Dear Wine Ladies,
At a recent dinner party I attended the hostess noticed a small amount of sediment that looked like tiny pieces of glass at the bottom of a bottle of white wine from Germany. I was a little hesitant to drink the wine but one of the guests assured us the wine was fine and there was no cause to worry. What were those little pebble-like stones and are they really harmless?
Those pebble-like wine stones you are describing are commonly referred to as “wine diamonds” or weinstein which literally translates to “wine stones” in German speaking countries.
What exactly are they and how did they end up at the bottom of the bottle? These wine diamonds are actually harmless crystalline deposits that naturally separate from wines during fermentation and aging. Potassium acid tartrate, the potassium salt of tartaric acid is the major component of this sediment. The presence of tartaric acid, along with malic acid are very important in winemaking as they help provide good structure, fruit flavours, crispness on the palate and an increased lifespan of the wine.
The majority of winemakers today recognize that the consumer is alarmed or put off by the presence of these crystalline deposits even though they are harmless. Rather than educating the public, many wineries employ a process called “cold stabilization” prior to bottling. This involves chilling the wine to just below zero degrees causing the potassium bitartrate to crystallize. The wine is then filtered and bottled. Having the wine undergo this process prior to leaving the winery assures a clean filtered wine with no sediment. In cases where the wine does not undergo cold stabilization at the winery, this precipitation of the tartrates could happen during cold weather transport or cold storage conditions.