Geographical authentication of virgin olive oil by GC-MS sesquiterpene hydrocarbon fingerprint: Verifying EU and single country label-declaration.

According to the last report from the European Union (EU) Food Fraud Network, olive oil tops the list of the most notified products. Current EU regulation states geographical origin as mandatory for virgin olive oils, even though an official analytical method is still lacking. Verifying the compliance of label-declared EU oils should be addressed with the highest priority level. Hence, the present work tackles this issue by developing a classification model (PLS-DA) based on the sesquiterpene hydrocarbon fingerprint of 400 samples obtained by HS-SPME-GC-MS to discriminate between EU and non-EU olive oils, obtaining an 89.6% of correct classification for the external validation (three iterations), with a sensitivity of 0.81 and a specificity of 0.95. Subsequently, multi-class discrimination models for EU and non-EU countries were developed and externally validated (with three different validation sets) with successful results (average of 92.2% of correct classification for EU and 96.0% for non-EU countries).

Functional and sensory properties of phenolic compounds from unripe grapes in vegetable food prototypes.

Unripe grapes (UGs) from thinning are an unexploited source of phenols useful as functional ingredient. However, phenols may negative affect sensory quality of food. Chemical and sensory properties of UG phenols in plant-based foods were not investigated before. With this aim, an extract from UGs, obtained by a green extraction technique, was used to fortify three plant-based food models: carbohydrates/acidic pH/sweet - beetroot purée, proteins/neutral pH/sweet - pea purée and starch/neutral pH - potato purée. Functional and sensory properties of phenol-enriched foods varied as a function of their composition and original taste. The amount of UG phenols recovered from potato purée was higher than that recovered from beetroot and pea purée, while the antioxidant activity detected in beetroot purée was higher than that in potato and pea purée. Significant variations of sourness, saltiness, bitterness and astringency were induced by UG phenols added to food models. Beetroot purée resulted more appropriate to counteract the negative sensations induced by UG phenols.

Bioactive Compounds and Stability of a Typical Italian Bakery Products "Taralli" Enriched with Fermented Olive Paste.

Olive paste (OP) is a novel by-product of olive mill industry composed of water, olive pulp, and skin. Due to its richness in bioactive compounds, OP exploitation for human consumption has recently been proposed. Starter driven fermented OP is characterized by a well-balanced lipid profile, rich in mono and polyunsaturated fatty acids, and a very good oxidative stability due to the high concentration of fat-soluble antioxidants. These characteristics make OP particularly suitable as a functional ingredient for food/feed industry, as well as for the formulation of nutraceutical products. New types of taralli were produced by adding 20% of fermented OP from black olives (cv Cellina di Nardò and Leccino) to the dough. The levels of bioactive compounds (polyphenols, triterpenic acids, tocochromanols, and carotenoids), as well as the fatty acid profile, were monitored during 180 days of storage and compared with control taralli produced with the same flour without OP supplementation. Taralli enriched with fermented OP showed significantly higher levels of bioactive compounds than conventional ones. Furthermore, enriched taralli maintained a low amount of saturated fatty acids and high levels of polyphenols, triterpenic acids, tocochromanols, and carotenoids, compared to the initial value, up to about 90 days in the usual conditions of retailer shelves.

Hazelnut as Ingredient in Dairy Sheep Diet: Effect on Sensory and Volatile Profile of Cheese.

The opportunity of replacing expensive feedstuffs with agro-industrial by-products in the diet of food producing animals is raising increasing interest while addressing global concern for the scarcity of natural resources and environmental impact of livestock farming. Hazelnut peels, rich in fiber and vitamins and characterized by a high concentration of fats, is considered a suitable ingredient to be included in the diet of ruminants. The aim of this research was to assess the effect of dietary hazelnut peels on the chemical and sensory properties of sheep cheese during refrigerated storage. To this purpose, 20 Comisana lactating ewes were randomly assigned to two experimental groups, control (C) and hazelnut peels (HP), balanced for parity, milk yield and body weight. Bulk milk collected from the 2 groups was used to produce 5 Pecorino cheeses for each group. After 40 d of aging, each cheese of each experimental group was divided into 3 pieces: 1 piece was sampled for analyses (C0, HP0) and 2 were wrapped in PVC film, simulating the condition of pre-wrapped products, and analyzed after 7 (C7, HP7) and 14 days of storage (C14, HP14) at 8°C with 80% moisture. The cheeses were analyzed for chemical and fatty acid composition, sensory analysis, odor active compounds and SmartNose. As expected, HP cheeses presented a higher lipid content compared to C, a lower content in SFA and PUFA, and a greater content in MUFA. A triangle test revealed a clear distinction between the 2 groups (α = 0.01) The sensory profile showed a significant effect on holes (P < 0.05) and a marginal production of off-flavors linked to spicy and acid attributes for HP cheeses The volatile profile of C and HP cheese samples showed a good similarity, partially explained by the short ripening time and the absence of 2-nonanone in HP7, suggesting a higher antioxidant protection grade of this cheese compared to the others. These results were confirmed by Smart Nose analysis. Further studies on vitamin content should be conducted in order to investigate the interactions between the presence of antioxidant volatile compounds and the oxidative stability of ewe cheese.

