Virgin Olive Oil Quality Research Articles

Copper chlorophyll in olive oils: identification and determination by LIF capillary electrophoresis

The green colour of virgin olive oils is due to chlorophyllic pigments, chlorophylls, pheophytins, pyropheophytins. The natural chlorophyllic pigments are totally absent in refined olive oil. Sometimes the colour of this oil is obtained by synthetic chlorophyll pigments as copper chlorophyll derivatives. The analysis of the pigment responsible for oil colour is of great importance, since it can be used to prove the authenticity and quality of virgin olive oils. A capillary zone electrophoresis (CZE) method, with LIF detection was developed to separate copper chlorophyll from others chlorophyll pigments and to determinate it in the olive oil. The separation occurs in a short time, less than 10 min, The elution time of copper chlorophyll is different enough of those of natural pigments. The standard deviation of the migration times of copper chlorophyll peak is RSD%=0.55. Copper chlorophyll peak was identified and quantified by external standard method. The limit of detection with a 3:1 signal-to-noise ratio was 5 μg/kg. Our CZE procedure is rapid and sensitive.

Bioactive constituents, flavors and aromas of virgin oils obtained by processing olives with a natural enzyme extract

AbstractTo enhance both virgin olive oil quality and yields, a natural enzyme extract (Bioliva) was used during processing of four Italian olive cultivars (Leccino, Caroleo, Dritta and Coratina) carried out with a percolation‐centrifugation extraction system. This biological formulation is essentially made up of natural enzyme species capable of degrading the major constituents of the vegetal cell membrane, such as pectin and cellulose. The oils of the second extraction (centrifuged oils), considered in this work, were fully characterized. The enzyme effects resulted in an enhanced incorporation of minor components (phenols, tocopherols, volatiles, carotenes, xanthophylls and chlorophylls) into the oil phase with consequent significant improvement of the analytical parameters related to typicality, flavor and shelflife. No significant modifications concerning triacylglycerols, fatty acids, and non‐glycerol compounds mainly related to genuineness were observed. A significant improvement of the oil outputs and the features of by‐products was also achieved. Another important outcome to be highlighted is the lower values concerning the emulsified fat, suspended solids, dry matter and COD (chemical oxygen demand) characterising the liquid effluent (olive juice).

Effect of viscosity, sodium caseinate and oil on bitterness perception of olive oil phenolics

Olive oil phenolics contribute to the sensory and technological quality of extra virgin olive oil (EVOV). Recent research indicates that these phenolics have a beneficial effect on health. However, their bitter taste limits use of EVOV or extracted phenolics as functional ingredients in many food products and it is therefore of interest to use different approaches to reduce their bitter taste. The effect of viscosity, sodium caseinate and oil on perceived bitterness was studied. A Stevens plot was made for the relationship between aqueous concentrations and bitterness perception. Increasing viscosity using carboxymethyl cellulose was found to have a relatively small effect on bitterness. Modification of existing flavour release models to describe the release of non-volatile tastants indicated that the small effect of viscosity on bitterness perception could be related to a small amount of tastants adsorbed onto the tongue compared to the total amount of tastants present in the sample. Adding sodium caseinate to an oil-free or a 65% oil in water system, caused a reduction in bitterness. Bitterness scores were estimated on the basis of the free (unbound) phenolics concentration in the aqueous phase and the relationship found from the Stevens plot. Estimated scores corresponded well to experimental findings, assuming relatively weak phenol–protein binding and oil–water partition coefficients around one.

Proposed parameters for monitoring quality of virgin olive oil (Koroneiki cv)

AbstractThe 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 ample 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.

Air exposure time of olive pastes during the extraction process and phenolic and volatile composition of virgin olive oil

AbstractThe time of exposure of olive pastes to air contact (TEOPAC) during malaxation was studied as a processing parameter that could be used to control endogenous oxidoreductases, such as polyphenoloxidase, peroxidase, and lipoxygenase, which affect virgin olive oil quality. Phenolic and volatile compounds were analyzed in the oils obtained using progressive TEOPAC at three ripening stages of olives. Multivariate statistical analysis was applied to the raw data. The phenolic concentration of virgin olive oil progressively decreased with increasing IEOPAC. On the contrary, a positive relationship was found with the concentration of several volatile compounds responsible for virgin olive oil aroma. The effect of TEOPAC, however, was strictly related to fruit ripening.

Virgin olive oil quality classification combining neural network and MOS sensors.

