Determination of Volatile Compounds in Wine by Automated Solid-Phase Microextraction and Gas Chromatography.

Solid-phase microextracfion in headspace mode has been applied to the determination of volatile compounds (3-methyl-1-butyl acetate, 3-mefhyl-1-bufanol, ethyl hexanoate, pentanol, hexanol, linalool, diethyl succinate, -terpineol, 2-phenylethyl acetate, geraniol, 2-phenylethanol and octanoic acid) in wine samples from the Denominación de Origen Calificada Rioja using gas chromatography and a flame ionization detector. After the preliminary tests, several parameters were optimized using a Plackett-Burman design to get the most relevant variables. These parameters were: extraction time, desorption time, split ratio, magnetic stirring, type of fibre, type of injection (headspace or direct sampling) and type of salt. Five wine samples were analysed under optimum conditions. Concentrations ranging from 0.0104 mg L-1 for pentanol and 48.9 mg L-1 for 3-methyl-1-butanol were obtained. Linalool, -terpineol and geraniol were not detected. Limit of detection ranging 0.00150-0.00800 mg L-1 and relative standard deviation ranging 1.1-5.7% were obtained

Determination of thiocyanate by carbonyl sulphide (OCS)generation and gas-phase molecular absorption spectrometry.

A method for determination of thiocyanate by gas-phase molecular absorption spectrometry is described. The proposed method is based on the continuous generation of carbonyl sulphide and preconcentration in a liquid nitrogen trap. Later, the product is volatilised and the absorbance at 224 nm is measured. Under the optimised conditions, the calibration graph was linear for 2-80 g ml-1, with a detection limit of 1 g ml-1. No metal ions interfered. The method was tested with saliva samples from non smokers and smokers; the results show that it is possible to distinguish between these two categories of individuals

Separation and determination of volatile compounds in synthetic wine samples by gas chromatography using UV-visible molecular absorption spectrometry as detector

This paper shows the separation and determination of eight compounds containing the OH group (ethanol, pentanol, 3-methyl-l-butanol, hexanol, phenol, benzyl-alcohol, phenylethanol and geraniol) in synthetic wine by gas chromatography using UV-Vis molecular absorption spectrometry as detection system. All the parameters affecting the separation and determination were optimised using some methods of experiment design. The analytical characteristics of each compound were calculated and detection limits ranging from 2.3 to 74 mg 1-1 have been obtained. © 2002 Elsevier Science B.V. All rights reserved

Ultrasound-assisted extraction of volatile compounds from wine samples: Optimisation of the method.

This study describes a liquid-liquid extraction technique for extracting volatile compounds from wine using dichloromethane and ultrasounds. This technique permits the simultaneous extraction of different samples with high reproducibility. After the preliminary tests, several parameters (sample volume, solvent volume and extraction time) were optimised using a factorial design to obtain the most relevant variables. The analytical characteristics were obtained such as calibration graphs, detection limits ranging from 0.0238 mg L-1 for 1-pentanol to 0.261 mg L-1 for octanoic acid, quantification limits and relative standard deviation from 2.1 to 6.2%. Extraction yields were calculated giving a range 9.16-1.2%. The optimised conditions were applied to the extraction of samples of young wines from the Denominación de Origen Calificada Rioja category using gas chromatography and a flame ionisation detector. © 2005 Elsevier B.V. All rights reserved

Quantitative Profiling of Volatile and Phenolic Substances in the Wine Vernaccia di Serrapetrona by Development of an HS-SPME-GC-FID/MS Method and HPLC-MS

A headspace solid-phase microextraction coupled to gas chromatography with mass spectrometry and flame ionization detection (HS-SPME-GC-MS/FID) method has been developed for quantifying the main volatiles of the Italian sparkling red wine Vernaccia di Serrapetrona, leading to establish that the divinylbenzene/carboxen/polydimethylsiloxanecoated (gray) fiber, an equilibration time of 15 min, and an extraction time of 15 min at a temperature of 35 °C are the conditions representing the best compromise in terms of sensitivity and time expense, to carry out the analyses. Among the volatiles quantified, 2-phenylethanol, 3-methylbutyl acetate, and ethyl esters levels resulted to be above their odor thresholds, thus being probably responsible for the aroma of this wine with their positive attributes. Phenolic compounds, namely gallic acid, p-coumaric acid, caffeic acid, (+)-catechin, and (+)-epicatechin, were also quantified using high-performance liquid chromatography-MS, thus obtaining an overall characterization of molecules fundamental for both the sensory and the healthy characteristics of the wine. The total phenolic content was found to be in the range of 19.25–61.67 mg l−1 with the most abundant compound being gallic acid (7.44–25.78 mg l−1). Main differences in volatile and phenolic compounds between samples were discussed and analyzed by chemometric techniques as principal component analysis

Volatile composition and sensory profile of wines obtained from partially defoliated vines: the case of Nero di Troia wine

The effects of defoliation treatments performed in the bunch-zone on volatile composition and sensory attributes of the corresponding wines were evaluated. Nero di Troia grapes were subjected to four different treatments: no leaf removal (N); leaf removal in the fruit-zone along the east side (at complete veraison) (E); leaf removal in the fruit-zone along the east and west side (at complete veraison) (E/W); almost complete leaf removal along the west side (at complete veraison) and at pre-harvest also along the east side (F). For each defoliation thesis, half of the wine was treated with oak chips in order to verify whether the treatments with oak chips can mask the effects of defoliation. Defoliation partially affected the volatile profiles. Data concerning the volatile profiles show that the highest concentrations of total acids were detected in N and E wines, while those of the total ethyl esters were detected in F wines, and the lowest terpenes concentrations were found in E wines. The oak-treated wines show the highest contents of 1-heptanol, 1-octanol, many ethyl esters, and total hydrocarbons. They were the only in which the whisky lactone was detected. From a sensory point of view, the wines from almost completely defoliated grapes exhibited the lowest scores of gustatory-olfactory intensity, persistence, and quality. The wines that were not treated with chips exhibited sensory profiles characterized by floral and fruity notes, while those treated with oak chips showed sensory profiles characterized by spicy and fruity notes

Characterization of volatile fraction of typical Irpinian wines fermented with a new starter yeast

Non-Saccharomyces yeasts are microorganisms that play an important role in the fermentation dynamics, compositions and flavour of wine. The aromatic compounds responsible for varietal aroma in wine are mainly terpenes, of which the most important group are the monoterpenes because of their volatility and odour if present in a free form. In fact, some terpenyl-glycosides do not contribute to the aroma unless they are hydrolysed. The glycosylated form of terpenes can be converted by hydrolysis with β-glycosidases produced by yeasts during the winemaking process, into aromatic compounds. In this study we utilized a non-Saccharomyces yeast, with a high extra-cellular glycosidase activity, isolated from grapes of cultivars typical of Irpinia region. This strain, identified as a Rhodotorula mucillaginosa (strain WLR12), was used to carry out an experimental winemaking process and the results were compared with those obtained with a commercial yeast starter. Chemical and sensorial analysis demonstrated that the wines produced with WLR12 strain had a more floral aroma and some sweet and ripened fruit notes compared to those obtained with commercial yeast. The data also showed an increasing of the free terpenes fraction that, however, did not significatively modify the bouquet of the wines