Fining Part One: Stabilizing White Wine and Being a Hero

White wine usually starts out looking like this, yummy, I know.  The grape solids usually sink (white layer at the bottom of carboy) but often this is not enough to make the wine clear enough to be acceptable to consumers.  To clarify the wine it is necessary to fine and/or filter it.  Fining agents usually include proteins like eggs, casein or milk.  As an intern I was asked to add 6 gallons of whole milk to a tank of white wine and I thought I was being punked.  Turns out I wasn't.  Since then I've frequently (on purpose) added egg whites to barrels (red wine too).

Fining and filtering not only serves the purpose of getting the wine clear, but also stable.  Many wine proteins are soluble at room temperature but if the wine gets too hot (like from leaving it in your car) the proteins precipitate out and float around the wine.  It looks like fine wisps of cotton gently floating around.  Since the proteins were denatured, cooling the wine back down does not make them go back into solution, forever changing the mouthfeel of the wine.  No bueno.

 

To avoid this unpleasant situation we heat stabilize the wine by adding Bentonite (a clay from volcanic ash) to the wine in tank (before bottling) to bind of the proteins and remove them from the wine in the first place.  When Bentonite is mixed with water (pic) it can absorb more than 7 times its original dry weight and expand to 18 times it's volume (!)

The dry stuff gets everywhere, so you need to wear a mask when mixing.  Here I am using a mixer to dissolve the Bentonite into hot water, the Bento is negatively charged and when mixed into the wine will attract the positively charged protein particles.  The weight of the combined molecules causes them to precipitate out of solution and fall to the bottom of the tank.  Then we rack the clean wine off the top and discard the sludge at the bottom.

We must also cold stabilize white wine not for protein precipitates but for tartrates.  While very pretty they are undesirable in wine.  This happens when tartrates (salts) from tartaric acid (the most abundant acid in wine) bind to lees, tannins or grape solids.  If exposed to low temperatures, the tartrates crystalize.

To prevent the crystals from forming in the bottle, we cool the tanks to almost freezing to crystalize and precipitate out any potential problems.  We do not use this method for protein stabilizations (heating up the tank to car-on-a-hot-summer-day temperatures) because cooling the wine does not negatively impact the wine they way cooking it would.  Bentonite is a much better option than cooking the wine to precipitate out the proteins and waiting for them to fall to the bottom of the tank.

This is totally unrelated to wine stabilization but while working in the cellar today I looked at the floor and it looked like I either worked at a winery, or an O.R. and a patient was bleeding out nearby.   I don't save lives but I think my work is pretty important too ;)

Saving good wine from going bad.

-L