistical analysis explained 78.9% of the total variance. The plot of discriminate functions showed an effect of the olive cultivar and growing area on the chlorophyll and carotenoid contents of the virgin olive oils. The results of this study are a contribution to the pigment characterization of the Italian monovarietal olive oils, which should be completed with more samples obtained from different crop seasons and different growing areas.