Miriam Ortega-Heras

Aroma composition of wine studied by different extraction methods

Abstract Several isolation and concentration methods have been developed for the analysis of volatile components in wine. However, it is generally admitted that none of them fulfill all the requirements for the isolation of aroma compounds and that it is necessary to combine different extraction methods to obtain the complete volatile fraction. Three extraction methods have been studied: liquid–liquid extraction, static headspace and a new method developed in our laboratory, which has the same principle as the dynamic headspace technique. The volatiles were swept along with a carrier gas and later condensed in a cold trap. The advantages and disadvantages of the three methods regarding sample preparation, component losses and artifact formation, have been evaluated. Also, the sensitivity and reproducibility have been compared. With the liquid–liquid extraction method used, a new compound has been described for the first time in wine. This compound is 5,6,7,7a-tetrahydro-4,4,7a-trimethylbenzofuran-2(4H)-one. Liquid–liquid extraction and static headspace show good reproducibility; although static headspace is useful for the analysis of highly volatile compounds, it is not able to detect trace compounds due to its lack of sensitivity. The new method allows to obtain an extract, free of artifacts and foreign substances that were not in the original wine. As no solvent is used, the extracts may be tasted and sensorially analyzed.

Effect of micro-oxygenation and wood type on the phenolic composition and color of an aged red wine.

Many studies have recently been published focused on the effects of micro-oxygenation on the quality of wines, its application modes, and doses, etc. However, there are still few scientific papers on how previously micro-oxygenated wines perform during storage or barrel aging. This study focused on the evolution of the phenolic composition, especially of anthocyanins, and color, together with astringency and tannins, during micro-oxygenation before barrel aging. In addition, to evaluate whether wine evolution during aging depends on barrel type, wines were aged in four different oak barrel types. Tempranillo wines, some micro-oxygenated before malolactic fermentation and others not, were aged for 12 months in American, French, Central European, and Spanish oak, following wine evolution during that period. The study was carried out for two consecutive vintages. Results showed that all wines evolved similarly; therefore, the micro-oxygenation treatment neither accelerated nor delayed the typical changes of aging. Slightly different evolutions were detected according to the barrel wood type, whether or not the wine was micro-oxygenated. The varied evolutions must therefore be associated with the differences from each oak type (structure, grain and density, composition, etc.).

Volatile compounds of red wines macerated with Spanish, American, and French oak chips.

The volatile composition of a red wine aged for 2 months with three different Spanish oak chips (Quercus pyrenaica and Quercus petraea) from different regions of Castilla y León was compared with that of wines aged with American and French chips. In general, the extraction kinetics showed that the maximum concentration of the volatile compounds extracted from wood can be reached in only 1 month. In the final wines, the levels of furanic aldehydes and eugenol were higher in the wines macerated with Spanish chips, whereas cis-whiskey-lactone, vanillin, and methyl vanillate showed higher levels in wines treated with American chips. Among the wines treated with the different Spanish chips, the differences observed in the volatile composition were more related to the geographical origin of the forest than to the botanical species. In general, the wines macerated with Spanish chips showed levels of oak-related volatile compounds that were more similar to those macerated with French chips than to those macerated with American chips.

Techniques for improving or replacing ageing on lees of oak aged red wines: The effects on polysaccharides and the phenolic composition

Alternative techniques to the ageing on lees are being looked for in order to guarantee the improvements provided by this technique but eliminating its disadvantages. The aim of this work was to study the effect of ageing on lees and other alternative techniques (addition of β-glucanase enzymes to the lees; use of different yeast commercial preparations with or without β-glucanase enzymes; use of non-toasted oak chips; and ageing on lees together with micro-oxygenation) on the phenolic compounds, colour, proteins, polysaccharides and sensorial characteristics of red wines during vinification and ageing in oak barrels for 6months on two consecutive vintages. Only the use of lees together with micro-oxygenation seemed to have a positive effect on the colour stability, due to the formation of new pigments that allows the intensity and blue notes of wines to be maintained during the barrel ageing process. All the techniques studied released total and neutral polysaccharides, although the type and content of these compounds depended on the technique used, and the yeast derivative added. No clear effect was observed with the use of β-glucanase enzymes. The sensory analysis showed that some of the wines treated were better valued than the control wines. The results obtained indicated that is difficult to select the technique that allows us to obtain the best quality wine.

Changes in Polysaccharide Composition during Sparkling Wine Making and Aging

The evolution in polysaccharide composition and molecular weights during sparkling wine making and aging was studied for the first time in this work. Different autochthonous grape varieties from Spain (Verdejo, Viura, Malvası́a, Albarı́n, Godello, Garnacha and Prieto Picudo) were used to elaborate sparkling wines following the champenoise method. Principal component analysis showed differentiation of wines according to polysaccharide families. This differentiation was due to the process of aging on yeast lees, but not to the variety employed. The content of mannoproteins during aging was positively correlated (r = 0.792) with total polysaccharides from grapes. After six months of aging the highest content of mannoproteins and polysaccharides rich in arabinose and galactose was obtained. Also a shift to lower molecular weights was observed. The combination of these two characteristics could imply a better foam stability and thus sensory quality of sparkling wines.

