Discrimination of white wines by Raman spectroscopy coupled with chemometric methods

Traceability of agro-alimentary products is very important to certify their origin. This work aimed to characterize wines obtained by the same cultivar (Nero d’Avola and Fiano) – grown in regions with different soil and climate conditions during three vintages (2003-2005) – employing isotopic analyses (NMR and IRMS) and sensory analyses.

Nowadays, the rapid growth of vineyards with organic practices and the use of copper as the only fun-gicide against downy mildew raises again the question of the effect of copper on varietal thiols in wine, especially 3-sulfanylhexan-1-ol (3SH) and its acetate (3SHA). A few decades ago, several works indicated that the use of copper in the vineyard had a negative effect on the content of varietal thiols in Sauvignon blanc wines [1, 2]. However, these studies only considered the concentration of the reduced form (RSH) of varietal thiols, without quantifying the oxidised ones. For this purpose, we proposed to monitor both reduced and oxidised forms of varietal thiols in wine under copper stress during alcoholic fermentation to have a more complete picture of the biological and chemical mechanisms.

The evaluation of new grapevine genotypes regarding their potential to produce high quality wines is the time limiting factor in the process of grapevine breeding. Hence, the development of quality-related markers useable in marker-assisted selection (MAS) as well as in prediction models for this bottleneck trait will tremendously enhance breeding efficiency. In extensive studies a training set of a segregating white wine F1 population (150 F1 genotypes = POP150; `Calardis Musqué´ x `Villard Blanc´) was deeply phenotyped and genotyped for model development and QTL analysis.

This work began as an intellectual game, in order to discuss the notion of wine quality in terms of terroir and territory spatial structure. Vine and wine quality has long been questioned by scientists. Each discipline approaching it with his own tools.

This study investigated if compositional differences between Shiraz and Cabernet Sauvignon grape varieties could influence the production of yeast-derived compounds. This work was based on the analysis of 40 experimental red wines made in triplicate fermentations from grapes harvested from two consecutive vintages in New South Wales (Australia). Grapes were picked at three maturity stages using berry sugar accumulation as physiological indicator, from nine commercial vineyards located in three different climatic regions (temperate, temperate-warm and warm-hot). A range of 30 yeast-derived wine volatiles including esters and alcohols were quantified by HS/SPME-GC/MS. Ammonia, amino-acids and lipids were analysed in the corresponding grapes. The juice total soluble solids (°Brix) in addition to the wine alcohol and residual sugar levels were also measured. The influence of grape maturity on wine ester composition was also variety dependent, particularly for higher alcohol acetate and ethyl ester of branched acids. This study highlights that varietal differences observed in Shiraz and Cabernet Sauvignon wines involve fermentation-derived compounds irrespective of the site (soil, climate, viticultural practices).