Recently, while drinking some older California wines from the 1950s and '60s the topics of "fining" and "filtration" came up. Now, I know most folks don't sit around and chat about such things, so an explanation is in order for our readers -- especially those who appreciate good wines but don't always know what gives them certain qualities.
No doubt you've seen wine that's hazy or cloudy. It probably looks that way because it hasn't been "fined." Fining is the removal of unstable molecules through their absorption into some other material. This process clarifies the wine, preventing that hazy effect. Over history, many fining agents have been used, from dried blood powder to various gums. Today's most common fining agents, which can be either organic or inorganic, are egg whites, or the albumin from egg whites, and a type of clay called bentonite. Other fining agents may be used at the wine makers' discretion. For example, gelatin -- which reacts with tannins to reduce astringency in wine -- also reacts with proteins and helps clarify the wine. Caseia, which works with wine's acids and tannins, not only clarifies the wine but reduces any undesirable color.
That said, the most important question remains to be addressed: Does fining affect the taste? That's what we really care about, right? The answer is yes; in general fining softens red wines by reducing bitter and astringent tannins. It helps clarify white wines, and that adds to our enjoyment. Now, most amateurs in blind tastings can't tell the difference between a wine that's been fined and one that hasn't. And some wine makers choose not to fine because they believe fining removes the wine's complexity and flavor. But most great wine makers can tell the difference and that's why they choose to fine.
Now as to "filtration." Obviously, this process involves straining solid particles from the wine with various filters. Natural settling helps achieve this goal, but two common types of filtration will do the job more effectively: sheet filtration and membrane filtration.
Sheet filtration involves a thick, finely divided element like cellulose powder or perlite. As the wine passes through the sheet, small particles are trapped, causing clear wine to pass through on the other side. Membrane filtration uses a thin plastic film to trap particles. This filtration can be so fine that it actually sterilizes the wine, removing bacteria and yeasts and possibly destabilizing the product once it's in the bottle. Most fine wines these days are not put through "sterile filtration."
As for the California Cabernets I mentioned earlier -- were these fined and filtered? Some in our group thought yes, because they seemed to lack a complexity of flavor. Actually, it's hard to know for sure unless you're there to see the processes, which are just two of several involved in the creation of wine. And neither filtration nor fining necessarily makes a wine bad or good. For instance, a red wine with lots of sediment can be just as flavorful as one that's clear.
Still, the next time you hear someone say, "This wine wasn't fined or filtered," you'll at least know what he's talking about. More importantly, I hope that knowledge enhances your enjoyment of what you're drinking. It's like old John Milton (1608-1674) said, "Wine . . . one sip of this will bathe the drooping spirits in delight beyond the bliss of dreams. Be wise and taste." And when all is said and done, filtered and fined, the individual taster is the final judge and jury.