Jose María López-Roca

Effect of Different Enological Practices on Skin and Seed Proanthocyanidins in Three Varietal Wines

Proanthocyanidins are important for wine quality since they participate in astringency, bitterness and color. Given the localization of proanthocyanidins in the berry (skin and seeds), different methods have been developed that help to modulate the release of these phenolic compounds. In this study, the effect of two low prefermentative temperature techniques (cold soak and must freezing with dry ice) and the use of macerating enzymes has been studied during the vinification of three different varietal wines (Monastrell, Syrah and Cabernet Sauvignon) to assess their influence on wine proanthocyanidin concentration and composition. Syrah wines showed the lowest proanthocyanidin content, together with the lowest mDP and the highest percentage of galloylation in its proanthocyanidins. Monastrell and Cabernet Sauvignon wines showed similar proanthocyanidin concentration. The application of the low temperature prefermentative maceration (cold soak) was the most effective treatment, increasing the proanthocyanidin concentration in Monastrell and Cabernet Sauvignon wines although neither of the treatments had any effect on Syrah wines. As regards the effect of the different treatments on the proanthocyanidin composition, the results seem to indicate that the observed increases were mainly due to an increase in seed proanthocyanidins, even in the case of cold soak treatments, which occur in the absence of ethanol, suggesting that ethanol is not so crucial in the extraction of seed proanthocyanidins.

The extraction of anthocyanins and proanthocyanidins from grapes to wine during fermentative maceration is affected by the enological technique.

The effect of three enological techniques (low temperature prefermentative maceration, must freezing with dry ice, and the use of a maceration enzyme) on the extraction of anthocyanins and proanthocyanidins from must to wine during fermentative maceration was studied to determine the extent to which these compounds are extracted and to assess the changes on their qualitative composition due to enological technique applied. The results showed that the dry ice treatment led to wines with high color intensity and high anthocyanin content, the maximum rate of extraction being observed the first 6 days of fermentative maceration. Regarding the effect of the different techniques on the quantitative and qualitative composition of proanthocyanidins, only the dry ice treatment seemed to favor the extraction of high molecular weight skin proanthocyanidins. The low temperature prefermentative maceration treatment led to the highest concentration of proanthocyanidins at the moment of pressing; however, this treatment, contrary to expectations, led to wines with the highest content of seed-derived proanthocyanidins. The use of the maceration enzyme also increased the concentration of proanthocyanidins during all of the fermentative process, as compared to a control wine, although the increase was not only due to skin proanthocyanidins but also seed proanthocyanidins. We have demonstrated in this study that maceration enzymes also facilitate seed phenolic extraction.

Improving Grape Phenolic Content and Wine Chromatic Characteristics through the Use of Two Different Elicitors: Methyl Jasmonate versus Benzothiadiazole

Benzothiadiazole (BTH) and methyl jasmonate (MeJ) have been described as exogenous elicitors of some plant defense compounds, polyphenols among them. The objective of this study was to determine whether the application of BTH or MeJ to grape clusters at the beginning of the ripening process had any effect on the accumulation of the main flavonoid compounds in grapes (anthocyanins, flavonols, and flavanols) and the technological significance of these treatments in the resulting wines. The results obtained after a 2 year experiment indicated that both treatments increased the anthocyanin, flavonol, and proanthocyanidin content of grapes. The wines obtained from the treated grapes showed higher color intensity and total phenolic content than the wines made from control grapes. The exogenous application of these elicitors, as a complement to fungicide treatments, could be an interesting strategy for vine protection, increasing, at the same time, the phenolic content of the grapes and the resulting wines.

Effect of Micro-oxygenation on Color and Anthocyanin-Related Compounds of Wines with Different Phenolic Contents

Several factors may affect the results obtained when micro-oxygenation is applied to red wines, the most important being the moment of application, the doses of oxygen, and the wine phenolic characteristics. In this study, three red wines, made from Vitis vinifera var. Monastrell (2005 vintage) and with different phenolic characteristics, were micro-oxygenated to determine as to how this technique affected the formation of new pigments in the wines and their chromatic characteristics. The results indicated that the different wines were differently affected by micro-oxygenation. In general, the micro-oxygenated wines had a higher percentage of new anthocyanin-derived pigments, being that this formation is more favored in the wines with the highest total phenol content. These compounds, in turn, significantly increased the wine color intensity. The wine with the lowest phenolic content was less influenced by micro-oxygenation, and the observed evolution in the degree of polymerization of tannins suggested that it might have suffered overoxygenation.

