Stefania Vichi

Determination of volatile phenols in virgin olive oils and their sensory significance

Volatile phenols are strong odorants produced by microbial activity and reported in several foods, but very scarce information is available on their presence in virgin olive oils (VOOs) and on their relation with VOO chemical and sensory quality. In the present paper, a factorial experimental design was applied for the development of a suitable solid-phase microextraction-gas chromatography/mass spectrometry (SPME-GC/MS) analytical method for the analysis of volatile phenols in olive oil. The memory effects demonstrated by SPME fibres required the optimization of desorption conditions to minimize experimental errors. A series of nine volatile phenols were identified and quantified for the first time in VOOs by analyzing samples with distinct off-flavours. Their limits of detection and quantification (microg/kg) were largely below the odour detection thresholds (ODTs) calculated in this study (mg/kg), confirming the capacity of the technique to assess the target compounds at early stages of the oil sensory alteration. The odour activity values (OAVs) of volatile phenols were calculated in VOOs facilitating a first assessment of their potential importance in the aroma of the product.

Assessment of Volatile and Sensory Profiles between Base and Sparkling Wines

This paper focuses on the study of the volatile, olfactometric, and sensory composition of base wines and their corresponding sparkling wines (14-24 months aging) obtained at semi-industrial scale during three consecutive harvests. The sensory profile of sparkling wine is more complex than that of base wine, with toasty, lactic, sweet, and yeasty notes being described by the panelists and an even sharper increase of these tastes in the cava reserve. On the other hand, during the second fermentation and subsequent aging in contact with lees, some compounds such as acetate and ethyl esters decrease in amount while others such as norisoprenoids, acetal, diacetyl, and furans appear or increase over time. These volatile compounds could be responsible for the sensory profile depending on their notes, as determined by sniffing. The differences in volatile composition are responsible for the changes observed in the sensory profile of cava with respect to base wine.

Determination of lipophilic marine toxins in mussels. Quantification and confirmation criteria using high resolution mass spectrometry

A multitoxin method has been developed for quantification and confirmation of lipophilic marine biotoxins in mussels by liquid chromatography coupled to high resolution mass spectrometry (HRMS), using an Orbitrap-Exactive HCD mass spectrometer. Okadaic acid (OA), yessotoxin, azaspiracid-1, gymnodimine, 13-desmethyl spirolide C, pectenotoxin-2 and Brevetoxin B were analyzed as representative compounds of each lipophilic toxin group. HRMS identification and confirmation criteria were established. Fragment and isotope ions and ion ratios were studied and evaluated for confirmation purpose. In depth characterization of full scan and fragmentation spectrum of the main toxins were carried out. Accuracy (trueness and precision), linearity, calibration curve check, limit of quantification (LOQ) and specificity were the parameters established for the method validation. The validation was performed at 0.5 times the current European Union permitted levels. The method performed very well for the parameters investigated. The trueness, expressed as recovery, ranged from 80% to 94%, the precision, expressed as intralaboratory reproducibility, ranged from 5% to 22% and the LOQs range from 0.9 to 4.8pg on column. Uncertainty of the method was also estimated for OA, using a certified reference material. A top-down approach considering two main contributions: those arising from the trueness studies and those coming from the precisions determination, was used. An overall expanded uncertainty of 38% was obtained.

Characterisation of volatile composition of white salsify (Tragopogon porrifolius L.) by headspace solid-phase microextraction (HS-SPME) and simultaneous distillation–extraction (SDE) coupled to GC–MS

Two analytical procedures were applied, HS-SPME and SDE, coupled to GC-MS to analyse the volatile composition of white salsify. More than 80 of volatile compounds which belonged to distinct chemical families were analysed. SDE led to the identification of mainly high molecular weight sesquiterpenes, acids and esters. Given that SDE involves high temperatures, heat-sensitive compounds may undergo chemical alteration or artefacts may appear. Results obtained show that SPME was useful for the analysis of alcohols and hydrocarbons of low molecular weight and high volatility that are involved in the characteristic volatile profile of salsify and its sensory perception.

Changes in the sorption of diverse volatiles by Saccharomyces cerevisiae lees during sparkling wine aging.

The volatile profile of sparkling wine is influenced by the retention and release of volatile compounds by lees during the aging process. Here we attempted to identify the volatiles that are most retained by lees in aging conditions and to study how their sorption varies during aging. We estimated the lees sorption capacity for several representative volatile compounds in sparkling wine samples at a range of time points during aging by assessing the volatiles sorbed on the lees surface and those present in the corresponding wines. The sorption of volatiles was proportional to their hydrophobicity, and their retention by the lees surface changed during aging. The sorption of less hydrophobic compounds decreased after the first 2 months of aging, while that of the most hydrophobic volatiles increased until 18 months, and decreased dramatically thereafter. These results indicate that the length of aging on lees determines the type and the amount of wine volatiles removed with lees in the disgorging step. While most polar aromas seem to be released from the lees surface at the earliest stages of aging, highly hydrophobic compounds and esters in general are progressively retained and subsequently desorbed into wine. Changes in the physicochemical properties of the lees cell surface were monitored during aging, but these could explain only the decrease in the sorption of less hydrophobic compounds.

Assessment of some diterpenoids in commercial distilled gin.

In the present study the qualitative and quantitative determination of diterpenoids in commercial distilled gin was carried out. This widely consumed juniper-based spirit is aromatized using Juniper (Juniperus communis) berries. Although juniper reportedly contains several diterpenic compounds, no studies have addressed the diterpenic composition of juniper-based spirits or beverages. With this objective, here we followed a multilevel factorial experimental design to optimize a direct immersion-solid phase microextraction (DI-SPME) method coupled to gas chromatography/mass spectrometry and analyzed eight commercial brands of gin. With total concentrations ranging from 10 to 190 microg L(-1), manool, manoyl oxide and trans-totarol were the most abundant diterpenoids of the 10 identified or tentatively identified at variable but not negligible concentrations in the distilled gin samples. The diterpenic composition allowed the brands to be differentiated. This indicates that these compounds contribute to the sensory characteristics of the distinct commercial brands, thus guaranteeing the authenticity and consequently the quality of the product.

