Bottles sit on their yeast lees inside the caves at Champagne Pommery. Wikimedia Commons

Back in December (of 2024), we ran a piece on “Cool summer sparkling” which resulted in some feedback requesting an updated primer on different sparkling wine styles. Therefore, this piece will cover the styles discussed: méthode traditionnelle, Charmat/Martinotti method, transfer method, Asti method and méthode ancestrale or pétillant naturel.

For reference, méthode traditionnelle is used in Champagne, Crémant, Sekt Austria Reserve, Winzersekt (and therefore VDP.Sekt) Cava, Franciacorta and wines inspired by them outside of Europe. Charmat/Martinotti, also called the tank method, is usually the method used for Prosecco (not always, though).

Transfer method is not used by default anywhere but is more commonly used in areas without strict production laws as a compromise between méthode traditionnelle (to gain the lees-aged characteristics and finer bubbles) and the tank method (which is much easier to bottle as it does not require disgorgement).

Asti is self-explanatory as the wines contain that name; e.g. Asti DOCG and Moscato d’Asti (which is lower alcohol and sweeter).

Pétillant naturel or Pet Nat wines are often labelled as such, with Bugey Cerdon AOC being a classic example of méthode ancestrale (most others include the term on the label so are easy to identify).

For the purposes of this exploration, I would like to invite you to approach it from a different perspective than the traditional study of step-by-step winemaking processes and think instead of a few branching decision points which have the most impact on the final wine.

First of all, for bubbles to happen, carbon dioxide has to be dissolved in the wine. The absolute cheapest method is to directly inject CO2 into the wine under pressure, and although it is used for some bulk styles of wine, it is not really relevant to this piece as most wine we review would not fit into that category. Therefore, we mainly concern ourselves with wines where the CO2 has occurred as a result of fermentation. This means that the fermentation has to happen under pressure, otherwise the CO2 would simply all escape.

We can divide the world of sparkling wine variously along two lines related to either:

1. Whether the fermentation responsible for this CO2 occurs during primary or secondary fermentation; and
2. The vessel used for that fermentation step.

For the first question primary fermentation methods derive their CO2 from sugar in the unfermented or partially fermented grape juice, therefore encompassing most pét nat or méthode ancestrale wines and all Asti-method wine. CO2 resulting from a second fermentation requires that a source of sugar is reintroduced (again, some pét nat or méthode ancestrale wines, all transfer wines, Charmat/Martinotti method wines and méthode traditionnelle).

We then split that further (using the second question mentioned above) into wines where the fermentation occurs in a tank; i.e. Charmat/Martinotti and Asti method; or in bottle, which basically covers all the others, including the transfer method.

The table below might help with visualising these distinctions.

As you can see from the table above, there are other considerations which play a role in determining the overall flavour balance of a sparkling wine, arguably a more important distinction to a drinker than dividing it along academic winemaking branches. These are the presence or intensity of ageing characteristics like yeast lees autolysis, oak influences and bottle development. These all require specific things to happen before they can occur and once you understand the CO2 source and vessel, it is easy to figure out which of the styles are most associated with these flavour profiles.

Oak influence is reserved for wines which complete primary fermentation before being bottled, ruling out all the primary ferment CO2 wines. Pet Nat has a *special exception because some experimenting winemakers might play around with oak in a pet nat before bottling it, but it is very unusual to see.

Yeast autolysis and dominant primary fruit characters are often at opposite ends of the spectrum, this is because the presence of those aged autolytic notes require ageing for extended periods, which usually results in a reduction of intense primary fruitiness. Autolysis characters are also much milder if the second fermentation occurs in tank as the wines are simply not held on their lees for long enough for it to make much of an impact.

The amount of contact between wine and the yeast lees is also proportionally higher in a bottle than in a large tank. Therefore, méthode traditionnelle wines have the most notable ageing characteristics such as biscuity flavours, brioche and toast and tank method wines rarely exhibit them. Again, pet nat wines can have yeast flavours as a *special exception, but usually because of the presence of yeast in the bottle you are drinking out of (if not disgorged).

In its most basic form, pétillant naturel or pet nat, and méthode ancestrale wines are bottled before they finish fermenting so they are considered bottle-fermented primary ferments. This also means that most pet nat wines do not have any residual sugar remaining after fermentation and there is no dosage added to these wines so they should be completely dry.

One thing to note about calling them primary ferments, in reality, things are not actually quite that simple and pet nat producers from the Loire Valley—and as a result, those who are watching what is happening there—have modified the method so they are letting wines finish fermentation to stability and then adding unfermented grape juice before it goes to bottle, essentially making something half-way between what we traditionally consider pet nat and méthode traditionnelle. This is made even murkier (forgive the pun) by the rising number of pet nats which are disgorged.

Yes, the world of wine is dynamic and ever-changing, which makes it so frustratingly confusing, but also so delicious.

Glossary

Disgorgement

This is the process by which the spent yeast cells in bottle-fermented sparkling wine are removed, allowing the wine to achieve a clearer appearance and stop further flavour contribution from those yeast lees.

Autolysis

This word is usually used to refer to the flavour of brioche, pastry and toast from ageing for extended periods (years) on the spent yeast lees in bottle after secondary fermentation has finished. This is a slightly simplistic explanation as the flavours are often a result of a more complex process involving low-temperature Maillard reactions, but that’s outside the remit of this primer.

Dosage

Colloquially used to refer to the amount of sweetness in sparkling wine, which can be expressed in grams per litre of sugar or using one of the dosage terms like Brut, Extra Brut etc. Technically, dosage should only refer to a liqueur d’expedition added as the last step of production, but it is often also applied incorrectly in much wine media to refer to residual sugar and vice versa, so be aware that there may not be any meaning implied by its use, depending on where you see it written.