Sweet Wine: Eiswein Just as late harvest wines have their spiritual home in

Sweet Wine: Eiswein

Just as late harvest wines have their spiritual home in Alsace (you might argue it was Germany, but the Beerenauslese and Trockenbeerenauslese Prädikat categories have much more to to with the careful selection of grapes affected by Noble Rot than true vendange tardive character), so eiswein also has its birthplace. In this case it most certainly is Germany, and there are few other locations in the world that have seen any success with the production of sweet wines using this unique and fascinating method.

It is of no surprise that, as is the case with botrytis, there are a number of myths and legends surrounding how the eiswein method was developed. Doubtless it was a serendipitous discovery, but just when and where it occurred is open to debate. Some put the occurrence as recently as the late 19th Century, when a bitter winter took the winemakers of Franconia by surprise. No doubt in such a situation the Franconians would have thought that all was lost, but in the face of great financial loss the frozen grapes were harvested and the surprising results widely appreciated.

Eiswein could be considered as an extreme form of the late harvest method; the grapes are left to hang on the vine long after the usual moment of harvest. No doubt during this time they develop some of the passerillage character which results from a combination of dehydration and the creation of complex compounds following isolation from the vine as it enters its dormant winter phase. But these grapes see an essential extra step. Whereas late harvest wines are commonly brought in from the vineyard during October or November, grapes destined to make eiswein are left until winter fastens her icy grip on the vines. The winemakers watch as frost takes control of the vineyard, freezing what little vegetation remains, as well as the fruit. It is this freezing process that is absolutely essential, but the wait for a suitable frost can be a nail-biting one; losses to birds, rot, or a mild winter with no suitable frost all threaten the winemaker's livelihood.

The grapes are ultimately harvested in December, or even in the ensuing January. The temperature must be low, below -8ºC to ensure that the grapes are sufficiently frozen and that they remain so on the way to the winery. Consequently, harvesting may be performed at night, or in the early morning, to ensure optimal conditions. The grapes are collected in whole bunches, a considerably easier process than the selection of individual berries affected by the rather more capricious Noble Rot, as required for Trockenbeerenauslese. Once back in the winery, the frozen grapes are pressed and the sweet juice, rich in sugar, acids and aromatic compounds, is collected and fermented. The ice crystals are held in the press, thereby concentrating the juice obtained, increasing its must weight, and achieving the necessary concentration of natural grape sugars that is necessary for producing a great sweet wine.

The must weight required for a wine to achieve classification as eiswein varies from one region of Germany to another (as it does for most levels of the Prädikat, from Kabinett up to Auslese - the only exception is Trockenbeerenauslese). Eiswein must hit at least 110º Oechsle in several regions, including Mosel-Saar-Ruwer, but this figure climbs as high as 128º for Baden. Note that in all cases, however, this is less than that required for Trockenbeerenauslese, which must be at least 150º Oechsle. This disparity in required must weight, the comparative ease of production of eiswein when compared to Trockenbeerenauslese (botrytis is much less reliable and consistent than the winter weather), the ability to increase must weight by extraction of ice in the winery (Auslese and higher Prädikats must obviously come in from the vineyard at the appropriate must weight) and the high prices achieved by highly prized examples of eiswein has meant that many winemakers favour the eiswein route, often turning over less exciting vineyard plots to the production of this particular sweet wine. Astute buyers will not be swayed by labels bearing the word Eiswein; it is the name of the winemaker that is most important.