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The present paper reports on the changes in the volatile composition of virgin olive oils (VOO) stored for 18 months. VOO samples of five Greek olive varieties were stored in dark glass bottles (headspace 0.5%) in a basement without central heating. Even after 18 months of storage, the basic quality characteristics of the samples, such as free acidity, K232, K270, and peroxide values, did not exceed the upper limits set by European Community Regulations for VOO. Regarding the lipoxygenase pathway products, responsible for the positive sensory notes, it was shown that their total amount remained stable during the storage period. Even though the physicochemical characteristics did not exceed the upper limits, high rates of formation of volatile oxidation products, which are responsible for the off-flavors, were observed. Among the volatile oxidation products, the highest rates of formation were monitored for heptanal, 2-heptenal, and pentanal followed by hexanal and nonanal. The formation rate of volatile oxidation products was higher in VOO from Lianolia and Asprolia compared to VOO from Koroneiki, Native from Zakynthos and Thiaki varieties. Finally, stepwise linear regression analysis (SLRA) selected linoleic acid and total phenol/ ortho-diphenols ratio as having the maximum correlation with the formation rate of 2-heptenal. Practical applications: This research reports on the changes in the quality characteristics of VOO, stored for 18 months, of the main olive varieties cultivated in the western Greece. Furthermore, it provides information on the changes in volatile composition, which is responsible for positive and negative flavor attributes. Results from this study may contribute to a better understanding of the relationships between minor and/or major components and the autoxidation process. Moreover, results could be useful to VOO packagers and marketers in order to estimate the shelf-life of individual varieties. VOO from Koroneiki, Native from Zakynthos and Thiaki varieties, which are characterized by low linoleic acid contents, can be preserved for a longer period compared to VOO from Lianolia and Asprolia varieties, which are characterized by high linoleic acid contents. During storage of virgin olive oil (VOO) for 18 months, lipoxygenase pathway products, responsible for the positive sensory notes, remained stable. Among the volatile oxidation products, the highest rates of formation were monitored for heptanal, 2-heptenal, and pentanal, followed by hexanal and nonanal. 2-heptenal was correlated with VOO unsaturation and has been suggested as oxidation marker during storage. [ABSTRACT FROM AUTHOR]

Abstract: In this work the effect of standard phenolic compounds such as trolox, phenolic acids (ferulic, gallic, protocatechuic and caffeic acid) and secoiridoids, extracted from virgin olive oil (VOO), on acrylamide formation in an emulsion system was investigated. The emulsion system was heated in an oil bath at different temperatures and for different periods of time. At 105 and 115°C the generated amounts of acrylamide were negligible during the monitoring time. At 125°C addition of standard phenolic compounds reduced acrylamide formation which was more pronounced at initial time of heating (20min) reaching up to 70%. Protocatechuic and gallic acid were more effective than trolox, caffeic and ferulic acid in acrylamide reduction at the final time intervals of heating (30–60min). On the contrary, addition of VOO extract in the emulsion system resulted in a remarkable increase of acrylamide level, which was ascribed to secoiridoids’ structure containing aldehydic groups. [ABSTRACT FROM AUTHOR]

Abstract: In this study the effect of olive oil and oregano phenolic compounds on antioxidant activity (AOA) and acrylamide formation in a model system and fresh potatoes was evaluated. The addition of oregano phenolic extract in the model system resulted in an increase of AOA and in a reduction of acrylamide content, up to 49%, after heating. On the contrary, addition of olive oil extract resulted in AOA reduction and a concentration-dependent effect on acrylamide formation was observed with a reduction up to 15% (p <0.05) followed by an increase up to 48%. The same trend, in acrylamide formation, was observed in fresh potatoes but to a lower extent. Finally, addition of tyrosol, oleuropein and p-hydroxyphenylacetic acid in the model system resulted in acrylamide reduction up to 50%. The discrepancy in acrylamide formation, caused by phenolic compounds, is ascribed to their structure and related to their terminal functional hydroxyl and aldehydic groups. [Copyright &y& Elsevier]

