Changes in volatile compounds and oil quality with malaxation time of Tunisian cultivars of Olea europea

While there has been considerable work examining the effect of malaxation time on different characteristics of olive oils, there have been few that deal with all the major aspects. Here, the influence of malaxation time was evaluated using major local Tunisian (cv. Chemlali and Chetoui) cultivars. Standard characteristics were measured as well as detailed analyses of volatile compounds were conducted. Headspace solid‐phase microextraction (HS‐SPME) was applied to the analysis of volatile compounds of virgin olive oils from Chemlali and Chetoui varieties with differing malaxation time. Twenty‐seven compounds were characterised by GC‐FID and GC–MS. Compounds belonging mainly to alcohols, esters, aldehydes, ketones and hydrocarbons chemical classes characterized the volatile profile. Significant differences in the proportion of volatiles from oils of different malaxation time were detected. The results suggest that besides genetic factors, malaxation time influences volatile formation. The main variables that were affected by malaxation time were the total amount of phenols and composition of the volatile compounds. At malaxation time of 30 min, Chemlali and Chetoui olive oils presented the highest total phenol content (244.19 and 877.63 mg kg^?1, respectively), while the lowest content was observed at 60 min from regardless of cultivars. In turn, this influenced the oxidative stability and peroxide value. It was also clear that the cultivars behaved differently and this prevented general conclusions being made for all of the quality characteristics.     

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.     

Cultivar and growing area effects on minor compounds of olive oil from autochthonous and European introduced cultivars in Tunisia

BACKGROUND: Antioxidant profile and volatile compounds were characterized in three virgin olive oils from European countries introduced and cultivated under the same orchard conditions in comparison to some autochthonous cultivars planted in different areas of Tunisia. RESULTS: Significant differences were observed between the oils. α‐Tocopherol content is more important in autochthonous Tunisian cultivars (cvs), higher (400 mg kg^?1) than in European cvs. Total phenols showed that Chétoui cv. (grown in Zaghouan) had the highest level (446 mg kg^?1), followed by Koroneiki (403 mg kg^?1) and Chétoui cvs (grown in Béja) (398 mg kg^?1). Koroneiki oils had the highest content of (3,4‐dihydroxyphenyl)ethanol and (p‐hydroxyphenyl)ethanol (20.5 and 43.5 mg kg^?1, respectively), whereas (3,4‐dihydroxyphenyl)ethanol was not detected in Arbequina, Arbosana or Chemlali cvs (grown in Sahel). Chétoui cv. presented the highest content of dialdehydic form of decarboxymethyl elenolic acid linked to (3,4‐dihydroxyphenyl)ethanol (171 mg kg^?1), whereas Chemlali (Sahel) cv. had the lowest content (29.6 mg kg^?1). The volatile compounds showed an increase in C6 compounds and decrease in pentene isomers in olive oils from varieties cultivated in other growing areas. CONCLUSION: Virgin olive oils studied demonstrate that the differences in phenols, tocopherol levels and volatile profiles may be explained by genetic factors and geographic areas, particularly altitude. Copyright © 2009 Society of Chemical Industry     

High performance size-exclusion chromatography analysis of polar compounds applied to refined, mild deodorized, extra virgin olive oils and their blends: An approach to their differentiation

An investigation was carried out to evaluate the use of High Performance Size-Exclusion Chromatography (HPSEC) of polar compounds of refined, mild deodorized, extra virgin olive oils as well as of their blends, in attempting to reveal significant differences in the amounts of the substance classes constituting polar compounds among these oils. Two sets of blends were prepared by mixing an extra virgin olive oil with both refined and mild deodorized olive oils in increasing amounts. The obtained data highlighted that the triacylglycerol oligopolymers were absent or present in traces in the extra virgin olive oil, while their mean amount was equal to 0.04 g/100 g and 0.72 g/100 g in mild deodorized and refined olive oils, respectively. Oxidized triacylglycerols and diacylglycerols were more abundant in mild deodorized oil and refined oil than in extra virgin olive oil. The Factorial Discriminant Analysis of the data showed that the HPSEC analysis could reveal the presence of refined/mild deodorized oils in extra virgin olive oils. In particular, the classification functions obtained allowed designation of mixtures containing at least 30 g/100 g of mild deodorized oil and all those containing refined olive oil as deodorized oil, therefore as oils subjected to at least a mild refining treatment.     

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.     

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.     

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     

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.     

Sensory and chemical evaluation of winey-vinegary defect in virgin olive oils

Winey-vinegary sensory defect was evaluated in virgin olive oil samples from a sensory and chemical point of view. Qualitative and quantitative differences were found in the profile of volatiles of extra-virgin olive oil samples without sensory defects and samples with high intensities of winey-vinegary sensory attribute. Several volatile compounds were found to be correlated to winey-vinegary sensory defect in virgin olive oils, acetic acid and ethyl acetate having correlation coefficients of 0.98 and 0.94 respectively. A synthetic sample was obtained with the sensory characteristics of the winey defect. Samples with low values of winey sensory defect were also studied and the evaluation of the presence of the defect using the content of four volatile compounds only was demonstrated. Received: 5 August 1999 / Revised version: 22 October 1999     

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.     

