“Hey, there’s something in the bottom of my glass!”

by Elizabeth Cooper in Wine & Beer

“Hey, there’s something in the bottom of my glass!”…or on the end of the cork or even stuck to the lip and inside neck of the bottle; but what is it? I’ve been getting this question a lot lately. With the arrival of the “natural” wine movement, we are seeing many more unfiltered, unrefined wines on the market. This resurgence of wines in the raw has brought on more customer confusion. There must be something wrong with this wine, right? Someone did not store or handle this properly, right? … I thought that this subject might be a helpful follow-up to my previous blog regarding wine allergies, et al.

First, the quick, easy answer: sediment. But what is it? Well, sediment is an innocuous, naturally occurring byproduct of the winemaking process that is commonly filtered out before bottling. These sediments fall into two categories: colloids and tartrates. Colloids are the smaller of the two and are typically made up of protein, cellulose fiber and spent yeast cells – they are not always visible in newer wines, as they build over time. As the wine ages, they join together to become noticeable solids in solution. Colloids can easily pass through commercial filters and even avoid some fining agents – so even filtered and refined wines, over time, will develop this type of naturally forming sediment. Delicate decanting can help to keep these particles from interfering with your experience.

Tartrates are much larger particles, and are harmless, naturally formed crystalline deposits that separate from wines during fermentation and aging. The principal component of this deposit is potassium bitartrate, a potassium salt of tartatic acid. Small amounts of pulp debris, dead yeast and precipitated phenolic materials such as tannins make up additional components of the potassium acid tartrate. In red wines, these tartrates take on a red pigment and are mistaken for colloid sediments in older wines or alarming flaws in newer vintages. Conversely, in white wines, tartrate crystallization takes on the shocking appearance of glass shards – prompting the rise in cold stabilizing and filtering.

Finally, when wine is shipped and stored, it is sometimes subjected to very cold temperatures, which will cause these supersaturated particles, tartrates and colloids alike, to seek each other out in solution and become solid particles. Again, no harm done, just not always pleasant to see.

You may be asking yourself – how come I don’t see all this stuff in grape juice? And why wouldn’t the winery carefully rack the wines to leave the tartrates in barrel or tank? Both good questions! First, tartrates are much less soluble in alcohol – so they are there in your juice; but just part of solution (yes, they are helping with the pucker factor!) Second, the tartrates start out in a supersaturated form, so while much are surely racked off prior to bottling, many do not form solids until after bottling. It seems that the wine industry at large finds the processes of stabilization, filtration and refinement to be much easier solutions to the harmless, yet somewhat unappealing particles and flocculation rather than long, drawn-out explanations on each bottle. It is probably not a difficult decision for large production wines as you are generally going for continuity and profile; but for smaller producers there lies the question – what am I stripping away with all of these process? Many would argue not much and the benefit is eye appeal; while others would argue that natural flavors, textures and aromas are lost – this is an argument from which I prefer to steer clear!

So, when opening a bottle of wine and discovering particles on the end of the cork or around the lip and upper neck of the bottle, what do you do? Take a deep breath. There is nothing wrong with your wine – in fact, your winemaker has gone to great lengths to be sure these natural by-products are there – take a clean cloth or napkin, carefully wipe the tartrates clear from the neck (don’t worry about the cork). Then, let the bottle sit for about 5 or 10 minutes to let the solids sink to the bottom of the bottle. Next, carefully pour your glass to find that most of the sediment remains at the bottom of the bottle. As you near to the end, you may need to sacrifice the last couple of ounces to the natural wine gods, or strain it if a wine emergency.

I wanted to address color in wine; but I think this is enough for one week, so next week look for “Why is my wine this color?” Until then, please feel free to email me directly with any question, comments, complaints.

Cin Cin,
Liz Cooper