A model based on neural networks has been designed to detect lampante virgin olive oils, a category of olive oil that cannot be consumed without a previous refining process according to the current regulation of the European Communities. The response of 7 metal oxide sensors analyzing 114 olive oil samples has been used in the design, training, and internal validation of the neural network with only 4.5% error in validation. The designed mathematical model, the equations of which are fully described, has been validated also with an external set of 13 samples of diverse varieties and geographical origins with 100% correct classification.

Influence of the type of olive‐crusher used on the quality of extra virgin olive oils

AbstractAn experimental investigation was carried out to evaluate the quality of virgin olive oils obtained when either a hammer‐crusher or a disk‐crusher were used for the olive paste preparation; the effect of the temperature rise caused by rapid olive crushing was also assessed. Oxidative degradation in the oils obtained from hammer‐crushed olives was significantly higher than in those obtained from disk‐crushed olives as shown by the levels of oxidised triacylglycerols and the results of the oven test. A significant inverse correlation (p <0.001) was found between the Rancimat induction time values and the amounts of oxidised triacylglycerols as determined by the high‐performance size exclusion chromatography analysis of polar compounds. These findings suggested that polar compound analyses, just as routine analyses, may be used as a suitable analytical tool to effectively evaluate the quality of virgin olive oils.

Effect of crop season on the composition of virgin olive oil with protected designation of origin “Les garrigues”

AbstractIn recent years a growing demand for agricultural produce with an identifiable geographical origin has developed. The aim of this work was to study differences in quality and composition of virgin olive oils produced over four consecutive crop seasons in the region of the protected designation of origin “Les Garrigues” (Catalonia, Spain), taking the harvesting period and the climatic conditions of the year into consideration. The results obtained in this study indicate that virgin olive oil composition is greatly influenced by climatic conditions, mainly the cumulative rainfall in the case of FA composition and phenolic compounds, and the minimum temperatures during harvest period in the case of chlorophyll, carotenoid pigments, and α‐tocopherol content. The harvest period influenced most of the parameters analyzed, apart from the PV and FFA content. Prediction models for carotenoid pigment content, oxidative stability, and bitter index were found.

Improving virgin olive oil quality by means of innovative extracting biotechnologies.

Three major virgin olive oil varieties (Dritta, Leccino, and Coratina) extracted by a modern centrifugation system aided with a new plant enzyme preparation (having prevalently pectolytic activity) were characterized. These oils showed a clearly enhanced quality standard, owing to higher levels of some important minor components (phenolics, volatiles, tocopherols, carotenes, and chlorophylls) and to frequently lower concentrations of oxidized triglycerides and diglycerides. The oils were therefore characterized by lower susceptibility to oxidation and longer shelf life, and their flavor, aroma, and color features appeared to be significantly improved. The saponifiable fraction was practically not affected as the enzymatic effects involved only the membranes of the oil droplets, where the nonglyceridic compounds are essentially located.

Enhancing the quality of virgin olive oil by use of a new vegetable enzyme extract during processing

The variations in composition of three major virgin olive oil varieties extracted with a mechanical percolation system aided with Bioliva (a novel plant enzyme extract) were studied in-depth. This biological technology (which was compared to a reference one) led to substantial improvements of the quality standard of products (oils). These, in fact, were richer in some biomarkers (phenolics, volatiles, vitamins and lipochromes). Consequently, they showed lower susceptibility to autoxidation, longer shelf-life and improved the quantity and composition of both flavour and aroma. The oil yields were notably improved as well.

Effect of olive paste kneading process time on the overall quality of virgin olive oil

AbstractThe influence of the olive paste malaxation time on the composition and the industrial output of oil was investigated. To this purpose, three Italian olive varieties (Leccino, Dritta, Caroleo) were processed with a centrifugal system for six malaxation periods (0, 15, 30, 45, 60 and 75 min). The concentrations of the majority of the oil constituents changed during the malaxation. However, these changes were not significant for all of them: the contents of β‐carotene, the major xanthophylls, chlorophylls a and b, pheophytins a and b in the oils increased progressively with increasing malaxing times, whereas the contents of simple and hydrolysable phenols (secoiridoid derivatives), o‐diphenols and total phenols decreased. A significant increase in total volatiles and green volatiles of the lipoxygenase cascade (C6 aldehydes, C6 alcohols, C5 alcohols and C5 carbonyls) was detected. An opposite trend was observed for the green C6 esters. As a result, the global analytical quality, flavour, aroma and shelf‐life of the oils were negatively affected. The oil yield increased substantially up to 45 min of paste malaxation times. Beyond 60 min, the yields tended to decrease.

