From Mold To Gold: The Fascinating Journey Of Botrytised Wines

Among the vast array of dessert wines on offer today, it may come as a surprise that some of the most sought-after types are made from rotten grapes (botrytis wines). That’s right - the likes of Sauternes, Tokaji and Beerenauslese all owe their rich sweetness to a fungus called ‘noble rot’, or the Latin ‘botrytis cinerea’.

How does fungus create a sweet wine?

Interestingly, this particular strand of grey rot is a common threat to fruit and vegetables, and is present in vineyards throughout most of the year. Its existence relies on damp, humid conditions which, when persistent, cause botrytis get out of hand, leading to natural degradation and ruin.

However, the balance of dry and humid conditions in certain regions allows its potential to be unlocked. For example, during the damp, misty mornings of Sauternes, botrytis attacks the grapes, leading to microscopic fissures and punctures in the skins. Then, its dry, sunny afternoons halt its spread and cause the water in the grapes to evaporate, leading to a higher concentration of sugars and acidity. Furthermore, the rot infuses its own flavours into the grapes, which can include honey, marmalade and beeswax.

Sauternes wines are made primarily from sémillon grapes, due to their thin skins which are more susceptible to botrytis, and their ability to create a rich body with honeyed flavours. Additionally, sauvignon blanc is often used to add a fresh acidity to the palette. In the Tokaj region, furmint is the primary suspect, and it is typically accompanied by Hárslevelű and Muscat to add fruitiness.

Production Of Botrytis Wines

The costly and labour-intensive process of making wine from these grapes contributes to their luxurious status. Not only do the shrivelled berries have to be picked individually by hand when they are ready, they also produce very small yields due to their low juice content, meaning large expanses of land can sometimes only produce a few hundred litres of wine in a harvest of several weeks. In addition, there is a risk of insufficient growth of the rot due to imperfect weather conditions.

The production of Sauternes wine involves careful pressing of the grapes, followed by a drawn-out fermentation process until the alcohol reaches around 14%. Due to the high concentration of sugar in the yield, what is created is a rich, naturally sweet wine. In areas such as Tokaj, however, a slightly different approach is employed, whereby the grapes are left longer to dry from rotting, and then soaked in grape juice, young wine or fermenting must. It is then left to age in oxidized barrels for at least two years.

And there you have it - an A to B explanation of how weather conditions align with rot to produce a naturally sweetened wine. Click here to discover the intensely rich flavours these wines have to offer, or take a look at our other blogs to learn more about fortified wines, sherry, or spirits.