Susana Buxaderas

Analysis of virgin olive oil volatile compounds by headspace solid-phase microextraction coupled to gas chromatography with mass spectrometric and flame ionization detection

The efficiency of headspace solid-phase microextraction (SPME) was evaluated for the qualitative and semi-quantitative analysis of virgin olive oil volatile compounds. The behaviour of four fibre coatings was compared for sensitivity, repeatability and linearity of response. A divinylbenzene-Carboxen-polydimethylsiloxane fibre coating was found to be the most suitable for the analysis of virgin olive oil volatiles. Sampling and chromatographic conditions were examined and the SPME method, coupled to GC with MS and flame ionization detection, was applied to virgin olive oil samples. More than 100 compounds were isolated and characterised. The presence of some of these compounds in virgin olive oil has not previously been reported. The main volatile compounds present in the oil samples were determined quantitatively.

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.

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.

Determination of free fatty acids and their ethyl esters in musts and wines

Abstract White must and wine fatty acids are present mainly in the free form, or esterified as ethyl esters, and both contribute to flavor and foam properties of wine. A reliable and sensitive analytical procedure for analyzing the free fatty acids (C6–C18) and their ethyl esters has been developed. Sulfuric acid (3%) in methanol was selected as a derivative reagent, and optimal derivatization conditions were established (3 h at room temperature). This reagent gives total methylation of fatty acids and partial transesterification of ethyl esters to methyl esters and, through the study of this transesterification, free and bound fractions were determined satisfactory.

Quality of base and sparkling wines as influenced by the type of fining agent added pre-fermentation

Abstract A comparison of the effect on base wines of pre-fermentative clarification between a fining mixture (potassium caseinate, bentonite and cellulose microcrystalline) and bentonite was carried out. Fining agents were added to two grape juices from different cultivars: Macabeo and Parellada. These varietal wines are used for making sparkling wine within the appellation (certified brand of origin) Cava. Vinification was done in parallel on an industrial scale (100 000 l). The use of the fining mixture in grape juice made the fermentations more complete and gave wines with less browning ability, more foam stability time and a lower content of nitrogenous fraction, polyphenols and some volatile compounds than the wines treated with single bentonite. Sensorial analysis showed that the wines produced with the use of different fining agents had different organoleptic characteristics. In addition, the effect of fining agent added pre-fermentatively was observed on some components of sparkling wines.

Improved size-exclusion high-performance liquid chromatographic method for the simple analysis of grape juice and wine polysaccharides

Abstract A size-exclusion HPLC method was developed for the separation and quantification of grape juice and wine polysaccharides. Polysaccharide extraction was carried out by precipitation and two chromatographic procedures were tested with the polysaccharide precipitate solution: direct injection, and fractionation of non-negatively charged (NCPS) and negatively charged (CPS) polysaccharides using an anion-exchange cartridge, before injection. The direct procedure (injection of the precipitate solution on two GPC columns and RI detection) was chosen, because the sum of areas of NCPS fractions represented 1.42% of the total area (sum of areas of NCPSs plus sum of areas of CPSs). The precision, linearity, sensitivity and accuracy of this method were established. Identification was performed by pectins and polyacrylic acids. The concentration of each polysaccharide identified according to the molecular mass was obtained by considering that the whole area (100%) contains the total number of polysaccharides determined by colorimetric method. Three polysaccharides were separated in grape juice (19 000; 2000 and 1000, approximately), whereas seven polysaccharides were obtained in wine (45 000; 19 000; 12 000; 7000; 4000; 2000 and 1000, approximately).

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.

Analytical conditions for the determination of 23 phenylthiocarbamyl amino acids and ethanolamine in musts and wines by high-performance liquid chromatography

Abstract An improved HPLC method, using phenyl isothiocyanate (PITC) as derivatization agent, was developed for the separation and determination of 23 amino acids and triethanolamine in must and wine, without any pretreatment of the samples. The stability of dry and dissolved phenylthiocarbamyl derivatives was studied. The effects of pH, polarity, temperature and the addition of an ion-pairing reagent to facilitate the chromatographic separation were investigated. Four Penedes musts and their wines, from Macabeo and Parellada varieties, were analysed. The free amino acid contents found were compared with published results for the same varieties.