All about Aszú

Sometimes we all need a little bit of sweetness and joy in our lives, so in those moments remember Tokaji and Aszú. It may be the oldest botrytised sweet wine in the world – Aszú was first mentioned in Hungary in the early 16th century, hundreds of years before Sauternes. It is undoubtedly among the world’s greatest sweet wines and is quite unique thanks to a combination of place, grapes and winemaking methods.

Sweet wines can be produced by various methods of physical concentration of the sugar in grapes – including late harvesting, freezing and air- or sun-drying – but the greatest and most complex rely on a microscopic fungus called Botrytis cinerea. Most of the time, this Janus-faced fungus causes devastating grey rot on fruit, leading to huge financial losses and damage. But rarely, in certain places and exactly the right conditions, it turns to ‘noble rot’, which brings an almost magical transformation of quality and complexity.

There are very few places in the world where noble rot happens fairly reliably, and one of those places is Tokaj, located in the far northeast of Hungary.

Sweet success

The pinnacle of Tokaji sweet wines is Aszú, the Hungarian word for grapes that have undergone both noble rot and shrivelling. The cool, continental Tokaj region climate makes this possible, with its sunny, breezy autumn afternoons that shrivel the berries, and densely foggy, autumn mornings that occur due to the confluence of the Bodrog and Tisza rivers close to the town of Tokaj, creating the humidity that allows botrytis to thrive.

The botrytis fungus infects the grapes through micro-fissures in the grape skin and through the stomata (air exchange pores). This means the skin becomes more permeable to water, so grapes dry out. The timing of this infection also matters – the grapes must be ripe (a minimum of 11.5% potential alcohol and with brown seeds) to avoid grey rot, and ideally overripe for the best quality.

Disznókő head winemaker László Mészáros explains that if botrytis infects just-ripe grapes early on, the fungal mycelium (a network of fine, hair-like hyphae) tends to develop on the surface of the skins, resulting in less refined wines with zesty flavours and some bitterness. If it occurs later, on riper fruit, it develops inside the berry, digesting more of the skins and giving a more creamy texture, with dried apricot and citrus notes, and greater finesse and elegance. Szepsy’s Istvan Szepsy Jr adds: ‘Low yields are important for more complex and flavourful grapes, but also earlier ripening – this gives more chance of overripening, which is key to having the right noble rot.’

Every year, producers leave grapes on the vine in the hope that the right botrytis will occur and will be followed by an Indian summer that will dry out the grapes, though this is unpredictable. When it does happen, the fungus change the biochemical composition of the whole grape, producing distinctive flavour characteristics such as dried apricot, peach, honey, caramel and quince. It favours the production of components such as glycerol, which enhances the texture and silky mouthfeel of the wine, and prefers to feed off glucose, leaving the sweeter-tasting fructose behind.

The right grape variety is crucial, too – it must be a variety that is prone to infection by botrytis, so with thin skins ideally with tight bunches and not many antifungal phytoalexin compounds. Luckily Tokaj’s most important grape, the thin-skinned Furmint, is quite susceptible to noble rot infection.

Painstaking process

Two other unique features of Tokaji Aszú are the grape-by-grape harvest by workers skilled in selecting good berries, and the unusual winemaking method. The pickers must painstakingly select from each bunch to avoid the bad rot, choosing only the berries that have noble rot and are properly shrivelled (just 8kg-10kg a day is typical).

Being so shrivelled and dry, the harvested berries can’t simply be pressed to extract juice, as happens in most sweet wines, but must be macerated in liquid. This maceration is an essential and unique step in Tokaji winemaking, involving soaking the aszú berries for eight to 60 hours – the secret is to extract good flavours and phenolics and avoid any mouldy notes or volatile acidity.

The timing of the maceration and type of maceration liquid used matters – in order of lowest extraction power to highest, it runs: unfermented juice; finished wine; still-fermenting wine late in the cycle; or actively fermenting wine. The winemaker must make a decision based on the quality and health of the aszú berries.

In years when botrytis is strong, the grape flesh is almost totally broken down and becomes creamy. This lends itself to less-extractive maceration using wine that has almost finished fermentation, says Mészáros, who prefers to use an actively fermenting must for an Aszú with more shrivelling and less botrytis. Gentle pressing follows, then fermentation and barrel ageing (at least 18 months by law).

Unlike Bordeaux’s Sauternes, with its lower acidity and higher alcohol, Tokaji Aszú isn’t suited to new barriques; larger barrels and used oak are preferred. Of course, the whole picture is much more complicated, but one takeaway is that Sauternes wines are more uniform in style (alcohol 13.5%-14%, acids 5.7-7g/L, sugar 120-150g/L) than Tokaji Aszú (alcohol 9%- 12.5%, acids 7-10g/L, sugar 120-300g/L, or at least 450g/L for Eszencia) – all adding to the endless fascination of the wine.

The story of Tokaji Aszú is indeed complex – rather like the gorgeous wines themselves – but whichever style you choose, the microclimate, grapes, winemaking and the magic of Botrytis cinerea all combine to make some of the most glorious, sweet-but-fresh, complex and long-lived wines in the world.

Tokaji Aszú Eszencia

Shades of sweetness

For Tokaji sweet wine styles beyond Aszú, the historic sweet (édes) Szamorodni has a name derived from Polish meaning ‘as it comes’. It is made from whole bunches with a mix of botrytis-affected and healthy berries, or from bunches with noble rot that have not shrivelled enough to be used for Aszú. With shorter oak ageing than Aszú (six months minimum) and produced in fresher, fruitier styles, Szamorodni is hailed for its potential to be more versatile, affordable and approachable than its fully noble-sweet counterpart.

Late harvest is typically the lightest, easiest-drinking and most affordable sweet style from the region. It may or may not have botrytis influence and it’s usually possible to make it every year (unlike Aszú). It is often lower in sugar (80-110g/L) than Aszú and does not require any oak ageing. It’s a style well understood all over the world and can serve as an introduction to Tokaji sweet wines.