Effect of cultivar and processing method on the contents of polyphenols in table olives

Polyphenols were determined by HPLC in the juice and oil of packed table olives. The phenolic compositions of the two phases were very different, hydroxytyrosol and tyrosol being the main polyphenols in olive juice and tyrosol acetate, hydroxtyrosol acetate, hydroxytyrosol, tyrosol, and lignans (1-acetoxypinoresinol and pinoresinol) in oil. The type of processing had a marked influence on the concentration of polyphenols in olive juice and little on the content in oil. The analyses carried out on 48 samples showed that turning color olives in brine had the highest concentration in polyphenols ( approximately 1200 mg/kg), whereas oxidized olives had the lowest ( approximately 200 mg/kg). Among olive cultivars, Manzanilla had a higher concentration than Hojiblanca and Gordal. The type of olive presentation also influenced the concentration of polyphenols in olives, decreasing in the order plain > pitted > stuffed. The results obtained in this work indicate that table olives can be considered a good source of phenolic antioxidants, although their concentration depends on olive cultivar and processing method.     

The use of Lactobacillus pentosus 1MO to shorten the debittering process time of black table olives (Cv. Itrana and Leccino): a pilot-scale application

Fifty lactobacilli isolated from black table olive brines were evaluated for their salt tolerance, resistance to oleuropein and verbascoside, and ability to grow in modified filter-sterilized brines. A strain of Lactobacillus pentosus was selected and used as a starter to ferment, in pilot plant, black olives (Itrana and Leccino cv.) in brines modified for pH, carbohydrate, and growth factor concentrations, at 28 degrees C. The temperature-controlled fermentation of Leccino cv. olives resulted in obtaining ready-to-eat, high-quality table olives in a reduced-time process. HPLC analysis of phenolic compounds from fermented olives showed a decrease of oleuropein, a glucoside secoiridoid responsible for the bitter taste of olive drupes, and an increase of the hydroxytyrosol concentration. The selected strain of L. pentosus (1MO) allowed the reduction of the debittering phase period to 8 days.     

Biophenols in table olives

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).     

Influence of cultivar and concentration of selected phenolic constituents on the in vitro chemiopreventive potential of olive oil extracts

One of the main olive oil phenolic compounds, hydroxytyrosol (3,4-DHPEA), exerts in vitro chemopreventive activities (antiproliferative and pro-apoptotic) on tumor cells through the accumulation of H(2)O(2) in the culture medium. However, the phenol composition of virgin olive oil is complex, and 3,4-DHPEA is present at low concentrations when compared to other secoiridoids. In this study, the in vitro chemopreventive activities of complex virgin olive oil phenolic extracts (VOO-PE, derived from the four Italian cultivars Nocellara del Belice, Coratina, Ogliarola, and Taggiasca) were compared to each other and related to the amount of the single phenolic constituents. A great chemopreventive potential among the different VOO-PE was found following this order: Ogliarola > Coratina > Nocellara > Taggiasca. The antiproliferative and pro-apoptotic activities of VOO-PE were positively correlated to the secoiridoid content and negatively correlated to the concentration of both phenyl alcohols and lignans. All extracts induced H(2)O(2) accumulation in the culture medium, but this phenomenon was not responsible for their pro-apoptotic activity. When tested in a complex mixture, the olive oil phenols exerted a more potent chemopreventive effect compared to the isolated compounds, and this effect could be due either to a synergistic action of components or to any other unidentified extract constituent.     

