Wine Tutor is a general reference guide to assist in understanding some of the intricacies of the physiology of grapes and wine production and the terminology used behind them. It is by no means a formal guide to understanding every detail but can help to explain why you like, or in some cases dislike, particular aspects of a wine.
As a grape ripens the acid in the grape (predominantly malic acid) weins and is replaced by sugars. Some styles of wine such as our Sparkling Cuvee, require a sufficiently early harvest to ensure a more acidic balance than that required for a table wine.
Whilst ripening, grapes go through a process called veraison. This is when red grapes change in colour from green to red (black), and white grapes become more translucent and in most cases a pale yellow. They both lose their green pea hardness and become springy and softer. Inside the grape the seed begins to ripen and transforms from a greenish brown to a dark chesnut brown when ripe. It is important to note that the juice from red grapes is white just like white grapes, however it is the time that this juice spends on its skins, extracting the color and pigment during the fermentation process, that provides the colour. This also provides some of the flavour profile and some of the tannin structure that we see in red wines. The tannin is offered from the grape seed.
Wine making is a fermentation process whereby the sugars in grapes are consumed by yeast, either inoculated into the wine by the winemaker using specific yeast strains, or naturally arriving from the indigenous yeasts in the atmosphere.
The two main by products created when the yeast consumes these natural grape sugars are carbon dioxide (CO2) and alcohol.
To make a wine "dry", the yeast consumes all the sugar, as per most red wines. However, if the fermentation process is stopped at any stage there will be residual sugar or "sweetness". This may be followed by a number to indicate how many grams per litre of sugar remains, e.g. RS50 is quite sweet.
Tannin is the drying agent and accompanying sensation that you experience when drinking red wine. Some white wines such as our DWC Chardonnay spend some time in older barrels to enhance the flavour profile, but due to the age of the barrels little tannin is imparted into the wine. Tannin comes from the seed of the grape and from oak barrels used in winemaking. The drying sensation is due to these tannins bonding with the proteins in your saliva and literally extracting them and binding them, forming larger molecules that give the sensation of dryness. Different wines offer different tannin structure, for example Cabernet Sauvignon generally has a very grippy or grainy mouthfeel, whereas Petit Verdot has a velour/chamois feel in the mouth.
Different barrels also offer different flavours and tannin profiles with American Oak generally being referred to as bold and richer in tannin structure than French Oak offering finer, more cedary structure under the same treatment and preparation.
Generally the flavours associated with the oak types are that American oak offers coconut and vanilla, with French oak offering cedar and spice. It is important to note though, that the region of harvest (in this case the forest), the producer of the barrel and the way in which they are used all influence the aromatics and flavours in the resulting wine.
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