Varietal classification of young red wines in terms of chemical and colour parameters

Six varietal red wines produced in Murcia (Spain) were analysed for selected enological and colour parameters (31 variables in total). As regards acid content there were no important differences among the vinifications studied. The initial content of glucose and fructose was quite high in all the wines, which resulted in very high ethanol content (between 14.1% in Cinsault Noir wine and 16.4% in Tempranillo wine). The colour of the wines was determined by means of the Yxy coordinates and CIELAB parameters, but not one of them could significantly differentiate among vinifications. Principal component analysis and discriminant analysis were used to identify and to explain differences among samples. Discriminant analysis allowed a clear separation of the 80.7% of the cases analysed by a selection of only three variables (L*, a*, C*). With a selection of 10 variables including x coordinate, colour intensity 1 and 2, pH, ionised anthocyanins, total phenolics, percentage of yellow pigments, total anthocyanins, hue and L* was possible to characterise the 95% of the cases analysed, but 100% in Monastrell-1, Tempranillo Graciano and Cinsault Noir wines.

Differences in major volatile compounds of red wines according to storage length and storage conditions

The effect of different ageing conditions on wine aroma compounds was studied. Wines aged under two different conditions (barrel ageing and bottle ageing) and for two different lengths of time (short term and long term) were analysed and the major volatile compounds were quantified. Esters and fatty acids decreased during storage. A cluster analysis showed that wines could be grouped according to the storage time and storage conditions. Step forward discriminant analysis showed that furfural, vanillin, isoamyl acetate and octanoic acid were the variables with the highest discriminant power, permitting a 100% correct classification of the studied samples.

Wine-making of High Coloured Wines: Extended Pomace Contact and Run-off of Juice Prior to Fermentation

The influence of two different oenological practices (pomace contact time and the running-off of the juice prior to fermentation) on the production of high coloured wines was analysed and tested with two vintages from the years 2001 and 2002. There were assayed three pomace contact times (15, 25 and 35 days) and 15 and 20% run-off treatments. The colour stability of the resulting wines was also evaluated, using an accelerated ageing process. Differences were observed in the colour characteristics between vintages. Larger berries in 2002 led to wines with a lower colour density although the effect of the studied practices was very similar both years. A pomace contact time longer than 15 days led to wines with poor and unstable colour both years. Running-off juice prior to fermentation produced wines with a higher colour density, lower yellow percentage and a higher polymerisation of the anthocyanins. These wines also showed the highest colour stability. The effect of the running-off treatments on wine colour was more pronounced in 2001 than in 2002 due to the different characteristics of the grapes. The extent of this practice must therefore be decided on a year-by-year basis to obtain the best characteristics.

Effect of Benzothiadiazole and Methyl Jasmonate on the Volatile Compound Composition of Vitis vinifera L. Monastrell Grapes and Wines

Benzothiadiazole and methyl jasmonate have been described as exogenous elicitors of some plant defence compounds. The objective of this study was to determine whether the application of benzothiadiazole and methyl jasmonate to Vitis vinifera L. Monastrell grape clusters at the beginning of the ripening process affects the synthesis of volatile compounds in grapes (as has been observed in other fruits) and whether this effect has a technological significance in the resulting wines. Results indicated that both treatments increased the levels of volatile compounds in grapes, especially terpenes and norisoprenoids in benzothiadiazole-treated grapes. The wines obtained from the treated grapes also showed higher levels of terpene and norisoprenoids. Wines from methyl jasmonate-treated grapes had levels of these volatile compounds almost two times higher than the wines made from control grapes. These differences in the volatile compound levels could be sensorially detected.

Effect of Wine Maceration Enzymes on the Extraction of Grape Seed Proanthocyanidins

Proanthocyanidins, which are located in the skins and seeds of grapes, are important for red wine quality since they participate in astringency, bitterness and colour stabilization. Maceration enzymes have long been used to improve the extraction of phenolic compounds from skins, but their role in seed degradation and the release of seed phenolic compounds is not well known. This contribution describes the effect of different pure enzyme activities (xylanase, cellulase, polygalacturonase and pectinmethylesterase) on the release of proanthocyanidins from seeds of Monastrell and Cabernet Sauvignon grapes. The results demonstrate that some enzymes, especially polygalacturonase and cellulase, favour the degradation of seed cell walls, promoting the diffusion of proanthocyanidins, although differences due to grape variety also exist.

Color and phenolic compounds of a young red wine as discriminanting variables of its ageing status

Abstract The purpose of this work is to characterize young red wines regarding their ageing status using objective color and phenolic compounds measurements as variables. Discriminant analysis was used to obtain functions that made it possible to classify wines. Using the above-mentioned variables, five classification functions were obtained that correctly classified 100% of the wine samples. To validate the model and to check its discriminanting potential we applied it to wines stored at different temperatures. The five functions correctly classified 81.6% of the wines regarding their ageing status.