Volatile Organic Compound markers of Botrytis cinerea infection in artificially inoculated intact grape berries

Wine production is a globally significant and intricate industry, characterized by diverse regions, grape varieties, and producers. Competitive advantage in wine production and marketing arises from localized natural attributes known as terroir, combined with transferable expertise in agronomic practices, winemaking methods, packaging, distribution, and marketing. Wine is a very globalized product with 40% of the total output exported. Globalization has prompted discussions on convergence of business and production practices across industries, driven by technological progress and adoption of international standards. However, persisting differences in cultural norms, institutional frameworks, and regulatory environments hinder full convergence.

Aim: Terroir is a French concept relating the qualities and quality of agricultural products to their physical and socio-cultural place of origin. It is increasingly used by business and policymakers as a marketing technique to provide economic benefits (e.g. Lenglet, 2014; Wine Australia, 2015), and to potentially preserve cultural heritage (e.g. Bauer, 2009) and the environment (e.g. Bowen, 2010)

s it is well known, myo and scyllo-inositol are two characteristic sugars of grape must and, for this reason, their quantification has been proposed to control the authenticity of the concentrated and rectificated grape must.

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

Oenological tannins are classified as hydrolysable and condensed tannins. Their use in winemaking is only authorized, to facilitate wine fining. Nevertheless, tannins could also be used to prevent laccase effects.