Gallina Toschi et al - Virgin and extra virgin olive oil: minor components, agronomic choices, extraction technology and quality

Tullia Gallina Toschi, Alessandra Bendini, Lorenzo Cerretani* e Giovanni Lercker**
Dipartimento di Scienze degli Alimenti, Università di Bologna, piazza Goidanich 60, 47521 Cesena (FC)

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Key words: olive fruit, virgin olive oil, water in oil, sensory characteristics.

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Abstract

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Virgin olive oils (VOO) are defined by the European Community as those “…oils obtained from the fruit of the olive tree solely by mechanical or other physical means under conditions that do not lead to alteration in the oil…”. This production method renders VOO different from other oils that undergo a refining process, which leads to loss of some of the minor components such as volatile molecules and polar phenolic compounds. The aroma of VOO is generated by several volatile components present at extremely low concentrations but strongly affect the quality of VOO. The volatiles present in VOO aroma belong to different chemical classes including various aldehydes, alcohols, esters, acids, ketons, hydrocarbons and furans and have been determined by a variety of analytical techniques. The concentration of volatile compounds is mainly dependent on the levels of enzymes involved in the lipoxygenase (LOX) pathway but the metabolite formation can be related not only to the ripening degree and storage time of fruits but also to the technological conditions used during and after oil extraction. Endogenous enzymes, through the LOX pathway, are responsible for the positive aroma perceptions of VOO whereas, sugar fermentations, aminoacid degradations, activities of exogenous enzymes from microbial activity and chemical oxidation are associated with the main sensory defects. The polar phenolic compounds of VOO belong to different classes: phenolic acids, phenyl ethyl alcohols, hydroxy-isochromans, flavonoids, lignans and secoiridoids. This last family is characteristic of Oleaceae plants and secoiridoids are the main compounds of phenolic fraction. This fraction is responsible for gustative perceptions (bitterness and pungency), antioxidant activity (higher shelf life) and health effects of VOO. The final quantity of phenols in VOO is influenced by some agronomic choices such as olive cultivar, climatic conditions during growth and the degree of olive ripening at picking stage. On the other hand many of these compounds are modified or lost during the production process of VOO. The partition coefficients between olive oil and by-products depend on some parameters adopted during the olive transformation process. This review focus on the studies of the main factors that influence the presence of minor compounds in VOO.

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