Impact of some agronomic practices on grape skins anthocyanin content

Initiatives have been ongoing in recent years to safeguard biodiversity in the oenological sector via a process of enhancement of ancient varieties, under a pressure of a market strongly oriented towards production deriving from native vines of specific geographical zones. In that sense, Aosta Valley
(Italy) has raised the need to preserve and characterize its minority vine varieties which have the potentiality to give varietal wines. Fumin represents the 7% of the production of the region with 16 hectares of vineyards and 753 hectolitres of derived wine. Due to its large phenolic potential, strong astringency and deep colour, it has long been, and is still today, assembled or blended with other varieties as occurs, for example, for the Torrette.

The above-ground parts of plants, which constitute the phyllosphere, have long been considered devoid of bacteria and fungi, at least in their internal tissues and microbial presence there was long considered a sign of disease. However, recent studies have shown that plants harbour complex bacterial communities, the so-called “microbiome”[1]. We are only beginning to unravel the origin of these bacterial plant inhabitants, their community structure and their roles, which in analogy to the gut microbiome, are likely to be of essential nature. Among their multifaceted metabolic possibilities, bacteria have been recently demonstrated to emit a wide range of volatile organic compounds (VOCs), which can greatly impact the growth and development of both the plant and its disease-causing agents.

Del Barrio-Galán, R.a, b, Gómez-Parrini, A.a, Peña-Neira, A.b a Lallemand Inc. Chile y Compañía Limitada, Rosario Norte 407, piso 6, Las condes, Santiago, Chile b Department of Agro-Industry and Enology, Faculty of Agronomical Sciences, University of Chile, Post Office Box 1004, Santa Rosa 11315, La Pintana, Santiago, Chile It is well known that polysaccharides, mainly mannoproteins, play an important role on physical, chemical and sensory quality of wines. The ageing of white wines on lees is used in order to release higher amounts of polysaccharides by the autolytic processes in order to obtain higher-quality wines. However, this technique is too slow, because the temperature and pH conditions are not the most suitable for this process. In addition, it can also involve certain disadvantages such as a greater demand on winery resources, a longer period of wine storage, the appearance of reduction notes and some microbiological alterations.

Lately several works highlighted the capacity of grape cell-wall material (CWM) to interact with proanthocyanidins (PA), indicating its potential use as fining agent for red wines.1–4 However, those studies were performed by using purified PAs and very high doses of CWM (almost ten-fold higher than those used in wine industry for other commercial fining agents). The present study focuses on the applicability of CWM from Cabernet sauvignon pomace as fining agent for red wines under real winery conditions. Grapes of cultivar Cabernet sauvignon were harvested at three different maturity levels
(unripe, mature, and overripe) and used for red winemaking. The pomace of such vinifications were used as source of CWM, and applied into red wines at two different concentrations: 0.2 g/L and 2.5 g/L.

Among nitrogen compounds included in white wines, the peptide fraction is certainly the least studied, however this fraction is quantitatively the most important (Feuillat, 1974). Existing studies concern the fraction below 1 kDa and only for white and sparkling wines (Bartolomé et al, 1997, Desportes et al 2000). In this report, we have developed methods to isolate peptides from reference white wines. Then, we have applied this methodology with bitter wine to answer a research question: is there a relation between peptides and the bitterness of white wine as for some cheese for example (Furtado, 1984)?