María José García’s research while affiliated with Polytechnic University of Valencia and other places

The aim of this research is to study the possibility of increasing the quality of red wins made with the Monastrell grape variety. A methodology was established to improve the concentration levels of polyphenol and aroma in these wines. Among flavonoids, the copigmenting effect of rutin stands out, and was tested in both winery and field applications. Buckwheat extract (Fagopyrum esculentum), in which rutin is the main flavonoid, may be of interest for viticulture given its biological activity. This paper focuses on researching the effect of applying the prefermentative vegetable extract of buckwheat (Fagopyrum esculentum) on the concentration of polyphenols and aroma compounds in vineyards. Simultaneously, a study was carried out to compare the effect of pure copigment (rutin) when applied in vineyards and cellars. Traditional vinification was done, plus prefermentative cold maceration. The application of buckwheat extract, and rutin extract to a lesser extent, to Monastrell grapes increased the concentration of malvidin and other anthocyanins, and total anthocyanins. After 12-month storage, no differences were observed in the percentage of copigmented, polymerised and free anthocyanin, the total polyphenol concentration, and the tannin quality parameters like DMACH (aldehyde p-dimethylaminoacimaldehyde) and the Gelatin Index. The concentrations of diethyl succinate, 2 phenylethyl acetate, vanillin and ethyl octanoate increased, while other compounds decreased when the copigment was added. The maceration technique followed during the vinification process had very little effect on polyphenolic compounds. The prefermentative maceration slightly increasing the concentration of total polyphenols, but had no effect on the parameters related to colour, anthocyanin concentration, nature of anthocyanins, their binding state or tannin quality parameters. The results showed that cold prefermentation maceration increased the concentration of some volatile compounds, including alcohols and esters, which should be considered important contributors to Monastrell wine aroma. The combination of the applying buckwheat extract and pure rutin together, and prefermentative cold maceration, positively affects the polyphenolic concentration and increases the concentration of quality volatile compounds.

The present work studies the effect of adding catechin and plant extract rich in catechin, Camellia sinensis (green tea) extract, on the volatile and polyphenolic composition of red wines made from Monastrell grapes. The aim of this research is to study the way to increase the red wine quality made with Monastrell variety of grapes. In one of them, the green tea extract was applied to grapes in vineyards 10 days before harvest. In another, catechin was applied to vineyards in the same way, and finally, catechin was applied during grape processing. Each trial was fermented by traditional vinification and prefermentative maceration for 5 days prior to alcoholic fermentation. A simple ANOVA analysis was used to evaluate if the application of copigments and winemaking techniques influenced wine composition. In addition, a multifactorial ANOVA was used to study the copigment treatment effect x winemaking technique interaction. Wine polyphenolic and volatile composition were analysed 12 months after fermentation. The application of green tea extract and catechin to vineyards increased (13%–16%) the concentration of anthocyanins in relation to the control to a greater extent when the initial polyphenolic concentration of grapes was lower. The volatile concentration rose when copigments (green tea extract and pure catechin) were applied to vineyards, in particular, hexyl acetate, ethyl octanoate and vanillin. The application of techniques like prefermentative maceration enhances the effects of copigments added to vineyards. The combination of the application of green extract or pure catechin with prefermentative cold maceration, had positive effects increasing polyphenols and volatile compounds concentration.

This work studies the effect of applying rosemary extract and caffeic acid on the polyphenolic and aromatic composition of Monastrell wines, as well as the influence of traditional winemaking or incorporating prefermentative maceration. For this purpose, three treatments were carried out in triplicate. In one of them, rosemary extract was applied on the clusters 10 days before harvest, caffeic acid was applied in the same way in another, and, finally, this acid was applied to grape before crushing. Each treatment was run by both traditional vinification and vinification with prefermentative maceration. After making wines, they were monitored for 12 months after fermentation. The application of rosemary extract, and that of caffeic acid but to a lesser extent, increased the color, the concentration of anthocyanins, and the percentage of polymerized anthocyanins, while prefermentation maceration gave rise to wines with a higher concentration of condensed tannins and polyphenols. Applying rosemary extract and caffeic acid in the vineyard also increased the concentration of esters and other compounds that favor wine aromatic quality, which was also enhanced by prefermentative maceration.

Several multivariate methods including partial least squares (PLS) regression, principal component regression (PCR) or multiple linear regression (MLR) have been applied to predict wine quality, based on the definition of chemical and phenolic parameters of grapes and wines harvested at different ripening levels. Three different models including grape phenolic maturity parameters (grape), wine phenolic parameters (wine) and a combination of grape and wine phenolic parameters (grape + wine) were analysed for each of the wine sensory attributes. The grape parameter model has been presented as the best test to predict wine quality based on sensory scores. On the other hand, wine models showed lower accuracy. The combination of grape and wine parameters presented intermediate results showing sometimes good predictability. Moreover, PLS and PCR appeared as more accurate multivariate methods compared to MLR. Although MLR showed higher correlation coefficients, lower RPD values were observed, displaying thus its lower prediction accuracy. Multivariate calibration statistics appeared as a promising tool to predict wine sensory quality in an easy and inexpensive way. © 2015, Institute of Agricultural and Food Information. All rights reserved.

