What are the key differences between the two well-established sweet wines made with botrytis-infused grapes?
The perfect mesoclimate for botrytis
The smooth onset of botrytis cinerea on white wine grapes requires certain growing conditions. Humidity in the early morning combined with aerated, sunny afternoons in autumn is a must for the fungus to remain benign and develop complex flavours as the berries shrivel to a perfect status.
Needless to say, both Sauternes of south Bordeaux, France and the Tokaj of northeastern Hungary enjoy the ideal terroir for botrytis, allowing the noble fungus to puncture microscopic holes through grape skins and nurture some of the world’s top expressions of these golden, lusciously sweet wines, which are capable of ageing for decades.
In the case of Sauternes, the cooler tributary Ciron feeds into the warmer Garonne, creating misty mornings in its communes and allowing the onset of botrytis in autumn. Meanwhile, the warm, sunny afternoons reduce the moisture and prevent the fungus from going rogue.
Likewise, the Tisza and Bodrog rivers that meet in Tokaj are the reasons behind the foggy autumn mornings that trigger the inception of botrytis, with the sunny and breezy afternoons safeguarding the healthy development of the fungus.
Despite sharing a similar mesoclimate, producers of Sauternes and Tokaji Aszú are using different grape varieties and taking a diverse approach in winemaking to create their own versions of ‘liquid gold’.
Choice of varieties
Sémillon is the primary grape for Sauternes due to its thin skins, which are highly susceptible to botrytis. The grape tends to provide a rich, textured body in addition to beeswax, citrus and honeyed stone fruit flavours to the sweet wine. Sauvignon Blanc is its crucial blending partner, providing fresh acidity and a lift to the palate. Sometimes Muscadelle is also added to provide further aroma complexity.
Furmint, on the other hand, is the diva of the Tokaj wine region. This versatile variety has the ability to go from bone-dry to lusciously sweet, with the high, mineral acidity being its ‘hallmark character’, according to Caroline Gilby MW, wine writer and consultant specialising in Central and Eastern European wines.
When making Tokaji Aszú, Furmint is ‘typically supported by Hárslevelű and Muscat to add fruitiness and fragrance’, says Gilby.
Making naturally botrytized wine can be costly and extremely labour-intensive, as it demands careful, manual selection in the field. The shrivelled berries have to be picked by hand only when they are ready. Also, producers may risk insufficient onset or even no-show of botrytis when the weather condition is less ideal.
The classic production method of Sauternes involves carefully pressing these precious, noble rot-infected berries, before painstakingly going through a slow fermentation process, often in partial or all-new barriques, until the alcohol level reaches around 14%.
Winemakers in Tokaj, however, adopt an ancient, arguably more flexible approach in extracting the botrytis flavours.
In fact, the first written records of the Aszú (the Hungarian word for shrivelled and botrytis-affected berries) method can be traced back to 1571, far before noble rot was recognised as a legitimate method of making sweet wines in France.
‘Sauternes are made from berries that are still juicy and can be pressed and fermented. The Aszú berries, however, are so raisined and dry. If you try to press them, you get a trickle of thick syrup, so sweet it barely ferments at all,’ explains Gilby.
Therefore, in order to extract sweetness and flavours, Aszú producers have to soak the sweet paste of botrytis-influenced, shrivelled berries in either grape juice, young wine or fermenting must. The wine is then aged in barrels under oxidative conditions for at least two years.
Indeed the word ‘Puttony(os)’ used as a unit to describe the sweetness of Tokaji Aszú refers to the bucket traditionally used to collect Aszú berries. Though today the sweetness of Tokaji is no longer measured by the number of Puttonyos added but based on residual sugar, said Gilby.
Tell them apart in blind tastings
If we are to blind taste quality Sauternes and Tokaji Aszú, what should we look for to tell them apart? Stephen Brook, contributing editor to Decanter, provides his thoughts.
‘In the past, the various quality levels of Aszú – 3, 4, 5, and 6 Puttonyos – were defined by strict rules requiring minimum levels of residual sugar, acidity, and sugar-free extract. They no longer exist in a rigorous form, so there is now a far greater stylistic variation among Aszú wines. But two trends are discernible,’ says Brook.
‘First, the wines are far sweeter than they used to be. The same is true of Sauternes, but Aszú wines have a much higher acidity, giving them a different character. Moreover, most Aszú wines used to be deliberately oxidative. There was much debate about whether oxidation was intrinsic to Aszú, but today few would argue that case.
‘So Aszú wines are no more likely to be oxidative in style than good Sauternes. In short, it is becoming increasingly difficult to tell the two wines apart, although the higher acidity and raciness of Aszú wines remains a major difference.’