Qualitative and semiquantitative analysis of phenolic compounds in extra virgin olive oils as a function of the ripening degree of olive fruits by different analytical techniques

Capillary electrophoresis (CE) can be effectively used as a fast screening tool to obtain qualitative and semiquantitative information about simple and complex phenolic compounds of extra virgin olive oil. Three simple phenols (tyrosol, hydroxytyrosol, and vanillic acid), a secoiridoid derivative (deacetoxy oleuropein aglycon), and two lignans (pinoresinol and acetoxypinoresinol) were detected as the main compounds in extra virgin olive oils by high-performance liquid chromatography (HPLC) and capillary zone electrophoresis (CZE). Spectrophotometric indices, radical scavenging activity, and oxidative stability of extra virgin olive oil samples obtained from olives hand-picked at different ripening degrees were statistically correlated with the CZE and HPLC quantification. The concentration of phenols in extra virgin olive oil decreased with ripeness of olive fruits. The high correlations found between CZE and the other analytical results indicate that CE can be applied as a rapid and reliable tool to routinely determine phenolic compounds in extra virgin olive oils.     

Hydroxytyrosol 4-beta-D-glucoside,an important phenolic compound in olive fruits and derived products

There is increasing interest in olive polyphenols because of their biological properties as well as their contribution to the color, taste, and shelf life of olive products. However, some of these compounds remain unidentified. It has been shown that hydroxytyrosol 4-beta-D-glucoside (4-beta-D-glucosyl-3-hydroxyphenylethanol) coeluted with hydroxytyrosol [(3,4-dihydroxyphenyl)ethanol] under reversed phase conditions in the phenolic chromatograms of olive pulp, vegetation water, and pomace of olive oil processing. A method to separate this compound from hydroxytyrosol by HPLC has been developed. The concentration of this glucoside increased in olive pulp with maturation and could be the main phenolic compound in mature olives. In contrast, the presence of this compound was not detected in olive oil by using HPLC-MS. The compound must be considered both in table olives and olive oil processing because of its glucose and hydroxytyrosol contribution to these products.     

Evaluation of phenolic compounds in virgin olive oil by direct injection in high-performance liquid chromatography with fluorometric detection

Hydrophilic phenols are the most abundant natural antioxidants of virgin olive oil (VOO), in which tocopherols and carotenes are also present. The prevalent classes of hydrophilic phenols found in VOO are phenyl alcohols, phenolic acids, secoiridoids such as the dialdehydic form of decarboxymethyl elenolic acid linked to (3,4-dihydroxyphenyl)ethanol or (p-hydroxypheny1)ethanol (3,4-DHPEA-EDA or p-HPEA-EDA) and an isomer of the oleuropein aglycon (3,4-DHPEA-EA), lignans such as (+)-1-acetoxypinoresinol and (+)-pinoresinol, and flavonoids. A new method for the analysis of VOO hydrophilic phenols by direct injection in high-performance liquid chromatography (HPLC) with the use of a fluorescence detector (FLD) has been proposed and compared with the traditional liquid-liquid extraction technique followed by the HPLC analysis utilizing a diode array detector (DAD) and a FLD. Results show that the most important classes of phenolic compounds occurring in VOO can be evaluated using HPLC direct injection. The efficiency of the new method, as compared to the liquid-liquid extraction, was higher to quantify phenyl alcohols, lignans, and 3,4-DHPEA-EA and lower for the evaluation of 3,4-DHPEA-EDA and p-HPEA-EDA.     

Polyphenol changes during fermentation of naturally black olives

The individual evolution of phenolic compounds has been studied during the natural fermentation of black olives for the first time. Cyanidin 3-rutinoside and cyanidin 3-glucoside were the main anthocyanins identified in fresh olives, and they were not detected after 1 month of storage either in brine or in olive. The fruit colors were different when aerobic or anaerobic conditions were used and as a consequence of the different anthocyanin polymerizations that took place. At time zero, the polyphenols observed in the olive juice were hydroxytyrosol-4-beta-glucoside, oleuropein, hydroxytyrosol, tyrosol, salidroside, and verbascoside and, after 12 months, the main phenol was hydroxytyrosol. The polyphenol content in the oil phase of olives was also analyzed. The dialdehydic form of elenolic acid linked to hydroxytyrosol and tyrosol, oleuropein aglycon, and ligstroside aglycon were the main compounds found at the beginning of fermentation but were not detected after 3 months. In contrast, hydroxytyrosol, hydroxytyrosol acetate, tyrosol, and tyrosol acetate were the main polyphenols detected in the oil phase of the final product. The acid hydrolysis of the initial glucosides (in olive juice) and the aglycons (in oil phase) was, therefore, the main reaction that took place during fermentation.     

