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Icewine (Eiswein) - how frost creates sweetness

Imagine harvesting grapes in the middle of a frosty winter, at night, at a temperature below minus eight degrees, when the berries are hard as little stones. It is not a mistake but the way to one of the most luxurious sweet wines in the world: icewine, in German Eiswein. It is made from grapes that froze naturally on the vine - the frost freezes the water out of them, leaving a small amount of concentrated, intensely sweet juice. The result is a wine of enormous sweetness, but also lively acidity, rare and expensive, because it is entirely dependent on capricious winter weather. Here is a guide to icewines: how they are made, where their sweetness comes from, how they differ from botrytised wines and why they are so special.

What icewine is

Icewine is a dessert wine produced from grapes that froze naturally on the vine, and are then harvested and pressed while still frozen. This is the key difference: unlike other wines, here the grapes must stay on the vines long after the normal harvest, until the first strong frosts of winter. They are harvested in the middle of a frosty night and pressed frozen, before they have time to thaw. It is a method entirely dependent on the weather: without a sufficiently strong frost icewine simply will not be made. This is why it is a rare, seasonal and risky wine to produce. Understanding that icewine is wine from grapes frozen on the vine, pressed in a frozen state, is the starting point for the rest. It is one of the most dramatic ways of producing wine. We cover sweet wines more in dry versus sweet wine.

Cryoconcentration: the magic of frost

The heart of how icewine is made is a phenomenon called cryoconcentration - concentration by frost. It works on a simple physical principle: water and sugar freeze at different temperatures. When grapes freeze at minus eight degrees or below (this threshold applies in Canada, in Germany minus seven), the water in the berry crystallises into ice, while the sugars, acids and other dissolved substances stay liquid thanks to their lower freezing point. This means that when the frozen berries are pressed, the ice crystals (pure water) stay in the press, and only a small amount of concentrated, sweet juice runs off. The frost literally separates the water from the essence of the fruit. This is why a large amount of grapes yields a tiny amount of intense must. Understanding cryoconcentration - frost freezes out the water, concentrating the rest - is the key to understanding these wines. It is physics turned into sweetness.

Where the sweetness and acidity come from

Icewines have a unique profile: enormous sweetness combined with lively acidity. Where does this combination come from? The concentrated must contains a great deal of residual sugar - well over 100 grams per litre, and the Canadian VQA standard requires a minimum of 35 degrees Brix (a measure of sugar) at harvest. This gives an intense sweetness. But the concentration affects everything: along with the sugar, the acids also concentrate, so the wine keeps a high acidity, which balances the sweetness and makes it not cloying but fresh and refreshing. Interestingly, icewines usually have low alcohol, often around 7 percent, because such a sweet must is hard to ferment completely. This combination - intense sweetness, lively acidity, low alcohol - makes them exceptionally elegant despite their density. Understanding this balance explains why icewine is not simply sweet but complex. It is sweetness with tension.

A table: icewine versus botrytised

Let us gather the difference between the two roads to sweetness:

The table shows that icewine and botrytised wine are two different roads to concentrated sweetness: one through frost, the other through mould. Icewine has a cleaner, more fruity profile. We cover the other road more in botrytised wines.

Canada and Germany

Several countries with sufficiently frosty winters produce icewines, but two stand out especially. Germany is the cradle of the style - it was there that Eiswein was born, as one of the highest levels of sweetness in the German tradition, made mainly from riesling. But today the largest producer of icewine in the world is Canada, where the province of Ontario accounts for over 90 percent of Canadian production. Canadian winters are reliably frosty, which makes production more certain than in warmer Germany. The main grapes there are vidal (a hardy hybrid) and riesling. Interestingly, the Canadian era of icewine began in 1984, when the Inniskillin winery, under the direction of its Austrian-born co-owner, produced the first commercial Canadian icewine. Today Canada is a power of this style. Understanding the role of climate explains why icewine is made only in cold countries. We cover German sweetness more in German riesling and Pradikat.

Why they are rare and expensive

Icewines are among the most expensive dessert wines, and there are many reasons for this. First, the yield is dramatically low: on average only about 5-10 percent of the original harvest ultimately reaches the bottle as icewine, because the ice stays in the press and a tiny amount of juice runs off. Second, the production is risky: the grapes must hang on the vines through the whole autumn and early winter, exposed to birds, disease and rot, waiting for a frost that may not come at the right moment. Third, the harvest is extreme: by hand, in the middle of a frosty night, when the berries are frozen, which demands enormous effort and precision of timing. All of this together makes icewine a luxury. Understanding these costs and risk explains the prices and helps appreciate how much work and luck hide in a small glass. It is an essence worth its price. It is a gamble with nature.

How it differs from botrytised

It is worth clearly distinguishing icewine from botrytised wine, because both are concentrated sweet wines, but they are made differently and taste differently. Botrytised wine (like Sauternes or Tokaji) owes its concentration to noble rot, which dehydrates the berries and adds its own notes of honey, apricot and spice - it gives a complex, honeyed wine of a mould character. Icewine owes its concentration to frost, which only freezes out the water, adding nothing - it gives a wine of a cleaner, more fruity, fresher profile, showcasing the fruit itself and the acidity. This is the key difference of flavour: botrytised is rich and honeyed, icewine clean and fruity. Both are outstanding, but in different ways. Understanding that frost concentrates clean fruit, and mould adds its own character, helps appreciate both styles. They are two philosophies of sweet wine. The choice between them is a matter of taste: clean fruit or the complex depth of mould.

How to sense it in the glass

Icewine is easy to recognise by its characteristic profile. You sense above all an intense but clean sweetness, balanced by a lively, almost sharp acidity, which makes the wine fresh rather than cloying. In the aroma clean, bright fruits dominate: peach, apricot, mango, tropical fruit, citrus, sometimes honey, but subtler than in botrytised wines. The texture is dense and sticky, but not heavy, and the low alcohol makes the wine light in feel. If a sweet wine is intensely fruity, very sweet, but at the same time crisp and acidic, that is a good clue that it is icewine. Serve it well chilled, in small glasses, with desserts or alone as a dessert. It is worth comparing icewine with a botrytised wine, to feel the difference between the clean fruit of frost and the complex depth of mould. Over time you will recognise this fresh, fruity sweetness. It is one of the most luxurious experiences in the world of wine.

The essentials in brief

Let us gather it up. Icewine (Eiswein) is made from grapes that froze naturally on the vine and are pressed in a frozen state. The phenomenon of cryoconcentration is at work: at a frost below minus eight degrees the water in the berry freezes into ice, and the sugar and acids stay liquid, so only a small amount of concentrated, sweet juice runs off the press. The result is a wine of intense sweetness (over 100 grams of sugar per litre), lively acidity and low alcohol (around 7 percent). The largest producer today is Canada (Ontario), the cradle is Germany. The wines are rare and expensive, because only 5-10 percent of the harvest reaches the bottle, and the production is risky. Unlike botrytised wines, icewines have a cleaner, fruity profile. Now you know how frost creates sweetness and why icewines are so special.

Note every wine in GustoNote - including whether it is an icewine and the notes you sense. Over time you will start to recognise the clean, fruity sweetness of icewines.