Fermentation and aging of wine: From grape to wine
What happens in between harvesting grapes and opening a bottle of wine?
Fermentation is the process by which the two grape sugars, glucose and fructose are converted to alcohol, assisted by certain myces such as sacchromyces. Fermentation may require anywhere from ten days to a month and is directly affected by the enzymes present, the temperature, the oxygen, etc. Natural fermentation will stop when the alcohol concentration is too high, at 16.5% under the most ideal conditions, or most often before it reaches this level.
In modern wine production, the grapes are harvested from the vineyards and taken to a winery where they pass through a machine called a destemmer-crusher. This separates the fruit from the stems and cracks the berries open to release the juice. To make white wine, the must is transferred to a press where pressure is applied to separate the juice from the skins.
In red wine production, the must from the crusher is transferred directly to a tank for fermentation, hence the seeds and skins go into the fermentation tank with the juice. The length of contact between the skin and the juice influences the color of red and blush wines and affects the taste of all wines. Sweet wine is produced when the fermentation process stops before all of the sugar has been converted into alcohol.
Aging and Maturation
“Like a good old bottle of wine …” old but not always good. Wine is a living organism, with a certain life span, going through phases of “youth”, “peak”, “maturity” and “end”.
The sun, the soil and the climate of a region, seriously affect the final taste of the wine, as does the tank in which the wine will go through the fermentation process. Stainless steel is a relatively neutral material which helps to maintain the flavours of the fresh grape fruit, as it is transformed into wine. This is mainly the case for white wine which is normally stored in stainless steel tanks until bottling. On the contrary, most red wines are not ready for consumption until they go through a maturation process in a barrel, allowing them to soften.
The aging process continues in the bottle, where the lack of oxygen, light, smells and noise will allow the wine to develop and accomplish its character
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