Chemical markers in wine related to low levels of yeast available nitrogen in the grape

Astringency sensation decreases slowly during the aging of red wine. Complex reactions of condensation and precipitation of wine polyphenols are involved in this phenomenon. Wine composition and conditions of aging, such as temperature and oxygen availability, strongly influence evolution of the phenol matrix. Recently, a Post-Fermentative cold Maceration (PFM) technique was tested with the aim of accelerating reactions leading to the reduction of astringency and exploiting chemical compounds not extracted from the solid parts of grapes during the previous traditional maceration phase. To this purpose, an innovative maceration system was engineered and used to perform PFM trials on marc derived from vinification of different varieties of red grapes.

Since 2012, EU Commission approved compulsory labeling of wines treated with allergenic additives or processing aids “if their presence can be detected in the final product” (EU Commission Implementing Regulation No. 579/2012 of 29 June 2012). The list of potential allergens to be indicated on wine labels comprises sulphur dioxide and milk- and egg- derived fining agents, including hen egg lysozyme, which is usually added in wines as preservative. In some non-EU countries, the list includes gluten, tree nuts and fish gelatins. With the exception of lysozyme, all these fining proteins were long thought to be totally removed by subsequent winemaking processings (e.g. bentonite addition).

Consumers typically prefer wines with floral and fruity aromas over those presenting green-pepper, vegetal or herbaceous notes. Pyrazines have been identified as causatives for herbaceous notes in wines, especially Bordeaux reds. However, pyrazines are not universally responsible for herbaceousness, and several other wine volatile compounds are known to produce distinct vegetal/herbaceous aromas in wines. Specifically, volatile aldehydes elicit sensations of herbaceousness or grassiness and have been described in wines well above their perception thresholds.

Viura is a synonym for Macabeo and currently it is the most widely planted white grape variety in D.O.Ca. Rioja, with 3,569 ha, representing 84% of the white grape cultivated area. It is a generous-yielding grape, presenting low values of titratable acidity and with large and compact clusters which makes it susceptible to Botrytis cinerea. Thus, this variety not always satisfies the wine grower’s prospects. Nowadays, the available plant material is scarce, moreover, it was selected on the basis of other quality criteria, not currently requested.

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.