Feasible application of a portable NIR-AOTF tool for on-field prediction of phenolic compounds during the ripening of olives for oil production

Olive fruits of three different cultivars (Moraiolo, Dolce di Andria, and Nocellara Etnea) were monitored during ripening up to harvest, and specific and total phenols were measured by HPLC (High Pressure Liquid Chromatography). On the same olive samples (n = 450), spectral detections were performed using a portable NIR (Near Infrared)-AOTF (Acousto Optically Tunable Filter) device in diffuse reflectance mode (1100-2300 nm). Prediction models were developed for the main phenolic compounds (e.g., oleuropein, verbascoside, and 3,4-DHPEA-EDA) and total phenols using Partial Least Squares (PLS). Internal cross-validation (leave-one-out method) was applied for calibration and prediction models developed on the data sets relative to each single cultivar. Validation of the models obtained as the sum of the three sample sets (total phenols, n = 162; verbascoside, n = 162; oleuropein, n = 148; 3,4-DHPEA-EDA, n = 162) were performed by external sets of data. Obtained results in term of R(2) (in calibration, prediction and cross-validation) ranged between 0.930 and 0.998, 0.874-0.942, and 0.837-0.992, respectively. Standard errors in calibration (RMSEC), cross-validation (RMSECV), and prediction (RMSEP) were calculated obtaining minimum error in prediction of 0.68 and maximum of 6.33 mg/g. RPD ratios (SD/SECV) were also calculated as references of the model effectiveness. This work shows how NIR-AOTF can be considered a feasible tool for the on-field and nondestructive measurement of specific and total phenols in olives for oil production.     

Comparative study on chemical changes in olive juice and brine during green olive fermentation

Changes in physicochemical characteristics, substrate depletion, and product formation during fermentation were followed in both brine and olive juice in order to achieve a complete knowledge of fermentation chemistry in Spanish-type green olives. Both spontaneous and controlled fermentations were investigated. Fermentation rate, irrespective of the type of fermentation, was lower in olive juice than in brine, but the main acid products eventually reached equilibrium. Final free acidity remained significantly (p < 0.05) higher, and combined acidity remained lower, in brine than in olive juice in both fermentations, but differences in final pH were not significant in controlled fermentation. Final concentrations of lactic and formic acids were significantly (p < 0. 05) higher, and those of ethanol and succinic acid were lower, in controlled fermentation than in spontaneous fermentation. Butanediol, attributable to Enterobacteriaceae growth, was formed only in the latter case. Calculated carbon recoveries were not significantly (p < 0.05) different in any case, giving a mean of some 78%.     

Main antimicrobial compounds in table olives

The inhibitors involved in the lactic acid fermentation of table olives were investigated in aseptic olive brines of the Manzanilla and Gordal varieties. Phenolic and oleosidic compounds in these brines were identified by high-performance liquid chromatography with ultraviolet and electrospray ionization mass spectrometry detection, and several substances were also characterized by nuclear magnetic resonance. Among these compounds, the dialdehydic form of decarboxymethyl elenolic acid linked to hydroxytyrosol showed the strongest antilactic acid bacteria activity, and its presence in brines could explain the growth inhibition of these microorganisms during olive fermentation. However, it was found that the dialdehydic form of decarboxymethyl elenolic acid, identified for the first time in table olives, and an isomer of oleoside 11-methyl ester were also effective against Lactobacillus pentosus and can, therefore, contribute to the antimicrobial activity of olive brines. It must also be stressed that the three new inhibitors discovered in table olive brines exerted a more potent antibacterial activity than the well-studied oleuropein and hydroxytyrosol.     