Use of HPSEC analysis of polar compounds to assess the influence of crushing temperature on virgin olive oil's quality

An experimental trial was carried out to evaluate, by means of determination of polar compounds and their subsequent HPSEC analysis, the influence of the hammer-crusher temperature during the olive paste preparation prior to oil extraction. Olives of Cima di Bitonto cultivar were processed utilising a laboratory-scale hammer-crusher conditioned at three different temperatures (12, 16 and 20 °C). The analytical results showed that the quality of the extracted oils was negatively influenced by increasing the crushing temperature. The oils obtained at higher crusher temperatures were more susceptible to oxidation than the oils obtained with crusher conditioned at lower temperatures. The HPSEC analysis of polar compounds was found to be useful to evaluate the oxidative and hydrolytic degradation levels of virgin olive oils also after slight thermal raising.

Characterisation of monovarietal virgin olive oils

This review analyses, how pedoclimatic aspects together with olive ripeness, harvest of olives, and the olive extraction system determine the chemical composition and sensory descriptors which assess the quality of virgin olive oils. Thus for monovarietal virgin olive oil, sensory descriptors evaluated by different European panels, volatile compounds produced through the lipoxygenase pathway, and series of compounds from unsaponifiable matter have been quantified.

Influence of olive processing on virgin olive oil quality

Virgin olive oil quality depends on different factors such as olive cultivar, olive tree cultivation and the operations of olive picking, storage and processing. Many investigations concerning these factors were carried out and, in particular, the influence of technological operations of olive processing on oil yields and quality was examined. Leafremoval and olive washing are important operations for the mechanical safety of the olive extracting equipment which operates at high speed and for the organoleptic quality of olive oil. The leaves mixed with olives may increase, in fact, the organoleptic attributes of ‘fresh-cut’ grass or ‘green’, especially if metallic crushers are used to prepare olive paste. Olive crushing has an important influence on organoleptic and nutritional qualities of virgin olive oil. When mill stones are used, the obtained oils have a lower intensity of bitterness and pungency because this crushing method helps to produce oil with a lower content of phenolic substances. When metallic crushers are used oils have, due to the violent action, a higher content of phenolic compounds and are more bitter and pungent. Olive paste malaxation influences the oil yields and also the antioxidant content of oil. With prolonged malaxation oil yields, generally, increase while the phenol content of oils decreases. When ‘difficult’ olive pastes are processed, it is possible to increase oil yields by using technological co-adjuvants such as talc and enzymatic products during the malaxation. The separation of oil from solid and liquid phases of olive paste is performed by using either pressure, percolation or centrifugation systems. All systems may provide good-quality oil if olive fruits are sound and at the correct ripeness, but the centrifugation system helps to avoid or reduce the risk of an organoleptic contamination. The new centrifugal decanters, operating without adding water (or only a minimal amount of water) to olive paste, save heat energy and the oils obtained are more fruity and have a higher content of natural phenolic antioxidants.

Validation of the oxygen radical absorbance capacity (ORAC) parameter as a new index of quality and stability of virgin olive oil

AbstractThe induction period (IP), determined using accelerated methods such as the Rancimat test, is a parameter that has been used to predict the shelf life of virgin olive oil. The oxygen radical absorbance capacity (ORAC) has recently been proposed as a quality index of virgin olive oil because it measures the efficiency of phenolic compounds in the protection against peroxyl radicals. This study aims to investigate relationships between the ORAC and IP values and proposes ORAC as a new parameter of virgin olive oil stability. The concentrations of phenolics, o‐diphenols, tocopherol, β‐carotene, lutein, and ORAC and IP values were determined in 33 virgin olive oils. Regression analyses showed that both ORAC and IP values correlate with total phenols and o‐diphenols with highly significant indices, whereas the correlations of both ORAC and IP with tocopherols, β‐carotene, and lutein were not significant. The ORAC values correlate with the IP values with low but significant indices (R=0.42; P<0.02). The results confirm the key role of phenolic compounds in accounting for the shelf life of virgin olive oil and suggest that the ORAC parameter may be used as a new index of quality and stability.