Roasted yellow split pea (YSP) flours were used to substitute wheat flour, at 10–20% (flour basis) in wheat bread formulations. Rheometry showed that roasted YSP flour addition increased elasticity and resistance to deformation and flow of the composite doughs, particularly at 20% substitution; instead, at 10% addition (either raw or roasted YSP flour), there were no effects on dough rheology and bread textural properties. Breads fortified with roasted YSP flour at levels >10% exhibited lower loaf-specific volume and harder crumb compared to control (bread without YSP flour). Moreover, only breads with 20% roasted YSP flour displayed a significantly higher staling extent and rate, compared to control, as assessed by large deformation mechanical testing and calorimetry (starch retrogradation) of crumb preparations. This formulation also showed a large increase in β-sheets and β-turns at the expense of α-helix and random coil conformations in protein secondary structure as assessed by FTIR spectroscopy. Roasting of YSP effectively masked the "beany" and "grass-like" off-flavors of raw YSP flour at 10% substitution. Overall, roasted YSP flour at the 10% level was successfully incorporated into wheat bread formulations without adversely affecting dough rheology, bread texture, and shelf-life, resulting in final products with a pleasant flavor profile. [ABSTRACT FROM AUTHOR]

The aim of this work was to recover and identify the phenolic compounds from olive mill wastewater (OMWW) samples belonging to two Italian ( Cellina and Coratina ) and three Greek ( Asprolia , Lianolia and Koroneiki ) olive cultivars. The OMWWs were processed using membrane technologies to obtain three fractions: microfiltrate (MF), ultrafiltrate (UF) and nanofiltrate (NF). These steps allowed purifying the OMWWs in order to achieve fractions with different profile and concentrations of polyphenols. In particular, the amount of polyphenols ranged from 2456 μg/mL to 5284 μg/mL in MF; from 1404 μg/mL to 3065 μg/mL in UF and from 373 μg/mL to 1583 μg/mL in NF. Among the cultivars analyzed Coratina followed by Lianolia showed the highest amount of verbascoside (VB) (308 μg/mL in Coratina versus 145 μg/mL in Lianolia , respectively) in UF fractions. Furthermore, UF fractions that showed adequate purification degree and polyphenol enrichments, were used for the identification of the phenolic compounds by liquid chromatography/diode array detection/electrospray ion trap tandem mass spectrometry (LC/DAD/ESI–MS n ) analysis. Twenty three compounds, belonging to the following classes of constituents: secoiridoids and their derivatives, phenyl alcohols, phenolic acid and derivatives, and flavonoids, were identified in almost all the UF fractions of the different cultivars. Finally, differences were observed among the cultivars regarding the presence of elenolic acid derivatives, hydroxytyrosol glucoside, and β-hydroxyverbascoside diastereoisomers. The results obtained showed that OMWW can be considered as raw material for the isolation of valuable bioactive compounds able to be used in food, cosmetic and pharmaceutical industry. [ABSTRACT FROM AUTHOR]

Virgin olive oil is oil with a high biological value, due to its polyphenol content. Virgin olive oils were subjected to heat treatment simulating common domestic processing, including boiling, frying and storage. These processes can affect the phenolic compounds content of oils to a certain degree, depending on each one treatment. Thermal oxidation of oils at 180 °C (frying) caused a significant decrease (p < 0.005) in hydroxytyrosol derivatives (60% reduction after 30 min and 90% reduction after 60 min) and, to a lower degree, in tyrosol derivatives. No changes were observed in the content of lignans (p > 0.005). On the other hand, thermal oxidation of oils at 100 °C (boiling) for 2 h caused a decrease by less than 20% in all classes of phenolic compounds. The reduction of phenolic compounds during storage under environmental conditions was correlated with the peroxide value. When the peroxide value did not exceed the level of 20 meq⋅kg-1, as was recorded for low linoleic acid oils and low oxygen availability at the bottles' headspace, a degree of reduction of approximately 30% in hydroxytyrosol derivatives and 10% in tyrosol derivatives was observed, while lignans remained unchanged. Finally, during both heating and storage under environmental conditions, the evolution of oxidized phenolic compounds was observed. The structures of these oxidized products were confirmed by HPLC-MS. [ABSTRACT FROM AUTHOR]