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Wine is any fermented fruit juice. People typically associate wine solely with grapes and it’s true that the vast majority of all wine that you’ll find almost anywhere is fermented grape juice, but wine can technically be made from other fruits like blueberries, raspberries, and strawberries.
Grapes have become the standard for wines for two reasons. First, there is an acid found in grapes but not other fruits which preserves the juice for decades or even centuries. Second, there is a lot more sugar in grapes than in other fruits and this helps produce stronger wines because almost all the sugar is transformed into alcohol. Sure, in its purest form, it’s grape juice gone “bad,” but there are additional elements in even the simplest of wines. With today’s wine making tools, you can be sure there’s so much more to a bottle than fruit and time. While enjoying a bottle of wine can be simple, understanding wine (good wine, at least) can be quite complex.
Wine: How is it Made?
There are various processing steps in making and producing wine; these are described shortly below.
Firstly, the grapes are allowed to ripen in the vineyard until they attain a suitable sugar content, which is about 18% or more, and the right level of acidity. During ripening in the vineyard, grapes may become infected by moulds, yeasts, and bacteria. These infections generally destroy desired flavours and colour and introduce undesirable acetic acid and oxidised flavours. However, the infection of white grapes with the rot fungus called Bortrytis cinerea is very advantageous. Infection of white grapes with this mould leads to the concentration of the juice in the berry and also gives a characteristic aroma to the wine.
The second step in the making of wine is the fermentation of the grapes with various yeasts and lactic acid bacteria. Grapes can be fermented by adding selected wine yeasts to dominate the yeast that originates from the vineyard (grape surface, leaves, and stems) and the winery environment (tanks, barrels, hoses). The addition of a selected yeast culture ensures a complete fermentation without the loss of aroma as well as the production of a wine of consistent flavour quality. Fermentation temperature and characteristics of the selected yeasts determine the amount and type of flavours produced. During spontaneous fermentation, a range of different yeasts grow at different stages of fermentation. Therefore, a winemaker must carefully guide spontaneous fermentations to reduce the risk of spoilage by unwanted microorganisms. Successful spontaneous fermentations can produce very flavourful wines with a variety of sensorial properties, e.g., aroma and consistency derived from the juice flavours.
Following yeast fermentation is a second fermentation by lactic acid bacteria, known as malolactic fermentation. During this process, lactic acid bacteria convert malic acid to lactic acid and carbon dioxide (CO2), which results in a lowering of the acidity of the wine. The metabolic activities of the bacteria also change the fruit flavour of wine and incorporate some flavour compounds. Temperature, pH, and availability of other sources of energy affect the rate of malic acid utilisation.
Subsequent to fermentation, wine is clarified by filtration and then stabilised. Wine flavours can continue to change while the wine is stored in wooden barrels, stainless steel tanks, and glass bottles. At this stage of the process, various yeasts and bacteria may well be present in the wine; thus, the wine flavours could be further modified. These yeasts are generally considered spoilage yeasts. Depending on the type of microorganism and the extent of their growth, desirable fruit flavours can be replaced by unpleasant odour and taste. Different wines benefit from prolonged or only short-term ageing.
The creation of wine is a simple process that would happen without any human intervention, if allowed:
- Pick Grapes
- Crush Grapes
- Collect Grape Juice
- Wait for Fermentation
Humans collect and crush grapes for the convenience of creating wine in larger quantities, but the juice would ferment in the grapes on the vine or on the ground if left alone.
What Is Fermentation?
The fermentation which creates wine is the process by which yeast consumes sugars and produces alcohol (and carbon dioxide). The more sugar that’s in the grapes, the more alcohol there will be in the resulting wine (if the process is allowed to continue to completion). Yeast exists naturally on grapes and grape vines, which is why fermentation occurs naturally, but wine makers may also add yeasts to better control the process.
Why Does Wine Taste the Way it Does?
People’s interest in wine is largely focused on its taste, but it probably wouldn’t taste very good if it were simply a matter of leaving jugs of grape juice in your basement for a couple of months. There are a lot of different factors which go into creating each wine’s unique taste:
- Grape variety
- Blending varieties together
- Fermentation time
- Fermentation container (wood, steel)
- Length of time of contact with grape skins
- Maturation time
- Maturation container
Then there are the geographical factors which, taken all together, the French call terroir:
- Soil type
- Topography (steepness of the slopes)
- Weather conditions
- Farming techniques
And this is just the beginning of what makes wine what it is.
Wine is quite simply the most delicious, most varied and most complex drink on the planet. It is incredible that the fermented juice of a single fruit, the grape, can offer us so many different styles of liquid. From the tingly, zesty, water-white, light and lively to the rich, purple-black, mellow and full-bodied. It comes both still and fizzy and at all points in between. It can be bone dry or tooth-rottingly sweet. You have to love wine!