**1. Introduction**

108 Olive Oil – Constituents, Quality, Health Properties and Bioconversions

Zeiner, M.; Steffan, I. & Cindric, I. J. (2005). Determination of Trace Elements in Olive Oil by

*Microchemical Journal,* Vol.81, (December 2004), pp. 171-176, ISSN 0026-265X Ziyadanoğullar, B.; Ceviziçi, D.; Temel, H. & Ziyadanoğullar, V. (2008). Synthesis,

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ICP-AES and ETA-AAS: A Pilot Study on The Geographical Characterization.

Characterization and Structure Effects on Preconcentration and Extraction of N, N' bis-(salicylaldehydene)-1,4-bis-(p-aminophenoxy) butane towards Some Divalent Cations. *Journal of Hazardeous Materials,* Vol.150, (April 2007), pp. 285-289, ISSN

> Virgin olive oil (VOO) is the supernatant of the fresh juice obtained from olives by crushing, pressure and centrifugation, without additional refining. Its flavour is characteristic and is markedly different from those of other edible fats and oils. The combined effect of odour (directly via the nose or indirectly through a retronasal path, via the mouth), taste and chemical responses (as pungency) gives rise to the sensation generally perceived as "flavour".

> Sensory analysis is an essential technique to characterize food and investigate consumer preferences. International cooperative studies, supported by the International Olive Oil Council (IOOC) have provided a sensory codified methodology for VOOs, known as the "COI Panel test". Such an approach is based on the judgments of a panel of assessors, conducted by a panel leader, who has sufficient knowledge and skills to prepare sessions of sensory analysis, motivate judgement, process data, interpret results and draft the report. The panel generally consists of a group of 8 to 12 persons, selected and trained to identify and measure the intensity of the different positive and negative sensations perceived. Sensory assessment is carried out according to codified rules, in a specific tasting room, using controlled conditions to minimize external influences, using a proper tasting glass and adopting both a specific vocabulary and a profile sheet that includes positive and negative sensory attributes (Dec-23/98-V/2010). Collection of the results and statistical elaboration must be standardized (EEC Reg. 2568/91, EC Reg. 640/08). The colour of VOO, which is not significantly related to its quality, may produce expectations and interferences in the flavour perception phase. In order to eliminate any prejudices that may affect the smelling and tasting phases, panelists use a dark-coloured (blue or amber-coloured) tasting glass.

> Many chemical parameters and sensory analyses (EEC Reg. 2568/91 and EC Reg. 640/08), with the latter carried out by both olfactory and gustatory assessments, can classify oils in different quality categories (extra virgin, virgin, lampant). Extra virgin olive oil (EVOO) extracted from fresh and healthy olive fruits (Olea europaea L.), properly processed and adequately stored, is characterized by an unique and measurable combination of aroma and taste. Moreover, the category of EVOO should not show any defects (e.g. fusty, musty, winey, metallic, rancid) that can originate from incorrect production or storage procedures.

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Sensory Analysis of Virgin Olive Oil 111

acetoxypinoresinol), phenyl-ethyl alcohols (hydroxytyrosol, tyrosol) and secoiridoids (aglycon derivatives of oleuropein and ligstroside). The latter are characteristic of EVOOs. Several investigations (Gutiérrez-Rosales et al., 2003; Mateos et al., 2004) have demonstrated that some phenols, and in particular secoiridoid derivatives of hydroxytyrosol, are the main contributors to the bitterness of olive oil; other phenolic molecules such as decarboxymethyl-ligstroside aglycone, which seems to be a key source of the burning sensation, can stimulate the free endings of the trigeminal nerve located in the palate and gustative buds giving rise to the chemesthetic perceptions of pungency and astringency (Andrewes et al., 2003). Using a trained olive oil sensory panel, some investigators (Sinesio et al., 2005) have studied the temporal perception of bitterness and pungency with a time-intensity (TI) evaluation technique. It has been shown that the bitterness curves had a faster rate of increase and decline than the pungency curves. It was also demonstrated that differences in kinetic perception are linked to the slower signal transmission of thermal nociceptors

On the other hand, approximately 180 compounds belonging to several chemical classes (aldehydes, alcohols, esters, ketones, hydrocarbons, acids) have been separated from the volatile fractions of EVOOs of different quality. Typical flavours and off-flavour compounds that affect the volatile fraction of an oil obtained from olives originate by different mechanisms: positive odours are due to molecules that are produced enzymatically by the so-called lipoxygenase (LOX) pathway. Specifically both C6 aldehydes, alcohols and their corresponding esters and minor amounts of C5 carbonyl compounds, alcohols and pentene dimers are responsible for pleasant notes. In contrast, the main defects or off-flavours are due to sugar fermentation (*winey*), amino acid (leucine, isoleucine, and valine) conversion (*fusty*), enzymatic activities of moulds (*musty*) or anaerobic microorganisms (*muddy*), and to

Volatile molecules can be perceived in very small amounts (micrograms per kilogram or ppb) and these compounds do not have the same contribution to the global aroma of EVOO; in fact, their influence must be evaluated not only on the basis of concentration, but also on their sensory threshold values (Angerosa et al., 2004; Kalua et al., 2007). In addition, antagonism and/or synergism among different molecules can occur, affecting the global flavour of EVOO. Chemical factors of molecules (volatility, hydrophobic character, size, shape, conformational structure), type and position of functional groups appear to affect the odour and taste intensity more than their concentration due to their importance in

In general, it is correct to surmise that from healthy olives, picked at the right degree of ripening and properly processed, it is always possible to obtain an EVOO, independent of the olive variety. However, from unhealthy olives or from those harvested off the ground it is inevitable to produce an olive oil characterized by unpleasant flavours and sensory defects. Thus, both natural (olive variety, environmental conditions, degree of ripening and health status of olives) and extrinsic (technological processing by olive farmer/mill worker)

Several agronomic and climatic parameters can affect the volatile and phenolic composition of VOOs. The genetic characteristics of the olive cultivar are some of the most important

establishing bonds with receptor proteins (Angerosa et al., 2004).

factors may profoundly influence olfactory and gustative notes.

compared to other neurons.

auto-oxidative processes (*rancid*).

Positive or negative sensory descriptors of VOO have been related to volatile and phenol profiles, which are responsible for aroma and taste, respectively.

The characteristic taste of VOO, and in particular some positive attributes such as bitterness and pungency that are related to important health benefits, is not completely understood or appreciated by consumers. In this respect, it is interesting to consider the degree of acceptability of VOO in several countries based on literature data. In this way, it is possible to lay the foundations for correct instruction of the sensory characteristics of EVOO. The main chemical, biochemical and technological processes responsible for the positive and negative (defects) descriptors of VOO are summarized in this chapter. An overview on the sensory methodologies proposed, applied and modified during the last 20 years is also presented.
