Wine Academy part 7: what makes wine sweet?


Jeroen van Mierlo teaches wine courses, in which he explains people the basics about wine. In this biweekly column ‘Wine Academy’ he answers the most asked questions about wine. In part 7 of the wine academy Jeroen answers the question: what makes wine sweet? He speaks about sugars, grapes and the process of creating alcohol.

What makes wine sweet?

One of the questions that Jeroen gets asked a lot during his wine course is ‘What makes wine sweet?’. The answer can be easily explained. The sweetness of the wine depends on the way the wine is made. A grape is naturally rich of sugars. To make wine you have to ferment the sugars from the grape juice into alcohol. When the wine makers decide that the wine will be a sweet one, they have to make an effort to ‘keep’ the sugars in there.

How do you make a wine sweet?

So you need to keep the sugars of the grapes in the wine. How do you go about this? There are multiple options, but one of them is stopping the fermentation process early. This way you will keep the sweetness because not all sugars are fermented yet. Another option is to concentrate the present sugars. This is a technique that is often used with desert wines. This is what gives them that delicious, rich, sweetness. The amount of sugars in these grapes is so high that eventually the wines will be really sweet as well.

Sweet wines you should really try

So now we know what makes wine sweet, it’s time to start enjoying some sweet wine. Wine Folly was nice enough to make a selection of white wines you and I should absolutely try and of course we would like to share these with you. Here you go:

  • Moscato d’Asti – Wines are “frizzante” (as in, somewhat sparkling) or “spumante” (full sparkling), with amazing aromas of perfume, Asian pear and peach. Moscato d’Asti is the perfect birthday cake wine.
  • Tokaji Azsú – This white wine is made with a rare white grape called Furmint. These grapes are picked once they’ve been infected with a special type of rot. While this sounds gross, the result is a richly sweet golden white wine with subtle flavors of saffron and ginger.
  • Sauternes – In Bordeaux, there is an area along the Garonne river that gets super moist and covered with fog – ideal conditions for developing the beneficial rot, Botrytis cinerea. Sémillon, Sauvignon Blanc, and Muscadelle grapes are blended together and wines reveal complex flavors of quince, marmalade, honey, ginger, and spice.
  • BA and TBA Riesling – In order to have the sweetest grapes, harvesters will hand select only those grape bunches affected with noble rot. These wines are sweet and textured, like honeycomb, but with tingly acidity.
  • Ice Wine – When making Ice Wine, the grapes are left on the vine until it gets so cold that they freeze. The grapes are pressed while still frozen so only the sugar oozes out. This syrupy liquid is then fermented into wine!
  • Rutherglen Muscat – There is a rare, red-colored variant of the Moscato grape that grows in Victoria, Australia. The grapes are harvested later in the season when they become partially brown so that the sweetness is more concentrated. The result is a wine with rich aromas of toffee, dried strawberries and hazelnuts that’s hauntingly sweet.
  • Recioto della Valpolicella – The fermentation stops before the sugars have all fermented, which produces a rich sweet red wine. Drinking Recioto is like liquid chocolate covered cherries.
  • Vintage Port – The Douro Valley in Portugal was the world’s second official wine region (demarcated in 1757) and is the home of true Port wine. While most of the Port wine we see in stores is basic quality Ruby Port, certain years are so good that they are recognized as “vintage” years. Vintage Port is a substantial step up in terms of quality and you can taste it.
  • X. Sherry – No, Pedro is not a guy, it’s a rare white wine grape from Southern Spain! The process of making PX (a sweet Sherry) involves allowing the wine to age in barrels for many years, causing the liquid to become brownish-black in color. Over time the fluid in the wine slowly evaporates (both water and alcohol), which concentrates the sugar level.


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