Benefits of Ambient Yeasts

What are some benefits of choosing ambient yeasts for primary alcoholic fermentation, and how are challenges best managed?

For most of wine’s history, fermentations were carried out by ambient yeasts: those found in the vineyard, the air, and the winery. (These are also known as wild, indigenous, or native yeasts and include ambient Saccharomyces yeast strains.) With time and greater understanding, it was clear that not all yeast strains were equal. By the 1970s, scientists began to isolate and develop specific ambient yeasts for commercial availability that could deliver predictable, desirable results, such as managing foam, accentuating specific aromatics, or encouraging healthy flocculation in sparkling wine. Now, hundreds of these selected, or cultured, yeasts are available on the market. Selected yeasts can improve the quality of fermentations while providing greater security and control for the winemaker. Why, then, do some of the greatest wineries in the world prefer to ferment with ambient yeast?

This essay will explore a few of the most beneficial reasons for choosing ambient yeast for primary alcoholic fermentation. It will also consider some challenges associated with ambient yeast and how winemakers can manage them.

A (Very) Brief Overview of Yeasts

Yeasts—microscopic unicellular fungi—unlock a wide range of sensory compounds through the process of fermentation. As yeasts break down carbon (largely glucose and fructose) via enzymes, a conversion to ethyl alcohol, carbon dioxide, and heat occurs. Acetaldehyde and a small amount of acetic acid, the main component of volatile acidity, are also produced. Other compounds produced include esters, aldehydes, fatty acids, ketones, volatile sulfur compounds, glycerol, and succinic acid. These comprise much of what we see, taste, smell, and feel in wine.