Cryoextraction for Late Harvest Concentration

Cryoextraction involves freezing harvested grapes artificially, rather than letting them freeze on the vine as ice wine grapes do. The OIV's International Code of Oenological Practices gives cryoextraction its own sheet (II.1.10.4) under the control of the sugar content of harvested grapes, whose objective is to increase the sugar content of the raw materials used. The same section, whose recommendation is Admitted, lists cryoselection by physical procedures, partially freezing grapes in a cold room, then pressing at a low temperature in order to produce a must with a higher sugar content, and sets it beside cryoselection in the vineyard without recourse to physical procedures, where grapes partially freeze on the vine before pressing, the route the OIV requires for icewine. Traditionally made sweet wines rely on basically three ways to concentrate sugar in grapes: botrytis or noble rot, freezing, and drying the grapes on the vine or after picking.

• Grapes picked and then frozen mechanically make "non-natural" ice wines, sometimes called "icebox wines" or "iced wine"
• Sauternes producers such as Château d'Yquem make use of cryoextraction
• The OIV's cryoextraction sheet (II.1.10.4) is flagged as one whose production conditions are being studied; the parent sheet on controlling the sugar content of harvested grapes (II.1.10) lists both cryoselection routes

Harvested grapes are frozen mechanically rather than on the vine: in cryoselection by physical procedures, grapes are partially frozen in a cold room and then pressed at a low temperature. The principle is the one ice wine relies on: only the water in the grape freezes, while sugars and other components do not. When pressed, frozen grapes leave their water behind as ice; for Eiswein, the water contained in the berries remains as ice on the wine press, while only the sweetest juice, whose freezing point is lower than that of water, is obtained as a highly concentrated must. The concentrated must then ferments slowly, because yeasts have great difficulty fermenting must with such a high sugar content.

• For natural ice wine, the grapes must be both picked and pressed while still frozen, and the very high sugar levels make for slow fermentations
• German ice wines generally have a residual sugar content of well over 100 grams per liter and a relatively low alcohol content, often only around 7% by volume

Sarah Jane Evans MW, weighing cryoextraction as a fallback for ice wine, put the trade-off plainly: "The romance may be lost, the complexity of flavour may disappear, but wine from frozen grapes will remain viable." For ice wine itself, freezing the grapes concentrates the acidity as well as the extract, so the wines can taste fresh as well as very sweet.

• Ice wine grapes tend not to be affected by Botrytis cinerea, which gives ice wines a refreshing acidity
• Eiswein's character rests on the dense concentration of the berry ingredients and a comparatively high degree of acidity

Cryoextraction sits outside the protected ice wine names. Germany's Weingesetz (§20) requires that the grapes used for Eiswein be frozen at harvest and at pressing, and under German law the grapes must freeze on the vine; artificial freezing, as practiced in New Zealand, is strictly prohibited. In British Columbia, the Wines of Marked Quality Regulation (B.C. Reg. 168/2018) requires Icewine grapes to have frozen naturally on the vine while the air temperature is -8°C or lower and to be pressed in a continuous process while the grapes are still frozen, and it refuses the Icewine category to any wine processed using an artificial method of concentrating sugar, including artificial refrigeration at a temperature below -4°C. The OIV's icewine definition likewise rests on cryoselection in the vineyard without recourse to physical procedures. Argentina's Las Perdices Ice, made using cryoextraction, cannot use the term Ice Wine on its label.

• OIV icewine prescriptions: harvesting and pressing at a recommended temperature of -7°C or lower, a minimum potential alcohol in the must of 15% by volume (110° Oechsle or 25.3 Brix), and an acquired alcoholic strength of at least 5.5% by volume
• British Columbia Icewine must reach at least 32° Brix after each pressing and an average of at least 35° Brix across combined pressings, with residual sugar of at least 100 g/L at bottling, and its tanks may not be cooled below -4°C during fermentation and cold stabilization
• In the Loire, the Quarts de Chaume Grand Cru specification bans any thermal treatment of the harvest involving a temperature below -5°C, applying from the 2020 harvest; mechanical freezing or cryoextraction, previously allowed there as an experiment, was to be phased out

Sarah Jane Evans MW presents cryoextraction as the answer if winters warm: just as grapes may be sprayed with botrytis spores to induce the infection, freezing will do the trick for ice wines. Sauternes producers such as Château d'Yquem make use of it. In Argentina, Viña Las Perdices made Las Perdices Ice, a sweet Malbec from Mendoza, using cryoextraction, with 10,000 bottles made in its first two vintages. For naturally frozen wine, the first documented German ice wine dates to 1830, when winegrowers near Bingen in Rhineland-Hesse discovered on February 11 that a sweet must could be obtained from frozen grapes.

• A 1982 amendment to the German Wine Law raised Eiswein to an independent attribute, with a minimum must weight of 110 to 128° Oechsle depending on the growing region
• After the poor 2011-12 winter, 470,000 liters of ice wine were declared in Rhineland-Palatinate and more than 90 percent was rejected by state inspectors; a new state law triggered by that winter requires growers to declare before the harvest the grapes they intend to use for ice wine, reporting by Nov. 15

Ice wine is a winemaker's gamble that carries the risk of total loss. On average only about 5-10% of the original harvest quantity is bottled as ice wine, with harvests often only between 300 and 500 liters per hectare. A 2013 estimate put the average at 100 to 200 liters of ice wine per acre, compared to more than 4,000 liters for other wines.

• If the freeze does not come quickly enough the grapes can rot, and if it is too severe no juice can be extracted
• Slovenian producer Slavko Prapotnik called -7°C a prescribed minimum in Slovenia but not enough for quality ice wine, and wine writer Robert Gorjak said the timeframe is shifting toward January

Primary sources (the OIV, German and British Columbia law texts, the INAO, and Wines of Germany): https://www.oiv.int/standards/international-code-of-oenological-practices/part-ii-oenological-treatments-and-practices/grapes, https://www.oiv.int/standards/international-code-of-oenological-practices/part-i-definitions/special-wines, https://www.gesetze-im-internet.de/weing_1994/__20.html, https://www.bclaws.gov.bc.ca/civix/document/id/complete/statreg/168_2018, https://www.winesofgermany.com/our-wine/wine-products/wine-product/418/eiswein, https://extranet.inao.gouv.fr/fichier/3.11-CDC-Quarts-de-Chaume-modifi%C3%A9.pdf. Secondary: https://www.decanter.com/features/sauternes-and-tokaji-offering-affordable-and-alternative-wines-246834/, https://www.winespectator.com/articles/whats-the-story-with-eiswein-5339, https://www.winespectator.com/articles/german-ice-wine-rules-tightened-49351, https://www.decanter.com/wine-news/fury-and-charges-of-egotism-as-loire-s-baumard-challenges-grand-cru-32645/, https://www.decanter.com/wine-news/argentina-exports-first-ice-wine-66131/. Last verified 2026-10-04