Natural and cultured yeast are both used in the Douro Valley but in different ways
One of the winemaker’s most important decisions is if he should use native yeasts or selected yeast strains for the fermentation. In this guest article Oscar Quevedo from the Quevedo Wines estate in the Douro explains the difference and why both types are used frequently in the Douro Valley. But for different types of wines.
One of the key elements, if not the most important after the grape in the winemaking process, is the yeast. Why is yeast so important? Because despite its small size (around 0.003 mm), this micro-organism has the very important task of transforming fructose into ethanol, the form of alcohol present in wine. The yeast can also have a strong impact on the character of the wine.
Yeast is present on the surface of the grapes and in the vines. Once the grapes are crushed, yeast starts its mission: it immediately begins transforming the sugar of the grapes into alcohol. Broadly speaking, it can tolerate temperatures between 10 C and 35 C; the higher the temperature, the quicker yeast works and reproduces itself. But over a certain temperature there is a risk of deviations or simply that the fermentation stops.
Are all yeasts equal?
But are all yeasts the same? No. Different vineyards within the same country or region have different yeasts. And which are the best? Probably there is no answer to that question as it depends on the kind of aroma and taste the winemaker prefers.
When the grapes arrive to the winery, the winemaker has two options. He can rely on the native yeasts that have been adapted to the local terroir. This is sometimes called “natural” yeast or indigenous yeast, since it is what is already “naturally” present on the grapes. Or he add a selected yeast, that is very likely brought from another wine region, possibly in another country, and was developed in laboratory to drive the fermentation into a certain kind of flavours and tastes. (1) Selected yeasts are sometimes called “cultured” yeast or even “industrial” yeast.
Yeasts in the Douro Valley
In the Douro we have two realities, depending if we are talking about Port or still wine. From what I see, I would say that most of the Port is made with native yeast.
On the other hand, for the Douro wines (2) a generous number of producers use selected yeast.
The fact that, within the same region, in the Douro, for one kind of wine we usually use native yeast and for another we rarely use it, is curious but not difficult to explain. Port is a worldwide reference; it is copied, imitated and even faked in several wine regions, little-know as well as respected wine regions in the world. But it looks as if no other place but the Douro can make something as fantastic as Port. And besides grape quality and winemakers’ skills developed through centuries, yeast plays a very important role. Thus, Port winemakers trust that the best yeast they can use is in the vineyards. Since centuries.
But then why use selected yeast in the still wines? It is like buying an insurance. You know that if all goes right the insurance is not necessary, but if it goes wrong, insurance guarantees you don’t lose everything.
In our case, as I guess you want to know, we use native yeast for all our Quevedo Ports, except for the rosé. And for our Douro table wines, we do sometimes buy an insurance!
In the future I think very “commercial” wines will continue to use selected yeast. But as yeast research develops, the number of selected yeast available will rise and more wine regions will use their own lab selected native yeast.
Is there any question about winemaking that you have been keeping for sometime and want to make now?
Ask it and we will try and answer it!
— by Oscar Quevedo
(1) The selected yeasts can of course also come from the wine region itself. On rare occasions the winery have even developed its own very local strain of selected yeast(s).
(2) “Douro wines” refers to the “table” wines of the Douro, i.e. the wines that are not fortified.
Oscar Quevedo runs Quevedo Wines together with his sister Cláudia Quevedo and the whole Quevedo family. The estate produces a wide range of port wines (famously their vintage and old tawnies) and Douro table wines. The port range includes the Quinta da Alegria. The Quevedo winery is located in San João da Pesqueira, a small town in the upper Douro Valley.
This article has appeared in a shorter version on the Quevedo blog.
This post is also available in: Swedish