27/07/2015 11:16 BST | Updated 27/07/2016 06:59 BST

What's So Noble About Noble Rot?

As part of my job at the WSET, I present at a lot of wine tasting events in the UK. One of the things that I keep hearing from UK wine drinkers is that they don't like sweet wines.

Fair enough, not everyone has a sweet tooth, but with the UK appetite for sugar, it just doesn't make sense to me. The problem we now have is that most people lump all 'sweet' wines in with those bland, sugary drinks that filled our supermarket shelves back in the 1970s. With a bit exploration, we'd find that there is a huge array of great wine ranging from off-dry to fully sweet.

These premium quality wines perfectly balance sumptuous sweetness with refreshing acidity and intensely delicious flavours. Some of my favourites are made by taking advantage of a rare natural occurrence - one which sounds a little bit grim at first...

Essentially, the winemaker allows a type of fungus to grow on the skins of the grapes during the late stages of ripening. Stay with me.

This fungus is technically known as botrytis cinerea, though it is more commonly and affectionately referred to as 'noble rot'.

What's so noble about it?

Well, firstly, noble rot is very rare - it occurs in very specific conditions in only a handful of tiny areas around the world. It requires misty, humid mornings and warm, sunny afternoons to grow successfully.

It can occur only when the grapes are fully ripe - well into Autumn in most northern hemisphere vineyards. If the fungus grows any earlier it is known as 'grey rot' which is much less welcomed by the winemaker. While grey rot aggressively attacks the grapes, splitting the skins and causing spoilage, noble rot is slower. Rather than destroying the grape, it punctures tiny holes in the grape skin.

Quite simply, the tiny holes allow water to evaporate out so the grape slowly shrivels, concentrating all that lovely sugar, flavour and acidity.

The sugar level is so high in these raisined grapes that the yeasts, whose job it is to convert sugar to alcohol during fermentation, simply run out of energy after a certain point. This leaves a final wine with plenty of leftover sugar and acidity to make the wine taste luscious yet refreshing.

The fungus itself doesn't taint the wine at all, but imparts a really lovely marmalade-like character. It is starting to sound nice now huh?

Two of the most famous examples made using noble rot are Sauternes, from Bordeaux, and Tokaji Aszú, from Hungary. Sauternes is aromatic, high in alcohol and is made from Sauvignon Blanc, Sémillon and the fragrant Moscatel. Tokaji is made from indigenous Hungarian grapes and tends to be lower in alcohol, deeper in colour and more nutty and savoury in style.

The concentrated flavours in these wines mean that they can stand up to an intensely sweet dessert or, as I particularly enjoy, a very ripe blue cheese. We know that having a sweet, acidic and strongly flavoured chutney with our cheese works well, so why not use a sweet, acidic and strong flavoured wine as well.

These wines are rare and expensive to make, meaning that they aren't often cheap. If you don't want to spend a lot on a wine you're unsure whether you will love, a great value route into noble rot wines is Australian 'Botrytised' Semillon/Sauvignon Blanc.

Bursting with apricot and marmalade flavours with well-balanced sweetness and refreshing acidity, these wines are ideal after dinner wines which won't leave a sickly sweet taste in your mouth. Have a go, and enjoy!

To learn more about sweet wines or to further your wine education, courses from the Wine & Spirit Education Trust (WSET) offer a step-by-step approach to building up your wine and spirits knowledge. Visit for more information and to find your nearest course provider.