Cryoextraction is the process by which grapes are frozen with refrigeration and pressed.
Winemakers subject grapes to temperatures around 20 degrees Fahrenheit (or -7 degrees Celsius), and press them while still frozen. Ice crystals remain in the press, while concentrated juice flows out. The resulting wine resembles ice wine.
The process of freeze distillation is similar in its concentrating effects, although it occurs after fermentation.
An alternative to the natural method is picking clusters of late-harvest grapes at the peak of their physical maturity and sweetness levels, freezing them artificially at controlled temperatures in refrigerators until they are solid and then pressing them.
Cryoextraction, Richter says, would kill the mysticism and the rarity of naturally frozen grape wine: "It would be similar to spraying botrytis fungus on the grapes in October to raise the harvest result of noble sweet wines.
As for cryoextraction, the North American method, The Oxford Companion to Wine (second edition) explains it this way: "Freshly picked grapes are held overnight in a special cold room at sub-zero temperatures.
Cryoextraction ultimately became the favored technique for the removal of cataracts from the mid to late 1960s through the late 1970s and early 1980s.
When extracapsular cataract extraction, phacoemulsification, and IOL implantation became the technique of choice, cryoextraction of cataracts was less often used.
Today cryoextraction of cataracts is used primarily if the lens is subluxed and extracapsular cataract extraction might lead to the lens falling into the vitreous cavity.
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