Julie is making a risotto for dinner, but she needed wine. It being Easter Monday, and our nation being absurdly Puritanical when it comes to alcohol sales, the liquer stores were closed. Instead, she bought some dealcoholized wine from the local grocery store. I read on the label how the alcohol was “gently removed” and wondered how it was done.
It turns out that there are several methods. Among them are the spinning cone and cold filtration. The cold filtration process is apparently patented, so my 6-second search came up pretty empty. On the other hand, the spinning code sounds like more fun and works this way:
Wine is fed into the top of the spinning cone column (a vertical cylinder roughly 40″ in diameter and 13′ in height) and flows down over a series of alternating stationary and rotary metal cones. Centrifugal force transforms the wine into a thin liquid film, which is contacted by ascending nitrogen gas fed into the bottom of the cone.
The nitrogen acts as a carrier to extract the volatilized aroma and flavor compounds from the wine. These essences are then condensed, separated and safeguarded while the liquid is run through the cone again, at slightly higher temperatures, to remove the alcohol. Then they are reintroduced to the dealcoholized wine and blended with unfermented varietal grape juice to create a beverage with less than 0.3% alcohol by volume.
This article also discusses the spinning cone approach to hangover-free wine. As this article notes, most ‘dealcoholized wine’ has about 0.5% alcohol in it. So, technically speaking, it’s not alcohol free. This four-page piece (PDF) seems to offer a decent survey of the popular methods of separating the juice from the lemon, so to speak. It’s got more information on the cold filtration process (described there-in as ‘thermal gradient processing’). It also explains that, unsurprisingly, we’re talking about a niche market here–about 0.5% (ironically enough) of all the wine consumed. Of course, that’s still 4.5 million litres of dealcoholized wine drunken (drunk? drank?) annually.