To make wine, you need grapes and... yeast.
Yeasts are microorganisms from the fungus family. They synthesize alcohol from grape sugars during alcoholic fermentation (AF). This biological process lasts from a few days to several months, and is accompanied by the release of carbon dioxide (CO2). In fact, when fermentation is in full swing, the vats foam up and can even overflow if they're too full, precisely because of the expansion of the gas (I've even caused a geyser once or twice...).
Yeasts are everywhere: in the atmosphere, on the grapes, in the nooks and crannies of cellars, pipes, pumps, etc., and there are many different strains. Some are beneficial, others not (known as contaminant yeasts).
To make wine, we can choose to let the yeasts present in situ develop (we call them indigenous yeasts), but we don't know who they are or how many there are. Or you may decide to bring in commercial yeasts selected for their fermentative abilities. In both cases, these are natural microorganisms: the selected yeasts have simply been isolated from the natural environment, then cultivated (they have not been created or synthesized, and are not GMO).
Personally, I've opted for selected yeasts, and to justify my choice, I like to draw a parallel with a restaurant where the yeasts are the chef and his brigade, and I'm the owner. Either I entrust the kitchen to the first person to come along, on the sole condition that he's from the village (indigenous), or I recruit the most competent Chef, even if it means he has to come from elsewhere. It all depends on the experience you want to offer your customers, but what interests me is the result: what you get on your plate or in your glass.
I'm convinced that fantastic wines can be made with indigenous yeasts, but I'm also convinced that this prowess has more to do with the skill of the winemaker than with the yeast. For me, the strain of yeast or its origin is not a sufficient criterion for determining the quality of a wine. It remains a tool.
Detox: I sometimes hear talk of chemical yeasts vs. indigenous yeasts and it pisses me off: there is no chemical yeast in wines. NEVER. It doesn't exist! Baking powder is an additive used... in pastry-making. Baking powder doesn't contain yeast! It's a baking powder. It works by releasingCO2, as in fermentation, hence the misnomer "yeast".
