The Art of Fermentation: Spontaneous vs. Cultivated Yeasts

Best tips for brewing at home with wild yeast

Brettanomyces, saccharomyces bayanus, saccharomyces cerevisiae, bruxellensis, claussenii, lactobacilli… Does that ring a bell? With this lexical field of wild yeasts, we explore a whole world of beer wort fermentation. Are you interested in learning a little more about the subject? Let’s go on an adventure together!

How does yeast work? What are the types of yeast?

Simply put, without the magical intervention of yeast, beer is just a wort, a cereal juice. We then add the traditional yeast to the wort and the fermentation process truly begins. For example, the traditional yeast used in breweries or microbreweries is easily recognizable and often comes from the same strain. This is the case when drinking a Unibroue, for example; the yeast characteristics stand out and make up a readily recognizable flavor profile.

There are different types of traditional (or non-wild) yeasts and they are numerous and varied. Here are some examples: Belgian yeast, Weizen-type yeast, Norwegian kveik yeast (with hints of orange zest, clove, and nutmeg), champagne yeast, Bohemian lager yeast, German Kölsch yeast, etc. The yeast works once added to the wort; temperature control is then crucial: the ideal is for low fermentation at around 10-13 degrees Celsius (like for a lager), high fermentation at around 18-21 degrees Celsius (like for an ale).

Sometimes it’s better to activate the yeast before seeding so it’s more vigorous, more lively! We would call it a seeded beer, whereas with a spontaneously fermented beer (like a lambic), we would use ambient wild bacteria and yeast. A small distinction! Also, certain conditions must be met for the yeast to “work”, such as the presence of nutrients, fermentable sugars, minerals, oxygen, nitrogen, etc.

What about our brave “wild” yeasts?

More specifically, they are integrated during fermentation. These organisms are resilient and can contaminate materials like barrels and even pipes. Rigorous handling is required, as well as impeccable hygiene, of course. “Wild has its reasons that reason does not know! Ideally, beers made with traditional yeast should be kept separate from beers made with wild yeast in separate productions.

What sets them apart? A more untamed, unpredictable character! The result will vary more when using wild yeast. Often, characteristics such as dryness or acidity are obtained. A longer fermentation time is often required when working with wild yeasts. Up to a few months!

The properties of wild yeast

“A brewer who knows how to dose well can produce flavors that are not only original, but also rustic and elegant, as refreshing as they are poignant, as dry as they are easy to drink,” say Martin Thibault and David Lévesque Gendron in Les saveurs gastronomiques de la bière. Amazing, isn’t it?

At the Brett&Sauvage nano-brewery, they add wild yeast from the Gaspesian flora that they have taken from an apple, currants, a native plant or from honey. The yeast is identified after it has been isolated, characterized, and sequenced, all before being used. They have fun with the “signature” characteristics of 100% Quebec wild yeast, says Rosemary Ahelo-White, brewer at Brett&Sauvage.

So-called wild yeasts are true gems! Brettanomyces bring flavors of horse, leather, mouse, flower, and earth; acetobacter create vinegary flavors and lactobacilli bring us to the side of plain yogurt!

So what about spontaneous fermentation? Spontaneous fermentation is to be distinguished because it takes place without the addition of yeast to the wort. It will be the ambient microbes, present on the beer ingredients, that will do all the work. Often, fruit will complement spontaneously fermented beers or beers made with wild yeast, as it pairs perfectly with the already present aromas in other ways.

Paule Gosselin is a passionate beer blogger based in Quebec. She is also a literature professor with a passion for craft beer products. Always on the lookout for trends, Paule shares her love for beer through her writing and tastings. Her beer chronicles are followed by a community of loyal readers.

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