Mar Vilanova

Assimilable nitrogen utilisation and production of volatile and non-volatile compounds in chemically defined medium by Saccharomyces cerevisiae wine yeasts

Surveys conducted worldwide have shown that a significant proportion of grape musts are suboptimal for yeast nutrients, especially assimilable nitrogen. Nitrogen deficiencies are linked to slow and stuck fermentations and sulphidic off-flavour formation. Nitrogen supplementation of grape musts has become common practice; however, almost no information is available on the effects of nitrogen supplementation on wine flavour. In this study, the effect of ammonium supplementation of a synthetic medium over a wide range of nitrogen values on the production of volatile and non-volatile compounds by two high-nitrogen-demand wine fermentation strains of Saccharomyces cerevisiae was determined. To facilitate this investigation, a simplified chemically defined medium that resembles the nutrient composition of grape juice was used. Analysis of variance revealed that ammonium supplementation had significant effects on the concentration of residual sugar, L-malic acid, acetic acid and glycerol but not the ethanol concentration. While choice of yeast strain significantly affected half of the aroma compounds measured, nitrogen concentrations affected 23 compounds, including medium-chain alcohols and fatty acids and their esters. Principal component analysis showed that branched-chain fatty acids and their esters were associated with low nitrogen concentrations, whereas medium-chain fatty esters and acetic acid were associated with high nitrogen concentrations.

Contribution by Saccharomyces cerevisiae yeast to fermentative flavour compounds in wines from cv. Albariño

A comparative study was made of the fermentation products of Spanish Albariño wines produced with spontaneous yeast flora and an indigenous selected Saccharomyces cerevisiae strain (Alb16). The content of fermentative volatile compounds was determined by gas-chromatography-FID. Fifteen compounds (5 alcohols, 7 esters and 3 acetates) were identified in the two Albariño wines studied. Higher alcohols, ethyl esters (except ethyl hexanoate and ethyl octanoate) and acetates were in greater concentration in the spontaneous fermentation wine than in that with selected Alb16 strain. Principal components analysis showed good separation between the different wines.

Early leaf removal impact on volatile composition of Tempranillo wines

BACKGROUND Early defoliation is a very innovative technique in viticulture used for yield management. The effects of early leaf removal performed manually and mechanically at two different phenological stages, pre-bloom and fruit set, on the volatile composition of Tempranillo (Vitis vinifera L.) wines were studied. Volatiles were identified and quantified by gas chromatography. RESULTS Early leaf removal only modified the total concentrations of C₆ compounds and acetates, whereas total alcohols, esters, volatile acids and terpenes remained generally unaffected. Early defoliation induced a significant reduction in C₆ compounds and increased the concentrations of acetates in Tempranillo wines. An effect of timing (pre-bloom vs fruit set) alone was observed for all acetates analysed. Regarding the method of defoliation (manual vs mechanical), significant differences in some ethyl ester (ethyl-2-methylbutyrate and ethyl octanoate) and volatile acid concentrations were observed among treatments. Ethyl octanoate, 2-phenylethyl acetate, 3-methylbutyl acetate and hexanoic acid, with OAV (odour activity value) > 1 and mainly fruity and floral odour descriptors, showed higher levels after early defoliation treatments compared with non-defoliated vines. Principal component analysis illustrated the difference in wines from defoliated and non-defoliated treatments based on their volatile composition. CONCLUSION It can be concluded that early leaf removal significantly modified the wine aroma compounds, increasing or decreasing several of these compounds.

Variability in chemical composition of Vitis vinifera cv Mencía from different geographic areas and vintages in Ribeira Sacra (NW Spain)

A chemical study was conducted from 2009 to 2012 to examine spatial and seasonal variability of red Vitis vinifera Mencía located in different geographic areas (Amandi, Chantada, Quiroga-Bibei, Ribeiras do Sil and Ribeiras do Miño) from NW Spain. Mencía samples were analysed for phenolic, (flavan-3-ols, flavonols, anthocyanins, acids and resveratrol), nitrogen (TAC, TAN, YAN and TAS) and volatiles compounds (alcohols, C6 compounds, ethyl esters, terpenes, aldehydes, acids, lactones, volatile phenols and carbonyl compounds) by GC-MS and HPLC. Results showed that the composition of Mencía cultivar was more affected by the vintage than the geographic area. The amino acid composition was less affected by both geographic origin and vintage, showing more varietal stability. Application of Principal Component Analysis (PCA) to experimental data showed a good separation of Mencía grape according to geographical origin and vintages. PCA also showed high correlations between the ripening ratio and C6 compounds, resveratrol and carbonyl compounds.

