Hi everyone! Today I'm here to talk about two of the strangest things that are pretty typically added to wines - a clay called Bentonite, and a resious polymer called PVPP, or Polyvinylpolypyrrolidone if you're fancy. Why would we want to add dirt and plastic to wine, you wonder? My gosh, that's an excellent question.
I'll start with bentonite-- at its most basic, it's a negatively-charged clay from Wyoming that swells to sevel times its dry size when wet. Because of this, when it's added to solution it has a very high surface area. It's the high surface area and the negative charge that we're taking advantage of when we use it in winemaking. Believe it or not, grapes contain protein, and when these proteins remain present in the wines made from the grapes. These proteins have a positive charge. End of story if that protein stayed stable in the wine, but unfortunately, protein tends to clump up after a certain amount of time passes, and it can form an unattractive haze in the bottle. It's much more noticeable in white wines than in reds, but certain light red wines may deposit a notable protein haze as well. How do we get rid of it? When we add bentonite into a wine and mix it up, the clay and the proteins will be attracted to one another due to their opposite charges (negative and positive), so the bentonite works to pull the protein out of the wine before it's put into bottle. We'll move the wine off that layer of clay and protein, so none of it is actually carried over into your glass. Don't worry-- you're not going to be drinking any dirt.
And what about PVPP? Well, this polymer is similar to bentonite in that we use it to remove undesirable compounds from the wine. It also swells up in water, increasing surface area, but we're not looking to remove proteins in this case, but polyphenols. Polyphenols are wide range of compounds, and they can do everything from causing certain white wines to turn a pinkish or brownish color, to just making a wine taste too bitter. When we add PVPP, we're doing it in exactly the same way as bentonite - swelling in water, mixing with the wine, and letting it settle out before moving the wine off the sediment.
So the next time you're enjoying a crystal clear white wine, give a little cheer to bentonite and PVPP, two ingredients that just might be the unsung heroes in producing that glass.
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