Influence of new generation fungicides on Saccharomyces cerevisiae growth, grape must fermentation and aroma biosynthesis.

The influence of ten new generation fungicides (ametoctradin, benthiavalicarb-isopropyl, boscalid, cyazofamid, dimethomorph, fenhexamid, kresoxim-methyl, mepanipyrim, metrafenone, and pyraclostrobin) on the fermentative activity of Saccharomyces cerevisiae yeast was initially evaluated in pasteurised red must. The presence of ametoctradin, dimethomorph and mepanipyrim seemed to affect sugars-to-ethanol yield in the stationary phase. The same fermentation experiments were carried out for these three fungicides in ecological red must from Vitis vinifera cv. Tempranillo. When ecological must was unfiltered, the fermentative activity of yeasts was unaffected by the presence of these selected fungicides. However, when ecological must was filtered beforehand, a slight decrease of biomass and ethanol production (in terms of biomass-to-ethanol yield and sugars-to-ethanol yield, respectively), as well as a decrease in fruity aroma, were registered with respect to the control wine.

Evolution of the aromatic profile in Garnacha Tintorera grapes during raisining and comparison with that of the naturally sweet wine obtained.

The postharvest dehydration is one of the most important steps in obtaining a high quality naturally sweet wine and it can play an important role in modulating the production and the release of volatile compounds. However, only a few studies have analysed the changes in the free and bound volatile compounds of grapes throughout the process. In this work, GC-MS was applied to determine the aromatic composition of Garnacha Tintorera grapes subjected to off-vine dehydration or raisining at several points during the process. The total water loss in 83 days was about 62% and the sugar concentration rose from 225 to 464 g/L. Within the free volatile compounds, isoamyl alcohols, benzaldehyde and guaiacol registered the largest increase above the concentration effect due to water loss; while within the bound volatile compounds were isoamyl alcohols, ethyl vanillate and benzoic acid. The aromatic profile of the raisins obtained were mainly caramelised, floral, phenolic and burned.

Floral, spicy and herbaceous active odorants in Gran Negro grapes from shoulders and tips into the cluster, and comparison with Brancellao and Mouratón varieties.

Within the framework of a more and more competitive market, the opportunity to obtain different wines from the same variety cultivated in the same vineyard is becoming of increasing importance. In this study the presence of aroma compounds in Gran Negro (Vitis vinifera L.) grapes was investigated in order to obtain its aroma potential fingerprint taking into consideration the separation of apical (tips) and basal (shoulders) berries of the clusters. In the final stages of maturation, differences were searched in the probable alcohol content, total acidity of the must, as well as in the aromatic composition of skin and flesh from shoulder and cluster tip berries. A GC-MS method was used to determine the aromatic composition. The obtained results showed that there was variability for their aromatic composition. These results are promising for those wine cellars that are considering the separation of berries from tips and shoulders of the clusters for the elaboration of wines with different qualities. For the berries from the tips of the clusters, aromatic alcohols and volatile phenols were mainly found in the flesh (15 and 2 times higher than in the skin, respectively); whereas aldehydes and C6 alcohols were mainly in the skin (4 and 3 times higher than in the flesh, respectively). For this reason, it could be recommended to separate berry skin before enzymatic maceration of the berry flesh must. For the berries from the shoulders of the clusters, the group of volatile phenols showed 2 times more concentration in the skin than in the flesh; it could be recommended to maintain berry skin during enzymatic maceration of the must. Overall, the tips showed a 40% lower level of C6 alcohols (contributing to herbaceous nuances). These results from Gran Negro were compared with those of Brancellao and Mouratón cultivars.

Aroma profile of Garnacha Tintorera-based sweet wines by chromatographic and sensorial analyses.

The aroma profiles obtained of three Garnacha Tintorera-based wines were studied: a base wine, a naturally sweet wine, and a mixture of naturally sweet wine with other sweet wine obtained by fortification with spirits. The aroma fingerprint was traced by GC-MS analysis of volatile compounds and by sensorial analysis of odours and tastes. Within the volatiles compounds, sotolon (73 µg/L) and acetoin (122 µg/L) were the two main compounds found in naturally sweet wine. With regards to the odorant series, those most dominant for Garnacha Tintorera base wine were floral, fruity and spicy. Instead, the most marked odorant series affected by off-vine drying of the grapes were floral, caramelized and vegetal-wood. Finally, odorant series affected by the switch-off of alcoholic fermentation with ethanol 96% (v/v) fit for human consumption followed by oak barrel aging were caramelized and vegetal-wood. A partial least square test (PLS-2) was used to detect correlations between sets of sensory data (those obtained with mouth and nose) with the ultimate aim of improving our current understanding of the flavour of Garnacha Tintorera red wines, both base and sweet. Based on the sensory dataset analysis, the descriptors with the highest weight for separating base and sweet wines from Garnacha Tintorera were sweetness, dried fruit and caramel (for sweet wines) vs. bitterness, astringency and geranium (for base wines).

Aroma potential of Brancellao grapes from different cluster positions.

In this study the presence of aroma compounds in grapes of Brancellao (Vitis vinifera L.) was investigated in order to obtain its aroma potential fingerprint. It is well known that differences exist in aromatic compounds amongst grapevine varieties at ripening stages. Within the framework of an increasingly competitive market, the chance of obtaining different wines from vines of the same variety grown at the same vineyard is becoming of increasing importance. This can be done through the managing of the vineyard, but also some wineries have assayed the separation of the tip and shoulder berries of the clusters of a specific variety with this objective. In this work it is evaluated that, in the final stages of maturation, differences exist in the probable alcoholic degree, total acidity of the must, as well as in the aromatic composition of skin and flesh of berries coming from the tips and shoulders of the clusters. Gas chromatography coupled to mass spectrometry (GC-MS) was used to determine the aromatic composition, in the skin and flesh of each sample, either tip or shoulder berries from the clusters. The obtained results showed that there was not variability for the probable alcoholic degree and total acidity between the shoulders and tips, whereas there was variability for their aromatic composition. For the berries from the tips of the clusters most of volatiles were found in the flesh (except aldehydes) and spicy and floral nuances (with the only exception of ß-ionone) were in higher proportions. For the berries from the shoulders of the clusters, most of volatiles were found in the skin (monoterpenes, norisoprenoids, aldehydes, and C6 alcohols), where the flesh was slightly richer in aromatic alcohols, volatile phenols and pantolactone; ß-ionone and herbaceous nuances were in higher proportions. These results are promising for those wineries that are considering the chance of separating berries from tips and shoulders of the clusters for the elaboration of different quality wines.