Evaluation of the aroma descriptors variability in Spanish grape cultivars by a quantitative descriptive analysis

Aroma descriptors variability was evaluated by quantitative descriptive analysis (QDA) in Spanish cultivars. Abariño, Mencía and Godello cultivars were evaluated by three expert panels by using monovarietal wines. The frequency and intensity of aroma descriptors was evaluated and geometric mean (GM) was calculated. The largest differences between cultivars were shown by principal component analysis (PCA). Albariño cultivar was characterised by Ripe fruit, Apple and Fruit descriptors; Mencía cultivar was Balsamic and Red fruit, while Citric, Grass, Pineapple, Toasting, Tropical, Dry grass, Pear, Melon and Floral were the attributes of the Godello cultivar. According to GM obtained of aroma attributes from, a positive correlation was found between Albariño and Godello cultivars. The QDA and PCA have contributing to define the aroma of different Spanish grape cultivars (Albariño, Mencía and Godello) by analysis of the monovarietal wines. The results obtained suggest that QDA is a good tool to evaluate the sensory variability of a product, when the tasting panel is good trained.

Determination of odorants in varietal wines from international grape cultivars (Vitis vinifera) grown in NW Spain

This work was carried out to investigate the odorants found in ten varietal wines from different international grape cultivars (Merlot, Cabernet Sauvignon, Pinot noir, Tempranillo, Sauvignon blanc, Riesling, Chardonnay, Pinot gris, Pinot blanc and Gewurztraminer) grown in northwest Spain. Monoterpenes, alcohols, fatty acids, ethyl esters, acetates and volatile phenols were determined by gas chromatographymass spectrometry (GC-MS). The results showed that Gewurztraminer white wines had the highest concentration of volatile compounds (35.7 mg/L). Monoterpenes, linalool, terpineol, citronellol and nerol were detected only in Riesling and Gewurztraminer white wines. In the red wines, Cabernet Sauvignon followed by Merlot wines showed the highest concentration of total volatile composition (55.60 mg/L and 50.90 mg/L respectively), characterised by a higher concentration of alcohols. Based on the individual odour threshold, white Gewurztraminer and red Pinot noir wines showed the highest total OAV value. ANOVA has shown significant differences among wines. Principal component analysis performed a grouping of the monovarietal wines – Sauvignon blanc-Pinot blanc-Riesling and Pinot gris gris-Gewurztraminer in the white wines, and Cabernet Sauvignon-Tempranillo in the red wines.

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.

Environmental and genetic variation of phenolic compounds in grapes (Vitis vinifera) from northwest Spain.

This research was supported by the Xunta de Galicia project (XUGA40301B94). Dr Vilanova acknowledges assistance from the Xunta de Galicia for the Isidro Parga Pondal Program.

Use of response surface methodology for the assessment of changes in the volatile composition of Moscato bianco (Vitis vinifera L.) grape berries during ripening.

The changes in the volatile composition of Moscato bianco grapes were evaluated during ripening. Grape berries were sampled for five weeks (16-20 °Brix) and sorted for each date in ten density classes (1.05-1.12g/cm(3)). The highest total concentration of free terpenes was found at 19.3 °Brix; however, total concentration of the bound fraction increased significantly throughout ripening. Response surface methodology was used to assess the simultaneous effect of sampling time and berry density on the volatile composition, which was satisfactorily fitted to regression models for some key terpene compounds. Total free and bound terpenes were more affected by grape density than by sampling date. The same behaviour was observed for free and bound linalool and bound nerol, whereas the stronger effect of sampling date was exhibited for bound t-rose oxide, c-rose oxide and geraniol. The results showed that the sampling strategy impacted strongly on the aroma quality of berries.

Effects of preflowering leaf removal on phenolic composition of tempranillo in the semiarid terroir of Western Spain

The effects of preflowering defoliation on the qualitative and quantitative composition of phenolic compounds in the grape skins of Tempranillo grapevines grown in a semiarid terroir of western Spain, Badajoz, were determined. Control vines were compared with defoliation carried out before flowering (ED) in 2009 and 2010. Forty-two phenolic compounds were identified and quantified in the grape skins, including anthocyanins, flavonols, flavanols (cathechin and epi-cathechin and the flavanol dimmers B1, B2, and B3), and hydroxycinnamic acids, as both simple and conjugated molecules. ED did not significantly alter the concentration of total anthocyanidins, although in 2009, 3-O-acylated monoglucosides and p-coumaroylglucoside forms were more abundant in this treatment. A nonsignificant tendency toward increased total flavanols due to defoliation treatment was observed. Leaf removal increased concentrations of flavonols (glycosides of myricetin, quercetin, kaempherol, and isorhamnetin), hydroxycinnamic acids, and stilbenes in season-specific ways. Preflowering leaf removal may contribute to increased concentrations of compounds that can form complexes with anthocyanins (copigments) and may thus improve wine color stability.