A quanti-qualitative study of a phenolic extract as a natural antioxidant in the frying processes.

The aim of this work was to evaluate the effects of a phenolic extract from olive mill waste water on the stabilization of refined olive oil and on French fry quality during the frying process. Frozen, pre-fried potatoes were fried at 180 °C for 8 min in refined olive oil enriched by different concentrations of a phenolic extract, while oil enriched by a common synthetic antioxidant (butylated hydroxytoluene) was used for comparison. The whole frying process took six hours. The phenolic extract has revealed as a very promising oil stabilizing agent during frying, playing an important role (dose-dependent) in preserving the antioxidants both in oil and in food, in reducing the formation of unwanted compounds (acrolein and hexanal), and in contrasting the acrylamide production. These results clearly show that the phenolic extract can be used as a source of natural antioxidants to replace (or avoid) synthetic additives in foods or beverages.

Genotoxicity of heterocyclic amines (HCAs) on freshly isolated human peripheral blood mononuclear cells (PBMC) and prevention by phenolic extracts derived from olive, olive oil and olive leaves.

In this study we investigated the genotoxic potential of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, (PhIP); 2-amino-3-methyl-3H-imidazo[4,5-f]quinoline, (IQ); 2-amino-3,8-dimethyl-imidazo[4,5-f]quinoxaline, (MeIQx) and 2-amino-3,4,8-trimethyl-3H-imidazo[4,5-f]quinoxaline (DiMeIQx) on human freshly isolated peripheral blood mononuclear cells (PBMC) by the comet assay. The preventive ability of three different phenolic extracts derived from olive (O-PE), virgin olive oil (OO-PE) and olive leaf (OL-PE) on PhIP induced DNA damage was also investigated. PhIP and IQ induced a significant DNA damage at the lowest concentration tested (100 µM), while the genotoxic effect of MeIQx and DiMeIQx become apparent only in the presence of DNA repair inhibitors Cytosine b-D-arabinofuranoside and Hydroxyurea (AraC/HU). The inclusion of metabolic activation (S9-mix) in the culture medium increased the genotoxicity of all HCAs tested. All three phenolic extracts showed an evident DNA damage preventive activity in a very low concentration range (0.1-1.0 µM of phenols) which could be easily reached in human tissues "in vivo" under a regular intake of virgin olive oil. These data further support the observation that consumption of olive and virgin olive oil may prevent the initiation step of carcinogenesis. The leaf waste could be an economic and simple source of phenolic compounds to be used as food additives or supplements.

Biofortification (Se): Does it increase the content of phenolic compounds in virgin olive oil (VOO)?

Extra-Virgin Olive Oil (EVOO) is a fundamental component of the Mediterranean diet and it may contain several anti-oxidant substances, such as phenols. Previous research has shown that this food may be enriched in phenols by spraying a sodium-selenate solution (100 mg L-1 Se) onto the crop canopy before flowering. The aim of this research was to evaluate the effect of this Se-fertilization before flowering (cv. Leccino) on the phenolic profile of EVOOs, and test to what extent such effects depend on the weather pattern, as observed in two contrasting experimental seasons (2013 and 2014). Results showed that Se-fertilisation enriched EVOOs both in selenium (up to 120 µg kg-1) and in phenols (up to 401 mg kg-1). This latter enrichment was related to an increase in PAL (L-Phenylalanine Ammonia-Lyase) activities and it was largely independent on the climatic pattern. Considering the phenolic profile, oleacein, ligustroside, aglycone and oleocanthal were the most affected compounds and were increased by 57, 50 and 32%, respectively. All these compounds, especially oleacein, have been shown to exert a relevant anti-oxidant activity, contributing both to the shelf-life of EVOOs and to positive effects on human health. It is suggested that Se-fertilisation of olive trees before flowering may be an interesting practice, particularly with poor cultivars and cold and rainy weather patterns, which would normally lead to the production of EVOOs with unfavourable phenolic profile.

