Raffaella Vito

Virgin olive oil odour notes: their relationships with volatile compounds from the lipoxygenase pathway and secoiridoid compounds

Abstract Fifty-one virgin olive oils of good quality, extracted with a laboratory mill in the same operative conditions from different unripe Italian, Greek and Spanish cultivars, were submitted to sensory evaluation, and to the determination of both polyphenols and the composition of volatile compounds produced through lipoxygenase (LOX) pathways. Univariate analysis was applied to the mentioned variables and some correlations were observed among them. Moreover, a Linear Regression Analysis (LRA) was carried out assuming, as dependent variable, each sensory attribute perceived by tasters and, as independent variables, all compounds derived, derived LOX pathways and polyphenols. The results obtained demonstrate the essential role played by hexanal in the formation of most attributes considered. The most relevant contributors among C 6 compounds from linolenic acid were trans -2-hexenal, trans -2-hexen-1-ol and cis -3-hexenyl acetate. Polyphenols contributed to the characterization of walnut husk, bitter and pungent characters, whereas C 5 compounds, especially 1-penten-3-one, strongly affected most attributes.

Influence of malaxation temperature and time on the quality of virgin olive oils

To study the influence of operative conditions adopted during the malaxation of pastes on the quality of resulting oils, we compared sensory characteristics, secoiridoid compounds and the volatile composition of oils extracted from homogeneous batches of olive fruits from Coratina and Frantoio cultivars by using different malaxation times and temperatures. Malaxation time, and especially temperature, negatively affected the intensity of sensory attributes and the content of secoiridoid compounds, modified the composition of metabolites arising from lipoxygenase (LOX) pathways, reducing volatile compounds displaying pleasant sensations and increasing those giving less attractive perceptions, and also elevated the production of 2-methyl butanal and 3-methyl butanal through amino acid conversion. Low temperatures and times, ranging between 30 and 45 min, according to the rheology of the olive pastes, were the optimal operative conditions for the malaxation.

Sensory evaluation of virgin olive oils by artificial neural network processing of dynamic head-space gas chromatographic data

A different approach to the traditional sensory method was used for the sensory quality evaluation of virgin olive oils. Two hundred and four oil samples differing in their quality, and extracted from olives of various varieties, ripeness, sanitary state and geographical origin, were submitted to sensory evaluation by a panel test and dynamic head-space analysis for the quantification of volatile fractions. An artificial neural network (ANN), using the back-propagation algorithm, was applied to the head-space results (input) with the aim of predicting panel test scores (output). It was found that the ANN was able to generalise well and to assign the sensory evaluations with a good degree of accuracy. The high proportion of correct answers (96%) suggested that sensory evaluation from the panel test could be successfully replaced by the dynamic head-space analysis-ANN coupled approach.

Virgin olive oil differentiation in relation to extraction methodologies

Sensory green attribute intensities, the total amount of complex phenolic compounds and the composition of volatile compounds from lipoxygenase pathways were measured in oils obtained from both industrial centrifugation plants and different kinds of laboratory mill. These data were evaluated by hierarchical cluster analysis, principal component analysis and linear discriminant analysis with the aim of distinguishing oil samples in relation to the extraction methodology. The statistical tests showed that the mentioned variables were able to differentiate oils according to the method adopted for their extraction from olive pastes. Oils from laboratory mills were clearly different from samples extracted industrially. This implies that results derived from investigations carried out using oils obtained from laboratory mills cannot be immediately transferred to oils from industrial plants. Oils from dual-phase decanters in industrial plants were more similar to samples extracted in conventional tri-phase industrial plants, even if they were all well differentiated according to the oil extraction methodology. © 2000 Society of Chemical Industry

Effect of fruit stone removal on the production of virgin olive oil volatile compounds

Abstract To verify if the quantitative composition of volatiles arising from lipoxygenase pathway was affected by the olive fruit stones, oils from whole olives and from the pulp-only tissues, respectively, were submitted to gas chromatographic determination of volatile compounds extracted by dynamic head-space. Results showed different quantitative compositions for the two oil kinds because of the greater accumulation of C 6 compounds from the lipoxygenase pathway in oils obtained from de-stoned olives, which is related to serious cellular disruption observed in the crushed pulp tissues. C 5 compounds were affected by the stone removal from fruits. Furthermore, the enzymatic oxidation of linoleic acid was promoted in oils obtained after removing fruit stones because of the more significant increase of the concentrations of corresponding C 6 metabolites.

Commercial extra virgin olive oils: Global Quality Index computation and pattern recognition by chemometrics

Purpose The purpose of this paper is to guide the choice of consumers, putting on the label an additional claim, which can provide more information on the sensory profile and the nutritional and preservation features of the marketed extra virgin olive oil. Design/methodology/approach In order to define the concept of global quality, the following parameters were considered: fruity, bitter, pungency, 1-penten-3-one, phenolic substances, tocopherols, peroxide value, free acidity, palmitic acid, stearic acid oleic acid linoleic acid, and the campesterol/stigmasterol ratio. The study was carried out on 143 commercial extra virgin olive oils. Findings The Global Quality Index was calculated as the square root of the sum of the squares of the individual local indices, according to three different algorithms. The computation obtained was recognised by chemometric analysis. Social implications A legislative amendment on the labelling could be proposed through an additional claim that safeguards the consumers on the health profile, inducing them to a more targeted purchase. Originality/value Three different global quality levels “excellent”, “good”, and “sufficient” have been determined. This clustering has also been recognised with a statistical approach. Since in the market, consumers can find extra virgin olive oils of different overall quality levels, it is possible to guide the choice of customers through an additional claim on the label, able to give more information on the sensory profile and the nutritional and preservation features of the product.