Contribution of phenolic compounds to virgin olive oil quality

Hydrophilic phenols are the most abundant natural antioxidants of virgin olive oil (VOO), in which, however, tocopherols and carotens are also present. The prevalent classes of hydrophilic phenols found in VOO are phenolic alcohols, phenolic acids, flavonoids, lignans and secoiridoids. Secoiridoids including aglycon derivatives of oleuropein, demethyloleuropein and ligstroside, that are present in olive fruit, are the most abundant phenolic antioxidants of VOO. In this paper, the phenolic composition of VOO as well as the agronomic and technological parameters that affect their concentration in the oil are discussed. The olive cultivar and the ripening stage of fruit, in fact, have always been the most studied agronomic aspects that affect phenolic concentration in VOO. However, the malaxation conditions and the extraction systems used to separate oil from olive pastes (i.e. pressure three-phases and two-phases centrifugation systems) are also of great importance.

Influence of volatile compounds on virgin olive oil quality evaluated by analytical approaches and sensor panels

Volatile compounds, retained by virgin olive oils during their extraction process, are responsible for the oil aroma. Approximately one hundred and eighty compounds, whose structure was assigned by means of gas chromatography-mass spectrometry, were found in virgin olive oil aromas. The analytical approaches to their determination are briefly discussed, considering the problems related to the volatile compound collection and to adsorbents used for their trapping. The sensory methodology for the evaluation of the organoleptic characteristics of the virgin olive oils are reported and typical flavours and off-flavours are described. Compounds responsible for flavours, including factors affecting the volatile fraction, and for off-flavours are carefully examined, also considering the causes that give rise to off-flavours. Relationships between volatile compounds and sensory characteristics, found by various researchers, are reviewed.

Comparison of different olive oil extraction systems and the effect of storage conditions on the quality of the virgin olive oil

Se ha estudiado el efecto de los diferentes metodos de extraccion del aceite de oliva en distintos parametros de calidad del aceite, tales como el indice de peroxido y los coeficientes de extincion K 232 y K 270 . Se ha extraido el aceite de oliva usando el sistema tradicional de Theocharis, sistemas por centrifugacion Alfa-Laval y Amenduni y mixto tipos Rapanelli Sinolea y Decanter. El aceite ha sido analizado antes y durante su conservacion en botellas de polietileno en ausencia de luz, con luz difusa y con luz solar. El aceite conservado en la oscuridad tuvo el indice de peroxido mas bajo. En general el proceso de oxidacion fue lento en la oscuridad y mas rapido en luz difusa y en presencia directa de luz solar.

Influence of a new crushing technique on the composition of the volatile compounds and related sensory quality of virgin olive oil

The influence of a new crusher i.e. blade crusher on the quality of virgin olive oil from two different italian cultivars (Coratina and Oliarola) was determined. In addition the quality of this oil was compared with that of olive oil extracted with the traditional hammer crusher. Tests were performed in an industrial oil mill using the two different crushing instruments. Results obtained showed that quality parameters i.e. free fatty acids, peroxide value, UV absorption and total phenols content as well as the phenolic composition of oils were not significantly affected by the two different crushers used. On the contrary, the use of the blade crusher influenced the composition of the volatile compounds. In particular, the oils obtained using the blade crusher showed significant increases of some aldehydes such as 1-hexanal and trans-2-hexenal, esters such as hexyl acetate and 3hexenyl acetate and a reduction of alcohols such as 1-hexanol. Moreover, the identified pigments of the oils produced using the blade crusher were found at concentrations slightly lower than those in oils obtained after using the hammer crusher. Finally, results of the sensory analysis showed an improved organoleptic quality for the oils obtained using the blade crusher due to an increase of the cut-grass and floral sensory notes.

Determination of the diglyceride content in greek virgin olive oils and some commercial olive oils by employing (31)P NMR spectroscopy.

In this study, the diglyceride contents of 96 samples of virgin olive oils from the regions of Crete, Lesvos, Messinia, Pilion, Zakynthos, Halkidiki, and Ilia, 15 samples of commercial extra virgin and pure olive oils, and 3 samples each of refined olive oils and pomace oils were determined by a facile method introduced in a previous publication. This method is based on the phosphitylation of the free hydroxyls of the diglycerides with 2-chloro-4,4,5,5-tetramethyldioxaphospholane and the integration of the appropriate peaks in the (31)P NMR spectra. This preliminary study showed interesting trends in the diglyceride content of the virgin olive oils from the various regions of Greece that can be used as simple criteria to assess the olive oil characteristics. Analysis of variance has been carried out for the diglyceride content of each region in an attempt to detect possible differences in the diglyceride levels among the various regions. Finally, the relationship between the ratio of 1,2-diglycerides to the total amount of diglycerides and the total amount of diglycerides has been used to monitor the quality of virgin olive oils, commercial olive oils, refined olive oils, and pomace oils.