Irrigation and fruit canopy position modify oil quality of olive trees (cv. Frantoio).

BACKGROUND: Fruit development and oil quality in Olea europaea L. are strongly influenced by both light and water availability. In the present study, the simultaneous effects of light environment and irrigation on fruit characteristics and oil quality were studied in a high-density orchard over two consecutive years. Olive fruits were harvested from three canopy positions (intercepting approximately 64%, 42% and 30% of above canopy radiation) of fully-productive trees subjected to full, deficit or complementary irrigation. RESULTS: Fruits receiving 61-67% of above canopy radiation showed the highest fruit weight, mesocarp oil content and maturation index, whereas those intercepting only 27-33% showed the lowest values. Palmitoleic and linoleic acids increased in oils obtained from fruits exposed to high light levels, whereas oleic acid and the oleic-linoleic acid ratio decreased. Neither canopy position, nor irrigation affected K232 , K270 , ΔK and the concentration of lignan in virgin olive oils (VOOs). Total phenols, 3,4-DHPEA-EDA [2-(3,4-hydroxyphenyl)ethyl (3S,4E)-4-formyl-3-(2-oxoethyl)hex-4-enoate] and p-HPEA-EDA (decarboxymethyl ligstroside-aglycone) increased in VOOs produced from fruits harvested from the top of the canopy, whereas full irrigation decreased total phenols and 3,4-DHPEA-EDA concentrations with respect to the complementary irrigation treatment. CONCLUSION: Light and water availability are crucial not only for tree productivity, but also they clearly affect olive oil quality. © 2017 Society of Chemical Industry.

Oleuropein aglycone and polyphenols from olive mill waste water ameliorate cognitive deficits and neuropathology.

AIM: In TgCRND8 (Tg) mice we checked the dose-response effect of diet supplementation with oleuropein aglycone (OLE) at 12.5 or 0.5 mg kg-1 of diet. We also studied the effects of dietary intake of the mix of polyphenols present in olive mill waste water administered at a total dose as high as the highest dose of OLE (50 mg kg-1 of diet) previously investigated. METHODS: Four month-old Tg mice were equally divided into four groups and treated for 8 weeks with a modified low fat (5.0%) AIN-76 A diet (10 g day-1  per mouse) as such, supplemented with OLE (12.5 or 0.5 mg kg-1 of diet) or with a mix of polyphenols (50 mg kg-1 of diet) found in olive mill waste water. Behavioural performance was evaluated by the step down inhibitory avoidance and object recognition tests. Neuropathology was analyzed by immunohistochemistry. RESULTS: OLE supplementation at 12.5 mg kg-1 of diet and the mix of polyphenols was found to improve significantly cognitive functions of Tg mice (P < 0.0001). Aß42 and pE-3Aß plaque area and number were significantly reduced in the cortex by OLE and in the cortex and hippocampus by the mix of polyphenols (P < 0.01, P < 0.001 and P < 0.0001). Similar autophagy induction was found in the brain cortex of differently treated mice. CONCLUSION: Our results extend previous data showing that the effects of OLE on behavioural performance and neuropathology are dose-dependent and not closely related to OLE by itself. In fact, diet supplementation with the same dose of a mix of polyphenols found in olive mill waste water resulted in comparable neuroprotection.

Oleuropein Prevents Azoxymethane-Induced Colon Crypt Dysplasia and Leukocytes DNA Damage in A/J Mice.

Previous studies have shown that the precursor of olive oil secoiridoids, Oleuropein (OL) has several in vitro chemopreventive properties. OL inhibits proliferation and induces apoptosis in breast, thyroid, prostate, and colorectal cancer (CRC) cells. Much less is known about the effects of OL on animal models of carcinogenesis. In this study, we investigated the ability of OL to prevent the azoxymethane (AOM)-induced colon cancer upset and DNA damage in mice. Animals, fed with a basal diet either enriched or not with OL (125 mg/kg), were injected with AOM (10 mg/kg, once a week for 6 weeks) and sacrificed after either 7 weeks for histological analysis of colon crypt dysplasia and evaluation of DNA damage in leukocytes or 17 weeks for counting the macroscopically observable colon tumors. An OL-enriched diet prevented the AOM-induced preneoplastic lesions in different colon segments, reducing the severity of crypt dysplasia and DNA damage in peripheral leukocytes. In addition, OL significantly reduced the AOM-induced tumor incidence from 57% to 14% (P < .05, chi-square test) in the medial colon segment. This study shows that OL is able to prevent CRC and DNA damage in mice treated with the carcinogen AOM. These results stimulate further human cancer prevention studies with OL-enriched food supplements that are actually available on the market.