Effect of bruising on respiration, superficial color, and phenolic changes in fresh Manzanilla olives (Olea europaea pomiformis): development of treatments to mitigate browning

The aim of the work was to study the postharvest changes in Manzanilla olives and to find treatments to mitigate damages because of bruises. The phenolic content in bruised and unbruised fruits exposed to air always decreased, but the loss in phenols and the respiratory activity were greater in bruised olives; these changes were related to the appearance of brown spots. Immersion of the picked fruits in a cold (8 °C) acidic solution (pH 3), ascorbic acid solution (100 mM), or sodium metabisulfite solution (100 mM) significantly reduced the loss in phenols in olives and led to lighter brown bruised areas. This immersion did not affect the behavior of the fruits during the lye treatment and the subsequent fermentation. In the final product, no influence on the surface color of unbruised olives was observed and there was a significant color improvement in the bruised areas of damaged olives.     

Effects of fly attack (Bactrocera oleae) on the phenolic profile and selected chemical parameters of olive oil

The phenolic fraction of virgin olive oil influences both its quality and oxidative stability. One of the principal threats of the quality of olive fruit is the olive fly ( Bactrocera oleae) as it alters the chemical composition. The attack of this olive pest has been studied in order to evaluate its influence on the quality of virgin olive oil (free acidity, peroxide value, fatty acid composition, water content, oxidative stability, phenols, and antioxidant power of phenolic fraction). The study was performed using several virgin olive oils obtained from olives with different degrees of fly infestation. They were acquired in different Italian industrial mills from the Abruzzo region. Qualitative and quantitative analyses of phenolic profiles were performed by capillary electrophoresis-diode array detection, and electrochemical evaluation of the antioxidant power of the phenolic fraction was also carried out. These analyses demonstrated that the degree of fly attack was positively correlated with free acidity ( r = 0.77, p < 0.05) and oxidized products ( r = 0.58, p < 0.05), and negatively related to the oxidative stability index ( r = -0.54, p < 0.05) and phenolic content ( r = -0.50, p < 0.05), mainly with secoiridoid compounds. However, it has been confirmed that the phenolic fraction of olive oil depends on several parameters and that a clear correlation does not exist between the percentages of fly attack and phenolic content.     

Effect of the maturation process of the olive fruit on the phenolic fraction of drupes and oils from Arbequina, Farga, and Morrut cultivars

The purpose of the work was to investigate the effect of the maturation process of the olive fruit on the phenolic fraction of drupes and oils from Arbequina, Farga, and Morrut cultivars. The level in the phenolic content of olive drupes declines rapidly during the black maturation phase. A general decreasing trend was observed too in the phenolic content of olive oils during the ripening process in the three varieties studied. Important differences in the high-performance liquid chromatography profile between varieties were observed. These included the presence of very low amounts of lignans in olive oils proceeding from the Morrut cultivar, and the presence of three peaks after elution of 3,4-DHPEA-EDA in the Farga and Morrut cultivars, which could be used as differentiating parameters. Sensory profile differences were observed between olive cultivars and due to the ripening process.     

Factors influencing phenolic compounds in table olives (Olea europaea)

The Mediterranean diet appears to be associated with a reduced risk of several chronic diseases including cancer and cardiovascular and Alzheimer's diseases. Olive products (mainly olive oil and table olives) are important components of the Mediterranean diet. Olives contain a range of phenolic compounds; these natural antioxidants may contribute to the prevention of these chronic conditions. Consequently, the consumption of table olives and olive oil continues to increase worldwide by health-conscious consumers. There are numerous factors that can affect the phenolics in table olives including the cultivar, degree of ripening, and, importantly, the methods used for curing and processing table olives. The predominant phenolic compound found in fresh olive is the bitter secoiridoid oleuropein. Table olive processing decreases levels of oleuropein with concomitant increases in the hydrolysis products hydroxytyrosol and tyrosol. Many of the health benefits reported for olives are thought to be associated with the levels of hydroxytyrosol. Herein the pre- and post-harvest factors influencing the phenolics in olives, debittering methods, and health benefits of phenolics in table olives are reviewed.     

