So the vines have been nurtured, the fruit picked, destemmed, crushed and pressed. The juice is resting in tank and now we’re entering the final stages of the winemaking process. But what is required to ensure you get a crystal clear wine in your glass?
Making the wine limpid and stable is that all important phase before bottling. The wine must not only smell and taste good, it needs to be aesthetically pleasing for the wine drinker of today. No cloudiness, no haze and no sediment. Well, that’s what we all desire anyway. Sediment and crystals in a wine are not in fact considered to be true wine faults, such as cork taint or oxidation, but they are common and come in varying degrees.
Sedimentation within the bottle is a natural occurrence in many wines, generally those designed to withstand some ageing, and it simply reflects the solid matter settling out of the wine. The most common crystals found in wine are tartrate crystals (also known as potassium hydrogen tartrate), and these are often found at the bottom of the bottle or in free suspension.
So how does the winemaker eradicate them? Most commercial wines undergo cold stabilisation before bottling, which involves chilling the wine enough to precipitate the crystals. Filtering may also be used, such as the sheet filter method, although this particular technique can go horribly wrong. Unclean sheets may add a wet cardboard taint to the wine. Too many, and the wine will have its flavour stripped.
Fining agents are a less aggressive solution to free radicals. You may have heard of Bentonite. This American clay is also used in fining juices. It attracts the larger solids, which can cause discolouration in white wines or make red wines taste bitter, to fall to the bottom so that the clear wine can be racked off. These fining agents don’t actually remain in the wine, so don’t be expecting a mouthful of American clay in your next glass of Echo Falls. Beaten egg whites essentially do the same job. This is the Europeans preferred fining technique.
Preservatives may be added in the less expensive bulk wines, the most common being ascorbic acid, with additional sulphur dioxide (I say additional because sulphur dioxide, or sulphites, are a natural byproduct of the winemaking process, so they are present in smaller quantities to start with). The better quality wines will rely on time, settling and racking, without the harsh filtration techniques.
If you come across a wine with sediment or crystals simply sieve the contents of the bottle into a decanter, and in the case of many good quality reds you’ll have a better drinking experience as a result. If it doesn’t particularly bother you either way, drink away.