Natural vs. Selected Yeasts
The importance of yeasts in winemaking
Yeasts are invisible but decisive agents in the creation of wine. They are the microorganisms responsible for turning the grape’s sugars into alcohol, releasing aromas and compounds that define the identity of the drink. More than a simple chemical process, fermentation is a sensory phenomenon, where the yeasts act as “translators” of the terroir, carrying into the glass the essence of the place where the grapes grew.
In the world of wine, there are two main approaches: spontaneous fermentation with natural yeasts and controlled fermentation with selected yeasts. Both have their champions and their critics. The first is associated with authenticity and the fullest expression of terroir; the second, with safety, consistency and predictability of the final result.
As a winemaker, I know that the choice between one and the other is not only technical — it is also philosophical. It involves understanding the potential of the vineyard, the style of wine desired and the audience it is meant for. Over the course of this article, we will explore what natural and selected yeasts are, their advantages and limitations, and how they influence the quality and style of the wine. In the end, you will see there are no universal answers, only different paths to tell the story of a wine.
Natural yeasts: complexity and expression of terroir
Natural yeasts, also called indigenous or wild, are those that live naturally on the skins of the grapes, in the cellars and on the winemaking equipment. They are not added by the winemaker: they begin fermentation spontaneously when they find the right conditions of temperature, sugar and oxygen. This microbial diversity is unique to each vineyard, working like a “fingerprint” of its location.
The great appeal of natural yeasts is the aromatic complexity they provide. Spontaneous fermentation is driven by multiple strains, each contributing different aromatic notes — floral, fruity, mineral or even saline, depending on the terroir. This results in wines with more sensory layers and, often, a more authentic character.
However, this method has its risks. Natural yeasts can be less resistant to alcohol and less efficient at converting sugars, which may cause slow or stuck fermentations. There is also a greater chance of undesirable aromas appearing, such as vinegary or excessively phenolic notes. That is why working with indigenous yeasts demands healthy vineyards, rigorous hygiene in the cellar and experienced technical oversight.
Regions such as Burgundy, Colares or the Douro use this method to create wines deeply tied to their territory. Here, unpredictability is seen as a virtue: each harvest faithfully reflects the conditions of that year.
Selected yeasts: precision and consistency in winemaking
Selected yeasts are specific strains of Saccharomyces cerevisiae isolated and studied in laboratories to guarantee predictable, safe results. They are chosen for characteristics such as resistance to alcohol, tolerance of different temperatures, speed of fermentation and the aromatic profile they lend the wine. When inoculated into the must, they quickly dominate fermentation, reducing the risk of intervention by undesirable yeasts.
The main benefit of this approach is consistency. Producers who need to maintain a recognisable style year after year — such as large-scale commercial brands or iconic wines with an established identity — find in selected yeasts a valuable tool. They allow the speed of fermentation to be controlled, specific aromas to be preserved and technical problems, such as incomplete fermentations, to be reduced.
On the other hand, uniformity can also be a limitation. The repeated use of the same strains tends to reduce the individual expression of terroir, creating wines that can sound more “international” in their sensory profile. That is why some producers opt for selected yeasts adapted to their region, seeking a balance between safety and identity.
In wines where predictability is fundamental, such as sparkling wines or harvests in regions with challenging climates, commercial yeasts are often the best choice.
Spontaneous vs. controlled fermentation: which is the better choice?
There is no single answer to this question. Spontaneous fermentation offers authenticity and a connection to terroir, but it demands patience, rigour and high-quality grapes. It is a craftsman’s approach that values the individuality of each harvest, ideal for small-production wines with a strong regional identity.
Controlled fermentation with selected yeasts, meanwhile, guarantees stability and repeatability, which is fundamental for wines destined for international markets that demand a consistent profile. Moreover, in difficult years or in less balanced vineyards, inoculation can be a way to save the production.
Many winemakers opt for a hybrid method: they begin fermentation with natural yeasts, to capture the authenticity of the terroir, and finish with a selected yeast, to ensure the process is completed. This technique combines the best of both worlds and reduces risks.
In the end, the choice depends on the philosophy of the producer, the profile desired and the conditions of the vineyard. The decision is as much artistic as it is technical.
Microbial diversity: the role of non-Saccharomyces yeasts
Although Saccharomyces cerevisiae is the protagonist in wine production, there are many other species of yeast — known as non-Saccharomyces — that play important roles in the early stages of fermentation. Species such as Hanseniaspora, Metschnikowia and Pichia can contribute floral, fruity and even mineral aromas.
These yeasts do not dominate fermentation to the end, but they create a richer aromatic spectrum before being overtaken by Saccharomyces. The presence of a healthy microbial diversity is also an indicator of balance in the vineyard’s ecosystem, usually associated with sustainable viticultural practices and the absence of excessive chemical treatments.
Today, some researchers and producers are studying ways to preserve or even inoculate specific non-Saccharomyces yeasts, in order to increase the complexity of the wines. This approach opens up new oenological possibilities, combining science and tradition to create unique profiles.
Conclusion: yeasts as the producer’s signature and guardians of terroir
Yeasts are far more than an agent of fermentation: they are guardians of a wine’s identity. To choose between natural and selected yeasts is to decide between paths that favour, respectively, authenticity or predictability.
There is no better or worse method — only what makes most sense for the style of wine one wishes to produce. A producer who values singularity and is willing to accept variation between harvests may lean towards spontaneous fermentation. Whoever needs consistency and safety will find in selected yeasts a strategic ally.
As a winemaker, I believe that knowing and mastering both approaches is essential. In the glass, the consumer should feel not only the flavour of the wine, but also the history and the choices that shaped it. After all, every fermentation is a living narrative, where the yeasts are the invisible protagonists.
From the page to the glass
- Cascale T Tinto — Spontaneously fermented at 690 metres, 18 months in French oak. Organic.
- Cascale Petroleiro Palhete em Talha — White and red varieties together in clay talha, sealed for eight months.
