Effect of different foliar nitrogen applications on the must amino acids and glutathione composition in Cabernet Sauvignon vineyard

Prefermentation steps of white winemaking are very important for controlling the stability and the sensory attributes of wines. Usually musts are clarified by cold settling to prevent the start of the fermentation, before racking big lees and thus limiting the appearance of vegetable or reduction off flavour while favouring an aromatic expression with low turbidity. Besides, to reach the protein stability, some white wines further require a bentonite fining, sometimes associated with negative effects on the sensory quality. This study aims to know the impact of musts heating after pressing on a Chardonnay wine in northern conditions by comparison with a classic cold racking of the must.

A method of suspect screening analysis to study grape metabolomics, was developed [1]. By performing ultra-high performance liquid chromatography (UHPLC) – high-resolution mass spectrometry (HRMS) analysis of the grape extract, averaging 320-450 putative grape compounds are identified which include mainly polyphenols. Identification of metabolites is performed by a new HRMS-database of putative grape and wine compounds expressly constructed (GrapeMetabolomics) which currently includes around 1,100 entries.

Bioactive polyphenols from grapes and wines, like stilbenes and flavonols (SaF), are often determined to nutritional evaluation, but also for many other purposes. The objective of this study was to quantify SaF in red wines from “Campanha Gaúcha”, a large and young viticultural region from South Brazil. Moreover, through statistical analysis, evaluate the influence of these compounds according to varieties, production process, harvest years and micro-regions of cultivation. A total of 58 samples of red wines were analyzed by high-performance liquid chromatography coupled to diode array detector (HPLC-DAD) for determination of trans-resveratrol (R), quercetin (Q), myricetin (M), kaempferol (K), trans-e-viniferin (V) and their precursor, cinnamic acid (C).

Wine color is one of the main organoleptic characteristics influencing its quality. It is of especial interest in red vinifications due to the economic resources that wineries have to invest for the extraction of the phenolic compounds responsible of wine color, compounds that are mainly located inside the skin cell vacuoles. Moreover, these phenolic compounds not only influence color but also other organoleptic properties such as body, mouthfeel, astringency and flavour. The transference of phenolic compounds from grapes to must during vinification is closely related with the type of grapes and the winemaking technique.

Vineyards are strongly exposed to fungal diseases, attacks from insects and competition with weeds. Most treatments used on grape vines contain synthetic active substances, which may be transferred to the wine. Such pesticides have a negative image because many active substances are potential health hazards. A specific oenological treatment allowing the reduction of pesticide residues in wine based on activated vegetable fibres (AVF) is under examination by the International Organisation for Vine and Wine. This technique works efficiently and alters the wine only little (Lempereur et al. 2014).