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Olive oil is the product obtained from the olive fruit. Several grades can be obtained, extra virgin olive oil being the top category. The balanced fatty acid composition of olive oil, particularly its high content of oleic acid, makes this product nutritionally important. In addition, virgin olive oil contains bioactive compounds such as unsaponifiable constituents and phenolic compounds. Polar phenols and volatile compounds are two of the most interesting classes of compounds in olive oil. The scientifically proven beneficial health effects related to VOO consumption and the unique sensory properties of this product make it versatile for several culinary uses. This chapter reviews olive oil composition, focusing on the flavour-active compounds and their changes due to the variety, environmental conditions, processing and technological factors. The culinary uses of olive oils are then presented, with emphasis on traditional uses, possible food pairing and innovative applications including substitution of other fats and molecular gastronomy.

Virgin olive oil is a high quality natural product obtained only by physical means. In addition to triacylglycerols it contains nutritionally important polar and non-polar antioxidant phenols and other bioactive ingredients. The polar fraction is a complex mixture of phenolic acids, simple phenols, derivatives of the glycosides oleuropein and ligstroside, lignans, and flavonoids. These compounds contribute significantly to the stability, flavor, and biological value of virgin olive. In the various stages of production, during storage and in the culinary uses, polar phenols and other valuable bioactive ingredients may be damaged. Oxidation, photo-oxidation, enzymic hydrolysis and heating at frying temperatures have a serious adverse effect. Due to the biological importance of the oil and its unique character, analytical methods have been developed to evaluate antioxidant activity or analyse complex phenol mixtures. These are based on radical scavenging assays and chromatographic techniques. Hyphenated methods are also used including liquid chromatography-mass spectrometry and liquid chromatography-nuclear magnetic resonance spectroscopy.

Publisher Summary Table olives have more or less the same health properties as olive oil, but this has been overlooked because, with the exception of Mediterranean countries, this product was seen as a piece of decoration for pizzas and breads. They are a highly functional food with a balanced content of fats made up mainly of monounsaturated oleic acid. They contain fiber, vitamins, minerals, phytosterols, triterpenic acids, and squalene and contribute to the daily intake of nutritional antioxidants, mainly phenols, such as verbascoside, hydroxytyrosol, tyrosol, luteolin, and apigenin 7-O-glycosides, as well as phenolic acids. Raw olives are bitter and not fit for consumption due to the high levels of bitter secoiridoids, mainly oleuropein. Oleuropein can be removed by natural methods, alkali treatment, drying, or salt curing. Profiles of phenolic compounds in the end products and, consequently, the nutritional value are influenced by the olive cultivar, the pre- and postharvest factors, the debittering methods, and the processing style. Olives' ripening stage strongly influences changes in phenolic content and the profile of bioactive phenols. During olive ripening, the concentration of total phenols usually increases progressively to a maximum level at the green-skin stage, decreasing sharply as ripening progresses. The harvesting method is also important for table olive quality. Numerous table olive processing methods are available. Each process is suitable for a particular olive variety and degree of ripeness and the processes may vary according to tradition and other cultural factors. Whatever the method used, a significant loss in phenols occurs during the various processing steps. The potential use of enzymes instead of traditional lye treatment can result in products richer in polyphenols.

Filtration of veiled virgin olive oil samples indicated a loss in stability that was assigned to a loss in total polyphenol content. Oil samples, after filtration, had quite similar peroxide values and absorbance in the UV region to the respective veiled ones. Nine months storage of veiled and filtered oils at ambient temperature, in the dark, revealed that gradual loss in stability, expressed as OSI values, was greater in the latter. This finding was reflected by the greater increase in peroxide values and also faster decrease in total polar phenol content in filtered samples. The RP-HPLC analysis of the phenolic fractions, at various stages of storage, indicated interesting differences in the evolution of individual phenols between the two types of samples. It is suggested that, not only the higher content, but also the forms of individual phenols liberated in veiled oils, due to hydrolytic processes, may be responsible for the unexpected high oxidative stability of this promising commercial category of virgin olive oil.

