What is yeast used for in wine?

Yeast in Winemaking: An Essential Protagonist

Winemaking is an ancient art that has evolved over time, yet one component has remained constant throughout the process: yeast. This microorganism is responsible for transforming grape must into the delicious wine so many of us enjoy. In this post, we will delve into the fascinating world of yeast in winemaking and explore its essential role in creating unique and memorable wines.

What Is Yeast?

Yeast is a single-celled microorganism belonging to the fungi kingdom. Its main function is fermentation, a process in which it converts sugars present in a medium into alcohol and carbon dioxide. This transformative ability makes it highly valuable in the production of foods and beverages such as bread, beer and, of course, wine.

Types of Yeasts in Winemaking

Although there are many types of yeasts, not all are suitable for winemaking. However, one stands out above the rest: Saccharomyces cerevisiae.

Saccharomyces cerevisiae: The Star of Winemaking

Saccharomyces cerevisiae is the most widely used yeast in winemaking. It is known for its ability to ferment efficiently and produce wines with desirable organoleptic characteristics. This yeast is alcohol-resistant, which allows it to survive and remain active even in musts with high sugar concentrations.

Difference Between Wine Yeast and Baker’s Yeast

Although both yeasts belong to the same genus, wine yeast and baker’s yeast have fundamental differences. Baker’s yeast is designed to produce large amounts of carbon dioxide, allowing bread to rise. Wine yeast, on the other hand, is optimised to produce alcohol and enhance the aromas and flavours of wine.

Fermentation Process: The Central Role of Yeast

Fermentation is the heart of winemaking. This is where yeast springs into action and transforms must into wine.

Alcoholic Fermentation

Alcoholic fermentation is the process by which yeast converts the sugars in the must into ethyl alcohol and carbon dioxide. This transformation is essential to obtain wine with the desired alcohol content.

Malolactic Fermentation

Although not carried out directly by yeast, malolactic fermentation is another crucial process in winemaking. In this stage, bacteria convert malic acid, present in the must, into lactic acid, softening the wine’s acidity and adding complexity.

Yeast’s Role in Fermentation

Yeast is not only responsible for alcohol production. It also plays a crucial role in forming compounds that define the wine’s aroma and flavour. These compounds include esters, aldehydes and terpenes, which contribute to the complexity and richness of the wine’s aromatic profile.

How Yeasts Influence Aromatic and Flavour Characteristics

Each yeast strain can produce different aromatic compounds. Therefore, the choice of yeast can significantly influence the final profile of the wine. Some yeasts enhance fruity notes, while others may contribute spicy or floral aromas.

Fermentation Process: The Heart of Winemaking

Winemaking is a meticulous dance between science and art, and at the centre of this dance lies the fermentation process. This is where yeast transforms grape must into the elixir we know as wine. But how does this process actually occur, and what role does yeast play? Let’s embark on a journey through the world of fermentation in winemaking.

Description of Alcoholic and Malolactic Fermentation

Alcoholic Fermentation

Alcoholic fermentation is the first step in transforming must into wine. During this process, yeasts consume the sugars present in the must and convert them into ethyl alcohol and carbon dioxide. This reaction not only increases the alcohol content but also releases heat and produces volatile compounds that will influence the wine's aroma and flavour.

Malolactic Fermentation

Malolactic fermentation is a secondary process that usually occurs after alcoholic fermentation. Although not carried out by yeasts but by bacteria, it is essential in winemaking. These bacteria transform malic acid—sharp and tart—into lactic acid, which is softer and rounder. This transformation alters the wine’s acidity, giving it a more velvety and complex texture.

Yeast’s Role in Fermentation

Yeast is the driving force behind alcoholic fermentation. Without it, must would simply remain a sweet juice. These microorganisms not only convert sugar into alcohol but also produce a host of secondary compounds that enrich the wine’s aromatic and flavour profile, including esters, aldehydes, acids and higher alcohols.

