Esperanza Fernández

Differentiation of white wines by their aromatic index

Wines from four Galician white varieties (Albariño, Loureira, Treixadura and Dona Branca) with 1992 to 1995 vintages have been analysed, in order to obtain their characterisation by the aromatic index. Monoterpenes, higher alcohols, ethyl esters, fatty acids, acetates, volatile phenols and heavy sulphur compounds were analysed by gas chromatography alone and together with mass spectrometry. Flavour compositions were similar for each wine obtained from grapes harvested in different years. Comparisons between odour unit values (OUV) from each wine variety and from these vintages were similar. However, odour profiles of Galician wines from these years were clearly differentiated. A correct differentiation could be achieved between samples elaborated with different varieties, when principal component and linear discriminant analysis were applied to the OUV data.

Aromatic Compounds in Wines Produced During Fermentation: Effect of Three Red Cultivars

The aromatic compounds produced during the fermentation of the red grape cultivars Caiño Tinto, Caiño Longo, and Caiño Bravo were analysed by gas chromatography (FID) on the wines of 2002 and 2003 vintages. In both years, significant differences (p < 0.001) were observed between the wines with respect to the concentrations of aromatic compounds. Caiño Longo wines had the highest concentrations of acetates and esters. The concentrations of ethyl ester and acetates in Caíño Bravo wines were comparatively very low. Principal components analysis confirmed these results: the wines made from the different cultivars and the vintages were clearly different.

Contribution of some grape-derived aromatic compounds to the primary aroma in red wines from cv. Caiño Tinto, cv. Caiño Bravo and cv. Caiño Longo grapes

The free volatile compounds of two successive vintages of cv. Caino Tinto, Caino Bravo and Caino Longo red wines, together with the volatile compounds released after the enzymatic hydrolysis of their glycosidically bound forms, were identified and quantified by gas chromatography using a flame ionization detector (GC/FID). All these wines possessed the same free volatile compounds; Caino Longo wines showed the highest concentrations and Caino Tinto wines the lowest. In all cases, the release of the bound forms of these compounds may contribute to the final aroma, from both a qualitative standpoint (with the appearance of free 4-terpineol, nerol and geraniol) and quantitative standpoint (notable increases were recorded for most of the compounds detected). The principal component analysis (PCA) showed a good separation of the different wine cultivars and vintages. Caino Tinto wines were more homogeneous between vintages than the others.

Differentiation of Spanish Alcoholic Drinks, Orujo, Obtained from Red and White Grape Pomace Distillation: Volatile Composition

A total of 61 samples of Galician (NW Spain) Orujo spirits, 28 from white grape pomace and 33 from red grape pomace, were analyzed by gas Chronoatography with flameionization detector (GC-FID) in order to determine which volatile compounds show significant differences (p ≤ 0.05). Orujo spirits obtained from white grape residues showed a higher concentration of methanol, hexanols, hexenols, ethyl lactate, benzaldehyde, 2-butanol, and rate 1-propanol/2-methyl-1-propanol, which indicated a high trend to the degradation by anaerobic microorganisms during the storage and alcoholic fermentation of the raw material. However, in the spirits from red grape, the concentration of ethyl esters was higher as was the concentration of the compounds that are derived from the activity of aerobic bacteria or oxygen contact with the fermented grape pomace, especially acetaldehyde and ethyl acetate.

Note: Effects of Oak Wood on the Aromatic Composition of Vitis vinifera L. var. treixadura Wines

Treixadura wines from the 1998 vintage were obtained from traditional vinification in a winery. After alcoholic fermentation, the wine was subjected to ageing in oak barrels for three months. One part of the wine is placed in barrels of American oak and the other part in French oak (Allier oak). Wine stored simultaneously in a stainless steel tank was used as a control. Chemical composition and volatile compounds of wines were analysed. There were no appreciable differences in alcohol and tartaric acid among the wines stored under different conditions, but differences were observed in pH, total and volatile acidity, reducing sugars, malic and lactic acids. Ageing in oak barrels resulted in an increase in volatile acidity and Folin—Ciocalteu index, and a decrease of free and total sulphur dioxide. Various monoterpenes, norisoprenoids, hexenols, sulphurs, volatile phenols, acetals and lactones increase their content notably when aged in barrels of both American and French oak. On the other hand, some acetates, ethyl esters and fatty acids were present in higher concentrations in the wine stored in stainless steel tank. Sensory results indicated that the wine aged in French (Allier) oak was better scored than when aged in American oak, as it provided subtle and delicate nuances of wood, which did not mask the fruity aroma of the Treixadura wine but contributed to its aromatic complexity.