Just one fermentation
One fermentation is enough: Méthode Ancestrale, Pét-Nat, Metodo Asti
With the Méthode Ancestrale, Pét-Nat, and Asti, the wine ferments only once. Fermentation hasn't yet finished when the wine goes into a sealed vessel, trapping the carbon dioxide from the final fermentation phase. There's no need for a tirage dosage of sugar and yeast.
What is the Méthode Ancestrale?
It starts with an ordinary must that begins fermenting normally. Before the sugar is fully consumed, the still-fermenting wine is bottled and sealed. It continues fermenting inside the bottle, and the resulting carbon dioxide dissolves into the wine. The sugar and yeast come entirely from the grape and the ongoing fermentation itself. The name means "ancestral method," since wines fizzed this way long before cellar masters learned to control the second fermentation deliberately.
After that, there are two options. Some producers leave the yeast in the bottle, leaving the wine slightly cloudy. Others riddle and disgorge as in the traditional method, resulting in a clear wine. The method is only regulated in a handful of French appellations. One well-known example is Blanquette de Limoux Méthode Ancestrale, made from the Mauzac grape; Clairette de Die in the Rhône Valley also has its own version, called méthode dioise ancestrale.
What is a Pét-Nat, and is it a sparkling wine or a semi-sparkling wine?
On the wine shelf, it often stands out for its crown cap and cloudy appearance: the Pét-Nat, short for pétillant naturel, meaning naturally sparkling. Winemakers in many countries use this name for wines made via the Méthode Ancestrale, typically with minimal intervention, no dosage, and often with the yeast left in the bottle. The style is fresh, fruity, sometimes a bit wild and yeasty. White, rosé, orange, and red versions exist, made from nearly any grape variety.
Legally, Pét-Nat isn't a category of its own. Neither EU law nor German wine law defines the term. Depending on its pressure, a Pét-Nat is classified as either a semi-sparkling wine at 1 to 2.5 bar or a sparkling wine from 3 bar upward, and is labeled accordingly. The term also makes no binding statement about alcohol content, residual sugar, or pressure. The only reliable indicator is the category stated on the label.
How is Asti Spumante made using the Metodo Asti?
Asti, too, ferments only once, though in a pressure tank rather than in the bottle. After pressing, the must from Moscato Bianco is kept cold so it doesn't start fermenting on its own. When needed, the winery brings a batch into the tank, warms it up, and lets fermentation begin. Inside the sealed tank, pressure builds, and while plenty of sugar still remains in the wine, the cellar master stops fermentation by chilling it. It's then filtered and bottled under counter-pressure.
The result is sweet, intensely fragrant with Muscat grape aromas, and noticeably lower in alcohol than a dry sparkling wine. Legally, Asti is classified as an aromatic quality sparkling wine: a dosage liqueur is prohibited, fermentation may only be controlled by physical means such as chilling, and production must take at least one month. Moscato d'Asti is stopped even earlier. It's only lightly sparkling and has around 5.5% ABV.
What's the difference between one fermentation and two?
With the two-step method, a finished, dry base wine is produced first, which the cellar master can taste, blend, and evaluate. Only then follows the second fermentation, with a precisely calculated tirage dosage. This makes pressure and flavor predictable. With a single fermentation, timing is everything: bottle too early, and the pressure may build up too much; bottle too late, and the wine will barely sparkle at all.
That's why Pét-Nats vary more from bottle to bottle and from year to year than Champagne does. Many enthusiasts particularly value this quality. One more related style deserves mention: Prosecco Sui Lieviti, formerly called Col Fondo, undergoes a second fermentation in the bottle and is not disgorged. It looks like a Pét-Nat but actually results from two fermentations. Asti, meanwhile, has no yeast in the bottle at all, since it ferments in a tank and is filtered.