Topic of the Week 5/31/2019 - Master

German red alternatives last week from , and . Thanks gents.

This week: Reverse osmosis

What is this winemaking technique used for? How does it work?

  • The best use is to take the minerals out of water so you don't have clogged misters (humidity control) or hard water spots on your windows from errant hose spray.

    It's used for a variety of composition changes in the wine ( microbial filtration, alcohol adjustment, deacidification, VA removal, smoke taint removal, 4ep/4eg removal, "rain"water removal). 


    How does it work? I read Clark Smith's book Postmodern Winemaking, and he explains it in detail, but I still believe that its some sort of witchcraft that has no business in a winery. "Never trust anything with a plug," he says, despite making a career on developing technology. 

  • The primary use in winemaking is de-alcoholization. 

    A portion of the wine is passed through a reverse osmosis machine, in which the wine is passed over a semi-permeable membrane under increased pressure. Alcohol, having a larger molecular composition is thereby separated from the wine. The alcohol (permeate now) can be distilled and either used for other purposes, or recombined with the wine in a prescribed amount, controlling the alcohol. OR the separated wine (retentate now) can be added back to the rest of the wine, sans alcohol, lowering the overall alcohol content of the final wine. 

    The advantage of this process is achieving the flavor of ripe grapes, but being able to control and lower the final alcohol of the wine. 

    Obviously its controversial. 

    Dunn does it.