Definition: Yeasts (the school of)

There are two schools of thought when it comes to winemaking. One favours natural yeasts, while the other prefers powdered cultured yeasts. Until a few years ago, wine was the result of a natural fermentation process, initiated by the yeast microflora present on the berries, known as wild yeasts. Then, selected yeasts from cultures appeared from the United States, sold in powder form, allowing better control of the complex microbiological process of fermentation. It was common for fermentation to fail to reach completion, or for defects such as volatile acidity to appear, which in the best case scenario required increased use of sulphur dioxide, but could also render a wine simply undrinkable. It is therefore understandable that selected yeasts, as is often the case with new products, were initially greeted with great enthusiasm. Yeast producers have gradually diversified their range and now offer a wide variety of yeasts, depending on the grape variety, style and even the desired aromatic expression. When a wine displays aromas of passion fruit or pineapple, this is not necessarily due to the typical characteristics of the grape variety, but perhaps more to the yeasts.

The most ambitious producers, however, are increasingly critical of the over-aromatisation of wines and their uniformity of taste. Does too much flavour kill the flavour? This question is leading more and more winemakers to opt for natural fermentation. This always involves a risk, as natural fermentation is triggered by a multitude of yeast types whose properties are generally little known or unknown. And even if they are known, the lessons learned only apply to a single vintage, as the yeast flora can be completely different from one year to the next. Experience and close monitoring of the fermentation process are required to ensure that production volumes remain reasonable. Natural yeasts can produce wines with character, but in the worst case scenario, they can also result in a completely failed vintage.