Yeast Impact on Wine Aroma and Flavor

If you are of the opinion that yeast selection does not matter and that the only role of yeast is to convert sugar into ethyl alcohol (ethanol), you may have been missing out on making more complex wines. And if you source grapes or fresh juice from a third party and you rely on indigenous yeast to ferment sugars, you’re playing Russian roulette with your wine, not knowing the outcome — that is unless you are fortunate enough to own a centuries-old vineyard in Burgundy endowed with an established microflora. With an unknown indigenous microflora, fermentation is often carried out by non-Saccharomyces yeast, some of which are not suited for winemaking conditions or which can quite possibly utilize and metabolize other substrates yielding unpredictable results that may lead to undesirable aromas and flavors. In general, non- Saccharomyces yeasts do not possess enological characteristics favorable to fermenting juice into wine. Yeasts have a very complex metabolism and do so much more than simply convert sugar into ethanol — they also produce many other metabolites and act on other juice and wine