Micro-encapsulation of refined olive oil: influence of capsule wall components and the addition of antioxidant additives on the shelf life and chemical alteration

BACKGROUND: Although refined olive oils (ROOs) exhibit lower quality and less stability toward thermal stress than extra‐virgin olive oils, these types of oil are gaining importance in the food industry. The inclusion of ROOs in processed food may alter the oxidative stability of the manufactured products, and therefore having technological alternatives to increase oil stability will be an important achievement. For this reason the main goal of this study was to assess the influence of the micro‐encapsulation process on the ROO chemical composition and its oxidative stability. Factors such as microcapsule wall constituents and the addition of the antioxidant butyl hydroxytoluene were investigated in order to establish the most appropriate conditions to ensure no alteration of the refined olive oil chemical characteristics. RESULTS: The optimised methodology exhibited high encapsulation yield (>98%), with micro‐encapsulation efficiency ranging from 35 to 69% according to the nature of the wall components. The encapsulation process slightly altered the chemical composition of the olive oil and protected the oxidative stability for at least 11 months when protein components were included as wall components. CONCLUSION: It was concluded that the presence of proteins constituents in the microcapsule wall material extended the shelf life of the micro‐encapsulated olive oil regardless the use of antioxidant additives. Copyright © 2012 Society of Chemical Industry     

Aroma compounds and sensory characteristics as biomarkers of quality of differently processed Tunisian virgin olive oils

The influence of the extraction system (continuous vs. discontinuous) and the degree of freshness of olives on the chemical composition and the quality of Chemlali and Chétoui virgin olive oil has been studied. Analytical data mainly concerning the volatile and sensory profiles revealed statistically significant differences in relation to the extraction system. All quality indices and sensory characteristics showed statistically significant differences associated with the degree of freshness of fruits. These results further confirm the general consensus that volatile compounds can be very useful as biomarkers of the quality of virgin olive oil and show correlations with the sensory characteristics.     

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.     

Contribution of olive seed to the phenolic profile and related quality parameters of virgin olive oil

BACKGROUND: Conflicting results have been reported about the effect of fruit de‐stoning on the virgin olive oil (VOO) phenolic profile. The aim of the present study was to determine whether olive seed plays any role in the synthesis of this oil phenolic fraction. RESULTS: Increases of around 25% of total phenolic compounds were observed in oils obtained from de‐stoned olive fruits in three main Spanish cultivars. To investigate the involvement of olive seed in determining the phenolic profile of VOO, whole intact olive fruits were added with up to 400% olive stones. Excellent regression coefficients were found in general for the decrease of total phenolic compounds and, particularly, of o‐diphenolics in the resulting oils. On the other hand, it was found that olive seed contains a high level of peroxidase (POX) activity (72.4 U g^?1 FW), accounting for more than 98% of total POX activity in the whole fruit. This activity is able to modify VOO phenolics in vitro, similar to the effect of adding stones during VOO extraction. CONCLUSION: Olive seed plays an important role in determining VOO phenolic profile during the process to obtain an oil that seems to be associated with a high level of POX activity. Copyright © 2007 Society of Chemical Industry     

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。     

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.     

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.     

Use of capillary electrophoresis with UV detection to compare the phenolic profiles of extra‐virgin olive oils belonging to Spanish and Italian PDOs and their relation to sensorial properties

BACKGROUND: There is much interest in foods that belong to Protected Designations of Origin (PDO) because the quality and other essential and exclusive characteristics are guaranteed because of a particular geographical environment. We have used a capillary electrophoretic method for the simple, rapid and simultaneous characterization and quantification of the polyphenolic fraction of extra‐virgin olive oil from different PDOs (18 compounds in less than 7 min). To demonstrate the usefulness of this method, we have analyzed 16 samples of a Spanish PDO and nine other samples belonging to an Italian PDO (n = 5). RESULTS: In this way, it was possible to compare the phenolic profiles of the oils of different zones of the same PDO, as well as the phenolic profiles of Spanish and Italian extra‐virgin olive oils. Univariate statistics were used for differentiating the oils produced in each PDO. Furthermore, the correlations among several of the phenolic compounds present in the extracts of olive oil and its sensorial properties were checked. decarboxylated oleuropein aglycon (DOA) (b) (peak 6) was the compound more related to the bitterness of the oils, Ac Pin (peak number 4) and the unidentified peak with t_mig 4.025 min played an important role in the pungent taste of the oils, and these two latter compounds and the peak 13 seemed to be related to the fruitiness of the oils. CONCLUSIONS: The electrophoretic method described in the current work has the ability to detect and quantify simultaneously 18 phenolic compounds (belonging to five different families) in less than 7 min. This technique could improve the characterization of this polar fraction and determine the geographical origin of olive oils or detect possible ‘PDO markers’. In fact, capillary electrophoresis coupled to statistical analysis enabled discrimination among olive oils belonging to two different PDOs considering eight phenolic compounds present in the extracts, and also identification of the phenolic compounds which could have more influence on several sensory attributes such as bitterness, pungency and fruitiness. Copyright © 2009 Society of Chemical Industry     

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.     

Characteristics of olive fruits and extra‐virgin olive oils obtained from olive trees growing in Appellation of Controlled Origin ‘Sierra Mágina’

Olives and olive oils from Appellation of Controlled Origin (ACO) ‘Sierra Mágina’ have been analysed during the 1997/98 harvest. The territory of this ACO has been subdivided into four zones of different characteristics. The olives were harvested on two occasions (November 1997 and January 1998). Various parameters were analysed, such as the ripening index, the average volume, the average weight of 100 olives and 100 stones, the pulp/stone ratio, the industrial yield, etc. From these olives, olive oils were extracted using an Abencor system, and the free acidity, the peroxide index, the coefficients K₂₇₀ and K₂₃₂ and the fatty acid composition were determined. The analysis of the results obtained, as well as principal component analysis, demonstrates a marked variability in the fruits, but the corresponding olive oils show fairly homogeneous compositions that are difficult to distinguish by sensory analysis. The olive oils from this ACO are extra‐virgin olive oils characterised by low acidity, a high content of oleic acid and a high ratio of unsaturated to saturated fatty acids. The most important sensory attributes are fruity, woody‐fig, green, bitter and pungent. Copyright © 2003 Society of Chemical Industry