Study of the effect of vintage, maturity degree, and irrigation on the amino acid and biogenic amine content of a white wine from the Verdejo variety.

BACKGROUND The aim of this study was to determine the effect of three factors directly related to the amino acid content of grapes and their interaction. These three factors were vintage, maturity degree and irrigation. The evolution of amino acid was also assessed during the winemaking along with the effect of maturity and irrigation on the biogenic amine formation. The grapes used for this study were of the Verdejo variety. RESULTS The results indicated that there was a strong vintage effect on amino acid content in grapes, which seemed to be clearly related to climatic conditions. The effect of maturity on amino acid content depended on vintage, irrigation and the amino acid itself although it was observed that irrigation caused the increase of most amino acids present in the berry. Irrigation did not affect the evolution of nitrogen compounds during the alcoholic fermentation process but the maturity degree in some of the amino acids tested did so. No direct relationship could be established between irrigation or maturity degree and biogenic amines. However, it should be noted that the biogenic amine content was very low. CONCLUSIONS Vintage has a strong effect on the amino acid content in grapes which appears to be related to weather conditions. No direct relationship has been found between irrigation or maturity degree and biogenic amines content. Furthermore, it is noted that biogenic amine content found in final wines was very low.

Effect of Aging on Lees and of Three Different Dry Yeast Derivative Products on Verdejo White Wine Composition and Sensorial Characteristics

A study was made of the effect of aging on lees and of three different commercial yeast derivative products of different composition and degree of purification on the phenolic compounds, color, proteins, polysaccharides, and sensorial characteristics of white wines. The results obtained showed that the lees and yeast derivative products can interact or adsorb some of the phenolic compounds present in wines, reducing their concentration. This reduction depends on the treatment applied, the phenolic compound analyzed, and the stage of vinification or aging process. The use of lees and yeast derivative products can reduce the color intensity and the browning of the wines immediately following treatment. The monosaccharide and polysaccharide content of yeast derivative products depends on the manufacturing process and degree of purification of the product, both of which have an influence on wine treatments. After 6 months in the bottle, both the aging on lees and the treatment with commercial yeast derivative products gave rise to wines with better sensorial characteristics than in the case of the control wines.

Use of Commercial Dry Yeast Products Rich in Mannoproteins for White and Rosé Sparkling Wine Elaboration.

In sparkling wines, mannoproteins released during yeast autolysis largely affect their final quality. This process is very slow and may take several months. The aim of this work was to study the effect of several commercial dry yeast autolysates on the chemical composition, foam, and sensory properties of white and rosé sparkling wines aged on lees for 9 months during two consecutive vintages. The addition of these products in the tirage phase did not affect either the content of phenolic compounds, amino acids, and biogenic amines or the foam properties. The commercial product with the highest mannoprotein content and the highest purity caused significant changes in the volatile composition of the wines and enhanced the fruity aromas in both Verdejo and Godello sparkling wines.

Multivariate analysis for the differentiation of sparkling wines elaborated from autochthonous Spanish grape varieties: volatile compounds, amino acids and biogenic amines

The aim of this work was to focus on the study of the volatile composition of white and rosé base wines elaborated from different autochthonous grape varieties in Spain (Verdejo,Viura, Malvasía, Albarín, Godello,PrietoPicudo and Garnacha) and the evolution of the sparkling wines elaborated from them following the “champenoise” method. The amino acids and biogenic amines were also studied. Multivariate analyses (factorial and stepwise discriminant) were carried out to study the influence of these compounds all together. Base and sparkling wines from Albarín, Verdejo, Godello and PrietoPicudo were the richest in most of the volatile compounds analyzed, especially of ethyl esters and alcohol acetates, compounds that contribute to the fruity aroma of wines. During the aging on lees in the bottle of sparkling wines, an increase in branched ethyl esters, ethyl lactate and γ-butyrolactone, and a decrease in terpenes (mainly citronellol and geraniol) were observed. In general, the levels of biogenic amines in all the sparkling wines studied were very low, which does not represent a negative effect on their quality and safety.

Effect of the aging on lees and other alternative techniques on the low molecular weight phenols of Tempranillo red wine aged in oak barrels.

The effect of different alternative techniques to the traditional aging on lees on the low molecular weight phenolic compounds of red wines was study as well as their evolution during the aging in oak wood barrels for six months. The study was carried out with Tempranillo red grapes from two consecutive vintages. The techniques assayed were the traditional aging on lees with or without the addition of exogenous β-glucanase enzymes, the use of yeast derivative preparations also with or without the addition of exogenous β-glucanase enzymes, the micro-oxygenation applied together with the aging on lees, and the use of non-toasted oak wood chips. Hydroxycinnamic acids were the compounds most affected by these treatments, mainly in the wines treated with chips and commercial yeast derivative products, which showed higher concentrations of the free acids, compounds that play an important role in wine stabilization color since they can act as anthocyanin copigments. The differences found between the assayed treatments were more important in the 2007 vintage than in the 2008. However, a more significant effect of micro-oxygenation in the 2008 vintage was observed, which could be related to the fact that in this vintage the treatment was longer. In the 2008 vintage, the differences between treatments decreased along the aging in barrel. This vintage effect could be associated to the differences in the phenolic concentration of the initial wines. In this sense more research should be done to corroborate this fact.