An olive oil – lemon juice Greek salad dressing was developed employing xanthan gum as stabilizer and gum arabic or propylene glycol alginate as emulsifier in various combinations. In general, samples containing xanthan gum arabic were more stable against oil droplet coalescence and less stable against creaming. The use of propylene glycol alginate in the place of gum arabic, on the other hand, resulted in emulsions of higher creaming stability. Application of steady shear rheology and determination of rheological parameter values from the shearing stress-rate of shear curves, indicated that the rheological properties of the dressings were decreased with storage. Dressing texture assessment preference tests indicated that potential consumers of the product may opt for a medium viscosity product and this has to be taken into consideration when designing polysaccharide – stabilized dressings exhibiting a decrease in their textural characteristics with storage time.

The overall quality of virgin olive oil (VOO) is closely related to its oxidative stability that is usually evaluated through the stability index measured by the Rancimat apparatus. Quality characteristics and also pro-oxidant and antioxidant content for 52 Greek VOO samples (Koroneiki cv) were used to build up a model capable of predicting stability. Collinearity diagnostics, variable selection, and regression analysis were applied to the experimental data to locate the contribution of each parameter to the keeping quality of the samples. The predictive ability of the model was confirmed for a second VOO sample set of the same cultivar. It was found that except for the peroxide value, which negatively influences the stability, other important parameters were α-tocopherol, total polar phenol and total chlorophyll content. It is concluded that the colorimetric determination of total polar phenols, the spectrometric determination of total chlorophylls and the high-performance liquid chromatography analysis of α-tocopherol, not presently included in the established methods of official analysis, can be used for a better evaluation of VOO quality. These parameters, which can be easily adopted as routine methods by the industry, seem to be of utmost importance for shelf life prediction and expiration dating if applied for the promotion of the most competitive products in the international olive oil market.

Intramolecular hydrogen bonds in crystals and in apolar media are well documented, however, the degree to which they persist in aqueous solution is controversial. We report here variable temperature gradient 1 H, 1 H– 13 C Gradient Enhanced Heteronuclear Single Quantum Correlation (GE-HSQC) and Gradient Enhanced Heteronuclear Multiple Bond Coherence (GE-HMBC) NMR studies of the flavonols quercetin and kaempferol and the flavone luteolin, in organic solvents and in mixtures of organic–aqueous solutions. It is demonstrated that the strong intramolecular hydrogen bond of the –CO(4) and –OH(5) moieties persists over a wide range of aqueous mixtures and, thus, provide a rare example of non-charged intramolecular hydrogen bonds, which is not overwhelmed by solvation with protic solvents, in particular in aqueous solution.

A large number of virgin olive oil samples obtained from different areas in Greece were analyzed for various quality parameters. The work focuses on the colorimetric determination of total phenols with the Folin-Ciocalteu reagent and its importance in predicting shelf life of virgin olive oil. The results indicate a good correlation of total polar phenol content with the stability of the oil. Colorimetric determination of ortho-diphenol content does not seem to be a better means for predicting virgin olive oil stability. RP-HPLC quantification of hydroxytyrosol and tyrosol in their free form gives poor results in the case of freshly extracted oils. It is concluded that until an easy-to-manage HPLC method will be available, which will quantify accurately both free and bound forms of hydroxytyrosol and other phenolics, the colorimetric method for the determination of total polar phenols remains a good practical means to evaluate the stability of virgin olive oil.