Effect of stoned olive pomace on rumen microbial communities and polyunsaturated fatty acid biohydrogenation: an in vitro study.

BACKGROUND: Stoned olive pomace (SOP), which represents approximately 50% of the conversion process of olives to olive oil, is largely not utilised and creates costs for its disposal and has negative environmental impacts. In vitro trial experiments were employed to study the effect of feeds integrated with this bio-waste, which is rich in polyphenols, on rumen biohydrogenation, using sheep rumen liquor as inoculum. RESULTS: Fatty acid (FA) analysis and a polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) approach aimed at characterising the microbial community indicated that including SOP in feeds at the level of 50 g/kg and 90 g/kg induced changes in the FA profile and microbial populations. The simultaneous decrease of Butyrivibrio proteoclasticus and accumulation of vaccenic acid was observed. A depression in the populations of Neisseria weaveri, Ruminobacter amylophilus and other unclassified bacteria related to members of the Lachnospiraceae and Pasteurellaceae families was detected, suggesting that these microbial groups may be involved in rumen biohydrogenation. CONCLUSIONS: Supplementation of feeds with SOP alters the rumen bacterial community, including bacteria responsible for the hydrogenation of vaccenic acid to stearic acid, thereby modifying the FA profile of the rumen liquor. Hence, a use of SOP aimed to produce meat or dairy products enriched in functional lipids can be hypothesised.

Preventive activity of olive oil phenolic compounds on alkene epoxides induced oxidative DNA damage on human peripheral blood mononuclear cells.

The aim of this study was to investigate the ability of epoxides of styrene (styrene-7,8-oxide; SO) and 1,3-butadiene (3,4-epoxy-1-butene; 1,2:3,4:-diepoxybutane) to cause oxidative stress and oxidative DNA damage on human peripheral blood mononuclear cells (PBMCs) and whether a complex mixture of olive oil phenols (OOPE) could prevent these effects. The DNA damage was measured by the single-cell gel electrophoresis (SCGE; comet assay). We found that the DNA damage induced by alkene epoxides could be prevented by N-acetyl-cysteine (10 mM) and catalase (100 U/ml). Alkene epoxides caused a significant (P < 0.05) increase of both peroxide concentration in extra- and intracellular environment and formamidopyrimidine DNA glycosylase (FPG)- and Endonuclease III (ENDO III)-sensitive sites in PBMCs, demonstrating the presence of oxidized bases. OOPE (1 µg of total phenols/ml) was able to prevent the alkene epoxide induced DNA damage both after 2 and 24 h of incubation. In addition, OOPE completely inhibited the SO-induced intracellular peroxide accumulation in PBMCs and prevented the oxidative DNA damage induced by SO, as evidenced by the disappearance of both FPG- and ENDO III-sensitive sites. This is the first study demonstrating the ability of OOPE to prevent the DNA damage induced by alkene epoxides providing additional information about the chemopreventive properties of olive oil.

Virgin olive oil phenolics extract inhibit invasion of HT115 human colon cancer cells in vitro and in vivo.

The decreased cancer risk associated with consumption of olive oil may be due to the presence of phenolics which can modulate pathways including apoptosis and invasion that are relevant to carcinogenesis. We have previously shown that a virgin olive oil phenolics extract (OVP) inhibited invasion of HT115 colon cancer cells in vitro. In the current study we assessed the in vitro effects of OVP (25 µg mL(-1)) on HT115 cell migration, spreading and integrin expression. Furthermore, the anti-metastatic activity of OVP - at a dose equivalent to 25 mg per kg per day for 2, 8 or 10 weeks - was assessed in a Severe Combined ImmunoDeficiency (SCID) Balb-c mouse model. After 24 h OVP did not inhibit cell migration but significantly reduced cell spreading on fibronectin (65% of control; p < 0.05) and expression of a range of α and ß integrins was modulated. In vivo, OVP by gavage significantly (p < 0.05) decreased not only tumour volume but also the number of metastases in SCID Balb-c mice. Collectively, the data suggest that - possibly through modulation of integrin expression - OVP decreases invasion in vitro and also inhibits metastasis in vivo.

