Cryoextraction for Late Harvest Concentration

Cryoextraction is a winemaking technique in which harvested grapes are artificially frozen, then pressed while still partially frozen so that water ice is excluded from the juice. The result is a more concentrated must, richer in sugars, acids, and aromatic compounds. Unlike noble rot, which relies on the fungus Botrytis cinerea, cryoextraction depends entirely on cold temperatures and is a reproducible, controllable process independent of vineyard conditions. The technique is distinct from traditional Eiswein or Icewine production, where grapes must freeze naturally on the vine before harvest.

• When partially frozen grapes are pressed, juice defrosts more rapidly in areas where sugar concentration is higher, due to a cryoscopic depression of the melting point in those zones
• Ice crystals formed during freezing tear the pectocellulose walls of grape skins, disorganizing the berry tissue and facilitating the transfer of aromatic compounds from skins into the must
• Two main variants exist: cryoextraction proper (freezing grapes before pressing) and supraextraction (freezing followed by defrosting before pressing), with both producing more aromatic wines than traditional methods

Harvested grapes are chilled mechanically to temperatures typically between -8°C and -12°C, forming ice crystals predominantly composed of pure water. When pressed, the frozen grape mass yields a much smaller volume of highly concentrated juice compared to unfrozen grapes. The concentrated must is then fermented slowly, often at cool temperatures, to develop complexity. Because the water is excluded as ice, sugar levels can increase significantly, with must Brix rising from around 20-25° to 35-40° or above, creating the intense sweetness characteristic of dessert wines made this way.

• Research comparing freezing methods found that liquid nitrogen freezing produced wines with higher levels of terpenoids and more intense aromas than ultrafast mechanical freezing, though both outperformed unfrozen reference wines
• Both freezing techniques increase phenolic content relative to wines made from unfrozen grapes, as cell wall disruption promotes polyphenol extraction from skins
• Fermentation of ultra-concentrated must proceeds slowly due to the osmotic stress on yeast; producers often use cold-tolerant or osmotolerant yeast strains and careful temperature management to prevent stuck fermentation

Wines made by cryoextraction are prized for their intense sweetness balanced by bright, preserved acidity and concentrated primary fruit aromatics. Because the process involves no fungal action, the flavor profile emphasizes clean stone fruit, citrus peel, honey, and floral notes rather than the caramelized, oxidative, or botrytis-driven complexity of noble-rot wines. The cold also prevents oxidation of the juices, helping preserve freshness and tension on the palate. Tasters often find notes of pear, quince, apricot, and orange blossom, with a silky, viscous texture.

• Unlike botrytized wines, cryoextracted wines tend to show greater purity of primary fruit character, as there is no fungal modification of grape aromatics
• The cold during processing acts as a natural antioxidant, helping to preserve delicate aromatic compounds that might otherwise be lost in warmer processing
• High residual sugar combined with preserved natural acidity gives these wines strong aging potential, with structural balance supporting development over many years in bottle

Cryoextraction occupies a legally distinct space from protected ice wine designations. In Germany, wine law strictly prohibits artificial freezing for any wine, including those not labeled Eiswein. In Canada, VQA rules require grapes for labeled Icewine to be naturally frozen on the vine at -8°C or below, with no artificial methods permitted. EU PDO rules reinforce this, explicitly prohibiting cryoextraction for wines using protected ice wine designations. Wines made by artificial freezing in these jurisdictions must be sold under alternative descriptions and cannot claim the protected Eiswein or Icewine names. In Australia and some other New World regions, artificial freezing is permitted and wines may be labeled accordingly under local rules.

• German Eiswein requires grapes to be harvested at a natural temperature of -7°C (19°F) or below, with the entire crop pressed while still frozen before it can thaw
• Canadian VQA Icewine requires natural freezing on the vine at -8°C (18°F) or below, a minimum of 35° Brix, and no artificial concentration methods
• Climate change has made passive on-vine freezing less reliable in borderline regions, increasing the commercial relevance of cryoextraction as an alternative for producers who cannot use the protected designations

The history of naturally frozen grape wines is long: the first documented Eiswein was produced in 1830 in Dromersheim near Bingen in Rheinhessen. In Canada, Inniskillin achieved its first successful Icewine harvest in 1984 using Vidal grapes protected by bird netting, after losing the 1983 crop to birds. Its 1989 Vidal Icewine won the Grand Prix d'Honneur at Vinexpo in Bordeaux in 1991, bringing global attention to Canadian Icewine. In Tokaj, Royal Tokaji was founded in 1990 by wine writer Hugh Johnson and investors after the fall of Communism, while Oremus was established in 1993 when the Álvarez family, owners of Vega Sicilia in Spain, acquired vineyards in Tolcsva. Both produce Tokaji Aszú using botrytized grapes, not cryoextraction. German estates such as J.J. Prüm and Egon Müller have defined Eiswein through decades of careful frost-wait decisions.

• Inniskillin's 1989 Vidal Icewine won the Grand Prix d'Honneur at the 1991 Vinexpo in Bordeaux, making it the first North American wine to receive this honor and placing Canadian Icewine on the world stage
• Royal Tokaji, founded in 1990 by Hugh Johnson and investors in the village of Mád, focuses on single-vineyard Aszú wines from first-growth sites including Nyulászó, Szt. Tamás, and Mézes Mály
• Oremus, owned by the Álvarez family of Vega Sicilia since 1993 and based in Tolcsva, produces Tokaji Aszú from Furmint and Hárslevelü across 33 hectares of classified vineyards

Cryoextraction demands precise temperature management, rapid processing, and careful hygiene. Frozen grapes are prone to oxidation if not handled quickly; modern producers use inert-gas purging and process grapes promptly after freezing. Fermentation of ultra-concentrated must poses the risk of stuck fermentation due to the high osmotic stress on yeast; producers typically use cold-tolerant or osmotolerant strains and may employ staged management to ensure fermentation completes. Equipment costs, including industrial freezers and specialized presses, limit accessibility, and small producers may share facilities. Yield loss is significant, as much of the grape weight is excluded as ice, making cryoextraction economically viable only for premium, small-lot production.

• The yield of liquid from frozen grapes is only around 10-20% of what unfrozen grapes would produce, as most of the water remains behind as ice during pressing
• Post-freeze storage of cryoextracted must requires careful temperature control and protection from oxygen to prevent volatile acidity from developing
• Regulatory compliance is essential: producers in Germany, Canada, and EU PDO jurisdictions must avoid the protected Eiswein and Icewine designations when using artificial freezing methods