Olive oils phenolic substances

FIGURE 19.7 Molecular structures of olive oil phenolic substances. (Adapted from Carrasco-Pancorbo, A. et al., J. Sep. Sci., 28, 837, 2005. With permission.)... 

Colorimetric determination of the total phenolic substances in foods and beverages were carried out through a number of years however, then the availability of separation techniques suggested the possibility to better highlight the composition of this very complex mixture. Different approaches were developed mainly by means of GC and GC-MS, with an obviously long procedure of extraction and derivatization (usually trimethylsilyl derivatives were used) that strongly limited the analytical approach to these classes of compounds, and were mainly limited to wine and somewhat less to olive oils. 

The importance of the Mediterranean diet led to increased research activity on olive oils, which mainly focused, among other issnes, on phenolic substances becanse of their biological activities and of the fact that virgin olive oils are the only vegetable oils that contain them, while tocopherols are widely distributed in such foods. Phenolic substances are responsible for the typical taste of olive oils, characterized by fruity, bitter, and pungent flavors. 

In 2006, International Olive Oil decided to validate a method for phenolic snbstance evalnation and the decision was to validate both a colorimetric and a HPLC method. The HPLC method is the one already validated by the Italian Technical Committee for Fats and Oils, based on the Cortesi s method. Phenolic substances are extracted by means of methanol/water 80/20 and injected on a RP C18 Spherisorb ODS-2 type colnmn, 25x0.46 cm, 5 jm particle size, and the detection is carried out at 280 nm. Syringic acid is used as the internal standard. 27 peaks are separated and identified, enclosing some oxidized forms of aglycones. 

Acute episodes are treated similar to phenolic poisonings with initial stabilization of breathing and cardiac monitoring. Dermal decontamination is accomplished by swabbing the affected area with olive oil. For ingested material the preferred method is administration of activated charcoal followed by a cathartic. Phenol and phenolic substances tend to exhibit an increased absorption rate at dilute concentrations and have a rapid onset of acute symptoms therefore, there is a potential for seizures. 

Numerous substances were characterised and tested in their defoaming capability by Ross and others A correlation of about 90% was achieved which can be viewed as success or disappointment, depending on the standpoint of the observer. Some substances such as phenol and pyridine do not spread on surfactant solutions but can well destroy foam, other exceptions are petroleum ether and olive oil which spread rapidly but have a very poor antifoaming efficiency ° ... 

Two plant oil sources, namely olive pomace and olive pomace oil were selected by our research team because of their content in athero-protective substances (such as PAF inhibitors) and phenolic/polyphenolic molecules (Karantonis et al., 2008), null cost since they are natural wastes of olive oil production, and fatty acid profile, which makes them likely candidates to partially substitute fish oil in compounded fish feeds. The reference diet (fish oil diet) contained 100% fish oil (cod liver oil) and its chemical composition is shown in Table 1, while the two experimental diets olive pomace and olive pomace oil diet were compounded by substituting 8% of fish oil of reference diet, respectively (Nasopoulou et al., 2011). 

Other groups of substances have been noted, but further investigation is needed to ascertain their identification among the surest ones, we would mention plastoquinones with a structure close to that of vitamin Ki, detected in chloroplasts (Kegel, 1962) and in olive oil (Therrault, 1963) a group of phenolic substances, whose presence has been observed in at least two oils [in parsley oil, the myristicin (Privett et al., 1963), and in olive oil, the oleoeuropein (Vazquez Romero et al., 1961)] and the vinylic esters and esters of diols (propane-1,2- and 1,3-diol, butane-1,3- and 1,4-diol) these last are found in corn seeds and consequently in the oil also (Bergelson et al., 1966). 

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