Reverse Osmosis is Not a Swear Word

Imagine you're at a 5 star Hawaiian resort, lounging on a raft in a gorgeous, salt-water infinity pool; that's a vacation.  Now imagine that same pool bisected by a semi-permeable membrane, with salt water on one side and fresh water on the other.  When water automatically flows down its gradient, from a high concentration (i.e. fresh water) to low one (i.e. sea water), well that's osmosis.  The semi-permeable membrane permits water flow through its microscopic interstices but blocks the salt crystals as they bump up against the divider.  Should we apply enough pressure, we could force Nature's hand and reverse the current's flow, pushing water from the salty side to the fresh water side.  Compelling water to travel uphill, from a lower to higher concentration, by application of external pressure, dear Brigade, is reverse osmosis.  This is the very principle behind desalinating sea water, squeezing the water out and leaving sea salt crystals behind.  Now let's contemplate a rainy spring that bloated orbs of sweet grapes into tasteless blobs.  Should this crop result in a diluted and weakened wine, you could use reverse osmosis to suck the excess water out and concentrate what's left behind.  This might occur more than winemakers care to admit; reverse osmosis is a dirty word.  So now consider that reverse osmosis enables an automated apparatus to pluck only the guiacol and 4-methylguiacol from smoke tainted wines.  Optimists are in awe of such scientific marvels.  Pessimists grumble that the subtlest, desirable phenols are invariably stripped away with the malodorous whiffs of smoke, charcoal, burnt bacon, and wet ashtray.

Reverse osmosis is controlled by a big machine that siphons a colorless, filtered "permeate" from the unfiltered, wine-colored "retentate."  The wine's color, flavor, varietal character, and choice aromas are retained in this "retentate," while the filtered stuff may or may not be discarded.  The RO machine exploits "nanofilter" technology to barricade most molecules behind its filter wall; only the tiniest compounds, generally set at 100 daltons or less, can shimmy through.  As it happens, water is the smallest component of wine, so it, naturally, comprises much of the filtrate.  Ethanol, acetic acid, ethyl acetate, and lactic acid are also pretty teeny and wash up in the filtrate, too.  Conversely, tartaric acid, citric acid, and malic acid are bigger than the chain link and remain behind.  We're told that anthocyanins (the ‘wine coloring' that gives wine its hue) and other phenolics (smells) are also too cumbersome to wiggle through the filter fence.

In the next step, the permeate is treated to remove particular compounds (like guiacol).  Right then, the residual residue is readily recombined with the retained retentate (righteous alliteration, yes?).  Companies that specialize in removing specific, undesirable molecules from finished wine promote their methods as minimally invasive, gentle, and above all selective.  Only the damnable taint is expunged while the remaining vino is essentially undisturbed, only better.  The two big companies that advertise this work are Memstar and VA Filtration.

We plan to employ the VA Filtration system.  According to their tricolored website, it's portable!  And easy!  You can rent it for days - or weeks!  (Maybe I can borrow it for home to filter the food particles from the backwash in my kids' water bottles).  Web aesthetics aside, the verbage on their site sounds sunny.  They explain the procedure in much the same way that I did to you.  In their own words, "The wine is separated into two streams (a permeate and concentrate stream) using nanofiltration membrane elements.  The system operates at pressures of between 225 and 350 psi. The permeate stream is then passed through a second stage treatment process, where the offensive compounds are removed.  This treated stream is then recombined with the concentrate stream and returned to the feed tank.  Each pass through the system reduces the G and 4MG levels by 25-30%."  In case you're stupefied, "G" is guiacol and "4MG" is methyl guiacol.  Psi represents a unit of pressure, the force needed to move liquid against its natural gradient.  At the very least, the scientific content appears solid, even if their ill-advised, pixilated logo reeks of unprofessional cheesiness.  (I am wary of the shockingly unprofessional use of rotating loops of flashing words).  But my gravest torment is the grim annotation completing the bottom of the web page.  Written entirely in caps is the warning:




What??!!  Aren't they supposed to be the experts?  Listen, as we become more familiar with the extent of our smoke blight, we'll keep you informed, too.