Stefania Urbani

Phenolic compounds in olive oil: antioxidant, health and organoleptic activities according to their chemical structure

Abstract.Hydrophilic phenols are the most abundant natural antioxidants of virgin olive oil (VOO), in which, however, tocopherols and carotenes are also present. The prevalent classes of hydrophilic phenols found in VOO are phenolic alcohols and acids, flavonoids, lignans and secoiridoids. Among these substances the last two classes include the most concentrate phenols of VOO. Secoiridoids, like aglycone derivatives of oleuropein, demethyloleuropein and ligstroside, are present in olive fruit as most abundant VOO phenolic antioxidants. Several important biological properties (antioxidant, anti-inflammatory, chemopreventive and anti-cancer) and the characteristic pungent and bitter tasty properties have been attributed to VOO phenols. Relationships between polyphenols activities and their chemical structures are discussed in this paper.

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.

Biological Activities of Phenolic Compounds of Extra Virgin Olive Oil

Over the last few decades, multiple biological properties, providing antioxidant, anti-inflammatory, chemopreventive and anti-cancer benefits, as well as the characteristic pungent and bitter taste, have been attributed to Extra Virgin Olive Oil (EVOO) phenols. In particular, growing efforts have been devoted to the study of the antioxidants of EVOO, due to their importance from health, biological and sensory points of view. Hydrophilic and lipophilic phenols represent the main antioxidants of EVOO, and they include a large variety of compounds. Among them, the most concentrated phenols are lignans and secoiridoids, with the latter found exclusively in the Oleaceae family, of which the drupe is the only edible fruit. In recent years, therefore, we have tackled the study of the main properties of phenols, including the relationships between their biological activity and the related chemical structure. This review, in fact, focuses on the phenolic compounds of EVOO, and, in particular, on their biological properties, sensory aspects and antioxidant capacity, with a particular emphasis on the extension of the product shelf-life.

Olive phenolic compounds: metabolic and transcriptional profiling during fruit development

BackgroundOlive (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.ResultsThe 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.ConclusionsMetabolic 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.

Functional milk beverage fortified with phenolic compounds extracted from olive vegetation water, and fermented with functional lactic acid bacteria

Functional milk beverages (FMB100 and FMB200) fortified with phenolic compounds (100 and 200mg/l) extracted from olive vegetable water, and fermented with γ-amino butyric acid (GABA)-producing (Lactobacillus plantarum C48) and autochthonous human gastro-intestinal (Lactobacillus paracasei 15N) lactic acid bacteria were manufactured. A milk beverage (MB), without addition of phenolic compounds, was used as the control. Except for a longer latency phase of FMB200, the three beverages showed an almost similar kinetic of acidification, consumption of lactose and synthesis of lactic acid. Apart from the beverage, Lb. plantarum C48 showed a decrease of ca. Log 2.52-2.24 cfu/ml during storage. The cell density of functional Lb. paracasei 15N remained always above the value of Log 8.0 cfu/ml. During fermentation, the total concentration of free amino acids markedly increased without significant (P > 0.05) differences between beverages. The concentration of GABA increased during fermentation and further storage (63.0 ± 0.6-67.0 ± 2.1mg/l) without significant (P > 0.05) differences between beverages. After fermentation, FMB100 and FMB200 showed the same phenolic composition of the phenol extract from olive vegetable water but a different ratio between 3,4-DHPEA and 3,4-DHPEA-EDA. During storage, the concentrations of 3,4-DHPEA-EDA, p-HPEA and verbascoside of both FMB100 and FMB200 decreased. Only the concentration of 3,4-DHPEA increased. As shown by SPME-GC-MS analysis, diactetyl, acetoin and, especially, acetaldehyde were the main volatile compounds found. The concentration of phenolic compounds does not interfere with the volatile composition. Sensory analyses based on triangle and paired comparison tests showed that phenolic compounds at the concentrations of 100 or 200mg/l were suitable for addition to functional milk beverages.

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.

Dietary extra-virgin olive oil rich in phenolic antioxidants and the aging process: long-term effects in the rat

The aim of the present work was to verify whether extra-virgin olive oil, a food naturally containing phenolic antioxidants, has the potential to protect from the pro-aging effects of a high-calorie diet. Male rats were fed from age 12 months to senescence a high-calorie diet containing either corn oil (CO), or extra-virgin olive oil with high (H-EVOO) or low (L-EVOO) amounts of phenols. The prolonged high fat intake led to obesity, liver lipid degeneration and insulin resistance, which were not counteracted by high phenol intake. No difference in overall survival was found at the end of the experiment in the animals treated with H-EVOO compared to the other groups. However, we did detect a protective effect of olive oil on some age-related pathologies and on blood pressure, of which the former was associated with the antioxidant content. Concomitantly, a decrease in DNA oxidative damage in blood cells and plasma TBARS and an increase in liver superoxide dismutase were detected following H-EVOO consumption. Thus, although olive oil phenols cannot reverse the detrimental effects of a prolonged intake of high amounts of fat, improving the quality of olive oil in terms of antioxidant content can be beneficial.

Pharmacology of Olive Biophenols

Abstract There are more than 100 different biophenols reported in olive samples. This chapter covers the chemistry, pharmacodynamics, pharmacokinetics, posology, adverse effects, and potential drug interactions of olives and major olive biophenols (OBP). Major biophenols detected in olive samples include hydroxytyrosol, tyrosol and their secoiridoid derivatives (oleuropein, oleuropein aglycone, and elenolic acid dialdehydes), verbascoside, lignans, and flavonoids. By far the majority of reports on the chemistry of OBP pertain to their ability to function as antioxidants, but other bioactivities include binding to lipids, proteins, carbohydrates, and nucleic acids. The majority of pharmacological studies have focused on just four compounds hydroxytyrosol, tyrosol, oleuropein, and verbascoside. Reported pharmacological properties include antioxidant, anti-inflammatory, cardiovascular, immunomodulatory, gastrointestinal, respiratory, autonomic, central nervous system, antimicrobial, anticancer and chemopreventive. While OBP are generally regarded as safe, further studies on potential adverse reactions may be required to demonstrate the safety of supplements with elevated levels of compounds.

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 an olive phenolic extract on the quality of vegetable oils during frying

The potential of a phenolic extract (PE) from olive vegetation water (OVW) to limit the negative effects of frying was tested after adding it at different concentrations to a refined olive oil (RO). Its efficacy was also compared to ROs containing butylated hydroxytoluene (BHT) and an extra virgin olive oil (EVOO) with a high polyphenol content. Analyses of the oils collected after 30min, 1, 2, 4, 6, 8, 10 and 12h of frying at 180°C, demonstrated that degradation of the polyphenols was proportional to the original content; at a concentration of at least 400mg/kg of polyphenols, PE was able to reduce oxidation of the tocopherols and the emission of low-molecular-weight aldehydes better than BHT and with similar results to the EVOO. In addition, secoiridoid oxidative compounds were examined by high-performance liquid chromatography/triple quadrupole tandem mass spectrometry with electrospray ionisation.