What's the difference between Late Harvest wine and Icewine? (August 9, 2012)
The sugars in grapes are converted into alcohol by the action of yeast. If the yeast is "stopped" by the addition of brandy during the fermentation process, residual sugar will be left in the wine. This is how port and sherry are produced. But there are other ways to make a wine sweet, either mechanically or naturally.
Winemakers can stop the yeast eating the sugars by filtering it out when the desired level of sweetness has been reached or by the addition of sulphur products to the fermenting must to kill the yeast. Or they can ensure that the grapes have so much sugar that the yeasts exhaust themselves before all the sugar has been consumed.
Icewine and Late Harvest wine belong to the latter category: the grape sugars are just too much for the yeasts.
As the name suggests, Late Harvest wines – usually Riesling – are picked later than the normal harvest. They are given at least two weeks to a month longer on the vine to build up the sugars in the berries. This additional time can further concentrate the sugars if the grapes begin to desiccate (i.e. lose water) and even more so if the bunches are attacked by a "noble" rot called Botrytis cinerea. This fungus, created by warm, humid conditions in the late fall, pierces the skin of the berries and causes them to collapse into shrivelled raisins. They look pretty disgusting, like bats hanging on the vine.
Like most advances in the history of beverage alcohol, this late harvest effect was discovered by accident. Outside Schloss Johannisberg in the Rheingau is an equestrian statute of a harvest messenger commemorating the serendipitous discovery of Late Harvest wines. The story goes that Heinrich von Bibra, the Prince-Bishop and Abbot of Fulda, went off hunting and forgot to sign permission for the monks to start the harvest. When his harvest messenger was dispatched 14 days after the due picking date the minion was waylaid by highwaymen, who further delayed him. When he finally got to the vineyards of Schloss Johannisberg the vines had been attacked by a fungus (Botrytis cinerea). The rotten grapes were given to the peasants, who made wine from them, and it turned out to be amazingly rich in sweetness.
In 1775 the monks at Schloss Johannisberg made the first, intentional, Late Harvest wine (which they called Spätlese – spät is German for late and lesen to gather). The Germans subsequently categorised their late harvest wines by the degree of sugar in the grapes at the time of harvest – above Spätlese came Auslese (selectively picked Late Harvest grapes), then Beerenauslese (selectively picked Late Harvest berries) and, the sweetest level, Trockenbeerenauslese (selectively picked Late Harvest dried berries).
Icewine was another accidental discovery. In 1794 in Franconia there was an unseasonal frost in November which froze the grape bunches as hard as marbles. The peasant farmers, unwilling to throw the harvest away, gathered it in and proceeded to press and ferment the frozen berries. The wine they made was the sweetest they had ever produced.
So what's the difference between Late Harvest and Icewine? Basically, time and sweetness levels. Late Harvest wines are picked usually by November, whereas Icewine has to wait for the first frost when the temperature drops to at least –8° Celsius for a sufficient amount of time to ensure that the grapes are fully frozen when they are brought to the press. This happens usually around Christmas time, although winemakers sometimes have to wait until February or March for the right conditions.
Icewine grapes must reach a sugar reading of at least 35° Brix at harvest; otherwise, they are downgraded to various levels of Late Harvest based on the German model – Special Select Late Harvest (30° Brix), Select Late Harvest (26° Brix) and Late harvest (22° Brix).
And of course, there is a corresponding drop in price from Icewine to Special Select Late Harvest and so on down.