E. Gómez-Plaza

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.

Application of enzyme preparations for extraction of berry skin phenolics in withered winegrapes

Postharvest withering of grapes strongly affects the content and extractability of phenolic compounds in the production of sfursat, fortified and passito wines. This work evaluated the effectiveness of enzymes applied individually and/or in multi-enzyme blends, on the extraction of anthocyanins, oligomeric flavanols and polymeric flavanols from withered grape skins during simulated maceration. The study was performed on Vitis vinifera L. cv. Nebbiolo and Barbera because of their different skin phenolic profile and cell wall composition. Our findings highlight that the relationship between skin mechanical properties (berry skin break force and energy) and extraction yield of phenolic compounds is variety dependent. Significant correlations were found between the skin softening associated with cell wall degradation and the extraction of anthocyanins and flavanols in Nebbiolo, for which polygalacturonase, individually or in multi-enzyme blends, plays an important role. In Barbera, the extractability of phenolic compounds was not affected by the presence of exogenous enzymes.