Grapes are in, and they are ready to be processed. While this process has happened since the beginning of September when the grapes first came in, now is a great time to discuss the differences in fermentation.
Fermentation is the process where yeast converts sugar into alcohol and CO2 (with some by products as well). Fermentation is the same process that bread dough goes through in order to rise, except we're after different end goals. We'll dive into some of the nuances of fermentation to get a better idea in how the lovely grape juice turns into our favourite beverage.
Like many people have taken up sourdough starter throughout the pandemic, one method of fermentation is using ambient yeast that is present on the grapes, and in the winery itself to undergo fermentation. While some may refer to this as "wild fermentation", there is some negative connotations that this may have. Some say that using ambient yeast is a true way of producing wine, as it highlights and showcases true terroir and regionality. Breweries are even using ambient yeast and some have even gone to the lengths of trademarking their own strains of yeast that are naturally found within the brewery. Ambient yeast can be slightly more difficult and complicated to control and work with, and a winemaker is truly at the whim of nature.
Many wineries however are using cultured yeasts for their fermentation. Different strains of yeast are needed for different fermentation, whether its sparkling wines, reds, whites, or dessert wines. Different strains of yeasts, and different temperatures of fermentation will also affect the finished flavour of the wine itself. White wines are typically fermented cool to preserve the natural fruit characteristics and higher acidity. Red wines however are usually fermented slightly warm to help get to higher alcohol levels and to aid in the colour extraction. Red wines are typically fermented with their skins and seeds, which is what gives the finished wine its colour.
While there's a lot more science that goes into fermentation, and a lot of know-how from the winemakers, this hopefully gives a rough breakdown of the beginning processes of making wine.