Sediment and Tartrate Crystals
pull a cork on a bottle of wine and see what looked like broken
glass glued to the bottom of the cork? Some people get freaked out
about it but the fact is, it's totally harmless. Others think it's
sediment, but they would be incorrect as well.
First, let's deal with tartrate crystals. They are formed when
a method called cold stabilization is performed on a wine. Cold
stabilization is often done in white wines to remove excess potassium
bitartrate, a natural substance found in grapes also known as "cream
of tartar." White grapes contain fairly large amounts
of potassium bitartrate. If most of it is not removed, the wine
will form crystals when placed in the refrigerator. These tartrate
crystals, sometimes called wine diamonds, will either cling to the underside of the cork, if the
bottle is on its side, or fall to the bottom of the bottle, if it's
standing up, where they appear to be ground glass to the uneducated
To remove excess potassium bitartrate before bottling, the wine
is placed in a stainless steel tank and its temperature dropped
to about 30 degrees F. The wine is held at that temperature for
a period of approximately 2-3 weeks. Excess potassium bitartrate
will then crystallize and drop to the bottom of the tank where it
is removed either by filtration or by pumping the wine out of the
tank until the hose is just above the bottom where the crystals
have formed. The "cold stabilized" wine is then bottled.
Some wineries prefer to skip this step, feeling that the process
detracts from the wine's flavor and nuance. Having the tartaric
crystals appear in the wine means nothing more than it was not cold
treated and, thus, may be of higher quality. The crystals have no
taste, just a little crunch if you eat them.
The sediment in wine bottles is completely different. The tumultuous act of fermentation
presses the grapes to where parts of the stem, seed and skin are
pulverized to the point where they become so small they disappear.
Seemingly, that is. The fact is, they are just suspended in the
wine. As the wine ages, these tiny particles begin to attract each
other and form a small mass that is now visible to the naked eye.
The longer the wine ages, the more chance they have to come together
and eventually will either form particles which fall to the bottom
of the bottle or will actually cling to the side or bottom.
Sediment is usually very bitter which is why the bottles should
be decanted or filtered to remove it, though most filters aren't
fine enough. Multiple layers of cheese cloth may do the trick
if you're filtering wine sediment, but not always.
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