May 09 2009
How is Wine Made? Part One
I want to back up a bit before moving into wine tasting and other specifics and talk about what wine is and how it is made.
The grape is the main ingredient of any wine. However, the species grown is different to the seedless grape often found in the supermarket or local convenience store. The species of grape grown for wine production is known as ‘vitis vinifera’ and are typically smaller and have thicker skins.
Although temperate areas with adequate rainfall are required for wine growing, In order to produce the best harvests, vines should be stressed. If there is too much rainfall the vines become lazy and they don’t produce enough good quality fruit. The climate that vines are grown ultimately influences the overall taste of the wine. In areas where temperatures are cooler, wine will inherently have a lower alcohol content and higher natural acidity.
The characteristics of the soil itself also influence the final taste of the wine. Certain minerals give the grapes added nutrients whilst growing. Also, some soils drain the water away from the vines during times of high rainfall so that the vines do not become saturated. In essence each vineyard has its own distinctive ‘terroir’ that ultimately determines the wine produced. ‘Terroir’ is a French term used to describe each vineyard’s individual personality attributed to its location, climate and soil type.
Fermentation occurs in all wine production. Fermentation is the process of converting sugar into alcohol. In order to start this process either cultured yeasts can be added to the grape juices or wild yeasts that naturally occur on the skins of the grape or in the soil of the vineyard can be used. The yeast interacts with the sugar, converting this to alcohol.
How White Wine is Made
When making white wine, the grapes are almost always crushed and de-stemmed before being transferred to the press, where they are squeezed, separating the juice from the pips. The skins, stems and pips are removed because they often contain butter tannins which are undesirable in white wines, although often sought after in reds. Sulphur dioxide is often added to the grape mixture during the process to prevent fermentation from occurring too early, the wine changing color and creating extremely strong flavors.
The fermentation process for white wine can take between a few days to a month and often occurs in cool temperatures in order to preserve a “freshness” of aroma and flavor. After fermentation whites can be bottled straight away, making them relatively cheap to produce. Some white wines are fermented throughout in oak barrels in a process called “barrel fermentation”, which can take between 6 and 12 months before being transferred to a tank for final filtration and fining.
Other wines are fermented in stainless steel tanks. Also, some varieties can undergo a second fermentation process call malo-lactic fermentation whereby the acidic malic acid is converted into lactic acid. This technique is most often used in Chardonnay and Semillon varietals “softening” the high acidity of the grape and producing a more neutral, creamy flavor.
Filtration and fining are the last processes that sometimes occur before bottling. Here, impurities within the wine are filtered away and also further additives are added. Some more traditional wine produces believe that filtration and fining remove some of the wines key aromas and flavours and do not believe the process to be worthwhile.
Next time I’ll go into red wine and sparkling wines.
