Olive oil phenolic constituents have been shown, in vitro, to be endowed with potent biological activities including, but not limited to, an antioxidant action. To date, there is no information on the absorption and disposition of such compounds in humans. We report that olive oil phenolics, namely tyrosol and hydroxytyrosol, are dose-dependently absorbed in humans after ingestion and that they are excreted in the urine as glucuronide conjugates. Furthermore, an increase in the dose of phenolics administered increased the proportion of conjugation with glucuronide.z 2000 Federation of European Biochemical Societies.

This paper focuses on comparing the main chemical characteristics of 16 fresh commercial samples of extra virgin olive oil obtained from four harvest years (1999-2002) and derived from both stoned and whole fruits. The qualitative and quantitative contents of minor polar compounds (MPCs) together with other reference analytical parameters (acidity, peroxides, UV absorption values and Rancimat test) were evaluated. An investigation of the MPCs and oil composition obtained from only stoned olives was also carried out. The acidity values of the oils from stoned fruits were always similar to or lower than those of the corresponding oils from whole fruits. For almost all the samples from stoned olives a better resistance to oxidation was revealed in comparison with the corresponding traditional oils. Five pairs obtained from the 2000 and 2001 harvests showed higher concentrations of both MPCs and hydroxytyrosol derivatives in the oils from stoned fruits, in agreement with their higher Rancimat values. Overall, our findings with regard to acidity values, % hydrolysis, the Rancimat test and the qualitative and quantitative distribution of MPCs suggest a higher antioxidant capacity of the oils from stoned olives.

Bitter taste of extra virgin olive oil is known to be affected by the phenolic composition. However, contribution of each individual phenol to this sensory note has not been clearly defined. The aims of this study were to verify whether there was a relationship between bitter sensation and phenolic compound concentration, to determine which compounds were involved in bitter taste and to evaluate quantitatively this correlation. Results confirmed that a positive correlation did exist between total phenolic amount and bitter intensity. Data processing showed that this correlation was significantly dependent upon a relationship between oleuropein aglycon (3,4‐DHPEA‐EA) and bitter intensity. An empirical exponential model was set up and validated.

The aim of this work was to set up a phenomenological model to predict the stability of extra virgin olive oil based on combined stability/instability indices. A screening of stability/instability indices was carried out by multivariate statistical analyses on company data for virgin olive oil. Screened indices were acidity, oleic acid content and bitter taste. The ability of these indices to predict stability was checked by measuring the following degradation parameters on 11 oil samples of different compositions planned by a fractional factorial design (FFD): peroxide value, UV spectroscopic indices, minor polar component content, oxidative status of fatty acids, antioxidant activity and sensory descriptors of aroma, taste and flavour. Experimental data were processed by multivariate statistical analyses. A combination of acidity, oleic acid content and bitter taste values was significantly able to predict oil stability expressed by the peroxide value, the K 232 UV index and the oxidative status of fatty acids.

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