Optimization of the temperature and oxygen concentration conditions in the malaxation during the oil mechanical extraction process of four Italian olive cultivars.

Response surface modeling (RSM) was used to optimize temperature and oxygen concentration during malaxation for obtaining high quality extra virgin olive oils (EVOOs). With this aim, those chemical variables closely related to EVOO quality, such as the phenolic and the volatile compounds, have been previously analyzed and selected. It is widely known that the presence of these substances in EVOOs is highly dependent on genetic, agronomic, and technological aspects. Based on these data, the two parameters were optimized during malaxation of olive pastes of four important Italian cultivars using some phenols and volatile compounds as markers; the optimal temperatures and oxygen levels, obtained by RSM, were as follows for each cultivar: 33.5 °C and 54 kPa of oxygen (Peranzana), 32 °C and 21.3 kPa (Ogliarola), 25 °C and 21.3 kPa (Coratina), and 33 °C and 21.3 kPa (Itrana). These results indicate the necessity to optimize these malaxing parameters for other olive cultivars.

Flash thermal conditioning of olive pastes during the olive oil mechanical extraction process: impact on the structural modifications of pastes and oil quality.

The quality of virgin olive oil (VOO) is strictly related to the concentrations of phenolic and volatile compounds, which are strongly affected by the operative conditions of the VOO mechanical extraction process. The aim of this work is to study the impact of a new technology such as flash thermal conditioning (FTC) on olive paste structural modification and on VOO quality. The evaluation of olive paste structure modification by cryo-scanning electron microscopy (cryo-SEM) showed that the application of FTC after crushing produces significant differences in terms of the breaking of the parenchyma cells and aggregation of oil droplets in comparison to the crushed pastes. The virgin olive oil flash thermal conditioning (VOO-FTC) featured a higher concentration of volatile compounds compared to that in the control, particularly of all saturated and unsaturated aldehydes and esters, whereas the phenolic concentration was higher in VOO obtained from the traditional process (VOO-C).

Effect of olive oil phenols on the production of inflammatory mediators in freshly isolated human monocytes.

Recent in vitro and in vivo studies suggest that the anti-inflammatory properties of extra virgin olive oil may be involved in the prevention of chronic degenerative diseases. In this study, the ability of olive oil phenols to influence the release of superoxide anions (O2-), prostaglandin E2 (PGE2) and tumor necrosis factor α (TNFα) and the expression of cyclooxygenase2 (COX2) in human monocytes, freshly isolated from healthy donors, was investigated. O2- were measured by superoxide dismutase-inhibitable cytochrome c reduction and PGE2 and TNFα production were determined in culture medium with appropriate enzyme immunoassay kits. COX2 mRNA and protein were evaluated by quantitative reverse transcription-polymerase chain reaction and Western immunoblotting, respectively. Treatment of monocytes for 24 h with 100 µM of hydroxytyrosol (3,4-DHPEA), tyrosol (p-HPEA) and their secoiridoid derivatives (3,4-DHPEA and p-HPEA linked to the dialdehydic form of elenolic acid: 3,4-DHPEA-EDA and p-HPEA-EDA, respectively) significantly (P<.05) inhibited the production of O2(-) as follows: 3,4-DHPEA (40%,), p-HPEA (9%), 3,4-DHPEA-EDA (25%) and p-HPEA-EDA (36%). Hydroxytyrosol also considerably reduced the expression of COX2 at both the mRNA and protein level (P<.05) and caused a clear dose-dependent reduction of PGE2 released into the culture medium (45% and 71% at 50 and 100 µM, respectively, P<.05). The COX2 mRNA was also efficiently inhibited by the secoiridoids. Moreover, it was shown that hydroxytyrosol increased the monocytes TNFα production. In addition to other chemopreventive properties, these results suggest that the health effects of olive oil phenols may be related to their ability to modulate the production of pro-inflammatory molecules, a property common to non-steroidal anti-inflammatory drugs.

Characterization of 3,4-DHPEA-EDA oxidation products in virgin olive oil by high performance liquid chromatography coupled with mass spectrometry.

Secoiridoid derivatives are the most important antioxidants of virgin olive oil (VOO), and their oxidation products could be used as molecular markers of VOO freshness to define the VOO autoxidation state. The aim of this research was to characterise the dialdehydic form of decarboxymethyl elenolic acid linked to hydroxytyrosol (3,4-DHPEA-EDA) oxidation products to find analytical indicators that could be used as early evaluation index of the VOO autoxidation state. 3,4-DHPEA-EDA was oxidised by enzymatic and Fenton reactions. Terpenic structure oxidation products accumulated in VOO during the autoxidation process, thus they may be used as early evaluation index of the VOO autoxidation state before fatty acids oxidation.

