Impact of organic inputs on soil biodiversity in vineyard systems. A monitoring approach during 20 years

Pour prévoir et gérer chaque année les principales caractéristiques de la maturation en Champagne, le CIVC (Comité Interprofessionnel du Vin de Champagne) a développé un ensemble de moyens de prévision et d’information très performants qui permettent aux différents acteurs de la filière viti-vinicole de prendre en compte ces informations à l’échelle de chaque terroir communal pour la recherche d’une qualité optimale.

Cabernet Sauvignon and Petite Sirah are the top red wine cultivars in CA, however, the hot climate in Fresno is not ideal for red Vitis Vinifera, particularly for berry color development. Mechanical pruning and irrigation were studied previously to significantly affect grapevine yield performance and berry quality. But there is lack of studies on cordon height and irrigation on mechanical pruned vineyard system.

The climatic component is one of the elements of the zoning of viticultural potential, alongside the geological and pedological components (Morlat, 1989; Lebon et al , 1993). Many climatic indices have thus been defined to estimate the potential for wine production at the scale of a region or a country (Carbonneau et al ., 1992). The main climatic variables used are temperature and radiation. We note in particular the indices of Branas, Huglin and Ribereau-Gayon (Huglin, 1986). However, few studies have been undertaken on the spatial variability of microclimatic conditions at the scale of a vineyard, a valley, or even a municipality.

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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