By Jen Pfeiffer
Have you ever wondered what that sediment is in an older red that you have saved for that special occasion? Do you know if it’s safe to drink? Why don’t we see sediment in white wines?
Put simply, sediment can form naturally in the winemaking process and also whilst maturing in bottle. Wine sediment is not harmful, in fact some people see it as a sign of quality. However wine sediment can often taste bitter and it is best to decant the wine (separate the clean wine from the sediment) before serving and drinking.
The initial sediment that forms during the winemaking process is called the “lees” and first forms at the end of alcoholic fermentation. The lees consist of dead yeast cells, proteins, stems, pips, bits of skin and other solid matter that settles to the bottom of the tank after a vigorous fermentation has been completed. Winemakers remove the lees by a process called “racking”, whereby the clean wine is pumped from the top of the tank, sometimes through a filter, to another tank, leaving the lees at the bottom.
In this modern age of winemaking, it is highly unlikely that any lees will be left in the wine prior to bottling. The sediment that forms in the bottle is a mix of tartrates, tannins and other products of the complex chemical changes that have taken place.
Tartrates are the most common form of sediment in bottled wine. Tartrates are a product of the naturally occurring tartaric acid that is found in grapes. Tartaric acid does not remain dissolved in alcohol as easily as it does in grape juice. As such it binds to potassium (also naturally occurring in grapes) after fermentation and forms potassium acid tartrates – the crystalline salt that creates the sediment in your bottle. In red wines, they are stained black and in white wines, the tartrates look like tiny diamonds.
All wines form tartrates naturally in the cellar. Modern winemaking has introduced cold stabilisation and fine filtration to remove the tartrate from the wine prior to bottling. This process has been done for many years on white wines, as the “white diamonds” formed in the bottle were sometimes mistaken for shards of glass. However, when it comes to red wines, it becomes the preference of the winemaker as to whether to remove these tartrates prior to bottling. When the tartrates are not removed, they naturally deposit over time into the bottle.
So, the next time you choose that old red for that special occasion, don’t be concerned about the appearance of sediment. Instead, stand the bottle upright for several hours before opening it. This will ensure the sediment settles to the bottom of the bottle. Decant the wine into another container, by pouring in one smooth motion and stopping when you see the appearance of the sediment. Then simply enjoy the pleasure of sharing that good bottle of wine with the company you are in.