Unprocessed olives are well-known sources of phenolic antioxidants with important biological properties. Processing methods to prepare table olives may cause a reduction of valuable phenols and may deprive the food of precious biological functions. The present work was undertaken to evaluate table olives produced in Greece as sources of biophenols. Commercially available olives were analyzed for their total phenol content by using the Folin-Ciocalteu reagent and for individual phenols by RP-HPLC. Samples were Spanish-style green olives in brine, Greek-style naturally black olives in brine, and Kalamata olives in brine. Most of the types of olives analyzed were found to be good sources of phenols. Hydroxytyrosol, tyrosol, and luteolin were the prevailing phenols in almost all of the samples examined. High levels of hydroxytyrosol were determined mainly in Kalamata olives and Spanish-style green olives, cultivar Chalkidiki (250-760 mg/kg).

The effect of 100, 500 and 1000 ppm of α-tocopherol on the oxidative stability of purified olive oil kept in the dark at 40 °C was studied. Purified olive oil was prepared by liquid column chromatography and was practically devoid of minor constituents with possible pro-oxidant or antioxidant activity. α-Tocopherol acted as antioxidant at all levels of addition, although the antioxidant effect was greater at 100 ppm than at higher concentrations. In the initial stage of autoxidation a slightly pro-oxidant effect was observed. In the presence of strong antioxidants naturally occurring in olive oil, such as ortho-diphenols, α-tocopherol did not show any significant additional antioxidant effect during the period of low peroxide accumulation.

In this study, four samples of essential oils obtained from plant species with a wide distribution in Greece and economic importance for the world-wide spice market and also carvacrol and thymol were tested for their possible antioxidant activity. The four plant species wereOriganum vulgare subsp.hirtum, O. onites, Coridothymus capitatus andSatureja thymbra. The essential oils were chemically characterised by gas chromatography-ion trap detection. All the essential oils examined and also carvacrol and thymol were found to have antioxidant activity when tested on TLC plates and by measuring peroxide values of lard stored at 35° C. The results indicate that the antioxidant effect may be related to the presence of carvacrol and thymol in essential oils.

The stability of 24 samples of Greek virgin olive oil was examined in relation to total polyphenol content, and individual phenols were determined by reversed-phase HPLC. Tyrosol, the major olive-oil phenol, is not correlated with the shelf-life of the oil. Total polyphenol content and hydroxytyrosol-to-tyrosol ratio have a significant linear correlation with the resistance of the oil to autoxidation.

Dietary Antioxidants. Olive Oil, Mediterranean Diet and Health. Phenolic Compounds in Olives and Olive Oil. Other Important Minor Constituents. Detection and Quantification of Phenolic Compounds in Olive Oil, Olives and Biological Fluids. Bioavailability and Antioxidant Effect of Olive Oil Phenolic Compounds in Humans. Olive Oil Phenols and Cell Damages. Antithrombotic and Antiatherogenic Lipid Minor Constituents from Olive Oil Minor. Olive Oil Hydroxy-isochromans. Conclusions.

A nondestructive analytical method based on NMR spectroscopy was developed for the determination of phospholipids in olive oil. The phospholipids extracted from virgin olive oil with a mixture of ethanol/water (2:1 v/v) were identified and quantified by high resolution (31)P NMR spectroscopy. The main phospholipids found in olive oil were phosphatidic acid, lyso-phosphatidic acid, and phosphatidylinositol. Validation of the (31)P NMR methodology for quantitative analysis of phospholipids in olive oil was performed. Sensitivity was satisfactory with detection limits of 0.25-1.24 mumol /mL. In addition, the composition of fatty acids in phospholipids model compounds and those in olive oil samples was estimated by employing one- and two-dimensional (1)H NMR. The results indicated that the fatty acid composition in phospholipids and triacylglycerols of olive oil was similar.

A staple food for thousands of years in the Mediterranean region, olive oil is now becoming popular all over the world. Olive oil has several unique characteristics that set it apart from other vegetable oils. Recent research suggests that olive oil produces many healthful benefits, including reduced risk of coronary heart disease. This second edition of Olive Oil includes new material from contributors and additional chapters that explore the most important aspects of chemistry, technology, quality, analysis and biological importance of olive oil. The topics selected will provide the reader with a solid background that will inspire and facilitate future research.