The influence of the malaxation temperature on the activity of polyphenoloxidase and peroxidase and on the phenolic composition of virgin olive oil.

The effect of the malaxation temperature under sealed conditions on the qualitative and quantitative composition of the phenolic compounds in virgin olive oils produced from four Italian cultivars was assessed for two atmospheric conditions. In both cases, the results show a positive relationship between temperature and the concentration of the derivatives of the secoiridoid aglycones; the effect of the temperature on the oxidoreductases that promote oxidation (polyphenoloxidase and peroxidase) was investigated to determine their optimal temperatures and thermal stability. While olive peroxidase (POD) showed the highest activity at 37°C and high stability in the temperature range tested, polyphenoloxidase (PPO) exhibited the optimum activity at approximately 50°C, but showed low stability at 40°C, with a large variation in stability according to the olive cultivar. These results may contribute to an understanding of the increase in the phenol concentration found in virgin olive oils obtained following higher temperatures of malaxation.

Long-term dietary extra-virgin olive oil rich in polyphenols reverses age-related dysfunctions in motor coordination and contextual memory in mice: role of oxidative stress.

The aim of this study was to evaluate the effects of olive oil phenols on brain aging in mice and to verify whether the antioxidant and antiinflammatory activities of these polyphenols were involved. C57Bl/6J mice were fed from middle age to senescence with extra-virgin olive oil (10% wt/wt dry diet) rich in phenols (total polyphenol dose/day, 6 mg/kg). Behavioral tests were employed to assess cognitive, motor, and emotional behavior after 6 or 12 months of treatment. Parameters of oxidative status and inflammation were measured in different brain areas at the same times and evaluated for correlation with behavioral changes. The treatment with olive oil phenols improved contextual memory in the step-down test to levels similar to young animals and prevented the age-related impairment in motor coordination in the rotarod test. This motor effect was correlated with reduced lipid peroxidation in the cerebellum (p<0.05), whereas the memory effect did not correlate with oxidation or inflammation parameters. In conclusion, this work points out that natural polyphenols contained in extra-virgin olive oil can improve some age-related dysfunctions by differentially affecting different brain areas. Such a modulation can be obtained with an olive oil intake that is normal in the Mediterranean area, provided that the oil has a sufficiently high content of polyphenols.

Olive phenolic compounds: metabolic and transcriptional profiling during fruit development.

BACKGROUND: Olive (Olea europaea L.) fruits contain numerous secondary metabolites, primarily phenolics, terpenes and sterols, some of which are particularly interesting for their nutraceutical properties. This study will attempt to provide further insight into the profile of olive phenolic compounds during fruit development and to identify the major genetic determinants of phenolic metabolism. RESULTS: The concentration of the major phenolic compounds, such as oleuropein, demethyloleuropein, 3-4 DHPEA-EDA, ligstroside, tyrosol, hydroxytyrosol, verbascoside and lignans, were measured in the developing fruits of 12 olive cultivars. The content of these compounds varied significantly among the cultivars and decreased during fruit development and maturation, with some compounds showing specificity for certain cultivars. Thirty-five olive transcripts homologous to genes involved in the pathways of the main secondary metabolites were identified from the massive sequencing data of the olive fruit transcriptome or from cDNA-AFLP analysis. Their mRNA levels were determined using RT-qPCR analysis on fruits of high- and low-phenolic varieties (Coratina and Dolce d'Andria, respectively) during three different fruit developmental stages. A strong correlation was observed between phenolic compound concentrations and transcripts putatively involved in their biosynthesis, suggesting a transcriptional regulation of the corresponding pathways. OeDXS, OeGES, OeGE10H and OeADH, encoding putative 1-deoxy-D-xylulose-5-P synthase, geraniol synthase, geraniol 10-hydroxylase and arogenate dehydrogenase, respectively, were almost exclusively present at 45 days after flowering (DAF), suggesting that these compounds might play a key role in regulating secoiridoid accumulation during fruit development. CONCLUSIONS: Metabolic and transcriptional profiling led to the identification of some major players putatively involved in biosynthesis of secondary compounds in the olive tree. Our data represent the first step towards the functional characterisation of important genes for the determination of olive fruit quality.