Development of a phenol-enriched olive oil with both its own phenolic compounds and complementary phenols from thyme

Besides affecting the oil's sensorial characteristics, the presence of herbs and spices has an impact on the nutritional value of the flavored oils. The aim of the study was to develop a new product based on the phenol-enrichment of a virgin olive oil with both its own phenolic compounds (secoiridoid derivatives) plus additional complementary phenols from thyme (flavonoids). We studied the effect of the addition of phenolic extracts (olive cake and thyme) on phenolic composition, oxidative stability, antioxidant activity, and bitter sensory attribute of olive oils. Results showed that flavonoids from thyme appeared to have higher transference ratios (average 89.7%) from the phenolic extract to oil, whereas secoiridoids from olive presented lower transference ratios (average 35.3%). The bitter sensory attribute of the phenol-enriched oils diminished with an increase of the concentration of phenols from thyme, which might denote an improvement in the consumer acceptance.     

Analysis of total contents of hydroxytyrosol and tyrosol in olive oils

The most abundant phenolic compounds in olive oils are the phenethyl alcohols hydroxytyrosol and tyrosol. An optimized method to quantify the total concentration of these substances in olive oils has been described. It consists of the acid hydrolysis of the aglycons and the extraction of phenethyl alcohols with a 2 M HCl solution. Recovery of the phenethyl alcohols from oils was very high (<1% remained in the extracted oils), and the limits of quantification (LOQ) were 0.8 and 1.4 mg/kg for hydroxytyrosol and tyrosol, respectively. Precision values, both intraday and interday, remained below 3% for both compounds. The final optimized method allowed for the analysis of several types of commercial olive oils to evaluate their hydroxytyrosol and tyrosol contents. The results show that this method is simple, robust, and reliable for a routine analysis of the total concentration of these substances in olive oils.     

Evaluation of the influence of thermal oxidation on the phenolic composition and on the antioxidant activity of extra-virgin olive oils

A comparison between the results obtained by using HPLC-UV, HPLC-MS, and CE-UV for characterizing the deterioration of extra-virgin olive oil during heating (180 degrees C) was investigated, taking into account phenolic compounds. The concentration of several compounds belonging to four families of phenols (simple phenols, lignans, complex phenols, and phenolic acids) was determined in the samples after the thermal treatment by all three techniques. Hydroxytyrosol, elenolic acid, decarboxymethyl oleuropein aglycon, and oleuropein aglycon reduced their concentration with the thermal treatment more quickly than other phenolic compounds present in olive oil. HYTY-Ac and Lig Agl were demonstrated to be quite resistant to this kind of treatment, and the behavior of lignans could be outstanding, as they belong to the family most resistant to thermal treatment. Several "unknown" compounds were determined in the phenolic profiles of the oils after the thermal treatment, and their presence was confirmed in refined olive oils. The oxidative stability index (OSI time) was reduced from 25 to 5 h after 3 h of heating, whereas the peroxide value showed a minimum after 1 h of heating.     

Influence of the decrease in oxygen during malaxation of olive paste on the composition of volatiles and phenolic compounds in virgin olive oil

The sensory and health properties of virgin olive oil (VOO) are highly related to its volatile and phenolic composition. Oxygen control in the pastes during malaxation may be a new technological parameter to regulate enzymatic activities, such as polyphenoloxidase, peroxidase, and lipoxygenase, which affect the phenolic and volatile composition of VOO. In this work, we monitored CO2 and O2 concentrations during industrial-scale olive paste malaxation with various initial O2 concentrations within the malaxer headspace. Results show that the O2 concentration in the malaxer headspace did not affect CO2 production during processing, whereas a strong influence was observed on the changes of the phenolic composition of olive pastes and VOOs, with high correlation coefficient for the total phenols (R = 0.94), especially for oleuropein and demethyloleuropein derivatives (R = 0.81). In contrast, aroma production during malaxation was minimally affected by the O2 concentration in the malaxer headspace.