Essential oils and extracts of aromatic herbs obtained by organic solvents have been extensively studied for their antioxidant activity in lipid substrates. Very little is known about the possible presence of antioxidants in polar extracts from herbs used in preparation of infusions and decoctions. In this work water extracts of six different herbs of the Lamiaceae family (dittany, lemon balm, mint, sage, sideritis and sweet marjoram) were prepared. The extracts were examined for their effect against lipid oxidation in comparison to a tea water extract. Sweet marjoram, sage and dittany extracts were found to have a remarkable capacity in retarding lipid oxidation. Examination by thin-layer chromatography of the freeze-dried extracts, before and after hydrolysis, showed that the extracts were rich in bound forms of phenolic compounds such as hydroxycinnamic acids and flavonoids. Rosmarinic and caffeic acids were detected in all extracts with the exception of those from mint and sideritis. These results indicate that certain plants used for the preparation of infusions could be further studied like tea as sources of antioxidants.

A combination of advanced nuclear magnetic resonance (NMR) methodologies for the analysis of complex phenolic mixtures that occur in natural products is described, with particular emphasis on caffeic acid and its ester derivative, rosmarinic acid. The combination of variable-temperature two-dimensional proton-proton double quantum filter correlation spectroscopy (H-1-H-1 DQF COSY) and proton-carbon heteronuclear multiple quantum coherence (H-1-C-13 HMQC) gradient NMR spectroscopy allows the identification and tentative quantification of caffeic and rosmarinic acids at 243 K in extracts from plants of the Lamiaceae family, without resorting to previous chromatographic separation of the components. The use of proton-carbon heteronuclear multiple bond correlation (H-1-C-13 HMBC) gradient NMR spectroscopy leads to the complete assignment of the correlations of the spins of H-2a and H-3a with the ester and carboxyl carbons of rosmarinic and caffeic acid, even at room temperature, and confirms the results of the above methodology. Quantitative results are in reasonable agreement with reverse phase HPLC measurements. J Agric Food Chem

Esterified 4α-monomethylsterols and triterpene alcohols were isolated from virgin olive oil by combined column chromatography-thin layer chromatography and their composition was assessed gas chromatographically using both packed and capillary columns. The compositions of the esterified 4α-monomethylsterol and triterpene alcohol fractions were compared with those of the total fractions which were isolated after saponification. Significant differences were observed between the distribution patterns of the total and esterified triterpene alcohol fractions, especially in the percentages of 24-methylenecycloartanol, butyrospermol and cycloartenol.

The polar fraction of virgin olive oil was separated into two main parts (A and B) using solid phase extraction. Analysis of individual components by RP-HPLC indicated that the part (A) contained only simple phenols and phenolic acids. Part (B) had a complex nature. The two parts tested for their antioxidant activity showed relatively high protection factors in safflower oil stored at 80°C. Part B was found to contribute more than part A to the stability of the oil. The antioxidant activity of both fractions was related to their content of total polyphenols and o-diphenols. Acidic and alkaline hydrolysis showed significant quantitative changes in the HPLC profiles indicating the presence of ether and ester bonds while high-performance anion exchange chromatography of sugars after hydrolysis gave evidence for the presence of only traces of glycosides. A first attempt to identify a characteristic chromatographic peak of part B by HPLC fractionation and mass spectrometry showed the presence of an ester of tyrosol most probably with a dicarboxylic acid. © 1997 SCI.

Introduction The oncoprotective role of food-derived polyphenol antioxidants has been described but the implicated mechanisms are not yet clear. In addition to polyphenols, phenolic acids, found at high concentrations in a number of plants, possess antioxidant action. The main phenolic acids found in foods are derivatives of 4-hydroxybenzoic acid and 4-hydroxycinnamic acid.