The activity of healthy olive microbiota during virgin olive oil extraction influences oil chemical composition.

The activity of olive microbiota during the oil extraction process could be a critical point for virgin olive oil quality. With the aim to evaluate the role of microbiological activity during the virgin olive oil extraction process, just before oil extraction freshly collected healthy olive fruits were immersed in contaminated water from an olive mill washing tank. The oils extracted were then compared with control samples from the same batch of hand-picked olives. The presence of lactic and enteric bacteria, fungi and Pseudomonas on the surface of olives was proved to be much higher in washed than in control olives, with increments in cfu/g between 2 and 3 orders of magnitude. The biogenesis of volatile compounds and the extraction of olive polyphenols and pigments were significantly influenced by the microbiological profile of olives even without any previous storage. In most cases the effect of olive microbiota on oil characteristics was greater than the effect exerted by malaxation time and temperature. Oils from microbiologically contaminated olives showed lower amounts of C5 volatiles and higher levels of C6 volatiles from the lipoxygenase pathway and some fermentation products. On the other hand, a decrease of chlorophylls, pheophytins, xanthophylls and the ratio chlorophyll/pheophytin was observed in these oils. Likewise, the microbiological activity during oil extraction led to significantly lower amounts of polyphenols, in particular of oleuropein derivatives. These differences in olive oil chemical composition were reflected in oil sensory characteristics by the decrease of the green and bitter attributes and by the modification of the oil color chromatic ordinates.

Ripening and storage conditions of Chétoui and Arbequina olives: Part I. Effect on olive oils volatiles profile

The distinctive aroma of virgin olive oil is mainly attributed to its volatile profile including components responsible for positive attributes and others for sensory defects resulting from chemical oxidation and exogenous enzymes. For this reason, the evolution of volatile compounds from Chétoui and Arbequina virgin olive oils during olive ripening and storage (at 4 and 25 °C during 4 weeks) was investigated. The profile of volatile phenols during olive storage was also studied. Quantitative differences in the volatile compounds during olive storage at 4 and 25 °C according to olive cultivar was determined. Concerning the volatile phenols, the Arbequina olives were the most affected by high storage temperature, as the formation of these compounds, especially 4-ethyl and 4-vinyl derivatives of phenol and guaiacol were more noticeable in Arbequina oils extracted from stored fruits at 25 °C.

Determination of volatile thiols in lipid matrix by simultaneous derivatization/extraction and liquid chromatography–high resolution mass spectrometric analysis. Application to virgin olive oil

A simple, reliable, selective and sensitive method for the determination of volatile thiols at trace levels in lipid matrices was developed. The method consisted of a single-step derivatization/extraction procedure followed by electrospray ionization-high performance liquid chromatography-high resolution mass spectrometry (ESI-HPLC-HRMS) analysis using ebselen as a derivatization agent. The analytical conditions were optimized in a lipid model system (triolein) and virgin olive oil (VOO), both spiked with seven representative volatile thiols. The method was validated and the sensitivity, precision, accuracy and selectivity were evaluated. The experimental limit of quantification (LOQ) of the tested thiols in the VOO matrix ranged from 0.05 to 0.5ng/kg. Moreover, the intra-day relative standard deviation (RSD) was in general lower than 10%, except for esters, which reached RSD values of around 13%. The inter-day RDS ranged between 9.6% and 36.6%. The recovery in VOO ranged from 79% to 20% for derivatives with the highest and lowest polarity, respectively. The methodology was applied to the analysis of some VOO samples. Within this first probe sample, some of the VOO analyzed presented concentrations of 4-methoxy-2-methyl-2-butanethiol above the LOQ, ranging between 0.2 and 1.9ng/kg. The advantage of using full-scan acquisition mode when working with HRMS is that it allows the use of a non-target approach based on the fragmentation of thiol derivatives yielding a main product ion at m/z 275.9922 [C13H10ONSe](+) and that corresponded to the ebselen moiety of the derivatives. Any positive finding satisfied the identification and confirmation criteria established during the validation: retention time drift <3-fold the standard deviation of the method, mass accuracy <2ppm with real resolution ≥20,000 (full width at half maximum) at the mass range of interest, and the presence of isotope ions containing (80)Se and (78)Se, respectively.

Evolution of Sesquiterpene Hydrocarbons in Virgin Olive Oil during Fruit Ripening

Despite the potential of sesquiterpene hydrocarbons in olive oil authentication, their metabolism in Olea europaea is poorly understood, and little is known about their biochemical regulation in olives as a function of ripening. To ascertain some metabolic relationships between sesquiterpene hydrocarbons and olive ripening, the content of sesquiterpene hydrocarbons was assessed in virgin olive oils from two olive varieties grown in the same geographical area and produced at different harvesting periods. During the ripening, the accumulation of sesquiterpenes in the olive itself, and thus in the oil, differed according to their molecular structure: bicyclic sesquiterpenes, showed decreasing concentrations the later the harvest, while acyclic farnesene-like compounds progressively increased through the olive ripening process. This is first evidence that the accumulation of sesquiterpene hydrocarbons in olive, and hence in olive oil, is modulated during ripening. Therefore, the degree of ripening of olives should be taken into consideration when considering the sesquiterpenic profile of virgin olive oil for their authentication.