Vinhos de talha: to pitch or not to pitch

AIM: Different heat tests are used to predict a white wine haze risk after bottling. The most used tests are 30-60 min. at 80°C. Nevertheless, there is a lack of information about the relationship between the wine haze observed after such tests and the turbidities observed in the bottles after the storage/transport of the wines in more realistic Summer conditions (35-46°C during 3-12 days)

Muscat of Alexandria is one of the oldest cultivars still existing, globally recognized for its distinctive aroma, and the primary grape variety cultivated in the Greek Island of Lemnos, yielding various white wines with designated origins.

The objective of the present work is to assess yeast effects on the development of wine varietal aroma throughout aging and on wine longevity.

Three independent experiments were carried out; two fermenting semi-synthetic musts fortified with polyphenols and aroma precursors extracted from Tempranillo (1) or Albariño (2) grapes and with synthetic precursors of polyfunctional mercaptans (PFMs), and a third in which a must, mixture of 6 different grape varieties was used. In all cases, fermentations were carried out by different Saccharomyces cerevisiae strains and one S. kudriavzevii, and the obtained wines were further submitted to anoxic accelerated aging to reproduce bottle aging. The volatile profile of the wines was analyzed using several chromatographic procedures, in order to provide a comprehensive evaluation of wine aroma. Aroma compounds analyzed included fermentation volatile metabolites, grape-derived aroma compounds including PFMs, and Strecker aldehydes (SA).

Results revealed that the effects of yeast on wine aroma throughout its self-life extend along three main axes:

1. A direct or indirect action on primary varietal aroma and on its evolution during wine
aging.

2. The direct production of SA during fermentation and/or their delayed formation by producing the required reagents (amino acids + dicarbonyls) for Strecker degradation
during anoxic aging.

3. Producing acids (leucidic, branched acids) precursors to fruity esters. More specifically, and leaving aside the infrequent de novo formation, the action of the different strains of yeast on primary varietal aroma takes four different forms:

1.- Speeding the hydrolysis of aroma precursors, which leads to early aroma formation without changing the amount of aroma formed. In the case of labile molecules, such as linalool, the enhancement of young wine aroma implies a short-living wine. 2.- Metabolizing the aroma precursor, reducing the amounts of aroma formed, which can be of advantage for negative aroma compounds, such as TDN or guaiacol; 3.- Transforming grape components into aroma precursors, increasing the amounts of aroma formed, as for ethyl cinnamate, leucidic acid or vinylphenols; 4.- Forming reactive species such as vinylphenols able to destroy varietal polyfunctional mercaptans.

Overall, it can be concluded that the yeast carrying alcoholic fermentation not only influences fermentative wine aroma but also affects to the wine varietal aroma, to its evolution during aging and to the development of oxidative off-odors

Valpolicella is an Italian region famous for the production of high quality red wines. Wines produced in its different sub-regions are believed to be aromatically different, as confirmed by recent studies in our laboratory. Aging is a very common practice in Valpolicella and it is required by the appellation regulation for periods up to four years. The aim of this study was to investigate the evolution, during aging, of volatile chemical composition of Valpolicella wines obtained from grapes harvested in different sub-regions during different vintages.

The use of cover crops (CCs) is widely proposed as an alternative to traditional soil management in vineyards to exploit a wide range of ecosystem services. The presence of a CC in the inter-row space is known to control spontaneous vegetation in vineyards, primarily through the biomass of the sown crop, which competes with other spontaneous species for soil resources.