The effect of prefermentative and postfermentative caffeic acid addition (CFA), prefermentative cold maceration and micro-oxygenation on the phenolic and color composition of Tempranillo wines was investigated. Cold soaking and dry ice addition were performed as prefermentative techniques. Wines were analyzed after the end of the malolactic fermentation, and after six and 12 months' storage. The results showed an important effect in wines to which CFA had been added, suggesting intramolecular copigmentation reactions through direct interaction between anthocyanins and free phenolic acids, thereby increasing the acylated anthocyanin fraction with an increase in color stability. The higher concentration of total phenols and lower hue values in CFA-added wines also contributed to the stability of these compounds during storage. Prefermentative cold maceration was shown to be influenced by the vintage. Phenolic acids, the acylated anthocyanin fraction, and total phenolics showed higher values in CFA-added and micro-oxygenated wines. No differences were found in color density between the control wines and both the prefermentative and postfermentative CFA-added wines. However, a higher anthocyanin polymeric fraction, and higher acylated anthocyanins, phenolic acids and total phenols, were observed in the CFA-added wines. The implications of this for the color stability of Tempranillo are also discussed.

Fining agents can also have an effect on the flavor components of the must, and other compounds which are important for the sensory characteristics and in the case of sparkling wine, the foam quality. The influence of fining agents and tirage solution, on volatile compounds, and foam characteristics of sparkling wines made from grapes of the Bobal variety was studied. The data obtained show how the fining agent affects the foam properties and the final volatile composition of sparkling wines. In this study, it was bentonite with gelatine that produced amounts of acetates and esters. The use of Colle 2P in the tirage solution means that more aromatic sparkling wines with better foam characteristics can be obtained.

The influence of the prefermentative addition of copigments and different winemaking technologies on the polyphenolic composition of Tempranillo red wines after malolactic fermentation was studied. Six experiments dealing with the prefermentative addition of caffeic acid, rutin, (+) catechin, white grape skin tannin, white grape seed tannin and control wines were realised. Three different winemaking technologies (traditional vinification, prefermentative cold maceration at 6–8°C and cold soak at 0–2°C with dry ice) were studied. Prefermentative addition of copigments increases anthocyanin copigmentation reactions and produces wines with a greater colour, a higher anthocyanin concentration, a superior contribution of anthocyanins to the colour of the wine, a superior percentage of tannins polymerised with polysaccharides and less astringency. Cold prefermentative maceration increases the extraction of polyphenols, the anthocyanin copigmentation reactions and the polymerisation reactions between tannins and polysaccharides. The effectiveness of the combination of copigments and prefermentative maceration treatments was demonstrated by the increase of the concentration of the polyphenolic compounds.

The chemical composition of 50 Spanish white wines, 1998 and 1999 vintages, from three subzones of the Designation of Origin Valencia (Alto Turia, Clariano and Valentino), was studied. The 35 components analysed were grouped according to the conventional parameters, alcohols and polyols, and esters. Discriminant analysis was applied to each one of these groups and to each one of the vintages; this did not allow us to correctly classify these wines in their corresponding subzone. To carry out a more exact classification of the studied wines in their corresponding subzone, it was necessary to carry out a discriminant analysis with the 35 parameters and the 50 wines (98% well classified). A stepwise discriminant analysis was used to eliminate the less significant variables. The discriminant analysis was also carried out using only 18 variables and this also led to successful results: 96% of the samples were correctly classified. Using only four parameters, total acidity, ashes (conventional parameters), pentanol (alcohols) and diethyl succinate (esters), we managed to successfully classify 84% of the wines studied into their corresponding subzone.

Ninety-one young varietal wines from the Valencian community (Spain), made from Cabernet Sauvignon, Tempranillo, Monastrell, and Bobal grapes, were tested on the basis of 33 variables: 9 conventional parameters, 10 alcohols and polyols, and 14 esters. Discriminant analysis was used to identify and explain the differences among samples, as well as to determine whether it is possible or not to differentiate among varieties. This differentiation (100% of the samples) has been possible due to the new discriminant analysis based on only 11 main variables: total acidity, cis-3-hexenol, methanol, glycerol, 2,3-butanediol, isobutyric alcohol, 1-pentanol, acetaldehyde, ethyl propionate, ethyl decanoato, and gamma-butyrolactone, which allow differentiating 100% of the 1994 vintage and 97% of the 1995 vintage.

The modern enology technology allows the elaboration of high quality wines that preserve the differentiating characteristics according to the vine, production area, fermentative yeasts or to the different technology used for the elaboration of wine. The study of 45 spanish white wines with « Denomination of Origin », 5 of those belong to Alto Turia, 6 to the Clariano, 14 to the Valentino, 10 to the Valdepeñas and 10 to the Rueda, allows to establish importants differences among them according to their chemical composition. This differentiation has been possible by means of the application of the Discriminant Analysis to 35 parameters related with the chemical composition of theses wines. In the first place these compounds have been grouped, according to their chemical affinity, in three groups: general component, alcohols and esters. Discriminant Analysis has been applied to each one of these groups, being observed that the esters allow to be carried out the classification of these wines in their corresponding groups, because only it confuses some wine of Clariano with those of Valentino. To carry out a correct classification of 45 wines studied in their corresponding « Denomination of Origin », it is necessary to appeal to carry out a Discriminant Analysis with the 35 compounds together, being, in this case, the compounds that contribute to this differentiation pratically the same ones that those which contribued to differentiate each group of variables separately.