How Yeasts Influence Aromatic and Flavour Characteristics

The type and strain of yeast used in fermentation can have a significant impact on the wine’s final profile. Some yeasts enhance fruity notes, while others can introduce spicy, earthy or floral aromas. The choice of yeast, along with fermentation conditions, will largely determine the wine’s character and personality.

Native Yeasts vs Commercial Yeasts

In winemaking, not all yeasts are the same. There is an ongoing debate in the industry about using native yeasts versus commercial yeasts. Both have their advantages and disadvantages, and the choice between them can influence the final wine.

Advantages and Disadvantages of Using Native Yeasts

Advantages

• Authenticity: Native yeasts reflect the terroir from which the grapes originate, resulting in wines with a unique and distinctive character.
• Complexity: These yeasts can produce a broader range of aromatic compounds, potentially leading to more complex wines.

Disadvantages

• Unpredictability: Fermentations with native yeasts can be less predictable and harder to control.
• Risk of Undesirable Flavours: There is a risk of developing unwanted aromas and flavours.

Advantages and Disadvantages of Using Commercial Yeasts

Advantages

• Consistency: Commercial yeasts offer more predictable and consistent fermentations.
• Control: They allow the winemaker greater control over the wine’s aromatic and flavour profile.

Disadvantages

• Less Authenticity: They may produce wines with less distinctive character compared to those fermented with native yeasts.
• Lower Diversity: May result in less aromatic diversity.

How to Choose the Right Yeast for the Wine You Want to Produce

Choosing the right yeast is a crucial decision in winemaking. Factors to consider include:

• Grape Variety: Some yeasts work better with certain grape varieties.
• Desired Profile: Depending on whether a fruity, spicy, floral or earthy wine is desired, a particular yeast will be selected.
• Fermentation Conditions: Temperature, pH and sugar content can influence the choice of yeast.

Innovations in Yeast Use: Revolutionising Winemaking

Winemaking is a centuries-old tradition, but that doesn’t mean it is exempt from innovation. In fact, the wine industry has seen significant advances in recent decades, many of which are related to yeast. These essential microorganisms have evolved in ways that are redefining how we understand and enjoy wine.

Yeasts for Red, White, Rosé and Sparkling Wines

Each type of wine has its own characteristics and, therefore, its own yeast requirements.

Red Wines

For red wines, winemakers seek yeasts that enhance tannic structure as well as fruity and spicy aromas. These yeasts must also be resistant to high tannin concentrations.

White Wines

In white wines, yeasts must highlight freshness, floral and citrus aromas and help achieve balanced acidity.

Rosé Wines

Rosé wines require yeasts that combine the traits needed for both reds and whites, providing freshness and fruity notes.

Sparkling Wines

Sparkling wines require a second fermentation in the bottle. Therefore, yeasts must work under high pressure while enhancing characteristic aromas such as toasted bread and pastry notes.

Premium Yeasts and Non-Alcoholic Yeasts

Premium Yeasts

Premium yeasts are strains selected for their unique characteristics, capable of contributing exceptional aromatic and flavour profiles. These yeasts are the result of years of research and offer winemakers tools to create high-end wines.

Non-Alcoholic Yeasts

With growing demand for non-alcoholic wines, non-alcoholic yeasts have emerged that are able to ferment without producing alcohol. These yeasts make it possible to obtain wines with the organoleptic qualities of traditional wine but without alcohol content.

How New Yeast Strains Are Revolutionising the Wine Industry

Research in yeast has led to the discovery of new strains that are transforming winemaking. These yeasts can:

• Increase wine longevity
• Improve disease resistance
• Enhance specific aromas and flavours
• Adapt to changing climatic conditions

These innovations help producers face modern challenges such as climate change and offer wines that cater to evolving consumer tastes.

Conclusion

Yeast in winemaking is far more than a simple fermenting agent. It is an ally that, thanks to research and innovation, offers endless possibilities for creating exceptional wines. Choosing the right yeast is essential to producing quality wines, and as consumers, it invites us to explore and discover new flavours and aromas in every glass.