Evaluación de indicadores de la calidad del aceite de oliva virgenfortalezas, debilidades y oportunidades

Zusammenfassung

The quality of virgin olive oil (VOO) is evaluated by physical-chemical parameters together with a sensory assessment carried out by trained assessors, the so-called �panel test�. Panel test is the method recognized by international organizations to qualify VOOs from organoleptic aspects. However, panel test is not exempt of some disadvantages like the subjectivity of panelists evaluating the samples, the time of analysis and its cost. For these reasons, new parameters have being suggested for evaluating VOO quality although some of them have a casual relationship with the sensory quality. Therefore, the information provided by each parameter about sensory quality has to be carefully analyzed to select only relevant information that complements panel test. The main objective of this thesis is to evaluate, by means of different analytical strategies, the validity of different chemical compounds (volatiles, phenols, alkyl esters, diacylglycerols and pyropheophytin) as trustworthy indicators of VOO sensory quality. Thus, the study emphasizes the weaknesses, strengths and opportunities of each one of the compounds from their applicability to the classification of VOO samples in their correct categories. Different analytical methodologies, based on spectroscopic and chromatographic techniques (GC, HPLC), have been used to quantify the different markers, using several sample preparation procedures such as solid phase extraction and microextraction, and column chromatography. Other methodologies (i.e. GC×GC chromatography and GC-olfactometry) have been used to go in depth in the chemical characterization of some sensory defects. The relationship between the described chemical compounds and the sensory quality has been evaluated, and three different behaviors that clarify their reliable utility from the point of view of quality have been detected. Thus, flavor compounds (volatiles and phenols) are directly responsible for VOO sensory descriptors; it means that they have a causal relation with the sensory quality. They could be used to give support or complement or even replace the panel test. In the case of alkyl esters and diacylglycerols, it has been pointed out the existence of an apparently causal relation, considering that these compounds are associated with VOO sensory quality but they are not directly responsible for their sensory descriptors; in fact, they are related to fermentative processes but they are not responsible for the aroma originated from these processes. Therefore, the information that they provide may be useful in evaluating only some aspects of VOO quality. Finally, pyropheophytin a (PPP) has a casual relation with sensory quality because it is not responsible for sensory descriptors of VOO aroma though a mathematical correlation with VOO quality categories has been described. PPP is not a marker to assess VOO sensory quality but VOO freshness on the basis of chemical and mathematical backgrounds. In conclusion, compounds that have a causal relation are the only ones that provide objective information about VOO sensory quality, because they are the stimulus of the sensations perceived by the consumers.